Preparation of telechelic oligomers by thermal degradation of propylene copolymers

The reactive end groups of nonvolatile oligomers obtained by controlled thermal degradation of poly(propylene-ran-ethylene) and poly(propylene-ran-1-butene) were determined by ¹H and ¹³C NMR spectroscopy. The molar ratio of unsaturated to saturated end groups was found to be about 9:1. The average number of unsaturated end groups per molecule was between 1.6 and 1.8, indicating that 60–80 mol% of the oligomer molecules were telechelic, having two terminal unsaturated end groups. These oligomers had a lower polydispersity than the raw material, despite their lower molecular weight and melting temperature. Although the end groups resulting from each monomer unit could be detected by ¹³C NMR, the end group composition differed from that of the main chains of the raw materials. The end group composition was satisfactorily explained by the differences in bond dissociation energy and activation energy of elementary reactions that occurred during thermal degradation, based on the monomer composition of the raw materials.     

Flat translation invariant surfaces in the 3-dimensional Heisenberg group

Flat translation invariant surfaces in 3-dimensional Heisenberg group are classified.     

Sugar-sensitive thin films composed of concanavalin A and sugar-bearing polymers.

Layered thin films composed of concanavalin A (Con A) and sugar-bearing polymers were prepared by a layer-by-layer deposition of Con A and the polymer on a solid surface. The sugar-induced disintegration was studied. Con A-polymer layered films could be successfully prepared using a maltose-bearing polymer (PV-MA), while melibiose- and glucose-bearing polymers (PV-MEA and PV-G) did not afford a layered film, due to a weak affinity of PV-MEA and PV-G to Con A. The Con A/PV-MA layered film was stable in pH 7 and 8 solutions, while in a pH 6 medium the film was slightly unstable. The Con A/PV-MA film was disintegrated upon the addition of sugars in solution owing to a preferential binding of the sugars to the binding site of Con A in the film. The disintegration rate was dependent on the type of sugar and its concentration. The Con A/PV-MA film was disintegrated rapidly upon the addition of methyl alpha-D-mannopyranoside, while the rate was slower upon the addition of the same concentration of D-mannose, D-glucose and methyl alpha-D-glucopyranoside. The present system may be useful for constructing sensitive devices that can release a drug or other functional molecules in response to sugars.     

Performance Change of the Oxidative Coupling of Methane Induced by the Modification Effect of Lithium on a Mn-Mg-O Solid Solution

Lithium made a Mn-Mg-O solid solution stable upon exposure of methane, decreased the ethane and ethylene formation rates, and increased the COx formation rate during the oxidative coupling of methane. On the other hand, on MgO, lithium inhibited COx formation markedly and enhanced the selectivity of ethane 47% to 76%.     

Observation of increase in Raman intensity of surface phonon polaritons on rough surfaces of ZnTe

An increase in Raman intensity of surface phonon polaritons has been observed in free-standing thin slabs (thickness ～ 7 μm) of single- crystal ZnTe with rough surfaces by a conventional Raman-scattering technique at room temperature. The samples with various root-mean- square roughness heights have been prepared by making use of final polishing powders with different mean-grit sizes, and the surface roughness has been confirmed by measuring the intensities of the diffuse scattering of the laser light. The increase of the Raman intensity is proportional to the mean-square height of the surface roughness, and the shift of the dispersion relation is also proportional to it. The frequency shift is explained by a perturbation theory of the surface-roughness-induced scattering.     

Hadroproduction of heavy quark flavors in QCD

Within the framework of perturbative QCD, we investigate the hadroproduction of charmed particles via two-gluon as well as quark-pair annihilation. The total production cross section is found to be sensitive to the choice of the scale parameter Q² and in general not free from non-perturbative effects. Charmed-particle production in the high-p_T region is also studied.     

Sustainable domino Michael reaction catalyzed by a Brønsted base on silica gel: synthesis of bicyclo[2.2.2]octane-2,5-dione derivatives

Domino Michael reactions of oxophorone and its derivatives 4 with Michael partners 3 have been effected to give bicyclo[2.2.2]octane-2,5-dione derivatives 7 by a catalytic amount of a Brønsted base (NMAP-Li) generated from N-methylaminopropylated silica gel (NMAP) and n-BuLi. The NMAP pellets were efficiently reused up to six times in 86% average yield.