131 research outputs found
Model selection for spectro-polarimetric inversions
Inferring magnetic and thermodynamic information from spectropolarimetric
observations relies on the assumption of a parameterized model atmosphere whose
parameters are tuned by comparison with observations. Often, the choice of the
underlying atmospheric model is based on subjective reasons. In other cases,
complex models are chosen based on objective reasons (for instance, the
necessity to explain asymmetries in the Stokes profiles) but it is not clear
what degree of complexity is needed. The lack of an objective way of comparing
models has, sometimes, led to opposing views of the solar magnetism because the
inferred physical scenarios are essentially different. We present the first
quantitative model comparison based on the computation of the Bayesian evidence
ratios for spectropolarimetric observations. Our results show that there is not
a single model appropriate for all profiles simultaneously. Data with moderate
signal-to-noise ratios favor models without gradients along the line-of-sight.
If the observations shows clear circular and linear polarization signals above
the noise level, models with gradients along the line are preferred. As a
general rule, observations with large signal-to-noise ratios favor more complex
models. We demonstrate that the evidence ratios correlate well with simple
proxies. Therefore, we propose to calculate these proxies when carrying out
standard least-squares inversions to allow for model comparison in the future.Comment: 16 pages, 2 figures, 8 tables, accepted for publication in Ap
Estimating the longitudinal magnetic field in the chromosphere of quiet-Sun magnetic concentrations
Details of the magnetic field in the quiet Sun chromosphere are key to our
understanding of essential aspects of the solar atmosphere. We aim to determine
the longitudinal magnetic field component (B_lon) of quiet Sun regions
depending on their size. We estimated B_lon by applying the weak-field
approximation (WFA) to high-spatial-resolution Ca II 854.2 nm data taken with
the Swedish 1m Solar Telescope. Specifically, we analyzed the estimates
inferred for different spectral ranges using the data at the original cadence
and temporally integrated signals. The longitudinal magnetic field in each
considered plasma structure correlates with its size. Using a spectral range
restricted to the line core leads to chromospheric longitudinal fields varying
from 50 G at the edges to 150-500 G at the center of the structure. These
values increase as the spectral range widens due to the photospheric
contribution. However, the difference between this contribution and the
chromospheric one is not uniform for all structures. Small and medium-sized
concentrations show a steeper height gradient in B_lon compared to their
chromospheric values, so estimates for wider ranges are less trustworthy.
Signal addition does not alleviate this situation as the height gradients in
B_lon are consistent with time. Finally, despite the amplified noise levels
that deconvolving processes may cause, data restored with the destretching
technique show similar results, though are affected by smearing. We obtained
B_lon estimates similar to those previously found, except for large
concentrations and wide spectral ranges. In addition, we report a correlation
between the height variation of B_lon compared to the chromospheric estimates
and the concentration size. This correlation affects the difference between the
photospheric and chromospheric magnetic flux values and the reliability of the
estimates for wider spectral ranges.Comment: 14 pages, 14 figures. Accepted for publication in Astronomy &
Astrophysics; abstract has been abridge
Olive oil characteristics of eleven cultivars produced in a high-density grove in Valladolid province (Spain)
The olive oil composition of eleven cultivars (cvs. Arbequina, Arbosana, Arroniz, Cornicabra, Frantoio, Hojiblanca, Manzanilla, Picual, Picudo, Redondilla and Royuela) cultivated in a high-density olive grove located in a non-traditional producing region (Valladolid, Spain) was studied during four consecutive crop seasons. The results showed that the 122 monovarietal olive oils studied could be classified as extra virgin oils, according to the quality parameters. Furthermore, the olive cultivar had a marked effect on the chemical composition and antioxidant activity. In general, olive oils from cvs. Picual and Cornicabra showed the highest total phenolic contents, oxidative stability, and tocopherols contents, whereas the worst results for oxidative stability were observed for cv. Redondilla olive oils, probably associated to the lowest contents of phenolics and tocopherols and the highest amounts of polyunsaturated fatty acids. Finally, it was found that, despite the different crop years evaluated, the quality-chemical profiles could be used to successfully discriminate the monovarietal oils under study (linear discriminant analysis sensitivities: 92 ± 5% for the repeated K-fold cross-validation), using the data of 15 non-redundant variables identified by the simulated annealing variable selection algorithm.The authors are grateful to the Foundation for
Science and Technology (FCT, Portugal) for financial support by
national funds FCT/MCTES to CIMO (UIDB/00690/2020) and Associate
Laboratories for Green Chemistry-LAQV (UIDB/50006/2020)
and SusTEC (LA/P/0007/2020). Nuno Rodrigues thanks to National
funding by FCT- Foundation for Science and Technology, P.I., through
the institutional scientific employment program-contract.info:eu-repo/semantics/publishedVersio
Non-local thermodynamic equilibrium inversions from a 3D MHD chromospheric model
The structure of the solar chromosphere is believed to be governed by
magnetic fields, even in quiet-Sun regions that have a relatively weak
photospheric field. During the past decade inversion methods have emerged as
powerful tools for analyzing the chromosphere of active regions. The
applicability of inversions to infer the stratification of the physical
conditions in a dynamic 3D solar chromosphere has not yet been studied in
detail.
