Entrainment, stopping, and transmission of microwave solitons of self-induced transparency in counter-propagating magnetized electron beam.

Based on numerical simulations of a boundary problem, we study various scenarios of microwave soliton formation in the process of cyclotron resonance interaction of a short electromagnetic pulse with a counter-propagating initially rectilinear electron beam taking into account the relativistic dependence of the cyclotron frequency on the electrons' energy. When a certain threshold in the pulse energy is exceeded, the incident pulse can propagate without damping in the absorbing beam, similar to the effect of self-induced transparency in optics. However, mutual motion of the wave and electrons can lead to some novel effects. For relatively small energy of the incident pulse, the microwave soliton is entrained by the electron beam opposite to the direction of the wave's group velocity. With an increase in the pulse energy, soliton stopping occurs. This regime is characterized by the close-to-zero pulse velocity and can be interpreted as a variety of the "light stopping." High-energy microwave solitons propagate in the direction of the unperturbed group velocity. Their amplitude may exceed the amplitude of the incident pulse, i.e., nonlinear self-compression takes place. A further increase in the incident energy leads to the formation of additional high-order solitons whose behavior is similar to that of the first-order ones. The characteristics of each soliton (its amplitude and duration) correspond to analytical two-parametric soliton solutions that are to be found from consideration of the unbounded problem.

Generation of Rogue Waves in Gyrotrons Operating in the Regime of Developed Turbulence.

Within the framework of the average approach and direct 3D PIC (particle-in-cell) simulations, we demonstrate that the gyrotrons operating in the regime of developed turbulence can sporadically emit "giant" spikes with intensities a factor of 100-150 greater than the average radiation power and a factor of 6-9 exceeding the power of the driving electron beams. Together with the statistical features such as a long-tail probability distribution, this allows the interpretation of generated spikes as microwave rogue waves. The mechanism of spikes formation is related to the simultaneous cyclotron interaction of a gyrating electron beam with forward and backward waves near the waveguide cutoff frequency as well as with the longitudinal deceleration of electrons.

Phase-Imposing Initiation of Cherenkov Superradiance Emission by an Ultrashort-Seed Microwave Pulse.

For the first time, we demonstrate experimentally the possibility of Cherenkov superradiant generation with a phase imposed by an ultrashort seed microwave pulse. The phases of seed and initiated Ka-band microwave pulses were correlated with the accuracy of 0.5-0.7 rad for the power ratio down to -35 dB. Characteristics of such a process were determined in the frame of a basic theoretical model that describes both spontaneous and stimulated emission of an electron beam moving in corrugated waveguides. The obtained results open up opportunities of reaching extremely high radiation power density in phased arrays of short-pulse coherently operating microwave generators.

Generation of Subterahertz Superradiance Pulses Based on Excitation of a Surface Wave by Relativistic Electron Bunches Moving in Oversized Corrugated Waveguides.

The first experiments on the observation of short pulsed superradiant (SR) emission with the excitation of a surface wave by a relativistic electron bunch moving in an oversized corrugated waveguide were performed. Subterahertz SR pulses with a central frequency of 0.14 THz, an ultrashort duration of 150 ps, and an extremely high peak power of 50-70 MW were generated. The experiments were based on a theoretical consideration including the quasioptical approach and direct particle-in-cell simulations.

Generation of electromagnetic fields of extremely high intensity by coherent summation of Cherenkov superradiance pulses.

We demonstrate both theoretically and experimentally the possibility of correlating the phase of a Cherenkov superradiance (SR) pulse to the sharp edge of a current pulse, when spontaneous emission of the electron bunch edge serves as the seed for SR processes. By division of the driving voltage pulse across several parallel channels equipped with independent cathodes we can synchronize several SR sources to arrange a two-dimensional array. In the experiments carried out, coherent summation of radiation from four independent 8-mm wavelength band SR generators with peak power 600 MW results in the interference maximum of the directional diagram with an intensity that is equivalent to radiation from a single source with a power of 10 GW.

[Atrial Fibrillation in Patients With Chronic Obstructive Pulmonary Disease Is Associated With Polymorphism of Interleukin 6 Gene].

