Amino acids as substrates for preparation of monomers with imide rings

The reaction of pyromellitic anhydride PMDA with some amino acids lead to monomers, which were used to synthesize new polymers. Application to glycine, D ,L -alanine and β-alanine gave three bis-acid chlorides. These are able to condense with glycols and diamines to yield a series of new copolyimides. Amino acids of two carboxylic groups D ,L -glutamic acid and D ,L -aspartic acid gave, in reaction with PMDA, two similar dianhydrides (4) and (5). However, the condensation with aromatic amines lead to two different compounds. It was proved that, under the conditions studied, formation of hexa-membered imide rings was impossible while penta-membered imides formed without difficulty. Thermogravimetric analyses of these polymers were also carried out.     

Bounds on the average message reassembly time in a packet data network

In this paper we compute lower and upper bounds on the mean reassembly time of a multipacket message under general assumptions. We show that the approximation which is known from the literature is in fact a lower bound. Simulation results give some hints on how to make a better approximation, according to the given bounds.     

Assessing the Interactions of Statins with Human Adenylate Kinase Isoenzyme 1: Fluorescence and Enzyme Kinetic Studies

Statins are the most effective cholesterol-lowering drugs. They also exert many pleiotropic effects, including anti-cancer and cardio- and neuro-protective. Numerous nano-sized drug delivery systems were developed to enhance the therapeutic potential of statins. Studies on possible interactions between statins and human proteins could provide a deeper insight into the pleiotropic and adverse effects of these drugs. Adenylate kinase (AK) was found to regulate HDL endocytosis, cellular metabolism, cardiovascular function and neurodegeneration. In this work, we investigated interactions between human adenylate kinase isoenzyme 1 (hAK1) and atorvastatin (AVS), fluvastatin (FVS), pravastatin (PVS), rosuvastatin (RVS) and simvastatin (SVS) with fluorescence spectroscopy. The tested statins quenched the intrinsic fluorescence of hAK1 by creating stable hAK1-statin complexes with the binding constants of the order of 10⁴ M⁻¹. The enzyme kinetic studies revealed that statins inhibited hAK1 with significantly different efficiencies, in a noncompetitive manner. Simvastatin inhibited hAK1 with the highest yield comparable to that reported for diadenosine pentaphosphate, the only known hAK1 inhibitor. The determined AK sensitivity to statins differed markedly between short and long type AKs, suggesting an essential role of the LID domain in the AK inhibition. Our studies might open new horizons for the development of new modulators of short type AKs.     

Optimisation and experimental verification of a dust-removal beater for the electrodes of electrostatic precipitators

The results of research into changes in vibrations of collecting electrodes are presented in the paper. The changes come from the optimisation of geometric and dynamic parameters of the shaking down system inelectrostatic precipitators (ESP). The computational verification was carried out using the finite element method on the MSC NASTRAN package. Vibrations and accelerations of the collecting electrodes were measured. The results were used in the comparative analysis and the analysis of spectral density of acceleration power. The paper shows how calculating methods completed by measurements allow us to solve important and sophisticated practical problem.     

Time-Domain Methods for Solving Problems of Linear Acoustics

This paper describes a class of high-order Taylor-Galerkin methods for solving problems of linear acoustics characterized by the classical (scalar) wave equation. The methods provide high-order temporal accuracy and unconditional stability on arbitrary nonuniform finite element meshes of varying element sizes and shape functions.     

Hydrodenitrogenation of indole over Mo2C catalyst: Insights into mechanistic events through DFT modeling

The molecular reaction mechanism of hydrodenitrogenation of indole was studied using density-functional theory calculations of the adsorbed o-ethylaniline surrounded by mobile hydrogen atoms. It was found that the hydrogenation of o-ethylaniline occurs through two steps: consisting in redistribution of the π electron density to form multiple partial MoC(ring) bonds with the surface upon adsorption, and a subsequent hydrogen attack directed on the aromatic ring or the amine group. The direction of the hydrogen attack and the associated energy barriers determine the rate constants of the early (DDN, direct denitrogenation) and late (HYD, hydrogenation) nitrogen removal steps, and thus rules the selectivity of indole hydrodenitrogenation to ethylcyclohexane or ethylbenzene.