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In recent years, possible therapeutic effects of transcranial direct current stimulation (tDCS) have been widely investigated in studies dealing with different types of neural pathologies. Initially, tDCS was applied for treatment of patients with motor stroke; later on, it was introduced into studies of patients with Alzheimer's disease, multiple sclerosis, Parkinson's disease, schizophrenia, and post-stroke aphasia. Recent reviews of tDCS application in patients with post-stroke aphasia did not provide coherent evidence on the tDCS efficiency. There were no uniform protocols of stimulation used, patients' selection criteria were highly divergent, and the reports of treatment outcomes varied dramatically. In this review, we will focus on the reported heterogeneity of tDCS effects, trying to disentangle its putative underpinnings rooted in the diversity of lesion types, aphasia severity, and recovery stages. Given the current theoretical models suggesting the qualitatively different patterns of brain activity to accompany post-stroke aphasia recovery, a number of physiological factors should be taken into account to choose optimal tDCS parameters. With this in mind, we assess results of ten studies applying tDCS in post-stroke aphasia treatment, and, based on this analysis, suggest directions for further research in this rapidly developing field. [ABSTRACT FROM AUTHOR]

Soft γ-ray repeaters exhibit bursting emission in hard X-rays and soft γ-rays. During the active phase, they emit random short (milliseconds to several seconds long), hard-X-ray bursts, with peak luminosities1 of 1036 to 1043 erg per second. Occasionally, a giant flare with an energy of around 1044 to 1046 erg is emitted2. These phenomena are thought to arise from neutron stars with extremely high magnetic fields (1014 to 1015 gauss), called magnetars1,3,4. A portion of the second-long initial pulse of a giant flare in some respects mimics short γ-ray bursts5,6, which have recently been identified as resulting from the merger of two neutron stars accompanied by gravitational-wave emission7. Two γ-ray bursts, GRB 051103 and GRB 070201, have been associated with giant flares2,8–11. Here we report observations of the γ-ray burst GRB 200415A, which we localized to a 20-square-arcmin region of the starburst galaxy NGC 253, located about 3.5 million parsecs away. The burst had a sharp, millisecond-scale hard spectrum in the initial pulse, which was followed by steady fading and softening over 0.2 seconds. The energy released (roughly 1.3 × 1046 erg) is similar to that of the superflare5,12,13 from the Galactic soft γ-ray repeater SGR 1806−20 (roughly 2.3 × 1046 erg). We argue that GRB 200415A is a giant flare from a magnetar in NGC 253. The γ-ray burst GRB 200415A is probably a giant flare emitted from a magnetar in the nearby starburst galaxy NGC 253. [ABSTRACT FROM AUTHOR]

The present work is devoted to determining the conditions of the joint operation of photoelectric converter-solar concentrator pairs, which are used in solar power plants with concentrators. Three-cascade photoconverters based on AB materials with different distributions of solar radiation in spectral ranges are studied. Concentrators of solar radiation are designed as the Fresnel lenses with silicon-on-glass structure. Refractive lens profile fabricated on the basis of Wacker RT604 silicone rubber is characterized by significant changes in refractive index with temperature. The effect of geometric parameters of the Fresnel lenses and their operating temperature on characteristics of solar radiation concentration in specified spectral intervals have been examined. The parameters of concentrators being paired with a photoelectric converter, which may ensure the efficient functioning of the solar power plant, have been calculated. [ABSTRACT FROM AUTHOR]

We have developed a method for determining parameters of radiation concentrator in solar power plants. To estimate the efficiency of concentrators in the form of Fresnel lenses in setups with three-junction photoelectric converters, the concept of the efficiency of the concentrator-photoelectric converter pair has been introduced. We have proposed a method for calculating the refracting profile of concentrators taking into account the dispersion relation for the refractive index and its variations with temperature for the material of the refracting profile of the concentrator (Wacker RT604 silicone compound). The results of calculation make it possible to achieve the maximal efficiency of the concentrator-photoelectric converter pair in the presence of chromatic aberrations in the optical system of solar radiation concentration. [ABSTRACT FROM AUTHOR]

The Nobeyama Radioheliograph observation results and data from the KONUS-Wind spectrometer mounted at the Wind and RHESSI satellites on several solar flares are jointly analyzed. The analysis results for data on the flare of July 18, 2002 are described. The hard X-rays were measured in the 18 keV-15 MeV range (KONUS-Wind), and spectroheliograph measurements were carried out in the radio range at frequencies of 17 and 34 GHz. Spatial distributions of the radio brightness were calculated for the flare of July 18, 2002; they show the presence of two sources at the footpoints and one source at the top of the supposed flaring loop. The energy spectra of hard X-rays, energy flux, and the total number of accelerated electrons were found from the KONUS spectrometer data. The number of accelerated X-ray emitted electrons was estimated as N ≥ 10, and the maximum X-ray energy flux was estimated as ∼5 × 10 erg cm s. The spectrum index varies in time from −4.6 to −3.6, i.e., the soft-hard-harder trend is implemented. The spectral index of the radio waves is α ≈ −0.3 at the flare start, attains the value α ≈ −0.5 at the flux maximum, and even change the sign further. The accelerated electron transport model in the flare loop plasma is suggested for interpretation of relationships between parameters of the radio emission and hard X-rays. [ABSTRACT FROM AUTHOR]

The studies of the cosmic gamma-ray bursts and soft gamma repeaters that have been performed in the Russian-American Konus-Wind experiment during the last several years have been summarized. The experiment has been continuously performed using the Konus Russian scientific instrument on the Wind American spacecraft since 1994 under the optimal interplanetary space conditions in the absence of noise caused by the Earth's radiation belts and the shadowing of detectors. Two high-sensitivity detectors have constantly observed the entire celestial sphere and recorded detailed time and spectral characteristics of bursts in a wide range of energies (20 keV-15 MeV). The Konus-Wind data have been widely used in the present-day multiwave studies of gamma-ray bursts. [ABSTRACT FROM AUTHOR]

The results of an investigation of afterpulses arising in a proportional counter due to the photoeffect on the cathode are presented. It was found that, as the gas amplification changes, the amplitude of afterpulses becomes proportional to the square amplitude of the primary pulse, and that the coefficient of proportionality can serve as a criterion for comparing the emission properties of cathodes made of various materials. Such a comparison was performed for cathodes of stainless steel, copper, beryllium and aluminum alloys. It was found that phosphatizing of aluminum produces a coating, which essentially reduces the photoeffect on the cathode. Unlike anodic oxidation, a phosphate layer possesses sufficient conductivity that prevents spontaneous discharges in a counter caused by accumulation of electrical charges followed by an electrical breakdown of the coating layer. [ABSTRACT FROM AUTHOR]