383 research outputs found
Disk galaxies with broken luminosity profiles from cosmological simulations
We present SPH cosmological simulations of the formation of three disk
galaxies with a detailed treatment of chemical evolution and cooling. The
resulting galaxies have properties compatible with observations: relatively
high disk-to-total ratios, thin stellar disks and good agreement with the
Tully-Fisher and the luminosity-size relations. They present a break in the
luminosity profile at 3.0 +- 0.5 disk scale lengths, while showing an
exponential mass profile without any apparent breaks, in line with recent
observational results. Since the stellar mass profile is exponential, only
differences in the stellar populations can be the cause of the luminosity
break. Although we find a cutoff for the star formation rate imposed by a
density threshold in our star formation model, it does not coincide with the
luminosity break and is located at 4.3 +- 0.4 disk scale lengths, with star
formation going on between both radii. The color profiles and the age profiles
are "U-shaped", with the minimum for both profiles located approximately at the
break radius. The SFR to stellar mass ratio increases until the break,
explaining the coincidence of the break with the minimum of the age profile.
Beyond the break we find a steep decline in the gas density and, consequently,
a decline in the SFR and redder colors. We show that most stars (64-78%) in the
outer disk originate in the inner disk and afterwards migrate there. Such
stellar migrations are likely the main origin of the U-shaped age profile and,
therefore, of the luminosity break.Comment: 8 pages, 4 figures. Accepted by ApJ
Supporting Data for the Characterization of PNA-DNA Four-Way Junctions
Holliday or DNA four-way junctions (4WJs) are cruciform/bent structures composed of four DNA duplexes. 4WJs are key intermediates in homologous genetic recombination and double-strand break repair. To investigate 4WJs in vitro, junctions are assembled using four asymmetric DNA strands. The presence of four asymmetric strands about the junction branch point eliminates branch migration, and effectively immobilizes the resulting 4WJ. The purpose of these experiments is to show that immobile 4WJs composed of DNA and peptide nucleic acids (PNAs) can be distinguished from contaminating labile nucleic acid structures. These data compare the electrophoretic mobility of hybrid PNA–DNA junctions vs. i) a classic immobile DNA 4WJ, J1 and ii) contaminating nucleic acid structures
Revisiting the Hubble sequence in the SDSS DR7 spectroscopic sample: a publicly available bayesian automated classification
We present an automated morphological classification in 4 types
(E,S0,Sab,Scd) of ~700.000 galaxies from the SDSS DR7 spectroscopic sample
based on support vector machines. The main new property of the classification
is that we associate to each galaxy a probability of being in the four
morphological classes instead of assigning a single class. The classification
is therefore better adapted to nature where we expect a continuos transition
between different morphological types. The algorithm is trained with a visual
classification and then compared to several independent visual classifications
including the Galaxy Zoo first release catalog. We find a very good correlation
between the automated classification and classical visual ones. The compiled
catalog is intended for use in different applications and can be downloaded at
http://gepicom04.obspm.fr/sdss_morphology/Morphology_2010.html and soon from
the CasJobs database.Comment: A&A in press, english corrections from language editor adde
The Opacity of Spiral Galaxy Disks VI: Extinction, stellar light and color
In this paper we explore the relation between dust extinction and stellar
light distribution in disks of spiral galaxies. Extinction influences our
dynamical and photometric perception of disks, since it can distort our
measurement of the contribution of the stellar component. To characterize the
total extinction by a foreground disk, Gonzalez et al. (1998) proposed the
``Synthetic Field Method'' (SFM), which uses the calibrated number of distant
galaxies seen through the foreground disk as a direct indication of extinction.
The method is described in Gonzalez et al. (1998) and Holwerda et al. (2005a).
