Quasi-classical versus non-classical spectral asymptotics for magnetic Schroedinger operators with decreasing electric potentials

We consider the Schroedinger operator H on L^2(R^2) or L^2(R^3) with constant magnetic field and electric potential V which typically decays at infinity exponentially fast or has a compact support. We investigate the asymptotic behaviour of the discrete spectrum of H near the boundary points of its essential spectrum. If the decay of V is Gaussian or faster, this behaviour is non-classical in the sense that it is not described by the quasi-classical formulas known for the case where V admits a power-like decay.Comment: Corrected versio

Formation of a microcomposite structure in the surface layer of yttrium-doped titanium

Surface layers containing oxides and carbides of titanium and yttrium are prepared by the electroexplosive doping of titanium with yttrium. The subsequent electron-beam irradiation leads to dispersion of the structure to a nano- and submicron state. The formation of two types of eutectics is revealed using scanning electron microscopy. The eutectics enriched in titanium and yttrium have a globular and plate-like shape, respectively. The formation of a modified surface layer (enriched in yttrium, carbides and oxides of titanium and yttrium) leads to a threefold increase in the microhardness of the titanium, a more than twofold decrease in the friction coefficient of the doped layer, and a more than 2.8-fold decrease in the wear rate

The Research on the Heterogeneity of Carbon Plasma Flow of the Facility UVNIPA-1-001

The main goal of this research is to investigate the carbon plasma flow of facility UVNIPA-1-001, analyse its structure and consider the magnetic separation as a way to enhance the quality of vacuum ion-plasma deposition method of film coating

Surface hardening alloy VT6 of electric explosion and by electron beam

The aim is to study the phase composition, structure and properties of the surface layer of the VT6 titanium alloy, subjected to combined treatment, consisting of alloying by the plasma of an electric explosion of a graphite fiber with a charge of the SiC powder and subsequent exposure by a high-intense electron beam. As a result of such treatment, a multiphase surface layer with a submicron and nanosize structure forms with the microhardness manifold exceeding its value in the sample volume are presented

МОДИФИКАЦИЯ ПОВЕРХНОСТИ СПЛАВА ВТ6 ПЛАЗМОЙ ЭЛЕКТРИЧЕСКОГО ВЗРЫВА ПРОВОДЯЩЕГО МАТЕРИАЛА И ОБЛУЧЕНИЕМ ЭЛЕКТРОННЫМ ПУЧКОМ

The results of investigations of phase composition, structure, and properties of VT6 titanium alloy surface layer subjected to combined processing, which consists of alloying by plasma of electric explosion of carbon-graphite fiber with SiC powder specimen and subsequent high-intensity electron-beam irradiation, are given. As a result of such a treatment, a multiphase surface layer with submicro- and nanosized structure the microhardness of which many times exceeds the value in the sample bulk.Приведены результаты исследования фазового состава, структуры и свойств поверхностного слоя титанового сплава ВТ6, подвергнутого комбинированной обработке, заключающейся в легировании плазмой электрического взрыва углеграфитового волокна с навеской порошка SiC и последующем облучении высокоинтенсивным электронным пучком. В результате такой обработки формируется многофазный поверхностный слой с субмикро- и наноразмерной структурой, микротвердость которого многократно превышают ее величину в объеме образца

Experimental Detection of the CNO Cycle

Borexino recently reported the first experimental evidence for a CNO neutrino. Since this process accounts for only about 1% of the Sun’s total energy production, the associated neutrino flux is remarkably low compared to that of the pp chain, the dominant hydrogen-burning process. This experimental evidence for the existence of CNO neutrinos was obtained using a highly radio-pure Borexino liquid scintillator. Improvements in the thermal stabilization of the detector over the last five years have allowed us to exploit a method of constraining the rate of 210Bi background. Since the CNO cycle is dominant in massive stars, this result is the first experimental evidence of a major stellar hydrogen-to-helium conversion mechanism in the Universe

Solar and geoneutrinos

Thanks to the progress of neutrino physics, today we are able of exploiting neutrinos as a tool to study astrophysical objects. The latter in turn serve as unique sources of elusive neutrinos, which fundamental properties are still to be understood. This contribution attempts to summarize the latest results obtained by measuring neutrinos emitted from the Sun and geoneutrinos produced in radioactive decays inside the Earth, with a particular focus on a recent discovery of the CNO-cycle solar neutrinos by Borexino. Comprehensive measurement of the pp-chain solar neutrinos and the first directional detection of sub-MeV solar neutrinos by Borexino, the updated 8B solar neutrino results of Super-Kamiokande, as well as the latest Borexino and KamLAND geoneutrino measurements are also discussed

Identification of the cosmogenic 11C background in large volumes of liquid scintillators with Borexino

Cosmogenic radio-nuclei are an important source of background for low-energy neutrino experiments. In Borexino, cosmogenic 11C decays outnumber solar pep and CNO neutrino events by about ten to one. In order to extract the flux of these two neutrino species, a highly efficient identification of this background is mandatory. We present here the details of the most consolidated strategy, used throughout Borexino solar neutrino measurements. It hinges upon finding the space-time correlations between 11C decays, the preceding parent muons and the accompanying neutrons. This article describes the working principles and evaluates the performance of this Three-Fold Coincidence (TFC) technique in its two current implementations: a hard-cut and a likelihood-based approach. Both show stable performances throughout Borexino Phases II (2012–2016) and III (2016–2020) data sets, with a 11C tagging efficiency of ∼90 % and ∼ 63–66 % of the exposure surviving the tagging. We present also a novel technique that targets specifically 11C produced in high-multiplicity during major spallation events. Such 11C appear as a burst of events, whose space-time correlation can be exploited. Burst identification can be combined with the TFC to obtain about the same tagging efficiency of ∼90% but with a higher fraction of the exposure surviving, in the range of ∼ 66–68 %