762 research outputs found
Biolog?a comparada de poblaciones colombianas de Anastrepha fraterculus y Anastrepha obliqua
57 p. Recurso Electr?nicoLa fruticultura es un rengl?n importante de la agricultura en Colombia, su
comercializaci?n se ve limitado por barreras fitosanitarias a nivel internacional, debido a
plagas cuarentenarias. Anastrepha obliqua y A. fraterculus son dos de las especies
cuarentenarias m?s importantes debido a que afecta la producci?n de cultivos frutales
como el mango y la guayaba. La informaci?n sobre aspectos b?sicos de bioecolog?a de
estas especies es pr?cticamente inexistente en Colombia. El objetivo del presente trabajo
fue obtener informaci?n sobre la biolog?a b?sica de A. obliqua y A. fraterculus que sirva
como base para el desarrollo y mejoramiento de estrategias para su control. Se
desarrollaron tablas de vida a partir de dos poblaciones por cada especie, colectadas en
diferentes regiones del pa?s, mantenidas en el Laboratorio de Entomolog?a de la
Universidad del Tolima. Se determinaron los ciclos de vida en laboratorio, se calcularon
?ndices poblacionales como mortalidad espec?fica y tasa neta de aumento. El an?lisis
demostr? que las poblaciones de A. fraterculus presentan diferencias significativas en
los estados huevo, larva I, larva III y pupa; en las poblaciones de A. obliqua se presentan
diferencias entre los estados huevo, larva I y pupa. A nivel interespec?fico las especies
no presentan diferencias significativas en la duraci?n de su ciclo. La poblaci?n con mayor
R0 y Rm es Zarzal 35,0458 y 0,064136, respectivamente. La poblaci?n con el R0 y Rm
m?s bajos fue Sibundoy, 9,6106 y 0,043471. Estos resultados sirven como base para
futuras investigaciones con el fin de mejorar las estrategias de control de estas especies.
Palabras clave: tabla de vida, par?metros demogr?ficos, moscas de la fruta.Colombian fruit production is an important economic sector in the agriculture; however,
its marketing is limited by phytosanitary barriers at the international level, due to
quarantine pests. Anastrepha obliqua and A. fraterculus are two of the most important
quarantine species because it affects the production of fruit crops such as mango and
guava. The knowledge on the basic bioecology of these species is incipient in Colombia.
The objective of this work was to obtain information about the basic biology of A. obliqua
and A. fraterculus? this information could offer information for the development and
improvement of management strategies. Life tables were obtained from two populations
for each species, collected in different regions of the country and reared in the
Entomology Laboratory of the University of Tolima. The life cycles in laboratory were
studied, population data like specific mortality and net rate of increase were calculated.
The populations of A. fraterculus presented significant differences between egg, larval I,
larval III and pupal stages; whereas in the populations of A. obliqua there were differences
between egg, larval I and pupal stages. At an interspecific level, species do not show a
greater difference in the duration of their cycle. The population with the highest R0 and
Rm was Zarzal 35.0458 and 0.064136, respectively. The population with the lowest R0
and Rm was Sibundoy, 9.6106 and 0.043471. These results serve as a basis for future
research in order to improve control strategies for these species.
Key words: life table, demographic parameters, fruit flies
The effects of a background potential in star cluster evolution: a delay in the relaxation time-scale and runaway collision processes
Runaway stellar collisions in dense star clusters are invoked to explain the
presence of very massive stars or blue stragglers in the center of those
systems. This process has also been explored for the first star clusters in the
Universe and shown to yield stars that may collapse at some points into an
intermediate mass black hole. Although the early evolution of star clusters
requires the explicit modeling of the gas out of which the stars form, these
calculations would be extremely time-consuming and often the effects of the gas
can be accurately treated by including a background potential to account for
the extra gravitational force. We apply this approximation to model the early
evolution of the first dense star clusters formed in the Universe by performing
-body simulations, our goal is to understand how the additional
gravitational force affects the growth of a very massive star through stellar
mergers in the central parts of the star cluster. Our results show that the
background potential increases the velocities of the stars, causing an overall
delay in the evolution of the clusters and in the runaway growth of a massive
star at the center. The population of binary stars is lower due to the
increased kinetic energy of the stars, initially reducing the number of stellar
collisions, and we show that relaxation processes are also affected. Despite
these effects, the external potential enhances the mass of the merger product
by a factor 2 if the collisions are maintained for long times.Comment: 16 pages. Accepted for publication in Astronomy and Astrophysic
Weather radar for urban hydrological applications: lessons learnt and research needs identified from 4 pilot catchments in North-West Europe
