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141.
Structural Chemistry - In the current study, the energetics of fractionally (and indeed arbitrary non-integer) charged species is explicitly discussed for the enhanced understanding of aromaticity... 相似文献
142.
Black PJ Cami-Kobeci G Edwards MG Slatford PA Whittlesey MK Williams JM 《Organic & biomolecular chemistry》2006,4(1):116-125
Alcohols have been employed as substrates for C-C bond-forming reactions which involve initial activation by the temporary removal of hydrogen to form an aldehyde. The intermediate aldehyde is converted into an alkene via a Horner-Wadsworth-Emmons reaction, nitroaldol and aldol reactions. The 'borrowed hydrogen' is then returned to the alkene to form a C-C bond. 相似文献
143.
144.
We show how to formulate two-point boundary-value problems in order to compute fully-developed laminar channel and tube flow profiles for viscoelastic fluid models. The formulation is applied to Couette and pressure-driven flows separately, or a combination of both. The application of this methodology is illustrated analytically for the Upper-Convected Maxwell Model, and it is applied computationally for the Phan-Thien/Tanner and Giesekus Models. Numerical solutions exist for the last two models [J.Y. Yoo, H.C. Choi, On the steady simple shear flows of the one-mode Giesekus fluid, Rheol. Acta 28 (1989) 13–24; P.J. Oliveira, F.T. Pinho, Analytical solution for fully developed channel and pipe flow of Phan-Thien–Tanner fluids, J. Fluid Mech. 387 (1999) 271–280; M.A. Alves, F.T. Pinho, P.J. Oliveira, Study of steady pipe and channel flows of a single-mode Phan-Thien–Tanner fluid, J. Non-Newtonian Fluid Mech. 101 (2001) 55–76], allowing verification of the computational technique. Subsequently, the computational algorithm is applied to the constant-volume polymer blend models of Maffettone and Minale [P.L. Maffettone, M. Minale, Equation of change for ellipsoidal drops in viscous flow, J. Non-Newtonian Fluid Mech. 84 (1999) 105–106 (Erratum), J. Non-Newtonian Fluid Mech. 78 (1998) 227–241] and Dressler and Edwards [M. Dressler, B.J. Edwards, The influence of matrix viscoelasticity on the rheology of polymer blends, Rheol. Acta 43 (2004) 257–282; M. Dressler, B.J. Edwards, Rheology of polymer blends with matrix-phase viscoelasticity and a narrow droplet size distribution, J. Non-Newtonian Fluid Mech. 120 (2004) 189–205]. Rheological and morphological properties of the model blends are thus obtained as functions of the spatial position within the channel, applied pressure drop, and shear rate at the wall. 相似文献
145.
Hyperfine Interactions - 相似文献
146.
We report the synthesis and structural characterisation of three five co-ordinate indium(III) bis-chelate complexes of imidodiphosphinates with general formula InCl{N(PR2X)2}2, (R=Ph or Pri, X=S or Se), formed from the 1:2 reaction of indium(III) trichloride and the potassium or sodium salt of the ligand in methanol/THF. The complexes consist of discrete monomeric, molecules and show a trigonal–bipyramidal co-ordination pattern. These are the first examples of five co-ordinate complexes containing this type of ligand, in contrast to other indium(III) and main group element complexes of similar ligands in which only the six co-ordinate tris-chelates are known. 相似文献
147.
Leon Glass Theodore J. Perkins Jonathan Mason Hava T. Siegelmann Roderick Edwards 《Journal of statistical physics》2005,121(5-6):969-994
We consider dynamics in a class of piecewise-linear ordinary differential equations and in an electronic circuit that model
genetic networks. In these models, gene activity varies continuously in time. However, as in Boolean or discrete-time switching
networks, gene activity is driven high or low based only on whether the activities of the regulating genes are high or low
(i.e., above or below certain thresholds). Depending on the “regulatory logic”, these models can exhibit simple dynamics,
like stable fixed points or oscillation, or chaotic dynamics. The observed qualitative and quantitative differences between
the dynamics in the idealized equations and the dynamics in the electronic circuit lead us to focus attention on the analysis
of the dynamics as a function of parameter values. We propose new techniques for solving the inverse problem – the problem
of inferring the regulatory logic and parameters from time series data. We also give new symbolic and statistical methods
for characterizing dynamics in these networks. 相似文献
148.
C. Wynter T.M. Clark B.J. Evans M.A. Edwards D. Radcliffe J.A. Hall 《Hyperfine Interactions》1998,112(1-4):231-234
Trends in the speciation of iron and sulfur in high iron/sulfur coals are well-established. Less is known concerning iron and sulfur speciation in low sulfur coals such as those investigated in this study. Low sulfur coals and their flyash from Thunder Bay, Ontario, Canada and Atikokan, West Virginia, U.S.A. have been investigated by means of 57Fe Mössbauer spectroscopy, X-ray diffraction and X-ray fluorescence. Virgin coals, containing approximately 0.1% Fe, exhibited Mössbauer spectra too low in intensity to characterize the phases present. The flyash exhibited well-resolved, simple doublets with ΔEQ=1.16 mm s?1 (Canada) and 1.26 mm s?1 (U.S.A.) and isomer shift values (w.r.t. Fe) of 0.22 mm s?1 and 0.23 mm s?1, respectively, characteristic of Fe3+. The linewidths of ~0.80 mm s?1 are unusually large. Treatment of the flyash with cold, hydrofluoric acid resulted in a sample that exhibited very little absorption in its 57Fe Mössbauer spectrum. This result, in conjunction with the linewidths, indicates that the Fe is present in the flyash mainly as a silicate glass. 相似文献
149.
C. S. Edwards P. Gill H. A. Klein A. P. Levick W. R. C. Rowley 《Applied physics. B, Lasers and optics》1994,59(2):179-185
We report some laser-cooling effects in a few172Yb+ ions held in a Paul trap. Pronounced cloud-to-crystal phase transitions have been observed as discontinuities in the Yb+ fluorescence spectrum of the 369 nm cooling transition. The first reported two-dimensional images of Yb+ clouds with evidence of crystal structure have been recorded using a photon-counting position-sensitive detector. An ion temperature of 100 mK has been estimated from the size of a single ion image. Step-wise cooling of a re-heated, few-ion Yb+ cloud was also observed. 相似文献