Kinetics of the γ-radiation-induced polymerization of ethylene in liquid carbon dioxide

The γ-radiation-induced polymerization of ethylene with the use of liquid carbon dioxide as a solvent, was studied from the viewpoint of kinetics. The polymerization was carried out at conversions less than 10% under the pressure ranging from 100 to 400 kg./cm.², dose rates 1.3 × 10⁴?1.6 × 10⁵ rad/hr., and temperatures of 20–90°C. The concentration of carbon dioxide varied up to 84.1 mole-%. The polymerization rate and the polymer molecular weight were observed to increase with reaction time. This observation, however, becomes less pronounced with increasing concentration of carbon dioxide and with rising temperature. The exponents of the pressure and the dose rate were determined to be 2.3 and 0.85 for the rate, and 2.0 and ?0.20 for the molecular weight, respectively. From the kinetic considerations for these results, the effect of carbon dioxide on the initiation and termination reaction in the polymerization was evaluated.     

TEMPO/NaBr/NaClO and NaBr/NaClO oxidations of cotton linters and ramie cellulose samples

Dried cotton linters and ramie cellulose samples were oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)/NaBr/NaClO and NaBr/NaClO (i.e., TEMPO-free) in water at pH 10. The carboxy contents, degrees of polymerization (DPs), X-ray diffraction patterns, and solid-state ¹³C NMR spectra were measured or obtained for the oxidized products with and without subsequent NaBH₄ reduction. Cellulose nanofibrils were prepared from the oxidized cellulose samples by sonication in water and observed by atomic force microscopy and transmission electron microcopy. Because the cellulose molecules were depolymerized with NaBr/NaClO, the depolymerization behavior of the cellulose samples with TEMPO/NaBr/NaClO can be mainly explained by depolymerization with NaBr/NaClO (i.e., not TEMPO-related compounds or reactions). However, because C6-aldehydes formed in the disordered regions periodically present along the longitudinal direction of each cellulose microfibril, the viscosity-average DP values of the TEMPO/NaBr/NaClO-oxidized cellulose samples decreased to 200–300, while those with subsequent NaBH₄ reduction exhibited much higher DP values. The nanofibrils prepared from the TEMPO/NaBr/NaClO-oxidized cellulose samples had smallest fibril heights or widths of 5–6 nm. However, significant amounts of unfibrillated bundles with heights of 10–40 mm were present in the nanofibril/water dispersions. The high carboxy contents of the TEMPO/NaBr/NaClO-oxidized cellulose samples (1.62–1.63 mmol/g) indicated that significant amounts of carboxy groups were likely present in the disordered regions, probably forming tail-like polyglucuronate chains. Solid-state ¹³C NMR analysis revealed that some of the glucosyl units originally with the tg C6–OH conformation were transformed to other conformations by TEMPO/NaBr/NaClO oxidation, while the crystalline C4 signal areas remained constant.

Graphic abstract

     

Electron-transfer state of 9-mesityl-10-methylacridinium ion with a much longer lifetime and higher energy than that of the natural photosynthetic reaction center

We have successfully achieved the electron-transfer (ET) state of 9-mesityl-10-methylacridinium ion, produced by a single step photoinduced electron transfer, which has a much longer lifetime (e.g., 2 h at 203 K) and higher energy (2.37 eV) than that of the natural system without loss of energy due to multistep electron-transfer processes.     

The uniqueness for minimal surfaces inS 3

We give a sufficient condition on a Jordan curve in the 3-dimensional open hemisphereH ofS ³ in terms of the Hopf fibering under which spans a unique compact generalized minimal surface inH. The maximum principle for minimal surfaces inS ³ is proved and plays an important role in the proof of the uniqueness theorem.Dedicated to Professor Shingo Murakami on his 60th birthdayThis work was carried out while the author was a visitor to the Max-Planck-Institut für Mathematik.     

