Several physicochemical analytical methods were used to study aqueous solutions and hydrogels based on L-cysteine and silver nitrate. It was found that anions played a decisive role in forming the threedimensional gel-network in dilute silver-cysteine solutions. The ability to use silver-cysteine solutions and hydrogels to prepare bactericidal fi bers and fabrics was examined.Self-assembly of supramolecular structures in solutions has recently attracted increased worldwide interest. This timely problem comprises studies of the formation of very important physicochemical and biological entities such as micelles, liposomes, lipoproteides, membranes, clusters, immune complexes, physical gels, etc.[1]. A common feature of the aforementioned entities is the absence of strong chemical bonds between the interacting components. The driving forces for forming the respective structures are electrostatic and van-der-Waals interactions, hydrophobic effects, H-bonds, and weak donor-acceptor bonds. Dilute gels occupy a special place among these entities. Only a few such molecular systems are known. In particular, they include the polysaccharide agar-agar, mixtures of muscle proteins, and calcium germinate [2].Gel formation in an aqueous solution with a low concentration of domestically produced L-cysteine and silver nitrate was fi rst established several years ago [3,4].The heightened interest in this system is completely understandable. First, the hydrogel is a unique model system for studying self-assembly processes in dilute aqueous solution (concentration 0.1% and lower). Second, the system can be used in medical practice as an independent medical preparation or as a matrix for formulating other preparations because of the presence of silver in it.The fact that silver in its various forms (ions, salts, colloidal solutions, nanoparticles) has been used for a long time in medical practice argues in favor of the second factor. The antibacterial properties of this element are well known. Interest in the use of silver to treat infectious diseases decreased with the emergence of antibiotics. However, many antibiotics have recently become obsolete because of the appearance of resistance to them in constantly evolving new strains of bacteria. This opens broad possibilities for the use of silver as an alternative to antibiotics that have become ineffective [5].A problematic issue for the use of silver nanoparticles and ions is the choice of the matrix for their practical application. Solutions of silver nanoparticles and ions, most often aqueous but other solvents are also employed, are used most commonly. Silver in such a form is used to prepare infusions, preservatives for various media, and disinfectants for medical instruments.Furthermore, materials consisting of either a solid compound (inorganic matrices, in particular silica gel) or condensed substances (gels, polymers) are often used as the matrix [6][7][8]. The practical application of silver is broadest for matrices of block polymers and gels such as suturing materials, w...

Three independent but complementary methods (OSL photoetching combined with etch rate profiling, spatially resolved PL and LST) were employed to Study the distribution of microdefects and electrically active centres in commercially available SI undoped. LEc-grown GaAs after different ingot-annealing treatments. A one-to-one correlation was obtained on comparing the microscale distribution of decoration precipitates (OPS), matrix precipitates (MPI) and microdefects (MMS) by the DSL and LST methods. Clustering of MPS is also revealed by PL intensity profiling and photoetch rate measurements. Two types of matrix microdefects are distinguishable by OSL photoetchlng In Samples after two-stage annealing. A high degree of homogeneity across the dislocation cells (after low-temperature and multiple annealing) was clearly revealed by a drastic decrease in the uniformity parameter (U) after DSL photoetching and by a significant decrease in the x intensity measured at the cell walls with respect to the cell interiors. Using the present results and recent data from the literature, an explanation of phase transitions during ingot annealing is proposed. This is based on the assumption that the final properties and structures after annealing are the result of two competitive processes: (i) formation of decoration and matrix microdefects; (ii) generation of electrically active point defects (clusters), presumably EL2

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615.9:66.013.8 R. A. Molchanova, and T. I. SamsonovaThis paper is devoted to a major area of concern and an approach for hygiene and toxicology studies allowing us to estimate the potential risk to workers from chemicals and to recommend protective measures aimed at preservation of health. We present tentative safe exposure levels in atmospheric air and maximum permissible concentrations in the workplace for a number of chemicals, obtained as a result of toxicology animal studies. We demonstrate the capabilities of a method for rapid assessment in vitro of the general acute toxicity on the AT-05 image analyzer.In production of synthetic fi bers, a rather large number of chemical compounds are used that are assigned to different classes and have different toxicological characteristics. The substances used can have a complicated and combined effect on the human body, expressed as various pathological signs and symptoms ranging from allergic reactions to long-term effects. Under a chemical load, there is a change in the functional activity of the cardiovascular and respiratory systems and also the gastrointestinal tract and endocrine glands. The more intense the exposure to some chemical substances, the broader the range of systems in the living organism that undergo pathological alterations. Accordingly, a necessary aspect of occupational safety in plants producing synthetic fi ber materials is toxicology and hygiene studies, making it possible to assess potential risk from chemical substances and to recommend protective measures aimed at preservation of health. Toxicology studies are the basis for developing health standards for hazardous substances: maximum permissible skin exposure level, tentative safe exposure level, maximum permissible concentrations in the workplace, atmospheric air, and water in bodies of water. Such studies are important for developing new technologies or for incorporating into existing technology chemical compounds that do not have health standards for workplace air, atmospheric air, fi shery and drinking water.For conducting toxicology and hygiene studies, a toxicology laboratory was set up as part of the Testing Center of the Scientifi c Research Institute of Synthetic Fibers (Federal State Unitary Enterprise). The laboratory is accredited by the Federal Service for Oversight of Consumer Protection and Welfare (Rospotrebnadzor) in the Accreditation System for laboratories conducting public health studies and technical competency tests, and is entered in the National Register (Accreditation Certifi cate No. GSEN.RU.TsOA.253 dated 13 February 2008).The scope of the laboratory's activities includes: 1. Conducting full toxicology tests on starting materials and manufactured products of chemical fi bers and polymer materials using laboratory animals. The investigations include a range of research studies to determine the actual risk of the appearance of acute and chronic signs and symptoms when workers are exposed to chemicals. Special attention is focused on studying the effect of chemical ...