Cu-Ni-Si基引线框架合金的组织和性能

设计了4种不同成分的引线框架铜合金,通过对比其硬度、强度、导电性以及软化温度等,分析了合金中P,Ni,Si,Cr合金元素对合金各性能的影响.研究结果表明:采用合理的热处理工艺可以使Cu-3Ni-0.6Si基合金在时效过程中析出尺寸在20～40 nm之间的δ-Ni2Si颗粒,使合金的强度和导电率达到良好的匹配;微量的P能有效地提高合金的强度、硬度和弹性模量,同时使Ni2Si析出颗粒的弥散度提高,尺寸减小,但会降低合金的导电率;少量的Cr能有效提高合金的强度和软化温度.     

高效解磷细菌与菌根真菌菌剂交互作用对杨树的促生效应

近年来,高效解磷细菌与菌根真菌互作对植物的促生效应受到广泛的关注。笔者分别制备3种单菌胶丸菌剂[蜡状芽孢杆菌(Bacillus cereus,JYZ-SD1)、荧光假单孢菌(pseudomonas fluores-cens,JW-JS1)、红绒盖牛肝菌(Xerocomus cheysenteron,Xc)]和3种复合胶丸菌剂[JYZ-SD1+Xc、JW-JS1+Xc、JYZ-SD1+JW-JS1+Xc]。将单菌胶丸菌剂和3菌复合胶丸菌剂对杨树施用后,测定其对苗木的生长及光合作用的影响,并与液体菌液和固体菌剂相比较。结果表明,JYZ-SD1、JW-JS1和Xc的3菌复合液体菌液对杨苗的促生及光合效应促进最大,3菌复合胶丸菌剂次之,但与其复合液体菌液无显著差异。JYZ-SD1的菌剂促生效果好于JW-JS1菌剂的处理。     

大跨度桥梁风场模拟及气动力计算

介绍了一种快速高效的用于大跨度桥梁风致振动分析的风场模拟方法,并对模拟风场的统计性质进行了讨论和验证。在此基础上进一步给出了大跨度桥梁抖振力和自激力的时域表达方式,其中针对自激力计算中涉及的参数识别问题,提出了一种简单实用的非线性参数识别方法,本文采用上述理论,获得了作用于香港汀九大桥上的风场和气动力,据此对大桥进行的抖振响应时域分析表明,计算结果与风洞试验结果吻合良好,说明文中述及的这套理论已达     

表面改性活性炭对CO2的吸附性能

研究了用H2O2,HNO3加醋酸铜溶液进行表面改性后的活性炭对CO2的吸附性能,分析了改性前后活性炭的表面化学性质,测定了273 K下的吸附等温线,用D-A方程对吸附等温线进行了很好的拟合,探讨了表面改性对活性炭表面化学性质的影响及其表面化学性质与吸附性能之间的关系.     

C57BL/6小鼠在肥胖建模过程中常见问题及处理对策

目的发现C57BL/6小鼠在肥胖模型造模过程中出现的问题,并找到解决这些问题的有效方法。方法对出现耳朵感染、脱毛和打架引起外伤的小鼠分别采取相应预防或局部处理措施,使其健康生长。结果打耳标时进行预防性消毒的小鼠耳朵感染风险下降,少量耳朵感染的小鼠经过消毒恢复健康。脱毛小鼠进行隔离消毒后皮毛恢复完整。受轻微外伤小鼠隔离消毒后恢复健康。结论本文提到的C57BL/6小鼠肥胖模型造模过程中出现的各种问题及处理对策可为其他相关科研人员提供参考。     

Crystal structure of a rhomboid family intramembrane protease

Escherichia coli GlpG is an integral membrane protein that belongs to the widespread rhomboid protease family. Rhomboid proteases, like site-2 protease (S2P) and gamma-secretase, are unique in that they cleave the transmembrane domain of other membrane proteins. Here we describe the 2.1 A resolution crystal structure of the GlpG core domain. This structure contains six transmembrane segments. Residues previously shown to be involved in catalysis, including a Ser-His dyad, and several water molecules are found at the protein interior at a depth below the membrane surface. This putative active site is accessible by substrate through a large 'V-shaped' opening that faces laterally towards the lipid, but is blocked by a half-submerged loop structure. These observations indicate that, in intramembrane proteolysis, the scission of peptide bonds takes place within the hydrophobic environment of the membrane bilayer. The crystal structure also suggests a gating mechanism for GlpG that controls substrate access to its hydrophilic active site.     

Averting biodiversity collapse in tropical forest protected areas

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad array of biodiversity groups have been unavailable for a sufficiently large and representative sample of reserves. Here we present a uniquely comprehensive data set on changes over the past 20 to 30 years in 31 functional groups of species and 21 potential drivers of environmental change, for 60 protected areas stratified across the world’s major tropical regions. Our analysis reveals great variation in reserve ‘health’: about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally. Habitat disruption, hunting and forest-product exploitation were the strongest predictors of declining reserve health. Crucially, environmental changes immediately outside reserves seemed nearly as important as those inside in determining their ecological fate, with changes inside reserves strongly mirroring those occurring around them. These findings suggest that tropical protected areas are often intimately linked ecologically to their surrounding habitats, and that a failure to stem broad-scale loss and degradation of such habitats could sharply increase the likelihood of serious biodiversity declines.     

负载型金属氧化物催化酯交换合成碳酸二甲酯

制备了多种以γ - Al2O3为载体的负载金属氧化物催化剂,考察其在由碳酸乙烯酯(EC)与甲醇(ME)酯交换法合成碳酸二甲酯(DMC)中的催化活性,其中以K2 O/γ - Al2 O3催化活性较好.同时考察了负载量、催化剂用量、甲醇与碳酸乙烯酯摩尔比、反应温度、反应时间等因素对反应的影响,最终确定最佳反应条件:催化剂为K2O/γ - Al2O3,甲醇与碳酸乙烯酯摩尔比为5,m(催化剂)∶m(甲醇)为1∶200,反应温度为65℃,反应时间为3h,在此条件下,碳酸二甲酯收率最佳为52.0％.     

锌配合物的制备及对环氧乙烷酯化反应的催化性能

以ZnBr2和四乙基溴化铵(Et4NBr)为原料,通过溶剂热法配位制备了锌配合物催化剂,研究了反应溶剂、加料方式、原料摩尔比、反应时间和反应温度对锌配合物制备收率的影响。较优的制备工艺条件为:乙醇为溶剂、采用反滴加料、n(Zn)∶n(N)=1∶2、制备温度为50℃、反应时间为0.5 h,锌配合物的收率达92.30%。采用X线衍射(XRD)、傅里叶红外光谱(FT-IR)、元素分析(EA)和发射光谱仪(ICP-AES)对锌配合物进行表征。结果表明:不同原料摩尔比制备的锌配合物是不同于原料的新物质,推断出锌配合物的化学式为(Et4N)2ZnBr4。另外,初步探索了锌配合物对环氧乙烷酯化反应的催化性能。结果表明:锌配合物催化剂具有优良的活性,环氧乙烷转化率达95.6%,副产二乙二醇(DEG)选择性不大于1.72%,循环使用5次后催化剂活性无明显下降。     

一种改进的成分数据的中心对称对数比变换

由于成分数据定和限制的约束,使得常用的多元统计方法对其失效．为了解决这个问题,文章提出了成分数据的加权对称对数比变换,并用双标图将其从图形的角度进行分析．实证研究部分显示所得结果更符合实际情况．