660 research outputs found
Optical and Radio observations of the bright GRB010222 afterglow: evidence for rapid synchrotron cooling?
We report photometric observations of the optical afterglow of GRB010222 in
V,R and I passbands carried out at UPSO, Naini Tal between 22-27 Feb 2001. We
determine CCD Johnson BV and Cousins RI photometric magnitudes for 31 stars in
the field of GRB010222 and use them to calibrate our measurements as well as
other published BVRI photometric magnitudes of GRB010222 afterglow. We
construct the light curve in V,R,I passbands and from a broken power-law fit
determine the decay indices of 0.74+/-0.05 and 1.35+/-0.04 before and after the
break at 0.7 days. Using reported X-ray flux measurements at 0.35 and 9.13 days
after the burst we determine X-ray to opt/IR spectral index of 0.61+/-0.02 and
0.75+/-0.02 on these two days. We also report upper limits to the radio flux
obtained from the RATAN-600 telescope and the GMRT, and millimeter-wave upper
limits obtained from the Plateau de Bure Millimeter interferometer. We argue
that the synchrotron cooling frequency is below the optical band for most of
the observing period. We also estimate an initial jet opening angle of about
2.0n^(1/8) degrees, where n is the number density of the ambient medium.Comment: 16 pages, 4 postscript figures, minor revisions according to
referee's comments, millimeter upper limit added, accepted for publication in
Bulletin of the Astronomical Society of Indi
Integration of Phytochrome and Cryptochrome Signals Determines Plant Growth during Competition for Light.
Plants in dense vegetation perceive their neighbors primarily through changes in light quality. Initially, the ratio between red (R) and far-red (FR) light decreases due to reflection of FR by plant tissue well before shading occurs. Perception of low R:FR by the phytochrome photoreceptors induces the shade avoidance response [1], of which accelerated elongation growth of leaf-bearing organs is an important feature. Low R:FR-induced phytochrome inactivation leads to the accumulation and activation of the transcription factors PHYTOCHROME-INTERACTING FACTORs (PIFs) 4, 5, and 7 and subsequent expression of their growth-mediating targets [2, 3]. When true shading occurs, transmitted light is especially depleted in red and blue (B) wavelengths, due to absorption by chlorophyll [4]. Although the reduction of blue wavelengths alone does not occur in nature, long-term exposure to low B light induces a shade avoidance-like response that is dependent on the cryptochrome photoreceptors and the transcription factors PIF4 and PIF5 [5-7]. We show in Arabidopsis thaliana that low B in combination with low R:FR enhances petiole elongation similar to vegetation shade, providing functional context for a low B response in plant competition. Low B potentiates the low R:FR response through PIF4, PIF5, and PIF7, and it involves increased PIF5 abundance and transcriptional changes. Low B attenuates a low R:FR-induced negative feedback loop through reduced gene expression of negative regulators and reduced HFR1 levels. The enhanced response to combined phytochrome and cryptochrome inactivation shows how multiple light cues can be integrated to fine-tune the plant's response to a changing environment
Acid mine drainage in semi-arid regions: the extent of the problem in the waters of reservoirs in the Iberian Pyrite Belt (SW Spain)
There are many reservoirs in the Iberian Pyrite Belt (IPB), SW Spain, which receive contributions from
watercourses affected by acid mine drainage processes, characterised by low pH values and high
concentrations of heavy metals and sulphates. When they reach the reservoirs, the waters increase
its pH, which will cause most of the metal load carried by the mining channel to precipitate into the
reservoir itself and accumulate on its floor. The silting of reservoirs is an environmental problem
which can affect the loss of storage capacity, their general functioning and aquatic ecosystems. A
study of these is vital to allow both preventative and corrective measures to be established. Climatic
conditions are the most significant external controlling factors in terms of the degree and type of
mining pollution. The study area presents characteristics typical of the semi-arid Mediterranean
climate, with annual precipitation of around 630 mm/year; moderate temperatures with average
annual values of 17.1 W
C and a temperature range of 50 W
C. The aim of this study is to carry out a physical–chemical characterization of the waters where they enter the reservoirs located in the IPB over the course of a hydrological year and to establish possible interdependencies between the various parameters.Financial support for this research was provided by DGCICYT National Plan, project no. CGL2010-21268-C02-01.info:eu-repo/semantics/publishedVersio
A High Signal-to-Noise Ratio Composite Spectrum of Gamma-ray Burst Afterglows
We present a composite spectrum of 60 long duration gamma-ray burst (GRB)
afterglows with redshifts in the range 0.35<z<6.7 observed with low resolution
optical spectra. The composite spectrum covers the wavelength range 700-6600 A
in the rest frame and has a mean signal-to-noise ratio of 150 per 1 A pixel and
reaches a maximum of ~300 in the range 2500-3500 A. Equivalent widths are
measured from metal absorption lines from the Lya line to ~5200 A, and
associated metal and hydrogen lines are identified between the Lyman break and
Lya line. The average transmission within the Lyman forest is consistent with
that found along quasar lines of sight. We find a temporal variation in fine
structure lines when dividing the sample into bursts observed within 2 hours
from their trigger and those observed later. Other lines in the predominantly
neutral gas show variations too, but this is most likely a random effect caused
by weighting of individual strong absorption lines and which mimics a temporal
variation. Bursts characterized with high or low prompt GRB energy release
produce afterglows with similar absorption line strengths, and likewise for
bursts with bright or faint optical afterglows. Bursts defined as dark from
their optical to X-ray spectral index have stronger absorption lines relative
to the optically bright bursts. The composite spectrum has strong CaII and MgII
absorption lines as commonly found in dusty galaxies, however, we find no
evidence for dust or a significant molecular content based on the non-detection
of diffuse interstellar bands. Compared to starburst galaxy spectra, the GRB
composite has much stronger fine structure lines, while metal absorption lines
are weaker.Comment: Accepted for publication in ApJ, 24 page
Uso de cultivos trampa para el control del gusano blanco de la papa.
