120 research outputs found
Mechanical tests and definition of new indexes of grape berry firmness. Evolution of berry skin hardness during alcoholic fermentation
The mechanical strength or firmness of a fruit is considered an important parameter to characterise its state of ripeness or conservation, as well as other parameters such as sugar level or color. The mechanical hardness of grapes influences the integrity and sanitary quality of the harvest. In this study, the mechanical characteristics of grapevine berries were studied at harvest time in order to determine their rheological properties (firmness and hardness of the berry skin) during alcoholic fermentation. Special indexes were defined measuring the energy needed to crush the berries to 50 % of their initial diameter, and applied successively to two different varieties. The entire berry firmness and the skin hardness were both different. Mechanical indexes linked to grape firmness were defined. Using these indexes, a significant effect on the firmness behavior due to variety was recorded: the skin of 'Grenache Noir' was found firmer and harder than 'Carignan Noir'. Furthermore, during the alcoholic fermentation, no change in skin hardness was observed for both varieties, despite changes in the composition of the must. These results give new information on mechanical properties of berries and could be used as an aid in the winemaking process. Indeed, they would probably help the winemaker to better choose the type of fermentation and maceration adapted to his grapes according to the type of wine he wishes to produce
Colloidal stability of tannins: astringency, wine tasting and beyond
Tannin-tannin and tannin-protein interactions in water-ethanol solvent
mixtures are studied in the context of red wine tasting. While tannin
self-aggregation is relevant for visual aspect of wine tasting (limpidity and
related colloidal phenomena), tannin affinities for salivary proline-rich
proteins is fundamental for a wide spectrum of organoleptic properties related
to astringency. Tannin-tannin interactions are analyzed in water-ethanol
wine-like solvents and the precipitation map is constructed for a typical grape
tannin. The interaction between tannins and human salivary proline-rich
proteins (PRP) are investigated in the framework of the shell model for
micellization, known for describing tannin-induced aggregation of beta-casein.
Tannin-assisted micellization and compaction of proteins observed by SAXS are
described quantitatively and discussed in the case of astringency
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Identification of structural features of condensed tannins that affect protein aggregation
A diverse panel of condensed tannins was used to resolve the confounding effects of size and subunit composition seen previously in tannin-protein interactions. Turbidimetry revealed that size in terms of mean degree of polymerisation (mDP) or average molecular weight (amw) was the most important tannin parameter. The smallest tannin with the relatively largest effect on protein aggregation had an mDP of ~7. The average size was significantly correlated with aggregation of bovine serum albumin, BSA (mDP: r=-0.916; amw: r=-0.925; p<0.01; df=27), and gelatin (mDP: r=-0.961; amw: r=-0.981; p<0.01; df=12). The procyanidin/prodelphinidin and cis-/trans-flavan-3-ol ratios gave no significant correlations. Tryptophan fluorescence quenching indicated that procyanidins and cis-flavan-3-ol units contributed most to the tannin interactions on the BSA surface and in the hydrophobic binding pocket (r=0.677; p<0.05; df=9 and r=0.887; p<0.01; df=9, respectively). Circular dichroism revealed that higher proportions of prodelphinidins decreased the apparent α-helix content (r=-0.941; p<0.01; df=5) and increased the apparent β-sheet content (r=0.916; p<0.05; df=5) of BSA
Euclid preparation TBD. The effect of baryons on the Halo Mass Function
The Euclid photometric survey of galaxy clusters stands as a powerful
cosmological tool, with the capacity to significantly propel our understanding
of the Universe. Despite being sub-dominant to dark matter and dark energy, the
baryonic component in our Universe holds substantial influence over the
structure and mass of galaxy clusters. This paper presents a novel model to
precisely quantify the impact of baryons on galaxy cluster virial halo masses,
using the baryon fraction within a cluster as proxy for their effect.
