Antiviral activity of cholesteryl esters of cinnamic acid derivatives

Cholesteryl 3",4"-dimethoxycinnamate (7) and a new synthesized o-coumaroyl ester of 3 beta-(2'-hydroxyethoxy)-cholest-5-en (13) exhibited a marked activity against poliovirus type 1 (Mahoney). Compound 7 showed an approximately 20-fold greater selectivity in its antiviral activity than compound 13. These compounds were selected from thirteen steryl esters of cinnamic acid derivatives through an in vitro antiviral screening against viruses belonging to taxonomic groups with causative agents of important human infectious diseases to which chemotherapy is indicated, i.e. Picornaviridae, Orthomyxoviridae, Paramyxoviridae and Herpesviridae.     

Molecular dynamics study of Ca2+ binding loop variants of parvalbumin with modifications at the `gateway' position

The helix–loop–helix (i.e. EF-hand) Ca²⁺ ion bindingmotif is characteristic of a large family of high-affinity Ca²⁺ion binding proteins, including the parvalbumins and calmodulins.In this paper we describe a set of molecular dynamics computationson the major parvalbumin from the silver hake (SHPV-B). In allvariants examined, both whole protein and fragments thereof,the ninth loop residue in the Ca²⁺ binding coordination sitein the CD helix–loop–helix region (the so-called`gateway' residue) has been mutated. The three gateway mutationsexamined are arginine, which has never been found at the gatewayposition of any EF-hand protein, cysteine, which is the residueobserved least in natural EF-hand sites, and serine, which isthe most common (by far) non-acidic residue substitution atthis position in EF-hand proteins in general, but never in parvalbumins.Results of the molecular dynamics simulations indicate thatall three modifications are disruptive to the integrity of themutated Ca²⁺ binding site in the whole parvalbumin protein.In contrast, only the arginine and cysteine mutations are disruptiveto the integrity of the mutated Ca²⁺ binding site in the CDfragment of the parvalbumin protein. Surprisingly, the serinevariant of the CD helix–loop–helix fragment exhibitedremarkable stability during the entire molecular dynamics simulation,with retention of the Ca²⁺ binding site. These results indicatethat there are no inherent problems (for Ca²⁺ ion binding) associatedwith the sequence of the CD helix–loop–helix fragmentthat precludes the incorporation of serine at the gateway position.Since the CD site is totally disrupted in the whole proteinserine variant, this indicates that the Ca²⁺ ion binding deficienciesare most likely related to the unique interaction that existsbetween the paired EF-hands in the whole protein. Our theoreticalresults correlate well with previous studies on engineered EF-handproteins and with all of our experimental evidence on the silverhake parvalbumin.     

Hydrogen sorption properties of ball-milled Mg–C nanocomposites

MgH₂ 75 at.%–C 25 at.% composites are synthesized by ball milling using different kinds of carbon additives: carbon black (CB), nanodiamonds (ND) and amorphous carbon soot (AC). X-ray diffraction analysis showed that the MgH₂ phase in the as-obtained composite powders is nanocrystalline (80–100 nm). The SEM observations revealed that the samples consist of 5–15 μm MgH₂ particles, surrounded and in some cases coated by carbon flakes. The composite containing nanodiamonds revealed strong decrease of the MgH₂ decomposition temperature with more than 100 °C, compared to ball-milled pure MgH₂. Important issue of the present study is also the low temperature hydriding of the ball-milled Mg–C nanocomposites, investigated by high-pressure DSC. The process starts at about 200 °C for all materials studied, but the hydriding mechanism looks different for the composites with different kinds of carbon additives. Whereas for Mg–carbon black it takes place in a relatively narrow temperature range, expressed by a single exothermic peak (200–300 °C) for the other two composites the hydriding is a multi-step process, featured by two overlapped exothermic peaks for Mg-nanodiamonds and by two well separated exothermic effects (at about 300 °C and 400 °C) for Mg-amorphous carbon soot. The observed difference in the hydriding behavior of the Mg–C composites is attributed to the different kind of carbon component, which is supposed to play a catalytic role as well as protects magnesium from oxidation. The incorporation of carbon into the MgH₂ particles results in the formation of high density of defects (dislocations and grain boundaries), which is supposed to be among the most possible reasons for the decreased hydride decomposition temperature. The Mg–C nanocomposites show reproducible hydriding/dehydriding behavior (thermodynamics and kinetics) during multiple cycling. Among the composites in the present study “Mg–carbon black” reveals the best hydriding characteristics – low temperature of hydriding in a relatively narrow temperature range by a single-step reaction and relatively fast hydriding kinetics.     

