Nanocrystalline columnar-structured diamond films with column diameters less than 100 nm and thicknesses in the range of 1-5 m were grown on silicon substrates by chemical vapor deposition ͑CVD͒ in a microwave plasma reactor with purified methane and hydrogen used as the reactants. Uniform conformal nucleation densities in excess of 10 12 cm Ϫ2 were accomplished prior to growth by seeding with explosively formed nanodiamonds, which resulted in good optical quality films. The film thickness was measured in situ by the laser reflectometry method. The grain size and optical quality of the films were characterized by scanning electron microscopy and Raman measurements. Broadband surface acoustic wave pulses were used to measure the anomalous dispersion in the layered systems. The experimental dispersion curves were fitted by theory, assuming the diamond film as an isotropic layer on an anisotropic silicon substrate, to determine mean values of the density and Young's modulus of the diamond films. The density was close to the density of single crystal diamond or polycrystalline diamond plates grown by the CVD technique, whereas the Young's modulus varied strongly with the nucleation density between 517 and 1120 GPa. Young's moduli close to the single crystal values were obtained for films grown with a nucleation density у10 12 cm Ϫ2. The thermal diffusivity in these films was measured by the traveling wave technique. The value for ϳ3.5-m-thick nanocrystalline diamond films with nucleation densities у10 12 cm Ϫ2 was ϳ7.2 cm 2 /s, whereas those with lower nucleation densities showed a value of ϳ5.5 cm 2 /s.

Background and Aims:Different additives have been used to prolong brachial plexus block. We evaluated the effect of adding dexmedetomidine to ropivacaine for supraclavicular brachial plexus blockade. The primary endpoints were the onset and duration of sensory and motor block and duration of analgesia.Materials and Methods:A total of 84 patients (20-50 years) posted for elective forearm and hand surgery under supraclavicular brachial plexus block were divided into two equal groups (Group R and RD) in a randomized, double-blind fashion. In group RD (n = 42) 30 ml 0.5% ropivacaine +1 ml (100 μg) of dexmedetomidine and group R (n = 42) 30 ml 0.5% ropivacaine +1 ml normal saline were administered in supraclavicular block. Sensory and motor block onset times and block durations, time to first analgesic use, total analgesic need, postoperative visual analog scale (VAS), hemodynamics and side-effects were recorded for each patient.Results:Though with similar demographic profile in both groups, sensory and motor block in group RD (P < 0.05) was earlier than group R. Sensory and motor block duration and time to first analgesic use were significantly longer and the total need for rescue analgesics was lower in group RD (P < 0.05) than group R. Post-operative VAS value at 12 h were significantly lower in group RD (P < 0.05). Intra-operative hemodynamics were significantly lower in group RD (P < 0.05) without any appreciable side-effects.Conclusion:It can be concluded that adding dexmedetomidine to supraclavicular brachial plexus block increases the sensory and motor block duration and time to first analgesic use, and decreases total analgesic use with no side-effects.

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and an increased VPP coupling as compared to the other isomer. This, however, is not the case, and therefore structure 3a' and 4a' are ruled out. Supplementary Material Available: Tables of crystal data, atomic coordinates and equivalent isotropic displacement coefficients, bond lengths, bond angles, anisotropic thermal parameters, and hydrogen atom parameters (10 pages); a table of observed and calculated structure factors (24 pages). Ordering information is given on any current masthead page.

Transition-metal chelates incorporating azo ligands have drawn much attention in recent years. Among these, complexes of arylazooximes, 1 arylazophenols, 2 arylazoimines, 3 alkylthioazobenzenes, 4 and sulfenylazobenzenes 5 are some notable examples. Interesting coordination modes and molecular structures, C-H bond activation, potential sites of facile electron transfer, and interesting electronic structure due to the presence of low-lying π* orbitals are some of the important properties exhibited by these. Herein we scrutinize the synthesis and structure of 2-(phenylazo)aniline (H 2 L) and bis chelate Pd II -(HL) 2 , wherein the ligand displays predominant azoimine character due to delocalization. Experimental SectionThe solvents used in the reactions were of reagent grade obtained from E. Merck, Calcutta, India, and were dried by reported procedures. 6 o-Phenylenediamine was recrystallized from ethanol-water (2/1 v/v) before use. Palladium chloride was purchased from Arrora Matthey, Calcutta, India. Disodium tetrachloropalladate was prepared by a reported procedure. 6 Microanalyses (C, H, N) were done on a Perkin-Elmer 240C elemental analyzer. IR spectra were recorded on a Perkin-Elmer 783 spectrometer with the sample prepared as KBr pellets. Electronic spectra were recorded on a Hitachi U-2001 spectrophotometer. 1 H NMR data were collected from Bruker AC-200 and Bruker

The first azo-imine chelate system, Pd(N(H)C(R)NNPh)(2) (Pd(RA)(2)), has been isolated in the form of diamagnetic solids by the 6e(-)-6H(+) reduction of bis(phenylazooximato)palladium(II), Pd(N(O)C(R)NNPh)(2) (abbreviated Pd(RB)(2)), with ascorbic acid in a mixed solvent (R = Ph, alpha-naphthyl). Selected spectral features are described. The X-ray structures of Pd(PhA)(2) and Pd(PhB)(2) have revealed trans-planar geometry consistent with metal oxidation state of +2. Bond length trends within the chelate rings are rationalized in terms of steric and electronic factors. In Pd(PhA)(2) a total of 10 ligand pi electrons are present, each formally monoanionic ligand contributing five. Model EHMO studies have revealed that the filled HOMO (a(u)) in Pd(RA)(2) is a bonding combination of two ligand pi orbitals with large azo contributions. The LUMO (b(g)) is roughly the corresponding antibonding combination. The outer pi-electron configuration of Pd(RA)(2) is (a(u))(2)(b(g))(0). Four successive voltammetric responses, two oxidative and two reductive, are observed. The E(1/2) range is -1.3 to +0.8 V vs SCE for Pd(PhA)(2) in a 1:9 MeCN-CH(2)Cl(2) mixture (Pt electrode). EPR and electronic spectra of the electrogenerated one-electron-oxidized complex Pd(PhA)(2)(+) are described. The azo-imine system is compared with imine-imine and azo-azo systems. Crystal data for the complexes are as follows. Pd(PhA)(2): crystal system monoclinic; space group C2/c; a = 18.167(5) Å, b = 7.420(3) Å, c = 16.527(6) Å; beta = 92.70(3) degrees; V = 2225(1) Å(3); Z = 4; R = 2.61%, R(w) = 3.58%. Pd(PhB)(2): crystal system monoclinic; space group P2(1)/n; a = 5.735(5) Å, b = 10.797(6) Å, c = 18.022(11) Å; beta = 97.73(6) Å; V = 1105(1) Å(3); Z = 2; R = 3.37%; R(w) = 3.40%.

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