3,605 research outputs found
Ultracold dense gas of deeply bound heteronuclear molecules
Recently, the quest for an ultracold and dense ensemble of polar molecules
has attracted strong interest. Polar molecules have bright prospects for novel
quantum gases with long-range and anisotropic interactions, for quantum
information science, and for precision measurements. However, high-density
clouds of ultracold polar molecules have so far not been produced. Here, we
report a key step towards this goal. Starting from an ultracold dense gas of
heteronuclear 40K-87Rb Feshbach molecules with typical binding energies of a
few hundred kHz and a negligible dipole moment, we coherently transfer these
molecules into a vibrational level of the ground-state molecular potential
bound by >10 GHz. We thereby increase the binding energy and the expected
dipole moment of the 40K-87Rb molecules by more than four orders of magnitude
in a single transfer step. Starting with a single initial state prepared with
Feshbach association, we achieve a transfer efficiency of 84%. While dipolar
effects are not yet observable, the presented technique can be extended to
access much more deeply bound vibrational levels and ultimately those
exhibiting a significant dipole moment. The preparation of an ultracold quantum
gas of polar molecules might therefore come within experimental reach.Comment: 5 pages, 5 figure
Interpolative multidimensional scaling techniques for the identification of clusters in very large sequence sets
<p>Abstract</p> <p>Background</p> <p>Modern pyrosequencing techniques make it possible to study complex bacterial populations, such as <it>16S rRNA</it>, directly from environmental or clinical samples without the need for laboratory purification. Alignment of sequences across the resultant large data sets (100,000+ sequences) is of particular interest for the purpose of identifying potential gene clusters and families, but such analysis represents a daunting computational task. The aim of this work is the development of an efficient pipeline for the clustering of large sequence read sets.</p> <p>Methods</p> <p>Pairwise alignment techniques are used here to calculate genetic distances between sequence pairs. These methods are pleasingly parallel and have been shown to more accurately reflect accurate genetic distances in highly variable regions of <it>rRNA </it>genes than do traditional multiple sequence alignment (MSA) approaches. By utilizing Needleman-Wunsch (NW) pairwise alignment in conjunction with novel implementations of interpolative multidimensional scaling (MDS), we have developed an effective method for visualizing massive biosequence data sets and quickly identifying potential gene clusters.</p> <p>Results</p> <p>This study demonstrates the use of interpolative MDS to obtain clustering results that are qualitatively similar to those obtained through full MDS, but with substantial cost savings. In particular, the wall clock time required to cluster a set of 100,000 sequences has been reduced from seven hours to less than one hour through the use of interpolative MDS.</p> <p>Conclusions</p> <p>Although work remains to be done in selecting the optimal training set size for interpolative MDS, substantial computational cost savings will allow us to cluster much larger sequence sets in the future.</p
Soft branes in supersymmetry-breaking backgrounds
We revisit the analysis of effective field theories resulting from
non-supersymmetric perturbations to supersymmetric flux compactifications of
the type-IIB superstring with an eye towards those resulting from the
backreaction of a small number of anti-D3-branes. Independently of the
background, we show that the low-energy Lagrangian describing the fluctuations
of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite
perturbations to marginal operators that were not fully considered in some
previous treatments. We take this as an indication that the breaking of
supersymmetry by anti-D3-branes or other sources may be spontaneous rather than
explicit. In support of this, we consider the action of an anti-D3-brane
probing an otherwise supersymmetric configuration and identify a candidate for
the corresponding goldstino.Comment: 36+5 pages. References added, minor typos correcte
Direct Evidence for Dominant Bond-directional Interactions in a Honeycomb Lattice Iridate Na2IrO3
Heisenberg interactions are ubiquitous in magnetic materials and have been
prevailing in modeling and designing quantum magnets. Bond-directional
interactions offer a novel alternative to Heisenberg exchange and provide the
building blocks of the Kitaev model, which has a quantum spin liquid (QSL) as
its exact ground state. Honeycomb iridates, A2IrO3 (A=Na,Li), offer potential
realizations of the Kitaev model, and their reported magnetic behaviors may be
interpreted within the Kitaev framework. However, the extent of their relevance
to the Kitaev model remains unclear, as evidence for bond-directional
interactions remains indirect or conjectural. Here, we present direct evidence
for dominant bond-directional interactions in antiferromagnetic Na2IrO3 and
show that they lead to strong magnetic frustration. Diffuse magnetic x-ray
scattering reveals broken spin-rotational symmetry even above Neel temperature,
with the three spin components exhibiting nano-scale correlations along
distinct crystallographic directions. This spin-space and real-space
entanglement directly manifests the bond-directional interactions, provides the
missing link to Kitaev physics in honeycomb iridates, and establishes a new
design strategy toward frustrated magnetism.Comment: Nature Physics, accepted (2015
The FPR2-induced rise in cytosolic calcium in human neutrophils relies on an emptying of intracellular calcium stores and is inhibited by a gelsolin-derived PIP2-binding peptide
