electron transport chain


  • In photophosphorylation, the energy of sunlight is used to create a high-energy electron donor which can subsequently reduce oxidized components and couple to ATP synthesis
    via proton translocation by the electron transport chain.

  • The energy released by reactions of oxygen and reduced compounds such as cytochrome c and (indirectly) NADH and FADH2 is used by the electron transport chain to pump protons
    into the intermembrane space, generating the electrochemical gradient over the inner mitochondrial membrane.

  • When electron transfer is reduced (by a high membrane potential or respiratory inhibitors such as antimycin A), Complex III may leak electrons to molecular oxygen, resulting
    in superoxide formation.

  • When organic matter is the electron source, the donor may be NADH or succinate, in which case electrons enter the electron transport chain via NADH dehydrogenase (similar
    to Complex I in mitochondria) or succinate dehydrogenase (similar to Complex II).

  • The generalized electron transport chain in bacteria is: Electrons can enter the chain at three levels: at the level of a dehydrogenase, at the level of the quinone pool,
    or at the level of a mobile cytochrome electron carrier.

  • At the inner mitochondrial membrane, electrons from NADH and FADH2 pass through the electron transport chain to oxygen, which provides the energy driving the process as it
    is reduced to water.

  • An electron transport chain (ETC[1]) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions
    (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane.

  • Many of the enzymes in the electron transport chain are embedded within the membrane.

  • The free energy released when a higher-energy electron donor and acceptor convert to lower-energy products, while electrons are transferred from a lower to a higher redox
    potential, is used by the complexes in the electron transport chain to create an electrochemical gradient of ions.

  • This entire process is called oxidative phosphorylation since ADP is phosphorylated to ATP by using the electrochemical gradient that the redox reactions of the electron transport
    chain have established driven by energy-releasing reactions of oxygen.

  • Complex IV[edit] In Complex IV (cytochrome c oxidase; EC, sometimes called cytochrome AA3, four electrons are removed from four molecules of cytochrome c and transferred
    to molecular oxygen (O2) and four protons, producing two molecules of water.

  • When electrons enter at a redox level greater than NADH, the electron transport chain must operate in reverse to produce this necessary, higher-energy molecule.

  • A common feature of all electron transport chains is the presence of a proton pump to create an electrochemical gradient over a membrane.

  • The overall electron transport chain can be summarized as follows: Complex I[edit] Further information: Respiratory complex I In Complex I (NADH ubiquinone oxidoreductase,
    Type I NADH dehydrogenase, or mitochondrial complex I; EC, two electrons are removed from NADH and transferred to a lipid-soluble carrier, ubiquinone (Q).

  • One example is blockage of ATP synthase, resulting in a build-up of protons and therefore a higher proton-motive force, inducing reverse electron flow.

  • Mitochondrial redox carriers[edit] Energy associated with the transfer of electrons down the electron transport chain is used to pump protons from the mitochondrial matrix
    into the intermembrane space, creating an electrochemical proton gradient across the inner mitochondrial membrane.

  • For example, electrons from inorganic electron donors (nitrite, ferrous iron, electron transport chain) enter the electron transport chain at the cytochrome level.

  • The reduced product, ubiquinol (QH2), freely diffuses within the membrane, and Complex I translocates four protons (H+) across the membrane, thus producing a proton gradient.

  • Via the transferred electrons, this energy is used to generate a proton gradient across the mitochondrial membrane by “pumping” protons into the intermembrane space, producing
    a state of higher free energy that has the potential to do work.

  • For example, E. coli (when growing aerobically using glucose and oxygen as an energy source) uses two different NADH dehydrogenases and two different quinol oxidases, for
    a total of four different electron transport chains operating simultaneously.

  • Organisms that use organic molecules as an electron source are called organotrophs.

  • This type of metabolism must logically have preceded the use of organic molecules and oxygen as an energy source.

  • [9] Photosynthetic electron transport chains, like the mitochondrial chain, can be considered as a special case of the bacterial systems.

  • Two electrons are removed from QH2 at the QO site and sequentially transferred to two molecules of cytochrome c, a water-soluble electron carrier located within the intermembrane

  • For example, in humans, there are 8 c subunits, thus 8 protons are required.

  • Complex I is one of the main sites at which premature electron leakage to oxygen occurs, thus being one of the main sites of production of superoxide.

  • Electron acceptors and terminal oxidase/reductase[edit] As there are a number of different electron donors (organic matter in organotrophs, inorganic matter in lithotrophs),
    there are a number of different electron acceptors, both organic and inorganic.

  • Each electron donor will pass electrons to an acceptor of higher redox potential, which in turn donates these electrons to another acceptor, a process that continues down
    the series until electrons are passed to oxygen, the terminal electron acceptor in the chain.

  • Therefore, the pathway through Complex II contributes less energy to the overall electron transport chain process.

  • Bacterial terminal oxidases can be split into classes according to the molecules act as terminal electron acceptors.

  • [11] This reflux releases free energy produced during the generation of the oxidized forms of the electron carriers (NAD+ and Q) with energy provided by O2.

  • Electrons may enter an electron transport chain at the level of a mobile cytochrome or quinone carrier.

  • Here, light energy drives electron transport through a proton pump and the resulting proton gradient causes subsequent synthesis of ATP.

  • [7] As the electrons move through the complex an electron current is produced along the 180 Angstrom width of the complex within the membrane.

  • They also function as electron carriers, but in a very different, intramolecular, solid-state environment.

  • At the same time, eight protons are removed from the mitochondrial matrix (although only four are translocated across the membrane), contributing to the proton gradient.

  • In bacteria, the electron transport chain can vary between species but it always constitutes a set of redox reactions that are coupled to the synthesis of ATP through the
    generation of an electrochemical gradient and oxidative phosphorylation through ATP synthase.

  • Dehydrogenases: equivalants to complexes I and II[edit] Bacteria can use several different electron donors.

  • Mitochondrial Complex III is this second type of proton pump, which is mediated by a quinone (the Q cycle).

  • Individual bacteria use multiple electron transport chains, often simultaneously.

  • The two other electrons sequentially pass across the protein to the Qi site where the quinone part of ubiquinone is reduced to quinol.

  • The flow of electrons through the electron transport chain is an exergonic process.

  • Bacterial electron transport chains may contain as many as three proton pumps, like mitochondria, or they may contain two or at least one.


Works Cited

[‘1. Lyall, Fiona (2010). “Biochemistry”. Basic Science in Obstetrics and Gynaecology. pp. 143–171. doi:10.1016/B978-0-443-10281-3.00013-0. ISBN 978-0-443-10281-3.
2. ^ Jump up to:a b Anraku Y (June 1988). “Bacterial electron transport chains”. Annual
Review of Biochemistry. 57 (1): 101–32. doi:10.1146/annurev.bi.57.070188.000533. PMID 3052268.
3. ^ Kracke F, Vassilev I, Krömer JO (2015). “Microbial electron transport and energy conservation – the foundation for optimizing bioelectrochemical
systems”. Frontiers in Microbiology. 6: 575. doi:10.3389/fmicb.2015.00575. PMC 4463002. PMID 26124754. – This source shows four ETCs (Geobacter, Shewanella, Moorella , Acetobacterium) in figures 1 and 2.
4. ^ Waldenström JG (2009-04-24). “Biochemistry.
By Lubert Stryer”. Acta Medica Scandinavica. 198 (1–6): 436. doi:10.1111/j.0954-6820.1975.tb19571.x. ISSN 0001-6101.
5. ^ Zorova LD, Popkov VA, Plotnikov EY, Silachev DN, Pevzner IB, Jankauskas SS, et al. (July 2018). “Mitochondrial membrane potential”.
Analytical Biochemistry. 552: 50–59. doi:10.1016/j.ab.2017.07.009. PMC 5792320. PMID 28711444.
6. ^ Lauren, Biochemistry, Johnson/Cole, 2010, pp 598-611
7. ^ Garrett & Grisham, Biochemistry, Brooks/Cole, 2010, pp 598-611
8. ^ Garrett R, Grisham
CM (2016). biochemistry. Boston: Cengage. p. 687. ISBN 978-1-305-57720-6.
9. ^ Jump up to:a b Stryer. Biochemistry. toppan. OCLC 785100491.
10. ^ Jonckheere AI, Smeitink JA, Rodenburg RJ (March 2012). “Mitochondrial ATP synthase: architecture,
function and pathology”. Journal of Inherited Metabolic Disease. 35 (2): 211–25. doi:10.1007/s10545-011-9382-9. PMC 3278611. PMID 21874297.
11. ^ Jump up to:a b Garrett RH, Grisham CM (2012). Biochemistry (5th ed.). Cengage learning. p. 664. ISBN
12. ^ Fillingame RH, Angevine CM, Dmitriev OY (November 2003). “Mechanics of coupling proton movements to c-ring rotation in ATP synthase”. FEBS Letters. 555 (1): 29–34. doi:10.1016/S0014-5793(03)01101-3. PMID 14630314. S2CID
13. ^ Berg JM, Tymoczko JL, Stryer L (2002-01-01). “A Proton Gradient Powers the Synthesis of ATP”. {{cite journal}}: Cite journal requires |journal= (help)
14. ^ Cannon B, Nedergaard J (January 2004). “Brown adipose tissue: function
and physiological significance”. Physiological Reviews. 84 (1): 277–359. doi:10.1152/physrev.00015.2003. PMID 14715917.
15. ^ Kim BH, Gadd GM (2008). “Introduction to bacterial physiology and metabolism”. Bacterial Physiology and Metabolism. Cambridge
University Press. pp. 1–6. doi:10.1017/cbo9780511790461.002. ISBN 978-0-511-79046-1.
16. ^ Mills EL, Kelly B, Logan A, Costa AS, Varma M, Bryant CE, et al. (October 2016). “Succinate Dehydrogenase Supports Metabolic Repurposing of Mitochondria to
Drive Inflammatory Macrophages”. Cell. 167 (2): 457–470.e13. doi:10.1016/j.cell.2016.08.064. PMC 5863951. PMID 27667687.
17. ^ EC
18. ^ Ingledew WJ, Poole RK (September 1984). “The respiratory chains of Escherichia coli”. Microbiological
Reviews. 48 (3): 222–71. doi:10.1128/mmbr.48.3.222-271.1984. PMC 373010. PMID 6387427.
Photo credit: https://www.flickr.com/photos/dok1/2431737309/’]




communicative rationality


  • “a rational person thinks like this”); 2. replaced foundationalism with fallibilism with regard to valid knowledge and how it may be achieved; 3. cast doubt on the idea that
    reason should be conceived abstractly beyond history and the complexities of social life, and have contextualized or situated reason in actual historical practices; 4. replaced a focus on individual structures of consciousness with a concern
    for pragmatic structures of language and action as part of the contextualization of reason; and 5. given up philosophy’s traditional fixation on theoretical truth and the representational functions of language, to the extent that they also
    recognize the moral and expressive functions of language as part of the contextualization of reason.

  • Furthermore…this perspective suggests no more than formal specifications of possible forms of life… it does not extend to the concrete form of life…[4] Concerning (2),
    Habermas clearly and explicitly understands communicative rationality according to the terms of a reconstructive science.

  • Even if it is accepted that rationality must be expanded to include normative and evaluative dimensions, it is not clear what it is that makes a speech act justified, because
    it is unclear what constitutes a good reason.

  • The relativists on the other hand can compare and contrast the rationality of various forms of society but are unable to take up a critical stance, because they can posit
    no standard of rationality outside the relative and variable content of the societies in question, which leads to absurd conclusions (e.g., that Nazism is morally equivalent to democracy because the standards for both are relative).

  • Thus, the simple process of reaching an understanding with others impels individuals to be accountable for what they say and to be able to justify the validity claims they
    raise concerning normative (WE), evaluative (I) and objective matters (IT).

  • Accepting the distinction between the different kinds of reasons that accompany the differentiation of the validity dimensions does not give any insight into what a good reason
    in a particular validity dimension would be.

  • In its essence the idea of communicative rationality draws upon the implicit validity claims that are inescapably bound to the everyday practices of individuals capable of
    speech and action.

  • Following Habermas, the argument relies on the following assumptions: (a) that communication can proceed between two individuals only on the basis of a consensus (usually
    implicit[citation needed]) regarding the validity claims raised by the speech acts they exchange; (b) that these validity claims concern at least three dimensions of validity: I, truthfulness WE, rightness IT, truth (c) that a mutual understanding
    is maintained on the basis of the shared presupposition that any validity claim agreed upon could be justified, if necessary, by making recourse to good reasons.

  • The clearest way to see this is to recognize that the validity dimensions implicit in communication signify that a speaker is open to the charge of being irrational if they
    place normative validity claims outside of rational discourse.

  • For example, in “From Communicative Rationality to Communicative Thinking: A Basis for Feminist Theory and Practice” by Jane Braatan, it is discussed that women have a less
    advantage to be involved in communicative rationality due to the history of discrimination in schools.

  • The modes of justification we use in our moral and political deliberations, and the ways we determine which claims of others are valid, are what matter most, and what determine
    whether we are being “rational”.

  • Concerning (1) it can be said that: [Communicative] rationality refers primarily to the use of knowledge in language and action, rather than to a property of knowledge.

  • Thus, Habermas can compare and contrast the rationality of various forms of society with an eye to the deeper and more universal processes at work, which enables him to justify
    the critique of certain forms (e.g., that Nazism is irrational and bad) and lend support to the championing of others (e.g., democracy is rational and good).

  • And since these people do not have the knowledge to participate in communicative rationality, they would have no reason to defend their reasoning or position in society.

  • This view of reason is concerned with clarifying the norms and procedures by which agreement can be reached, and is therefore a view of reason as a form of public justification.

  • In fact, it complicates the issue because it makes it clear that there are different procedures unique to each validity dimension and that these dimensions cannot be reduced
    to one another.

  • Many philosophical contextualists take reason to be entirely context-dependent and relative.

  • formally and semantically integrated) rationality that characterized pre-modern worldviews has, since modern times, been emptied of its content and divided into three purely
    “formal” realms: (1) cognitive-instrumental reason; (2) moral-practical reason; and (3) aesthetic-expressive reason.

  • According to Habermas, the phenomena that need to be accounted for by the theory are the “intuitively mastered rules for reaching an understanding and conducting argumentation”,
    possessed by subjects who are capable of speech and action.

  • The result of the theory is a conception of reason that Habermas sees as doing justice to the most important trends in twentieth century philosophy, while escaping the relativism
    which characterizes postmodernism, and also providing necessary standards for critical evaluation.

  • However, these validity dimensions should be related to one another and understood as complementary pieces in a broader conception of rationality.

