Stable multiple-charged localized optical vortices in cubic-quintic nonlinear media

The stability of two-dimensional bright vortex solitons in a media with focusing cubic and defocusing quintic nonlinearities is investigated analytically and numerically. It is proved that above some critical beam powers not only one- and two-charged but also multiple-charged stable vortex solitons do exist. A vortex soliton occurs robust with respect to symmetry-breaking modulational instability in the self-defocusing regime provided that its radial profile becomes flattened, so that a self-trapped wave beam gets a pronounced surface. It is demonstrated that the dynamics of a slightly perturbed stable vortex soliton resembles an oscillation of a liquid stream having a surface tension. Using the idea of sustaining effective surface tension for spatial vortex soliton in a media with competing nonlinearities the explanation of a suppression of the modulational instability is proposed.Comment: 4 pages, 3 figures. Submitted to Journal of Optics A. The proceedings of the workshop NATO ARW, Kiev 2003 Singular Optics 200

Fast recognition of marine particles in underwater digital holography

The issue of fast recognition of marine particles in situ by digital holography methods is considered. An algorithm for the classification of marine particles by morphological features is proposed. Preliminary results and estimation of accuracy of the proposed algorithm are presented

Digital holographic camera for plankton monitoring

A submersible digital holographic camera for measuring plankton and other particles is described. The camera provides underwater recording of digital holograms of water volume containing plankton followed by automatic restoration of holographic images of plankton species, determination of their sizes, shapes, and concentrations, and their recognition and classification. Particles with sizes of 200 μm and larger are analyzed. The water volume registered per exposure is about 1 L. The special features of the software for automatic information retrieval from digital holograms are discussed. Examples of application of the camera as an integral part of the hardware-software complex for field measurements are given. Prospects for application of this complex for ecological monitoring are discussed. The recognition criterion of the digital holographic camera and the data volume and the averaging time required for obtaining statistically reliable data on plankton species are also given

Stability of two-dimensional spatial solitons in nonlocal nonlinear media

We discuss existence and stability of two-dimensional solitons in media with spatially nonlocal nonlinear response. We show that such systems, which include thermal nonlinearity and dipolar Bose Einstein condensates, may support a variety of stationary localized structures - including rotating spatial solitons. We also demonstrate that the stability of these structures critically depends on the spatial profile of the nonlocal response function.Comment: 8 pages, 9 figure

Современные векторы российской дипломатии на постсоветском пространстве

The countries of the post-Soviet space are of particular importance for Russia’s geopolitical interests. This primarily concerns the political and economic processes taking place in them. Moreover, of great importance are the approaches of the post-Soviet countries to cooperation with Russia and integration processes in the post-Soviet space. In view of significant negative trends in the international arena, the consolidation of the post-Soviet space is acquiring paramount significance. Numerous challenges and complexity of the tasks that Russia is facing in the present region underscore the need for a balanced, pragmatic and forward-looking approach in bilateral and multilateral relations with the states. The focus of Russian diplomacy is still on Ukraine, the countries of the South Caucasus and Central Asia, Moldova and Belarus. These countries are the priority partners of Russia, the priority of its foreign policy.Особую важность для геополитических интересов России представляют страны постсоветского пространства. В первую очередь, это касается происходящих в них политических и экономических процессов. Большое значением имеют подходы стран постсоветского пространства к сотрудничеству с Россией и их позиции в отношении интеграционных процессов на постсоветском пространстве. Ввиду значительных негативных тенденций на международной арене объединение постсоветского пространства, налаживание новых форм сотрудничества и взаимодействия приобретает первостепенное значение. Сложность и комплексность задач, стоящих перед Россией на постсоветском пространстве, подчеркивает необходимость взвешенного и прагматичного, нацеленного на перспективу подхода в двусторонних и многосторонних отношениях с государствами. В фокусе внимания российской дипломатии по-прежнему находится Украина, страны Южного Кавказа и Центральной Азии, Молдавия и Белоруссия. Именно данные страны являются приоритетными партнерами России, приоритетом ее внешней политики

