3,999 research outputs found
Resonant Spin Hall Conductance in Two-Dimensional Electron Systems with Rashba Interaction in a Perpendicular Magnetic Field
We study transport properties of a two-dimensional electron system with
Rashba spin-orbit coupling in a perpendicular magnetic field. The spin orbit
coupling competes with Zeeman splitting to introduce additional degeneracies
between different Landau levels at certain magnetic fields. This degeneracy, if
occuring at the Fermi level, gives rise to a resonant spin Hall conductance,
whose height is divergent as 1/T and whose weight is divergent as at
low temperatures. The Hall conductance is unaffected by the Rashba coupling.Comment: 4 pages, 4 figure
Holographic Superconductors with Ho\v{r}ava-Lifshitz Black Holes
We discuss the phase transition of planar black holes in Ho\v{r}ava-Lifshitz
gravity by introducing a Maxwell field and a complex scalar field. We calculate
the condensates of the charged operators in the dual CFTs when the mass square
of the complex scalar filed is and , respectively. We
compute the electrical conductivity of the \hl superconductor in the probe
approximation. In particular, it is found that there exists a spike in the
conductivity for the case of the operator with scaling dimension one. These
results are quite similar to those in the case of Schwarzschild-AdS black
holes, which demonstrates that the holographic superconductivity is a robust
phenomenon associated with asymptotic AdS black holes.Comment: 12 pages, 7 figures,refs adde
Magnetic Field Effect on the Phase Transition in AdS Soliton Spacetime
We investigate the scalar perturbations in an AdS soliton background coupled
to a Maxwell field via marginally stable modes. In the probe limit, we study
the magnetic field effect on the holographic insulator/superconductor phase
transition numerically and analytically. The condensate will be localized in a
finite circular region for any finite constant magnetic field. Near the
critical point, we find that there exists a simple relation among the critical
chemical potential, magnetic field, the charge and mass of the scalar field.
This relation indicates that the presence of the magnetic field causes the
phase transition hard.Comment: 15 pages, 3 figures, 2 tables. contents improved and references adde
The Progenitor of Supernova 2004dj in a Star Cluster
The progenitor of type II-plateau supernova (SN) 2004dj is identified with a
supergiant in a compact star cluster known as "Sandage Star 96" (S96) in the
nearby spiral galaxy NGC 2403, which was fortuitously imaged as part of the
Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey from Feb 1995
to Dec 2003 prior to SN 2004dj. The superior photometry of BATC images for S96,
taken with 14 intermediate-band filters covering 3000-10000\AA, unambiguously
establishes the star cluster nature of S96 with an age of Myr, a
reddening of mag and a total mass of M. The compact star cluster nature of S96 is also consistent
with the lack of light variations in the past decade. The SN progenitor is
estimated to have a main-sequence mass of 12M. The comparison
of our intermediate-band data of S96 with the post-outburst photometry obtained
as the SN has significantly dimmed, may hopefully conclusively establish the
nature of the progenitor.Comment: 4 pages; 3 figures. To accept for Publications in ApJ Letters, but
slightly longer in this perprin
Analysis of decays in the perturbative QCD approach
Within the framework of perturbative QCD approach, we study the charmless
two-body decays . Using the decays constants
and the light-cone distribution amplitudes for these mesons derived from the
QCD sum rule method, we find the following results: (a) Our predictions for the
branching ratios are consistent well with the QCDF results within errors, but
much larger than the naive factorization approach calculation values. (b) We
predict that the anomalous polarizations occurring in the decays also happen in the decays , while do not happen in
the decays . Here the contributions from the annihilation diagrams
play an important role to explain the lager transverse polarizations in the
decays , while they are not sensitive to the polarizations in
decays . (c) Our predictions for the direct CP-asymmetries agree
well with the QCDF results within errors. The decays have larger direct CP-asymmetries, which
could be measured by the present LHCb experiments.Comment: 12pages, 1figures. arXiv admin note: substantial text overlap with
arXiv:1203.5913, arXiv:1203.591
Resonant spin Hall conductance in quantum Hall systems lacking bulk and structural inversion symmetry
Following a previous work [Shen, Ma, Xie and Zhang, Phys. Rev. Lett. 92,
256603 (2004)] on the resonant spin Hall effect, we present detailed
calculations of the spin Hall conductance in two-dimensional quantum wells in a
strong perpendicular magnetic field. The Rashba coupling, generated by
spin-orbit interaction in wells lacking bulk inversion symmetry, introduces a
degeneracy of Zeeman-split Landau levels at certain magnetic fields. This
degeneracy, if occuring at the Fermi energy, will induce a resonance in the
spin Hall conductance below a characteristic temperature of order of the Zeeman
energy. At very low temperatures, the spin Hall current is highly non-ohmic.
