A 250 GHz continuous-wave (CW) gyrotron has been developed at the IAP RAS jointly with GYCOM Ltd., as a prototype of the microwave source for the envisaged prospective nuclear fusion power plants ...(DEMO). The main applications of such a tube are electron cyclotron resonance heating and electron cyclotron resonance current drive of magnetically confined plasma as well as its diagnostics based on collective Thomson scattering in various reactors for controlled thermonuclear fusion (e.g., tokamaks and stellarators). The results of the preliminary experimental tests in a pulsed mode of operation are presented. The microwave power of up to 330 kW with an efficiency of 30% without collector depression was obtained. At an accelerating voltage of 55 kV and an electron beam current of 12.5 A (which corresponds to the design parameters for CW operation), the measured output power was about 200 kW. The TEM
mode content evaluated at the tube output is not less than 98.6%.
Protein aggregation and formation of amyloid fibrils are associated with many diseases and present a ubiquitous problem in protein science. Hen egg white lysozyme (HEWL) can form fibrils both from ...the full length protein and from its fragments. In the present study, we simulated unfolding of the amyloidogenic fragment of HEWL encompassing residues 49–101 to study the conformational aspects of amyloidogenesis. The accelerated molecular dynamics approach was used to speed up the sampling of the fragment conformers under enhanced temperature. Analysis of conformational transformation and intermediate structures was performed. During the unfolding, the novel short-living and long-living β-structures are formed along with the unstructured random coils. Such β-structure enriched monomers can interact with each other and propagate into fibril-like forms. The stability of oligomers assembled from these monomers was evaluated in the course of MD simulations with explicit water. The residues playing a key role in fibril stabilization were determined. The work provides new insights into the processes occurring at the early stages of amyloid fibril assembly.
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•Thermal denaturation of amyloidogenic fragment of HEWL was studied by accelerated MD.•Amyloidogenic fragment of HEWL forms β-enriched structures at high temperature.•Denatured fragments of HEWL can form stable dimers and tetramers.
Abstract
The article is devoted to the problems of using innovative technologies in the process of training future specialists in the field of applied physics and engineering. The necessity of ...development and implementation of innovative technologies in higher education is substantiated. The effectiveness of the proposed technologies is evaluated in terms of the formation of professional competencies of bachelors. The article considers innovative approaches and the corresponding educational technologies. The experience of the development and integration of innovative technologies in the educational process of a technical university is described on the example of teaching mathematical subjects for students. The article describes the experience of the effective use of electronic educational environment of the university to create original elements of electronic educational resources, considers the possibility of introducing students to VR \ AR technologies in the framework of project activities. The article discusses the results of a training experiment in which students of technical training areas participated.
Thermodynamic solvation properties of mixtures of water with tetrahydrofuran at 298 K are studied. The Gibbs free energies and enthalpies of solvation of n-octane and toluene are determined ...experimentally. For molecular dynamics simulations of the binary solvent, we have modified a TraPPE-UA model for tetrahydrofuran and combined it with the SPC/E potential for water. The excess thermodynamic functions of neon, xenon, and hard spheres with two different radii are calculated using the particle insertion method. Simulated and real systems share the same characteristic trends for the thermodynamic functions. A maximum is present on dependencies of the enthalpy of solvation from the composition of solvent at 70–90 mol % water, making it higher than in both of the cosolvents. It is caused by a high enthalpy of cavity formation in the mixtures rich with water due to solvent reorganization around the cavity, which is shown by calculation of the enthalpy of solvation of hard spheres. Addition of relatively small amounts of tetrahydrofuran to water effectively suppresses the hydrophobic effect, leading to a quick increase of both the entropy and enthalpy of cavity formation and solvation of low polar molecules.
