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91.
92.
对全国各地用原子吸收光谱仪测定10批次大活络丸中12种无机元素及建立的指纹图谱,尝试用成分数据分析法、向量相似法和模糊聚类法建立全国无机元素的指纹图谱和中药质量控制标准方法,获得较满意的结果。研究表明,建立无机元素指纹图谱控制中成药中无机元素的质量,具有很好的实用性和可操作性,用于全国各地不同厂家生产的大活络丸无机元素的质量控制是切实可行的。 相似文献
93.
Dr. Ana M. Castilla Dr. Mark A. Miller Prof. Jonathan R. Nitschke Dr. Maarten M. J. Smulders 《Angewandte Chemie (International ed. in English)》2016,55(36):10616-10620
The derivation and application of a statistical mechanical model to quantify stereochemical communication in metal–organic assemblies is reported. The factors affecting the stereochemical communication within and between the metal stereocenters of the assemblies were experimentally studied by optical spectroscopy and analyzed in terms of a free energy penalty per “incorrect” amine enantiomer incorporated, and a free energy of coupling between stereocenters. These intra‐ and inter‐vertex coupling constants are used to track the degree of stereochemical communication across a range of metal–organic assemblies (employing different ligands, peripheral amines, and metals); temperature‐dependent equilibria between diastereomeric cages are also quantified. The model thus provides a unified understanding of the factors that shape the chirotopic void spaces enclosed by metal–organic container molecules. 相似文献
94.
95.
Peter-Th. Wilrich 《Accreditation and quality assurance》2007,12(5):231-240
Interlaboratory experiments often contain results that strongly deviate from other results obtained in the same laboratory
under repeatability conditions, or laboratory means that strongly deviate from other laboratory means. In ISO 5725-2 [1] and IUPAC [2], the basic standards for the organisation and analysis of interlaboratory experiments for the determination of precision
of a measurement method, outlier tests are performed in order to detect such situations and to finally decide whether these
values are retained in the analysis or discarded as outliers. This outlier treatment, which always has a subjective aspect,
becomes unnecessary by using robust estimates of the repeatability and reproducibility standard deviation. This paper proposes
to use Rousseeuw’s Q
n as an extremely robust and efficient estimate of the standard deviation. Two examples show the performance of the new method. 相似文献
96.
97.
The knowledge of hydrocarbon/water phase equilibria is important in the design and operation of equipment for petroleum transport and refining and petrochemical plants. The presence of water in a hydrocarbon mixture can affect the product quality and damage the operation equipment due to corrosion and formation of gas hydrates. Tracing the concentration of hydrocarbons in aqueous media is also important for technical purposes like preventing oil spills and for ecological concerns such as predicting the fate of these organic pollutants in the environment. 相似文献
98.
Skin Bond Electron Relaxation Dynamics of Germanium Manipulated by Interactions with H2, O2, H2O,H2O2, HF,and Au 下载免费PDF全文
Lihong Wu Maolin Bo Yongling Guo Prof. Yan Wang Can Li Prof. Yongli Huang Prof. Chang Q Sun 《Chemphyschem》2016,17(2):310-316
Although germanium performs amazingly well at sites surrounding hetero‐coordinated impurities and under‐coordinated defects or skins with unusual properties, having important impact on electronic and optical devices, understanding the behavior of the local bonds and electrons at such sites remains a great challenge. Here we show that a combination of density functional theory calculations, zone‐resolved X‐ray photoelectron spectroscopy, and bond order length strength correlation mechanism has enabled us to clarify the physical origin of the Ge 3d core‐level shift for the under‐coordinated (111) and (100) skin with and without hetero‐coordinated H2, O2, H2O, H2O2, HF impurities. The Ge 3d level shifts from 27.579 (for an isolated atom) by 1.381 to 28.960 eV upon bulk formation. Atomic under‐coordination shifts the binding energy further to 29.823 eV for the (001) and to 29.713 eV for the (111) monolayer skin. Addition of O2, HF, H2O, H2O2 and Au impurities results in quantum entrapment by different amounts, but H adsorption leads to polarization. 相似文献
99.
Dr. Artur Ciesielski Jürgen Weippert Dr. Artur Böttcher Yuyoung Shin Georgian Melinte Prof. Dr. Ovidiu Ersen Dr. Cinzia Casiraghi Prof. Dr. Xinliang Feng Prof. Dr. Klaus Müllen Prof. Dr. Manfred M. Kappes Prof. Dr. Paolo Samorì Dr. Marco Cecchini 《Chemphyschem》2016,17(3):352-357
Providing a quantitative understanding of the thermodynamics involved in molecular adsorption and self‐assembly at a nanostructured carbon material is of fundamental importance and finds outstanding applications in the graphene era. Here, we study the effect of edge perchlorination of coronene, which is a prototypical polyaromatic hydrocarbon, on the binding affinity for the basal planes of graphite. First, by comparing the desorption barrier of hydrogenated versus perchlorinated coronene measured by temperature‐programmed desorption, we quantify the enhancement of the strength of physisorption at the single‐molecule level though chlorine substitution. Then, by a thermodynamic analysis of the corresponding monolayers based on force‐field calculations and statistical mechanics, we show that perchlorination decreases the free energy of self‐assembly, not only enthalpically (by enhancing the strength of surface binding), but also entropically (by decreasing the surface concentration). The functional advantage of a chemically modulated 2D self‐assembly is demonstrated in the context of the molecule‐assisted liquid‐phase exfoliation of graphite into graphene. 相似文献
100.
Eleftheria Batagianni Arkadios Marathianos Aikaterini Koraki Andreas-Philippos Maroudas 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(3):140-151
The cationic polymerization of ethyl, n-butyl and iso-butyl vinyl ether, EVE, BVE and iBVE, respectively, was efficiently conducted using bis(η5-cyclopentadienyl)dimethyl hafnium, Cp2HfMe2, or bis(η5-cyclopentadienyl)dimethyl zirconium, Cp2ZrMe2 in combination with either tris(pentafluorophenyl)borate, B(C6F5)3, or tetrakis(pentafluorophenyl)borate dimethylanilinum salt, [B(C6F5)4]?[Me2NHPh]+, as initiation systems. The evolution of polymer yield, molecular weight and molecular weight distribution with time was examined. In addition, the influence of the initiating system, the monomer and the reaction conditions on the control of the polymerization was studied. Furthermore, statistical copolymers of EVE with BVE were prepared employing Cp2HfMe2 and [B(C6F5)4]?[Me2NHPh]+ as the initiation system. The reactivity ratios were estimated using both linear graphical and non-linear methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The glass transition temperatures, Tg, of the copolymers were measured by Differential Scanning Calorimetry, DSC, and the results were compared with predictions based on several theoretical models. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. 相似文献