Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.003.0005
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter discusses the object or objects responsible for gramma-ray bursts (GRBs). Until now, there are few absolute certainties with regard to the progenitors of GRBs. One clear standout is the ...
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This chapter discusses the object or objects responsible for gramma-ray bursts (GRBs). Until now, there are few absolute certainties with regard to the progenitors of GRBs. One clear standout is the progenitors of soft gamma-ray repeaters (SGRs) which are very obviously neutron stars. There are a number of corroborating lines of evidence for this progenitor association: (1) some well-localized SGRs are associated with supernova remnants, suggesting they are byproducts of recent supernovae; (2) there is quiescent X-ray emission from the sites of SGRs, similar to a class of neutron stars called “anomalous X-ray pulsars”; (3) Galactic SGRs tend to be found in the Galactic plane, where most young neutron stars reside; and (4) the ringdown emission after SGR pulses is periodic, with periods comparable to that of slowly rotating neutron stars (few seconds).Less
This chapter discusses the object or objects responsible for gramma-ray bursts (GRBs). Until now, there are few absolute certainties with regard to the progenitors of GRBs. One clear standout is the progenitors of soft gamma-ray repeaters (SGRs) which are very obviously neutron stars. There are a number of corroborating lines of evidence for this progenitor association: (1) some well-localized SGRs are associated with supernova remnants, suggesting they are byproducts of recent supernovae; (2) there is quiescent X-ray emission from the sites of SGRs, similar to a class of neutron stars called “anomalous X-ray pulsars”; (3) Galactic SGRs tend to be found in the Galactic plane, where most young neutron stars reside; and (4) the ringdown emission after SGR pulses is periodic, with periods comparable to that of slowly rotating neutron stars (few seconds).
Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- book
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.001.0001
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
Gamma-ray bursts are the brightest—and, until recently, among the least understood—cosmic events in the universe. Discovered by chance during the Cold War, these evanescent high-energy explosions ...
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Gamma-ray bursts are the brightest—and, until recently, among the least understood—cosmic events in the universe. Discovered by chance during the Cold War, these evanescent high-energy explosions confounded astronomers for decades. But a rapid series of startling breakthroughs beginning in 1997 revealed that the majority of gamma-ray bursts are caused by the explosions of young and massive stars in the vast star-forming cauldrons of distant galaxies. New findings also point to very different origins for some events, serving to complicate but enrich our understanding of the exotic and violent universe. This book is an introduction to this fast-growing subject, written by an astrophysicist who is at the forefront of today's research into these incredible cosmic phenomena. The book gives readers a concise and accessible overview of gamma-ray bursts and the theoretical framework that physicists have developed to make sense of complex observations across the electromagnetic spectrum. The book traces the history of remarkable discoveries that led to our current understanding of gamma-ray bursts, and reveals the decisive role these phenomena could play in the grand pursuits of twenty-first century astrophysics, from studying gravity waves and unveiling the growth of stars and galaxies after the big bang to surmising the ultimate fate of the universe itself. This book is an essential primer to this exciting frontier of scientific inquiry, and a must-read for anyone seeking to keep pace with cutting-edge developments in physics today.Less
Gamma-ray bursts are the brightest—and, until recently, among the least understood—cosmic events in the universe. Discovered by chance during the Cold War, these evanescent high-energy explosions confounded astronomers for decades. But a rapid series of startling breakthroughs beginning in 1997 revealed that the majority of gamma-ray bursts are caused by the explosions of young and massive stars in the vast star-forming cauldrons of distant galaxies. New findings also point to very different origins for some events, serving to complicate but enrich our understanding of the exotic and violent universe. This book is an introduction to this fast-growing subject, written by an astrophysicist who is at the forefront of today's research into these incredible cosmic phenomena. The book gives readers a concise and accessible overview of gamma-ray bursts and the theoretical framework that physicists have developed to make sense of complex observations across the electromagnetic spectrum. The book traces the history of remarkable discoveries that led to our current understanding of gamma-ray bursts, and reveals the decisive role these phenomena could play in the grand pursuits of twenty-first century astrophysics, from studying gravity waves and unveiling the growth of stars and galaxies after the big bang to surmising the ultimate fate of the universe itself. This book is an essential primer to this exciting frontier of scientific inquiry, and a must-read for anyone seeking to keep pace with cutting-edge developments in physics today.
