2,099 research outputs found
Quantum critical behavior in the heavy Fermion single crystal Ce(NiPd)Ge
We have performed magnetic susceptibility, specific heat, resistivity, and
inelastic neutron scattering measurements on a single crystal of the heavy
Fermion compound Ce(NiPd)Ge, which is believed to
be close to a quantum critical point (QCP) at T = 0. At lowest
temperature(1.8-3.5 K), the magnetic susceptibility behaves as with m/mole
(0.0025 emu/mole). For 1 K, the specific heat can be fit to the formula
with of order 700 mJ/mole-K.
The resistivity behaves as for temperatures below 2
K. This low temperature behavior for and is in accord
with the SCR theory of Moriya and Takimoto\cite{Moriya}. The inelastic neutron
scattering spectra show a broad peak near 1.5 meV that appears to be
independent of ; we interpret this as Kondo scattering with 17 K. In
addition, the scattering is enhanced near =(1/2, 1/2, 0) with maximum
scattering at = 0.45 meV; we interpret this as scattering from
antiferromagnetic fluctuations near the antiferromagnetic QCP.Comment: to be published in J. Phys: Conference Serie
Towards an Accurate Identification of Pyloric Neuron Activity with VSDi
Voltage-sensitive dye imaging (VSDi) which enables simultaneous optical recording of many neurons in the pyloric circuit of the stomatogastric ganglion is an important technique to supplement electrophysiological recordings. However, utilising the technique to identify pyloric neurons directly is a computationally exacting task that requires the development of sophisticated signal processing procedures to analyse the tri-phasic pyloric patterns generated by these neurons. This paper presents our work towards commissioning such procedures. The results achieved to date are most encouraging
Shadowing in the nuclear photoabsorption above the resonance region
A model based on the hadronic fluctuations of the real photon is developed to
describe the total photonucleon and photonuclear cross sections in the energy
region above the nucleon resonances. The hadronic spectral function of the
photon is derived including the finite width of vector-meson resonances and the
quark-antiquark continuum. The shadowing effect is evaluated considering the
effective interaction of the hadronic component with the bound nucleons within
a Glauber-Gribov multiple scattering theory. The low energy onset of the
shadowing effect is interpreted as a possible signature of a modification of
the hadronic spectral function in the nuclear medium. A decrease of the
-meson mass in nuclei is suggested for a better explanation of the
experimental data.Comment: 8 pages, 7 figure
Photoproduction of mesons in nuclei at GeV energies
In a transport model that combines initial state interactions of the photon
with final state interactions of the produced particles we present a
calculation of inclusive photoproduction of mesons in nuclei in the energy
range from 1 to 7 GeV. We give predictions for the photoproduction cross
sections of pions, etas, kaons, antikaons, and invariant mass
spectra in ^{12}C and ^{208}Pb. The effects of nuclear shadowing and final
state interaction of the produced particles are discussed in detail.Comment: Text added in summary in general reliability of the method,
references updated. Phys. Rev. C (2000) in pres
Good practices for a literature survey are not followed by authors while preparing scientific manuscripts
The number of citations received by authors in scientific journals has become
a major parameter to assess individual researchers and the journals themselves
through the impact factor. A fair assessment therefore requires that the
criteria for selecting references in a given manuscript should be unbiased with
respect to the authors or the journals cited. In this paper, we advocate that
authors should follow two mandatory principles to select papers (later
reflected in the list of references) while studying the literature for a given
research: i) consider similarity of content with the topics investigated, lest
very related work should be reproduced or ignored; ii) perform a systematic
search over the network of citations including seminal or very related papers.
We use formalisms of complex networks for two datasets of papers from the arXiv
repository to show that neither of these two criteria is fulfilled in practice
Digital Signal Processing
Contains research objectives and summary of research on seven research projects.Joint Services Electronics Program (Contract DAAB07-76-C-1400)U. S. Navy - Office of Naval Research (Contract N00014-75-C-0951-NR 049-308)National Science Foundation (Grant ENG71-02319-AO2
Positron-molecule interactions: resonant attachment, annihilation, and bound states
This article presents an overview of current understanding of the interaction
of low-energy positrons with molecules with emphasis on resonances, positron
attachment and annihilation. Annihilation rates measured as a function of
positron energy reveal the presence of vibrational Feshbach resonances (VFR)
for many polyatomic molecules. These resonances lead to strong enhancement of
the annihilation rates. They also provide evidence that positrons bind to many
molecular species. A quantitative theory of VFR-mediated attachment to small
molecules is presented. It is tested successfully for selected molecules (e.g.,
methyl halides and methanol) where all modes couple to the positron continuum.
Combination and overtone resonances are observed and their role is elucidated.
In larger molecules, annihilation rates from VFR far exceed those explicable on
the basis of single-mode resonances. These enhancements increase rapidly with
the number of vibrational degrees of freedom. While the details are as yet
unclear, intramolecular vibrational energy redistribution to states that do not
couple directly to the positron continuum appears to be responsible for these
enhanced annihilation rates. Downshifts of the VFR from the vibrational mode
energies have provided binding energies for thirty species. Their dependence
upon molecular parameters and their relationship to positron-atom and
positron-molecule binding energy calculations are discussed. Feshbach
resonances and positron binding to molecules are compared with the analogous
electron-molecule (negative ion) cases. The relationship of VFR-mediated
annihilation to other phenomena such as Doppler-broadening of the gamma-ray
annihilation spectra, annihilation of thermalized positrons in gases, and
annihilation-induced fragmentation of molecules is discussed.Comment: 50 pages, 40 figure
An aggregating U-Test for a genetic association study of quantitative traits
We propose a novel aggregating U-test for gene-based association analysis. The method considers both rare and common variants. It adaptively searches for potential disease-susceptibility rare variants and collapses them into a single “supervariant.” A forward U-test is then used to assess the joint association of the supervariant and other common variants with quantitative traits. Using 200 simulated replicates from the Genetic Analysis Workshop 17 mini-exome data, we compare the performance of the proposed method with that of a commonly used approach, QuTie. We find that our method has an equivalent or greater power than QuTie to detect nine genes that influence the quantitative trait Q1. This new approach provides a powerful tool for detecting both common and rare variants associated with quantitative traits
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