732 research outputs found
Component-aware Orchestration of Cloud-based Enterprise Applications, from TOSCA to Docker and Kubernetes
Enterprise IT is currently facing the challenge of coordinating the
management of complex, multi-component applications across heterogeneous cloud
platforms. Containers and container orchestrators provide a valuable solution
to deploy multi-component applications over cloud platforms, by coupling the
lifecycle of each application component to that of its hosting container. We
hereby propose a solution for going beyond such a coupling, based on the OASIS
standard TOSCA and on Docker. We indeed propose a novel approach for deploying
multi-component applications on top of existing container orchestrators, which
allows to manage each component independently from the container used to run
it. We also present prototype tools implementing our approach, and we show how
we effectively exploited them to carry out a concrete case study
Dusty tails of evaporating exoplanets. II. Physical modelling of the KIC 12557548b light curve
Evaporating rocky exoplanets, such as KIC 12557548b, eject large amounts of
dust grains, which can trail the planet in a comet-like tail. When such objects
occult their host star, the resulting transit signal contains information about
the dust in the tail. We aim to use the detailed shape of the Kepler light
curve of KIC 12557548b to constrain the size and composition of the dust grains
that make up the tail, as well as the mass loss rate of the planet. Using a
self-consistent numerical model of the dust dynamics and sublimation, we
calculate the shape of the tail by following dust grains from their ejection
from the planet to their destruction due to sublimation. From this dust cloud
shape, we generate synthetic light curves (incorporating the effects of
extinction and angle-dependent scattering), which are then compared with the
phase-folded Kepler light curve. We explore the free-parameter space thoroughly
using a Markov chain Monte Carlo method. Our physics-based model is capable of
reproducing the observed light curve in detail. Good fits are found for initial
grain sizes between 0.2 and 5.6 micron and dust mass loss rates of 0.6 to 15.6
M_earth/Gyr (2-sigma ranges). We find that only certain combinations of
material parameters yield the correct tail length. These constraints are
consistent with dust made of corundum (Al2O3), but do not agree with a range of
carbonaceous, silicate, or iron compositions. Using a detailed, physically
motivated model, it is possible to constrain the composition of the dust in the
tails of evaporating rocky exoplanets. This provides a unique opportunity to
probe to interior composition of the smallest known exoplanets.Comment: 18 pages, 11 figures, A&A accepte
Fissure ridges: A reappraisal of faulting and travertine deposition (travitonics)
The mechanical discontinuities in the upper crust (i.e., faults and related fractures) lead to the uprising of geothermal fluids to the Earth’s surface. If fluids are enriched in Ca2+ and HCO3‐, masses of CaCO3 (i.e., travertine deposits) can form mainly due to the CO2 leakage from the thermal waters. Among other things, fissure‐ridge‐type deposits are peculiar travertine bodies made of bedded carbonate that gently to steeply dip away from the apical part where a central fissure is located, corresponding to the fracture trace intersecting the substratum; these morpho‐tectonic features are the most useful deposits for tectonic and paleoseismological investigation, as their development is contemporaneous with the activity of faults leading to the enhancement of permeability that serves to guarantee the circulation of fluids and their emergence. Therefore, the fissure ridge architecture sheds light on the interplay among fault activity, travertine deposition, and ridge evolution, providing key geo‐chronologic constraints due to the fact that travertine can be dated by different radio-metric methods. In recent years, studies dealing with travertine fissure ridges have been consider-ably improved to provide a large amount of information. In this paper, we report the state of the art of knowledge on this topic refining the literature data as well as adding original data, mainly focusing on the fissure ridge morphology, internal architecture, depositional facies, growth mechanisms, tectonic setting in which the fissure ridges develop, and advantages of using the fissure ridges for neotectonic and seismotectonic studies
Evidence for the disintegration of KIC 12557548 b
Context. The Kepler object KIC 12557548 b is peculiar. It exhibits
transit-like features every 15.7 hours that vary in depth between 0.2% and
1.2%. Rappaport et al. (2012) explain the observations in terms of a
disintegrating, rocky planet that has a trailing cloud of dust created and
constantly replenished by thermal surface erosion. The variability of the
transit depth is then a consequence of changes in the cloud optical depth.
Aims. We aim to validate the disintegrating-planet scenario by modeling the
detailed shape of the observed light curve, and thereby constrain the cloud
particle properties to better understand the nature of this intriguing object.
