Study of reaction of finely-divided silica with barium carbonate by TG and DTA

The reaction between equimolar silica and barium carbonate powders in oxygen, air or carbon dioxide was studied by means of TG and DTA. The particle size of the silica showed appreciable effects on the reactivity of the silica, on the activation energy of the reaction, and on the formation of an intermediate silicate, Ba₂SiO₄. The formation of Ba₂SiO₄ is depressed by a decrease in the silica particle size or by an increase in the partial pressure of carbon dioxide in the ambient atmosphere.

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Zusammenfassung Die Reaktion zwischen äquimolaren Siliciumdioxid und Bariumcarbonatpulvern wurde in Sauerstoff, Luft oder Kohlendioxid mittels TG und DTA studiert. Die Teilchengröße von Siliciumdioxid zeigte eine bedeutende Wirkung auf die Reaktivität desselben und auf die Aktivierungsenergie der Reaktion, sowie die Bildung eines intermediären Silikats der Formel Ba₂SiO₄. Die Bildung des Ba₂SiO₄ wird durch die Abnahme der Teilchengröße des Siliciumdioxid sowie durch die Zunahme des Partialdrucks des Kohlendioxids in der Atmosphäre zurückgedrängt.

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Résumé On a étudié, par TG et ATD, la réaction de mélanges équimolaires pulvérulents de silice et de carbonate de baryum dans l'oxygène, l'air ou l'anhydride carbonique. La taille des particules de silice influence considérablement la réactivité de celle-ci, l'énergie d'activation de la réaction ainsi que la formation d'un silicate intermédiaire, Ba₂SiO₄. La diminution des dimensions des particules de silice ou l'augmentation de la pression partielle de l'anhydride carbonique réduisent la formation de Ba₂SiO₄.

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, , . , , , Ba₂SiO₄. Ba₂SiO₄ .

     

Binding forces in complexation ofp-alkylphenols withβ-cyclodextrin and methylatedβ-cyclodextrins

Fluorescence spectroscopy has been used to determine the binding constants (K) for inclusion complexes of six kinds ofp-Akyphenols with-cyclodextrin (-CDx), heptakis(2,6-di-O-methyl)--CDx (DMe--CDxg), and heptakis(2,3,6-tri-O-methyl)--CDx (TMe--CDx). The stability of the inclusion complex of each cyclodextrin increases with increasing alkyl chain length of thep-alkylphenol. TheK values decrease in the order of DMe--CDx,-CDx, and TMe--CDx for each guest. In complexation of 3-(p-hydroxyphenyl)-1-propanol (3) with-CDx as well as with DMe--CDx, negative enthalpy (H) and positive entropy changes (S) have been obtained, suggesting both van der Waals and hydrophobic interactions as binding forces. The inclusion of 3 by TMe--CDx, however, is an enthalpically favorable but entropically unfavorable process. The van der Waals interactions may be the main binding forces for complexing3 with TMe--CDx.     

1-ethyl-3-methylimidazolium based ionic liquids containing cyano groups: synthesis, characterization, and crystal structure

New 1-ethyl-3-methylimidazolium (EMI) salts [EMI][C(CN)3] and [EMI][Ag(CN)2] were prepared and characterized. The C(CN)3 salt has a melting point at -11 degrees C and shows a low viscosity (18 cP) and a high ionic conductivity (1.8 x 10(-2) S cm(-1)) at room temperature. This conductivity is less than that of [EMI][N(CN)2] salt (2.7 x 10(-2) S cm(-1)), possibly due to the larger molecular weight of the anion. The first EMI salt containing Ag(I) complexes [EMI][Ag(CN)2] has a higher melting point of 73 degrees C. In the crystal, the C-H...pi interionic interactions between cations construct zigzag chains in the cationic two-dimensional layer. Close Ag..Ag interionic contacts of 3.226(1) A were observed in the one-dimensional anionic chain, and the relatively high melting point among the EMI salts with a monoanion appears to be governed essentially by these direct Ag...Ag interactions.     

Influences of stable iodine upon the concentration of radioactive iodine by marine organisms

Uptake and loss of radioactive iodine by marine organisms were studied in the artificial seawater in which the concentration as well as chemical forms of both stable and radioactive iodine were controlled. The concentration factors of radioactive iodine by these organisms were clearly dependent upon the concentration of stable iodide ion in the culture media while the concentration of stable iodate ion did not affect the uptake and loss of radioactive iodine. It was observed that the higher the concentration of iodide ion was in the culture media the shorter the biological half-life of radioactive iodine became, and thus the lower the concentration factor resulted in.     

