Review on uranium in soil: levels, migration

The problems of radioactive contamination of biosphere with the 238U in recent years have attracted a large number of experts in various fields of knowledge. Natural radionuclides are an integral part of the biosphere. They are concentrated everywhere: in rocks, in soil, water, air and food. Various types of phosphorus fertilizers and other natural ameliorants used in agriculture are also an additional source of heavy natural radionuclides. The review describes the behaviour and migration of 238U in biosphere, which depend on various factors acting simultaneously. It is noted that the behaviour of 238U in the soil depends on the forms of its presence in it and the physical and chemical properties of the soil. The processes of sorption and desorption of 238U by different soil types are significant indicators

Moving zero-gap Wannier-Mott excitons in graphene

We demonstrate the possibility of existence of indirect moving Wannier-Mott excitons in graphene. Electron-hole binding is conditioned by the trigonal warping of conic energy spectrum. The binding energies are found for the lowest exciton states. These energies essentially depend on the value and direction of exciton momentum and vanish when the exciton momentum tends to the conic points. The ways to observe the exciton states are discussed. The opportunity of experimental observation of zero-gap excitons by means of external electron scattering is examined.Comment: 6 pages, 7 figure

A transverse current rectification in graphene superlattice

A model for energy spectrum of superlattice on the base of graphene placed on the striped dielectric substrate is proposed. A direct current component which appears in that structure perpendicularly to pulling electric field under the influence of elliptically polarized electromagnetic wave was derived. A transverse current density dependence on pulling field magnitude and on magnitude of component of elliptically polarized wave directed along the axis of a superlattice is analyzed.Comment: 12 pages, 6 figure

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Observation of an Excited Bc+ State

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

Методики томографической визуализации ушка левого предсердия при планировании интервенционного лечения фибрилляции предсердий

Due to intracardiac circulatory changes atrial fibrillation creates conditions for thrombus formation in the left atrial appendage (LAA). The presence of thrombus in LAA is poor prognostic factor of subsequent cardiovascular events. It is the source of up to 64% of ischemic stroke cases, and concomitant anticoagulant therapy leads to a high frequency of hemorrhagic conversion. For patient with symptomatic and drug-refractory arrhythmia is recommended surgical rhythm correction or electrical cardioversion. There is a high risk of cardioembolic stroke during the intervention, so it is necessary to exclude LAA thrombosis at pre-operation stage. The main method of LAA visualization is transesophageal echocardiography, but today computed tomography and, less, magnetic resonance tomography become important. The purpose of this review is to analyze the possibilities of each visualisation technique and their role in the diagnostic algorithm when examining patients before catheter ablation of atrial fibrillation sources.Изменение внутрисердечной гемодинамики на фоне неправильного ритма фибрилляции предсердий создает условия для формирования тромбов в полости ушка левого предсердия. Наличие тромба в ушке является неблагоприятным прогностическим фактором последующих кардиоваскулярных событий, являясь источником до 64% случаев ишемических инсультов, а сопутствующая антикоагулянтная терапия приводит к большой частоте геморрагической транcформации. Симптомная и рефрактерная к медикаментозному лечению фибрилляция предсердий требует хирургической коррекции ритма или электрической кардиоверсии. Во время вмешательства существует высокий риск кардиоэмболического инсульта, поэтому на дооперационном этапе для его профилактики необходимо исключить тромбоз ушка левого предсердия. Основной метод визуализации ушка – чреспищеводная эхокардиография, но на сегодняшний день определенный вклад вносит компьютерная томография и, в меньшей степени, магнитно-резонансная томография. Целью данного научного обзора было изучение возможностей каждой методики и их роли в диагностическом алгоритме при обследовании пациентов перед катетерной абляцией источников фибрилляции предсердий

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu