611 research outputs found
Assessment of high speed internet for remote sensing data acquisition and exchange in Colombia and Latin America
New remote sensing platforms and data programs have dramatically increased the availability of satellite image data for analysis of climate, agriculture, environment and society. Particularly important new sensor systems include the USA’s MODIS system, Brazil and China’s CBER platform, and India’s IRS satellite. These and other systems have created considerable benefits to the international community of remote sensing analysts. Today, we have more data with greater options regarding spatial, radiometric and temporal resolution. While having these greater options is a positive development, substantial problems remain in acquiring and managing large data volumes. Data providers and consumers must support significant costs in copying remote sensing data to tapes and disks. Internet transfer of satellite imagery is only possible on broadband networks. Even then, download times can be considerable. Downloads may be interrupted if the Internet connections are unstable. How can we improve the acquisition of large volumes of remote sensing data for environmental analysis? What alternatives are available to remote sensing researchers to acquire near-real time satellite imagery for research use? This paper assesses the potential of high-speed Internet as a medium for transferring large satellite imagery data sets between the United States and Colombia, between Colombia and other Latin American countries and within Colombia. Academic and research networks have led developments in high-speed Internet. Many countries throughout the world are installing the infrastructure needed to develop these networks. In the United States this system is referred to as Internet 2. Latin American countries are developing a system called RedCLARA (Cooperación Latinoamerican
The relationship between indoor and outdoor levels of PM10 and its chemical composition at schools in a coastal region in Spain
PM10 levels and its chemical composition were studied inside and outdoor of seven primary schools (3 in urban
environment, 3 in industrial environment, 1 in rural environment) located in the Mediterranean coast in an area
with an important industrial nucleus dedicated to the treatment of raw mineral materials. The main objective of
this work is a comparison between these levels obtained inside and outside schools and also asses the influence of
various natural and anthropogenic emission sources on particles concentrations found inside. The indoor airborne
samples were collected using RespiCon TM. In the three outdoor sampling stations was used a minivol air sampler
type 3.1 LVS of Derenda. PM10 Chemical composition was obtained by ICP-MS (elements) and ion chromatography
The ratio I/O (indoor/outdoor) has been calculated taking into account only the samples taken in the same
conditions. In all schools the ratio I/O for PM10 was greater than unity (between 1.3 and 7.8), indicating that
existed significant indoor sources of these particles. In the three schools located in the industrial environment
were collected PM10 samples inside and outside in non-teaching periods. Comparing the values of I/O when the
classrooms were unoccupied with respect to the average value of these same schools when the classrooms are
occupied, the behaviour is different depending on the location. On the other hand, a sample in an industrial
school was obtained when some infrastructure works were being carried out outside of school. This caused a
significant increase in the concentration of particles in the interior (I/O ¼ 19.9). From the levels of As, Ni, Cd, Pb,
Al, B, Zn, Mg, Sb, F , ClO2-, NO3- and SO4
2- in PM10 inside and outside of each school, also the ratios I/O were
calculated. These chemical ratios I/O were higher than unity in all cases and generally higher than those recorded
in the case of PM10. Finally, Pearson correlation coefficients (r) between the elements and anions and the PM10,
and between the different elements and anions were calculated for the purpose of establishing the existence of
common emission sources
Evidence for enhanced chromospheric Ca II H & K emission in stars with close-in extrasolar planets
The planet-star interaction is manifested in many ways. It was found out that
a close-in exoplanet causes small but measurable variability in the cores of a
few lines in the spectra of several stars which corresponds to the orbital
period of the exoplanet. Stars with and without exoplanets may have different
properties. The main goal of our study is to search for influence which
exoplanets might have on atmospheres of their host stars. Unlike the previous
studies, we do not study changes in the spectrum of a host star or differences
between stars with and without exoplanets. We aim to study a large number of
stars with exoplanets, current level of their chromospheric activity and look
for a possible correlation with the exoplanetary properties. To analyse the
chromospheric activity of stars we exploit our own (2.2m ESO/MPG telescope) and
publicly available archival spectra (Keck Observatory Archive), measure the
equivalent widths of the cores of Ca II H and K lines and use them as a tracer
of their activity. Subsequently, we search for their dependence on the orbital
parameters and mass of the exoplanet. We found a statistically significant
evidence that the equivalent width of the Ca II K line emission and log R'_{HK}
activity parameter of the host star varies with the semi-major axis and mass of
the exoplanet. Stars with T_eff <= 5500 K having exoplanets with semi-major
axis a <= 0.15 AU (P_orb <= 20 days) have a broad range of Ca II K emissions
and much stronger emission in general than stars at similar temperatures but
with higher values of semi-major axes. Ca II K emission of cold stars (T_eff <=
5500 K) with close-in exoplanets (a <= 0.15 AU) is also more pronounced for
more massive exoplanets. The overall level of the chromospheric activity of
stars may be affected by their close-in exoplanets. Stars with massive close-in
exoplanets may be more active.Comment: 9 pages, 8 figures, 1 tabl
The Mass-Radius Relationship for Very Low Mass Stars: Four New Discoveries from the HATSouth Survey
We report the discovery of four transiting F-M binary systems with companions
between 0.1-0.2 Msun in mass by the HATSouth survey. These systems have been
characterised via a global analysis of the HATSouth discovery data, combined
with high-resolution radial velocities and accurate transit photometry
observations. We determined the masses and radii of the component stars using a
combination of two methods: isochrone fitting of spectroscopic primary star
parameters, and equating spectroscopic primary star rotation velocity with
spin-orbit synchronisation. These new very low mass companions are HATS550-016B
(0.110 -0.006/+0.005 Msun, 0.147 -0.004/+0.003 Rsun), HATS551-019B (0.17
-0.01/+0.01 Msun, 0.18 -0.01/+0.01 Rsun), HATS551-021B (0.132 -0.005/+0.014
Msun, 0.154 -0.008/+0.006 Rsun), HATS553-001B (0.20 -0.02/+0.01 Msun, 0.22
-0.01/+0.01 Rsun). We examine our sample in the context of the radius anomaly
for fully-convective low mass stars. Combining our sample with the 13 other
well-studied very low mass stars, we find a tentative 5% systematic deviation
between the measured radii and theoretical isochrone models.Comment: 17 pages, 8 figures, accepted for publication in MNRA
Observability of the General Relativistic Precession of Periastra in Exoplanets
The general relativistic precession rate of periastra in close-in exoplanets
can be orders of magnitude larger than the magnitude of the same effect for
Mercury. The realization that some of the close-in exoplanets have significant
eccentricities raises the possibility that this precession might be detectable.
We explore in this work the observability of the periastra precession using
radial velocity and transit light curve observations. Our analysis is
independent of the source of precession, which can also have significant
contributions due to additional planets and tidal deformations. We find that
precession of the periastra of the magnitude expected from general relativity
can be detectable in timescales of <~ 10 years with current observational
capabilities by measuring the change in the primary transit duration or in the
time difference between primary and secondary transits. Radial velocity curves
alone would be able to detect this precession for super-massive, close-in
exoplanets orbiting inactive stars if they have ~100 datapoints at each of two
epochs separated by ~20 years. We show that the contribution to the precession
by tidal deformations may dominate the total precession in cases where the
relativistic precession is detectable. Studies of transit durations with Kepler
might need to take into account effects arising from the general relativistic
and tidal induced precession of periastra for systems containing close-in,
eccentric exoplanets. Such studies may be able to detect additional planets
with masses comparable to that of Earth by detecting secular variations in the
transit duration induced by the changing longitude of periastron.Comment: 13 pages, 5 figures. Accepted for publication in Ap
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