Field-induced anisotropy in concentrated systems of rigid particles and macromolecules

This paper presents experimental results on the use of spectroscopic optical polarimetry to study structure in dense systems of rigid particles and rigid polymer liquid crystals. These measurements probe microstructural anisotropy induced by the application of electric fields in the case of dense suspensions of rigid spheres, or flow fields in the case of polymer liquid crystals. It is demonstrated that conservative linear dichroism can measure moments of the particle pair distribution function in dense suspensions. In liquid crystals, the dichroism is a result of field-induced anisotropy in the defect structure of the material.     

A comparative evaluation of time-of-event counting for low-level radioactivity measurements

A comparison is made in this paper of the number of radioactive atoms which can be detected by means of two data analysis methods. One method is the conventional data acquisition and reduction method and the other measures and records the time of each detected decay event. By use of simulation methods it is shown that under appropriate conditions the latter method can detect a smaller number of atoms of a decaying radionuclide in the presence of a constant background component.This paper is based on work sponsored by the Division of Chemical Sciences of the Department of Energy and performed under DOE Contract DE-AC06-76RLO-1830.     

Studying the Avalanching Behaviour of a Powder in a Rotating Disc

The use of a rotating disc to study the avalanching behaviour of a powder is discussed. It is shown that the strange attractor plotted in discreet time maps summarizes useful information on the rheological behaviour of powders and powder mixtures. In particular it is shown that the avalanching behaviour is related to the particle size distribution of the powder and that one can study the changes in rheological behaviour as another powder is mixed with it. The strange attractor patterns generated are dependent upon the environmental conditions under which the experiments are carried out. For this reason the measurements are referred to as an assessment of the holistic powder rheology. The potential use of the disc to study the holistic rheology of powder systems is outlined.     

Constructing {kappa}-like Models of Arithmetic

A model (M, <, ...) is -like if M has cardinality but, forall M, the cardinality of {x M : x < a} is strictly lessthan . In this paper we shall give constructions of -like modelsof arithmetic satisfying an arbitrarily large finite part ofPA but not PA itself, for various singular cardinals . The mainresults are: (1) for each countable nonstandard M ₂–Th(PA)with arbitrarily large initial segments satisfying PA and eachuncountable of cofinality there is a cofinal extension K ofM which is -like; also hierarchical variants of this resultfor _n–Th(PA); and (2) for every n 1, every singular and every M B_n+exp+¬ I_n there is a -like model K elementarilyequivalent to M.     

EVALUATION OF PORPHYRIN CHARACTERISTICS REQUIRED FOR PHOTODYNAMIC THERAPY

The cytotoxicity (in the dark), phototoxicity (red light) and subcellular localization (using confocal laser scanning microscopy) were determined for 15 porphyrins (1-15) in C6 glioma cells. The partition coefficient in 2-octanol was also determined for each porphyrin at pH 7.4. The cytotoxicity increased with pi (log of partition coefficient) up to pi values of +2. The 7 porphyrins with cationic side chains exhibited a classical parabolic correlation between phototoxicity and pi, with maximal activity at a pi value of approximately 1.0. There was also a significant correlation between subcellular localization and degree of phototoxicity, with the three most photosensitive porphyrins all possessing cationic side chains, and all three localizing in mitochondria.     

Rapid,quantitative analysis of americium,curium and plutonium isotopes in Hanford samples using extraction chromatography and precipitation plating

Recently developed methods for the rapid, quantitative analysis of americium (Am), curium (Cm), and plutonium (Pu) isotopes in Hanford soil, sludge, and waste-tank samples are described. After dissolution, dilutions are made as necessary based on alpha-energy analysis of a small aliquot of the original solution. Isotopic tracers are then added and Am-Cm and Pu are separated by extraction chromatography, coprecipitated with neodymium fluoride, and counted. Examples of alpha spectra are given, and results obtained for Hanford sludge samples are presented.