Cleaning graphene : a first quantum/classical molecular dynamics approach

Graphene outstanding properties created a huge interest in the condensed matter community and unprecedented fundings at the international scale in the hope of application developments. Recently, there have been several reports of incomplete removal of the polymer resists used to transfer as-grown graphene from one substrate to another, resulting in altered graphene transport properties. Finding a large-scale solution to clean graphene from adsorbed residues is highly desirable and one promising possibility would be to use hydrogen plasmas. In this spirit, we couple here quantum and classical molecular dynamics simulations to explore the kinetic energy ranges required by atomic hydrogen to selectively etch a simple residue, a CH3 group, without irreversibly damaging the graphene. For incident energies in the 2-15 eV range, the CH3 radical can be etched by forming a volatile CH4 compound which leaves the surface, either in the CH4 form or breaking into CH3+H fragments, without further defect formation. At this energy, adsorption of H atoms on graphene is possible and further annealing will be required to recover pristine graphene.Comment: 9 figures, 27 page

Broadband dielectric spectroscopy on benzophenone: alpha relaxation, beta relaxation, and mode coupling theory

We have performed a detailed dielectric investigation of the relaxational dynamics of glass-forming benzophenone. Our measurements cover a broad frequency range of 0.1 Hz to 120 GHz and temperatures from far below the glass temperature well up into the region of the small-viscosity liquid. With respect to the alpha relaxation this material can be characterized as a typical molecular glass former with rather high fragility. A good agreement of the alpha relaxation behavior with the predictions of the mode coupling theory of the glass transition is stated. In addition, at temperatures below and in the vicinity of Tg we detect a well-pronounced beta relaxation of Johari-Goldstein type, which with increasing temperature develops into an excess wing. We compare our results to literature data from optical Kerr effect and depolarized light scattering experiments, where an excess-wing like feature was observed in the 1 - 100 GHz region. We address the question if the Cole-Cole peak, which was invoked to describe the optical Kerr effect data within the framework of the mode coupling theory, has any relation to the canonical beta relaxation detected by dielectric spectroscopy.Comment: 11 pages, 7 figures; revised version with new Fig. 5 and some smaller changes according to referees' demand

Pathogenesis of Mastoiditis Complications in Children

Purpose: To review our recent experience in the diagnosis and treatment of acute mastoiditis and its complications in children.Materials and Methods: 26 children with acute mastoiditis were included in the study. Complications occurred in 15,4 % of episodes.Results: All patients were split into 3 groups. Group 1 included 13 children whose recovery was due to the application of paracentesis and antibiotic treatment; group 2 included 11 children who underwent mastoid surgical intervention; group 3 included 2 children with delitescent mastoid disease diagnosed after complications development. Complications were found in 3 patients: subperiosteal abscess – in 1 patient, peripheral facial palsy – in 2 patients with masked mastoiditis.Summary: Complications of acute mastoiditis occur in cases where the aditus ad antrum is obstructed with edematous mucosa or inflammatory granulation tissue. Antibiotic treatment at the onset of symptoms of the acute otitis media does not prevent complications

Organizational work on revision the resolutions of industrial safety expertise

The issues of examination of industrial safety as a tool for conformity of industrial equipment with the requirements of regulatory documents are considered. It’s underlined that at present, the regulatory framework for industrial safety is intensively developing. It’s proved that in order to ensure the quality of the preparation of the resolutions of industrial safety expertise the development of a standard for expert organization that will set the requirements for the structure and content of report documentation would be expedientРассматриваются вопросы экспертизы промышленной безопасности как инструмента подтверждения соответствия промышленного оборудования требованиям нормативной документации. Подчеркивается, что в настоящее время нормативная база по промышленной безопасности интенсивно развивается. Доказывается, что для обеспечения качества при подготовке заключений по результатам экспертизы промышленной безопасности целесообразна разработка стандарта экспертной организации, устанавливающего требования к составу и содержанию отчетной документаци