Water structure analysis considering dielectric spectrum in microwave range

In this paper the analysis of the water dielectric spectrum in the relaxation (1 cm) and microwave (100 mu) range on the basis of the theoretical results presented in Ref. was made. The absorption spectrum in the microwave range as well as the relaxation spectrum are shown to be the results of the orientational polarization. In the framework of the existing water structure models this result corresponds to the models in which one assume two types of the molecules for the fixed time moment. They are the molecules having a hydrogen bonds and ones free from them. Free molecules either can be located in the voids or can make the exchange between the clasters. In the analysis suggested we do not use the definite water structure model. The dielectric spectrum parameters allow us estimate the value of the abnormal water expansion within the freezing process. Our results agree well with the experimental data

Dielectric relaxation of water absorbed in porous glass

The dielectric spectroscopy method was applied to the investigation of water absorbed on the inner surface of porous glass. The measurements were done using broad band dielectric spectrometry (BEDS) over a wide range of frequency (20 Hz to 1 MHz) and temperature (-100 °C to +300 °C). The dielectric response was found to be very sensitive to the geometrical micro- and mesostructural features of the porous matrix and the structure and mobility of the water filling the pores. The hindered dynamics of water molecules located within the pores and affected by the surfaces reflect the geometrical structure of the porous matrix. The analysis of the dielectric parameters as a function of the temperature enabled us to characterize the physical parameters of the dielectric spectra over an extended frequency range. © 2001 American Chemical Society

Self-consistent analytical solution of a problem of charge-carrier injection at a conductor/insulator interface

We present a closed description of the charge carrier injection process from a conductor into an insulator. Common injection models are based on single electron descriptions, being problematic especially once the amount of charge-carriers injected is large. Accordingly, we developed a model, which incorporates space charge effects in the description of the injection process. The challenge of this task is the problem of self-consistency. The amount of charge-carriers injected per unit time strongly depends on the energy barrier emerging at the contact, while at the same time the electrostatic potential generated by the injected charge- carriers modifies the height of this injection barrier itself. In our model, self-consistency is obtained by assuming continuity of the electric displacement and the electrochemical potential all over the conductor/insulator system. The conductor and the insulator are properly taken into account by means of their respective density of state distributions. The electric field distributions are obtained in a closed analytical form and the resulting current-voltage characteristics show that the theory embraces injection-limited as well as bulk-limited charge-carrier transport. Analytical approximations of these limits are given, revealing physical mechanisms responsible for the particular current-voltage behavior. In addition, the model exhibits the crossover between the two limiting cases and determines the validity of respective approximations. The consequences resulting from our exactly solvable model are discussed on the basis of a simplified indium tin oxide/organic semiconductor system.Comment: 23 pages, 6 figures, accepted to Phys.Rev.

PERFORMANCE OPTIMIZATION OF THE DIODE-PUMPED SOLID-STATE LASER FOR SPACE APPLICATIONS

Subject of Research. Thermophysical and optical techniques of parameter regulation for diode pumped solid-state laser are studied as applied to space laser communication and laser ranging lines. Methods. The investigations are carried out on the base of the original design of diode pumped solid-state laser module that includes the following: Nd:YAG slab element, diode pumped by 400W QCW produced by NORTHROP GRUMMAN; two-pass unstable resonator with rotation of the laser beam aperture about its axis through 1800; the output mirror of the resonator with a variable reflection coefficient; hyperthermal conductive plates for thermal stabilization of the laser diode generation modes. The presence of thermal conductive plates excludes conventional running water systems applied as cooling systems for solid-state laser components. The diodes temperature stabilization is achieved by applying the algorithm of pulse-width modulation of power of auxiliary electric heaters. To compensate for non-stationary thermal distortions of the slab refractive index, the laser resonator scheme comprises a prism reflector with an apex angle of 1200. Narrow sides of the prism are covered with reflective coating, and its wide side is sprayed with antireflection coating. The beam aperture is turned around its axis through 1800 because of triple reflection of the beam inside the prism. The turning procedure leads to compensating for the output beam phase distortions in view of symmetric character of the aberrations of slab refractive index. To suppress parasitic oscillations inside the slab, dielectric coatings of wide sides of the slab are used. Main Results. We have demonstrated theoretically and experimentally that the usage of hyperthermal conductive plates together with the algorithm of pulse-width modulation provides stabilizing of the diode substrate temperature accurate within ± 0.1 °С and smoothing the temperature distribution along the plate surface accurate within 1 °С. Optical schematic diagram of the laser resonator keeps the laser beam divergence not exceeding a diffraction limit more than twice under a light pump power of 100 W. We have also shown that to increase the lasing efficiency, slab multilayer dielectric coatings made of SiO2 и ZrO2 should be used. Practical Relevance. We have proposed original design of the diode pumped solid-state laser module optimizing the generation and pump modes of solid-state lasers by the temperature stabilization technique for laser diode array and by compensation of the slab aberrations. The techniques are also applicable under space conditions; that is an important factor at developing the space-based lasers

