Nitric oxide mediates local activity-dependent excitatory synapse development

Learning related paradigms play an important role in shaping the development and specificity of synaptic networks, notably by regulating mechanisms of spine growth and pruning. The molecular events underlying these synaptic rearrangements remain poorly understood. Here we identify NO signaling as a key mediator of activity-dependent excitatory synapse development. We find that chronic blockade of NO production in vitro and in vivo interferes with the development of hippocampal and cortical excitatory spine synapses. The effect results from a selective loss of activity-mediated spine growth mechanisms and is associated with morphological and functional alterations of remaining synapses. These effects of NO are mediated by a cGMP cascade and can be reproduced or prevented by postsynaptic expression of vasodilator-stimulated phosphoprotein phospho-mimetic or phospho-resistant mutants. In vivo analyses show that absence of NO prevents the increase in excitatory synapse density induced by environmental enrichment and interferes with the formation of local clusters of excitatory synapses. We conclude that NO plays an important role in regulating the development of excitatory synapses by promoting local activity-dependent spine-growth mechanisms

Structure and phase composition of the superalloy on the basis of Ni-Al-Cr alloyed by Re and La

Qualitative and quantitative studies of the structure, phase composition, morphology of phase of the high-rhenium alloys additionally doped with La were carried out by TEM and SEM methods. The alloy was obtained by directional solidification method. It was shown that introduction of Re and La to an alloy leads to formation of new phases: [beta] and [chi] , which bring serious irregularities in the structure of quasicuboids of [gamma]'-phase

The structure of heat-resisting alloy modified by thermal treatment and alloyed by rhenium and lanthanum

The paper presents the scanning and transmission electron microscope investigations of the structure, phase composition, and morphology of heat-resisting alloy modified by thermal treatment and additionally alloyed by rhenium and lanthanum. Rhenium alloy is obtained by the directional crystallization technique. The structural investigations are carried out for three alloy states, i.e. 1) original (after the directional crystallization); 2) 1150°С annealing during 1 h and 1100°С annealing during 480 h; 3) 1150°С annealing during 1 h and 1100°С annealing during 1430 h. It is shown that fcc-based [gamma]- and [gamma]'-phases are primary in all states of the alloy. [gamma]'-phase has L12 structure, while [gamma]-phase is a disordered phase. Rhenium and lanthanum are phase-forming elements. Investigations show that high-temperature annealing modifies the structural and phase conditions of the heat-resisting alloy

The structure of heat-resisting alloy modified by thermal treatment and alloyed by rhenium and lanthanum

The paper presents the scanning and transmission electron microscope investigations of the structure, phase composition, and morphology of heat-resisting alloy modified by thermal treatment and additionally alloyed by rhenium and lanthanum. Rhenium alloy is obtained by the directional crystallization technique. The structural investigations are carried out for three alloy states, i.e. 1) original (after the directional crystallization); 2) 1150°С annealing during 1 h and 1100°С annealing during 480 h; 3) 1150°С annealing during 1 h and 1100°С annealing during 1430 h. It is shown that fcc-based [gamma]- and [gamma]'-phases are primary in all states of the alloy. [gamma]'-phase has L12 structure, while [gamma]-phase is a disordered phase. Rhenium and lanthanum are phase-forming elements. Investigations show that high-temperature annealing modifies the structural and phase conditions of the heat-resisting alloy

The effect of aluminum ion implantation on the grain size and structure of UFG titanium

Using the transmission electron microscopy technique, we have studied the structural-phase state of UFG titanium with an average grain size ~0.2 μm implanted with aluminum ions. An MEVVA-V.RU source has been used to implant the specimen at room temperature, implantation time 5.25 hours, and irradiation dose 1⋅1018 ion/cm2. To produce the UFG titanium samples, we have employed the combined multiple uniaxial pressing technique (abc-pressing) followed by grooved rolling and subsequent annealing at 573 K for one hour. The samples have been studied in two states: 1) before implantation (initial state) and 2) after implantation at a distance 70-100 nm from the sample surface. We have obtained the aluminum concentration profile of implanted α-Ti. It has been established that the maximum concentration of aluminum is 70 at.% and the thickness of the implanted layer is 200 nm. We have determined the grain distribution functions over the grain size, calculated the grain anisotropy coefficient before and after implantation. It has been established that implantation decreases the average longitudinal and transversal sizes of α-Ti grains, and reduces the anisotropy coefficient by three times. It has been established that aluminum implantation into titanium brings about formation of a whole set of phases with different crystal lattices, namely, β-Ti, TiAl3, Ti3Al, TiC, and TiO2

