Optical properties of graphite-like carbon films

A model of the electronic structure of graphite-like carbon films, describing the semiconductor properties of this material, is presented. Spectra of optical constants of microcrystalline carbon films in the region λ = 0.4–8.0 μm were studied by the spectral ellipsometry and IR reflection methods. A number of distinctive features of the spectra, associated with both the appearance of C---C- and C---H_n-type bonds and direct energy gaps, were found. Analysis of the optical data using the proposed model makes possible a common interpretation of our results and literature data. Values of a parameter Θ, which is an averaged qualitative parameter of structural distortions within carbon microcrystallites as compared with crystalline graphite, are determined from comparison of theoretical results and experimental data.     

Modeling, histological study and pathogenetic aspects of experimental traumatic osteomyelitis

The tibial diaphysis osteotomy with limited separation of periosteum on the ends of the fragments with subsequent local infection by Staphylococcus aureus culture was conducted. In 90% of observations chronic inflammation was revealed in affected bones while morphological investigation conduction. An acute traumatic disorders of intraosseous blood circulation (the bone infarction) and local staphylococcal infection play the main role in the traumatic osteomyelitis pathogenesis.     

Mutagenic and antimutagenic activities of human whole blood, plasma and albumin

The seeds of Crepis capillaris were used to examine the mutagenic und antimutagenic properties of human whole blood, plasma, serum albumin and gamma-globulin by recording chromosomal and chromatid aberrations. The antimutagenic activity was determined by preliminary, simultaneous, and subsequent biosubstrate treatments of the seeds. The whole and twice-diluted blood, as well as plasma, induced aberrations exceeding the level of self-arbitrary mutagenesis by 3.7-5.3 and 2.6-3.1 times, respectively. When the blood was diluted to its 20% concentration, the antimutagenic efficiency of biological fluids was recorded. Human serum albumin and gamma-globulin were found to have an antimutagenic effect. In the dilutions having no antimutagenic effect, blood, plasma, and albumin showed their ability to be effectively decrease the level of induced aberrations.     

Activation energy of electron-stimulated quenching of the photoluminescence of n-type porous silicon

The degradation of photoluminescence of porous silicon by kilovolt electrons and the mechanism and activation energy of this process have been investigated. Quantitative relations between the integral intensity of the photoluminescence and the irradiation dose and substrate temperature are obtained. The mechanism of the process is discussed and its activation energy is determined. Pis’ma Zh. Tekh. Fiz. 23, 44–50 (September 26, 1997)     

Pathology of AIDS in children

AIDS in children is a multisystem disease. The various infections, degenerative, proliferative and vascular lesions can be classified into three categories based on the known, presumed or undetermined pathogenesis. The primary lesions are due to HIV infection. The associated lesions are related to direct or indirect sequelae of HIV infection or its treatment. The third category is of lesions of undetermined pathogenesis. The pediatric pathologist plays an important role in the study and management of AIDS by demonstrating new pathologic lesions, by making the etiologic diagnosis of infection in children with AIDS, and by providing clinicopathologic correlation which leads to better understanding of the disease process and its natural history. Diagnosis of neoplastic disorders is also made by the pathologist. There is a dearth of systematic pathologic study of AIDS in children in developing countries. Although no basic differences between pathologic lesions in pediatric AIDS in Western countries, and in developing countries is expected, such a study would lead to better understanding and better management of the disorder as it affects children from the developing countries.     

The nervous system function of patients with periodontitis

Analysis of the function of the nervous system, based on clinical, neurological, and psychological studies in 78 patients with generalized periodontitis, revealed central regulation disorders without signs of organic lesions of the brain in 76% patients. The authors claim that stress and a high level of personal anxiety may be responsible for the development of these disorders, which was confirmed by the results of psychological testing.     

Sites of alcohol and volatile anaesthetic action on GABA(A) and glycine receptors

Volatile anaesthetics have historically been considered to act in a nonspecific manner on the central nervous system. More recent studies, however, have revealed that the receptors for inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are sensitive to clinically relevant concentrations of inhaled anaesthetics. The function of GABA(A) and glycine receptors is enhanced by a number of anaesthetics and alcohols, whereas activity of the related GABA rho1 receptor is reduced. We have used this difference in pharmacology to investigate the molecular basis for modulation of these receptors by anaesthetics and alcohols. By using chimaeric receptor constructs, we have identified a region of 45 amino-acid residues that is both necessary and sufficient for the enhancement of receptor function. Within this region, two specific amino-acid residues in transmembrane domains 2 and 3 are critical for allosteric modulation of both GABA(A) and glycine receptors by alcohols and two volatile anaesthetics. These observations support the idea that anaesthetics exert a specific effect on these ion-channel proteins, and allow for the future testing of specific hypotheses of the action of anaesthetics.     

Pressure-induced phase transition of quartz-type GaPO4

This study attempted to identify the determinants of acute lower respiratory-tract infections (ALRI) among children under five years of age, by comparing hundred children hospitalized with ALRI with a control group. Data on socio-demographic, biological and environmental characteristics were collected by interviewing mothers and anthropometric measurements were carried out to assess the nutritional status of the children. Risk of disease in the presence of each exposure was calculated in the univariate analysis and the best explanatory variables among them were identified in the multivariate analysis. The following variables were found to increase the risk of ALRI: (1) history of wheezing, (2) low birth weight, (3) passive smoking, (4) male sex, (5) delivery by cesarean section (6) sharing of sleeping space, (7) not being exclusively breast fed upto the completion of four months, (8) stunting, (9) having pets. The findings highlight some simple strategies which would help in prevention of ALRI.