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Search Results: 1 - 10 of 299002 matches for " J. Cooper "
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Collinear Points in Permutations
J. Cooper,J. Solymosi
Mathematics , 2004,
Abstract: Consider the following problem: how many collinear triples of points must a transversal of (Z/nZ)^2 have? This question is connected with venerable issues in discrete geometry. We show that the answer, for n prime, is between (n-1)/4 and (n-1)/2, and consider an analogous question for collinear quadruples. We conjecture that the upper bound is the truth and suggest several other interesting problems in this area.
Quantitative Analysis of Neurotransmitter Pathways Under Steady State Conditions – A Perspective
Arthur J. L. Cooper
Frontiers in Endocrinology , 2013, DOI: 10.3389/fendo.2013.00179
Abstract: In a contribution to this Research Topic Erkki Somersalo and Daniela Calvetti carried out a mathematical analysis of neurotransmitter pathways in brain, modeling compartmental nitrogen flux among several major participants – ammonia, glutamine, glutamate, GABA, and selected amino acids. This analysis is important because cerebral nitrogen metabolism is perturbed in many diseases, including liver disease and inborn errors of the urea cycle. These diseases result in an elevation of blood ammonia, which is neurotoxic. Here, a brief description is provided of the discovery of cerebral metabolic compartmentation of nitrogen metabolism – a key feature of cerebral glutamate–glutamine and GABA–glutamine cycles. The work of Somersalo and Calvetti is discussed as a model for future studies of normal and pathological cerebral ammonia metabolism.
On the possibility that STS "gap-maps" of cuprate single crystals are dominated by k-space anisotropy and not by nano-scale inhomogeneity
J. R. Cooper
Physics , 2007,
Abstract: The results of a computer analysis of a simple 2D quantum mechanical tunnelling model are reported. These suggest that the spatial dependence of the superconducting energy gap observed by Scanning Tunnelling Spectroscopy (STS) studies of single crystals of the high Tc superconductor Bi:2212 is not necessarily caused by nanoscale inhomogeneity. Instead the spatial dependence of the STS data could arise from the momentum (k) dependence of the energy gap, which is a defining feature of a d-wave superconductor. It is possible that this viewpoint could be exploited to obtain k-dependent information from STS studies.
Thermodynamical identities---a systematic approach
J. B. Cooper
Physics , 2011,
Abstract: We present a systematic approach to thermodynamical identities and illustrate the power of these methods by displaying Mathematica notebooks to deal with a large variety of such identities. In concrete examples these can involve rather tedious, not to way impossible, computations when done by hand.
An Empirical Pair-breaking Picture for the Non-linear Meissner Effect in d-wave Superconductors
J. R. Cooper
Physics , 2000,
Abstract: A empirical model is proposed for the observed variation of the London penetration depth of cuprate superconductors with applied magnetic field $H$ below the lower critical field H_c1. It is suggested that the Doppler shift of the quasi-particle energies near the d-wave nodes could cause pair-breaking and that this could be responsible for the non-linear Meissner effect (NLME) investigated in recent experiments. This picture gives a somewhat better description of the observed temperature and field dependencies than the original theory proposed by Yip and Sauls. A calculation based on weak-coupling BCS theory suggests that when there is a finite supercurrent, the state for which pairs are broken in a small angular range around the nodes can have a lower free energy than the d_x^2-y^2 state.
Records and Flower Preferences of Masarid Wasps (Hymenoptera: Vespidae)
Kenneth W. Cooper,J. Bequaert
Psyche , 1950, DOI: 10.1155/1950/38980
Abstract:
On the Mathematics of Thermodynamics
J. B. Cooper,T. Russell
Physics , 2011,
Abstract: We show that the mathematical structure of Gibbsian thermodynamics flows from the following simple elements: the state space of a thermodynamical substance is a measure space together with two orderings (corresponding to "warmer than" and "adiabatically accessible from") which satisfy certain plausible physical axioms and an area condition which was introduced by Paul Samuelson. We show how the basic identities of thermodynamics, in particular the Maxwell relations, follow and so the existence of energy, free energy, enthalpy and the Gibbs potential function. We also discuss some questions which we have not found dealt with in the literature, such as the amount of information required to reconstruct the equations of state of a substance and a systematic approach to thermodynamical identities.
