Experimental study of homogeneous nucleation from the bismuth supersaturated vapor: evaluation of the surface tension of critical nucleus.

The homogeneous nucleation of bismuth supersaturated vapor is studied in a laminar flow quartz tube nucleation chamber. The concentration, size, and morphology of outcoming aerosol particles are analyzed by a transmission electron microscope (TEM) and an automatic diffusion battery (ADB). The wall deposit morphology is studied by scanning electron microscopy. The rate of wall deposition is measured by the light absorption technique and direct weighting of the wall deposits. The confines of the nucleation region are determined in the "supersaturation cut-off" measurements inserting a metal grid into the nucleation zone and monitoring the outlet aerosol concentration response. Using the above experimental techniques, the nucleation rate, supersaturation, and nucleation temperature are measured. The surface tension of the critical nucleus and the radius of the surface of tension are determined from the measured nucleation parameters. To this aim an analytical formula for the nucleation rate is used, derived from author's previous papers based on the Gibbs formula for the work of formation of critical nucleus and the translation-rotation correction. A more accurate approach is also applied to determine the surface tension of critical drop from the experimentally measured bismuth mass flow, temperature profiles, ADB, and TEM data solving an inverse problem by numerical simulation. The simulation of the vapor to particles conversion is carried out in the framework of the explicit finite difference scheme accounting the nucleation, vapor to particles and vapor to wall deposition, and particle to wall deposition, coagulation. The nucleation rate is determined from simulations to be in the range of 10(9)-10(11) cm(-3) s(-1) for the supersaturation of Bi(2) dimers being 10(17)-10(7) and the nucleation temperature 330-570 K, respectively. The surface tension σ(S) of the bismuth critical nucleus is found to be in the range of 455-487 mN/m for the radius of the surface of tension from 0.36 to 0.48 nm. The function σ(S) changes weakly with the radius of critical nucleus. The value of σ(S) is from 14% to 24% higher than the surface tension of a flat surface.

Evaluation of surface tension and Tolman length as a function of droplet radius from experimental nucleation rate and supersaturation ratio: metal vapor homogeneous nucleation.

Zinc and silver vapor homogeneous nucleations are studied experimentally at the temperature from 600 to 725 and 870 K, respectively, in a laminar flow diffusion chamber with Ar as a carrier gas at atmospheric pressure. The size, shape, and concentration of aerosol particles outcoming the diffusion chamber are analyzed by a transmission electron microscope and an automatic diffusion battery. The wall deposit is studied by a scanning electron microscope (SEM). Using SEM data the nucleation rate for both Zn and Ag is estimated as 10(10) cm(-3) s(-1). The dependence of critical supersaturation on temperature for Zn and Ag measured in this paper as well as Li, Na, Cs, Ag, Mg, and Hg measured elsewhere is analyzed. To this aim the classical nucleation theory is extended by the dependence of surface tension on the nucleus radius. The preexponent in the formula for the vapor nucleation rate is derived using the formula for the work of formation of noncritical embryo [obtained by Nishioka and Kusaka [J. Chem. Phys. 96, 5370 (1992)] and later by Debenedetti and Reiss [J. Chem. Phys. 108, 5498 (1998)]] and Reiss replacement factor. Using this preexponent and the Gibbs formula for the work of formation of critical nucleus the dependence of surface tension on the radius R(S) of the surface of tension is evaluated from the nucleation data for above-mentioned metals. For the alkali metals and Ag the surface tension was determined to be a strong function of R(S). For the bivalent metals (Zn, Hg, and Mg) the surface tension was independent of radius in the experimental range. A new formula for the Tolman length delta as a function of surface tension and radius R(S) is derived by integration of Gibbs-Tolman-Koenig equation assuming that delta is a monotonic function of radius. The formula derived is more correct than the Tolman formula and convenient for the elaboration of experimental data. Using this formula the values of delta are determined as a function of R(S) from the experimental nucleation data. It is determined that all the metals considered are characterized by strong dependence of delta on radius; for the bivalent metals delta changes sign.

[Neuromyalgic syndrome in children's infections]. / Neiromialgicheskii sindrom pri infektsionnykh zabolevaniiakh u detei.

Neuromyalgic syndrome (NMS) is clinically and electroneuromyographically (ENMG) first-ever described in 50 children aged 2-13. Muscular pains and pains along peripheral nerves occur in post-infection period of acute respiratory viral infections (ARVI), intestinal and parotitoviral infections with transient (in 3-6 days), dysfunction of peripheral nervous system and muscles. NMS is characterized by predominant involvement of lower limb muscles in pathologic process and by rarely developing generalized form. There are 3 types of changes of nerve conductivity and excitability with conductive blocks absence and disturbances regression that enable to distinguish these dysfunctions from ENMG changes in polyneuropathy. Provoked by infection, transitory non-specific inflammatory muscular reaction and functional disorders of nerve conductivity and excitability may be considered as one of the possible mechanisms of NMS development. More than 20 years of clinical and research experience of in neuroinfections clinic, supports the validity of NMS distinguishing among children acute infections for further diagnostic differentiation with polyneuropathy, viral meningitis and ARVI.

[Chromatographic analysis of low molecular weight fraction of cerebrospinal fluid in children with acute neuroinfections]. / Khromatograficheskoe opredelenie sostava nizkomolekuliarnoi fraktsii tserebrospinal'noi zhidkosti pri ostrykh neiroinfektsiiakh u detei.

Low molecular-weight (oligopeptide) fraction of the cerebrospinal fluid was analyzed by high-performance reversed phase liquid chromatography in 30 children with bacterial and viral neuroinfections. The incidence and height of chromathoraphic peaks in bacterial meningitis depended on the disease etiology, stage, and severity. Qualitative and quantitative composition of low molecular-weight fraction of the liquor varied in patients with viral neuroinfections, depending on the severity of the cerebral parenchyma involvement. Differences in chromatographic profiles in complicated and uneventful course of neuroinfections indicate a possible damaging, protective, or regulatory effect of the liquor peptides. These data focus the attention on the role of oligopeptides in the genesis of neuroinfectious process, significance of search for peptide markers, their further isolation, identification, and development of test systems available for clinical application.

[The lung cancer morbidity of the population of the Noril'sk industrial district]. / Zabolevaemost' naseleniia Noril'skogo promyshlennogo raiona rakom legkogo.

The report is concerned with an analysis of lung cancer morbidity (1979-1986) in the population of the Norilsk industrial region versus age. In the 50-59 and 60-69 years age groups, it was found to be 2.1-2.5 times the national and Krasnoyarsk regional levels. Carcinogenic hazards involved in processing ores of different metals contribute to such morbidity.