189 research outputs found
Constraints on a possible variation of the fine structure constant from galaxy cluster data
We propose a new method to probe a possible time evolution of the fine
structure constant from X-ray and Sunyaev-Zeldovich measurements of
the gas mass fraction () in galaxy clusters. Taking into account a
direct relation between variations of and violations of the
distance-duality relation, we discuss constraints on for a class of
dilaton runaway models. Although not yet competitive with bounds from high-
quasar absorption systems, our constraints, considering a sample of 29
measurements of , in the redshift interval , provide
an independent estimate of variation at low and intermediate
redshifts. Furthermore, current and planned surveys will provide a larger
amount of data and thus allow to improve the limits on variation
obtained in the present analysis.Comment: 7 pages, 2 figures, accepted for publication in JCA
Exploring the spectroscopic diversity of type Ia supernovae with DRACULA: a machine learning approach
The existence of multiple subclasses of type Ia supernovae (SNeIa) has been
the subject of great debate in the last decade. One major challenge inevitably
met when trying to infer the existence of one or more subclasses is the time
consuming, and subjective, process of subclass definition. In this work, we
show how machine learning tools facilitate identification of subtypes of SNeIa
through the establishment of a hierarchical group structure in the continuous
space of spectral diversity formed by these objects. Using Deep Learning, we
were capable of performing such identification in a 4 dimensional feature space
(+1 for time evolution), while the standard Principal Component Analysis barely
achieves similar results using 15 principal components. This is evidence that
the progenitor system and the explosion mechanism can be described by a small
number of initial physical parameters. As a proof of concept, we show that our
results are in close agreement with a previously suggested classification
scheme and that our proposed method can grasp the main spectral features behind
the definition of such subtypes. This allows the confirmation of the velocity
of lines as a first order effect in the determination of SNIa subtypes,
followed by 91bg-like events. Given the expected data deluge in the forthcoming
years, our proposed approach is essential to allow a quick and statistically
coherent identification of SNeIa subtypes (and outliers). All tools used in
this work were made publicly available in the Python package Dimensionality
Reduction And Clustering for Unsupervised Learning in Astronomy (DRACULA) and
can be found within COINtoolbox (https://github.com/COINtoolbox/DRACULA).Comment: 16 pages, 12 figures, accepted for publication in MNRA
Clinical features and outcomes of elderly hospitalised patients with chronic obstructive pulmonary disease, heart failure or both
Background and objective: Chronic obstructive pulmonary disease (COPD) and heart failure (HF) mutually increase the risk of being present in the same patient, especially if older. Whether or not this coexistence may be associated with a worse prognosis is debated. Therefore, employing data derived from the REPOSI register, we evaluated the clinical features and outcomes in a population of elderly patients admitted to internal medicine wards and having COPD, HF or COPD + HF.
Methods: We measured socio-demographic and anthropometric characteristics, severity and prevalence of comorbidities, clinical and laboratory features during hospitalization, mood disorders, functional independence, drug prescriptions and discharge destination. The primary study outcome was the risk of death.
Results: We considered 2,343 elderly hospitalized patients (median age 81 years), of whom 1,154 (49%) had COPD, 813 (35%) HF, and 376 (16%) COPD + HF. Patients with COPD + HF had different characteristics than those with COPD or HF, such as a higher prevalence of previous hospitalizations, comorbidities (especially chronic kidney disease), higher respiratory rate at admission and number of prescribed drugs. Patients with COPD + HF (hazard ratio HR 1.74, 95% confidence intervals CI 1.16-2.61) and patients with dementia (HR 1.75, 95% CI 1.06-2.90) had a higher risk of death at one year. The Kaplan-Meier curves showed a higher mortality risk in the group of patients with COPD + HF for all causes (p = 0.010), respiratory causes (p = 0.006), cardiovascular causes (p = 0.046) and respiratory plus cardiovascular causes (p = 0.009).
