Estimations of electron-positron pair production at high-intensity laser interaction with high-Z targets

Electron-positron pairs' generation occuring in the interaction of $10^{18}$-$10^{20}$~W/cm$^2$ laser radiation with high-Z targets are examined. Computational results are presented for the pair production and the positron yield from the target with allowance for the contribution of pair production processes due to electrons and bremsstrahlung photons. Monte-Carlo simulations using the PRIZMA code confirm the estimates obtained. The possible positron yield from high-Z targets irradiated by picosecond lasers of power $10^2$-$10^3$~TW is estimated to be $10^9$-$10^{11}$

Examination of the astrophysical S-factors of the radiative proton capture on 2H, 6Li, 7Li, 12C and 13C

Astrophysical S-factors of radiative capture reactions on light nuclei have been calculated in a two-cluster potential model, taking into account the separation of orbital states by the use of Young schemes. The local two-body potentials describing the interaction of the clusters were determined by fitting scattering data and properties of bound states. The many-body character of the problem is approximatively accounted for by Pauli forbidden states. An important feature of the approach is the consideration of the dependence of the interaction potential between the clusters on the orbital Young schemes, which determine the permutation symmetry of the nucleon system. Proton capture on 2H, 6Li, 7Li, 12C, and 13C was analyzed in this approach. Experimental data at low energies were described reasonably well when the phase shifts for cluster-cluster scattering, extracted from precise data, were used. This shows that decreasing the experimental error on differential elastic scattering cross sections of light nuclei at astrophysical energies is very important also to allow a more accurate phase shift analysis. A future increase in precision will allow more definite conclusions regarding the reaction mechanisms and astrophysical conditions of thermonuclear reactions.Comment: 40p., 9 fig., 83 ref. arXiv admin note: substantial text overlap with arXiv:1005.1794, arXiv:1112.1760, arXiv:1005.198

Microscopics of meson degrees of freedom in nucleons and mesons in nuclei - what can be seen in the process of quasielastic knockout of mesons by high-energy electrons

Developed earlier concept of quasielastic knock out of pions from nucleons by high-energy electrons is propounded as a tool for checking microscopical model ($^3P_0$ - fluctuation) for decay of N to different channels $\pi+B$ and Preparata model of nucleus structure.Comment: 6 pages, 5 figures, Talk given at 16 Baldin Symposium in June 200

In memoriam two distinguished participants of the Bregenz Symmetries in Science Symposia: Marcos Moshinsky and Yurii Fedorovich Smirnov

Some particular facets of the numerous works by Marcos Moshinsky and Yurii Fedorovich Smirnov are presented in these notes. The accent is put on some of the common interests of Yurii and Marcos in physics, theoretical chemistry, and mathematical physics. These notes also contain some more personal memories of Yurii Smirnov.Comment: Submitted for publication in Journal of Physics: Conference Serie

SURVIVAL OF LIVER CELLS, IMMOBILIZED ON 3D-MATRIXES, IN LIVER FAILURE MODEL

It was examined a new method for correction of hepatic failure by transplantation of liver support biounit (liver cells, immobilized on biocompatible and biodegradable 3D-matrixes ElastoPOB®) into small intestine mesentery. It was determined that after modeling of acute hepatic failure on dogs by 65–70% liver resection) and transplantation liver support biounit the restoration of disturbed biochemical indecies (such as total protein, lactate, cytolytic ensymes-ALT, AST, ALP, LDH, fibrinogen, protrombine index and others) took place more rapidly on 9–14th day instead of 18th day in control. It was made a preposition about efficiency of the suggested method for correction both acute hepatic failure because even 90 days after transplantation of liver support biounit alive hepatocytes and neogenic plethoric vessels, growing through matrix were revealed

Influence of the re-scattering process on polarization observables in reaction gamma + d --> p + p + pi- in Delta - resonance region

Influence of the effects of the pion-nucleon and nucleon-nucleon re-scattering on the polarization observables of the reaction gamma + d = p + p + pi- in Delta - isobar region is investigated. Pion-nucleon and nucleon-nucleon re-scattering are studied in the diagrammatic approach. Relativistic-invariant forms of the pion photoproduction and pion-nucleon scattering operators are used. The unitarization procedure in K-matrix approach is applied for the resonance partial amplitudes. It is shown a considerable influence of the re-scattering effects on the polarization observables of this reaction in the Delta - resonance region for the large momenta of the final protons.Comment: 16 pages, 5 Postscript figure

Искусственный нервный проводник для направленного роста периферических нервов (кадаверное исследование)

