Radical copolymerization of N-alkylmaleimides with isobutene and the properties of the resulting alternating copolymers

Radical copolymerization of N-methylmaleimide (MeMI) as well as other N-alkylmaleimides (RMI) and isobutene (IB) was carried out with 2,2′-azobis(isobutyronitrile) as an initiator at 60°C. The initial rate of the copolymerization (R_p) was dependent on the monomer composition and was maximum at the 40 mol % of MeMI in the feed. A solvent effect on the R_p and the monomer reactivity ratio was observed in this copolymerization system, i.e., copolymerization in chloroform produced a higher R_p and an alternating tendency compared with those in dioxane (r_MeMI = 0.14, r_1B = 0 in chloroform and r_MeMI = 0.47, r_1B = 0 in dioxane). The alternating copolymer of RMI and IB shows a high glass transition temperature (T_g) and excellent thermal stability, e.g., the T_g and the thermal decomposition temperature (T_d) were 152 and 363°C, respectively, for the alternating copolymer of MeMI and IB. Both the T_g and T_d increased as the concentration of the MeMI unit in the copolymers increased. Colorless transparent sheets were obtained from press molding the alternating copolymers. They showed excellent mechanical and optical properties. © 1996 John Wiley & Sons, Inc.     

Syntheses and radical polymerizations of novel optically active vinyl and isopropenyl carbamates having L-leucine structures

Syntheses and radical polymerizations of vinyl and isopropenyl carbamates having L -leucine methyl ester structures, N-vinyloxycarbonyl-L -leucine methyl ester (VOC-L-M) and N-isopropenyloxycarbonyl-L -leucine methyl ester (IOC-L-M), were carried out. VOC-L-M and IOC-L-M were prepared by the reactions of L -leucine methyl ester with vinyl and isopropenyl chloroformates in the presence of sodium hydrogen carbonate. The radical polymerization of VOC-L-M with AIBN (1 mol %) in bulk, chlorobenzene, methanol, and N,N-dimethylformamide afforded the corresponding polymer (poly(VOC-L-M)) with M _n 7,400–19,000. Meanwhile, IOC-L-M afforded no polymer with AIBN at 60°C but afforded a polymer having low molecular weight with BPO at 80°C. The glass transition temperatures of poly(VOC-L-M) and poly(IOC-L-M) were 53 and 65°C, respectively. The 10% weight loss temperatures of poly(VOC-L-M) and poly(IOC-L-M) under nitrogen were 255 and 173, respectively. The copolymerization parameters of VOC-L-M (M₁) and vinyl acetate (M₂) were evaluated as r₁ = 0.92 and r₂ = 0.63. © 1996 John Wiley & Sons, Inc.     

Carbon Monoxide Oxidation by Polyoxometalate‐Supported Gold Nanoparticulate Catalysts: Activity,Stability, and Temperature‐ Dependent Activation Properties

Nanoparticulate gold supported on a Keggin‐type polyoxometalate (POM), Cs₄[α‐SiW₁₂O₄₀]?n H₂O, was prepared by the sol immobilization method. The size of the gold nanoparticles (NPs) was approximately 2 nm, which was almost the same as the size of the gold colloid precursor. Deposition of gold NPs smaller than 2 nm onto POM (Au/POM) was essential for a high catalytic activity for CO oxidation. The temperature for 50 % CO conversion was ?67 °C. The catalyst showed extremely high stability for at least one month at 0 °C with full conversion. The catalytic activity and the reaction mechanism drastically changed at temperatures higher than 40 °C, showing a unique behavior called a U‐shaped curve. It was revealed by IR measurement that Au^δ+ was a CO adsorption site and that adsorbed water promoted CO oxidation for the Au/POM catalyst. This is the first report on CO oxidation utilizing Au/POMs catalysts, and there is a potential for expansion to various gas‐phase reactions.     

Water-soluble constituents of dill

From the water-soluble portion of the methanol extract of dill (fruit of Anethum graveolens L.), which has been used as a spice and medicine, thirty-three compounds, including a new monoterpenoid, six new monoterpenoid glycosides, a new aromatic compound glucoside and a new alkyl glucoside were obtained. Their structures were clarified by spectral investigation.     

