Neil Tennant
- Published in print:
- 2012
- Published Online:
- September 2012
- ISBN:
- 9780199655755
- eISBN:
- 9780191742125
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199655755.001.0001
- Subject:
- Philosophy, Logic/Philosophy of Mathematics, Metaphysics/Epistemology
This account of rational belief revision explains how a rational agent ought to proceed when adopting a new belief — a difficult matter if the new belief contradicts the agent’s old beliefs. Belief ...
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This account of rational belief revision explains how a rational agent ought to proceed when adopting a new belief — a difficult matter if the new belief contradicts the agent’s old beliefs. Belief systems are modeled as finite dependency networks. So one can attend not only to what the agent believes, but also to the variety of reasons the agent has for so believing. The computational complexity of the revision problem is characterized. Algorithms for belief revision are formulated, and implemented in Prolog. The implementation tests well on a range of simple belief‐revision problems that pose a variety of challenges for any account of belief‐revision. The notion of ‘minimal mutilation’ of a belief system is explicated precisely. The proposed revision methods are invariant across different global justificatory structures (foundationalist, coherentist, etc.). They respect the intuition that, when revising one's beliefs, one should not hold on to any belief that has lost all its former justifications. The limitation to finite dependency networks is shown not to compromise theoretical generality. This account affords a novel way to argue that there is an inviolable core of logical principles. These principles, which form the system of Core Logic, cannot be given up, on pain of not being able to carry out the reasoning involved in rationally revising beliefs. The book ends by comparing and contrasting the new account with some major representatives of earlier alternative approaches, from the fields of formal epistemology, artificial intelligence and mathematical logic.Less
This account of rational belief revision explains how a rational agent ought to proceed when adopting a new belief — a difficult matter if the new belief contradicts the agent’s old beliefs. Belief systems are modeled as finite dependency networks. So one can attend not only to what the agent believes, but also to the variety of reasons the agent has for so believing. The computational complexity of the revision problem is characterized. Algorithms for belief revision are formulated, and implemented in Prolog. The implementation tests well on a range of simple belief‐revision problems that pose a variety of challenges for any account of belief‐revision. The notion of ‘minimal mutilation’ of a belief system is explicated precisely. The proposed revision methods are invariant across different global justificatory structures (foundationalist, coherentist, etc.). They respect the intuition that, when revising one's beliefs, one should not hold on to any belief that has lost all its former justifications. The limitation to finite dependency networks is shown not to compromise theoretical generality. This account affords a novel way to argue that there is an inviolable core of logical principles. These principles, which form the system of Core Logic, cannot be given up, on pain of not being able to carry out the reasoning involved in rationally revising beliefs. The book ends by comparing and contrasting the new account with some major representatives of earlier alternative approaches, from the fields of formal epistemology, artificial intelligence and mathematical logic.
Louis A. Girifalco
- Published in print:
- 2007
- Published Online:
- January 2008
- ISBN:
- 9780199228966
- eISBN:
- 9780191711183
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199228966.003.0013
- Subject:
- Physics, History of Physics
The results of the special theory of relativity are so peculiar that a huge number of experiments have been done to check its validity. The contraction of space, the slowing down of time, and the ...
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The results of the special theory of relativity are so peculiar that a huge number of experiments have been done to check its validity. The contraction of space, the slowing down of time, and the equivalence of mass and energy had to be experimentally verified before they could be accepted; and they were. Electron-positron annihilation, accelerator experiments, muon decay measurements, and a host of other experiments were performed. All verified special relativity and none contradicted it.Less
The results of the special theory of relativity are so peculiar that a huge number of experiments have been done to check its validity. The contraction of space, the slowing down of time, and the equivalence of mass and energy had to be experimentally verified before they could be accepted; and they were. Electron-positron annihilation, accelerator experiments, muon decay measurements, and a host of other experiments were performed. All verified special relativity and none contradicted it.
Isaac Levi
- Published in print:
- 2004
- Published Online:
- January 2005
- ISBN:
- 9780199270705
- eISBN:
- 9780191601774
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0199270708.001.0001
- Subject:
- Philosophy, Metaphysics/Epistemology
This book is a continuation of Isaac Levi’s work on formal epistemology, focusing on the problem of contraction. It argues that the problem of how to contract is essential both to an account of ...
