146 research outputs found
Observation of Valley Zeeman and Quantum Hall Effects at Q Valley of Few-Layer Transition Metal Disulfides
In few-layer (FL) transition metal dichalcogenides (TMDC), the conduction
bands along the Gamma-K directions shift downward energetically in the presence
of interlayer interactions, forming six Q valleys related by three-fold
rotational symmetry and time reversal symmetry. In even-layers the extra
inversion symmetry requires all states to be Kramers degenerate, whereas in
odd-layers the intrinsic inversion asymmetry dictates the Q valleys to be
spin-valley coupled. In this Letter, we report the transport characterization
of prominent Shubnikov-de Hass (SdH) oscillations for the Q valley electrons in
FL transition metal disulfide (TMDs), as well as the first quantum Hall effect
(QHE) in TMDCs. Our devices exhibit ultrahigh field-effect mobilities (~16,000
cm2V-1s-1 for FL WS2 and ~10,500 cm2V-1s-1 for FL MoS2) at cryogenic
temperatures. Universally in the SdH oscillations, we observe a valley Zeeman
effect in all odd-layer TMD devices and a spin Zeeman effect in all even-layer
TMD devices.Comment: 20 pages, 4 figure
High frequency of Machado-Joseph disease identified in Southeastern Chinese kindreds with spinocerebellar ataxia
<p>Abstract</p> <p>Background</p> <p>Machado-Joseph disease (MJD), caused by a CAG repeat expansion located in exon10 of the <it>ATXN3 </it>gene, is now regarded as one of the most common spinocerebellar ataxia (SCA) in the world. The relative frequency of MJD among SCA has previously been estimated at about 50% in the Chinese population and has been reported to be related to the frequency of large normal alleles in some populations. Taq polymerase has been used for PCR in nearly all studies reported previously.</p> <p>Methods</p> <p>Normal and expanded alleles of <it>ATXN3 </it>were detected via PCR using LA Taq DNA polymerase (better for GC-rich sequences) and denaturing polyacrylamide gel electrophoresis in 150 normal individuals and 138 unrelated probands from autosomal dominant SCA families. To compare reaction efficiency, 12 MJD patients' expanded alleles were amplified with La Taq and Taq polymerase respectively in the same amplifying systems and reaction conditions.</p> <p>Results</p> <p>Normal alleles ranged from 12 to 42 CAG repeats. The most common allele contained 14 repeats with a frequency of 23.3%, which corroborates previous reports. The frequency of large normal alleles (>27 repeats) was 0.28, which was very high relative to previous reports. The frequency of MJD in SCA patients was 72.5%, which was significantly higher than those in previous reports about the Chinese and other Asian populations. This frequency was one of the highest reported worldwide, with only Portuguese and Brazilian populations exhibiting higher proportions. All 12 expanded alleles were amplified in PCR with La Taq polymerase, whereas only 2 expanded alleles were amplified with Taq polymerase.</p> <p>Conclusion</p> <p>We have first reported the highest relative frequency of MJD in Asia, and we attribute this high frequency to a more efficient PCR using LA Taq polymerase and hypothesized that large ANs may act as a reservoir for expanded alleles in the Southeastern Chinese population.</p
Determination of Decabrominated Diphenyl Ether in Soils by Soxhlet Extraction and High Performance Liquid Chromatography
This study described the development of a method based on soxhlet extraction combining high performance liquid chromatography (soxhlet-HPLC) for the accurate detection of BDE-209 in soils. The solvent effect of working standard solutions in HPLC was discussed. Results showed that 1 : 1 of methanol and acetone was the optimal condition which could totally dissolve the BDE-209 in environmental samples and avoid the decrease of the peak area and the peak deformation difference of BDE-209 in HPLC. The preliminary experiment was conducted on the configured grassland (1 μg/g) to validate the method feasibility. The method produced reliable reproducibility, simulated soils (n=4) RSD 1.0%, and was further verified by the analysis e-waste contaminated soils, RSD range 5.9–11.4%. The contamination level of BDE-209 in burning site was consistent with the previous study of Longtang town but lower than Guiyu town, and higher concentration of BDE-209 in paddy field mainly resulted from the long-standing disassembling area nearby. This accurate and fast method was successfully developed to extract and analyze BDE-209 in soil samples, showing its potential use for replacing GC to determinate BDE-209 in soil samples
Rapid Degradation of Phenanthrene by Using Sphingomonas sp. GY2B Immobilized in Calcium Alginate Gel Beads
