微观应变测定原理及应用

介绍了Ｘ射线测定多晶体材料微观应变的新方法。该方法依据多晶体衍射Ｘ射线服从振幅／强度叠加原理，认为微细晶粒和畸变晶粒对衍射强度的贡献是能够分离的；又根据布拉格方程，导出两者在衍射线角的位移上的关系，并进一步推出测定晶粒尺寸及微观应变的表达式，从而实现了多晶不完善材料晶粒以后尺寸及微观应变的直接测量。     

Development and validation of an LC method for the determination of emtricitabine and related compounds in the drug substance

A robust, precise, sensitive, linear, and simple RP LC method coupled with UV for the determination of emtricitabine or 2′,3′‐dideoxy‐5‐fluoro‐3′‐thiacytidine (FTC) and its related substances is described. The method uses an RP C18 column (25 cm×4.6 mm i.d.), 5 μm kept at a temperature of 35°C. The mobile phases for gradient elution consist of ACN, phosphate buffer (pH 4.4), and water. The flow rate is 1.0 mL/min and UV detection is performed at 280 nm. A system suitability test (SST) was developed to verify the adequate performance of the chromatographic system. The developed method was further validated with respect to robustness, precision, sensitivity, and linearity. A central composite design was applied to examine the robustness of the method. The method shows good precision, sensitivity, linearity, and robustness. Three commercial FTC samples were examined using this method. This method is suitable to be used for the determination of related substances and assay of FTC.     

平衡移动法测定配合物组成和稳定常数的研究进展

平衡移动法是测定配合物组成和稳定常数的一种重要方法，本文综述了该法的研究进展，引用参考文献３０篇。     

The rate of convergence of the S matrix for the renormalized Numerov and log-derivative methods

The convergence of the S matrix for the renormalized Numerov method, the original log-derivative method, and one recent version of this method is studied. A single- and a two-channel problem are analyzed and the percent relative errors for the S matrix and transition probabilities are calculated.     

Neutron flux characterization of the beam port of the Missouri University of Science and Technology Reactor

Alpha spectrometry is used for qualitative and quantitative analysis of actinides in biological and environmental samples. This technique requires a thin, homogenous and carrier-free deposit. Numerous methods for source preparation are electrolytic deposition, spontaneous deposition, micro-precipitation, direct evaporation, vacuum sublimation, etc. The most widely used method for preparation of actinides for alpha spectrometry is electro-deposition of actinides onto a stainless steel planchette. This procedure is time consuming, requires elaborate equipment and is expensive. Micro-precipitation method on the other hand is comparatively faster and more reliable. Thus, the present study was taken-up to optimize various parameters for rapid alpha source preparation of actinides by micro-precipitation method.

     

利用光吸收特性鉴定直、支链淀粉纯品质量

本文报道依据马铃薯及谷物直、支链淀粉的光吸收特性来鉴定直、支链淀粉纯品质量,与用碘结合量测定直、支链淀粉标准物质的纯度相比较,其方法简单可靠。     

Microdetermination of copper using dithiooxamide crayons and the ring-oven technique

A method for the microdetermination of copper in air pollution investigations, using a dithiooxamide crayon and the ring-oven technique is presented. The limit of detection for the method is 0.04 μg, and the quantitative determination is applicable in the range of 0.05 to 0.5 μg of copper. The method is free from interferences that might be of significance in the study of air samples.     

Estimation of the zeta potential and the dielectric constant using velocity measurements in the electroosmotic flows

In this paper we develop a method for the determination of the zeta potential zeta and the dielectric constant epsilon by exploiting velocity measurements of the electroosmotic flow in microchannels. The inverse problem is solved through the minimization of a performance function utilizing the conjugate gradient method. The present method is found to estimate zeta and epsilon with reasonable accuracy even with noisy velocity measurements.     