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This book is a continuation of Isaac Levi’s work on formal epistemology, focusing on the problem of contraction. It argues that the problem of how to contract is essential both to an account of justified or legitimate belief change, and to modal judgment conditional on a supposition. It presents a formal characterization of mild contraction, which is similar to what Pagnucco and Rott called “severe withdrawal”. This difference in terminology reflects a difference in philosophical perspective that is explained by the author.Less
This book is a continuation of Isaac Levi’s work on formal epistemology, focusing on the problem of contraction. It argues that the problem of how to contract is essential both to an account of justified or legitimate belief change, and to modal judgment conditional on a supposition. It presents a formal characterization of mild contraction, which is similar to what Pagnucco and Rott called “severe withdrawal”. This difference in terminology reflects a difference in philosophical perspective that is explained by the author.
Brendan O'Leary
- Published in print:
- 2001
- Published Online:
- November 2003
- ISBN:
- 9780199244904
- eISBN:
- 9780191600050
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0199244901.003.0002
- Subject:
- Political Science, Comparative Politics
Brandan O’Leary sets up a framework for a broad theory of right‐sizing the state. He addresses the distinctiveness of modern state borders, the centrality of nationality and ethnicity that makes ...
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Brandan O’Leary sets up a framework for a broad theory of right‐sizing the state. He addresses the distinctiveness of modern state borders, the centrality of nationality and ethnicity that makes public officials concerned with ‘right‐peopling’ their states, and territorial expansion, maintenance and contraction, which oblige public officials to consider ‘right‐sizing’. His theory builds on Ernest Gellner's theory of nationalism and Ian Lustick's theory of state expansion and contraction. The author also classifies different strategies of eliminating and managing ethnic differences and existing borders.Less
Brandan O’Leary sets up a framework for a broad theory of right‐sizing the state. He addresses the distinctiveness of modern state borders, the centrality of nationality and ethnicity that makes public officials concerned with ‘right‐peopling’ their states, and territorial expansion, maintenance and contraction, which oblige public officials to consider ‘right‐sizing’. His theory builds on Ernest Gellner's theory of nationalism and Ian Lustick's theory of state expansion and contraction. The author also classifies different strategies of eliminating and managing ethnic differences and existing borders.
Haruo Sugi (ed.)
- Published in print:
- 1998
- Published Online:
- March 2012
- ISBN:
- 9780198523970
- eISBN:
- 9780191724480
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198523970.001.0001
- Subject:
- Neuroscience, Techniques
Despite extensive physiological, biochemical, and structural studies, the mechanisms of muscle contraction operating in living muscle fibres are still not clearly understood. This book aims to ...
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Despite extensive physiological, biochemical, and structural studies, the mechanisms of muscle contraction operating in living muscle fibres are still not clearly understood. This book aims to describe and assess various experimental methods currently used in the field of muscle research. For each method discussed, there is a comprehensive description of its advantages, problems, and limitations. Each chapter also contains a summary of the central results that have been obtained using each method.Less
Despite extensive physiological, biochemical, and structural studies, the mechanisms of muscle contraction operating in living muscle fibres are still not clearly understood. This book aims to describe and assess various experimental methods currently used in the field of muscle research. For each method discussed, there is a comprehensive description of its advantages, problems, and limitations. Each chapter also contains a summary of the central results that have been obtained using each method.
Torstein Theodor Tollefsen
- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780199237142
- eISBN:
- 9780191717321
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199237142.003.0003
- Subject:
- Religion, Early Christian Studies
The Logos is the centre of all the logoi, i.e. the divine acts of will that are eternally conceived but expressed at the moment of creation. Through the logoi a well-ordered cosmos is instituted. The ...
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The Logos is the centre of all the logoi, i.e. the divine acts of will that are eternally conceived but expressed at the moment of creation. Through the logoi a well-ordered cosmos is instituted. The logoi are the principles behind procession (creation) and convertion, and behind the metaphysical structure that Maximus calls expansion and contraction. The chapter ends with a discussion of the ontological structure of created being, especially of rational nature, i.e. man.Less
The Logos is the centre of all the logoi, i.e. the divine acts of will that are eternally conceived but expressed at the moment of creation. Through the logoi a well-ordered cosmos is instituted. The logoi are the principles behind procession (creation) and convertion, and behind the metaphysical structure that Maximus calls expansion and contraction. The chapter ends with a discussion of the ontological structure of created being, especially of rational nature, i.e. man.
