1,241 research outputs found
Biopesticide activity from drimanic compounds to control tomato pathogens
Indexación: Scopus.Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 μg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 μg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens. © 2018 by the authors.https://www.mdpi.com/1420-3049/23/8/205
Asymptotics and zeros of Sobolev orthogonal polynomials on unbounded supports
In this paper we present a survey about analytic properties of polynomials
orthogonal with respect to a weighted Sobolev inner product such that the
vector of measures has an unbounded support. In particular, we are focused in
the study of the asymptotic behaviour of such polynomials as well as in the
distribution of their zeros. Some open problems as well as some new directions
for a future research are formulated.Comment: Changed content; 34 pages, 41 reference
A revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars
We present DECam imaging combined with Gaia DR2 data to study the Canis Major
overdensity. The presence of the so-called Blue Plume stars in a low-pollution
area of the color-magnitude diagram allows us to derive the distance and proper
motions of this stellar feature along the line of sight of its hypothetical
core. The stellar overdensity extends on a large area of the sky at low
Galactic latitudes, below the plane, and between 230. According to the orbit derived for Canis Major, it presents an
on-plane rotation around the Milky Way. Moreover, additional overdensities of
Blue Plume stars are found around the plane and across the Galaxy, proving that
these objects are not only associated with that structure. The spatial
distribution of these stars, derived using Gaia astrometric data, confirms that
the detection of the Canis Major overdensity results more from the warped
structure of the Milky Way disk than from the accretion of a dwarf galaxy.Comment: 11 pages, 9 figures, accepted for publication in MNRA
The evolution of Balmer jump selected galaxies in the ALHAMBRA survey
We present a new color-selection technique, based on the Bruzual & Charlot
models convolved with the bands of the ALHAMBRA survey, and the redshifted
position of the Balmer jump to select star-forming galaxies in the redshift
range 0.5 < z < 1.5. These galaxies are dubbed Balmer jump Galaxies BJGs. We
apply the iSEDfit Bayesian approach to fit each detailed SED and determine
star-formation rate (SFR), stellar mass, age and absolute magnitudes. The mass
of the haloes where these samples reside are found via a clustering analysis.
Five volume-limited BJG sub-samples with different mean redshifts are found to
reside in haloes of median masses slightly
increasing toward z=0.5. This increment is similar to numerical simulations
results which suggests that we are tracing the evolution of an evolving
population of haloes as they grow to reach a mass of at z=0.5. The likely progenitors of our samples at z3 are Lyman
Break Galaxies, which at z2 would evolve into star-forming BzK galaxies,
and their descendants in the local Universe are elliptical galaxies.Hence, this
allows us to follow the putative evolution of the SFR, stellar mass and age of
these galaxies. From z1.0 to z0.5, the stellar mass of the volume
limited BJG samples nearly does not change with redshift, suggesting that major
mergers play a minor role on the evolution of these galaxies. The SFR evolution
accounts for the small variations of stellar mass, suggesting that star
formation and possible minor mergers are the main channels of mass assembly.Comment: 14 pages, 10 figures. Submitted to A&A. It includes first referee's
comments. Abstract abridged due to arXiv requirement
Near-Earth asteroids spectroscopic survey at Isaac Newton Telescope
The population of near-Earth asteroids (NEAs) shows a large variety of
objects in terms of physical and dynamical properties. They are subject to
planetary encounters and to strong solar wind and radiation effects. Their
study is also motivated by practical reasons regarding space exploration and
long-term probability of impact with the Earth. We aim to spectrally
characterize a significant sample of NEAs with sizes in the range of 0.25
- 5.5 km (categorized as large), and search for connections between their
spectral types and the orbital parameters. Optical spectra of NEAs were
obtained using the Isaac Newton Telescope (INT) equipped with the IDS
spectrograph. These observations are analyzed using taxonomic classification
and by comparison with laboratory spectra of meteorites. A total number of 76
NEAs were observed. We classified 44 of them as Q/S-complex, 16 as B/C-complex,
eight as V-types, and another eight belong to the remaining taxonomic classes.
Our sample contains 27 asteroids categorized as potentially hazardous and 31
possible targets for space missions including (459872) 2014 EK24, (436724) 2011
UW158, and (67367) 2000 LY27. The spectral data corresponding to (276049) 2002
CE26 and (385186) 1994 AW1 shows the 0.7 m feature which indicates the
presence of hydrated minerals on their surface. We report that Q-types have the
lowest perihelia (a median value and absolute deviation of AU)
and are systematically larger than the S-type asteroids observed in our sample.
