3,147 research outputs found
Magnetocrystalline Anisotropy Energy of a Transition Metal Monolayer: A Non-perturbative Theory
The magnetocrystalline anisotropy energy for a monolayer of Fe and
Ni is determined using a fully convergent tight-binding calculation including
- hybridization. The spin-orbit interaction is treated
non-perturbatively. Remarkably, we find and
important contributions to due to the lifting of degeneracies near
the Fermi-level. This is supported by the calculated decrease of the anisotropy
energy with increasing temperature on a scale of several hundred K. Our results
clarify the present debate on the origin of .Comment: 11 pages (RevTeX) with 2 figures, appended as Postscript file
The Azimuthal Asymmetry at large p_t seem to be too large for a ``Jet Quenching''
We discuss simple generic model of ``jet quenching'' in which matter
absorption is defined by one parameter. We show that as absorption grows, the
azimuthal asymmetry v_2 grows as well, reaching the finite limit with a simple
geometric interpretation. It turns out, that this limit is still below the
experimental values for 6 > p_t > 2 GeV, according to preliminary data from
STAR experiment at RHIC. We thus conclude that ``jet quenching'' models alone
cannot account for the observed phenomenon, and speculate about alternative
scenarios.Comment: 3 pages, 2 figs, 1 table. The final version contaning note added in
proofs for PRC, which reflects experimental development which seem to suggest
that the geometrical model for v2 is in fact correct description of data at
pt=2-10 Ge
Molecular evidence of the haploid origin in wheat (Triticum aestivum L.) with Aegilops kotschyi cytoplasm and whole genome expression profiling after haploidization
Aegiolops kotschyi cytoplasmic male sterile system often results in part of haploid plants in wheat (Triticum aestivum L.). To elucidate the origin of haploid, 235 wheat microsatellite (SSR) primers were randomly selected and screened for polymorphism between haploid (2n = 3x = 21 ABD) and its parents, male-sterile line YM21 (2n = 6x = 42 AABBDD) and male fertile restorer YM2 (2n = 6x = 42 AABBDD). About 200 SSR markers yielded clear bands from denatured PAGE, of which 180 markers have identifiable amplification patterns, and 20 markers (around 8%) resulted in different amplification products between the haploid and the restorer, YM2. There were no SSR markers that were found to be distinguishable between the haploid and the male sterile line YM21. In addition, different distribution of HMW-GS between endosperm and seedlings from the same seeds further confirmed that the haploid genomes were inherited from the maternal parent. After haploidization, 1.7% and 0.91% of total sites were up- and down-regulated exceeding twofold in the shoot and the root of haploid, respectively, and most of the differentially expressed loci were up/down-regulated about twofold. Out of the sensitive loci in haploid, 94 loci in the shoot, 72 loci in the root can be classified into three functional subdivisions: biological process, cellular component and molecular function, respectively
Optical Evidence of Multiphase Coexistence in Single Crystalline (La,Pr,Ca)MnO3
We investigated temperature (T)- and magnetic field-dependent optical
conductivity spectra (\s\w) of a La_5/8-yPr_yCa_3/8MnO_3 (y~0.35) single
crystal, showing intriguing phase coexistence at low T. At T_C < T < T_CO, a
dominant charge-ordered phase produces a large optical gap energy of ~0.4 eV.
At T < T_C, at least two absorption bands newly emerge below 0.4 eV. Analyses
of (\s\w) indicate that the new bands should be attributed to a ferromagnetic
metallic and a charge-disordered phase that coexist with the charge-ordered
phase. This optical study clearly shows that La_5/8-yPrCa_3/8MnO_3 (y~0.35) is
composed of multiphases that might have different lattice strains.Comment: A single file with 9 figures embedded, to appear in Phys. Rev.
