7,035 research outputs found
Calculated NMR T_2 relaxation due to vortex vibrations in cuprate superconductors
We calculate the rate of transverse relaxation arising from vortex motion in
the mixed state of YBa_2Cu_3O_7 with the static field applied along the c axis.
The vortex dynamics are described by an overdamped Langevin equation with a
harmonic elastic free energy. We find that the variation of the relaxation with
temperature, average magnetic field, and local field is consistent with
experiments; however, the calculated time dependence is different from what has
been measured and the value of the rates calculated is roughly two orders of
magnitude slower than what is observed. Combined with the strong experimental
evidence pointing to vortex motion as the dominant mechanism for T_2
relaxation, these results call into question a prior conclusion that vortex
motion is not significant in T_1 measurements in the vortex state.Comment: 6 pages, 5 figures, to be published in Phys. Rev.
The dynamic dipole polarizabilities of the Li atom and the Be+ ion
The dynamic dipole polarizabilities for the Li atom and the Be+ ion in the 2s
and 2p states are calculated using the variational method with a Hylleraas
basis. The present polarizabilities represent the definitive values in the
non-relativistic limit. Corrections due to relativistic effects are also
estimated. Analytic representations of the polarizabilities for frequency
ranges encompassing the n=3 excitations are presented. The recommended
polarizabilities for ^7Li and ^9Be+ were 164.11 \pm 0.03 a.u. and 24.489 \pm
0.004 a.u.
Calculations of polarizabilities and hyperpolarizabilities for the Be ion
The polarizabilities and hyperpolarizabilities of the Be ion in the
state and the state are determined. Calculations are performed
using two independent methods: i) variationally determined wave functions using
Hylleraas basis set expansions and ii) single electron calculations utilizing a
frozen-core Hamiltonian. The first few parameters in the long-range interaction
potential between a Be ion and a H, He, or Li atom, and the leading
parameters of the effective potential for the high- Rydberg states of
beryllium were also computed. All the values reported are the results of
calculations close to convergence. Comparisons are made with published results
where available.Comment: 18 pp; added details to Sec. I
Experimental verification of a self-consistent theory of the first-, second-, and third-order (non)linear optical response
We show that a combination of linear absorption spectroscopy, hyper-Rayleigh
scattering, and a theoretical analysis using sum rules to reduce the size of
the parameter space leads to a prediction of the two-photon absorption
cross-section of the dye AF455 that agrees with two-photon absorption
spectroscopy. Our procedure, which demands self-consistency between several
measurement techniques and does not use adjustable parameters, provides a means
for determining transition moments between the dominant excited states based
strictly on experimental characterization. This is made possible by our new
approach that uses sum rules and molecular symmetry to rigorously reduce the
number of required physical quantities.Comment: 10 pages, 9 figure
Dissecting the genetic components of a quantitative trait locus for blood pressure and renal pathology on rat chromosome 3
Background: We have previously confirmed the importance of rat chromosome 3 (RNO3) genetic loci on blood pressure elevation, pulse pressure (PP) variability and renal pathology during salt challenge in the stroke-prone spontaneously hypertensive (SHRSP) rat. The aims of this study were to generate a panel of RNO3 congenic sub-strains to genetically dissect the implicated loci and identify positional candidate genes by microarray expression profiling and analysis of next-generation sequencing data.
Method and results: A panel of congenic sub-strains were generated containing Wistar-Kyoto (WKY)-introgressed segments of varying size on the SHRSP genetic background, focused within the first 50 Mbp of RNO3. Haemodynamic profiling during salt challenge demonstrated significantly reduced systolic blood pressure, diastolic blood pressure and PP variability in SP.WKYGla3a, SP.WKYGla3c, SP.WKYGla3d and SP.WKYGla3e sub-strains. Only SBP and DBP were significantly reduced during salt challenge in SP.WKYGla3b and SP.WKYGla3f sub-strains, whereas SP.WKYGla3g rats did not differ in haemodynamic response to SHRSP. Those sub-strains demonstrating significantly reduced PP variability during salt challenge also demonstrated significantly reduced renal pathology and proteinuria. Microarray expression profiling prioritized two candidate genes for blood pressure regulation (Dnm1, Tor1b), localized within the common congenic interval shared by SP.WKYGla3d and SP.WKYGla3f strains, and one candidate gene for salt-induced PP variability and renal pathology (Rabgap1), located within the region unique to the SP.WKYGla3d strain. Comparison of next-generation sequencing data identified variants within additional positional genes that are likely to affect protein function.
