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111.
The kinetics of the reactions of hydroxyl radical with n-octane (k1), n-nonane (k2), and n-decane (k3) at 240-340 K and a total pressure of approximately 1 Torr has been studied using relative rate combined with discharge flow and mass spectrometer (RR/DF/MS) technique. The rate constant for these reactions was found to be positively dependent on temperature, with an Arrhenius expression of k1 = (2.27 +/- 0.21) x 10(-11)exp[(-296 +/- 27)/T], k2 = (4.35 +/- 0.49) x 10(-11)exp[(-411 +/- 32)/T], and k3 = (2.26 +/- 0.28) x 10(-11)exp[(-160 +/- 36)/T] cm3 molecule(-1) s(-1) (uncertainties taken as 2sigma), respectively. Our results are in good agreement with previous studies at and above room temperature using different techniques. Assuming that the reaction of alkane with hydroxyl radical is the predominant form for loss of these alkanes in the troposphere, the atmospheric lifetime for n-octane, n-nonane, and n-decane is estimated to be about 43, 35, and 28 h, respectively. 相似文献
112.
The recombination reactions of free radicals formed from the photolysis of a series of polymerisation photoinitiators were studied using time-resolved infrared spectroscopy. All molecules showed Zeeman magnetic field effects (MFEs) in the field range 0-37 mT and those molecules that produced radical pairs with average hyperfine couplings greater than 5 mT showed substantial inverted field effects at fields of less than 10 mT (so-called low field effects, LFEs). Monte Carlo simulations with full treatment of all the isotropic hyperfine couplings in the spin Hamiltonian reproduced well the observed field effects. The use of the usual analysis based on the calculated B1/2 value for the radical pair was found to be inappropriate in systems with substantial LFEs, but simple correlations between this B1/2 value and the observed field features were established. 相似文献
113.
Jonathan D. Woodward Rnal Backov Khalil A. Abboud Daniel R. Talham 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(9):1027-1029
The one‐dimensional chain catena‐poly[[aqua(2,2′:6′,2′′‐terpyridyl‐κ3N)nickel(II)]‐μ‐cyano‐κ2N:C‐[bis(cyano‐κC)nickelate(II)]‐μ‐cyano‐κ2C:N], [Ni(terpy)(H2O)]‐trans‐[Ni‐μ‐(CN)2‐(CN)2]n or [Ni2(CN)4(C15H11N3)(H2O)], consists of infinite linear chains along the crystallographic [10] direction. The chains are composed of two distinct types of nickel ions, paramagnetic octahedral [Ni(terpy)(H2O)]2+ cations (with twofold crystallographic symmetry) and diamagnetic planar [Ni(CN)4]2? anions (with the Ni atom on an inversion center). The [Ni(CN)4]2? units act as bidentate ligands bridging through two trans cyano groups thus giving rise to a new example of a trans–trans chain among planar tetracyanonickelate complexes. The coordination geometry of the planar nickel unit is typical of slightly distorted octahedral nickel(II) complexes, but for the [Ni(CN)4]2? units, the geometry deviates from a planar configuration due to steric interactions with the terpyridine ligands. 相似文献
114.
The following complex oxynitride perovskites have been prepared: LaMg1/3Ta2/3O2N, LaMg1/2Ta1/2O5/2N1/2, and BaSc0.05Ta0.95O2.1N0.9. Synchrotron X-ray powder diffraction analyses show that LaMg1/3Ta2/3O2N and LaMg1/2Ta1/2O5/2N1/2 are isostructural to the oxide La2Mg(Mg1/3Ta2/3)O6 (space group P21/n), whereas BaSc0.05Ta0.95O2.1N0.9 has a simple cubic symmetry similarly to BaTaO2N. The orderings of octahedral cations are markedly diminished in the above oxynitrides, as compared with the related oxides such as La2Mg(Mg1/3Ta2/3)O6 and Ba2ScTaO6. The optical band gaps are similar for the homologous compositions, LaMg1/3Ta2/3O2N, LaMg1/2Ta1/2O5/2N1/2 and LaTaON2 (1.9 eV), and BaSc0.05Ta0.95O2.1N0.9 and BaTaO2N (1.8 eV), while the absorption edges become broader for the complex derivatives. As revealed from the impedance spectroscopic analysis, the oxynitrides have clearly different dielectric components from those of comparable oxides containing Ta5+. Impedance spectroscopy reveals interesting capacitor geometry in BaSc0.05Ta0.95O2.1N0.9 in which the semiconducting oxynitride grains are separated by insulating secondary phases. Most notably BaSc0.05Ta0.95O2.1N0.9 has a bulk component with a high relative permittivity (κ=7300) and the grain boundary component with an even higher κ. 相似文献
115.
