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

Накопичення та розподіл цинку і марганцю у водній екосистемі Яворівського водосховища, Львівська область, Україна

The paper presents results of investigations of zinc and manganese concentration in the water, bottom deposits and ichthyofauna of Yavoriv water reservoir, which was formed in 2002 in frames of project of Yavoriv sulfur quarry revitalization. Mentioned elements are characterized by wide spectrum of action in fish body, which, depending on their concentration, can be either physiologic or toxic. It was revealed, that concentration of Zn and Mn in the water of Yavoriv water reservoir varied considerably depending on place of samples taking. The lowest Zn concentration in the water was below 1 MPL (maximum permitted level), namely 0.6 µg/l, and the highest – more than 7 MPL (70.5 µg/l). Similar differences were observed concerning Mn concentration in the water – the range of determined values varied from 3.3 (0.3 MPL) to 48.6 µg/l. The same peculiarities of Zn and Mn distribution were estimated in regard to their content in bottom deposits. In particular, difference of Zn concentration in samples of bottom deposits was near 23 times – from 5.4 to 230.0 mg/kg depending on the point of samples taking. Mn content in bottom deposits varies from 61.5 to 1500 mg/kg. Zn and Mn concentration in skeletal muscles, gills and skin of perch and rudd didn’t exceed MPL regardless their content in the water and bottom deposits. In most of cases, gills accumulated these elements more than other investigated tissues.В роботі представлені результати дослідження вмісту Цинку та Марганцю у воді, донних відкладах та іхтіофауні Яворівського водосховища, яке було створено у 2002 році в рамках проекту з відновлення територій Яворівського сірчаного карʼєру. Вказані елементи характеризуються широким спектром дії в організмі риб, яка, залежно від їх концентрації, може бути фізіологічною чи токсичною. Було встановлено, що концентрація Цинку та Марганцю у воді Яворівського водосховища значно відрізнялася залежно від місця відбору проби. Найнижчий вміст Цинку у воді був нижчим ніж 1 ГДК (гранично допустимої концентрації), а саме 0,6 мкг/л, а найвищий – на рівні понад 7 ГДК (70,5 мкг/л). Подібні відмінності були відмічені стосовно вмісту Марганцю у воді – діапазон встановлених концентрацій змінювався від 3,3 (0,3 ГДК) до 48,6 мкг/л. Подібні особливості розподілу Цинку і Марганцю були встановлені також стосовно їхнього вмісту у донних відкладах. Зокрема, різниці у вмісті Цинку в зразках донних відкладів становили близько 23 разів – від 5,4 до 230 мг/кг залежно від місця відбору зразка. Вміст Марганцю у донних відкладах змінювався від 61,5 до 1500 мг/кг. Концентрація цинку та марганцю в скелетних мʼязах, зябрах і шкірі окуня та краснопірки не перевищувала ГДК, незалежно від їхнього вмісту у воді та донних відкладах. В більшості випадків, зябра накопичували ці елементи більшою мірою, ніж інші досліджувані тканини

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

Вміст кобальту та нікелю у воді, донних відкладах та іхтіофауні Яворівського водосховища

Arrangement of fishponds and recreation water basins are among most actual directions of technogenic environment recultivation. However, mentioned approach demands constant monitoring of different pollutants content in abiotic and biotic components of created hydroecosystem. This paper presents results of investigations of cobalt and nickel concentration in the water, bottom deposits and ichthyofauna of Yavoriv water storage basin – water reservoir, which was formed in the place of sulfur career. Mentioned elements are characterized by wide spectrum of action in fish body, which, depending on their concentration, can be either physiologic or toxic. During the experiment was revealed, that cobalt concentration in the water of Yavoriv water storage basin was within the normal range, while nickel concentration exceed MPL from 1.26 to 7.65 times depending on sampling place. Concentration of abovementioned elements in the bottom deposits of water basin in different fields of it varied greatly, wherein well–defined correlation between cobalt and nickel level in the water and bottom deposits wasn’t observed. The researches testified also the existence of tissue, organic and species peculiarities of cobalt and nickel accumulation in the body of rudd and perch. In particular, the biggest content of researched elements was observed in the gills of the fishes. Herewith, cobalt concentration in rudd gills exceeds MPL in 3.25 times, in perch gills – in 4.75 times. Nickel concentration in the muscles, gills and skin of rudd exceeds existing normative values in 1.16, 2.25 and 2.32 times respectively; in the muscles, gills and skin of perch – in 1.08, 6.84 and 3.1 times respectively. Створення рибогосподарських та рекреаційних водойм є одним з актуальних напрямів рекультивації техногенного середовища. Разом з тим, даний підхід вимагає постійного моніторингу вмісту полютантів різної природи у абіотичних та біотичних компонентах утвореної гідроекосистеми. В даній роботі представлені результати досліджень вмісту кобальту та нікелю у воді, донних відкладах та іхтіофауні Яворівського водосховища – водойми, утвореної на місці сірчаного карʼєру. Вказані елементи характеризуються широким спектром дії в організмі риб, яка, залежно від їх концентрації, може бути як фізіологічною, так і токсичною. При виконанні досліджень було встановлено, що рівень кобальту у воді Яворівського водосховища знаходився в межах норми, в той час як концентрація нікелю перевищувала ГДК від 1,26 до 7,65 раза залежно від місця відбору проб. Вміст вказаних елементів у донних відкладах водойми в різних ділянках значно відрізнявся між собою, при цьому не було встановлено чіткої залежності між рівнем вказаних елементів у воді та донних відкладах. Проведені дослідження свідчать також про існування органно–тканинних та видових особливостей накопичення кобальту та нікелю в організмі краснопірки та окуня. Так, найбільший вміст вказаних елементів спостерігався у зябрах досліджуваних риб, при цьому вміст кобальту у зябрах краснопірки перевищував ГДК у 3,25 раза, у зябрах окуня – у 4,75 раза. Вміст нікелю у мʼязах, зябрах та шкірі краснопірки перевищував нормативні значення відповідно у 1,16; 2,52 та 2,32 раза; у мʼязах, зябрах та шкірі окуня – відповідно у 1,08; 6,84 та 3,1 раза

