Photostability of Isovaline and its Precursor 5-Ethyl-5- methylhydantoin Exposed to Simulated Space Radiations

Aqueous solutions of isovaline and its precursor molecule, 5-ethyl-5-methylhydantoin, were irradiated with ultraviolet and γ-ray photons, to evaluate their structural stability against space radiation. The degree of photolysis was measured and irradiation products were identified using chiral, reversed-phase and ion-exchange high-performance liquid chromatography. The experimental results show that the degree of photolysis of 5-ethyl-5-methylhydantoin is more significant than that of isovaline under ultraviolet light irradiation, while the results under γ-ray irradiation are the opposite. As the products of isovaline photolysis, aspartic acid, serine, glutamic acid and alanine were dominantly detected.     

A study of multiple biomarkers in coke oven workers--a cross-sectional study in China

We conducted a cross-sectional molecular epidemiological study of coke oven workers exposed to the established carcinogen polycyclic aromatic hydrocarbons (PAHs) to evaluate the relationships between both traditional 'exposure markers' and a series of biomarkers, including urinary 1-hydroxypyrene as a marker of internal dose, leukocyte aromatic DNA adducts as markers of biologically effective dose, serum p53 protein as a response marker and genetic polymorphisms of cytochrome P4501A1 and glutathione S-transferase MI as susceptibility markers. Twenty-five male subjects each were randomly selected from the top, middle and bottom work areas of the oven, and the control plant. They were matched for age and smoking status. The mean levels of PAH exposure, monitored by stationary and personal samplers, and of worker urinary 1-hydroxypyrene differed significantly between the top, middle and bottom of the oven and control work areas. The highest stationary and personal PAH concentrations and 1-hydroxypyrene levels were demonstrated at the top work area. Good correlations were found between the stationary PAH levels, personal PAH levels and urinary 1-hydroxypyrene levels. No positive correlations were demonstrated between aromatic DNA adduct levels and current or cumulative PAH exposure dose. In the presence of genetic polymorphisms of cytochrome P4501A1, a positive correlation was demonstrated between aromatic DNA adducts and urinary 1-hydroxypyrene levels. There was also a significant correlation between serum p53 protein levels and the cumulated benzo[a]pyrene exposure dose. Although these biomarkers have certain limitations, they are applicable to cancer epidemiology, and may contribute to our understanding of the mechanisms of carcinogenesis.     

Transcutaneous Blood Flow Measurement by Electromagnetic Induction

A new induction flowmeter which can measure the blood flow from the skin surface is discussed theoretically and experimentally. A pair of electrodes placed on the skin detect the EMF induced by the interaction of the blood flow and a magnetic field applied from outside the skin. The relation between the EMF and the flow rate, which is obtained theoretically, is also confirmed experimentally within the error of 10 percent.     

Serological study of Japanese encephalitis in Nepal

Antibodies against Japanese encephalitis virus (JEV) were examined in 356 serum samples from individuals visiting Tribhuvan University Teaching Hospital using neutralization test. A total of 13.2% (47/356) seropositivity was observed. Antibody positivity against both Nakayama-NIH and Beijing-1 strains was seen in 7.9% subjects. Infection by Nakayama-NIH strain alone was seen to be 4.2% while 1.1% of study populations were found to be infected only by Beijing-1 strain. High antibody titer was observed in the 20-40 years age-group and did not increase with age. Seropositivity was more common in zone-A (Tarai) area compared to zone-B (Hills) and zone-C (Mountains). Spectrum of antigenicity of JEV in zone-A as shown by neutralization test was identical to Indian isolates (strains). Difference in seropositivity was observed against Nakayama-NIH and Beijing-1 strain in zone-B and C indicating recent spread of JEV in these areas.     

Atomic processes in the thermal destruction of zeolites as investigated by molecular dynamics and computer graphics

The destruction processes of various zeolites, such as a silicalite with the ZSM-5 structure (SiO₂-MFI), Cu-ZSM-5, and a silicalite with the faujasite structure (SiO₂-FAU), with increasing temperature were investigated by using molecular dynamics and computer graphics methods. The mobility of atoms in SiO₂-MFI was increased and the framework became unstable, as the temperature was increased. Finally the framework was destroyed to an amorphous phase. Increasing the Al content led to a decrease in the heat-resistance in Cu-ZSM-5. The change in the Si-O, Al-O, and Cu-Al distances as well as the change in the pairs of Si-O bonds are discussed to clarify the mechanism of Cu-ZSM-5 destruction. The destruction process of SiO₂-FAU was also investigated in order to understand the effect of framework structure, and it was suggested that the presence of the 4-membered ring provides one of the reasons for the inferior heat-resistance of SiO₂-FAU to that of SiO₂-MFI.     

Rate of swelling of sodium polyacrylate

The kinetics of the swelling of sodium polyacrylate (NaPA), a hydrophilic polymer, was studied gravimetrically, by microscopic observation, and calorimetrically. The swelling process followed first-order kinetics and the rate constant was of the order of 10^?2 s^?1. The gravimetric method, however, was not useful for kinetic studies. The rate constant was depressed by the addition of sodium chloride. The activation energy of the swelling was 46.0 ± 6.2 (kJ mol^?1) and decreased with the increase in sodium chloride concentration. In acid solution, the activation energy was almost the same as that in water. The heat of the swelling was 196 ± 17 J g^?1 and did not vary with the addition of sodium chloride. © 1993 John Wiley & Sons, Inc.     

Radiation protection system at the RIKEN RI beam factory

The RIKEN RI (radioactive isotope) Beam Factory is scheduled to commence operations in 2006, and its maximum energy will be 400 MeV u(-1) for ions lighter than Ar and 350 MeV u(-1) for uranium. The beam intensity will be 1 pmicroA (6 x 10(12) particles s(-1)) for any element at the goal. For the hands-on-maintenance and the rational shield thickness of the building, the beam loss must be controlled with several kinds of monitors. Three types of radiation monitors will be installed. The first one consists of a neutron dose equivalent monitor and an ionisation chamber, which are commercially available area monitors. The second one is a conventional hand-held dose equivalent monitor wherein the logarithmic signal is read by a programmable logic controller based on the radiation safety interlock system (HIS). The third one is a simple plastic scintillator called a beam loss monitor. All the monitors have threshold levels for alarm and beam stop, and HIS reads all these signals.     

High-performance C60 and picene thin film field-effect transistors with conducting polymer electrodes in bottom contact structure

C₆₀ and picene thin film field-effect transistors (FETs) in bottom contact structure have been fabricated with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) electrodes for a realization of mechanical flexible organic FETs. The C₆₀ thin film FETs showed n-channel enhancement-type characteristics with the field-effect mobility μ value of 0.41 cm² V^?1 s^?1, while the picene thin film FET showed p-channel enhancement-type characteristics with the μ of 0.61 cm² V^?1 s^?1. The μ values recorded for C₆₀ and picene thin film FETs are comparable to those for C₆₀ and picene thin film FETs with Au electrodes.