Alessio Corti
- Published in print:
- 2007
- Published Online:
- September 2007
- ISBN:
- 9780198570615
- eISBN:
- 9780191717703
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198570615.003.0001
- Subject:
- Mathematics, Geometry / Topology
This introductory chapter provides a detailed sketch of the key ideas of the proof of existence of klt flips in dimension n assuming minimal model programs in dimension n-1, following the work of ...
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This introductory chapter provides a detailed sketch of the key ideas of the proof of existence of klt flips in dimension n assuming minimal model programs in dimension n-1, following the work of Shokurov and Hacon and McKernan. A summary of each chapter of the book is included.Less
This introductory chapter provides a detailed sketch of the key ideas of the proof of existence of klt flips in dimension n assuming minimal model programs in dimension n-1, following the work of Shokurov and Hacon and McKernan. A summary of each chapter of the book is included.
Richard Sorabji
- Published in print:
- 2002
- Published Online:
- May 2007
- ISBN:
- 9780199256600
- eISBN:
- 9780191712609
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199256600.003.0003
- Subject:
- Philosophy, General
Chrysippus (Stoic, 3rd century BCE) gives an intellectualist account of emotions: they are value judgements stating that the situation is good or bad, and that it is appropriate to react accordingly. ...
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Chrysippus (Stoic, 3rd century BCE) gives an intellectualist account of emotions: they are value judgements stating that the situation is good or bad, and that it is appropriate to react accordingly. In appetite and fear, pursuit and avoidance, in pleasure and distress, a felt expansion or sinking (contraction) of soul are judged appropriate. All other emotions fall under these four generic emotions. Shocks to soul (e.g., expansion and sinking) and to body are not part of the emotion, but only necessary accompaniments. The judgements are not involuntary appearances, but voluntary assents to how things appear. Most should be reconsidered, as mistaken, assent withheld, and the emotion thus eradicated. This leaves motivation intact, since we can keep both good emotions which involve no mistake (eupatheiai), and unemotional judgements (eklogai) about what is natural and preferable, though it falls short of being good. Preferable things can be desired ‘with reservation’.Less
Chrysippus (Stoic, 3rd century BCE) gives an intellectualist account of emotions: they are value judgements stating that the situation is good or bad, and that it is appropriate to react accordingly. In appetite and fear, pursuit and avoidance, in pleasure and distress, a felt expansion or sinking (contraction) of soul are judged appropriate. All other emotions fall under these four generic emotions. Shocks to soul (e.g., expansion and sinking) and to body are not part of the emotion, but only necessary accompaniments. The judgements are not involuntary appearances, but voluntary assents to how things appear. Most should be reconsidered, as mistaken, assent withheld, and the emotion thus eradicated. This leaves motivation intact, since we can keep both good emotions which involve no mistake (eupatheiai), and unemotional judgements (eklogai) about what is natural and preferable, though it falls short of being good. Preferable things can be desired ‘with reservation’.
Richard Sorabji
- Published in print:
- 2002
- Published Online:
- May 2007
- ISBN:
- 9780199256600
- eISBN:
- 9780191712609
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199256600.003.0005
- Subject:
- Philosophy, General
First movements of the soul for the Stoic materialists include bites, which are small contractions of the physical soul sensed in distress. First movements of the body include pallor, tears, and ...
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First movements of the soul for the Stoic materialists include bites, which are small contractions of the physical soul sensed in distress. First movements of the body include pallor, tears, and sexual irritation. All are involuntary shocks unlike the judgements which constitute emotion, and emotional therapy should ignore them as unimportant. First movements are first clearly described by Cicero, bites by Galen. For Seneca (1st century CE), Posidonius' revision of Stoicism around 100 BCE was wrong to say that emotion can occur without the relevant judgements in the case of animals, of disowned judgements, and of emotion changed by wordless music. In all three cases we have not emotion, but only first movements.Less
First movements of the soul for the Stoic materialists include bites, which are small contractions of the physical soul sensed in distress. First movements of the body include pallor, tears, and sexual irritation. All are involuntary shocks unlike the judgements which constitute emotion, and emotional therapy should ignore them as unimportant. First movements are first clearly described by Cicero, bites by Galen. For Seneca (1st century CE), Posidonius' revision of Stoicism around 100 BCE was wrong to say that emotion can occur without the relevant judgements in the case of animals, of disowned judgements, and of emotion changed by wordless music. In all three cases we have not emotion, but only first movements.
