烟台市社区体育场地设施现状调查分析

通过对烟台市社区体育场地设施的实际调查,找出影响烟台市社区体育场地设施的主要因素,提出完善社区体育场地设施的方法和途径.为政府部门和体育主管部门制定社区体育发展提供客观依据.     

甲型流感病毒PB1-PA蛋白作用位点的发现与分析

 基于共进化理论,探究了甲型流感病毒PB1蛋白与PA蛋白上具有共同进化可能性的保守九聚片段 (C9MP)。结构信息显示PB1蛋白的第1-15位氨基酸与PA蛋白的第239-716位氨基酸具有相互作用域;对该区域变异分布的分析发现,PA蛋白第670位氨基酸Q所在的C9MP与PB1蛋白的第9位氨基酸F、第12位氨基酸V和第13位氨基酸P所在的C9MP在PB1-MP1相互作用面上具有最低的共进化值。结合DSSP程序的分析表明,由PA蛋白第670位氨基酸Q与PB1蛋白的第9位氨基酸F、第12位氨基酸V与第13位氨基酸P构成的区域可能成为潜在的相互作用位点。     

(MH)_n(M=Li,Na;n=1～4)小分子团簇的分子形貌的理论研究

研究分子的形状和大小对于进一步探究分子的物理化学性质起着重要作用.使用MELD精密从头计算中的CISD方法,采用6-31+G(d,p)基组,结合自编的程序,计算并研究金属氢化物(MH)n(M=Li,Na;n=1~4)团簇分子中的1个电子所受到的作用势(PAEM)及特征,探讨了化学键的单电子作用势的势垒Dpb与化学键的键长,团簇分子的单电子作用势的势垒tDpb与团簇分子的结合能的关系.结果表明,Dpb可以用来表征化学键的强度,tDpb可以用来表征团簇的稳定性.此外,还描绘出金属氢化物团簇的分子形貌,探讨了它们各自的特征,为进一步探讨和认识较大的锂和钠氢化物团簇(MH)n(n≥5)结构和性质奠定基础.     

水合碱金属离子团簇Rb~+(H_2O)_n和Cs~+(H_2O)_n的量子化学研究

应用高水平的从头计算方法QCISD/aug-cc-pVDZ,对气相中的Rb+(H2O)n和Cs+(H2O)n(n=1～6)体系进行研究,优化几何构型,对能量最低的结构,计算结合能和振动频率.结果表明,随着水分子数目的增加,对于Rb+和Cs+,RMO和总结合能有相同的变化趋势;电荷分布显示位于离子上的正电荷逐渐减小,位于氧原子上的负电荷逐渐增大,位于氢原子上的正电荷变化不明显.     

The synthesis and characterization of a Co-N/C composite catalyst for the oxygen reduction reaction in acidic solution

A non-precious metal Co-N/C catalyst for the oxygen reduction reaction (ORR) was synthesized by heating a mechanical mixture of cobalt chloride, urea and acetylene black under a nitrogen atmosphere. The catalyst was characterized by XRD and XPS. The electrocatalytic activity in the ORR was evaluated by linear sweep voltammetry in 0.5 mol L⁻¹ H₂SO₄ solution. The results show that the Co-N/C catalyst aids the reduction of oxygen. The presence of elemental cobalt in the precursor allows nitrogen atoms to embed themselves in the graphite matrix to form pyridinic and graphitic type C-N structures as the ORR active sites. The effect of heat-treating temperature on the catalytic activity was also investigated. The results also show that the Co-N/C catalyst is most active when pyrolyzed at 600°C. The obtained Co-N/C catalyst loses some activity after initial exposure to the H₂SO₄ solution because of leaching, but is then stable for up to 20 h immersion. The catalyst is also stable when charged, which is supported by the cyclic voltammetry results.     

Carbon and nitrogen stable isotope analyses of mammal bone fossils from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River,China

Based on AMS ¹⁴C dating data, carbon and nitrogen isotope analyses were conducted on mammal bone collagen of deer, cattle and pigs from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River. These analyses were conducted to reconstruct palaeodiets of mammals, palaeoecology, palaeoenviroment and previous human activities in the study area. Results show that the collagen loss of bone did not change the in vivo isotopic composition of carbon and nitrogen stable isotopes, and most of the bone fossils were well preserved. The bone collagen of samples from deer had a mean δ¹³C of -23.1‰ and a mean δ¹⁵N of 4.7‰, suggesting that deer subsisted in a closed habitat and fed on branches and leaves. The bone collagen of cattle had a mean δ¹³C of –19.6‰ and a mean δ¹⁵N of 5.2‰, which indicates that cattle subsisted in an open habitat and fed on grasses and stems. The δ¹³C values show that both deer and cattle fed on C₃ plants and lived in the same ecosystem, but the t-test results show that deer δ¹³C and δ¹⁵N values were both more negative than those of cattle, indicating that they inhabited different niches. The δ¹³C and δ¹⁵N values of cattle partially overlapped those of deer, suggesting some competition in diets between them. The t-tests show that the δ¹³C and δ¹⁵N values of pigs were more positive than those of cattle and deer, which signifies that pigs occupied a higher trophic level compared to cattle and deer. The wide range of pig δ¹³C values demonstrates that pig trading had been taking place from early Neolithic Age to late Bronze Age. There were no significant differences in deer δ¹³C and δ¹⁵N values among different archaeological periods, making it clear that climatic, ecological and environmental conditions were kept relatively stable from 2200 to 4200 a BP. This stability may have been responsible for the extensive and complete cultural layers at the Zhongba site. The minimum number of samples required to estimate the mean δ¹³C values of deer, pigs and cattle are 8, 73 and 16, respectively, and for mean δ¹⁵N values of deer, pigs and cattle, the minimum numbers are 4, 5 and 6, respectively.     

基于单片机技术的试卷装订机设计

本文通过对高校使用的试卷装订机进行分析,指出了现有装订机所存在的弊端。为了提高装订机的装订性能,本文将现有装订机使用过程中的动作进行了分解,结合单片机技术,设计出了一款新颖的装订机,实践证明,该装订机能大大提高试卷装订效率。     

关于丹东地区技术作业站站址选择的研究

介绍了丹东地区枢纽现状,分析了枢纽存在的问题。随着沈丹客专和东北部铁路通道工程的引入,有必要新建丹东地区技术作业站。从车站站型及车流组织情况入手,通过工程投资对比,对金山湾和新前阳两个方案的优缺点进行分析研究,推荐采用新前阳站址方案。     

赤水丹霞世界自然遗产地种子植物区系

调查统计显示,赤水世界自然遗产地拥有种子植物171科692属1 715种,其中裸子植物7科12属13种,被子植物164科680属1 702种.分析表明赤水遗产地种子植物区系具有以下特征:(1)区系物种组成丰富,优势科明显;单种科和非单种单属科较多,反映区系科分化明显;2～5种少型属和单种属分别占统计属数的40.03%a...     

剪切波速与天然孔隙比的相关性分析

为了提高沈阳城区土层剪切波速估值的准确性,采用单孔速度检层法实测土层剪切波速,采用符合国标规定的取土器采取Ⅰ级土样,按《土工试验方法标准》(GB50123-1999)进行室内土工试验,取得大量实测剪切波速与天然孔隙比数据.通过回归分析得出两者之间的经验关系式为vs=-598.18e0+712.65,经检验相关系数R=0.903.用该关系式估算沈阳城区土层剪切波速简便易行,且准确性高.