Er:YAl(3)(BO(3))(4) glassy thin films from polymeric precursor and sol-gel methods: Waveguides for integrated optics

This paper presents the characterization of single-mode waveguides for 980 and 1550 nm wavelengths. High quality planar waveguide structure was fabricated from Y(1-x)Er(x)Al(3)(BO(3))(4) multilayer thin films with x = 0.02, 0.05, 0.1, 0.3, and 0.5, prepared through the polymeric precursor and sol-gel methods using spin-coating. The propagation losses of the planar waveguides varying from 0.63 to 0.88 dB/cm were measured at 632.8 and 1550 nm. The photoluminescence spectra and radiative lifetimes of the Er(3+) (4)I(13/2) energy level were measured in waveguiding geometry. For most samples the photoluminescence decay was single exponential with lifetimes in between 640 mu s and 200 mu s, depending on the erbium concentration and synthesis method. These results indicate that Er doped YAl(3)(BO(3))(4) compounds are promising for low loss waveguides. (C) 2009 Elsevier B.V. All fights reserved.

Antimycobacterial and antitumor activities of Palladium(II) complexes containing isonicotinamide (isn): X-ray structure of trans-[Pd(N(3))(2)(isn)(2)]

Complexes of the type trans-[PdX(2)(isn)(2)] {X = Cl (1), N(3) (2), SCN (3), NCO (4); isn = isonicotinamide} were synthesized and evaluated for in vitro antimycobacterial and antitumor activities. The coordination mode of the isonicotinamide and the pseudohalide ligands was inferred by IR spectroscopy. Single crystal X-ray diffraction determination on 2 showed that coordination geometry around Pd(II) is nearly square planar, with the ligands in a trans configuration. All the compounds demonstrated better in vitro activity against Mycobacterium tuberculosis than isonicotinamide and pyrazinamide. Among the complexes, compound 2 was found to be the most active with MIC of 35.89 mu M. Complexes 1-4 were also screened for their in vitro antitumor activity towards LM3 and LP07 murine cancer cell lines. (C) 2010 Elsevier Masson SAS. All rights reserved.

Ruled Weingarten hypersurfaces in Sn+1

In this paper we classify the connected ruled Weingarten hypersurfaces in Sn+1, n >= 3.

Thermoluminescence and synchrotron radiation studies on the persistent luminescence of BaAl(2)O(4)/Eu(2+),Dy(3+)

The persistent luminescence materials, barium aluminates doped with Eu(2+) and Dy(3+) (BaAl(2)O(4): Eu(2+),Dy(3+)), were prepared with the combustion synthesis at temperatures between 400 and 600 degrees C as well as with the solid state reaction at 1500 degrees C. The concentrations of Eu(2+)/Dy(3+) (in mol% of the Ba amount) ranged from 0.1/0.1 to 1.0/3.0. The electronic and defect energy level structures were studied with thermoluminescence (TL) and synchrotron radiation (SR) spectroscopies: UV-VUV excitation and emission, as well as with X-ray absorption near-edge structure (XANES) methods. Theoretical calculations using the density functional theory (DFT) were carried out in order to compare with the experimental data. (C) 2010 Elsevier Inc. All rights reserved.

Characterization of anodic silicon oxide films grown in room temperature ionic liquids

The electroformation of silicon oxide was performed in two room temperature ionic liquids (RTIL), 1-butyl-3-methyl-imidazolium bis(trifluoromethane sulfonyl) imide (BMITFSI) and N-n-butyl-N-methylpiperidinium bis(trifluoromethane sulfonyl) imide (BMPTFSI). This phenomenon was studied by electrochemical techniques and it was observed that the oxide growth follows a high-field mechanism. X-ray Photoelectron Spectroscopy experiments have shown that a non-stoichiometric oxide film was formed, related to the low water content present in both RTILs (< 30 ppm). The roughness values obtained by using AFM technique of the silicon surface after etching with HF was 1.5 nm (RMS). The electrochemical impedance spectroscopy at low frequencies range was interpreted as a resistance in parallel with a CPE element, the capacitance obtained was associated with the dielectric nature of the oxide formed and the resistance was interpreted considering the chemical dissolution of the oxide by the presence of the TFSI anion. The CPE element was associated with the surface roughness and the very thin oxide film obtained. (C) 2007 Elsevier Ltd. All rights reserved.

Conformational preferences for some 2-substituted N-methoxy-N-methylacetamides through spectroscopic and theoretical studies

The analysis of the IR carbonyl band of the 2-substituted N-methoxy-N-methylacetamides Y-CH(2)C(O)-N(OMe)Me (Y = F1, OMe 2, OPh 3, Cl 4), supported by B3LYP/6-311++G(3df, 3pd) calculations along with the NBO analysis for 1-4, indicated the existence of cis-gauche conformers i.e. (c) and (g) for 1 and 3, (c(1), c(2)) and (g(1), g(2)) for 2, and (c) and (g(1), g(2)) for 4. In the gas phase, the g conformer population prevails over the c one, for 1 and 3, the (c(1) + c(2)) population prevails over the (g(1) + g(2)) one for 2, and the (g(1) + g(2)) conformer population is more abundant than (c) one for 4. In n-hexane solution, the cis conformer is more abundant for 1-3. The occurrence of Fermi resonance in the nu(CO) region, in n-hexane, precludes the estimative of relative populations of the (c, g(1), g(2)) conformers for 4. The SCI-PCM calculations agree with the solvent effect on the nu(CO) band component relative intensities for 1-3. NBO analysis showed that the n(N) -> pi.(CO), orbital interaction is the main factor which stabilizes the gauche (g, g(1), g(2)) conformers for 1-4 into a larger extent relative to the cis (c, c(1), c(2)) ones. The n(y) -> pi(.)(Co,) sigma(C-Y) -> pi.(CO,) pi(CO) -> sigma(C-Y) and 7co orbital interactions still contribute, but into a minor extent for the stabilization of the gauche conformers relative to the cis ones. The existence of some pyramidalization at the nitrogen atom of the Weinreb amides 1-4 is responsible for the occurrence of Y(delta)-(4)center dot center dot center dot O(delta)-(9) and Y(delta)-(4)center dot center dot center dot N(delta)-(7) short contacts in the gauche (g, g(1), g(2)) conformers, which originates strong repulsive Coulombic interactions, acting in opposition to the large orbital stabilization of the gauche conformer with respect to the cis one. Therefore, a delicate balance of the Coulombic and orbital interactions seems to be responsible for the observed stabilization of the gauche (g, g(1), g(2)) and cis (c, c(1), c(2)) conformers, both in the gas phase and in the solution for 1-4. However, the cis conformer predominance, in non polar solvents, for the 2-substituted N-methoxy-N-methyl acetamides 1-3, bearing in a first raw (fluorine and oxygen) atoms, is in the opposite direction to the gauche conformer preference for the corresponding 2-substituted N,N-dialkyl-acetamides. (C) 2010 Elsevier B.V. All rights reserved.