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Antiphospholipid syndrome (APS) is an autoimmune disease with multifactorial and polygenic pathogenesis. Recently, the genetic predisposition in APS has been subjected to wide discussion. The aim of this study is to determine the prevalence of DRB1 and DQB1 loci in Bulgarian population of healthy persons and patients with primary (PAPS) and secondary (SAPS) APS. Patients are divided in 5 groups: I-29 patents with systemic lupus erythematosus (SLE) with SAPS, II-35 patients with PAPS, III-32 women with spontaneous abortions without aPL, IV-15 patients with different thrombosis (deep venous thromboses, pulmonary embolism, mesenterial thrombosis, myocardial infarction, stroke) without laboratory data for APS, and V-16 SLE patients without clinical and laboratory data for APS. SAPS patients have more frequently DRB1*03 and DQB1*02 and more rarely DRB1*11 and DQB1*03 in comparison with healthy subjects and patients with PAPS. Patents with PAPS, those with spontaneous abortions and patients with thrombotic events but without antiphospholipid antibodies (aPL) have DRB1*03, DRB1*11, DQB1*02 and DQB1*03 alleles similar to the general population. There are no differences between group I (SLE+APS) and group V (SLE) in DRB1* and DQB1*alleles.

The spatial distribution of the plasma parameters--electron density and temperature as well as plasma and floatingpotentials--in the region of plasma expansion of an inductively-driven low-pressure discharge in hydrogen is studied by probe diagnostics. Electron cooling and a decrease of the electron den-sity with formation of regions with different axial gradients are outlined as basic features of the expanding plasmas. Thermal con-ductivity and electron energy flux from the driver are consi plasma density is also shown. Index Terms--Hydrogen discharges, inductive discharges, low-pressure discharges, plasma expansion, probe diagnostics.

Results from diagnostics of diffusion-controlled stationary gas discharges maintained in the field of propagating surface waves are presented in this study. The set of the plasma parameters obtained includes: 1) the plasma density [bar]n, averaged over the discharge cross section, and its axial profile [bar]n(z); 2) the electron-neutral elastic collision frequency v; 3) the parameter [mu] which describes the radial profile of the plasma density; 4) the parameter [THETA], the power absorbed on average by an electron, and its axial variation [THETA] (z); 5) the electron temperature [T.sub.e] (z); and 6) the gas temperature [T.sub.g]. The mechanisms of electron heating and discharge self-consistency are discussed. Index Terms--Gas-discharge plasma diagnostics, radio-frequency diagnostics techniques, surface-wave-sustained discharges.

The dynamics in the self-organization of surface wave sustained discharges were examined through experiments. Microwave discharges maintained in an argon gas in a continuous wave regime at a constant applied power and varying gas pressure were investigated. The increase of the losses in the discharge with the pressure increase altered the discharge structure. At first the plasma column shortened by keeping its cross section constant and later it contracted into small diameter discharge channels.

Shielding the bias applied to the probe by the sheath formed around it and determination of parameters of unperturbed plasmas are in the basis of the probe diagnostics. The results from a two-dimensional model of a discharge with a probe inserted in it show that the probe influences the spatial distribution of the plasma parameters in the entire discharge. The increase (although slight) in the electron temperature, due to the increased losses of charged particles on the additional wall in the discharge (mainly the probe holder), leads to redistribution of the plasma density and plasma potential, as shown by the results obtained at the floating potential of the probe. The deviations due to the bias applied to the probe tip are stronger in the ion saturation region of the probe characteristics. The pattern of the spatial redistribution of the plasma parameters advances together with the movement of the probe deeper in the discharge. Although probe sheaths and probe characteristics resulting from the model are shown, the study does not aim at discussions on the theories for determination of the plasma density from the ion saturation current. Regardless of the modifications in the plasma behavior in the entire discharge, the deviations of the plasma parameters at the position of the probe tip and, respectively, the uncertainty which should be added as an error when the accuracy of the probe diagnostics is estimated do not exceed 10%. Consequently, the electron density and temperature obtained, respectively, at the position of the plasma potential on the probe characteristics and from its transition region are in reasonable agreement with the results from the model of the discharge without a probe. Being in the scope of research on a source of negative hydrogen ions with the design of a matrix of small radius inductive discharges, the model is specified for a low-pressure hydrogen discharge sustained in a small-radius tube. [ABSTRACT FROM AUTHOR]

Experimental results showing development of modulation instability and tendency to soliton formation in pulsed gas discharges sustained by surface waves are presented. The measurements are performed in argon discharges at gas pressure 13-1.3[multiplied by][10.sup.3] Pa sustained by pulsed microwave power at 2.45 GHz. The changes along the discharge length of the shape of the pulses of the total light emission, which is an indication for the plasma density, and of the wave electric field creating the discharge, are registrated. The cases when the modulation instability arises from the level of fluctuations in the plasma and when it is forced by the applied signal producing the discharge are demonstrated. The obtained results are discussed in terms of weak nonlinearity superimposed on the mechanism of strong ionization nonlinearity responsible for the discharge creation itself. A separation of a solitary-like wave from the leading edge of the pulse is also reported as an experimental result. Index Terms - Ionization nonlinearity, modulation instability, pulsed microwave discharges, solitary waves, surface wave sustained discharges.