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991.
Meizhu Liu Conrad Kamienski Maurice Morton Lewis J. Fetters 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1387-1396
The behavior of isoprene and styrene polymerizations initiated by the complex of n-butylsodium and n-,s-dibutylmagnesium (sodium tributylmagnesiate) has been examined. The styrene-benzene system was found to yield stable active centers and polymers of predictable molecular weight and narrow molecular weight distributions. Isoprene, however, did not follow this behavior and yielded polydisperse material having molecular weights lower than those predicted on the basis that only n-butylsodium is capable of initiating chain growth. The polyisprene microstructure was found to consist of ~60% 3,4 and ~40% 1,4 units. 相似文献
992.
993.
994.
Jennifer K. Angelosante Breia J. Lewis Lisa E. Cooper Rebecca A. Swanson Christopher J. A. Daley 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2263-2272
Herein, two improved synthetic pathways to biologically relevant Cys-Xxx-Cys analogue ligands used in conjunction with metals as metalloenzyme models (Ni for carbon monoxide dehydrogenase/acetyl-CoA synthase A-cluster; Co and Fe for nitrile hydratase) are reported. 相似文献
995.
996.
Erli Lu Oliver J. Cooper Jonathan McMaster Floriana Tuna Eric J. L. McInnes William Lewis Alexander J. Blake Stephen T. Liddle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(26):6814-6818
We report the uranium(VI) carbene imido oxo complex [U(BIPMTMS)(NMes)(O)(DMAP)2] ( 5 , BIPMTMS=C(PPh2NSiMe3)2; Mes=2,4,6‐Me3C6H2; DMAP=4‐(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two‐electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T‐shaped motif with respect to the carbene, which is consistent with an inverse trans‐influence. Complex 5 reacts with tert‐butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPMTMS)(O)2(DMAP)2] ( 6 ). 相似文献
997.
In an important paper on the physics of small amplitude oscillations, Titze showed that the essence of the vertical phase difference, which allows energy to be transferred from the flowing air to the motion of the vocal folds, could be captured in a surface wave model, and he derived a formula for the phonation threshold pressure with an explicit dependence on the geometrical and biomechanical properties of the vocal folds. The formula inspired a series of experiments [e.g., R. Chan and I. Titze, J. Acoust. Soc. Am 119, 2351-2362 (2006)]. Although the experiments support many aspects of Titze's formula, including a linear dependence on the glottal half-width, the behavior of the experiments at the smallest values of this parameter is not consistent with the formula. It is shown that a key element for removing this discrepancy lies in a careful examination of the properties of the entrance loss coefficient. In particular, measurements of the entrance loss coefficient at small widths done with a physical model of the glottis (M5) show that this coefficient varies inversely with the glottal width. A numerical solution of the time-dependent equations of the surface wave model shows that adding a supraglottal vocal tract lowers the phonation threshold pressure by an amount approximately consistent with Chan and Titze's experiments. 相似文献
998.
Zhou H Singh H Parsons ZD Lewis SM Bhattacharya S Seiner DR LaButti JN Reilly TJ Tanner JJ Gates KS 《Journal of the American Chemical Society》2011,133(40):15803-15805
Hydrogen peroxide is a cell signaling agent that inactivates protein tyrosine phosphatases (PTPs) via oxidation of their catalytic cysteine residue. PTPs are inactivated rapidly during H(2)O(2)-mediated cellular signal transduction processes, but, paradoxically, hydrogen peroxide is a rather sluggish PTP inactivator in vitro. Here we present evidence that the biological buffer bicarbonate/CO(2) potentiates the ability of H(2)O(2) to inactivate PTPs. The results of biochemical experiments and high-resolution crystallographic analysis are consistent with a mechanism involving oxidation of the catalytic cysteine residue by peroxymonocarbonate generated via the reaction of H(2)O(2) with HCO(3)(-)/CO(2). 相似文献
999.
Boettcher SW Warren EL Putnam MC Santori EA Turner-Evans D Kelzenberg MD Walter MG McKone JR Brunschwig BS Atwater HA Lewis NS 《Journal of the American Chemical Society》2011,133(5):1216-1219
Arrays of B-doped p-Si microwires, diffusion-doped with P to form a radial n(+) emitter and subsequently coated with a 1.5-nm-thick discontinuous film of evaporated Pt, were used as photocathodes for H(2) evolution from water. These electrodes yielded thermodynamically based energy-conversion efficiencies >5% under 1 sun solar simulation, despite absorbing less than 50% of the above-band-gap incident photons. Analogous p-Si wire-array electrodes yielded efficiencies <0.2%, largely limited by the low photovoltage generated at the p-Si/H(2)O junction. 相似文献
1000.