Theory of radiation trapping by the accelerating solitons in optical fibers

We present a theory describing trapping of the normally dispersive radiation by the Raman solitons in optical fibers. Frequency of the radiation component is continuously blue shifting, while the soliton is red shifting. Underlying physics of the trapping effect is in the existence of the inertial gravity-like force acting on light in the accelerating frame of reference. We present analytical calculations of the rate of the opposing frequency shifts of the soliton and trapped radiation and find it to be greater than the rate of the red shift of the bare Raman soliton. Our findings are essential for understanding of the continuous shift of the high frequency edge of the supercontinuum spectra generated in photonic crystal fibers towards higher frequencies.Comment: Several misprints in text and formulas corrected. 10 pages, 9 figures, submitted to Phys. Rev.

АТP as the marker of power exchange condition at the experimental ischemia of the myocardium due to metabolic drugs introduction

For the purpose of definition of an adequate marker of a power exchange condition at the experimental ischemia of the myocardium due introduction of metabolic drugs, the experimental research on 60 rats-males of Wistar line has been spent. At experimental myocardial ischemia it has been found out energy-saving effects of trimetazidine, cytoflavin, meldonium, phosphocreatine, which were reached by different ways and in different degre

Looking at a soliton through the prism of optical supercontinuum

A traditional view on solitons in optical fibers as robust particle-like structures suited for informa- tion transmission has been significantly altered and broadened over the past decade, when solitons have been found to play the major role in generation of octave broad supercontinuum spectra in photonic-crystal and other types of optical fibers. This remarkable spectral broadening is achieved through complex processes of dispersive radiation being scattered from, emitted and transformed by solitons. Thus solitons have emerged as the major players in nonlinear frequency conversion in optical fibers. Unexpected analogies of these processes have been found with dynamics of ultracold atoms and ocean waves. This colloquium focuses on recent understanding and new insights into physics of soliton-radiation interaction and supercontinuum generation.Comment: http://rmp.aps.org/abstract/RMP/v82/i2/p1287_1 (some figures have been deleted due to space limits imposed by archive

Formation of self-organized organic-inorganic hybrids

The morphology features and peculiarities of current-voltage characteristics of selforganized organic–silicon hybrids were investigated. The organic layers were formed by chemical bath deposition at room temperatures of phosphorus doped n-type FZ Si-patterned substrate. The pattern was formed by etching in anisotropic etch on the base of aqueous solution of potassium hydrate KOH and isopropyl alcohol. The following aqueous solutions of organic heterocyclic aromatic compounds were used for hybrids formation: sulfacyl sodium, procainamide hydrochloride (novocain) and lamotridgine. These hybrids have shown different types of morphology. This depends on substrate properties, time deposition and organic concentration in water solution. The photovoltaic effect of organic-pattern silicon is the result of chemisorptions of functional amine, amide, carboxyl, thiols and halogen groups on silicon pattern-type surface. At the same time these results have proven that the substrate of start and classic morphology in pyramid form is favored for formation of organic-silicon hybrids for photovoltaic application.Досліджено морфологічні властивості та особливості характеристик струм–напруга для самоорганізованих кремнійорганічних гібридів. Органічні шари було одержано хімічним осадженням за кімнатної температури легованих фосфором візерункових кремнієвих субстратів FZ n-типу. Візерунок формували витравлюванням в анізотропних травниках на основі водного розчину гідрату калію КОН та ізопропилового спирту. В подальшому для отримання гібридів використовували водні розчини органічних гетероциклічних сполук: сульфосаліцилового натрію, гідро хлориду прокаінаміду (новокаїну) і ламотріджину. Ці гібриди показали різну морфологію. Вона залежить від властивостей субстрату, часу осадження та концентрації органічної складової у водних розчинах. Фотогальванічний ефект кремнійорганічного рисунка є результатом хемосорбції функціональних груп амінів, амідів, карбоксилу, тріолів та галогену на поверхні кремнію. Водночас, ці результати підтверджують,що субстрат початкової і класичної морфології у вигляді піраміди кращий для утворення кремнійорганічних гібридів фотогальванічного застосування.Исследованы морфологические свойства и особенности характеристик ток–напряжение для самоорганизующихся кремнийорганических гибридов. Органические слои были получены химическим осаждением при комнатной температуре легированных фосфором узорчатых кремниевых субстратов FZ n-типа. Узор формировали вытравливанием в анизотропных травителях на основе водного раствора гидрата калия KOH и изопропилового спирта. В дальнейшем для получения гибридов использовали водные растворы органических гетероциклических соединений: сульфосалицилового натрия, гидрохлорида прокаинамида (новокаина) и ламотритриджина. Эти гибриды показали различную морфологию. Она зависит от свойств субстрата, времени осаждения и концентрации органической составляющей в водных растворах. Фотогальванический эффект кремнийорганического рисунка является результатом хемосорбции функциональных групп аминов, амидов, карбоксила, триолов и галогена на поверхности кремния. В то же самое время, эти результаты подтверждают, что субстрат начальной и классической морфологии в виде пирамиды является предпочтительным для образования кремнийорганических гибридов фотогальванического применения