The strain Sphingomonas sp. GY2B is a high efficient phenanthrene-degrading strain isolated from crude oil contaminated soils that displays a broad-spectrum degradation ability towards PAHs and related aromatic compounds. This paper reports embedding immobilization of strain GY2B in calcium alginate gel beads and the rapid degradation of phenanthrene by the embedded strains. Results showed that embedded immobilized strains had high degradation percentages both in mineral salts medium (MSM) and 80% artificial seawater (AS) media, and had higher phenanthrene degradation efficiency than the free strains. More than 90% phenanthrene (100 mg·L−1) was degraded within 36 h, and the phenanthrene degradation percentages were >99.8% after 72 h for immobilized strains. 80% AS had significant negative effect on the phenanthrene degradation rate (PDR) of strain GY2B during the linear-decreasing stage of incubation and preadsorption of cells onto rice straw could improve the PDR of embedded strain GY2B. The immobilization of strain GY2B possesses a good potential for application in the treatment of industrial wastewater containing phenanthrene and other related aromatic compounds
A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies
We have conducted a systematic search of low-mass black holes (BHs) in active
galactic nuclei (AGNs) with broad Halpha emission lines, aiming at building a
homogeneous sample that is more complete than previous ones for fainter, less
highly accreting sources. For this purpose, we developed a set of elaborate,
automated selection procedures and applied it uniformly to the Fourth Data
Release of the Sloan Digital Sky Survey. Special attention is given to
AGN--galaxy spectral decomposition and emission-line deblending. We define a
sample of 309 type 1 AGNs with BH masses in the range -- \msun (with a median of solar mass), using the
virial mass estimator based on the broad Halpha line. About half of our sample
of low-mass BHs differs from that of Greene & Ho, with 61 of them discovered
here for the first time. Our new sample picks up more AGNs with low accretion
rates: the Eddington ratios of the present sample range from to ~1,
with 30% below 0.1. This suggests that a significant fraction of low-mass BHs
in the local Universe are accreting at low rates. The host galaxies of the
low-mass BHs have luminosities similar to those of field galaxies,
optical colors of Sbc spirals, and stellar spectral features consistent with a
continuous star formation history with a mean stellar age of less than 1 Gyr.Comment: Accepted for publication in Ap
Tunable Coupling Architectures with Capacitively Connecting Pads for Large-Scale Superconducting Multi-Qubit Processors
We have proposed and experimentally verified a tunable inter-qubit coupling
scheme for large-scale integration of superconducting qubits. The key feature
of the scheme is the insertion of connecting pads between qubit and tunable
coupling element. In such a way, the distance between two qubits can be
increased considerably to a few millimeters, leaving enough space for arranging
control lines, readout resonators and other necessary structures. The increased
inter-qubit distance provides more wiring space for flip-chip process and
reduces crosstalk between qubits and from control lines to qubits. We use the
term Tunable Coupler with Capacitively Connecting Pad (TCCP) to name the
tunable coupling part that consists of a transmon coupler and capacitively
connecting pads. With the different placement of connecting pads, different
TCCP architectures can be realized. We have designed and fabricated a few
multi-qubit devices in which TCCP is used for coupling. The measured results
show that the performance of the qubits coupled by the TCCP, such as and
, was similar to that of the traditional transmon qubits without TCCP.
Meanwhile, our TCCP also exhibited a wide tunable range of the effective
coupling strength and a low residual ZZ interaction between the qubits by
properly tuning the parameters on the design. Finally, we successfully
implemented an adiabatic CZ gate with TCCP. Furthermore, by introducing TCCP,
we also discuss the realization of the flip-chip process and tunable coupling
qubits between different chips.Comment: Main text: 7 pages, 6 figure
Anti–SARS-CoV Immunoglobulin G in Healthcare Workers, Guangzhou, China
Low level of immunity for SARS-CoV among well healthcare workers reinforces the need for infection control measures in hospitals to prevent epidemics
Advances in automated tongue diagnosis techniques
This paper reviews the recent advances in a significant constituent of traditional oriental medicinal technology, called tongue diagnosis. Tongue diagnosis can be an effective, noninvasive method to perform an auxiliary diagnosis any time anywhere, which can support the global need in the primary healthcare system. This work explores the literature to evaluate the works done on the various aspects of computerized tongue diagnosis, namely preprocessing, tongue detection, segmentation, feature extraction, tongue analysis, especially in traditional Chinese medicine (TCM). In spite of huge volume of work done on automatic tongue diagnosis (ATD), there is a lack of adequate survey, especially to combine it with the current diagnosis trends. This paper studies the merits, capabilities, and associated research gaps in current works on ATD systems. After exploring the algorithms used in tongue diagnosis, the current trend and global requirements in health domain motivates us to propose a conceptual framework for the automated tongue diagnostic system on mobile enabled platform. This framework will be able to connect tongue diagnosis with the future point-of-care health system
Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector
A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
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