Defect formation in the intermediate layers of YBa₂Cu₃O₇₋δ superconductors depending on oxygen сontents

In YBa₂Cu₃O₇₋δ superconductors with 0≤δ0.3 the subthreshold defect formation in the intermediate layers is not observed. The subthreshold defect formation is related to the Coulomb ejection of atoms from the lattice sites in the field of the weakly damped low-frequency collective excitations enhanced by irradiation in YBa₂Cu₃O₇₋δ superconductors with δ≤0.3

Subthreshold defect formation in YBa₂Cu₃O₇₋δ at nonuniform heating of electron gas in electromagnetic field

In YBa₂Cu₃O₇₋δ high temperature superconductors with δ<0.3 the irradiation by super high-frequency electromagnetic field with impulse power 10⁴-10⁶ W gives rise to a decrease of the rates of annihilation and capture of positrons, a growth of resistance, residual resistance, thermopower and the block of diffusive transitions of Au atoms, which are caused by the subthreshold defect formation in the intermediate layers. The irradiation effect is enhanced with rise of the number of defects in samples and does not depend on an impulse power. The defect formation is related to the excitation of low-frequency weakly damped collective excitations under irradiation, whose propagation through the crystal is accompanied by the Coulomb ejection of atoms from the lattice sites and the transformation and transport of defects

Big bounce from spin and torsion

The Einstein-Cartan-Sciama-Kibble theory of gravity naturally extends general relativity to account for the intrinsic spin of matter. Spacetime torsion, generated by spin of Dirac fields, induces gravitational repulsion in fermionic matter at extremely high densities and prevents the formation of singularities. Accordingly, the big bang is replaced by a bounce that occurred when the energy density $\epsilon\propto gT^4$ was on the order of $n^2/m_\textrm{Pl}^2$ (in natural units), where $n\propto gT^3$ is the fermion number density and $g$ is the number of thermal degrees of freedom. If the early Universe contained only the known standard-model particles ($g\approx 100$), then the energy density at the big bounce was about 15 times larger than the Planck energy. The minimum scale factor of the Universe (at the bounce) was about $10^{32}$ times smaller than its present value, giving \approx 50 \mum. If more fermions existed in the early Universe, then the spin-torsion coupling causes a bounce at a lower energy and larger scale factor. Recent observations of high-energy photons from gamma-ray bursts indicate that spacetime may behave classically even at scales below the Planck length, supporting the classical spin-torsion mechanism of the big bounce. Such a classical bounce prevents the matter in the contracting Universe from reaching the conditions at which a quantum bounce could possibly occur.Comment: 6 pages; published versio

From graphene oxide towards aminated graphene facile synthesis, its structure and electronic properties

In this paper we present a facile method for the synthesis of aminated graphene derivative through simultaneous reduction and amination of graphene oxide via two-step liquid phase treatment with hydrobromic acid and ammonia solution in mild conditions. The amination degree of the obtained aminated reduced graphene oxide is of about 4 at.%, whereas C/O ratio is up to 8.8 as determined by means of X-ray photoelectron spectroscopy. The chemical reactivity of the introduced amine groups is further verified by successful test covalent bonding of the obtained aminated graphene with 3-Chlorobenzoyl chloride. The morphological features and electronic properties, namely conductivity, valence band structure and work function are studied as well, illustrating the influence of amine groups on graphene structure and physical properties. Particularly, the increase of the electrical conductivity, reduction of the work function value and tendency to form wrinkled and corrugated graphene layers are observed in the aminated graphene derivative compared to the pristine reduced graphene oxide. As obtained aminated graphene could be used for photovoltaic, biosensing and catalysis application as well as a starting material for further chemical modifications

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Measurement of e+e- -> pi+pi- cross section with CMD-2 around rho-meson

The cross section of the process e+e- -> pi+pi- has been measured using about 114000 events collected by the CMD-2 detector at the VEPP-2M e+e- collider in the center-of-mass energy range from 0.61 to 0.96 GeV. Results of the pion form factor determination with a 0.6% systematic uncertainty are presented. Implications for the hadronic contribution to the muon anomalous magnetic moment are discussed.Comment: 17 pages, 4 figures, submitted to PL

Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at sqrt (s) = 13 TeV with the ATLAS detector

A search is presented for dark matter produced in association with a hadronically decaying W or Z boson using 3.2 fb−1 of pp collisions at View the MathML sources=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet compatible with a W or Z boson and with large missing transverse momentum are analysed. The data are consistent with the Standard Model predictions and are interpreted in terms of both an effective field theory and a simplified model containing dark matter

ОБРАЗОВАНИЕ НА СОВРЕМЕННОМ ЭТАПЕ

The undergraduate and graduate systems currently used in higher education are not suitable for most specialties. It is necessary to fully preserve the traditions of the Soviet school, rooted in pre-revolutionary times and capable of ensuring Russia's well-being tomorrow.Системы бакалавриата и магистратуры не подходят для большинства специальностей отечественной системы образования. Необходимо всемерно хранить традиции советской школы, уходящие своими корнями в дореволюционное время и способные завтра обеспечить благополучие России