Heats of formation and kinetics of decomposition of nitroalkanes

Heats of formation of solid, liquid, and gaseous nitroalkanes have been shown mostly to obey group additivity. Group values have been obtained for carbon atoms attached to one, two, and three nitro groups. The heat of formation of 1,1,1,3,5,5,5,-heptanitropentane, either solid or liquid, cannot be fitted to the scheme, even allowing for gauche effects. The differences between observed and estimated values for 1,1,1-fluorodinitroalkanes and 1,2-dinitroethane are larger than expected and should be further investigated. Activation energies have been calculated for decomposition by five-center elimination of HONO from mononitro- and dinitroalkanes using thermochemistry and estimated activation energies for the reverse reactions. The key data for these estimates were previously reported activation energies for the decomposition of nitroethane and 1,2-dinitropropane. The calculations also gave values for the heats of formation (in kcal/mole) of nitroethylene 12.4, and 1-nitropropylene 5.6, and 2-nitropropylene 1.6. Activation energies were calculated for the competing unimolecular reaction, C? N bond fission, from thermochemistry and previously reported activation energies for the decomposition of 1,1- and 2,2-dinitropropane. Comparison of Arrhenius parameters for the two competing processes, namely, HONO and C? N bond fission, shows that, for the geminate dinitroethanes and dinitropropanes, C? N bond fission is faster about 370°K and, for the mononitroalkanes and for all the mononitroalkanes and dinitroalkanes, C? N bond fission is faster above 770°K.     

Development of models for prediction of the antioxidant activity of derivatives of natural compounds

Antioxidants are important for maintaining the appropriate balance between oxidizing and reducing species in the body and thus preventing oxidative stress. Many natural compounds are being screened for their possible antioxidant activity. It was found that a mushroom pigment Norbadione A, which is a pulvinic acid derivative, shows an antioxidant activity; the same was found for other pulvinic acid derivatives and structurally related coumarines. Based on the results of in vitro studies performed on these compounds as a part of this study quantitative structure–activity relationship (QSAR) predictive models were constructed using multiple linear regression, counter-propagation artificial neural networks and support vector regression (SVR). The models have been developed in accordance with current QSAR guidelines, including the assessment of the models applicability domains. A new approach for the graphical evaluation of the applicability domain for SVR models is suggested. The developed models show sufficient predictive abilities for the screening of virtual libraries for new potential antioxidants.     

小环化合物中饱和碳质子化学位移的计算

小环化合物由于其张力、构型、构象和各向异性效应等原因,环碳上质子化学位移缺乏规律性,难以预测,对此作者曾提出一种近似算法。本文根据303种小环化合物中饱和碳质子的化学位移实验数据,将适于计算这类质子化学位移的公式表述为:     

Concentrations of 239,240Pu and 241Am of marine products in coastal waters of Ibaraki

More than 200 samples of marine products have been collected and analyzed for plutonium and almost 100 samples for americium around Hitachi, Tokai and Oarai in the pacific coast of Ibaraki prefecture. The data have shown that the concentration factor (CF) values for plutonium were 330 for bivalve, 770 for abalone (muscle) and 610 for brown algae. For americium, the CF was calculated as 2400 for bivalve, 1000 for abalone (muscle) and 420 for brown algae.     

Total synthesis of pinnatoxins A and G and revision of the mode of action of pinnatoxin A

Pinnatoxins belong to an emerging class of potent marine toxins of the cyclic imine group. Detailed studies of their biological effects have been impeded by unavailability of the complex natural product from natural sources. This work describes the development of a robust, scalable synthetic sequence relying on a convergent strategy that delivered a sufficient amount of the toxin for detailed biological studies and its commercialization for use by other research groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland-Claisen rearrangement of a complex α,α-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive evidence for its mode of action as a potent inhibitor of nicotinic acetylcholine receptors selective for the human neuronal α7 subtype. The comprehensive electrophysiological, biochemical, and computational studies support the view that the spiroimine subunit of pinnatoxins is critical for blocking nicotinic acetylcholine receptor subtypes, as evidenced by analyzing the effect of a synthetic analogue of pinnatoxin A containing an open form of the imine ring. Our studies have paved the way for the production of certified standards to be used for mass-spectrometric determination of these toxins in marine matrices and for the development of tests to detect these toxins in contaminated shellfish.     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

