2,069 research outputs found
Effects of relative orientation of the molecules on electron transport in molecular devices
Effects of relative orientation of the molecules on electron transport in
molecular devices are studied by non-equilibrium Green's function method based
on density functional theory. In particular, two molecular devices, with the
planer Au and Ag clusters sandwiched between the Al(100) electrodes
are studied. In each device, two typical configurations with the clusters
parallel and vertical to the electrodes are considered. It is found that the
relative orientation affects the transport properties of these two devices
completely differently. In the Al(100)-Au-Al(100) device, the conductance
and the current of the parallel configuration are much larger than those in the
vertical configuration, while in the Al(100)-Ag-Al(100) device, an
opposite conclusion is obtained
High photo-excited carrier multiplication by charged InAs dots in AlAs/GaAs/AlAs resonant tunneling diode
We present an approach for the highly sensitive photon detection based on the
quantum dots (QDs) operating at temperature of 77K. The detection structure is
based on an AlAs/GaAs/AlAs double barrier resonant tunneling diode combined
with a layer of self-assembled InAs QDs (QD-RTD). A photon rate of 115 photons
per second had induced 10nA photocurrent in this structure, corresponding to
the photo-excited carrier multiplication factor of 10^7. This high
multiplication factor is achieved by the quantum dot induced memory effect and
the resonant tunneling tuning effect of QD-RTD structure.Comment: 10 pages,5 figures. Submitted to Applied Physics Letter
Isolation, identification and complete genome sequence analysis of a strain of foot-and-mouth disease virus serotype Asia1 from pigs in southwest of China
Abstract Backgroud Foot-and-mouth disease virus (FMDV) serotype Asia1 generally infects cattle and sheep, while its infection of pigs is rarely reported. In 2005-2007, FMD outbreaks caused by Asia1 type occurred in many regions of China, as well as some parts of East Asia countries. During the outbreaks, there was not any report that pigs were found to be clinically infected. Results In this study, a strain of FMDV that isolated from pigs was identified as serotype Asia1, and designated as "Asia1/WHN/CHA/06". To investigate the genomic feature of the strain, complete genome of Asia1/WHN/CHA/06 was sequenced and compared with sequences of other FMDVs by phylogenetic and recombination analysis. The complete genome of Asia1/WHN/CHA/06 was 8161 nucleotides (nt) in length, and was closer to JS/CHA/05 than to all other strains. Potential recombination events associated with Asia1/WHN/CHA/06 were found between JS/CHA/05 and HNK/CHA/05 strains with partial 3B and 3C fragments. Conclusion This is the first report of the isolation and identification of a strain of FMDV type Asia1 from naturally infected pigs. The Asia1/WHN/CHA/06 strain may evolve from the recombination of JS/CHA/05 and HNK/CHA/05 strains.</p
Heat shock transcription factor 1 preserves cardiac angiogenesis and adaptation during pressure overload
To examine how heat shock transcription factor 1 (HSF1) protects against maladaptive hypertrophy during pressure overload, we subjected HSF1 transgenic (TG), knockout (KO) and wild type (WT) mice to a constriction of transverse aorta (TAC), and found that cardiac hypertrophy, functions and angiogenesis were well preserved in TG mice but were decreased in KO mice compared to WT ones at 4 weeks, which was related to HIF-1 and p53 expression. Inhibition of angiogenesis suppressed cardiac adaptation in TG mice while overexpression of angiogenesis factors improved maladaptive hypertrophy in KO mice. In vitro formation of vasculatures by microvascular endothelial cells was higher in TG mice but lower in KO mice than in WT ones. A siRNA of p53 but not a HIF-1 gene significantly reversed maladaptive hypertrophy in KO mice whereas a siRNA of HIF-1 but not a p53 gene induced maladaptive hypertrophy in TG mice. Heart microRNA analysis showed that miR-378 and miR-379 were differently changed among the three mice after TAC, and miR-378 or siRNA of miR-379 could maintain cardiac adaptation in WT mice. These results indicate that HSF1 preserves cardiac adaptation during pressure overload through p53-HIF-1-associated angiogenesis, which is controlled by miR-378 and miR-379
Grand canonical Monte Carlo simulation on adsorption of aniline on the ice surface
