Dosimetry of fast neutrons in 1W nuclear reactor with plastic nuclear-track detectors

A nuclear reactor at Kinki University is operated at the maximum of 1W. It produces fission neutrons as much as gamma-rays. To facilitate its use for neutron radiobiology, fast neutrons inside the reactor were measured with nuclear-track detectors TS 16 N and a pair of ion chambers. The angular dependence of TS 16 N response, an anisotropy of fast neutron fluxes in the reactor and misuse of the kerma factor assumed for radiation protection business are the major causes of discrepancy is measured doses by the two methods. Correction factors for the three causes are proposed. After correction, neutron doses estimated with TS 16 N and chambers agree within 5%. The dose-rate at the reactor's center is about 20 tissue-cGy/h. This is the first in situ dosimetry of fast neutrons in a reactor with track detectors attached to biologic samples. Our routine usage has demonstrated that, if used with caution, TS 16 N elements are handy, reliable monitors for fast neutron dosimetry as they are insensitive to contaminated gamma-rays and small enough to be attached to biologic samples.     

Hydrogenation of olefins in supercritical CO(2) catalyzed by palladium nanoparticles in a water-in-CO(2) microemulsion

Nanometer-sized metallic palladium particles can be synthesized by hydrogen reduction of Pd2+ ions dissolved in the water core of a water-in-CO2 microemulsion. The Pd nanoparticles, stabilized by the micromeulsion and uniformly dispersed in the supercritical fluid phase, are effective catalysts for hydrogenation of olefins. Examples of rapid and efficient hydrogenation of water-soluble and CO2-soluble olefins catalyzed by the Pd nanoparticles in supercritical CO2 are given.     

Molecular Recognition of Nucleic Acid Bases in Water by Hydrogen Bonding of Poly(vinyldiaminotriazine)

Poly(2-vinyl-4,6-diamino-1,3,5-triazine) efficiently binds nucleic acid bases and nucleosides in water by using complementary hydrogen bonding. The binding activity decreases in the order: U, T > A C, G. The corresponding monomer shows virtually no activity, indicating a predominant role of polymer effect for the molecular recognition in water.     

Synthesis of disubstituted cucurbit[6]uril and its rotaxane derivative

Synthesis of diphenyl cucurbit[6]uril (CB[6]) has been achieved via co-oligomerization of diphenyl glycoluril and unsubstituted glycoluril. The unsymmetrically substituted CB[6], Ph(2)CB[6], was further converted to a rotaxane incorporating bis(dinitrophenyl)spermine. [reaction: see text]     

The relationship between the chemical structure of nematic liquid crystals and their pretilt angles

About 50 different additives in one or more of three different nematic mixtures have been investigated to clarify the relationship between the chemical structure of the liquid crystal and the pretilt angle on a polyimide surface. The pretilts found for cells have been explained within our recently proposed population distribution model. For compounds with cyano-groups at one end, we find that the in-plane order is governed both by the surface-mesogen interaction and by the relative strength of the intermolecular interactions in the nematic phase. This strength is nearly linear in alkyl chain length for the compounds investigated. Changes in the strength due to variations in the core of the molecules can be calculated easily by using group contributions from the known Parachors. The in-plane order can be treated as a simple product of the contributions from the liquid crystal and from the polyimide. Different polar end groups will give different angles between the surface and the optical axis of the individual mesogens in the first monolayer. The cyano-group gives the highest angle and alkyl groups the lowest. For nitro-compounds the dimers formed are so strongly bound that they do not break up at the surface. Nitro-compounds will thus act as dialkyl compounds. For dialkyl compounds the pretilt angles are dominated by the difference between the chain lengths at the two ends of the molecule.     

Dansyl-Modified γ-Cyclodextrin as a fluorescent sensor for molecular recognition

The crystal structure of thiamine iodide sesquihydrate has been determined by X-ray diffraction methods as a host-guest model for coenzyme-substrate interactions. The asymmetric unit contains two chemical units. Both the thiamine molecules A and B, which are crystallographically independent, assume the usualF conformation and have a disordered hydroxyethyl side chain. An iodide anion (or a water molecule) bridges the pyrimidine and thiazolium rings of molecule A (or B) by forming a hydrogen bond with the amino group and an electrostatic contact with the thiazolium ring to stabilize the molecular conformation. In the crystal the thiamine molecules self-associate to form a pipe-like polymeric structure, in which four thiamine hosts surround an iodide guest and hold it through C(2)-H...I hydrogen bonds and thiazolium...I electrostatic interactions. Crystal data: C₁₂H₁₇N₄OS⁺·I^– · 1.5 H₂O, monoclinic,P2₁/c, a=12.585(2), b=25.303(5), c=12.030(2) Å, =115.15(1)°,V=3468(1) ų,Z=8,D _c=1.606 g cm^–3,R=0.045 for 3328 observed reflections. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP. 82156 (13 pages).     

Chemical constituents of Glycosmis citrifolia (Willd.) Lindl. Structures of four new acridones and three new quinolone alkaloids

The structures of two new dimeric acridone alkaloids, glycobismine-D (1) and -E (2), having a novel linkage as binary acridones, three monomeric acridones, glycocitrine-IV (3), -V (4), and -VI (5), and three quinolone alkaloids, glycocitlone-A (6), -B (7), and -C (8) from Glycosmis citrifolia (Willd.) Lindl. (Rutaceae) have been elucidated by spectrometric studies.     

Action spectra for photoreactivation of mutation of prototrophy in strains of Escherichia coli possessing and lacking photoreactivating-enzyme activity

Abstract— The action spectrum and dose-rate dependence for photoreactivation of mutation to prototrophy in late-lag-phase cultures of Escherichia coli H³r30 (which lacks active photo-reactivating enzyme) are roughly similar to those for photoprotection from killing in other strains. It is suggested that photoreactivation of this mutation in H/r30 is an indirect effect, similar in mechanism to photoprotection. The action spectrum and dose-rate dependence for photoreactivation of mutation to prototrophy in late-lag-phase cultures of E. coli H³r30-R (which possesses active photoreactivating enzyme) are roughly similar to those for photoreactivation of killing in most other strains. It is suggested that photoreactivation of this mutation in H/r30-R is a direct effect at long wavelengths, but that there is an indirect component at short wavelengths. A quite different interpretation of these data is noted. Finally, it is found that, under the conditions of these experiments, indirect photoreactivation of killing in H/r30 and H/r30-R is weak or nonexistent.