Transillumination imaging through scattering media by use of photorefractive polymers

We demonstrate the use of a near-infrared-sensitive photorefractive polymer with high efficiency for imaging through scattering media, using an all-optical holographic time gate. Imaging through nine scattering mean free paths is performed at 800 nm with a mode-locked continuous-wave Ti:sapphire laser

Sonoluminescence and collapse dynamics of multielectron bubbles in helium

Multielectron bubbles (MEBs) differ from gas-filled bubbles in that it is the Coulomb repulsion of a nanometer thin layer of electrons that forces the bubble open rather than the pressure of an enclosed gas. We analyze the implosion of MEBs subjected to a pressure step, and find that despite the difference in the underlying processes the collapse dynamics is similar to that of gas-filled bubbles. When the MEB collapses, the electrons inside it undergo strong accelerations, leading to the emission of radiation. This type of sonoluminescence does not involve heating and ionisation of any gas inside the bubble. We investigate the conditions necessary to obtain sonoluminescence from multielectron bubbles and calculate the power spectrum of the emitted radiation.Comment: 6 figure

Charged-Surface Instability Development in Liquid Helium; Exact Solutions

The nonlinear dynamics of charged-surface instability development was investigated for liquid helium far above the critical point. It is found that, if the surface charge completely screens the field above the surface, the equations of three-dimensional (3D) potential motion of a fluid are reduced to the well-known equations describing the 3D Laplacian growth process. The integrability of these equations in 2D geometry allows the analytic description of the free-surface evolution up to the formation of cuspidal singularities at the surface.Comment: latex, 5 pages, no figure

Effect of chromophore-chromophore electrostatic interactions in the NLO response of functionalized organic-inorganic sol-gel materials

In the last years, important non-linear optical results on sol-gel and polymeric materials have been reported, with values comparable to those found in crystals. These new materials contain push-pull chromophores either incorporated as guest in a high Tg polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages; however they require significant improvement at the molecular level - by designing optimized chromophores with very large molecular figure of merit, specific to each application targeted. Besides, it was recently stated in polymers that the chromophore-chromophore electrostatic interactions, which are dependent of chromophore concentration, have a strong effect into their non-linear optical properties. This has not been explored at all in sol-gel systems. In this work, the sol-gel route was used to prepare hybrid organic-inorganic thin films with different NLO chromophores grafted into the skeleton matrix. Combining a molecular engineering strategy for getting a larger molecular figure of merit and by controlling the intermolecular dipole-dipole interactions through both: the tuning of the push-pull chromophore concentration and the control of TEOS (Tetraethoxysilane) concentration, we have obtained a r33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r33 around 50 pm/V at 831 nm for a new optimized chromophore structure.Comment: 10 pages, 11 figures, 1 tabl

Пункты пропуска через государственную границу. Проблемы и пути их решения

The article deals with development of the system of border checkpoints operating within the objects of transport infrastructure.A classification of three blocks of tasks related to infrastructure, control technologies, and administration has been proposed.The necessity of unification of requirements for design, construction, reconstruction, equipment and technical equipment of buildings, premises and facilities necessary for organization of border, customs and other types of control carried out at checkpoints, their integration with transport infrastructure facilities (sea and river ports, airports, railway stations) at the design stage are explained.Optimization approaches are proposed, including use of promising information technology in organization and operation of border checkpoints. In addition, it is concluded that it is necessary to organize training and advanced training of specialists in this field on the basis of transport universities.В статье рассматриваются вопросы развития системы международных пунктов пропуска, функционирующих в пределах объектов транспортной инфраструктуры.Предложена классификация трёх блоков задач, связанных с инфраструктурой, технологиями пропуска, администрированием.Аргументируется необходимость унификации требований к проектированию, строительству, реконструкции,оборудованию и техническому оснащению зданий, помещений и сооружений, необходимых для организации пограничного, таможенного и иных видов контроля, осуществляемого в пунктах пропуска, их интеграции с объектами транспортной инфраструктуры (морскими и речными портами, аэропортами, железнодорожными станциями) на стадии проектирования,Предлагаются оптимизационные подходы, в том числе, использование перспективных информационных технологий при организации и эксплуатации международных пунктов пропуска.Кроме того, делается вывод о необходимости организации подготовки и повышения квалификации специалистовв данной области на базе транспортных вузов

Stability of multi-electron bubbles in liquid helium

The stability of multi-electron bubbles in liquid helium is investigated theoretically. We find that multi-electron bubbles are unstable against fission whenever the pressure is positive. It is shown that for moving bubbles the Bernoulli effect can result in a range of pressures over which the bubbles are stable.Comment: 7 pages, 5 figure

Realizability of Polytopes as a Low Rank Matrix Completion Problem

This article gives necessary and sufficient conditions for a relation to be the containment relation between the facets and vertices of a polytope. Also given here, are a set of matrices parameterizing the linear moduli space and another set parameterizing the projective moduli space of a combinatorial polytope

Use of Sorghum for Enhancing the Biodiversity and Nutritional Value of Semi-Desert Pasture Ecosystems

The article presents the results of studies on the adaptive potential of sorghum used for restoration of degraded pasture ecosystems, increasing their biodiversity and nutritional value. The region chosen for the experiment is a semi-desert arid part of southern Russia. The aridity coefficient is 0.11–0.30 which is typical of the arid zone. The annual volume of precipitation is 125-265 mm. Two varieties of sorghum – Travinka and Caravan – were studied. They were grown with different thickness: 10 thousand, 20 thousand and 40 thousand plants per 1 hectare. During the growing season, there was soil and atmospheric drought. The best indicators of green mass yield were recorded for Travinka for the variant “40 thousand plants per hectare – 7.9 tons per hectare, and for Caravan for the variant “20 thousand plants per hecrate – 3.9 tons per hectare. Compared with natural pasture, sorghum productivity is 18 times higher by green mass yield and 26 times higher by dry mass yield (the best options). The analysis of the chemical composition and nutritional value of sorghum showed that compared to the plants of natural pasture, sorghum is a more nutritious fodder plant. Its nutritional value is more by 0.24 feed units per 1 kg and by 1.9 % by the mass of crude protein. It is better than other plants by the content of sugar content (79 g per 1 kg) and macronutrients

The effect of pressure on statics, dynamics and stability of multielectron bubbles

The effect of pressure and negative pressure on the modes of oscillation of a multi-electron bubble in liquid helium is calculated. Already at low pressures of the order of 10-100 mbar, these effects are found to significantly modify the frequencies of oscillation of the bubble. Stabilization of the bubble is shown to occur in the presence of a small negative pressure, which expands the bubble radius. Above a threshold negative pressure, the bubble is unstable.Comment: 4 pages, 2 figures, accepted for publication in Physical Review Letter