Meta/para-selectivity variation by sulfide/sulfoxide conversion of 6-substituted β-cyclodextrin. Hydrolyses of nitrophenyl acetates. ag

Hydrolyses of m- and p-nitrophenyl acetates by 6-deoxy-6-alkylthio-β-cyclodextrins and the corresponding sulfoxides were studied to show that the small chemical conversion from the sulfides to the sulfoxides led to a change of meta/para-selectivity in the hydrolysis of the β-cyclodextrin moiety.     

Effect of BaF2 in the formation of Y2BaCuO5 particles in Y-Ba-Cu-O superconductor

The YBCO superconductor was synthesized with BaF₂. The synthesis temperature of the specimen with BaF₂ was to be considerably lower than that for the unused one. The BaF₂ decomposes during the heat treatment, and does not influence the structure and critical temperature. The critical current density,J _c, in the specimen is 1×10⁸ A/m² at 77 K and 0.5T. However,J _c is actually lower for the QMG specimen because the Y₂BaCuO₅ particles are larger than those of the QMG specimen.     

Thermometric titration of some molybdates,molybdic acid,and molybdenum trioxide

A thermometric titrator equipped with differential thermistor is used for the titration of molybdenum in sodium molybdate, potassium molybdate, magnesium molybdate, tetramethylammonium molybdate, and tetraethylammonium molybdate, based on their reactions with hydrochloric acid, and in ammonium paramolybdate, molybdic acid, and molybdenum trioxide, based on their reactions with sodium hydroxide. Orthomolybdates and ammonium paramolybdate were determined in the 0.5–0.005 M range; sufficient solid molybdic acid or molybdenum trioxide was taken to give a final 0.01–0.5 M solution in 20 ml of water. The method is simple and very quick. The standard deviation varies from 0.5 to 1.5% depending on the amount of sample taken.     

PHOTOREVERSIBILITY OF UV-INDUCED THYMINE DIMERS AND ABNORMAL MORPHOGENESIS IN SEA-URCHIN EMBRYOS

Abstract— Irradiation of synchronously dividing 16-cell embryos of a sea-urchin ( Hemicentrotus pul-cherrimus ) with 200 J m⁻² of UV light (254 nm) resulted in the complete inhibition of normal pluteus-larva formation when the embryos were cultured in the dark after UV-irradiation. Illumination of the UV-irradiated embryos with visible light (11 W m⁻²) for 1 h immediately after the UV-irradiation reversed the abnormal morphogenesis. Measurement of thymine dimers indicates that the degree of UV-induced abnormal morphogenesis is greatly correlated with the amount of thymine dimers in the DNA of the embryos. The degree of the photoreversal decreased with an increase in the interval between UV-irradiation and exposure to visible light. Visible light was ineffective as to the reversibility of both thymine dimers and the abnormal morphogenesis at 60 min after the UV-irradiation, when the UV-irradiated 16-cell embryos entered the next cell cycle.     

Inhibitory effect of heat shock protein 70 on apoptosis induced by photodynamic therapy in vitro

We examined the apoptotic effects of photodynamic therapy (PDT) in leukemia cells (HL60) and lymphoma cells (Raji). Moreover, we also investigated the relationship of apoptosis induced by PDT to heat shock protein (HSP) expression. To induce 80% of cell death by PDT, HL60 cells required 6 microg/mL and Raji cells required 9 microg/mL of Photofrin. PDT induced apoptosis in 77.2% of HL60 and in 0.4% of Raji at lethal dose (LD80) conditions. The cell line in which apoptosis is predisposed may be more susceptible to PDT compared with the cell line in which necrosis is predisposed. Furthermore, HSP-70 was expressed constitutively in Raji cells but not in HL60 cells. Heat treatment of HL60 cells induced expression of HSP-70 and resulted in significant reduction of PDT-mediated apoptosis. From the results of this experiment, it is suggestive that HSP-70 contributes to inhibition of apoptosis mediated by PDT.     

Production of ultrafine particles of high-temperature tetragonal WO<Subscript>3</Subscript> by dc arc discharge in Ar–O<Subscript>2</Subscript> gases

Ultrafine particles of WO₃ are successfully produced by dc arc discharge in Ar-O₂ gases. Particle sizes are distributed from 10 nm to 1 m depending on production conditions: gas pressure, collection position and discharge current. Observations of the cooled particles by electron microscopy indicate that the WO₃ particles are tetragonal, a phase that is usually only stable above 725 °C. The octahedral crystals are bounded by eight {1 0 1} faces and occasionally truncated by {1 0 0} and/or {0 0 1} faces. This method of producing WO₃ by dc arc discharge therefore affords a high-temperature phase that is preserved upon cooling to room temperature.     

The behavior of isolated free eddies in a rotating fluid: Laboratory experiment

It is demonstated that an isolated free eddy similar to a Gulf Stream cyclonic ring can be generated in a rotating laboratory basin by applying local cooling to the free surface of the working fluid (water). Visual observations show that the resulting stratified eddy is inherently stable and preserves its monopolar structure even in the presence of bottom slope. On a sloping bottom, the eddy cuurent along with the eddy's water mass migrates away from the formation region. Characteristics of the eddy migration due to bottom slope are also presented.     

Reaction of (diacetoxyiodo)benzene with excess of trifluoromethanesulfonic acid. A convenient route to para-phenylene type hypervalent iodine oligomers

Reaction of (diacetoxyiodo)benzene [PhI(OAc)₂] in trifluoromethanesulfonic acid (TfOH) resulted in oligomerization of PhI(OAc)₂. Quenching with NaBr gave the bromide salts of hypervalent iodine oligomers that were determined by thermolysis with KI to be a para phenylene type of oligomers. Neutralization of the reaction mixture of PhI(OAc)₂ and TfOH with aqueous NaHCO₃ yielded the triflate salts of iodine oligomers. Furthermore, quenching the reaction mixture with aromatic substrates afforded arylated iodine oligomers. These iodine oligomers were found to be 3-4 of the number average degree of polymerization (P_n) by GC analysis of the thermolysis products and ¹H NMR analysis. The major products, trimer and tetramer, were synthesized independently.