402 research outputs found
Diagnóstico de producción en ganado lechero en pastoreo de un grupo ganadero de validación y transferencia de tecnología
The regionalization of framing issues for producers Livestock Group of Validation and Technology Transfer (GGAVATT) from San Jose Miahuatlán Veracruz, Mexico, under the current production of native grass prairie with mainly during the months of higher temperature have a poor performance and thus milk production declines which promotes a great use of concentrated feeds which causes an increase in production cost and less use to them. For this purpose we made a diagnosis of current conditions GGAVATT production, yielding information that helps us source and compared to determine precisely what the effect of applying the proposed alternative. We propose an alternative implementation of pastures with improved pastures needed to produce a greater amount of forage per unit area especially in the colder months.La regionalización de la problemática encuadrando a los productores del Grupo Ganadero de Validación y Transferencia de Tecnología (GGAVATT) de San José Miahuatlán Veracruz, México, bajo la actual situación de producción de praderas básicamente con gramas nativas que durante los meses de menor frío tienen un pobre desempeño y por ende la producción de leche se deteriora lo cual promueve una gran utilización de alimentos concentrados lo que provoca un incremento en el costo de producción y una menor utilidad para estos. Para dicho propósito se realizó un diagnóstico de las condiciones actuales de producción del GGAVATT, arrojando información que nos sirve de partida y de comparación para determinar con precisión cuál es el efecto de aplicar la alternativa propuesta. Se plantea como alternativa la implantación de praderas con pastos mejorados que permitan producir una mayor cantidad de forrajes por unidad de superficie sobre todo en los meses de menor temperatura
Fossil Groups Origins III. Characterization of the sample and observational properties of fossil systems
(Abridged) Fossil systems are group- or cluster-sized objects whose
luminosity is dominated by a very massive central galaxy. In the current cold
dark matter scenario, these objects formed hierarchically at an early epoch of
the Universe and then slowly evolved until present day. That is the reason why
they are called {\it fossils}. We started an extensive observational program to
characterize a sample of 34 fossil group candidates spanning a broad range of
physical properties. Deep band images were taken for each candidate and
optical spectroscopic observations were obtained for 1200 galaxies. This
new dataset was completed with SDSS DR7 archival data to obtain robust cluster
membership and global properties of each fossil group candidate. For each
system, we recomputed the magnitude gaps between the two brightest galaxies
() and the first and fourth ranked galaxies ()
within 0.5 . We consider fossil systems those with mag or mag within the errors. We find
that 15 candidates turned out to be fossil systems. Their observational
properties agree with those of non-fossil systems. Both follow the same
correlations, but fossils are always extreme cases. In particular, they host
the brightest central galaxies and the fraction of total galaxy light enclosed
in the central galaxy is larger in fossil than in non-fossil systems. Finally,
we confirm the existence of genuine fossil clusters. Combining our results with
others in the literature, we favor the merging scenario in which fossil systems
formed due to mergers of galaxies. The large magnitude gap is a
consequence of the extreme merger ratio within fossil systems and therefore it
is an evolutionary effect. Moreover, we suggest that at least one candidate in
our sample could represent a transitional fossil stage.Comment: 14 pages, 11 figures, accepted for publication in A&
Metagenomic ene-reductases for the bioreduction of sterically challenging enones
Ene-reductases (ERs) of the Old Yellow Enzyme family catalyse asymmetric reduction of activated alkenes providing chiral products. They have become an important method in the synthetic chemists' toolbox offering a sustainable alternative to metal-catalysed asymmetric reduction. Development of new biocatalytic alkene reduction routes, however needs easy access to novel biocatalysts. A sequence-based functional metagenomic approach was used to identify novel ERs from a drain metagenome. From the ten putative ER enzymes initially identified, eight exhibited activities towards widely accepted mono-cyclic substrates with several of the ERs giving high reaction yields and stereoselectivities. Two highly performing enzymes that displayed excellent co-solvent tolerance were used for the stereoselective reduction of sterically challenging bicyclic enones where the reactions proceeded in high yields, which is unprecedented to date with wild-type ERs. On a preparative enzymatic scale, reductions of Hajos–Parish, Wieland–Miescher derivatives and a tricyclic ketone proceeded with good to excellent yields
The effect of low solubility organic acids on the hygroscopicity of sodium halide aerosols
In order to accurately assess the influence of fatty acids on the
hygroscopic and other physicochemical properties of sea salt aerosols,
hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl,
NaBr and NaI) have been chosen to be investigated in this study. The
hygroscopic properties of sodium halide sub-micrometre particles covered with
organic acids have been examined by Fourier-transform infrared spectroscopy
in an aerosol flow cell. Covered particles were generated by flowing
atomized sodium halide particles (either dry or aqueous) through a heated
oven containing the gaseous acid. The obtained results indicate that gaseous
organic acids easily nucleate onto dry and aqueous sodium halide particles.
On the other hand, scanning electron microscopy (SEM) images indicate that
lauric acid coating on NaCl particles makes them to aggregate in small
clusters. The hygroscopic behaviour of covered sodium halide particles in
deliquescence mode shows different features with the exchange of the halide
ion, whereas the organic surfactant has little effect in NaBr particles,
NaCl and NaI covered particles experience appreciable shifts in their
deliquescence relative humidities, with different trends observed for each
of the acids studied. In efflorescence mode, the overall effect of the
organic covering is to retard the loss of water in the particles. It has
been observed that the presence of gaseous water in heterogeneously
nucleated particles tends to displace the cover of hexanoic acid to
energetically stabilize the system
The Calogero-Moser equation system and the ensemble average in the Gaussian ensembles
From random matrix theory it is known that for special values of the coupling
constant the Calogero-Moser (CM) equation system is nothing but the radial part
of a generalized harmonic oscillator Schroedinger equation. This allows an
immediate construction of the solutions by means of a Rodriguez relation. The
results are easily generalized to arbitrary values of the coupling constant. By
this the CM equations become nearly trivial.
