Frontal cortex functional activity modulation impact on the stereotypic, emotional and postural behavior in rats during the interictal period of pilocarpine-induced chronic epileptogenesis

The cholinergic mechanisms role determination in epileptogenesis attracts the attention of researchers. Pilocarpine administration in rats contributes to chronic form of epileptiform activity development characterized by the presence of a pronounced acute stage and an interictal period - free from behavioral convulsive reactions. We consider the most important feature of the pilocarpine-induced seizures interictal period might be the change of various forms of nonconvulsive behavior. Attempts to investigate the animals’ behavioral reactions details during the seizure-free interictal period, as well as to determine the mechanisms of similar types of behavior formation, are interesting. The purpose of the work is to investigate the motor, stereotypic and aggressive-defensive behavior of rats throughout the interictal period of pilocarpine-induced convulsive syndrome with a frontal cortex functional activity change. It was found that the severity of non-convulsive behavioral reactions in the interictal period during pilocarpine-induced chronic seizures is mostly determined by the frontal cortex functional state. At the same time, the frontal cortex hyperactivation is an important feature of pilocarpine-induced chronic epileptogenesis.  The authors proved that when the frontal cortex is activated in rats, there is an increase in horizontal and vertical motor activity, as well as the expressiveness of emotional reactions in the “open field” test and the strengthening of the aggressive-defensive behavior. In conditions of this part of the cortex selective destruction the opposite behavioral effects are noted which confirms the important role of the frontal cortex in the interictal non-convulsive behavior formation. Observed behavioral effects during the frontal cortex functional activity modulation, according to the authors, indicate the reasonability of regulatory influences searching aiming forward this brain part to activate complex mechanisms aimed to pilocarpine-induced chronic epileptiform activity elimination

Diagnostics and treatment of tumor-lysis syndrome during chemotherapy of non-Hodgkin’s lymphoma

Tumor lysis syndrome (TLS) is one of the most dangerous and serious emergency conditions in oncological practice, especially in pediatric oncology. It is characterized by acute and massive lysis of tumor cells during chemotherapy (CT), which leads to serious hematological and organ disorders in a short time. Aim: to define risk factors of developing the TLS, to form risk groups depending on the primary disease, to identify symptoms of a group of risk factors. Materials and methods. 120 cases of clinical TLS development in the CT department of Dnipro State Multi-Field Clinical Hospital № 4 were selected and analyzed. Straight and sideway signs of the development of clinical TLS were identified, the effectiveness of allopurinol and acetazolamide in the systemic treatment of TLS was estimated

Features of the Algorithmic Implementation of Difference Analogues of the Logistic Equation with Delay

The logistic equation with delay or Hutchinson’s equation is one of the fundamental equations of population dynamics and is widely used in problems of mathematical ecology. We consider a family of mappings built for this equation based on central separated differences. Such difference schemes are usually used in the numerical simulation of this problem. The presented mappings themselves can serve as models of population dynamics; therefore, their study is of considerable interest. We compare the properties of the trajectories of these mappings and the original equation with delay. It is shown that the behavior of the solutions of the mappings constructed on the basis of the central separated differences does not preserve, even with a sufficiently small value of the time step, the basic dynamic properties of the logistic equation with delay. In particular, this map does not have a stable invariant curve bifurcating under the oscillatory loss of stability of a nonzero equilibrium state. This curve corresponds in such mappings to the stable limit cycle of the original continuous equation. Thus, it is shown that such a difference scheme cannot be used for numerical modeling of the logistic equation with delay

Засоби формоутворення сучасної круглої скульптури

The basic means of formations of the form for a round sculpture, that was formed during XX century,were described in article. Questions of mutual influence of space and sculptural plastics were covered.В статье описаны основные средства формообразования круглой скульптуры, что формировалась на протяжении ХХ столетия. Освещены вопросы взаимного влияния пространства и скульптурной пластики.У статті описано основні засоби формоутворення круглої скульптури, що формувалися протягом ХХ століття. Висвітлено питання взаємовпливу простору і скульптурної пластики

Influence of levetiracetam, lithium chloride and valproic acid on the amphetamine-enhanced reactions of the self-stimulation in rats

Целью работы была оценка эффектов леветирацетама на подкрепляющие свойства самостимуляции латерального гипоталамуса у крыс по сравнению с референс-препаратами лития хлоридом и вальпроевой кислотой в условиях амфетамин-индуцированного усиления реакции самостимуляции у крыс. Леветирацетам в этих условиях дозозависимо повышал порог и снижал максимальную частоту реакций самораздражения, что позволяет предположить его ингибирующее действие на систему вознаграждения, которое сходно с действием лития хлорида и отличается от действия вальпроевой кислоты.The purpose of this work was an estimation of levetiracetam effects on reinforcing properties of self-stimulation of the lateral hypothalamus in rats as compared to the reference drugs lithium chloride and valproic acid in amphetamine-induced amplification reaction of self-stimulation in rats.The experimental data suggest that the levetiracetam has a strong influence on behavior, in particular the supporting system of the brain, which is similar to the action of lithium chloride and different from the effect of valproic acid

Особенности алгоритмической реализации разностных аналогов логистического уравнения с запаздыванием

