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Use of Nuclear Spin Noise Spectroscopy to Monitor Slow Magnetization Buildup at Millikelvin Temperatures 下载免费PDF全文
Maria Theresia Pöschko Dr. David Peat Prof. John Owers‐Bradley Prof. Norbert Müller 《Chemphyschem》2016,17(19):3035-3039
At ultralow temperatures, longitudinal nuclear magnetic relaxation times become exceedingly long and spectral lines are very broad. These facts pose particular challenges for the measurement of NMR spectra and spin relaxation phenomena. Nuclear spin noise spectroscopy is used to monitor proton spin polarization buildup to thermal equilibrium of a mixture of glycerol, water, and copper oxide nanoparticles at 17.5 mK in a static magnetic field of 2.5 T. Relaxation times determined in such a way are essentially free from perturbations caused by excitation radiofrequency pulses, radiation damping, and insufficient excitation bandwidth. The experimental spin‐lattice relaxation times determined on resonance by saturation recovery with spin noise detection are consistently longer than those determined by using pulse excitation. These longer values are in better accordance with the expected field dependence trend than those obtained by on‐resonance experiments with pulsed excitation. 相似文献
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Roger Parsons Robert Peat Robert M. Reeves 《Journal of Electroanalytical Chemistry》1975,62(1):151-161
The adsorption of urea on mercury from aqueous 1 M KNO3 has been determined from capacity and electrocapillary measurements. A Langmuir isotherm is obeyed with a saturation molecular area of 24 × 10?10 m2 per molecule. The standard free energy of adsorption is a quadratic function of charge with maximum adsorption occurring at a charge of +8 μC cm?2. These data are interpreted in terms of the partially oriented urea dipole, the contribution of water dipoles and nitrate ions also being considered. 相似文献
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A new approach for the synthesis of 2-vinyl monoprotected 1,3-diols has been developed. By employing different Lewis acid, either anti-anti or anti-syn stereoisomer can be selectively prepared. 相似文献
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K.S. Peat 《Journal of sound and vibration》2009,319(3-5):1097-1106
This paper considers the plane-wave end correction that should be applied at the junction between a plain and a perforated pipe of equal diameter in the absence of mean flow. A general theory is developed that results in an equation for the end correction of all such junctions. The theory is verified by experimental results for the end correction obtained via the measurement of resonant frequency of a Helmholtz resonator whose neck is formed of a plain section and then a perforated section of pipe, before termination into free space. It is shown that in most practical situations within automotive silencers the perforated pipe will be long enough for the nature of the termination to be irrelevant. A simple formula is developed to evaluate this long-length limit and from it the dependence of the end correction upon all the parameters within the problem becomes explicit. 相似文献
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K. S. Peat 《Applied Scientific Research》1977,33(5-6):481-499
The effects of viscosity on the propagation of a St. Andrew's cross wave which is generated by a simple-harmonic localized
disturbance in a rotating stratified fluid are considered. A similarity solution of the linearised equations shows that the
velocities decay and that the wave width increases away from the disturbance. Previous solutions in a stratified non-rotating
fluid are recovered by letting the rotation tend to zero. The solutions are also valid in the limit of a homogeneous rotating
fluid. Further solutions for waves in a realistic ocean and in an isothermal atmosphere on a rotating Earth are also included. 相似文献
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Newman J Dolezal O Fazio V Caradoc-Davies T Peat TS 《Journal of computer-aided molecular design》2012,26(5):497-503
Part of the latest SAMPL challenge was to predict how a small fragment library of 500 commercially available compounds would bind to a protein target. In order to assess the modellers' work, a reasonably comprehensive set of data was collected using a number of techniques. These included surface plasmon resonance, isothermal titration calorimetry, protein crystallization and protein crystallography. Using these techniques we could determine the kinetics of fragment binding, the energy of binding, how this affects the ability of the target to crystallize, and when the fragment did bind, the pose or orientation of binding. Both the final data set and all of the raw images have been made available to the community for scrutiny and further work. This overview sets out to give the parameters of the experiments done and what might be done differently for future studies. 相似文献
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In this study we investigated the use of a DNA dosimeter to accurately measure changes in ultraviolet B radiation (UVBR; 280-315 nm) under Antarctic ozone hole conditions. Naked DNA solution in quartz tubes was exposed to ambient solar radiation at Rothera Research Station, Antarctica, between October and December 1998 for 3 h during UVBR peak hours (1200-1500 h). Trends in UVBR-mediated DNA damage (formation of cyclobutane pyrimidine dimers [CPD]) were related to cloud cover, ozone-column depth and spectroradiometric measurements of ambient radiation. Ozone-column depths ranged from 130 to 375 DU during the study period, resulting in highly variable UVBR doses, from 1.6 to 137 kJ m(-2) over the 3 h exposure, as measured by spectroradiometry. There was a strong positive correlation (86%) between dosimeter CPD concentrations and DNA-weighted UVBR doses. Ozone depth was a strong predictor of DNA damage (63%), and there was no significant relationship between CPD formation and cloud cover. Subtle changes in spectral characteristics caused by ozone depletion were detected by the biodosimeter; the highest CPD concentrations were observed in October when ozone-mediated shifts favored shorter wavelengths of UVBR. We conclude that the DNA biodosimeter is an accurate indicator of biologically effective UVBR, even under highly variable ozone conditions. 相似文献