Dynamical quark effects on light quark masses

Light quark masses are calculated in lattice QCD with two degenerate flavors of dynamical quarks. The calculations are made with improved actions with lattice spacing a = 0.22-0.11 fm. In the continuum limit we find m(M&Smacr;)(ud)(2 GeV) = 3.44(+0.14)(-0.22) MeV using the pi and rho meson masses as physical input, and m(M&Smacr;)(s)(2 GeV) = 88(+4)(-6) MeV or 90(+5)(-11) MeV with the K or straight phi meson mass as additional input. The quoted errors represent statistical and systematic combined, the latter including those from continuum and chiral extrapolations, and from renormalization factors. Compared to quenched results, two flavors of dynamical quarks reduce quark masses by about 25%.     

Effects of food on bioavailability of two indomethacin capsules containing different sizes of particles

Two different indomethacin capsules, a commercial one containing fine drug particles and an experimental capsule containing 125-177 microns particles, were employed in this study. The commercial preparation showed faster in vitro dissolution than the experimental one. When administered to humans having normal acidity of the gastric juices, the commercial capsule exhibited higher Cmax and smaller Tmax and mean residence time (MRT) than the experimental one both in fasting and nonfasting states, although the two capsules were equivalent in area under the serum concentration-time curve (AUC). The ingestion of a breakfast delayed the gastrointestinal absorption from both preparations, which resulted in larger Tmax's and MRT's and smaller Cmax's in the nonfasting state. Food, however, did not have any significant effect on the AUC's of the preparations.     

Mechanism of formation of unusual photodegradation products from friedelin

From the photolysate of friedelin1, 3,4-seco-3-nor-friedelan-2-al2 and 3,4-seco-3-nor-friedelan-2-oic acid3 were obtained in addition to the expected photoproducts. Evidence is provided that2 and3 are autoxidation products of the ketene13 produced by α-cleavage of1 followed by hydrogen transfer.     

Raman and luminescence processes under the resonant two-photon excitation of an excitonic molecule in CuCl

Emission spectra and its decay time under the resonant two-photon excitation of an excitonic molecule in CuCl were observed using a tunable dye laser. The Raman and luminescence processes were separated from their different decay times. The ratios of these two processes were estimated for the transverse and longitudinal excitons, respectively, at various band widths of the exciting laser.     

Magnetische Eigenschaften der Lanthanid-Nickel-Verbindungen LnNi5

Zusammenfassung Im Temperaturbereich 4–300° K werden Messungen der magnetischen Suszeptibilität in Abhängigkeit von der Temperatur an sechsLnNi₅-Verbindungen angegeben (Ln=Ce, Pr, Nd, Gd, Ho bzw. Tm). Die paramagnetischen Momente von Gd, Ho und Tm inLnNi₅-Verbindungen stimmen gut mit den für eine Anordnung aus freien dreifach positiven Ionen zu erwartenden Werten überein. TmNi₅ zeigt bei tiefen Temperaturen Tendenz zuVan Vleck-Paramagnetismus. Ferromagnetische Ordnungen treten bei GdNi₅, HoNi₅ und TmNi₅ im Temperaturbereich 22–33° K auf. Die Sättigungsmomente der Ho- und Tm-Verbindungen sind — vermutlich wegen der Kristallfeld-wechselwirkung — kleiner als gJ. Nickel scheint in PrNi₅ und NdNi₅ magnetisch zu sein.

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Magnetic characteristics of lanthanide-nickel (LnNi ₅) compounds

Magnetic susceptibility-temperature measurements are presented for sixLnNi₅ compounds, withLn=Ce, Pr, Nd, Gd, Ho and Tm, for the temperature range 4 to 300° K. Paramagnetic moments of the Gd, Ho and Tm in theLnNi₅ compounds are in good agreement with those expected for an assemblage of free tripositive ions. TmNi₅ exhibits a tendency towardVan Vleck paramagnetism at low temperatures. Ferromagnetic ordering is exhibited by GdNi₅, HoNi₅ and TmNi₅ at temperatures ranging from 22 to 33° K. The saturation moments of the Ho and Tm compounds are less than gJ presumably because of the crystal field interaction. Nickel appears to be magnetic in PrNi₅ and NdNi₅.

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Mit 4 Abbildungen

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Herrn Prof. Dr.H. Nowotny gewidmet

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Diese Arbeit wurde durch eine Stiftung des Army Research Office, Durham, gefördert     

Protection of protein secondary structure by saccharides of different molecular weights during freeze-drying

The protective effects of saccharides with various molecular weights (glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltoheptaose, dextran 1060, dextran 4900, and dextran 10200) against lyophilization-induced structural perturbation of model proteins (BSA, ovalbumin) were studied. Fourier transform infrared (FT-IR) analysis of the proteins in initial solutions and freeze-dried solids indicated that maltose conferred the greatest protection against secondary structure change. The structure-stabilizing effect of maltooligosaccharides decreased in increasing the number of saccharide units. Larger molecules of dextran also showed a smaller structure-stabilizing effect. Increasing the effective saccharide molecular size by a borate-saccharide complexation reduced the protein structure-stabilizing effect of all of the saccharides except glucose. The results indicate that the larger saccharide molecules, and/or the complex formation with borate ion, reduce the free and accessible hydroxyl groups to interact with and stabilize the protein structure by a water-substitution mechanism.     

Total synthesis of the marine alkaloids (-)-lepadins a, b, and c based on stereocontrolled intramolecular acylnitroso-Diels-Alder reaction

The first syntheses of (-)-lepadins A and C, as well as a new synthesis of (-)-lepadin B, have been achieved from commercially available (S)-malic acid. The methodology is based on an intramolecular hetero-Diels--Alder reaction of the acylnitroso compound, affording the bicyclic oxazino lactam with trans selectivity, which was converted to the cis-decahydroquinoline via asymmetric enolate hydroxylation followed by intramolecular aldol cyclization. The total syntheses proceed by employing cis-decahydroquinoline bearing the (E)-iodoalkenyl group as the common key intermediate, which underwent a convergent coupling with the (E)-hexenyl unit via a palladium-catalyzed Suzuki cross-coupling reaction for the elaboration of the octadienyl side chain at the C5 position.     

A New Crystal Form,Polymorphism, and Multi‐Morphology in Biodegradable Poly(3‐hydroxypropionate)

Summary: A new crystal morphology (δ form) of poly(3‐hydroxypropionate) (PHP) is found in cast and melt‐crystallized PHPs with low molecular weight, in which the PHP chains possibly adopt a 2₁ helix rather than the trans conformation found in the β or γ form. The fusion temperature‐ and the crystallization temperature‐dependent polymorphism are responsible for the dual morphologies and the unique growth kinetics of spherulites in the melt‐crystallized PHPs.

a) A dual‐morphology developed at 70 °C in PHP films after melting at 117 °C and b) that formed during cooling at a rate of 1 °C · min⁻¹ from 130 °C.