A theoretical investigation of molecular core binding and relaxation energies in a series of oxygen-containing organic molecules of interest in the study of surface oxidation of polymers

Nonempirical LCAO MO SCF computations (in the ΔSCF formalism) have been carried out of binding energies and relaxation energies for an extensive series of oxygen-containing organic systems encompassing most of the common functionalities. The molecules for which experimental data are available for comparison demonstrate the adequacy of the treatment for describing the relative binding energies for both the C_ls and O_ls core levels. A sound basis is therefore provided for the discussion of relative core binding energies (C_ls and O_ls) for functionalities for which experimental data are not available, that is, hydroperoxides, peroxides, peroxyacids, and peroxyesters, a knowledge of which is essential for investigations of the surface oxidation of polymers by means of ESCA. C_ls shifts are discussed in terms of primary and secondary substituent effects of oxygen, which greatly simplify the analysis of complex unresolved spectra, whereas for the O_ls levels a similar but less straightforward situation exists. The relaxation energies associated with both C_ls and O_ls core ionization follow a dependence on the binding energy for a given structural type.     

Determination of the composition of mixtures of fatty acid polymorphs by DTA

The effect of various solvents on the crystal structure of pure stearic acid crystallized from them was studied using X-ray and differential thermal analysis. The latent heat of the phase transition, ΔH_t, was measured for the two well-defined forms B and C.X-Ray diffractograms are the means for the identification of crystal modifications. However, only qualitative information about the composition present in the mixture can be inferred from the relative peak intensities.Differential thermal analysis of the phase transitions at 54°C (for B) and 64°C (for A) furnishes quantitative data for each component present in the mixture.Values of 0 and 4.9 cal g^?1 for the phase transition enthalpies were measured for the pure C form and B form, respectively. Intermediate values were found for mixtures of C and B.The interplay between the crystallization conditions (type of solvent, cooling rate and flow regime) dictates the formation of various crystal structure modifications.     

Development of certified reference samples of solutions of trihalomethanes

A method for the metrological certification of reference samples (RS) of solutions of organic compounds was proposed. The method is based on a procedure of sample preparation that uses both calculated and experimental data and involves the evaluation of the purity of the reagents employed. Impurity components were identified. Procedures for the determination of impurity components in source materials by gas chromatography with flame-ionization detection were developed. Calibration coefficients for halogen-containing impurity components in reference to an internal standard were determined experimentally or calculated. Certified reference samples of solutions of trichloromethane, bromodichloromethane, dibromochloromethane, and tribromomethane were designed for the quality control of drinking water     

Positive equilibria of a class of power-law kinetics

This paper studies a class of power-law kinetics, PL-ILK, for whose subset, PL-TIK, analogues of the Deficiency Zero Theorem and the Deficiency One Theorem (DOT) for mass action systems are valid. The DOT also includes the necessary and sufficient condition of Boros for uniqueness in the non-weakly reversible case. To our knowledge, this is the first set of kinetics beyond mass action kinetics (MAK) for which the DOT has been shown to be valid. A further interesting property of PL-TIK is a certain “robustness” relative to dependence of linkage classes: existence of a positive equilibrium for each linkage class implies the existence of a positive equilibrium for the whole network. For MAK systems, the PL-ILK property is equivalent to the reactant deficiency of the linkage class containing the zero complex being one, and zero for all other linkage classes. As shown in the Supplementary Materials, an initial survey of MAK and BST systems already reveals numerous examples with PL-ILK kinetics.     

Characterisation of salts of drug substances

The properties of the solid-state of drug substances are critical factors that determine the choice of an appropriate salt form for the development of the pharmaceutical formulation. The most relevant properties may affect the therapeutic efficacy, toxicity, bioavailability, pharmaceutical processing and stability. The salt form must fulfil the needs of the targeted formulation, be suitable for full-scale production and its solid-state properties maintained batchwise as well as over time. Comparison of the solid-state properties of different salt candidates may be quite complicated if each salt candidate exist as different solid phases: polymorphs, solvates or amorphous forms. Thermal analysis, microcalorimetry and combined techniques, X-ray diffraction, solubility, intrinsic dissolution, sorption-desorption and stability studies are basic techniques for the characterisation of the salt candidates. Some examples show the role of the salt form as well as the polymorphic form in the characteristics of the solid-state. Thermal analysis and combined techniques are efficient for the detection of unexpected phase transitions and for the comparison of the suitability of the salt candidates prepared for salt selection. This revised version was published online in July 2006 with corrections to the Cover Date.     

