Luminescence study of tetravalent uranium in aqueous solution.

The luminescence spectrum of U4+ in aqueous solution was observed in the UV-Vis region with the lifetime < 20 ns at room temperature by excitation light corresponding to the 5f-5f electronic transition. All the luminescence peaks were assigned to individual electronic transitions.

Development of a pumping laser system for x-ray laser research.

A two-beam chirped-pulse-amplification Nd:glass laser system dedicated to x-ray laser research is described. Each beam provides an output energy of 20 J with a typical pulse duration of 1.3 ps.

Mutation rate and novel tt mutants of Arabidopsis thaliana induced by carbon ions.

Irradiation of Arabidopsis thaliana by carbon ions was carried out to investigate the mutational effect of ion particles in higher plants. Frequencies of embryonic lethals and chlorophyll-deficient mutants were found to be significantly higher after carbon-ion irradiation than after electron irradiation (11-fold and 7.8-fold per unit dose, respectively).

8-oxoguanine lesioned B-DNA molecule complexed with repair enzyme hOGG1: a molecular dynamics study.

The molecular dynamics (MD) simulation of DNA mutagenic oxidative lesion, 7,8-dihydro-8-oxoguanine (8-oxoG), complexed with the repair enzyme, human oxoguanine glycosylase 1 (hOGG1), was performed for 1 nanosecond (ns) in order to describe the dynamical process of DNA-enzyme complex formation. After 900 picoseconds of MD the lesioned DNA and enzyme formed a complex that lasted until the end of the simulation at 1 ns. The complex was mainly represented by the overlapping van der Waals surfaces of DNA and enzyme molecules.

Adsorption of radionuclides on silica and their uptake by rice plants from silica-multitracer solutions: the effects of pH.

We investigated the effect of solution pH on the adsorption on silica of a mixture radionuclides 83Rb, 85Sr, 54Mn, 65Zn, 88Y, and 75Se generated from irradiation of Ag in a 135-MeV/nucleon 12C beam accelerated by the RIKEN Ring Cyclotron and 137Cs obtained commercially. Then, we related these findings to their uptake by a rice plant (Oryza sativa L. cv.

Vertical profile of tritium concentration in air during a chronic atmospheric HT release.

The vertical profiles of tritium gas and tritiated water concentrations in air, which would have an influence on the assessment of tritium doses as well as on the environmental monitoring of tritium, were measured in a chronic tritium gas release experiment performed in Canada in 1994. While both of the profiles were rather uniform during the day because of atmospheric mixing, large gradients of the profiles were observed at night. The gradient coefficients of the profiles were derived from the measurements.

Analysis of dose distribution for heavily exposed workers in the first criticality accident in Japan.

The first criticality accident in Japan occurred in a uranium processing plant in Tokai-mura on September 30, 1999. The accident, which occurred while a large amount of enriched uranyl nitrate solution was being loaded into a tank, led to a chain reaction that continued for 20 h. Two workers who were pouring the uranium solution into the tank at the time were heterogeneously exposed to neutrons and gamma rays produced by nuclear fission.

Measuring nonequilibrium temperature of forced oscillators.

The meaning of temperature in nonequilibrium thermodynamics is considered by using a forced harmonic oscillator in a heat bath, where we have two effective temperatures for the position and the momentum, respectively. We propose a concrete model of a thermometer to testify the validity of these different temperatures from the operational point of view. It is found that the measured temperature depends on a specific form of interaction between the system and a thermometer, which means that the zeroth law of thermodynamics cannot be immediately extended to nonequilibrium cases.

Population kinetics of lithiumlike and berylliumlike ions in low temperature dense recombining plasma.

A collisional-radiative model for the lithiumlike and berylliumlike ions has been constructed. In this model, virtually all the doubly excited levels of the berylliumlike ions are taken into account. Time-differential coupled rate equations for the level populations of the lithiumlike and berylliumlike ions are solved under a recombining plasma condition, and the population kinetics of these ions, especially for the validity of quasisteady state (QSS) approximation and the population flux into and out of excited levels, is discussed.

