Large-scale RPA calculations of chiroptical properties of organic molecules: Program RPAC

The computational considerations involved in calculating ordinary and rotatory intensities and electronic excitation energies in the random phase approximation (RPA ) are examined. We employ a localized orbital formulation in order to analyze the results in terms of local and charge-transfer excitations. Occupied orbitals are localized by the Foster–Boys procedure. The virtual space is transformed into a localized “valence” set that maximizes dipole strengths with the occupied counterparts, and a delocalized remainder. The two-electron integral transformation is performed with an efficient algorithm, based on Diercksen's, that generates only the particle–hole-type integrals required in the RPA . The lowest solutions of the RPA equations are obtained iteratively using a modification of the Davidson-Liu simultaneous vector expansion method. This allows the inclusion of the entire set of particle–hole states supported by a basis set of up to 102 orbitals. Calculations at this level give better excitation energies and intensities than SDCI methods, at substantial savings in computational effort. Comparative timings, computed results and analysis in terms of localized orbitals are given for planar and distorted ethylene using extended atomic orbital bases including diffuse functions. The results for planar ethylene are in excellent agreement with experiment.     

On tensor products of Banach lattices

Using techniques from harmonic analysis (more specifically Varopoulos' theory of tensor algebras) we study some tensor products of Banach lattices. Our main result is that if the Banach latticeB satisfies a certain additional property, the Gillespie factorization property, then a natural quotient of the spaceB^B is anL ^l-space, and we identify the kernel of this quotient map.     

Loud Speech in Realistic Environmental Noise: Phonetogram Data, Perceptual Voice Quality, Subjective Ratings, and Gender Differences in Healthy Speakers

A new method for cancelling background noise from running speech was used to study voice production during realistic environmental noise exposure. Normal subjects, 12 women and 11 men, read a text in five conditions: quiet, soft continuous noise (75 dBA to 70 dBA), day-care babble (74 dBA), disco (87 dBA), and loud continuous noise (78 dBA to 85 dBA). The noise was presented over loudspeakers and then removed from the recordings in an off-line processing operation. The voice signals were analyzed acoustically with an automatic phonetograph and perceptually by four expert listeners. Subjective data were collected after each vocal loading task. The perceptual parameters press, instability, and roughness increased significantly as an effect of speaking loudly over noise, whereas vocal fry decreased. Having to make oneself heard over noise resulted in higher SPL and F0, as expected, and in higher phonation time. The total reading time was slightly longer in continuous noise than in intermittent noise. The women had 4 dB lower voice SPL overall and increased their phonation time more in noise than did the men. Subjectively, women reported less success making themselves heard and higher effort. The results support the contention that female voices are more vulnerable to vocal loading in background noise.     

How does the EAS look like in thermal neutrons?

The first experimental data on detection of thermal neutrons accompanying extensive air showers (EASs) which were obtained at two prototypes of the future novel PRISMA EAS array are reported. The operation of this array (even in the minimum prototype version) and its ability to yield completely new information on the hadron and electron components of the EAS were experimentally checked.     

Two-photon absorption cross sections: an investigation of the accuracy of calculated absolute and relative values

We have studied the basis set and electron correlation effects on the ab initio calculations of two-photon absorption cross sections of water. Various series of correlation consistent basis sets up to triply augmented basis sets of valence pentuple zeta level as well as the popular 6-31G(d) basis set have been employed in combination with several coupled cluster, configuration interaction, and density functional theory methods. We find that it is very difficult to obtain converged values of the cross sections for even a small molecule such as water. Acknowledging these difficulties in obtaining a fully converged cross section for a given state, we also investigated the possibility of determining relative cross sections for a series of organic molecules. However, we did not find consistency between the relative cross sections calculated at the Hartree-Fock level and several coupled-cluster methods using the 6-31G(d) and aug-cc-pVDZ basis sets. However, we could reproduce the relative ordering of the two-photon absorption cross sections of the molecules studied at the Hartree-Fock level.     

Analytical applications of laser-enhanced lonization spectrometry in flames and furnaces

This paper is concerned with a critical analysis of the analytical performance of laser-enhanced ionization (LEI) spectrometry in flames and furnaces as an ultra-sensitive trace-element technique. Updated tables of LEI detection limits, both in flames and furnaces, are given. Special attention is paid to interference phenomena which are unique to the LEI technique. Ways of reducing their influence on the analytical signals are proposed. Finally, advantages and disadvantages of LEI spectrometry as a tool for ultra-sensitive trace element analysis are discussed.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Influence of Spot Size and Spectral Width of the Pump Radiation on the Efficiency of Laser-Diode-Pumped Solid-State Lasers

When mini-solid-state lasers are end-pumped by diode lasers, it is important to have a good overlap between the pump beam and the oscillating mode and to have a pump spectrum that is narrow compared to the width of the absorption peak in the gain medium. We have theoretically studied the influence of the beam radius and the spectral width of the pump on the performance of diode-pumped devices. From the rate equations, the lasing threshold and the circulating intensity is evaluated numerically and the results can be used as a guideline in the design of intracavity doubling lasers. It is also shown that single-mode operation is more difficult when the pump spectrum becomes to wide.     

Icebreaking Operations in the Northern Baltic—A Simulation Study

Journal of the Operational Research Society - An icebreaking situation in the northern Baltic is considered. Two icebreakers are deployed to assist freight ships to and from three harbours in...