1,349 research outputs found
Naphthoquinone derivatives and lignans from the Paraguayan crude drug
Schmeda-Hirschmann,G. Laboratorio de Quımica de Productos Naturales,Instituto de Quımica de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.The Paraguayan crude drug âtayıš pytaÂŽâ is used to treat cancer, wounds and inflammation.
It consist of the bark and trunkwood of Tabebuia heptaphylla (Bignoniaceae). A phytochemical
study of the crude drug gave, in addition to previously described naphthoquinones and
the known lignans cycloolivil and secoisolariciresinol, three new lapachenol (lapachonone)-,
two naphthofuran-, a chromone and a naphthalene derivative. The structures were elucidated
by means of high field NMR spectroscopy. The biological activity of the main compound
lapachol and the related α-lapachone as well as the lignans cycloolivil and secoisolariciresinol
can explain, at least in part, the effect atributed to the crude drug in Paraguayan folk medicine
Talking Democracy at the United Nations. Power, Regime Type, and the Democratization of International Rule
Institutions, Decisions and Collective Behaviou
To be or not to be? Lebensdynamiken internationaler Organisationen im Spannungsfeld von internationaler AutoritÀt und nationalstaatlicher SouverÀnitÀt
Die Forschung zu internationalen Organisationen (IOs), die sich bisher ĂŒberwieâgend mit der Entstehung und dem Design von IOs beschĂ€ftigte, steht aufgrund desBrexits und der AnkĂŒndigung verschiedener Staaten aus dem Internationalen Strafâgerichtshof auszutreten vor neuen Herausforderungen. Austritte von Mitgliedsstaaâten sind nur eine Form von staatlichem Handeln, das die AutoritĂ€t von IOs beeinâtrĂ€chtigt. Dieser Beitrag argumentiert, dass neben Austritten auch BudgetkĂŒrzunâgen, Personalblockaden, MandatsbeschrĂ€nkungen und die Verletzung zentralerNormen IOs unter Druck setzen. Die zentrale Frage hierbei ist, wie IOs selbst mitdiesen Herausforderungen umgehen. Basierend auf Theorien der Multilateralisâmus- und der Organisationsforschung analysiert dieser Beitrag Nicht-Reaktion,Vermeiden von Aufmerksamkeit, Anpassung und Resilienz-Bildung. Diese Herausâforderungen und Reaktionen werden anhand des historischen Beispiels des Völkerâbundes illustriert. AbschlieĂend werden mögliche Annahmen hinsichtlich des instiâtutionellen Designs von IOs, der Art der Herausforderung, des Status des herausâfordernden Staates und der Positionen der ĂŒbrigen Mitgliedsstaaten diskutiert, umdie Varianz in den Reaktionen von IOs zu erklĂ€ren. Institutions, Decisions and Collective Behaviou
Enno BĂŒnz (Hrsg.), Geschichte der Stadt Leipzig. Bd. 1: Von den AnfĂ€ngen bis zur Reformation. Unter Mitw. v. Uwe John. Leipzig, Leipziger UniversitĂ€tsverlag 2015
Biotransformations of imbricatolic acid by Aspergillus niger and Rhizopus nigricans cultures
Guillermo Schmeda-Hirschmann and Carlos Aranda
Laboratorio de QuĂmica de Productos Naturales, Instituto de QuĂmica de Recursos Naturales,
Universidad de Talca, Casilla 747, Talca, Chile.
Jaime A. RodrĂguez and Cristina Theoduloz. Depto. de Ciencias BĂĄsicas BiomĂ©dicas, Facultad de Ciencias de la Salud, Universidad de Talca,
Casilla 747, Talca, ChileMicrobial transformation of imbricatolic acid (1) by Aspergillus niger afforded
1α-hydroxyimbricatolic acid (2), while transformation with Rhizopus nigricans yielded 15-
hydroxy-8,17-epoxylabdan-19-oic acid (3). When the diterpene 1 was added to a
Cunninghamella echinulata culture, the main products were the microbial metabolites
mycophenolic acid (4) and its 3-hydroxy derivative 5. All the structures were elucidated by
spectroscopic methods. The cytotoxicity of these compounds towards human lung
fibroblasts and AGS cells was assessed. While 4 and 5 showed low cytotoxicity, with IC50
values > 1000 ΌM against AGS cells and fibroblasts, 1α-hydroxyimbricatolic acid (2)
presented moderate toxicity towards these targets, with IC50 values of 307 and 631 ÎŒM,
respectively. The structure of 2 is presented for the first time
The cosmic growth of the active black hole population at 1<z<2 in zCOSMOS, VVDS and SDSS
We present a census of the active black hole population at 1<z<2, by
constructing the bivariate distribution function of black hole mass and
Eddington ratio, employing a maximum likelihood fitting technique. The study of
the active black hole mass function (BHMF) and the Eddington ratio distribution
function (ERDF) allows us to clearly disentangle the active galactic nuclei
(AGN) downsizing phenomenon, present in the AGN luminosity function, into its
physical processes of black hole mass downsizing and accretion rate evolution.