Graham Priest
- Published in print:
- 2005
- Published Online:
- May 2006
- ISBN:
- 9780199263288
- eISBN:
- 9780191603631
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/0199263280.003.0002
- Subject:
- Philosophy, Logic/Philosophy of Mathematics
This chapter analyzes and criticizes the argument of Aristotle in Metaphysics, Book Gamma, against those who would violate the Law of Non-Contradiction, together with what a number of later ...
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This chapter analyzes and criticizes the argument of Aristotle in Metaphysics, Book Gamma, against those who would violate the Law of Non-Contradiction, together with what a number of later commentators have made of them.Less
This chapter analyzes and criticizes the argument of Aristotle in Metaphysics, Book Gamma, against those who would violate the Law of Non-Contradiction, together with what a number of later commentators have made of them.
Roger Traub, MD and Miles Whittington, PhD
- Published in print:
- 2010
- Published Online:
- May 2010
- ISBN:
- 9780195342796
- eISBN:
- 9780199776276
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195342796.001.0001
- Subject:
- Neuroscience, Molecular and Cellular Systems, Development
This book reviews a number of clinical neuropsychiatric conditions in which brain oscillations play an essential role. It discusses how the intrinsic properties of neurons, and the interactions ...
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This book reviews a number of clinical neuropsychiatric conditions in which brain oscillations play an essential role. It discusses how the intrinsic properties of neurons, and the interactions between neurons – mediated by both chemical synapses and by gap junctions – can lead to oscillations in populations of cells. The discussion is based largely on data derived from in vitro systems (hippocampus, cerebral and cerebellar cortex) and from network modeling. Finally, the book considers how brain oscillations can provide insight into normal brain function as well as pathophysiology.Less
This book reviews a number of clinical neuropsychiatric conditions in which brain oscillations play an essential role. It discusses how the intrinsic properties of neurons, and the interactions between neurons – mediated by both chemical synapses and by gap junctions – can lead to oscillations in populations of cells. The discussion is based largely on data derived from in vitro systems (hippocampus, cerebral and cerebellar cortex) and from network modeling. Finally, the book considers how brain oscillations can provide insight into normal brain function as well as pathophysiology.
Roger D. Roger and Miles A. Whittington
- Published in print:
- 2010
- Published Online:
- May 2010
- ISBN:
- 9780195342796
- eISBN:
- 9780199776276
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195342796.003.0001
- Subject:
- Neuroscience, Molecular and Cellular Systems, Development
In a previous monograph, the authors described an experimental model of the 40 Hz oscillations produced in vivo by visual stimulation. The model involved tetanic stimulation of one or two sites in a ...
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In a previous monograph, the authors described an experimental model of the 40 Hz oscillations produced in vivo by visual stimulation. The model involved tetanic stimulation of one or two sites in a hippocampal slice, and was able to produce synchronized oscillations in the presence of axonal conduction delays. The monograph showed how network simulations and in vitro studies complement each other, for example in elucidating the cellular mechanisms by such long-range synchrony could occur. The present monograph continues this type of research, but focuses on additional sorts of oscillations, many of which depend on gap junctions.Less
In a previous monograph, the authors described an experimental model of the 40 Hz oscillations produced in vivo by visual stimulation. The model involved tetanic stimulation of one or two sites in a hippocampal slice, and was able to produce synchronized oscillations in the presence of axonal conduction delays. The monograph showed how network simulations and in vitro studies complement each other, for example in elucidating the cellular mechanisms by such long-range synchrony could occur. The present monograph continues this type of research, but focuses on additional sorts of oscillations, many of which depend on gap junctions.
Roger D. Roger and Miles A. Whittington
- Published in print:
- 2010
- Published Online:
- May 2010
- ISBN:
- 9780195342796
- eISBN:
- 9780199776276
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195342796.003.0006
- Subject:
- Neuroscience, Molecular and Cellular Systems, Development
One factor in schizophrenia may be a decrease in NMDA receptor mediated excitation of interneurons, both acting during brain development and also more acutely. The NMDA receptor antagonist, ketamine, ...
