Observable effects caused by vacuum pair creation in the field of high-power optical lasers

We consider the possibility of an experimental proof of vacuum e+e- pair creation in the focus of two counter-propagating optical laser beams with an intensity of the order of 10^20 - 10^22 W/cm^2. Our approach is based on the collisionless kinetic equation for the distribution function of the e+e- pairs with the source term for particle production. As a possible experimental signal of vacuum pair production we consider the refraction of a high-frequency probe laser beam by the produced e+e- plasma to be observed by an interference filter. The generation of higher harmonics of the laser frequency in the self-consistent electric field is also investigated.Comment: 7 pages, 7 figures; typos corrected, Eq.(16) corrected, reference adde

From Coulomb excitation cross sections to non-resonant astrophysical rates in three-body systems: 17^{17}Ne case

Coulomb and nuclear dissociation of $^{17}$Ne on light and heavy targets are studied theoretically. The dipole E1 strength function is determined in a broad energy range including energies of astrophysical interest. Dependence of the strength function on different parameters of the $^{17}$Ne ground state structure and continuum dynamics is analyzed in a three-body model. The discovered dependence plays an important role for studies of the strength functions for the three-body E1 dissociation and radiative capture. The constraints on the $[s^2]/[d^2]$ configuration mixing in $^{17}$Ne and on $p$-wave interaction in the $^{15}$O+$p$ channel are imposed based on experimental data for $^{17}$Ne Coulomb dissociation on heavy target.Comment: 12 pages, 13 figure

Long-Time Asymptotics of Perturbed Finite-Gap Korteweg-de Vries Solutions

We apply the method of nonlinear steepest descent to compute the long-time asymptotics of solutions of the Korteweg--de Vries equation which are decaying perturbations of a quasi-periodic finite-gap background solution. We compute a nonlinear dispersion relation and show that the $x/t$ plane splits into $g+1$ soliton regions which are interlaced by $g+1$ oscillatory regions, where $g+1$ is the number of spectral gaps. In the soliton regions the solution is asymptotically given by a number of solitons travelling on top of finite-gap solutions which are in the same isospectral class as the background solution. In the oscillatory region the solution can be described by a modulated finite-gap solution plus a decaying dispersive tail. The modulation is given by phase transition on the isospectral torus and is, together with the dispersive tail, explicitly characterized in terms of Abelian integrals on the underlying hyperelliptic curve.Comment: 45 pages. arXiv admin note: substantial text overlap with arXiv:0705.034

