Laser-diode-pumped phosphosilicate-fiber Raman laser with an output power of 1 W at 1.48 mum

An all-fiber 1.48-mum generator based on a laser-diode-pumped Yb-doped double-clad laser and a cascaded Raman wavelength converter has been developed. Second-order Raman Stokes radiation was generated in a phosphosilicate-fiber resonator formed by two pairs of Bragg gratings. A slope efficiency of the Raman converter of 48% with respect to the power emitted by the double-clad Yb laser has been achieved. We obtained an output power of 1 W at a slope efficiency of 34% with respect to the laser-diode array power, with a total optical-to-optical efficiency of 23%.     

A quantum-topological analysis of short (strong) H bonds in three-dimensional periodic crystals

The characteristics of the critical electron density points of the O-H···A fragment (A = O or N) in molecular crystals with short H bonds were analyzed in terms of the Bader quantum-topological theory of molecular structure. The wave functions (B3LYP/6-31G** approximation) of the ground state of 26 three-dimensional periodic crystals with experimentally determined structures were used. Intermediate-type interactions separating the limiting cases of covalent and closed shell-type interactions were found to be characterized by the following geometric parameters: 2.45 Å ≤ D(O···O) ≤ 2.6 Å, 1.35 Å ≤ d(H···O) ≤ 1.65 Å, and 1.0 Å ≤ d(O-H) ≤ 1.10 Å. Such interactions are observed in molecular crystals with the O-H···A fragment and high bridge proton mobility. Differences between H···O and H···N interactions were quantitatively characterized by the dependence of ρ _b on d(H···A), where A = O or N. The dependence parameter values were shown to be determined by the nature of the A atom that forms the H bond. The influence of the crystalline environment on systems with strong H bonds manifested itself by changes in the position of the bridge proton. The d(O-H)/d(H···O) ratio was, however, the same for gas-phase complexes and molecular crystals with weakly bent O-H···O fragments (∠O-H···O > 160°).     

Size Effect in Nanocomposites Based on Molecular Ferroelectric Diisopropylammonium Bromide

Physics of the Solid State - We present the results of studies of the dielectric properties of nanocomposites based on Al2O3 oxide films with a pore size of 330 and 60 nm with particles of an...     

On the Possibilities of Multidimensional Equidistant Absorption Spectroscopy in a Wide Frequency Range in Studies of Fractions of Thermal Distillation of Oil

Optics and Spectroscopy - The features and possibilities of absorption molecular spectroscopy of complex mixtures of organic compounds have been studied by the example of fractions of thermal...     

Introducing tox-Profiles of Chemical Reactions

In this Essay, we present a critical analysis of two common practices in modern chemistry—that is, of using speculations about the “greenness” and “nontoxicity” of developed synthesis procedures and of a priori labelling various compounds derived from natural sources as being environmentally safe. We note that every organic molecule that contains functional groups should be biologically active. Thus, analysis of the particular greenness and the potential environmental impact of a given chemical process should account for the biological activity of all its components in a measureable (rather than empirical) way. We highlight the necessity of clarifying discussions on biological activity and toxicity and propose possible ways of introducing tox-Profiles as a reliable overview of the overall toxicity of chemical reactions.     

Functionalization of Polyethyleneimine with Hollow Cyclotriveratrylene and Its Subsequent Supramolecular Interaction with Doxorubicin

In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host–guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform.     

Interaction of N,N'-Di(4-chlorophenyl)diimide 1,1'-Binaphtyl-4,4',5,5',8,8'-hexacarboxylic Acid with Thiourea Dioxide in Solution and Thin Film

Crystallography Reports - The reactions of interaction of N,N'-di(4-chlorophenyl)diimide 1,1'-binaphtyl-4,4',5,5',8,8'-hexa-carboxylic acid (cubogen red) with thiourea dioxide...     

Chemisorption Synthesis of the Ion-Polymeric Heteronuclear Gold(III)–Bismuth(III) Complex ([Au{S2CN(C3H7)2}2]3[Bi2Cl9])n Based on [Bi2{S2CN(C3H7)2}6]: 13C MAS NMR,Supramolecular Structure,and Thermal Behavior

Russian Journal of Coordination Chemistry - Chemisorption synthesis on the basis of the binuclear compound [Bi2{S2CN(C3H7)2}6] (I) and preparative isolation of the ion-polymeric heteronuclear...     

Exponential decay in the stark effect

LetH=–+V+Fx ₁ withV(x ₁,x ) analytic in the first variable andV(x ₁+ia, x ) bounded and decreasing to zero asx for eacha . Let be an eigenvector of –+V with negative eigenvalue. Among our results we show that forF0, (,e ^–H ) decays exponentially at a rate governed by the positions of the resonances ofH. This exponential decay is in marked contrast to conventional atomic resonances for which power law decay is the rule.Research supported by NSF Grant No. MCS 78-00101.