To obtain good statistics, the method was applied to a set of HST/WFPC2 fields
Holwerda et al. (2005b) and radial extinction profiles were derived, based on
these counts. In the present paper, we explore the relation of opacity with
surface brightness or color from 2MASS images, as well as the relation between
the scalelengths for extinction and light in the I band. We find that there is
indeed a relation between the opacity (A_I) and the surface brightness,
particularly at the higher surface brightnesses. No strong relation between
near infrared (H-J, H-K) color and opacity is found. The scalelengths of the
extinction are uncertain for individual galaxies but seem to indicate that the
dust distribution is much more extended than the stellar light. The results
from the distant galaxy counts are also compared to the reddening derived from
the Cepheids light-curves Freedman et al. (2001). The extinction values are
consistent, provided the selection effect against Cepheids with higher values
of A_I is taken into account. The implications from these relations for disk
photometry, M/L conversion and galaxy dynamical modeling are briefly discussed.Comment: 9 pages, 2 tables, 10 figures, accepted by A&
Multi-Dimensional, Compressible Viscous Flow on a Moving Voronoi Mesh
Numerous formulations of finite volume schemes for the Euler and
Navier-Stokes equations exist, but in the majority of cases they have been
developed for structured and stationary meshes. In many applications, more
flexible mesh geometries that can dynamically adjust to the problem at hand and
move with the flow in a (quasi) Lagrangian fashion would, however, be highly
desirable, as this can allow a significant reduction of advection errors and an
accurate realization of curved and moving boundary conditions. Here we describe
a novel formulation of viscous continuum hydrodynamics that solves the
equations of motion on a Voronoi mesh created by a set of mesh-generating
points. The points can move in an arbitrary manner, but the most natural motion
is that given by the fluid velocity itself, such that the mesh dynamically
adjusts to the flow. Owing to the mathematical properties of the Voronoi
tessellation, pathological mesh-twisting effects are avoided. Our
implementation considers the full Navier-Stokes equations and has been realized
in the AREPO code both in 2D and 3D. We propose a new approach to compute
accurate viscous fluxes for a dynamic Voronoi mesh, and use this to formulate a
finite volume solver of the Navier-Stokes equations. Through a number of test
problems, including circular Couette flow and flow past a cylindrical obstacle,
we show that our new scheme combines good accuracy with geometric flexibility,
and hence promises to be competitive with other highly refined Eulerian
methods. This will in particular allow astrophysical applications of the AREPO
code where physical viscosity is important, such as in the hot plasma in galaxy
clusters, or for viscous accretion disk models.Comment: 26 pages, 21 figures. Submitted to MNRA
Thermal analysis of water in reinforced plasma-polymerised poly(2-hydroxyethyl acrylate) hydrogels
Thermal analysis of water in reinforce hydrogels of plasma-polymerised poly(2-hydroxyethyl acrylate) (plPHEA) grafted onto macroporous poly(methyl methacrylate) (PMMA) are explained in a simple thermodynamic framework based on the transition diagram. Water in bulk PHEA was also analysed for comparison with plPHEA. These two hydrophilic polymers were prepared with a broad range of water mass fractions from 0.05 to 0.72. Thermal transition diagrams of water/PHEA and water/plPHEA were determined showing less undercooling of water crystallisation in plPHEA than in PHEA. Kinetics of water crystallisation for high and low water contents were studied in both hydrophilic systems following several thermal treatments. Water crystallises much faster in plPHEA than in PHEA for high water contents. For low water contents, crystallisation becomes possible holding at 30 degrees C for some time due to water segregation in both PHEA systems. However, much less water is segregated from the water/plPHEA mixture due to the influence of the hydrophobic component.This work was supported by a Marie Curie Host Fellowship and by the Spanish Science and Technology Ministry through the MAT2001-2678-C02-01 and MAT2002-04239-C03-03 projects. CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Serrano Aroca, Á.; Monleón Pradas, M.; Gómez Ribelles, JL.; Rault, J. (2015). Thermal analysis of water in reinforced plasma-polymerised poly(2-hydroxyethyl acrylate) hydrogels. European Polymer Journal. 72:523-534. https://doi.org/10.1016/j.eurpolymj.2015.05.032S5235347
PREDIRCAM eHealth platform for individualized telemedical assistance for lifestyle modification in the treatment of obesity, diabetes, and cardiometabolic risk prevention: a pilot study (PREDIRCAM 1)
Background:
Healthy diet and regular physical activity are powerful tools in reducing diabetes and cardiometabolic risk.