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One factor in schizophrenia may be a decrease in NMDA receptor mediated excitation of interneurons, both acting during brain development and also more acutely. The NMDA receptor antagonist, ketamine, given to normal volunteers, can elicit psychotic symptoms. Ketamine also affects gamma (30 – 70 Hz) and beta oscillations experimentally, in in vitro brain slices. The effects of ketamine, however – whether to enhance or diminish oscillation power, and acting on which frequency range – depend on the brain region in question. There is no pan-cortical phenomenology of oscillations.Less
One factor in schizophrenia may be a decrease in NMDA receptor mediated excitation of interneurons, both acting during brain development and also more acutely. The NMDA receptor antagonist, ketamine, given to normal volunteers, can elicit psychotic symptoms. Ketamine also affects gamma (30 – 70 Hz) and beta oscillations experimentally, in in vitro brain slices. The effects of ketamine, however – whether to enhance or diminish oscillation power, and acting on which frequency range – depend on the brain region in question. There is no pan-cortical phenomenology of oscillations.
Thomas Koshy
- Published in print:
- 2008
- Published Online:
- January 2009
- ISBN:
- 9780195334548
- eISBN:
- 9780199868766
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195334548.003.0005
- Subject:
- Mathematics, Combinatorics / Graph Theory / Discrete Mathematics
This chapter presents Catalan numbers in an interesting, historical perspective, beginning with the well-known triangulation problem. In addition, it develops three recursive formulas for Cn, an ...
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This chapter presents Catalan numbers in an interesting, historical perspective, beginning with the well-known triangulation problem. In addition, it develops three recursive formulas for Cn, an approximate value for Cn, a relationship with the gamma function, and Shapiro's identity. It also shows how the parenthesization and triangulation problems are closely related.Less
This chapter presents Catalan numbers in an interesting, historical perspective, beginning with the well-known triangulation problem. In addition, it develops three recursive formulas for Cn, an approximate value for Cn, a relationship with the gamma function, and Shapiro's identity. It also shows how the parenthesization and triangulation problems are closely related.
Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.003.0001
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This introductory chapter presents the background story on the discovery and research on gamma-ray bursts (GRB). In 1963, Soviet Premier Nikita Khrushchev and U.S. President John F. Kennedy agreed to ...
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This introductory chapter presents the background story on the discovery and research on gamma-ray bursts (GRB). In 1963, Soviet Premier Nikita Khrushchev and U.S. President John F. Kennedy agreed to the Partial Test Ban Treaty. Ratifying nations agreed that all nuclear weapons testing would be conducted underground from then on: no longer would tests be conducted in oceans, in the atmosphere, or in space. The United States, led by a team at the Los Alamos National Laboratory, promptly began the ambitious Vela Satellite Program to test for “non-compliance” with the Treaty. Not long after Los Alamos employee Ray Klebesadel began detecting GRBs. In 1973, Klebesadel and his colleagues Ian Strong and Roy Olson published a paper entitled “Observations of Gamma-Ray Bursts of Cosmic Origin” the Astrophysical Journal, which marked the beginning of the GRB enigma that to this day captivates the imagination and keeps astronomers scratching their heads.Less
This introductory chapter presents the background story on the discovery and research on gamma-ray bursts (GRB). In 1963, Soviet Premier Nikita Khrushchev and U.S. President John F. Kennedy agreed to the Partial Test Ban Treaty. Ratifying nations agreed that all nuclear weapons testing would be conducted underground from then on: no longer would tests be conducted in oceans, in the atmosphere, or in space. The United States, led by a team at the Los Alamos National Laboratory, promptly began the ambitious Vela Satellite Program to test for “non-compliance” with the Treaty. Not long after Los Alamos employee Ray Klebesadel began detecting GRBs. In 1973, Klebesadel and his colleagues Ian Strong and Roy Olson published a paper entitled “Observations of Gamma-Ray Bursts of Cosmic Origin” the Astrophysical Journal, which marked the beginning of the GRB enigma that to this day captivates the imagination and keeps astronomers scratching their heads.
Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.003.0002
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter discusses the definition, emission, and central engine of gamma-ray bursts (GRBs). Before the afterglow era, GRBs were essentially defined by observations of their high-energy emission. ...
