Fabrication and optical reflection behavior of a two-dimensional barium titanate ceramic photonic crystal

We demonstrate a method for fabricating a two-dimensional hexagonal array of nanoscale barium titanate ceramic pillars. A precursor array was prepared by introducing a sol solution into an electron-beam resist mold with air holes and subsequently dry etching the unnecessary gel layer formed on the mold. A ceramic array, consisting of barium titanate ceramic pillars with a radius of 85 nm, a lattice constant of 450 nm, and a height of 500 nm, was fabricated by sintering the precursor array at 1073 K. The reflection spectra for the ceramic array in the visible range revealed the underlying photonic band gaps, which were in good agreement with results calculated using a plane-wave method. PACS 77.84.-s; 42.70.-a; 42.70.Qs     

Effects of three dithiocarbamates on tissue distribution and excretion of cadmium in mice

N-Benzyl-D-glucamine dithiocarbamate (BGD), N-p-hydroxymethylbenzyl-D-glucamine dithiocarbamate (HBGD), and N-p-carboxybenzyl-D-glucamine dithiocarbamate (CBGD) were compared for their relative efficacies in the distribution and excretion of cadmium in mice exposed to cadmium. Mice were injected intraperitoneally with 109CdCl2 (1 mg of Cd/kg and 2 microCi of 109Cd/one animal). Three days later, they were injected with chelating agents (400 mumol/kg) every other day for 2 weeks. After injections of BGD and HBGD, cadmium was excreted mainly in the feces through the bile, and the fecal excretion of cadmium by HBGD was significantly higher than that by BGD or CBGD. These chelating agents increased the urinary excretion of cadmium to a small extent. The hepatic cadmium content was decreased only after HBGD injection. Also, the injection of HBGD caused a much greater decrease in renal cadmium content than did BGD or CBGD. These chelating agents did not result in the redistribution of cadmium to the brain, testes, or heart. The growth of mice was only slightly retarded by injections of these chelating agents. The results of this study indicate that the injection of HBGD to mice pretreated with cadmium can remove cadmium from the body, mainly through fecal excretion, without redistribution of cadmium to other tissues such as the brain, testes, and heart, more effectively than BGD or CBGD.     

Flow-injection spectrophotometric determination of acetyl-coenzyme A with immobilized phosphotransacetylase

Phosphotransacetylase (PTA) is immobilized on AF-Tresyl TOYOPEARL 650 gel and used on-line in a stainless-steel column (10 × 4 mm i.d.). CoA-SH liberated enzymatically from acetyl-CoA is reacted with Ellman's reagent [5,5′-dithiobis(2-nitrobenzoic acid)] in the carrier stream. The calibration graph for acetyl-CoA is linear from 4 × 10^?6 to 4 × 10^?4 M and the detection limits is 8 × 10^?7 M. The immobilized enzyme can be employed for over 4 months without any significant decrease in activity. The enzyme retains its activity in methanol even though the initial rate of reaction is decreased.     

Catalytic asymmetric synthesis of descurainin via 1,3-dipolar cycloaddition of a carbonyl ylide using Rh2(R-TCPTTL)4

A catalytic asymmetric synthesis of descurainin has been achieved by incorporating an enantioselective 1,3-dipolar cycloaddition, a stereoselective alkene hydrogenation, an oxidation with Fremy’s salt and a regioselective demethylation with NbCl₅ as the key step. The 1,3-dipolar cycloaddition of a carbonyl ylide derived from tert-butyl 2-diazo-5-formyl-3-oxopetanoate with 4-hydroxy-3-methoxyphenylacetylene in the presence of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(R)-tert-leucinate], Rh₂(R-TCPTTL)₄, provided an 8-oxabicyclo[3.2.1]octane skeleton in 95% ee.     

Mesostructured organosilica with a 9-mesityl-10-methylacridinium bridging unit: photoinduced charge separation in the organosilica framework

Polycondensation of 9-mesityl-10-methylacridinium-bridged organosilane in the presence of a nonionic surfactant yielded a mesostructured organosilica solid with a functional framework that exhibited long-lived photoinduced charge separation.     

Analysis of Th, U, Pu, and Am in radioactive metal waste using extraction chromatography

In order to analyze actinide elements in radioactive metal waste, the dissolution and chemical separation conditions were optimized. The surfaces of a type 304 stainless steel plate and of pipe waste sampled from the prototype advanced thermal reactor (Fugen) were dissolved in mixed acid solution (HNO₃:HCl:H₂O = 1:1:4). The resulting solution was evaporated to dryness and dissolved with 2 mol/dm³ of HNO₃ to prepare sample solutions. In order to analyze trivalent actinide elements in the sample solution containing a large amount of Fe(III) (>0.1 g) using TRU resin, the effect of Fe(III) concentration on the recovery of Am(III) and reduction effect of Fe(III) to Fe(II) with ascorbic acid were studied. On the basis of results of this study, chemical separation scheme was constructed and Pu and Am in the sample solutions were separated. Thorium and U in the sample solutions were separated with UTEVA resin. High recoveries for all experimented elements were obtained from the analysis of spiked sample solutions, the effectiveness of the method was confirmed.     

An intense pulsed positron beam

A positron pulsing system for an intense positron beam generated by an electron linac is reported. The pulsing system generates an intense pulsed positron beam of variable energy and variable pulse period. The pulsed positron beam is used as a non-destructive probe for various material research. In this paper, we also discuss applications of the pulsed positron beam: positron lifetime spectroscopy, age-momentum correlation spectroscopy, positronium time-of-flight measurement, and positron annihilation-induced Auger electron spectroscopy with a time-of-flight technique.     

Development of ion transportation, extraction and neutralization systems for atomic beam resonance method

A device that produces a low-energy and largely spin polarized RI beam based on the atomic beam resonance method (RIABR) has been developed. We have performed measurements of stopping and drifting an incoming RI ion beam in a gas chamber, extraction of the ions into a vacuum region, and neutralization of the extracted low-energy ion beam. The drift efficiency of RI ions in a gas and the extraction efficiency at a Laval-type glass nozzle were found to be 0.72±0.04 and 0.033, respectively. The result of the experiment for the neutralization is also discussed.     

Enantioselective Palladium(0)‐Catalyzed Nazarov‐Type Cyclization

A Pd⁰‐catalyzed asymmetric Nazarov‐type cyclization is described. The optimized ligand for the reaction incorporates a weakly coordinating pyridine ring into a TADDOL‐derived phosphoramidite (TADDOL=α,α,α,α‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanol). The reaction leads to the formation of cyclopentenones as single diastereoisomers that incorporate two contiguous asymmetric centers, one tertiary and one an all‐carbon‐atom quaternary stereocenter, in high yield and optical purity. It is noteworthy that the reaction does not require that substrates should be activated by aryl substituents.