29,807 research outputs found
Search for quantum dimer phases and transitions in a frustrated spin ladder
A two-leg spin-1/2 ladder with diagonal interactions is investigated
numerically. We focus our attention on the possibility of columnar dimer phase,
which was recently predicted based on a reformulated bosonization theory. By
using density matrix renormalization group technique and exact diagonalization
method, we calculate columnar dimer order parameter, spin correlation on a
rung, string order parameters, and scaled excitation gaps. Carefully using
various finite-size scaling techniques, our results show no support for the
existence of columnar dimer phase in the spin ladder under consideration.Comment: 5 pages, 4 figures. To be published in Phys. Rev.
Deep Learning the Effects of Photon Sensors on the Event Reconstruction Performance in an Antineutrino Detector
We provide a fast approach incorporating the usage of deep learning for
evaluating the effects of photon sensors in an antineutrino detector on the
event reconstruction performance therein. This work is an attempt to harness
the power of deep learning for detector designing and upgrade planning. Using
the Daya Bay detector as a benchmark case and the vertex reconstruction
performance as the objective for the deep neural network, we find that the
photomultiplier tubes (PMTs) have different relative importance to the vertex
reconstruction. More importantly, the vertex position resolutions for the Daya
Bay detector follow approximately a multi-exponential relationship with respect
to the number of PMTs and hence, the coverage. This could also assist in
deciding on the merits of installing additional PMTs for future detector plans.
The approach could easily be used with other objectives in place of vertex
reconstruction
Tumor marker oreintated chemotherapy in cancer of unknown primary site: A case report and literature review
Liquid-vapor oscillations of water in hydrophobic nanopores
Water plays a key role in biological membrane transport. In ion channels and
water-conducting pores (aquaporins), one dimensional confinement in conjunction
with strong surface effects changes the physical behavior of water. In
molecular dynamics simulations of water in short (0.8 nm) hydrophobic pores the
water density in the pore fluctuates on a nanosecond time scale. In long
simulations (460 ns in total) at pore radii ranging from 0.35 nm to 1.0 nm we
quantify the kinetics of oscillations between a liquid-filled and a
vapor-filled pore. This behavior can be explained as capillary evaporation
alternating with capillary condensation, driven by pressure fluctuations in the
water outside the pore. The free energy difference between the two states
depends linearly on the radius. The free energy landscape shows how a
metastable liquid state gradually develops with increasing radius. For radii
larger than ca. 0.55 nm it becomes the globally stable state and the vapor
state vanishes. One dimensional confinement affects the dynamic behavior of the
water molecules and increases the self diffusion by a factor of two to three
compared to bulk water. Permeabilities for the narrow pores are of the same
order of magnitude as for biological water pores. Water flow is not continuous
but occurs in bursts. Our results suggest that simulations aimed at collective
phenomena such as hydrophobic effects may require simulation times longer than
50 ns. For water in confined geometries, it is not possible to extrapolate from
bulk or short time behavior to longer time scales.Comment: 20 pages, 4 figures, 3 tables; to be published in Proc. Natl. Acad.
Sci. US
Reconstruction of Fractional Quantum Hall Edges
We study the interplay of interaction, confining potential and effects of
finite temperature at the edge of a quantum Hall liquid. Our exact
diagonalization calculation indicates that edge reconstruction occurs in the
fractional quantum Hall regime for a variety of confining potential, including
ones that correspond to a "sharp" edge. Our finite temperature Hartree-Fock
calculation for integer quantum Hall edges indicates that reconstruction is
suppressed above certain temperature. We discuss the implication of our results
on recent edge tunneling and microwave absorption experiments.Comment: Revised version. 5 papges RevTex with 5 eps figures embedded in the
tex
FISH mapping and molecular organization of the major repetitive sequences of tomato
This paper presents a bird's-eye view of the major repeats and chromatin types of tomato. Using fluorescence in-situ hybridization (FISH) with Cot-1, Cot-10 and Cot-100 DNA as probes we mapped repetitive sequences of different complexity on pachytene complements. Cot-100 was found to cover all heterochromatin regions, and could be used to identify repeat-rich clones in BAC filter hybridization. Next we established the chromosomal locations of the tandem and dispersed repeats with respect to euchromatin, nucleolar organizer regions (NORs), heterochromatin, and centromeres. The tomato genomic repeats TGRII and TGRIII appeared to be major components of the pericentromeres, whereas the newly discovered TGRIV repeat was found mainly in the structural centromeres. The highly methylated NOR of chromosome 2 is rich in [GACA](4), a microsatellite that also forms part of the pericentromeres, together with [GA](8), [GATA](4) and Ty1-copia. Based on the morphology of pachytene chromosomes and the distribution of repeats studied so far, we now propose six different chromatin classes for tomato: (1) euchromatin, (2) chromomeres, (3) distal heterochromatin and interstitial heterochromatic knobs, (4) pericentromere heterochromatin, (5) functional centromere heterochromatin and (6) nucleolar organizer regio
Recommended from our members
Quantitative MRI Musculoskeletal Techniques: An Update.
OBJECTIVE. For many years, MRI of the musculoskeletal system has relied mostly on conventional sequences with qualitative analysis. More recently, using quantitative MRI applications to complement qualitative imaging has gained increasing interest in the MRI community, providing more detailed physiologic or anatomic information. CONCLUSION. In this article, we review the current state of quantitative MRI, technical and software advances, and the most relevant clinical and research musculoskeletal applications of quantitative MRI
- …