Role of bromine on the thermal and optical properties of photo-thermo-refractive glass

Photo-thermo-refractive (PTR) glass is a photosensitive silicate glass doped with cerium, silver, and fluorine. The precipitation of a minor crystalline phase after UV-exposure and thermal treatment induces a refractive index change, which is large enough to create diffractive optical elements. In this work we present a first attempt to understand the role of bromine on thermal and optical properties of PTR glass. We reveal that at least 75% of the concentration of bromine of commercial PTR glass is necessary to produce photo-induced crystallization. We also show that an increase of the bromine concentration will increase the mean refractive index of virgin PTR glass. Further thermal treatments induce a decrease of the mean refractive index of PTR glass. This decrease is finally shown to be larger in UV-exposed glass if photo-induced crystallization is present. We also show that bromine concentration will decrease water concentration in PTR glass and have an impact on the losses in visible. We demonstrate that the higher the bromine concentration, the higher the shift of the silver containing particles absorption band. In addition, if bromine concentration is high enough to produce photosensitivity, an increase of scattering due to the crystallization process is observed.     

Synthesis of functionalized 1‐trimethylsiloxy‐substituted O‐trimethylsilyl alkylphosphonites and their derivatives

Nucleophilic addition of trimethylsilyl esters of tricoordinate organophosphorus acids to various functionalized aldehydes with vinyl, aryl, and heterocyclic fragments is proposed as a convenient method for the synthesis of new 1‐trimethylsiloxysubstituted alkylphosphonites and their derivatives at mild conditions. Also the new functionalized derivatives of these phosphonites, including amino groups as well as certain properties of these compounds as important precursors of new functionalized 1‐hydroxyalkylorganophosphorus acids, are presented. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:352–359, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20430     

Non-linear elastic behavior of filler aggregates

A filled rubber network consists of polymer chains which are suspended between filler aggregates. In this contribution, the nonlinear elastic behavior of the aggregated filler particles inside the rubber matrix is investigated. Previously, by using scaling theory, the influence of initial length and fractal dimension of aggregates on the elastic response of aggregated structures was studied. Here we additionally take into account a deformation induced evolution of the aggregate structure. To this end, the directional topology of the aggregate structure is represented by its backbone chain. Thus, the analytical approach proposed describes not only the geometrically but also the physically non-linear behavior of aggregates. Our solution can further be generalized for colloidal structures as for example granular materials or suspended solid structures. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modification of anode surface in organic light-emitting diodes by chalcogenes

Influence of thin chalcogen X (S, Se, Te) interlayer between anode (indium-tin oxide, ITO) and a layer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) used as a hole-transport layer (HTL) on the operating characteristics of organic light-emitting diodes (OLEDs) of composition ITO/X/TPD/Alq₃/Yb (Alq₃ - aluminum 8-quinolinolate) has been investigated. It was found that the sulphur layer decreases operating voltage and enhances operating stability of a device while the selenium or tellurium interlayers impair these characteristics.     

Limit Correlation Functions for Fixed Trace Random Matrix Ensembles

Universal limits for the eigenvalue correlation functions in the bulk of the spectrum are shown for a class of nondeterminantal random matrices known as the fixed trace or the Hilbert-Schmidt ensemble. These universal limits have been proved before for determinantal Hermitian matrix ensembles and for some special classes of the Wigner random matrices. Research supported by Sonderforschungsbereich 701 “Spektrale Strukturen und Topologische Methoden in der Mathematik”. Research supported by Sonderforschungsbereich 701 “Spektrale Strukturen und Topologische Methoden in der Mathematik,” and grants RFBR-05-01-00911, DFG-RFBR-04-01-04000, and NS-638.2008.1.     

Evidence for double acoustic windows in the dolphin, Tursiops truncatus

In a bottlenose dolphin positions of sound receiving areas on the head surface were determined by comparing the acoustic delays from different sound-source positions. For this investigation, auditory brainstem responses (ABRs) to short tone pips were recorded and their latencies were measured at different sound source positions. After correction for the latency dependence on response amplitude, the difference in ABR latencies was adopted as being the difference of the acoustic delays. These delay differences were used to calculate the position of the sound-receiving point. Measurements were conducted at sound frequencies from 16 to 128 kHz, in half-octave steps. At probe frequencies of 16 and 22.5 kHz, the receiving area was located 21.7-26 cm caudal of the melon tip, which is near the bulla and auditory meatus. At higher probe frequencies, from 32 to 128 kHz, the receiving area was located from 9.3 to 13.1 cm caudal of the melon tip, which corresponds to a proximal part of the lower jaw. Thus, at least two sound-receiving areas (acoustic windows) with different frequency sensitivity were identified.     

