Continuum mixing and coupled channel effects inc\bar c andb\bar b quarkonium

We apply the unitarized quark model to heavy \(c\bar c\) and \(b\bar b\) quarkonium and study mass shifts and mixings induced by hadronic coupled channel effects. In particular, we study the two-meson continuum mixing in the quarkonium wave functions. It is found that the continuum component is 2–20% in the \(c\bar c\) and \(b\bar b\) states, measured as the squared sum of two-meson amplitudes \((D\bar D,D\bar D^ * + cc,D^ * \bar D^ * ,F\bar F,F\bar F^ * + cc,F^ * \bar F^ * for c\bar c)\) . It is the largest for states near or above the first threshold. These continuum mixings reduce the predicted radiative widths by 5–30%. The mass shifts of theP andF wave \(q\bar q\) states are similar to those ofS andD wave states previously studied. The computed resonance mixing matrices are explicitly given, enabling future calculations of relativistic effects, QCD effects, etc., to include also the coupled channel effects.     

Synthesis of Arenethiolate Complexes of Divalent and Trivalent Lanthanides from Metallic Lanthanides and Diaryl Disulfides: Crystal Structures of [{Yb(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] and Ln(SPh)(3)(hmpa)(3) (Ln = Sm, Yb; hmpa = Hexamethylphosphoric Triamide)

A convenient and one-pot synthetic method of lanthanide thiolate compounds was developed. An excess of metallic samarium, europium, and ytterbium directly reacted with diaryl disulfides in THF to give selectively Ln(II) thiolate complexes, [Ln(SAr)(&mgr;-SAr)(thf)(3)](2) (1, Ln = Sm; 2, Ln = Eu; Ar = 2,4,6-triisopropylphenyl), Yb(SAr)(2)(py)(4) (3, py = pyridine), and [{Ln(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] (6, Ln = Sm; 7, Ln = Eu; 8, Ln = Yb; hmpa = hexamethylphosphoric triamide). Reaction of metallic lanthanides with 3 equiv of disulfides afforded Ln(III) thiolate complexes, Ln(SAr)(3)(py)(n)()(thf)(3)(-)(n)() (9a, Ln = Sm, n = 3; 9b, Ln = Sm, n = 2; 10, Ln = Yb, n = 3) and Ln(SPh)(3)(hmpa)(3) (11, Ln = Sm; 12, Ln = Eu; 13, Ln = Yb). Thus, Ln(II) and Ln(III) thiolate complexes were prepared from the same source by controlling the stoichiometry of the reactants. X-ray analysis of 8 revealed that 8 has the first ionic structure composed of triply bridged dinuclear cation and benezenethiolate anion [8, orthorhombic, space group P2(1)2(1)2(1) with a = 21.057(9), b = 25.963(7), c = 16.442(8) ?, V = 8988(5) ?(3), Z = 4, R = 0.040, R(w) = 0.039 for 5848 reflections with I > 3sigma(I) and 865 parameters]. The monomeric structures of 11 and 13 were revealed by X-ray crystallographic studies [11, triclinic, space group P&onemacr; with a = 14.719(3), b = 17.989(2), c = 11.344(2) ?, alpha = 97.91(1), beta = 110.30(2), gamma = 78.40(1) degrees, V = 2751.9(9) ?(3), Z = 2, R = 0.045, R(w) = 0.041 for 7111 reflections with I > 3sigma(I) and 536 parameters; 13, triclinic, space group P&onemacr; with a = 14.565(2), b = 17.961(2), c = 11.302(1) ?, alpha = 97.72(1), beta = 110.49(1), gamma = 78.37(1) degrees, V = 2706.0(7) ?(3), Z = 2, R = 0.031, R(w) = 0.035 for 9837 reflections with I > 3sigma(I) and 536 parameters]. A comparison with the reported mononuclear and dinuclear lanthanide thiolate complexes has been made to indicate that the Ln-S bonds weakened by the coordination of HMPA to lanthanide metals have ionic character.     

