4,722 research outputs found
Revisiting the 16 Cygni planet host at unprecedented precision and exploring automated tools for precise abundances
The binary system 16 Cygni is key in studies of the planet-star chemical
composition connection, as only one of the stars is known to host a planet.
This allows us to better assess the possible influence of planet interactions
on the chemical composition of stars that are born from the same cloud and
thus, should have a similar abundance pattern. In our previous work, we found
clear abundance differences for elements with Z between both components
of this system, and a trend of these abundances as a function of the
condensation temperature (T), which suggests a spectral chemical
signature related to planet formation. In this work we show that our previous
findings are still consistent even if we include more species, like the
volatile N and neutron capture elements (Z 30). We report a slope with
T of dex K, that is good agreement
with both our previous work and recent results by Nissen and collaborators. We
also performed some tests using ARES and iSpec to automatic measure the
equivalent width and found T slopes in reasonable agreement with our
results as well. In addition, we determine abundances for Li and Be by spectral
synthesis, finding that 16 Cyg A is richer not only in Li but also in Be, when
compared to its companion. This may be evidence of planet engulfment,
indicating that the T trend found in this binary system may be a chemical
signature of planet accretion in the A component, rather than a imprint of the
giant planet rocky core formation on 16 Cyg B.Comment: 11 pages, 5 figures, accepted for publication in A&
Reactivity Effects in a Very-High-Temperature Pebble-Bed Reactor
The very-high-temperature reactor (VHTR) is one of the most promising and innovative designs selected by the Generation IV International Forum. Although previous papers have focused on the study and optimization of several parameter of a VHTR conceptual design, there is still much work needed to achieve the commercial introduction of this technology. The primary aim of this study is to obtain the reactivity effects of such parameters as the temperature of the fuel, moderator, and reflector, and the poisoning by 135Xe and 149Sm in the VHTR critically. To reach this goal, the widely-used MCNP6 code was employed in order to simulate the neutronics of the VHTR. The viability of the utilization of the MCNP6 code and the developed model for the study of the physics of the VHTR core was confirmed through the calculation and comparison with benchmarks provided by the IAEA. Based on the results of the temperature coefficients of reactivity obtained, a negative reactivity effect on the system of about 12 pcm/K was found, as is expected in all the nuclear fission reactors, while the combined effect of fission products 135Xe and 149Sm implies a negative reactivity of 3475 pcm
Alginate-based beads and core-shell capsules loaded with corn oil for potential delivery of functional compounds
info:eu-repo/semantics/publishedVersio
Desenvolvimento de leite achocolatado com probiĂłtico utilizando metodologia baseada no consumidor.
O desenvolvimento de produtos inovadores ĂŠ fundamental para as indĂşstrias como estratĂŠgia para manter e alcançar o sucesso no mercado. No presente estudo foi utilizada metodologia descritiva para o desenvolvimento de leite achocolatado (4,5% e 9% de açúcar e 1,5% e 2,5% de cacao) com probiĂłtico (8,2 x 106UFC/mL de Lactobacillus acidophilus), a saber: Marque tudo que se aplica (CATA) atravĂŠs da participação de oitenta consumidores. Essa metodologia foi aplicada visando caracterizar sensorialmente a bebida e obter informaçþes sobre os atributos que dirigiram a preferĂŞncia do consumidor, a fim de alcançar um produto com elevada aceitação. Foi possĂvel desenvolver leite achocolatado com probiĂłtico nĂŁo fermentado com adequada aceitabilidade. A amostra preferida foi formulada com elevado conteĂşdo de açúcar e cacao, indicando que essas caracterĂsticas dirigiram a preferĂŞncia. As questĂľes CATA propiciaram bom poder discriminativo entre as amostras, sugerindo que a metodologia rĂĄpida de caracterização sensorial foi eficiente quando aplicada no desenvolvimento do produto.Food: the tree that sustains life. 854
Accurate Atmospheric Parameters at Moderate Resolution Using Spectral Indices: Preliminary Application to the MARVELS Survey
Studies of Galactic chemical and dynamical evolution in the solar
neighborhood depend on the availability of precise atmospheric parameters
(Teff, [Fe/H] and log g) for solar-type stars. Many large-scale spectroscopic
surveys operate at low to moderate spectral resolution for efficiency in
observing large samples, which makes the stellar characterization difficult due
to the high degree of blending of spectral features. While most surveys use
spectral synthesis, in this work we employ an alternative method based on
spectral indices to determine the atmospheric parameters of a sample of nearby
FGK dwarfs and subgiants observed by the MARVELS survey at moderate resolving
power (R~12,000). We have developed three codes to automatically normalize the
observed spectra, measure the equivalent widths of the indices and, through the
comparison of those with values calculated with pre-determined calibrations,
derive the atmospheric parameters of the stars. The calibrations were built
using a sample of 309 stars with precise stellar parameters obtained from the
analysis of high-resolution FEROS spectra. A validation test of the method was
conducted with a sample of 30 MARVELS targets that also have reliable
atmospheric parameters from high-resolution spectroscopic analysis. Our
approach was able to recover the parameters within 80 K for Teff, 0.05 dex for
[Fe/H] and 0.15 dex for log g, values that are lower or equal to the typical
external uncertainties found between different high-resolution analyzes. An
additional test was performed with a subsample of 138 stars from the ELODIE
stellar library and the literature atmospheric parameters were recovered within
125 K for Teff, 0.10 dex for [Fe/H] and 0.29 dex for log g. These results show
that the spectral indices are a competitive tool to characterize stars with the
intermediate resolution spectra.Comment: Accepted for publication in AJ. Abstract edited to comply with arXiv
standards regarding the number of character
Integral field spectroscopy with SINFONI of VVDS galaxies. I. Galaxy dynamics and mass assembly at 1.2 < z < 1.6
Context. Identifying the main processes of galaxy assembly at high redshifts
is still a major issue to understand galaxy formation and evolution at early
epochs in the history of the Universe. Aims. This work aims to provide a first
insight into the dynamics and mass assembly of galaxies at redshifts 1.2<z<1.6,
the early epoch just before the sharp decrease of the cosmic star formation
rate. Methods. We use the near-infrared integral field spectrograph SINFONI on
the ESO-VLT under 0.65 seeing to obtain spatially resolved spectroscopy on nine
emission line galaxies with 1.2<z<1.6 from the VIMOS VLT Deep Survey. We derive
the velocity fields and velocity dispersions on kpc scales using the Halpha
emission line. Results. Out of the nine star-forming galaxies, we find that
galaxies distribute in three groups: two galaxies can be well reproduced by a
rotating disk, three systems can be classified as major mergers and four
galaxies show disturbed dynamics and high velocity dispersion. We argue that
there is evidence for hierarchical mass assembly from major merger, with most
massive galaxies with M>10^11Msun subject to at least one major merger over a 3
Gyr period as well as for continuous accretion feeding strong star formation.