Conclusion: This study has identified distinct intervals on RNO3-containing genes that may be important for blood pressure regulation and renal pathology during salt challenge
Non-Markovian Fermionic Stochastic Schr\"{o}dinger Equation for Open System Dynamics
In this paper we present an exact Grassmann stochastic Schr\"{o}dinger
equation for the dynamics of an open fermionic quantum system coupled to a
reservoir consisting of a finite or infinite number of fermions. We use this
stochastic approach to derive the exact master equation for a fermionic system
strongly coupled to electronic reservoirs. The generality and applicability of
this Grassmann stochastic approach is justified and exemplified by several
quantum open system problems concerning quantum decoherence and quantum
transport for both vacuum and finite-temperature fermionic reservoirs. We show
that the quantum coherence property of the quantum dot system can be profoundly
modified by the environment memory.Comment: 10.5 pages, 3 figure
Simulation studies of a phenomenological model for elongated virus capsid formation
We study a phenomenological model in which the simulated packing of hard,
attractive spheres on a prolate spheroid surface with convexity constraints
produces structures identical to those of prolate virus capsid structures. Our
simulation approach combines the traditional Monte Carlo method with a modified
method of random sampling on an ellipsoidal surface and a convex hull searching
algorithm. Using this approach we identify the minimum physical requirements
for non-icosahedral, elongated virus capsids, such as two aberrant flock house
virus (FHV) particles and the prolate prohead of bacteriophage , and
discuss the implication of our simulation results in the context of recent
experimental findings. Our predicted structures may also be experimentally
realized by evaporation-driven assembly of colloidal spheres
Non-Markovian Quantum Trajectories of Many-Body Quantum Open Systems
A long-standing open problem in non-Markovian quantum state diffusion (QSD)
approach to open quantum systems is to establish the non-Markovian QSD
equations for multiple qubit systems. In this paper, we settle this important
question by explicitly constructing a set of exact time-local QSD equations for
-qubit systems. Our exact time-local (convolutionless) QSD equations have
paved the way towards simulating quantum dynamics of many-body open systems
interacting with a common bosonic environment. The applicability of this
multiple-qubit stochastic equation is exemplified by numerically solving
several quantum open many-body systems concerning quantum coherence dynamics
and dynamical control.Comment: 8 pages, 2 figures. manuscript revised and reference update
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Distinctive Structural and Molecular Features of Myelinated Inhibitory Axons in Human Neocortex.
Numerous types of inhibitory neurons sculpt the performance of human neocortical circuits, with each type exhibiting a constellation of subcellular phenotypic features in support of its specialized functions. Axonal myelination has been absent among the characteristics used to distinguish inhibitory neuron types; in fact, very little is known about myelinated inhibitory axons in human neocortex. Here, using array tomography to analyze samples of neurosurgically excised human neocortex, we show that inhibitory myelinated axons originate predominantly from parvalbumin-containing interneurons. Compared to myelinated excitatory axons, they have higher neurofilament and lower microtubule content, shorter nodes of Ranvier, and more myelin basic protein (MBP) in their myelin sheath. Furthermore, these inhibitory axons have more mitochondria, likely to sustain the high energy demands of parvalbumin interneurons, as well as more 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP), a protein enriched in the myelin cytoplasmic channels that are thought to facilitate the delivery of nutrients from ensheathing oligodendrocytes. Our results demonstrate that myelinated axons of parvalbumin inhibitory interneurons exhibit distinctive features that may support the specialized functions of this neuron type in human neocortical circuits
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