With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial ...susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22 774 and 84 572 annually. Rates of extended-spectrum β-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.
Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts1-3. Recent observations of a Galactic FRB4-8 suggest that at least some FRBs originate from magnetars, but the origin ...of cosmological FRBs is still not settled. Here we report the detection of1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref.9). These observations show irregular short-time variation ofthe Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (au; Earth-Sun distance) ofthe source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy10-12 show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.
The TET (ten-eleven translocation) family of α-ketoglutarate (α-KG)-dependent dioxygenases catalyzes the sequential oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), ...5-formylcytosine and 5-carboxylcytosine, leading to eventual DNA demethylation. The TET2 gene is a bona fide tumor suppressor frequently mutated in leukemia, and TET enzyme activity is inhibited in IDH1/2-mutated tumors by the oncometabolite 2-hydroxyglutarate, an antagonist of α-KG, linking 5mC oxidation to cancer development. We report here that the levels of 5hmC are dramatically reduced in human breast, liver, lung, pancreatic and prostate cancers when compared with the matched surrounding normal tissues. Associated with the 5hmC decrease is the substantial reduction of the expression of all three TET genes, revealing a possible mechanism for the reduced 5hmC in cancer cells. The decrease of 5hmC was also observed during tumor development in different genetically engineered mouse models. Together, our results identify 5hmC as a biomarker whose decrease is broadly and tightly associated with tumor development.
Microstructural aspects have fundamental influences on the fatigue crack characteristics of materials. In this paper, effects of inclusions, grain boundaries (GBs) and grain orientations on the ...fatigue crack initiation and propagation behavior in a 2524-T3 aluminum alloy have been investigated using in-situ scanning electron microscope (SEM) fatigue testing and electron back scattering diffraction (EBSD). The results show that, potential fatigue cracks tend to nucleate along coarse and closely spaced inclusion particles or high-angle GBs. Coarse inclusion particles drastically accelerate local crack growth rates. A model of series crack growing stages is given based on the observation of initiation and growth of cracks at the inclusion region. GBs serve to impede the crack tip from propagation and cause large angle crack deflections, which greatly affects local crack propagation behaviors. In addition, fatigue crack shows a strong tendency to propagate transgranularly grains with high Schmid factors (SFs) and avoid grains with low SFs.
► A more detailed three-dimensional model of PTC was proposed by combining FVM and MCRT method. ► Corresponding codes and solving methods were developed and applied to an LS2 PTC. ► Numerical results ...proved that the model and method is feasible and reliable. ► More details of the characteristics in the receiver were revealed and discussed. ► Typical HTF types and residual gas conditions were further studied.
In this paper, a more detailed three-dimensional computational model of the whole parabolic trough solar collector (PTC) system and corresponding numerical simulations by combining the Finite Volume Method (FVM) and the Monte Carlo Ray-Trace (MCRT) method were presented. Corresponding codes and solving methods were also developed and applied to simulate and analyze the total involuted photo-thermal conversion process of an experimental LS2 PTC system. The numerical results were compared with experimental data and good agreement was obtained, proving that the model and method used in the present study is feasible and reliable. More details of the characteristics of solar concentrating, solar collecting, fluid dynamics, coupled heat transfer and the whole flow and temperature fields in the receiver were also revealed and discussed. Then some typical heat transfer fluid (HTF) types and residual gas conditions were further studied. It was revealed that the properties of these HTFs/conditions and their varying relations of the fluid temperature affected the characteristics of fluid dynamics, coupled heat transfer and the whole temperature distributions in the receiver, thus affected the thermal loss and the collector efficiency synthetically.
We have investigated the spin texture of surface Fermi arcs in the recently discovered Weyl semimetal TaAs using spin- and angle-resolved photoemission spectroscopy. The experimental results ...demonstrate that the Fermi arcs are spin polarized. The measured spin texture fulfills the requirement of mirror and time-reversal symmetries and is well reproduced by our first-principles calculations, which gives strong evidence for the topologically nontrivial Weyl semimetal state in TaAs. The consistency between the experimental and calculated results further confirms the distribution of chirality of the Weyl nodes determined by first-principles calculations.
We prove exactly that the squared entanglement of formation, which quantifies the bipartite entanglement, obeys a general monogamy inequality in an arbitrary multiqubit mixed state. Based on this ...kind of exotic monogamy relation, we are able to construct two sets of useful entanglement indicators: the first one can detect all genuine multiqubit entangled states even in the case of the two-qubit concurrence and n-tangles being zero, while the second one can be calculated via quantum discord and applied to multipartite entanglement dynamics. Moreover, we give a computable and nontrivial lower bound for multiqubit entanglement of formation.
Aim
To gain deeper insights into the clostridial community dynamics and chemical transformations during the ensiling of alfalfa.
Methods and Results
Direct‐cut alfalfa silage (with the dry matter ...content of 240 g kg−1) was prepared with or without the addition of a lactic acid bacterial inoculant and sucrose. Silages were sampled at 0, 3, 7, 14, 28 and 56 days after ensiling and their bacterial community was determined using high‐throughput sequencing with a special focus on the clostridial community. A clostridial fermentation occurred in the control silage, with high contents of acetic acid, butyric acid and ammonia nitrogen and Clostridia counts; while the inoculated silage was well preserved, with low pH and high lactic acid content. Lactic acid bacteria dominated the bacterial community during the ensiling process. In the control silage, Weissella confusa, Lactobacillus brevis, Enterococcus mundtii and Pediococcus acidilactici were identified at the beginning of the fermentation. Thereafter, W. confusa, Lactobacillus helsingborgensis and Bifidobacterium asteroides appeared and quickly prevailed. In the inoculated silage, Lactobacillus plantarum dominated the whole ensiling process. The genus Clostridium dominated the clostridial community, and was depressed with the inoculated treatment. Clostridium perfringens, Garciella sp. and Clostridium baratii were the main initiators of the clostridial fermentation of the control silage, while Clostridium tyrobutyricum became the most abundant Clostridia with prolonged ensiling. Overall in the inoculated silage, little changes in the clostridial community were observed throughout the ensiling period. Treating alfalfa silage with a homolactic acid‐based bacterial inoculant prevented a clostridial fermentation resulting in more efficient fermentation.
