Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil

We report stable laser-driven proton beam acceleration from ultrathin foils consisting of two ion species: heavier carbon ions and lighter protons. Multi-dimensional particle-in-cell (PIC) simulations show that the radiation pressure leads to very fast and complete spatial separation of the species. The laser pulse does not penetrate the carbon ion layer, avoiding the proton Rayleigh-Taylor-like (RT) instability. Ultimately, the carbon ions are heated and spread extensively in space. In contrast, protons always ride on the front of the carbon ion cloud, forming a compact high quality bunch. We introduce a simple three-interface model to interpret the instability suppression in the proton layer. The model is backed by simulations of various compound foils such as carbon-deuterium (C-D) and carbon-tritium (C-T) foils. The effects of the carbon ions' charge state on proton acceleration are also investigated. It is shown that with the decrease of the carbon ion charge state, both the RT-like instability and the Coulomb explosion degrade the energy spectrum of the protons. Finally, full 3D simulations are performed to demonstrate the robustness of the stable two-ion-species regime.Comment: 14 pages, 10figures, to be published in PO

Multi-GeV Electron Generation Using Texas Petawatt Laser

We present simulation results and experimental setup for multi-GeV electron generation by a laser plasma wake field accelerator (LWFA) driven by the Texas Petawatt (TPW) laser. Simulations show that, in plasma of density n(e) = 2 - 4 x cm(-3), the TPW laser pulse (1.1 PW, 170 fs) can self-guide over 5 Rayleigh ranges, while electrons self-injected into the LWFA can accelerate up to 7 GeV. Optical diagnostic methods employed to observe the laser beam self-guiding, electron trapping and plasma bubble formation and evolution are discussed. Electron beam diagnostics, including optical transition radiation (OTR) and electron gamma ray shower (EGS) generation, are discussed as well.Physic

Electrically-driven phase transition in magnetite nanostructures

Magnetite (Fe$_{3}$O$_{4}$), an archetypal transition metal oxide, has been used for thousands of years, from lodestones in primitive compasses[1] to a candidate material for magnetoelectronic devices.[2] In 1939 Verwey[3] found that bulk magnetite undergoes a transition at T$_{V}$ $\approx$ 120 K from a high temperature "bad metal" conducting phase to a low-temperature insulating phase. He suggested[4] that high temperature conduction is via the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering upon cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial.[5-11] Here we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.Comment: 17 pages, 4 figure

Following autophagy step by step

Autophagy is an evolutionarily conserved lysosomal degradation route for soluble components of the cytosol and organelles. There is great interest in identifying compounds that modulate autophagy because they may have applications in the treatment of major diseases including cancer and neurodegenerative disease. Hundeshagen and colleagues describe this month in BMC Biology a screening assay based on flow cytometry that makes it possible to track distinct steps in the autophagic process and thereby identify novel modulators of autophagy

Preparation For Laser Wakefield Experiments Driven By The Texas Petawatt Laser System

Laboratories around the world are planning petawatt laser driven experiments. The Texas petawatt laser offers the ability to demonstrate laser wake field acceleration (LWFA) in a unique regime with pulse duration (similar to 160 fs) shorter than other petawatt scale systems currently in operation or under development. By focusing the 1.25 PW, 200 J, 160 Is pulses to peak intensity similar to 10(19) W/cm(2), multi-GeV electron bunches can be produced from a low density He gas jet. The rarefied plasma density (5x10(16) - 10(17) cm(-3)) required for near-resonant LWFA minimizes plasma lensing and offers long dephasing length for electron acceleration over distances (similar to 10 cm) exceeding the Rayleigh range. Because of the high power, the laser can be focused to a spot (r(0) similar to 100 microns) greater than the plasma wavelength (r(0) > lambda(p)), thus minimizing radial propagation effects. Together these properties enable the laser pulse to self-guide without the use of a preformed channel lending simplicity and stability to the overall acceleration process. Particle-in-cell (PIC) simulations show the laser experiences self-focusing which, because of ultrashort pulse duration, does not lead to a collapse of the wakefield and can generate over 3 GeV electron energy. The presented material will include details of initial measurements of the Texas petawatt laser system, simulations of laser wakefield acceleration for the given laser parameters and the experimental setup currently under construction.Physic

Dissemination of Invasive Mosquito Species, Aedes (Stegomyia) aegypti (L., 1762) and Aedes (Stegomyia) albopictus (Skuse, 1895) in the South of Krasnodar Region, Russia

