Structural and physicochemical properties of silver-rich Ag–Al alloys

The X-ray diffraction, Scanning Electron Microscopy, Differential Scanning Calorimetry, dilatometric and electrical conductivity measurements were used to study the structural and physicochemical properties of selected silver-rich alloys from Ag–Al system. All the studied alloys, containing from 10 to 37 at. % of Al (Ag₉₀Al₁₀, Ag₈₅Al₁₅, Ag₇₇Al₂₃, Ag₇₅Al₂₅, Ag₇₂Al₂₈, Ag₇₀Al₃₀, Ag₆₃Al₃₇), were prepared from high purity metals by melting in a glove-box filled with a high purity argon atmosphere. The obtained X-ray diffraction patterns and microstructure observation of alloys containing up to 15 at. % of Al suggested that in this range only solid solution of silver exists. The thermal analysis showed heat effects related to phase transitions in Ag–Al system. In addition, the thermal expansion studies revealed an anomalous behavior in expansion for some composition of alloys associated with the phase transition. The electrical conductivity values rapidly changed, which may be associated with the formation of different phase areas in the Ag–Al system.Based on the results obtained in this work and critically reviewed literature data a thermodynamic re-optimization of the binary Ag–Al system using CALPHAD method was proposed. A good agreement between calculation and experiment was found.     

大口径光学元件装夹转运结构设计及分析

为了实现大口径光学元件的安全装夹、转运,通过光学元件开槽与不开槽两种装夹方式的分析,得出开槽夹紧转运方式将带来微裂纹、应力集中、成本高等缺陷,提出了利用摩擦力克服光学零件的重力和惯性力的低应力装夹转运方案。通过对光学元件低应力夹紧结构设计,并利用有限元分析方法,得到不开槽装夹方式下,光学元件的最大主应力为1.11 MPa,最大切应力为0.73 MPa,远低于光学元件破坏的强度极限,且受力均匀,无应力集中现象。     

埋地管道腐蚀防护--防腐层与阴极保护存在的问题分析

在埋地管道研究工作中,关于其腐蚀的防护一直是研究的焦点问题,但现阶段常用的防护手段多为防腐层与阴极防护。为此,在文中主要对二者的保护措施展开了相应地阐述,并重点分析了2种保护手段存在的问题,旨在为后续的管道防腐研究提供相应的参考。     

红色红曲菌组蛋白去乙酰化酶MrSir2的原核表达及活性分析

根据基因组序列信息,利用cDNA末端快速扩增技术(rapid-amplification of cDNA ends,RACE)得到了红色红曲菌中组蛋白去乙酰化酶mrsir2基因的完整cDNA序列,其编码序列(coding sequence,CDS)为1539 bp,编码512个氨基酸,含有一个SIR2蛋白保守结构域。根据大肠杆菌的密码子的偏好性对mrsir2序列进行优化,优化后的序列与p ET-28b载体连接后转入宿主菌E.coli BL21中进行IPTG诱导表达,并优化表达条件。实验结果表明:在16℃条件下用终浓度为0.25 mM的IPTG诱导培养16 h后,目的蛋白Mr Sir2可溶性表达效果良好。Ni2+柱亲和层析纯化后的Mr Sir2重组蛋白在SDS-PAGE上显示为一条约75 ku大小的条带,蛋白定量浓度达1.97 mg/mL,经Western blot鉴定为目的蛋白,测定酶活为78.5(OD/min/mg),780μM的二氢香豆素(dihydrocoumarin,DHC)对Mr Sir2蛋白的酶活抑制率为47%。Mr Sir2蛋白的可溶性表达为全面了解其酶学特征提供了材料,也为体外分析蛋白相互作用奠定了基础。     

Bacteriophages vB_Sen-TO17 and vB_Sen-E22, Newly Isolated Viruses from Chicken Feces,Specific for Several Salmonella enterica Strains

