172 research outputs found
Transcriptome profiling of ripening nectarine (Prunus persica L. Batsch) fruit treated with 1-MCP
A large-scale transcriptome analysis has been conducted using mPEACH1.0 microarray on nectarine (Prunus persica L. Batsch) fruit treated with 1-methylcyclopropene (1-MCP). 1-MCP maintained flesh firmness but did not block ethylene biosynthesis. Compared with samples at harvest, only nine genes appeared to be differentially expressed when fruit were sampled immediately after treatment, while a total of 90 targets were up- or down-regulated in untreated fruit. The effect of 1-MCP was confirmed by a direct comparison of transcript profiles in treated and untreated fruit after 24 h of incubation with 106 targets differentially expressed. About 30% of these targets correspond to genes involved in primary metabolism and response processes related to ethylene, auxin, and other hormones. In treated fruit, altered transcript accumulation was detected for some genes with a role in ripening-related events such as softening, colour development, and sugar metabolism. A rapid decrease in flesh firmness and an increase in ethylene production were observed in treated fruit maintained for 48 h in air at 20 ºC after the end of the incubation period. Microarray comparison of this sample with untreated fruit 24 h after harvest revealed that about 45% of the genes affected by 1-MCP at the end of the incubation period changed their expression during the following 48 h in air. Among these genes, an ethylene receptor (ETR2) and three ethylene responsive factors (ERF) were present, together with other transcription factors and ethylene-dependent genes involved in quality parameter changes
Prostatectomia com anastomose de uretra para o tratamento de adenocarcinoma prostático
O artigo não apresenta resumo
Unknown I.I.D. Prophets: Better Bounds, Streaming Algorithms, and a New Impossibility
A prophet inequality states, for some α ∈ [0, 1], that the expected value achievable by a gambler who
sequentially observes random variables X1, . . . , Xn and selects one of them is at least an α fraction
of the maximum value in the sequence. We obtain three distinct improvements for a setting that
was first studied by Correa et al. (EC, 2019) and is particularly relevant to modern applications in
algorithmic pricing. In this setting, the random variables are i.i.d. from an unknown distribution and
the gambler has access to an additional βn samples for some β ≥ 0. We first give improved lower
bounds on α for a wide range of values of β; specifically, α ≥ (1 + β)/e when β ≤ 1/(e − 1), which is
tight, and α ≥ 0.648 when β = 1, which improves on a bound of around 0.635 due to Correa et al.
(SODA, 2020). Adding to their practical appeal, specifically in the context of algorithmic pricing,
we then show that the new bounds can be obtained even in a streaming model of computation
and thus in situations where the use of relevant data is complicated by the sheer amount of data
available. We finally establish that the upper bound of 1/e for the case without samples is robust
to additional information about the distribution, and applies also to sequences of i.i.d. random
variables whose distribution is itself drawn, according to a known distribution, from a finite set of
known candidate distributions. This implies a tight prophet inequality for exchangeable sequences
of random variables, answering a question of Hill and Kertz (Contemporary Mathematics, 1992),
but leaves open the possibility of better guarantees when the number of candidate distributions is
small, a setting we believe is of strong interest to applications
Multiple Stellar Populations outside the tidal radius of NGC1851 through Gaia DR3 XP Spectra
Ancient Galactic Globular Clusters (GCs) have long fascinated astronomers due
to their intriguing multiple stellar populations characterized by variations in
light-element abundances. Among these clusters, Type-II GCs stand out as they
exhibit stars with large differences in heavy-element chemical abundances.
These enigmatic clusters, comprising approximately 17\% of analyzed GCs with
MPs, have been hypothesized to be the remnants of accreted dwarf galaxies. We
focus on one of the most debated Type~II GCs, NGC1851, to investigate its MPs
across a wide spatial range of up to 50 arcmin from the cluster center. By
using Gaia DR3 low-resolution XP spectra, we generate synthetic photometry to
perform a comprehensive analysis of the spatial distribution and kinematics of
the canonical and anomalous populations within this GC. By using appropriate
CMDs from the synthetic photometry in the BVI bands and in the
band introduced in this work, we identify distinct stellar sequences associated
with different heavy-element chemical composition. Our results suggest that the
canonical and the anomalous populations reside both inside and outside the
tidal radius of NGC1851, up to a distance that exceeds by 3.5 times its tidal
radius. However, 80\% of stars outside the tidal radius are consistent
with belonging to the canonical population, emphasizing its dominance in the
cluster's outer regions. Remarkably, canonical stars exhibit a more circular
on-sky morphology, while the anomalous population displays an elliptical shape.
Furthermore, we delve into the kinematics of the multiple populations. Our
results reveal a flat/increasing velocity dispersion profile in the outer
regions and hints of a tangentially anisotropic motion in the outer regions,
indicating a preference for stars to escape on radial orbits.Comment: 13 pages, 10 figures, accepted for publication in A&
Differential reddening in the direction of 56 Galactic globular clusters
The presence of differential reddening in the direction of Galactic globular
clusters (GCs) has proven to be a serious limitation in the traditional
colour-magnitude diagram (CMD) analysis. Here, we estimate local reddening
variations in the direction of 56 Galactic GCs. To do that, we use the public
catalogs derived as part of the Hubble Space Telescope UV Legacy Survey of
Galactic Globular Clusters, which include photometry in the F275W, F336W,
F438W, F606W, and F814W filters. We correct photometry for differential
reddening finding that for 21 out of 56 GCs the adopted correction procedure
significantly improves the CMDs. Moreover, we measure the reddening law in the
direction of these clusters finding that exhibits a high level of
variability within the Galaxy, ranging from to . The updated
values of have been used to improve the determination of local
reddening variations and derive high-resolution reddening maps in the direction
of the 21 highly-reddened targets within our sample. To compare the results of
the different clusters, we compute the 68 percentile of the
differential-reddening distribution, . This
quantity ranges from 0.003 mag to 0.030 mag and exhibits a significant
anti-correlation with the absolute module of the Galactic latitude and a strong
correlation with the average reddening in the direction of each cluster.
