Comparative behavior of Pd and Ag deposition phenomenon on clean α-Al2O3 (001) surface—A first principle study

The nature of bonding at the interface between deposited silver/palladium and clean Al-terminated (001) surface of α-Al₂O₃ has been investigated using a periodic ab initio method. Substantial inter-planar relaxations within the alumina were found at both the interfaces and the bulk. The periodic calculation with both Ag and Pd deposition shows that 10% of loading on alumina results maximum stability. Surface energy and work function calculations were performed to propose the stability for the metals on the studied surfaces. The deposited Ag forms a three-dimensional (3-D) cluster on top of the alumina surface. The Pd cluster formed on the alumina surface is two-dimensional (2-D) and is distorted to accommodate the Ag cluster in its domain. A further low index calculation can explain the reason for a higher stability of the membrane generated over alumina support with silver and palladium. The results are discussed in view of the existing experimental data and models of metal-oxide interface and a reason for the difference of activity of the metal interaction with alumina surface is postulated.     

Kinetics of adsorption of extended ligands on DNA at small fillings

In the present work, the adsorption kinetics of extended ligands on DNA duplexes at small fillings when molecules of DNA duplexes are on the underlayer within diffusion layer has been investigated. Both diffusion of ligands in solution (diffusion stage) and adsorption of ligands (kinetic stage) are taken into consideration at adsorption of ligands on DNA duplexes. Nonlinear system of differential equations describing adsorption of ligands where not only diffusion stage but also kinetic stage is taken into account, is obtained, moreover the equations allow localizing duplexes in arbitrary place within diffusion layer. Numeric solution of the equations makes possible to investigate the filling kinetics of DNA duplexes by ligands depending on parameters controlling adsorption process. It has been shown that depending on relation between adsorption parameters different kinetic regimes of adsorption – kinetic, complex, and diffusion regimes may be realized.     

International Society of Chronobiology: Membership Information

Most variables of interest in laboratory medicine show predictable changes with several frequencies in the span of time investigated. The waveform of such nonsinusoidal rhythms can be well described by the use of multiple components rhythmometry, a method that allows fitting a linear model with several cosine functions. The method, originally described for analysis of longitudinal time series, is here extended to allow analysis of hybrid data (time series sampled from a group of subjects, each represented by an individual series). Given k individual series, we can fit the same linear model with m different frequencies (harmonics or not from one fundamental period) to each series. This fit will provide estimations for 2m + 1 parameters, namely, the amplitude and acrophase of each component, as well as the rhythm-adjusted mean. Assuming that the set of parameters obtained for each individual is a random sample from a multivariate normal population, the corresponding population parameter estimates can be based on the means of estimates obtained from individuals in the sample. Their confidence intervals depend on the variability among individual parameter estimates. The vari-ance-covariance matrix can then be estimated on the basis of the sample covariances. Confidence intervals for the rhythm-adjusted mean, as well as for the amplitude-acrophase pair, of each component can then be computed using the estimated covariance matrix. The p-values for testing the zero-amplitude assumption for each component, as well as for the global model, can finally be derived using those confidence intervals and the t and F distributions. The method, validated by a simulation study and illustrated by an example of modeling the circadian variation of heart rate, represents a new step in the development of statistical procedures in chronobiology.     

Spinning of hydroalcoholic chitosan solutions

We investigated the spinning of hydroalcoholic chitosan solutions. The dope composition was optimized in order to obtain a continuous alcogel fiber by water evaporation on heating the extruded hydroalcoholic solution. This alcogel fiber was then neutralized in aqueous alkali baths and washed in water to eliminate the residual alcohol and salts before final drying. Depending on the alcohol content in the filament at the neutralization step, on specific alcohol–chitosan interactions and on the nature and concentration of the coagulation base, the process yielded semicrystalline chitosan fibers with different proportions of anhydrous and hydrated allomorphs. Contrarily to the classical annealing method, the formation of mainly anhydrous crystals was obtained without significant molecular weight decrease by neutralizing the polymer in hydrophobic conditions. The control of allomorph content was shown to be related to the hydrophobicity of the solvent (alcohol fraction) at the neutralization step.     

First record of dicephalia in a bull shark Carcharhinus leucas (Chondrichthyes: Carcharhinidae) foetus from the Gulf of Mexico,U.S.A.

