Experimental and numerical study on improvement performance by wave parallel flow field in a proton exchange membrane fuel cell

The performance and operation stability of proton exchange membrane fuel cells(PEMFCs)are closely related to the transportation of reactants and water management in the membrane electrode assembly(MEA)and flow field.In this paper,a new three-dimensional wave parallel flow field(WPFF)in cathode was designed and analyzed throughout simulation studies and an experimental method.The experimental results show that the performance of PEMFC with WPFF outperforms that of PEMFC with straight parallel flow field(SPFF).Specifically,the peak power density increased by 13.45%for the PEMFC with WPFF as opposed to PEMFC with SPFF.In addition,the flow field with area of 11.56 cm^(2) was formed by the assembly of transparent end plate used for cathode and the traditional graphite plate used for anode.To understand the mechanism of the novel flow field improving the performance of PEMFC,a model of PEMFC was proposed based on the geometry,operating conditions and MEA parameters.The thickness of gas diffusion layers(GDL),catalytic layers(CL)and proton exchange membrane were measured by scanning electron microscope.The simulation result shows that compared with SPFF,the WPFF based PEMFC promote the oxygen transfer from flow channel to the surface of CL through GDL,and it was beneficial to remove the liquid water in the flow channel and the MEA.

Effect of Metallothionein on Cell Cycle,Apoptosis Rate and Subsets Distribution of Lymphocytes in Peripheral Blood of Dairy Cattle under Heat Stress

[Objective] This study aimed to research the effect of metallothionein on cell cycle, apoptosis rate and subsets distribution of lymphocytes in peripheral blood of dairy cows under heat stress, so as to perfect the regulative mechanism re- searches of MT to anti-heat stress. [Method] Twenty lactating Chinese Holstein cows were randomly divided into four groups （A, B, C and D）, and injected with 0, 4.0, 8.0 and 12.0 mg Zn-metallothionein, respectively by intravenous route. Blood sam- ples were collected at 1＂, 16~, 31~, 46~ and 61~ day, and the dynamic changes of cell cycle, apoptosis rate and subsets distribution of lymphocytes were determined. [Result] The apoptosis rate of cells in group B and C was lower than those in group A by 26.63% （P〉0.05） and 24.84% （P〉0.05） respectively. The number of cells in the Gc/G1 phage in trial groups was increased and the number of cells in the S and GJM phages tended to decrease, but there were no significant differences （P〉 0.05）. The number of CD3~ T cell in three trial groups was greater than those in group A by 7.02% （P〉0.05）, 5.45% （P〉0.05） and 3.85% （P〉0.05） respectively, while the number of CD4~ T cell in trial groups was higher than those in control group by 31.04% （P〈0.05）, 35.68% （P〈0.05） and 39.34% （P〈0.05） respectively. The number of CD8＇ T cell and the levels of CD4＊/CD8~ in trial groups were increased observ- ably, but significant difference （P〈0.05） was observed in the levels of CD4~/CD8~ between groups A and C only. It demonstrated that exogenous Zn-metallothionein can decrease apoptosis rate, improve cell cycle and regulate subsets distribution of lymphocytes in dairy cattle in a dose-dependent manner. [Conclusion] This study will provide scientific basis for safe utilization of MT in dairy industry.

Salivary microbiota may predict the presence of esophageal squamous cell carcinoma

The aim is to explore the predictive value of salivary bacteria for the presence of esophageal squamous cell carcinoma (ESCC). Saliva samples were obtained from 178 patients with ESCC and 101 healthy controls, and allocated to screening and verification cohorts, respectively. In the screening phase, after saliva DNA was extracted, 16S rRNA V4 regions of salivary bacteria were amplified by polymerase chain reaction (PCR) with high-throughput sequencing. Highly expressed target bacteria were screened by Operational Taxonomic Units clustering, species annotation and microbial diversity assessment. In the verification phase, the expression levels of target bacteria identified in the screening phase were verified by absolute quantitative PCR (Q-PCR). Receiver operating characteristic (ROC) curves were plotted to investigate the predictive value of target salivary bacteria. LEfSe analysis revealed higher proportions of Fusobacterium, Streptococcus and Porphyromonas, and Q-PCR assay showed significantly higher numbers of Streptococcus salivarius, Fusobacterium nucleatum and Porphyromonas gingivalis in patients with ESCC, when compared with healthy controls (all P < 0.05). The areas under the ROC curves for Streptococcus salivarius, Fusobacterium nucleatum, Porphyromonas gingivalis and the combination of the three bacteria for predicting patients with ESCC were 69%, 56.5%, 61.8% and 76.4%, respectively. The sensitivities corresponding to cutoff value were 69.3%, 22.7%, 35.2% and 86.4%, respectively, and the matched specificity were 78.4%, 96.1%, 90.2% and 58.8%, respectively. These highly expressed Streptococcus salivarius, Fusobacterium nucleatum and Porphyromonas gingivalis in the saliva, alone or in combination, indicate their predictive value for ESCC.