Therefore, highly-reddened GCs located in the proximity of the Galactic plane
typically show higher differential-reddening variations across their field of
view.Comment: 14 pages, 14 figures, accepted for pubblication in MNRAS. The
photometric catalogs corrected for differential reddening are publicly
available at this website: http://progetti.dfa.unipd.it/GALFOR
Photometric binaries, mass functions, and structural parameters of 78 Galactic open clusters
Binary stars play a crucial role in our understanding of the formation and
evolution of star clusters and their stellar populations. We use Gaia Data
Release 3 to homogeneously analyze 78 Galactic open clusters and the unresolved
binary systems they host, each composed of two main sequence (MS) stars. We
first investigated the structural parameters of these clusters, such as the
core radius and the central density, and determined the cluster mass function
(MF) and total mass by interpolating the density profile of each cluster. We
measured the fraction of binaries with a large mass ratio and the fraction of
blue straggler stars (BSSs), and finally investigated possible connections
between the populations of binary stars and BSSs with the main parameters of
the host cluster. {Remarkably, we find that the MFs of 78 analyzed open
clusters follow a similar trend and are well reproduced by two single power-law
functions, with a change in slope around masses of 1. The fraction
of binary stars ranges from 15\% to more than 60\% without
significant correlation with the mass and the age of the host cluster.
Moreover, we detect hints of a correlation between the total fraction of binary
stars and the central density of the host cluster. We compared the fraction of
binary stars with that of BSSs, finding that clusters with high and low central
density exhibit different trends. The fraction of binaries does not
significantly change with the mass of the primary star and the mass ratio. The
radial distribution of binary stars depends on cluster age. The binaries of
clusters younger than 800\,Myr typically show a flat radial distribution,
with some hints of a double peak. In contrast, the binaries of the remaining
clusters are more centrally concentrated than the single stars, which is
similar to what is observed in globular clusters.Comment: 27 pages, 27 figures, accepted for publication in Astronomy &
Astrophysic
A deep dive into the Type II Globular Cluster NGC 1851
About one-fifth of the Galactic globular clusters (GCs), dubbed Type II GCs,
host distinct stellar populations with different heavy elements abundances. NGC
1851 is one of the most studied Type II GCs, surrounded by several
controversies regarding the spatial distribution of its populations and the
presence of star-to-star [Fe/H], C+N+O, and age differences. This paper
provides a detailed characterization of its stellar populations through Hubble
Space Telescope (HST), ground-based, and Gaia photometry. We identified two
distinct populations with different abundances of s-process elements along the
red-giant branch (RGB) and the sub-giant branch (SGB) and detected two
sub-populations among both s-poor (canonical) and s-rich (anomalous) stars. To
constrain the chemical composition of these stellar populations, we compared
observed and simulated colors of stars with different abundances of He, C, N,
and O. It results that the anomalous population has a higher CNO overall
abundance compared to the canonical population and that both host stars with
different light-element abundances. No significant differences in radial
segregation between canonical and anomalous stars are detected, while we find
that among their sub-populations, the two most chemical extremes are more
centrally concentrated. Anomalous and canonical stars show different 2D spatial
distributions outside ~3 arcmin, with the latter developing an elliptical shape
and a stellar overdensity in the northeast direction. We confirm the presence
of a stellar halo up to ~80 arcmin with Gaia photometry, tagging 14 and five of
its stars as canonical and anomalous, respectively, finding a lack of the
latter in the south/southeast field.Comment: Accepted for publication on MNRA
Multiple Stellar Populations in Metal-Poor Globular Clusters with JWST: a NIRCam view of M 92
Recent work on metal-intermediate globular clusters (GCs) with [Fe/H]=
and has illustrated the theoretical behavior of multiple populations in
photometric diagrams obtained with the James Webb Space Telescope (JWST). These
results are confirmed by observations of multiple populations among M-dwarfs of
47 Tucanae. Here, we explore the multiple populations in metal-poor GCs with
[Fe/H]=2.3. We take advantage of synthetic spectra and isochrones that
account for the chemical composition of multiple populations to identify
photometric diagrams that separate the distinct stellar populations of GCs. We
derived high-precision photometry and proper motion for main-sequence stars in
the metal-poor GC M 92 from JWST and Hubble Space Telescope (HST) images. We
identified a first generation (1G) and two main groups of second-generation
stars (2G and 2G) and investigated their kinematics and
chemical composition. We find isotropic motions with no differences among the
distinct populations. The comparison between the observed colors of M 92 stars
and the colors derived by synthetic spectra reveals that helium abundance of
2G and 2G stars are higher than that of the 1G by and , respectively. The vs. color-magnitude diagram shows that below the knee, MS
stars exhibit a wide color broadening due to multiple populations. We constrain
the amount of oxygen variation needed to reproduce the observed MS width, which
is consistent with results on red-giant branch stars. We conclude that multiple
populations with masses of 0.1-0.8 share similar chemical
compositions.Comment: 15 pages, 9 figures. Submitted to ApJ on April 6th, 202
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