102 research outputs found

    МОЛОЧАИ (EUPHORBIA L., EUPHORBIACEAE) ВОСТОЧНОЙ ЕВРОПЫ И КАВКАЗА В ЗЕРКАЛЕ НОВОЙ СИСТЕМЫ РОДА

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    The separation of the genus Euphorbia L. on subgenera and sections recently has been significantly revised on the ground of molecular-phylogenetic data. The paper contains the revised system of the genus for East Europe and the Caucasus given with these changes. Species occurring in the studied area belong to subgen. Esula Pers. (93 species) and Chamaesyce Raf. (10 species). In subgen. Esula 16 sections of 21 totally recognized are known in East Europe and the CaucasusРазделение рода Euphorbia L. на подроды и секции недавно существенно пересмотрено на основании молекулярно-филогенетических данных. В работе приводится система рода для Восточной Европы и Кавказа с учетом этих изменений. Виды, распространенные на этой территории, относятся к подродам Esula Pers. (93 вида) и Chamaesyce Raf. (10 видов). В подроде Esula из 21 выделенной секции на исследуемой территории представлены 16

    On the absence of bound-state stabilization through short ultra-intense fields

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    We address the question of whether atomic bound states begin to stabilize in the short ultra-intense field limit. We provide a general theory of ionization probability and investigate its gauge invariance. For a wide range of potentials we find an upper and lower bound by non-perturbative methods, which clearly exclude the possibility that the ultra intense field might have a stabilizing effect on the atom. For short pulses we find almost complete ionization as the field strength increases.Comment: 34 pages Late

    On the Influence of Pulse Shapes on Ionization Probability

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    We investigate analytical expressions for the upper and lower bounds for the ionization probability through ultra-intense shortly pulsed laser radiation. We take several different pulse shapes into account, including in particular those with a smooth adiabatic turn-on and turn-off. For all situations for which our bounds are applicable we do not find any evidence for bound-state stabilization.Comment: 21 pages LateX, 10 figure

    Ionization Probabilities through ultra-intense Fields in the extreme Limit

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    We continue our investigation concerning the question of whether atomic bound states begin to stabilize in the ultra-intense field limit. The pulses considered are essentially arbitrary, but we distinguish between three situations. First the total classical momentum transfer is non-vanishing, second not both the total classical momentum transfer and the total classical displacement are vanishing together with the requirement that the potential has a finite number of bound states and third both the total classical momentum transfer and the total classical displacement are vanishing. For the first two cases we rigorously prove, that the ionization probability tends to one when the amplitude of the pulse tends to infinity and the pulse shape remains fixed. In the third case the limit is strictly smaller than one. This case is also related to the high frequency limit considered by Gavrila et al.Comment: 16 pages LateX, 2 figure

    Multiphoton Ionization as Time-Dependent Tunneling

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    A new semiclassical approach to ionization by an oscillating field is presented. For a delta-function atom, an asymptotic analysis is performed with respect to a quantity h, defined as the ratio of photon energy to ponderomotive energy. This h appears formally equivalent to Planck's constant in a suitably transformed Schroedinger equation and allows semiclassical methods to be applicable. Systematically, a picture of tunneling wave packets in complex time is developped, which by interference account for the typical ponderomotive features of ionization curves. These analytical results are then compared to numerical simulations and are shown to be in good agreement.Comment: 36 pages (also printable half size), uuencoded compressed tarred Latex file with 9 Postscript figures included automaticall

    Isotope shift in the electron affinity of chlorine

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    The specific mass shift in the electron affinity between ^{35}Cl and ^{37}Cl has been determined by tunable laser photodetachment spectroscopy to be -0.51(14) GHz. The isotope shift was observed as a difference in the onset of the photodetachment process for the two isotopes. In addition, the electron affinity of Cl was found to be 29138.59(22) cm^{-1}, giving a factor of 2 improvement in the accuracy over earlier measurements. Many-body calculations including lowest-order correlation effects demonstrates the sensitivity of the specific mass shift and show that the inclusion of higher-order correlation effects would be necessary for a quantitative description.Comment: 16 pages, 6 figures, LaTeX2e, amsmat

    R-matrix Floquet theory for laser-assisted electron-atom scattering

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    A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The theory is non-perturbative and applicable to a non-relativistic many-electron atom or ion in a homogeneous linearly polarized field. It is based on the use of channel functions built from field-dressed target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.

    On the results of the First Scientific Forum «Genetic Resources of Russia»: prospects for development, research and practical potential of bio-collections

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    Nine separate scientific conferences and school-conferences dedicated to the conservation, development, study and practical use of biological collections of various types were held under the auspices of the First Scientific Forum “Genetic Resources of Russia”, which took place in Saint Petersburg on 21-24 June 2022. A total of more than 300 oral presentations were made at these events. The Forum plenary sessions, which included 25 lectures, attracted more than 1,500 participants. The development prospects, research and scientific-practical potential of biological collections were thoroughly discussed at the events of the Forum. The results of these discussions are presented in this publication in the form of a Forum resolution. The strategic role of biological collections for the conservation of genetic diversity, for the scientific and technological development of society and for the provision of educational processes is emphasized. This strategic framework, which should be developed and maintained, also makes it possible to implement practical tasks related to meeting the challenges in the field of food and environmental security, health care and technological independence in the rapidly developing spheres of the economy

    On the results of the Second Scientific Forum “Genetic Resources of Russia”

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    The Second Scientific Forum “Genetic Resources of Russia” was held in St. Petersburg, June 26-28, 2023. Thе Forum comprised nine associated scientific conferences and conference schools dedicated to the establishment, formation, conservation, development, studying and utilization of biological (bioresource) collections as well as to the activities of bioresource centers, and a round table entitled “Statutory Legal Regulation and Standards for the Work with Bioresource Collections”. More than 700 researchers representing over a hundred scientific institutions and universities from Russia and other countries participated in the Forum. In total, more than 200 oral presentations were made during those events (including 16 talks at the Forum’s Plenary Session). The participants of the Forum events thoroughly discussed the results of the Federal Scientific and Technical Program for the Development of Genetic Technologies for 2019-2030 associated with the establishment and development of bioresource collections for research in the field of genetic technologies, the prospects for the promotion of this sector, and the regulatory legal framework in the sphere of ensuring conservation and development of biological (bioresource) collections, establishment and functioning of bioresource centers, and their sustainable and rational utilization in scientific research and development activities. The outcome of those discussions is presented in this publication in the form of the Forum’s Resolution. Upon reviewing the results of the Federal Scientific and Technical Program for the Development of Genetic Technologies for 2019-2030 pertaining to the establishment and development of bioresource collections for research in the field of genetic technologies, the Forum recognized them as successful. The Forum approved the draft of the legal act “On Bioresource Centers and Biological (Bioresource) Collections”, which is currently under consideration in the State Duma of the Russian Federation and emphasized the need for its soonest adoption
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