Papa-Solanum tuberosu
The wideband backend at the MDSCC in Robledo. A new facility for radio astronomy at Q- and K- bands
The antennas of NASA's Madrid Deep Space Communications Complex (MDSCC) in
Robledo de Chavela are available as single-dish radio astronomical facilities
during a significant percentage of their operational time. Current
instrumentation includes two antennas of 70 and 34 m in diameter, equipped with
dual-polarization receivers in K (18 - 26 GHz) and Q (38 - 50 GHz) bands,
respectively. We have developed and built a new wideband backend for the
Robledo antennas, with the objectives (1) to optimize the available time and
enhance the efficiency of radio astronomy in MDSCC; and (2) to tackle new
scientific cases impossible to that were investigated with the old, narrow-band
autocorrelator. The backend consists of an IF processor, a FFT spectrometer
(FFTS), and the software that interfaces and manages the events among the
observing program, antenna control, the IF processor, the FFTS operation, and
data recording. The whole system was end-to-end assembled in August 2011, at
the start of commissioning activities, and the results are reported in this
paper. Frequency tunings and line intensities are stable over hours, even when
using different synthesizers and IF channels; no aliasing effects have been
measured, and the rejection of the image sideband was characterized. The first
setup provides 1.5 GHz of instantaneous bandwidth in a single polarization,
using 8192 channels and a frequency resolution of 212 kHz; upgrades under way
include a second FFTS card, and two high-resolution cores providing 100 MHz and
500 MHz of bandwidth, and 16384 channels. These upgrades will permit
simultaneous observations of the two polarizations with instantaneous
bandwidths from 100 MHz to 3 GHz, and spectral resolutions from 7 to 212 kHz.Comment: 9 pages, 8 figures. Accepted to Astronomy and Astrophysic
DETECCIÓN DE ANTICUERPOS CONTRA Lawsonia intracellularis EN PORCINOS PROVENIENTES DE GRANJAS TECNIFICADAS DEL VALLE DE LIMA Y HUARAL
El presente estudio tuvo como objetivo detectar la presencia de anticuerpos contra Lawsonia intracellularis en cerdos de granjas tecnificadas de los valles de Lima y Huaral. Los anticuerpos fueron detectados mediante la prueba de inmunofluorescencia indirecta en muestras de suero de 197 cerdos de tres edades diferentes. El 38.7% de los sueros analizados resultaron positivos, correspondiendo el 18.9, 44.3 y 45.5% a las granjas ubicadas en las zonas de Huaraz, Cieneguilla y Lurín, respectivamente. La prevalencia registrada en animales destetados, de engorde y en hembras de reemplazo fue de 24.6, 47.6 y 44.7%, respectivamente. La presencia de anticuerpos evidencia la exposición de los cerdos a la bacteria, por lo que se debe reconocer a la Lawsonia intracellularis como un nuevo agente etiológico de diarreas que afecta la industria porcina en el Perú.The aim of the present study was to detect antibodies against Lawsonia intracellularis in pigs from well-managed farms in Lima and Huaral valleys. Antibodies were detected using the indirect immunofluorescence test in 197 serum samples from pigs of three different ages. 38.7% of the samples were positive, corresponding 18.9, 44.3 and 45.5% to farms located in the areas of Huaraz, Cieneguilla and Lurín, respectively. The prevalence recorded in weaned and fattened pigs, and gilts were 24.6, 47.6 y 44.7%, respectively. The presence of antibodies indicates that these pigs have been exposed to the bacteria, so Lawsonia intracellularis should be considered as a new microorganism causing diarrhea and therefore, affecting the pig industry in the countr
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