Richard Sorabji
- Published in print:
- 2002
- Published Online:
- May 2007
- ISBN:
- 9780199256600
- eISBN:
- 9780191712609
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199256600.003.0008
- Subject:
- Philosophy, General
For Posidonius, the value judgements proposed by Chrysippus are not sufficient for emotion because they can remain intact while emotion fades through exhaustion, and because emotion requires us also ...
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For Posidonius, the value judgements proposed by Chrysippus are not sufficient for emotion because they can remain intact while emotion fades through exhaustion, and because emotion requires us also to imagine what is judged and to pay attention to it. Posidonius' explanation is that in exhaustion and without imagination, the movements of the irrational capacities are missing. These movements are spatial movements of physical soul, but not yet identified, like Seneca's first movements, with contractions and suchlike. Further, whereas Posidonius' emphasis is that in special cases the movements can be sufficient for emotion, Seneca's emphasis is that first movements need not lead on to emotion at all, because emotion is something of a very different kind, namely judgement.Less
For Posidonius, the value judgements proposed by Chrysippus are not sufficient for emotion because they can remain intact while emotion fades through exhaustion, and because emotion requires us also to imagine what is judged and to pay attention to it. Posidonius' explanation is that in exhaustion and without imagination, the movements of the irrational capacities are missing. These movements are spatial movements of physical soul, but not yet identified, like Seneca's first movements, with contractions and suchlike. Further, whereas Posidonius' emphasis is that in special cases the movements can be sufficient for emotion, Seneca's emphasis is that first movements need not lead on to emotion at all, because emotion is something of a very different kind, namely judgement.
YANG YANG
- Published in print:
- 2007
- Published Online:
- January 2012
- ISBN:
- 9780197264089
- eISBN:
- 9780191734809
- Item type:
- chapter
- Publisher:
- British Academy
- DOI:
- 10.5871/bacad/9780197264089.003.0016
- Subject:
- Political Science, International Relations and Politics
This chapter examines the possibilities for building a science and technology foundation to the EU–China relationship. China and Europe face quite different societal changes in the next twenty years ...
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This chapter examines the possibilities for building a science and technology foundation to the EU–China relationship. China and Europe face quite different societal changes in the next twenty years but, for both, science and technology (S&T) is part of the solution: China must embrace technology in order to deal with the problems of rapid but uneven growth, not least as they contribute to human and environmental insecurity; Europe must embrace technology to deal with weak growth, demographic contraction, and declining productivity. Moreover, many of the dimensions of these problems extend beyond bilateral and multilateral relations to questions of global governance. Therefore, the China–Europe strategic partnership on knowledge-based growth and development will become an important facet of their interaction in the next generation.Less
This chapter examines the possibilities for building a science and technology foundation to the EU–China relationship. China and Europe face quite different societal changes in the next twenty years but, for both, science and technology (S&T) is part of the solution: China must embrace technology in order to deal with the problems of rapid but uneven growth, not least as they contribute to human and environmental insecurity; Europe must embrace technology to deal with weak growth, demographic contraction, and declining productivity. Moreover, many of the dimensions of these problems extend beyond bilateral and multilateral relations to questions of global governance. Therefore, the China–Europe strategic partnership on knowledge-based growth and development will become an important facet of their interaction in the next generation.
S. R. Osmani
- Published in print:
- 1991
- Published Online:
- January 2008
- ISBN:
- 9780198286370
- eISBN:
- 9780191718441
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198286370.003.0010
- Subject:
- Economics and Finance, Development, Growth, and Environmental
Bangladesh has avoided a recurrence of famine since 1974, but this does not imply that there has been improvement in the underlying trend of persistent hunger. This chapter analyses the changes that ...
