Computerized enumeration of staggered alkane conformers

An alkanoid is defined as a tree (in the graph-theoretical sense) which can be embedded in the diamond lattice. It corresponds to a staggered conformer of an alkane. A computer program for enumerating non-overlapping alkanoids is described. In these systems there is no pair of coalescing vertices. Results for the unbranched and branched alkanoids are given separately, and the symmetry groups of the systems are determined.     

The effect of the shear rate-dependent thermal conductivity of non-newtonian fluids on the heat transfer in a pipe flow

The present study investigates the effect of the shear rate-dependent thermal conductivity of non-Newtonian fluids on the heat transfer enhancement in a pipe flow. The constant heat flux as thermal boundary condition was adopted in the thermally developed region. The present analytical results show the heat transfer enhancement over those of a shear rate-independent thermal conductivity fluid. The heat transfer coefficient ratio (h/h_o) linearly increase with the non-dimensional average velocity difference which is the product of the shear rate-dependence of the thermal conductivity and wall-shear rate.     

Electrochemical behavior of chalcopyrite in presence of Thiobacillus ferrooxidans

1 Introduction The bioleaching research has a great progress in metallurgy industry. A significant number of commercial applications have emerged and are able to compete with conventional processing, especially the application for the copper recovery. Fur…     

Assessment of antibacterial activity of fractions from burdock leaf against food-related bacteria

The chemical composition and antibacterial activities of burdock leaves fractions against six food-related bacteria (Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis, Escherichia coli, Shigella dysenteriae and Salmonella typhimurium) were first investigated. The burdock leaves extract was fractioned with ethyl acetate, n-butanol and water, named as EF, BF and WF. The data from minimum inhibitory concentration (MIC) values showed that EF and other fractions effectively inhibited the growth of all test bacterial pathogens, the antibacterial activity of EF being much greater than BF and WF. The time–kill study indicated that EF exhibited significant bactericidal activity against all the six pathogens. At 12 h, EF was bactericidal for 4/6, 6/6 and 6/6 strains at 1× MIC, 3× MIC and 5× MIC, respectively. For all the fractions, the antibacterial capacity had a significant correlation with total phenolic content, suggesting that the activities were probably due to the combined action of phenolic compounds. The phenolic compounds of the fractions were then identified for the first time. After activity-guide fractionation and separation by flash chromatogram, two purified active compounds (chlorogenic acid, rutin) were obtained, and identified by UPLC–MS/MS. The ethyl acetate fraction based on its lower MIC values, concentration and time-dependent antibacterial and bactericidal activities could be useful in control of foodborne bacterial pathogens.     

肠出血性大肠杆菌O157∶H7变种Q蛋白对志贺毒素表达的影响

1株肠出血性大肠杆菌O157∶H7变种EC169菌株,携带stx基因但不表达志贺毒素。通过高效热不对称交错聚合酶链式反应（high-efficiency thermal asymmetric interlaced polymerase chain reaction,hiTAIL-PCR）hiTAILPCR扩增得到EC169 stx1及其上游核苷酸片段并克隆测序,结果表明：EC169 q基因与标准株sakai q基因相比存在6个SNP位点。通过PCR扩增O157∶H7高毒株EC150 q基因全长,并构建表达载体pkk223-q分别转化EC169和低毒株EC157。反转录荧光定量PCR实验结果表明,外源q基因在EC169和EC157重组菌中可高效表达,并引起EC157stx转录水平上调,但EC169重组菌stx转录水平不变。反向乳胶凝集实验结果亦证实EC157重组菌志贺毒素表达量提高,而EC169重组菌志贺毒素表达量不变。Q蛋白变异可能并非EC169志贺毒素不表达的主要原因。     

