Context. The dense, cold regions where high-mass stars form are poorly characterized, yet they represent an ideal opportunity to learn more about the initial conditions of high-mass star formation ...(HMSF) since high-mass starless cores (HMSCs) lack the violent feedback seen at later evolutionary stages. Aims. We investigate the initial conditions of HMSF by studying the dynamics and chemistry of HMSCs. Methods. We present continuum maps obtained from the Submillimeter Array (SMA) interferometry at 1.1 mm for four infrared dark clouds (IRDCs, G28.34 S, IRDC 18530, IRDC 18306, and IRDC 18308). For these clouds, we also present line surveys at 1 mm/3 mm obtained from IRAM 30 m single-dish observations. Results. (1) At an angular resolution of 2′′ (~104 AU at an average distance of 4 kpc), the 1.1 mm SMA observations resolve each source into several fragments. The mass of each fragment is on average >10 M⊙, which exceeds the predicted thermal Jeans mass of the entire clump by a factor of up to 30, indicating that thermal pressure does not dominate the fragmentation process. Our measured velocity dispersions in the lines obtained by 30 m imply that non-thermal motion provides the extra support against gravity in the fragments. (2) Both non-detection of high-J transitions and the hyperfine multiplet fit of N2H+ (J = 1 → 0), C2H (N = 1 → 0), HCN(J = 1 → 0), and H13CN(J = 1 → 0) indicate that our sources are cold and young. However, the obvious detection of SiO and the asymmetric line profile of HCO+(J = 1 → 0) in G28.34 S indicate a potential protostellar object and probable infall motion. (3) With a large number of N-bearing species, the existence of carbon rings and molecular ions, and the anti-correlated spatial distributions between N2H+/NH2D and CO, our large-scale high-mass clumps exhibit similar chemical features to small-scale low-mass prestellar objects. Conclusions. This study of a small sample of IRDCs illustrates that thermal Jeans instability alone cannot explain the fragmentation of the clump into cold (T ~ 15 K), dense (>105 cm-3) cores and that these IRDCs are not completely quiescent.
The excessively high atmospheric CO2 concentration is associated with rapidly evolving industrial, commercial, and residential uses of fossil fuels, which has caused global warming and climate ...crisis. Photocatalytic or electrocatalytic reduction of CO2 into value-added hydrocarbon fuels has provided a promising and sustainable solution to addressing these issues simultaneously. Multicarbon products (C2+) with higher energy densities are generally desirable in fueling transportation and other industries. However, the low selectivity and subsequently a higher cost toward these C2+ products have severely limited their larger scale production. Here, we review the strategies of controlling the C2+ product selectivity during the photocatalytic and electrocatalytic CO2 reduction reaction (CRR) processes with their catalytic reaction mechanisms. This review starts with the fundamentals on photocatalytic and electrocatalytic CRR, which is followed by discussions about how reaction mechanisms and process pathways affect the C2+ product selectivity and the main strategies to improve both photocatalysis and electrocatalysis systems. Finally, some outlook for future work and challenges in improving the C2+ product selectivity is included.
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Here, we present a temperature (T) dependent comparison between field-effect and Hall mobilities in field-effect transistors based on few-layered WSe2 exfoliated onto SiO2. Without dielectric ...engineering and beyond a T-dependent threshold gate-voltage, we observe maximum hole mobilities approaching 350 cm(2)/Vs at T = 300 K. The hole Hall mobility reaches a maximum value of 650 cm(2)/Vs as T is lowered below ~150 K, indicating that insofar WSe2-based field-effect transistors (FETs) display the largest Hall mobilities among the transition metal dichalcogenides. The gate capacitance, as extracted from the Hall-effect, reveals the presence of spurious charges in the channel, while the two-terminal sheet resistivity displays two-dimensional variable-range hopping behavior, indicating carrier localization induced by disorder at the interface between WSe2 and SiO2. We argue that improvements in the fabrication protocols as, for example, the use of a substrate free of dangling bonds are likely to produce WSe2-based FETs displaying higher room temperature mobilities, i.e. approaching those of p-doped Si, which would make it a suitable candidate for high performance opto-electronics.
Low temperature is one of the important factors limiting wheat yield in cold regions. Expansins are nonenzymatic proteins that loosen cell walls and play important roles in diverse biological ...processes related to cell wall modification, including development and stress tolerance. Many studies have shown that expansins are involved in resistance to various abiotic stresses, such as heat and drought. However, the role of expansins in response to low‐temperature stress remains unclear.