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Bangladesh has avoided a recurrence of famine since 1974, but this does not imply that there has been improvement in the underlying trend of persistent hunger. This chapter analyses the changes that occurred as well as the tasks ahead, arguing that vulnerability still remains. The prevailing food policies accentuate rather than relieve the problem of endemic hunger, and the relatively successful overall economic growth has not been adequate in eliminating regular undernourishment. For food policies to regulate the process of entitlement contraction, an equitable diffusion of modern agricultural technology and elimination of credit constraints faced by small farmers are suggested.Less
Bangladesh has avoided a recurrence of famine since 1974, but this does not imply that there has been improvement in the underlying trend of persistent hunger. This chapter analyses the changes that occurred as well as the tasks ahead, arguing that vulnerability still remains. The prevailing food policies accentuate rather than relieve the problem of endemic hunger, and the relatively successful overall economic growth has not been adequate in eliminating regular undernourishment. For food policies to regulate the process of entitlement contraction, an equitable diffusion of modern agricultural technology and elimination of credit constraints faced by small farmers are suggested.
D. Gary Miller
- Published in print:
- 2010
- Published Online:
- January 2011
- ISBN:
- 9780199583423
- eISBN:
- 9780191723438
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199583423.003.0010
- Subject:
- Linguistics, Historical Linguistics, Theoretical Linguistics
Words of more than two syllables tend toward moraic balance, while even those are subject to the acceleration processes that yield triplet formation. Triplets tend to shorten to disyllables, which in ...
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Words of more than two syllables tend toward moraic balance, while even those are subject to the acceleration processes that yield triplet formation. Triplets tend to shorten to disyllables, which in Ancient Greek, where all disyllables are stable, acquire duple timing when not inhibited by semantic or morphological considerations. This mora‐preference hierarchy is applied to the solution of problems in sound change, particularly in Latin, Greek, and Germanic. Stressed open syllable lengthening can be ranked higher than disyllabism. Different rankings follow from the instability engendered by competing processes. This unified account sheds light on problems as diverse as word localization in poetry, syncope, iambic shortening, monosyllabic lengthening, trisyllabic contraction, and even some consonantal changes, such as assibilation in Ancient Greek, Hittite, and Finnish. Finally, implications are adduced for optimality of the trochaic foot.Less
Words of more than two syllables tend toward moraic balance, while even those are subject to the acceleration processes that yield triplet formation. Triplets tend to shorten to disyllables, which in Ancient Greek, where all disyllables are stable, acquire duple timing when not inhibited by semantic or morphological considerations. This mora‐preference hierarchy is applied to the solution of problems in sound change, particularly in Latin, Greek, and Germanic. Stressed open syllable lengthening can be ranked higher than disyllabism. Different rankings follow from the instability engendered by competing processes. This unified account sheds light on problems as diverse as word localization in poetry, syncope, iambic shortening, monosyllabic lengthening, trisyllabic contraction, and even some consonantal changes, such as assibilation in Ancient Greek, Hittite, and Finnish. Finally, implications are adduced for optimality of the trochaic foot.
Daniel Kernell
- Published in print:
- 2006
- Published Online:
- September 2009
- ISBN:
- 9780198526551
- eISBN:
- 9780191723896
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198526551.003.0002
- Subject:
- Neuroscience, Molecular and Cellular Systems
This is a tutorial chapter, mainly aiming to introduce the neuromuscular system. Treated items include basic aspects of skeletal muscle and peripheral axon physiology, principles of sensory and motor ...
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This is a tutorial chapter, mainly aiming to introduce the neuromuscular system. Treated items include basic aspects of skeletal muscle and peripheral axon physiology, principles of sensory and motor muscle innervation, and (very briefly) some general points concerning motor functions of the central nervous system. For muscles, items include: muscle metabolism, excitation-contraction coupling, and the mechanisms for force generation. For axons, items include: intra-axonal transport processes, membrane properties, and the mechanisms and speed of the axonal conduction of action potentials (spikes). The different motor unit and muscle fibre types of limb muscles are introduced and a brief description is given of electromyographic techniques for recording motor unit activity.Less
This is a tutorial chapter, mainly aiming to introduce the neuromuscular system. Treated items include basic aspects of skeletal muscle and peripheral axon physiology, principles of sensory and motor muscle innervation, and (very briefly) some general points concerning motor functions of the central nervous system. For muscles, items include: muscle metabolism, excitation-contraction coupling, and the mechanisms for force generation. For axons, items include: intra-axonal transport processes, membrane properties, and the mechanisms and speed of the axonal conduction of action potentials (spikes). The different motor unit and muscle fibre types of limb muscles are introduced and a brief description is given of electromyographic techniques for recording motor unit activity.
