The Bipolaron in the Strong Coupling Limit

The bipolaron are two electrons coupled to the elastic deformations of an ionic crystal. We study this system in the Fr?hlich approximation. If the Coulomb repulsion dominates, the lowest energy states are two well separated polarons. Otherwise the electrons form a bound pair. We prove the validity of the Pekar–Tomasevich energy functional in the strong coupling limit, yielding estimates on the coupling parameters for which the binding energy is strictly positive. Under the condition of a strictly positive binding energy we prove the existence of a ground state at fixed total momentum P, provided P is not too large. Tadahiro Miyao: This work was supported by Japan Society for the Promotion of Science (JSPS). Permanent address: The graduate school of natural science and technology, Okayama university, Okayama 700-8530, Japan. Submitted: December 14, 2006. Accepted: March 20, 2007.     

CRYSTAF Analysis of Polyethylene Synthesized with Phillips Catalyst

Crystallization analysis fractionation (CRYSTAF) was used for the first time to investigate the solution crystallization behavior of ethylene homopolymers and copolymers made with Phillips CrO_x/SiO₂ catalyst. Interestingly, the crystallization peak temperatures (T_p) of copolymers of ethylene and cyclopentene increased with increasing cyclopentene molar fraction in the copolymer. Comparing two factors (short chain branches (SCBs) and cyclopentene incorporation), decreasing SCB frequency is proposed as the dominant factor to explain the increase of crystallization peak temperatures with increasing cyclopentene incorporation. In addition, SCB frequency and molecular weight might be the two significant factors determining the crystallization temperature of polyethylene made with Phillips CrO_x/SiO₂ catalyst with different cocatalysts (triethylaluminum and diethylaluminum ethoxide).     

Coexistence of two different side chain packing structures in a smectic phase of liquid-crystalline side chain polymers

Ten varieties of liquid-crystalline side chain polymers, poly(cholesteryl-ω-(methacryloyloxy)alkanoates) (pChMO-n, n = 1, 2, 3, 4, 5, 7, 9, 10, 11 and 15; the carbon number of the alkyl chain), were studied by differential scanning calorimetry and small angle X-ray scattering. On and after the first cooling run from the isotropic state, these polymethacrylates gave the same smectic phase. X-ray investigations showed that pChMO-n with short spacers (n = 1-7) has a two layer (bilayer) S_A packing structure, and pChMO-n with a longer spacer (n= 15) has a single layer (monolayer) S_A packing structure. However, these two types of packing structure appear simultaneously in pChMO-n (n = 9s-11) below their phase transition temperature. To clarify the manner of the coexistence of the two different structures the smectic layer spacing and X-ray diffraction patterns were examined by small angle X-ray scattering at various temperatures.     

Electroreductive intramolecular coupling of aromatic beta- and gamma-imino esters: a new synthetic method for N-alkoxycarbonyl-2-aryl-3-ones and cis-2-aryl-3-ols of pyrrolidines and piperidines

The electroreduction of aromatic beta- and gamma-imino esters prepared from beta-alanine and GABA in the presence of chlorotrimethylsilane and subsequent N-alkoxycarbonylation of the resulting five- and six-membered cyclized amines gave mixed ketals of N-alkoxycarbonyl-2-arylpyrrolidin-3-ones and 2-arylpiperidin-3-ones, respectively. The best result of the electroreductive intramolecular coupling was achieved using Bu(4)NClO(4) as a supporting electrolyte and a Pb cathode in THF. Acid hydrolysis of the mixed ketals afforded N-alkoxycarbonyl-2-arylpyrrolidin-3-ones and 2-arylpiperidin-3-ones in good yields. The reduction of these ketones with NaBH(4) in methanol afforded the corresponding N-alkoxycarbonyl-cis-2-arylpyrrolidin-3-ols and cis-2-arylpiperidin-3-ols diastereospecifically.     

CLL = (L,L; 0, 0) measurements and a structure due to a P partial wave in the pp system

Measurements of C_LL of pp elastic scattering near θ_c.m. = 90° at thirteen energies between 300 and 800 MeV are reported. These, together with previous values of C_NN, are used to extract values of two quantities, $\text{?}{}_{\mathrm{<mtext>s</mtext>}}$ and $\text{?}{}_{\mathrm{<mtext>t</mtext>}}$, which contain only spin-singlet and only coupled spin-triplet partial waves, respectively. The $\text{?}{}_{\mathrm{<mtext>s</mtext>}}$ curve, which is not dependent on C_LL, exhibits the behavior expected for the previously conjectured ¹D₂ resonance. The $\text{?}{}_{\mathrm{<mtext>t</mtext>}}$ curve also exhibits a resonance-like behavior, which could be due either to the ³P₀ or the ³P₂ partial wave.     

Regioselective synthesis of dihydrofurans from 2,2-dibromo-1,3-diketone and olefin using copper

2,2-Dibromo-1,3-diketones reacted with copper powder and olefin to give 4,5-dihydrofuran derivatives in a highly regioselective fashion.     

Supported Noble Metal Catalysts and Adsorbents with Soft Lewis Acid Functions

Heterogeneous noble metal catalysts exhibit various functions. Although their redox functions have been extensively studied, we focused on their soft Lewis acid functions. Supported Au, Pt, and Pd catalysts electrophilically attack the π-electrons of soft bases such as alkynes, alkenes, and aromatic compounds to perform addition and substitution reactions. Hydroamination, intramolecular cyclization of alkynyl carboxylic acids, isomerization of allylic esters, vinyl exchange reactions, Wacker oxidation, and oxidative homocoupling of aromatics are introduced based on a discussion of the active species and reaction mechanisms. Furthermore, the adsorption of sulfur compounds, which are soft bases, onto the supported AuNPs is discussed. The adsorption and removal of 1,3-dimethyltrisulfane (DMTS), which is the compound responsible for the stale odor of “hine-ka” in alcoholic beverages, particularly Japanese sake, is described.     

Crystal and molecular structure of iso-grayanotoxin II

The crystal and molecular structure of a grayanotoxin derivative, iso-grayanotoxin II, is presented. The crystal is orthorhombic, space group . The molecule is based on a tetracyclic structure consisting of two five-membered, one six-membered, and one seven-membered rings with various conformations.     

Color transfer method preserving perceived lightness

Color transfer originally proposed by Reinhard et al. is a method to change the color appearance of an input image by using the color information of a reference image. The purpose of this study is to modify color transfer so that it works well even when the scenes of the input and reference images are not similar. Concretely, a color transfer method with lightness correction and color gamut adjustment is proposed. The lightness correction is applied to preserve the perceived lightness which is explained by the Helmholtz–Kohlrausch (H–K) effect. This effect is the phenomenon that vivid colors are perceived as brighter than dull colors with the same lightness. Hence, when the chroma is changed by image processing, the perceived lightness is also changed even if the physical lightness is preserved after the image processing. In the proposed method, by considering the H–K effect, color transfer that preserves the perceived lightness after processing is realized. Furthermore, color gamut adjustment is introduced to address the color gamut problem, which is caused by color space conversion. The effectiveness of the proposed method is verified by performing some experiments.