The Dresselhaus coupling due to the lack of structure inversion symmetry
partially or completely suppresses the spin Hall resonance. The condition for
the resonant spin Hall conductance in the presence of both Rashba and
Dresselhaus couplings is derived using a perturbation method. In the presence
of disorder, we argue that the resonant spin Hall conductance occurs when the
two Zeeman split extended states near the Fermi level becomes degenerate due to
the Rashba coupling and that the the quantized charge Hall conductance changes
by 2e^2/h instead of e^2/h as the magnetic field changes through the resonant
field.Comment: 9 pages, 7 figures. This is a sequel to Physical Review Letters 90,
256603 (2004
The Molecular Biology Toolkit (MBT): a modular platform for developing molecular visualization applications
BACKGROUND: The large amount of data that are currently produced in the biological sciences can no longer be explored and visualized efficiently with traditional, specialized software. Instead, new capabilities are needed that offer flexibility, rapid application development and deployment as standalone applications or available through the Web. RESULTS: We describe a new software toolkit – the Molecular Biology Toolkit (MBT; ) – that enables fast development of applications for protein analysis and visualization. The toolkit is written in Java, thus offering platform-independence and Internet delivery capabilities. Several applications of the toolkit are introduced to illustrate the functionality that can be achieved. CONCLUSIONS: The MBT provides a well-organized assortment of core classes that provide a uniform data model for the description of biological structures and automate most common tasks associated with the development of applications in the molecular sciences (data loading, derivation of typical structural information, visualization of sequence and standard structural entities)
Quantitative and functional post-translational modification proteomics reveals that TREPH1 plays a role in plant thigmomorphogenesis
Plants can sense both intracellular and extracellular mechanical forces and
can respond through morphological changes. The signaling components responsible
for mechanotransduction of the touch response are largely unknown. Here, we
performed a high-throughput SILIA (stable isotope labeling in
Arabidopsis)-based quantitative phosphoproteomics analysis to profile changes
in protein phosphorylation resulting from 40 seconds of force stimulation in
Arabidopsis thaliana. Of the 24 touch-responsive phosphopeptides identified,
many were derived from kinases, phosphatases, cytoskeleton proteins, membrane
proteins and ion transporters. TOUCH-REGULATED PHOSPHOPROTEIN1 (TREPH1) and MAP
KINASE KINASE 2 (MKK2) and/or MKK1 became rapidly phosphorylated in
touch-stimulated plants. Both TREPH1 and MKK2 are required for touch-induced
delayed flowering, a major component of thigmomorphogenesis. The treph1-1 and
mkk2 mutants also exhibited defects in touch-inducible gene expression. A
non-phosphorylatable site-specific isoform of TREPH1 (S625A) failed to restore
touch-induced flowering delay of treph1-1, indicating the necessity of S625 for
TREPH1 function and providing evidence consistent with the possible functional
relevance of the touch-regulated TREPH1 phosphorylation. Bioinformatic analysis
and biochemical subcellular fractionation of TREPH1 protein indicate that it is
a soluble protein. Altogether, these findings identify new protein players in
Arabidopsis thigmomorphogenesis regulation, suggesting that protein
phosphorylation may play a critical role in plant force responses
PT Symmetry as a Generalization of Hermiticity
The Hilbert space in PT-symmetric quantum mechanics is formulated as a linear
vector space with a dynamic inner product. The most general PT-symmetric matrix
Hamiltonians are constructed for 2*2 and 3*3 cases. In the former case, the
PT-symmetric Hamiltonian represents the most general matrix Hamiltonian with a
real spectrum. In both cases, Hermitian matrices are shown to be special cases
of PT-symmetric matrices. This finding confirms and strengthens the early
belief that the PT-symmetric quantum mechanics is a generalization of the
conventional Hermitian quantum mechanics.Comment: 13 page
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