At present, the search for effective ways of restoring peripheral nerves with anatomical damage continues. Autoplasty still remains the gold standard, which, however, is not without its drawbacks. The use of nerve implants for promoting directional axon growth is essential and promising.Objective: to study the biomechanical properties of laboratory samples of an artificial nerve conduit (NGC) made of hybrid biomaterials and to, on cadaveric material, assess the technical feasibility of using them in surgical practice to repair extended peripheral nerve defects.Material and methods. The objects of the study were three electrospun NGC samples: from synthetic material (polycaprolactone, PCL) and hybrid biomaterials (PCL + gelatin or PCL + collagen). The work compared the physical and mechanical properties of NGC: stiffness, plasticity, elasticity, brittleness, resistance to chemical attack, their ability to be impregnated with liquid media, permeability, possibility of making an anastomosis between the implant and the nerve during surgical procedure. Cadaveric material was the object of the study: we used a dissected superficial sensory branch of the human right radial nerve, 2 mm in diameter, isolated on the forearm, about 12 cm in length, because it most corresponded to the diameter of the NGC samples tested. After surgery, the echogenic features of the implants and their anastomoses with the nerve were assessed by ultrasound imaging.Results. It was found that hybrid NGC samples, based on their biomechanical properties, are fundamentally suitable for use in surgical practice, to ensure growth and replacement of a peripheral nerve defect. However, the best composition of a nerve guide can be established after comparative preclinical study of the biocompatible and functional properties of hybrid material samples.Conclusion. The physical and mechanical properties of the investigated NGC samples made of hybrid biomaterials meet the technical requirements for implantable nerve conduits for surgical application.В настоящее время продолжаются поиски эффективных способов восстановления периферических нервов при анатомическом нарушении их целостности. Золотым стандартом по-прежнему остается аутопластика, которая, однако, не лишена недостатков. Актуальным и перспективным является метод применения нервных имплантатов для направленного роста аксонов.Цель: изучить биомеханические свойства лабораторных образцов искусственного нервного проводника (ИНП) – нервного кондуита, изготовленных из гибридных биоматериалов, и на кадаверном материале оценить техническую возможность их применения в хирургической практике для восстановления протяженных дефектов периферических нервов.Материал и методы. Объектами исследования служили изготовленные методом электроспиннинга три образца ИНП: из синтетического материала – поликапролактона (ПКЛ) и гибридных биоматериалов (ПКЛ с желатином или коллагеном). В ходе работы сравнивались физические и механические свойства ИНП: жесткость, пластичность, эластичность, хрупкость, устойчивость образцов к химическому воздействию, их способность к пропитыванию жидкими средами, проницаемость, возможность наложения анастомоза между имплантатом и нервом во время хирургической операции. В качестве кадаверного материала использовали поверхностную чувствительную ветвь правого лучевого нерва человека диаметром 2 мм, выделенную на предплечье протяженностью около 12 см, как наиболее соответствующую диаметру тестируемых образцов ИНП. После хирургической операции оценивали эхогенные признаки имплантатов и их анастомозов с нервом методом ультразвуковой визуализации.Результаты. Установлено, что образцы ИНП из гибридных материалов по биомеханическим свойствам принципиально пригодны для использования в хирургической практике для обеспечения роста и замещения дефекта периферических нервов. Однако наилучший состав нервного проводника может быть установлен после проведения сравнительных доклинических исследований биосовместимых и функциональных свойств образцов из гибридных материалов.Заключение. Физические и механические свойства исследуемых образцов ИНП из гибридных биоматериалов соответствуют техническим требованиям, предъявляемым к имплантируемым нервным проводникам при их хирургическом применении

Экспериментальные подходы к созданию тканеспецифического матрикса для биоискусственной печени

