Polarization reversal and jump-like domain wall motion in stoichiometric LiTaO 3 produced by vapor transport equilibration

The polarization reversal and domain structure evolution has been studied in stoichiometric lithium tantalate prepared by vapor transport equilibration process. The first in situ visualization of domain kinetics has demonstrated the jump-like motion of few strictly oriented plane domain walls, which leads to short isolated current pulses in the switching current data. The proposed model of jump-like domain wall motion caused by interaction with pinning centers representing the areas with increased value of the threshold field is based on the effect of retardation of bulk screening. The derived formulas were applied successfully for analysis of the field dependence of the total switching time. The durations of wall jumps and wall stays (rest times) extracted from the switching current data are analyzed separately. The deceleration of the wall motion velocity during jump is controlled by the trail of residual depolarization field produced by bound charges and screening charges in the area behind the wall. The duration of the rest time is governed by the bulk screening of residual depolarization field. The value of Hurst exponent 0.75 obtained by fractal analysis of the switching current data has confirmed the essential influence of prehistory on the domain wall motion. The measurements of the coercive field by switching in bipolar triangular pulses in wide range of the field ramp rate have allowed us to extract the record low value of coercive field 60 V/mm for quasi-static polarization reversal. © 2012 American Institute of Physics

Measurement of young's modulus and hardness of Al-50 wt % Sn alloy phases using nanoindentation

The nanoindentation method was used to measure the Young's modulus and hardness of the phases of the alloy Al-50 wt % Sn: α-aluminum and eutectic. Samples are obtained in different ways, i.e., traditionally via the transition of the melt into a homogeneous structural state by heating to a certain temperature, followed by cooling using the cooling rate greater by the order than that of the traditional method and via the addition of 0.06 wt % Ti and 1 wt % Zr to the binary alloy. It has been found that the most significant effect of the Al-50 wt % Sn phases on the Young's modulus is the transition of the melt into a homogeneous structural state and the introduction of Zr into the melt. As part of the mathematical theory of elasticity, a numerical evaluation of the interfacial pressure that arises due to the difference between Young's modulus of α aluminum and eutectic has been performed. The calculation has showed that the extra pressure is nine times less for the alloy formed through the transition of the melt into a homogeneous structural state than for the alloy produced via a traditional way. © 2013 Pleiades Publishing, Ltd

Assessment of the Use of the Potential of Agricultural Lands in Voronezh Region

The uniqueness and specifics of the land significantly affects both the organization of agricultural production and the rural area management. In order to make well-founded management decisions the economic subjects and public authorities need scientific grounding for assessment of land potential and its use efficiency. The authors suggest using three approaches to land quality and use assessment: agro-climatic potential, land quality score and agricultural production per hectare. Uniting these approaches into single assessment procedure produces a fairly objectively estimation of the economic potential of agricultural land in each selected territory

Ethyl 2-(4-hydr­oxy-1-methyl-2-oxo-1,2-dihydro­quinolin-3-yl)acetate

In the title compound, C14H15NO4, the bicyclic fragment and the ester group form a dihedral angle of 86.7 (2)°. Inter­molecular O—H⋯O and C—H⋯O hydrogen bonding connects mol­ecules into a helix along the crystallographic b axis

Research on the possibility of extending the shelf life of cheese raw material and heat-treated cheese by their freezing for further use in HoReCa

The article presents the results of a study of the regularities of changes in the functional properties and quality indicators of heat-treated cheeses made from frozen cheese raw material or frozen after thermomechanical processing for further use in HoReCa. The objects of the study were: Caliatta cheese — a semi-hard ripening cheese intended as the main raw material in the production of heat-treated cheese, as well as heat-treated «pizzacheese», subjected to freezing at temperatures of minus 14 ±2 °Cand minus 55 ±2 °Cand low-temperature storage at a temperature of minus 14 ±2 °Cfor 270 days, followed by defrosting at a temperature of 20 ±2 °C. To confirm the possibility of using the freezing technique in order to increase the shelf life of both the original cheese raw material and heat-treated cheese, their microbiological and physicochemical indicators were determined by standardized methods. Studies of structural and mechanical (rheological) properties were carried out on a Weissenberg rheogoniometer, recording changes in the elastic modulus (G’) and dynamic viscosity (h’). The length of the cheese thread, as one of the main functional properties of the «pizza-cheese», was assessed with a fork test after baking. Organoleptic characteristics were assessed by flavor, texture and appearance. Research results have shown that low-temperature storage of frozen cheese can be considered as a way to retard biological and physicochemical changes, which is a safe way to increase shelf life. Freezing cheese raw material increases the length of the cheese thread in proportion to the temperature and duration of the low-temperature storage. When obtaining heat-treated cheese from both unfrozen and frozen cheese raw material, a significant deterioration in the desired functional properties is observed. Thus, the receipt of heat-treated cheese from the original cheese raw material for further use in the production of pizza is justified only by economic feasibility. Freezing «pizza-cheese» at a temperature of minus 55 ±2 °C, made from unfrozen cheese raw material, ensures the preservation of functional properties and increases the shelf life up to 150 days