Effect of a Magnetic Field on the Dipole Echo in Glasses with Nuclear Quadrupole Moments

The effect of a magnetic field on the dipole echo amplitude in glasses at temperatures of about 10 mK caused by nonspherical nuclei with electric quadrupole moments has been studied theoretically. It has been shown that in this case, the two-level systems (TLS's) that determine the glass properties at low temperatures are transformed into more complicated multilevel systems. These systems have new properties as compared to usual TLS's and, in particular, exhibit oscillations of electric dipole echo amplitude in magnetic field. A general formula that describes the echo amplitude in an arbitrary split TLS has been derived with perturbation theory. Detailed analytic and numerical analysis of the formula has been performed. The theory agrees qualitatively and quantitatively well with experimental data.Comment: 5 pages, 3 figure

Scaling the Temperature-dependent Boson Peak of Vitreous Silica with the high-frequency Bulk Modulus derived from Brillouin Scattering Data

The position and strength of the boson peak in silica glass vary considerably with temperature $T$. Such variations cannot be explained solely with changes in the Debye energy. New Brillouin scattering measurements are presented which allow determining the $T$-dependence of unrelaxed acoustic velocities. Using a velocity based on the bulk modulus, scaling exponents are found which agree with the soft-potential model. The unrelaxed bulk modulus thus appears to be a good measure for the structural evolution of silica with $T$ and to set the energy scale for the soft potentials.Comment: Accepted for publication in Physical Review Letter

Innovative manufacturing techniques of the profiled drawing tool

In this article, the new technique of fast production of the tool of irregular shape for profiling of variable thickness wall tubes is described. The specific technological sequence is given, recommendations about computer modeling are made, and the explaining illustration for one of characteristic cases of chosen tube type profiling is given. There is an introduction defining relevance of the solved problem, and recommendations about its solution are made. © 2019 Published under licence by IOP Publishing Ltd.The reported study was funded by the state budget themes “Theoretical foundations for the development of new processes and machines for improving the competitiveness of manufactured products”, “Developing the theoretical foundations of technologies and equipment for producing new types of metal products”

Power parameters of the process of hardening of cylindrical parts by a toroidal roller by the method of surface plastic deformation

A theoretical study of the influence of various technological factors on the force parameters of the hardening process of a cylindrical blank by a method of surface plastic deformation was performed. Based on the approximate model of plastic deformation propagation, an engineering technique has been developed that allows one to specify the force regimes of the surface hardening process with a toroidal roller, taking into account the required degree of deformation of the hardened layer, taking into account the mutual influence of the geometric parameters of the workpiece, the deforming roller and the required depth of cold work. The results of the theoretical study are in good agreement with the known experimental data and can be used in the development of technological operations for hardening machine parts by rolling in rollers or balls. © 2019 IOP Publishing Ltd. All rights reserved

Universal behavior of internal friction in glasses below T : anharmonicity vs relaxation

Comparison of the internal friction at hypersonic frequencies between a few K and the glass transition temperature Tg for various glasses brings out general features. At low temperature, internal friction is only weakly dependent on the material. At high temperature but still below Tg the internal friction for strong glasses shows a T-independent plateau in a very wide domain of temperature; in contrast, for fragile glass, a nearly linear variation of internal friction with T is observed. Anharmonicity appears dominant over thermally activated relaxational processes at high temperature.Comment: accepted in Physical Review

Generic Global Rigidity in Complex and Pseudo-Euclidean Spaces

In this paper we study the property of generic global rigidity for frameworks of graphs embedded in d-dimensional complex space and in a d-dimensional pseudo-Euclidean space R$^{2}$ with a metric of indefinite signature). We show that a graph is generically globally rigid in Euclidean space iff it is generically globally rigid in a complex or pseudo-Euclidean space. We also establish that global rigidity is always a generic property of a graph in complex space, and give a sufficient condition for it to be a generic property in a pseudo-Euclidean space. Extensions to hyperbolic space are also discussed.Engineering and Applied Science

Interaction of quasilocal harmonic modes and boson peak in glasses

The direct proportionality relation between the boson peak maximum in glasses, $\omega_b$, and the Ioffe-Regel crossover frequency for phonons, $\omega_d$, is established. For several investigated materials $\omega_b = (1.5\pm 0.1)\omega_d$. At the frequency $\omega_d$ the mean free path of the phonons $l$ becomes equal to their wavelength because of strong resonant scattering on quasilocal harmonic oscillators. Above this frequency phonons cease to exist. We prove that the established correlation between $\omega_b$ and $\omega_d$ holds in the general case and is a direct consequence of bilinear coupling of quasilocal oscillators with the strain field.Comment: RevTex, 4 pages, 1 figur

Перитонеальная лазерная допплеровская флоуметрия в прогнозировании и диагностике третичного перитонита

