47,027 research outputs found
Escherichia coli of sequence type 3835 carrying blaNDM-1, blaCTX-M-15, blaCMY-42 and blaSHV-12
New Delhi metallo-β-lactamase (NDM) represents a serious challenge for treatment and public health. A carbapenem-resistant Escherichia coli clinical strain WCHEC13-8 was subjected to antimicrobial susceptibility tests, whole genome sequencing and conjugation experiments. It was resistant to imipenem (MIC, >256 μg/ml) and meropenem (MIC, 128 μg/ml) and belonged to ST3835. blaNDM-1 was the only carbapenemase gene detected. Strain WCHEC13-8 also had a plasmid-borne AmpC gene (blaCMY-42) and two extended-spectrum β-lactamase genes (blaCTX-M-15 and blaSHV-12). blaNDM-1 and blaSHV-12 were carried by a 54-kb IncX3 self-transmissible plasmid, which is identical to plasmid pNDM-HF727 from Enterobacter cloacae. blaCMY-42 was carried by a 64-kb IncI1 plasmid and blaCTX-M-15 was located on a 141-kb plasmid with multiple F replicons (replicon type: F36:A4:B1). blaCMY-42 was in a complicated context and the mobilisation of blaCMY-42 was due to the transposition of IS Ecp1 by misidentifying its right-end boundary. Genetic context of blaNDM-1 in strain WCHEC13-8 was closely related to those on IncX3 plasmids in various Enterobacteriaceae species in China. In conclusion, a multidrug-resistant ST3835 E. coli clinical strain carrying blaNDM-1, blaCTX-M-15, blaCMY-42 and blaSHV-12 was identified. IncX3 plasmids may be making a significant contribution to the dissemination of blaNDM among Enterobacteriaceae in China
Temporal and Spectral Correlations of Cyg X-1
Temporal and spectral properties of X-ray rapid variability of Cyg X-1 are
studied by an approach of correlation analysis in the time domain on different
time scales. The correlation coefficients between the total intensity in 2-60
keV and the hardness ratio of 13-60 keV to 2-6 keV band on the time scale of
about 1 ms are always negative in all states. For soft states, the correlation
coefficients are positive on all the time scales from about 0.01 s to 100 s,
which is significantly different with that for transition and low states.
Temporal structures in high energy band are narrower than that in low energy
band in quite a few cases. The delay of high energy photons relative to low
energy ones in the X-ray variations has also been revealed by the correlation
analysis. The implication of observed temporal and spectral characteristics to
the production region and mechanism of Cyg X-1 X-ray variations is discussed.Comment: 17 pages, 6 figures included, to appear in Ap
Equilibrium states of the pressure function for products of matrices
Let be a non-trivial family of complex
matrices, in the sense that for any , there exists such that . Let be the pressure function of . We show
that for each , there are at most ergodic -equilibrium states of
, and each of them satisfies certain Gibbs property.Comment: 12 pages. To appear in DCD
Microwave-mediated heat transport through a quantum dot
The thermoelectric effect in a quantum dot (QD) attached to two leads in the
presence of microwave fields is studied by using the Keldysh nonequilibrium
Green function technique. When the microwave is applied only on the QD and in
the linear-response regime, the main peaks in the thermoelectric figure of
merit and the thermopower are found to decrease, with the emergence of a set of
photon-induced peaks. Under this condition the microwave field can not generate
heat current or electrical bias voltage. Surprisingly, when the microwave field
is applied only to one (bright) lead and not to the other (dark) lead or the
QD, heat flows mostly from the dark to the bright lead, almost irrespectively
to the direction of the thermal gradient. We attribute this effect to
microwave-induced opening of additional transport channels below the Fermi
energy. The microwave field can change both the magnitude and the sign of the
electrical bias voltage induced by the temperature gradient.Comment: 5 figur
Structural, optical, magnetic and electrical properties of Zn1-x Co (x) O thin films
Despite a considerable effort aiming at elucidating the nature of
ferromagnetism in ZnO-based magnetic semiconductor, its origin still remains
debatable. Although the observation of above room temperature ferromagnetism
has been reported frequently in the literature by magnetometry measurement, so
far there has been no report on correlated ferromagnetism in magnetic, optical
and electrical measurements. In this paper, we investigate systematically the
structural, optical, magnetic and electrical properties of Zn1-x Co (x) O:Al
thin films prepared by sputtering with x ranging from 0 to 0.33. We show that
correlated ferromagnetism is present only in samples with x > 0.25. In
contrast, samples with x < 0.2 exhibit weak ferromagnetism only in magnetometry
measurement which is absent in optical and electrical measurements. We
demonstrate, by systematic electrical transport studies that carrier
localization indeed occurs below 20-50 K for samples with x < 0.2; however,
this does not lead to the formation of ferromagnetic phase in these samples
with an electron concentration in the range of 6 x 10(19) cm(-3) 1 x 10(20)
cm(-3). Detailed structural and optical transmission spectroscopy analyses
revealed that the anomalous Hall effect observed in samples with x > 0.25 is
due to the formation of secondary phases and Co clusters.Comment: 28 pages, 8 figure
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