983 research outputs found
Band structure of (Sr3Sc2O5)Fe2As2 as a possible parent phase for new FeAs superconductors
By means of first-principles FLAPW-GGA calculations, we have investigated the
electronic properties of the newly synthesized layered phase -
(Sr3Sc2O5)Fe2As2. The electronic bands, density of states and Fermi surface
have been evaluated. The resembling of our data for (Sr3Sc2O5)Fe2As2 with band
structure pictures of known FeAs superconducting materials may be considered as
the theoretical background specifying the possibility for (Sr3Sc2O5)Fe2As2 to
become a parent phase for new FeAs superconductors.Comment: 10 pages, 4 figures, 3 table
Investigation of industrial compositions SONKOR as corrosion inhibitors of mild steel in neutral media containing hydrogen sulfide
Electrochemical and corrosion behavior of mild steel in neutral media containing hydrogen sulfide has been investigated by weight-loss and electrochemical methods and protective effect of industrial compositions SONKOR has been determined. It has been shown that in 3 % NaCl compositions SONKOR have weak protective effect but it increases greatly in presence of hydrogen sulfide in the solution. At concentration of H2S = 0,6 gram per liter maximal protective effect has SONKOR 9801 (85.57 %) and SONKOR 9920А (81.97 %). Inhibitors SONKOR 9021С (70.82 %), 9510А (73.11 %) и 9701 (67.87 %) show less protective effect
Band structure of SrFeAsF and CaFeAsF as parent phases for a new group of oxygen-free FeAs superconductors
By means of first-principle FLAPW-GGA calculations, we have investigated the
electronic properties of the newly discovered layered quaternary systems
SrFeAsF and CaFeAsF as parent phases for a new group of oxygen-free FeAs
superconductors. The electronic bands, density of states, Fermi surfaces,
atomic charges, together with Sommerfeld coefficients and molar Pauli
paramagnetic susceptibility have been evaluated and discussed in comparison
with oxyarsenide LaFeAsO - a parent phase for a new class of high-temperature
(Tc about 26-56K) oxygen-containing FeAs superconductors. Similarity of our
data for SrFeAsF and CaFeAsF with the band structure of oxygen-containing FeAs
superconducting materials may be considered as theoretical background
specifying the possibility of superconductivity in these oxygen-free systems.Comment: 12 pages, 3 figure
The influence of various factors on recovery process of motor control of paretic limbs muscles in patients with pyramidal syndrome
In order to study the specific features of central nervous system reaction to restoration of the cranial vault bone defects by distraction, osteosynthesis method, the electroneuromyographic examination was performed in 28 patients of 16—62 years (average age — 40,1 ± 2,6 years) with pyramidal syndrome in late recovery or residual period, of the disease (severe brain injury cerebral stroke). The main trends in electroneuromyographic indice — "cerebrospinal index" — in patients during the replacement process of post-traumatic or simulated cranial vault bone defects using transosseous distraction osteosynthesis were analyzed. The specific features of the central nervous system responses to surgical treatment, age, etiology, the brain structures initial lesion severity and disease duration were studied. As the results of the research it was established that replacement of defects of calvarium bones by transosseous distraction osteosynthesis in patients with consequences of craniocerebral trauma or stroke had. more intensive positive influence on motor zones of cerebral cortex, that shows itself in increase of effectiveness of motor control, in middle age people, at traumatic etiology of disease, at moderate pyramidal insufficiency and. at remoteness of the disease up to 1 year. Obtained data is expedient to take into account at primary selection of patients for operative treatment
BILATERAL INTERRELATIONS OF ENMGAND EEG-CHARACTERISTICS OF PYRAMID INSUFFICIENCY IN PATIENTS WITH THE CONSEQUENCES OF STROKE AND OF BRAIN INJURY
The aim. of the work was to estimate the degree of intensity of interhemispheric interaction with use of complex neurophysiological (electroneuromyography, electroencephalography) testing of 163 patients of 12—74 years in residual period, of ischemic (n = 108) and hemorrhagic (n = 22) hemispheric stroke and. severe craniocerebral injury with brain contusion (n = 33). Obtained, data testifies to the distinct negative influence of postinsult/ posttraumatic cerebral defect on functional characteristica of counter-lateral ("intact") hemisphere that is reflected in proportional changes of all the spectrum, of analyzed, neurophysiological signs. These changes affects all the tested, modules of neuromotor system, and. can be observed over a long period, after the stroke or craniocerebral injury
Electronic Structure of KFeSe from First Principles Calculations
Electronic structure and magnetic properties for iron-selenide KFeSe
are studied by first-principles calculations. The ground state is stripe-like
antiferromagnetic with calculated 2.26 magnetic moment on Fe atoms; and
the , coupling strengths are calculated to be 0.038 eV and 0.029 eV.
