440 research outputs found
Emerg. Infect. Dis
The multidrug-resistant (MDR) Salmonella enterica serotype Newport strain that produces CMY-2 β-lactamase(Newport MDR-AmpC) was the source of sporadic cases and outbreaks in humans in France during 2000–2005. Because this strain was not detected in food animals, it was most likely introduced into France through imported food products
Origin of Quasi-Periodic Pulsation at the Base of Kink Unstable Jet
We study a blowout jet that occurs at the west limb of the Sun on August
29, 2014 using high-resolution imaging/spectroscopic observations
provided by SDO/AIA and IRIS. An inverse -shape flux-rope appears
before the jet{--} morphological indication of the onset of kink instability.
The twisted field lines of kink-unstable flux-rope reconnect at its bright knot
and launch the blowout jet at 06:30:43 UT with an average speed of 234
km s. Just after the launch, the northern leg of the flux rope erupts
completely. The time-distance diagrams show multiple spikes or bright dots,
which is the result of periodic fluctuations, i.e., quasi-periodic fluctuations
(QPPs). The wavelet analysis confirms that QPPs have a dominant period of
03 minutes. IRIS spectra (Si~{\sc iv}, C~{\sc ii}, and Mg~{\sc ii})
may also indicate the occurrence of magnetic reconnection through existence of
broad complex profiles and bi-directional flows in the jet. Further, we
have found that line broadening is periodic with a period of 03
minutes, and plasma upflow is always occurs when the line width is high, i.e.,
multiple reconnection may produce periodic line broadening. The EM curves also
show the same period of 03 minutes in different temperature bins. The
images and EM show that this jets spire is mainly cool
(chromospheric/transition region) rather than hot (coronal) material. Further,
line broadening, intensity, and EM curves have a period of 03 minutes,
which strongly supports that multiple magnetic reconnection triggers QPPs in
the blowout jet.Comment: The Astrophysical Journal (In press), 25 pages, 12 figure
Measurement of the Branching Fraction of the Decay in Fully Reconstructed Events at Belle
We present an analysis of the exclusive
decay, where represents an
electron or a muon, with the assumption of charge-conjugation symmetry and
lepton universality. The analysis uses the full data sample
collected by the Belle detector, corresponding to 711 fb of integrated
luminosity. We select the events by fully reconstructing one meson in
hadronic decay modes, subsequently determining the properties of the other
meson. We extract the signal yields using a binned maximum-likelihood fit to
the missing-mass squared distribution in bins of the invariant mass of the two
pions or the momentum transfer squared. We measure a total branching fraction
of , where the
uncertainties are statistical and systematic, respectively. This result is the
first reported measurement of this decay.Comment: 23 pages, 19 figure
Recombination and Population Structure in Salmonella enterica
Salmonella enterica is a bacterial pathogen that causes enteric fever and gastroenteritis in humans and animals. Although its population structure was long described as clonal, based on high linkage disequilibrium between loci typed by enzyme electrophoresis, recent examination of gene sequences has revealed that recombination plays an important evolutionary role. We sequenced around 10% of the core genome of 114 isolates of enterica using a resequencing microarray. Application of two different analysis methods (Structure and ClonalFrame) to our genomic data allowed us to define five clear lineages within S. enterica subspecies enterica, one of which is five times older than the other four and two thirds of the age of the whole subspecies. We show that some of these lineages display more evidence of recombination than others. We also demonstrate that some level of sexual isolation exists between the lineages, so that recombination has occurred predominantly between members of the same lineage. This pattern of recombination is compatible with expectations from the previously described ecological structuring of the enterica population as well as mechanistic barriers to recombination observed in laboratory experiments. In spite of their relatively low level of genetic differentiation, these lineages might therefore represent incipient species
Fate of the H-NS–Repressed bgl Operon in Evolution of Escherichia coli
