[en] Transverse momenta and rapidities of Λ particles produced in central nucleus-nucleus collisions at 4.5 GeV/c per nucleon (cC, CNe, ONe, CCu, CZr, CPb, OPb) have been studied and compared with those from ineiolastic He-Li interactns at the same incident momentum. Polarization of Λ hyperons was found to be consistent (within the errors) with zero (αP=-0.06+-0.11) for 224 Λ particles from central collisions. The upper limit of anti Λ/Λ production ratio was estimated to be less than 10^-2 at a 90% confidence level. The analyzed experimental data were obtained using the triggered 2 m streamer spectrometer SKM-200

No abstract available

[en] Properties of strontium titanate SrTiO₃ (STO) depend to a great extent on the substitutional dopants and defects of crystal structure. The ion beam implantation method was used for doping STO (001) crystals with Fe at different doses. Implanted samples were then annealed at 350°C in oxygen to induce recrystallization and remove oxygen vacancies produced during ion implantation process. The effect of Fe doping and post-implantation annealing was studied by X-ray Absorption Near Edge Spectroscopy (XANES) method and Superconducting Quantum Interference Device (SQUID). XANES allowed to monitor the change in structure of STO crystals and in the local environment of Fe following the implantation and annealing steps. SQUID measurements revealed correlation between magnetic moment and Fe implantation dose. Ferromagnetic hysteresis was observed on selected Fe-implanted STO at 5 K. The observed magnetic properties can be correlated with the several Fe oxide phases in addition to the presence of O/Ti vacancies

[en] Recent studies of the quality factor degradation mechanisms in superconducting RF niobium cavities at high surface magnetic fields revealed that RF performance may depend on the total hydrogen content in the 40 nm thick near-surface layer. Hydrogen distribution in niobium and its near-surface content variations after different chemical surface treatments has been addressed in previous studies. However, only chemical treatments were studied while heat treatments are equally important. In this work we use the elastic recoil detection (ERD) technique to systematically study the distribution of hydrogen in niobium sheet and cavity cutout samples subjected to chemical and heat treatments typically performed on niobium cavities. Our results indicate the near-surface segregation of hydrogen at the niobium oxide/niobium interface, and do not show any significant variation in hydrogen content after various heat and chemical treatments. We do not observe a direct correlation between total hydrogen content and the high field Q slope. Consequences of the observed hydrogen segregation are discussed in the framework of the NbH_x phase diagram.

[en] Experimental data on Pb-Pb central collisions were obtained by means of emulsion magnetic chambers containing the lead target irradiated with the Pb beam in the magnetic field of 1.8 Tesla at CERN in December, 1994 and November, 1996. 50 μm thick emulsion layers were placed perpendicular to the beam. Results of data analysis show existence of certain peculiar patterns in several central collisions (e.g. ring-like events, jets, multiple narrow spikes in secondary particle pseudorapidity distributions, etc.) The methods of pattern recognition theory, in particular, wavelet technique (the method of localized spectral analysis), used in target diagram analysis, reveal the detailed features of such structures

[en] 'Full-Text:' Some integral proofs of nonspecific cellular resistance was studied at liquidators of the consequences of Chernobyl AES crash 4-4.5 years ago radiation influence in doses 20-25 rem. The share of blood mononuclears with viral inclusion bodies and degree of its viral effect, metabolic and phagocytic monocyte activity in NBT-test were appraised. Lysosomal-cationic test was used for the revealing of functional state of granulocytes. It was established that at all patients influenced by low doses of radiation there were increased proofs of viral effect of mononuclears in comparison with control group of healthy donors. At the same time most liquidators had functional defects of monocytes and granulocytes. Consequently, there may occur nonspecific (antiviral) cellular resistance disorders under the influence of radiation low doses which in its turn may lead to development, unfavourable course, chronization of infection diseases, forming of immunocomplex pathology, neoplastic processes. The perspective way of prophylaxis radiation low doses induced unfavourable consequences is the correction of nonspecific cellular resistance disorders (Olifen, Interlock). (author)

[en] Nuclear emulsion was exposed to xenon nuclei accelerated at the JINR Nuclotron. Visual and automated scanning of the extracted beam profile was performed using the exposed emulsion film.

[en] We studied the effect of the growth cell geometry on the temperature fields and the uniformity of semiconductor layers grown by thermal crystallization method from a discrete liquid source. Calculation results show that the radius of local sources practically does not change the temperature field of the substrate. When the radius of the local evaporators was changed from 2 to 6.5 mm, the observed increase in the maximum temperature did not exceed 2 K. However, increasing the distance between the substrate and the temperature screen fundamentally changes the temperature of the substrate. An increase in the distance from 2 to 25 mm caused a decrease in the substrate temperature by 20 K. It is shown that to achieve uniformity of better than 90% need to use a hexagonal arranged system of round local sources with the radius of r = 0.6 cm. (paper)

[en] Medium energy ion scattering (MEIS) was used to study the distribution of ion-implanted As and Sb dopants in Si with excess vacancies and SIMOX substrates as well as the effects of thermal treatments. Extra vacancies in Si were generated by N or O pre-implantation at high temperatures. Under these conditions, effects related to the different chemical nature of the pre-implanted species are expected. The annealing behavior and depth distribution of the Sb atoms differed for O compared to N pre-implanted Si. After long annealing times, the oxygen containing samples (SIMOX and O pre-implanted Si) presented higher substitutionality. The nitrogen pre-implanted Si presented the lowest amount of segregated Sb and a more uniform dopant distribution. For both N and O pre-implanted samples a large dopant loss to the atmosphere during annealing was observed

[en] Luminescence of amorphous Si quantum dots (Si QDs) in a hydrogenated silicon nitride (SiN_x:H) matrix was examined over a broad range of stoichiometries from Si_3N_2_._0_8 to Si_3N_4_._1_4, to optimize light emission. Plasma-enhanced chemical vapor deposition was used to deposit hydrogenated SiN_x films with excess Si on Si (001) substrates, with stoichiometry controlled by variation of the gas flow rates of SiH_4 and NH_3 gases. The compositional and optical properties were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection, spectroscopic ellipsometry, photoluminescence (PL), time-resolved PL, and energy-filtered transmission electron microscopy. Ultraviolet-laser-excited PL spectra show multiple emission bands from 400 nm (3.1 eV) to 850 nm (1.45 eV) for different Si_3N_x compositions. There is a red-shift of the measured peaks from ∼2.3 eV to ∼1.45 eV as Si content increases, which provides evidence for quantum confinement. Higher N content samples show additional peaks in their PL spectra at higher energies, which we attribute to defects. We observed three different ranges of composition where Tauc band gaps, PL, and PL lifetimes change systematically. There is an interesting interplay of defect luminescence and, possibly, small Si QD luminescence observed in the intermediate range of compositions (∼Si_3N_3_._1_5) in which the maximum of light emission is observed