The logistic equation with delay or Hutchinson’s equation is one of the fundamental equations of population dynamics and is widely used in problems of mathematical ecology. We consider a family of mappings built for this equation based on central separated differences. Such difference schemes are usually used in the numerical simulation of this problem. The presented mappings themselves can serve as models of population dynamics; therefore, their study is of considerable interest. We compare the properties of the trajectories of these mappings and the original equation with delay. It is shown that the behavior of the solutions of the mappings constructed on the basis of the central separated differences does not preserve, even with a sufficiently small value of the time step, the basic dynamic properties of the logistic equation with delay. In particular, this map does not have a stable invariant curve bifurcating under the oscillatory loss of stability of a nonzero equilibrium state. This curve corresponds in such mappings to the stable limit cycle of the original continuous equation. Thus, it is shown that such a difference scheme cannot be used for numerical modeling of the logistic equation with delay.Логистическое уравнение с запаздыванием или уравнение Хатчинсона представляет собой одно из фундаментальных уравнений популяционной динамики и находит широкое применение в задачах математической экологии. В работе рассматривается семейство отображений, построеннное для этого уравнения на основе центральных разделенных разностей. Такие разностные схемы обычно используются при численном моделировании данной задачи. Представленные отображения сами по себе могут служить моделями динамики популяций, поэтому их изучение представляет значительный интерес. В работе сопоставляются свойства траекторий данных отображений и исходного уравнения с запаздыванием. Показано, что поведение решений отображений, построенных на основе центральных разделенных разностей, не сохраняет, даже при достаточно малой величине шага по времени, основных динамических свойств логистического уравнения с запаздыванием. В частности, у этого отображения при колебательной потере устойчивости ненулевого состояния равновесия не бифурцирует устойчивая инвариантная кривая. Эта кривая соответствует в таких отображениях устойчивому предельному циклу исходного непрерывного уравнения. Тем самым показано, что такая разностная схема не может быть использована для численного моделирования логистического уравнения с запаздыванием

Взаимодействие двух волн в модели Ферми – Паста – Улама

The work is devoted to the dynamic properties of the solutions of boundary value problems associated with the classical system of Fermi – Pasta – Ulam (FPU). We study this problem in infinite-dimensional case, when a countable number of roots of characteristic equations tend to an imaginary axis. Under these conditions, we built a special non-linear partial differential equation, which plays the role of a quasinormal form, i.e, it defines the dynamics of the original boundary value problem with the initial conditions in a sufficiently small neighborhood of the equilibrium state. The modified Korteweg de Vries (KdV) equation and the Korteweg de Vries Burgers (KdVB) one are quasinormal forms depending on the parameter values. Under some additional assumptions, we apply the procedure of renormalization to the obtained boundary value problems. This procedure leads to an infinite-dimensional system of ordinary differential equations. We describe a method of folding this system in the special boundary value problem, which is an analogue of the normal form. The main result is that the analytical methods of nonlinear dynamics explored the interaction of waves moving in different directions, in the problem of the FPU. It was shown that waves influence on each other is asymptotically small and does not change the shape of waves, contributing only a shift in their speed, which does not change over time.Работа посвящена исследованию динамических свойств решений краевых задач, связанных с классической системой Ферми – Паста – Улама (ФПУ). При исследовании локальной динамики этих задач может реализовываться критический случай бесконечной размерности. В этих условиях построено специальное нелинейное уравнение с частными производными, которое играет роль квазинормальной формы, т.е. определяет в главном поведение всех решений исходной краевой задачи с начальными условиями из достаточно малой окрестности состояния равновесия. В зависимости от значений параметров в качестве квазинормальных форм выступают модифицированное уравнение Кортевега – де Вриза (КДВ) и уравнение Кортевега – де Вриза – Бюргерса (КДВБ). При некоторых дополнительных предположениях к полученным краевым задачам применена процедура повторной нормализации, приводящая к бесконечномерной системе обыкновенных дифференциальных уравнений, описан способ сворачивания этой системы в краевую задачу – аналог нормальной формы. Построенные квазинормальные формы позволяют судить о динамике задачи ФПУ. Основной результат работы состоит в том, что аналитическими методами нелинейной динамики изучен вопрос о взаимодействии волн, движущихся в разных направлениях, в задаче ФПУ. При рассмотрении так называемых регулярных решений описано влияние волн друг на друга, которое задается специальным интегральным соотношением. Показано, что это влияние является асимптотически малым и не меняет форму волн, внося вклад только в их скоростной сдвиг, который не меняется по времени

Anomalous terahertz photoconductivity caused by the superballistic flow of hydrodynamic electrons in graphene

Light incident upon materials can induce changes in their electrical conductivity, a phenomenon referred to as photoresistance. In semiconductors, the photoresistance is negative, as light-induced promotion of electrons across the band gap enhances the number of charge carriers participating in transport. In superconductors, the photoresistance is positive because of the destruction of the superconducting state, whereas in normal metals it is vanishing. Here we report a qualitative deviation from the standard behavior in metallic graphene. We show that Dirac electrons exposed to continuous wave (CW) terahertz (THz) radiation can be thermally decoupled from the lattice by 50~K which activates hydrodynamic electron transport. In this regime, the resistance of graphene constrictions experiences a decrease caused by the THz-driven superballistic flow of correlated electrons. We analyze the dependencies of the negative photoresistance on the carrier density, and the radiation power and show that our superballistic devices operate as sensitive phonon-cooled bolometers and can thus offer a picosecond-scale response time. Beyond their fundamental implications, our findings underscore the practicality of electron hydrodynamics in designing ultra-fast THz sensors and electron thermometers.Comment: 7 pages, 3 figure