Interaction between poly[(R)-3-hydroxybutyrate] depolymerase and biodegradable polyesters evaluated by atomic force microscopy

Adsorption of PHB depolymerase from Ralstonia pickettii T1 to biodegradable polyesters such as poly[(R)-3-hydroxybutyrate] (PHB) and poly(l-lactic acid) (PLLA) was investigated by atomic force microscopy (AFM). The substrate-binding domain (SBD) with histidines within the N-terminus was prepared and immobilized on the AFM tip surface via a self-assembled monolayer with a nitrilotriacetic acid group. Using the functionalized AFM tips, the force-distance measurements for polyesters were carried out at room temperature in a buffer solution. In the case of AFM tips with immobilized SBD and their interaction with polyesters, multiple pull-off events were frequently recognized in the retraction curves. The single rupture force was estimated at approximately 100 pN for both PLLA and PHB. The multiple pull-off events were recognized even in the presence of a surfactant, which will prevent nonspecific interactions, but reduced when using polyethylene instead of polyesters as a substrate. The present results provide that the PHB depolymerase adsorbs specifically to the surfaces of polyesters and that the single unbinding event evaluated here is mainly associated with the interaction between one molecule of SBD and the polymer surface.     

Analysis of mitochondrial membrane potential in the cells by microchip flow cytometry

The mitochondrial membrane potential (DeltaPsi(m)) is an important indicator of the energetic state of both the mitochondria and the cells. To develop a sensitive, convenient, and rapid method for the measurement of DeltaPsi(m), we carried out cell fluorescence assays using the Agilent 2100 bioanalyzer system which, unlike the conventional flow cytometry, is based on microfluidic technology employing fluorescence detection with a 3,3'-dihexyloxacarbocyanine iodide (DiOC(6)(3)) fluorescent probe. The use of DiOC(6)(3) in the fluorometer was shown to be feasible for monitoring variations in DeltaPsi(m) in the mitochondria isolated from rat liver and treated with rotenone, succinate, ADP, and carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP). Flow cytometry analysis showed severe reduction of fluorescence intensity in Jurkat cells after treatment with 1.0 and 10 microM FCCP. However, fluorescence microscopy demonstrated obvious accumulation of fluorescence in the mitochondria and induction of diffuse cytoplasmic fluorescence not localized to the mitochondria in these cells. The dose response range of DiOC(6)(3) in the Agilent 2100 bioanalyzer system for yielding sufficient fluorescence intensity in the mitochondria of the cells was 20 nm-2.0 microM. Furthermore, significant reduction of fluorescence intensity in the cells stained with 2.0 microM DiOC(6)(3) was observed after treatment with 10 microM FCCP for 30 min. These results indicate that the Agilent 2100 bioanalyzer is potentially useful for monitoring DeltaPsi(m) in cell assays.     

Synthesis and antitumor activities of water-soluble benzoylphenylureas

Water-soluble benzoylphenylurea derivatives were synthesized as candidate prodrugs and their antitumor activities were examined in vivo against P388 leukemia. Some of the prodrugs were highly soluble in water and showed good antitumor activities against P388 leukemia cells in mice when injected intravenously.     

Unambiguous Determination of the Absolute Configurations of Acetylene Alcohols by Combination of the <Emphasis Type="Italic">Sonogashira</Emphasis> Reaction and the CD Exciton Chirality Method – Exciton Coupling between Phenylacetylene and Benzoate Chromophores

Summary. The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –^* transition (_max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (_max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –^* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –^* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –^* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner.     

Tests for a given linear structure of the mean direction of the langevin distribution

This paper deals with Watson statistic T _w and likelihood ratio (LR) statistic T _l for testing hypothesis H _0s: V (a given s-dimensional subspace) based on a sample of size n from a p-variate Langevin distribution M _p(, ). Asymptotic expansions of the null and non-null distributions of T _w and T _l are obtained when n is large. Asymptotic expressions of those powers are also obtained. It is shown that the powers of them are coincident up to the order n ^-1 when is unknown.     

Convenient Preparation of Self-Assembled Monolayers Derived from Calix[4]resorcinarene Derivatives Exhibiting Resistance to Desorption

Crown conformers of O-carboxymethylated calix[4]resorcinarenes (CRA-CMs) bearing four perfluorooctyl- and octylazobenzene residues at the lower rim of the cyclic skeleton were synthesized to investigate the resistance to desorption of CRA-CMs forming self-assembled monolayers on aminosilylated silica substrates and the surface energy photocontrol based on E- to-Z photoisomerization of the azobenzene moiety. In comparison with CRA-CM monolayers on silica substrates, the desorption of CRA-CMs on the aminated substrate was remarkably suppressed even when CRA-CM monolayers were sonicated in polar solvents and even in water. The high desorption-resistance was attributable to multi-point adsorption of CRA-CMs through COOH/NH₂ interactions. UV-Vis spectral studies revealed that CRA-CM substituted with p-octylazobenzene exhibited high E- to-Z photoisomerizability up to 92% in self-assembled monolayers, while less photoisomerizability was observed for CRA-CM bearing p-perfluorooctylazobenzenes due to the steric hindrance of the larger perfluoroalkyl chains. Photoinduced changes of contact angles for water up to 8.3° were observed for a CRA-CM monolayer.