419 research outputs found
Theoretical study of the mechanism of dry oxidation of 4H-SiC
Possible defect structures, arising from the interaction of O-2 molecules with an ideal portion of the SiC/SiO2 interface, have been investigated systematically using density functional theory. Based on the calculated total energies and assuming thermal quasiequilibrium during oxidation, the most likely routes leading to complete oxidation have been determined. The defect structures produced along these routes will remain at the interface in significant concentration when stopping the oxidation process. The results obtained for their properties are well supported by experimental findings about the SiC/SiO2 interface. It is found that carbon-carbon bonds can explain most of the observed interface states but not the high density near the conduction band of 4H-SiC
Defects in SiO2 as the possible origin of near interface traps in the SiCâSiO2 system: A systematic theoretical study
A systematic study of the level positions of intrinsic and carbon defects in SiO2 is presented, based on density functional calculations with a hybrid functional in an alpha-quartz supercell. The results are analyzed from the point of view of the near interface traps (NIT), observed in both SiC/SiO2 and Si/SiO2 systems, and assumed to have their origins in the oxide. It is shown that the vacancies and the oxygen interstitial can be excluded as the origin of such NIT, while the silicon interstitial and carbon dimers give rise to gap levels in the energy range inferred from experiments. The properties of these defects are discussed in light of the knowledge about the SiC/SiO2 interface
Observations of Stellar Objects at a Shell Boundary in the Star-Forming Complex in the Galaxy IC1613
The single region of ongoing star formation in the galaxy IC 1613 has been
observed in order to reveal the nature of compact emission-line objects at the
edges of two shells in the complex, identified earlier in H-alpha line images.
The continuum images show these compact objects to be stars. Detailed
spectroscopic observations of these stars and the surrounding nebulae were
carried out with an integral field spectrograph MPFS mounted on the 6m
telescope of the Special Astrophysical Observatory. The resulting stellar
spectra were used to determine the spectral types and luminosity classes of the
objects. An Of star we identified is the only object of this spectral type in
IC 1613. The results of optical observations of the multi-shell complex are
compared to 21cm radio observations. The shells harboring the stars at their
boundaries constitute the most active part of the star-forming region. There is
evidence that shocks have played an important role in the formation of the
shells.Comment: 10 pages, 5 PS and 1 color JPEG figur
Detection of an intergalactic meteor particle with the 6-m telescope
On July 28, 2006 the 6-m telescope of the Special Astrophysical Observatory
of the Russian Academy of Sciences recorded the spectrum of a faint meteor. We
confidently identify the lines of FeI and MgI, OI, NI and molecular-nitrogen
N_2 bands. The entry velocity of the meteor body into the Earth's atmosphere
estimated from radial velocity is equal to 300 km/s. The body was several tens
of a millimeter in size, like chondrules in carbon chondrites. The radiant of
the meteor trajectory coincides with the sky position of the apex of the motion
of the Solar system toward the centroid of the Local Group of galaxies.
