Phase transitions and phase diagram of the ferroelectric perovskite NBT-BT by anelastic and dielectric measurements

The complex elastic compliance and dielectric susceptibility of (Na_{0.5}Bi_{0.5})_{1-x}Ba_{x}TiO_{3} (NBT-BT) have been measured in the composition range between pure NBT and the morphotropic phase boundary included, 0 <= x <= 0.08. The compliance of NBT presents sharp peaks at the rhombohedral/tetragonal and tetragonal/cubic transitions, allowing the determination of the tetragonal region of the phase diagram, up to now impossible due to the strong lattice disorder and small distortions and polarizations involved. In spite of ample evidence of disorder and structural heterogeneity, the R-T transition remains sharp up to x = 0.06, whereas the T-C transition merges into the diffuse and relaxor-like transition associated with broad maxima of the dielectric and elastic susceptibilities. An attempt is made at relating the different features in the anelastic and dielectric curves to different modes of octahedral rotations and polar cation shifts. The possibility is also considered that the cation displacements locally have monoclinic symmetry, as for PZT near the morphotropic phase boundary.Comment: 11 pages, 9 figures, submitted to Phys. Rev.

Speeding Strings

There is a class of single trace operators in ${\cal N}=4$ Yang-Mills theory which are related by the AdS/CFT correspondence to classical string solutions. Interesting examples of such solutions corresponding to periodic trajectories of the Neumann system were studied recently. In our paper we study a generalization of these solutions. We consider strings moving with large velocities. We show that the worldsheet of the fast moving string can be considered as a perturbation of the degenerate worldsheet, with the small parameter being the relativistic factor $\sqrt{1-v^2}$. The series expansion in this relativistic factor should correspond to the perturbative expansion in the dual Yang-Mills theory. The operators minimizing the anomalous dimension in the sector with given charges correspond to periodic trajectories in the mechanical system which is closely related to the product of two Neumann systems.Comment: v3: added a reference to the earlier wor

On stress/strain state in a rotating disk

In the framework of mechanics of continuum bodies, the problem of stress/strain state in a high-speed rotating disk of constant thickness has been considered. The material of the disk is assumed to be homogeneous, elastic/perfectly-plastic. In the plastic zone, the stresses and plastic strains are related by some associated law similar to the one employed in deformation theory of plasticity. The general algorithm of the solution covers any smooth plasticity function. At some steps of the algorithm, it is possible to get analytical expressions, particularly, for the quadratic Mises yield criterion. For the given model, the notion of control parameters (external and internal) has been introduced. The allowable boundaries of external parameters have been defined as well. For some states of the disk, the coherent values of external parameters have been obtained. The results are represented graphically to show various states of the disk. The usage of piecewise plasticity functions has been briefly discussed. The results obtained can be used in preliminary engineering design and related numerical codes.info:eu-repo/semantics/publishedVersio

Рабочая смена: восполнит ли молодежь кадровый дефицит в промышленности и аграрно-промышленном комплексе?

Дефицит квалифицированных рабочих кадров остается острой проблемой со времен кризиса 2008—2009 гг. В статье обсуждаются результаты двух социологических исследований, проведенных в регионах России с отчетливой отраслевой специализацией и предусматривавших анкетный опрос учащихся учреждений профтехобразования, а также экспертные интервью с руководством предприятий, отраслевых ассоциаций, торгово-промышленных палат и руко-водителями учреждений профтехобразования. Собранный материал дает информацию о том, какой контингент и почему приходит учиться рабочим профессиям; каким видит молодежь свое трудоустройство по окончании обучения; почему предприятиям по-прежнему сложно восполнять кадровый дефицит; появилась ли у бизнеса возможность долгосрочно планировать свои кадровые потребности, а у системы профтехобразования — эффективно на них отвечать. Показано, что выбор рабочей профессии определяется надеждой на достойно оплачиваемую работу, возможностью в короткий срок получить профессию и легкостью поступления в образовательное учреждение. Больше половины учащихся согласны практически со всеми позитивными утверждениями относительно рабочих профессий, но в то же время две трети понимают, что они связаны с тяжелыми либо опасными условиями труда. Хотя по окончании производственной практики большинство респондентов убедились в верности выбора профессии, в цеха и на поля идут далеко не все, что связано с невысокой зарплатой молодых кадров и/ или местом локализации предприятия при наличии альтернативы в виде работы в торговле или сервисе. Короткий горизонт планирования и низкий уровень рентабельности не позволяют предприятиям просчитывать свои кадровые потребности и формировать кадровый резерв, что дезориентирует систему профобразования и консервирует дисбалансы на рынке труда. Улучшению ситуации, по мнению как молодежи, так и экспертов, способствовало бы проведение государством более последовательной и эффективной политики поддержки промышленности и аграрно-промышленном ком-плексе (АПК)