Friedel oscillation in charge profile and position dependent screening around a superconducting vortex core.

We calculate microscopically the charge distribution around a vortex in type II superconductors by solving the Bogoliubov-de Gennes equation and the Poisson equation simultaneously. Our calculations show that the charge density depletion occurs in the vortex center and the Friedel oscillation appears over the coherence length when k(F)xi is small. We also calculate the density-density correlation function K(r,r(')) as a function of two spatial variables, r and r('), and find that K(r,r(')) is strongly dependent on the distance from the vortex center.

Effect of humic acid on the bioavailability of radionuclides to rice plants.

We investigated the effect of humic acid and solution pH on the uptake of the radionuclides, (83)Rb, (137)Cs, (54)Mn, (65)Zn, (88)Y, (102)Rh, and (75)Se in rice plants by the multitracer technique. The addition of humic acid to a culture medium containing SiO(2) increased the uptake of Mn and Zn at pH 4.3, whereas their uptake was decreased at pH 5.

Analyses of absorbed dose to tooth enamel against external photon exposure.

Absorbed dose to tooth enamel was examined against external photon exposure by measurements with thermoluminescence dosemeters (TLDs) and Monte Carlo calculations. TLDs were placed in a realistic physical phantom to measure dose to the teeth region in a head. A voxel-type phantom was constructed from computed tomography (CT) images of the physical phantom.

Dynamical matching of Josephson vortex lattice with sample edge in layered high-Tc superconductors: origin of the periodic oscillation of flux flow resistance.

We numerically investigate Josephson vortex flow states in layered high-T(c) superconductors motivated by a recent experimental observation for accurate periodic magnetic field dependences of the Josephson vortex flow resistance over a wide range of magnetic field (0.5-4.0 T).

Hydration in proteins observed by high-resolution neutron crystallography.

It is well known that water molecules surrounding a protein play important roles in maintaining its structural stability. Water molecules are known to participate in several physiological processes through the formation of hydrogen bonds. However, the hydration structures of most proteins are not known well at an atomic level at present because X-ray protein crystallography has difficulties to localize hydrogen atoms.

Effects of heavy-ion radiosurgery on the hemopoietic function of the silkworm Bombyx mori.

To study the effects of heavy-ion radiosurgery on the hemopoietic function of a silkworm, hemopoietic organs of larvae were locally irradiated with carbon-ion beams, and the changes in the hemocyte density and in the hemocyte function were investigated. When the larvae were irradiated by 50 Gy to 300 Gy carbon ions on the 3rd day of the 4th instar, the hemocyte densities did not change for a while, though they gradually increased at a later stage, but were finally still significantly lower than those of unirradiated controls. The hemocyte densities of the larvae irradiated at different developmental stages showed suppressed increments, and carbon-ion irradiation given to larvae at early stages compared to the later stages had a significant suppressive effect on the hemocyte densities.

Particulate and dissolved elemental loads in the Kuji River related to discharge rate.

In order to investigate influences of discharge rates on fluvial transport behavior of elements in the Kuji River, Japan, suspended and dissolved phase concentrations in the river water were measured together with the water flow rates. The concentrations of suspended particulate matter (SPM) increased by two or three orders of magnitude with the water discharge, and also had seasonal variations. Adsorptive elements or heavy metal elements, which tend to form insoluble compounds, were present generally as suspended forms in the river waters, and their dissolved form concentrations tended to increase with the water discharge.

Picosecond snapshot of the speckles from ferroelectric BaTiO3 by means of x-ray lasers.

A picosecond x-ray laser speckle has been conducted to study the dynamics of a disordered surface domain structure (BaTiO3 with 90 degrees c/a domains) as a function of temperature for the first time. The transient surface structures induced by ferroelectric domains decrease as temperature increases towards the Curie temperature T(c) and completely disappear above T(c). The dramatic change of the spatial configuration of the c/a domains was observed to occur from a temperature 2 degrees C below T(c), near which the average correlated domain size at equilibrium decreases as (T(c)-T)(0.

Empirical method for prediction of the coordination environment of Eu(III) by time-resolved laser-induced fluorescence spectroscopy.

