Synthesis,vibrational, and conformational properties of novel polyazadioxime chain molecules

Novel large polyazadioxime molecules 4,5,8,9-tetraaza-3,6,7,10-tetramethyl -3,5,7,9-dodecatetraene-2, 11-dione-2, 11-dioxime (H₂doxN₄) and 4,5,8,9,12, 13-hexaaza-3,6,7,10,11,14-hexamethyl-3, 5,7,9,11,13-hexadecahexane-2,15-dione-2, 15-dioxime (H₂doxN₆) were synthesized. The molecular geometries of these molecules as well as smaller dioxime molecules, H₂dox and H₂doxN₂ were optimized by using modified intermediate neglect of differential overlap (MNDO) calculations. The optimized conformations for all the molecules under study are close to the all-E, all-s trans conformation of C_2h symmetry group. However, the energy barriers of internal rotation around the N-N single bonds were found to be low. Therefore some distortions of the polyazabackbone through internal rotation the N-N bonds have been evidenced. By infrared and Raman spectroscopies in the solid state as well as in solution. From the MNDO calculations and vibrational spectroscopy, the polyaza chain molecules under study appear as a poorly conjugated system and can be represented as a sequence of single and double bond alternation.     

Memory-free conic anchoring of liquid crystals on a solid substrate

We show that the anchoring memory of liquid crystals on solid substrates can be completely removed by grafting highly mobile polymer chains. Using grafted polystyrene, we obtain uniform, stable, and reproducible memory-free and conically degenerated anchoring of the nematic 5CB. The symmetry of the conic anchoring enables two different zenithal anchoring breakings, towards homeotropic and planar states. Under external torques we observe both of them, with weak thresholds.     

Towards a monolithic optical cavity for atom detection and manipulation

We study a Fabry-Perot cavity formed from a ridge waveguide on a AlGaAs substrate. We experimentally determined the propagation losses in the waveguide at 780 nm, the wavelength of Rb atoms. We have also made a numerical and analytical estimate of the losses induced by the presence of the gap which would allow the interaction of cold atoms with the cavity field. We found that the intrinsic finesse of the gapped cavity can be on the order of F∼30, which, when one takes into account the losses due to mirror transmission, corresponds to a cooperativity parameter for our system C∼1.     

Variational problem in the non-negative orthant of ℝ<Superscript>3</Superscript>: reflective faces and boundary influence cones

In this paper we consider the variational problem in the non-negative orthant of ℝ³. The solution of this problem gives the large deviation rate function for the stationary distribution of an SRBM (Semimartingal Reflecting Brownian Motion). Avram, Dai and Hasenbein (Queueing Syst. 37, 259–289, 2001) provided an explicit solution of this problem in the non-negative quadrant. Building on this work, we characterize reflective faces of the non-negative orthant of ℝ ^d , we construct boundary influence cones and we provide an explicit solution of several constrained variational problems in ℝ³. Moreover, we give conditions under which certain spiraling paths to a point on an axis have a cost which is strictly less than the cost of every direct path and path with two pieces.     

An agricultural investment problem subject to probabilistic constraints

Computational Management Science - Motivated by a model introduced by Moiseev, we consider a problem of optimal investment into agricultural infrastructure (irrigation, storage) under uncertainty...     

On the distribution function with respect to conditional expectation on Riesz spaces

The notion of distribution function with respect to a conditional expectation is defined and studied in the framework of Riesz spaces.     

Burkholder theorem in Riesz spaces

The main purpose of this paper is to give a vector lattice version of a Theorem by Burkholder about convergence of martingales. The proof is based on a vector lattice analogue of Austin’s sample function theorem, proved recently by Grobler, Labuschagne and Marraffa and on a new characterization of elements of the sup-completion of a universally complete vector lattice do not belong to the space.

     

Monitoring fatigue cracks and stress intensity factors based on local strains

A method for crack detection and stress intensity factor measurement in plate structures is presented by using strain gauges and applying the Body Force Method (BFM). The BFM is based on elastic solutions for concentrated loads and the principle of linear superposition allowing e.g. the calculation of the strain field in a cracked body. The inverse problem is solved applying the PSO (particle swarm optimization) and the unknown parameters are crack position, length and inclination as well as loading quantities. Experiments are carried out under cyclic loading using pre-cracked plates made of aluminum alloy. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new flavonoid and other constituents from Centaurea nicaeensis All. var. walliana M

A new flavone glucoside, apigenin 4'-(6″-methylglucuronide) (1), together with six known compounds, cirsilineol, jaceosidin, melitensin, apigenin, apigenin 7-(6″-methylglucuronide) and prunasin, were isolated from the ethanolic extract of the aerial parts of Centaurea nicaeensis All. var. walliana M. (Asteraceae) collected from Souk-Ahras, eastern Algeria. The structures were established by spectral analysis, mainly HRESI-MS, UV and 2D-NMR experiments (COSY, HSQC and HMBC).     

Antimonide-based lasers and DFB laser diodes in the 2–2.7 μm wavelength range for absorption spectroscopy

We report on Fabry–Pérot semiconductor lasers and single frequency distributed feedback lasers based on GaInAsSb/AlGaAsSb quantum wells. The laser structures were grown by molecular beam epitaxy on GaSb substrates. The devices were etched either by wet process or by inductively coupled plasma (ICP) process. Electron-beam lithography was used to deposit a metal Bragg grating on each side of the laser ridge to fabricate the DFB lasers. The devices all operate in the continuous wave regime at room temperature with a single frequency emission above 2.6 μm and good tuning properties, making them well adapted to tunable diode laser absorption spectroscopy. PACS 42.55.Px; 42.62.Fi