International audienceThis study investigates the impact of rainfall estimates of different spatial resolutions on the hydraulic outputs of the models of four of the EU RainGain project’s pilot locations (the Cranbrook catchment (UK), the Herent catchment (Belgium), the Morée-Sausset catchment (France) and the Kralingen District (The Netherlands)). Two storm events, one convective and one stratiform, measured by a polarimetric X-band radar located in Cabauw (The Netherlands) were selected for analysis. The original radar estimates, at 100 m and 1 min resolutions, were aggregated to a spatial resolution of 1000 m. These estimates were then applied to the high-resolution semi-distributed hydraulic models of the four urban catchments, all of which have similar size (between 5 and 8 km2), but different morphological, hydrological and hydraulic characteristics. When doing so, methodologies for standardising rainfall inputs and making results comparable were implemented. The response of the different catchments to rainfall inputs of varying spatial resolution is analysed in the light of model configuration, catchment and storm characteristics. Rather surprisingly, the results show that for the two events under consideration the spatial resolution (i.e. 100 m vs 1000 m) of rainfall inputs does not have a significant influence on the outputs of urban drainage models. The present study will soon be extended to more storms as well as model structures and resolutions, with the final aim of identifying critical spatial-temporal resolutions for urban catchment modelling in relation to catchment and storm event characteristics
The physical origin of super-competitive accretion during the formation of the first supermassive black holes
Numerical simulations have shown the occurence of a scenario termed
''super-competitive accretion'', a term that describes a situation where only
the central few objects grow supermassive while a larger number of stars
compete for the reservoir, with significant accretion flows of
M yr. This scenario particularly implies that the presence of
fragmentation will not necessarily impeed the formation of a central massive
object. We here explore this phenomenon using analytical estimates for growth
via collisions and accretion, considering accretion due to self-gravity as well
as Bondi-Hoyle accretion. Particularly, we explore under what conditions the
accretion onto the central massive object breaks down, and derive a criterion
that depends on the mass of the most massive object and the mass in fragments.
For compact clusters with sizes about ~pc, we further find that the mass
growth by collisions is comparable to the growth via accretion. Our results are
validated through the comparison with numerical simulations, and we overall
conclude that super-competitive accretion is a valid mechanism for the
formation of very massive objects in the early Universe.Comment: 9 pages, 5 figures. Accepted for publication in MNRA
Evaluación de diferentes técnicas de análisis estadÃstico para su aplicación a la prospección de yacimientos minerales : Centro de aplicación: Area de Campana Mahuida
Fil: Reinoso, Margarita S.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
A comparative evaluation of interest point detectors and local descriptors for visual SLAM
Abstract In this paper we compare the behavior of different interest points detectors and descriptors under the
conditions needed to be used as landmarks in vision-based simultaneous localization and mapping (SLAM).
We evaluate the repeatability of the detectors, as well as the invariance and distinctiveness of the descriptors,
under different perceptual conditions using sequences of images representing planar objects as well as 3D scenes.
We believe that this information will be useful when selecting an appropriat
Variability in concentrations of potentially toxic elements in urban parks from six European cities
Use of a harmonised sampling regime has allowed comparison of concentrations of copper, chromium, nickel, lead and zinc in six urban parks located in different European cities differing markedly in their climate and industrial history. Wide concentrations ranges were found for copper, lead and zinc at most sites, but for chromium and nickel a wide range was only seen in the Italian park, where levels were also considerably greater than in other soils. As might be expected, the soils from older cities with a legacy of heavy manufacturing industry (Glasgow, Torino) were richest in potentially toxic elements (PTEs); soils from Ljubljana, Sevilla and Uppsala had intermediate metal contents, and soils from the most recently established park, in the least industrialised city (Aveiro), displayed lowest concentrations. When principal component analysis was applied to the data, associations were revealed between pH and organic carbon content; and between all five PTEs. When pH and organic carbon content were excluded from the PCA, a distinction became clear between copper, lead and zinc (the "urban" metals) on the one hand, and chromium and nickel on the other. Similar results were obtained for the surface (0-10 cm depth) and sub-surface (10-20 cm depth) samples. Comparisons with target or limit concentrations were limited by the existence of different legislation in different countries and the fact that few guidelines deal specifically with public-access urban soils intended for recreational use
Formation of supermassive stars in the first star clusters
The formation of supermassive stars is believed to be an essential
intermediate step for the formation of the massive black hole seeds that become
the supermassive black holes powering the quasars observed in the early
Universe. Numerical simulations have shown that supermassive stars can form in
atomic-cooling halos when protostars reach accretion rates higher than
M yr and fragmentation is suppressed on pc scales.
It is however still uncertain if a supermassive star still emerges when
fragmentation occurs at smaller scales and a cluster of stars is formed
instead. In this work we explore the problem of massive object formation due to
the interplay of collisions and accretion in star clusters at low metallicity.