Improvement of culture conditions forl-proline production by a recombinant strain ofSerratia marcescens

Serratia marcescens SP511 was previously reported to be anl-proline-producing strain that harbors a recombinant plasmid carrying the mutant type of the proline operon. This strain produced 65 g/L ofl-proline in a medium containing 22% sucrose and urea after 5 d of incubation under the conventional culture conditions. We searched for more suitable culture conditions for more abundantl-proline production by SP511. To improve the supply of a nitrogen source to cells, ammonium was used instead of urea and fed to a culture under control of the pH of the medium. The concentrations of MgSO₄ and K₂HPO₄ were increased, and in addition, sucrose was continuously added to the culture at a final concentration of 32%. Under these conditions, the cell amount was increased twofold over that under the previous conditions andl-proline production reached a maximum of more than 100 g/L after 4 d of incubation.     

Enzymes in Organic Synthesis: Application to the Problems of Carbohydrate Recognition (Part 1)

Carbohydrates on cell surfaces are information molecules. Although only seven or eight monosaccharides are commonly used as building blocks in mammalian systems, the multifunctionality of these monomers can lead to the assembly of an immense variety of complex structures. Millions of different tetrasaccharide structures, for example, can be constructed from this small number of building blocks, if branching, the stereochemistry of glycosidic linkages, and the modification of hydroxyl and amino groups are taken into consideration. Oligosaccharides therefore represent an effective class of biomolecules that code for a vast amount of information required in various biological recognition processes, such as intercellular communication, signal transduction, cell adhesion, infection, cell differentiation, development and metastasis. The pace of development of pharmaceuticals based on carbohydrates has, however, been slower than that based on other classes of biomolecules. Part of the reason is the lack of technologies for the study of complex carbohydrates. There is no method to amplify oligosaccharides for sequence analysis. There is no machine available for automated synthesis of oligosaccharides. In addition, the possibly poor bioavailability and difficulties in the large-scale synthesis of carbohydrates have undoubtedly contributed to this slow pace. The enzymatic and chemoenzymatic methods, especially those based on aldolases and glycosyltransferases, described here appear to be useful for the synthesis of mono- and oligosaccaharides and related molecules. Further advances in glycobiology will probably lead to the development of new technologies for the study of carbohydrate recognition and for the synthesis of bioactive carbohydrates and mimetics to control the recognition processes.     

On the electrical conductivity of intermediate valence compounds

The electrical resistivity of the hybridized 4f-(5d/6s) system interacting with LA phonons is calculated by applying the memory function method to the periodic Anderson model in Hartree-Fock approximation. We propose a new mechanism to explain in part the anomalous resistivity of mixed valence compounds such as CePd₃. For finite hybridizationV a finite fraction of 4f electrons participates in electrical conduction leading to an essential change of the normald band current. Resistivity and the fraction of 4f electrons increase with increasing value of [V/(E–)]² where (E–) is the distance between the effective positionE of the 4f level and the chemical potential. In typical mixed valence systems [V/(E–)]² is strongly temperature dependent and decreases with increasing temperature. This explains the high temperature resistivity behaviour of CePd₃. For (E–) being small compared to the Debye-temperature the resistivity is enhanced and becomes extremely sensitive to small changes of (E–).Work performed within the research program of the Sonderforschungsbereich 125, Aachen-Jülich-Köln     

Detection of varicocele by using 99mTc-diethylenetriamine pentaacetic acid human serum albumin (99mTc-DTPA human serum albumin)

In order to detect the varicocele, scrotal scintigraphies by using 99mTc-HSA-D were performed in 14 patients with male infertile or palpable mass in left scrotum on physical examinations. Abnormal pooling of 99mTc-HSA-D, indicative of varicocele lesion, could be found in left scrotum in 9 cases, confirmed surgically or clinically. Compared with 99mTc-HSA, 99mTc-HSA-D was superior in high uptake ratio of varicocele to soft tissue and in nonvisualization of bladder. Thus, 99mTc-HSA-D scrotal scintigraphy seemed to be of a great use to detect the varicocele.     

