共查询到20条相似文献，搜索用时 649 毫秒
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采用考虑旋轨耦合的从头算方法计算研究1,2-C2H4Br2的光解.计算了分子的若干电子态的垂直激发能.用MS-CASPT2/CASSI-SO方法计算了1,2-C2H4Br2分子C—Br解离的势能曲线.根据计算结果,清晰地指认了1,2-C2H4Br2分子的解离通道:C2H4Br+Br(2P3/2)和C2H4Br+Br*(2P1/2). 相似文献
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2008年10月24日出版的美国Science杂志刊登了我国大连化学物理研究所杨学明研究员与合作者在C1+H2反应的百绝热动力学研究方面取得的重要进展,这一成果解决了一个长期以来极具急论性的C1+H2. 相似文献
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张立敏 《中国科学院研究生院学报》2010,27(3):289-305
综述了近几年来关于三原子分子离子(CS+2, SO+2, CO+2)的光激发和光解离动力学研究结果.实验是在射流气束条件下进行的.首先利用一束电离激光使中性三原子分子通过共振增强多光子电离制备出振动态选择的三原子分子离子,再用一束或两束解离激光激发获得母体分子离子的光解离谱(母体离子的凹陷谱和碎片离子的增强谱).由此研究了三原子分子离子(CS+2, SO+2, CO+2)电子态的光激发和光解离动力学. 相似文献
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采用TCLP、国标、SPLP和SEP(F1+F2)4种不同重金属浸提方法对稳定化前后砷污染场地土壤进行毒性评估,实验结果表明,有效砷浸出率变化趋势为SEP(F1+F2)TCLP国标SPLP。当体系的p H在2.88~6.0范围内变化时,随p H增大,有效砷的浸出浓度减小;而当体系p H在7.0~9.0范围内变化时,有效砷的浸出浓度随体系p H增大而增大。生物有效性评估结果显示,两土样中砷的生物可给度明显降低,分别降低了22.2%和13.2%。ANC(酸中和容量)实验结果表明,稳定化处理前后两种土壤样品的酸中和能力变化不大。该试验可以为砷污染修复提供数据支持和方法参考。 相似文献
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激发态是分子存在的重要形态,它具有与基态分子迥然不同的性质。对其结构和动力学特性的研究是分子科学的一个主要内容,也是当代化学物理学科的重要前沿。研究激发态分子的主要手段是分子光谱。但经典光谱的光谱分辨率和时间分辨能力都不足以研究短寿命的激发态以及态－态之间的复杂相互作用。我们瞄准了这个意义重大而又有相当难度的课题,从１９８３年起,先后在中国科学院重大项目（激光与物质相互作用）,“七五”国家自然科学基金重大项目（分子反应动力学）及“八五”国家攀登计划（态－态反应动力学及原子分子激发态）的支持下,建… 相似文献
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文章在NH4NO3H2ONaNO2发泡机制的研究基础上,建立了获得较高反应速率和适当发泡剂量的NH3-NO-2-H+发泡体系的发泡机理,从而提出无后效快速发泡技术。 相似文献
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本研究主要目的在于探索适用于宽带光纤放大器和蓝绿光激光器用稀土掺杂基质玻璃材料。通过对掺Er3+重金属氧氟玻璃的光谱性质和析晶稳定性研究以及稀土离子掺杂重金属氧卤玻璃的上转换发光研究,为其在宽带掺Er3+光纤放大器和蓝绿光波段激光器中的潜在应用提供基础。研究结果表明：重金属PbF2的加入提高了掺Er3+硅酸盐玻璃和锗酸盐玻璃的带宽特性和增益性能;首次在Er3+/Yb3+共掺和Er3+单掺硅酸盐玻璃发现上转换蓝光;重金属氟化铅的加入提高了Er3+单掺锗酸盐和碲酸盐玻璃的上转换发光;在室温下同时观察到Er3+的上转换蓝光、绿光和红光,分别是由于Er3+离子2H9/2→4I15/2, 2H11/2→4I15/2, 4S3/2→4I15/2, 和4F9/2→4I15/2跃迁;混合卤化铅效应调整Tm3+/Yb3+共掺碲酸盐有利于基质玻璃析晶性能的改善和上转换发光性能的提高;在室温下同时观察到Tm3+的上转换蓝光和红光,分别是由于Tm3+离子的1G4→3H6和1G4→3H4跃迁;首次在碲酸盐基质玻璃中发现OH-吸收对Er3+和Tm3+的上转换发光具有重要影响。 相似文献
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Thermodynamic systems with variable mass, like liquid/vapor equilibria and chemical reactions, are represented as networks having discrete elements and connections using bond graph symbols. The mass bond has special properties which are explained by entropy and volume stripping and indicate the reason why the derivative of the free enthalpy, not the internal energy, is the driving effort of chemical reactions. Chemical friction is represented by RS-fields that dissipate power which is different from the observed heat rate of chemical reactions. Different reticulations apply to reactions near and far from chemical equilibrium; their relation to experimental reaction kinetics and order of reaction is discussed. 相似文献
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Covalent organic frameworks (COFs) have been at the forefront of porous-material research in recent years. With predictable structural compositions and controllable functionalities, the structures and properties of COFs could be controlled to achieve targeted materials. On the other hand, the predesigned structure of COFs allows fruitful postsynthetic modifications to introduce new properties and functions. In this review, the postsynthetic functionalizations of COFs are discussed and their impacts towards structural qualities and performances are comparatively elaborated on. The functionalization involves the formation of specific interactions (covalent or coordination/ionic bonds) and chemical reactions (oxidation/reduction reaction) with pendant groups, skeleton and reactive linkages of COFs. The chemical stability and performance of COFs including catalytic activity, storage, sorption and opto-electronic properties might be enhanced by specific postsynthetic functionalization. The generality of these strategies in terms of chemical reactions and the range of suitable COFs places them as a pivotal role for the development of COF-based smart materials. 相似文献
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Fast and catalyst-free cross-linking strategy is of great significance for construction of covalently cross-linked hydrogels. Here, we report the condensation reaction between o-phthalaldehyde (OPA) and N-nucleophiles (primary amine, hydrazide and aminooxy) for hydrogel formation for the first time. When four-arm poly(ethylene glycol) (4aPEG) capped with OPA was mixed with various N-nucleophile-terminated 4aPEG as building blocks, hydrogels were formed with superfast gelation rate, higher mechanical strength and markedly lower critical gelation concentrations, compared to benzaldehyde-based counterparts. Small molecule model reactions indicate the key to these cross-links