Half-metallicity and efficient spin injection in AlN/GaN:Cr (0001) heterostructure

First-principles investigations of the structural, electronic and magnetic properties of Cr-doped AlN/GaN (0001) heterostructures reveal that Cr segregates into the GaN region, that these interfaces retain their important half-metallic character and thus yield efficient (100 %) spin polarized injection from a ferromagnetic GaN:Cr electrode through an AlN tunnel barrier - whose height and width can be controlled by adjusting the Al concentration in the graded bandgap engineered Al(1-x)Ga(x)N (0001) layers.Comment: submitted for publicatio

Somatometric and Index Indicators for Assessing the Physical State of Patients with Gastric Cancer

The purpose of the research was to study physical health of patients with gastric cancer, the identification of markerspredictors of gastric cancer.Material and methods. This article presents the results of a survey with 150 patients diagnosed with stomach cancer. The research was conducted on the basis of the department of oncoabdominal surgery of Krasnoyarsk Regional Clinical Oncological Hospital named after A.I. Kryzhanovskiy in the period from 2016 to 2017. Patients with established gastric cancer, awaiting for surgical treatment, were examined using anthropometric methods of research. We evaluated the physical status of patients of different age diagnosed with stomach cancer. We also calculated body mass index and Tanner’s index of sexual dimorphism (1968), according to the last we determined the type of gender dimorphism. Distribution of healthy men and women in the population of the Krasnoyarsk Territory was taken for comparison.Results. We have obtained the following markers: overweight and obesity, sex inversion in men of the II period of adulthood and the elderly to gynecomorphy, and in women of the II period of adulthood – to mesomorphy.Conclusions. These markers are used for assessment of the physical status of patients with stomach cancer. They, together with the already known risk factors of gastric cancer development, will help to identify groups with an increased risk for gastric cancer development at the stage of medical examination of the population

Electronic structure and light-induced conductivity in a transparent refractory oxide

Combined first-principles and experimental investigations reveal the underlying mechanism responsible for a drastic change of the conductivity (by 10 orders of magnitude) following hydrogen annealing and UV-irradiation in a transparent oxide, 12CaO.7Al2O3, found by Hayashi et al. The charge transport associated with photo-excitation of an electron from H, occurs by electron hopping. We identify the atoms participating in the hops, determine the exact paths for the carrier migration, estimate the temperature behavior of the hopping transport and predict a way to enhance the conductivity by specific doping.Comment: 4 pages including 4 figure

Electronic band structure and carrier effective mass in calcium aluminates

First-principles electronic band structure investigations of five compounds of the CaO-Al2O3 family, 3CaO.Al2O3, 12CaO.7Al2O3, CaO.Al2O3, CaO.2Al2O3 and CaO.6Al2O3, as well as CaO and alpha-, theta- and kappa-Al2O3 are performed. We find that the conduction band in the complex oxides is formed from the oxygen antibonding p-states and, although the band gap in Al2O3 is almost twice larger than in CaO, the s-states of both cations. Such a hybrid nature of the conduction band leads to isotropic electron effective masses which are nearly the same for all compounds investigated. This insensitivity of the effective mass to variations in the composition and structure suggests that upon a proper degenerate doping, both amorphous and crystalline phases of the materials will possess mobile extra electrons

Structure peculiarities of cementite and their influence on the magnetic characteristics

The iron carbide $Fe_3C$ is studied by the first-principle density functional theory. It is shown that the crystal structure with the carbon disposition in a prismatic environment has the lowest total energy and the highest energy of magnetic anisotropy as compared to the structure with carbon in an octahedron environment. This fact explains the behavior of the coercive force upon annealing of the plastically deformed samples. The appearance of carbon atoms in the octahedron environment can be revealed by Mossbauer experiment.Comment: 10 pages, 3 figures, 3 tables. submitted to Phys.Rev.