Conclusions. These results point towards a galaxy formation and assembly
scenario which involves several processes, possibly acting in parallel, with
major mergers and continuous gas accretion playing a major role. Well
controlled samples representative of the bulk of the galaxy population at this
key cosmic time are necessary to make further progress.Comment: 23 pages, 22 figures, accepted for publication in A&
Social sciences research in neglected tropical diseases 2: A bibliographic analysis
The official published version of the article can be found at the link below.Background
There are strong arguments for social science and interdisciplinary research in the neglected tropical diseases. These diseases represent a rich and dynamic interplay between vector, host, and pathogen which occurs within social, physical and biological contexts. The overwhelming sense, however, is that neglected tropical diseases research is a biomedical endeavour largely excluding the social sciences. The purpose of this review is to provide a baseline for discussing the quantum and nature of the science that is being conducted, and the extent to which the social sciences are a part of that.
Methods
A bibliographic analysis was conducted of neglected tropical diseases related research papers published over the past 10 years in biomedical and social sciences. The analysis had textual and bibliometric facets, and focussed on chikungunya, dengue, visceral leishmaniasis, and onchocerciasis.
Results
There is substantial variation in the number of publications associated with each disease. The proportion of the research that is social science based appears remarkably consistent (<4%). A textual analysis, however, reveals a degree of misclassification by the abstracting service where a surprising proportion of the "social sciences" research was pure clinical research. Much of the social sciences research also tends to be "hand maiden" research focused on the implementation of biomedical solutions.
Conclusion
There is little evidence that scientists pay any attention to the complex social, cultural, biological, and environmental dynamic involved in human pathogenesis. There is little investigator driven social science and a poor presence of interdisciplinary science. The research needs more sophisticated funders and priority setters who are not beguiled by uncritical biomedical promises
The age-mass-metallicity-activity relation for solar-type stars: comparisons with asteroseismology and the NGC 188 open cluster
Context. The Mount Wilson Caâii index log is the accepted standard metric of calibration for the chromospheric activity versus age relation for FGK stars. Recent results claim its inability to discern activity levels, and thus ages, for stars older than ~2 Gyr, which would severely hamper its application to date disk stars older than the Sun.
Aims. We present a new activity-age calibration of the Mt. Wilson index that explicitly takes mass and [Fe/H] biases into account; these biases are implicit in samples of stars selected to have precise ages, which have so far not been appreciated.
Methods. We show that these selection biases tend to blur the activity-age relation for large age ranges. We calibrate the Mt. Wilson index for a sample of field FGK stars with precise ages, covering a wide range of mass and [Fe/H] , augmented with data from the Pleiades, Hyades, Mâ67 clusters, and the Ursa Major moving group.
Results. We further test the calibration with extensive new Gemini/GMOS log ()R'HK) data of the old, solar [Fe/H] clusters, Mâ67 and NGC 188. The observed NGC 188 activity level is clearly lower than Mâ67. We correctly recover the isochronal age of both clusters and establish the viability of deriving usable chromospheric ages for solar-type stars up to at least ~6 Gyr, where average errors are ~0.14 dex provided that we explicitly account for the mass and [Fe/H] dimensions. We test our calibration against asteroseismological ages, finding excellent correlation (Ď = + 0.89). We show that our calibration improves the chromospheric age determination for a wide range of ages, masses, and metallicities in comparison to previous age-activity relations
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the
distribution of arrival directions of the cosmic rays with energies
eV. These show a correlation with the distribution
of nearby extragalactic objects, including an apparent excess around the
direction of Centaurus A. If the particles responsible for these excesses at
are heavy nuclei with charge , the proton component of the
sources should lead to excesses in the same regions at energies . We here
report the lack of anisotropies in these directions at energies above
(for illustrative values of ). If the anisotropies
above are due to nuclei with charge , and under reasonable
assumptions about the acceleration process, these observations imply stringent
constraints on the allowed proton fraction at the lower energies
Standalone vertex ďŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
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