Precisely Control Relationship between Sulfur Vacancy and H Absorption for Boosting Hydrogen Evolution Reaction

Ef fective and robust catalyst is the core of water splitting to produce hydrogen.Here, we report an anionic etching method to tailor the sulfur vacancy(VS) of NiS_(2) to further enhance the electrocatalytic performance for hydrogen evolution reaction(HER). With the VS concentration change from 2.4% to 8.5%, the H* adsorption strength on S sites changed and NiS_(2)-VS 5.9% shows the most optimized H* adsorption for HER with an ultralow onset potential(68 m V) and has long-term stability for 100 h in 1 M KOH media. In situ attenuated-total-reflection Fourier transform infrared spectroscopy(ATR-FTIRS) measurements are usually used to monitor the adsorption of intermediates. The S-H* peak of the Ni S_(2)-VS 5.9% appears at a very low voltage, which is favorable for the HER in alkaline media. Density functional theory calculations also demonstrate the Ni S_(2)-VS 5.9% has the optimal |ΔG^(H*)| of 0.17 e V. This work offers a simple and promising pathway to enhance catalytic activity via precise vacancies strategy.

Lymphangiogenesis, Lymphatic Endothelial Cells and Lymphatic Metastasis in Head and Neck Cancer—A Review of Mechanisms

Lymphatic metastasis is a continuous and complicated process. The detailed mechanisms of lymphatic metastasis are still not very clear, despite considerable research efforts in recent years. Previously, it was commonly accepted that there were no lymphatic vessels in the primary tumor. However, recent studies have demonstrated that lymphatic vessels are detectable in certain types of cancer, and more and more evidence has shown that cancer cells invade into local lymph nodes mainly via peritumoral lymphatic vessels, Moreover, activated endothelial cells may also be important, having an influence on lymphatic metastasis of cancer cells. This article, based on recent research findings, provides an in-depth discussion of the relationship between lymphangiogenesis, tumor-derived lymphatic endothelial cells and lymphatic metastasis in head and neck cancer.

A Stiffness Variable Passive Compliance Device with Reconfigurable Elastic Inner Skeleton and Origami Shell

Devices with variable stiffness are drawing more and more attention with the growing interests of human-robot interaction,wearable robotics,rehabilitation robotics,etc.In this paper,the authors report on the design,analysis and experiments of a stiffness variable passive compliant device whose structure is a combination of a reconfigurable elastic inner skeleton and an origami shell.The main concept of the reconfigurable skeleton is to have two elastic trapezoid four-bar linkages arranged in orthogonal.The stiffness variation generates from the passive deflection of the elastic limbs and is realized by actively switching the arrangement of the leaf springs and the passive joints in a fast,simple and straightforward manner.The kinetostatics and the compliance of the device are analyzed based on an efficient approach to the large deflection problem of the elastic links.A prototype is fabricated to conduct experiments for the assessment of the proposed concept.The results show that the prototype possesses relatively low stiffness under the compliant status and high stiffness under the stiff status with a status switching speed around 80 ms.

Evaluation of the dual vascular supply patterns in ground-glass nodules with a dynamic volume computed tomography