Коксование высоковязкой обводненной нефти

Objectives. A characteristic feature of oil production is an increase in the volume of highviscosity bituminous oil. In Russia, technologies based on the use of water vapor are used for their extraction. The use of such technologies leads to a large amount of water in the product stream from the production well. Preparation of oil for processing involves its stabilization, desalination, and dewatering. Since the densities of the extracted oil and the water contained in it are comparable, traditional preparation schemes for processing of high-viscosity bituminous oil are ineffective. One of the possible solutions to the problem involving such oil in the fuel, energy, and petrochemical balance is to use a coking process at the first stage of its processing. This aim can be achieved by studying the influence of the process conditions of coking high-viscosity water-containing oil on the yield and characteristics of the resulting products.Methods. Coking of oil with a density of 1.0200 g/cm3 at 50 °C and with 18 wt % water content was carried out in a laboratory installation in a “cube.” A hollow cylindrical apparatus was used as a reactor and was placed in a furnace. The temperature and pressure in the reactor were maintained at 500–700 °C and 0.10–0.35 MPa, respectively.Results. An increase in the coking process temperature results in an increase in the amount of gaseous products, a decrease in the amount of the coke generated, and a higher dependence of the amount of liquid products on temperature with a maximum yield at 550–600 °C. The process temperature also affects the composition of liquid products. At a lower temperature, the amount of gasoline and kerosene fractions in liquid products is higher. With an increase in pressure, a higher amount of gaseous products, coke, and low-molecular-weight hydrocarbon fractions in liquid products could also be obtained. The characteristics of the coke produced in the coking process are similar to those of commercially produced grades. It is noted that when coking water-containing oil, up to 98% of the emulsion water goes with liquid products, and the remaining amount of water remains in the formed coke.Conclusions. Results showed the possible application of the coking process at the initial stage of processing high-viscosity bituminous oil. In this case, the dewatering stage is significantly simplified since the technological scheme of delayed coking allows the separation of the gasoline fraction from water.  Цели. Возрастание доли высоковязкой и битуминозной нефти является характерной особенностью современной нефтедобычи. В России при ее добыче применяют технологии, основанные на использовании водяного пара. Применение таких технологий приводит к тому, что продуктовый поток, выходящий из добывающей скважины, может содержать большое количество воды. Подготовка нефти к переработке предполагает ее стабилизацию, обессоливание и обезвоживание. Вследствие того, что плотность добываемой нефти и содержащейся в ней воды сопоставимы, традиционные схемы подготовки к переработке высоковязкой и битуминозной нефти являются малоэффективными. Одним из возможных решений проблемы вовлечения такой нефти в топливно-энергетический и нефтехимический баланс является использование на первом этапе ее переработки процесса коксования. Для реализации этой идеи необходимо изучить влияние условий коксования высоковязкой обводненной нефти на выход и характеристики образующихся продуктов.Методы. Объектом исследования была нефть с плотностью при 50 °С 1.0200 г/см³, содержащая 18 мас. % воды. Коксование проводили на лабораторной установке в «кубе». В качестве реактора использовался пустотелый цилиндрический аппарат, размещаемый в печи. Температура в реакторе варьировалась от 500 до 700 °С, давление от 0.10 до 0.35 МПа.Результаты. Проведенные исследования показали, что при возрастании температуры коксования выход газообразных продуктов увеличивается, образование кокса уменьшается, а зависимость выхода жидких продуктов имеет экстремальный характер с максимумом в области температур 550–600 °C. Температура процесса влияет на состав жидких продуктов. При более низкой температуре в жидких продуктах выше содержание бензиновой и керосиновой фракций. Повышение давления приводит к возрастанию выхода газообразных продуктов, кокса и содержания в жидких продуктах низкомолекулярныхфракций углеводородов. Образующийся в процессе кокс по своим характеристикам близок к промышленно выпускаемым маркам. Отмечено, что при коксовании обводненной нефти до 98% водной эмульсии уходит с жидкими продуктами коксования, и лишь небольшое количество воды остается в образовавшемся коксе.Выводы. Представленные результаты показывают возможность использования процесса коксования на начальном этапе переработки высоковязкой и битуминозной нефти. В этом случае существенно упрощается проведение стадии ее обезвоживания, так как в технологической схеме замедленного коксования предусмотрено отделение бензиновой фракции от воды.

Laser acceleration of ion beams

We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.Comment: 4 pages, 4 figures, Talk at the Helmholtz International Summer School "Dense Matter in heavy Ion Collisions and Astrophysics", August 21 - September 1, 2006, JINR Dubna, Russia; v2, misprints correcte

Current state and prospects of protoplast technology and potato somatic hybridization (review)

Wild Solanum species have often been used as sources of important agricultural traits, including resistance to various diseases, pests, and abiotic factors. However, their large-scale use in potato breeding is limited by complex barriers of sexual incompatibility with Solanum tuberosum. Fusion of protoplasts enzymatically isolated from somatic cells is one of the approaches to overcoming sexual incompatibility. The diverse nuclear and cytoplasmic traits exhibited by potato somatic hybrids provide new genetic material for breeding programs, which is confirmed by the creation of a large number of somatic hybrids of cultivated potatoes with wild Solanum species. The research in development of somatic potato hybrids by means of protoplast fusion has been carried out for more than 40 years already. In this review, the prospects for the use of this technology in modern potato breeding are considered. Genomic, transcriptomic, and proteomic studies provide further insight into the fundamental processes underlying the somatic hybrids formation, such as cell wall formation, chromosomal rearrangements in fusion products, regeneration, and also make a significant contribution to understanding the processes of genome stabilization. Improvement in the methods of molecular screening of both genome and cytoplasm also contributes to the expansion of the field of application of somatic hybrids in breeding. Finally, it has been shown that somatic hybridization promotes the introgression of important agricultural traits, primarily resistance to pathogens

On the Cauchy Problem for the Korteweg-de Vries Equation with Steplike Finite-Gap Initial Data I. Schwartz-Type Perturbations

We solve the Cauchy problem for the Korteweg-de Vries equation with initial conditions which are steplike Schwartz-type perturbations of finite-gap potentials under the assumption that the respective spectral bands either coincide or are disjoint.Comment: 29 page