5,997 research outputs found
Persistent spin current in mesoscopic ferrimagnetic spin ring
Using a semiclassical approach, we study the persistent magnetization current
of a mesoscopic ferrimagnetic ring in a nonuniform magnetic field. At zero
temperature, there exists persistent spin current because of the quantum
fluctuation of magnons, similar to the case of an antiferromagnetic spin ring.
At low temperature, the current shows activation behavior because of the
field-induced gap. At higher temperature, the magnitude of the spin current is
proportional to temperature T, similar to the reported result of a
ferromagnetic spin ring.Comment: 6 pages, 3 figures, one more reference adde
Spin and charge transport in U-shaped one-dimensional channels with spin-orbit couplings
A general form of the Hamiltonian for electrons confined to a curved
one-dimensional (1D) channel with spin-orbit coupling (SOC) linear in momentum
is rederived and is applied to a U-shaped channel. Discretizing the derived
continuous 1D Hamiltonian to a tight-binding version, the Landauer-Keldysh
formalism (LKF) for nonequilibrium transport can be applied. Spin transport
through the U-channel based on the LKF is compared with previous quantum
mechanical approaches. The role of a curvature-induced geometric potential
which was previously neglected in the literature of the ring issue is also
revisited. Transport regimes between nonadiabatic, corresponding to weak SOC or
sharp turn, and adiabatic, corresponding to strong SOC or smooth turn, is
discussed. Based on the LKF, interesting charge and spin transport properties
are further revealed. For the charge transport, the interplay between the
Rashba and the linear Dresselhaus (001) SOCs leads to an additional modulation
to the local charge density in the half-ring part of the U-channel, which is
shown to originate from the angle-dependent spin-orbit potential. For the spin
transport, theoretically predicted eigenstates of the Rashba rings, Dresselhaus
rings, and the persistent spin-helix state are numerically tested by the
present quantum transport calculation.Comment: 16 pages, 7 figure
Water Requirements For Waterfowl Areas Near the Great Salt Lake Parts V-VI
This report reviews activities on this project since the Progress Report, Part IV, June 1961.
The summer of 1961 has been one of the driest on record for Ogden Bay and Howard Slough Refuge. The extreme shortage of irrigation water has resulted in very little flow in the Howard Slough which originates from return flow. The available water from the Weber River for the Ogden Bay Refuge was also the lowest on record. The scarcity of water at these two refuges has resulted in increased salinity.
Most of the routine work on the project during the summer was done by Ming Change Tsai, graduate assistant in civil engineering who resided at the Ogden Bay Refuge. Mr. Tsai has been assisted in the care of the salinity lysimiters at Ogden Bay Refuge, and in the salinity surveys at the other refuges by Daya Kaushik, graduate assistant in wildlife resources
Spectra of Free Diquark in the Bethe-Salpeter Approach
In this work, we employ the Bethe-Salpeter (B-S) equation to investigate the
spectra of free diquarks and their B-S wave functions. We find that the B-S
approach can be consistently applied to study the diqaurks with two heavy
quarks or one heavy and one light quarks, but for two light-quark systems, the
results are not reliable. There are a few free parameters in the whole scenario
which can only be fixed phenomenologically. Thus, to determine them, one has to
study baryons which are composed of quarks and diquarks.Comment: 16 pages, no figure
Energy Spectrum of Bloch Electrons Under Checkerboard Field Modulations
Two-dimensional Bloch electrons in a uniform magnetic field exhibit complex
energy spectrum. When static electric and magnetic modulations with a
checkerboard pattern are superimposed on the uniform magnetic field, more
structures and symmetries of the spectra are found, due to the additional
adjustable parameters from the modulations. We give a comprehensive report on
these new symmetries. We have also found an electric-modulation induced energy
gap, whose magnitude is independent of the strength of either the uniform or
the modulated magnetic field. This study is applicable to experimentally
accessible systems and is related to the investigations on frustrated
antiferromagnetism.Comment: 8 pages, 6 figures (reduced in sizes), submitted to Phys. Rev.
