1,273 research outputs found
Strong Two--Body Decays of Light Mesons
In this paper, we present results on strong two-body decay widths of light
mesons calculated in a covariant quark model. The model is based on
the Bethe-Salpeter equation in its instantaneous approximation and has already
been used for computing the complete meson mass spectrum and many electroweak
decay observables. Our approach relies on the use of a phenomenological
confinement potential with an appropriate spinorial Dirac structure and 't
Hooft's instanton--induced interaction as a residual force for pseudoscalar and
scalar mesons. The transition matrix element for the decay of one initial meson
into two final mesons is evaluated in lowest order by considering conventional
decays via quark loops as well as Zweig rule violating instanton--induced
decays generated by the six--quark vertex of 't Hooft's interaction; the latter
mechanism only contributes if all mesons in the decay have zero total angular
momentum. We show that the interference of both decay mechanisms plays an
important role in the description of the partial widths of scalar and
pseudoscalar mesons.Comment: 35 pages, 7 figure
Synthesis, characterization and antifungal assessment of optically active bis-organotin compounds derived from (S)-BINOL diesters
Background: Organotin(IV) derivatives have appeared recently as potential biologically active metallopharmaceuticals exhibiting a variety of therapeutic activities. Hence, it is important to study the synthesis of new organotin compounds with low toxicity that may be of pharmacological interest.Objectives:This study focuses on the synthesis of new bis-stannylated derivatives with C2 symmetry that could be tested as antifungal agents against two clinical important fungal species, Cryptococcus neoformans and Candida albicans.Methods:The radical addition of triorganotin hydrides (R3SnH) and diorganotin chlorohydrides (R2ClSnH) to bis-α,β-unsaturated diesters derived from (S)-BINOL led to the corresponding new bis-stannylated derivatives with C2 symmetry. Nine pure organotin compounds were synthesized with defined stereochemistry. Four of them were enantiomerically pure and four were diastereoisomeric mixtures.Results:All new organotin compounds were fully characterized, those with phenyl ligands bonded to tin were the most active compounds against both the strains (Cryptococcus neoformans and Candida albicans), with activity parameters of IC50 close to those of the reference drug (amphotericin B).Conclusion:Nine pure organotin compounds with C2 symmetry were synthesized with defined stereochemistry and their antifungal properties were tested against two clinical important fungi with IC values close to those of the reference drug. The structure-containing preferably two or three phenyl groups joined to the tin atom were highly active against both the strains compared with those possessing tri-n-butyl groups.Fil: Costantino, Andrea Rosana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto de QuĂmica del Sur. Universidad Nacional del Sur. Departamento de QuĂmica. Instituto de QuĂmica del Sur; ArgentinaFil: Neudörfl, Jörg M.. Universitat zu Köln; Alemania. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas; ArgentinaFil: Ocampo, Romina Andrea. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto de QuĂmica del Sur. Universidad Nacional del Sur. Departamento de QuĂmica. Instituto de QuĂmica del Sur; ArgentinaFil: Svetaz, Laura Andrea. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas; ArgentinaFil: Zacchino, Susana Alicia Stella. Universitat zu Köln; AlemaniaFil: Koll, Liliana Cristina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto de QuĂmica del Sur. Universidad Nacional del Sur. Departamento de QuĂmica. Instituto de QuĂmica del Sur; ArgentinaFil: Mandolesi, Sandra Delia. Universidad Nacional del Sur; Argentin
Dual character of the electronic structure in YBa2Cu4O8: conduction bands of CuO2 planes and CuO chains
We use microprobe Angle-Resolved Photoemission Spectroscopy (muARPES) to
separately investigate the electronic properties of CuO2 planes and CuO chains
in the high temperature superconductor, YBa2Cu4O8. In the CuO2 planes, a two
dimensional (2D) electronic structure with nearly momentum independent bilayer
splitting is observed. The splitting energy is 150 meV at (pi,0), almost 50%
larger than in Bi2Sr2CaCu2O(8+d) and the electron scattering at the Fermi level
in the bonding band is about 1.5 times stronger than in the antibonding band.
The CuO chains have a quasi one dimensional (1D) electronic structure. We
observe two 1D bands separated by ~ 550meV: a conducting band and an insulating
band with an energy gap of ~ 240meV. We find that the conduction electrons are
well confined within the planes and chains with a non-trivial hybridization.Comment: 4 pages, 4 figure
Wärmespeicherkraftwerke - Ein Lösungsansatz für das Residuallastproblem im Stromsektor
Der Ausbau variabler erneuerbarer Stromquellen wie der Windkraft und der Photovoltaik fĂĽhrt im Zuge der Energiewende
zu dem Phänomen der ähnlich variablen Residuallast für thermische Kraftwerke, deren Auslastung und Wirtschaftlichkeit
infolge stetig sinkt. Dabei besteht der Anspruch, auch die Residuallast langfristig mit erneuerbarer Energie zu decken.
Gleichzeitig kann die sicher abrufbare Leistung konventioneller thermischer Kraftwerke nicht einfach aufgegeben werden.
Im vorliegenden Beitrag wird ein neues Geschäftsmodell für thermische Kraftwerke zur Diskussion gestellt, das diesen gordischen Knoten möglicherweise lösen kann
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