BACKGROUND In recent years,the detection rate of ground-glass nodules(GGNs)has been improved dramatically due to the popularization of low-dose computed tomography(CT)screening with high-resolution CT technique.This presents challenges for the characterization and management of the GGNs,which depends on a thorough investigation and sufficient diagnostic knowledge of the GGNs.In most diagnostic studies of the GGNs,morphological manifestations are used to differentiate benignancy and malignancy.In contrast,few studies are dedicated to the assessment of the hemodynamics,i.e.,perfusion parameters of the GGNs.AIM To assess the dual vascular supply patterns of GGNs on different histopathology and opacities.METHODS Forty-seven GGNs from 47 patients were prospectively included and underwent the dynamic volume CT.Histopathologic diagnoses were obtained within two weeks after the CT examination.Blood flow from the bronchial artery[bronchial flow(BF)]and pulmonary artery[pulmonary flow(PF)]as well as the perfusion index(PI)=[PF/(PF+BF)]were obtained using first-pass dual-input CT perfusion analysis and compared respectively between different histopathology and lesion types(pure or mixed GGNs)and correlated with the attenuation values of the lesions using one-way ANOVA,student’s t test and Pearson correlation analysis.RESULTS Of the 47 GGNs(mean diameter,8.17 mm;range,5.3-12.7 mm),30(64%)were carcinoma,6(13%)were atypical adenomatous hyperplasia and 11(23%)were organizing pneumonia.All perfusion parameters(BF,PF and PI)demonstrated no significant difference among the three conditions(all P>0.05).The PFs were higher than the BFs in all the three conditions(all P<0.001).Of the 30 GGN carcinomas,14 showed mixed GGNs and 16 pure GGNs with a higher PI in the latter(P<0.01).Of the 17 benign GGNs,4 showed mixed GGNs and 13 pure GGNs with no significant difference of the PI between the GGN types(P=0.21).A negative correlation(r=-0.76,P<0.001)was demonstrated between the CT attenuation values and the PIs in the 30 GGN carcinomas.CONCLUSION The GGNs are perfused dominantly by the PF regardless of its histopathology while the weight of the BF in the GGN carcinomas increases gradually during the progress of its opacification.

Expression profile of CYP402C1 and its role in resistance to imidacloprid in the whitefly, Bemisia tabaci

Bemisia tabaci(Gennadius)(Hemiptera:Aleyrodidae)is a cosmopolitan insect pest causing serious damage to crop production.Cytochromes P450(CYPs)of B.tabaci are widely known to be involved in the metabolic resistance to a variety of insecticides,continuously increasing the difficulty in controlling this pest.In this study,four P450 genes(CYP6CMI,CYP6CXl,CYP6CX3,and CYP402CI)in B.tabaci exhibited correlations with the resistance to imidacloprid.We have focused on trying to understand the function and metabolism capacity of CYP402C1.The expression profiles of CYP402C1 were examined by reverse transcription quantitative real-time PCR and fluorescence in situ hybridizations.Its role in resistance to imidacloprid was investigated by RNA interference,transgenic Drosophila melanogaster,and heterologous expression.The results showed that CYP402CI was highly expressed in the active feeding stages of B.tabaci,such as nymphs and female adults.CYP402C1 was mainly expressed in midguts of nymphs and adults,especially in the filter chamber.Knockdown of CYP402CI significantly decreased the resistance of B.tabaci to imidacloprid by 3.96-fold(50%lethal concentration:186.46 versus 47.08 mg/L).Overexpression of CYP402CI in a transgenic D.melanogaster line(Gal4>UAS-CYP402CI)significantly increased the resistance to imidacloprid from 12.68-to 14.92-fold(129.01 and 151.80 mg/L versus 1925.14 mg/L).The heterologous expression of CYP402CI showed a metabolism ability of imidacloprid(imidacloprid decreased by 12.51%within 2 h).This study provides new insights for CYP402C1 function in B.tabaci and will help develop new strategies in B.tabaci control and its insecticide resistance.