The first recorded incidence of dicephalia in a bull shark Carcharhinus leucas is reported from a foetus collected by a fisherman in the Gulf of Mexico near Florida, U.S.A. External examination, Radiography and magnetic resonance imaging revealed a case of monosomic dicephalia where the axial skeleton and internal organs were found to divide into parallel systems anterior to the pectoral girdle resulting in two well‐developed heads.     

A modified metabolic model for mixed culture fermentation with energy conserving electron bifurcation reaction and metabolite transport energy

A modified metabolic model for mixed culture fermentation (MCF) is proposed with the consideration of an energy conserving electron bifurcation reaction and the transport energy of metabolites. The production of H₂ related to NADH/NAD⁺ and Fdred/Fdox is proposed to be divided in three processes in view of energy conserving electron bifurcation reaction. This assumption could fine‐tune the intracellular redox balance and regulate the distribution of metabolites. With respect to metabolite transport energy, the proton motive force is considered to be constant, while the transport rate coefficient is proposed to be proportional to the octanol–water partition coefficient. The modeling results for a glucose fermentation in a continuous stirred tank reactor show that the metabolite distribution is consistent with the literature: (1) acetate, butyrate, and ethanol are main products at acidic pH, while the production shifts to acetate and propionate at neutral and alkali pH; (2) the main products acetate, ethanol, and butyrate shift to ethanol at higher glucose concentration; (3) the changes for acetate and butyrate are following an increasing hydrogen partial pressure. The findings demonstrate that our modified model is more realistic than previous proposed model concepts. It also indicates that inclusion of an energy conserving electron bifurcation reaction and metabolite transport energy for MCF is sound in the viewpoint of biochemistry and physiology. Biotechnol. Bioeng. 2013; 110: 1884–1894. © 2013 Wiley Periodicals, Inc.     

Speciation of phytate ion in aqueous solution. Non covalent interactions with biogenic polyamines

Abstract

The noncovalent interactions of phytate (Phy^6-) with biogenic amines were studied potentiometrically in aqueous solution, at t= 25°C. Several species are formed in the different H+-Phy^6--amine (A) systems, which have the general formula A_p(Phy)H_q^(12-q)-, with p ≤ 3 and 6 ≤ q ≤ 10. The stability of these species is strictly dependent on the charges involved in the formation equilibria. For the equilibrium pH_iAⁱ⁺ + H_j(Phy)⁽¹²-^j)- = A_p(Phy)H_q(^12q)-, (q = pi + j)we found the relationship logK= aζ (ζ is the charge product of reactants), where a= 0.35(0.03, valid for all the amines; this roughly indicates an average free energy contribution per bond -ΔG⁰ = 4.0 ± 0.2 kJ mol^-1. A slightly more sophisticated equation is also proposed for predicting the stability of these species. Owing to the quite high (partially protonated) phytate charge, the stability of A_p(Phy)H_q^(12-q)- species is quite high, making phytate a strong amine sequestering agent in a wide pH range.     

弱硅化腕足类化石酸处理方法的改进

本文介绍了一种获取灰岩中弱硅化腕足类化石的酸处理方法。以四川省布拖县浪珠乡万吨山剖面上奥陶统铁足菲克组近顶部的生屑灰岩为实验对象, 通过准备样品、悬吊样品、配酸解液、酸解样品等实验流程, 配合遮盖液(如二乙酸纤维素丙酮溶液)的使用, 可获得保存精美的、弱硅化的腕足类实体化石, 且该化石保存有主突起、铰齿和匙形台等重要的细小结构。相较于传统方法, 该方法可获取硅化程度更低的壳相化石。该方法为灰岩中其他多门类弱硅化保存的化石之酸解分析提供了新思路和参考。     

Direct and inverse relationships between Riccati systems coupled with multiplicative terms

An analytical and computational framework for the derivation of solitary solutions to biological systems describing the cooperation and competition of species and expressed by the system of Riccati equations coupled with multiplicative terms is presented in this paper. It is demonstrated that relationships between these solitary solutions can be either direct or inverse. Thus, an infinitesimal perturbation of one population would lead to an infinitesimal change in the other population – if only both solitary solutions are coupled with the direct relationship. But, in general, that is not true if solitary solutions are coupled with the inverse relationship – an infinitesimal perturbation of one population may result into a non-infinitesimal change in the other population. Necessary and sufficient conditions for the existence of solitary solutions are derived in the space of the system's parameters and initial conditions.