  • This purely formal “division of labour” has been criticized by Nikolas Kompridis, who sees in it too strong a division between practical and aesthetic reasoning, an unjustifiably
    hard distinction between the “right” and the “good”, and an unsupportable priority of validity to meaning.

  • Additionally, there are strict limits which a “post-metaphysical” theory (see below) must respect – namely the clarification of procedures and norms upon which our public
    deliberation depends.

  • According to the theory of communicative rationality, the potential for certain kinds of reason is inherent in communication itself.

  • Moreover, the speech acts shared between individuals in communication are laden with three different types of validity claims, all of which quietly but insistently demand
    to be justified with good reasons.

  • This is a very simple way of describing the procedures of justification unique to objective validity claims.

  • However, if one claims or implies with their speech acts that ‘abortion is acceptable in certain cases’, one’s reasons for claiming this must be of a different nature.

  • Communicative rationality or communicative reason (German: kommunikative Rationalität) is a theory or set of theories which describes human rationality as a necessary outcome
    of successful communication.

  • Hence the role that Habermas sees for communicative reason is formulating appropriate methods by which to conduct our moral and political discourse.

  • What this means is that Habermas has, through the formal pragmatic analysis of communication, revealed that rationality should not be limited to the consideration and resolution
    of objective concerns.

  • A mutual understanding can be achieved through communication only by fusing the perspectives of individuals, which requires they reach an agreement (even if it is only assumed)
    on the validity of the speech acts being shared.

  • According to “Public Sphere and Communicative Rationality: Interrogating Habermas’s Eurocentrism”, Habermas does not take into account that there are different societies that
    happen across the world because certain countries and societies suffer from different weaknesses.

  • [7] More recently, Nikolas Kompridis has taken issue with Habermas’ conception of rationality as incoherent and insufficiently complex, proposing a “possibility-disclosing”
    role for reason that goes beyond the narrow proceduralism of Habermas’ theory.

  • This points towards a productive interpenetration of the validity dimensions, for example the use of moral insights by the sciences without their having to sacrifice theoretical
    rigor, or the inclusion of psychological data into resources of moral philosophy.

  • Standards of justification[edit] Of course a very important issue arises from this, which is that what constitutes a good or acceptable justification varies from context to

  • The speaker would have to draw on insights into, for instance, the vulnerability of individuals under the weight of life’s circumstances, the kinds of rights that humans deserve,


Works Cited

[‘Habermas, Jürgen. Communication and the Evolution of society. Beacon Press, 1979, p. 18.
2. ^ Habermas 1992
3. ^ Jump up to:a b Kompridis 2006
4. ^ Jump up to:a b Cooke 1994
5. ^ Foucault 1988, Calhoun 1992
6. ^ Cohen 1995, Fraser 1987, Ryan
7. ^ Eley 1992
8. ^ Gunaratne, Shelton A. (2006). “Public Sphere and Communicative Rationality: Interrogating Habermas’s Eurocentrism”. Journalism & Communication Monographs. 8 (2): 93–156. doi:10.1177/152263790600800201. S2CID 143082836.
9. ^
Rienstra, Byron (2006). “Weakening Habermas : the undoing of communicative rationality” (PDF). Politikon: South African Journal of Political Studies. 33 (3): 313–339. doi:10.1080/02589340601122950. S2CID 143790471.
10. ^ Braaten, Jane (1995). “From
Communicative Rationality to Communicative Thinking: A Basis for Feminist Theory and Practice ByJane Braaten”. Feminists Read Habermas (RLE Feminist Theory). Routledge. doi:10.4324/9780203094006-12. ISBN 9780203094006.
11. ^ Devenney, Mark (2009).
“The limits of communicative rationality and deliberative democracy”. Journal of Power. 2: 137–154. doi:10.1080/17540290902760915. S2CID 144963807.
12. ^ Schaefer, Michael (2013). “Communicative versus Strategic Rationality: Habermas Theory of Communicative
Action and the Social Brain”. PLOS ONE. 8 (5): e65111. Bibcode:2013PLoSO…865111S. doi:10.1371/journal.pone.0065111. PMC 3666968. PMID 23734238. S2CID 15684145.
13. Calhoun, C., 1992, ed., Habermas and the Public Sphere (Cambridge, Massachusetts:
MIT Press).
14. Cohen, J.L., 1995, “Critical Social Theory and Feminist Critiques: The Debate with Jürgen Habermas”, in Johanna Meehan, ed., Feminists Read Habermas: Gendering the Subject of Discourse (New York: Routledge), pp. 57–90.
15. Cook,
M., 1994, Language and Reason: A Study in Habermas’s Pragmatics (Cambridge, Massachusetts: MIT Press).
16. Eley, G., 1992, “Nations, Publics, and Political Cultures: Placing Habermas in the Nineteenth Century”, in Craig Calhoun, ed., Habermas and
the Public Sphere (Cambridge, Massachusetts: MIT Press), pp. 289–339.
17. Foucault, M., 1988, “The Ethic of Care for the Self as a Practice of Freedom”, in James Bernauer and David Rasmussen, eds., The Final Foucault (Cambridge, Massachusetts: MIT
Press), pp. 1–20.
18. Fraser, N., 1987, “What’s Critical About Critical Theory? The Case of Habermas and Gender”, in Seyla Benhabib and Drucilla Cornell, eds., Feminism as Critique: On the Politics of Gender (Cambridge: Polity Press), pp. 31–56.
19. Habermas,
J., 1992, “Themes in Postmetaphysical Thinking”, in Postmetaphysical Thinking: Philosophical Essays, W. Hohengarten, trans. (Cambridge, Massachusetts: MIT Press), pp. 28–57.
20. Kompridis, N., 2006, Critique and Disclosure: Critical Theory between
Past and Future. Cambridge, Massachusetts:MIT Press.
21. Ryan, M.P., 1992, “Gender and Public Access: Women’s Politics in Nineteenth-Century America”, in Craig Calhoun, ed., Habermas and the Public Sphere (Cambridge, Massachusetts: MIT Press),
pp. 259–288.
Photo credit: https://www.flickr.com/photos/audreyjm529/506493250/’]




inertial electrostatic confinement


  • Because the motion provided by the field creates the energy levels needed for fusion, not random collisions with the rest of the fuel, the bulk of the plasma does not have
    to be hot and the systems as a whole work at much lower temperatures and energy levels than MCF devices.

  • Commercial applications Since fusion reactions generates neutrons, the fusor has been developed into a family of compact sealed reaction chamber neutron generators[78] for
    a wide range of applications that need moderate neutron output rates at a moderate price.

  • These loss mechanisms appear to be greater than the rate of fusion in such devices, meaning they can never reach fusion breakeven and thus be used for power production.

  • Their study showed that by 1-2 Tesla magnetic field it is possible to increase the discharge current and neutron production rate more than ten times with respect to the ordinary

  • [6] This puts on minimum criteria on power plant designs which do fusion using hot Maxwellian plasma clouds.

  • In 1962, he filed a patent on a design using a positive inner cage to concentrate plasma, in order to achieve nuclear fusion.

  • [13] Spitzer took the ideal gas laws and adapted them to an ionized plasma, developing many of the fundamental equations used to model a plasma.

  • Another problem is higher energy ions which have so much energy that they can escape the machine.

  • Most IEC designs achieve this by pulling the electrons or ions across a potential well, beyond which the potential drops and the particles continue to move due to their inertia.

  • [64] This is also the first (suggested) application of carbon nanotubes directly in any fusion reactor.

  • This may allow the plasma to be optimized, whereby cold electrons would reduce radiation losses and hot ions would raise fusion rates.

  • Overall the physical process is similar to the colliding beam fusion, although beam devices are linear instead of spherical.

  • Researcher had problems with a very thin ion-turning region very close to a solid surface[32] where ions could be conducted away.

  • Meanwhile, magnetic mirror theory and direct energy conversion were developed by Richard F. Post’s group at LLNL.

  • As the negatively charged electrons and positively charged ions in the plasma move in different directions in an electric field, the field has to be arranged in some fashion
    so that the two particles remain close together.

  • Nevins argued mathematically, that the fusion gain (ratio of fusion power produced to the power required to maintain the non-equilibrium ion distribution function) is limited
    to 0.1 assuming that the device is fueled with a mixture of deuterium and tritium.

  • Rider focused his arguments within the ion population and did not address electron-to-ion energy exchange or non-thermal plasmas.

  • A number of detailed theoretical studies have pointed out that the IEC approach is subject to a number of energy loss mechanisms that are not present if the fuel is evenly
    heated, or “Maxwellian”.

  • [41] Thermalization[edit] This is an energy distribution comparison of thermalized and non-thermalized ions The primary problem that Rider has raised is the thermalization
    of ions.

  • Rider argued that if such system was sufficiently heated, it could not be expected to produce net power, due to high X-ray losses.

  • Inertial electrostatic confinement, or IEC, is a class of fusion power devices that use electric fields to confine the plasma rather than the more common approach using magnetic
    fields found in magnetic confinement fusion (MCF) designs.

  • [34] Marble kept ions on orbits that do not intersect grid wires—the latter also improves the space charge limitations by multiple nesting of ion beams at several energies.

  • In theory, this makes them more suitable for using alternative aneutronic fusion fuels, which offer a number of major practical benefits and makes IEC devices one of the more
    widely studied approaches to fusion.

  • This sort of voltage is easily achieved in common electrical devices; a typical cathode-ray tube operates in this range.

  • • Phoenix Nuclear Labs has developed a commercial neutron source based on a fusor, achieving neutrons per second with the deuterium-deuterium fusion reaction for 132 hours
    of continuous operation.

  • [87] • University of Sydney has built several IEC devices and also low power, low beta ratio polywells.

  • Brillouin limit[edit] In 1945, Columbia University professor Léon Brillouin, suggested that there was a limit to how many electrons one could pack into a given volume.

  • The electric field does work on the ions heating them to fusion conditions.

  • In addition, collisions heat the grids, which limits high-power devices.

  • As they accelerate, the electric field does work on the ions, heating them to fusion conditions.

  • Most IEC devices directly accelerate their fuel to fusion conditions, thereby avoiding energy losses seen during the longer heating stages of MCF devices.

  • [58] No fusor has come close to producing a significant amount of fusion power.

  • [62] The ion oscillation is predicted to maintain the equilibrium distribution of the ions at all times, which would eliminate any power loss due to Coulomb scattering, resulting
    in a net energy gain.

  • Fusors are popular with amateurs,[57] because they can easily be constructed, can regularly produce fusion and are a practical way to study nuclear physics.

  • These mechanisms are more powerful when the atomic mass of the fuel increases, which suggests IEC also does not have any advantage with aneutronic fuels.

  • Fusion occurs in this lower-potential area when ions moving in different directions collide.

  • In his work with vacuum tubes, Philo Farnsworth observed that electric charge would accumulate in regions of the tube.

  • 2000s[edit] Despite demonstration in 2000 of 7200 hours of operation without degradation at high input power as a sealed reaction chamber with automated control the FusionStar
    project was canceled and the company NSD Ltd was founded.

  • [75] Because the electron has a mass and diameter much smaller than the ion, the electron temperature can be several orders of magnitude different than the ions.

  • As they do, they exchange energy, causing their energy to spread out (in a Wiener process) heading to a bell curve (or Gaussian function) of energy.

  • If they impact with another ion they may undergo fusion.

  • [36] Where B is the magnetic field, the permeability of free space, m the mass of confined particles, and c the speed of light.

  • Very high output neutron sources may be used to make products such as molybdenum-99[39] and nitrogen-13, medical isotopes used for PET scans.

  • [68] In a Penning trap fusion reactor, first the magnetic and electric fields are turned on.

  • This device has an inner cage to make the field, and four ion guns on the outside.

  • An ion with a charge of one can reach this temperature by being accelerated across a 15,000 V drop.

  • Collisions also spray high-mass ions into the reaction chamber, pollute the plasma, and cool the fuel.

  • [84] Universities[edit] • Tokyo Institute of Technology has four IEC devices of different shapes: a spherical machine, a cylindrical device, a co-axial double cylinder and
    a magnetically assisted device.

  • [59] In response they built POPS,[60][61] a machine with a wire cage, where ions are moving at steady-state, or oscillating around.

  • Fusors can also use ion guns rather than electric grids.

  • [70] These optics made static voltage surfaces in free space.

  • • Eindhoven Technical University[88] • Amirkabir University of Technology and Atomic Energy Organization of Iran have investigated the effect of strong pulsed magnetic fields
    on the neutron production rate of IEC device.


Works Cited

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Oliphant, M. L. E.; Harteck, P.; Rutherford, L. (1934-05-01). “Transmutation Effects Observed with Heavy Hydrogen”. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. The Royal Society. 144 (853): 692–703. Bibcode:1934RSPSA.144..692O.
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o ^ Elmore, William C.; Tuck, James L.; Watson, Kenneth M. (1959). “On the Inertial-Electrostatic Confinement of a Plasma”. Physics of Fluids. AIP Publishing. 2 (3): 239. Bibcode:1959PhFl….2..239E. doi:10.1063/1.1705917.
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Grad, H. Theory of Cusped Geometries, I. General Survey, NYO-7969, Inst. Math. Sci., N.Y.U., December 1, 1957
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o ^ Jump up to:a b c Hirsch, Robert L. (1967). “Inertial-Electrostatic
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o ^ Inertial Electrostatic
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Photo credit: https://www.flickr.com/photos/robin1966/15184419268/’]






  • The supposed last poem in the Epic Cycle is called the Telegony and is thought to tell the story of Odysseus’ last voyage, and of his death at the hands of Telegonus, his
    son with Circe.

  • Two stories in particular are well known: When Helen of Troy is abducted, Menelaus calls upon the other suitors to honour their oaths and help him to retrieve her, an attempt
    that leads to the Trojan War.

  • Euryclea seems to suggest a name like Polyaretos, “for he has much been prayed for” but Autolycus “apparently in a sardonic mood” decided to give the child another name commemorative
    of “his own experience in life”:[13] “Since I have been angered with many, both men and women, let the name of the child be Odysseus”.

  • Odysseus has now revealed himself in all his glory (with a little makeover by Athena); yet Penelope cannot believe that her husband has really returned—she fears that it is
    perhaps some god in disguise, as in the story of Alcmene (mother of Heracles)—and tests him by ordering her servant Euryclea to move the bed in their wedding-chamber.

  • The return of Ulysses, illustration by E. M. Synge from the 1909 Story of the World children’s book series (book 1: On the shores of Great Sea) When the disguised Odysseus
    returns after 20 years, he is recognized only by his faithful dog, Argos.

  • [citation needed] In one version of Odysseus’s end, he is eventually turned into a horse by Athena.