Daniel Kernell
- Published in print:
- 2006
- Published Online:
- September 2009
- ISBN:
- 9780198526551
- eISBN:
- 9780191723896
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198526551.003.0008
- Subject:
- Neuroscience, Molecular and Cellular Systems
Muscle force may be graded by two mechanisms (often used in parallel): (a) by activating a larger or smaller number of units (recruitment gradation), (b) by changing the spike-frequency for already ...
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Muscle force may be graded by two mechanisms (often used in parallel): (a) by activating a larger or smaller number of units (recruitment gradation), (b) by changing the spike-frequency for already recruited units (rate gradation). Recruitment gradation typically takes place such that, within a given muscle, weak and slow units are more easily activated than stronger and faster ones (size principle). However, task-related modifications of this pattern are also known. The gain of recruitment gradation will be influenced by changes of the intra-pool distribution of synaptic ‘driving’ currents, and the gain of rate gradation might be altered by synaptic modification of neuronal discharge characteristics. Furthermore, the firing characteristics of motoneurone pools will also be influenced by the presence of the recurrent Renshaw inhibition. The force of a maximum voluntary contraction (MVC) may come close to, and for some muscles incidentally attain, the maximum evocable force.Less
Muscle force may be graded by two mechanisms (often used in parallel): (a) by activating a larger or smaller number of units (recruitment gradation), (b) by changing the spike-frequency for already recruited units (rate gradation). Recruitment gradation typically takes place such that, within a given muscle, weak and slow units are more easily activated than stronger and faster ones (size principle). However, task-related modifications of this pattern are also known. The gain of recruitment gradation will be influenced by changes of the intra-pool distribution of synaptic ‘driving’ currents, and the gain of rate gradation might be altered by synaptic modification of neuronal discharge characteristics. Furthermore, the firing characteristics of motoneurone pools will also be influenced by the presence of the recurrent Renshaw inhibition. The force of a maximum voluntary contraction (MVC) may come close to, and for some muscles incidentally attain, the maximum evocable force.
Daniel Kernell
- Published in print:
- 2006
- Published Online:
- September 2009
- ISBN:
- 9780198526551
- eISBN:
- 9780191723896
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198526551.003.0009
- Subject:
- Neuroscience, Molecular and Cellular Systems
The functional properties of neurones, synapses, and muscles often change as a result of preceding use. In the short term (minutes to hours), such changes are typically rather rapidly reversible and ...
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The functional properties of neurones, synapses, and muscles often change as a result of preceding use. In the short term (minutes to hours), such changes are typically rather rapidly reversible and may be expressed as either a net increase (potentiation) or a net depression (fatigue) of input-output relations. For voluntary motor activity, such changes may take place within (e.g., central fatigue) as well as outside (e.g., peripheral fatigue) the central nervous system. In such activity, an increasing degree of muscle and/or central fatigue will be experienced as an increasing sense of effort needed for continued action. In muscle physiology a distinction is made between high- and low-frequency fatigue, and extensive studies have been performed as to the role of energy metabolism, cross-bridge interactions, excitation-contraction coupling and neuromuscular transmission. The various manners in which motoneurone properties are matched to muscle characteristics might help to counteract fatigue-related declines of motor output.Less
The functional properties of neurones, synapses, and muscles often change as a result of preceding use. In the short term (minutes to hours), such changes are typically rather rapidly reversible and may be expressed as either a net increase (potentiation) or a net depression (fatigue) of input-output relations. For voluntary motor activity, such changes may take place within (e.g., central fatigue) as well as outside (e.g., peripheral fatigue) the central nervous system. In such activity, an increasing degree of muscle and/or central fatigue will be experienced as an increasing sense of effort needed for continued action. In muscle physiology a distinction is made between high- and low-frequency fatigue, and extensive studies have been performed as to the role of energy metabolism, cross-bridge interactions, excitation-contraction coupling and neuromuscular transmission. The various manners in which motoneurone properties are matched to muscle characteristics might help to counteract fatigue-related declines of motor output.
