First chemical study of anaspidean Syphonota geographica: structure of degraded sterols aplykurodinone-1 and -2

Two unprecedented degraded sterols, aplykurodinone-1 (1) and -2 (2), have been isolated from the skin of the marine anaspidean Syphonota geographica, collected along the coasts of Greece. The structures and the relative stereochemistry were established by spectroscopic analysis and confirmed by chemical correlation with related known compounds.     

Production and Accumulation of 4-<Emphasis Type="Italic">O</Emphasis>-Methyl-α-<Emphasis Type="SmallCaps">d</Emphasis>-Glucuronosyl-Xylotriose by Growing Culture of Thermophilic <Emphasis Type="Italic">Anoxybacillus</Emphasis> sp. Strain JT-12

A thermophilic Anoxybacillus sp. strain JT-12, isolated from soil, produced acidic xylotriose, 4-O-methyl-α-d-glucuronosyl-xylotriose (MeGlcAX₃), as a main product from birchwood xylan and accumulated them in the culture under optimum conditions at pH 7.0 and 55 °C using 0.75% (w/v) birchwood xylan as a carbon source for 42–72 h. The acidic xylotriose was purified by ethanol precipitation and high-performance liquid chromatography using NH₂ Lichosher® 100 column. The results of electrospray ionization mass spectrometry, mass to charge ratio (m/z) 603.23, confirmed that the purified sample was acidic xylotriose that had benefits and applications in many fields.     

Nitrogen bridgehead compounds. Part 35. Structures of α-formyl-2,3-polymethylene-3,4-dihydroquinazolin-4-ones

The structures of the title compounds bearing a five-, six- or seven-membered A ring have been investigated by uv and ¹H and ¹³C nmr spectroscopy. The imine-enol-enamine (I-II-III) tautomerism of these compounds depends greatly on the ring size. A significant solvent-dependence is observed only for the five-membered-ring compounds 1 and 2 , which in ethanolic solution exist predominantly in the imine form I, and in chloroform solution in the enol form II. The compounds with a six-membered A ring, 3 and 4 , are mainly in the enamine form III. On protonation, 3 and 4 change into the E and Z isomeric mixture of the enol tautomer II. The seven-membered-ring compound 5 is a mixture of the imine I and the enamine III tautomers.     

First-return integrals

Properties of first-return integrals of real functions defined on the unit interval are explored. In particular, first-return integrals are shown to be continuous but not absolutely continuous.     

Influence of the type of alkyl group on hydrolysis and polycondensation of tetraalkoxysilane

The early stage of hydrolysis and polycondensation of tetraalkoxysilanes (TAOS) in the closed TAOS-C₂H₅OH-H₂O-HCl system at 40°C was studied by the trimethylsilylation technique combined with the gas-liquid and gel permeation chromatographies. Tetramethoxy, tetraethoxy, tetra (n-propoxy) and tetra (n-butoxy) silanes were used as TAOS. The tendencies of variation with time in the distribution and molecular weight of silicate species in the solutions were almost the same in all the TAOS solutions, suggesting that the differences in the alkyl group of the TAOS had little effect on the hydrolysis and polycondensation.     

Vacuum ultraviolet photolysis of CClF2CH2Cl

Photolysis of CClF₂CH₂Cl was studied by 147 nm vacuum ultraviolet irradiation. In the presence of NO; CF₂CH₂, CF₂CHCl, and CClF₂CN were produced. These products represent three different reaction paths; the molecular dechlorination, molecular dehydrochlorination, and chlorine radical elimination reactions. The reactant pressure and the addition gas (He or NO) pressure effects upon the product yield were studied. © 1994 John Wiley & Sons, Inc.     

High energy radiation fluences in the ISS-USLab: Ion discrimination and particle abundances

The ALTEA (Anomalous Long Term Effects on Astronauts) detector was used to characterize the radiation environment inside the USLab of the International Space Station (ISS), where it measured the abundances of ions from Be to Fe. We compare the ALTEA results with Alteino results obtained in the PIRS module of the Russian segment of the ISS, and normalize to the high energy Si abundances given by Simpson. These are the first particle spectral measurements, which include ions up to Fe, performed in the USLab. The small differences observed between those made inside the USLab and the Simpson abundances can be attributed to the transport through the spacecraft hull. However, the low abundance of Fe cannot be attributed to only this process.     

Preparation and photoactivity of nanostructured anatase, rutile and brookite TiO2 thin films

Photoactive films consisting of pure anatase, brookite or rutile TiO2 were prepared by dip coating from water dispersions obtained by using TiCl4 as the precursor under similar mild experimental conditions.     

Using a factored dual in augmented Lagrangian methods for semidefinite programming

In the context of augmented Lagrangian approaches for solving semidefinite programming problems, we investigate the possibility of eliminating the positive semidefinite constraint on the dual matrix by employing a factorization. Hints on how to deal with the resulting unconstrained maximization of the augmented Lagrangian are given. We further use the approximate maximum of the augmented Lagrangian with the aim of improving the convergence rate of alternating direction augmented Lagrangian frameworks. Numerical results are reported, showing the benefits of the approach.     

Compactness and Vitali’s compactness criterion in vector-valued F-seminormed function spaces

Results of compactness for vector-valued F-seminormed function spaces and a general Vitali’s compactness criterion under the W-property are exhibited.