Quenching of neutron E2 effective charge in neutron-rich nuclei and the ground-state spin-parity of 17C

The electric quadrupole moment of ¹⁷B and the g-factor of ¹⁷C were measured by using the fragmentation-induced nuclear polarization technique combined with the β-NMR method. The experimental quadrupole moment of ¹⁷B is found strikingly close to that of the neutron closed-shell isotope ¹³B, indicating a strong quenching of the neutron E2 core-polarization charge. From the result obtained for the ¹⁷C g-factor, we can conclude that the ground-state spin-parity of ¹⁷C is 3/2⁺. Received: 1 May 2001 / Accepted: 4 December 2001     

Development of highly diastereo- and enantioselective direct asymmetric aldol reaction of a glycinate Schiff base with aldehydes catalyzed by chiral quaternary ammonium salts

A highly efficient direct asymmetric aldol reaction of a glycinate Schiff base with aldehydes has been achieved under mild organic/aqueous biphasic conditions with excellent stereochemical control, using chiral quaternary ammonium salt 1b as a phase-transfer catalyst. The initially developed reaction conditions, using 2 equiv of aqueous base (1% NaOH (aq)), exhibited inexplicably limited general applicability in terms of aldehyde acceptors. The mechanistic investigation revealed the intervention of an unfavorable yet inevitable retro aldol process involving the chiral catalyst. On the basis of this information, a reliable procedure has been established by use of a catalytic amount of 1% NaOH (aq) and ammonium chloride, which tolerates a wide range of aldehydes to afford the corresponding anti-beta-hydroxy-alpha-amino esters almost exclusively in an essentially optically pure form.     

Photoconductive properties of organic-inorganic hybrid films of layered perovskite-type niobate

A hybrid film of layered niobate and an organic amphiphile was prepared by the Langmuir-Blodgett (LB) method. Trimethylammonium-exchanged perovskite-type niobates ((CH(3))(3)NHSr(2)Nb(3)O(10)) were exfoliative to form an aqueous suspension. A monolayer of octadecylamine was produced on such an aqueous dispersion as a template for a hybrid film. A hybrid film was transferred as a Y-type LB film onto a hydrophilic glass plate or an ITO substrate. The structure of a deposited film was investigated with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic force microscopy (AFM) measurements, indicating a layer-by-layer structure with a single or double sheet of niobate as an inorganic composite. From the cyclic voltammogram on an ITO electrode modified with the Y-type 10 layered film, the lower edge of the conduction band of a niobate layer was determined to be - 0.6 V (vs Ag/AgCl). ac impedance and dc measurements were carried out on 1, 5, and 10-layered LB films (2 mm (electrode spacing) x 8 mm (width)) with aluminum electrodes. The freshly deposited samples behaved as an insulator under the illumination of 280 nm light (2.04 x 10(16) quanta s(-1)). Photoconductivities appeared, however, when they were preirradiated with a 150 W Xe lamp (ca. 2 x 10(18) quanta s(-1)) for 0.5-8.5 h. The process was denoted as photomodification. From the FT-IR and XRD results, it was deduced that the photomodification of LB films caused the decomposition of organic templates (octadecylammonium) accompanied by the collapse of layer-by-layer structures. dc analyses on the 5- and 10-layered films after photomodification also showed that they behaved as a photosemiconductor under UV light illumination.     

Inhibitory effect of validamine, valienamine and valiolamine on activities of carbohydrases in rat small intestinal brush border membranes

Three pseudo-aminosugars, validamine, valienamine and valiolamine, produced by Streptomyces hygroscopicus subsp. limoneus showed potent inhibitory action on rat small intestinal carbohydrase activities such as sucrase, maltase, glucoamylase, isomaltase and trehalase activities, but negligible action on lactase activity and pancreatic alpha-amylase activity. Where inhibition was seen, kinetic analysis showed fully competitive inhibition of the carbohydrase activities by all three inhibitors. Valiolamine has more potent carbohydrase inhibitory activity than validamine or valienamine, and the apparent Ki values of valiolamine for sucrase, maltase, glucoamylase, isomaltase and trehalase activities were 3.2 x 10(-7), 2.9 x 10(-6), 1.2 x 10(-6), 9.1 x 10(-7) and 4.9 x 10(-5) M, respectively, which are 10(-5) to 10(-3) times smaller than the apparent Km values.     

Production of spin-polarized 17N beam using inverse-kinematics low-energy transfer reactions

A new method to produce spin-polarized radioactive nuclear beams has been developed, which takes advantage of the low-energy transfer reaction in inverse kinematics. The method provides beam energies of a convenient range so that they may be implanted in a thin stopper, yet allowing the stopper to be spatially separated from the production target. The presence of polarizations of sizes at least $\left|P\right|\sim 0.5 \%$ has been confirmed for a ¹⁷N beam obtained from ⁹Be(¹⁸O,¹⁷N) reaction at $\theta_{\rm Lab} \sim -1.7\,^{\circ}$ .     

Ligand coupling of 2-pyridyl sulfoxides having an sp2 stereocenter at the α-position: A novel preparation of α-stilbazoles

Ligand coupling of (E)- and (Z)-styryl 2-pyridyl sulfoxides with methylmagnesium bromide gave (E)-and (Z)-2-styrylpyridine, respectively in a stereospecific manner. A number of (E)-2-styrylpyridine derivatives were prepared by the coupling reaction. Methyl styryl sulfoxide and 2,2′-bipyridyl were obtained as by-products. The mechanism of the reaction is discussed based on quantitative analysis of the products.     

Optical characteristic variations in gamma ray irradiated polarization-maintaining optical fibers

Optical Review - Polarization-maintaining (PM) optical fibers are introduced in fiber optic communication systems and optical fiber sensors to improve their performances. It is known that...     

Arginine Side Chains as a Dispersant for Individual Single‐Wall Carbon Nanotubes

Charged peptides and proteins disperse single‐wall carbon nanotubes (SWCNTs) in aqueous solutions. However, little is known about the role of their side chains in their interactions with SWCNTs. Homopolypeptide–SWCNT systems are ideal for investigating the mechanisms of such interactions. In this study, we demonstrate that SWCNTs are individually dispersed by poly‐L ‐arginine (PLA). The debundled SWCNTs exhibited a distinct fluorescence. The dispersibility of SWCNTs with PLA was greater than that of SWCNTs with poly‐L ‐lysine (PLL). Molecular dynamics simulations suggest that the side chains of PLA have stronger interactions with the sidewalls of SWCNTs compared with those of PLL. The guanidinium group at the end of the side chain of an arginine residue plays an important role in the interaction with SWCNTs, likely through hydrophobic, van der Waals, and π–π interactions. PLA can be useful as a tool for the dispersion of SWCNTs and can be used to non‐covalently anchor materials to SWCNTs with strong binding.