Measurement of the whole-body 137Cs in residents around the Chernobyl nuclear power plant

To understand the current situation of internal radiation exposure in the population around the Chernobyl Nuclear Power Plant (CNPP), we examined the 137Cs body burden in six residents of Belarus, Ukraine and Russia in 2002 and 2004 using the whole-body counter (WBC) at Nagasaki University (Japan). The data were compared with those of our previous study performed in 1993-1994 using the same method. In 2002 and 2004, peaks of 137Cs were detected in two residents from Gomel, which was heavily contaminated by the CNPP accident, one from Minsk (Belarus) and one from Kiev (Ukraine), but another resident from Minsk showed no 137Cs peaks. The results of the present study suggests that residents around the CNPP are still exposed to chronic 137Cs internal irradiation, probably due to the daily consumption of contaminated domestic foods, but the risk of any disease by the irradiation is quite low. Long-term follow-up of WBC around the CNPP is useful and may contribute to radiation safety regulation together with a reduction of unnecessary radiophobia for the residents.     

Remarks on 4cst-elements for incompressible materials

Three-node triangular elements obtained from the intersecting diagonals of quadrilaterals are thoroughly investigated for the penalty method formulation of incompressible problems such as Stokes flow, Navier-Stokes flow, and small-deformation rubber elasticity. Equivalence of the present formulation to the one using 4-node quadrilateral isoparametric elements with selective reduced integration, is presented. Convergence, instability phenomenon, smoothing of the pressure distribution are studied together with decompositions into triangular elements.     

Enhanced tumor metastases in rats following cryosurgery of primary tumor

The incidence of tumor metastases was studied in WKA/Hok rats after cryosurgery and surgical excision of primary tumors. When rats with syngeneic fibrosarcoma, KMT-17, were treated by cryosurgery 5 days after transplantation of the tumor, 15 out of 31 rats (48.4%) died with tumor metastases. In contrast only 4 out of 34 (11.8%) died with tumor metastasis after surgical excision. Because tumor cells either in the regional lymph nodes or in the peripheral blood were already detectable in about half of the rats treated by either cryosurgery or surgical excision, mechanical and physical control of enhanced metastasis by cryosurgery is ruled out. The development of anti-tumor immunity was delayed in the rats treated by cryosurgery as compared with that in rats treated by surgical excision. This was investigated by means of Winn's assay. A marked reduction of tumor metastasis was seen after the surgical removal of cryonecrotized tumor tissue, while implantations of cryonecrotized tumor tissue into the rats treated by surgical excision resulted in an increment of metastasis. The mechanism of the enhanced metastasis observed in this experimental investigation is discussed from an immunological point of view.     

Decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate anion catalyzed by cross-linked poly(4-vinylpyridinium) salts

Summary Catalysis of cationic polyelectrolytes for the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate anion was studied in a buffer solution (pH=9.0). Cross-linked poly (4-vinylpyridinium) salts prepared from 4-vinylpyridine and , -dibromides were used as cationic catalysts. The cross-linked catalysts were found to accelerate markedly the decarboxylation in comparison with the linear water-soluble analogues. Effect of the polymer structure such as the length of (CH₂)_x linkages between positive charges on the catalytic activity was examined. It was suggested that the acceleration by the cross-linked polymer catalysts would be due to the hydrophobic microenvironment around the catalytic sites.     

Influence of glass substrate thickness in laser scribing of glass

The thickness of the glass substrate used in liquid crystal displays continues to be decreased from its original thickness of 1.1 mm for the purpose reducing size and weight. The aim of this study was to clarify the influence of the glass substrate thickness during laser scribing with crack propagation caused by laser heating followed by quick quenching. The laser scribe conditions for soda-lime glass substrates with thickness equal to or less than 1.1 mm were obtained in laser irradiation experiments. Two-dimensional thermal elasticity analysis was conducted with a finite element method based on the scribable conditions obtained in the experiment. The laser scribable conditions can then be estimated by the upper limit of the maximum surface temperature, T_max, and the lower limit of the maximum tensile stress, σ_tmax, in the cooling area, regardless of the glass substrate thickness. There is a substrate thickness with which the maximum tensile stress σ_tmax becomes the largest under each scribe condition. The substrate thickness with which σ_tmax becomes the largest is obtained at a faster scribe velocity for thinner glass substrate and at slower scribe velocity for thicker glass substrate. Owing to these relations, the crack depth also has almost the same tendency as σ_tmax.     

Higher-order aberration corrector for an image-forming system in a transmission electron microscope

We developed a new electron optical system with three dodecapoles to compensate for spherical aberration and six-fold astigmatism, which generally remains in a two-hexapole type corrector. In this study, we applied the corrector for image-forming system in transmission electron microscope. Compensation for higher-order aberration was demonstrated through a diffractogram tableau using a triple three-fold astigmatism field system, which was then compared with a double hexapole field system. Using this electron optical system, six-fold astigmatism was measured to be less than 0.1 mm at an acceleration voltage of 60 kV, showing that the system successfully compensated for six-fold astigmatism.     

Effect of the Preparation Conditions of Ru/CeO2 Catalysts for the Liquid Phase Oxidation of Benzyl Alcohol

Ceria colloidal particles with a mean crystallite size of 2 nm were synthesized by a solvothermal reaction. The Ru/CeO₂ catalyst prepared from the CeO₂ colloids exhibited higher activity than the catalyst prepared from Ce(NO₃)₃. Temperature-programmed reduction analysis indicated that the reduction of surface Ce⁴⁺ was accelerated by highly dispersed Ru species on the CeO₂ particles and occurred at low temperatures. The single component CeO₂ sample prepared by the coagulation of the CeO₂ colloid was more easily reduced and re-oxidized than the CeO₂ sample prepared by the precipitation method from Ce(NO₃)₃. The higher activity of Ru/CeO₂ prepared from the CeO₂ colloids came from the inherent nature of the CeO₂ support itself.     

Pseudomonas aeruginosa as a model microorganism for investigation of chemotactic behaviors in ecosystem

Motile bacteria sense changes in the concentration of chemicals in environments and respond in a behavioral manner. This behavioral response is called chemotaxis. Bacterial chemotaxis can be viewed as an important prelude to metabolism, prey-predator relationships, symbiosis, infections, and other ecological interactions in biological communities. Genome analysis reveals that a large number of environmental motile bacteria possess a number of genes involved in chemosensing and chemotatic signal transduction. Pseudomonas aeruginosa has a very complex chemosensory system with more than 20 chemotaxis (che) genes in five distinct clusters and 26 chemoreceptor (methyl-accepting chemotaxis protein [mcp]) genes. Among the 26 MCPs of P. aeruginosa, nine have been identified as MCPs for amino acids, inorganic phosphate, oxygen, ethylene, and volatile chlorinated aliphatic hydrocarbons, whereas 3 MCPs were demonstrated to be involved in biofilm formation and biosynthesis of type IV pilus. Six che genes are essential for chemotactic responses, while genes in Pil-Chp cluster and Wsp cluster are involved in type IV pilus synthesis and twitching motility and biofilm formation, respectively. P. aeruginosa, with its complex chemotaxis system, is a better model microorganism for investigating ecological aspects of chemotaxis in environmental bacteria than Escherichia coli and Salmonella enterica serovar Typhimurium, which possess a relatively simpler chemotaxis system.