The properties of isolated chiral skyrmions in thin magnetic films

Axisymmetric solitonic states (chiral skyrmions) have been predicted theoretically more than two decades ago. However, until recently they have been observed in a form of skyrmionic condensates (hexagonal lattices and other mesophases). In this paper we report experimental and theoretical investigations of isolated chiral skyrmions discovered in PdFe/Ir(111) bilayers two years ago (Science 341 , 636 (2013)). The results of spin-polarized scanning tunneling microscopy analyzed within the continuum and discrete models provide a consistent description of isolated skyrmions in thin layers. The existence region of chiral skyrmions is restricted by strip-out instabilities at low fields and a collapse at high fields. We demonstrate that the same equations describe axisymmetric localized states in all condensed matter systems with broken mirror symmetry, and thus our findings establish basic properties of isolated skyrmions common for chiral liquid crystals, different classes of noncentrosymmetric magnets, ferroelectrics, and multiferroics.Comment: 12 pages, 12 figure

Geologic Development of the Karymshina Caldera, Kamchatka, Russia, with Special Reference to Its Hydrothermal Systems

ABSTRACT Data on a caldera discovered in 2006 are reported. The caldera formed in southern Kamchatka during Eopleistocene time (1.2 to 1.5 Ma). The caldera boundaries have been reconstructed and its dimensions determined (approximately 15-25 km). The area of study contains several groups of thermal springs: the Bol'she-Bannaya, Mal. Bannaya, Karymchina, Karymshina, and VerkhneParatunka ones. The largest are the Bol'she-Bannaya springs; these were investigated extensively by many different methods during the 1970s. The reconstruction of the boundary to the large caldera that exists in the are

Theory of vortex states in magnetic nanodisks with induced Dzyaloshinskii-Moriya interactions

Vortex states in magnetic nanodisks are essentially affected by surface/interface induced Dzyaloshinskii-Moriya interactions. Within a micromagnetic approach we calculate the equilibrium sizes and shape of the vortices as functions of magnetic field, the material and geometrical parameters of nanodisks. It was found that the Dzyaloshinskii-Moriya coupling can considerably increase sizes of vortices with "right" chirality and suppress vortices with opposite chirality. This allows to form a bistable system of homochiral vortices as a basic element for storage applications.Comment: 8 pages, 8 figure

Calculation of thermal parameters of SiGe microbolometers

The thermal parameters of a SiGe microbolometer were calculated using numerical modeling. The calculated thermal conduction and thermal response time are in good agreement with the values found experimentally and range between 2x10$^-7$ and 7x10$^-8$ W/K and 1.5 and 4.5 ms, respectively. High sensitivity of microbolometer is achieved due to optimization of the thermal response time and thermal conduction by fitting the geometry of supporting heat-removing legs or by selection of a suitable material providing boundary thermal resistance higher than 8x10$^-3$ cm$^2$K/W at the SiGe interface.Comment: 11 pages, 6 figure

Change in stability of solid solution at radiation influence

Stability of solid solution at radiation influence has been investigated. Expressions for diffusion streams of binary alloy components, which specify the existence of temperature interval in which the phenomenon of ascending diffusion of elements is observed, were received. Vacancy characters of diffusion, configuration entropy, and potential energy of atomic bonds were considered at derivation. The ascending diffusion testifies to stability infringement of homogeneous solid solution - stratification. Influence of radiation is connected with increase in concentration of vacancies which changes the energy of atomic bonds and, simultaneously, accelerates diffusion processes. The condition of alloy stability with regard to stratification at radiating influence was obtaine

Polaron physics and crossover transition in magnetite probed by pressure-dependent infrared spectroscopy

The optical properties of magnetite at room temperature were studied by infrared reflectivity measurements as a function of pressure up to 8 GPa. The optical conductivity spectrum consists of a Drude term, two sharp phonon modes, a far-infrared band at around 600 cm$^{-1}$, and a pronounced mid-infrared absorption band. With increasing pressure both absorption bands shift to lower frequencies and the phonon modes harden in a linear fashion. Based on the shape of the MIR band, the temperature dependence of the dc transport data, and the occurrence of the far-infrared band in the optical conductivity spectrum the polaronic coupling strength in magnetite at room temperature should be classified as intermediate. For the lower-energy phonon mode an abrupt increase of the linear pressure coefficient occurs at around 6 GPa, which could be attributed to minor alterations of the charge distribution among the different Fe sites.Comment: 7 pages, 7 figure

ABOUT THE OPPORTUNITIES TO Influence MICROORGANISMS ON THE IRON HOMEOSTASIS IN THE HOST ORGANISM (Literature review)

Iron homeostasis, aimed at depriving the pathogen of available iron, takes an important role in protecting human body against pathogens. When infection occurs, microorganisms must overcome iron deficiency in a host organism. This review describes microorganisms' ways of gaining iron in the host organism, presents present-day data on changing of iron homeostasis during infection and the main regulators of this process. Theoretical substantiation was given of the possibility of microorganisms' influence on iron homeostasis due to ability to inactivate hepcidin - antihepcidin activity

Discretization of variational regularization in Banach spaces

Consider a nonlinear ill-posed operator equation $F(u)=y$ where $F$ is defined on a Banach space $X$. In general, for solving this equation numerically, a finite dimensional approximation of $X$ and an approximation of $F$ are required. Moreover, in general the given data \yd of $y$ are noisy. In this paper we analyze finite dimensional variational regularization, which takes into account operator approximations and noisy data: We show (semi-)convergence of the regularized solution of the finite dimensional problems and establish convergence rates in terms of Bregman distances under appropriate sourcewise representation of a solution of the equation. The more involved case of regularization in nonseparable Banach spaces is discussed in detail. In particular we consider the space of finite total variation functions, the space of functions of finite bounded deformation, and the $L^\infty$--space

High-Performance Mn-Al-O Catalyst on Reticulated Foam Materials for Environmentally Friendly Catalytic Combustion

MnOx supported on alumina and La2O3-modified alumina have been prepared and characterized as methane combustion catalysts. X-ray diffraction (XRD) analysis has revealed the significant low-temperature interaction between MnOx and alumina, resulting in a solid solution Mn-La-γ*-Al2O3 and a hexaaluminate formation upon thermal treatment at 900-1000 ºC and 1300 ºC, respectively. Mn-Al-O and Mn-La-Al-O catalysts washcoated on highly porous reticulated foam materials (RFM) have been prepared by two methods, such as: 1) a wet impregnation of a washcoating alumina layer on RFM by Mn and La nitrate solutions, 2) a dip coating of RFM into Mn-La-Al-containing suspension. The chemical compositions of RFM were cordierite, Ni, and NiCr-alloy. The catalytic activity of washcoated RFM in the methane combustion has been compared with one of granulated catalysts. The influence of alumina form (γ-Al2O3, (γ+χ)-Al2O3, α-Al2O3), manganese loading (5 and 10 wt.%), modifying agent (La2O3) on catalytic activity have been studied. Catalytic performances of Mn-Al-O and Mn-La-Al-O catalysts washcoated on RFM and pretreated in methane-containing atmosphere at 1100 ºC have been investigated. The Mn-Al-O catalyst modified by La2O3 and supported on RFM have been tested in a prototype catalytic water heating boiler and demonstrated a considerable reduction in the emissions of NOx and CO compared to the conventional household boilers. The washcoating of the Mn-La-Al-O catalyst over surface of RFM provides a substantial reduction of toxic  emissions during the catalytic fuel combustion. While an optimal foam structure and composition of the RFM provide improved heat and mass transfer properties of the catalyst in fuel combustion