Influence of bubble clustering on multibubble sonoluminescence

Influence of clustering of cavitation bubbles on multibubble sonoluminescence (MBSL) in standing wave fields is studied through measurement of MBSL intensity with a photomultiplier tube and observation of corresponding bubble behavior with a high-speed video camera and an intensified charge-coupled device one. It is clarified that, when the SL is quenched suddenly at excessive ultrasonic power, the behavior of bubbles clearly changes; the bubbles which form dendritic branches of filaments change into clusters due to the secondary Bjerknes force. The cluster is composed of several bubbles surrounded by many tiny bubbles, in which bubbles repeatedly coalesce and fragment, and run away from pressure antinodes. When the clusters are broken up by forced fluid motion, the quenching of MBSL is suppressed.     

Spin distributions in the vibrational excitations of closed-shell nuclei

Self-consistent Hartree-Fock and RPA calculations with the Skyrme-type interaction SGII are used for a systematic investigation of the 1⁺ and the triplet 0^?, 1^?, 2^? states in ⁴⁰Ca and ²⁰⁸Pb. Response functions to spin-dependent multipole operators are calculated and the particle-hole structure of the spin-dependent collective states is studied. Collective spin-dependent 0^? and 1^? states above the giant dipole resonance as well as a collective spin-independent 2^? state (twist mode) are identified. Transition spin and current densities are calculated for the collective excitations and found to be useful for the study of these excitation modes.     

Dual Meissner effect and magnetic displacement currents

The dual Meissner effect is observed without monopoles in quenched SU(2) QCD with Landau gauge fixing. Magnetic displacement currents that are time-dependent Abelian magnetic fields act as solenoidal currents squeezing Abelian electric fields. Monopoles are not always necessary for the dual Meissner effect. A mean-field calculation suggests that the dual Meissner effect through the mass generation of the Abelian electric field is related to a gluon condensate A(a)(mu)A(a)(mu) not equal 0 of mass dimension 2.     

The first samarium(II)-mediated aryl radical cyclisation onto an aromatic ring

Intramolecular arylation of aryl radicals was mediated by SmI(2)/HMPA in the presence of i-PrOH to give spirocycles and/or reduced cine-cyclised products, while the reaction in the absence of i-PrOH gave the rearomatised fused rings.     

Gluonic excitation of the three-quark system in SU(3) lattice QCD

We present the first study of the gluonic excitation in the three-quark (3Q) system in SU(3) lattice QCD with beta=5.8 and 16(3) x 32 at the quenched level. For the spatially fixed 3Q system, we measure the gluonic excited-state potential, which is responsible for the properties of hybrid baryons. The lowest gluonic-excitation energy in the 3Q system is found to be about 1 GeV in the hadronic scale. This large gluonic-excitation energy is expected to bring about the success of the simple quark model without gluonic modes.     

Synthesis and evaluation of 6-nitro-7-(1-piperazino)quinazolines: dual-acting compounds with inhibitory activities toward both tumor necrosis factor-alpha (TNF-alpha) production and T cell proliferation

We investigated the chemical modifications of the nitroquinazoline derivative (1) through the replacement of the NH group at the C(4)-position with several N-alkyl groups to increase the lipophilicity at the C(4)-position. Among them, we found that the N-methyl analogue (5a) showed a 2-fold loss in the inhibitory activity toward tumor necrosis factor-alpha (TNF-alpha) production in vitro as compared with the NH analogue (1); however, 5a exhibited an oral inhibitory activity on TNF-alpha production with an ED50 value of 26 mg/kg, whereas 1 did not. Moreover, the oral bioavailability of 5a was higher than that of 1 (1, F=1%; 5a, F=21%), and the calculated ClogP value for 5a was higher than that for 1. These results suggest that the improved lipophilicity of 5a compared with that of 1 reflects its greater inhibitory activity on TNF-alpha production in vivo as well as oral bioavailability.