Joint Russian and Bulgarian Academies of Sciences Database of Intermolecular Potentials and Diffusion Coefficients for Components of the CVD Processes in Microelectronics

The goal of the database (DB) EPIDIF-JRB is to promote the modeling of gas-phase transport processes in CVD technologies in microelectronics. The transport properties (molecular diffusion coefficients, viscosity, and thermal conductivity) of pure gases and gas mixtures in the temperature range 250 to 2000K and at a pressure <0.1MPa are calculated using (1) the Chapman–Enskog method in binary collision approximation and (2) the three-parameter Lennard–Jones (m–6) intermolecular potentials (IP) with 8<m<100 for interactions of atoms and quasi-spherical molecules, and (3) the four-parameter m–6–3 Stockmayer IP for dipole molecules. In addition to the IP parameters a _ii , a _jj , and a _ij , the DB also supplies their variance–covariance matrix. For heavy globular molecules [such as CF₄, SiH₄, Si(CH₃)₄, and WF₆], the influence of the vibrational excitation on their effective size is considered. In this case, the isotropic Lennard–Jones (m–6) IP with temperature-dependent parameters was defined. At present, the DB EPIDIF-JRB contains 40 species of importance to Si gas-phase epitaxy processes and IP parameters for 820 pair interactions. It can be used to calculate the viscosity of pure gases and gas mixtures with any k components (k<11), and their binary diffusion coefficients, and to estimate their uncertainty as well.     

Lipopolysaccharide and interleukin 1 augment the effects of hypoxia and inflammation in human pulmonary arterial tissue

The combined effects of hypoxia and interleukin 1, lipopolysaccharide, or tumor necrosis factor alpha on the expression of genes encoding endothelial constitutive and inducible nitric oxide synthases, endothelin 1, interleukin 6, and interleukin 8 were investigated in human primary pulmonary endothelial cells and whole pulmonary artery organoid cultures. Hypoxia decreased the expression of constitutive endothelial nitric oxide synthase (NOS-3) mRNA and NOS-3 protein as compared with normoxic conditions. The inhibition of expression of NOS-3 corresponded with a reduced production of NO. A combination of hypoxia with bacterial lipopolysaccharide, interleukin 1 beta, or tumor necrosis factor alpha augmented both effects. In contrast, the combination of hypoxia and the inflammatory mediators superinduced the expression of endothelin 1, interleukin 6, and interleukin 8. Here, we have shown that inflammatory mediators aggravate the effect of hypoxia on the down-regulation of NOS-3 and increase the expression of proinflammatory cytokines in human pulmonary endothelial cells and whole pulmonary artery organoid cultures.     

VVER-1000 radial reflector modeling by diffusion nodes

The two commonly used approaches to describe the VVER radial reflectors in diffusion codes, by core-reflector albedos and by a ring of diffusion assembly size nodes, are discussed. The advantages and disadvantages of the first approach are presented first, then the Koebke's equivalence theory is outlined and its implementation for the VVER radial reflectors is discussed. Results for the VVER-1000 reactor are presented.     

Glycosylasparaginase-catalyzed synthesis and hydrolysis of beta-aspartyl peptides

beta-Aspartyl di- and tripeptides are common constituents of mammalian metabolism, but their formation and catabolism are not fully understood. In this study we provide evidence that glycosylasparaginase (aspartylglucosaminidase), an N-terminal nucleophile hydrolase involved in the hydrolysis of the N-glycosidic bond in glycoproteins, catalyzes the hydrolysis of beta-aspartyl peptides to form L-aspartic acid and amino acids or peptides. The enzyme also effectively catalyzes the synthesis of beta-aspartyl peptides by transferring the beta-aspartyl moiety from other beta-aspartyl peptides or beta-aspartylglycosylamine to a variety of amino acids and peptides. Furthermore, the enzyme can use L-asparagine as the beta-aspartyl donor in the formation of beta-aspartyl peptides. The data show that synthesis and degradation of beta-aspartyl peptides are new, significant functions of glycosylasparaginase and suggest that the enzyme could have an important role in the metabolism of beta-aspartyl peptides.     

Perturbation bounds for orthogonal canonical forms and numericalcontrollability analysis

A first-order perturbation analysis of the orthogonal canonical forms of linear multivariable systems is presented. To avoid ill posedness, a numerical system structure which is invariant to small perturbations in the data is defined. It is shown that the orthogonal canonical forms may be, like the system controllability matrix, unreliable as a tool for numerical controllability analysis     

Dehydration products of gypsum: positron annihilation and dielectric measurements

Bassanite (CaSO₄·1/2 H₂O) and anhydrite (CaSO₄) are the low-temperature products of gypsum (CaSO₄·2H₂O) dehydration, which are obtained at about 373 and 433 K, respectively. These sulphates have non-centrosymmetric crystallographic point groups, but dielectric measurements do not reveal any piezo- or ferroelectric characteristic, and they practically behave like linear dielectrics. Positron lifetime spectra exhibit the existence of two different positron states, besides a free positron state. There is positronium formation in the three sulphates, and there is also evidence for the presence of a highly populated positron bound state which may be a complex state associated with positrons bound to SO ₄ ^2– ions. Parameter S estimated from the Doppler curve and the average positron lifetime show unquestionably the sensitivity of positrons to the phase transitions gypsum-bassanite and bassanite-anhydrite.     

Characteristics of thin chromium films obtained by different methods of deposition

The main parameters of chromium films used for preparation of photomasks for microelectronics have been investigated. The changes of pinhole density, the wear resistance and the etching time of layers obtained by thermal evaporation, electron beam evaporation and radio-frequency sputtering have been followed. Comparison of the characteristics of chromium films deposited by evaporation using chromium of different grades of purity and shape of the particles has been made. Analysis of the film composition has been carried out by SIMS and AES methods. It has been shown that chromium coatings with minimum pinholes and very good wear resistance can be obtained on substrates of soda-lime glasses for photoplates.     

Erweiterung des Eigenschaftspotentials der Legierung Al Mg5Si2Mn durch eine gezielte Wärmebehandlung

To enlarge the mechanical properties in castings, appropriate heat treating is essential. Heat treatable aluminium alloys only reach best possible properties as a result of heat treating. This exposition deals with the investigation of an ideal solution heat treatment temperature and artificial ageing parameters for an AlMgSi cast alloy, to be precise MAXXALLOY®—59, in permanent mould casting. The determination of temperature and holding time parameters for the heat treatment have been conducted by relevant literature research, calculations with software Thermo-Calc®, castings and differential scanning calorimetry tests. For verification of ascertained values, extensive microscopic examinations and mechanical tests (tensile tests and measurements of hardness) have been performed. The results indicate that cast parts in heat treated condition and T4 (8 days naturally aged) compared to as-cast parts show remarkable higher tensile, hardness and ductility values. For that reason the chosen parameters for solution annealing, based on scientific examinations, have been proved to be optimal.