Single particle nonlocality with completely independent reference states
J. J. Cooper,J. A. Dunningham
Physics , 2008, DOI: 10.1088/1367-2630/10/11/113024
Abstract: We describe a scheme to demonstrate the nonlocal properties of a single particle by showing a violation of Bell's inequality. The scheme is experimentally achievable as the only inputs are number states and mixed states, which serve as references to `keep track of the experiment'. These reference states are created completely independently of one another and correlated only after all the measurement results have been recorded. This means that any observed nonlocality must solely be due to the single particle state. All the techniques used are equally applicable to massive particles as to photons and as such this scheme could be used to show the nonlocality of atoms.
Application of infrared remote sensing to constrain in-situ estimates of ice crystal particle size during SPartICus
S. J. Cooper ,T. J. Garrett
Atmospheric Measurement Techniques (AMT) & Discussions (AMTD) , 2011,
Abstract: In a prior paper (Cooper and Garrett, 2010), an infrared remote sensing technique was developed that quantifies the effective radius re of ice crystals in cirrus clouds. By accounting for a broad range of expected inversion uncertainties, this retrieval scheme isolates those radiometric signatures that can only occur if the cirrus has nominally "small" values of re below 20 μm. The method is applicable only for specific cloud and atmospheric conditions. However, it can be particularly useful in constraining in-situ estimates of cirrus cloud re obtained from aircraft. Recent studies suggest that airborne measurements may be compromised by the shattering of ice crystals on airborne instrument inlets, so robust, independent confirmation of these measurements is needed. Here, we expand the Cooper and Garrett (2010) retrieval scheme to identify ice clouds that are likely to have "large" values of re greater than 20 μm. Using MODIS observations, we then compare assessments of cirrus cloud re with in-situ measurements obtained during three test cases from the 2010 SPartICus campaign. In general, there is good agreement between retrievals and in-situ measurements for a "small" and "large" crystal case. For a more ambiguously "small" re case, the 2D-S cloud probe indicates values of re that are slightly larger than expected from infrared retrievals, possibly indicating a slight bias in the 2D-S results towards large particles. For our test cases, there is no evidence to suggest that an FSSP-100 with unmodified inlets produces measurements of re in cirrus that are strongly biased low.
Application of infrared remote sensing to constrain in-situ estimates of ice crystal particle size during SPartICus
S. J. Cooper,T. J. Garrett
Atmospheric Measurement Techniques Discussions , 2011, DOI: 10.5194/amtd-4-3055-2011
Abstract: In a prior paper (Cooper and Garrett, 2010), an infrared remote sensing technique was developed that quantifies the effective radius re of ice crystals in cirrus clouds. By accounting for a broad range of expected inversion uncertainties, this retrieval scheme isolates those radiometric signatures that can only occur if the cirrus has nominally "small" values of re below 20 μm. The method is applicable only for specific cloud and atmospheric conditions. However, it can be particularly useful in constraining in-situ estimates of cirrus cloud re obtained from aircraft. Recent studies suggest that airborne measurements may be compromised by the shattering of ice crystals on airborne instrument inlets, so robust, independent confirmation of these measurements is needed. Here, we expand the Cooper and Garrett (2010) retrieval scheme to identify ice clouds that are likely to have "large" values of re greater than 20 μm. Using MODIS observations, we then compare assessments of cirrus cloud re with in-situ measurements obtained during three test cases from the 2010 SpartICus campaign. In general, there is good agreement between retrievals and in-situ measurements for a "small" and "large" crystal case. For a more ambiguously "small" re case, the 2D-S cloud probe indicates values of re that are slightly larger than expected from infrared retrievals, possibly indicating a slight bias in the 2D-S results towards large particles. There is no evidence to support that an FSSP-100 with unmodified inlets produces measurements of re in cirrus that are strongly biased low, as has been claimed.
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