Objective of the study was to investigate the current borders of the invasive species Ae. aegypti and Ae. albopictus distribution in the south of the Krasnodar Region and climatic factors limiting their expansion. Material and methods. Mosquito larvae, pupa and imago were collected in 21 inhabited localities in August–September, 2017, using conventional entomological methods, and identified through standard morphological keys. Climatic data found on the website pogoda. ru were analyzed using SPSS program. Results and conclusions. Ae. albopictus is widely spread along the Black Sea coast, from Adler to Novorossiysk (Ozereyevka), as well as on the north slopes of Caucasus up to Maikop. Additional investigations are required to specify the northern border of species distribution and to evidence the existence of established populations here. Ae. aegypti were not found in the south of the Krasnodar Region. The obtained data suggest a possibility of much wider spreading of dengue, Chikungunya and Zika fevers in case of pathogen importation to the south of Krasnodar Region, than was assumed earlier

Magnetic field generation through angular momentum exchange between circularly polarized radiation and charged particles

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation

Поражения сердца у детей на фоне течения COVID-19

Ongoing research on SARS-CoV-2 showed the ability of a pathogen to affect cardio-vascular system in the form of myocarditis, dysrhythmia, cardiac failure, etc. According to an infectious diseases hospital in Omsk, changes in the heart were recorded in 3.3% of children hospitalized with COVID-19. Authors conducted a retrospective study of 24 children aged 1—17 years 11 months with a new coronavirus infection who recieved treatment in an infectious diseases hospital at the Budgetary Healthcare Institution of Omsk Oblast City Children's Clinical Hospital №3 in Omsk from October 2020 to December 2021. It was found that heart lesions were more often recorded in children over 10 years old, all males. In most patients, cardiac lesions developed in presence of concomitant pathology and were combined with lung damage. Clinical manifestations indicating involvement in the pathological process of the cardiovascular system appeared in addition to respiratory infection. They were mild and nonspecific.Продолжающиеся исследования в отношении SARS-CoV-2 показали возможность возбудителя поражать сердечно-сосудистую систему в виде миокардитов, нарушений ритма, сердечной недостаточности и др. По данным инфекционного стационара г. Омска, изменения со стороны сердца регистрировались у 3,3% госпитализированных детей с COVID-19. Материалы и методы. Было проведено ретроспективное исследование историй болезни 24 детей в возрасте от 1 года до 17 лет 11 месяцев с новой коронавирусной инфекцией, находившихся на лечении в инфекционном стационаре БУЗОО ГДКБ №3 г. Омска в период с октября 2020 года по декабрь 2021 г. Результаты. Было выявлено, что поражения сердца чаще регистрируются в группе детей старше 10 лет, мужского пола. У большинства пациентов поражения сердца развивались на фоне сопутствующей патологии и сочетались с поражением легких. Клинические проявления, свидетельствующие о вовлечении в патологический процесс сердечно-сосудистой системы, появлялись на фоне респираторной инфекции, были слабо выражены и неспецифичны

A new view of electrochemistry at highly oriented pyrolytic graphite

Major new insights on electrochemical processes at graphite electrodes are reported, following extensive investigations of two of the most studied redox couples, Fe(CN)64–/3– and Ru(NH3)63+/2+. Experiments have been carried out on five different grades of highly oriented pyrolytic graphite (HOPG) that vary in step-edge height and surface coverage. Significantly, the same electrochemical characteristic is observed on all surfaces, independent of surface quality: initial cyclic voltammetry (CV) is close to reversible on freshly cleaved surfaces (>400 measurements for Fe(CN)64–/3– and >100 for Ru(NH3)63+/2+), in marked contrast to previous studies that have found very slow electron transfer (ET) kinetics, with an interpretation that ET only occurs at step edges. Significantly, high spatial resolution electrochemical imaging with scanning electrochemical cell microscopy, on the highest quality mechanically cleaved HOPG, demonstrates definitively that the pristine basal surface supports fast ET, and that ET is not confined to step edges. However, the history of the HOPG surface strongly influences the electrochemical behavior. Thus, Fe(CN)64–/3– shows markedly diminished ET kinetics with either extended exposure of the HOPG surface to the ambient environment or repeated CV measurements. In situ atomic force microscopy (AFM) reveals that the deterioration in apparent ET kinetics is coupled with the deposition of material on the HOPG electrode, while conducting-AFM highlights that, after cleaving, the local surface conductivity of HOPG deteriorates significantly with time. These observations and new insights are not only important for graphite, but have significant implications for electrochemistry at related carbon materials such as graphene and carbon nanotubes

Epidemiological Welfare Provision in the Republic of Dagestan in View of Travel Industry Boost

Sustainable growth of touristic economy sector in the Republic of Dagestan exposes the need for well-timed and adequate response to epidemic and ecological hazards. In this connection investigated have been several peculiarities specific to economic activity and medical services of the republic, which precondition a threat to epidemiological welfare of the population and make possible dissemination of infections over the boundaries of republic’s natural foci