Uranium determination by133Xe in meteorites; comparative study with fission track and/or239Np methods and thermal release character of133Xe

Uranium concentrations in three types of inclusions of the Allende (C III), a bulk sample of the Plainview (H5), and a bulk and 5 to 15 density separates of the Huckitta pallasite were determined and discussed by comparing the results from homogenized fission track and/or²³⁹Np analyses with the¹³³Xe results. Stepwise heating experiment revealed that the¹³³Xe release from the Plainview is bimordal and incomplete by a simple heating at 1600 °C, and that the¹³³Xe releases in the Huckitta bulk and metallic samples are multitudinous but can be extracted rather completely at 1600–1700 °C. In the Huckitta, uranium-rich phase (∼100 ppb) was in the lightest density fraction of d=2.9–3.3, but the bulk uranium was found to be mostly from the heavy metal-rich fraction of d>4.2.     

Remarkable reactivities of the xanthone ketyl radical in the excited state compared with that in the ground state

The properties and reactivities of the xanthone (Xn) ketyl radical (XnH*) in the doublet excited state (XnH*(D1)) were examined by using two-color two-laser flash photolysis. The absorption and fluorescence of XnH*(D1) were observed for the first time. Several factors governing the deactivation processes of XnH*(D1) such as interaction and reaction with solvent molecules were discussed. The remarkable change of reactivity of XnH*(D1) compared with that in the ground state (XnH*(D0)) was indicated from the experimental results. The rapid halogen abstraction of XnH*(D1) from some halogen donors such as carbon tetrachloride (CCl4) was found to occur. The halogen abstraction occurred more efficiently in the polar solvents than in the nonpolar solvents. It is suggested that the polar solvents promote the spin distribution of XnH*(D1) of the phenyl ring favorable to the halogen abstraction.     

Synthesis and anti-HIV-1 activity of novel 10-thiaisoalloxazines,a structural analog of C-5 and/or C-6 substituted pyrimidine acyclonucleoside

A series of novel 10-thiaisoalloxazine derivatives bearing an alkoxymethyl or benzyloxymethyl moiety at the N-1 position has been synthesized through the bromination of 1-substituted-5-hydroxyuracils and subsequent condensation with aminobenzenethiol in a one-pot reaction. Contrary to the previous report, the formation of intermediary 5,6-diethoxy-5-hydroxy-5,6-dihydrouracil seems to be not the necessary factor for the formation of the thiaisoalloxazines, since the reaction proceeds in tetrahydrofuran (THF) or acetonitrile far more smoothly than in ethanol. The anti-human immunodeficiency virus (HIV)-1 activity of the resulted thiaisoalloxazine derivatives was evaluated in lymphocyte cells based on the inhibitory activity against the viral-induced cytopathic activity. Among the derivatives, compounds 6, 7, and 8 bearing an alkoxymethyl moiety at the N-1 position exhibited modest inhibitory activity towards the cytotopathic effect of HIV-1.     

Synthesis and reactivities of 10-S-3 trithiadiazapentalene derivatives

1,3-Bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidinethiones 3a-f reacted with bromine to give trithiadiazapentalene derivatives 5a-f , bearing the exocyclic C-N double bonds, in moderate yields. The molecular structure of 5b was elucidated by the X-ray crystallographic analysis. The treatment of 5b-f with hydrochloric acid gave the ring-opening products, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazo-lidinones 9b-f , accompanied by the production of elemental sulfur. Reduction of 5b , 5d , and 5e with sodium borohydride gave the ring-opening compounds, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidines 13b , 13d , and 13e respectively.     

Constituents of Crinoidea, 4. Isolation and structure of ceramides and glucocerebrosides from the feather star Comanthus japonica

Five ceramides, JC-1-JC-5, and four glucocerebrosides, JCer-1-JCer-4, have been isolated from their parent ceramide and glucocerebroside molecular species JC and JCer obtained from the less polar lipid fraction of the chloroform/methanol extract of the feather star Comanthus japonica. The structures of these sphingolipids have been determined on the basis of chemical and spectroscopic evidence. Reversed-phase HPLC was effective at isolating these sphingolipids, revealing very close resemblance in their structures. JC-1, JC-3, JC-4, JC-5 and JCer-2, JCer-4 are newly found ceramides and glucocerebrosides, respectively.     

Association behavior of a nitrilotriacetic-acid-modified dye in a poly(vinyl alcohol) film containing Ni(II)-adsorbed gold nanoparticles.

The association behavior of the dyes 5(6)-carboxyfluorescein and nitrilotriacetic acid (NTA)-modified 5(6)-carboxyfluorescein (F-NTA) in a poly(vinyl alcohol) (PVA) film and in a PVA film containing metal nanoparticles is investigated. Well-dispersed gold nanoparticles (AuNps) and Ni(II)-adsorbed AuNps are formed in the PVA film using in situ photochemical fabrication method. 5(6)-carboxyfluorescein and F-NTA are doped into the films. The F-NTA forms an H-aggregate in the PVA film containing Ni(II)-adsorbed AuNps. It is suggested that the interaction between NTA and Ni(II) adsorbed on the AuNps promotes the formation of the H-aggregate.     

Isolation and structure determination of six glucocerebrosides from the starfish Luidia maculata

Two new glucocerebrosides, luidiacerebroside A (2) and B (6), were isolated from the cerebroside molecular species obtained from the less polar fraction of the CHCl3/MeOH extract of the starfish Luidia maculata using HPLC. Four known cerebrosides, CE-2b (1), astrocerebroside B (3), acanthacerebroside B (4), and CE-3-2 (5) have also been isolated and characterized. The structures of these cerebrosides were determined on the basis of chemical and spectroscopic evidence. Mass spectrometry of dimethyl disulfide derivatives was useful for the determination of the double-bond position in the long-chain base.     

Fine structures of zeolite-Linde-L (LTL): surface structures, growth unit and defects

High-resolution electron microscopy (HREM) has been used to image the surface structure of nano- and micrometer-sized synthetic crystals of zeolite-Linde-L (LTL). Columnar holes and rotational, nano-sized, wheel-like defects were observed within the crystals, where the hole has a minimum size equal to that of the rotational defect. Predictions of surface structure from atomistic computer simulation concur with the observations from HREM and provide insight into the crystal growth mechanism of perfect and defective LTL. Analysis of the energetics of the formation of rotational defect structures reveals that the driving force for defect creation is thermodynamic and furthermore, the rotational defects could be created in high concentrations. Formation of a columnar hole is found to be slightly energetically unfavourable and therefore we speculate that the incidence of both rotational and nano-sized vacancy defects is strongly dependent on kinetic factors and reaction conditions. The morphology of nano- and microcrystalline LTL is contradistinct and we use insights from simulation to propose an explanation of the disparity in crystal shape.     

Towards slow μ− production via muon catalyzed fusion

Slow ^– production via dd-CF using a two-layer arrangement is investigated. To determine its feasibility, experimental measurements are now in progress using the muonic X-ray detection method. The following experimental steps are being considered: (1) measurement of the number of ^– stopped inside a solid H₂/D₂ layer by detecting p K X-rays, (2) hot d emission detection by placing a secondary target at a distance of 10–30 mm from the layer and by detecting specific delayed X-rays, (3) measurement of the disappearance of d emission as the added D₂ layer is increased, (4) dd-CF measurement by detecting fusion protons, and (5) slow ^– emission detection. Results of the initial test experiment are presented.