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This chapter discusses the definition, emission, and central engine of gamma-ray bursts (GRBs). Before the afterglow era, GRBs were essentially defined by observations of their high-energy emission. The landscape of such observations—the light curves and spectra of the events—exhibits at once great diversity and elements of commonality that bind different events together. GRBs are like fingerprints: no two are alike, but they share common properties. Those common elements provide strong constraints both on the nature of the “engine” that supplies the energy to the event and the physical processes that drive the emission we see. Since the 1990s, GRB monitors in space have observed more than one hundred GRBs. Since 2004, the NASA GRB satellite called Swift has been discovering GRBs at a rate of about two per week.Less
This chapter discusses the definition, emission, and central engine of gamma-ray bursts (GRBs). Before the afterglow era, GRBs were essentially defined by observations of their high-energy emission. The landscape of such observations—the light curves and spectra of the events—exhibits at once great diversity and elements of commonality that bind different events together. GRBs are like fingerprints: no two are alike, but they share common properties. Those common elements provide strong constraints both on the nature of the “engine” that supplies the energy to the event and the physical processes that drive the emission we see. Since the 1990s, GRB monitors in space have observed more than one hundred GRBs. Since 2004, the NASA GRB satellite called Swift has been discovering GRBs at a rate of about two per week.
Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.003.0003
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter focuses on the search for afterglows of gamma-ray bursts (GRBs). In 1996, Peter Mészáros (Pennsylvania State University) and Martin J. Rees (Cambridge University) began developing a ...
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This chapter focuses on the search for afterglows of gamma-ray bursts (GRBs). In 1996, Peter Mészáros (Pennsylvania State University) and Martin J. Rees (Cambridge University) began developing a detailed theory of afterglows, positing that long-lived emission should be observed at all wavelengths—a panchromatic phenomenon—as a natural consequence of synchrotron emission from a decelerating blastwave. Though no convincing afterglow had been found to date, the afterglow revolution beginning the following year would quickly confirm the basic theory. The chapter presents the panchromatic observations of GRB afterglows and then discusses afterglow theory and its significant modifications over the years.Less
This chapter focuses on the search for afterglows of gamma-ray bursts (GRBs). In 1996, Peter Mészáros (Pennsylvania State University) and Martin J. Rees (Cambridge University) began developing a detailed theory of afterglows, positing that long-lived emission should be observed at all wavelengths—a panchromatic phenomenon—as a natural consequence of synchrotron emission from a decelerating blastwave. Though no convincing afterglow had been found to date, the afterglow revolution beginning the following year would quickly confirm the basic theory. The chapter presents the panchromatic observations of GRB afterglows and then discusses afterglow theory and its significant modifications over the years.
Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.003.0004
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
Prompt and afterglow emission of gamma-ray bursts (GRBs) are largely driven by the central engine behavior, the explosion properties, and the physics of relativistic shocks. Those seconds, minutes, ...
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Prompt and afterglow emission of gamma-ray bursts (GRBs) are largely driven by the central engine behavior, the explosion properties, and the physics of relativistic shocks. Those seconds, minutes, and days after the main event tell a remarkable story about how the progenitors of GRBs end their life. But it is the context—where GRBs occur inside and out of galaxies and throughout cosmic time—that tell us how the progenitors lived. Indeed, GRB locations are treated like a crime scene, extracting forensic evidence to make a case about the lifecycle of a GRB progenitor. This chapter discusses local-, galactic-, and universal-scale observations of GRBs.Less
Prompt and afterglow emission of gamma-ray bursts (GRBs) are largely driven by the central engine behavior, the explosion properties, and the physics of relativistic shocks. Those seconds, minutes, and days after the main event tell a remarkable story about how the progenitors of GRBs end their life. But it is the context—where GRBs occur inside and out of galaxies and throughout cosmic time—that tell us how the progenitors lived. Indeed, GRB locations are treated like a crime scene, extracting forensic evidence to make a case about the lifecycle of a GRB progenitor. This chapter discusses local-, galactic-, and universal-scale observations of GRBs.
Joshua S. Bloom
- Published in print:
- 2011
- Published Online:
- October 2017
- ISBN:
- 9780691145570
- eISBN:
- 9781400837007
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691145570.003.0006
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter focuses on how gamma-ray bursts (GRBs) are emerging as unique tools in the study of broad areas of astronomy and physics by virtue of their special properties. The unassailable fact ...