THE INFLUENCE OF DENTAL IMPLANTATION ON THE STATE OF THE BALANCE OF ANTIOXIDANTPROOXIDANT SYSTEM OF ORAL LIQUID IN PATIENTS WITH PARTIAL ADENTIA

Aim. The purpose of the study is to evaluate the influence of treatment of partial adentia by means of the dental implantation over the changes in antioxidant-prooxidant balance of oral liquid.Materials and methods. The study was performed on 40 testees divided into 2 groups: the control group (conditionally healthy people) and the test group (patients with adentia of 1-4 teeth). During the initial examination all the testees underwent the sampling of oral liquid. The oral liquid of patients was sampled at three stages of treatment: at the suture release after the dental implantation, at the installation of the healing abutment and at the installation of orthopedic constructions. The concentration of the products of oxidative modifications of biomolecules was determined in oral liquid as well as the state of the system of antioxidant protection.Results. As a result of a study, it was revealed that the antioxidant activity decreased by 20,7% against the background of the increase in intensity of oxidative processes in oral liquid of patients with partial adentia by 1,8 times. During the treatment it was revealed that the tendency of the gradual increase in general antioxidant potential to the control indices and the decrease in oxidative stress in oral liquid took place. The activity of superoxide dismutase and catalase in oral liquid of patients of the 2nd group sampled at the initial examination was higher than the control indices by 71,6% and 53,4% respectively. At the second stage of the treatment the activity of superoxide dismutase remained increased by 59,1% while the catalase activity decreased by 2,4 times up to the indices 1,6 times lower than the control indices. At this stage it may be noted that the catalase insufficiency is relative which can lead to the increased concentration of hydrogen peroxide against the background of the increased activity of superoxide dismutase. At the 3rd and the 4th stages of the treatment the catalase activity increased by 25,9% in comparison with the indices of the previous stage of the study while the activity of superoxide dismutase decreased to the control indices. The correlation of changes in enzymatic activity of antioxidant protection was close to one.Conclusion. The imbalance of antioxidant-prooxidant system at early stages of treatment may provoke the complications development that’s why the attention must be paid to the perspectives of possible antioxidant correction. In general, the results of the study proved the absence of negative influence of the material used in the dental implant on metabolic systems of oral liquid

Magnetic properties of the magnetoelectric compound Cu2OSeO3: Magnetization and 77Se NMR study

We present magnetization and77Se Nuclear Magnetic Resonance (NMR) measurements in single crystals of the magneteoelectric compound Cu2OSeO3. The temperature and field dependence of the magnetization suggest a ferrimagnetic ordering at Tc≃ 60 K in a 3up-1down configuration. The easy axis of the magnetization is along the [100] crystallographic direction. The77Se NMR line shape data collected at 14.09 T are consistent with the symmetries imposed by the cubic P213 space group in the temperature range 20-290 K and confirm that the magnetic transition is not accompanied by any lowering of the crystal symmetry as has recently been proposed by Bos et al. [Phys. Rev. B 78 094416 (2008)]

Atomic and electronic structure of nanostructured few-layer graphene with self-aligned boundaries synthesized on SiC/Si(001) wafers

This work was partially supported by the Russian Academy of Sciences, Russian Foundation for Basic Research (grant № 17-02-01139, 17-02-01291), Beijing Institute of Technology Research Fund Program for Young Scholars, and Science Foundation Ireland

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