<p>Abstract</p> <p>Background</p> <p>The molecular basis for neutrophil recognition of chemotactic peptides is their binding to specific G-protein-coupled cell surface receptors (GPCRs). Human neutrophils express two pattern recognition GPCRs, FPR1 and FPR2, which belong to the family of formyl peptide receptors. The high degree of homology between these two receptors suggests that they share many functional and signal transduction properties, although they exhibit some differences with respect to signaling. The aims of this study were to determine whether FPR2 triggers a unique signal that allows direct influx of extracellular calcium without the emptying of intracellular calcium stores, and whether the gelsolin-derived PIP<sub>2</sub>-binding peptide, PBP10, selectively inhibits FPR2-mediated transient rise in intracellular Ca<sup>2+</sup>.</p> <p>Results</p> <p>The transient rise in intracellular Ca<sup>2+ </sup>induced by agonists for FPR1 or FPR2 in human neutrophils occurred also in the presence of a chelator of Ca<sup>2+ </sup>(EGTA). PBP10 inhibited not only FPR2-induced oxidase activity, but also the transient rise in intracellular Ca<sup>2+</sup>.</p> <p>Conclusions</p> <p>Ca<sup>2+ </sup>signaling mediated <it>via </it>FPR2 follows the same route as FPR1, which involves initial emptying of the intracellular stores. PBP10 inhibits selectively the signals generated by FPR2, both with respect to NADPH-oxidase activity and the transient rise in intracellular Ca<sup>2+ </sup>induced by agonist exposure.</p
A multi‐ethnic analysis of immune‐related gene expression signatures in patients with ovarian clear cell carcinoma
10.1002/path.5769The Journal of Patholog
Large Anomalous Hall effect in a silicon-based magnetic semiconductor
Magnetic semiconductors are attracting high interest because of their
potential use for spintronics, a new technology which merges electronics and
manipulation of conduction electron spins. (GaMn)As and (GaMn)N have recently
emerged as the most popular materials for this new technology. While Curie
temperatures are rising towards room temperature, these materials can only be
fabricated in thin film form, are heavily defective, and are not obviously
compatible with Si. We show here that it is productive to consider transition
metal monosilicides as potential alternatives. In particular, we report the
discovery that the bulk metallic magnets derived from doping the narrow gap
insulator FeSi with Co share the very high anomalous Hall conductance of
(GaMn)As, while displaying Curie temperatures as high as 53 K. Our work opens
up a new arena for spintronics, involving a bulk material based only on
transition metals and Si, and which we have proven to display a variety of
large magnetic field effects on easily measured electrical properties.Comment: 19 pages with 5 figure
Characteristics comparison of optimal L-band Er-doped ASE sources in different configurations
In this paper, we investigate the 1480nm pumped L-band erbium doped fiber amplified spontaneous emission source of three major configurations: one-stage double-pass forward pump configuration, two-stage with C-band ASE injection configuration, one-stage double-pass bi-directional pump configuration. The characteristics are compared in terms of the output power, pumping conversion efficiency, bandwidth, and mean wavelength stability. It is shown that the one-stage double-pass bi-directional pump configuration has a better performance than the other two configurations
Differences in Disease Severity but Similar Telomere Lengths in Genetic Subgroups of Patients with Telomerase and Shelterin Mutations
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Clinical and physiological effects of transcranial electrical stimulation position on motor evoked potentials in scoliosis surgery
<p>Abstract</p> <p>Background</p> <p>During intraoperative monitoring for scoliosis surgery, we have previously elicited ipsilateral and contralateral motor evoked potentials (MEP) with cross scalp stimulation. Ipsilateral MEPs, which may have comprised summation of early ipsilaterally conducted components and transcallosally or deep white matter stimulated components, can show larger amplitudes than those derived purely from contralateral motor cortex stimulation. We tested this hypothesis using two stimulating positions. We compared intraoperative MEPs in 14 neurologically normal subjects undergoing scoliosis surgery using total intravenous anesthetic regimens.</p> <p>Methods</p> <p>Trancranial electrical stimulation was applied with both cross scalp (C3C4 or C4C3) or midline (C3Cz or C4Cz) positions. The latter was assumed to be more focal and result in little transcallosal/deep white matter stimulation. A train of 5 square wave stimuli 0.5 ms in duration at up to 200 mA was delivered with 4 ms (250 Hz) interstimulus intervals. Averaged supramaximal MEPs were obtained from the tibialis anterior bilaterally.</p> <p>Results</p> <p>The cross scalp stimulating position resulted in supramaximal MEPs that were of significantly higher amplitude, shorter latency and required lower stimulating intensity to elicit overall (Wilcoxon Signed Rank test, p < 0.05 for all), as compared to the midline stimulating position. However, no significant differences were found for all 3 parameters comparing ipsilaterally and contralaterally recorded MEPs (p > 0.05 for all), seen for both stimulating positions individually.</p> <p>Conclusions</p> <p>Our findings suggest that cross scalp stimulation resulted in MEPs obtained ipsilaterally and contralaterally which may be contributed to by summation of ipsilateral and simultaneous transcallosally or deep white matter conducted stimulation of the opposite motor cortex. Use of this stimulating position is advocated to elicit MEPs under operative circumstances where anesthetic agents may cause suppression of cortical and spinal excitability. Although less focal in nature, cross scalp stimulation would be most suitable for infratentorial or spinal surgery, in contrast to supratentorial neurosurgical procedures.</p
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