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This chapter focuses on how gamma-ray bursts (GRBs) are emerging as unique tools in the study of broad areas of astronomy and physics by virtue of their special properties. The unassailable fact about GRBs that makes them such great probes is that they are fantastically bright and so can be seen to the farthest reaches of the observable Universe. In parallel with the ongoing study of GRB events and progenitors, new lines of inquiry have burgeoned: using GRBs as unique probes of the Universe in ways that are almost completely divorced from the nature of GRBs themselves. Topics discussed include studies of gas, dust, and galaxies; the history of star formation; measuring reionization and the first objects in the universe; neutrinos, gravitational waves, and cosmic rays; quantum gravity and the expansion of the universe; and the future of GRBs.Less
This chapter focuses on how gamma-ray bursts (GRBs) are emerging as unique tools in the study of broad areas of astronomy and physics by virtue of their special properties. The unassailable fact about GRBs that makes them such great probes is that they are fantastically bright and so can be seen to the farthest reaches of the observable Universe. In parallel with the ongoing study of GRB events and progenitors, new lines of inquiry have burgeoned: using GRBs as unique probes of the Universe in ways that are almost completely divorced from the nature of GRBs themselves. Topics discussed include studies of gas, dust, and galaxies; the history of star formation; measuring reionization and the first objects in the universe; neutrinos, gravitational waves, and cosmic rays; quantum gravity and the expansion of the universe; and the future of GRBs.
Hoby Hetherington
- Published in print:
- 2010
- Published Online:
- January 2011
- ISBN:
- 9780195342765
- eISBN:
- 9780199863617
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195342765.003.0004
- Subject:
- Neuroscience, Disorders of the Nervous System
Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) enable the noninvasive regional assessment of major metabolites in the human brain including: N-acetyl aspartate (NAA), ...
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Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) enable the noninvasive regional assessment of major metabolites in the human brain including: N-acetyl aspartate (NAA), glutamate, gamma amino butyric acid (GABA) and phosphocreatine (PCr). In epilepsy, neuronal impairment and bioenergetic alterations result in decreased levels of NAA and PCr in both the primary focus and networks involved in seizure propagation. The alterations in NAA and PCr are not due solely to neuronal loss, but are correlated with functional decline and hiostologic changes at a cellular level, suggesting a significant role for bioenergetic impairment in the pathophysiology of epilepsy. Alterations in brain GABA levels have been used to titrate and evaluate the effectiveness of antiepileptic medications targeting the GABAergic system.Less
Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) enable the noninvasive regional assessment of major metabolites in the human brain including: N-acetyl aspartate (NAA), glutamate, gamma amino butyric acid (GABA) and phosphocreatine (PCr). In epilepsy, neuronal impairment and bioenergetic alterations result in decreased levels of NAA and PCr in both the primary focus and networks involved in seizure propagation. The alterations in NAA and PCr are not due solely to neuronal loss, but are correlated with functional decline and hiostologic changes at a cellular level, suggesting a significant role for bioenergetic impairment in the pathophysiology of epilepsy. Alterations in brain GABA levels have been used to titrate and evaluate the effectiveness of antiepileptic medications targeting the GABAergic system.
Gary L. Wenk
- Published in print:
- 2010
- Published Online:
- September 2010
- ISBN:
- 9780195388541
- eISBN:
- 9780199863587
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195388541.003.0006
- Subject:
- Neuroscience, Behavioral Neuroscience, Neuroendocrine and Autonomic
Glutamate is an amino acid that your brain uses as a neurotransmitter and it is almost always is excitatory. GABA is also an amino acid that your brain uses as a neurotransmitter and it is almost ...
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Glutamate is an amino acid that your brain uses as a neurotransmitter and it is almost always is excitatory. GABA is also an amino acid that your brain uses as a neurotransmitter and it is almost always inhibitory. These two neurotransmitters are widespread in your brain and tend to compete for turning your neurons on or off. Glutamate makes and breaks connections between neurons; this action allows your brain to learn. For example, if you consume a chemical that blocks the actions of glutamate you become amnestic, unable to remember anything new. The street drugs PCP and ketamine block glutamate receptors and depress the activity of your brain. Your brain makes its own PCP-like neurotransmitter called angeldustin. Chemicals that enhance the action of GABA, such as alcohol, barbiturates, or any of the popular drugs related to Valium and Librium, can make us sleepy, send us into a coma, or kill us by turning off too many neurons in the brain.Less
Glutamate is an amino acid that your brain uses as a neurotransmitter and it is almost always is excitatory. GABA is also an amino acid that your brain uses as a neurotransmitter and it is almost always inhibitory. These two neurotransmitters are widespread in your brain and tend to compete for turning your neurons on or off. Glutamate makes and breaks connections between neurons; this action allows your brain to learn. For example, if you consume a chemical that blocks the actions of glutamate you become amnestic, unable to remember anything new. The street drugs PCP and ketamine block glutamate receptors and depress the activity of your brain. Your brain makes its own PCP-like neurotransmitter called angeldustin. Chemicals that enhance the action of GABA, such as alcohol, barbiturates, or any of the popular drugs related to Valium and Librium, can make us sleepy, send us into a coma, or kill us by turning off too many neurons in the brain.