Electric field gradients in s-, p- and d-metal diborides and the effect of pressure on the band structure and Tc_c in MgB2_2

Results of FLMTO-GGA (full-potential linear muffin-tin orbital -- generalized gradient approximation) calculations of the band structure and boron electric field gradients (EFG) for the new medium-T$_c$ superconductor (MTSC), MgB$_2$, and related diborides MB$_2$, M=Be, Al, Sc, Ti, V, Cr, Mo and Ta are reported. The boron EFG variations are found to be related to specific features of their band structure and particularly to the M-B hybridization. The strong charge anisotropy at the B site in MgB$_2$ is completely defined by the valence electrons - a property which sets MgB$_2$ apart from other diborides. The boron EFG in MgB$_2$ is weakly dependent of applied pressure: the B p electron anisotropy increases with pressure, but it is partly compensated by the increase of core charge assymetry. The concentration of holes in bonding $\sigma$ bands is found to decrease slightly from 0.067 to 0.062 holes/B under a pressure of 10 GPa. Despite a small decrease of N(E$_F$), the Hopfield parameter increases with pressure and we believe that the main reason for the reduction under pressure of the superconducting transition temperature, T$_c$, is the strong pressure dependence of phonon frequencies, which is sufficient to compensate the electronic effects.Comment: 12 pages, 3 figure

Generalized stacking fault energetics and dislocation properties: compact vs. spread unit dislocation structures in TiAl and CuAu

We present a general scheme for analyzing the structure and mobility of dislocations based on solutions of the Peierls-Nabarro model with a two component displacement field and restoring forces determined from the ab-initio generalized stacking fault energetics (ie., the so-called $\gamma$-surface). The approach is used to investigate dislocations in L1$_{0}$ TiAl and CuAu; predicted differences in the unit dislocation properties are explicitly related with features of the $\gamma$-surface geometry. A unified description of compact, spread and split dislocation cores is provided with an important characteristic "dissociation path" revealed by this highly tractable scheme.Comment: 7 two columns pages, 2 eps figures. Phys. Rev. B. accepted November 199

Metal-polymer complexes of cobalt(II) and Copper(II) with hyperbranched polyester polycarboxylic acids

Hyperbranched polyester polycarboxylic acids of the second and third generations for use as high-efficiency complexing agents are synthesized. On the basis of these compounds, new metal-polymer complexes of cobalt(II) and copper(II) are prepared for the first time. As evidenced by IR and ERR studies, the central atom in these metal polycarboxylates occurs in the axially symmetric system MO6. The thermal stability of polymer copper complexes is improved with increases in the content of metal ions, the degree of functionalization, and the generation number of the polyacid platform. © 2013 Pleiades Publishing, Ltd

Cyclotron enhancement of tunneling

A state of an electron in a quantum wire or a thin film becomes metastable, when a static electric field is applied perpendicular to the wire direction or the film surface. The state decays via tunneling through the created potential barrier. An additionally applied magnetic field, perpendicular to the electric field, can increase the tunneling decay rate for many orders of magnitude. This happens, when the state in the wire or the film has a velocity perpendicular to the magnetic field. According to the cyclotron effect, the velocity rotates under the barrier and becomes more aligned with the direction of tunneling. This mechanism can be called cyclotron enhancement of tunneling

Diagnostics of soils located in the gradient of urban-technogenic impact

The rapidly progressing urbanization results in decline of environmentally valuable forest territory. Intact ecosystems bordering urban communities suffer from heavy technogenic pressure and degrade irreversibly over time. This situation necessitates studies that analyze the ecological condition of major components of forest ecosystems exposed to various levels of such pressure. The survey was carried out in the city of Petrozavodsk in sites with degraded, slightly disturbed, and undisturbed forest ecosystems. For each site, the soil condition was assessed, the tree stand and the living ground cover were described. As a result, it was found that soils in the slightly disturbed forest ecosystem generally corresponded to the natural background (Ferric Illuvial Podzol). Changes in their morphological and chemical properties compared to soils in the undisturbed reference plot were identified. The thickness and ash content of the upper organic horizon in the slightly disturbed site changed. The forest ecosystem was in the transitional stage (from I–II to III) of recreational digression and required infrastructural improvements. The forest ecosystem in the built-up site was totally destroyed. Irreversible transformation of its natural environment resulted in the loss of woody and ground vegetation. The native zonal soils were ruined, and their diagnostic horizons cannot be identified. There was observed a large amount of rocks and anthropogenic inclusions throughout the profile. According to the Russian soil classification, these formations belong to the subgroup of organo-mineral strata of technogenic surface formations. The collected data can be used as the basis for ecological monitoring of urban soils. Based on the findings, recommendations were given on how to conserve and improve the sanitary and esthetic functions of forest areas adjoining urban built-up land