The design of non-destructive testing systems relates to the solution of the problem of analysis of observability. It is the assessment of the opportunities of the set of measured parameters to ...diagnose the object, to identify emerging defects and the specific modes of operation. The term 'observability' in control theory does not correspond to the tasks of diagnosis and requires the model of the object's state. The proposed concept of 'diagnostic observability' allows to use this term in tasks which aren't related to the control. It doesn't require the model of the object's state, and realizes the estimation on the array of measurements performed for various diagnosed states of the object. The set of diagnostic state variables is determined as coordinates of diagnostic orthogonal space. The proposed principle of diagnostic observability is determined by the method of construction of the space of the diagnostics and by the analysis of the images of states of object. It can become a new basis for building an effective universal adaptive systems of non-destructive testing of complex technical and other objects.
Abstract
Fatigue crack growth kinetics of various titanium alloys BT6 (α+β structure) and 3M (α-structure) under constant amplitude loading with different types of cyclic disturbances in the form of ...over- and underloading at a loading frequency of 25 Hz was investigated.The tests were conducted on a servohydraulic testing machine under controlled load with simultaneous automatic recording of loading parameters and readings from a crack opening gauge. Tests were carried out on compact specimens with an edge crack which were subjected to off-centre loading. The crack opening data was converted into crack length using a yield strength measurement method. Experimental results, namely fatigue crack growth curves and fatigue fracture kinetic diagrams, were analyzed. It is shown that crack growth kinetics depends mainly on the type of alternating loading amplitude sequences. Reliability estimation of crack growth on the basis of crack opening gauge and study of fractographic features of materials fracture has been carried out.
Increases in oscillatory β activity in the basal ganglia are regarded as one of the main electrophysiological biomarkers of impaired motor control in Parkinson’s disease. The functional role of ...dynamic changes in rhythmic activity during movement execution is still not fully understood. Microelectrode recording analysis addressed rhythmic neuronal activity in the subthalamic nucleus in nine patients with Parkinson’s disease during neurosurgical operations to implant deep brain stimulation systems. The results revealed a significant positive correlation between the amplitudes of α (7–12 Hz) and low β (12–20 Hz) activity in the subthalamic nucleus and evaluations of motor symptoms in patients with Parkinson’s disease. The amplitude of rhythmic α activity, in contrast to that of β rhythms, was also found to decrease significantly when patients performed motor tests. Moreover, the extent of decreases in α activity correlated directly with the severity of bradykinesia. The results obtained suggest that, along with β activity, the rhythmic α-activity of neurons in the subthalamic nucleus also plays a role in motor control in patients with Parkinson’s disease.
High-performance liquid chromatography (HPLC) and Raman spectroscopy have been used to study the thermal degradation of amoxicillin trihydrate. Heating this compound at 60°C for 6 h led to an ...increase in the impurity contents, each not exceeding 1%. HPLC and Raman spectroscopy can be used to evaluate the quality of an amoxicillin sample obtained after thermal degradation at 80°C.
Objective The aim was to reveal the role of oscillatory unit activity in nonspecific nuclei of thalamus in the cognitive and movement human activity. Methods The extracellular activity of neurons in ...nonspecific human brain thalamic nuclei (Rt, CM-Pf, MD) obtained by means of microelectrode technique during stereotactic neurosurgical operations was analyzed. Oscillatory neuronal activity was investigated in awake patients with spasmodic torticollis at rest and in response to presentation of cognitive tasks and voluntary movement performance. Results Analysis of single unit activity at rest allowed to reveal several patterns of spontaneous neuronal activity with tendency to periodicity in low-frequency range: low-threshold Ca2+ -dependent rhythmic bursts pattern (3–5 Hz) and grouping pattern (1–2 Hz). Stabilization of oscillatory neuronal activity (3–5 Hz) of bursting pattern accompanied by local synchronization was observed in neurons during both voluntary and involuntary pathological distonic movement realization. Appearance and/or stabilization of low-frequency rhythmicity also should be noted as an aftereffect of cognitive tasks on mathematic operations and during test on sensoroimotor tracking. Conclusions In general the data obtained shows involvement of rhythmic processes in nonspecific thalamic nuclei in the higher integrative functions of the brain. Key message microelectrode, single unit activity, thalamus, oscillations.
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