Neil Tennant
- Published in print:
- 2012
- Published Online:
- September 2012
- ISBN:
- 9780199655755
- eISBN:
- 9780191742125
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199655755.003.0001
- Subject:
- Philosophy, Logic/Philosophy of Mathematics, Metaphysics/Epistemology
This chapter distinguishes logic as a theory of belief‐statics from our sought account of belief dynamics. The various kinds of belief change are classified. These are: surrendering, adopting or ...
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This chapter distinguishes logic as a theory of belief‐statics from our sought account of belief dynamics. The various kinds of belief change are classified. These are: surrendering, adopting or switching individual beliefs; and thereby contracting, expanding or revising one’s system of beliefs. Our account of the epistemic norms involved is agent-centric. The idealized figure of the logical paragon (as opposed to the completely fictional figure of the ‘logical saint’) is introduced as the guiding model of a rational agent who is thoroughly competent in matters of belief change. The chapter discusses what a theory of belief change needs to characterize or make feasible. Two key constraints are formulated: both minimal mutilation and minimal bloating of systems of belief undergoing contractions and revisions needs to be explicated (and ensured). The explicit goal is to provide a computationally implementable account of belief change. The chapter foreshadows welcome results to be proved about the computational complexity of the contraction problem. It stresses that our account of belief dynamics will be able to cope with differences among different schools, or ‘‐isms’, in epistemology, regarding permissible global patterns of support or justification among beliefs. The chapter includes an important discussion of methodology, invoking the contrast between propositional and first-order logic as a case study, in order to highlight the virtues of simplicity in formal modeling. This chapter promises to be an account of belief change under judiciously chosen simplifying assumptions that nevertheless allow a rich structure to come into focus, and challenging problems to emerge.Less
This chapter distinguishes logic as a theory of belief‐statics from our sought account of belief dynamics. The various kinds of belief change are classified. These are: surrendering, adopting or switching individual beliefs; and thereby contracting, expanding or revising one’s system of beliefs. Our account of the epistemic norms involved is agent-centric. The idealized figure of the logical paragon (as opposed to the completely fictional figure of the ‘logical saint’) is introduced as the guiding model of a rational agent who is thoroughly competent in matters of belief change. The chapter discusses what a theory of belief change needs to characterize or make feasible. Two key constraints are formulated: both minimal mutilation and minimal bloating of systems of belief undergoing contractions and revisions needs to be explicated (and ensured). The explicit goal is to provide a computationally implementable account of belief change. The chapter foreshadows welcome results to be proved about the computational complexity of the contraction problem. It stresses that our account of belief dynamics will be able to cope with differences among different schools, or ‘‐isms’, in epistemology, regarding permissible global patterns of support or justification among beliefs. The chapter includes an important discussion of methodology, invoking the contrast between propositional and first-order logic as a case study, in order to highlight the virtues of simplicity in formal modeling. This chapter promises to be an account of belief change under judiciously chosen simplifying assumptions that nevertheless allow a rich structure to come into focus, and challenging problems to emerge.
Neil Tennant
- Published in print:
- 2012
- Published Online:
- September 2012
- ISBN:
- 9780199655755
- eISBN:
- 9780191742125
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199655755.003.0004
- Subject:
- Philosophy, Logic/Philosophy of Mathematics, Metaphysics/Epistemology
This is the heart of the formal theory. Mathematically rigorous definitions are provided of all the formal notions that have been gently introduced in the earlier discussion. The main data type of a ...