Conclusion
Distinct changes in the bacterial community with a special focus on the clostridial community were associated with the development of the clostridial fermentation during the ensiling of alfalfa.
Significance and Impact of the Study
High‐throughput sequencing based on a novel Clostridia‐specific primer set proved a potentially useful tool to study the clostridial community dynamics, and could aid to elucidate the mechanism by which the clostridial fermentation develops during the ensiling of alfalfa.
Upper digestive endoscopy with biopsy and histopathological evaluation of the biopsy material is the standard method for diagnosing gastric cancer (GC). However, this procedure may not be widely ...available for screening in the developing world, whereas in developed countries endoscopy is frequently used without major clinical gain. There is a high demand for a simple and non-invasive test for selecting the individuals at increased risk that should undergo the endoscopic examination. Here, we studied the feasibility of a nanomaterial-based breath test for identifying GC among patients with gastric complaints.
Alveolar exhaled breath samples from 130 patients with gastric complaints (37 GC/32 ulcers / 61 less severe conditions) that underwent endoscopy/biopsy were analyzed using nanomaterial-based sensors. Predictive models were built employing discriminant factor analysis (DFA) pattern recognition, and their stability against possible confounding factors (alcohol/tobacco consumption; Helicobacter pylori) was tested. Classification success was determined (i) using leave-one-out cross-validation and (ii) by randomly blinding 25% of the samples as a validation set. Complementary chemical analysis of the breath samples was performed using gas chromatography coupled with mass spectrometry.
Three DFA models were developed that achieved excellent discrimination between the subpopulations: (i) GC vs benign gastric conditions, among all the patients (89% sensitivity; 90% specificity); (ii) early stage GC (I and II) vs late stage (III and IV), among GC patients (89% sensitivity; 94% specificity); and (iii) ulcer vs less severe, among benign conditions (84% sensitivity; 87% specificity). The models were insensitive against the tested confounding factors. Chemical analysis found that five volatile organic compounds (2-propenenitrile, 2-butoxy-ethanol, furfural, 6-methyl-5-hepten-2-one and isoprene) were significantly elevated in patients with GC and/or peptic ulcer, as compared with less severe gastric conditions. The concentrations both in the room air and in the breath samples were in the single p.p.b.v range, except in the case of isoprene.
The preliminary results of this pilot study could open a new and promising avenue to diagnose GC and distinguish it from other gastric diseases. It should be noted that the applied methods are complementary and the potential marker compounds identified by gas-chromatography/mass spectrometry are not necessarily responsible for the differences in the sensor responses. Although this pilot study does not allow drawing far-reaching conclusions, the encouraging preliminary results presented here have initiated a large multicentre clinical trial to confirm the observed patterns for GC and benign gastric conditions.
Trans‐4‐Hydroxy‐l‐proline (trans‐Hyp) is a valuable chiral building block for the synthesis of pharmaceutical intermediates. Bioconversion of l‐proline using recombinant strain with ...proline‐4‐hydroxylase (P4H) is a preferred biocatalytic process in the economical production of trans‐Hyp. In this study, a recombinant E. coli overexpressing hydroxylase (P4H), γ‐glutamyl kinase and glutamate‐semialdehyde dehydrogenase (ProBA) genes were constructed by knocking out the key genes in the metabolism. These key genes contained putA encoding proline dehydrogenase (PutA) in the l‐proline metabolism and other catalytic enzyme genes, sucAB encoding α‐ketoglutarate dehydrogenase (SucAB), aceAK encoding isocitratelyase (AceA) and isocitrate dehydrogenase kinase/phosphatase (AceK) in the TCA cycle. This recombinant strain coupled the synthetic pathway of trans‐Hyp with TCA cycle of the host strain. It inhibited the consumption of l‐proline completely and promoted the accumulation of 2‐oxoglutarate (2‐OG) as a co‐substrate, which realized the highest conversion of glucose to trans‐Hyp. A fed‐batch strategy was designed, capable of producing 31·0 g l−1 trans‐Hyp from glucose. It provided a theoretical basis for commercial conversion of glucose to trans‐Hyp.
Significance and Impact of the Study:Trans‐4‐Hydroxy‐l‐proline (trans‐Hyp) is a valuable chiral building block for the synthesis of pharmaceutical intermediates. Unsatisfactory microbial bioconversion resulted in a low yield of trans‐Hyp. In this study, we blocked the unwanted blunting pathways of host strain and make the cell growth couple with the trans‐Hyp synthesis from glucose. Finally, a recombinant Escherichia coli with short‐cut and efficient trans‐Hyp biosynthetic pathway was obtained. It provided a theoretical basis for commercial production of trans‐Hyp.
Significance and Impact of the Study:Trans‐4‐Hydroxy‐l‐proline (trans‐Hyp) is a valuable chiral building block for the synthesis of pharmaceutical intermediates. Unsatisfactory microbial bioconversion resulted in a low yield of trans‐Hyp. In this study, we blocked the unwanted blunting pathways of host strain and make the cell growth couple with the trans‐Hyp synthesis from glucose. Finally, a recombinant Escherichia coli with short‐cut and efficient trans‐Hyp biosynthetic pathway was obtained. It provided a theoretical basis for commercial production of trans‐Hyp.
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