Gate-tunable electroluminescence in Aviram-Ratner-type molecules: Kinetic description

Project No. 0116U002067 Grant No. 871284A theoretical study of the mechanisms of electroluminescence (EL) generation in photoactive molecules with donor and acceptor centers linked by saturated σ-bonds (molecules of the Aviram-Ratner-type) is presented. The approach is based on the kinetics of single-electron transitions between many-body molecular states. This study shows that the EL polarity arises due to asymmetric coupling of molecular orbitals of the photochromic part of the molecule to the electrodes. The gate voltage controls the power of the EL through the occupancy of the excited singlet state. The shifting of the orbital energies forms a resonant or a non-resonant path for the transmission of electrons through the molecule. The action of the gate voltage is reflected in specific critical voltages. An analytical dependence of the critical voltages on the energies of molecular states involved in the formation of EL, as well as on the gate voltage, was derived for both positive and negative polarities. Conditions under which the gate voltage lowers the absolute value of the bias voltage that is responsible for the activation of the resonance mechanism of EL formation were also established. This is an important factor in control of EL in molecular junctions.publishersversionpublishe

Multi-stability and polariton formation in microcavity polaritonic waveguides

Nonlinear polaritons in microcavity waveguides are demonstrated to exhibit multi-stable behaviour and rich dynamics, including filamentation and soliton formation. We find that the multi-stability originates from co-existense of different transverse modes of the po- laritonic waveguide. Modulational stability and conditions for multi-mode polariton solitons are studied. Soliton propagation in tilted, relative to the pump momentum, waveguides is demonstrated and a critical tilt angle for the soliton propagation is found

Features of superexchange nonresonant tunneling conductance in anchored molecular wires

NAS Ukraine via Project No. 0116U002067A modified superexchange model is used to clarify the physical mechanisms for the formation of nonresonant tunneling conductance in terminated molecular wires. Due to the specific relationship between its key parameters, this model has wider areas of applicability compared to the flat-barrier model and the standard superexchange model, which are widely involved for the physical interpretation of experimental results. Moreover, the results obtained in the two latest models appear in the modified model as characteristic limiting cases. Our estimates show that the exponential decay of conductance, characterized by an attenuation factor β (per repeating unit), is limited by the conditions β ≤ 1.2 and β ≥ 3.7 for the flat-barrier and standard models, respectively. At the same time, the modified superexchange model yields β > 0, which, thus, allows us to analyze the tunneling conductance in molecular wires containing both saturated and conjugated bonds. We also show that for a small number of N repeating wire units (about 3-6 depending on the value of β), the exponential dependence of conductance on N is violated and, accordingly, contact conductance is not identical to conductance at N = 0. Formulas are found which, on the basis of experimental data, make it possible to establish the values of superexchange parameters as well as indicate the conditions of possible hybridization between the orbitals of the anchor groups and the adjacent end units belonging to the interior wire region. One example is the establishment of features in the tunneling conductance of terminated alkane chains caused by the nature of their anchor groups.publishersversionpublishe