  • In a famous passage, Dante has Odysseus relate a different version of his voyage and death from the one told by Homer.

  • In S. M. Stirling’s Island in the Sea of Time (1998), first part to his Nantucket series of alternate history novels, Odikweos (“Odysseus” in Mycenaean Greek) is a “historical”
    figure who is every bit as cunning as his legendary self and is one of the few Bronze Age inhabitants who discerns the time-travellers’ real background.

  • [42] Perhaps Odysseus’ most famous contribution to the Greek war effort is devising the strategy of the Trojan Horse, which allows the Greek army to sneak into Troy under
    cover of darkness.

  • Guided by Circe’s instructions, Odysseus and his crew cross the ocean and reach a harbor at the western edge of the world, where Odysseus sacrifices to the dead and summons
    the spirit of the old prophet Tiresias for advice.

  • Odysseus discovered Achilles by offering gifts, adornments and musical instruments as well as weapons, to the king’s daughters, and then having his companions imitate the
    noises of an enemy’s attack on the island (most notably, making a blast of a trumpet heard), which prompted Achilles to reveal himself by picking a weapon to fight back, and together they departed for the Trojan War.

  • Some have supposed that “there may originally have been two separate figures, one called something like Odysseus, the other something like Ulixes, who were combined into one
    complex personality.

  • The second novel in particular, The Sea of Monsters (2006), is a loose adaptation of The Odyssey, with protagonists Percy and Annabeth seeking to save their satyr friend Grover
    from Polyphemus, and facing many of the same obstacles Odysseus faced over the course of the journey.

  • After he tells them his story, the Phaeacians, led by King Alcinous, agree to help Odysseus get home.

  • By most accounts, Thetis, Achilles’ mother, disguises the youth as a woman to hide him from the recruiters because an oracle had predicted that Achilles would either live
    a long uneventful life or achieve everlasting glory while dying young.

  • The Greek word used is, literally the man of many turns, and other translators have suggested alternate English translations, including “man of twists and turns” (Fagles 1996)
    and “a complicated man” (Wilson 2018).

  • [17] In the Iliad and Odyssey Homer uses several epithets to describe Odysseus, starting with the opening, where he is described as “the man of many devices” (in the 1919
    Murray translation).

  • The poem, like the others of the cycle, is “lost” in that no authentic version has been discovered.

  • Other stories from the Trojan War[edit] Roman mosaic depicting Odysseus at Skyros unveiling the disguised Achilles;[36] from La Olmeda, Pedrosa de la Vega, Spain, 5th century
    AD Since a prophecy suggested that the Trojan War would not be won without Achilles, Odysseus and several other Achaean leaders are described in the Achilleid as having gone to Skyros to find him.

  • This epic describes his travails, which lasted for 10 years, as he tries to return home after the Trojan War and reassert his place as rightful king of Ithaca.

  • Bloom’s day turns out to bear many elaborate parallels to Odysseus’ ten years of wandering.

  • Frederick Rolfe’s The Weird of the Wanderer (1912) has the hero Nicholas Crabbe (based on the author) travelling back in time, discovering that he is the reincarnation of
    Odysseus, marrying Helen, being deified and ending up as one of the three Magi.

  • Thematically, it uses Odysseus’ backstory and struggle as a metaphor for dealing with the aftermath of war (the novel being written immediately after the end of the Second
    World War).

  • [41] Together with Diomedes, Odysseus fetches Achilles’ son, Pyrrhus, to come to the aid of the Achaeans, because an oracle had stated that Troy could not be taken without

  • Some late Roman sources indicate that Odysseus schemed to kill his partner on the way back, but Diomedes thwarts this attempt.

  • Odysseus protests that this cannot be done since he made the bed himself and knows that one of its legs is a living olive tree.

  • He in turn offers a first-person account of some of the same events Homer relates, in which Ulysses appears directly.

  • [52] Alfred, Lord Tennyson’s poem “Ulysses” (published in 1842) presents an aging king who has seen too much of the world to be happy sitting on a throne idling his days away.

  • He always champions the Achaean cause, especially when others question Agamemnon’s command, as in one instance when Thersites speaks against him.

  • Next Odysseus meets the spirit of his own mother, who had died of grief during his long absence.

  • According to Bernard Knox, “For the plot of the Odyssey, of course, her decision is the turning point, the move that makes possible the long-predicted triumph of the returning

  • Suzanne Vega’s song “Calypso” from 1987 album Solitude Standing shows Odysseus from Calypso’s point of view, and tells the tale of him coming to the island and his leaving.

  • According to the Iliad and Odyssey, his father is Laertes[20] and his mother Anticlea, although there was a non-Homeric tradition[21][22] that Sisyphus was his true father.

  • [48] As Ulysses, he is mentioned regularly in Virgil’s Aeneid written between 29 and 19 BC, and the poem’s hero, Aeneas, rescues one of Ulysses’ crew members who was left
    behind on the island of the Cyclopes.

  • Odysseus and his crew remain with her on the island for one year, while they feast and drink.

  • Thetis says that the arms of Achilles will go to the bravest of the Greeks, but only these two warriors dare lay claim to that title.

  • Upon their arrival, Philoctetes (still suffering from the wound) is seen still to be enraged at the Danaans, especially at Odysseus, for abandoning him.

  • One tradition says Odysseus convinces a Trojan captive to write a letter pretending to be from Palamedes.

  • [16] In Etruscan religion the name (and stories) of Odysseus were adopted under the name Uthuze, which has been interpreted as a parallel borrowing from a preceding Minoan
    form of the name (possibly *Oduze, pronounced /’ot͡θut͡se/); this theory is supposed to explain also the insecurity of the phonologies (d or l), since the affricate /t͡θ/, unknown to the Greek of that time, gave rise to different counterparts.

  • Odysseus cleverly discovers which among the women before him is Achilles when the youth is the only one of them to show interest in examining the weapons hidden among an array
    of adornment gifts for the daughters of their host.

  • Circe, being attracted to Odysseus’ resistance, falls in love with him and releases his men.

  • A great warrior, Pyrrhus is also called Neoptolemus (Greek for “new warrior”).

  • Men, says Ulisse, are not made to live like brutes, but to follow virtue and knowledge.

  • He tells how he set out with his men from Circe’s island for a journey of exploration to sail beyond the Pillars of Hercules and into the Western sea to find what adventures
    awaited them.

  • Although his first instinct is to shoot Odysseus, his anger is eventually diffused by Odysseus’ persuasive powers and the influence of the gods.

  • [32] After Patroclus is slain, it is Odysseus who counsels Achilles to let the Achaean men eat and rest rather than follow his rage-driven desire to go back on the offensive—and
    kill Trojans—immediately.

  • [37] The story of the death of Palamedes has many versions.

  • Penelope announces in her long interview with the disguised hero that whoever can string Odysseus’ rigid bow and shoot an arrow through twelve axe shafts may have her hand.

  • [43] Odysseus and Diomedes steal the Palladium that lay within Troy’s walls, for the Greeks were told they could not sack the city without it.

  • He finds his way to the hut of one of his own former slaves, the swineherd Eumaeus, and also meets up with Telemachus returning from Sparta.

  • Rick Riordan’s novel series Percy Jackson & the Olympians, which centres on the presence of Greek mythology in the 21st century, incorporates several elements from Odysseus’s

  • In Book 19 of the Odyssey, where Odysseus’ early childhood is recounted, Euryclea asks the boy’s grandfather Autolycus to name him.

  • Journey home to Ithaca[edit] Further information: Homer’s Ithaca and Returns from Troy Odysseus is probably best known as the eponymous hero of the Odyssey.

  • Leaving the task of civilizing his people to his son, he gathers together a band of old comrades “to sail beyond the sunset”.

  • [45] Xenagoras writes that Odysseus with Circe had three sons, Romos (Ancient Greek: ), Anteias (Ancient Greek:) and Ardeias (Ancient Greek: ), who built three cities and
    called them after their own names.

  • [29] Later on, after many of the heroes leave the battlefield due to injuries (including Odysseus and Agamemnon), Odysseus once again persuades Agamemnon not to withdraw.

  • Odysseus and his crew escape, but Odysseus rashly reveals his real name, and Polyphemus prays to Poseidon, his father, to take revenge.

  • Novels[edit] The bay of Palaiokastritsa in Corfu as seen from Bella vista of Lakones, considered to be the place where Odysseus disembarked and met Nausicaa for the first

  • Odysseus and the Sirens, Ulixes mosaic at the Bardo National Museum in Tunis, Tunisia, 2nd century AD Odysseus and his men return to Circe’s island, and she advises them on
    the remaining stages of the journey.

  • Odysseus’ ship is the only one to escape.

  • Odikweos first aids William Walker’s rise to power in Achaea and later helps bring Walker down after seeing his homeland turn into a police state.

  • Head of Odysseus wearing a pileus depicted on a 3rd-century BC coin from Ithaca Pausanias at the Description of Greece writes that at Pheneus there was a bronze statue of
    Poseidon, surnamed Hippios (Ancient Greek: ), meaning of horse, which according to the legends was dedicated by Odysseus and also a sanctuary of Artemis which was called Heurippa (Ancient Greek:), meaning horse finder, and was founded by Odysseus.

  • However, the sailors foolishly open the bag while Odysseus sleeps, thinking that it contains gold.

  • Middle Ages and Renaissance[edit] Dante Alighieri, in the Canto XXVI of the Inferno segment of his Divine Comedy (1308–1320), encounters Odysseus (“Ulisse” in Italian) near
    the very bottom of Hell: with Diomedes, he walks wrapped in flame in the eighth ring (Counselors of Fraud) of the Eighth Circle (Sins of Malice), as punishment for his schemes and conspiracies that won the Trojan War.

  • [49] In post-classical tradition Odysseus is one of the most recurrent characters in Western culture.

  • The next day Odysseus and Telemachus visit the country farm of his old father Laërtes.

  • Plato in his dialogue Hippias Minor examines a literary question about whom Homer intended to portray as the better man, Achilles or Odysseus.

  • Other tales[edit] According to some late sources, most of them purely genealogical, Odysseus had many other children besides Telemachus.

  • [25] Odysseus himself, under the guise of an old beggar, gives the swineherd in Ithaca a fictitious genealogy: “From broad Crete I declare that I am come by lineage, the son
    of a wealthy man.

  • Odysseus’ attempts to avoid his sacred oath to defend Menelaus and Helen offended Roman notions of duty, and the many stratagems and tricks that he employed to get his way
    offended Roman notions of honour.

  • He is also in some respects antithetical to Telamonian Ajax (Shakespeare’s “beef-witted” Ajax): while the latter has only brawn to recommend him, Odysseus is not only ingenious
    (as evidenced by his idea for the Trojan Horse), but an eloquent speaker, a skill perhaps best demonstrated in the embassy to Achilles in book 9 of the Iliad.

  • James Joyce’s novel Ulysses (first published 1918–1920) uses modern literary devices to narrate a single day in the life of a Dublin businessman named Leopold Bloom.

  • Odysseus tries to avoid it by feigning lunacy, as an oracle had prophesied a long-delayed return home for him if he went.

  • Other sources say that Odysseus and Diomedes goad Palamedes into descending a well with the prospect of treasure being at the bottom.


Works Cited

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William Bedell (1968). The Ulysses theme. p. 11.
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line” (κλέπτουσι μύθους οἱ μεγάλοι βασιλῆς // ἢ τᾶς ἀσώτου Σισυφιδᾶν γενεᾶς): Chorus in Ajax 189–190, translated Archived 18 April 2005 at the Wayback Machine by R. C. Trevelyan.
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Room Scrap Book, 1837. Fisher, Son & Co. Archived from the original on 5 December 2022. Retrieved 5 December 2022.Landon, Letitia Elizabeth (1836). Fisher’s Drawing Room Scrap Book, 1837. Fisher, Son & Co. Archived from the original on 5 December
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“poetical illustration”. Fisher’s Drawing Room Scrap Book, 1837. Fisher, Son & Co. Archived from the original on 9 December 2022. Retrieved 9 December 2022.
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Eyvind Johnson: Strändernas svall, Bonniers 2004”. Lysmasken (in Swedish). Archived from the original on 1 September 2004.
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veinte lecturas de la Odisea, Madrid, Gredos).
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et al. (2008). “Bracers or bracelets? About the functionality and meaning of Bell Beaker wrist-guards”. Proceedings of the Prehistoric Society. University of Leiden. 74. p. 122.
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Folktale Adaptations in Homer, Tennyson and Pratt”. In: Folklore 91, no. 1 (1980): 46–62. http://www.jstor.org/stable/1259818 Archived 15 March 2022 at the Wayback Machine.
o ^ Ready, Jonathan L. “ATU 974 The Homecoming Husband, The Returns of Odysseus,
and the End of Odyssey 21.”. In: Arethusa 47, no. 3 (2014): 265–85. https://www.jstor.org/stable/26314683 Archived 15 March 2022 at the Wayback Machine.
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Strabo, Geography, 3.2.13”. Archived from the original on 24 October 2021. Retrieved 12 February 2022. {{cite web}}: External link in |title= (help)
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Photo credit: https://www.flickr.com/photos/ell-r-brown/17720403638/’]




kaluza-klein theory


  • Equations of motion from the Kaluza hypothesis The equations of motion are obtained from the five-dimensional geodesic hypothesis[3] in terms of a 5-velocity : This equation
    can be recast in several ways, and it has been studied in various forms by authors including Kaluza,[3] Pauli,[25] Gross & Perry,[26] Gegenberg & Kunstatter,[27] and Wesson & Ponce de Leon,[28] but it is instructive to convert it back to the
    usual 4-dimensional length element , which is related to the 5-dimensional length element as given above: Then the 5D geodesic equation can be written[29] for the spacetime components of the 4-velocity: The term quadratic in provides the 4D
    geodesic equation plus some electromagnetic terms: The term linear in provides the Lorentz force law: This is another expression of the “Kaluza miracle”.

  • [32] In this version of the theory, it is noted that solutions to the equation may be re-expressed so that in four dimensions, these solutions satisfy Einstein’s equations
    with the precise form of the Tμν following from the Ricci-flat condition on the five-dimensional space.

  • Thus, by applying a single idea: the principle of least action, to a single quantity: the scalar curvature on the bundle (as a whole), one obtains simultaneously all of the
    needed field equations, for both the spacetime and the gauge field.

  • Because the energy–momentum tensor is normally understood to be due to concentrations of matter in four-dimensional space, the above result is interpreted as saying that four-dimensional
    matter is induced from geometry in five-dimensional space.

  • Start with the alternate form of the geodesic equation, written for the covariant 5-velocity: This means that under the cylinder condition, is a constant of the five-dimensional
    motion: Kaluza’s hypothesis for the matter stress–energy tensor Kaluza proposed[3] a five-dimensional matter stress tensor of the form where is a density, and the length element is as defined above.

