837 research outputs found
Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+
Frequency and dc magnetic field dependences of dynamic susceptibility in
diluted paramagnets LiYF:Ho have been measured at liquid helium
temperatures in the ac and dc magnetic fields parallel to the symmetry axis of
a tetragonal crystal lattice. Experimental data are analyzed in the framework
of microscopic theory of relaxation rates in the manifold of 24
electron-nuclear sublevels of the lowest non-Kramers doublet and the first
excited singlet in the Ho ground multiplet split by the crystal
field of S symmetry. The one-phonon transition probabilities were computed
using electron-phonon coupling constants calculated in the framework of
exchange charge model and were checked by optical piezospectroscopic
measurements. The specific features observed in field dependences of the in-
and out-of-phase susceptibilities (humps and dips, respectively) at the
crossings (anti-crossings) of the electron-nuclear sublevels are well
reproduced by simulations when the phonon bottleneck effect and the cross-spin
relaxation are taken into account
THIACALIX[4]ARENES DERIVATIVES: FROM SELF-ASSEMBY TO FUNCTIONAL MATERIALS
This work was supported by the by Russian Science Foundation, project # 19-13-00095
The algebraic hyperstructure of elementary particles in physical theory
Algebraic hyperstructures represent a natural extension of classical
algebraic structures. In a classical algebraic structure, the composition of
two elements is an element, while in an algebraic hyperstructure, the
composition of two elements is a set. Algebraic hyperstructure theory has a
multiplicity of applications to other disciplines. The main purpose of this
paper is to provide examples of hyperstructures associated with elementary
particles in physical theory.Comment: 13 page
Constraints on Conformal Windows from Holographic Duals
We analyze a beta function with the analytic form of
Novikov-Shifman-Vainshtein-Zakharov result in the five dimensional
gravity-dilaton environment. We show how dilaton inherits poles and fixed
points of such beta function through the zeros and points of extremum in its
potential. Super Yang-Mills and supersymmetric QCD are studied in detail and
Seiberg's electric-magnetic duality in the dilaton potential is explicitly
demonstrated. Non-supersymmetric proposals of similar functional form are
tested and new insights into the conformal window as well as determinations of
scheme-independent value of the anomalous dimension at the fixed point are
presented.Comment: Fig. 5b is corrected to match the discussion in the tex
Компьютерное моделирование ветровых нагрузок на высотные здания
The paper presents the results of numerical simulation of wind pressure on high rise buildings being under construction and planned in Yekaterinburg city (Russia). Simulation is performed in the program ANSYS. The simulated building is placed in a domain that is the numerical analogue of wind tunnel. Domain sizes are chosen in such a way that simulated buildings do not affect the flow of air on its boundaries. Shear stress transport (SST) turbulence model is used. In order to validate the numerical model the paper presents the results of experimental study and numerical simulation of external air flow around the cylindrical body with the diameter of 8 mm, placed on the way of free submerged jet of air. The cylinder which has simple geometry form was used due to the need to achieve the generality of the outcomes. A comparison of the results of calculation of wind pressure with the experimental data blasting building models in wind tunnels is done.В статье представлены результаты численного моделирования задачи определения ветровых давлений на строящиеся или проектируемые в г. Екатеринбурге (Россия) высотные здания. Задача решается в пакете ANSYS. Моделируемое здание и его окружение помещаются в домен, который является численным аналогом ветровой трубы. Размеры домена назначаются таким образом, чтобы объекты, входящие в домен, не влияли на движение воздуха у внешних границ домена. Для расчета используется модель SST. Для проверки правильности численной модели приводится сравнение результатов расчета с экспериментальными данными обдувки цилиндра диаметром 8 мм. Такая модель простой формы выбрана для удобства сравнения. Приведено сравнение численных результатов расчета давлений ветра на высотные здания с результатами обдувки в ветровых трубах
Natural fourth generation of leptons
We consider implications of a fourth generation of leptons, allowing for the
most general mass patterns for the fourth generation neutrino. We determine the
constraints due to the precision electroweak measurements and outline the
signatures to search for at the LHC experiments. As a concrete framework to
apply these results we consider the minimal walking technicolor (MWTC) model
where the matter content, regarding the electroweak quantum numbers,
corresponds to a fourth generation.Comment: 21 pages, 11 figures, 1 table; version to appear in JHE
Coordination Polymers based on calixarene derivatives: Structures and properties
© 2017 Elsevier B.V. The solid-state structures of 1D–3D Coordination Polymers based on the macrocyclic calixarene backbone have been reviewed, based on the chemical nature of appended substituents on the macrocycle platform. The coordination propensity of this class of ligands is analysed, taking into account the different coordinating atoms/groups that can be located on the macrocyclic ligand: (1) the unmodified inherently coordinating thiacalix[4]arene with the S bridges as donor atoms; (2) different conformations of calix[n] arene units, with appended O donor atoms; (3) the chemical modification of the upper rim of calix[n]arenes and thiacalix[n] arenes, with coordinating groups, in particular the use of the sulfonate groups; (4) calix[4]arenes, thiacalix[4] arenes and tetramercaptothiacalix[4]rene that have been modified at their lower rim (mono, di and tetra substitution) with coordinating groups like cyano, carboxylate, pyridyl and pyrazolyl groups. All the formed coordination networks have been described. A special attention has been drawn to the structural and functional properties of these extended networks: magnetic, luminescence, adsorption and catalytic properties. Perspectives and future challenges in this emerging field are also discussed
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