Spectroscopic studies of the stability of monolayers of 2-docosylamino-5-nitropyridine at the air/water interface

Monolayers of 2-docosylamino-5-nitropyridine (DCANP) at the air/water interface were investigated by UV/Vis spectroscopy. The combination of this method with the classic constant-area relaxation technique yields insight into the longtime stability and the collapse behavior of monolayers. We have demonstrated that monolayers of DCANP are certainly stable under standard deposition conditions. At surface pressures above 20 mN/m monolayer instabilities lead to the formation of a three-dimensional head-to-head multilayered structure.     

Sonochemical preparation of GaSb nanoparticles

A room temperature sonochemical method for the preparation of GaSb nanoparticles using less hazardous Ga and antimony chloride (SbCl(3)) as the precursors has been described. The formation of GaSb has been confirmed by means of XRD, EDAX, and XPS characterization. TEM and SAED results show that the as-prepared solid consists of nanosized GaSb crystals with sizes in the range 20-30 nm. The photoacoustic spectrum result reveals that the GaSb nanoparticles have a direct band gap of about 1.21 eV. On the basis of the control experiments and the extreme conditions produced by ultrasound, an ultrasound-assisted in-situ reduction/combination mechanism has been proposed to explain the reaction.     

Structure of hadron matter: Hierarchy,democracy, or potentiality?

An attempt is made to give a methodological and physical characterization to the concept of the structure of matter. The methodological status of theories describing the structure of hadrons is discussed. A parallelism is drawn between the quark model as a theory of the mathematical composite structure of hadrons and Plato's theory of matter. The merger of the bootstrap idea with a quark substructure of hadrons is discussed. A third approach to the structure of hadron matter is presented. It resembles the Aristotelian conception of primary matter on which form is imprinted potentially.     

Argon matrix absorption spectra of ClO, BrO, and IO and emission spectra of IO

Absorption spectra of ClO, BrO, and IO and the emission spectrum of IO have been observed from argon matrix samples prepared by microwave discharging the reagent mixture before condensation. Vibronic progressions were observed for each system. The spectroscopic scopic constants T_e, ω′_e, ω_ex′_e, ω″_e, and ω_ex″_e were evaluated from the absorption and emission data for comparison with gas-phase constants. Very good agreement is found for ClO. The argon matrix observations dictate a revision of the gas-phase vibronic assignments for BrO. The ground-state vibrational fundamental and T_e for argon matrix isolated IO are similar to the gas-phase values, but a lower excited-state spacing is found in the matrix.     

Microwave–assisted synthesis of <Emphasis Type="Italic">submicrometer</Emphasis> GaO(OH) and Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> rods

Submicrometer sized gallium oxide hydroxide (GaO(OH)) and gallium oxide (Ga₂O₃) rods have been successfully fabricated on a large scale by refluxing an aqueous solution of Ga(NO₃)₃ and NH₄OH in a simple domestic microwave oven (DMO). The structures, morphologies, compositions and physical properties of the as–synthesized and calcined products have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), selected area energy dispersive X-ray spectroscopy (SAEDS), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), and energy dispersive X-ray (EDX) analysis. TEM images show that submicrometer sized as–synthesized Ga O(OH) rods have diameters of 0.3–0.5 m and lengths of 3.2–3.5 m. The calcined product consists of submicrometer rods with diameters of 0.4–0.5 m and lengths of 5–5.5 m. XRD, EDX and SAED analysis together indicate that the as–synthesized product has an orthorhombic gallium oxide hydroxide (GaO(OH)) crystal structure, and that the calcined product is rhombohedral Ga₂O₃. A possible mechanism for the formation of submicrometer sized GaO(OH) rods is discussed briefly.     

Soliton-based Y-branch in photorefractive crystals induced through dispersion-shifted optical fiber

We experimentally demonstrate for what is believed to be the first time that a dispersion-shifted fiber can be used to electro-optically induce a soliton Y-branch structure in a photorefractive centrosymmetric paraelectric crystal (potassium lithium tantalate niobate). The application of a nonstationary external bias field enables us to stabilize the spatially partially coherent behavior of the optical beam at the fiber output. Furthermore, we show the switching capabilities of this soliton-based device in the optical communication field guiding a probe beam at a nonphotorefractive wavelength (1557 nm).     

Wasserzusatz

Ohne Zusammenfassung     

Duality in robust optimization: Primal worst equals dual best

We study the dual problems associated with the robust counterparts of uncertain convex programs. We show that while the primal robust problem corresponds to a decision maker operating under the worst possible data, the dual problem corresponds to a decision maker operating under the best possible data.     

Frequency– and Time-domain BEM Analysis of Rigid Track on a Half-Space with Vibration Barriers

The rapid development of high-speed trains like the TGV or the ICE in recent years results in high dynamic loads causing vibrations which propagate from the train-track structure into the ground and further into nearby buildings. In this context it is important to develop rigid tracks with improved dynamic behaviour and to investigate possible means of vibration reduction. The boundary element method in frequency and time domain is used to simulate train-track structures subjected to dynamic loading and the reduction of vibrations which for instance can be achieved via a trench running parallel to the rigid track. In this context the non-causality error, which arises when the time-domain BEM algorithm is applied to mathematically concave domains, is discussed and the substructure method is proposed as a solution to this problem. A two-layered cylindrical elastic structure on a half-space with a trench is added as an example of a possible application.