UNLABELLED: It can be suggested that development of atrial fibrillation (AF) in patients with chronic obstructive pulmonary disease (COPD) is directly related to the system of inflammation. Genetic polymorphism of factors of this system can be one of components of mechanism of AF in COPD. Aim: to elucidate polymorphic markers of genes of factors of the system of inflammation associated with AF in patients with COPD. Material and methods. We examined 208 patients with COPD (52 with and 156 without AF). Examination included spirometry, echocardiography, and study of frequencies of polymorphic markers G(-238)A, G(-308)A of tumor necrosis factor (TNF) gene, C(-819)T of interleukin (IL) 10 gene, G(-174)C of IL-6 gene, rs2228145(AC) of IL-6R gene, and rs2069762(A/C) of IL-2 gene. RESULTS. Factors associated with AF were left atrial volume (odds ratio [OR] 1.021, 95% confidence interval [ClI] 1.004-1.043, p = 0,027), right atrial volume (OR 1.02, 95% CI 1.001-1.040, p=0.021), and carriage of C allele of polymorphic marker G(-174)C of IL-6 gene (OR 6.02, 95% Cl 1.87-19.38, p = 0.003). CONCLUSION: C allele of polymorphic marker G(-174)C of IL-6 gene can be considered to be independently associated with development of AF in patients with COPD.

Conversion of an electromagnetic wave into a periodic train of solitons under cyclotron resonance interaction with a backward beam of unexcited electron-oscillators.

The possibility of the conversion of intense continuous microwave radiation into a periodic train of short pulses by means of resonant interaction with a beam of unexcited cyclotron electron oscillators moving backward is shown. In such a system there is a certain range of parameters where the incident stationary signal splits into a train of short pulses and each of them can be interpreted as a soliton. It is proposed to use this effect for amplitude modulation of radiation of short wavelength gyrotrons.

[Laboratory monitoring of the efficacy and safety of anticoagulants].

Currently, the pharmaceutical market there are a large number of anticoagulants, each of which has a number of features. An important factor influencing the choice of drug, is whether or not the methodology of fixing its efficacy and safety. The aim of this review is to describe current approaches to the control of the efficacy and safety of anticoagulants.

3D quasioptical theory of terahertz superradiance of an extended electron bunch moving over a corrugated surface.

We consider the superradiance of an extended relativistic electron bunch moving over a periodically corrugated surface for the generation of multimegawatt terahertz pulses. To study the above process we have developed a three-dimensional, self-consistent, quasioptical theory of Cherenkov stimulated emission which includes a description of the formation of an evanescent wave over a corrugated surface and its excitation by rf current induced in the electron bunch.

[Mechanisms of development of thromboembolic complications in patients with atrial fibrillation].

Thomboembolism is the most threatening complication in patients with atrial fibrillation. Main source of embolism is the left atrial thrombosis. Mechanisms of development of thromboembolic complications in patients with arrhythmias are far from being deciphered. In this review we discuss possible mechanisms of formation of intracardiac thrombus - abnormalities of functioning of the hemostasis system, endothelial dysfunction, inflammatory reactions, fibrosis of the left atrial wall, genetic traits.

High-power terahertz-range planar gyrotrons with transverse energy extraction.

To increase the output power of terahertz gyrotrons to several hundred kilowatts, we suggest using a planar geometry of interaction space with a sheet electron beam and transverse energy extraction. An advantage of this scheme in comparison with conventional cylindrical geometry is the possibility to ensure effective mode selection over the open transverse coordinate in combination with radiation outcoupling that leads to a substantial reduction of Ohmic losses. Similar to unstable resonators in optics for further growth of the radiation power it is beneficial to introduce waveguide tapering.

Modulation instability of an electromagnetic wave interacting with a counterpropagating electron beam under condition of cyclotron resonance absorption.

In this paper, transmission of a monochromatic wave through a counterpropagating electron beam under the condition of cyclotron resonance absorption is studied by theoretical analysis and numerical simulation. Conditions of the modulation instability (MI) are analyzed. The MI strongly affects the regimes of transmission. We also derive explicit periodic stationary solutions expressed in terms of elliptic Jacobi functions, as well as bright- and dark-soliton solutions. Analysis of these solutions allows obtaining threshold values of the driving power and frequency for the different regimes of transmission, such as cyclotron absorption, multifrequency self-modulation oscillations, and stationary single-frequency propagation. The theoretical predictions are verified by numerical simulation. In this way, we obtain the conditions at which a continuous-wave driving signal disintegrates into a close-to-periodic train of microwave soliton pulses.

[Risk and benefit of oral anticoagulants in atrial fibrillation].

Thromboembolism is the main cause of death and disability of patients with atrial fibrillation. Indirect anticoagulants are effective means of primary and secondary prevention of thromboembolic complications. However in a number of patients risk associated with therapy with indirect anticoagulants might exceed potential benefit. The principle problem requiring solution in a patient with atrial fibrillation is individual comparative assessment of risk of development of thromboembolic and hemorrhagic complications. Modern stratification scales which allow solving this problem are considered in this review.

Self-induced transparency and electromagnetic pulse compression in a plasma or an electron beam under cyclotron resonance conditions.