Моделирование управления потоками данных в корпоративных IP-сетях

Розглянуто моделі трьох методів управління мережевим трафіком, що забезпечують недопущення перевантажень телекомунікаційних каналів. В основу апаратної моделі лягла технологія обмеження потоків даних через мережеві вузли. Програмна модель є регулятором, який на основі порівняння вхідного та бажаного значень завантаженості каналів виробляє команди для джерел трафіку. Третя модель використовує методи теорії автоматичного управління для обмеження потоків трафіку, а саме оптимальний по швидкодії регулятор. Наводиться структура і опис всіх цих моделей, а також проаналізовані переваги та недоліки кожної з моделей за такими критеріями: швидкодія регулятора, тобто швидкість, з якою регулятор виробляє необхідну керуючу дію; вплив затримок передачі даних на своєчасність регулюючої дії; види трафіку, які здатен регулювати регулятор; простота розрахунку та реалізації регулятора; ефективне використання наявних мережевих ресурсів.Three network traffic management models preventing telecommunication links overloads have been considered here. Hardware model is based upon limitation of data streams flowing through network nodes. Program model is presented by a controller which by means of comparing input and desired values of channel load generates commands for the traffic sources. The third model uses the methods of automatic control theory to manage the flow of traffic, in particular the regulator with optimal performance. The structure and description of all models, as well as the advantages and disadvantages of each model, by such criteria: speed of controller (the speed with which the controller produces management commands); the impact of data transferring delays on the timeliness of the managing; types of traffic which can be managed by the controller; simplicity of controller's calculation and implementation; effective use of available network resources, are included.Рассмотрены модели трех методов управления сетевым трафиком, которые обеспечивают недопущение перегрузок телекоммуникационных каналов. В основу аппаратной модели легла технология ограничения потоков данных, проходящих через сетевые узлы. Программная модель является регулятором, который на основе сравнения входного и желаемого значений загруженности каналов вырабатывает команды для источников трафика. Третья модель использует методы теории автоматичного управления для ограничения потоков трафика, а именно оптимальный по быстродействию регулятор. Приводится структура и описание всех этих моделей, а также проанализированы преимущества и недостатки каждой моделей по следующим критериям: быстродействие регулятора, то есть скорость, с которой регулятор вырабатывает необходимое управляющее воздействие; влияние задержек передачи данных на своевременность регулирующего воздействия; виды трафика, которые способен ограничивать регулятор; простота расчета и реализации регулятора; эффективное использование имеющихся сетевых ресурсов

Hardening by ion implantation of VT1-0 alloy having different grain size

The paper presents a transmission electron microscopy (TEM) study of the structural and phase state of commercially pure titanium implanted by aluminum ions. TEM study has been carried out for two types of grains, namely coarse (0.4 µm) and small (0.5 µm). This paper presents details of the yield stress calculations and the analysis of strength components for the both grain types in two areas of the modified layer: at a distance of 0-150 nm (surface area I) and ∼300 nm (central area II) from the irradiated surface. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress in areas I and II. Thus, near the ion-alloyed layer, the yield stress decreases with the increase of the grain size, whilst area II demonstrates its increase. Moreover, the contribution to the general hardening of the alloy made by certain hardening mechanisms differs from contributions made by each of these mechanisms in each certain case

Modification of structural phase state and mechanical properties of poly-grained titanium alloy implanted by aluminum ions

The paper presents TEM analysis of microstructure, phase composition, and mechanical properties of commercially pure titanium. These properties of two types of grains are compared before and after modification of titanium by aluminum ions, namely: large grains (1.4 μm) and small (0.5μm) grains. The analysis shows that ion implantation results in a considerable improvement of mechanical properties of both large and small grains throughout their implantation depth. However, with increase of the grain size, the stress in the ion-modified surface layer decreases while in the subsurface layer it increases