Refractive index variation in nonaqueous sterically stabilized copolymer particles

We present procedures for preparing sterically stabilized polymer particles whose refractive index can be controlled over a range of a few percent. Particle sphericity and size distribution are such that suspensions crystallize at high concentrations. This at least ensures that Brownian motion dominates over particle settling and that the polydispersity is no more than about 10%. Of particular interest are new particles comprising poly(methylmethacrylate-co-trifluoroethylacrylate) that can be optically matched in single solvent, namely cis-decalin.     

The 5 resonance in the O(α, γ)Ne reaction at Eα = 4.65 MeV

A resonance at E_α = 4647 keV in the ¹⁶O(α, γ)²⁰Ne reaction has been located and assigned to a 5⁻ state in ²⁰Ne at 8447 ± 3 KeV. The radiative width of the 5⁻ to 3⁻ transition has been measured and found to be 13 ± 3 meV corresponding to a transition strength of 26 ± 6 Weisskopf units. Comparisons are made with rotational and shell model predictions.     

Book Reviews

Linear Algebra, 2nd edition by Serge Lang (1971). Addison-Wesley Publishing Company.

Linear Algebra with Applications by Hugh G. Campbell. Appleton-Century-Crofts, New York, 1971. xiii + 396 pp. + A45.An Engineering Approach to Linear Algebra, by W. W. Sawyer. Cambridge University Press, Cambridge, 1972. 304 pp. ($11.50)

An Engineering Approach to Linear Algebra, By W. W. Sawyer. Cambridge University Press, Cambridge, 1972. 304 pp. ($11.50) Sparse Matrices, by R. P. Tewarson. ($11.95)

Sparse Matrices, by R. P. Tewarson. ($11.95)     

Excited state hydrogen bond dynamics: coumarin 102 in acetonitrile-water binary mixtures

The time dependent change in the intermolecular response of solvent molecules following photoexcitation of Coumarin 102 (C102) has been measured in acetonitrile-water binary mixtures. Experiments were performed on mixtures of composition x(CH3CN) = 0.25, 0.50, 0.75, and 1.00. At low water concentrations (x(H2O) < or = 0.25) the solvent response is consistent with previous measurements probing dipolar solvation. With increasing water concentration (x(H2O) > or = 0.50) an additional response is found subsequent to dipolar solvation, exhibited as a rapid gain in the solvent's polarizability on a approximately 250 fs time scale. Monte Carlo simulations of the C102:binary mixture system were performed to quantify the number of hydrogen-bonding interactions between C102 and water. These simulations indicate that the probability of the C102 solute being hydrogen bound with two water molecules, both as donors at the carbonyl site, increases in a correlated fashion with the amplitude of the additional response in the measurements. We conclude that excitation of C102 simultaneously weakens and strengthens hydrogen bonding in complexes with two inequivalently bound waters.     

Probing orbital structure of polyatomic molecules by high-order harmonic generation

The effects of electronic structure and symmetry are observed in laser driven high-order harmonic generation for laser aligned conjugated polyatomic molecular systems. The dependence of the harmonic yield on the angle between the molecular axis and the polarization of the driving laser field is seen to contain the fingerprint of the highest occupied molecular orbitals in acetylene and allene, a good quantitative agreement with calculations employing the strong field approximation was found. These measurements support the extension of the recently proposed molecular orbital imaging techniques beyond simple diatomic molecules to larger molecular systems.     

Application of an Artificial Neural Network for Modelling the Thermal Dynamics of a Building’s Space and its Heating System

Artificial neural networks (ANNs) have been used for modelling the thermal dynamics of a building’s space, its water heating system and the influence of solar radiation. A multi-layer feed-forward neural network, using a Levenberg-Marquardt backpropagation-training algorithm, has been applied to predict the future internal temperature. Real weather data for a number of winter months, together with a validated building model (based on the building constructions data), were used to train the network in order to generate a mapping between the easily measurable inputs (outdoor temperature, solar irradiance, heating valve position and the building indoor temperature) and the desired output, i.e., the predicted indoor temperature. The objective of this work was to investigate the potential of using an ANN with singular value decomposition method (SVD) to predict the indoor temperature to shut down the heating system controller early for saving the energy consumption for heating inside the building.     

A two-sided Arnoldi algorithm with stopping criterion and MIMO selection procedure

In this paper we introduce a two-sided Arnoldi method for the reduction of high order linear systems and we propose useful extensions, first of all a stopping criterion to find a suitable order for the reduced model and secondly, a selection procedure to significantly improve the performance in the multi-input multi-output (MIMO) case. One application is in micro-electro-mechanical systems (MEMS). We consider a thermo-electric micro thruster model, and a comparison between the commonly used Arnoldi algorithm and the two-sided Arnoldi is performed.