Alternating copolymerization of benzofuran with crotononitrile and α-chloroacrylonitrile

The copolymerizations of benzofuran with α,α- or α,β-disubstituted acrylic monomers were studied. The alternating copolymer of benzofuran and crotononitrile was prepared in the presence of an excess amount of crotononitrile with respect to benzofuran, ethylaluminum dichloride, and azobisisobutyronitrile. The intrinsic viscosity of copolymers was 0.1–0.2 dl/g. Crotononitrile is known to possess a polar carbon–carbon double bond from ¹³C-NMR spectroscopy but the alternating copolymerizability with benzofuran is low. It was found that the order of alternating copolymerizability of acrylic monomers is as follows: This fact may be attributed to the steric hindrance of the β-methyl of crotononitrile. The induced shifts by complexation with ethylaluminum dichloride on ¹³C-NMR spectra of the two isomers of crotononitrile are almost same but the copolymerizability of cis isomer is higher than that of trans isomer. α-Chloroacrylonitrile shows the highest alternating copolymerizability with benzofuran in the presence of weak Lewis acid such as ethoxyaluminum chloride. Alternating copolymerizability of acrylic monomers seems to be in proportion to their e value. The reactivity of cis- and trans-crotononitrile may depend on the nature of a ternary complex composed of aluminum compound, crotononitrile, and benzofuran.     

Effect of the Head Group of Surfactant on the Miscibility of Sodium Chloride and Surfactant in an Adsorbed Film and Micelle

The thermodynamic treatment of a surfactant mixture was applied to the mixture of sodium chloride, NaCl, with octyl methyl sulfoxide (OMS) and that with decyldimethylphosphine oxide (DePO). The surface tension of aqueous solutions of the mixtures was measured as a function of the total concentration and the composition of the mixtures at 298.15 K. The total surface densities of the mixtures and the composition of the adsorbed films and micelles were evaluated by applying thermodynamic equations to the expeimental results. It was found that the adsorbed film and micelle are almost composed of the surfactant and there is slight attractive interaction between the ions of NaCl and the head groups of OMS and DePO molecules in the adsorbed films and micelles. A difference in the miscibility of NaCl and surfactant was observed between the OMS and DePO systems and attributed to the difference in the hydration of the head group between OMS and DePO molecules. The comparison of these results with those of the mixtures of NaCl with tetraethylene glycol monooctyl ether (C(8)E(4)) and dodecylammonium chloride (DAC) indicated that the small difference in the miscibility in an adsorbed film and micelle among these nonionic surfactant systems arises from the difference in hydration and structure of the head groups and the large one between the nonionic surfactant and DAC systems results from electrostatic interactions between dodecylammonium and sodium ions. Copyright 2001 Academic Press.     

Determination of D- and L-amino acids in mouse kidney by high-performance liquid chromatography.

A method for the enantiomeric analysis of amino acids of mammalian tissues is described. An excellent resolution of D- and L-enantiomers of common protein amino acids was achieved by employing a combination of thin-layer chromatography and high-performance liquid chromatography. D-Enantiomers and L-enantiomers of glutamate, aspartate, glutamine, asparagine, serine, threonine, alanine, proline, tyrosine, valine, methionine, isoleucine, leucine, phenylalanine and histidine, as well as glycine were derivatized with 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide. The amino acid diastereomers were separated by two-dimensional thin-layer chromatography. Each amino acid diastereomer was then analysed by reversed-phase high-performance liquid chromatography for the resolution of D- and L-enantiomers. Very sharp peaks were obtained using a conventional octadecylsilyl-bonded column, and the possibility of analysing these amino acids (except tyrosine and histidine) in subnanomole amounts was indicated. The method was used to demonstrate the presence of D-enantiomers of alanine, proline and serine in mouse kidney.     

Photofragmentation of cluster ions: the visible photoabsorption spectrum of Ar2N 2 +

The absolute cross section for photodissociation of Ar₂N ₂ ⁺ was measured as a function of wavelength in the 470–550 nm range. A structureless broad band was observed; the cross section has a maximum of ～ 210 × 10^?18 cm² at ～ 500 nm. The measurement of the photofragment time-of-flight spectrum shows that(1) N ₂ ⁺ , Ar⁺ and Ar ₂ ⁺ are produced in the photodissociation of Ar₂N ₂ ⁺ in the wavelength range studied, and that(2) the observed visible absorption band is ascribable to a parallel-type transition of Ar₂N ₂ ⁺ , which possibly retains a linear geometry.     

Stereocontrolled,straightforward synthesis of 3-substituted methyl 7α-methoxy-1-oxacephems

Stereocontrolled and industrially feasible synthesis of a new antibiotic $\text{1a}$ and related derivatives, which is characterized by using all the carbon atoms of the penicillin skeleton, is described.     

Sharp diffraction peaks from chaotic structures

Recently various models for spatially chaotic structures have been proposed. We study the diffraction patterns produced by plane chaotic waves incident on one-dimensional chaotic point scatterers. The spacing between the scatterers and the dynamics of the incident wave are given by a logistic map or standard map. We find a sharp diffraction peak when the incident dynamics is produced by the same map as the structure of the spatial configuration. The diffraction pattern is symmetric about the incident direction only if the map dynamics is invertible. Diffraction patterns with chaotic incident waves have a large signal-to-noise ratio and are well suited for pattern identification. We discuss possible applications to the scattering of microwaves from aperiodic structures. (c) 1997 American Institute of Physics.     

Superconductivity and metal-insulator transition in Cu(Ir<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Rh<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>S<Subscript>4</Subscript>

A new thiospinel CuIr₂S₄ exhibits a metal-insulator (M-I) transition at 226 K, while CuRh₂S₄ shows a superconducting transition at 4.70 K. We present a systematic study of electrical and magnetic properties of Cu(Ir_1?x Rh _x )₂S₄. TheM-I transition of CuIr₂S₄ is accompanied by a structural phase transition from tetragonal symmetry in insulating phase to cubic symmetry in high temperature metallic phase. With increasing Rh contentx, the sharpM-I transition shifts to lower temperature forx≦0.10. The samples show semiconductive behavior for 0.10≦0.30 between 4.2 and 300 K, and recover the metallic state forx≧0.50. The superconducting transition may occur for very close tox=1.00. Magnetic susceptibility shows the jump at theM-I transition temperature and the variation ofx leads to a systematic change of the magnetic susceptibilities, which is consistent with the electrical characteristic feature.     

Measurement of electric quadrupole moments of neutron-rich nuclei14B and15B

The experimental study of nuclear moments of several neutron-rich nuclei, using the phenomenon of ejectile spin polarization in the projectile fragmentation reaction, is reported. The spin-polarized fragments¹⁴B and¹⁵B were produced in the fragmentation of¹⁸O projectiles on a Nb target at 64.7 MeV/u. They were implanted into a Mg single crystal, and the quadrupole momentsQ were determined by the-NMR method. The results, ¦Q(¹⁴B)¦ =29.84 ±0.75 mb and ¦Q(¹⁵B)¦=38.01 ±1.08 mb, are compared with theoretical models. Shell model calculations in a 0 model space, using effective charges commonly accepted in this mass region, predict values about 40% larger than the experimentalQ(¹⁵B). Agreement is obtained when a much smaller effective charge for neutrons is employed. The method was also applied to the measurement of the magnetic moments of¹⁷N and¹⁷B. The result reveals an important contribution of configurations with excess neutrons coupled to formJ =2⁺.