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81.
MacKay Cameron; McKee Sean; Mulholland Anthony J. 《IMA Journal of Applied Mathematics》2006,71(5):670-691
** Email: ajm{at}maths.strath.ac.uk Particle dispersion from a high chimney is considered and anexpression for the subsequent concentration of the particulatedeposited on the ground is derived. We consider the generalcase wherein the effects of both diffusion and convection onthe steady state ground concentration of particulate are incorporated.Two key parameters emerge from this analysis: the ratio of diffusionto convection and the nondimensionalised surface mass transferrate. We also solve the inverse problem of recovering thesetwo parameters given the boundary concentration profile andprovide an estimate of the concentration flux above the chimneystack. 相似文献
82.
83.
Bathelt CM Ridder L Mulholland AJ Harvey JN 《Journal of the American Chemical Society》2003,125(49):15004-15005
The mechanism and selectivity of aromatic hydroxylation by cytochrome P450 enzymes is explored using new B3LYP density functional theory computations. The calculations, using a realistic porphyrin model system, show that rate-determining addition of compound I to an aromatic carbon atom proceeds via a transition state with partial radical and cationic character. Reactivity is shown to depend strongly on ring substituents, with both electron-withdrawing and -donating groups strongly decreasing the addition barrier in the para position, and it is shown that the calculated barrier heights can be reproduced by a new dual-parameter equation based on radical and cationic Hammett sigma parameters. 相似文献
84.
Voltage-pulsed and laser-pulsed atom probe tomography of a multiphase high-strength low-carbon steel
The differences in artifacts associated with voltage-pulsed and laser-pulsed (wavelength = 532 or 355 nm) atom-probe tomographic (APT) analyses of nanoscale precipitation in a high-strength low-carbon steel are assessed using a local-electrode atom-probe tomograph. It is found that the interfacial width of nanoscale Cu precipitates increases with increasing specimen apex temperatures induced by higher laser pulse energies (0.6-2 nJ pulse(-1) at a wavelength of 532 nm). This effect is probably due to surface diffusion of Cu atoms. Increasing the specimen apex temperature by using pulse energies up to 2 nJ pulse(-1) at a wavelength of 532 nm is also found to increase the severity of the local magnification effect for nanoscale M2C metal carbide precipitates, which is indicated by a decrease of the local atomic density inside the carbides from 68 ± 6 nm(-3) (voltage pulsing) to as small as 3.5 ± 0.8 nm(-3). Methods are proposed to solve these problems based on comparisons with the results obtained from voltage-pulsed APT experiments. Essentially, application of the Cu precipitate compositions and local atomic density of M2C metal carbide precipitates measured by voltage-pulsed APT to 532 or 355 nm wavelength laser-pulsed data permits correct quantification of precipitation. 相似文献
85.
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87.
Isomerization of brain imaging agents aryltropane cocaine analogs have been examined by HPLC under chemical conditions similar to those encountered during radiolabeling. 相似文献
88.
Nicholas P. Mulholland 《Tetrahedron letters》2005,46(6):937-939
A silicon-tethered intramolecular radical cyclisation, in tandem with a radical trapping with allyltri-n-butylstannane forms the basis of a new synthetic strategy to the cyclopentane core of the antitumoral antibiotic substance viridenomycin isolated from Streptomyces viridochromogenes and S. gannmycicus. 相似文献
89.
An expansion solution in the physical plane is developed for subsonic compressible fluid flow past an obstacle. Assuming that
the stream is inviscid, isentropic, irrotational and steady, it is shown that the velocity potential may be expressed as a
series of homogeneous Heun functions and radial distance terms.
The basis of this analysis is Ludford's formal discussion of corresponding singularities in Bergman's Linear Integral Operator
Method. A modification of these results permits reduction of the governing nonlinear partial differential equation to an ordinary,
nonhomogeneous, linear differential equation.
The expansion solution is compared with the Rayleigh-Janzen method and the Prandtl-Glauert theory. The comparison indicates
that this expansion gives better results than other methods currently used. The simplicity and economy of this expansion solution
facilitates direct practical application. 相似文献
90.
The paper describes the application of liquid chromatography interfaced to a triple quadrupole mass spectrometer utilising the multiple reaction monitoring (MRM) mode. The technique was shown to provide detection limits lower than 0.01% for the analysis of prednisone in the presence of hydrocortisone. Prednisone was mixed in concentrations from 0.500 to 0.0005 ppm (corresponding to 1% to 0.001% of the hydrocortisone concentration). These solutions were assayed using MRM observing the product ion transitions of 359.2→147.1 and 359.2→171.2 and was shown to be capable of detecting co-eluting impurities at concentrations of less than 0.001% of the major component. The assay of prednisone was shown to be linear over the range 0.500–0.0005 ppm with a correlation coefficient of 0.999 and a precision of 6.9% at the concentration of 0.005 ppm. The analysis was carried out using both atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI) as an interface. However, for these compounds APCI provided significantly more sensitive data compared to ESI. 相似文献