  • The resulting field equations provide both the equations of general relativity and of electrodynamics; the equations of motion provide the four-dimensional geodesic equation
    and the Lorentz force law, and one finds that electric charge is identified with motion in the fifth dimension.

  • Let one also introduce the four-dimensional spacetime metric , where Greek indices span the usual four dimensions of space and time; a 4-vector identified with the electromagnetic
    vector potential; and a scalar field .

  • The hypothesis for the metric implies an invariant five-dimensional length element : Field equations from the Kaluza hypothesis The field equations of the five-dimensional
    theory were never adequately provided by Kaluza or Klein because they ignored the scalar field.

  • [22] Kaluza hypothesis In his 1921 article,[3] Kaluza established all the elements of the classical five-dimensional theory: the metric, the field equations, the equations
    of motion, the stress–energy tensor, and the cylinder condition.

  • But in that case, a fifth component was added to the electromagnetic vector potential, representing the Newtonian gravitational potential, and writing the Maxwell equations
    in five dimensions.

  • Space–time–matter theory One particular variant of Kaluza–Klein theory is space–time–matter theory or induced matter theory, chiefly promulgated by Paul Wesson and other members
    of the Space–Time–Matter Consortium.

  • Furthermore, vacuum equations are typically assumed for which where and The vacuum field equations obtained in this way by Thiry[8] and Jordan’s group[10][11][13] are as follows.

  • Klein’s Nature article[5] suggested that the fifth dimension is closed and periodic, and that the identification of electric charge with motion in the fifth dimension can
    be interpreted as standing waves of wavelength , much like the electrons around a nucleus in the Bohr model of the atom.

  • Kaluza also introduced the “cylinder condition” hypothesis, that no component of the five-dimensional metric depends on the fifth dimension.

  • Applying Fubini’s theorem and integrating on the fiber, one gets Varying the action with respect to the component , one regains the Maxwell equations.

  • The general equations can be shown to be sufficiently consistent with classical tests of general relativity to be acceptable on physical principles, while still leaving considerable
    freedom to also provide interesting cosmological models.

  • The equations of motion, the Euler–Lagrange equations, can be then obtained by considering where the action is stationary with respect to variations of either the metric on
    the base manifold, or of the gauge connection.

  • The full Kaluza field equations are generally attributed to Thiry,[8] who obtained vacuum field equations, although Kaluza[3] originally provided a stress–energy tensor for
    his theory, and Thiry included a stress–energy tensor in his thesis.

  • Without this restriction, terms are introduced that involve derivatives of the fields with respect to the fifth coordinate, and this extra degree of freedom makes the mathematics
    of the fully variable 5D relativity enormously complex.

  • However, Klein’s approach to a quantum theory is flawed[citation needed] and, for example, leads to a calculated electron mass in the order of magnitude of the Planck mass.

  • Variations with respect to the base metric gives the Einstein field equations on the base manifold, with the energy–momentum tensor given by the curvature (field strength)
    of the gauge connection.

  • In physics, Kaluza–Klein theory (KK theory) is a classical unified field theory of gravitation and electromagnetism built around the idea of a fifth dimension beyond the common
    4D of space and time and considered an important precursor to string theory.

  • The same hypothesis for the 5D metric that provides electromagnetic stress–energy in the Einstein equations, also provides the Lorentz force law in the equation of motions
    along with the 4D geodesic equation.

  • The connection on the fiber bundle is related to the electromagnetic field strength as That there always exists such a connection, even for fiber bundles of arbitrarily complex
    topology, is a result from homology and specifically, K-theory.

  • The fact that the Lorentz force law could be understood as a geodesic in five dimensions was to Kaluza a primary motivation for considering the five-dimensional hypothesis,
    even in the presence of the aesthetically unpleasing cylinder condition.

  • Yet correspondence with the Lorentz force law requires that we identify the component of 5-velocity along the fifth dimension with electric charge: where is particle mass,
    and is particle electric charge.

  • With no free parameters, it merely extends general relativity to five dimensions.

  • Then the spacetime component gives a typical “dust” stress–energy tensor: The mixed component provides a 4-current source for the Maxwell equations: Just as the five-dimensional
    metric comprises the four-dimensional metric framed by the electromagnetic vector potential, the five-dimensional stress–energy tensor comprises the four-dimensional stress–energy tensor framed by the vector 4-current.

  • This equation shows the remarkable result, called the “Kaluza miracle”, that the precise form for the electromagnetic stress–energy tensor emerges from the 5D vacuum equations
    as a source in the 4D equations: field from the vacuum.

  • Applying the variational principle to the base metric , one gets the Einstein equations with the stress–energy tensor being given by sometimes called the Maxwell stress tensor.

  • Hence a measurement of any dramatic change to the cross-section predicted by the Standard Model is crucial in probing the physics beyond it.

  • Einstein equations[edit] The equations governing ordinary gravity in free space can be obtained from an action, by applying the variational principle to a certain action.

  • However, the article does demonstrate that electromagnetism and gravity share the same number of dimensions, and this fact lends support to Kaluza–Klein theory; whether the
    number of dimensions is really or in fact is the subject of further debate.

  • In modern geometry, the extra fifth dimension can be understood to be the circle group U(1), as electromagnetism can essentially be formulated as a gauge theory on a fiber
    bundle, the circle bundle, with gauge group U(1).

  • Standard Model particles besides the top quark and W boson do not make big contributions to the cross-section observed in the decay, but if there are new particles beyond
    the Standard Model, they could potentially change the ratio of the predicted Standard Model cross-section to the experimentally observed cross-section.

  • The classic results of Thiry and other authors presume the cylinder condition: Without this assumption, the field equations become much more complex, providing many more degrees
    of freedom that can be identified with various new fields.

  • Klein solved a Schroedinger-like wave equation using an expansion in terms of fifth-dimensional waves resonating in the closed, compact fifth dimension.

  • Group theory interpretation In 1926, Oskar Klein proposed that the fourth spatial dimension is curled up in a circle of a very small radius, so that a particle moving a short
    distance along that axis would return to where it began.

  • Compactification does not produce group actions on chiral fermions except in very specific cases: the dimension of the total space must be 2 mod 8, and the G-index of the
    Dirac operator of the compact space must be nonzero.

  • Ten components are identified with the 4D spacetime metric, four components with the electromagnetic vector potential, and one component with an unidentified scalar field
    sometimes called the “radion” or the “dilaton”.

  • Klein suggested that the geometry of the extra fifth dimension could take the form of a circle, with the radius of .

  • [8] See Williams[19] for a complete set of 5D curvature tensors under the cylinder condition, evaluated using tensor-algebra software.

  • Note that the scalar field cannot be set to a constant without constraining the electromagnetic field.

  • But Thiry argued[6] that the interpretation of the Lorentz force law in terms of a five-dimensional geodesic militates strongly for a fifth dimension irrespective of the cylinder

  • It is studied in its own right as an object of geometric interest in K-theory.

  • The earlier treatments by Kaluza and Klein did not have an adequate description of the scalar field and did not realize the implied constraint on the electromagnetic field
    by assuming the scalar field to be constant.

  • Paul Wesson and colleagues have pursued relaxation of the cylinder condition to gain extra terms that can be identified with the matter fields,[24] for which Kaluza[3] otherwise
    inserted a stress–energy tensor by hand.

  • Combining the previous Kaluza result for in terms of electric charge, and a de Broglie relation for momentum , Klein obtained[5] an expression for the 0th mode of such waves:
    where is the Planck constant.

  • The quantization of electric charge could then be nicely understood in terms of integer multiples of fifth-dimensional momentum.

  • By applying the variational principle to the action one obtains precisely the Einstein equations for free space: where Rij is the Ricci tensor.

  • In their setup, the vacuum has the usual 3 dimensions of space and one dimension of time but with another microscopic extra spatial dimension in the shape of a tiny circle.

  • [1] The five-dimensional (5D) theory developed in three steps.

  • For example, on the simplest of principles, one might expect to have standing waves in the extra compactified dimension(s).

  • However, an attempt to convert this interesting geometrical construction into a bona-fide model of reality flounders on a number of issues, including the fact that the fermions
    must be introduced in an artificial way (in nonsupersymmetric models).


Works Cited

[‘1. Nordström, Gunnar (1914). “Über die Möglichkeit, das elektromagnetische Feld und das Gravitationsfeld zu vereinigen” [On the possibility of unifying the gravitational and electromagnetic fields]. Physikalische Zeitschrift (in German). 15: 504.
2. ^
Pais, Abraham (1982). Subtle is the Lord …: The Science and the Life of Albert Einstein. Oxford: Oxford University Press. pp. 329–330.
3. ^ Jump up to:a b c d e f g h Kaluza, Theodor (1921). “Zum Unitätsproblem in der Physik”. Sitzungsber. Preuss.
Akad. Wiss. Berlin. (Math. Phys.) (in German): 966–972. Bibcode:1921SPAW…….966K.
4. ^ Jump up to:a b c Klein, Oskar (1926). “Quantentheorie und fünfdimensionale Relativitätstheorie”. Zeitschrift für Physik A (in German). 37 (12): 895–906. Bibcode:1926ZPhy…37..895K.
5. ^ Jump up to:a b c d Klein, Oskar (1926). “The Atomicity of Electricity as a Quantum Theory Law”. Nature. 118 (2971): 516. Bibcode:1926Natur.118..516K. doi:10.1038/118516a0. S2CID 4127863.
6. ^ Jump up to:a b c Goenner,
H. (2012). “Some remarks on the genesis of scalar–tensor theories”. General Relativity and Gravitation. 44 (8): 2077–2097. arXiv:1204.3455. Bibcode:2012GReGr..44.2077G. doi:10.1007/s10714-012-1378-8. S2CID 13399708.
7. ^ Lichnerowicz, A.; Thiry,
M. Y. (1947). “Problèmes de calcul des variations liés à la dynamique classique et à la théorie unitaire du champ”. Compt. Rend. Acad. Sci. Paris (in French). 224: 529–531.
8. ^ Jump up to:a b c d Thiry, M. Y. (1948). “Les équations de la théorie
unitaire de Kaluza”. Compt. Rend. Acad. Sci. Paris (in French). 226: 216–218.
9. ^ Thiry, M. Y. (1948). “Sur la régularité des champs gravitationnel et électromagnétique dans les théories unitaires”. Compt. Rend. Acad. Sci. Paris (in French). 226:
10. ^ Jump up to:a b c Jordan, P. (1946). “Relativistische Gravitationstheorie mit variabler Gravitationskonstante”. Naturwissenschaften (in German). 11 (8): 250–251. Bibcode:1946NW…..33..250J. doi:10.1007/BF01204481. S2CID 20091903.
11. ^
Jump up to:a b c Jordan, P.; Müller, C. (1947). “Über die Feldgleichungen der Gravitation bei variabler “Gravitationslonstante””. Z. Naturforsch. (in German). 2a (1): 1–2. Bibcode:1947ZNatA…2….1J. doi:10.1515/zna-1947-0102. S2CID 93849549.
12. ^
Ludwig, G. (1947). “Der Zusammenhang zwischen den Variationsprinzipien der projektiven und der vierdimensionalen Relativitätstheorie”. Z. Naturforsch. (in German). 2a (1): 3–5. Bibcode:1947ZNatA…2….3L. doi:10.1515/zna-1947-0103. S2CID 94454994.
13. ^
Jump up to:a b c Jordan, P. (1948). “Fünfdimensionale Kosmologie”. Astron. Nachr. (in German). 276 (5–6): 193–208. Bibcode:1948AN….276..193J. doi:10.1002/asna.19482760502.
14. ^ Ludwig, G.; Müller, C. (1948). “Ein Modell des Kosmos und der Sternentstehung”.
Annalen der Physik. 2 (6): 76–84. Bibcode:1948AnP…437…76L. doi:10.1002/andp.19484370106. S2CID 120176841.
15. ^ Scherrer, W. (1941). “Bemerkungen zu meiner Arbeit: “Ein Ansatz für die Wechselwirkung von Elementarteilchen””. Helv. Phys. Acta
(in German). 14 (2): 130.
16. ^ Scherrer, W. (1949). “Über den Einfluss des metrischen Feldes auf ein skalares Materiefeld”. Helv. Phys. Acta. 22: 537–551.
17. ^ Scherrer, W. (1950). “Über den Einfluss des metrischen Feldes auf ein skalares Materiefeld
(2. Mitteilung)”. Helv. Phys. Acta (in German). 23: 547–555.
18. ^ Brans, C. H.; Dicke, R. H. (November 1, 1961). “Mach’s Principle and a Relativistic Theory of Gravitation”. Physical Review. 124 (3): 925–935. Bibcode:1961PhRv..124..925B. doi:10.1103/PhysRev.124.925.
19. ^
Jump up to:a b c Williams, L. L. (2015). “Field Equations and Lagrangian for the Kaluza Metric Evaluated with Tensor Algebra Software” (PDF). Journal of Gravity. 2015: 901870. doi:10.1155/2015/901870.
20. ^ Ferrari, J. A. (1989). “On an approximate
solution for a charged object and the experimental evidence for the Kaluza-Klein theory”. Gen. Relativ. Gravit. 21 (7): 683. Bibcode:1989GReGr..21..683F. doi:10.1007/BF00759078. S2CID 121977988.
21. ^ Coquereaux, R.; Esposito-Farese, G. (1990).
“The theory of Kaluza–Klein–Jordan–Thiry revisited”. Annales de l’Institut Henri Poincaré. 52: 113.
22. ^ Williams, L. L. (2020). “Field Equations and Lagrangian of the Kaluza Energy-Momentum Tensor”. Advances in Mathematical Physics. 2020: 1263723.
23. ^ Appelquist, Thomas; Chodos, Alan; Freund, Peter G. O. (1987). Modern Kaluza–Klein Theories. Menlo Park, Cal.: Addison–Wesley. ISBN 978-0-201-09829-7.
24. ^ Wesson, Paul S. (1999). Space–Time–Matter, Modern Kaluza–Klein
Theory. Singapore: World Scientific. ISBN 978-981-02-3588-8.
25. ^ Pauli, Wolfgang (1958). Theory of Relativity (translated by George Field ed.). New York: Pergamon Press. pp. Supplement 23.
26. ^ Gross, D. J.; Perry, M. J. (1983). “Magnetic monopoles
in Kaluza–Klein theories”. Nucl. Phys. B. 226 (1): 29–48. Bibcode:1983NuPhB.226…29G. doi:10.1016/0550-3213(83)90462-5.
27. ^ Gegenberg, J.; Kunstatter, G. (1984). “The motion of charged particles in Kaluza–Klein space–time”. Phys. Lett. 106A (9):
410. Bibcode:1984PhLA..106..410G. doi:10.1016/0375-9601(84)90980-0.
28. ^ Wesson, P. S.; Ponce de Leon, J. (1995). “The equation of motion in Kaluza–Klein cosmology and its implications for astrophysics”. Astronomy and Astrophysics. 294: 1. Bibcode:1995A&A…294….1W.
29. ^
Williams, Lance L. (2012). “Physics of the Electromagnetic Control of Spacetime and Gravity”. Proceedings of 48th AIAA Joint Propulsion Conference. 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 30 July 2012 – 01 August 2012. Atlanta,
Georgia. Vol. AIAA 2012-3916. doi:10.2514/6.2012-3916. ISBN 978-1-60086-935-8. S2CID 122586403.
30. ^ David Bleecker, “Gauge Theory and Variational Principles Archived 2021-07-09 at the Wayback Machine” (1982) D. Reidel Publishing (See chapter 9)
31. ^
Ravndal, F., Oskar Klein and the fifth dimension, arXiv:1309.4113 [physics.hist-ph]
32. ^ 5Dstm.org
33. ^ L. Castellani et al., Supergravity and superstrings, vol. 2, ch. V.11.
34. ^ Khachatryan, V.; et al. (CMS Collaboration) (2011). “Search
for microscopic black hole signatures at the Large Hadron Collider”. Physics Letters B. 697 (5): 434–453. arXiv:1012.3375. Bibcode:2011PhLB..697..434C. doi:10.1016/j.physletb.2011.02.032. S2CID 122803232.
35. ^ Pardo, Kris; Fishbach, Maya; Holz,
Daniel E.; Spergel, David N. (2018). “Limits on the number of spacetime dimensions from GW170817”. Journal of Cosmology and Astroparticle Physics. 2018 (7): 048. arXiv:1801.08160. Bibcode:2018JCAP…07..048P. doi:10.1088/1475-7516/2018/07/048. S2CID
2. Kaluza, Theodor (1921). “Zum Unitätsproblem in der Physik”. Sitzungsber. Preuss. Akad. Wiss. Berlin. (Math. Phys.): 966–972. Bibcode:1921SPAW…….966K. https://archive.org/details/sitzungsberichte1921preussi
3. Klein, Oskar (1926).
“Quantentheorie und fünfdimensionale Relativitätstheorie”. Zeitschrift für Physik A. 37 (12): 895–906. Bibcode:1926ZPhy…37..895K. doi:10.1007/BF01397481.
4. Witten, Edward (1981). “Search for a realistic Kaluza–Klein theory”. Nuclear Physics B.
186 (3): 412–428. Bibcode:1981NuPhB.186..412W. doi:10.1016/0550-3213(81)90021-3.
5. Appelquist, Thomas; Chodos, Alan; Freund, Peter G. O. (1987). Modern Kaluza–Klein Theories. Menlo Park, Cal.: Addison–Wesley. ISBN 978-0-201-09829-7. (Includes reprints
of the above articles as well as those of other important papers relating to Kaluza–Klein theory.)
6. Duff, M. J. (1994). “Kaluza–Klein Theory in Perspective”. In Lindström, Ulf (ed.). Proceedings of the Symposium ‘The Oskar Klein Centenary’.
Singapore: World Scientific. pp. 22–35. ISBN 978-981-02-2332-8.
7. Overduin, J. M.; Wesson, P. S. (1997). “Kaluza–Klein Gravity”. Physics Reports. 283 (5): 303–378. arXiv:gr-qc/9805018. Bibcode:1997PhR…283..303O. doi:10.1016/S0370-1573(96)00046-4.
S2CID 119087814.
8. Wesson, Paul S. (2006). Five-Dimensional Physics: Classical and Quantum Consequences of Kaluza–Klein Cosmology. Singapore: World Scientific. Bibcode:2006fdpc.book…..W. ISBN 978-981-256-661-4.
Photo credit: https://www.flickr.com/photos/brentschmidt/5042785753/’]