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This is the heart of the formal theory. Mathematically rigorous definitions are provided of all the formal notions that have been gently introduced in the earlier discussion. The main data type of a step is defined, and the central concept of a dependency network is defined in terms of steps. The concept of a minimally mutilating contraction can then be explicated. Interest in the computational complexity of the contraction problem is motivated by thoroughly surveying known results about the (sometimes horrendous) complexities of various other decision problems of a logical nature. This is in order to provide a context within which the complexity results for contraction should strike the reader as both interesting and welcome. The contraction problem is rigorously characterized, including the hard version that involves the (now precisely explicated) desideratum of minimal mutilation. The simplest version of the contraction problem is shown to be NP-complete; the harder version, involving minimal mutilation, is shown to be at just the next level up in the so-called polynomial hierarchyLess
This is the heart of the formal theory. Mathematically rigorous definitions are provided of all the formal notions that have been gently introduced in the earlier discussion. The main data type of a step is defined, and the central concept of a dependency network is defined in terms of steps. The concept of a minimally mutilating contraction can then be explicated. Interest in the computational complexity of the contraction problem is motivated by thoroughly surveying known results about the (sometimes horrendous) complexities of various other decision problems of a logical nature. This is in order to provide a context within which the complexity results for contraction should strike the reader as both interesting and welcome. The contraction problem is rigorously characterized, including the hard version that involves the (now precisely explicated) desideratum of minimal mutilation. The simplest version of the contraction problem is shown to be NP-complete; the harder version, involving minimal mutilation, is shown to be at just the next level up in the so-called polynomial hierarchy
Neil Tennant
- Published in print:
- 2012
- Published Online:
- September 2012
- ISBN:
- 9780199655755
- eISBN:
- 9780191742125
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199655755.003.0005
- Subject:
- Philosophy, Logic/Philosophy of Mathematics, Metaphysics/Epistemology
The chapter explain the concept of a greedy algorithm, and provide four successively less-greedy versions of a contraction algorithm. Here, the earlier work familiarizing the reader with dependency ...
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The chapter explain the concept of a greedy algorithm, and provide four successively less-greedy versions of a contraction algorithm. Here, the earlier work familiarizing the reader with dependency networks and their coloration conventions is key. The chapter discusses further possible sophistications of our approach, which would involve relaxing some of our simplifying assumptions: (i) making use of information about relative entrenchment of beliefs; (ii) being able to give up transitional steps among beliefs, in addition to beliefs themselves; and (iii) weakening the degree of support that the premises of a step afford its conclusion, so that it is probabilistic rather than apodeictic. The fourth version of our algorithm addresses (i).Less
The chapter explain the concept of a greedy algorithm, and provide four successively less-greedy versions of a contraction algorithm. Here, the earlier work familiarizing the reader with dependency networks and their coloration conventions is key. The chapter discusses further possible sophistications of our approach, which would involve relaxing some of our simplifying assumptions: (i) making use of information about relative entrenchment of beliefs; (ii) being able to give up transitional steps among beliefs, in addition to beliefs themselves; and (iii) weakening the degree of support that the premises of a step afford its conclusion, so that it is probabilistic rather than apodeictic. The fourth version of our algorithm addresses (i).
Neil Tennant
- Published in print:
- 2012
- Published Online:
- September 2012
- ISBN:
- 9780199655755
- eISBN:
- 9780191742125
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199655755.003.0006
- Subject:
- Philosophy, Logic/Philosophy of Mathematics, Metaphysics/Epistemology
Here something unusual is done: the chapter states all the details of a Prolog program, for the simplest version of the contraction algorithm. Details of programs are hardly ever disclosed in books ...
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Here something unusual is done: the chapter states all the details of a Prolog program, for the simplest version of the contraction algorithm. Details of programs are hardly ever disclosed in books (or articles) in AI. Usually, the reader has to take on trust authors' claims about what their computer programs have actually accomplished, or how they generally behave on various problem sets, because the authors never reveal any details of the programs they (or their graduate students) might have written. The author of this book composed this Prolog program himself, and it actually works (at lightning speed, one might add) in a beautifully thorough fashion on a wide range of contraction problems in the literature. The various modules of the program are laid out and explained.Less
Here something unusual is done: the chapter states all the details of a Prolog program, for the simplest version of the contraction algorithm. Details of programs are hardly ever disclosed in books (or articles) in AI. Usually, the reader has to take on trust authors' claims about what their computer programs have actually accomplished, or how they generally behave on various problem sets, because the authors never reveal any details of the programs they (or their graduate students) might have written. The author of this book composed this Prolog program himself, and it actually works (at lightning speed, one might add) in a beautifully thorough fashion on a wide range of contraction problems in the literature. The various modules of the program are laid out and explained.