Self-Consistency of the Theory of Elementary Stage Rates of Reversible Processes and the Equilibrium Distribution of Reaction Mixture Components

An analysis is presented of one of the key concepts of physical chemistry of condensed phases: the theory self-consistency in describing the rates of elementary stages of reversible processes and the equilibrium distribution of components in a reaction mixture. It posits that by equating the rates of forward and backward reactions, we must obtain the same equation for the equilibrium distribution of reaction mixture components, which follows directly from deducing the equation in equilibrium theory. Ideal reaction systems always have this property, since the theory is of a one-particle character. Problems arise in considering interparticle interactions responsible for the nonideal behavior of real systems. The Eyring and Temkin approaches to describing nonideal reaction systems are compared. Conditions for the self-consistency of the theory for mono- and bimolecular processes in different types of interparticle potentials, the degree of deviation from the equilibrium state, allowing for the internal motions of molecules in condensed phases, and the electronic polarization of the reagent environment are considered within the lattice gas model. The inapplicability of the concept of an activated complex coefficient for reaching self-consistency is demonstrated. It is also shown that one-particle approximations for considering intermolecular interactions do not provide a theory of self-consistency for condensed phases. We must at a minimum consider short-range order correlations.     

A Simple Method of the Determination of the Structural Heterogeneity of Microporous Solids

A new procedure for determining the structural heterogeneity of microporous solids is presented. Applying the concept of a general adsorption isotherm equation, a method for solving this equation for adsorption in micropores is developed, and the applicability of a new simple algorithm for determining the parameters of microporous structure of two commercial carbons is shown. Copyright 2001 Academic Press.     

Regularities of formation of emboli of liquid polymer solutions in aqueous medium

Work on creating the basis for embolic compositions for the treatment of a wide range of pathologies of various organs was conducted. This basis is a solution of a biocompatible water-insoluble polymer in a biocompatible water-soluble solvent. Formation of the embolus in such an aqueous medium takes place in the transition of the solvent into the aqueous phase and the formation of a solid polymer clot occluding a blood vessel. Criteria for selection of the polymer and the solvent for the basis were formulated, and a number of polymers and solvents that meet these criteria were selected for further research. Research on the solubility of the selected polymers in solvents was carried out, and the rheoviscometric characteristics of polymer solutions, as well as parameters of solid emboli formation of polymer solutions in aqueous media, were found. The solution of cellulose acetate plasticized with OPADRY CA 500F190000 polyethylene glycol in dimethylsulfoxide with concentration of no less than 60 g/L was recognized as optimal for further studies.     

Assessment of the determination of water-soluble ionic composition of atmospheric aerosols from the analysis of crossed halves of filters

The water-soluble ionic composition of atmospheric aerosols is a key parameter for estimating its anthropogenic or natural origin. This evaluation depends on the reliability of the performed measurements. The differential approach for the evaluation of the measurement uncertainty was used for estimating, separately, the uncertainty associated with the extraction step, by difference from the observed intermediate precision and the combination of all the other uncertainty components affecting the estimated intermediate precision. The intermediate precision was estimated from the difference of results of the analysis, in different days, of several pairs of filters resulting from cross-changing of their halves. The precision associated with the symmetry of filters division, affecting the homogeneity of studied combined pairs of filters, was subtracted from the observed dispersion of results. The resulting detailed model of measurement performance allowed defining strategies for cost of analysis or magnitude of measurement uncertainty reduction. Measurements are fit for the analysis of urban aerosols since the expanded relative measurement uncertainty is smaller than a target value of 30 %.     

Thermodynamics of solutions of methanol and solvating components

A model is proposed to correlate the excess Gibbs free energies and excess enthalpies of binary solutions of methanol and a solvating component. Solution nonideality from ideal solutions is given by the sum of the chemical contribution term, which is due to self-association of methanol and solvation between methanol and a nonassociating component, and the physical contribution term with allowance for the NRTL equation. The model uses the following data for methanol: two enthalpies for formation of the hydrogen bonds for the dimer and all larger polymeric species, three equilibrium constants of stepwise association for the dimer, trimer and other polymeric species, and an equilibrium constant for cyclic species of more than tetramer. The association model further includes an additional solvation equilibrium to allow for the interaction between the terminal hydroxyl group of methanol polymeric species and a solvating component. The model is extended to predict vapor—liquid equilibria, liquid—liquid equilibria and excess enthalpies for ternary solutions containing methanol and two nonassociating components from only binary information. Calculated results are in good agreement with experimental data as shown by selected illustrative examples.     