partially observable markov decision process


  • [16] Another line of approximate solution techniques for solving POMDPs relies on using (a subset of) the history of previous observations, actions and rewards up to the current
    time step as a pseudo-state.

  • These solutions typically attempt to approximate the problem or solution with a limited number of parameters,[7] plan only over a small part of the belief space online, or
    summarize the action-observation history compactly.

  • Policy and value function[edit] Unlike the “originating” POMDP (where each action is available from only one state), in the corresponding Belief MDP all belief states allow
    all actions, since you (almost) always have some probability of believing you are in any (originating) state.

  • Instead, it must maintain a sensor model (the probability distribution of different observations given the underlying state) and the underlying MDP.

  • However, by interacting with the environment and receiving observations, the agent may update its belief in the true state by updating the probability distribution of the
    current state.

  • At the same time, the agent receives an observation which depends on the new state of the environment, , and on the just taken action, , with probability (or sometimes depending
    on the sensor model).

  • A consequence of this property is that the optimal behavior may often include (information gathering) actions that are taken purely because they improve the agent’s estimate
    of the current state, thereby allowing it to make better decisions in the future.

  • In this approach, the value function is computed for a set of points in the belief space, and interpolation is used to determine the optimal action to take for other belief
    states that are encountered which are not in the set of grid points.

  • [2] Formally, the belief MDP is defined as a tuple where • is the set of belief states over the POMDP states, • is the same finite set of action as for the original POMDP,
    • is the belief state transition function, • is the reward function on belief states, • is the discount factor equal to the in the original POMDP.

  • [9][10] For example, adaptive grids and point-based methods sample random reachable belief points to constrain the planning to relevant areas in the belief space.

  • The POMDP framework is general enough to model a variety of real-world sequential decision processes.

  • [2] An exact solution to a POMDP yields the optimal action for each possible belief over the world states.

  • [15] Similar to MDPs, it is possible to construct online algorithms that find arbitrarily near-optimal policies and have no direct computational complexity dependence on the
    size of the state and observation spaces.

  • [13] Online planning algorithms approach large POMDPs by constructing a new policy for the current belief each time a new observation is received.

  • A POMDP models an agent decision process in which it is assumed that the system dynamics are determined by an MDP, but the agent cannot directly observe the underlying state.

  • Such a policy only needs to consider future beliefs reachable from the current belief, which is often only a very small part of the full belief space.

  • Another dynamic programming technique called policy iteration explicitly represents and improves the policy instead.

  • Since the state is Markovian (by assumption), maintaining a belief over the states solely requires knowledge of the previous belief state, the action taken, and the current

  • is where is the value derived in the previous section and The belief MDP reward function () is the expected reward from the POMDP reward function over the belief state distribution:

  • More recent work makes use of sampling techniques, generalization techniques and exploitation of problem structure, and has extended POMDP solving into large domains with
    millions of states.

  • An MDP does not include the observation set, because the agent always knows with certainty the environment’s current state.

  • The agent takes an action , which causes the environment to transition to state with probability .

  • Parity objectives are defined via parity games; they enable to define complex objectives such that reaching a good state every 10 timesteps.

  • Alternatively, an MDP can be reformulated as a POMDP by setting the observation set to be equal to the set of states and defining the observation conditional probabilities
    to deterministically select the observation that corresponds to the true state.


Works Cited

[‘Åström, K.J. (1965). “Optimal control of Markov processes with incomplete state information”. Journal of Mathematical Analysis and Applications. 10: 174–205. doi:10.1016/0022-247X(65)90154-X.
2. ^ Jump up to:a b Kaelbling, L.P., Littman, M.L., Cassandra,
A.R. (1998). “Planning and acting in partially observable stochastic domains”. Artificial Intelligence. 101 (1–2): 99–134. doi:10.1016/S0004-3702(98)00023-X.
3. ^ Sondik, E.J. (1971). The optimal control of partially observable Markov processes
(PhD thesis). Stanford University. Archived from the original on October 17, 2019.
4. ^ Smallwood, R.D., Sondik, E.J. (1973). “The optimal control of partially observable Markov decision processes over a finite horizon”. Operations Research. 21
(5): 1071–88. doi:10.1287/opre.21.5.1071.
5. ^ Sondik, E.J. (1978). “The optimal control of partially observable Markov processes over the infinite horizon: discounted cost”. Operations Research. 26 (2): 282–304. doi:10.1287/opre.26.2.282.
6. ^
Hansen, E. (1998). “Solving POMDPs by searching in policy space”. Proceedings of the Fourteenth International Conference on Uncertainty In Artificial Intelligence (UAI-98). arXiv:1301.7380.
7. ^ Hauskrecht, M. (2000). “Value function approximations
for partially observable Markov decision processes”. Journal of Artificial Intelligence Research. 13: 33–94. arXiv:1106.0234. doi:10.1613/jair.678.
8. ^ Lovejoy, W. (1991). “Computationally feasible bounds for partially observed Markov decision
processes”. Operations Research. 39: 162–175. doi:10.1287/opre.39.1.162.
9. ^ Jump up to:a b Jesse Hoey; Axel von Bertoldi; Pascal Poupart; Alex Mihailidis (2007). “Assisting Persons with Dementia during Handwashing Using a Partially Observable
Markov Decision Process”. Proc. International Conference on Computer Vision Systems (ICVS). doi:10.2390/biecoll-icvs2007-89.
10. ^ Jump up to:a b Jesse Hoey; Pascal Poupart; Axel von Bertoldi; Tammy Craig; Craig Boutilier; Alex Mihailidis. (2010).
“Automated Handwashing Assistance For Persons With Dementia Using Video and a Partially Observable Markov Decision Process”. Computer Vision and Image Understanding (CVIU). 114 (5): 503–519. CiteSeerX doi:10.1016/j.cviu.2009.06.008.
11. ^
Pineau, J., Gordon, G., Thrun, S. (August 2003). “Point-based value iteration: An anytime algorithm for POMDPs” (PDF). International Joint Conference on Artificial Intelligence (IJCAI). Acapulco, Mexico. pp. 1025–32.
12. ^ Hauskrecht, M. (1997).
“Incremental methods for computing bounds in partially observable Markov decision processes”. Proceedings of the 14th National Conference on Artificial Intelligence (AAAI). Providence, RI. pp. 734–739. CiteSeerX
13. ^ Roy, Nicholas;
Gordon, Geoffrey (2003). “Exponential Family PCA for Belief Compression in POMDPs” (PDF). Advances in Neural Information Processing Systems.
14. ^ David Silver and Joel Veness (2010). Monte-Carlo planning in large POMDPs. Advances in neural information
processing systems.
15. ^ Nan Ye, Adhiraj Somani, David Hsu, and Wee Sun Lee (2017). “DESPOT: Online POMDP Planning with Regularization”. Journal of Artificial Intelligence Research. 58. arXiv:1609.03250. doi:10.1613/jair.5328.
16. ^ Michael H.
Lim, Tyler J. Becker, Mykel J. Kochenderfer, Claire J. Tomlin, and Zachary N. Sunberg (2023). “Optimality Guarantees for Particle Belief Approximation of POMDPs”. Journal of Artificial Intelligence Research. 77. arXiv:2210.05015. doi:10.1613/jair.1.14525.
17. ^
Francois-Lavet, V., Rabusseau, G., Pineau, J., Ernst, D., Fonteneau, R. (2019). On overfitting and asymptotic bias in batch reinforcement learning with partial observability. Journal of Artificial Intelligence Research (JAIR). Vol. 65. pp. 1–30. arXiv:1709.07796.
18. ^
Jump up to:a b c d e Chatterjee, Krishnendu; Chmelík, Martin; Tracol, Mathieu (2016-08-01). “What is decidable about partially observable Markov decision processes with ω-regular objectives”. Journal of Computer and System Sciences. 82 (5): 878–911.
doi:10.1016/j.jcss.2016.02.009. ISSN 0022-0000.
19. ^ Hauskrecht, M., Fraser, H. (2000). “Planning treatment of ischemic heart disease with partially observable Markov decision processes”. Artificial Intelligence in Medicine. 18 (3): 221–244. doi:10.1016/S0933-3657(99)00042-1.
PMID 10675716.
20. ^ Chadès, I., McDonald-Madden, E., McCarthy, M.A., Wintle, B., Linkie, M., Possingham, H.P. (16 September 2008). “When to stop managing or surveying cryptic threatened species”. Proc. Natl. Acad. Sci. U.S.A. 105 (37): 13936–40.
Bibcode:2008PNAS..10513936C. doi:10.1073/pnas.0805265105. PMC 2544557. PMID 18779594.
21. ^ Kochenderfer, Mykel J. (2015). “Optimized Airborne Collision Avoidance”. Decision Making Under Uncertainty. The MIT Press.
22. ^ Kochenderfer, Mykel J.;
Wheeler, Tim A.; Wray, Kyle H. (2022). Algorithms for decision making. Cambridge, Massachusetts; London, England: MIT Press. p. 678. ISBN 9780262047012.
23. ^ Moss, Robert J. (Sep 24, 2021). “WATCH: POMDPs: Decision Making Under Uncertainty POMDPs.jl.
Crying baby problem” (video). youtube.com. The Julia Programming Language.
Photo credit: https://www.flickr.com/photos/randihausken/6158504080/’]





biochemical cascade


  • In the first one, first messenger cross through the cell membrane, binding and activating intracellular receptors localized at nucleus or cytosol, which then act as transcriptional
    factors regulating directly gene expression.

  • A biochemical cascade, also known as a signaling cascade or signaling pathway, is a series of chemical reactions that occur within a biological cell when initiated by a stimulus.

  • This response is slower than the first because it involves more steps, like transcription of genes and then the effect of newly formed proteins in a specific target.

  • The pathways are a series of reactions, in which a zymogen (inactive enzyme precursor) of a serine protease and its glycoprotein co-factors are activated to become active
    components that then catalyze the next reaction in the cascade, ultimately resulting in cross-linked fibrin.

  • This stimulus, known as a first messenger, acts on a receptor that is transduced to the cell interior through second messengers which amplify the signal and transfer it to
    effector molecules, causing the cell to respond to the initial stimulus.

  • The complex formed produces or releases second messengers that integrate and adapt the signal, amplifying it, by activating molecular targets, which in turn trigger effectors
    that will lead to the desired cellular response.

  • This response is quick, as it involves regulation of molecules that are already present in the cell.

  • The secondary messengers like or could also induce or repress gene expression, via transcriptional factors.

  • The transcriptional factors are activated by the primary messengers, in most cases, due to their function as nuclear receptors for these messengers.

  • These receptors may have intrinsic catalytic activity or may be coupled to effector enzymes, or may also be associated to ionic channels.