R. A. H. Neave and A. J. N. W. Prag
- Published in print:
- 2005
- Published Online:
- January 2012
- ISBN:
- 9780197262962
- eISBN:
- 9780191734533
- Item type:
- chapter
- Publisher:
- British Academy
- DOI:
- 10.5871/bacad/9780197262962.003.0015
- Subject:
- Archaeology, Archaeological Methodology and Techniques
This chapter discusses the role of the skull in forming the face and in identifying individuality, particularly in reconstructing ancient faces that bear semblance to the dead. Skulls serve as the ...
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This chapter discusses the role of the skull in forming the face and in identifying individuality, particularly in reconstructing ancient faces that bear semblance to the dead. Skulls serve as the armature of the face, where tissue, muscles and the skin are attached to form a distinct face. Whereas a surgeon removes layers of skin and tissue to reveal the skull, a medical artist builds each muscle in the skull by using well-established statistics for the flesh thickness and adds layers of clay for the skin. In general, the reconstruction of the face involves the use of a plaster cast replica of the skull. In such replicas, pegs are inserted to the cast to mark the thickness of the skull. In the whole process of face reconstruction, the skull, the medical and the pathological evidence provided by the skull and the post cranial skeleton dictate the formation of the face. In instances when the skull is absent or inaccessible, portraits found on the coffins are vital for reconstruction. While face reconstruction may seem simple, the process of reconstructing faces is a difficult task. Reconstruction of the face requires painstaking work, and knowledge of pathology, anatomy, dentistry and much more to build a case for history. Nevertheless, the painstaking work of face reconstruction is important in the field of forensics and in medical applications. Some of the cases of face reconstruction described in this chapter include the face reconstruction of Phillip II of Macedon, the face reconstruction of the Great Harwood case, the recreation of the faces of the Grave Gamma and the Seianti.Less
This chapter discusses the role of the skull in forming the face and in identifying individuality, particularly in reconstructing ancient faces that bear semblance to the dead. Skulls serve as the armature of the face, where tissue, muscles and the skin are attached to form a distinct face. Whereas a surgeon removes layers of skin and tissue to reveal the skull, a medical artist builds each muscle in the skull by using well-established statistics for the flesh thickness and adds layers of clay for the skin. In general, the reconstruction of the face involves the use of a plaster cast replica of the skull. In such replicas, pegs are inserted to the cast to mark the thickness of the skull. In the whole process of face reconstruction, the skull, the medical and the pathological evidence provided by the skull and the post cranial skeleton dictate the formation of the face. In instances when the skull is absent or inaccessible, portraits found on the coffins are vital for reconstruction. While face reconstruction may seem simple, the process of reconstructing faces is a difficult task. Reconstruction of the face requires painstaking work, and knowledge of pathology, anatomy, dentistry and much more to build a case for history. Nevertheless, the painstaking work of face reconstruction is important in the field of forensics and in medical applications. Some of the cases of face reconstruction described in this chapter include the face reconstruction of Phillip II of Macedon, the face reconstruction of the Great Harwood case, the recreation of the faces of the Grave Gamma and the Seianti.
Daniel Kernell
- Published in print:
- 2006
- Published Online:
- September 2009
- ISBN:
- 9780198526551
- eISBN:
- 9780191723896
- Item type:
- book
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198526551.001.0001
- Subject:
- Neuroscience, Molecular and Cellular Systems
This book presents a summary of knowledge concerning somatic motoneurones, the cells which link the central nervous system to the skeletal muscles. There are two functional kinds of such ...
