411 research outputs found
Multifaceted contributions : health workers and smallpox eradication in India
Smallpox eradication in South Asia was a result of the efforts of many grades of health-workers. Working from within the confines of international organisations and government structures, the role of the field officials, who were of various nationalities and also drawn from the cities and rural enclaves of the countries in these regions, was crucial to the development and deployment of policies. However, the role of these personnel is often downplayed in official histories and academic histories, which highlight instead the roles played by a handful of senior officials within the World Health Organization and the federal governments in the sub-continent. This article attempts to provide a more rounded assessment of the complex situation in the field. In this regard, an effort is made to underline the great usefulness of the operational flexibility displayed by field officers, wherein lessons learnt in the field were made an integral part of deploying local campaigns; careful engagement with the communities being targeted, as well as the employment of short term workers from amongst them, was an important feature of this work
The Interior Dynamics of Water Planets
The ever-expanding catalog of detected super-Earths calls for theoretical
studies of their properties in the case of a substantial water layer. This work
considers such water planets with a range of masses and water mass fractions (2
to 5 M_Earth, 0.02% to 50% H2 O). First, we model the thermal and dynamical
structure of the near-surface for icy and oceanic surfaces, finding separate
regimes where the planet is expected to maintain a subsurface liquid ocean and
where it is expected to exhibit ice tectonics. Newly discovered exoplanets may
be placed into one of these regimes given estimates of surface temperature,
heat flux, and gravity. Second, we construct a parameterized convection model
for the underlying ice mantle of higher ice phases, finding that materials
released from the silicate iron core should traverse the ice mantle on the
timescale of 0.1 to 100 megayears. We present the dependence of the overturn
times of the ice mantle and the planetary radius on total mass and water mass
fraction. Finally, we discuss the implications of these internal processes on
atmospheric observables.Comment: 9 page 4 figure
On the Possible Properties of Small and Cold Extrasolar Planets: Is OGLE-2005-BLG-390Lb Entirely Frozen?
Extrasolar planets as light as a few Earths are now being detected. Such
planets are likely not gas or ice giants. Here, we present a study on the
possible properties of the small and cold extrasolar planets, applied to the
case of the recently discovered planet OGLE-2005-BLG-390Lb (Beaulieu et al.
2006). This planet (5.5[+5.5/-2.7] Earth masses) orbits
2.6[+1.5/-0.6]-astronomical units away from an old M-type star of the Galactic
Bulge. The planet should be entirely frozen given the low surface temperature
(35 to 47 K). However, depending on the rock-to-ice mass ratio in the planet,
the radiogenic heating could be sufficient to make the existence of liquid
water within an icy crust possible. This possibility is estimated as a function
of the planetary mass and the illumination received from the parent star, both
being strongly related by the observational constraints. The results are
presented for water-poor and water-rich planets. We find that no oceans can be
present in any cases at 9-10 Gyr, a typical age for a star of the Bulge.
However, we find that, in the past when the planet was < 5-billion-years old,
liquid water was likely present below an icy surface. Nevertheless, the planet
is now likely to be entirely frozen.Comment: Accepted for publication in Ap
Cross-Layer Early Reliability Evaluation for the Computing cOntinuum
Advanced multifunctional computing systems realized in forthcoming technologies hold the promise of a significant increase of the computational capability that will offer end-users ever improving services and functionalities (e.g., next generation mobile devices, cloud services, etc.). However, the same path that is leading technologies toward these remarkable achievements is also making electronic devices increasingly unreliable, posing a threat to our society that is depending on the ICT in every aspect of human activities. Reliability of electronic systems is therefore a key challenge for the whole ICT technology and must be guaranteed without penalizing or slowing down the characteristics of the final products. CLERECO EU FP7 (GA No. 611404) research project addresses early accurate reliability evaluation and efficient exploitation of reliability at different design phases, since these aspects are two of the most important and challenging tasks toward this goal
Mass-radius relationships for exoplanets
For planets other than Earth, interpretation of the composition and structure
depends largely on comparing the mass and radius with the composition expected
given their distance from the parent star. The composition implies a
mass-radius relation which relies heavily on equations of state calculated from
electronic structure theory and measured experimentally on Earth. We lay out a
method for deriving and testing equations of state, and deduce mass-radius and
mass-pressure relations for key materials whose equation of state is reasonably
well established, and for differentiated Fe/rock. We find that variations in
the equation of state, such as may arise when extrapolating from low pressure
data, can have significant effects on predicted mass- radius relations, and on
planetary pressure profiles. The relations are compared with the observed
masses and radii of planets and exoplanets. Kepler-10b is apparently 'Earth-
like,' likely with a proportionately larger core than Earth's, nominally 2/3 of
the mass of the planet. CoRoT-7b is consistent with a rocky mantle over an
Fe-based core which is likely to be proportionately smaller than Earth's. GJ
1214b lies between the mass-radius curves for H2O and CH4, suggesting an 'icy'
composition with a relatively large core or a relatively large proportion of
H2O. CoRoT-2b is less dense than the hydrogen relation, which could be
explained by an anomalously high degree of heating or by higher than assumed
atmospheric opacity. HAT-P-2b is slightly denser than the mass-radius relation
for hydrogen, suggesting the presence of a significant amount of matter of
higher atomic number. CoRoT-3b lies close to the hydrogen relation. The
pressure at the center of Kepler-10b is 1.5+1.2-1.0 TPa. The central pressure
in CoRoT-7b is probably close to 0.8TPa, though may be up to 2TPa.Comment: Added more recent exoplanets. Tidied text and references. Added extra
"rock" compositions. Responded to referee comment
Effects of experimental warming on carbon sink function of a temperate pristine mire : the PEATWARM project.