RESEARCH OF ROLE MODELS OF INTERACTION BETWEEN A UNIVERSITY AND AN INDUSTRIAL PARTNER IN THE FIELD OF INTELLECTUAL PROPERTY

The article systematizes the existing role models of interaction between the university and the industrial partner in the field of intellectual property, as well as the corresponding schemes of division and consolidation of intellectual rights

Folded Three-Spin String Solutions in AdS_5 x S^5

We construct a spinning closed string solution in AdS_5 x S^5 which is folded in the radial direction and has two equal spins in AdS_5 and a spin in S^5. The energy expression of the three-spin solution specified by the folding and winding numbers for the small S^5 spin shows a logarithmic behavior and a one-third power behavior of the large total AdS_5 spin, in the long string and in the short string located near the boundary of AdS_5 respectively. It exhibits the non-regular expansion in the 't Hooft coupling constant, while it takes the regular one when the S^5 spin becomes large.Comment: 14 pages, LaTeX, no figures, a reference adde

An assessment of CFD applied to steady flow in a planar diffuser upstream of an automotive catalyst

Flow maldistribution across automotive exhaust catalysts significantly affects their conversion efficiency. Flow behaviour can be predicted using computational fluid dynamics (CFD). This study investigates the application of CFD to modelling flow in a 2D system consisting of a catalyst monolith downstream of a wide-angled planar diffuser presented with steady flow. Two distinct approaches, porous medium and individual channels, are used to model monoliths of length 27 mm and 100 mm. Flow predictions are compared to particle image velocimetry (PIV) measurements made in the diffuser and hot wire anemometry (HWA) data taken downstream of the monolith. Both simulations compare favourably with PIV measurements, although the models underestimate the degree of mixing in the shear layer at the periphery of the emerging jet. Tangential velocities are predicted well in the central jet region but are overestimated elsewhere, especially at the closest measured distance, 2.5 mm from the monolith. The individual channels model is found to provide a more consistently accurate velocity profile downstream of the monolith. Maximum velocities, on the centre line and at the secondary peak near to the wall, are reasonably well matched for the cases where the flow is more maldistributed. Under these conditions, a porous medium model remains attractive because of low computational demand

Structure of Erm-modified 70S ribosome reveals the mechanism of macrolide resistance

Many antibiotics inhibit bacterial growth by binding to the ribosome and interfering with protein biosynthesis. Macrolides represent one of the most successful classes of ribosome-targeting antibiotics. The main clinically relevant mechanism of resistance to macrolides is dimethylation of the 23S rRNA nucleotide A2058, located in the drug-binding site, a reaction catalyzed by Erm-type rRNA methyltransferases. Here, we present the crystal structure of the Erm-dimethylated 70S ribosome at 2.4 Å resolution, together with the structures of unmethylated 70S ribosome functional complexes alone or in combination with macrolides. Altogether, our structural data do not support previous models and, instead, suggest a principally new explanation of how A2058 dimethylation confers resistance to macrolides. Moreover, high-resolution structures of two macrolide antibiotics bound to the unmodified ribosome reveal a previously unknown role of the desosamine moiety in drug binding, laying a foundation for the rational knowledge-based design of macrolides that can overcome Erm-mediated resistance