贵金属Ag中光学和磁光性质的研究实验

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Tunnelling splittings in the high resolution microwave and UV spectra of the benzonitrile—water complex: modelling the internal motion in its S0 and S1 states

Refined values of the barriers to internal motion in the 1:1 complex between benzonitrile and water in the gas phase have been determined from analyses of its fully resolved microwave and ultraviolet spectra. Both spectra exhibit tunnelling splittings associated with this motion. Modelling this behaviour using a semi-rigid Hamiltonian for an internal rotation of water around its C ₂ axis yields values of V ₂ = 440 ± 30 cm^?1 and 450 ± 30 cm^?1 in the ground and excited electronic states, respectively. These relatively high barriers are a consequence of two hydrogen bonds between the interacting species.     

TO LEARN OR TO CHANGE: OPTIMAL R&D INVESTMENTS UNDER UNCERTAINTY IN THE CASE OF CLIMATE CHANGE

When studying R&D investments in technologies that address potential damage from climate change (termed as “research to change” or RTC), current literature overlooks the effects of purchased learning (i.e., learn through scientific research, termed as “research to learn” or RTL) about climate change. We investigate interactions between optimal R&D investments in RTC and RTL under uncertainty in climate change and research outcomes, while accounting for the positive impact that successful RTL may have on RTC outcome. We find that simultaneously investing in both RTL and RTC may be optimal when the probability that climate change imposes a specific level of damage is either moderate or very high and when RTL cost is relatively low. Whenever RTL and RTC are conducted simultaneously, then they substitute. However, when it is not optimal to conduct RTC and RTL simultaneously, then an increase in RTC cost decreases, at least weakly, RTL investment (i.e., RTL and RTC complement). When the probability that climate change imposes damage increases, then the optimal RTL investment may first decrease and then increase. Moreover, we identify conditions under which either the precautionary principle or the learn‐then‐act principle should be followed regarding R&D investments.     

Dispersion of solid particles in turbulant flow through pipe expansions

Studies of the effects upon gas-liquid two-phase flows of pipefittings such as expansions, contractions, bends, and valveshave usually concentrated upon pressuredrop correlations andhave not attempted to determine changes in the distributionsof the gas and liquid phases caused by the fitting. However,it is known that such information is important if, for example,flow separators, which divide the gas and liquid phases in avariety of industrial processes, are to function efficiently.It is therefore important to gain an understanding of the influenceupon phase distributions of the common pipe fittings mentionedabove, which will be found in almost any industrial pipeworksystem. As a first step, the dispersion of solid particles carriedby turbulent gas flows through a pipe expansion has been modellednumerically. The commercial fluid-flow code CFDS-FLOW{smalltilde}hDas been used to model the gas flow, together with aneddy interaction model for determination of the motion of thesolid particles. Mean particle velocities and root-mean-squarevalues of the particle velocity fluctuations, as well as particleconcentrations, are evaluated and compared with recent experimentalresults. The influence of different eddy-length and eddy-lifetimespecifications upon the dispersion of particles of various sizesis investigated. It is found that the different eddy characteristicshave little effect on predicted mean particle velocities, whereasfluctuations in particle velocities and particle concentrationare sensitive to the changes made. By comparing the resultswith experimental data, it is possible to draw conclusions aboutthe relative merits of the different eddy specifications.     

Uniqueness Theorems for the Inverse Problem of Elastodynamic Boundary Scattering

A uniqueness theorem is established for the elastodynamic problemof direct scattering of harmonic small-amplitude waves by anobstacle embedded in an isotropic medium with spatially varyingparameters. Uniqueness theorems are then developed for the inverseproblem of boundary determination of the obstacle associatedwith this direct scattering problem. In particular, it is shownfor nondegenerate elastodynamic problems that knowledge of boththe lamellar and the solenoidal far-field patterns is necessaryto reconstruct the obstacle's boundary.     

MEASURING THE COSTS OF REALLOCATING WATER FROM AGRICULTURE: A MULTI‐MODEL APPROACH

ABSTRACT. Increasing demand for water by environmental interests, coupled with the diminishing prospects for constructing new water diversion projects, is forcing farmers in the western United States to cope with reduced surface water deliveries. The cost of improving instream water quality by reducing agricultural diversions is shown to depend mainly on how the supply reductions are allocated among users and on the extent of water trading. A central contribution of this paper is a methodology for measuring the impacts of water supply policy reforms on irrigated agriculture. The paper nests three empirical models in a general conceptual framework. The models differ in terms of their degree of detail and assumptions about input substitution. By comparing model results, it is possible to place bounds on the consequences of policy changes, and to identify critical factors determining economic impacts. The models are applied to the problem of improving water quality in the San Francisco Bay/Delta estuary.     

A study of the adsorption of the amphiphilic penicillins cloxacillin and dicloxacillin onto human serum albumin using surface tension isotherms

The interaction of human serum albumin (HSA) with two structurally similar anionic amphiphilic penicillins, cloxacillin and dicloxacillin, at 25 °C has been examined by surface tension measurements under conditions at which the HSA molecule was positively (pH 4.5) or negatively charged (pH 7.4). Measurements were at fixed HSA concentrations (0.0125 and 0.125% w/v) and at drug concentrations over a range including, where possible, the critical micelle concentration (cmc). Interaction between anionic drugs and positively charged HSA at pH 7.4 resulted in an increase of the cmc of each drug as a consequence of its removal from solution by adsorption. Limited data for cloxacillin at pH 4.5 indicated an apparent decrease of the cmc in the presence of HSA suggesting a facilitation of the aggregation by association with the protein. Changes in the surface tension-log (drug concentration) plots in the presence of HSA have been discussed in terms of the adsorption of drug at the air-solution and protein-solution interfaces. Standard free energy changes associated with the micellization of both drugs and their adsorption at the air-solution interface have been calculated and compared.     

Polarizabilities and excitation energies from the multiplicative Kohn-Sham (MKS) approach

The conventional Kohn-Sham expressions for the static isotropic polarizability and vertical excitation energy are evaluated using Kohn-Sham orbitals and eigenvalues determined directly from theoretical electron densities. For a series of small molecules, polarizabilities determined from wavefunction-based BD(T) electron densities differ, on average, by about 2% from conventional BD(T) polarizabilities when the LDA exchange-correlation integrand is used in the electric Hessian matrix. Also polarizabilities determined from Kohn-Sham densities, using the B97-2 hybrid functional, are close to the conventional B97-2 values. To quantify the dependence on the choice of exchange-correlation integrand, calculations are performed also using the HCTH integrand. Rydberg excitation energies determined from BD(T) and B97-2 densities exhibit errors due to inaccuracies in the asymptotic exchange-correlation potential. This category of excitation energy is relatively insensitive to the choice of exchange-correlation integrand; valence excitations can be more sensitive.     

Multidimensional Reconstruction by Set-valued Approximations

Some generalizations of the notion of univariate data interpolationare presented, inducing the concept of set-valued interpolationin a general metric space. Consequently methods for univariateinterpolation or smoothing of multidimensional geometrical dataare suggested. In particular the application of these methodsto 3-D body recognition from cross-sectional data is discussed.Preliminary analysis of the interpolation process is presentedand the capability of reconstructing bodies of complex topologiesis exemplified.