As an application an expansion for in terms of eigenfunctions of
the CM equation system is obtained, where X and Y are matrices taken from one
of the Gaussian ensembles, and the brackets denote an average over the angular
variables.Comment: accepted by J. Phys.
Evidencia de la respuesta a un enterramiento a corto plazo de la fauna macrobentónica asociada a la fanerógama marina del Mediterráneo Cymodocea nodosa
Sedimentation and burial affect a variety of habitats worldwide, especially within coastal marine systems. In the Mediterranean, seagrasses like Cymodocea nodosa are commonly subjected to sedimentation and, although the response of C. nodosa has been documented, few studies have included macrofaunal responses. We used a manipulative field experiment to examine the effects of a single small-scale, pulse burial event on benthic invertebrate macrofauna. Burial did not affect the total abundance, richness, or diversity of higher taxa nor the live abundance or diversity after 5 days. However, live higher taxa richness decreased by day 3. After 5 days, such decrease reversed and partial recovery seemed to occur. Almost 2 months later, three of the buried plots remained with some additional sedimentation, but the other three had lost their sediment. We compared faunal metrics of buried plots between days 5 and 54 and found greater diversity on day 54, providing evidence that macrofaunal recovery apparent 5 days after burial seemed to persist. Although we likely underestimated the effects and can only be conservative with our conclusions, taken together our results suggest small-scale, pulse burial events can have some negative effects on the C. nodosa-associated benthic macrofaunal community, but the community can recover within a few weeks.La sedimentación y el enterramiento afectan a una gran variedad de hábitats en todo el mundo, especialmente en los sistemas costeros marinos. En el Mediterráneo, las fanerógamas marinas como Cymodocea nodosa suelen estar expuestas a la sedimentación y, a pesar de que la respuesta de C. nodosa ha sido documentada previamente, muy pocos estudios hacen referencia a cómo responde la macrofauna. Se ha usado un experimento manipulativo en el campo para examinar los efectos de un enterramiento súbito y puntual a pequeña escala sobre la fauna de invertebrados macrobentónicos. El enterramiento no afectó a la abundancia total, riqueza o diversidad de especies, ni tampoco a la abundancia o diversidad de individuos vivos 5 días después del enterramiento. Sin embargo, la riqueza de taxones vivos disminuyó a partir del día 3. Pasados 5 días, esa disminución revirtió y parece tener lugar una recuperación parcial. Casi 2 meses después, tres de las parcelas enterradas todavía presentaron algún tipo de sedimentación adicional, pero las otras tres habían perdido el sedimento. Se compararon las métricas de la fauna encontrada en los días 5 y 54 en las parcelas enterradas, y se encontró una alta diversidad para el día 54, evidenciando que la aparente recuperación que tuvo lugar 5 días después del enterramiento parece persistir. A pesar de que probablemente hemos subestimado los efectos y debemos ser conservadores con nuestras conclusiones, al examinar los resultados conjuntamente, sugieren que estos eventos repentinos y puntuales de enterramiento a pequeña escala pueden tener efectos negativos sobre la comunidad de fauna macrobentónica asociada a C. nodosa, la cual se recuperaría en unas pocas semanas
Fossil group origins : VII. Galaxy substructures in fossil systems
This work has been partially funded by the MINECO (grant AIA2013-43188-P). M.G. acknowledges financial support from MIUR PRIN2010-2011 (J91J12000450001). Funding for the Sloan Digital Sky Survey (SDSS) and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, and the Max Planck Society, and the Higher Education Funding Council for England.Context. Fossil groups (FG) are expected to be the final product of galaxy merging within galaxy groups. In simulations, they are predicted to assemble their mass at high redshift. This early formation allows for the innermost M galaxies to merge into a massive central galaxy. Then, they are expected to maintain their fossil status because of the few interactions with the large-scale structure. In this context, the magnitude gap between the two brightest galaxies of the system is considered a good indicator of its dynamical status. As a consequence, the systems with the largest gaps should be dynamically relaxed. Aims. In order to examine the dynamical status of these systems, we systematically analyze, for the first time, the presence of galaxy substructures in a sample of 12 spectroscopically-confirmed fossil systems with redshift z 0:25. Methods. We apply a number of tests to investigate the substructure in fossil systems in the two-dimensional space of projected positions out to R200. Moreover, for a subsample of five systems with at least 30 spectroscopically-confirmed members we also analyze the substructure in the velocity and in the three-dimensional velocity-position spaces. Additionally, we look for signs of recent mergers in the regions around the central galaxies. Results. We find that an important fraction of fossil systems show substructure. The fraction depends critically on the adopted test, since each test is more sensitive to a particular type of substructure. Conclusions. Our interpretation of the results is that fossil systems are not, in general, as relaxed as expected from simulations. Our sample of 12 spectroscopically-confirmed fossil systems need to be extended to compute an accurate fraction, but our conclusion is that this fraction is similar to the fraction of substructure detected in nonfossil clusters. This result points out that the magnitude gap alone is not a good indicator of the dynamical status of a system. However, the subsample of five FGs for which we were able to use velocities as a probe for substructures is dominated by high-mass FGs. These massive systems could have a different evolution compared to low-mass FGs, since they are expected to form via the merging of a fossil group with another group of galaxies. This merger would lengthen the relaxation time and it could be responsible for the substructure detected in present-time massive FGs. If this is the case, only low-mass FGs are expected to be dynamically old and relaxed.Publisher PDFPeer reviewe
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