Observations of faint sporadic meteors with FAVOR TV CCD camera confirmed the
radiant at a higher than 96% confidence level. We conclude that this meteor
particle is likely to be of extragalactic origin. The following important
questions remain open: (1) How metal-rich dust particles came to be in the
extragalactic space? (2) Why are the sizes of extragalactic particles larger by
two orders of magnitude (and their masses greater by six orders of magnitude)
than common interstellar dust grains in our Galaxy? (3) If extragalactic dust
surrounds galaxies in the form of dust (or gas-and-dust) aureoles, can such
formations now be observed using other observational techniques (IR
observations aboard Spitzer satellite, etc.)? (4) If inhomogeneous
extragalactic dust medium with the parameters mentioned above actually exists,
does it show up in the form of irregularities on the cosmic microwave
background (WMAP etc.)?Comment: 9 pages, 6 EPS figure
Single-Photon Entanglement in the keV Regime via Coherent Control of Nuclear Forward Scattering
Generation of single-photon entanglement is discussed in nuclear forward
scattering. Using successive switchings of the direction of the nuclear
hyperfine magnetic field, the coherent scattering of photons on nuclei is
controlled such that two signal pulses are generated out of one initial pump
pulse. The two time-resolved correlated signal pulses have different
polarizations and energy in the keV regime. Spatial separation of the entangled
field modes and extraction of the signal from the background can be achieved
with the help of state-of-the-art x-ray polarizers and piezoelectric fast
steering mirrors.Comment: minor changes, updated to the final version; 4 pages, 2 figure
Modulational instability of bright solitary waves in incoherently coupled nonlinear Schr\"odinger equations
We present a detailed analysis of the modulational instability (MI) of
ground-state bright solitary solutions of two incoherently coupled nonlinear
Schr\"odinger equations. Varying the relative strength of cross-phase and
self-phase effects we show existence and origin of four branches of MI of the
two-wave solitary solutions. We give a physical interpretation of our results
in terms of the group velocity dispersion (GVD) induced polarization dynamics
of spatial solitary waves. In particular, we show that in media with normal GVD
spatial symmetry breaking changes to polarization symmetry breaking when the
relative strength of the cross-phase modulation exceeds a certain threshold
value. The analytical and numerical stability analyses are fully supported by
an extensive series of numerical simulations of the full model.Comment: Physical Review E, July, 199
Analysis of Epidemiological Situation on Leptospiroses in the Amur-River Region. Operational Experience in the Flood Area in 2013, and Forecasting for 2014
For the first time ever mobile SAET units have performed complex investigation of epidemiological situation on leptospiroses in order to provide sanitary-epidemiological welfare of the population in the Amur-River region devastated by high water in 2013. Analyzed have been contemporary published and archival data on morbidity rate and epizootic activity of the natural leptospirosis foci in the Amur-River territory up to 2013. Summarized is the information concerning monitoring over natural focal infections (in particular leptospiroses) in the flooding area, obtained by specialized antiepidemic teams from Irkutsk Research Anti-Plague Institute of Siberia and Far East deployed in Belogorsk town of the Amur Region and Khabarovsk city in 2013. Epizootiological situation during the high water period in the Jewish Autonomous Region has been defined as an extremely adverse, unlike the Khabarovsk Territory and the Amur Region where epizootic process is less expressed. Therewith aggravation of epidemiological situation on leptospiroses in the Amur-River Region in 2014 is not ruled out
Triplet p-wave superconductivity in low-density extended Hubbard model with Coulomb repulsion
We analyze superconducting instabilities in 3D and 2D extended Hubbard model
with Coulomb repulsion between electrons on neighboring sites in the limit of
low electron density () on simple cubic (square) lattice.
We show that in a realistic strong-coupling case ( and are
the onsite and the intersite Coulomb repulsions, the bandwidth) the main SC
instability corresponds to the p-wave pairing and in the leading order is
correctly described by the equations obtained earlier in the absence of the
intersite Coulomb interaction V=0.Comment: 6 pages, 4 figures, accepted for JETP Letter
Results of Immunological Screening for Natural-Focal and «Exotic» Infectious Diseases among Certain Population Groups of the Khabarovsk Territory, the Amur Region and the Jewish Autonomous Region
Displayed are the results of examination of immuno-competent local population of the Khabarovsk Territory, the Jewish Autonomous Region, the Amur Region, as well as foreign residents living and temporarily working in the areas, on a wide range of natural-focal bacterial and viral infectious diseases including the causative agents of some âexoticâ infections too. Investigations have been carried out with the participation of experts from the specialized anti-epidemic team No. 1 (Irkutsk Research Anti-Plague Institute), who worked in the Amur Region, and a group of laboratory-epidemiological specialists from the team No. 2 - deployed in the Khabarovsk Territory and the Jewish Autonomous Region during the flooding in August-September 2013. The total of 1335 blood sera samples has been tested using serological methods. The findings have revealed the presence of immuno-competent population in the three regions of the Far Eastern Federal district in reference to the agents of natural-focal infectious diseases: tularemia, leptospirosis, yersinioses, hemorrhagic fever with renal syndrome, human granulocytic anaplasmosis, tick-borne borrelioses, tick-borne viral encephalitis, Californian encephalitis serogroup, Sindbis, West Nile and Dengue fevers. Circulation of Batai and Crimean-Congo hemorrhagic fever viruses has not been revealed based on serological assays
- âŠ