Methods. We analysed the six publicly-available quarters of raw Kepler data,
phase-folded the light curve and fitted it to a model for the trailing dust
cloud. Constraints on the particle properties were investigated with a
light-scattering code. Results. The light curve exhibits clear signatures of
light scattering and absorption by dust, including a brightening in flux just
before ingress correlated with the transit depth and explained by forward
scattering, and an asymmetry in the transit light curve shape, which is easily
reproduced by an exponentially decaying distribution of optically thin dust,
with a typical grain size of 0.1 micron. Conclusions. Our quantitative analysis
supports the hypothesis that the transit signal of KIC 12557548 b is due to a
variable cloud of dust, most likely originating from a disintegrating object.Comment: 5 pages, 4 figures. Accepted for publication in Astronomy and
Astrophysic
Simulation of spatial variability in crop leaf area index and yield using agroecosystem modeling and geophysics-based quantitative soil information
Agroecosystem models that simulate crop growth as a function of weather conditionsand soil characteristics are among the most promising tools for improving crop yield and achieving more sustainable agricultural production systems. This study aims at using spatially distributed crop growth simulations to investigate how field-scale patterns in soil properties obtained using geophysical mapping affect the spatial variability of soil water content dynamics and growth of crops at the square kilometer scale. For this, a geophysics-based soil map was intersected with land use information. Soilhydraulic parameters were calculated using pedotransfer functions. Simulations of soilwater content dynamics performed with the agroecosystem model AgroC were com-pared with soil water content measured at two locations, resulting in RMSE of 0.032and of 0.056 cm3cm−3, respectively. The AgroC model was then used to simulate thegrowth of sugar beet (Beta vulgaris L.), silage maize (Zea maysL.), potato (SolanumtuberosumL.), winter wheat (Triticum aestivumL.), winter barley (Hordeum vulgareL.), and winter rapeseed (Brassica napusL.) in the 1- by 1-km study area. It was found that the simulated leaf area index (LAI) was affected by the magnitude of simulated water stress, which was a function of both the crop type and soil characteristics. Simulated LAI was generally consistent with the observed LAI calculated from normalized difference vegetation index (LAINDVI) obtained from RapidEye satellite data. Finally, maps of simulated agricultural yield were produced for four crops, and it was found that simulated yield matched well with actual harvest data and literature values. Therefore, it was concluded that the information obtained from geophysics-based soilmapping was valuable for practical agricultural applications
Search for an exosphere in sodium and calcium in the transmission spectrum of exoplanet 55 Cancri e
[Abridged] The aim of this work is to search for an absorption signal from
exospheric sodium (Na) and singly ionized calcium (Ca) in the optical
transmission spectrum of the hot rocky super-Earth 55 Cancri e. Although the
current best-fitting models to the planet mass and radius require a possible
atmospheric component, uncertainties in the radius exist, making it possible
that 55 Cancri e could be a hot rocky planet without an atmosphere. High
resolution (R110000) time-series spectra of five transits of 55 Cancri e,
obtained with three different telescopes (UVES/VLT, HARPS/ESO 3.6m &
HARPS-N/TNG) were analysed. Targeting the sodium D lines and the calcium H and
K lines, the potential planet exospheric signal was filtered out from the much
stronger stellar and telluric signals, making use of the change of the radial
component of the orbital velocity of the planet over the transit from -57 to
+57 km/sec. Combining all five transit data sets, we detect a signal
potentially associated with sodium in the planet exosphere at a statistical
significance level of 3. Combining the four HARPS transits that cover
the calcium H and K lines, we also find a potential signal from ionized calcium
(4.1 ). Interestingly, this latter signal originates from just one of
the transit measurements - with a 4.9 detection at this epoch.