Short-chain branching in γ-radiation-induced polymerization of ethylene

In an attempt to elucidate the mechanism of chain-branch formation in the polymerization of ethylene, the effect of reaction conditions on short-chain branching in γ-radiationinduced polymerization of ethylene was investigated by using infrared spectroscopy. The concentration of methyl groups, i.e., the frequency of short-chain branching, increases with temperature and pressure and is independent of ethylene conversion to polymer and radiation intensity. The number of methyl groups per polymer molecule increases almost proportionally with the degree of polymerization. These facts indicate that short-chain branching occurs mainly by the mechanism of intramolecular hydrogen transfer. The effect of pressure on the rate of chain branching can be postulated by considering the transition state to be six-membered rings in hydrogen transfer reactions. The activation energy of chain branching is found to exceed that of propagation by 6 kcal./mole.     

Remarkable effect of 2[small alpha]-modification on the VDR antagonistic activity of 1small alpha-hydroxyvitamin D3-26,23-lactones

Novel 2[small alpha]-methyl-, 2[small alpha]-(3-hydroxypropyl)- and 2[small alpha]-(3-hydroxypropoxy)-substituted 25-dehydro-1[small alpha]-hydroxyvitamin D-26,23-lactone derivatives were efficiently synthesized Reformatsky type allylation and palladium-catalyzed alkenylative cyclization processes, and their biological activities were evaluated. Introducing functional groups into the 2[small alpha]-position of the vitamin D-26,23-lactones resulted in remarkable enhancement of their antagonistic activity on vitamin D receptor (VDR).     

Simultaneous detection of 19 K‐ras mutations by free‐solution conjugate electrophoresis of ligase detection reaction products on glass microchips

We demonstrate here the power and flexibility of free‐solution conjugate electrophoresis (FSCE) as a method of separating DNA fragments by electrophoresis with no sieving polymer network. Previous work introduced the coupling of FSCE with ligase detection reaction (LDR) to detect point mutations, even at low abundance compared to the wild‐type DNA. Here, four large drag‐tags are used to achieve free‐solution electrophoretic separation of 19 LDR products ranging in size from 42 to 66 nt that correspond to mutations in the K‐ras oncogene. LDR‐FSCE enabled electrophoretic resolution of these 19 LDR‐FSCE products by CE in 13.5 min (E = 310 V/cm) and by microchip electrophoresis in 140 s (E = 350 V/cm). The power of FSCE is demonstrated in the unique characteristic of free‐solution separations where the separation resolution is constant no matter the electric field strength. By microchip electrophoresis, the electric field was increased to the maximum of the power supply (E = 700 V/cm), and the 19 LDR‐FSCE products were separated in less than 70 s with almost identical resolution to the separation at E = 350 V/cm. These results will aid the goal of screening K‐ras mutations on integrated “sample‐in/answer‐out” devices with amplification, LDR, and detection all on one platform.     

Formation of Anatase Nanocrystals in Sol-Gel Derived TiO2-SiO2 Thin Films with Hot Water Treatment

We have successfully prepared transparent and porous anatase nanocrystals-dispersed films by treating the sol-gel derived TiO₂-SiO₂ films containing poly(ethylene glycol), PEG, with hot water. This process was done at temperatures lower than 100°C under atmospheric pressure, and thus anatase nanocrystals-dispersed films can be formed on various kinds of substrates including organic polymers with poor heat resistance. The changes in structure and composition of the TiO₂-SiO₂ gel films with hot water treatment were related to the formation process of anatase nanocrystals in the TiO₂-SiO₂ gel films with hot water treatment. The formation of anatase nanocrystals was found to proceed to hydrolysis of Si–O–Ti bonds and dissolution of SiO₂ component. In addition, porous film structure formed by leaching of PEG with hot water treatment led to homogenous dispersion of anatase nonocrystals in the films.     

Palladium charcoal-catalyzed deprotection of O-allylphenols

Allyl aryl ethers can be easily cleaved by the use of 10% Pd/C under mild and basic conditions. The present reaction would involve a SET process rather than a π-allyl-palladium complex. The scope and limitation of this new deprotective methodology is also described.