Constructed on the premise of quasi-adiabaticity, the model includes two
parameters calibrated using non-radiative cosmological hydrodynamical
simulations and a single large-scale simulation from the Magneticum set, which
includes the physical processes driving galaxy formation. As a main result of
our analysis, we demonstrate that this model delivers a remarkable one percent
relative accuracy in determining the virial dark matter-only equivalent mass of
galaxy clusters, starting from the corresponding total cluster mass and baryon
fraction measured in hydrodynamical simulations. Furthermore, we demonstrate
that this result is robust against changes in cosmological parameters and
against varying the numerical implementation of the sub-resolution physical
processes included in the simulations. Our work substantiates previous claims
about the impact of baryons on cluster cosmology studies. In particular, we
show how neglecting these effects would lead to biased cosmological constraints
for a Euclid-like cluster abundance analysis. Importantly, we demonstrate that
uncertainties associated with our model, arising from baryonic corrections to
cluster masses, are sub-dominant when compared to the precision with which
mass-observable relations will be calibrated using Euclid, as well as our
current understanding of the baryon fraction within galaxy clusters.Comment: 18 pages, 10 figures, 4 tables, 1 appendix, abstract abridged for
arXiv submissio
Euclid Preparation. XXVIII. Forecasts for ten different higher-order weak lensing statistics
Recent cosmic shear studies have shown that higher-order statistics (HOS)
developed by independent teams now outperform standard two-point estimators in
terms of statistical precision thanks to their sensitivity to the non-Gaussian
features of large-scale structure. The aim of the Higher-Order Weak Lensing
Statistics (HOWLS) project is to assess, compare, and combine the constraining
power of ten different HOS on a common set of -like mocks, derived from
N-body simulations. In this first paper of the HOWLS series, we computed the
nontomographic (, ) Fisher information for the
one-point probability distribution function, peak counts, Minkowski
functionals, Betti numbers, persistent homology Betti numbers and heatmap, and
scattering transform coefficients, and we compare them to the shear and
convergence two-point correlation functions in the absence of any systematic
bias. We also include forecasts for three implementations of higher-order
moments, but these cannot be robustly interpreted as the Gaussian likelihood
assumption breaks down for these statistics. Taken individually, we find that
each HOS outperforms the two-point statistics by a factor of around two in the
precision of the forecasts with some variations across statistics and
cosmological parameters. When combining all the HOS, this increases to a
times improvement, highlighting the immense potential of HOS for cosmic shear
cosmological analyses with . The data used in this analysis are
publicly released with the paper.Comment: 33 pages, 24 figures, main results in Fig. 19 & Table 5, version
published in A&
Euclid preparation: XV. Forecasting cosmological constraints for the Euclid and CMB joint analysis
The combination and cross-correlation of the upcoming Euclid data with cosmic microwave background (CMB) measurements is a source of great expectation since it will provide the largest lever arm of epochs, ranging from recombination to structure formation across the entire past light cone. In this work, we present forecasts for the joint analysis of Euclid and CMB data on the cosmological parameters of the standard cosmological model and some of its extensions. This work expands and complements the recently published forecasts based on Euclid-specific probes, namely galaxy clustering, weak lensing, and their cross-correlation. With some assumptions on the specifications of current and future CMB experiments, the predicted constraints are obtained from both a standard Fisher formalism and a posterior-fitting approach based on actual CMB data. Compared to a Euclid-only analysis, the addition of CMB data leads to a substantial impact on constraints for all cosmological parameters of the standard Λ-cold-dark-matter model, with improvements reaching up to a factor of ten. For the parameters of extended models, which include a redshift-dependent dark energy equation of state, non-zero curvature, and a phenomenological modification of gravity, improvements can be of the order of two to three, reaching higher than ten in some cases. The results highlight the crucial importance for cosmological constraints of the combination and cross-correlation of Euclid probes with CMB data
Euclid Preparation TBD. Characterization of convolutional neural networks for the identification of galaxy-galaxy strong lensing events
Forthcoming imaging surveys will potentially increase the number of known
galaxy-scale strong lenses by several orders of magnitude. For this to happen,
images of tens of millions of galaxies will have to be inspected to identify
potential candidates. In this context, deep learning techniques are
particularly suitable for the finding patterns in large data sets, and
convolutional neural networks (CNNs) in particular can efficiently process
large volumes of images. We assess and compare the performance of three network
architectures in the classification of strong lensing systems on the basis of
their morphological characteristics. We train and test our models on different
subsamples of a data set of forty thousand mock images, having characteristics
similar to those expected in the wide survey planned with the ESA mission
\Euclid, gradually including larger fractions of faint lenses. We also evaluate
the importance of adding information about the colour difference between the
lens and source galaxies by repeating the same training on single-band and
multi-band images. Our models find samples of clear lenses with
precision and completeness, without significant differences in the performance
of the three architectures. Nevertheless, when including lenses with fainter
arcs in the training set, the three models' performance deteriorates with
accuracy values of to depending on the model. Our
analysis confirms the potential of the application of CNNs to the
identification of galaxy-scale strong lenses. We suggest that specific training
with separate classes of lenses might be needed for detecting the faint lenses
since the addition of the colour information does not yield a significant
improvement in the current analysis, with the accuracy ranging from
to for the different models
Euclid preparation. XXIX. Water ice in spacecraft part I: The physics of ice formation and contamination
Molecular contamination is a well-known problem in space flight. Water is the
most common contaminant and alters numerous properties of a cryogenic optical
system. Too much ice means that Euclid's calibration requirements and science
goals cannot be met. Euclid must then be thermally decontaminated, a long and
risky process. We need to understand how iced optics affect the data and when a
decontamination is required. This is essential to build adequate calibration
and survey plans, yet a comprehensive analysis in the context of an
astrophysical space survey has not been done before.