We explain these observational evidences by thermal fatigue fragmentation as
the main process for the rejuvenation of NEA surfaces. In general terms, the
taxonomic distribution of our sample is similar to the previous studies and
matches the broad groups of the inner main belt asteroids. Nevertheless, we
found a wide diversity of spectra compared to the standard taxonomic types.Comment: Accepted in Astronomy & Astrophysics (A&A
Cova de les Malladetes (Valencia, Spain). New insights about the Early Upper Palaeolithic in the Mediterranean Basin of the Iberian Peninsula
New excavations carried out at Cova de les Malladetes confirm and improve previous information on the archaeological sequence of this site. A total of 29 new dates allow to specify the chronology of the Aurignacian (levels XIVA-XII) and Gravettian (levels XI-VII). Furthermore, concerning the results obtained during the 1970 excavation, three new levels were identified: level XIVB, which represents a short temporal human occupation hiatus, and levels XV and XVI with some hearths and anthropic evidence, although the lithic material does not permit a cultural attribution. This paper presents data obtained from the analysis of archaeobotanical, micro and macrofaunal assemblages and lithic and osseous industry. Results are relevant concerning the paleoclimatic and paleoenvironmental characterisation of the Early Upper Palaeolithic, as well as for assessing the human occupation patterns during the Gravettian and Aurignacian. Moreover, we evaluate the chronological implications of the basal levels (XIVB, XV and XVI), drawing attention to the absence of an important temporal gap between this phase and the start of the Early Upper Palaeolithic at the site. Finally, our new data extend the information provided by other sites in the Spanish Mediterranean region, allowing a more defined characterisation of the Early Upper Palaeolithic, especially regarding the Evolved Aurignacian chronology and its techno-typological structure, with the presence of Roc-de-Combe subtype Dufour bladelets
Lorentz violating electrodynamics
After summarizing the most interesting results in the calculation of
synchrotron radiation in the Myers-Pospelov effective model for Lorentz
invariance violating (LIV) electrodynamics, we present a general unified way of
describing the radiation regime of LIV electrodynamics which include the
following three different models : Gambini-Pullin, Ellis et al. and
Myers-Pospelov. Such unification reduces to the standard approach of radiation
in a dispersive and absortive (in general) medium with a given index of
refraction. The formulation is presented up to second order in the LIV
parameter and it is explicitly applied to the synchrotron radiation case.Comment: 11 pages, extended version of the talk given by L.F. Urrutia in the
VI Mexican School: Approaches to Quantum Gravity, Playa del Carmen, Mexico,
Nov. 2004. Minor chages in the text and added reference
Stellar populations of galaxies in the ALHAMBRA survey up to . II. Stellar content of quiescent galaxies within the dust-corrected stellar masscolour and the colourcolour diagrams
Our aim is to determine the distribution of stellar population parameters
(extinction, age, metallicity, and star formation rate) of quiescent galaxies
within the rest-frame stellar masscolour and colourcolour diagrams
corrected for extinction up to . These novel diagrams reduce the
contamination in samples of quiescent galaxies owing to dust-reddened galaxies,
and they provide useful constraints on stellar population parameters. We set
constraints on the stellar population parameters of quiescent galaxies
combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code
MUFFIT, making use of composite stellar population models. The extinction
obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from
the sample of red galaxies. The distributions of stellar population
parameters across these rest-frame diagrams are revealed after the dust
correction and are fitted by the LOESS method to reduce uncertainty effects.
Quiescent galaxy samples defined via classical diagrams are typically
contaminated by a % fraction of DSF galaxies. A significant part of the
galaxies in the green valley are actually obscured star-forming galaxies
(%). Consequently, the transition of galaxies from the blue cloud to
the red sequence, and hence the related mechanisms for quenching, seems to be
much more efficient and faster than previously reported. The rest-frame stellar
masscolour and colourcolour diagrams are useful for constraining
the age, metallicity, extinction, and star formation rate of quiescent galaxies
by only their redshift, rest-frame colours, and/or stellar mass. Dust
correction plays an important role in understanding how quiescent galaxies are
distributed in these diagrams and is key to performing a pure selection of
quiescent galaxies via intrinsic colours.Comment: (37 pages, 29 figures, accepted for publication in A&A
Efectos de los estrógenos como contaminantes emergentes en la salud y el ambiente
Los contaminantes emergentes son sustancias que tienen el potencial de dañar al ser humano, flora y fauna, y no están regulados por la legislación. Los estrógenos son parte de esta definición, es decir, contaminantes emergentes, que cuando incrementan su concentración en el ser humano o el ambiente causan daño. Los seres humanos están expuestos a concentraciones altas de estrógenos debido a su uso como parte de terapias de reemplazo hormonal o métodos anticonceptivos. Flora y fauna están expuestas a los estrógenos cuando se incorporan al ambiente por descargas de agua residual municipal, efluentes de plantas de tratamiento o por escurrimientos con desechos de la ganadería y otras actividades pecuarias. En este trabajo se presenta una revisión del estado del conocimiento sobre los efectos de los estrógenos en los seres humanos y la vida silvestre. Asimismo, se identifican el origen antropogénico, presencia y características de los estrógenos en el ambiente. Por último, se señalan algunos procesos de tratamiento para reducir o eliminar los estrógenos del agua
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