Solvent Effects on the Structure-Activity Relationship of Pharmacological Active 3-Substituted-5,5-Diphenylhydantoins

Absorption spectra of eight 3-substituted-5,5-diphenylhydantoins have been recorded in fourteen solvents in the range 200–400 nm. The effect of solvent dipolarity/polarizability and solvent/solute hydrogen bonding interactions are analyzed by means of the linear solvation energy relationship (LSER) concept proposed by Kamlet and Taft. The lipophilic activity of the investigated hydantoins was estimated by the calculation of log ₁₀ P values with the Advanced Chemistry Development Software. The calculated values of log ₁₀ P were correlated with the ratio of the contributions of specific solvent interactions, and, by employing the linear dependence thus obtained, the pharmacological activity of the studied hydantoin derivatives is discussed.     

LC–MS Determination of Sterols in Olive Oil

Sterols in olive oils have been analyzed by liquid chromatography coupled to mass spectrometry with atmospheric-pressure chemical ionization in positive-ion mode. A simple procedure based on saponification and extraction of the compounds from olive oils was studied. Validation of the method included calibration and determination of recovery and repeatability was carried out. Good linearity was obtained up to 100 mg kg^?1 for all the sterols studied except β-sitosterol, for which linearity was obtained up to 2,000 mg kg^?1. Recovery ranged from 88 to 110%, detection limits from 0.9 to 3.1 mg kg^?1, and precision was good. The method has been successfully used for analysis of sterols in different types of oil. The predominant sterol was β-sitosterol; other minor components, for example sitostanol and cholesterol, were also detected. Total sterol content depended on the type of oil, and ranged from 687 to 2,479 mg kg^?1. Stigmasterol and the amount of erythrodiol plus uvaol can be used to distinguish between olive oil and seed oil.     

Effect of polyvinylalcohols on the thermostability of lipase fromCandida rugosa

Lipase fromCandida rugosa was stabilized against thermal inactivation in the presence of polyvinylalcohols (PVA) of different molecular weights. The apparent rate constant of the lipase inactivation, k_d, at 49°C is 0.049/min and 0.022/min in the absence and in the presence of PVA (mol wt 22,000), respectively. The improvement of the lipase thermostability by adding PVA was confirmed by differential scanning calorimetry. The presence of PVA had also an effect on the hydrolytic activity of the enzyme. Furthermore, lipase was modified by covalent linkage to PVA by means of an original procedure. With respect to the native enzyme, the modified lipase has a slightly lower specific activity, but it is more stable against heat denaturation (k _d 0.032/min at 49°C).     

Hall effects and entropy generation applications for peristaltic flow of modified hybrid nanofluid with electroosmosis phenomenon

The electroosmotic peristaltic flow of modified hybrid nanofluid in presence of entropy generation has been presented in this thermal model. The Hall impact and thermal radiation with help of nonlinear relations has also been used to modify the analysis. The assumed flow is considered due to a non-uniform trapped channel. The properties of modified hybrid nanofluid model are focused with interaction of three distinct types of nanoparticles namely copper ($Cu)$, silver ($Ag$) and aluminum oxide ($A{l}_2{O}_3).$ The mathematical modeling and significances of entropy generation and Bejan number are identified. With certain flow assumptions, the governing equations are attained for optimized peristaltic electroosmotic problem. Widely used assumptions of long wave length and low Reynolds number reduced the governing equations in ordinary differential equations. The ND solver is flowed for the solution process. The physical significant of results is observed by assigning the numerical values to parameters.     

A sensitive spectrophotometric method for lead determination by flow injection analysis with on-line preconcentration

A new flow injection (FI) system for the determination of Pb(II) at trace level with a preconcentration step and spectrophotometric detection is proposed. It is based on preconcentration of lead ions on chitosan and dithizone-lead complex formation in aqueous medium (pH 9). The chemicals and FIA variables influencing the performance of the system were optimized and applied to the determination of lead in natural, well, and drinking water samples. It is a simple, highly sensitive, and low cost alternative methodology. The method provided a linear rage between 25 and 250 μg l⁻¹, a detection limit of 5.0 ng ml⁻¹ and a sample throughput of 15 h⁻¹. The obtained results of spiked samples are in good agreement between the proposed method and ICP-AES.     

Transformation of dynamic DSC results into isothermal data for the curing kinetics study of the resol resins

Kinetics of thermosetting polymers curing is difficult to study by isothermal methods based on the differential scanning calorimetry (DSC) technique. The difficulty is due to the low sensitivity of the equipment for total reaction heat measurements during high temperature process. The aim of this paper is to display the equivalence between a dynamic model, the Ozawa method, and an isothermal isoconversional fit, which allows predicting the isothermal behavior of the resol resins cure through dynamic runs by DSC. In this work, lignin–phenol–formaldehyde and commercial phenol–formaldehyde resol resins were employed. In addition, the isothermal kinetic parameters for both resins were performed by means of transformation of the data obtained from the dynamic Ozawa method.     

On the expansion of hole in main chain polymers determined by positron annihilation

The temperature dependence of positron annihilation characteristics, ₃ andI ₃, has been studied on sample of poly(butadiene), poly(isobutylene) and poly(chloroprene). The temperature range was between 15 and 470 K. The rate of expansion of holes or free-volume in all samples was deduced belowT _g as well aboveT _g as appr. 3·10^–3 K^–1 and 2·10^–2 K^–1, respectively. These values are very close to the rate of the mean squared displacement of scatterer<r ²>observed in neutron scattering experiments. A possibility to use an inverse value of free-volume,V _f ^–1 for study of viscoelastic state of polymers is demonstrated.     

Causal logic of Minkowski space

It is shown that double-orthogonal sets (diamonds) in Minkowski space form an orthomodular complete lattice. Connection with empirical logic of Randall and Foulis is discussed.     

Magnetic moments and the high field susceptibilities of MnFe2O4

An extended version of the noncollinear spin model bySawatzky et al. is developed to derive a dependence of the differential high field susceptibility on the degree of inversion of the ferrite MnFe₂O₄. Using the available data on the main molecular field coefficients it is shown that the present model imposes restrictions on values of. Determination of from the measurements of the field dependence of the saturated moments at low temperatures on samples with varying degrees of inversion reveals good quantitative agreement with the present model.     

OUH体系的结构和分析势能函数

采用密度泛涵B3LYP方法优化出了OUH分子的各种结构，确定了最稳定构型和离解能，以及它们的谐性力常数，并导出双原子分子UH,UO的Murrell-Sorbie势能函数及其光谱数据。采用多体项展式方法，导出OUH(X^4A')基态分子的分析势能函数，获得OUH(X^4A')体系的势能面，考察了这个势能函数的基本性质，正确地复现出OUH分子的平衡结构特征，结果表明：U+OH,O+UH,H+UO的反应均为无阈能的放热能反应。为进一步探讨OUH体系的反应动力学过程打下了基础。