1,935 research outputs found
Entropy on the von Neumann lattice and its evaluation
Based on the recently introduced averaging procedure in phase space, a new
type of entropy is defined on the von Neumann lattice. This quantity can be
interpreted as a measure of uncertainty associated with simultaneous
measurement of the position and momentum observables in the discrete subset of
the phase space. Evaluating for a class of the coherent states, it is shown
that this entropy takes a stationary value for the ground state, modulo a unit
cell of the lattice in such a class. This value for the ground state depends on
the ratio of the position lattice spacing and the momentum lattice spacing. It
is found that its minimum is realized for the perfect square lattice, i.e.,
absence of squeezing. Numerical evaluation of this minimum gives 1.386....Comment: 14 pages, no figures; J. Phys. A, in pres
The BB Gun: A Harmless Toy or Deadly Weapon? Practical Guidance for Objective Fact Finding in a Criminal Case
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Coping Styles, Quality of Life, and Sexual Trauma in Women Veterans
The purpose of the following study was to evaluate sexual trauma and the effects on women veteran's quality of life ratings and current and past coping strategies. Participants were screened for sexual trauma history and divided into five mutually exclusive categories: 1)childhood sexual trauma, 2)civilian adult sexual trauma, 3)military sexual trauma, 4)multiple sexual trauma, and 5)no sexual trauma. Results of the study were mixed, retaining some hypotheses and rejecting others. Results regarding differences in QOL for the sexual trauma groups were rejected, as none of the QOL analyses were significant. Issues of small effect size for the QOL measure and low power to detect differences are discussed as limitations in the current study. Several significant findings were detected in the coping analyses. As predicted, the no trauma group was found to use significantly more approach coping strategies than the sexual trauma group for the past problem. Additionally, the sexual trauma group used significantly more avoidant coping techniques for past problem than the no trauma group. No between group differences were detected for sexual trauma type, however, several significant differences emerged in the comparisons of the multiple sexual trauma and military sexual trauma group's past coping compared to the no sexual trauma group's coping strategies. For past coping, the no trauma group used more approach strategies than the military or multiple trauma group. Past and current significant CRI subscale differences were also detected. Results regarding the relationship between QOL and CRI were rejected, as the two scales were not found to correlate significantly. Trauma history and avoidant coping were also nonsignificant predictors for General Life Satisfaction on the QOL measure. Additional exploratory analyses are presented as well as implications for research, theory and clinical practice
Theory of a magnetic microscope with nanometer resolution
We propose a theory for a type of apertureless scanning near field microscopy
that is intended to allow the measurement of magnetism on a nanometer length
scale. A scanning probe, for example a scanning tunneling microscope (STM) tip,
is used to scan a magnetic substrate while a laser is focused on it. The
electric field between the tip and substrate is enhanced in such a way that the
circular polarization due to the Kerr effect, which is normally of order 0.1%
is increased by up to two orders of magnitude for the case of a Ag or W tip and
an Fe sample. Apart from this there is a large background of circular
polarization which is non-magnetic in origin. This circular polarization is
produced by light scattered from the STM tip and substrate. A detailed retarded
calculation for this light-in-light-out experiment is presented.Comment: 17 pages, 8 figure
Wave-packet dynamics in slowly perturbed crystals: Gradient corrections and Berry-phase effects
We present a unified theory for wave-packet dynamics of electrons in crystals
subject to perturbations varying slowly in space and time. We derive the
wave-packet energy up to the first order gradient correction and obtain all
kinds of Berry-phase terms for the semiclassical dynamics and the quantization
rule. For electromagnetic perturbations, we recover the orbital magnetization
energy and the anomalous velocity purely within a single-band picture without
invoking inter-band couplings. For deformations in crystals, besides a
deformation potential, we obtain a Berry-phase term in the Lagrangian due to
lattice tracking, which gives rise to new terms in the expressions for the
wave-packet velocity and the semiclassical force. For multiple-valued
displacement fields surrounding dislocations, this term manifests as a Berry
phase, which we show to be proportional to the Burgers vector around each
dislocation.Comment: 12 pages, RevTe
Optimized local modes for lattice dynamical applications