116.
A variety of β-S-substituted aldehydes undergo efficient and regioselective rhodium catalyzed hydroacylation reactions with 1,3-disubstituted and 1,1,3-trisubstituted allenes, to deliver β,γ-unsaturated ketone products. Regioselectivites are controlled primarily by steric factors. The reactions are catalyzed by the complex [Rh(dppe)]ClO4. 相似文献
117.
S. S. Ang M. R. Hoque C.-C Chen D. Woodward 《International Journal of Electronics》2013,100(12):793-803
This paper describes a new differential sample-and-hold technique of current measurement for neural probing. The design utilizes bottom plate sampling (BPS) and T-transmission switches to mitigate signal coupling and a differential sample-and-hold technique to reduce charge injection and clock feed through. The circuit was fabricated in a 0.35?µm CMOS process and tested using different input loads to model the electrochemical properties of the microelectrode. Test results matched closely with the simulation results, proving that the concept of the sample-and-hold current measurement circuit is valid for neural probing. 相似文献
118.
Design of a telemedicine system using a mobile telephone 总被引:8,自引:0,他引:8
Woodward B. Istepanian R.S.H. Richards C.I. 《IEEE transactions on information technology in biomedicine》2001,5(1):13-15
This paper describes the design of a prototype integrated mobile telemedicine system that is compatible with existing mobile telecommunications networks and upgradable for use with third-generation networks. The system, when fully developed, will enable a doctor to monitor remotely a patient who is free to move around for sports medicine and for emergency situations 相似文献
119.
Simon Woodward Montserrat Diéguez Oscar Pàmies 《Coordination chemistry reviews》2010,254(17-18):2007-2030
This review describes recent development in the use of sugar-derived ligands in the selective synthesis of organic molecules. Developments in the recent literature (2004–2009) are highlighted in the areas of hydrogenation, 1,2- and 1,4-additions of nucleophiles to CO and CNR based substrates, cross-coupling, hydroformylation, oxidation and other reactions. Connections to earlier studies are also noted were relevant. Some suggestions as to the underlying features that make sugar-based ligands highly useful modular ligands in selective catalysis are given. Finally, advice is presented (for the non-specialist) on optimal entry points and basic starting materials for sugar-ligand synthesis. 相似文献
120.
Matthias Welker Simon Woodward Prof. Luis F. Veiros Prof. Maria José Calhorda Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(19):5620-5629
Reaction of the cyclic thioacetal (RS)2CHCHO [R=1/2×? (CH2)3? ] with HCCCOMe, followed by treatment with TsCl/DABCO (Ts=tosyl, DABCO=1,4‐diazabicyclo[2.2.2]octane) affords the mono‐protected 1,4‐benzoquinone dithioacetal. The reactivity of this SR‐protected 1,4‐benzoquinone has been compared with the behavior of the analogous OR‐protected acetal in copper‐catalyzed additions of ZnMe2 by using chiral phosphoramidite ligands. The activation energy for 1,4‐methylation of the latter OR‐acetals with ZnMe2 (>95 % ee) has been determined for two CuX2 pre‐catalysts (X=OAc, 12.2 kcal mol?1; X=OTf, 6.7 kcal mol?1; Tf=triflate). The dithioacetal SR aromatizes in the presence of CuI/ZnMe2 giving 1,4‐HOC6H4S(CH2)3SMe through C? S bond formation. The disparate behavior of these two very closely related substrates is in accordance with the formation of closely related cuprate intermediates that were optimized by DFT calculations, supporting the synthetic and kinetic studies and thus defining the mechanisms of both pathways. 相似文献