一种基于动态可寻址会话的服务器无感知计算

服务器无感知计算作为云原生范式中快速发展的新兴技术,因其按需付费、自动资源伸缩和底层环境屏蔽等特点而受到越来越多的开发人员欢迎.FaaS(函数即服务)作为Serverless架构的主要实现方式,以函数粒度对应用进行解耦和执行.大多数云服务提供商也为应用开发人员提供了基于Serverless架构的应用搭建服务,这些服务允许开发人员以函数的形式部署代码,并根据实际的请求量进行自动扩缩容.然而,在部署有状态函数时,由于Serverless架构的无状态特性,管理其中的有状态数据变得复杂,往往无法满足Serverless中函数对有状态数据的访问性能要求.因此,本文提出了一种基于有状态和动态可寻址会话机制的服务器无感知计算系统XFaaS,实现了低开销的有状态数据访问和更高的应用吞吐.实验结果表明,通过采用XFaaS系统部署有状态函数的方式,可以降低有状态数据访问时延3个数量级,并提高2倍以上的函数最大吞吐量.

Novel oxygen-enrichment method using annular air curtain for single-head roadway of plateau mine

The low-oxygen environment restricts the exploitation of mineral resources on plateaus and affects miner’s safety.This paper proposes an oxygen-enrichment method using an annular air curtain.Through numerical simulation and experiments,it was confirmed that the proposed method improves the breathing environment in the single-head roadway of a plateau mine.Computational fluid dynamics(CFD)was used to investigate the oxygen-enriching effect and oxygen spatial distribution regularities after using the proposed oxygen-enrichment method in the single-head roadway of a plateau mine.The reliability of the CFD model was confirmed by experiment.Orthogonal testing was conducted to investigate the influence degree and optimal level combination of factors influencing oxygen enrichment.The results demonstrate that the annular air curtain effectively prevented oxygen loss,thus forming a local oxygen-rich space and improving the effective utilization rate of oxygen.Oxygen supply concentration and velocity are positively correlated with the oronasal oxygen mass fraction through a linear function,while the air curtain outlet wind velocity is negatively correlated with the oronasal oxygen mass fraction through a linear function.The annular air curtain diameter and oronasal oxygen mass fraction do not have an obvious functional relationship.When the annular air curtain diameter was greater than 0.9 m,the oronasal oxygen mass fraction was stable at approximately 25.30%.The influencing factors of the novel oxygen-enrichment method are,in descending order,as follows:oxygen supply concentration,annular air curtain diameter,air curtain outlet wind velocity,and oxygen supply velocity.The optimal level combination is oxygen supply concentration of 100%,oxygen supply velocity of 11 m/s,air curtain outlet wind velocity of 1.5 m/s,and annular air curtain diameter of 0.9 m.

Low-dose IL-2 mitigates glucocorticoid-induced Treg impairment and promotes improvement of SLE

Dear Editor,Previous studies have proved that regulatory T cell(Treg)insufficiency contributed to the development of autoimmune conditions including systemic lupus erythematosus(SLE).Conventional immunosuppressive treatment was reported to downregulate beneficial Tregs together with pathogenic effector immune cells,which may impede a rapid achievement of optimal therapeutic effects.

Raman imaging analysis of intracellular biothiols independent of the aggregation of sensing substrates

The content of biothiols in cells is highly associated with the occurrence and development of several diseases.However,due to their active chemical properties,thiol-contained molecules are normally volatile during the detection process,rendering precise analysis of intracellular biothiols challenging.In this study,5,5’-dithiobis-(2-nitrobenzoic acid)(DTNB)is covalently modified on the surface of gold nanorods(AuNRs),constructing sensing substrates for in situ Raman imaging analysis of biothiols in cells.Au NRs are able to serve as ideal surface-enhanced Raman scattering substrates,and thus Raman signals of DTNB are greatly amplified by AuNRs.Meanwhile,the disulfide bond of DTNB can be broken by thiols,thereby releasing part of DTNB from the surface of AuNRs.As a result,three kinds of main biothiols are sensitively quantified with DTNB-modified AuNRs according to the variation of Raman signals,and DTNB-modified Au NRs exhibit far better analytical performance than a commercial probe.In addition,the sensing substrates can be readily delivered to cytoplasm with the transmembrane of Au NRs,and are capable of responding to biothiols in cells.Notably,the Raman approach is established by the breaking of chemical bonds rather than the aggregation of substrates,which is more inclined to analyze intracellular biothiols with a desirable spatial resolution.Therefore,fluctuation of biothiols in glioma cells is evidently observed via Raman imaging.Overall,this work provides an alternative strategy for designing Raman sensors to visualize active molecules in cells.

Assessing current and future soil erosion under changing land use based on InVEST and FLUS models in the Yihe River Basin,North China

The Yihe River Basin is a key area for water conservation and soil erosion control in northern China.The excessive development of land resources is a major factor causing soil erosion and ecological degradation.However,the impacts of land use change on soil erosion in the basin are not yet clearly.Understanding the complex relationship between land use and soil erosion is an important way to promote the development of land resources utilization and ecological construction from cognition to decision-making.This study simulated the temporal-spatial changes of soil erosion in the basin from 1956 to 2020 using Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model,and evaluated the changes of soil erosion under different land use scenarios from 2020 to 2050 using Future Land Use Simulation(FLUS)model.From 1956 to 2020,the overall soil erosion intensity showed a slight decreasing trend,and the average annual soil erosion modulus was 38.21 t/ha/year.Soil erosion intensity was higher in the central and northern mountainous areas,while it was lower in the flat alluvial plains in the south.Arable land(4.07 t/ha/year)was the largest contributor to the amount of soil erosion,and land use changes caused the soil erosion intensity to fluctuate and decrease after 1995.From 2020 to 2050,soil erosion varied widely under different land use scenarios,and the land use pattern targeting ecological priority development would effectively mitigate soil erosion.Therefore,optimizing land use patterns and structures are critical initiatives to prevent soil erosion.