Theory and algorithm of the inversion method for pentadiagonal matrices

A recently developed inversion method for pentadiagonal matrices is reconsidered in this work. The mathematical structure of the previously suggested method is fully developed. In the process of establishing the mathematical structure, certain determinantial relations specific to pentadiagonal matrices were also established. This led to a rather general necessary and sufficient condition for the method to work. All the so called forward and backward leading principal submatrices need to be non-singular. While this condition sounds restrictive it really is not so. These are in fact the conditions for forward and backward Gauss Eliminations without any pivoting requirement. Additionally, the method is more effective computational complexity wise then recently published competitive methods.     

The correlations of the enthalpy of vaporization and the surface tension of molecular liquids

Correlation relations based on Stefan's rule, which defined dependence between the enthalpy of vaporization, the surface tension, the molar volume and the molar mass of a substance, were obtained. For development of the correlation equations two computational procedures were used: a method of the least squares and a method of artificial neural networks. The method of artificial neural networks was shown to give somewhat better results than the linear least-squares procedure. The average deviation of the calculated values from the experimental ones did not exceed 6% for training set of substances and 10% for control set (the method of the least squares). For the method of artificial neural networks it is 3% and 8%, respectively.     

The investigation of the resolution enhancement transformation and the analysis of complex overlapping peaks in gamma-ray spectra

A method is proposed for the resolution enhancement transformation (RET) of the γ-ray spectrum, which is not only a simple convolution operation but also have a definite analytical significance because of the introduction of the parameter ω representing the degree of the resolution enhancement. We apply the RET to the peak detection method for complex overlapping peaks. The validity of this method is ascertained by the analysis of X-ray overlapping peaks.     

Accuracy and precision of flowing afterglow mass spectrometry for the determination of the deuterium abundance in the headspace of aqueous liquids and exhaled breath water

We have assessed the accuracy and precision of our flowing afterglow mass spectrometric method (FA-MS) for absolute measurements of deuterium abundance in water using standardised tap water/D(2)O mixtures within the D/H range from 155 ppm (local tap water) to 1104 ppm, prepared by the gravimetric method. The results of this study show that a precision and accuracy of 1% can be achieved for the deuterium abundance in water samples. This is quite adequate for the main application, which is the rapid, non-invasive measurement of total body water by deuterium analysis of breath water vapour using the D(2)O dilution method.     

烷基自由基β位裂解反应类反应势垒与速率常数的精确计算

提出反应类等键方法并用于高温燃烧机理中一类重要反应——烷基自由基β位裂解反应的反应势垒和速率常数的精确校正计算. 通过10种不同从头算水平对类反应中5个代表反应的反应势垒的计算发现, 用反应类等键反应方法和直接从头算方法获得的5 个代表反应的反应势垒最大绝对偏差的平均值分别为5.32 和16.16 kJ·mol^-1, 表明反应类等键反应方法计算的反应势垒对不同水平从头算方法的依赖性小, 可在较低从头算水平计算得到精确的反应势垒, 解决大分子体系反应势垒的精确计算问题. 此外应用反应类等键反应方法在BHandHLYP/cc-pVDZ 从头算水平计算了3 个代表反应的速率常数, 并与文献报道的实验值进行了比较, 其在500-2000 K温度区间内计算速率常数与实验速率常数中较大值与较小值的比值k_max/k_min的平均值为1.67, 最大值也仅有2.49. 表明应用反应类等键反应方法在较低从头算水平即可对同类反应的速率常数进行精确计算.最后在BHandHLYP/cc-pVDZ从头算水平用反应类等键反应方法计算了13个烷基自由基β位裂解反应的速率常数.     

Combination of hydrazine polyanion strategy and ring-closing metathesis in the synthesis of heterocycles

An efficient method for the synthesis of cyclic hydrazine derivatives starting from disubstituted hydrazines is reported. The method is based on the selective alkylation of hydrazine dianions with bromoalkenes and subsequent cyclization using Grubbs’ catalysts. The described method provides fast and easy access to the substrates for ring-closing metathesis and the corresponding heterocycles containing a hydrazine moiety. The scope and limitations of the new method are also demonstrated.     