Conclusion: In this real-life cohort of hospitalized elderly patients, the coexistence of COPD and HF significantly worsened prognosis at one year. This finding may help to better define the care needs of this population
A quantitative analysis of gilthead seabream (Sparus aurata) juvenile dentition as a tool to assess the effect of diet
Gilthead seabream (Sparus aurata Linnaeus, 1758 (Perciformes, Sparidae)) is an important aquaculture species in the Mediterranean Sea basin. Yet, quantitative data on its dentition under standard farming conditions are currently lacking. Furthermore, it is unknown if the dentition can adapt to food of different sizes. Here, we describe the lower jaw dentition of juvenile S. aurata fed a standard pellet size (4 mm) and present a detailed analysis of 11 representative teeth. Overall, the number of teeth showed large individual variation, but it was not significantly related to fish length. Considerable left–right differences were observed, without clear side dominance. We also assessed the influence of feeding S. aurata a smaller (2 mm) or larger (6 mm) pellet size. Four months of feeding with different pellet sizes did not cause detectable differences in total tooth number on the dentaries at the time of harvest, nor in size of the teeth assumed to be most relevant in food processing. If and how different pellet sizes may nevertheless affect digestion, and eventually fish health, is subject for further studies
Constraining the dark energy and smoothness parameter with type Ia Supernovae and Gamma-Ray Bursts
The existence of inhomogeneities in the observed Universe modifies the
distance-redshift relations thereby affecting the results of cosmological tests
in comparison to the ones derived assuming spatially uniform models. By
modeling the inhomogeneities through a Zeldovich-Kantowski-Dyer-Roeder (ZKDR)
approach which is phenomenologically characterized by a smoothness parameter
, we rediscuss the constraints on the cosmic parameters based on
Supernovae type Ia and Gamma-Ray Bursts (GRBs) data. The present analysis is
restricted to a flat CDM model with the reasonable assumption that
does not clump. A -analysis using 557 SNe Ia data from the
Union2 Compilation Data (Amanullah {\it et al.} 2010) constrains the pair of
parameters () to ()
and . A similar analysis based only on 59 Hymnium GRBs (Wei
2010) constrains the matter density parameter to be () while all values for the smoothness parameter
are allowed. By performing a joint analysis, it is found that and . As a general result, although
considering that current GRB data alone cannot constrain the smoothness
parameter our analysis provides an interesting cosmological probe for
dark energy even in the presence of inhomogeneities.Comment: 7 pages, 4 figures, corrected version accepted for publication in
Physical Review
Application of an universal DNA microarray to cyanobacterial diversity assessment
peer reviewedOur technological goal was to test the new technology of DNA microarrays in the field of biodiversity assessments. The efficiency of DNA microarrays; was compared against the "classical" methods for measuring and monitoring the biodiversity. We use cyanobacteria from freshwater lakes as model organisms belonging to a well defined phylum of much ecological relevance. The combination of the information about cyanobacterial biodiversity together with the data describing the water quality of the lakes may reveal useful information to design management actions to control the unwanted mass developments of cyanobacteria. Such blooms prevent the use of water for drinking and for recreation and can be toxic to animals and humans. The possibility to automate the microarray technology in water quality monitoring will be an interesting alternative to time-consuming microscopic enumerations.MIDI-CHI
Genomics of Aerobic Cellulose Utilization Systems in Actinobacteria
Cellulose degrading enzymes have important functions in the biotechnology industry, including the production of biofuels from lignocellulosic biomass. Anaerobes including Clostridium species organize cellulases and other glycosyl hydrolases into large complexes known as cellulosomes. In contrast, aerobic actinobacteria utilize systems comprised of independently acting enzymes, often with carbohydrate binding domains. Numerous actinobacterial genomes have become available through the Genomic Encyclopedia of Bacteria and Archaea (GEBA) project. We identified putative cellulose-degrading enzymes belonging to families GH5, GH6, GH8, GH9, GH12, GH48, and GH51 in the genomes of eleven members of the actinobacteria. The eleven organisms were tested in several assays for cellulose degradation, and eight of the organisms showed evidence of cellulase activity. The three with the highest cellulase activity were Actinosynnema mirum, Cellulomonas flavigena, and Xylanimonas cellulosilytica. Cellobiose is known to induce cellulolytic enzymes in the model organism Thermobifida fusca, but only Nocardiopsis dassonvillei showed higher cellulolytic activity in the presence of cellobiose. In T. fusca, cellulases and a putative cellobiose ABC transporter are regulated by the transcriptional regulator CelR. Nine organisms appear to use the CelR site or a closely related binding site to regulate an ABC transporter. In some, CelR also regulates cellulases, while cellulases are controlled by different regulatory sites in three organisms. Mining of genome data for cellulose degradative enzymes followed by experimental verification successfully identified several actinobacteria species which were not previously known to degrade cellulose as cellulolytic organisms
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