We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS
and SDSS), that cover a wide range of 3 dex in luminosity over our redshift
interval of interest. We investigate the cosmic evolution of the AGN population
as a function of AGN luminosity, black hole mass and accretion rate. Compared
to z = 0, we find a distinct change in the shape of the BHMF and the ERDF,
consistent with downsizing in black hole mass. The active fraction or duty
cycle of type-1 AGN at z~1.5 is almost flat as a function of black hole mass,
while it shows a strong decrease with increasing mass at z=0. We are witnessing
a phase of intense black hole growth, which is largely driven by the onset of
AGN activity in massive black holes towards z=2. We finally compare our results
to numerical simulations and semi-empirical models and while we find reasonable
agreement over certain parameter ranges, we highlight the need to refine these
models in order to match our observations.Comment: 31 pages, 28 figures, accepted for publication in MNRA
Rotating magnetic solution in three dimensional Einstein gravity
We obtain the magnetic counterpart of the BTZ solution, i.e., the rotating
spacetime of a point source generating a magnetic field in three dimensional
Einstein gravity with a negative cosmological constant. The static
(non-rotating) magnetic solution was found by Clement, by Hirschmann and Welch
and by Cataldo and Salgado. This paper is an extension of their work in order
to include (i) angular momentum, (ii) the definition of conserved quantities
(this is possible since spacetime is asymptotically anti-de Sitter), (iii)
upper bounds for the conserved quantities themselves, and (iv) a new
interpretation for the magnetic field source. We show that both the static and
rotating magnetic solutions have negative mass and that there is an upper bound
for the intensity of the magnetic field source and for the value of the angular
momentum. The magnetic field source can be interpreted not as a vortex but as
being composed by a system of two symmetric and superposed electric charges,
one of the electric charges is at rest and the other is spinning. The rotating
magnetic solution reduces to the rotating uncharged BTZ solution when the
magnetic field source vanishes.Comment: Latex (uses JHEP3.cls), 12 pages. Published versio
Critical behavior of gravitating sphalerons
We examine the gravitational collapse of sphaleron type configurations in
Einstein--Yang--Mills--Higgs theory. Working in spherical symmetry, we
investigate the critical behavior in this model. We provide evidence that for
various initial configurations, there can be three different critical
transitions between possible endstates with different critical solutions
sitting on the threshold between these outcomes. In addition, we show that
within the dispersive and black hole regimes, there are new possible endstates,
namely a stable, regular sphaleron and a stable, hairy black hole.Comment: Latex, 14 pages, 8 figure
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Earthâs carbon deficit caused by early loss through irreversible sublimation
Carbon is an essential element for life, but its behavior during Earthâs accretion is not well understood. Carbonaceous grains in meteoritic and cometary materials suggest that irreversible sublimation, and not condensation, governs carbon acquisition by terrestrial worlds. Through astronomical observations and modeling, we show that the sublimation front of carbon carriers in the solar nebula, or the soot line, moved inward quickly so that carbon-rich ingredients would be available for accretion at 1 astronomical unit after the first million years. On the other hand, geological constraints firmly establish a severe carbon deficit in Earth, requiring the destruction of inherited carbonaceous organics in the majority of its building blocks. The carbon-poor nature of Earth thus implies carbon loss in its precursor material through sublimation within the first million years
Electric multipole plasmons in deformed sodium clusters
The random-phase-approximation (RPA) method with separable residual forces
(SRPA) is proposed for the description of multipole electric oscillations of
valence electrons in deformed alkali metal clusters. Both the deformed mean
field and residual interaction are derived self-consistently from the Kohn-Sham
functional. SRPA drastically simplifies the computational effort which is
urgent if not decisive for deformed systems. The method is applied to the
description of dipole, quadrupole and octupole plasmons in deformed sodium
clusters of a moderate size. We demonstrate that, in clusters with the size
N>50, Landau damping successfully competes with deformation splitting and even
becomes decisive in forming the width and gross structure of the dipole
plasmon. Besides, the plasmon is generated by excitations from both ground
state and shape isomers. In such clusters familiar experimental estimates for
deformation splitting of dipole plasmon are useless.Comment: 27 pages, 10 figure
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