The simple and convenient measurement of the dissociation constant of an indicator, thymol blue, was achieved by using a portable diode-laser/fiber-optic thermal lensing spectroscopy, which consisted of a visible diode laser, a photodiode, and an optical fiber. It gives comparable results to the cited value obtained from a conventional UV/VIS spectroscopy.

The electrocatalytic reduction of dioxygen by Co(TTFP)(Y)2 {Y=H2O or HO-} is investigated by cyclic voltammetry, spectroelectrochemistry, hydrodynamic voltammetry at a glassy carbon electrode in dioxygen-saturated aqueous solutions. Electrocatalytic reduction of dioxygen by CoⅡ(TTFP)(Y)2 establishes a pathway of 2e- reduction to form hydrogen peroxide, and then the generated hydrogen peroxide is reduced to water by CoⅠ(TTFP)(Y)2 at more negative potential. CoⅡ(TTFP)(Y)2 may bind dioxygen to produce the adduct complex [CoⅡ-O2 or CoⅢ-O2] which exhibits a Soret band at 411 nm and Q band at 531 nm.

The characteristics of the ablation plume generated by 532 nm Nd: YAG laser irradiation of a Pb(Zr0.52Ti0.48)O3 (PZT) target have been investigated using a pulsed-field time-of-flight mass spectrometer (TOFMS). The relative abundance of O+, Ti+, Zr+, Pb+, TiO+, and ZrO+ ions has been measured and discussed. TiO+ and ZrO+ ions were also found to be particularly stable within the laser ablation plasma with respect to PbO+ species. The behavior of the temporal distributions of each ionic species was studied as a function of the delay time between the laser shot and the ion extraction pulse. The most probable velocity of each ablated ion is estimated to be Vmp=1.1-1.6x 105 cm/s at a laser fluence of 1.2 J/cm2, which is typically employed for the thin film deposition of PZT. The TOF distribution of Ti+ and Zr+ ions shows a trimodal distribution with one fast and two slow velocity components. The fast velocity component (6.8x 10' cm/s) appears to consist of directly ablated species via nonthermal process. The second component, originated from the thermal evaporation process, has a characteristic velocity of 1.4-1.6 x 105 cm/s. The slowest component (1.2 x 105 cm/s) is composed of a dissociation product formed from the corresponding oxide ion.

The intrinsic and equilibrium isotope effects on the 13C NMR chemical shift of the cyclooctanone-2-D were investigated. Equilibrium constants and changes in the free energies, enthalpy, entropy, which are derived from the temperature dependence of the isotope shifts, are reported for this isotopomer.

The mechanism by which pyrrhotite is depressed by diethylenetriamine (DETA) during pentlandite flotation has been studied. Amyl xanthate is observed to adsorb on pyrrhotite to form both dixanthogen and iron xanthate. In the presence of DETA, the amount of xanthate adsorbed on pyrrhotite is substantially reduced as evidenced by infrared and UV/Vis spectroscopy. However, DETA does not adsorb on pyrrhotite as evidenced by infrared and X-ray photoelectron spectroscopy. DETA shifts the potential of the onset of xanthate adsorption on pyrrhotite by approximately 200 mV toward anodic direction, which is thought to be due to the increased solubility of surface oxidized species on pyrrhotite in the presence of DETA. A window of selectivity for the separation of pentlandite and pyrrhotite is provided by the results obtained in this study.

13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) and Continuous Set of Gauge Transformations (CSGT) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts GIAO and CSGT calculations at the HF/6-31G and HF/6-31G* levels are sufficiently accurate to aid in experimental peak assignments. The isotropic 13C chemical shifts X-substituted silatranes at HF/6-31G* level are approximately 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The 15N chemical shift parameters demonstrate a very clear correlation with Si-N distance, especially when we use the polarization function. Changes in anisotropy, 3a as well as in the 15N isotropic chemical shifts are due primarily to changes in the value of a.. But in case of "Si the correlations are not as clean as for the 15N chemical shift.

2,4-Di-(2-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 2,4-di-(2-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3,4-di-(2-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3,4-di-(2-vinyloxyethoxy)benzylidenecyanoacetate (4b), 2,5-di-(2-vinyloxyethoxy)benzylidenemalononitrile (6a), and methyl 2,5-di-(2-vinyloxyethoxy)benzylidenecyanoacetate (6b) were prepared by the condensation of 2,4-di-(2-vinyloxyethoxy)benzaldehyde (1), 3,4-di-(2-vinyloxyethoxy)benzaldehyde (3), and 2,5-di-(2-vinyloxyethoxy)benzaldehyde (5) with malononitrile or methyl cyanoacetate, respectively. Trifunctional divinyl ether monomers 2, 4 and 6 were polymerized readily by free radical initiators to give optically transparent swelling poly(vinyl ethers) 7-9. Polymers 7-9 were not soluble in common organic solvents such as acetone and DMSO due to crosslinking. Polymer 7-9 showed a thermal stability up to 300 ℃ in TGA thennograms.

Vanadium oxide catalyst supported on ZrO2-WO3 was prepared by adding the Zr(OH)4 powder into a mixed aqueous solution of ammonium metavanadate and ammonium metatungstate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using solid-state 51V NMR and FTIR. In the case of calcination temperature at 773 K, for the samples containing low loading V2O5 below 18 wt % vanadium oxide was in a highly dispersed state, while for samples containing high loading V2O5 equal to or above 18 wt % vanadium oxide was well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of ZrO2-WO3. The ZrV2O7 compound was formed through the reaction Of V2O5 and ZrO2 at 873 K and the compound decomposed into V2O5 and ZrO2 at 1073 K, which were confirmed by FTIR and 51V NMR.

The Lewis acid mediated intramolecular additions of allylsilanes to acetal substrates are described. Excellent regio- and diastereoselectivity are achieved by boron trifluoride promoted cyclization of allysilane-acetals 5 and 8 derived from hydroxy allysilances 3. Cyclizations occur in moderate to high yields, providing directr routes to cis-2, 6-disubstituted 4-methylenetetrahydropyrans 6 and 9.

An equivalent retention has been experimentally observed in thermal field-flow fractionation (ThFFF) for different polymer-solvent systems. It is shown that iso-retention between two sets of polymer-solvent systems can be obtained by adjusting the temperature difference (ΔT) according to the difference in the ratio of ordinary diffusion coefficient to thermal diffusion coefficient. This method uses a compensation of field strength (ΔT) in ThFFF at a fixed condition of cold wall temperature. It is applied for the calculation of molecular weight of polymers based on a calibration run of different standards obtained at an adjusted AT. The polymer standards used in this study are polystyrene (PS), polymethylmethacrylate (PMMA), and polytetrahydrofuran (PTHF). Three carrier solvents, tetrahydrofuran (THF), methylethylketone (MEK) and ethylacetate (ETAc) were employed. Though the accuracy in the calculation of molecular weight is dependent on the difference in the slope of log λ vs. log M which is related to Mark-Houwink constant a, it shows reasonable agreement within about 6% of relative error in molecular weight calculation for the polymer-solvent systems having similar a value.