The number of water molecules in the inner-sphere (N(H2O)) was determined for Eu(III) and the strength of ligand field (R(E/M)) was evaluated for a variety of coordination environments from the luminescence lifetime and the relative intensity at 615 nm and at 592 nm, by time-resolved laser-induced fluorescence spectroscopy. When R(E/M) and deltaN(H2O) for Eu(III) with a known coordination environment were plotted clear regularity was apparent between the location of the R(E/M)-deltaN(H2O) plot and the coordination environment of Eu(III). Here, deltaN(H2O) was calculated by use of the equation, deltaN(H2O)=9-N(H2O).

Modelling the effect of incorporated halogenated pyrimidine on radiation-induced DNA strand breaks.

Purpose: To estimate the enhancement of DNA strand breaks induced by low linear energy transfer (LET) radiation in the presence of halogenated pyrimidines and to examine complexity and clustering properties of damage that could provide a correlation between DNA damage and lethality.

Materials And Methods: Monte Carlo track structure methods were used to model and estimate the induction of strand breakage by X-ray photons with and without the incorporated Br/I deoxyuridine in cell-mimetic conditions. The increase of DNA strand break induction was modelled by taking into account the direct energy deposition and the reactions of radicals.

Reduction of survival and induction of chromosome aberrations in tobacco irradiated by carbon ions with different linear energy transfers.

Purpose: To determine the relationship between linear energy transfer (LET) and the relative biological effectiveness (RBE) for survival reduction and chromosome aberration induction in plants.

Materials And Methods: Tobacco seeds were exposed to carbon ions having LET ranging from 92 to 260 keV microm(-1). Survival ratc was determined at 7 weeks after sowing.

Monte Carlo simulation of strand-break induction on plasmid DNA in aqueous solution by monoenergetic electrons.

The radiation-induced process of strand breaks on pBR322 plasmid DNA in aqueous solution for different energy electrons was studied by Monte Carlo simulation. Assumptions of induction mechanisms of single- and double-strand breaks (SSBs and DSBs) used in the simulation are that SSB is induced by OH or H reaction with DNA and that DSB is induced by two SSBs on the opposite strands within 10 bp. Dose-response relationships of SSBs and DSBs were demonstrated for monoenergetic electrons of 100 eV, 10 keV, 1 keV and 1 MeV, and the yields of SSB and DSB were calculated.

Radiation-induced reactions via the lowest excited states in cinnamic acid crystals.

Radiation-induced reactions of cinnamic acid derivatives have been examined and compared with photoreactions in the crystalline state; all the reaction products were exactly the same as those of the photoreactions, indicating that the reactions proceed only via the lowest excited state to give [2 + 2] cycloadducts, E/Z isomerization products, or starting molecules.

Interaction between small-scale zonal flows and large-scale turbulence: a theory for ion transport intermittency in Tokamak plasmas.

Interaction between small-scale zonal flows and large-scale turbulence is investigated. The key mechanism is identified as radially nonlocal mode coupling. Fluctuating energy can be nonlocally transferred from the unstable longer to the stable or damped shorter wavelength region, so that the turbulence spectrum is seriously deformed and deviates from the nonlinear power law structure.

Disruption analysis of DR1420 and/or DR1758 in the extremely radioresistant bacterium Deinococcus radiodurans.

The extremely radioresistant bacterium Deinococcus radiodurans encodes two genes that are homologous to those involved in bacterial lysine biosynthesis. In lysine biosynthesis, these genes are involved in the aminoadipate pathway and the diaminopimelate (DAP) pathway. DR1420 is homologous to lysZ, which is essential for bacterial lysine biosynthesis via the aminoadipate pathway, and DR1758 is homologous to lysA, which is essential for lysine biosynthesis via the DAP pathway.

Measurement of neutron dose with an organic liquid scintillator coupled with a spectrum weight function.

A dose evaluation method for neutrons in the energy range of a few MeV to 100 MeV has been developed using a spectrum weight function (G-function), which is applied to an organic liquid scintillator of 12.7 cm in diameter and 12.7 cm in length.