Chitin nanocrystal-assisted 3D bioprinting of gelatin methacrylate scaffolds

In recent years,there has been an increasing focus on the application of hydrogels in tissue engineering.The integration of 3D bioprinting technology has expanded the potential applications of hydrogels.However,few commercially available hydrogels used for 3D biological printing exhibit both excellent biocompatibility and mechanical properties.Gelatin methacrylate(GelMA)has good biocompatibility and is widely used in 3D bioprinting.However,its low mechanical properties limit its use as a standalone bioink for 3D bioprinting.In this work,we designed a biomaterial ink composed of GelMA and chitin nanocrystal(ChiNC).We explored fundamental printing properties of composite bioinks,including rheological properties,porosity,equilibrium swelling rate,mechanical properties,biocompatibility,effects on the secretion of angiogenic factors and fidelity of 3D bioprinting.The results showed that adding 1%(w/v)ChiNC to 10%(w/v)GelMA improved the mechanical properties and printability of the GelMA hydrogels,promoted cell adhesion,proliferation and vascularization and enabled the printing of complex 3D scaffolds.This strategy of incorporating ChiNC to enhance the performance of GelMA biomaterials could potentially be applied to other biomaterials,thereby expanding the range of materials available for use.Furthermore,in combination with 3D bioprinting technology,this approach could be leveraged to bioprint scaffolds with complex structures,further broadening the potential applications in tissue engineering.

Healing the defects in CsPbI_(3)solar cells by CsPbBr_(3)quantum dots

Cesium lead iodide(CsPbI_(3))is a promising photo-absorber for perovskite photovoltaics due to its high thermal stability and relatively small bandgap.However,there are many defects in solution processed polycrystalline CsPbI_(3)films especially at the grain boundaries(GBs),which limit the power conversion efficiency(PCE)of CsPbI_(3)solar cells.In this work,we introduced CsPbBr_(3)quantum dots(QDs)on top of the CsPbI_(3)film to passivate the defects.As CsPbBr_(3)QDs have a small size and a similar crystal structure as the CsPbI_(3),they are excellent modifiers to fill in the GBs and heal the defects.Moreover,we find there is an anion exchange reaction between the CsPbBr_(3)QDs and CsPbI_(3)films,which is evidenced by photoluminescence spectra and grazing incidence X-ray diffraction patterns.The QDs treated films show enhanced carrier lifetime and reduced defect density.Additionally,the ligands on CsPbBr_(3)QDs increase the hydrophobicity of the films.As a result,the QDs treated CsPbI_(3)solar cells prepared at high temperature obtain PCEs exceeding 16%with high stability.

四川盆地川西坳陷须家河组三段致密砂岩储层成岩作用及孔隙演化

综合利用岩心、铸体薄片、阴极发光、X-射线衍射、扫描电镜、包裹体分析和孔渗数据等资料,对四川盆地川西坳陷须三段致密砂岩储层成岩作用和孔隙演化进行了分析。研究发现川西坳陷须三段主要发育岩屑石英砂岩和岩屑砂岩,结构成熟度与成分成熟度差—中等;储集空间类型主要为以岩屑粒内溶孔和长石粒内溶孔为主的次生孔隙,孔隙度多小于6%,渗透率多小于1×10^(-3)μm^(2),属于典型的致密砂岩储层。须三段砂岩主要经历了压实、溶蚀、胶结和交代等成岩作用改造,具体演化过程为压实作用→早期大气淡水溶蚀→早期石英、长石、高岭石等黏土矿物、方解石和白云石胶结→中期有机酸溶蚀→中期石英、高岭石等黏土矿物、铁方解石和铁白云石胶结→晚期粗晶—巨晶方解石充填裂缝。通过定量计算研究区砂岩储层的成岩演化过程可知,砂岩原始孔隙度为37.30%,经压实作用孔隙度减小为9.55%,早期溶蚀使孔隙度增至12.15%,此后因早期胶结作用孔隙度减小为9.49%,随后有机酸溶蚀使得孔隙度增至10.14%,最后经中期胶结作用和晚期粗晶—巨晶方解石充填裂缝,现今孔隙度减小为3.95%。尽管溶蚀作用产生次生溶孔(增孔率8.71%),但压实作用和胶结作用导致的减孔效应(减孔率分别为74.39%和23.72%),为须三段砂岩储层致密化的关键因素。