In the enterobacterial species Escherichia coli and Salmonella enterica, expression of horizontally acquired genes with a higher than average AT content is repressed by the nucleoid-associated protein H-NS. A classical example of an H-NS–repressed locus is the bgl (aryl-β,D-glucoside) operon of E. coli. This locus is “cryptic,” as no laboratory growth conditions are known to relieve repression of bgl by H-NS in E. coli K12. However, repression can be relieved by spontaneous mutations. Here, we investigated the phylogeny of the bgl operon. Typing of bgl in a representative collection of E. coli demonstrated that it evolved clonally and that it is present in strains of the phylogenetic groups A, B1, and B2, while it is presumably replaced by a cluster of ORFans in the phylogenetic group D. Interestingly, the bgl operon is mutated in 20% of the strains of phylogenetic groups A and B1, suggesting erosion of bgl in these groups. However, bgl is functional in almost all B2 isolates and, in approximately 50% of them, it is weakly expressed at laboratory growth conditions. Homologs of bgl genes exist in Klebsiella, Enterobacter, and Erwinia species and also in low GC-content Gram-positive bacteria, while absent in E. albertii and Salmonella sp. This suggests horizontal transfer of bgl genes to an ancestral Enterobacterium. Conservation and weak expression of bgl in isolates of phylogenetic group B2 may indicate a functional role of bgl in extraintestinal pathogenic E. coli
Multilocus Sequence Typing as a Replacement for Serotyping in Salmonella enterica
Salmonella enterica subspecies enterica is traditionally subdivided into serovars by serological and nutritional characteristics. We used Multilocus Sequence Typing (MLST) to assign 4,257 isolates from 554 serovars to 1092 sequence types (STs). The majority of the isolates and many STs were grouped into 138 genetically closely related clusters called eBurstGroups (eBGs). Many eBGs correspond to a serovar, for example most Typhimurium are in eBG1 and most Enteritidis are in eBG4, but many eBGs contained more than one serovar. Furthermore, most serovars were polyphyletic and are distributed across multiple unrelated eBGs. Thus, serovar designations confounded genetically unrelated isolates and failed to recognize natural evolutionary groupings. An inability of serotyping to correctly group isolates was most apparent for Paratyphi B and its variant Java. Most Paratyphi B were included within a sub-cluster of STs belonging to eBG5, which also encompasses a separate sub-cluster of Java STs. However, diphasic Java variants were also found in two other eBGs and monophasic Java variants were in four other eBGs or STs, one of which is in subspecies salamae and a second of which includes isolates assigned to Enteritidis, Dublin and monophasic Paratyphi B. Similarly, Choleraesuis was found in eBG6 and is closely related to Paratyphi C, which is in eBG20. However, Choleraesuis var. Decatur consists of isolates from seven other, unrelated eBGs or STs. The serological assignment of these Decatur isolates to Choleraesuis likely reflects lateral gene transfer of flagellar genes between unrelated bacteria plus purifying selection. By confounding multiple evolutionary groups, serotyping can be misleading about the disease potential of S. enterica. Unlike serotyping, MLST recognizes evolutionary groupings and we recommend that Salmonella classification by serotyping should be replaced by MLST or its equivalents
Measurement of the energy dependence of the ee → , and exclusive cross sections
Abstract We report the first measurement of the exclusive cross sections e + e − → B B ¯ , e + e − → B B ¯ ∗ , and e + e − → B ∗ B ¯ ∗ in the energy range from 10.63 GeV to 11.02 GeV. The B mesons are fully reconstructed in a large number of hadronic final states and the three channels are identified using a beam-constrained-mass variable. The shapes of the exclusive cross sections show oscillatory behavior with several maxima and minima. The results are obtained using data collected by the Belle experiment at the KEKB asymmetric-energy e + e − collider
Evidence for the decay ω →π ω (2012) →π ( Ξ)
Using a data sample of
980 fb collected with the Belle detector operating at the KEKB asymmetric-energy ee collider, we present evidence for the Ω(2012) in the resonant substructure of Ω → π ( Ξ) (( Ξ) = KΞ + KΞ ecays. The significance of the decays. The significance of the Ω(2012) signal is 4.2σ after considering the systematic uncertainties. The ratio of the branching fraction of Ω → π Ω(2012) π ( Ξ) relative to that of Ω → π Ω is calculated to be
0.220±0.059(stat.)±0.035(syst.). The individual ratios of the branching fractions of the two isospin modes are also determined and found to be B (Ω → π Ω(2012)) x B(Ω(2012) → Ξ) / B(Ω → π KΞ
= (9.6±3.2(stat.) ±1.8(syst.))%
and
B (Ω → π Ω(2012)) x B(Ω(2012) → Ξ) / B(Ω → π Ξ)
=(5.5±2.8(stat.) ±0.7(syst.))
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