Atomic force microscopy study of TiO2 sol–gel films thermally treated under NH3 atmosphere

Multilayered TiO₂ films were obtained by sol–gel and dipping deposition on quartz substrate followed by thermal treatment under NH₃ atmosphere. In an attempt to understand the close relationship between microstructural characteristics and the synthesis parameters, a systematic research of the structure and the morphology of NH₃ modified TiO₂ sol–gel films by XRD and Atomic Force Microscopy is reported. The surface morphology has been evaluated in terms of grains size, fractal dimension and surface roughness. For each surface, it was found a self-similar behavior (with mean fractal dimension in the range of 2.67–3.00) related to an optimum morphology favorable to maintain a nano-size distribution of the grains. The root mean square (RMS) roughness of the samples was found to be in the range of 0.72–6.02 nm.     

Time-harmonic crack problems in functionally graded piezoelectric solids via BIEM

In-plane crack analysis of functionally graded piezoelectric solids under time-harmonic loading is performed by using a non-hypersingular traction based boundary integral equation method (BIEM). The material parameters are assumed to vary quadratically with both spatial variables. A frequency dependent fundamental solution, as well as its derivatives and asymptotic expressions, is derived in closed-form by using an appropriate algebraic transformation for the displacement vector and the Radon transform. Numerical results for the stress intensity factors (SIFs) are discussed for different examples. The accuracy of the presented method is checked by comparison with available results from the literature. Investigated are the effects of the inhomogeneity parameters, the frequency of the applied electromechanical load and the geometry of the crack scenario on the K-factors.     

Predictive (un)distortion model and 3-D reconstruction by biplane snakes

This paper is concerned with the three-dimensional (3-D) reconstruction of coronary vessel centerlines and with how distortion of X-ray angiographic images affects it. Angiographies suffer from pincushion and other geometrical distortions, caused by the peripheral concavity of the image intensifier (II) and the nonlinearity of electronic acquisition devices. In routine clinical practice, where a field-of-view (FOV) of 17-23 cm is commonly used for the acquisition of coronary vessels, this distortion introduces a positional error of up to 7 pixels for an image matrix size of 512 x 512 and an FOV of 17 cm. This error increases with the size of the FOV. Geometrical distortions have a significant effect on the validity of the 3-D reconstruction of vessels from these images. We show how this effect can be reduced by integrating a predictive model of (un)distortion into the biplane snakes formulation for 3-D reconstruction. First, we prove that the distortion can be accurately modeled using a polynomial for each view. Also, we show that the estimated polynomial is independent of focal length, but not of changes in anatomical angles, as the II is influenced by the earth's magnetic field. Thus, we decompose the polynomial into two components: the steady and the orientation-dependent component. We determine the optimal polynomial degree for each component, which is empirically determined to be five for the steady component and three for the orientation-dependent component. This fact simplifies the prediction of the orientation-dependent polynomial, since the number of polynomial coefficients to be predicted is lower. The integration of this model into the biplane snakes formulation enables us to avoid image unwarping, which deteriorates image quality and therefore complicates vessel centerline feature extraction. Moreover, we improve the biplane snake behavior when dealing with wavy vessels, by means of using generalized gradient vector flow. Our experiments show that the proposed methods in this paper decrease up to 88% the reconstruction error obtained when geometrical distortion effects are ignored. Tests on imaged phantoms and real cardiac images are presented as well.     

Relationship between the strain constant and viscosity of glasses above the glass transition temperature

The relationship between the strain constant and viscosity of glasses above the glass transition temperature is established. The process variables of soft glass molding and pressing operations should be calculated using this constant.     

Molecular weight characteristics of 2-naphthyl methacrylate copolymers obtained by radical polymerization in different solvents

Summary The influence of the chemical nature of the polymerization medium on the molecular weight characteristics of the copolymers 2-naphthyl methacrylate/styrene and 2-naphthyl methacrylate/acrylonitrile was investigated by gel permeation chromatography. The results obtained show that the influence of the nature of the solvent used on the molecular weight characteristics could be attributed to the different chain transfer constants. The contribution of the monomer complexes which affects mainly the relative reactivity ratios of the comonomers may be neglected.Dedicated to Professor Ivan M. Panayotov to his 60. birthday with the best wishes     

Mechano mathematical models for mechatronic systems for vibration jaw crushing processes

The aim of this paper is creation, investigation of mono frequency and poly frequency plane and spatial vibrations of two mass vibration systems with a suitable adjustment of the mechanical system. The physical object is a vibrating jaw crusher. The mechanical and mathematical modeling is created on the basis of a two mass dynamic model with six degrees of freedom in plane case—three for each mass and 12 degrees of freedom in spatial model—six for each mass. The influence of the elastic linkages between the two masses and also the energy mutual linkages between the coordinates of the two bodies are investigated.

Natural frequencies and amplitudes of movement are obtained by means of computer experiment in plane and spatial aspect. The obtained results can be used for optimization of the constructive parameters of the vibrating jaw crusher and also for improving harmful resonance effects