618 research outputs found
Early Detection with Pulse Oximetry of Hypoxemic Neonatal Conditions. Development of the IX Clinical Consensus Statement of the Ibero-American Society of Neonatology (SIBEN)
This article reviews the development of the Ninth Clinical Consensus Statement by SIBEN (the Ibero-American of Neonatology) on “Early Detection with Pulse Oximetry (SpO2) of Hypoxemic Neonatal Conditions”. It describes the process of the consensus, and the conclusions and recommendations for screening newborns with pulse oximetry
Quasi-ballistic transport in HgTe quantum-well nanostructures
The transport properties of micrometer scale structures fabricated from
high-mobility HgTe quantum-wells have been investigated. A special photoresist
and Ti masks were used, which allow for the fabrication of devices with
characteristic dimensions down to 0.45 m. Evidence that the transport
properties are dominated by ballistic effects in these structures is presented.
Monte Carlo simulations of semi-classical electron trajectories show good
agreement with the experiment.Comment: 3 pages, 3 figures; minor revisions: replaced "inelastic mean free
path" with "transport mean free path"; corrected typing errors; restructered
most paragraphs for easier reading; accepted for publication in AP
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ExoMars entry, descent and landing science
The entry, descent and landing of ExoMars offer a rare (once-per-mission) opportunity to perform in situ investigation of the martian environment over a wide altitude range. Entry, Descent and Landing System (EDLS) measurements can provide essential data for atmospheric scientific investigations.
We intend to perform atmospheric science measurements by exploiting data from EDLS engineering sensors and exploiting their readings beyond the expected engineering information
In Situ Investigation of Iron Meteorites at Meridiani Planum Mars
The Mars Exploration Rover Opportunity has encountered four iron meteorites at its landing site in Meridiani Planum. The first one, informally named "Heat Shield Rock", measuring approx.30 by 15 cm, was encountered in January 2005 [1, 2] and officially recognized as the first iron meteorite on the martian surface with the name "Meridiani Planum" after the location of its find [3]. We will refer to it as "Heat Shield Rock" to avoid confusion with the site. Between July and October 2009, separated approx.10 km from Heat Shield Rock, three other iron meteorite fragments were encountered, informally named "Block Island" (approx.60 cm across), "Shelter Island" (approx.50 by 20 cm), and "Mackinac Island" (approx.30 cm across). Heat Shield Rock and Block Island, the two specimens investigated in detail, are shown in Figure 1. Here, we focus on the meteorites chemistry and mineralogy. An overview in the mission context is given in [4]; other abstracts discuss their morphology [5], photometric properties [6], and their provenance [7]
TThermodynamics of the thermoelectric working fluid close to the superconducting phase transition
The bottleneck in state-of-the-art thermoelectric power generation and
cooling is the low performance of thermoelectric materials. While the adverse
effects of lattice phonons on performance can be mitigated, the main difficulty
remains to obtain a large thermoelectric power factor as the Seebeck
coefficient and the electrical conductivity cannot be increased independently.
Here, relating the thermoelastic properties of the electron gas that performs
the thermoelectric energy conversion, to its transport properties, we analyze
theoretically whether an electronic phase transition can enhance thermoelectric
conversion and at what cost. More precisely, we consider the
metal-to-superconductor phase transition in a model two-dimensional system, and
we seek to quantify the contribution of the 2D fluctuating Cooper pairs to the
power factor in the close vicinity of the critical temperature . In
addition, we provide experimental evidence of the rapid increase of the Seebeck
coefficient without decreasing the electrical conductivity near in
a 100-nm Ba(FeCo)As thin film with high structural quality
resulting in a power factor enhancement of approximately 300. This level of
performance cannot be achieved in a system with low structural quality as shown
experimentally with our sample degraded by ion bombardment as defects preclude
the strong enhancement of the Seebeck coefficient near the phase transition.
Finally, we theoretically discuss the ideal thermoelectric conversion
efficiency (i.e. disregarding adverse phonon effects) and show that driving the
electronic system to the vicinity of a phase transition may be an innovative
path towards a strong performance increase but at the cost of a narrow
temperature range of use of such materials.Comment: Submission to SciPos
An Atlas of Warm AGN and Starbursts from the IRAS Deep Fields
We present 180 AGN candidates based on color selection from the IRAS
slow-scan deep observations, with color criteria broadened from the initial
Point-Source Catalog samples to include similar objects with redshifts up to
z=1 and allowing for two-band detections. Spectroscopic identifications have
been obtained for 80 (44%); some additional ones are secure based on radio
detections or optical morphology, although yet unobserved spectroscopically.
