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91.
J. H. Northern G. A. D. Ritchie E. P. Smakman J. H. van Helden R. J. Walker G. Duxbury 《Applied physics. B, Lasers and optics》2011,102(1):37-42
We report observations of rapid passage signals induced in samples of N2O and CH4 present in a multipass cell with an optical path length of 5 m. The effect of laser power and chirp rate upon the signals
has been studied by utilising two different chirped quantum cascade lasers operating around 8 μm. The rapid passage signals
exhibit an increasing delay in the switch from absorption to emission as a function of increased gas pressure (up to 8 Torr
of gas). By comparing a selection of transitions in N2O and CH4, we show that, unlike ammonia, this ‘pressure shift’ is independent of the transition dipole moment, spectroscopic branch
probed and laser chirp rate. As the transition dipole moment is much larger in nitrous oxide than methane, we believe that
this indicates that N2O–N2O collisions are more efficient at removing coherence from the polarised sample than CH4–CH4 collisions. We have also observed this pressure shift in a short path length of 40 cm, although with a much reduced value,
indicating that propagation effects are important in this optically thick minimally damped system. 相似文献
92.
Passier R Ritchie JP Toro C Diaz C Masunov AE Belfield KD Hernandez FE 《The Journal of chemical physics》2010,133(13):134508
Herein we report the experimental and theoretical study of the temperature dependence of a thiacarbocyanine dye in its monomer, H- and J-aggregates states. We demonstrate the ability to control the ratio of monomer, H- and/or J-aggregates with heat. We link such a control to the conformation dependence of the molecule. An alternative way to gain access to the dominating species without changing the concentration as a complete switching mechanism between all the present species is proposed. The results presented in this work lead to a better understanding of thiacarbocyanine dye's behavior. 相似文献
93.
Giovanna Cancelliere Alessia Ciogli Ilaria D’Acquarica Francesco Gasparrini Jelena Kocergin Domenico Misiti Marco Pierini Harald Ritchie Patrizia Simone Claudio Villani 《Journal of chromatography. A》2010,1217(7):990-999
Three brush-type chiral stationary phases (CSPs) differing in the particle size of the starting silica particles have been prepared by covalent grafting of the π-acidic bis-(3,5-dinitrobenzoyl)-derivative of trans-1,2-diaminocyclohexane (DACH-DNB). Starting silica particles of 4.3, 2.6 and 1.9 micron were used to generate the final CSPs using an improved, highly reproducible synthetic methodology, that allowed to assemble and surface-graft the whole chiral selector in only two steps. The different CSPs have been packed in columns of various length and diameters, and fully characterized in terms of flow permeability, kinetic performances and enantioselectivity using a set of test solutes. Very high speed and high resolution applications together with stereodynamic HPLC examples are demonstrated on the columns with reduced particle diameters, on which separations of several enantiomeric pairs are routinely obtained with analysis times in the 15–40 s range. 相似文献
94.
This article describes the construction and validation of a three-dimensional model of the human CCR5 receptor using a homology-based approach starting from the X-ray structure of the bovine rhodopsin receptor. The reliability of the model is assessed through molecular dynamics and docking simulations using both natural agonists and a synthetic antagonist. Some important structural and functional features of the receptor cavity and the extracellular loops are identified, in agreement with data available from site-directed mutagenesis. The results of this study help to explain the structural basis for the recognition, activation, and inhibition processes of CCR5 and may provide fresh insights for the design of HIV-1 entry blockers. 相似文献
95.
Thomas Logan Ritchie 《Journal of statistical physics》2006,122(3):381-398
We provide an explicit construction of the thermodynamic jamming limit for the parking process and other finite range exclusion
schemes on
. By means thereof, a strong law of large numbers for occupation densities is accomplished, and, amongst other results, the
so called “super-exponential” (i.e. gamma) decay of pair correlation functions is established.
Mathematics Subject Classification (1991): 60K99 相似文献
96.
Ritchie C Burkholder E Kögerler P Cronin L 《Dalton transactions (Cambridge, England : 2003)》2006,(14):1712-1714
Unsymmetrical functionalization of a discrete alpha-{SiW12O40} Keggin with two heterometallic building blocks, a Cu(II) dimer and a Cu(II) monomer, results in the formation of [{Cu2(O2CMe)2(5,5'-dimethyl-2,2'-bipy)2}{Cu(5,5'-dimethyl-2,2'-bipy)2}SiW12O40] that displays interesting physical properties. 相似文献
97.
Burke Ritchie 《Optics Communications》2008,281(13):3492-3494
The photon equation of motion previously applied to the Lamb shift is here applied to the anomalous magnetic moment of the electron. Exact agreement is obtained with the QED result of Schwinger. The photon theory treats the radiative correction to the photon in the presence of the electron rather than its inverse as in standard QED. The result is found to be first order in the photon-electron interaction rather than second order as in standard QED, introducing an ease of calculation hitherto unavailable. 相似文献
98.
99.
E. Ritchie 《The Journal of the Operational Research Society》1984,35(10):949-952
The E.O.Q. is derived for constant, continuous demand. For linear increasing demand, Donaldson's analytical solution considers demand bounded by a time horizon H. Although this is mathematically convenient for obtaining a solution, it complicates the calculation of the optimal replenishment policy. Extending the time horizon so that it no longer influences the replenishment times simplifies the calculation of the optimal policy, which is then equivalent to the E.O.Q. calculation for constant demand. 相似文献
100.