DC-SIGN (CD209) Promoter −336 A/G (rs4804803) Polymorphism Associated with Susceptibility of Kawasaki Disease
Kawasaki disease (KD) is characterized by systemic vasculitis of unknown etiology. High-dose intravenous immunoglobulin (IVIG) is the most effective therapy for KD to reduce the prevalence of coronary artery lesion (CAL) formation. Recently, the α2, 6 sialylated IgG was reported to interact with a lectin receptor, specific intracellular adhesion molecule-3 grabbing nonintegrin homolog-related 1 (SIGN-R1) in mice and dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) in human, and to trigger an anti-inflammatory cascade. This study was conducted to investigate whether the polymorphism of DC-SIGN (CD209) promoter −336 A/G (rs4804803) is responsible for susceptibility and CAL formation in KD patients using Custom TaqMan SNP Genotyping Assays. A total of 521 subjects (278 KD patients and 243 controls) were investigated to identify an SNP of rs4804803, and they were studied and showed a significant association between the genotypes and allele frequency of rs4804803 in control subjects and KD patients (P = 0.004 under the dominant model). However, the promoter variant of DC-SIGN gene was not associated with the occurrence of IVIG resistance, CAL formation in KD. The G allele of DC-SIGN promoter −336 (rs4804803) is a risk allele in the development of KD
Differential microbicidal effects of human histone proteins H2A and H2B on Leishmania promastigotes and amastigotes
Recent studies have shown that histone proteins can act as antimicrobial peptides in host defense against extracellular bacteria, fungi, and Leishmania promastigotes. In this study, we used human recombinant histone proteins to further study their leishmaniacidal effects and the underlying mechanisms. We found that the histones H2A and H2B (but not H1(0)) could directly and efficiently kill promastigotes of Leishmania amazonensis, L. major, L. braziliensis, and L. mexicana in a treatment dose-dependent manner. Scanning electron microscopy revealed surface disruption of histone-treated promastigotes. More importantly, the preexposure of promastigotes to histone proteins markedly decreased the infectivity of promastigotes to murine macrophages (Mφs) in vitro. However, axenic and lesion-derived amastigotes of L. amazonensis and L. mexicana were relatively resistant to histone treatment, which correlated with the low levels of intracellular H2A in treated amastigotes. To understand the mechanisms underlying these differential responses, we investigated the role of promastigote surface molecules in histone-mediated killing. Compared with the corresponding controls, transgenic L. amazonensis promastigotes expressing lower levels of surface gp63 proteins were more susceptible to histone H2A, while L. major and L. mexicana promastigotes with targeted deletion of the lipophosphoglycan 2 (lpg2) gene (but not the lpg1 gene) were more resistant to histone H2A. We discuss the influence of promastigote major surface molecules in the leishmaniacidal effect of histone proteins. This study provides new information on host innate immunity to different developmental stages of Leishmania parasites
Unification of Dark Matter and Dark Energy in a Modified Entropic Force Model
In Verlinde's entropic force scenario of gravity, Newton's laws and Einstein
equations can be obtained from the first pinciples and general assumptions.
However, the equipartition law of energy is invalid at very low temperatures.
We show clearly that the threshold of the equipartition law of energy is
related with horizon of the universe. Thus, a one-dimension Debye (ODD) model
in the direction of radius of the modified entropic force (MEF) maybe suitable
in description of the accelerated expanding universe. We present a Friedmann
cosmic dynamical model in the ODD-MEF framework. We examine carefully
constraints on the ODD-MEF model from the Union2 compilation of the Supernova
Cosmology Project (SCP) collaboration, the data from the observation of the
large-scale structure (LSS) and the cosmic microwave background (CMB), i.e. SNe
Ia+LSS+CMB. The combined numerical analysis gives the best-fit value of the
model parameters and , with
. The corresponding age of the universe agrees with the
result of D. Spergel {\it et al.}\cite{Spergel2003} at 95% confidence level.
The numerical result also yields an accelerated expanding universe without
invoking any kind of dark energy. Taking as a
running parameter associated with the structure scale , we obtain a possible
unified scenario of the asymptotic flatness of the radial velocity dispersion
of spiral galaxies, the accelerated expanding universe and the Pioneer 10/11
anomaly in the entropic force framework of Verlinde.Comment: 23 pages, 6 figure
Crystal Structure of the Zorbamycin-Binding Protein ZbmA, the Primary Self-Resistance Element in Streptomyces flavoviridis ATCC21892
The bleomycins (BLMs), tallysomycins (TLMs), phleomycin, and zorbamycin (ZBM) are members of the BLM family of glycopeptide-derived antitumor antibiotics. The BLM-producing Streptomyces verticillus ATCC15003 and the TLM-producing Streptoalloteichus hindustanus E465-94 ATCC31158 both possess at least two self-resistance elements, an N-acetyltransferase and a binding protein. The N-acetyltransferase provides resistance by disrupting the metal-binding domain of the antibiotic that is required for activity, while the binding protein confers resistance by sequestering the metal-bound antibiotic and preventing drug activation via molecular oxygen. We recently established that the ZBM producer, Streptomyces flavoviridis ATCC21892, lacks the N-acetyltransferase resistance gene and that the ZBM-binding protein, ZbmA, is sufficient to confer resistance in the producing strain. To investigate the resistance mechanism attributed to ZbmA, we determined the crystal structures of apo and Cu(II)-ZBM-bound ZbmA at high resolutions of 1.90 and 1.65 Å, respectively. A comparison and contrast with other structurally characterized members of the BLM-binding protein family revealed key differences in the protein–ligand binding environment that fine-tunes the ability of ZbmA to sequester metal-bound ZBM and supports drug sequestration as the primary resistance mechanism in the producing organisms of the BLM family of antitumor antibiotics
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