Sadashi Sawamura

SPECTROSCOPIC STUDY OF 4-AMINOBENZOPHENONE IN SUPERCRITICAL CF3H AND CO2 :LOCAL DENSITY AND ONSAGER'S REACTION CAVITY RADIUS

The measured bathochromic shifts of 4-aminobenzophenone (4ABP) in CF3H are explained by Onsagers reaction field theory (ORFT) if the cavity radius is the sum of Van der Waals radii of solute and solvent, while in CO2, the cavity radius is the solutes Van der Waals radius. The experimental local densities around 4ABP have been estimated and show a maximum at a reduced density of 0.5 for CF3H and 0.7 for CO2. Simulations are consistent with the high local densities found at low bulk densities and suggest possible explanations for the different radii used for CF3H and CO2.

Prediction Analysis for Measles Epidemics

A newly devised procedure of prediction analysis, which is a linearized version of the nonlinear least squares method combined with the maximum entropy spectral analysis method, was proposed. This method was applied to time series data of measles case notification in several communities in the UK, USA and Denmark. The dominant spectral lines observed in each power spectral density (PSD) can be safely assigned as fundamental periods. The optimum least squares fitting (LSF) curve calculated using these fundamental periods can essentially reproduce the underlying variation of the measles data. An extension of the LSF curve can be used to predict measles case notification quantitatively. Some discussions including a predictability of chaotic time series are presented.

Investigation of the soil radon variation during the winter months in Sapporo, Japan.

Soil radon was measured from late October 2000 to January 2001 at three test sites on the campus of Hokkaido University in Sapporo, Japan. Factors affecting radon concentrations were investigated with relation to meteorological data, as well as soil 226Ra content, mineral composition, water content, and pH, Eh and conductivity. Soil radon varied with time and with sampling site appreciably, in a manner unaltered by the surface geology. However, the ratio of radon isotopes (220Rn/222Rn) in the soil was constant within each sampling site, regardless of varying concentration of these nuclides during the monitoring period. Snow covering on the soil surfaces may affect the 222Rn concentration.

Spectral Study of Measles Epidemics: The Dependence of Spectral Gradient on the Population Size of the Community.

We have carried out spectral analysis of measles notifications in several communities in Denmark, UK and USA. The results confirm that each power spectral density (PSD) shows exponential characteristics, which are universally observed in the PSD for time series generated from nonlinear dynamical system. The exponential gradient increases with the population size. For almost all communities, many spectral lines observed in each PSD can be fully assigned to linear combinations of several fundamental periods, suggesting that the measles data are substantially noise-free. The optimum least squares fitting curve calculated using these fundamental periods essentially reproduces an underlying variation of the measles data, and an extension of the curve can be used to predict measles epidemics. For the communities with large population sizes, some PSD patterns obtained from segment time series analysis show a close resemblance to the PSD patterns at the initial stages of a period-doubling bifurcation process for the so-called susceptible/exposed/infectious/recovered (SEIR) model with seasonal forcing. The meaning of the relationship between the exponential gradient and the population size is discussed.

Density dependence of the Stokes shift and solvent reorganization energy in supercritical fluids

Abstract The Stokes shifts of coumarin 153 (C153) in CF 3 H, CO 2 and C 2 H 6 have been measured at several reduced densities (0.3–1.8). For C153 in CF 3 H, the shifts increase with a decrease in reduced density and show a maximum value at a reduced density of 0.5. In non-polar solvents, the shifts are not dramatically altered as a function of reduced density but slightly increase with a decrease in the reduced density.

Humic acids as a scavenger of manganese(II) and zinc(II) in soil environment using a radiotracer technique

The uptake of manganese(II) and zinc(II) by humic acids (HA) was investigated using a radiotracer technique in order to elucidate their ability of scavenging heavy metals released into the soil environment. Metal uptake by HA was affected by aqueous pH, in which the amounts of Mn(II) and Zn(II) associated with HA showed a similar pattern against pH. These facts indicate that interactions of Mn(II) and Zn(II) with HA would be ionic in character, and affected by properties of the carboxyl groups in HA.

Investigation of the sorption of Zn(II) on surface soils using a radiotracer technique

Abstract Radiometric sorption experiments were carried out on surface soil samples collected from several sites around Sapporo city (Hokkaido, Japan) in order to evaluate their capacities for the sorption of Zn(II). The maximum sorption (Am) of Zn(II), obtained from the sorption isotherm, was only 2–5% of the cation exchange capacity (CEC). The Am values were correlated with the pH of the soil suspensions, which indicates that zinc sorption would occur competitively with protons in the suspension. The effect of organic matter on the Zn(II) uptake was estimated from the Am change of the individual samples before and after heat treatment. Coordinate uptake of the Zn(II) into the degrading organic matrices was believed not to be important for Zn(II) sorption in some of the present soil samples.

Sorptive behavior of Zn(II) on a lake sediment by sequential extraction-radiotracer technique.

A sequential extraction-radiotracer technique was applied to a sediment core sample collected from lake Biwa (Japan) in order to evaluate relative importance of the fractionated solid components to sorb Zn(II) ions. The core was previously divided into three parts from the surface of the sediment; upper (0-6 cm), middle (6-12 cm) and bottom (12-18 cm). The solid residue after each chemical treatment was collected to perform a sorption experiment by using (65)Zn as a tracer. A difference in the amount of Zn(II) sorption was observed among original samples without any chemical treatments at each depth. The amounts were very small (10(-5) -10(-4) mol Zn(II) 100 g(-1) of dry sample) in all fractions of the sediment. Electrochemical measurements of cadmium and copper ion sorption supported the results from the radiometric sorption experiment. The effects of several potential factors on zinc sorption were investigated. Ion exchange of zinc with protons on the mineral surfaces was a significant cause of the zinc sorption.

Fluence to Dose Conversion Coefficients for Electrons up to 200 MeV in Localized Exposure

To estimate radiation hazards in the accidental exposure to energetic electrons, effective doses were calculated with the EGS4 Monte Carlo simulation code and the MIRD-5 human phantom for high energy electron beams like those from a LINAC in which non-uniform exposure of the human body would occur. The calculations show that the effective doses depend on the incident electron energy and beam size and on the place of the exposure of the body.

Sorption of manganese(II) and zinc(II) to soils alluvial in origin

The sorption of manganese(II) and zinc(II) on soil samples collected from Sapporo (Japan) and Tiksi (Russia) was investigated using a radiotracer technique to elucidate the abilities of soil organic matter as a scavenger of heavy metals released to the soil environment. The sorbed amounts of both manganese and zinc metals to organic soil components were estimated to be different on different soils, depending on the pH of aqueous phase. The degree of humification of pertinent soils was suggested as a parameter which could describe the properties of the organic soil matter in complexing with heavy metals.