Based on our previous transcriptome data of a winter wheat cultivar Dongnongdongmai 2 (DN2), we found that one of the expansin genes, TaEXPA8, was significantly induced by low temperature, indicating a role for TaEXPA8 in cold resistance. In this study, the paralogous TaEXPA8 genes TaEXPA8‐A, TaEXPA8‐B and TaEXPA8‐D were cloned by RT‐PCR. These three genes were then transformed into Arabidopsis by the floral dip method. Expression patterns of TaEXPA8 genes in different tissues and in response to several abiotic stresses and hormones were detected by quantitative real‐time PCR (qRT‐PCR).
The results showed that TaEXPA8‐A and TaEXPA8‐B were expressed mainly in roots, while TaEXPA8‐D was expressed predominantly in flowers. TaEXPA8 genes were induced by low‐temperature and drought. The overexpression of TaEXPA8‐B and TaEXPA8‐D enhanced low‐temperature resistance and had increased superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity and soluble protein, MDA and proline content.
In summary, our study suggested that the expansins TaEXPA8‐B and TaEXPA8‐D are involved in the response to low temperature and possibly play a role in cold resistance by activating the protective enzyme system.
Purpose
Increasing evidence suggested that microRNA plays an important role in ovarian cancer. In this study, the role of miR-92 in ovarian cancer was investigated.
Methods
In this study, miR-92 ...expression in clinical sample was evaluated, role of miR-92 was investigated in vitro, and underlying mechanism was investigated using Chip, co-IP, and western blot.
Results
In this study, we show that miR-92 is overexpressed in ovarian cancer tissue compared with normal cancer tissue. Transfection of miR-92 increased proliferation of ovarian cancer cell, and increased migration capacity and colony formation were observed after miR-92 transfection; we found that expression of LATS2 was decreased by miR-92, and this was further confirmed by luciferase assay, which proved that miR-92 is targeting 3′ of the endogenous LATS2 gene. Downregulation of LATS2 resulted in increased translocation of YAP1 and upregulation of PD-L1, which subsequently suppressed NK cell function and promoted T cell apoptosis. Moreover, co-transfection of YAP1-targeted shRNA could relieve miR-92-induced immune suppression effect. Mechanically, immunoprecipitation (IP) was used to show that LATS2 interacted with YAP1 and subsequently limited nuclear translocation of YAP1; chromatin immunoprecipitation (ChIP) was used to confirm that YAP1 could bind to enhancer region of PD-L1 to enhance transcription activity of PD-L1.
Conclusions
Our data revealed a novel mechanism which finally resulted in immune suppression in ovarian cancer.
•A formula of steel slag and bentonite mixtures (SBM) to construct a hydraulic barrier.•The saturated hydraulic conductivity (ks) and microstructure of SBM was studied.•A better steel slag gradation ...reduces ks significantly due to less macropores.•Compact SBM at water content 1–2% wetter than the optimum value reduces ks a lot.•Water washing treatment of steel slag reduces ks of SBM by one order of magnitude.
The feasibility of using steel slag and bentonite mixtures to construct the hydraulic barrier of a landfill cover was explored in the present study. Fine-grained steel slag (SS; particle diameter < 1 mm) and sodium-activated calcium bentonite (SACB) were used to prepare compacted specimens, and the saturated hydraulic conductivity (ks) was measured using a flexible-wall permeameter. Influential factors including SACB content (BC), SS gradation, water-washing treatment of SS and compaction water content (ωcomp) were investigated. The hydraulic conductivity results were interpreted in microscopic scale through mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). It was found that when BC was below 10%, the ks value of the specimens prepared with well graded SS was about one order of magnitude lower than that of the specimens prepared with poorly graded SS. This was due to less macropores caused by better SS gradation. Yet, the effects of SS gradation on ks diminished as BC further increased to 15%, suggesting the dominant role of BC on ks at high BC. Water-washing treatment of SS helped reduce ks significantly to 1.2 × 10−10 m/s at BC of 10%, owing to less multivalent cations and hence lower osmotic swelling reduction caused by cations. Controlling ωcomp 1–2% wetter than the optimum water content (ωopt) also helped reduce ks significantly, owing to the reduction of macropores. Accordingly, it is suggested to use well-graded SS mixed with 10% SACB and then compact at ωcomp slightly wetter than ωopt to the degree of compaction greater than 90% in engineering practice.
The survival benefit of liver transplantation depends on candidate disease severity, as measured by MELD score. However, donor liver quality may also affect survival benefit. Using US data from the ...SRTR on 28 165 adult liver transplant candidates wait‐listed between 2001 and 2005, we estimated survival benefit according to cross‐classifications of candidate MELD score and deceased donor risk index (DRI) using sequential stratification. Covariate‐adjusted hazard ratios (HR) were calculated for each liver transplant recipient at a given MELD with an organ of a given DRI, comparing posttransplant mortality to continued wait‐listing with possible later transplantation using a lower‐DRI organ. High‐DRI organs were more often transplanted into lower‐MELD recipients and vice versa. Compared to waiting for a lower‐DRI organ, the lowest‐MELD category recipients (MELD 6–8) who received high‐DRI organs experienced significantly higher mortality (HR = 3.70; p < 0.0005). All recipients with MELD ≥20 had a significant survival benefit from transplantation, regardless of DRI. Transplantation of high‐DRI organs is effective for high but not low‐MELD candidates. Pairing of high‐DRI livers with lower‐MELD candidates fails to maximize survival benefit and may deny lifesaving organs to high‐MELD candidates who are at high risk of death without transplantation.
