10,650 research outputs found
Actinomicetos termoalcalófilos del área subtropical de Jujuy, Argentina
El objetivo de este trabajo fue examinar los actinomicetos termoalcalófilos presentes en el área subtropical de Jujuy, Argentina, caracterizada por el cultivo de la caña de azúcar. Se aislaron en medio con novobiocina las especies Laceyella putida, Laceyella sacchari, Thermoactinomyces intermedius, Thermoactinomyces vulgaris y Thermoflavimicrobium dichotomicum a partir de la rizósfera de plantas y de renuevos de caña de azúcar, asà como de suelos de pastura y de monte natural. El pH de los suelos era casi neutro a ligeramente alcalino, excepto en un solo caso en que el suelo estaba acidificado por licor láctico. El número de actinomicetos encontrados sobre los tejidos vivos y en el bagazo recién obtenido o almacenado según el método de Ritter fue pequeño en comparación con el observado sobre las hojas en descomposición. L. sacchari predominó respecto de T. vulgaris. Se aislaron especies termoalcalófilas de Laceyella, Thermoactinomyces, Thermoflavimicrobium, Saccharomonospora, Streptomyces y Thermononospora de los residuos compostados de caña de azúcar utilizando medio sin novobiocina. El aire capturado cerca de pilas de bagazo en compostaje contenÃa esporos de estos organismos.The objective of this study was to examine the alkalithermophilic actinomycete communities in the subtropical environment of Jujuy, Argentina, characterized by sugarcane crops. Laceyella putida, Laceyella sacchari, Thermoactinomyces intermedius, Thermoactinomyces vulgaris and Thermoflavimicrobium dichotomicum were isolated on the media with novobiocin, from sugar cane plants and renewal rhizospheres, and grass and wood soils. Soil pH was almost neutral or lightly alkaline, except for grass soil acidified by lactic liquor. A smaller number of actinomycetes was found on the living plants and bagasse (recently obtained or stored according to the Ritter method) with respect to decomposed leaves on the soil. Thermophilic species of Laceyella, Thermoactinomyces, Thermoflavimicrobium, Saccharomonospora, Streptomyces and Thermononospora were isolated on the media without novobiocin, from composted sugar cane residues. Air captured near composted bagasse piles, contained alkalithermophilic actinomycete spores.Fil: Carrillo, L.. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias; ArgentinaFil: Benitez Ahrendts, Marcelo Rafael. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias; ArgentinaFil: Maldonado, Marcos Javier. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias; Argentin
Quasar-galaxy associations revisited
Gravitational lensing predicts an enhancement of the density of bright,
distant QSOs around foreground galaxies. We measure this QSO-galaxy correlation
w_qg for two complete samples of radio-loud quasars, the southern 1Jy and
Half-Jansky samples. The existence of a positive correlation between z~1
quasars and z~0.15 galaxies is confirmed at a p=99.0% significance level
(>99.9%) if previous measurements on the northern hemisphere are included). A
comparison with the results obtained for incomplete quasar catalogs (e.g. the
Veron-Cetty and Veron compilation) suggests the existence of an `identification
bias', which spuriously increases the estimated amplitude of the quasar-galaxy
correlation for incomplete samples. This effect may explain many of the
surprisingly strong quasar-galaxy associations found in the literature.
Nevertheless, the value of w_qg that we measure in our complete catalogs is
still considerably higher than the predictions from weak lensing. We consider
two effects which could help to explain this discrepancy: galactic dust
extinction and strong lensing.Comment: 9 pages, 6 figures, MNRAS accepte
Branching rate expansion around annihilating random walks
We present some exact results for branching and annihilating random walks. We
compute the nonuniversal threshold value of the annihilation rate for having a
phase transition in the simplest reaction-diffusion system belonging to the
directed percolation universality class. Also, we show that the accepted
scenario for the appearance of a phase transition in the parity conserving
universality class must be improved. In order to obtain these results we
perform an expansion in the branching rate around pure annihilation, a theory
without branching. This expansion is possible because we manage to solve pure
annihilation exactly in any dimension.Comment: 5 pages, 5 figure
R-Band Imaging of Fields Around 1<z<2 Radiogalaxies
We have taken deep -band images of fields around five radiogalaxies:
0956+47, 1217+36, 3C256, 3C324 and 3C294 with . 0956+47 is found to
show a double nucleus. Our data on 1217+36 suggest the revision of its
classification as a radiogalaxy. We found a statistically significant excess of
bright () galaxies on scales of 2 arcmin around the radiogalaxies
(which have ) in our sample. The excess has been determined
empirically to be at level. It is remarkable that this excess
is not present for galaxies within the same area, suggesting that
the excess is not physically associated to the galaxies but due to intervening
groups and then related to gravitational lensing.Comment: 20 pages, uuencoded compressed PostScript including tables. Figures
available upon request. To appear in the March 1995 issue of The Astronomical
Journa
An Unusual Hydrogen Migration/C−H Activation Reaction with Group 3 Metals
A novel hydrogen migration from the phenyl ring to the pyridine ring of an yttrium pyridyl complex supported by a 1,1′-ferrocene diamide ligand is reported. Density functional theory calculations were instrumental in probing the mechanism for this transformation
Criticality in the collapse of spherically symmetric massless scalar fields in semi-classical loop quantum gravity
In a recent paper we showed that the collapse to a black hole in
one-parameter families of initial data for massless, minimally coupled scalar
fields in spherically symmetric semi-classical loop quantum gravity exhibited a
universal mass scaling similar to the one in classical general relativity. In
particular, no evidence of a mass gap appeared as had been suggested by
previous studies. The lack of a mass gap indicated the possible existence of a
self-similar critical solution as in general relativity. Here we provide
further evidence for its existence. Using an adaptive mesh refinement code, we
show that "echoes" arise as a result of the discrete self-similarity in
space-time. We also show the existence of "wiggles" in the mass scaling
relation, as in the classical theory. The results from the semi-classical
theory agree well with those of classical general relativity unless one takes
unrealistically large values for the polymerization parameter.Comment: 7 pages, RevTe
Reaction of Group III Biheterocyclic Complexes
Group III alkyl complexes supported by a ferrocene diamide ligand (1,1′-fc(NSitBuMe_2)_2) have been found to be reactive toward aromatic N-heterocycles such as 1-methylimidazole and pyridines. These reactions were investigated experimentally and computationally. An initial C−H activation event is followed by a coupling reaction to form biheterocyclic complexes, in which one of the rings is dearomatized. In the case of 1-methylimidazole, the biheterocyclic compound could not be isolated and further led to an imidazole ring-opened product; in the case of pyridines, it transformed into an isomer with extended conjugation of double bonds. Mechanisms for both reactions are proposed on the basis of experimental and computational results. DFT calculations were also used to show that an energetically accessible pathway for the ring-opening of pyridines exists
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