  • [2] Different parts of the embryo have different concentrations of hedgehog signaling proteins, which give cells information to make the embryo develop properly and correctly
    into a head or a tail.

  • It is the case for the vast majority of responses as a consequence of the binding of the primary messengers to membrane receptors.

  • Another example, sonic hedgehog signaling pathway, is one of the key regulators of embryonic development and is present in all bilaterians.

  • [6] Another example, sonic hedgehog signaling pathway, is one of the key regulators of embryonic development and is present in all bilaterians.

  • [15] This specialized cell is capable of:[16] Regulate glucose metabolism[4][5][17] Via (transducers of regulated)/ Expression of enzymes for synthesis, storage and distribution
    of glucose Synthesis of acute phase proteins[18][19][20] Via (acute phase response element) Expression of reactive protein, globulin protease inhibitors, complement, coagulation and fibrinolytic systems and iron homeostasis Regulate iron homeostasis
    (acute phase independent)[4][20][21] Via Hepcidin expression Regulate lipid metabolism Via (response element) Expression of Exocrine production of bile salts and other compounds Degradate of toxic substances Via Expression of transporters
    Endocrine production Via (growth hormone response element) and expression Via (thyroid hormone response element) Angiotensinogen expression Regenerate itself by hepatocyte mitosis Cell growth, proliferation, survival, invasion and motility
    The hepatocyte also regulates other functions for constitutive synthesis of proteins (albumin) that influences the synthesis or activation of other molecules (synthesis of urea and essential amino acids), activate vitamin D, utilization of
    vitamin K, transporter expression of vitamin A and conversion of thyroxine.

  • The cadherin pathway also has an important function in survival and proliferation because it regulates the concentration of cytoplasmic.

  • When is free in the cytoplasm, normally it is degraded, however if the signalling is activated, degradation is inhibited and it is translocated to the nucleus where it forms
    a complex with transcription factors.

  • [8] Negative cascades include: Ischemic cascade Cell-specific biochemical cascades Epithelial cells[edit] Adhesion is an essential process to epithelial cells so that epithelium
    can be formed and cells can be in permanent contact with extracellular matrix and other cells.

  • In order to function, integrins have to form complexes with proteins.

  • Biochemical cascades include: The Complement system The Insulin Signaling Pathway The Sonic hedgehog Signaling Pathway The Adrenergic receptor Pathways The Acetylcholine receptor
    Pathways The Mitogen-activated protein kinase cascade Conversely, negative cascades include events that are in a circular fashion, or can cause or be caused by multiple events.

  • [13][14] Hepatocytes[edit] The hepatocyte is a complex and multifunctional differentiated cell whose cell response will be influenced by the zone in hepatic lobule, because
    concentrations of oxygen and toxic substances present in the hepatic sinusoids change from periportal zone to centrilobular zone.

  • then is responsible for activation of several proteins, like (leads to activation of pathway, which consequently leads to activation of) and (can also activate).

  • then is responsible for activation of several proteins, like (leads to activation of pathway, which consequently leads to activation of) and (can also activate).

  • These receptors, that recognize the antigen soluble (cells) or linked to a molecule on Antigen Presenting Cells ( cells), do not have long cytoplasm tails, so they are anchored
    to signal proteins, which contain a long cytoplasmic tails with a motif that can be phosphorylated ( immunoreceptor tyrosine-based activation motif) and resulting in different signal pathways.

  • These receptors, that recognize the antigen soluble (cells) or linked to a molecule on Antigen Presenting Cells ( cells), do not have long cytoplasm tails, so they are anchored
    to signal proteins, which contain a long cytoplasmic tails with a motif that can be phosphorylated ( immunoreceptor tyrosine-based activation motif) and resulting in different signal pathways.

  • [43] The leukocyte adhesion cascade steps and the key molecules involved in each step After a vascular injury occurs, platelets are activated by locally exposed collagen (glycoprotein
    VI receptor), locally generated thrombin , platelet-derived (receptor) and that is either released from damaged cells or secreted from platelet dense granules.

  • [43] The leukocyte adhesion cascade steps and the key molecules involved in each step After a vascular injury occurs, platelets are activated by locally exposed collagen (glycoprotein
    VI receptor), locally generated thrombin , platelet-derived (receptor) and that is either released from damaged cells or secreted from platelet dense granules.

  • The differentiation of cells to plasma cells is also an example of a signal mechanism in lymphocytes, induced by a cytokine receptor.

  • The differentiation of cells to plasma cells is also an example of a signal mechanism in lymphocytes, induced by a cytokine receptor.

  • One example of a protein that binds to adaptor proteins and become activated is that is very important in the lymphocyte signal pathways.

  • One example of a protein that binds to adaptor proteins and become activated is that is very important in the lymphocyte signal pathways.

  • In this case, some interleukins bind to a specific receptor, which leads to activation of pathway.

  • In this case, some interleukins bind to a specific receptor, which leads to activation of pathway.

  • The canonical signaling involves binding of to and co-receptor, leading to phosphorylation and inhibition of β-catenin degradation, resulting in its accumulation and translocation
    to the nucleus, where it acts as a transcription factor.

  • The canonical signaling involves binding of to and co-receptor, leading to phosphorylation and inhibition of β-catenin degradation, resulting in its accumulation and translocation
    to the nucleus, where it acts as a transcription factor.

  • This pathway can be triggered via two mechanisms: physiological stimulus (like reduced O2 tension) and activation of the prostacyclin receptor.

  • This pathway can be triggered via two mechanisms: physiological stimulus (like reduced O2 tension) and activation of the prostacyclin receptor.

  • The antigen receptor and signal protein form a stable complex, named or , in or cells, respectively.

  • The antigen receptor and signal protein form a stable complex, named or , in or cells, respectively.

  • Consequently, the protein is translated and inhibits , allowing immunoglobulin genes transcription and activation of (important for the secretory apparatus formation and enhancing
    of protein synthesis).

  • Consequently, the protein is translated and inhibits , allowing immunoglobulin genes transcription and activation of (important for the secretory apparatus formation and enhancing
    of protein synthesis).

  • These proteins after phosphorylation become activated and allow binding of others enzymes that continue the biochemical cascade.

  • These proteins after phosphorylation become activated and allow binding of others enzymes that continue the biochemical cascade.

  • [50][51][52] Also, the coreceptors play an important role because they can improve the antigen/receptor binding and initiate parallel cascade events, like activation Kinase.

  • [50][51][52] Also, the coreceptors play an important role because they can improve the antigen/receptor binding and initiate parallel cascade events, like activation Kinase.

  • The activation leads to a higher expression of enzymes involved in glutathione syntheses and metabolism, that have a key role in antioxidant response.

  • The activation leads to a higher expression of enzymes involved in glutathione syntheses and metabolism, that have a key role in antioxidant response.

  • It is characterized by binding of to Frizzled and activation of G proteins and to an increase of intracellular levels of calcium through mechanisms involving.

  • It is characterized by binding of to Frizzled and activation of G proteins and to an increase of intracellular levels of calcium through mechanisms involving.

  • The family is essential for signal transduction in these cells, because it is responsible for phosphorylation of.

  • [62] Extrinsic regulation is made by signals from the niche, where stem cells are found, which is able to promote quiescent state and cell cycle activation in somatic stem

  • In fetal stem cells, mitogens promote a relatively rapid transition through cooperative action of cyclin and cyclin to inactivate family proteins.

  • [58][59] Under certain circumstances adenosine stimulates bone destruction and in other situations it promotes bone formation, depending on the purinergic receptor that is
    being activated.

  • The signaling pathway leads to sperm cells capacitation; however, adenylyl cyclase in sperm cells is different from the somatic cells.

  • [61] At cell cycle level there is an increase of complexity of the mechanisms in somatic stem cells.

  • In the absence of mitogenic signals, and the transition are suppressed by cell cycle inhibitors including and family proteins.

  • This reduces the sensitivity of stem cells to mitogenic signals by inhibiting cyclin complexes.

  • There are some signaling pathways, such as (Leukemia inhibitory factor/Janus kinase/Signal transducer and activator of transcription 3) and (Bone morphogenetic proteins/ Mothers
    against decapentaplegic/ Inhibitor of differentiation), mediated by transcription factors, epigenetic regulators and others components, and they are responsible for self-renewal genes expression and inhibition of differentiation genes expression,

  • As a result, is hypophosphorylated and inhibits, promoting quiescence in -phase of the cell cycle.

  • [58] Adenosine may have opposite effects on bone metabolism, because while certain purinergic receptors stimulate adenylyl cyclase activity, others have the opposite effect.

  • In addition, calcium and together work to activate , which goes on to phosphorylate other molecules, leading to altered cellular activity.

  • Stem cells[edit] Self-renewal and differentiation abilities are exceptional properties of stem cells.

  • [68] Concomitantly, oocyte growth is initiated by binding of to its receptor in the oocyte, leading to the activation of , allowing oocyte survival and development.

  • [63] Asymmetric division is characteristic of somatic stem cells, maintaining the reservoir of stem cells in the tissue and production of specialized cells of the same.

  • The Rankl and Rank signaling pathway regulates osteoclastogenesis, as well as, the survival and activation of osteoclasts.

  • is activated and degrades, leading to cell cycle progression and oocyte maturation.

  • [110] The database is a collection of manually drawn pathway maps for metabolism, genetic information processing, environmental information processing such as signal transduction,
    ligand–receptor interaction and cell communication, various other cellular processes and human diseases, all based on extensive survey of published literature.

  • Pathway construction can have either a data-driven objective or a knowledge-driven objective Data-driven pathway construction is used to generate relationship information
    of genes or proteins identified in a specific experiment such as a microarray study.

  • [104] Knowledge-driven pathway construction entails development of a detailed pathway knowledge base for particular domains of interest, such as a cell type, disease, or system.

  • [107] Data repositories, which contain information regarding sequence data, metabolism, signaling, reactions, and interactions are a major source of information for pathway

  • [113] Pathway resources are expanded by utilizing homology information to translate pathway content between species and extending existing pathways with data derived from
    conserved protein interactions and coexpression.

  • [104] Pathway-related databases and tools Kegg [edit] The increasing amount of genomic and molecular information is the basis for understanding higher-order biological systems,
    such as the cell and the organism, and their interactions with the environment, as well as for medical, industrial and other practical applications.

  • The Kegg resource[109] provides a reference knowledge base for linking genomes to biological systems, categorized as building blocks in the genomic space, the chemical space,
    wiring diagrams of interaction networks and reaction networks, and ontologies for pathway reconstruction (database).

  • [114] In short, provides a means to rapidly interrogate complex experimental data for pathway-level changes in a diverse range of organisms.

  • [111] Genmapp [edit] Gene Map Annotator and Pathway Profiler [112] a free, open-source, stand-alone computer program is designed for organizing, analyzing, and sharing genome
    scale data in the context of biological pathways.

  • The pathway is further refined to include context-specific annotations such as species, cell/tissue type, or disease type.

  • Pathway building is the process of identifying and integrating the entities, interactions, and associated annotations, and populating the knowledge base.

  • The Reactome database containing a framework of possible reactions which, when combined with expression and enzyme kinetic data, provides the infrastructure for quantitative
    models, therefore, an integrated view of biological processes, which links such gene products and can be systematically mined by using bioinformatics applications.

  • [121][122] Pathway-oriented approaches for analyzing microarray data, by grouping long lists of individual genes, proteins, and/or other biological molecules according to
    the pathways they are involved in into smaller sets of related genes or proteins, which reduces the complexity, have proven useful for connecting genomic data to specific biological processes and systems.

  • The basic unit of the Reactome database is a reaction; reactions are then grouped into causal chains to form pathways[115] The Reactome data model allows us to represent many
    diverse processes in the human system, including the pathways of intermediary metabolism, regulatory pathways, and signal transduction, and high-level processes, such as the cell cycle.

  • Pathway-oriented approaches In the post-genomic age, high-throughput sequencing and gene/protein profiling techniques have transformed biological research by enabling comprehensive
    monitoring of a biological system, yielding a list of differentially expressed genes or proteins, which is useful in identifying genes that may have roles in a given phenomenon or phenotype.

  • [117] Although the primary curational domain is pathways from Homo sapiens, electronic projections of human pathways onto other organisms are regularly created via putative
    orthologs, thus making Reactome relevant to model organism research communities.

  • [119] In summary, Reactome provides high-quality curated summaries of fundamental biological processes in humans in a form of biologist-friendly visualization of pathways
    data, and is an open-source project.

  • In addition, a large number of pathway analytic methods exploit pathway knowledge in public repositories such as Gene Ontology or Kyoto Encyclopedia of Genes and Genomes,
    rather than inferring pathways from molecular measurements.

  • For instance, it can refer to the analysis physical interaction networks (e.g., protein–protein interactions), kinetic simulation of pathways, and steady-state pathway analysis
    (e.g., flux-balance analysis), as well as its usage in the inference of pathways from expression and sequence data.

  • Several functional enrichment analysis tools and algorithms[129] have been developed to enhance data interpretation.

  • [120] With DNA microarrays and genome-wide gene engineering, it is possible to screen global gene expression profiles to contribute a wealth of genomic data to the public

  • In addition, tools can be used to analyze the roles of genes in metabolic pathways and show the biological relationships between genes or gene-products and may represent metabolic

  • By using a combined approach of Microarray-Bioinformatic technologies, a potential metabolic mechanism contributing to colorectal cancer has been demonstrated[131] Several
    environmental factors may be involved in a series of points along the genetic pathway to.

  • Applications of pathway analysis in medicine Colorectal cancer[edit] A program package MatchMiner was used to scan names for cloned genes of interest are scanned, then are
    input into GoMiner, which leveraged the to identify the biological processes, functions and components represented in the gene profile.

  • [131] Parkinson’s disease [edit] Cellular models are instrumental in dissecting a complex pathological process into simpler molecular events.

  • Emerging evidence that dietary restriction can forestall the development of is consistent with a major “metabolic” component to these disorders, and provides optimism that
    these devastating brain disorders of aging may be largely preventable.

  • Classical cellular models appear to be the correct choice for preliminary studies on the molecular action of new drugs or potential toxins and for understanding the role of
    single genetic factors.

  • Moreover, the availability of novel cellular systems, such as cybrids or induced pluripotent stem cells, offers the chance to exploit the advantages of an in vitro investigation,
    although mirroring more closely the cell population being affected.

  • In such a multifaceted picture, it is particularly important to identify experimental models that simplify the study of the different networks of proteins and genes involved.


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rewilding (conservation biology)


  • It is also distinct from other forms of restoration in that, while it places emphasis on recovering geographically specific sets of ecological interactions and functions that
    would have maintained ecosystems prior to human influence,[1] rewilding is open to novel or emerging ecosystems which encompass new species and new interactions.

