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The kinetics and mechanism for the C6H5 + CH20 reaction were studied by the cavity ringdown spectrometric (CRDS) and pulsed laser photolysis/mass spectrometric (PLP/MS) methods at temperatures between 298 and 1083 K. The rate constant calculated for the H-abstraction process using the canonical variational transition-state theory with a 1.1 kcal/mol barrier agrees closely with the investigated result over the entire range of temperatures examined.

NdNbO4- xCuO ( x = 0, 0·15, 0·2, 0·3, 0·4, 0·5, 1 wt-%) ceramics with improved sintering characteristic and microwave dielectric properties were prepared by conventional mixed oxide route. The effects of CuO addition on the microstructures and microwave dielectric properties of NdNbO4 ceramics were investigated systematically. Microscopic analysis showed that CuO doped NdNbO4 ceramics possess second phases of CuNb2O6 and Nd2Cu2O5. With a further increase in the amount of CuO, Cu3Nb2O8 phase appeared in the system. The addition of CuO effectively reduced the sintering temperature of NdNbO4 ceramics by ∼275°C. The microwave dielectric properties were strongly dependent on the CuO addition. Optimal microwave dielectric properties of εr = 19·76, τƒ = −24 ppm °C−1 and Q׃ = 39 000 GHz were observed for 0·2 wt-%CuO doped NdNbO4 ceramics sintered at 975°C for 4 h. [ABSTRACT FROM AUTHOR]

Cubic pyrochlore structure Bi1·5MgNb1·5O7 (BMN) nanopowders were successfully prepared by the aqueous sol-gel method. The phase formation and morphology were investigated. The uniform pure phased cubic pyrochlore nanopowders with average crystallite size of 14 nm were achieved after thermal treatment at temperature as low as 500°C for 2 h. With increasing heat treatment temperature from 500 to 700°C, the average crystallite size increased from 14 to 39 nm. No intermediary phase was observed in powders after calcination at temperatures from 400 to 700°C for 2 h. For comparison, BMN powders were synthesised by the conventional solid state reaction method. The phase evolution of the solid method prepared powders with calcination temperatures was investigated by X-ray diffraction. Cubic pyrochlore phase started to form at 750°C with intermediate phases of Bi1·7Nb0·3O3·3 and Bi5Nb3O15. After calcination at 950°C, cubic pyrochlore BMN main phase with small BiNbO4 amount was detected. [ABSTRACT FROM AUTHOR]

Whey protein concentrate (WPC 80) was hydrolyzed by Alcalase 2.4 L and Protamex to 5, 10, 15 and 20% degree of hydrolysis (DH). WPC 80 and its hydrolysates were analyzed, compared and used for measuring some functional properties. All hydrolysates were different from WPC 80 in protein, moisture and ash content. Free amino groups and protein solubility increased with increasing DH. The peptides produced by hydrolysis had smaller molecular sizes, and their average molecular weight decreased as the DH increased. Except hydrolysates generated by Alcalase 2.4 L at 5% DH, all others showed poor emulsifying and foaming properties compared with unhydrolyzed WPC 80. Gelation properties of WPC 80 and its hydrolysates were different. The global amino acid compositions did not differ significantly between the different hydrolysates, and they were very close among WPC 80 and its hydrolysates except for Methionine, Glycine, Histidine and Valine. [ABSTRACT FROM AUTHOR]

The mechanism for the OH+HNO[sub 3] reaction has been studied by ab initio molecular orbital calculations at the G2M(cc3) level of theory. Four complexes and four transition states have been found and confirmed by intrinsic reaction coordinate analyses. The commonly assumed six-membered ring complex formed by hydrogen bonding of the OH radical with HNO[sub 3], -ON(O)OH...OH-, was found to be stable by 8.1 kcal/mol; its decomposition producing NO[sub 3]+H[sub 2]O was predicted to have a barrier of 11.6 kcal/mol. A five-membered ring complex, -ON(O)OH...O(H)-, with the H atom of the OH radical placed out of the ring plane, was found to have a stability of 5.3 kcal/mol; it fragments to form NO[sub 3]+H[sub 2]O with a barrier of 6.6 kcal/mol. Two additional complexes, which are the mirror image of each other with a 7.4 kcal/mol binding energy, were found to be related to the OH exchange reaction with a 13.3 kcal/mol barrier above the complexes. The direct abstraction process producing H[sub 2]O[sub 2] and NO[sub 2] was predicted to have a large barrier of 24.4 kcal/mol, insignificant to atmospheric chemistry. The rate constant has been calculated at 200-1500 K and 0-760 Torr. The results show that the reaction has strong pressure and tunneling effects below room temperature. In addition, the rate constants for the decay of OH and OD (in OD+DNO[sub 3]) evaluated by kinetic modeling compare reasonably well with experimental data below room temperature. The unusually pronounced kinetic isotope effect observed experimentally, k[sub H]/k[sub D]>=10, could be accounted for by the combination of the greater tunneling rate in the H system and the large redissociation rate of stabilized complexes in the D system. The rate constant predicted for the production of H[sub 2]O and NO[sub 3] in the temperature range 750-1500 K can be effectively represented by the expression k=1.45x10[sup -23] T[sup 3.5] exp(+839/T) cm[sup 3]/s. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetic anisotropy, exchange couplings, and spin-driven ferroelectricity in recently discovered multiferroic oxide α - Cu2V2O7 have been investigated using first-principles calculation and symmetry analysis. Density functional theory (DFT) calculations predict easy a -axis anisotropy, while applying an on-site Hubbard correction (DFT + U) converts the easy axis into b direction. These results can explain the discrepancy of easy axis between previous theoretical prediction and experimental results. The third-nearest-neighbor exchange interaction is proved to be dominant for the antiferromagnetic structure. The nearest-neighbor Dzyaloshinskii-Moriya interaction plays an important role in the origins of spin canting, and the canted magnetic moments are oriented predominantly along the c axis. Although the spin-dependent p - d hybridization mechanism induces a sizable electric polarization, the observed large polarization can be mainly attributed to the exchange-striction mechanism including spin-lattice coupling. [ABSTRACT FROM AUTHOR]

The electronic structure, magnetic exchange interactions, and spin-driven ferroelectricity in skyrmion host GaV4S8 have been studied on the basis of first-principles calculations and symmetry analysis. We find the reconstruction of band structure with the increasing value of Hubbard parameter U. The ferromagnetic ground state is determined by the symmetric exchange interaction along interplane bonds. The antisymmetric Dzyaloshinskii-Moriya interaction along intraplane bonds plays a major role in the origins of cycloidal and skyrmion phases. The exchange-striction mechanism is identified as the main origin of spin-driven polarization. Moreover, two spin-current mechanisms expressed by P1∝rab×(Sa×Sb) and P2∝Sa×Sb appear in the cycloid, while only the former mechanism appears in the skyrmion. [ABSTRACT FROM AUTHOR]

Objective: To testify the availability and the clinical efficacy of the skin-stretching device., Methods: The skin-stretching device designed by ZHOU Li-an, which was used in the treatment of the granulation wound, the donor site of flap, and the skin defect after the excision of tumor by skin traction technique at the wound edges., Results: The usage time of skin-stretching device was 15-720 minutes, it could be used preoperatively, intraoperatively and postoperatively. Followed up 16 cases for 6 to 12 months, the device was effective., Conclusion: The skin stretching device is practical and effective in wound closure of skin defect.