Based on analogy to the well-known process of the self-induced transparency of an optical pulse propagating through a passive two-level medium we describe similar effects for a microwave pulse interacting with a cold plasma or rectilinear electron beam under cyclotron resonance condition. It is shown that with increasing amplitude and duration of an incident pulse the linear cyclotron absorption is replaced by the self-induced transparency when the pulse propagates without damping. In fact, the initial pulse decomposes to one or several solitons with amplitude and duration defined by its velocity. In a certain parameter range, the single soliton formation is accompanied by significant compression of the initial electromagnetic pulse. We suggest using the effect of self-compression for producing multigigawatt picosecond microwave pulses.

[The system of hemostasis in patients with atrial fibrillation: markers of left auricular thrombosis].

Thrombosis of the left atrial appendage (LAA) is considered to be main cause of thromboembolic complications of atrial fibrillation (AF). Aim of this work was to study parameters of the hemostasis system in patients with AF in dependence on the presence of thrombus in the LAA. We examined 92 patients (58 men and 34 women) who at hospital admission had AF attack which lasted more than 48 hours. In patients with thrombus in the LAA according to data of transesophageal echocardiography differed magnitude of mean pulmonary artery pressure (odds ratio [OR] 1.053 95% confidence interval [CI] 1.007 to 1.102, p=0.024), diameter of left ventricular (LV) outflow tract (OR 7.711 95% CI 1.291 to 46.029, p=0.025), LV ejection fraction less than 40% (OR 0.286 95% CI 0.081 to 1.008, p=0.051), levels of type 1 plasminogen activator inhibitor-PAI-1 (OR 0.641 95% CI 0.422 to 0.974, p=0.037), and D-dimer (OR 1.003, 95% CI 1.000 to 1.006, p=0.046). Factors independently related to the presence of thrombus in LAA turned out only levels of PAI-1 (OR 0.51, 95% CI 0.276 to 0.936, p=0.03) and D-dimer (OR 1.01, 95% CI 1.001 to 1.014, p=0.026). Thus depletion of the system of fibrinolysis can lead to thrombus formation in the LAA and increase risk of development of thromboembolic complications.

[Predictors of intracardiac thrombosis in patients with atrial fibrillation: factors of hemostasis, markers of inflammation, and genetic factors].

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. Many patients with nonvalvular AF have substantial rates of stroke and thromboembolism. The left atrial appendage (LAA) is a common source of cardiac thrombus formation associated with systemic embolism. Recent findings have suggested a link between inflammatory and haemostatic disturbance and genesis of the LAA thrombus. In this review, we describe the genetic variations probably involved in the pathogenesis of LAA thrombosis, their functional implications, and their association with thromboembolic risk. We consider polymorphisms in coagulation factors and the inflammatory markers.

[Detection of left atrial auricular thrombus in patients with atrial fibrillation and risk factors of thromboembolic complications: the role of transesophageal echocardiography and multispiral computer tomography].

Transesophageal echocardiography (TEE) is routinely used for visualization of left auricular thrombi in patients with atrial fibrillation (AF). Multispiral computed tomography (MSCT) with the use of contrast preparations is a novel method of visualization of intracardiac structures. Forty three patients (27 men, 16 women aged 46-81 years) with duration of atrial fibrillation > 48 hours and scheduled for sinus rhythm restoration were included in this study. TEE and MSCT were carried out in all patients during first 3 days of hospitalization. If according to both methods there were no thrombi in the left auricle cardioversion was performed. If data of one of the methods were suspicious of left auricular thrombus cardioversion was not performed. In these patients both investigations were repeated after 8 weeks of therapy with warfarin. If initially detected mass decreased or disappeared at the background of indirect anticoagulants, it was considered to be a thrombus. In 1/3 of patients repeat examination allowed to reject initial diagnosis of left auricular thrombosis. Simultaneous application of TEE and MSCT detected more thrombi than the use of either of these methods. Rate of detection of thrombi in left atrial auricle with the use of both methods was 32%.

Generation of Cherenkov superradiance pulses with a peak power exceeding the power of the driving short electron beam.

Theoretical investigation of a short electron beam (extended bunch) interaction with a backward wave propagating in a slow wave structure demonstrates the possibility of producing ultrashort superradiance pulses with a peak power which exceeds the power of the driving beam (conversion factor K>1). It is shown that a nonuniform slow wave structure with optimized profile is beneficial in order to increase the conversion factor. The results of theoretical analysis are confirmed by the experiments. At X band using the SINUS-150 accelerator (4 ns, 330 kV, 2.6 kA) 0.6-0.8 ns superradiance pulses with a peak power of 1.2 GW and a conversion factor of 1.5 were obtained. Similar experiments at Ka-band based on the RADAN-303 accelerator (1 ns, 290 kV, 2.5 kA) demonstrated production of the superradiance (SR) pulse with duration 200 ps and peak power about 1 GW (conversion factor of 1.4).