Increasing Olefin Metathesis Activity of Silica-Supported Molybdenum Imido Adamantylidene Complexes through E Ligand σ-Donation

Molybdenum imido adamantylidene complexes with different substituents on the imido ligand (dipp=2,6-diisopropylphenyl, Ar_F5=C₆F₅, and ^tBu) having distinct electron donating abilities were investigated for the metathesis of internal and terminal olefins, for both molecular and silica-supported species using standardized protocols. Here we show that surface immobilization of these compounds results in dramatically increased activity compared to their molecular counterparts. Additionally, we show that electron withdrawing imido groups increase the activity of the compound towards terminal olefins while they simultaneously decrease the ability to metathesize internal olefins. Furthermore, these systems also show high stability when used as initiators in olefin metathesis, although the species that display higher initial activity deactivate faster than those that show more a more moderate reaction rate at first. Our catalytic studies, augmented by DFT calculations, show that all investigated compounds have a remarkably small energy difference between the trigonal bipyramidal (TBP) and square planar (SP) configurations of the metallacyclobutane intermediates, which has previously been linked to high activity.     

血站采血护士角色定位的探讨

目的:讨论血站采血护士的角色定位,为献血者提供优质服务。方法:对血站采血护士角色定位的重要性和角色特征进行探讨,明确血站采血护士的角色功能。结果:血站采血护士承担着无偿献血的宣传者和招募者、献血者健康教育的指导者和教育者、献血者献血行为的支持者和协助者、献血不良反应的观察者和护理者等角色,要成功实现采血护士的职业角色,要求采血护士具有良好的职业道德、高效的学习能力、过硬的护理技能、良好的沟通能力、优良的心理素质、符合角色的职业形象和具有高效的执行能力。结论:血站采血护士准确进行角色定位,通过优质的献血服务促进献血者的保留,实现自身职业价值。     

天津大学图书馆赠书管理工作的实践与思考

赠书是高校图书馆丰富馆藏、缓解购书经费不足以及宣传图书馆的重要途径。分析了天津大学图书馆赠书工作存在的问题,详细论述了图书馆采取的赠书管理方法及产生的成效,并对进一步完善赠书工作提出了建议。     

谈高校社会捐赠与构建和谐社会

指出了高校社会捐赠对构建和谐社会的重要意义,提出了加快高校社会捐赠事业发展的几点建议。     

大学生无偿献血意识和行为现况调查分析

目的：为了解大学生对无偿献血的认识和态度,探索适合大学生无偿献血知识宣传的模式及健康教育方法。方法：采用多阶段分层整群抽样方法,随机抽取大理学院在校的1143名大学生作为研究对象,采用自编的统一问卷进行现场调查。结果：调查显示大学生献血率为36.05%,其中男生献血率占42.86%,女生献血率占32.59%,男女生献血率有显著性差异（χ^2=11.685,P〈0.01）。大学生对献血知识的认知程度与心理因素是影响其无偿献血行为的主要原因,男生最主要的无偿献血动机是认为献血光荣,女生的动机是帮助灾难受害者,有显著性差异（χ^2=78.441,P〈0.01）。男生未献血的主要原因是担心献血会感染疾病,女生则是以自己实际因素不符合为主要原因,有显著性差异（χ^2=50.702,P〈0.01）。结论：大学生是无偿献血的主力军,加强献血知识的宣传力度,有针对性地消除男女生对献血的错误认识,能更好地保证无偿献血工作的可持续发展。     

液相中镍催化剂催化合成气甲烷化的初步研究

采用液相还原法制备非负载型镍催化剂,将非负载型镍催化剂分散在液相供氢溶剂十氢萘中,催化合成气甲烷化反应。在高压反应釜内,考察了反应温度、物质的量比等操作条件下,镍催化剂催化合成气甲烷化反应的反应活性。并对催化剂进行XRD、SEM、H2-TPR表征分析。研究结果表明,在330℃、催化剂用量为2%时,产品气中甲烷含量可达89.39%,CO和H2的转化率分别为94.56%和92.60%;催化剂用量为4%时,产品气中甲烷含量可高达94.26%,CO的转化率可达到99%以上。合成气甲烷化反应的最佳操作温度为330℃,H2/CO物质的量比最佳为2.20~2.67。     

Evaluation of Electron Donation as a Mechanism for the Stabilisation of Chalcogenate‐Protected Gold Nanoclusters

Models based on Au(111) face have been extensively used to describe self‐assembled monolayers, as well nanoparticles and nanoclusters. However, for very small clusters (<2 nm), the chemisorption of ligands leads to surface reconstruction, making necessary the use of a more reliable model that is able to simulate the main electronic and geometrical features of these small systems. In this work, a simple model to describe the geometries and the metal–ligand bonding in chalcogenate‐protected gold nanoclusters is proposed. Three different models with Au_n⁺ and [XCH₃]^? (n=10, 15, 19, 22 and X=S, Se, Te) are used in this work. The obtained structures are in close agreement not only with the available crystallographic data, but also with much more expensive computational procedures, confirming that the proposed models are robust enough to describe the metal–ligand bonding. The results reveal that the Au–X distances are dependent on both the nature of the chalcogen and the coordination mode. The shortest Au–X distances are observed in the face‐centred cubic mode, indicating that the central gold atom seems to play a role in determining the adsorption strength. The proposed models show unambiguously chalcogen→cluster σ‐donation, as supported by energy decomposition analysis coupled with the natural orbitals for chemical valence and natural bond orbital analyses. In all cases, the metal–ligand interactions are characterised as being more covalent than electrostatic.     

企业慈善捐赠行为的研究综述：现实发展和理论演进

经济全球化背景下，作为企业社会责任的重要表现形式之一，企业慈善捐赠行为得到了迅速的发展。从现实发展阶段和理论演进过程两个方面评述了企业慈善捐赠行为的主要研究进展，并基于研究现状和研究不足，提出了未来的研究展望。