扩缩方孔蜂窝蓄热体强化传热的数值模拟

为提高烟气余热回收率,提出一种扩缩方孔蜂窝蓄热体,通过用户自定义函数(UDF)实现烟气和空气周期切换时流体种类和进口速度、温度等参数的改变,基于ANSYS Fluent软件建立了新型蓄热体的三维非稳态传热数值模型。通过比较模型预测值与文献实验值进行了模型验证。利用模型研究了新型蓄热体方孔扩缩角、扩缩节距和总长度对其传热和流阻性能的影响。通过温度云图分析了扩缩通道强化蓄热体性能的机理。结果表明,缩放通道能有效提高蜂窝蓄热体的传热性能,在压力损失增加不多的前提下,蓄热体效能最多提高约5个百分点。扩缩方孔蜂窝蓄热体长度越长,其传热性能越好;对于一定长度的新型蓄热体,扩缩节距(或扩缩角)不变时,蓄热体传热性能随扩缩角(或节距)增大而增强。扩缩角过大时,新型蓄热体流动阻力很大,综合性能不佳。

Antibacterial mechanism of Cu-bearing 430 ferritic stainless steel

Copper(Cu)-bearing stainless steel has testified its effectiveness to reduce the risk of bacterial infections.However,its antibacterial mechanism is still controversial.Therefore,three 430 ferritic stainless steels with different Cu contents are selected to conduct deeper research by the way of bacterial inactivation from two aspects of material and biology.Hereinto,electrochemical and antibacterial results show that the increase in Cu content simultaneously improves the corrosion resistance and antibacterial property of 430 stainless steel.In addition,it is found that Escherichia coli(E.coli)on the surface 430 Cu-bearing stainless steel by the dry method of inoculation possesses a rapid inactivation ability.X-ray photoelectron spectroscopy(XPS)aids with ion chelation experiments prove that Cu(Ⅰ)plays a more crucial role in the contact-killing efficiency than Cu(Ⅱ),resulting from more production of reactive oxygen species(ROS).

Strategic Asset Allocation for China's Foreign Reserves:A Copula Approach

In this paper, we study strategic asset allocation for China＇s foreign reserves using a risk- based approach. Four aspects of the risk management are investigated： an investment universe, dependence structure, allocation strategies under risk minimization and trade-off between risks and returns. A regime-switching copula model is developed to investigate the dynamic dependence between assets. One regime emphasizes a short-term safe asset and the other regime emphasizes a long-term safe asset. The optimal allocation is derived following two strategies： risk minimization and trade-off between risks and returns in utility maximization with disappointment avoidance, lf the central bank focuses solely on risk minimization, the asymmetries in the asset return dependence encourage the flight to safety. However, if higher risks are allowed in exchange for higher returns, even the exchange is very conservative, and the asymmetries would discourage the flight to safety. Therefore, we suggest that China should mitigate its flight to safety after 2008 and increase holdings of short-term bank deposits, long-term treasury bonds and euro bonds.

Currency Exposure in China under the New Exchange Rate Regime： National Level Evidence

The present paper studies China＇s national level currency exposure since 2005 when the country adopted a new exchange rate regime allowing the renminbi （RMB） to move towards greater flexibility. Using generalized autoregressive conditional heteroskedastic and constant conditional correlation-generalized autoregressive conditional heteroskedastic methods to estimate the augmented capital asset pricing models with orthogonalized stock returns, we find that China equity indexes are significantly exposed to exchange rate movements. In a static setting, there is strong sensitivity of stock returns to movements of China＇s trade- weighted exchange rate, and to the bilateral exchange rates except the RMB/dollar rate. However, in a dynamic framework, exposure to all the bilateral currency pairs under examination is significant. The results indicate that under the new exchange rate regime, China＇s gradualist approach to moving towards greater exchange rate flexibility has managed to keep exposure to a moderate level. However, we find evidence that in a dynamic setting, the exposure of the RMB to the dollar and other major currencies is significant. For China, the challenge of managing currency risk exposure is looming greater.