Micromagnetic and Magnetoresistance Studies of Ferromagnetic La\u3csub\u3e0.83\u3c/sub\u3eSr\u3csub\u3e0.13\u3c/sub\u3eMnO\u3csub\u3e2.98\u3c/sub\u3e Crystals

Magnetic force microscopy (MFM) and atomic force microscopy (AFM) were used to investigate the surface topography and micromagnetic structure of La0.83Sr0.13MnO2.98 single crystals with colossal magnetoresistance (CMR). The crystals were grown by fused salt electrolysis and characterized by chemical analysis, X-ray diffraction, magnetic and transport measurements. The crystals are rhombohedral (R 3 c). Magnetic and transport measurements indicate that the ferromagnetic ordering at 310 K is associated with an insulator-metal transition at the same temperature. A maximum negative magnetoresistance (-62 %) is observed at 290 K in an applied magnetic field of 5 T. The magnetoresistance increases in magnitude sharply (1.8 %), comparing to the rest of the change, with increasing magnetic field up to 20 G, and then it increases slowly with increasing field. MFM and AFM were used to study the (110) surface as well as a number of unspecified surfaces. Surface topography of an as-grown crystal exhibits well-developed surface corrugations due to extensive twinning. The corrugation angle at twin boundaries can be related to the unit cell parameters, surface and twinning planes. Magnetic force microscopy images show that magnetic domain boundaries are pinned to the crystallographic twins; a small number of unpinned boundaries are observed. The statistical analysis of domain boundary angle distribution is consistent with cubic magnetocrystalline anisotropy with easy axis along [100] directions for this material. Unusual magnetization behavior in the vicinity of topological defects on the surface is also reported. MFM contrast was found to disappear above the ferromagnetic Curie temperature; after cooling a new magnetic structure comprised of Bloch walls of opposite chiralities developed

Prospects for Establishment of Technological Complexes in Machine Building Industry on The Basis of Electromechatronic Propulsion Systems

The authors consider prospects for technological complex establishment in machine building industry on the basis of electromechatronic propulsion systems for production of innovative products with different novelty levels: world, state, brunch, region, etc

Glucose-induced down regulation of thiamine transporters in the kidney proximal tubular epithelium produces thiamine insufficiency in diabetes

Increased renal clearance of thiamine (vitamin B1) occurs in experimental and clinical diabetes producing thiamine insufficiency mediated by impaired tubular re-uptake and linked to the development of diabetic nephropathy. We studied the mechanism of impaired renal re-uptake of thiamine in diabetes. Expression of thiamine transporter proteins THTR-1 and THTR-2 in normal human kidney sections examined by immunohistochemistry showed intense polarised staining of the apical, luminal membranes in proximal tubules for THTR-1 and THTR-2 of the cortex and uniform, diffuse staining throughout cells of the collecting duct for THTR-1 and THTR-2 of the medulla. Human primary proximal tubule epithelial cells were incubated with low and high glucose concentration, 5 and 26 mmol/l, respectively. In high glucose concentration there was decreased expression of THTR-1 and THTR-2 (transporter mRNA: −76% and −53% respectively, p<0.001; transporter protein −77% and −83% respectively, p<0.05), concomitant with decreased expression of transcription factor specificity protein-1. High glucose concentration also produced a 37% decrease in apical to basolateral transport of thiamine transport across cell monolayers. Intensification of glycemic control corrected increased fractional excretion of thiamine in experimental diabetes. We conclude that glucose-induced decreased expression of thiamine transporters in the tubular epithelium may mediate renal mishandling of thiamine in diabetes. This is a novel mechanism of thiamine insufficiency linked to diabetic nephropathy

Theory of Functional Connections and Nelder-Mead optimization methods applied in satellite characterization

The growing population of man-made objects with the build up of mega-constellations not only increases the potential danger to all space vehicles and in-space infrastructures (including space observatories), but above all poses a serious threat to astronomy and dark skies. Monitoring of this population requires precise satellite characterization, which is is a challenging task that involves analyzing observational data such as position, velocity, and light curves using optimization methods. In this study, we propose and analyze the application of two optimization procedures to determine the parameters associated with the dynamics of a satellite: one based on the Theory of Functional Connections (TFC) and another one based on the Nelder-Mead heuristic optimization algorithm. The TFC performs linear functional interpolation to embed the constraints of the problem into a functional. In this paper, we propose to use this functional to analytically embed the observational data of a satellite into its equations of dynamics. After that, any solution will always satisfy the observational data. The second procedure proposed in this research takes advantage of the Nealder-Mead algorithm, that does not require the gradient of the objective function, as alternative solution. The accuracy, efficiency, and dependency on the initial guess of each method is investigated, analyzed, and compared for several dynamical models. These methods can be used to obtain the physical parameters of a satellite from available observational data and for space debris characterization contributing to follow-up monitoring activities in space and astronomical observatories.Comment: Submitted to Acta Astronautic

Configuration of a thin circular membrane subject to solar pressure

This paper addresses the preliminary design of a parabolic structure suitable for specific space applications, such as in solar power collector systems, which relies upon the sole use of an initially flat circular membrane rigidly constrained across its perimeter. In particular, the possibility for this concept to make use of solar pressure as a means of obtaining the intended parabolic curvature is explored. Assuming the membrane´s film as an ideally reflecting surface, parametric studies are conducted in order to determine several parameters of interest as functions of its radius and thickness. In order to do so, a set of numerical simulations are carried out using the finite element code ABAQUS®. It is shown that the shape of the deformed membrane is very close to parabolic, therefore being capable of concentrating sunlight power over a focal plane

Membrane-based space energy collector: A conceptual study

In this work the shape characteristics of a parabolic structure that consists of an initially flat circular membrane subject to solar radiation pressure in the space environment are examined. This problem arises in the analysis of space systems such as solar power collectors and solar sails. This paper presents parametric studies aimed at determining the power concentration capacity of a non-ideally reflecting flat circular membrane as a function of its radius size and thickness. The shape of the deformed membrane is close to parabolic. Both numerical simulations and analytical study show that the thin membrane subject solely to solar radiation pressure can concentrate the sunlight power several hundred times