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This book presents a summary of knowledge concerning somatic motoneurones, the cells which link the central nervous system to the skeletal muscles. There are two functional kinds of such motoneurones: the alpha motoneurones innervating skeletal muscle fibres and the smaller gamma motoneurones which exclusively innervate muscle fibres of complex intramuscular sense organs, the muscle spindles. This book deals primarily with the alpha motoneurones, which together constitute the main output interface of the central nervous system and without which no muscle action is possible. The study of motoneurones is important for general insights as to how neurones work, because the alpha motoneurone is probably the best understood kind of nerve cell so far in neuroscience. Motoneurones of the spinal cord were the first type of central nerve cell to be subjected to detailed physiological measurements, and much is known about how their activity is regulated by synapses from other neurones. For most of the individual neurones within the central nervous system, the precise functional tasks are difficult to define. However, for alpha motoneurones much is known about their short- and long-term interactions with their main targets, the skeletal muscle fibres. Functions of neurones must be analyzed in relation to the response properties of their target cells. Therefore, this book deals with both, summarizing classical as well as recent knowledge concerning motoneurones and their muscle fibres (i.e., motor units).Less
This book presents a summary of knowledge concerning somatic motoneurones, the cells which link the central nervous system to the skeletal muscles. There are two functional kinds of such motoneurones: the alpha motoneurones innervating skeletal muscle fibres and the smaller gamma motoneurones which exclusively innervate muscle fibres of complex intramuscular sense organs, the muscle spindles. This book deals primarily with the alpha motoneurones, which together constitute the main output interface of the central nervous system and without which no muscle action is possible. The study of motoneurones is important for general insights as to how neurones work, because the alpha motoneurone is probably the best understood kind of nerve cell so far in neuroscience. Motoneurones of the spinal cord were the first type of central nerve cell to be subjected to detailed physiological measurements, and much is known about how their activity is regulated by synapses from other neurones. For most of the individual neurones within the central nervous system, the precise functional tasks are difficult to define. However, for alpha motoneurones much is known about their short- and long-term interactions with their main targets, the skeletal muscle fibres. Functions of neurones must be analyzed in relation to the response properties of their target cells. Therefore, this book deals with both, summarizing classical as well as recent knowledge concerning motoneurones and their muscle fibres (i.e., motor units).
Xun Gu
- Published in print:
- 2010
- Published Online:
- January 2011
- ISBN:
- 9780199213269
- eISBN:
- 9780191594762
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199213269.003.0003
- Subject:
- Biology, Biomathematics / Statistics and Data Analysis / Complexity Studies
Many organisms have undergone genome-wide or local chromosome duplication events during their evolution. As a result, many genes are represented as several paralogs in the genome with related but ...
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Many organisms have undergone genome-wide or local chromosome duplication events during their evolution. As a result, many genes are represented as several paralogs in the genome with related but distinct functions (gene families). Since gene duplication is thought to have provided the raw materials for functional innovations, it is desirable to identify amino acid sites that are responsible for functional divergence from the sequence analysis of a gene family. A series of statistical models has been developed, based on the principle that functional divergence between duplicate genes is highly correlated with the change of evolutionary rate after the gene duplication. This chapter discusses these statistical and computational methods. These include the Poisson-gamma model for protein sequence evolution, the Markov chain model for type-I functional divergence, and statistical methods for type-II functional divergence.Less
Many organisms have undergone genome-wide or local chromosome duplication events during their evolution. As a result, many genes are represented as several paralogs in the genome with related but distinct functions (gene families). Since gene duplication is thought to have provided the raw materials for functional innovations, it is desirable to identify amino acid sites that are responsible for functional divergence from the sequence analysis of a gene family. A series of statistical models has been developed, based on the principle that functional divergence between duplicate genes is highly correlated with the change of evolutionary rate after the gene duplication. This chapter discusses these statistical and computational methods. These include the Poisson-gamma model for protein sequence evolution, the Markov chain model for type-I functional divergence, and statistical methods for type-II functional divergence.
Ivan Soltesz
- Published in print:
- 2006
- Published Online:
- May 2009
- ISBN:
- 9780195177015
- eISBN:
- 9780199864713
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195177015.003.0007
- Subject:
- Neuroscience, Neuroendocrine and Autonomic, Techniques
This chapter begins with a discussion of measures of interneural diversity. It then considers how alterations in diversity modulate neuronal functions. It examines the effects of altering diversity ...
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This chapter begins with a discussion of measures of interneural diversity. It then considers how alterations in diversity modulate neuronal functions. It examines the effects of altering diversity in a network model of interneurons on network coherence (i.e., on synchrony of firing). Alpha, beta, and gamma measures of diversity are described. The concept of interneuronal diversity and evolution is briefly considered.Less
This chapter begins with a discussion of measures of interneural diversity. It then considers how alterations in diversity modulate neuronal functions. It examines the effects of altering diversity in a network model of interneurons on network coherence (i.e., on synchrony of firing). Alpha, beta, and gamma measures of diversity are described. The concept of interneuronal diversity and evolution is briefly considered.