We present a new scheme for the construction of highly localized lattice
Wannier functions. The approach is based on a heuristic criterion for
localization and takes the symmetry constraints into account from the start. We
compare the local modes thus obtained with those generated by other schemes and
find that they also provide a better description of the relevant vibrational
subspace.Comment: 6 pages, ReVTeX, plus four postscript files for figure
Study of Nd-Fe-B Alloys with Nonstoichiometric Nd Content in Optimal Magnetic State
Characterization of two rapid-quenched Nd-Fe-B alloys with nonstoichiometric Nd content in the optimized magnetic state was carried out using the X-ray diffractometry (XRD), (57)Fe Mossbauer spectroscopic phase analysis (MS), electron microscopy (TEM), high resolution TEM (HREM) and Superconducting Quantum Interference Device (SQUID) magnetometer. The experimental results demonstrate the fundamental difference in the structure and magnetic properties of the two investigated alloys in the optimized magnetic state. The Nd-Fe-B alloy with the reduced Nd content (Nd(4.5)Fe(77)B(18.5)) was found to have the nanocomposite structure of Fe(3)B/Nd(2)Fe(14)B and partly alpha-Fe/Nd(2)Fe(14)B, with mean grain size below 30 nm. On the other side, the overstoichiometric Nd(14)Fe(79)B(7) alloy has almost a monophase structure with the dominant content of the hard magnetic phase Nd(2)Fe(14)B (up to 95 wt. %) and a mean crystallite size about 60 nm, as determined by XRD and TEM analysis. The results of magnetic measurements on SQUID magnetometer also suggest the nanocomposite structure of the Nd-low alloy and nanocrystalline decoupled structure of the Nd-rich alloy after the optimal heat treatment.open
Influence of dietary protein on glomerular filtration before and after bariatric surgery: a cohort study
BACKGROUND:
Obesity-associated elevations in glomerular filtration rate (GFR) are common and may play a role in the development of kidney disease, so identifying the underlying mechanism is important. We therefore studied whether reductions in dietary protein intake, which is known to modulate GFR, explain why GFR decreases after bariatric surgery-induced weight loss.
STUDY DESIGN:
Cohort study with participants as their own controls.
SETTING & PARTICIPANTS:
8 severely obese patients with normal kidney function were recruited from bariatric surgery centers in Indianapolis, IN. All participants were placed on a fixed-protein (50-g/d) diet for 1 week before and after a minimum of a 20-kg weight loss by bariatric surgery and were followed up closely by dieticians for adherence.
PREDICTOR:
Ad lib versus low-protein diet before versus after bariatric surgery.
OUTCOME:
Measured GFR, using repeated-measures analysis, was used to estimate the independent effects of diet and surgery.
MEASUREMENT:
GFR was measured using plasma iohexol clearance.
RESULTS:
A median of 32.9 (range, 19.5-54.4)kg was lost between the first presurgery visit and first postsurgery visit. Dietetic evaluations and urinary urea excretion confirmed that patients generally adhered to the study diet. GFRs on an ad lib diet were significantly higher before compared to after surgery (GFR medians were 144 (range, 114-178) and 107 (range, 85-147) mL/min, respectively; P=0.01). Although bariatric surgery (-26mL/min; P=0.005) and dietary sodium intake (+7.5mL/min per 100mg of dietary sodium; P=0.001) both influenced GFR, consuming a low-protein diet did not (P=0.7).
LIMITATIONS:
Small sample size; mostly white women; possible lack of generalizability.
CONCLUSIONS:
The decrease in GFR observed after bariatric surgery is explained at least in part by the effects of surgery and/or dietary sodium intake, but not by low dietary protein consumption
Quantifying gene network connectivity in silico: Scalability and accuracy of a modular approach
Large, complex data sets that are generated from microarray experiments, create a need for systematic analysis techniques to unravel the underlying connectivity of gene regulatory networks. A modular approach, previously proposed by Kholodenko and co-workers, helps to scale down the network complexity into more computationally manageable entities called modules. A functional module includes a gene\u27s mRNA, promoter and resulting products, thus encompassing a large set of interacting states. The essential elements of this approach are described in detail for a three-gene model network and later extended to a ten-gene model network, demonstrating scalability. The network architecture is identified by analysing in silico steady-state changes in the activities of only the module outputs, communicating intermediates, that result from specific perturbations applied to the network modules one at a time. These steady-state changes form the system response matrix, which is used to compute the network connectivity or network interaction map. By employing a known biochemical network, the accuracy of the modular approach and its sensitivity to key assumptions are evaluated
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