This study aims to establish the diagnostic capabilities of non-local
thermodynamical equilibrium (NLTE) inversion techniques of Stokes profiles
induced by the Zeeman effect in the Ca II 8542 line.
We computed the Ca II atomic level populations in a snapshot from a 3D
radiation-MHD simulation of the quiet solar atmosphere in non-LTE using the 3D
radiative transfer code Multi3d. These populations were used to compute
synthetic full-Stokes profiles in the Ca II 8542 line using 1.5D radiative
transfer and the inversion code Nicole. The profiles were then spectrally
degraded to account for finite filter width and Gaussian noise was added to
account for finite photon flux. These profiles were inverted using Nicole and
the results were compared with the original model atmosphere.
Our NLTE inversions applied to quiet-Sun synthetic observations provide
reasonably good estimates of the chromospheric magnetic field, line-of-sight
velocities and somewhat less accurate, but still very useful, estimates of the
temperature. Three dimensional scattering of photons cause cool pockets in the
chromosphere to be invisible in the line profile and consequently they are also
not recovered by the inversions. To successfully detect Stokes linear
polarization in this quiet snapshot, a noise level below 10^{-3.5} is
necessary.Comment: Accepted for publication in Astronomy & Astrophysic
Seed storage conditions change the germination pattern of clonal growth plants in Mediterranean salt marshes.
8 páginas, 4 tablas, 8 figuras.The effect of salinity level and extended exposure to different salinity and flooding conditions on germination patterns of three saltmarsh clonal growth plants (Juncus subulatus, Scirpus litoralis, and S. maritimus) was studied. Seed exposure to extended flooding and saline conditions significantly affected the outcome of the germination process in a different, though predictable, way for each species, after favorable conditions for germination were restored. Tolerance of the germination process was related to the average salinity level measured during the growth/germination season at sites where established individuals of each species dominated the species cover. No relationship was found between salinity tolerance of the germination process and seed response to extended exposure to flooding and salinity conditions. The salinity response was significantly related to the conditions prevailing in the habitats of the respective species during the unfavorable (nongrowth/nongermination) season. Our results indicate that changes in salinity and hydrology while seeds are dormant affect the outcome of the seed-bank response, even when conditions at germination are identical.
Because these environmental-history-dependent responses differentially affect seed germination, seedling density, and probably sexual recruitment in the studied and related species, these influences should be considered for wetland restoration and managementFinancial support from the Spanish Ministry of the Environment (MMA, project 05/99) and the Junta de Andalucía (research group 4086)enabled us to carry out the present work.Peer reviewe
Seed storage conditions change the germination pattern of clonal growth plants in Mediterranean salt marshes.
8 páginas, 4 tablas, 8 figuras.The effect of salinity level and extended exposure to different salinity and flooding conditions on germination patterns of three saltmarsh clonal growth plants (Juncus subulatus, Scirpus litoralis, and S. maritimus) was studied. Seed exposure to extended flooding and saline conditions significantly affected the outcome of the germination process in a different, though predictable, way for each species, after favorable conditions for germination were restored. Tolerance of the germination process was related to the average salinity level measured during the growth/germination season at sites where established individuals of each species dominated the species cover. No relationship was found between salinity tolerance of the germination process and seed response to extended exposure to flooding and salinity conditions. The salinity response was significantly related to the conditions prevailing in the habitats of the respective species during the unfavorable (nongrowth/nongermination) season. Our results indicate that changes in salinity and hydrology while seeds are dormant affect the outcome of the seed-bank response, even when conditions at germination are identical.
Because these environmental-history-dependent responses differentially affect seed germination, seedling density, and probably sexual recruitment in the studied and related species, these influences should be considered for wetland restoration and managementFinancial support from the Spanish Ministry of the Environment (MMA, project 05/99) and the Junta de Andalucía (research group 4086)enabled us to carry out the present work.Peer reviewe
New factors for protein transport identified by a genome-wide CRISPRi screen in mammalian cells
Protein and membrane trafficking pathways are critical for cell and tissue homeostasis. Traditional genetic and biochemical approaches have shed light on basic principles underlying these processes. However, the list of factors required for secretory pathway function remains incomplete, and mechanisms involved in their adaptation poorly understood. Here, we present a powerful strategy based on a pooled genome-wide CRISPRi screen that allowed the identification of new factors involved in protein transport. Two newly identified factors, TTC17 and CCDC157, localized along the secretory pathway and were found to interact with resident proteins of ER-Golgi membranes. In addition, we uncovered that upon TTC17 knockdown, the polarized organization of Golgi cisternae was altered, creating glycosylation defects, and that CCDC157 is an important factor for the fusion of transport carriers to Golgi membranes. In conclusion, our work identified and characterized new actors in the mechanisms of protein transport and secretion, and opens stimulating perspectives for the use of our platform in physiological and pathological contexts.Includes Wellcome Trust, MRC and H202
Role of age and comorbidities in mortality of patients with infective endocarditis
Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality.
Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk.
Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality.
Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group
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