分析电镜Cliff-Lorimer 因子测量及薄标样标准化探讨

采用电子探针矿物标样,即均匀性和稳定性符合显微定量分析要求的国标样品,制备成适于分析电镜（ＡＥＭ）成分分析的薄样品,测量了一组Ｃｌｉｆ－Ｌｏｒｉｍｅｒ（ＣＬ）因子,考察了用不同型号的分析电镜分析时ＣＬ因子的变化,提出了仪器校正因子ＫＩ＝εＢ／εＡ,对原子序数小于２０的较轻元素其ＣＬ应考虑作ＫＩ校正;作者建议采用易于制成薄晶片的黑云母标样来统一不同分析条件下的ＣＬ因子,并应建立适于分析电镜定量分析的无机薄标样通用技术条件。     

Analysis of the reactivity of small cobalt clusters

The electronic structures of small cobalt clusters have been calculated within the local spin density approximation using the LCAO method. The calculations were done for simple geometries with the optimized number of interatomic bonds, and both for the bond length of the cobalt dimer and the bulk metal. The Fermi energy is found to be smaller for Co _N clusters withN=3, 4, 5 andN>10 than for the other ones. The variation of the Fermi energy with the cluster size correlates in a striking way with the observed H₂ tendency for chemisorption as found for cobalt clusters in a supersonic beam. Furthermore, the magnetic moments are somewhat smaller for these active clusters. In addition the lowest unoccupied levels of majority spin appear close to the highest occupied levels of minority spin which is not the case for the inert clusters.     

Diffusion of spheres in crowded suspensions of rods

Translational tracer diffusion of spherical macromolecules in crowded suspensions of rodlike colloids is investigated. Experiments are done using several kinds of spherical tracers in fd-virus suspensions. A wide range of size ratios L/2a of the length L of the rods and the diameter 2a of the tracer sphere is covered by combining several experimental methods: fluorescence correlation spectroscopy for small tracer spheres, dynamic light scattering for intermediate sized spheres, and video microscopy for large spheres. Fluorescence correlation spectroscopy is shown to measure long-time diffusion only for relatively small tracer spheres. Scaling of diffusion coefficients with a/xi, predicted for static networks, is not found for our dynamical network of rods (with xi the mesh size of the network). Self-diffusion of tracer spheres in the dynamical network of freely suspended rods is thus fundamentally different as compared to cross-linked networks. A theory is developed for the rod-concentration dependence of the translational diffusion coefficient at low rod concentrations for freely suspended rods. The proposed theory is based on a variational solution of the appropriate Smoluchowski equation without hydrodynamic interactions. The theory can, in principle, be further developed to describe diffusion through dynamical networks at higher rod concentrations with the inclusion of hydrodynamic interactions. Quantitative agreement with the experiments is found for large tracer spheres, and qualitative agreement for smaller spheres. This is probably due to the increasing importance of hydrodynamic interactions as compared to direct interactions as the size of the tracer sphere decreases.     

广东省高校大学生膳食调查及营养配餐推荐

本调查报告采用问卷法了解广东主要高校大学生一周内熟食进食量及用餐情况，计算出每人每日热量和各种营养素的摄人量，采用Microsoft Excel软件进行数据处理和统计分析，并用中国营养学会制订的DRIs(膳食营养素参考摄人量)和中国居民膳食指南及平衡膳食宝塔进行比较分析，且通过微量元素检测对结果进行了验证，最后提供了为期一周的营养配餐作为膳食参考。主要调查结果如下：男女生的蛋白质、尼克酸、维生素C、维生素E、碘和男生锰的摄入量已经满足人体需要。男生铁和锰的摄入量基本满足需要。男女生的能量、脂肪、膳食纤维、维生素A、硫胺素、核黄素、钙、锌的摄人量都不足，且女生铁的摄人量同样不足。男女生一日三餐热量分配结构十分不平衡，早餐的热量摄入均偏低，膳食结构也不合理。在分析广东省大学生膳食状况的基础上，推出五套营养配餐方案供高校膳食部门和大学生参考选用。