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

Performance evaluation of implementation of regional special-purpose programs

© 2015, Asian Social Science. All rights reserved. The article analyses the algorithm of development and implementation of regional special-purpose programs on the example of the special-purpose program “Rural Youth of the Republic of Tatarstan for 2011-2015”; the assessment of the program using performance indicators that include the level of execution of the planned funding is conducted; the level of achievement of the performance indicator; the effectiveness of budget spending; the effective implementation of the long-term program in the reporting under report

Boundary layer structure in turbulent thermal convection and its consequences for the required numerical resolution

Results on the Prandtl-Blasius type kinetic and thermal boundary layer thicknesses in turbulent Rayleigh-B\'enard convection in a broad range of Prandtl numbers are presented. By solving the laminar Prandtl-Blasius boundary layer equations, we calculate the ratio of the thermal and kinetic boundary layer thicknesses, which depends on the Prandtl number Pr only. It is approximated as $0.588Pr^{-1/2}$ for $Pr\ll Pr^*$ and as $0.982 Pr^{-1/3}$ for $Pr^*\ll\Pr$, with $Pr^*= 0.046$. Comparison of the Prandtl--Blasius velocity boundary layer thickness with that evaluated in the direct numerical simulations by Stevens, Verzicco, and Lohse (J. Fluid Mech. 643, 495 (2010)) gives very good agreement. Based on the Prandtl--Blasius type considerations, we derive a lower-bound estimate for the minimum number of the computational mesh nodes, required to conduct accurate numerical simulations of moderately high (boundary layer dominated) turbulent Rayleigh-B\'enard convection, in the thermal and kinetic boundary layers close to bottom and top plates. It is shown that the number of required nodes within each boundary layer depends on Nu and Pr and grows with the Rayleigh number Ra not slower than \sim\Ra^{0.15}. This estimate agrees excellently with empirical results, which were based on the convergence of the Nusselt number in numerical simulations

Synthesis and structure of new N-alkoxy-N-(1-pyridinium)urea chlorides

New N-[1-(4-amino)pyridinium]-N-methoxyurea chloride, N-[1-(2-amino)pyridinium]-N-methoxyurea chloride and their analogs were synthesized by N-alkoxy-N-chloroureas reaction with the proper pyridines in acetonitrile or ether solution by improved procedure. XRD study of N-[1-(4-amino)pyridinium]-N-methoxyurea and N-[1-(2 amino)pyridinium]-N-methoxyurea revealed the elongation of N-N+ bonds and some shortening of MeO-N bonds, qunonoid deformation of pyridine rings compare to it unsubstituted analog. The substantial pyramidality of central nitrogen atom in O-N-N+ moiety and N-C carbamoyl bonds difference were established too. The structure summary of N-alkoxy-N-(1-pyridinium)ureas salts and other derivatives of 1-(N-alkoxyamino)pyridinium salts has been done

Local polarization reversal in KTP single crystals

The research was made possible in part by RFBR (grant 16-02-00724) and by President of Russian Federation grant for young scientists (Contract 14.Y30.17.2837-MK). The equipment of the Ural Center for Shared Use “Modern nanotechnology” Ural Federal University was used

Non-Oberbeck-Boussinesq effects in turbulent thermal convection in ethane close to the critical point

As shown in earlier work (Ahlers et al., J. Fluid Mech. 569, p.409 (2006)), non-Oberbeck Boussinesq (NOB) corrections to the center temperature in turbulent Rayleigh-Benard convection in water and also in glycerol are governed by the temperature dependences of the kinematic viscosity and the thermal diffusion coefficient. If the working fluid is ethane close to the critical point the origin of non-Oberbeck-Boussinesq corrections is very different, as will be shown in the present paper. Namely, the main origin of NOB corrections then lies in the strong temperature dependence of the isobaric thermal expansion coefficient \beta(T). More precisely, it is the nonlinear T-dependence of the density \rho(T) in the buoyancy force which causes another type of NOB effect. We demonstrate that through a combination of experimental, numerical, and theoretical work, the latter in the framework of the extended Prandtl-Blasius boundary layer theory developed in Ahlers et al., J. Fluid Mech. 569, p.409 (2006). The latter comes to its limits, if the temperature dependence of the thermal expension coefficient \beta(T) is significant.Comment: 18 pages, 15 figures, 3 table

Physiological and biochemical features of fig cultivars (<I>Ficus carica</I> L.) from the collection of the Nikita Botanical Gardens

Background. Identification of promising fig cultivars (Ficus carica L.) with high content of bioactive compounds in fruits and increased adaptability to moisture deficiency is important for breeding and fruit growing in arid regions.Methods. The chemical analysis of fruits was performed using conventional methods. The content of essential elements was measured on a Kvant 2MT atomic absorption spectrophotometer. Drought resistance was assessed using the method of determining the water-holding capacity and resistance to dehydration in the leaves of fruit crops.Results. Fruits of cv. ‘Muason’ demonstrated the highest dry matter content (26.60 ± 1.30%), total phenolic compounds (169.0±26.0 mg%), sugars (mono: 15.03 ± 1.25%, and total: 17.46 ± 0.56%), water-soluble pectin (1.17%), total pectin substances (1.99%), and K (13565 ± 805 mg/kg); fruits of cv. ‘Pomoriysky’ had the maximum content of Ca (532 ± 65 mg/kg), Mg (982 ± 121 mg/kg), and Mn (1.98 ± 0.182 mg/kg); ‘Sabrutsiya Rozovaya’ excelled in the content of ascorbic acid (17.32 ± 0.78 mg%), Fe (15.413 ± 1.989 mg/kg), Zn (10.688 ± 1.338 mg/kg), and Cu (1.435 ± 0.132 mg/kg). ‘Sabrutsiya Rozovaya’ showed high drought resistance, ‘Pomoriysky’ had a medium degree of resistance, while ‘Muason’ demonstrated low water regime values. The loss of 15–20% of moisture by the leaves is critical: dehydration exceeding this limit leads to the impossibility of restoring satisfactory turgor. Conclusion. Fruits of the studied fig cultivars belong to the group of products with high K and Mg content, and satisfactory content of Fe, Zn and Mn. ‘Sabrutsiya Rozovaya’, a potentially adaptable cultivar with resistance to hydrothermal stress, was identified for its increased water-retaining capacities and high reparative ability of leaf tissues. It is recommended for use in the breeding for drought resistance and for establishment of large-scale plantations in arid regions

Polarization reversal in Rb:KTP and KTA single crystals

The equipment of the Ural Center for Shared Use “Modern nanotechnology” Ural Federal University was used. This research was made possible in part by President of Russian Federation Grant for young scientists (grant No. МК-1217.2019.2)

The role of humidity on the domain growth during local switching in RKTP single crystals

The equipment of the Ural Center for Shared Use “Modern Nanotechnology” UrFU was used. This research was made possible in part by President of Russian Federation Grant for young scientists (grant No. МК-1217.2019.2)