Mutual-focusing of two co-propagating beams and formation of trapped spatial breather pair in saturable nonlinear media

In this paper, using parabolic equation approach, coupled propagation of two coaxially co-propagating and mutually incoherent bright cylindrical beams in saturable nonlinear medium has been investigated. Considering the coupling coefficient equal to unity (κ=1), a detailed account of formation of spatial soliton pair (i.e. both beams are stationary trapped) and spatial breather pair (i.e. width of each beam oscillates with the propagation distance) has been provided and existence of spatially trapped breather pair (i.e. average width of each breather of the pair does not change with the propagation distance) has been shown. Conditions of formation of trapped spatial breather pair and their existence line has also been revealed for arbitrary beam width ratio of the beams. It is revealed that spatial soliton pairs are just a special case of trapped breather pair. The regions (conditions) of mutual-focusing and mutual-defocusing of spatial soliton pair/breather pair have also been identified. Lastly, the law of trapped breather pair formation is proposed.     

Structure of the Boronic Acid Dimer and the Relative Stabilities of Its Conformers

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Kinetics of diamminesilver(I)-catalysed oxidation of sulphur(IV) by dioxygen in ammonia buffers

The kinetics of the silver(I)-catalysed autoxidation of SO₃ ^2– into SO₄ ^2– in ammonia–ammonium nitrate buffer obeyed the rate law:R _obs=k₁ k₂ K[Ag^I]_T[SO₃ ^2-}][O₂] / ([NH₃]+K[SO₃ ^2-])(k₁+k₂[O₂])The values of k ₁, k ₂/k _–1 and K were found to be 1.2l mol^–1 s^–1, 5.3 × 10² l mol^–1 and 0.6 respectively at 30 °C. Two alternative free radical mechanisms have been proposed.     

An X-Ray Crystallographic Study of <Emphasis Type="Italic">N</Emphasis>-Methyl-3-nitro-4-(nitromethyl)-4<Emphasis Type="Italic">H</Emphasis>-chromen-2-amine

Abstract  

4H-chromenes are among the essential groups of biologically important compounds used as synthetic ligands for drug designing and discovery process. In this study, we have presented the single-crystal structure analysis of racemic 4H-chromene derivative namely N-methyl-3-nitro-4-(nitromethyl)-4H-chromen-2-amine. The optical rotation measurement data is supporting that the title compound is racemic in nature. The compound was crystallized in monoclinic crystal system in the non-centrosymmetric space group P2₁ with unit cell parameters a = 5.1041 (3), b = 7.7519 (4), c = 14.7974 (8), α = 90°, β = 97.088 (5)° and γ = 90°. The nitro group of title compound is disordered over two orientations (N3A/O4A/O5A & N3B/O4B/O5B) with the refined site-occupancy ratio of 0.626(6)/0.374(6). The structure was solved by direct methods using the program SHELXS-97 and refined by SHELXL-97 with the full-matrix least square procedure to a final R-value of 0.0429 and Goodness of Fit (GooF) of 0.982. The molecules in the unit cell are stabilized by N–H···O and C–H···O types of hydrogen bonds. The intermolecular hydrogen bonds are forming C (6) motifs, which is observed to contribute the crystal packing stability. Moreover, the intramolecular hydrogen bonds are forming S (6) motif essential to stabilize the molecular structure of title compound.     

Volumetric and Acoustic Properties of Phenylboronic Acid in Water at Selected Temperatures

Journal of Solution Chemistry - Measurements of density and speed of sound are reported for phenylboronic acid–water solutions for molalities ranging from 0.0098 to...     

Conductivity modification of ZnO film by low energy Fe ion implantation

In this paper we report the structural, optical and electrical behaviours of ZnO films implanted with 300 keV Fe¹⁰⁺ ions. From UV-vis spectroscopy it is observed that the band gap of the films decreases after implantation. Photoluminescence yield seems to increase in the implanted samples. From Hall measurements it is observed that the unimplanted sample shows n-type conductivity for the entire temperature range (100-300 K), whereas after implantation the samples show p-type conductivity for ≤200 K. The DC resistivity of the implanted samples is found to be lower than that of the unimplanted sample. We have found that the magnetoresistance of our samples is positive in the temperature range 200-300 K, but it becomes negative below 200 K.