communication oraleInternational audienceWithin the PEATWARM project, we use Sphagnum peatlands as a model to analyse their vulnerability to climate change using an experimental system (ITEX) that simulates in situ an increase in average temperature. We aim to determine the effects of temperature increase on the vegetation, the balance of above- and belowground gas fluxes (CO2 and CH4), the microbial diversity and activity in Sphagnum mosses and in peat, and the dynamics of labile and recalcitrant organic matter of peat. The ultimate objective is the creation of a biogeochemical model of C coupled with N and S cycles that includes interactions between these key compartments
Could we identify hot Ocean-Planets with CoRoT, Kepler and Doppler velocimetry?
Planets less massive than about 10 MEarth are expected to have no massive
H-He atmosphere and a cometary composition (50% rocks, 50% water, by mass)
provided they formed beyond the snowline of protoplanetary disks. Due to inward
migration, such planets could be found at any distance between their formation
site and the star. If migration stops within the habitable zone, this will
produce a new kind of planets, called Ocean-Planets. Ocean-planets typically
consist in a silicate core, surrounded by a thick ice mantle, itself covered by
a 100 km deep ocean. The existence of ocean-planets raises important
astrobiological questions: Can life originate on such body, in the absence of
continent and ocean-silicate interfaces? What would be the nature of the
atmosphere and the geochemical cycles ?
In this work, we address the fate of Hot Ocean-Planets produced when
migration ends at a closer distance. In this case the liquid/gas interface can
disappear, and the hot H2O envelope is made of a supercritical fluid. Although
we do not expect these bodies to harbor life, their detection and
identification as water-rich planets would give us insight as to the abundance
of hot and, by extrapolation, cool Ocean-Planets.Comment: 47 pages, 6 Fugures, regular paper. Submitted to Icaru
Stacking, correlations and electronic dispersion in the photoexcited state of 1T-TaS<sub>2</sub>
Here we perform angle and time-resolved photoelectron spectroscopy on the commensurate Charge Density Wave phase of 1T-TaS2. Data with different probe pulse polarization are employed to map the dispersion of electronic states below or above the chemical potential. The experimental results are compared to Density-Functional Theory calculations with a self-consistent evaluation of the coulomb repulsion. Both out-of-plane dimerization and electronic correlations must be included in order to obtain good agreement with the experimental data. Upon Photoexcitation, the fluctuations of CDW order erase the band dispersion near to the chemical potential and halve the charge gap size. This transient phase sets within half a period of the coherent lattice motion and is likely favored by strong electronic correlations
DNA Nucleobase Synthesis at Titan Atmosphere Analog by Soft X-rays
Titan, the largest satellite of Saturn, has an atmosphere chiefly made up of
N2 and CH4 and includes traces of many simple organic compounds. This
atmosphere also partly consists of haze and aerosol particles which during the
last 4.5 gigayears have been processed by electric discharges, ions, and
ionizing photons, being slowly deposited over the Titan surface. In this work,
we investigate the possible effects produced by soft X-rays (and secondary
electrons) on Titan aerosol analogs in an attempt to simulate some prebiotic
photochemistry. The experiments have been performed inside a high vacuum
chamber coupled to the soft X-ray spectroscopy beamline at the Brazilian
Synchrotron Light Source, Campinas, Brazil. In-situ sample analyses were
performed by a Fourier transform infrared spectrometer. The infrared spectra
have presented several organic molecules, including nitriles and aromatic CN
compounds. After the irradiation, the brownish-orange organic residue (tholin)
was analyzed ex-situ by gas chromatographic (GC/MS) and nuclear magnetic
resonance (1H NMR) techniques, revealing the presence of adenine (C5H5N5), one
of the constituents of the DNA molecule. This confirms previous results which
showed that the organic chemistry on the Titan surface can be very complex and
extremely rich in prebiotic compounds. Molecules like these on the early Earth
have found a place to allow life (as we know) to flourish.Comment: To appear in Journal of Physical Chemistry A.; Number of pages: 6;
Number of Figures: 5; Number of Tables: 1; Number of references:49; Full
paper at http://pubs.acs.org/doi/abs/10.1021/jp902824
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