383 research outputs found
Algebraic Quantization, Good Operators and Fractional Quantum Numbers
The problems arising when quantizing systems with periodic boundary
conditions are analysed, in an algebraic (group-) quantization scheme, and the
``failure" of the Ehrenfest theorem is clarified in terms of the already
defined notion of {\it good} (and {\it bad}) operators. The analysis of
``constrained" Heisenberg-Weyl groups according to this quantization scheme
reveals the possibility for new quantum (fractional) numbers extending those
allowed for Chern classes in traditional Geometric Quantization. This study is
illustrated with the examples of the free particle on the circumference and the
charged particle in a homogeneous magnetic field on the torus, both examples
featuring ``anomalous" operators, non-equivalent quantization and the latter,
fractional quantum numbers. These provide the rationale behind flux
quantization in superconducting rings and Fractional Quantum Hall Effect,
respectively.Comment: 29 pages, latex, 1 figure included with EPSF. Revised version with
minor changes intended to clarify notation. Acepted for publication in Comm.
Math. Phy
Cyclic Alopecia and Abnormal Epidermal Cornification in Zdhhc13-Deficient Mice Reveal the Importance of Palmitoylation in Hair and Skin Differentiation
Many biochemical pathways involved in hair and skin development have not been investigated. Here, we reported on the lesions and investigated the mechanism underlying hair and skin abnormalities in Zdhhc13skc4 mice with a deficiency in DHHC13, a palmitoyl-acyl transferase encoded by Zdhhc13. Homozygous affected mice showed ragged and dilapidated cuticle of the hair shaft (CUH, a hair anchoring structure), poor hair anchoring ability, and premature hair loss at early telogen phase of the hair cycle, resulting in cyclic alopecia. Furthermore, the homozygous affected mice exhibited hyperproliferation of the epidermis, disturbed cornification, fragile cornified envelope (CE, a skin barrier structure), and impaired skin barrier function. Biochemical investigations revealed that cornifelin, which contains five palmitoylation sites at cysteine residues (C58, C59, C60, C95, and C101), was a specific substrate of DHHC13 and that it was absent in the CUH and CE structures of the affected mice. Furthermore, cornifelin levels were markedly reduced when two palmitoylated cysteines were replaced with serine (C95S and C101S). Taken together, our results suggest that DHHC13 is important for hair anchoring and skin barrier function and that cornifelin deficiency contributes to cyclic alopecia and skin abnormalities in Zdhhc13skc4 mice
Anisotropic transport in the two-dimensional electron gas in the presence of spin-orbit coupling
In a two-dimensional electron gas as realized by a semiconductor quantum
well, the presence of spin-orbit coupling of both the Rashba and Dresselhaus
type leads to anisotropic dispersion relations and Fermi contours. We study the
effect of this anisotropy on the electrical conductivity in the presence of
fixed impurity scatterers. The conductivity also shows in general an anisotropy
which can be tuned by varying the Rashba coefficient. This effect provides a
method of detecting and investigating spin-orbit coupling by measuring
spin-unpolarized electrical currents in the diffusive regime. Our approach is
based on an exact solution of the two-dimensional Boltzmann equation and
provides also a natural framework for investigating other transport effects
including the anomalous Hall effect.Comment: 10 pages, 1 figure included. Discussion of experimental impact
enlarged; error in calculation of conductivity contribution corrected (cf.