Aniline has been found to have frequent environmental occurrence and high toxicity. However, little study has been performed on its environmental fate. Here, we employed Grand Canonical Monte Carlo simulations (GCMC) to investigate the adsorption behavior of aniline on hexagonal ice surface at 200 K using our modified force field of aniline and TIP5P force field of water. The results indicate that the adsorption isotherm of aniline exhibits a “monolayer saturation plateau”, starting with a rapid increase, then a plateau, and finally a condensed phase. Under very low surface coverage, the adsorption isotherm apparently follows Langmuir type adsorption isotherm although anilines can be adsorbed to various sites. Within the range of the apparent Langmuir-type adsorption isotherm, adsorbed anilines are independent from each other and most anilines are almost parallel to the ice surface and form two N−H•••O hydrogen bonds. With the increase of coverage, the adsorbed anilines can interact with each other, resulting in the deviation from the apparent Langmuir-type adsorption isotherm. In addition, the adsorption energy from GCMC simulation (−65.91 kJ mol−1) is well consistent that from our validating quantum chemistry calculation (−69.34 kJ mol−1), further confirming the reliability of our GCMC simulation results.Peer reviewe
SDSS J163459.82+204936.0: A Ringed Infrared-Luminous Quasar with Outflows in both Absorption and Emission Lines
SDSS J1634+2049 is a local (z = 0.1293) infrared-luminous quasar with LIR=
10^11.91 Lsun. We present a detailed multiwavelength study of both the host
galaxy and the nucleus. The host galaxy demonstrates violent, obscured star
formation activities with SFR ~ 140 Msun yr^-1, estimated from either the PAH
emission or IR luminosity. The optical to NIR spectra exhibit a blueshifted
narrow cuspy component in Hb, HeI5876,10830 and other emission lines
consistently with an offset velocity of ~900 km/s, as well as additional
blueshifting phenomena in high-ionization lines , while there exist blueshifted
broad absorption lines (BALs) in NaID and HeI*3889,10830, indicative of the AGN
outflows producing BALs and emission lines. Constrained mutually by the several
BALs with CLOUDY, the physical properties of the absorption-line outflow are
derived as follows: 10^4 < n_H <= 10^5 cm^-3, 10^-1.3 <= U <= 10^-0.7 and
10^22.5<= N_H <= 10^22.9 cm^-2 , similar to those derived for the emission-line
outflows. The similarity suggests a common origin. Taking advantages of both
the absorption lines and outflowing emission lines, we find that the outflow
gas is located at a distance of 48 - 65 pc from the nucleus, and that the
kinetic luminosity of the outflow is 10^44-10^46 erg s^-1. J1634+2049 has a
off-centered galactic ring on the scale of ~ 30 kpc that is proved to be formed
by a recent head-on collision by a nearby galaxy. Thus this quasar is a
valuable object in the transitional phase emerging out of dust enshrouding as
depicted by the co-evolution scenario.Comment: 13 figures, 6 tables; accepted for publication in Ap
Analysis of Density Wave Oscillations in Helically Coiled Tube Once-Through Steam Generator
Helically coiled tube Once-Through Steam Generator (H-OTSG) is one of the key equipment types for small modular reactors. The flow instability of the secondary side of the H-OTSG is particularly serious, because the working condition is in the range of low and medium pressure. This paper presents research on density wave oscillations (DWO) in a typical countercurrent H-OTSG. Based on the steady-state calculation, the mathematical model of single-channel system was established, and the transfer function was derived. Using Nyquist stability criterion of the single variable, the stability cases were studied with an in-house computer program. According to the analyses, the impact law of the geometrical parameters to the system stability was obtained. RELAP5/MOD3.2 code was also used to simulate DWO in H-OTSG. The theoretical analyses of the in-house program were compared to the simulation results of RELAP5. A correction factor was introduced to reduce the error of RELAP5 when modeling helical geometry. The comparison results agreed well which showed that the correction is effective
Ethyl 5-(4-chlorophenyl)-2-[(Z)-(methoxycarbonyl)methylene]-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a]pyrimidine-6-carboxylate
The title compound, C19H17ClN2O5S, was synthesized by the reaction of ethyl 6-(4-chlorophenyl)-2-mercapto-4-methyl-1,6-dihydropyrimidine-5-carboxylate and dimethyl acetylenedicarboxylate in methanol. In the molecule, the nearly planar thiazole ring, with a mean deviation from the plane of 0.0108 (3) Å, is fused with a dihydropyrimidine ring in a flattened half-chair conformation
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