These spectroscopic identifications include 13 Sy 1 galaxies, 17 Sy 2 Seyferts,
29 starbursts, 7 LINER systems, and 13 emission-line galaxies so heavily
reddened as to remain of ambiguous classification. The optical magnitudes range
from R=12.0-20.5; counts suggest that incompleteness is important fainter than
R=15.5. Redshifts extend to z=0.51, with a significant part of the sample at
z>0.2. The sample includes slightly more AGN than star-forming systems among
those where the spectra contain enough diagnostic feature to make the
distinction. The active nuclei include several broad-line objects with strong
Fe II emission, and composite objects with the absorption-line signatures of
fading starbursts. These AGN with warm far-IR colors have little overlap with
the "red AGN" identified with 2MASS; only a single Sy 1 was detected by 2MASS
with J-K > 2. Some reliable IRAS detections have either very faint optical
counterparts or only absorption-line galaxies, potentially being deeply
obscured AGN. The IRAS detections include a newly identified symbiotic star,
and several possible examples of the "Vega phenomenon", including dwarfs as
cool as type K. Appendices detail these candidate stars, and the
optical-identification content of a particularly deep set of high-latitude IRAS
scans (probing the limits of optical identification from IRAS data alone).Comment: ApJ Suppl, in press. Figures converted to JPEG/GIF for better
compression; PDF with full-resolution figures available before publication at
http://www.astr.ua.edu/keel/aoagn.pd
Amazonian chemical weathering rate derived from stony meteorite finds at Meridiani Planum on Mars
© The Author(s) 2016.Spacecraft exploring Mars such as the Mars Exploration Rovers Spirit and Opportunity, as well as the Mars Science Laboratory or Curiosity rover, have accumulated evidence for wet and habitable conditions on early Mars more than 3 billion years ago. Current conditions, by contrast, are cold, extremely arid and seemingly inhospitable. To evaluate exactly how dry today's environment is, it is important to understand the ongoing current weathering processes. Here we present chemical weathering rates determined for Mars. We use the oxidation of iron in stony meteorites investigated by the Mars Exploration Rover Opportunity at Meridiani Planum. Their maximum exposure age is constrained by the formation of Victoria crater and their minimum age by erosion of the meteorites. The chemical weathering rates thus derived are ~1 to 4 orders of magnitude slower than that of similar meteorites found in Antarctica where the slowest rates are observed on Earth
Mineralogy and chemistry of cobbles at Meridiani Planum, Mars, investigated by the Mars Exploration Rover Opportunity
Numerous loose rocks with dimensions of a few centimeters to tens of centimeters and with no obvious physical relationship to outcrop rocks have been observed along the traverse of the Mars Exploration Rover Opportunity. To date, about a dozen of these rocks have been analyzed with Opportunity’s contact instruments, providing information about elemental chemistry (Alpha Particle X‐ray Spectrometer), iron mineralogy and oxidation states (Mössbauer Spectrometer) and texture (Microscopic Imager). These “cobbles” appear to be impact related, and three distinct groups can be identified on the basis of chemistry and mineralogy. The first group comprises bright fragments of the sulfate‐rich bedrock that are compositionally and texturally indistinguishable from outcrop rocks. All other cobbles are dark and are divided into two groups, referred to as the “Barberton group” and the “Arkansas group,” after the first specimen of each that was encountered by Opportunity. Barberton group cobbles are interpreted as meteorites with an overall chemistry and mineralogy consistent with a mesosiderite silicate clast composition. Arkansas group cobbles appear to be related to Meridiani outcrop and contain an additional basaltic component. They have brecciated textures, pointing to an impact‐related origin during which local bedrock and basaltic material were mixed
Starbursts and the triggering of the activity in nearby powerful radio galaxies
We present high quality long-slit spectra for three nearby powerful radio
galaxies 3C293, 3C305, PKS1345+12. These were taken with the aim of
characterising the young stellar populations (YSP), and thereby investigating
the evolution of the host galaxies, as well as the events that triggered the
activity. Isochrone spectral synthesis modelling of the wide wavelength
coverage spectra of nuclear and off-nuclear continuum-emitting regions have
been used to estimate the ages, masses and luminosities of the YSP component,
taking full account of reddening effects and potential contamination by
activity-related components. We find that the YSP make a substantial
contribution to the continuum flux in the off-nuclear regions on a radial scale
of 1 - 20kpc in all three objects. Moreover, in two objects we find evidence
for reddened post-starburst stellar populations in the near-nuclear regions of
the host galaxies. The YSP are relatively old (0.1- 2Gyr), massive and make up
a large proportion (~1 - 50%) of the total stellar mass in the regions of
galaxies sampled by the observations. Overall, these results are consistent
with the idea that AGN activity in some radio galaxies is triggered by major
gas-rich mergers. Therefore, these radio galaxies form part of the subset of
early-type galaxies that is evolving most rapidly in the local universe.
Intriguingly, the results also suggest that the radio jets are triggered
relatively late in the merger sequence, and that there is an evolutionary link
between radio galaxies and luminous/ultra-luminous infrared galaxies.Comment: 17 pages, 13 figures, accepted for publication in MNRA
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