Shortage of donor organs for liver transplantation in the treatment of end-stage liver disease dictates the need to develop alternative methods that include technologies on tissue engineering and regenerative medicine. Objective: to study the ability of a tissue-specific matrix from decellularized human liver fragments (DHLF) to maintain adhesion and proliferation of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) and HepG2 under static conditions and in a flow-through bioreactor. Materials and methods. Treatment with surfactants (SAS) – sodium dodecyl sulfate, Triton X-100 – followed by exposure to DNase was used for decellularization of human liver fragments (no more than 8 mm3). Biochemical screening included the determination of DNA quantity in the test samples. Efficiency of surfactant washing was assessed by the cytotoxicity of the matrix in the NIH 3T3 fibroblast culture. Viability and metabolic activity of cells were assessed via vital staining with a complex of fluorescent dyes LIVE/DEAD ® and PrestoBlue™ (Invitrogen, USA). Morphological examination of the liver cell-engineered constructs was carried out through histological staining and scanning electron microscopy with lanthanide contrast. Results. It was shown that the liver decellularization method used allows to obtain a biocompatible matrix with a residual DNA quantity <1%, which is capable of maintaining adhesion and proliferation of hAT-MSCs and HepG2. On day 7 of cultivation in the bioreactor, there was formation of a single conglomerate of the DHLF matrix with numerous groups of viable cells with a high nuclear-cytoplasmic ratio. The urea content in the culture medium is 1.5 ± 0.1 mmol/L, exceeding that of samples obtained under static conditions. This indicates the metabolic activity of HepG2 in the composition of the obtained culture systems. It was shown that constant flow of the culture medium in the perfusion bioreactor increased the proliferative activity of HepG2 and allowed to provide a more uniform colonization by matrix cells in comparison with static cultivation conditions. Conclusion. The conditions for uniform colonization of DHLFs in a flow-through bioreactor with cell cultures were established. The ability of the matrix to maintain adhesion and proliferation of hADSCs and HepG2 for 11 days indicates that it could be used in liver tissue engineering.Дефицит донорских органов для трансплантации печени при лечении терминальных стадий печеночной недостаточности диктует необходимость разработки альтернативных методов, к которым относятся технологии тканевой инженерии и регенеративной медицины. Целью работы было исследование способности тканеспецифического матрикса из децеллюляризованных фрагментов печени человека (ДФПч) поддерживать адгезию и пролиферацию мезенхимальных стромальных клеток жировой ткани человека (МСК ЖТч) и HepG2 в статических условиях и в проточном биореакторе. Материалы и методы. Для децеллюляризации фрагментов (не более 8 мм3) печени человека использовали обработку поверхностноактивными веществами (ПАВ) – додецилсульфатом натрия, Тритоном Х-100 с последующей экспозицией в ДНКазе. Биохимические исследования включали определение количества ДНК в исследуемых образцах. Эффективность отмывки от ПАВ оценивали по цитотоксичности матрикса на культуре фибробластов NIH 3T3. Оценку жизнеспособности и метаболической активности клеток проводили методом прижизненного окрашивания комплексом флюоресцентных красителей LIVE/DEAD ® и PrestoBlue™ (Invitrogen, США). Морфологическое исследование клеточно-инженерных конструкций печени проводили с использованием методов гистологического окрашивания и сканирующей электронной микроскопии с лантаноидным контрастированием. Результаты. Показано, что использованная методика децеллюляризации печени позволяет получать биосовместимый матрикс с остаточным количеством ДНК менее 1%, способный поддерживать адгезию и пролиферацию МСК ЖТч и HepG2. В биореакторе на 7-е сутки культивирования наблюдали образование единого конгломерата матрикса ДФПч с многочисленными группами жизнеспособных клеток с высоким ядерно-цитоплазматическим отношением. Содержание мочевины в культуральной среде превышает значение для образцов, полученных в статических условиях, и составляет 1,5 ± 0,1 ммоль/л, что свидетельствует о метаболической активности HepG2 в составе полученных культуральных систем. Показано, что постоянный поток культуральной среды перфузионного биореактора способствовал росту пролиферативой активности HepG2 и позволил обеспечить более равномерную колонизацию клетками матрикса по сравнению со статическими условиями культивирования. Заключение. Найдены условия равномерного заселения ДФПч в проточном биореакторе клеточными культурами. Способность матрикса поддерживать адгезию и пролиферацию МСК ЖТч и HepG2 в течение 11 суток свидетельствует о возможности его использования в тканевой инженерии печени

Prospects in Analytical Atomic Spectrometry

Tendencies in five main branches of atomic spectrometry (absorption, emission, mass, fluorescence and ionization spectrometry) are considered. The first three techniques are the most widespread and universal, with the best sensitivity attributed to atomic mass spectrometry. In the direct elemental analysis of solid samples, the leading roles are now conquered by laser-induced breakdown and laser ablation mass spectrometry, and the related techniques with transfer of the laser ablation products into inductively-coupled plasma. Advances in design of diode lasers and optical parametric oscillators promote developments in fluorescence and ionization spectrometry and also in absorption techniques where uses of optical cavities for increased effective absorption pathlength are expected to expand. Prospects for analytical instrumentation are seen in higher productivity, portability, miniaturization, incorporation of advanced software, automated sample preparation and transition to the multifunctional modular architecture. Steady progress and growth in applications of plasma- and laser-based methods are observed. An interest towards the absolute (standardless) analysis has revived, particularly in the emission spectrometry.Comment: Proofread copy with an added full reference list of 279 citations. A pdf version of the final published review may be requested from Alexander Bol'shakov <[email protected]