11,495 research outputs found
Thermal rectification and negative differential thermal resistance in lattices with mass gradient
We study thermal properties of one dimensional(1D) harmonic and anharmonic
lattices with mass gradient. It is found that the temperature gradient can be
built up in the 1D harmonic lattice with mass gradient due to the existence of
gradons. The heat flow is asymmetric in the anharmonic lattices with mass
gradient. Moreover, in a certain temperature region the {\it negative
differential thermal resistance} is observed. Possible applications in
constructing thermal rectifier and thermal transistor by using the graded
material are discussed.Comment: 4 pages 5 eps figs. Accepted for pub. in Phys. Rev. B Rap. Com
A bi-layer multi-time coordination method for optimal generation and reserve schedule and dispatch of a grid-connected microgrid
With the integration of more microgrids in distribution networks, its optimal autonomous operation becomes more important to reduce its operating cost and its influence on the main grid. This paper proposes a bi-layer multi-time coordination method for optimal generation and reserve schedule and dispatch of a grid-connected microgrid to reduce the impact of uncertainties of renewable sources, loads, and random component failures on power balance, operating costs, and system reliability. The reserve is refined into positive and negative reserves related to power shortage and power surplus. In the days ahead schedule layer, generating units are committed, and relaxed bidirectional reserve boundaries are predicted for the next day. In the real-time dispatch layer, generation output is dynamically adjusted and the reserve is dispatched using a successive approximation based on real-time data. A test microgrid is analyzed to illustrate the effectiveness of the proposed approach
An all fiber source of frequency entangled photon pairs
We present an all fiber source of frequency entangled photon pairs by using
four wave mixing in a Sagnac fiber loop. Special care is taken to suppress the
impurity of the frequency entanglement by cooling the fiber and by matching the
polarization modes of the photon pairs counter-propagating in the fiber loop.
Coincidence detection of signal and idler photons, which are created in pair
and in different spatial modes of the fiber loop, shows the quantum
interference in the form of spatial beating, while the single counts of the
individual signal (idler) photons keep constant. When the production rate of
photon pairs is about 0.013 pairs/pulse, the envelope of the quantum
interference reveals a visibility of , which is close to the
calculated theoretical limit 97.4%Comment: 11 pages, 6 figures, to appear in Phys. Rev.
Superconductivity at 36 K in Gadolinium-arsenide Oxides GdOFFeAs
In this paper we report the fabrication and superconducting properties of
GdOFFeAs. It is found that when x is equal to 0.17,
GdOFFeAs is a superconductor with the onset transition
temperature T 36.6K. Resistivity anomaly near 130K was
observed for all samples up to x = 0.17, such a phenomenon is similar to that
of LaOFFeAs. Hall coefficient indicates that
GdOFFeAs is conducted by electron-like charge carriers.Comment: 3 pages, 4 figure
Electrical stimulation for pain relief in knee osteoarthritis: systematic review and network meta-analysis
SummaryObjectiveTo investigate the efficacy of different electrical stimulation (ES) therapies in pain relief of patients with knee osteoarthritis (OA).MethodElectronic databases including MEDLINE, Embase and Cochrane Library were searched through for randomized controlled trials (RCTs) comparing any ES therapies with control interventions (sham or blank) or with each other. Bayesian network meta-analysis was used to combine both the direct and indirect evidence on treatment effectiveness.Results27 trials and six kinds of ES therapies, including high-frequency transcutaneous electrical nerve stimulation (h-TENS), low-frequency transcutaneous electrical nerve stimulation (l-TENS), neuromuscular electrical stimulation (NMES), interferential current (IFC), pulsed electrical stimulation (PES), and noninvasive interactive neurostimulation (NIN), were included. IFC is the only significantly effective treatment in terms of both pain intensity and change pain score at last follow-up time point when compared with the control group. Meanwhile, IFC showed the greatest probability of being the best option among the six treatment methods in pain relief. These estimates barely changed in sensitivity analysis. However, the evidence of heterogeneity and the limitation in sample size of some studies could be a potential threat to the validity of results.ConclusionIFC seems to be the most promising pain relief treatment for the management of knee OA. However, evidence was limited due to the heterogeneity and small number of included trials. Although the recommendation level of the other ES therapies is either uncertain (h-TENS) or not appropriate (l-TENS, NMES, PES and NIN) for pain relief, it is likely that none of the interventions is dangerous.Level of evidenceLevelⅡ, systematic review and network meta-analysis of RCTs
Cloning and sequence analysis of the defective in anther dehiscence1 (DAD1) gene fragment of Chinese kale
To clone the defective in anther dehiscence1 (DAD1) gene fragment of Chinese kale, about 700 bp product was obtained by PCR amplification using Chinese kale genomic DNA as the template and a pair of specific primers designed according to the conserved sequence of DAD1 genes of Arabidopsis thaliana and Brassica rapa. The amplified product was ligated into the T vector and sequenced. The results show that the gene fragment was 678 bp long without introns. It shared 89% identity with the nucleotide sequence of the DAD1 gene of A. thaliana and the sequence identity was as high as 97 to 99% with those of other plants belonging to the same genus as Chinese kale. The amino acid sequence deduced from the nucleotide sequence had 91% identity with that of A. thaliana. It was shown that the cloned fragment was a part of Chinese kale DAD1 gene.Key words: Chinese kale, Brassica oleracea var. alboglabra, defective in anther dehiscence1 (DAD1), gene clone
Dimeric 2G12 as a Potent Protection against HIV-1
We previously showed that broadly neutralizing anti-HIV-1 antibody 2G12 (human IgG1) naturally forms dimers that are more potent than monomeric 2G12 in in vitro neutralization of various strains of HIV-1. In this study, we have investigated the protective effects of monomeric versus dimeric 2G12 against HIV-1 infection in vivo using a humanized mouse model. Our results showed that passively transferred, purified 2G12 dimer is more potent than 2G12 monomer at preventing CD4 T cell loss and suppressing the increase of viral load following HIV-1 infection of humanized mice. Using humanized mice bearing IgG “backpack” tumors that provided 2G12 antibodies continuously, we found that a sustained dimer concentration of 5–25 µg/ml during the course of infection provides effective protection against HIV-1. Importantly, 2G12 dimer at this concentration does not favor mutations of the HIV-1 envelope that would cause the virus to completely escape 2G12 neutralization. We have therefore identified dimeric 2G12 as a potent prophylactic reagent against HIV-1 in vivo, which could be used as part of an antibody cocktail to prevent HIV-1 infection
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