基于单链抗体的呋喃唑酮酶联免疫检测方法的建立

目的:为快速检测呋喃唑酮(furazolidone,FZD)在动物性食品中的残留量。方法:基于单链抗体的间接竞争酶联免疫吸附实验法建立了FZD检测方法。结果:最佳抗原工作质量浓度为2μg/m L,最佳抗体稀释倍数为1∶500,一抗最佳反应时间为60 min,二抗最佳反应时间为45 min,四甲基联苯胺最佳显色时间为20 min。FZD检测试剂盒在10~100 ng/m L范围具有较好的线性关系,IC50值为13.01 ng/m L,检出限为1.28 ng/m L,回收率为73.38%~84.52%。结论:与抗FZD单克隆抗体相比,所建立的检测试剂盒检测范围更广,且具有很高的灵敏度以及很好的特异性和稳定性。     

金属离子对低糖酵母发酵活性的影响

该研究考察了3种金属离子对低糖酵母发酵活力的影响。首先,采用响应面设计法对酵母发酵培养基进行了优化。通过Plackett-Burman设计试验筛选出3个主要因素：镁离子（Mg2+）、锌离子（Zn2+）、锰离子（Mn2+）。在这个基础上应用最陡爬坡路径法逼近最大响应值区域,然后利用响应面分析法确定最佳培养基配方为酵母抽提物（FM888） 10 g/L、蛋白胨（FM318） 20 g/L、葡萄糖20 g/L、六水合氯化镁 6.95 g/L、氯化锌1.78 mg/L、一水合硫酸锰0.069 mg/L。其次,将优化培养基配方应用于低糖酵母发酵,干酵母活力可达426.86 mL/g。经过3次平行试验的验证,实际的平均发酵活力与预测的发酵活力值相近,比优化前提高了24.8%。此研究对低糖酵母的工业化生产具有一定的指导意义。     

蜂王浆对D-半乳糖衰老模型大鼠学习记忆行为的影响

以成年SD大鼠为实验材料,采用D-半乳糖连续腹腔注射制作亚急性衰老的大鼠模型,造模成功后连续灌胃蜂王浆,运用Morris水迷宫观察各组大鼠的空间学习记忆行为;荧光分光光度法检测各组大鼠脑组织中单胺类神经递质去甲肾上腺素(NE)、多巴胺(DA)的含量;检测各组大鼠脑组织中超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量。结果显示：D-半乳糖衰老模型大鼠的空间学习记忆能力明显下降,与正常组大鼠相比,潜伏期由15.52s延长至21.62s,在探索实验中,穿过原站台的次数明显减少,由7.5次减少至4.25次(P＜0.05),游泳轨迹类型发生明显变化;与正常组相比模型大鼠脑组织中NE、DA含量显著降低,SOD活性显著降低,MDA含量显著升高(P＜0.05)。蜂王浆组大鼠空间学习记忆能力明显提高,与模型组相比,潜伏期由21.62s缩短至14.34s(P＜0.05);其中脑组织NE、DA含量提高,与模型组相比,低剂量组有显著性差异(P＜0.05),高剂量组有极显著性差异(P＜0.01);SOD活性显著增高,MDA含量显著降低(P＜0.05)。结果表明：蜂王浆可提高模型大鼠的空间学习记忆能力及脑组织中单胺类神经递质的含量、SOD活性,降低MDA含量。由此推测,蜂王浆可调节神经递质的合成及提高学习记忆能力,具有良好的延缓衰老、提高记忆的保健作用。     

The biomethane producing potential in China: A theoretical and practical estimation

Biomethane has been developed rapidly in many countries as a renewable energy which upgraded from biogas. China also began to pay attention to it even though we still at a initial stage, primarily, understanding the biomethane potential and development prospect, choosing appropriate biomass as the biomethane source is very important. In this work, the theoretical and practical biomethane producing potential from five main biomass resources in China were estimated with appropriate methods based on the data collected, and during calculation, two appropriate energy crops were assumed to be planted on marginal lands for biomethane production. Our estimation showed that the theoretical and practical biomethane potentials in China can reach to 888.78 and 316.30 billion m³ per year, agricultural waste should be the preferential development biomass, and planting energy crops on marginal lands is the most promising way to enhance biomethane production in China. Finally, biomethane is compared with natural gas, and the result showed that 48.15% of the practical biomethane potential can meet the total Chinese natural gas consumption in 2013.