Various international scientific and health organizations have advocated the use of new technologies to solve
these problems. The PREDIRCAM project explores the contribution that a technological system could offer for
the continuous monitoring of lifestyle habits and individualized treatment of obesity as well as cardiometabolic
risk prevention.
Methods:
PREDIRCAM is a technological platform for patients and professionals designed to improve the effectiveness
of lifestyle behavior modifications through the intensive use of the latest information and communication
technologies. The platform consists of a web-based application providing communication interface with
monitoring devices of physiological variables, application for monitoring dietary intake, ad hoc electronic
medical records, different communication channels, and an intelligent notification system. A 2-week feasibility
study was conducted in 15 volunteers to assess the viability of the platform.
Results:
The website received 244 visits (average time/session: 17 min 45 s). A total of 435 dietary intakes were recorded
(average time for each intake registration, 4 min 42 s ± 2 min 30 s), 59 exercises were recorded in 20 heart
rate monitor downloads, 43 topics were discussed through a forum, and 11 of the 15 volunteers expressed a
favorable opinion toward the platform. Food intake recording was reported as the most laborious task. Ten of
the volunteers considered long-term use of the platform to be feasible.
Conclusions:
The PREDIRCAM platform is technically ready for clinical evaluation. Training is required to use the platform
and, in particular, for registration of dietary food intake
Galaxy Formation Theory
We review the current theory of how galaxies form within the cosmological
framework provided by the cold dark matter paradigm for structure formation.
Beginning with the pre-galactic evolution of baryonic material we describe the
analytical and numerical understanding of how baryons condense into galaxies,
what determines the structure of those galaxies and how internal and external
processes (including star formation, merging, active galactic nuclei etc.)
determine their gross properties and evolution. Throughout, we highlight
successes and failings of current galaxy formation theory. We include a review
of computational implementations of galaxy formation theory and assess their
ability to provide reliable modelling of this complex phenomenon. We finish
with a discussion of several "hot topics" in contemporary galaxy formation
theory and assess future directions for this field.Comment: 58 pages, to appear in Physics Reports. This version includes minor
corrections and a handful of additional reference
Linking personality to larval energy reserves in rainbow trout (Oncorhynchus mykiss).
There is a surging interest in the evolution, ecology and physiology of personality differences. However, most of the studies in this research area have been performed in adult animals. Trait variations expressed early in development and how they are related to the ontogeny of an animal's personality are far less studied. Genetic differences as well as environmental factors causing functional variability of the central serotonergic system have been related to personality differences in vertebrates, including humans. Such gene-environment interplay suggests that the central serotonergic system plays an important role in the ontogeny of personality traits. In salmonid fishes, the timing of emergence from spawning nests is related to energy reserves, aggression, and social dominance. However, it is currently unknown how the size of the yolk reserve is reflected on aggression and dominance, or if these traits are linked to differences in serotonergic transmission in newly emerged larvae. In this study we investigated the relationship between yolk reserves, social dominance, and serotonergic transmission in newly emerged rainbow trout (Oncorhynchus mykiss) larvae. This was conducted by allowing larvae with the same emergence time, but with different yolk sizes, to interact in pairs for 24 h. The results show that individuals with larger yolks performed more aggressive acts, resulting in a suppression of aggression in individuals with smaller yolks. A higher brain serotonergic activity confirmed subordination in larvae with small yolks. The relationship between social dominance and yolk size was present in siblings, demonstrating a link between interfamily variation in energy reserves and aggression, and suggests that larger yolk reserves fuel a more aggressive personality during the initial territorial establishment in salmonid fishes. Furthermore, socially naïve larvae with big yolks had lower serotonin levels, suggesting that other factors than the social environment causes variation in serotonergic transmission, underlying individual variation in aggressive behavior
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