Relevance. The article is devoted to one of the most difficult and controversial problems in the treatment of intra-abdominal infection, the prediction and diagnosis of tertiary peritonitis. The technique of peritoneal laser Doppler flowmetry (PLDF) makes it possible to assess the degree of visceral microcirculation disorders in various diseases of the abdominal organs.Aim of study. To identify early, trigger indicators of peritoneal microcirculation in tertiary peritonitis, obtained by the PLDF method.Material and methods. A retrospective analysis of the results of treatment of 48 patients operated on for secondary diffuse purulent peritonitis in the clinic of general surgery of the Astrakhan State Medical University in the period from 2015 to 2019 was carried out. All patients were divided into two equal groups: the main group with subsequently developed tertiary peritonitis, and the comparison group with arrested peritonitis. The study of peritoneal microcirculation was performed at the time of laparotomy, after debridement, 24 and 48 hours later. A total of 768 scans were performed. Evaluation was carried out using the APACHE II scales , abdominal index and SOFA scale. Spearman’s rank correlation test was one of the main statistical methods.Results. Twenty-four hours after the primary operation, the values of the percentage of microcirculation, standard deviation and coefficient of variation showed a direct correlation with the development of tertiary peritonitis. According to Spearman’s criterion, the closeness of the relationship according to these indicators was: r=0.71, r=0.55, r=0.63, respectively, at p≤0.05. After 48 hours, all the studied values of microcirculation made it possible to diagnose tertiary peritonitis. The data obtained correlated with the data obtained by the systems for assessing the severity of the patient’s condition.Conclusion. 1. The generally accepted scales for assessing the severity of patients’ condition (APACHE II, abdominal index and SOFA) used in patients with diffuse purulent peritonitis do not allow predicting the risk of tertiary peritonitis 24 hours after surgery. The data obtained as a result of the scoring on the above scales becomes representative 48 hours after the initial intervention. 2. The percentage of microcirculation, standard deviation and coefficient of variation can be used as early screening indicators of peritonetal laser Doppler flowmetry to predict tertiary peritonitis 24 hours after primary surgery. 3. The whole range of indicators of peritoneal laser Doppler flowmetry allows the degree of impairment of the tissue microcirculation in patients with peritonitis to be objectively assessed even 48 hours after the initial operation and to be diagnostic criteria of tertiary peritonitis.Актуальность. Статья посвящена одной из самых сложных и дискуссионных проблем в лечении интраабдоминальной инфекции — прогнозированию и диагностике третичного перитонита. Методика перитонеальной лазерной допплеровской флоуметрии (ПЛДФ) позволяет оценить степень нарушений висцеральной микроциркуляции при различных заболеваниях органов брюшной полости.Цель исследования. Выявить ранние, триггерные показатели перитонеальной микроциркуляции при третичном перитоните, полученные методом ПЛДФ.Материал и методы. Проведен ретроспективный анализ результатов лечения 48 пациентов, оперированных по поводу вторичного разлитого гнойного перитонита в клинике общей хирургии Астраханского ГМУ в период с 2015 по 2019 г. Все больные разделены на две равные группы: основную — с развившемся в последующем третичным перитонитом, и сравнения — с купирующимся перитонитом. Исследование перитонеальной микроциркуляции выполнялось в момент лапаротомии, после санации, через 24 и 48 часов. Всего выполнено 768 сканирований. Оценку проводили по шкалам APACHE II, индексу брюшной полости и шкале SOFA. Одним из основных статистических методов был тест ранговой корреляции Спирмена.Результаты. Через 24 часа после первичной операции значения процента микроциркуляции, среднеквадратического отклонения и коэффициента вариации показали прямую корреляционную зависимость с развитием третичного перитонита. По критерию Спирмена теснота связи по данным показателям составила: r=0,71, r=0,55, r=0,63 соответственно при p≤0,05. Через 48 часов все исследуемые значения микроциркуляции позволяли диагностировать третичный перитонит. Полученные данные коррелировали с данными, полученными по системам оценки тяжести состояния больных.Выводы:Общепринятые шкалы оценки тяжести состоянии больных (APACHE II, индекс брюшной полости и SOFA), используемые у больных с разлитым гнойным перитонитом, не позволяют через 24 часа после операции прогнозировать риск развития третичного перитонита. Данные, полученные в результате балльной оценки по вышеперечисленным шкалам, становятся репрезентативными через 48 часов после первичного вмешательства.В качестве ранних скрининговых показателей перитонеальной лазерной допплеровской флоуметрии для прогнозирования третичного перитонита через 24 часа после первичной операции могут быть использованы: процент микроциркуляции, среднее квадратичное отклонение и коэффициент вариации.Весь спектр показателей перитонеальной лазерной допплеровской флоуметрии позволяет объективно оценить степень нарушения тканевой микроциркуляции у больных с перитонитом и через 48 часов после первичной операции являться диагностическими критериями развития третичного перитонита

Magnetic Technique for Nondestructive Evaluation of Residual Stresses

A technique has been designed for measuring planar components of stray fields from ferromagnetic samples placed in a constant magnetizing field. The technique is based on recording the field of magnetization reversal of a thin magnetic film with the small coercive force being the sensor device of a microwave detector. The possibility of measuring the deformation inhomogeneities caused by mechanical treatment when manufacturing products from ferromagnetic materials is demonstrated. The results of the magnetic measurements agree with the data from X-ray diffraction analysis.

Research and improvement of the process of two-stage profiling of tubes for special purposes

Roll-forming process is used in manufacturing multi-beam oil tubes, while reducing their outer profile diameter and forming star-like profile. In this paper a steel tubes are studied with a drawing and pushing processes. This study gets into different issues including elastoplastic behavior, contacts and friction using finite element analysis. In simulations, a plane symmetric steady-state model is used. Numerical results are compared with experimental results. A better understanding and modelling of the behavior of materials lead to a new form of roller tool with significant advantages. © 2019 Published under licence by IOP Publishing Ltd.The reported study was funded by the state budget themes “Theoretical foundations for the development of new processes and machines for improving the competitiveness of manufactured products”, “Developing the theoretical foundations of technologies and equipment for producing new types of metal products”