In this paper we look at other spacecraft with well-documented outgassing
records, and we review the formation of thin ice films. A mix of amorphous and
crystalline ices is expected for Euclid. Their surface topography depends on
the competing energetic needs of the substrate-water and the water-water
interfaces, and is hard to predict with current theories. We illustrate that
with scanning-tunnelling and atomic-force microscope images.
Industrial tools exist to estimate contamination, and we must understand
their uncertainties. We find considerable knowledge errors on the diffusion and
sublimation coefficients, limiting the accuracy of these tools. We developed a
water transport model to compute contamination rates in Euclid, and find
general agreement with industry estimates. Tests of the Euclid flight hardware
in space simulators did not pick up contamination signals; our in-flight
calibrations observations will be much more sensitive.
We must understand the link between the amount of ice on the optics and its
effect on Euclid's data. Little research is available about this link, possibly
because other spacecraft can decontaminate easily, quenching the need for a
deeper understanding. In our second paper we quantify the various effects of
iced optics on spectrophotometric data.Comment: 35 pages, 22 figures, A&A in press. Changes to previous version:
language edits, added Z. Bolag as author in the arxiv PDF (was listed in the
ASCII author list and in the journal PDF, but not in the arxiv PDF). This
version is identical to the journal versio
Euclid preparation. XXXI. Performance assessment of the NISP Red-Grism through spectroscopic simulations for the Wide and Deep surveys
This work focuses on the pilot run of a simulation campaign aimed at
investigating the spectroscopic capabilities of the Euclid Near-Infrared
Spectrometer and Photometer (NISP), in terms of continuum and emission line
detection in the context of galaxy evolutionary studies. To this purpose we
constructed, emulated, and analysed the spectra of 4992 star-forming galaxies
at using the NISP pixel-level simulator. We built the
spectral library starting from public multi-wavelength galaxy catalogues, with
value-added information on spectral energy distribution (SED) fitting results,
and from Bruzual and Charlot (2003) stellar population templates. Rest-frame
optical and near-IR nebular emission lines were included using empirical and
theoretical relations. We inferred the 3.5 NISP red grism spectroscopic
detection limit of the continuum measured in the band for star-forming
galaxies with a median disk half-light radius of \ang{;;0.4} at magnitude ABmag for the Euclid Wide Survey and at ABmag for the Euclid Deep Survey. We found a very good
agreement with the red grism emission line detection limit requirement for the
Wide and Deep surveys. We characterised the effect of the galaxy shape on the
detection capability of the red grism and highlighted the degradation of the
quality of the extracted spectra as the disk size increases. In particular, we
found that the extracted emission line signal to noise ratio (SNR) drops by
45 when the disk size ranges from \ang{;;0.25} to \ang{;;1}. These
trends lead to a correlation between the emission line SNR and the stellar mass
of the galaxy and we demonstrate the effect in a stacking analysis unveiling
emission lines otherwise too faint to detect.Comment: 23 pages, 21 figure
Euclid preparation. TBD. Forecast impact of super-sample covariance on 3x2pt analysis with Euclid
Deviations from Gaussianity in the distribution of the fields probed by
large-scale structure surveys generate additional terms in the data covariance
matrix, increasing the uncertainties in the measurement of the cosmological
parameters. Super-sample covariance (SSC) is among the largest of these
non-Gaussian contributions, with the potential to significantly degrade
constraints on some of the parameters of the cosmological model under study --
especially for weak lensing cosmic shear. We compute and validate the impact of
SSC on the forecast uncertainties on the cosmological parameters for the Euclid
photometric survey, obtained with a Fisher matrix analysis, both considering
the Gaussian covariance alone and adding the SSC term -- computed through the
public code PySSC. The photometric probes are considered in isolation and
combined in the `32pt' analysis. We find the SSC impact to be
non-negligible -- halving the Figure of Merit of the dark energy parameters
(, ) in the 32pt case and substantially increasing the
uncertainties on , and for cosmic shear;
photometric galaxy clustering, on the other hand, is less affected due to the
lower probe response. The relative impact of SSC does not show significant
changes under variations of the redshift binning scheme, while it is smaller
for weak lensing when marginalising over the multiplicative shear bias nuisance
parameters, which also leads to poorer constraints on the cosmological
parameters. Finally, we explore how the use of prior information on the shear
and galaxy bias changes the SSC impact. Improving shear bias priors does not
have a significant impact, while galaxy bias must be calibrated to sub-percent
level to increase the Figure of Merit by the large amount needed to achieve the
value when SSC is not included.Comment: 22 pages, 13 figure
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