Kinetics of dehydroxylation and evaluation of the crystallinity of kaolinite

This study presents results on the kinetics of kaolinite dehydroxylation. The accuracy of various methods of determining the values for the kinetic parameters and their sensitivity in detecting the mechanism of reaction is investigated. In particular, the differential order of reaction method of Baker, the general method of Achar et al., the integral method of Boy and Bohme, and the method of Coats and Redfern as modified by Fong and Chen are considered.

Kaolinites from well-known sources are used to study the influence of crystallinity on the values of kinetic parameters. The statistical significance of the various mathematical methods for the assessment of the data obtained from non-isothermal thermogravimetry is determined by comparison with experimental and theoretical data using a computer programme developed for this purpose. The study demonstrates that the kinetic parameters can be used to quantify the degree of crystallinity of kaolinite and also confirms other findings that the dehydroxylation of kaolinite is a second-order reaction.     

Suitability of nitric-sulphuric acid decomposition for the determination of tungsten and molybdenum in geochemical exploration

A mixture of nitric and sulphuric acids is used for the decomposition of geochemical samples for the estimation of tungsten. In the resulting sample solution tungsten is determined colorimetrically by the dithiol method. The decomposition procedure suggested works well for scheelite mineral. However wolframite is only partially decomposed. The same sample solution is used for estimation of molybdenum by the thiocyanate method. The method is suitable for batch analysis and results in a high throughput.     

Determination of chemical composition of solid inorganic substances and materials using the principles of stoichiography and voltammetry

The state of the art in determination of the phase composition of complex inorganic solids by chemical and electrochemical methods is discussed. The theoretical and practical essentials of stoichiography and the new stoichiographic method of differential dissolution (DD) are reported. The unique feature of this method is that reference samples of the analyzed solid phases are not necessary. The development of this stoichiographic method was strongly affected by voltammetry. The application of the DD method for determining the chemical composition of various substances and materials is presented. The complementary use of voltammetry and DD for the detection, identification, and quantitative determination of inhomogeneity of the chemical composition of high-temperature superconductors was shown to be efficient.     

荧光素与牛血清蛋白作用的光谱研究与分析应用

研究了在生理条件下,荧光素与牛血清白蛋白相互作用形成复合物,最大吸收峰的波长480nm,比荧光素红移9nm。该法简便、快速,线性范围宽,干扰少,灵敏度较高,用于牛血蛋白样品测定的结果准确。     

Logic-structure approach to the evaluation and prediction of physicochemical characteristics of organic compounds

An efficient method is proposed for computerized screening, highly effective for a number of properties of structures. This method is identical to the problem of classification, and it is solved by a pattern recognition method based on a logic-structure approach (method of logic correlations). Whether or not a substance belongs within a certain indicated range of properties is determined by the presence or absence of informative local features of topology of the compound's structure and the spatial positioning of the atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1349–1355, June, 1990.We wish to express our appreciation to M. Kh. Klin for interest in this work and for constructive criticism.     

Improvement of the coupled-cluster singles and doubles method via scaling same- and opposite-spin components of the double excitation correlation energy

There has been much interest in cost-free improvements to second-order M?ller-Plesset perturbation theory (MP2) via scaling the same- and opposite-spin components of the correlation energy (spin-component scaled MP2). By scaling the same- and opposite-spin components of the double excitation correlation energy from the coupled-cluster of single and double excitations (CCSD) method, similar improvements can be achieved. Optimized for a set of 48 reaction energies, scaling factors were determined to be 1.13 and 1.27 for the same- and opposite-spin components, respectively. Preliminary results suggest that the spin-component scaled CCSD (SCS-CCSD) method will outperform all MP2 type methods considered for describing intermolecular interactions. Potential energy curves computed with the SCS-CCSD method for the sandwich benzene dimer and methane dimer reproduce the benchmark CCSD(T) potential curves with errors of only a few hundredths of 1 kcal mol(-1) for the minima. The performance of the SCS-CCSD method suggests that it is a reliable, lower cost alternative to the CCSD(T) method.