  • [1] Empowered by a directive from the International Union for the Conservation of Nature to produce a document on rewilding that reflected a global scale inventory of underlying
    goals as well as practices, the group sought a ‘unifying definition’, producing the following: ‘Rewilding is the process of rebuilding, following major human disturbance, a natural ecosystem by restoring natural processes and the complete
    or near complete food web at all trophic levels as a self-sustaining and resilient ecosystem with biota that would have been present had the disturbance not occurred.

  • While rewilding initiatives can be controversial, the United Nations has listed rewilding as one of several methods needed to achieve massive scale restoration of natural
    ecosystems, which they say must be accomplished by 2030[2] as part of the 30×30 campaign.

  • [88] Harm to conservation[edit] Some conservationists have expressed concern that rewilding ‘could replace the traditional protection of rare species on small nature reserves’,
    which could potentially lead to an increase in habitat fragmentation and species loss.

  • 3Cs rewilding therefore relied on protecting ‘core’ areas of wild land, linked together by ‘corridors’ allowing passage for ‘carnivores’ to move around the landscape and perform
    their functional role.

  • The group wrote, ‘Commonalities in the concept of rewilding lie in its aims, whereas differences lie in the methods used, which include land protection, connectivity conservation,
    removing human infrastructure, and species reintroduction or taxon replacement.’

  • Advocates of the approach maintain that communities where species evolved in response to Pleistocene megafauna (but now lack large mammals) may be in danger of collapse,[39][40]
    while critics argue that it is unrealistic to assume that communities today are functionally similar to their state 10,000 years ago.

  • However, although it is generally undebated that predators occupy an important role in ecosystems, there is no general agreement about whether wild predators keep herbivore
    populations in check, or whether their influence is of more subtle nature (see Ecology of fear).

  • [28][32] Types of rewilding Passive rewilding[edit] A red deer at the Oostvaardersplassen nature reserve, a rewilding site in the Netherlands Passive rewilding (also referred
    to as ecological rewilding)[33] aims to restore natural ecosystem processes via minimal or the total withdrawal of direct human management of the landscape.

  • [89] Rewilding in different locations Both grassroots groups and major international conservation organizations have incorporated rewilding into projects to protect and restore
    large-scale core wilderness areas, corridors (or connectivity) between them, and apex predators, carnivores, or keystone species (species which interact strongly with the environment, such as elephant and beaver).

  • [11] In 1967, The Theory of Island Biogeography by Robert H. MacArthur and Edward O. Wilson established the importance of considering the size and fragmentation of wildlife
    conservation areas, stating that protected areas remained vulnerable to extinctions if small and isolated.

  • The ultimate goal of rewilding is the restoration of functioning native ecosystems containing the full range of species at all trophic levels while reducing human control
    and pressures.

  • Examples include ‘Sanctuary Nature Recovery Programme’ (at Broughton) and ‘nature restoration project’, the preferred term used by the Cambrian Wildwood project, an area aspiring
    to encompass 7,000 acres in Wales.

  • [16][17][18][19] In a 2021 report for the launch of the UN Decade on Ecosystem Restoration, the United Nations listed rewilding as one of several restoration methods which
    they state should be used for ecosystem restoration of over 1 billion hectares.

  • Barlow noted that a consequence for such native fruits following the loss of their megafaunal seed dispersal partners was range constriction during the Holocene, made increasingly
    severe since the mid-20th century by rapid human-driven climate change.

  • As stated in an article on environmental law, ‘These dam removals provide perhaps the best example of large-scale environmental remediation in the twenty-first century.

  • [9][10] History Rewilding was developed as a method to preserve functional ecosystems and reduce biodiversity loss, incorporating research in island biogeography and the ecological
    role of large carnivores.

  • [112] In 2020, nature writer Melissa Harrison reported a significant increase in attitudes supportive of rewilding among the British public, with plans recently approved for
    the release of European bison, Eurasian elk, and great bustard in England, along with calls to rewild as much as 20% of the land in East Anglia, and even return apex predators such as the Eurasian lynx, brown bear, and grey wolf.

  • [95] The Tijuca National Park is part of heavily fragmented Atlantic Forest, where there is potential to restore many more seed dispersal interactions if seed dispersing mammals
    and birds are reintroduced to forest patches where the tree species diversity remains high.

  • These might include species reintroductions or translocations and/or habitat engineering and the removal of man-made structures.

  • Ward challenge Jørgensen’s criticism and provide existing examples of rewilding programs which ‘have been developed and governed within the understanding that human and non-human
    world are inextricably entangled’.

  • [90] Projects include the Yellowstone to Yukon Conservation Initiative in North America (also known as Y2Y) and the European Green Belt, built along the former Iron Curtain,
    transboundary projects, including those in southern Africa funded by the Peace Parks Foundation, community-conservation projects, such as the wildlife conservancies of Namibia and Kenya, and projects organized around ecological restoration,
    including Gondwana Link, regrowing native bush in a hotspot of endemism in southwest Australia, and the Area de Conservacion Guanacaste, restoring dry tropical forest and rainforest in Costa Rica.

  • [126][127] This happened in line with Vera’s proposal that grazing animals played a significant role in the shaping of European landscapes before the Neolithic – the wood-pasture

  • [14] With the creation of the Society for Conservation Biology in 1985, conservationists began to focus on reducing habitat loss and fragmentation.

  • [80] Criticism Compatibility with economic activity[edit] A view expressed by some national governments and officials within multilateral agencies such as the United Nations,
    is that excessive rewilding, such as large rigorously enforced protected areas where no extraction activities are allowed, can be too restrictive on people’s ability to earn sustainable livelihoods.

  • While small-scale efforts are generally well regarded the increased popularity of rewilding has generated controversy, especially regarding large-scale projects.

  • This has been done in an effort to restore salmon populations specifically but with other species in mind.

  • While the intrinsic value of plants is an ethical foundation for many forms of plant conservation, the Pittsburgh wild-planting of pawpaw also entails an animal conservation

  • The island state of Tasmania has become an important location for rewilding efforts because, as an island, it is easier to remove feral cat populations and manage other invasive

  • [100] Many projects also employ domestic water buffalo as a grazing analogue for the extinct European water buffalo.

  • They also contend that rewilding programs may draw funding away from ‘more scientifically supported conservation projects’.

  • [120] In 2019 a pair of white storks built a nest in an oak tree at Knepp, part of a group imported from Poland, the result of a programme to re-introduce that species to
    England run by the Roy Dennis Wildlife Foundation, which has overseen reintroductions of other extinct bird species to the UK.

  • [55] Because part of Barlow’s activities occurred on public and private lands for which she did not expressly obtain planting permission,[56] this form of rewilding action
    could be referred to as guerrilla rewilding,[57][58] which is an adaptation of the established term guerrilla gardening.

  • [82] David Nogués-Bravo and Carsten Rahbek assert that the benefits of rewilding lack evidence and that such programs may inadvertently lead to ‘de-wilding’, through the extinction
    of local and global species.

  • Once ranging from Alaska to France, Saigas are now extinct in Europe and North America, and a critically endangered species globally.By restoring large herbivores, greenhouse
    gas levels may be lowered.

  • [28] A study in a tropical forest in Guyana found that an increase in mammal species from 5 to 35 increased tree and soil carbon storage by four to five times, compared to
    an increase of 3.5 to four times with an increase of tree species from 10 to 70.

  • [68][69][70][71][72] That pawpaw planting sites chosen by citizens center on damaged riverine forests of old industrial sites in Pittsburgh, Pennsylvania, and Ypsilanti, Michigan,
    may account for the lack of controversy regarding their actions.

  • [41] Eighteen years later Connie Barlow, in her book The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms (2000),[42] explored the
    specifics of temperate North American plants whose fruits displayed the characteristics of megafauna dispersal syndrome.

  • Within range, or slightly poleward of range, wild plantings are underway for a common subcanopy tree of the eastern United States.

  • To resolve this, von Essen and Allen contend that rewilding needs to shift towards full alignment with mainstream conservation and welcome full sovereignty, or instead take
    full responsibility for the care of animals who have been reintroduced.

  • [22][23][24][25] An example of this would be rewilding pasture land, thereby reducing the number of cows and sheep and increasing the number of trees.

  • When disease mangament practices restored the population, the Serengeti returned to a carbon sink state.

  • [85] Ole Martin Moen argues that rewilding projects should be brought to an end because they unnecessarily increase wild animal suffering and are expensive, and the funds
    could be better spent elsewhere.

  • [46] In 2005 Barlow and Lee Barnes (co-founders of Torreya Guardians[47][48][49][50]) began obtaining seeds from mature horticultural plantings in states northward of Florida
    and Georgia for distribution to volunteer planters whose lands contained forested habitats potentially suitable for this native of Florida.

  • In 2011, the ‘Rewilding Europe’ initiative was established with the aim of rewilding one million hectares of land in ten areas including the western Iberian Peninsula, Velebit,
    the Carpathians and the Danube delta by 2020, mostly abandoned farmland among other identified candidate sites.

  • [12] In 1987, William D. Newmark’s study of extinctions in national parks in North America added weight to the theory.

  • Referring to the span of project types they stated, ‘Rewilding now incorporates a variety of concepts, including Pleistocene megafauna replacement, taxon replacement, species
    reintroductions, retrobreeding, release of captive-bred animals, land abandonment, and spontaneous rewilding.’

  • [20][21] Guiding principles[edit] Since its origin, the term rewilding has been used as a signifier of particular forms of ecological restoration projects (or advocacy thereof)
    that have ranged widely in scope and geographic application.

  • [77] Predators[edit] Predators may be required to ensure that browsing and grazing animals are kept from over-breeding/over-feeding, destroying vegetation complexity,[11]
    as may be concluded from mass-starvations which happened in Oostvaardersplassen.

  • In practice rewilding as effected by private landowners and managers takes many different forms, with emphases placed on varying aspects.

  • [79] By analogy, wildebeest populations in the Serengeti are primarily controlled by food constraints despite the presence of many predators.

  • A key feature of rewilding is its focus on replacing human interventions with natural processes.

  • As in other countries, rewilding in England remains controversial to the extent that some of its more ambitious aims are being ‘domesticated’ both in a proactive attempt to
    make it less controversial and in reactive response to previous controversy.

  • Before reintroductions, the national park did not have large or intermediate -sized seed dispersers, meaning that the increased dispersal of tree seeds following the reintroductions
    can have a large effect on forest regeneration in the national park.

  • [75] Beavers are another important example of ecosystem engineers.

  • The dams also create wetlands for plant, insect, and bird life.

  • The reintroduction and management of the Tasmanian devil in this state, and dingoes on the mainland, is being trialled in an effort to contain introduced predators, as well
    as over-populations of kangaroos.

  • Work at nature’s scale, 5.

  • ‘[84] Erica von Essen and Michael Allen, using Donaldson and Kymlicka’s political animal categories framework, assert that wildness standards imposed on animals are arbitrary
    and inconsistent with the premise that wild animals should be granted sovereignty over the territories that they inhabit and the right to make decisions about their own lives.

  • In North America, a major project aims to restore the prairie grasslands of the Great Plains.

  • Thanks to them, and to a donation of 195,094 ha made by Kristine, in 2018 an area was converted into a National Park, and the jaguar was reintroduced into it, a species that
    had been extinct in the region for seven decades.

  • [98] Other projects around the country include:[97] • Barrington Wildlife Sanctuary, NSW – many species • Mongo Valley, NSW – koalas • Bungador Stoney Rises Nature Reserve,
    Victoria – spotted-tail quoll, koala, long-nosed potoroo • Mount Zero-Taravale Sanctuary, Queensland – several species • Dirk Hartog Island National Park, Western Australia – many species • Marna Banggara, SA – also red-tailed phascogales
    and bandicoots • Clarke Island/Lungtalanana, Tasmania – several species • Other locations around Tasmania – Tasmanian devils and (proposed) emus Europe[edit] Urban green space at Trinity College Dublin that has been left to overgrow intentionally.

  • Support people and nature together, 2.

  • [96] Australia[edit] Rewilding is newer in Australia than in Europe and North America, but there are many projects under way across the country as of 2023.


Works Cited

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74. ^ Jump up to:a
b “European Bison bonasus Through grazing, foraging, wallowing and trampling, the hefty bison boosts habitat diversification”. Rewilding Britain. Retrieved 3 January 2022.
75. ^ Sandom, Christopher J; Hughes, Joelene; Macdonald, David W (2012).
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119. ^ Further reading: Isabella Tree, Wilding: The return of Nature to a British Farm, charting
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124. ^ “In this first episode of Rewilding Mapperton, Luke
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125. ^ “Home – Alladale”. 18 November 2022. Retrieved 6 August 2023.
126. ^ Cossins, Daniel
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127. ^ Kolbert, Elizabeth (24 December 2012). “Dept. of Ecology: Recall of the Wild”. The New Yorker. pp. 50–60.
128. ^ Buurmans, Meghan Debating the ‘wild’: What the Oostvaardersplassen
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Photo credit: https://www.flickr.com/photos/rittysdigiez/909609509/’]




planck constant


  • Applying this new approach to Wien’s displacement law showed that the “energy element” must be proportional to the frequency of the oscillator, the first version of what is
    now sometimes termed the “Planck–Einstein relation”: Planck was able to calculate the value of from experimental data on black-body radiation: his result, J⋅s, is within 1.2% of the currently defined value.

  • The size of these “packets” of energy, which would later be named photons, was to be the same as Planck’s “energy element”, giving the modern version of the Planck–Einstein
    relation: Einstein’s postulate was later proven experimentally: the constant of proportionality between the frequency of incident light and the kinetic energy of photoelectrons was shown to be equal to the Planck constant .

  • [citation needed] Reduced Planck constant ℏ In many applications, the Planck constant naturally appears in combination with as , which can be traced to the fact that in these
    applications it is natural to use the angular frequency (in radians per second) rather than plain frequency (in cycles per second or hertz).

  • [32] Eventually, following upon Planck’s discovery, it was speculated that physical action could not take on an arbitrary value, but instead was restricted to integer multiples
    of a very small quantity, the “[elementary] quantum of action”, now called the Planck constant.

  • Planck’s constant was formulated as part of Max Planck’s successful effort to produce a mathematical expression that accurately predicted the observed spectral distribution
    of thermal radiation from a closed furnace (black-body radiation).

  • Let us call each such part the energy element ε; — Planck, On the Law of Distribution of Energy in the Normal Spectrum[2] With this new condition, Planck had imposed the quantization
    of the energy of the oscillators, “a purely formal assumption … actually I did not think much about it …” in his own words,[14] but one that would revolutionize physics.