Two newly discovered bacteriophages, isolated from chicken feces and infecting Salmonella enterica strains, are described in this report. These phages have been named vB_Sen-TO17 and vB_Sen-E22, and we present their molecular and functional characterization. Both studied viruses are able to infect several S. enterica strains and develop lytically, but their specific host ranges differ significantly. Electron microscopic analyses of virions have been performed, and full genome sequences were determined and characterized, along with molecular phylogenetic studies. Genomes of vB_Sen-TO17 (ds DNA of 41,658 bp) and vB_Sen-E22 (dsDNA of 108,987 bp) are devoid of homologs of any known or putative gene coding for toxins or any other proteins potentially deleterious for eukaryotic cells. Both phages adsorbed efficiently (>95% adsorbed virions) within 10 min at 42 °C (resembling chicken body temperature) on cells of most tested host strains. Kinetics of lytic development of vB_Sen-TO17 and vB_Sen-E22, determined in one-step growth experiments, indicated that development is complete within 30–40 min at 42 °C, whereas burst sizes vary from 9 to 79 progeny phages per cell for vB_Sen-TO17 and from 18 to 64 for vB_Sen-E22, depending on the host strain. Virions of both phages were relatively stable (from several percent to almost 100% survivability) under various conditions, including acidic and alkaline pH values (from 3 to 12), temperatures from −80 °C to 60 °C, 70% ethanol, chloroform, and 10% DMSO. These characteristics of vB_Sen-TO17 and vB_Sen-E22 indicate that these phages might be considered in further studies on phage therapy, particularly in attempts to eliminate S. enterica from chicken intestine.     

Governance choices and policy outcomes in the Latin American and caribbean electricity sector

The paper first provides, for Latin America and the Caribbean, country-specific synthetic quantitative measures of the degree of adoption of governance reforms in the electricity sector, focusing on four key dimensions (market structure, private sector participation (PSP), regulatory autonomy and operational organization). These measures are then correlated with standard policy performance outcomes measures. The findings suggest that, the reforms, considered jointly, were statistically significantly associated with higher technical and process quality but not with social or service improvements. Considered individually, increased regulatory autonomy enjoyed the highest positive correlation with desirable outcomes, but PSP has no significant correlation with any of the outcomes. In sum, as of 2018, governance reforms, considered jointly, had still not delivered on some promised payoffs, notably in addressing energy poverty, although the sensitivity analysis suggests that, for some indicators, the relationships are stronger for larger than for smaller countries.     

人工监督神经网络在煤层裂缝发育区识别中的应用

针对在地震属性应用中难以精细识别煤层裂缝发育区边界的难题,开展了基于人工监督神经网络技术的煤层裂缝发育区应用研究。从地震资料中获取倾角导向体以提取高质量的地震属性,以多属性为指导进行人工拾取样点,并基于多层感知器进行神经网络机器训练学习,建立裂缝的最优属性集,拓展整体数据后获得裂缝概率体,从而识别划分出煤层裂缝发育区。该技术在山西阳泉新元矿区进行了应用,煤层裂缝发育区的识别结果明显优于属性直接识别,但勘探区内暂无钻井资料,预测效果还有待进一步验证。     

Study of the surfactant role in latex–aerogel systems by scanning transmission electron microscopy on aqueous suspensions

For insulation applications, boards thinner than 2 cm are under design with specific thermal conductivities lower than 15 mW m^?1 K^?1. This requires binding slightly hydrophobic aerogels which are highly nanoporous granular materials. To reach this step and ensure insulation board durability at the building scale, it is compulsory to design, characterise and analyse the microstructure at the nanoscale. It is indeed necessary to understand how the solid material is formed from a liquid suspension. This issue is addressed in this paper through wet‐STEM experiments carried out in an Environmental Scanning Electron Microscope (ESEM). Latex–surfactant binary blends and latex–surfactant–aerogel ternary systems are studied, with two different surfactants of very different chemical structures. Image analysis is used to distinguish the different components and get quantitative morphological parameters which describe the sample architecture. The evolution of such morphological parameters during water evaporation permits a good understanding of the role of the surfactant.     

Research on heat dissipation performance and flow characteristics of air‐cooled battery pack

With the depletion of fossil fuels and the aggravation of environmental pollution, the research and development speed of electric vehicles has been accelerating, and the thermal management of battery pack has become increasingly important. This paper selects the electric vehicle battery pack with natural air cooling as the study subject, conducts simulation analysis of the heat dissipation performance of battery packs with and without vents. Then this paper researches on the influence of internal flow field and external flow field. Field synergy principle is used to analyze the effect of velocity field and temperature field amplitude. The results show the following: it is found that the maximum temperature rise and the internal maximum temperature difference of the battery pack with vents are reduced by about 23.1% and 19.9%, raising speed value can improve the heat dissipation performance, and raising temperature value can decrease the heat dissipation performance. Reasonable design of the vents can make the inner and outer flow field work synergistically to achieve the best cooling effect. Then the reference basis for the air cooling heat dissipation performance analysis of electric vehicle, battery pack structure arrangement, and air‐inlet and air‐outlet pattern choosing are offered.