Structural Interpretation of Eyring Activation Parameters for Tensile Yielding Behavior of Isotactic Polypropylene Solids

The temperature and strain rate dependence of the stress-strain curves of isotactic polypropylene were analyzed on the basis of Eyring kinetic theory. The molecular and structural basis underlying the parameters, such as activation volume and activation energy, used by the Eyring analysis were studied using the lamellar cluster theory, where a stacked lamella acts as a basic structural unit under yielding and necking deformation. It was suggested that, at lower temperatures, the activation volume corresponds to chain slippage within crystalline lamellae in the lamellar clusters whereas at higher temperature the increase in activation volume results in intralamellar slip corresponding to the α₂ relaxation.     

Chlorofluorocarbons adsorption structures and energetic over faujasite type zeolites—a first principle study

Adsorption of ozone depleting chlorofluorocarbons (CFC) over zeolite is of major global environmental concern. The current communication describes first-principle calculation performed on faujasite models to investigate the nature of CFCs including fluoro, chlorofluoro and hydrofluoro/chloro carbons (CF₄, CF₃Cl, CF₂Cl₂, CFCl₃, CHF₃, CHCl₃) adsorption. Experimentally it is observed that separation of halocarbons are possible using Na–Y, though the cause is unknown. Reactivity index within the helm of Hard Soft Acid Base (HSAB) principle was used to monitor the activity of the interacting CFCs using Density Functional Theory (DFT) to propose a qualitative order. The importance of both H-bonding and cation–F/Cl interactions in determining the low-energy sorption sites were monitored and rationalized. The host guest interactions show a distinctive difference between the adsorption phenomenon between H–Y and Na–Y and as well for Cl and F. It is observed that Cl has more favorable interaction with hydrogen of H–Y compared to Na–Y and for F the situation is just reversed. To validate this trend periodic optimization calculations were performed. The interaction energy as obtained matches well with the reactivity index order resulted from cluster calculations. This study is a combination of DFT and periodic calculation to rationalize the electronic phenomenon of the interaction process.     

Synthesis and characterization of α-, β- and γ-cyclodextrin-nicotinamide

Abstract

α-, β- and γ-cyclodextrin-nicotinamide (α-, β- and γ-CDNA) were synthesized as NADH coenzyme models, and the binding abilities were investigated. CDNA binds a negatively charged guest stronger than unmodified cyclodextrin because of the electrostatic interaction between the nicotinamide residue and the guest molecule. Different binding abilities were measured and were dependent on cavity size.     

Detection of heterogeneity and estimation of population characteristics from the field survey data: 1987/88 Japanese feasibility study of the southern hemisphere Minke whales

To get reliable information of the age structure of whale population, Japan conducted a feasibility study of scientific research in the Antarctic in 1987/88. Though the sample was not large enough, it was the first data free from the problem of selectivity and whaling ground bias. From the analysis, it was found that the biological characteristics are highly heterogeneous spatially or other ways. Considering this, we recognize that the survey should be designed to collect the sample from the whole research area uniformly to obtain unbiased estimates of population characteristics. However, in an actual biological field survey, it is difficult to keep the sampling fractions thecisely the same for each sampling units. Therefore, it is important to detect the heterogeneity in the sample, and poststratify the data corresponding to the heterogeneity. The methodology of the estimation and model evaluation presented here will be useful for the development of biological field survey in general.     

Substituent effect on the acetolysis of neophyl p-bromobenzenesulfonates

The substituent effect on the acetolysis of neophyl brosylates was analyzed successfully based on the analysis method of Yukawa-Tsuno. The basic concept of this method was strongly supported.     

Regioselective phenyl-substitution effects on the solvatochromism of 2-phenylimidazo[1,2-a]pyrazin-3(7H)-one derivatives: expansion of the color variation range of a visible indicator for the proton donor ability of solvents

Phenyl-substitution to the C8 position of an imidazopyrazinone ring resulted in the significant bathochromic shift of the lowest energy band, while the substitution to the C6 position does not produce such a shift. This provides evidence that a color variation range of the solvatochromism of 2-phenylimidazopyrazinone derivatives depends strongly on the position of phenyl-substitution. Results indicated that an imidazopyrazinone with the phenyl groups at the C2 and C8 positions acts as a potential indicator of the proton donor ability of solvents.     

Catalytic activity of β-cyclodextrin-histamine

We modified cyclodextrin (CD) by a histamine group to make a model of -chymotrypsin. Enzymatic turnover reaction was realized with CD-histamine at around neutral pH value. Compared with amino-CD, it is ascertained that this catalytic activity of CD-histamine is caused by an imidazole group. Using several substrates in the hydrolytic reactions, it shows that CD-histamine has a structural selectivity for substrates which are structurally different to each other.     

Preparation of mesoporous silicas using food grade emulsifiers and its application for enzyme supports

A novel mesoporous silica (TMPS) was synthesized via self-assembly using a myristic acid ester of pentaglycerol. The ester is obtained from catalytic esterification and it is commercially available as a food grade emulsifier. TMPS material was employed for preparation of a biocatalyst in order to examine the ability as an enzyme support in comparison with the other mesoporous silica materials having a channel or a cage-like pore system. The used TMPS materials possessed the interconnected channel-like pore system with the pore sizes of 9.2, 12, and 16 nm. The materials successfully entrapped lipase into their mesopores with the high loadings. The resultant lipase/TMPS conjugates functioned as the biocatalyst for hydrolysis of p-nitrophenyl propionate (p-NPP), having the higher activity than those of the used mesoporous silica conjugates. The high activities were ascribed to the textural properties such as the small particle length, large pore size and the three-dimensional pore connectivity that permit the accessibility of p-NPP to the immobilized lipases during the reactions. Consequently, we concluded that TMPS materials are of the suitable mesoporous support for the enzymes.