Eq. (A14)), no changes in qualitative results and physical consequence
Nonequilibrium Transport through a Kondo Dot in a Magnetic Field: Perturbation Theory
Using nonequilibrium perturbation theory, we investigate the nonlinear
transport through a quantum dot in the Kondo regime in the presence of a
magnetic field. We calculate the leading logarithmic corrections to the local
magnetization and the differential conductance, which are characteristic of the
Kondo effect out of equilibrium. By solving a quantum Boltzmann equation, we
determine the nonequilibrium magnetization on the dot and show that the
application of both a finite bias voltage and a magnetic field induces a novel
structure of logarithmic corrections not present in equilibrium. These
corrections lead to more pronounced features in the conductance, and their form
calls for a modification of the perturbative renormalization group.Comment: 16 pages, 7 figure
Vertical silicon nanowire platform for low power electronics and clean energy applications
10.1155/2012/492121Journal of Nanotechnology
Analysis of the correlation between strength and fractal dimension of gravelly soil in debris-flow source areas
peer-reviewedParticle size distribution of gravelly soil plays a crucial role in debris flow initiation. For better understanding the mechanism of debris flow formation, two crucial mechanical property parameters of the gravelly soil are required to be studied meticulously: hydraulic conductivity and strength. With the aim of measuring the composition of the gravelly soil, 182 soil samples were taken from debris flow prone areas. With the aid of a sieve test, the particle size distribution of the samples can be obtained and analyzed. Then fractal theory was employed to compute the fractal dimension of the soil samples. By analyzing the results of sieve test (particle size distribution curves) and the results of the fractal theory calculations, the relationship between fractal dimension and particle size distribution can be explored. The results illustrate that the particle compositions of the gravelly soil tends to remain uniform as the fractal dimension increases. Moreover, as the coarse particle content increases, the fractal dimension decreases. To better understand the formation mechanism of debris flows, direct shear tests were conducted. Subsequently the experimental results were analyzed. By analysis, the following conclusions can be drawn: the soil strength decreases as the fractal dimension increases, and for soils with lower moisture content and identical dry density, a linear relationship between fractal dimension and cohesion force was identified. Moreover, cohesion force and internal friction force both decrease as the fractal dimension increases, but the internal friction angle decreases slightly while the cohesion force decreases greatly. Therefore we concluded that soil strength decreased mainly due to the reduction in cohesion force.PUBLISHEDpeer-reviewe
Search for the Chiral Magnetic Effect in Au+Au collisions at GeV with the STAR forward Event Plane Detectors
A decisive experimental test of the Chiral Magnetic Effect (CME) is
considered one of the major scientific goals at the Relativistic Heavy-Ion
Collider (RHIC) towards understanding the nontrivial topological fluctuations
of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is
expected to result in a charge separation phenomenon across the reaction plane,
whose strength could be strongly energy dependent. The previous CME searches
have been focused on top RHIC energy collisions. In this Letter, we present a
low energy search for the CME in Au+Au collisions at
GeV. We measure elliptic flow scaled charge-dependent correlators relative to
the event planes that are defined at both mid-rapidity and at
forward rapidity . We compare the results based on the
directed flow plane () at forward rapidity and the elliptic flow plane
() at both central and forward rapidity. The CME scenario is expected
to result in a larger correlation relative to than to , while
a flow driven background scenario would lead to a consistent result for both
event planes[1,2]. In 10-50\% centrality, results using three different event
planes are found to be consistent within experimental uncertainties, suggesting
a flow driven background scenario dominating the measurement. We obtain an
upper limit on the deviation from a flow driven background scenario at the 95\%
confidence level. This work opens up a possible road map towards future CME
search with the high statistics data from the RHIC Beam Energy Scan Phase-II.Comment: main: 8 pages, 5 figures; supplementary material: 2 pages, 1 figur
Functional mechanisms underlying pleiotropic risk alleles at the 19p13.1 breast-ovarian cancer susceptibility locus
A locus at 19p13 is associated with breast cancer (BC) and ovarian cancer (OC) risk. Here we analyse 438 SNPs in this region in 46,451 BC and 15,438 OC cases, 15,252 BRCA1 mutation carriers and 73,444 controls and identify 13 candidate causal SNPs associated with serous OC (P=9.2 Ă 10-20), ER-negative BC (P=1.1 Ă 10-13), BRCA1-associated BC (P=7.7 Ă 10-16) and triple negative BC (P-diff=2 Ă 10-5). Genotype-gene expression associations are identified for candidate target genes ANKLE1 (P=2 Ă 10-3) and ABHD8 (P<2 Ă 10-3). Chromosome conformation capture identifies interactions between four candidate SNPs and ABHD8, and luciferase assays indicate six risk alleles increased transactivation of the ADHD8 promoter. Targeted deletion of a region containing risk SNP rs56069439 in a putative enhancer induces ANKLE1 downregulation; and mRNA stability assays indicate functional effects for an ANKLE1 3âČ-UTR SNP. Altogether, these data suggest that multiple SNPs at 19p13 regulate ABHD8 and perhaps ANKLE1 expression, and indicate common mechanisms underlying breast and ovarian cancer risk
Measurement of the cross section for isolated-photon plus jet production in pp collisions at âs=13 TeV using the ATLAS detector
The dynamics of isolated-photon production in association with a jet in protonâproton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fbâ1. Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti- algorithm with radius parameter and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photonâjet invariant mass and the scattering angle in the photonâjet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements
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