Unfortunately, due to the low significance of the measured sodium signal and
the potentially variable Ca signal, we estimate the p-values of these
signals to be too high (corresponding to <4) to claim unambiguous
exospheric detections. By comparing the observed signals with artificial
signals injected early in the analysis, the absorption by Na and Ca are
estimated to be at a level of approximately 2.3 and 7.0 respectively, relative to the stellar spectrum.Comment: 15 pages, 8 figures, submission updated after English language
editing, submission updated to correct a mistaken cross-reference noticed in
A&A proo
Iron metabolism and lymphocyte characterisation during Covid-19 infection in ICU patients: An observational cohort study
Background: Iron metabolism and immune response to SARS-CoV-2 have not been described yet in intensive care patients, although they are likely involved in Covid-19 pathogenesis. Methods: We performed an observational study during the peak of pandemic in our intensive care unit, dosing D-dimer, C-reactive protein, troponin T, lactate dehydrogenase, ferritin, serum iron, transferrin, transferrin saturation, transferrin soluble receptor, lymphocyte count and NK, CD3, CD4, CD8 and B subgroups of 31 patients during the first 2 weeks of their ICU stay. Correlation with mortality and severity at the time of admission was tested with the Spearman coefficient and Mann-Whitney test. Trends over time were tested with the Kruskal-Wallis analysis. Results: Lymphopenia is severe and constant, with a nadir on day 2 of ICU stay (median 0.555 109/L; interquartile range (IQR) 0.450 109/L); all lymphocytic subgroups are dramatically reduced in critically ill patients, while CD4/CD8 ratio remains normal. Neither ferritin nor lymphocyte count follows significant trends in ICU patients. Transferrin saturation is extremely reduced at ICU admission (median 9%; IQR 7%), then significantly increases at days 3 to 6 (median 33%, IQR 26.5%, p value 0.026). The same trend is observed with serum iron levels (median 25.5 μg/L, IQR 69 μg/L at admission; median 73 μg/L, IQR 56 μg/L on days 3 to 6) without reaching statistical significance. Hyperferritinemia is constant during intensive care stay: however, its dosage might be helpful in individuating patients developing haemophagocytic lymphohistiocytosis. D-dimer is elevated and progressively increases from admission (median 1319 μg/L; IQR 1285 μg/L) to days 3 to 6 (median 6820 μg/L; IQR 6619 μg/L), despite not reaching significant results. We describe trends of all the abovementioned parameters during ICU stay. Conclusions: The description of iron metabolism and lymphocyte count in Covid-19 patients admitted to the intensive care unit provided with this paper might allow a wider understanding of SARS-CoV-2 pathophysiology
Doppler tomography as a tool for detecting exoplanet atmospheres
High-resolution Doppler spectroscopy is a powerful tool for identifying molecular species in the atmospheres of both transiting and non-transiting exoplanets. Currently, such data is analysed using cross-correlation techniques to detect the Doppler shifting signal from the orbiting planet. In this paper we demonstrate that, compared to cross-correlation methods currently used, the technique of Doppler tomography has improved sensitivity in detecting the subtle signatures expected from exoplanet atmospheres. This is partly due to the use of a regularizing statistic, which acts to suppress noise, coupled to the fact that all the data is fit simultaneously. In addition, we show that the technique can also effectively suppress contanimating spectral features that may arise due to overlapping lines, repeating line patterns, or the use of incorrect linelists. These issues can confuse conventional cross-correlation approaches, primarily due to aliasing issues inherent in such techniques, whereas Doppler tomography is less susceptible to such effects. In particular, Doppler tomography shows exceptional promise for simultaneously detecting multiple line species (e.g. isotopologues), even when there are high contrasts between such species – and far outperforms current CCF analyses in this respect. Finally, we demonstrate that Doppler tomography is capable of recovering molecular signals from exoplanets using real data, by confirming the strong detection of CO in the atmosphere of τ Boo b. We recover a signal with a planetary radial velocity semi-amplitude Kp = 109.6 ± 2.2 km s−1, in excellent agreement with the previously reported value of 110.0 ± 3.2 km s−1
The relation between stellar magnetic field geometry and chromospheric activity cycles – II The rapid 120-day magnetic cycle of <i>τ</i> Bootis
One of the aims of the BCool programme is to search for cycles in other stars and to understand how similar they are to the Sun. In this paper, we aim to monitor the evolution of τ Boo’s large-scale magnetic field using high-cadence observations covering its chromospheric activity maximum. For the first time, we detect a polarity switch that is in phase with τ Boo’s 120-day chromospheric activity maximum and its inferred X-ray activity cycle maximum. This means that τ Boo has a very fast magnetic cycle of only 240 days. At activity maximum τ Boo’s large-scale field geometry is very similar to the Sun at activity maximum: it is complex and there is a weak dipolar component. In contrast, we also see the emergence of a strong toroidal component which has not been observed on the Sun, and a potentially overlapping butterfly pattern where the next cycle begins before the previous one has finished
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