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The faba bean (Vicia faba L.) is a potential source of proteins for poultry, mainly for laying hens whose protein requirements are lower than those of other birds such as growing broilers and turkeys. However, this feedstuff contains anti-nutritional factors, that is, vicine (V) and convicine (C) that are already known to reduce laying hen performance. The aim of the experiment reported here was to evaluate the effects of a wide range of dietary V and C concentrations in laying hens. Two trials were performed with laying hens fed diets including 20% or 25% of faba bean genotypes highly contrasting in V+C content. In Trial 1, faba beans from two tannin-containing cultivars, but with high or low V+C content were dehulled in order to eliminate the tannin effect. In addition to the contrasting levels of V+C in the two cultivars, two intermediate levels of V+C were obtained by mixing the two cultivars (70/30 and 30/70). In Trial 2, two isogenic zero-tannin faba bean genotypes with high or low V+C content were used. In both trials, a classical corn–soybean diet was also offered to control hens. Each experimental diet was given to 48 laying hens for 140 (Trial 1) or 89 (Trial 2) days. Laying performance and egg quality were measured. The redox sensitivity of red blood cells (RBCs) was assessed by measuring hemolysis and reduced glutathione (GSH) concentration in these cells. Egg weight was significantly reduced by the diets containing the highest concentrations of V+C (P<0.0001) in Trial 1 and slightly reduced (P<0.10) in Trial 2, but only weak linear relationships between egg weight and dietary V+C concentration were established. No negative effect of V+C level was observed for egg quality parameters. In contrast, certain parameters (i.e. Haugh units, yolk color) were improved by feeding low V+C diets (P<0.05). Hemolysis of RBCs was higher in hens fed high V+C diets. A decrease in GSH concentration in RBCs of hens fed the highest levels of V+C was observed. Faba bean genotypes with low concentrations of V+C can therefore be used in laying hen diets up to 25% without any detrimental effects on performance levels or egg characteristics, without any risk of hemolysis of RBCs.
We investigate the process of galaxy formation as can be observed in the only currently forming galaxies - the so-called Tidal Dwarf Galaxies, hereafter TDGs - through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a bona fide galaxy. We have now detected CO in 9 TDGs with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 108M⊙. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H2. Although uncertainties are still large for individual objects as the geometry is unknown, we find that the “dynamical” masses of TDGs, estimated from the CO line widths, do not seem to be greater than the “visible” masses (HI + H2 + a stellar component), i.e., TDGs require no dark matter. We provide evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.
Head-on collisions of spiral galaxies can bring large quantities of gas out of spiral disks and into the intergalactic medium. Only two clear cases (UGC 12914/5 and UGC 813/6) of such collisions are known (Condon et al. 1993, 2002) and in both cases several 109 M⊙ of neutral gas is found in the bridge between the two galaxies which are now separating. About half of the gas is molecular. The gas, atomic or molecular, is brought out by collisions between clouds, which then acquire an intermediate velocity and end up between the galaxies. The bridges contain no old stars and in each case only one HII region despite the large masses of molecular gas, such that the star formation efficiency is very low in the bridges. The collisions occurred 20 – 50 million years ago, much greater than the collapse time for dense cores. We (Braine et al. 2003, 2004) show that collisions between molecular clouds, and not only between atomic gas clouds, bring gas into the bridges. It is not currently known whether the galaxies and bridges are bound or whether they will continue to separate, releasing several 109 M⊙ of neutral gas into the intergalactic medium.
A candidate Tidal Dwarf Galaxy, ce-61, was identified in the merger system IC 1182 in the Hercules supercluster. The multi-wavelength data we obtained so far do not prove, however, that it is kinematically detached from the IC 1182 system and gravitationally bound.
We review the observational evidences for tidal dwarf galaxies, a class of small galaxies formed out of the tidal debris of collisions between massive galaxies. Tidal dwarfs are found far from the interacting parent galaxies, associated with massive clouds of atomic hydrogen located at the tip of long tidal tails. These newly formed galaxies are among the best cases for the study of galaxy formation in the nearby Universe.
This spatial experiment is under construction and has been defined as a 2 years mission on board SOHO, a satellite dedicated to the Sun which will be launched in mid 95. The main objectives are the detection of solar low degree acoustic modes and solar gravity modes for improving our knowledge of the solar nuclear region.
The life and evolution of galaxies are dramatically affected by environmental effects. Interactions with the intergalactic medium and collisions with companions cause major perturbations in the morphology and contents of galaxies: in particular stars and gas clouds may be gravitationally pulled out from their parent galaxies during tidal encounters, forming rings, tails and bridges. This debris of collisions lies at the origin of a new generation of small galaxies, the so-called “tidal dwarf galaxies” (hereafter TDGs). Such an exotic way of forming galaxies was put forward by Schweizer (1978) and by Mirabel et al. (1992), who clearly observed the genesis of a star-forming object, out of material tidally expelled from the interacting system NGC 4038/39 (“The Antennae”). Recent studies, based on optical and HI observations, have shown that TDGs actually form a class of “recycled” objects with some properties similar to the more classical dwarf irregulars (dIrr) and blue compact dwarf galaxies (BCDs).
