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81.
The preparation of two new tripodal "pinwheel" type anion hosts based on a triethylbenzene core and bipyridinium or ethylnicotinium arms is reported. The new materials bind anions via CH...anion interactions. Complexes with Br(-) and PF(6)(-) have been characterised by X-ray crystallography as both solvates in a pure form. In the bipyridinium host CH...F interactions to PF(6)(-) induce a chiral C(3) symmetric conformation that is disrupted in the hydrate. The compound is also selective for ATP(2-) in aqueous acetonitrile. 相似文献
82.
We propose a new coherent state quantum key distribution protocol that eliminates the need to randomly switch between measurement bases. This protocol provides significantly higher secret key rates with increased bandwidths than previous schemes that only make single quadrature measurements. It also offers the further advantage of simplicity compared to all previous protocols which, to date, have relied on switching. 相似文献
83.
We report the experimental transformation of quadrature entanglement between two optical beams into continuous variable polarization entanglement. We extend the inseparability criterion proposed by Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)]] to polarization states and use it to quantify the entanglement. We propose an elaboration utilizing two quadrature entangled pairs for which all three Stokes operators between a pair of beams are entangled. 相似文献
84.
A. Warwick R. Chapman J.L. Durell J.N. Mo J.A. Kuehner P. Skensved 《Nuclear Physics A》1981,356(1):33-47
Angular distributions of α-particles from the reaction 209Bi(t, α)208Pb (ground state) have been measured at bombarding energies Et = 8.5 MeV and Et = 9.0 MeV. Zero-range (ZR) DWBA analyses of the data are used to determine the radial extent of the wave function of the orbit in which the transferred proton is bound in 209Bi. The applicability of the sub-Coulomb ZR DWBA treatment is investigated by comparison of ZR and exact finite-range DWBA calculations. A value of the (t, α) normalization constant of (20.8 ± 3.1) × 104 MeV2 · fm3, based on forward dispersion relations, has been obtained from this comparison. The asymptotic amplitude of the wave function is measured directly and the rms radius is extracted via a Woods-Saxon model. A value of √〈r2〉 = 6.10?0.08+0.12 fm, corresponding to a point proton and to a local Woods-Saxon potential, is obtained. The rms radius and radial wave function of the proton are compared with the results of electron scattering and muonic atom data on targets of 209Bi and 208Pb and with the results of Hartree-Fock calculations. 相似文献
85.
86.
Reservoir storage and containment of greenhouse gases 总被引:4,自引:0,他引:4
This paper deals with the problem of disposal of industrial waste greenhouse gases (CO2) into deep reservoirs. The simulator TOUGH2 was used to model the injection of 100 kg/s of CO2 for 10 years into an aquifer 3 km deep with the object of evaluating the long-term storage prospects for this gas. Depending on the permeability structure above the injection point, some gas may escape to the surface. In the most favourable case, all of the gas dissolves into the water, and the resulting dense fluid settles in the aquifer over several thousand years. Consequently, underground storage provides a promising sink for reducing CO2 emissions to the atmosphere. 相似文献
87.
Riser operating modes are vital to designing a circulating fluidized bed (CFB) reactor for a required process of either a gas-solid or a gas-catalytic nature. Different operating modes provide different solids’ residence times and mixing behaviors, which define the reactions’ efficiency and yield. The literature demonstrates distinct operating modes resulting from observed differences in slip factors and the range of particle velocities and their associated residence time distribution. The present research uses positron emission particle tracking (PEPT) in a riser of B-type bed material to determine the different operating modes by measuring (i) particle velocities and residence time distribution, (ii) population densities of these particles in the cross-sectional area of the riser, and (iii) solids flow pattern at the bottom of the riser. Data treatment defines four distinct solids hold-up regimes in the riser and proposes a "phase diagram" depicting the existence of the different operating modes (dilute, dense, core-annulus and combined) as a function of the superficial gas velocity and solids circulation flux in the riser. The delineated regimes have good agreement with available literature data and known industrial operations. Comparison with literature data for risers using A-type powders is also fair. The diagram enables CFB designers to better delineate operating characteristics. 相似文献
88.
89.
Many subsurface solute transport studies employ numerical modeling techniques to estimate solute arrival times. Simplifying assumptions must be made to define the modeling domain within a mathematical framework. One common assumption is that the vertical flow is negligible such that the flow field can be simulated with a two-dimensional model. Reducing the vertical dimension reduces the number of flow paths that a solute can take. In a heterogenous medium, artificially removing the 3rd dimension may lead to erroneous results. We investigate the error in the simulated solute breakthrough associated with a two-dimensional model. We also use a stochastic solution of solute arrival time to derive a transform of a two-dimensional ln (k) field so that solute transport more closely resembles three-dimensional transport behavior. The moment equations for two- and three-dimensional domains were solved simultaneously to calculate this transform. The results indicate that the removal of the vertical variability (3D 2D) introduces a 5–10% error in the predicted solute breakthrough. The error tends to increase with increased hydraulic conductivity variance. Numerical experiments confirm that the transform developed herein decreases the relative error of particle breakthrough curves. 相似文献
90.
Adam N. Swinburne Martin J. Paterson Kathrin H. Fischer Sara Jane Dickson Emma V. B. Wallace Warwick J. Belcher Andrew Beeby Dr. Jonathan W. Steed Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1480-1492
A series of tri‐ and tetrapodal viologen‐based anion receptors showing a colourimetric response to carboxylates, such as acetate, have been synthesised. Alteration of the anion binding sites allows for binding site competition within a receptor. This results in a delayed colourimetric response for urea derivatives compared with pyridinium systems because the anions are initially bound to the periphery of the receptor, away from the viologen unit. DFT calculations and experimental measurements allow the colour change to be assigned to an anion–receptor charge‐transfer process, facilitated by the exceptionally low reduction potential of the cationic host compounds. Evidence for electron transfer to give the viologen radical cation is also seen in some cases. 相似文献