Structure and linear spectroscopic properties of near IR polymethine dyes

We performed a detailed experimental investigation and quantum-chemical analysis of a new series of near IR polymethine dyes with 5-butyl-7,8-dihydrobenzo[cd]furo[2,3-f]indolium terminal groups. We also synthesized and studied two neutral dyes, squaraine and tetraone, with the same terminal groups and performed a comparison of the spectroscopic properties of this set of “near IR” dyes (polymethine, squaraine, and tetraone) with an analogous set of “visible” dyes with simpler benzo[e]indolium terminal groups. From these measurements, we find that the dyes with dihydrobenzo[cd]furo[2,3-f]indolium terminal groups are characterized by a remarkably large shift ≈300 nm (≈200 nm for tetraone) of their absorption bands towards the red region. We discuss the difference in electronic structure for these molecules and show that the “near IR” dyes are characterized by an additional weak fluorescence band from the higher lying excited states connected with the terminal groups. Absorption spectra for the longest polymethines are solvent-dependent and are characterized by a broadening of the main band in polar solvents, which is explained by ground state symmetry breaking and reduced charge delocalization within the polymethine chromophore. The results of these experiments combined with the agreement of quantum chemical calculations moves us closer to a predictive capability for structure-property relations in cyanine-like molecules.     

Stationary ring solitons in field theory — Knots and vortons

We review the current status of the problem of constructing classical field theory solutions describing stationary vortex rings in Minkowski space in 3+1 dimensions. We describe the known up to date solutions of this type, such as the static knot solitons stabilized by the topological Hopf charge, the attempts to gauge them, the anomalous solitons stabilized by the Chern–Simons number, as well as the non-Abelian monopole and sphaleron rings. Passing to the rotating solutions, we first discuss the conditions ensuring that they do not radiate, and then describe the spinning Q$Q$-balls, their twisted and gauged generalizations reported here for the first time, spinning skyrmions, and rotating monopole–antimonopole pairs. We then present the first explicit construction of global vortons as solutions of the elliptic boundary value problem, which demonstrates their non-radiating character. Finally, we describe the analogs of vortons in the Bose–Einstein condensates, analogs of spinning Q$Q$-balls in the non-linear optics, and also moving vortex rings in superfluid helium and in ferromagnetics.     

Passivation at semiconductor/electrolyte interface: Role of adsorbate solvation and reactivity in surface atomic and electronic structure modification of III-V semiconductor

These studies are focused on understanding the role played by a solvent in chemical and electronic processes occurred in the course of semiconductor surface passivation at semiconductor/electrolyte interface. It is shown that the chemical reactivity of the ionic adsorbate at a semiconductor/electrolyte interface can be changed considerably through interaction with solvent molecules. The reactivity of anions depends essentially on the solvating solvent: hydrated ions could be either slightly electrophilic or slightly nucleophilic, whereas the ions solvated by alcohol molecules are always strongly nucleophilic. Mechanism of interaction of such solvated ions with the semiconductor surface atoms depends on the solvent, as is demonstrated by the example of processes occurred at GaAs(1 0 0)/sulfide solution interfaces. It is found that on adsorption of HS⁻ ions from different solvents the AsS bonds with solvent-dependent ionic character are formed on a GaAs(1 0 0) surface. The surface obtained in such a way possesses different ionization energy and exhibit different electronic properties dependent on the solvent.     

A simple method for timing an XFEL source to high-power lasers

We propose a technique for timing an X-ray free-electron laser (XFEL) to a high-power conventional laser with femtosecond accuracy, yielding the relative jitter between pump and X-ray probe, and allowing sorting of experimental results over a certain time window. The same electron bunch is used to produce both an XFEL pulse and an ultrashort optical pulse by means of an optical radiator downstream of the X-ray undulator. Being produced by the same electron bunch, these pulses are perfectly synchronized. Cross-correlation techniques will allow to determine relative jitter between the optical pulse (and, thus, the XFEL pulse) and a pulse from an external pump-laser. Technical realization of the proposed timing scheme uses an optical-replica synthesizer setup to be installed after the final bunch-compression stage of the XFEL for electron bunch diagnostics purposes. A number of critical issues are quantitatively analyzed.