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  • Author or Editor: Y.X. Liu x
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Abstract

By using the critical point theory, the existence of periodic solutions to second order nonlinear p-Laplacian difference equations is obtained. The main approach used is a variational technique and the saddle point theorem. The problem is to solve the existence of periodic solutions of second order nonlinear p-Laplacian difference equations.

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Abstract  

The effect of excipients on the secondary structure of lyophilized proteins was studied through second-derivative Fourier transform infrared (FTIR) spectroscopic analysis. The glass transition temperature (T g), denaturation temperature (T d) and moisture content were determined by differential scanning calorimetry (DSC) and thermogravimetry (TG). T g, T d and the preservation of protein secondary structure were found to be dependent upon the type and amount of the excipient included in the formulation. Meanwhile, the lyophilized proteins easily adsorbed amounts of moisture during storage to reduce their T gs and stability.

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DSC and TG-DTA techniques were used to investigate micro-sized silver powder particles and the adsorption of ethyl cellulose on these particles in a solution of ethyl acetate. The apparent specific heat of the silver particles was determined, and the kinetics of temperature-programmed desorption (TPD) of these adsorbed silver particles was investigated. Results show that the apparent specific heat and desorption kinetic parameters obtained by thermal analysis techniques could be used to characterize certain physico-chemical properties of such a particulate system.

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In this paper studies on the oscillation regularity of the classical B–Z reaction system, and the calorimetric curves of the reaction system measured at three temperatures, 25, 27 and 29°C are described. A new way is presented for studying the regularity properties of chemical oscillation phenomena from the viewpoint of reaction heat effects.

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Abstract  

Mn2O3/-Al2O3 catalysts were prepared by the impregnation method, and the maximum monolayer dispersion capacity or dispersion threshold value of Mn2O3 on the surface of -Al2O3 was determined to be 13.08% from the decomposition mass loss of supported Mn(NO3)2 in the monolayer state. This was compared with the values estimated from a close-packed monolayer model and an interaction model. It was confirmed that the high activities and selectivities of the catalysts for benzoic acid hydrogenation to benzaldehyde are due to the monolayer dispersion of the Mn2O3 on the surface of -Al2O3.

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Eight cultivars of dry-land wheat (Triticum aestivum L.) historically planted in Shaanxi Province, China, were grown in plots with irrigation and drought treatments during the growing seasons of 2011–2014, so as to characterize the differences in the rate and duration of the grain-filling stage among cultivars. The experimental results showed no obvious change among cultivars with respect to the duration of the grain-filling stage and no significant correlation between duration and grain weight. The filling rates of all three phases (lag, linear, and mature periods) showed significant differences among cultivars and had a greater effect on the grain weight than the duration of the filling stage, even though drought decreased the filling rate in the linear and mature periods. A lower filling rate led to a lighter grain weight in inferior grains than in superior grains. For the superior and inferior grains in the central spikelets, modern cultivars possess faster filling rates, especially in the lag and linear periods, whereas for the whole spike, no significant trend with cultivar replacement was observed. Faster filling rates with stable filling durations will be beneficial in obtaining additional yield increases.

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Abstract  

The transformation equation for the thermokinetics of consecutive first-order reactions has been deduced, and a thermokinetic research method of irreversible consecutive first-order reactions, which can be used to determine the rate constants of two steps simultaneously, is proposed. The method was validated and its theoretical basis was verified by the experimental results.

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Abstract  

The exfoliated poly(vinyl chloride) (PVC)/montmorillonite (MMT) nanocomposites were synthesized by in situ intercalated polymerization of vinyl chloride (VC) in the presence of organic-intercalated montmorillonite (OMMT). Their structures and thermal properties were characterized. The results showed that layered silicates are well exfoliated and uniformly distributed in PVC matrix during in situ intercalated polymerization of VC in the presence of OMMT. The glass transition temperatures of PVC phases in the PVC/MMT nanocomposites are all lower than that of pristine PVC due to the incorporation of the exfoliated silicate layers in PVC matrix. The 5% mass loss temperature (T 5%), the dehydrochlorination temperature (T max1) of the PVC matrix decreased due to the free and interlayer water in MMT, the low thermal stability, and the enhanced dehydrochlorination of the PVC matrix by alkyl ammonium pre-treated MMT. However, the thermal decomposition temperature of the dehydrochlorinated PVC (T max2) and char at 600C are slightly increased in the presence of silicate layers.

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In this paper, 633 species (involving 10 classes, 48 families, 205 genera) collected from the alpine meadow on the eastern Qinghai-Tibet plateau were studied. We tested potential factors affecting variation in mean germination time (MGT), i.e., plant traits (adult longevity, dispersal mode and seed size) or phylogeny, to evaluate if these factors were independent or they had interaction. Nested ANOVA showed that taxonomic membership accounted for the majority of MGT variation (70%), and in the generalized linear model, family membership could explain independently the largest proportion of MGT variation (29%). The strong taxonomic effect suggests that MGT variation within taxonomic membership is constrained. The other plant traits could also explain MGT variation independently (1% by adult longevity and dispersal mode, respectively, and 2% by seed size). Thus, the phylogeny was an important constraint to maintain the stability of species, and we could simplify the question if we regarded the phylogeny as an individual factor, but we could not negate the adaptive significance of the relationship between other plant traits and seed MGT. In addition, a large percentage of the variance remained unexplained by our model, thus important selective factors or parameters may have been left out of this analysis. We suggest that other possible correlates may exist between seed germination time and additional ecological factors (for example, altitude, habitat and post-dispersal predation) or phylogenetic related morphological and physiological seed attributes (e.g., endosperm mass) that were not evaluated in this study.

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Abstract

Dodecylamine hydrochloride C12H25NH3·Cl(s) and bis-dodecylammonium tetrachlorozincate (C12H25NH3)2ZnCl4(s) were synthesized by the method of liquid phase reaction. The constant-volume energy of combustion of dodecylamine hydrochloride was measured by means of a RBC-II precision rotating-bomb combustion calorimeter at T = (298.15 ± 0.001) K. The standard molar enthalpy of formation of C12H25NH3·Cl(s) was calculated to be (C12H25NH3·Cl, s) = −(706.79 ± 3.97) kJ mol−1 from the constant-volume energy of combustion. In accordance with Hess’ law, a reasonable thermochemical cycle was designed and the enthalpy change of the synthesis reaction of the complex (C12H25NH3)2ZnCl4(s) was determined by use of an isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of (C12H25NH3)2ZnCl4(s) was calculated as [(C12H25NH3)2ZnCl4, s] = −(1862.14 ± 7.95) kJ mol−1 from the standard molar enthalpy of formation of C12H25NH3·Cl(s) and other auxiliary thermodynamic data.

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