Simulation of wavepacket tunneling of interacting identical particles

We demonstrate a new method of simulation of nonstationary quantum processes, considering the tunneling of two {\it interacting identical particles}, represented by wave packets. The used method of quantum molecular dynamics (WMD) is based on the Wigner representation of quantum mechanics. In the context of this method ensembles of classical trajectories are used to solve quantum Wigner-Liouville equation. These classical trajectories obey Hamilton-like equations, where the effective potential consists of the usual classical term and the quantum term, which depends on the Wigner function and its derivatives. The quantum term is calculated using local distribution of trajectories in phase space, therefore classical trajectories are not independent, contrary to classical molecular dynamics. The developed WMD method takes into account the influence of exchange and interaction between particles. The role of direct and exchange interactions in tunneling is analyzed. The tunneling times for interacting particles are calculated.Comment: 11 pages, 3 figure

Does it make sense to study heart rate variability in episodes of paroxysmal atrial fibrillation during the 24-hour electrocardiographic monitoring?

Aim. To study the characteristics of heart rate variability (HRV) in episodes of paroxysmal atrial fibrillation (AF) and sinus rhythm (SR) during the 24-hour Holter electrocardiographic (ECG) monitoring and to assess the presence and nature of their relationships. Material and methods. We analyzed 37 records of 24-hour Holter ECG monitoring obtained from patients with paroxysmal AF. For analysis, records were selected from the Long Term Atrial Fibrillation database (LTAFDB) (n=26), as well as from the long-term storage database “Myocard-holter” of the Sverdlovsk Regional Clinical Hospital № 1 (n=11). Each record contained at least 120 min of SR and at least 120 min of paroxysmal AF episodes. In addition, 48 HRV indices were calculated independently for SR and for AF episodes, after which the 96 HRV parameters obtained for each record were subjected to exploratory data analysis. Results. Analysis of HRV in AF paroxysm showed a significant increase in the RMSSD, SD1, pNN50 indices, which confirmed the great importance of para-sympathetic influence in the regulation of AF. Despite the fact that single HRV parameters in AF are not directly related to any single parameters in SR, we have shown that the AF is not completely chaotic and independent of the characteristics of baseline HR variability. We found that for some of the HRV indices determined during AF paroxysm (PAF_CVI, PAF_pNN20, PAF_pNN50, PAF_ApEn, PAF_SDNN, PAF_SD2), up to 74% of the variance of these indices can be explained using multivariate linear models, including 4 HRV indices for SR and taken as predictors. It was shown that among all the indices analyzed, only the PAF_HTI, calculated in paroxysmal AF, had a moderate negative correlation with the duration of AF episodes (r=0,60, p<0,01). Conclusion. It is shown that the study of HRV indices on AF paroxysm has a wide clinical and electrophysiological potential. The paper proposes statistical models that demonstrate the relationship between HRV in SR and in the rhythm of AF episode. The PAF_HTI index, assessed on episodes of AF, showed a relationship with the duration of AF episodes, which suggests the expediency of using HRV characteristics on AF to assess the possibility of SR recovery. © 2022, Silicea-Poligraf. All rights reserved

Tensor Ayy and vector Ay analyzing powers in the H(d,d')X and ^{12}C(d,d')X reactons at initial deuteron momenta of 9 GeV/c in the region of baryonic resonances excitation

The angular dependence of the tensor Ayy and vector Ay analyzing powers in the inelastic scattering of deuterons with a momentum of 9.0 GeV/c on hydrogen and carbon have been measured. The range of measurements corresponds to the baryonic resonance excitation with masses 2.2--2.6 GeV/c^2. The Ayy data being in good agreement with the previous results demonstrate an approximate $t$ scaling up to -1.5 (GeV/c)^2. The large values of A_y show a significant role of the spin-dependent part of the elementary amplitude of the NN->NN* reaction. The results of the experiment are compared with model predictions of the plane-wave impulse approximation.Comment: 7 pages, 7 figures. submitted to Yad.Fi

Additional possibilites risk stratification of ischemic stroke in patients with atrial fibrillation and one risk factor for thromboembolic complications on cha2ds2-vasс scale

The article considers the risk stratification issues of ischemic stroke in patients with atrial fibrillation, proposed to use additional criteria to facilitate the decision on the appointment or not appointment of anticoagulant therapy in this group of patientsВ статье рассмотрены вопросы стратификации риска развития ишемического инсульта у пациентов с фибрилляцией предсердий, предложены к использованию дополнительные критерии, призванные облегчить принятие решения о назначении или не назначении антикоагулянтной терапии данной группе пациенто