A practical synthesis of 4′-thioribonucleosides

A practical synthesis of 4′-thioribonucleosides starting from inexpensive l-arabinose is described. 1,4-Anhydro-2,3-O-isopropylidene-4-thioribitol, which was prepared by using a novel reductive ring-contraction reaction, was converted to the 5-O-silylated sulfoxides. The Pummerer-type thioglycosylation of the sulfoxides gave the 4′-thioribonucleosides stereoselectively.     

Evidence of conformational equilibrium of 1-ethyl-3-methylimidazolium in its ionic liquid salts: Raman spectroscopic study and quantum chemical calculations

Raman spectra of liquid 1-ethyl-3-methylimidazolium (EMI+) salts, EMI(+)BF4-, EMI(+)PF6-, EMI(+)CF3SO3-, and EMI(+)N(CF3SO2)2-, were measured over the frequency range 200-1600 cm(-1). In the range 200-500 cm(-1), we found five bands originating from the EMI+ ion at 241, 297, 387, 430, and 448 cm(-1). However, the 448 cm(-1) band could hardly be reproduced by theoretical calculations in terms of a given EMI+ conformer, implying that the band originates from another conformer. This is expected because the EMI+ involves an ethyl group bound to the N atom of the imidazolium ring, and the ethyl group can rotate along the C-N bond to yield conformers. The torsion energy for the rotation was then theoretically calculated. Two local minima with an energy difference of ca. 2 kJ mol(-1) were found, suggesting that two conformers are present in equilibrium. Full geometry optimizations followed by normal frequency analyses indicate that the two conformers are those with planar and nonplanar ethyl groups against the imidazolium ring plane, and the nonplanar conformer is favorable. It elucidates that bands at 241, 297, 387, and 430 cm(-1) mainly originate from the nonplanar conformer, whereas the 448 cm(-1) band does originate from the planar conformer. Indeed, the enthalpy for conformational change from nonplanar to planar EMI+ experimentally obtained by analyzing band intensities of the conformers at varying temperatures is practically the same as that evaluated by theoretical calculations. We thus conclude that the EMI+ ion exists as either a nonplanar or planar conformer in equilibrium in its liquid salts.     

The effect of fluorination: a crystallographic and computational study of mesogenic alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates

The series of alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates (F8-n) shows a systematic change of crystal structures depending on the length of the alkyl chain: separate packing of perfluorooctyl (Rf) and alkyl (Rh) chains from each other for shorter (n=2) and longer (n=11) members, alternate packing of Rf and Rh chains for middle (n=6,7) members, and an intermediate type of packing for n=4. Semiempirical MO calculations show slightly repulsive interactions between the Rf chains, and attractive ones between Rf and Rh chains and between Rh and the core of a molecular pair. It is concluded that fluorination determines the molecular shape of the crystal structures by making the chain rigid. It is confirmed that the interactions between Rf chains are small compared with those between other moieties and that they are forced to aggregate owing to the exclusion from other moieties. Thus, the effect is dependent on the geometries and intermolecular interactions of the other moieties.     

Crystal Structure, Electric and Magnetic Properties of Layered Cobaltite β-NaxCoO2

The layered oxide thermoelectric material β-Na_0.67CoO₂ has been studied by powder neutron diffraction, electric and magnetic measurements. This compound includes an edge-sharing CoO₆ slab and a highly vacant Na⁺ sheet in a unit cell (space group symmetry C2/m, a=4.9023(4) Å, b=2.8280(2) Å, c=5.7198(6) Å and β=105.964(6)° at 300 K). The evaluated formal valence of cobalt ion, +3.33(1), is ascribed to the coexistence of Co³⁺ and Co⁴⁺ in the ratio 2:1. Polycrystalline β-Na_0.67CoO₂, a p-type thermoelectric material, exhibits metallic behavior of the electric resistivity below 300 K. The Curie-Weiss-type magnetic susceptibility indicates antiferromagnetic interactions between magnetic cobalt ions in the edge-sharing CoO₆ slab.