The states around are dominated by the Fe-3d orbitals which hybridize
noticeably to the Se-4p orbitals. While the band structure of KFeSe is
similar to a heavily electron-doped BaFeAs or FeSe system, the Fermi
surface of KFeSe is much closer to \fs11 system since the electron
sheets around is symmetric with respect to - exchange. These
features, as well as the absence of Fermi surface nesting, suggest that the
parental KFeSe could be regarded as an electron over-doped 11 system
with possible local moment magnetism.Comment: accepted by Chinese Physics Letter, to appear as Chinese Physics
Letter, Vol 28, page 057402 (2011
Effects of Ru Substitution on Dimensionality and Electron Correlations in Ba(Fe_{1-x}Ru_x)_2As_2
We report a systematic angle-resolved photoemission spectroscopy study on
Ba(FeRu)As for a wide range of Ru concentrations (0.15
\emph{x} 0.74). We observed a crossover from two-dimension to
three-dimension for some of the hole-like Fermi surfaces with Ru substitution
and a large reduction in the mass renormalization close to optimal doping.
These results suggest that isovalent Ru substitution has remarkable effects on
the low-energy electron excitations, which are important for the evolution of
superconductivity and antiferromagnetism in this system.Comment: 4 pages, 4 figure
Band structure of new superconducting AlB_2-like ternary silicides M(Al_{0.5}Si_{0.5})_2 and M(Ga_{0.5}Si_{0.5})_2 (M= Ca, Sr and Ba)
The electronic band structures of the new superconducting (with T_c up to
7.7K) ternary silicides M(A_{0.5}Si_{0.5})_2 (M= Ca, Sr, Ba; A= Al, Ga) in the
AlB_2-type structure have been investigated using the full-potential LMTO
method. The calculations showed that the trend in transition temperatures
doesn't follow the changes in the density d-states at the Fermi level and
probably is associated with phonon-mode frequencies.Comment: 7 pagers, 1 table, 7 figure
Electron transport, penetration depth and upper critical magnetic field of ZrB12 and MgB2
We report on the synthesis and measurements of the temperature dependence of
resistivity, R(T), the penetration depth, l(T), and upper critical magnetic
field, Hc2(T), for polycrystalline samples of dodecaboride ZrB12 and diboride
MgB2. We conclude that ZrB12 as well as MgB2 behave like simple metals in the
normal state with usual Bloch-Gruneisen temperature dependence of resistivity
and with rather low resistive Debye temperature, TR=280 K, for ZrB12 (as
compared to MgB2 with TR=900 K). The R(T) and l(T) dependencies of ZrB12 reveal
a superconducting transition at Tc=6.0 K. Although a clear exponential
l(T)dependence in MgB2 thin films and ceramic pellets was observed at low
temperatures, this dependence was almost linear for ZrB12 below Tc/2. These
features indicate s-wave pairing state in MgB2, whereas a d-wave pairing state
is possible in ZrB12. A fit to the data gives a reduced energy gap
2D(0)/kTc=1.6 for MgB2 films and pellets, in good agreement with published data
for 3D \pi - sheets of the Fermi surface. Contrary to conventional theories we
found a linear temperature dependence of Hc2(T) for ZrB12 (Hc2(0)=0.15 T).Comment: 8 pages, 10 figures, submitted to JET
Electronic structure and possible pseudogap behavior in iron based superconductors
Starting from the simplified analytic model of electronic spectrum of iron -
pnictogen (chalcogen) high - temperature superconductors close to the Fermi
level, we discuss the influence of antiferromagneting (AFM)scattering both for
stoichiometric case and the region of possible short - range order AFM
fluctuations in doped compounds. Qualitative picture of the evolution of
electronic spectrum and Fermi surfaces (FS) for different dopings is presented,
with the aim of comparison with existing and future ARPES experiments. Both
electron and hole dopings are considered and possible pseudogap behavior
connected with partial FS "destruction" is demonstrated, explaining some recent
experiments.Comment: 5 pages, 4 figures, published versio
- …