is the fast formation of heterocycle phthalimidine product or isoindole (bis)hemiaminal intermediates, depending on the N-nucleophiles. The second-order rate constant for the formation of phthalimidine linkage (4.3 M−1 s−1) is over 3000 times and 200 times higher than those for acylhydrazone and oxime formation from benzaldehyde, respectively, and comparable to many cycloaddition click reactions. Based on the versatile OPA chemistry, various hydrogels can be readily prepared from naturally derived polysaccharides, proteins or synthetic polymers without complicated chemical modification. Moreover, biofunctionality is facilely imparted to the hydrogels by introducing amine-bearing peptides via the reaction between OPA and amino group. 相似文献
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中国旅游发展的社区响应领域积累了大量的经验研究,但是这些研究却很少关注旅游发展社区响应的理论分析模型,以至于难以确定已有研究的理论贡献。本文综述了国外文献中有关旅游发展社区响应的9种理论模型,并且比较了这些理论模型的理论内涵、使用情形以及相关的应用研究,对于理解中国国内旅游发展社区响应的经验研究提供了理论分析工具,有助于推进中国旅游学者把他们的研究定位于不同的理论模型脉络下增进该领域的理论贡献。未来研究应关注不同旅游发展阶段、社区利益群体对旅游发展响应的差异及内在原因;关注主-客、客-客、主-主互动对旅游发展响应的差异;吸收情感、权力、政治互信等变量对旅游发展社区响应的影响;关注不同社区群体社会表征对旅游发展的响应机制。 相似文献
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Modern molecular beam studies of chemical reaction dynamics aim at determining the structure and dynamics of transition states and reaction intermediates directly from the experimental data. The experimental and theoretical progress which is being made in this endeavour is now revealing the essential unity of spectroscopic and reaction dynamics in the molecular systems which govern high temperature combustion and atmospheric photochemistry. 相似文献
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原电池反应或电解池反应的本质都是氧化还原反应,因此无论是原电池还是电解池的电极反应都要遵循氧化还原反应的规律,特别是得失电子总数与化合价降低或升高的总值相等。原电池反应或电解池反应本质上又都是离子反应,电极反应式通常情况下也是以类似离子方程式的形式出现,因此电极反应式也要遵循离子方程式的电荷守恒和原子守恒。灵活运用这些守恒规律就能突破高考难点中电极反应式的书写。 相似文献
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Models for chemical reaction kinetics typically assume well-mixed conditions, in which chemical compositions change in time but are uniform in space. In contrast, many biological and microfluidic systems of interest involve non-uniform flows where gradients in flow velocity dynamically alter the effective reaction volume. Here, we present a theoretical framework for characterizing multi-step reactions that occur when an enzyme or enzymatic substrate is released from a flat solid surface into a linear shear flow. Similarity solutions are developed for situations where the reactions are sufficiently slow compared to a convective time scale, allowing a regular perturbation approach to be employed. For the specific case of Michaelis-Menten reactions, we establish that the transversally averaged concentration of product scales with the distance x downstream as x(5/3). We generalize the analysis to n-step reactions, and we discuss the implications for designing new microfluidic kinetic assays to probe the effect of flow on biochemical processes. 相似文献
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Dingtao Zhao Feng Wang Jiuchang Wei Liang Liang 《International Journal of Information Management》2013
This study explores how online comments influence public reactions to organizational crisis discourses based on five scenarios depicting typical online comment patterns. Through an empirical study involving 621 participants, several key findings are obtained. First, online comments have a significant effect on post-crisis reactions involving emotions, attitudes and behavioral intentions. However, except in the case of perceived comment manipulation, public reaction patterns associated with overwhelmingly positive and non-overwhelmingly positive comments are not significantly different and are friendlier to the crisis organization than the other three patterns. Moreover, reactions associated with the pattern in which there are no online comments are quite similar to those associated with the pattern of non-overwhelmingly negative comments. Second, positive emotions enhance perceived organizational integrity, whereas negative emotions reduce this perception. Third, perceived comment manipulation has a negative moderating effect on the relationship between positive emotion and perceived organizational integrity and a positive moderating effect on the relationship between negative emotion and perceived organizational integrity. Finally, emotions and perceived organizational integrity are found to be predictors of loyalty and boycott intentions. The findings of the study extend the present knowledge on crisis communication by highlighting the impact of online comments on the post-crisis reactions of the public and also provide crisis managers with guidelines on how to deploy appropriate crisis communication strategies. 相似文献