  • He examined how the entropy of the oscillators varied with the temperature of the body, trying to match Wien’s law, and was able to derive an approximate mathematical function
    for the black-body spectrum,[2] which gave a simple empirical formula for long wavelengths.

  • Photon energy[edit] The Planck relation connects the particular photon energy E with its associated wave frequency f: This energy is extremely small in terms of ordinarily
    perceived everyday objects.

  • [37] Equivalently, the order of the Planck constant reflects the fact that everyday objects and systems are made of a large number of microscopic particles.

  • [12] Planck’s law may also be expressed in other terms, such as the number of photons emitted at a certain wavelength, or the energy density in a volume of radiation.

  • Significance of the value[edit] The Planck constant is one of the smallest constants used in physics.

  • This view has been replaced by fully modern quantum theory, in which definite trajectories of motion do not even exist; rather, the particle is represented by a wavefunction
    spread out in space and in time.

  • When the product of energy and time for a physical event approaches the Planck constant, quantum effects dominate.

  • Many of the most important equations, relations, definitions, and results of quantum mechanics are customarily written using the reduced Planck constant rather than the Planck
    constant , including the Schrödinger equation, momentum operator, canonical commutation relation, Heisenberg’s uncertainty principle, and Planck units.

  • Approaching this problem, Planck hypothesized that the equations of motion for light describe a set of harmonic oscillators, one for each possible frequency.

  • The expression formulated by Planck showed that the spectral radiance of a body for frequency ν at absolute temperature T is given by , where is the Boltzmann constant, is
    the Planck constant, and is the speed of light in the medium, whether material or vacuum.

  • In many cases, such as for monochromatic light or for atoms, quantization of energy also implies that only certain energy levels are allowed, and values in between are forbidden.

  • In modern terms, if is the total angular momentum of a system with rotational invariance, and the angular momentum measured along any given direction, these quantities can
    only take on the values Uncertainty principle[edit] Main article: Uncertainty principle The Planck constant also occurs in statements of Werner Heisenberg’s uncertainty principle.

  • Bohr solved this paradox with explicit reference to Planck’s work: an electron in a Bohr atom could only have certain defined energies where is the speed of light in vacuum,
    is an experimentally determined constant (the Rydberg constant) and .

  • [2] He also made the first determination of the Boltzmann constant from the same data and theory.

  • [21][22] Before Einstein’s paper, electromagnetic radiation such as visible light was considered to behave as a wave: hence the use of the terms “frequency” and “wavelength”
    to characterize different types of radiation.

  • An amount of light more typical in everyday experience (though much larger than the smallest amount perceivable by the human eye) is the energy of one mole of photons; its
    energy can be computed by multiplying the photon energy by the Avogadro constant, [38], with the result of 216 kJ, about the food energy in three apples.

  • This fixed value is used to define the Si unit of mass, the kilogram: “the kilogram […] is defined by taking the fixed numerical value of h to be when expressed in the unit
    J⋅s, which is equal to, where the metre and the second are defined in terms of speed of light c and duration of hyperfine transition of the ground state of an unperturbed caesium-133 atom ΔνCs.

  • [2] Planck later referred to the constant as the “quantum of action”.

  • The energy transferred by a wave in a given time is called its intensity.

  • This reflects the fact that on a scale adapted to humans, where energies are typical of the order of kilojoules and times are typical of the order of seconds or minutes, the
    Planck constant is very small.

  • Planck tried to find a mathematical expression that could reproduce Wien’s law (for short wavelengths) and the empirical formula (for long wavelengths).

  • This approach also allowed Bohr to account for the Rydberg formula, an empirical description of the atomic spectrum of hydrogen, and to account for the value of the Rydberg
    constant in terms of other fundamental constants.

  • Bohr also introduced the quantity , now known as the reduced Planck constant or Dirac constant, as the quantum of angular momentum.

  • However, the energy account of the photoelectric effect did not seem to agree with the wave description of light.

  • [33] This was a significant conceptual part of the so-called “old quantum theory” developed by physicists including Bohr, Sommerfeld, and Ishiwara, in which particle trajectories
    exist but are hidden, but quantum laws constrain them based on their action.

  • Related to this is the concept of energy quantization which existed in old quantum theory and also exists in altered form in modern quantum physics.

  • The inverse relationship between the uncertainty of the two conjugate variables forces a tradeoff in quantum experiments, as measuring one quantity more precisely results
    in the other quantity becoming imprecise.

  • [44]: 104  Because the fundamental equations look simpler when written using as opposed to , it is usually rather than that gives the most reliable results when used in order-of-magnitude

  • [18] Einstein’s explanation for these observations was that light itself is quantized; that the energy of light is not transferred continuously as in a classical wave, but
    only in small “packets” or quanta.

  • This expression included a constant, , which is thought to be for Hilfsgrösse (auxiliary variable),[8] and subsequently became known as the Planck constant.

  • The constant was postulated by Max Planck in 1900 as a proportionality constant needed to explain experimental black-body radiation.

  • The correct quantization rules for electrons – in which the energy reduces to the Bohr model equation in the case of the hydrogen atom – were given by Heisenberg’s matrix
    mechanics in 1925 and the Schrödinger wave equation in 1926: the reduced Planck constant remains the fundamental quantum of angular momentum.

  • Planck constant: Common symbols: SI unit : joule per hertz (joule seconds) ; Other units: electronvolt per hertz (electronvolt seconds); Reduced Planck constant: Common symbols:
    SI unit: joule-seconds; Other units: electronvolt-seconds History Origin of the constant[edit] Main article: Planck’s law Plaque at the Humboldt University of Berlin: “Max Planck, who discovered the elementary quantum of action h, taught here
    from 1889 to 1928.

  • This kinetic energy (for each photoelectron) is independent of the intensity of the light,[18] but depends linearly on the frequency;[20] and if the frequency is too low (corresponding
    to a photon energy that is less than the work function of the material), no photoelectrons are emitted at all, unless a plurality of photons, whose energetic sum is greater than the energy of the photoelectrons, acts virtually simultaneously
    (multiphoton effect).

  • Classical physics cannot explain either quantization of energy or the lack of classical particle motion.

  • Given numerous particles prepared in the same state, the uncertainty in their position, , and the uncertainty in their momentum, , obey where the uncertainty is given as the
    standard deviation of the measured value from its expected value.

  • For this reason, it is often useful to absorb that factor of 2π into the Planck constant by introducing the reduced Planck constant[39][40]: 482  (or reduced Planck’s constant[41]: 5
    [42]: 788 ), equal to the Planck constant divided by [39] and denoted by (pronounced h-bar[43]: 336 ).

  • [7]: 141  Also around this time, but unknown to Planck, Lord Rayleigh had derived theoretically a formula, now known as the Rayleigh–Jeans law, that could reasonably predict
    long wavelengths but failed dramatically at short wavelengths.


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to if we used , and to is we used . In an order-of-magnitude estimate, we take that the constant of proportionality is 1. Now, the actual correct answer is ;[46]: 45  therefore, if we choose to use as one of our parameters, our estimate
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2. ^ Notable examples of such usage include Landau and Lifshitz[68]: 20  and Giffiths,[69]: 3  but there are many others, e.g.[70][71]: 449  [72]: 284
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it may mean that the angular momentum of an atom can only rise or fall by discrete amounts when electrons leave or return. It is readily seen that this view presents less difficulty to the mind than the more usual interpretation, which is believed
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112. ^ Stern, Otto (December 1921). “Ein Weg zur experimentellen Prüfung der Richtungsquantelung im Magnetfeld”. Zeitschrift für Physik. 7 (1): 249–253. doi:10.1007/BF01332793.
113. ^
Heisenberg, Werner (December 1922). “Zur Quantentheorie der Linienstruktur und der anomalen Zeemaneflekte”. Zeitschrift für Physik. 8 (1): 273–297. doi:10.1007/BF01329602.
114. ^ Kramers, H. A.; Pauli, W. (December 1923). “Zur Theorie der Bandenspektren”.
Zeitschrift für Physik. 13 (1): 351–367. doi:10.1007/BF01328226.
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fundamental equations of quantum mechanics”. Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character. 109 (752): 642–653. doi:10.1098/rspa.1925.0150.
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Photo credit: https://www.flickr.com/photos/chitrasudar/2536282942/’]




vicarious liability


  • So if a director or officer is expressly authorised to make representations of a particular class on behalf of the company, and fraudulently makes a representation of that
    class to a third party causing loss, the company will be liable even though the particular representation was an improper way of doing what he was authorised to do.

  • Criminal law imparts separate and distinct liability upon each actor considered a person under the law, and therefore a corporation and the corporation’s employee may both
    be charged with having committed exactly the same crime, in addition to any civil liability for which the law imposes.

  • [12] If liability for the particular tort requires a state of mind, then to be liable, the director or senior officer must have that state of mind and it must be attributed
    to the company.

  • Whether by virtue of their actual or ostensible authority as agents acting within their authority (see Lloyd v Grace, Smith & Co. [1912] AC 716) or as employees acting in
    the course of their employment (see Armagas Limited v Mundogas S.A. [1986] 1 AC 717), their acts and omissions and their knowledge could be attributed to the company, and this could give rise to liability as joint tortfeasors where the directors
    have assumed responsibility on their own behalf and not just on behalf of the company.

  • Unless an applicable statute provides otherwise, an actor remains subject to liability although the actor acts as an agent or an employee, with actual or apparent authority,
    or within the scope of employment.

  • An employer may be held liable under principles of vicarious liability if an employee does an authorized act in an unauthorized way.

  • For instance, an employer will be held liable if it is shown that the employee had gone on a mere detour in carrying out their duties, such as stopping to buy a beverage or
    use an automated teller machine while running a work-related errand, whereas an employee acting in their own right rather than on the employer’s business is undertaking a “frolic” and will not subject the employer to liability.

  • The extent of authority is a question of fact and is significantly more than the fact of an employment which gave the employee the opportunity to carry out the fraud.

  • [1] The law has developed the view that some relationships by their nature require the person who engages others to accept responsibility for the wrongdoing of those others.

  • [8] One example is in the case of a bank, finance company or other lienholder performing a repossession of an automobile from the registered owner for non-payment, the lienholder
    has a non-delegable duty not to cause a breach of the peace in performing the repossession, or it will be liable for damages even if the repossession is performed by an agent.

  • Vicarious liability is a form of a strict, secondary liability that arises under the common law doctrine of agency, respondeat superior, the responsibility of the superior
    for the acts of their subordinate or, in a broader sense, the responsibility of any third party that had the “right, ability or duty to control” the activities of a violator.

  • Parental liability In the United States, the question of parental responsibility generally follows the common law principle that a parent is not civilly liable for injuries
    resulting from a child’s negligence merely because of the parent-child relationship.

  • Employers may also be liable under the common law principle represented in the Latin phrase, (one who acts through another acts in one’s own interests).

  • This requirement means that whether a repossession is performed by the lienholder or by an agent, the repossessor must not cause a breach of the peace or the lienholder will
    be held responsible.

  • [11][10] Liability of corporations in tort In English law, a corporation can only act through its employees and agents so it is necessary to decide in which circumstances
    the law of agency or vicarious liability will apply to hold the corporation liable in tort for the frauds of its directors or senior officers.

  • If only the employee is sued, then that employee may seek indemnification from the employer if the conduct was within the course and scope of their employment.

  • [5] For an act to be considered within the course of employment, it must either be authorized or be so connected with an authorized act that it can be considered a mode, though
    an improper mode, of performing it.

  • A company secretary routinely enters into contracts in the company’s name and has administrative responsibilities that would give apparent authority to hire cars.

  • Although the employer is liable under respondeat superior for the employee’s conduct, the employee, too, remains jointly liable for the harm caused.

  • That is a parallel concept to vicarious liability and strict liability, in which one person is held liable in criminal law or tort for the acts or omissions of another.

  • As the American Law Institute’s Restatement of the Law of Agency, Third § 7.01 states, An agent is subject to liability to a third party harmed by the agent’s tortious conduct.


Works Cited

[‘1. “Religious Tech. Center v. Netcom On-Line Comm., 907 F. Supp. 1361 (N.D. Cal 1995)”. Google Scholar. Retrieved 6 September 2017. citing 3 Nimmer on Copyrihgt § 12.04(A)(1), at 12-70 (1995)
2. ^ Quill, Eoin (2014). Torts in Ireland. Dublin 12:
Gill & Macmillan. p. 506.
3. ^ Sykes, Alan O. (January 1988). “The Boundaries of Vicarious Liability: An Economic Analysis of the Scope of Employment Rule and Related Legal Doctrines”. Harvard Law Review. 101 (3): 563–609. doi:10.2307/1341141. JSTOR
4. ^ “Vicarious Liability, Report No. 56 | Office of Justice Programs”. www.ojp.gov. Retrieved 2021-08-30.
5. ^ Hollis v Vabu [2001] HCA 44, (2001) 207 CLR 21, High Court (Australia).
6. ^ Deatons Pty Ltd v Flew [1949] HCA 60, (1949)
79 CLR 370, High Court (Australia).
7. ^ Hilton v. Thomas Burton (Rhodes) Ltd. [1961] 1 W.L.R. 705.
8. ^ Abrams, Jim (19 December 2005). “Federal Law Puts Brakes on Vicarious Liability for Auto Rental Firms”. Wells Media Group, Inc. Insurance
Journal. Retrieved 6 September 2017.
9. ^ “MBank El Paso, NA v. Sanchez, 836 SW 2d 151 (1992)”. Google Scholar. Retrieved 6 September 2017.
10. ^ Jump up to:a b Freer, Alice B. (1964). “Parental Libality for the Torts of Children”. Kentucky Law
Journal. 53: 254. Retrieved 6 September 2017.
11. ^ “Parental Liability for Damages Caused by Their Children”. Office of Legislative Research. Connecticut General Assembly. 4 February 2011. Retrieved 6 September 2017.
12. ^ “Vicarious Liability”.
LII / Legal Information Institute. Retrieved 2021-08-30.
13. ^ Peebles, K.A. (2011). “Negligent hiring and the information age: How state legislatures can save employers from inevitable liability”. William & Mary Law Review. 53: 1397. Retrieved
6 September 2017.
14. ^ “Lister v. the Romford Ice and Cold Storage Co. Ltd”. Internet Archive. Retrieved 6 September 2017.
15. ^ Meah, Nafees; Petchey, Philip (January 2005). “Liability of Churches and Religious Organizations for Sexual Abuse
of Children by Ministers of Religion”. Common Law World Review. 34 (1): 39–61. doi:10.1350/clwr. S2CID 144364324.
2. H Laski, ‘Basis of Vicarious Liability’ (1916) 26 Yale Law Journal 105
3. Department of Trade & Industry. Company
Law Review: Attribution of Liability (PDF)
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