Room temperature ferromagnetism in chemically synthesized ZnO rods
We report structural and magnetic properties of pure ZnO rods using X-ray
diffraction (XRD), magnetization hysteresis (M-H) loop and near edge x-ray fine
structure spectroscopy (NEXAFS) study at O K edge. Sample of ZnO was prepared
by co-precipitation method. XRD and selective area electron diffraction
measurements infer that ZnO rods exhibit a single phase polycrystalline nature
with wurtzite lattice. Field emission transmission electron microscopy, field
emission scanning electron microscopy micrographs infers that ZnO have rod type
microstructures with dimension 200 nm in diameter and 550 nm in length. M-H
loop studies performed at room temperature display room temperature
ferromagnetism in ZnO rods. NEXAFS study reflects absence of the oxygen
vacancies in pure ZnO rods.Comment: 8 Pages, 3 Figure
Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets
We present longitudinal field muon spin relaxation (SR) measurements in
the unilluminated state of the photo-sensitive molecular magnetic Co-Fe
Prussian blue analogues MCo[Fe(CN)] HO, where
M=K and Rb with and , respectively. These results are
compared to those obtained in the stoichiometric limit,
Co[Fe(CN)] HO, which is not photo-sensitive. We find
evidence for correlation between the range of magnetic ordering and the value
of in the unilluminated state which can be explained using a site
percolation model.Comment: 7 pages, 12 figure
Distribution and Excretion of TEGDMA in Guinea Pigs and Mice
The monomer triethyleneglycoldimethacrylate (TEGDMA) is used as a diluent in many resin-based dental materials. It was previously shown in vitro that TEGDMA was released into the adjacent biophase from such materials during the first days after placement. In this study, the uptake, distribution, and excretion of 14C-TEGDMA applied via gastric, intradermal, and intravenous administration at dose levels well above those encountered in dental care were examined in vivo in guinea pigs and mice as a test of the hypothesis that TEGDMA reaches cytotoxic levels in mammalian tissues. 14C-TEGDMA was taken up rapidly from the stomach and small intestine after gastric administration in both species and was widely distributed in the body following administration by each route. Most 14C was excreted within one day as 14 CO2. The peak equivalent TEGDMA levels in all mouse and guinea pig tissues examined were at least 1000-fold less than known toxic levels. The study therefore did not support the hypothesis
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Very strong intrinsic supercurrent carrying ability and vortex avalanches in (Ba,K)Fe2As2 superconducting single crystals
We report that single crystals of (Ba,K)Fe2As2 with Tc = 32 K have a pinning
potential, U0, as high as 10^4 K, with U0 showing very little field
depend-ence. In addition, the (Ba,K)Fe2As2 single crystals become isotropic at
low temperatures and high magnetic fields, resulting in a very rigid vortex
lattice, even in fields very close to Hc2. The rigid vortices in the two
dimensional (Ba,K)Fe2As2 distinguish this compound from 2D high Tc cuprate
superconductors with 2D vortices, and make it being capable of cearrying very
high critical current.Flux jumping due to high Jc was also observed in large
samples at low temperatures.Comment: 4 pages, 7 figures. submitte
Melting of Charge/Orbital Ordered States in NdSrMnO: Temperature and Magnetic Field Dependent Optical Studies
We investigated the temperature ( 15 290 K) and the magnetic
field ( 0 17 T) dependent optical conductivity spectra of a
charge/orbital ordered manganite, NdSrMnO. With variation
of and , large spectral weight changes were observed up to 4.0 eV. These
spectral weight changes could be explained using the polaron picture.
Interestingly, our results suggested that some local ordered state might remain
above the charge ordering temperature, and that the charge/orbital melted state
at a high magnetic field (i.e. at 17 T and 4.2 K) should be a three
dimensional ferromagnetic metal. We also investigated the first order phase
transition from the charge/orbital ordered state to ferromagnetic metallic
state using the - and % -dependent dielectric constants . In
the charge/orbital ordered insulating state, was positive and
. With increasing and , was
increased up to the insulator-metal phase boundaries. And then,
abruptly changed into negative and , which was
consistent with typical responses of a metal. Through the analysis of using an effective medium approximation, we found that the melting
of charge/orbital ordered states should occur through the percolation of
ferromagnetic metal domains.Comment: submitted to Phys. Rev.
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