Study on the Kinetics of Non-isothermal Dehydration of Alkaline Earth Metal Selenites

The dehydration kinetics of crystallohydrates of beryllium, magnesium and calcium selenites were studied under non-isothermal conditions. The values of the activation energy of dehydration, the pre-exponential factor in Arrhenius equation and the change of entropy for the formation of the activated complex were calculated using the calculation procedure of Coats and Redfern. Thermal stability and activation energy of dehydration of the crystallohydrates were found to increase by the same order. The relationships observed were interpreted using Klopman’s generalized perturbation theory of chemical reactivity. The same theory was applied to explain the differences in the IR spectra of the selenite crystallohydrates studied.     

Generalized nets in neurology: an example of mathematical modelling

The purpose of this paper is to explain the basic theory of generalized nets (GNs) and their applications in the context of the differential diagnosis of neurological diseases. We define formally the concepts of a GN and transitions of a GN and also outline some remarks on their theory. The work here constructs an example which aims to trace the process of diagnosing different signs and symptoms in neurology. This will enable the interested reader to see the scope of nets in general as tools for the modelling, simulation, optimization and control of real processes.     

Kinetic Isotope Effect as a Tool To Investigate the Oxygen Reduction Reaction on Pt-based Electrocatalysts – Part II: Effect of Platinum Dispersion

We investigated the oxygen reduction reaction (ORR) mechanism on Pt nanoparticles (NPs) dispersed on several carbon blacks with various physicochemical properties (i. e. specific surface ranging from 80 to 900 m² g⁻¹, different graphitization degree, etc.). Using the kinetic isotope effect (KIE) along with various electrochemical characterizations, we determined that the rate determining step (RDS) of the ORR is a proton-independent step when the density of Pt NPs on the surface of the carbon support is high. Upon decrease of the density of Pt NPs on the surface, the RDS of the ORR starts involving a proton, as denoted by an increase of the KIE >1. This underlined the critical role played by the carbon support in the oxygen reduction reaction electrocatalysis by Pt supported on high surface area carbon.     

Non-isothermal kinetics of thermal degradation of chitin

Thermogravimetric studies of chitin in air atmosphere were carried out at six rates of linear increase of the temperature. The kinetics and mechanism of the thermal decomposition reaction were evaluated from the TG data by iso-conversional calculation procedure of Kissinger–Akahira–Sunose recommended from ICTAC kinetics committee, as well as 27 mechanism functions. The comparison of the results obtained showed that they strongly depend on the selection of proper mechanism function for the process. Therefore, it is very important to determine the most probable mechanism function. In this respect, the iso-conversion calculation procedure turned out to be the most appropriate one. In the present work, the values of the apparent activation energy E, pre-exponential factor A in Arrhenius equation, as well as the changes of entropy ΔS ^≠, enthalpy ΔH ^≠, and Gibbs free energy ΔG ^≠ for the formation of the activated complex from the reagent are calculated. All the calculations were performed using programs compiled by ourselves.     

Engineering of glucose oxidase for direct electron transfer via site-specific gold nanoparticle conjugation

Optimizing the electrical communication between enzymes and electrodes is critical in the development of biosensors, enzymatic biofuel cells, and other bioelectrocatalytic applications. One approach to address this limitation is the attachment of redox mediators or relays to the enzymes. Here we report a simple genetic modification of a glucose oxidase enzyme to display a free thiol group near its active site. This facilitates the site-specific attachment of a maleimide-modified gold nanoparticle to the enzyme, which enables direct electrical communication between the conjugated enzyme and an electrode. Glucose oxidase is of particular interest in biofuel cell and biosensor applications, and the approach of "prewiring" enzyme conjugates in a site-specific manner will be valuable in the continued development of these systems.     

Engineering of a redox protein for DNA-directed assembly

Engineered enzyme conjugate of the small laccase enzyme from Streptomyces coelicolor and zinc finger DNA binding domain from Zif268 is demonstrated to bind double stranded DNA in a site specific manner while retaining enzymatic activity.     

Surface memory effect in nematics with smectic C short-range order and hydrogen bonded molecules

A surface memory effect (SME) is found in the dimerized nematic with short range smectic C order of 4-n-octyloxybenzoic acid (OOBA) in a cell whose walls have been covered with an obliquely evaporated SiO or ITO layer. The recording and erasure processes are discussed and erasure in the nematic phase is realized. A mechanism for the surface memorization is presented which takes into account the specific character of dimerized nematics preceding cooling into a smectic C phase.     

On the bramble-hilbert lemma

The aim of this paper is to give an improvement of a result by Bramble and Hilbert [2] concerning upper bounds for linear functionals on certain Sobolev spaces by showing that the constants in the estimate are independent of the bounded Lipschitz domain Ω.     

Electrochemical Studies of Intramolecular Electron Transfer in Laccase from Trametes versicolor

This paper describes electrochemical behavior of laccase from the fungus Trametes versicolor. The issues related to discrimination of the redox potentials corresponding to copper centers T1 and T2/T3 in the active site and possible mechanism of intramolecular electron transfer have been discussed. The electron‐transfer rate constant for laccase immobilized on carbon electrode is 3.4 s^?1. The bioelectrocatalytic activity of the enzyme was studied in the presence of 1,4‐hydroquinone (HQ). The kinetics of HQ oxidation is very fast (K_M=3.8 μM). However, the catalytic activity of laccase in the presence of high concentration of HQ decreases drastically. It is suggested that the T2/T3 copper center is able to accept electrons from HQ molecules directly via intramolecular channel.