We model a small embedded cluster of accreting protostars following sub-parsec
scale fragmentation during the collapse of a primordial gas cloud and follow
its evolution by performing -body plus hydrodynamical simulations. Our
results show that supermassive stars with 10 and 10 M are
always formed due to the interplay of collisions and accretion, and in some
cases these objects are part of a binary system. The resulting supermassive
star is surrounded by tens of smaller stars with typical masses in the range
- M.Comment: 16 pages, 20 figures, accepted by MNRA
Investigation of proton damage in III-V semiconductors by optical spectroscopy
We studied the damage produced by 2MeV proton radiation on epitaxially grown InGaP/GaAs structure by means of spatially resolved Raman and photoluminescence (PL) spectroscopy. The irradiation was performed parallel to the sample surface in order to determine the proton penetration range in both compounds. An increase in the intensity of longitudinal optical phonons and a decrease in the luminescence were observed. We associate these changes with the creation of defects in the damaged region, also responsible for the observed change of the carrier concentration in the GaAs layer, determined by the shift of the phonon-plasmon coupled mode frequency. From the spatially resolved profile of the PL and phonon intensities, we obtained the proton range in both materials and we compared them with stopping and range of ions in matter simulations. The comparison between the experimentally obtained proton range and simulations shows a very good agreement for GaAs but a discrepancy of 20% for InGaP. This discrepancy can be explained in terms of limitations of the model to simulate the electronic orbitals and bonding structure of the simulated compound. In order to overcome this limitation, we propose an increase in 40% in the electronic stopping power for InGaP.This work was supported by BEC.AR FUNDACION
YPF-CONICET 2013 (Argentina) and DFG within
Grant No. SFB 787. ARG thanks the Spanish Ministry
of Economy and Competitiveness (MINECO) for its
support through Grant No. SEV-2015-0496 in the framework
of the Spanish Severo Ochoa Centre of Excellence
program.Peer reviewe
Sports grass : behaviour of AZ-1 cultivar of Pennisetum clandestinum Hochst. ex Chiov. (kikuyo). Paraná, Entre RÃos, Argentina
A fines de 2001 se incorporó al mercado
argentino el cultivar AZ-1 de Pennisetum
clandestinum Hochst. ex Chiov. (kikuyo) para
ser utilizado en campos deportivos o con fines
ornamentales. Con el propósito de caracterizar
esta variedad comercial en el departamento
Paraná (provincia de Entre RÃos, Argentina)
se evaluó su comportamiento y aptitud
para césped ornamental y/o deportivo en
condiciones de mantenimiento para césped
de calidad, bajo dos condiciones de drenaje.
Se evaluaron cobertura, color, textura, distancia
de entrenudos, grosor de estolones y perÃodo
de dormición. El ensayo se realizó en
Oro Verde, departamento Paraná, en un suelo
Molisol y consistió en 2 tratamientos: con y
sin drenaje, con 4 repeticiones cada uno. El
tamaño de la parcela fue de 2,5 por 5,0 m. El
diseño experimental utilizado fue parcelas
apareadas y las mediciones se realizaron
desde junio hasta noviembre de 2005. Las
caracterÃsticas climáticas locales son: temperatura
media anual de 18,1°C y un régimen
isohigro de 947,6 mm de precipitación anual.
El cultivar se comportó como apto para césped en las caracterÃsticas y condiciones de
manejo evaluadas, sin diferencias entre los
tratamientos con y sin drenaje. Presentó rápida
implantación, niveles altos de cobertura,
color claro y uniforme, textura media y
estolones gruesos a medianos a través del
tiempo. En invierno no perdió cobertura ni
color. Se caracterizó como un césped no apto
para campos deportivos de alta exigencia,
pero recomendable para clubes de bajo presupuesto
y mantenimiento.At the end of 2001, the AZ-1 cultivar of
Pennisetum clandestinum Hochst. ex Chiov.
(kikuyugrass) was incorporated into the
Argentinean market to be used in sports fields
or for ornamental purposes. In order to
characterize such commercial variety in the
geographic department of Paraná (Entre RÃos,
Argentina), its behavior and aptitude were
assessed as ornamental grass and/or sports
grass both under high quality grass maintenance
conditions and under two drainage
conditions. Cover, colour, texture, internodes
distance, stolon thickness, and dormancy
period were evaluated. The trial was carried
out in Oro Verde, department of Paraná in the
province of Entre RÃos in a Molisol soil and it
consisted of two treatments: with and without
drainage and each treatment being repeated
four times. The plot size was 2.5 x 5.0 m. The
experimental design used was the paired - plot
design and measurements were taken from
June to November 2005. The area weather
conditions are the following: average annual
temperature of 18.1°C and an isohydro
regimen of 947.6 mm of annual rainfall. The
cultivar behaved as suitable for grass under
the evaluated management conditions and
characteristics, not showing differences as
regards the treatments with or without
drainage. It presented quick implantation, high
cover levels, light and uniform colour, medium
texture and thick stolons through time. In winter,
cover and colour kept invariable. It was
characterized as a grass not suitable for sports
fields with high requirements, but advisable for
low budget and maintenance condition clubs.Fil: Galli, MartÃn.Fil: Carponi, MarÃa S..Fil: Reinoso, Patricia D..Fil: Laurencena, MarÃa I..Fil: Butus, Marina.Fil: Scorciapino, Claudia
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