Transplanting livers with a high donor risk index into candidates with lower MELD scores fails to maximize survival benefit and may deny lifesaving organs to high MELD candidates who are at high risk of death without transplantation.
Studies have shown that linezolid (LZD) can be used to treat extensively drug-resistant tuberculosis (XDR-TB).
To conduct a systematic review and meta-analysis to assess existing evidence concerning ...efficacy and safety of LZD for XDR-TB treatment.
The MEDLINE@OVID, PubMed, EMBASE, the Cochrane Library, Clinical Trials, Sinomed, CMCI, CNKI, VIP and Wanfang databases were systematically searched for randomised controlled trials, cohort studies, case series or case reports on XDR-TB patients treated with LZD from January 2000 to December 2016. Summary estimates of the rate of sputum culture conversion, treatment success and adverse effects were calculated; data that could not be combined were summarised and described qualitatively. The combined results were examined for heterogeneity, sensitivity and publishing bias.
Twenty-two original studies covering a total of 302 patients with XDR-TB fulfilled the inclusion criteria. Pooled estimates for sputum culture conversion and treatment success rates were respectively 93.2% and 67.4% in XDR-TB patients on LZD treatment. The pooled estimates for the rate of myelosuppression, peripheral neuropathy, optic neuritis and adverse reactions of the gastrointestinal tract were respectively 42.5%, 26.0%, 19.0% and 35.0%. Heterogeneity was mostly due to the initial dose of LZD (≤600 mg/d or >600 mg/d), as patients with a high initial dose of LZD were more likely to have myelosuppression (48.4% vs. 24.8%,
= 0.010) and adverse events of the gastrointestinal tract (41.3% vs.15.4%,
= 0.100).
LZD appears to be effective for XDR-TB, but adverse events are common. An LZD dose of ≤600 mg/d as the initial dose for treating XDR-TB patients is recommended.
In recent years, the application of graphitic carbon nitride (g-C3N4) for electrochemical CO2 reduction reaction (eCO2RR) has aroused strong interest. However, this material is still facing severe ...activity issue towards eCO2RR so far, and studies on its catalytic mechanism have not been sufficiently implemented either. Herein, we report an Ag-decorated sulfur-doped graphitic carbon nitride/carbon nanotube nanocomposites (Ag–S–C3N4/CNT) for efficient eCO2RR to carbon monoxide (CO). The resulting Ag–S–C3N4/CNT catalyst exhibits a notable performance in eCO2RR, yielding a high current density of −21.3 mA/cm2 at −0.77 VRHE and maximum CO Faradaic efficiency over 90% in H-type cell. Strikingly, when combining with flow cell configuration, the fabricated nanocomposites permit an industrial scale and cost-effective eCO2RR, showing a current density larger than 200 mA/cm2 and the Faradaic efficiency of CO over 80% in a wide potential window, delivering the best eCO2RR performance among the C3N4-derivatives. Moreover, the catalytic mechanism of this nanocomposite
has been further explored through density functional theory (DFT) and electrochemical methods carefully. Our work not only sheds light on industrial scale eCO2RR to CO but also leads to new insights on the application of C3N4-based composite materials in electrocatalytic processes.
Ag-decorated sulfur-doped C3N4/CNT nanocomposites were synthesized as a highly active and selective eCO2RR catalyst. The resulting nanocomposites exhibit excellent performance in eCO2RR to CO, yielding a high current density of −21.3 mA/cm2 at −0.77 VRHE and maximum CO Faradaic efficiency over 90% in H-cell. In addition, when combining with flow cell configuration, the obtained catalyst delivers the best eCO2RR performance among C3N4-derivatives, with a current density larger than 200 mA/cm2 and great CO Faradaic efficiency over 80% in a wide potential window. Display omitted
•C3N4-based nanomaterial has been developed as an efficient catalyst towards electrochemical CO2 reduction reaction.•Systematic studies were carried out to understand the catalytic mechanism of the C3N4-derivates.•The best electrochemical CO2 reduction performance among the C3N4-based materials was achieved
We report a successful observation of pressure-induced superconductivity in a topological compound Bi 2 Te 3 with T c of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations ...with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the hole-type carrier in the pressure-induced superconducting Bi 2 Te 3 single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi 2 Te 3 due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor.
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