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/9780198526551.003.0005
- Subject:
- Neuroscience, Molecular and Cellular Systems
This chapter describes the morphology of individual gamma and (mainly) alpha motoneurones as well as the composition and localization of motoneuronal populations (pools) innervating different muscles ...
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This chapter describes the morphology of individual gamma and (mainly) alpha motoneurones as well as the composition and localization of motoneuronal populations (pools) innervating different muscles and muscle portions. Within the ventral horn of the spinal cord, motoneuronal cell bodies for a given muscle lie within an elongated rostro-caudal ‘column’, and cells of different sizes and properties are generally intermingled. Each motoneurone has several dendrites, typically extending to distances of many cell body diameters in all directions. Reconstructions of dendritic trees are described and the relationships are analyzed between the dimensions of dendrites, sizes of cell bodies, and conduction velocities of motor axons. Furthermore, the possible relationships are discussed between various aspects of motoneuronal cytochemistry, morphological characteristics, and functional properties. Large motoneurones seem to be more vulnerable than smaller ones in various kinds of disease (e.g., poliomyelitis).Less
This chapter describes the morphology of individual gamma and (mainly) alpha motoneurones as well as the composition and localization of motoneuronal populations (pools) innervating different muscles and muscle portions. Within the ventral horn of the spinal cord, motoneuronal cell bodies for a given muscle lie within an elongated rostro-caudal ‘column’, and cells of different sizes and properties are generally intermingled. Each motoneurone has several dendrites, typically extending to distances of many cell body diameters in all directions. Reconstructions of dendritic trees are described and the relationships are analyzed between the dimensions of dendrites, sizes of cell bodies, and conduction velocities of motor axons. Furthermore, the possible relationships are discussed between various aspects of motoneuronal cytochemistry, morphological characteristics, and functional properties. Large motoneurones seem to be more vulnerable than smaller ones in various kinds of disease (e.g., poliomyelitis).
Klaus A. Miczek and Eric W. Fish
- Published in print:
- 2005
- Published Online:
- May 2009
- ISBN:
- 9780195168761
- eISBN:
- 9780199865444
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780195168761.003.0005
- Subject:
- Neuroscience, Behavioral Neuroscience, Neuroendocrine and Autonomic
This chapter summarizes the evidence describing the roles that monoamines—5-hydroxytryptamine (5-HT), norepinephrine (NE), and dopamine (DA)—exert in the mediation of aggressive behavior. Aggression ...
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This chapter summarizes the evidence describing the roles that monoamines—5-hydroxytryptamine (5-HT), norepinephrine (NE), and dopamine (DA)—exert in the mediation of aggressive behavior. Aggression is diverse in its behavioral patterns and functions, and endogenous amines, acids, steroids, and peptides may have different effects on each kind of aggression. The importance of escalated forms of aggression is highlighted in an effort to model the harmful acts of aggression and violence in humans. Monoamines have powerful modulatory effects on aggression, and reciprocally, aggression alters monoamines. It is important to delineate the specific conditions and behaviors—when 5-HT appears to be inhibitory, and when NE and DA are aggression stimulating. The effects of monoamines are likely to be due to their interactions with other neurotransmitters, such as gamma-aminobutyric acid (GABA) and glutamate, and neuropeptides, such as vasopressin and opioids.Less
This chapter summarizes the evidence describing the roles that monoamines—5-hydroxytryptamine (5-HT), norepinephrine (NE), and dopamine (DA)—exert in the mediation of aggressive behavior. Aggression is diverse in its behavioral patterns and functions, and endogenous amines, acids, steroids, and peptides may have different effects on each kind of aggression. The importance of escalated forms of aggression is highlighted in an effort to model the harmful acts of aggression and violence in humans. Monoamines have powerful modulatory effects on aggression, and reciprocally, aggression alters monoamines. It is important to delineate the specific conditions and behaviors—when 5-HT appears to be inhibitory, and when NE and DA are aggression stimulating. The effects of monoamines are likely to be due to their interactions with other neurotransmitters, such as gamma-aminobutyric acid (GABA) and glutamate, and neuropeptides, such as vasopressin and opioids.