Discovery of ultra-compact dwarfs (UCDs) in the past 15 years blurs the once thought clear division between classic globular clusters (GCs) and early-type galaxies. The intermediate nature of UCDs, which are larger and more massive than typical GCs but more compact than typical dwarf galaxies, has triggered hot debate on whether UCDs should be considered galactic in origin or merely the most extreme GCs. Previous studies of various scaling relations, stellar populations and internal dynamics did not give an unambiguous answer to the primary origin of UCDs. In this contribution, we present the first ever detailed study of global dynamics of 97 UCDs (rh ≳ 10 pc) associated with the central cD galaxy of the Virgo cluster, M87. We found that UCDs follow a different radial number density profile and different rotational properties from GCs. The orbital anisotropies of UCDs are tangentially-biased within ~ 40 kpc of M87 and become radially-biased with radius further out. In contrast, the blue GCs, which have similar median colors to our sample of UCDs, become more tangentially-biased at larger radii beyond ~ 40 kpc. Our analysis suggests that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially-biased orbital structure of UCDs at large radii is in general agreement with the scenario that most UCDs originated from the tidally threshed dwarf galaxies.
De Haas-van Alphen oscillations of the organic metal θ-(ET)4ZnBr4(C6H4Cl2) are studied in pulsed magnetic fields up to 81 T. The long decay time of the pulse allows determining reliable field-dependent amplitudes of Fourier components with frequencies up to several kiloteslas. The Fourier spectrum is in agreement with the model of a linear chain of coupled orbits. In this model, all the observed frequencies are linear combinations of the frequency linked to the basic orbit α and to the magnetic-breakdown orbit β.
In around ≈25% of early-type galaxies (ETGs) UV emission from young stellar populations is present. Molecular gas reservoirs have been detected in these systems (e.g. Young et al. (2011), providing the fuel for this residual star-formation. The environment in which this molecular gas is found is quite different than that in spiral galaxies however, with harsher radiation fields, deeper potentials and high metallicity and alpha-element abundances. Here we report on one element of our multi-faceted programme to understand the similarities and differences between the gas reservoirs in spirals and ETGs. We use spatially resolved observations from the CARMA mm-wave interferometer to investigate the size of the molecular reservoirs in the the CO-rich ATLAS3D ETGs (survey described in Alatalo et al. 2012, submitted). We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scale-lengths (Fig 1, left). Amongst ETGs, we find that the extent of the molecular gas is independent of the kinematic misalignment, despite the many reasons why misaligned gas might have a smaller extent. The extent of the molecular gas does depend on environment, with Virgo cluster ETGs having less extended molecular gas reservoirs (Fig 1, right). Whatever the cause, this further emphases that cluster ETGs follow different evolutionary pathways from those in the field. Full details of this work will be presented in Davis et al. (2012), submitted.
Merging systems at low redshift provide the unique opportunity to study the processes related to star formation in a variety of environments that presumably resemble those seen at higher redshifts. Previous studies of distant starbursting galaxies suggest that stars are born in turbulent gas, with a higher efficiency than in MW-like spirals. We have investigated in detail the turbulent-driven regime of star-formation in nearby colliding galaxies combining high resolution VLA B array Hi maps and UV GALEX observations. With these data, we could check predictions of our state-of-the-art simulations of mergers, such as the global sharp increase of the fraction of dense gas, as traced by the SFR, with respect to the diffuse gas traced by Hi during the merging stage, following the increased velocity dispersion of the gas. We present here initial results obtained studying the SFR-Hi relation at 4.5 kpc resolution. We determined SFR/Hi mass ratios that are higher in the external regions of mergers than in the outskirts of isolated spirals, though both environments are Hi dominated. SFR/Hi increases towards the central regions following the decrease of the atomic gas fraction and possibly the increased star–formation efficiency. These results need to be checked with a larger sample of systems and on smaller spatial scales. This is the goal of the on-going Chaotic THINGS project that ultimately will allow us to determine why starbursting galaxies deviate from the Kennicutt-Schmidt relation between SFR density and gas surface density.
According to a popular scenario supported by numerical models, the mass assembly and growth of massive galaxies, in particular the Early-Type Galaxies (ETGs), is, below a redshift of 1, mainly due to the accretion of multiple gas–poor satellites. In order to get observational evidence of the role played by minor dry mergers, we are obtaining extremely deep optical images of a complete volume limited sample of nearby ETGs. These observations, done with the CFHT as part of the ATLAS3D, NGVS and MATLAS projects, reach a stunning 28.5 – 29 mag.arcsec−2 surface brightness limit in the g' band. They allow us to detect the relics of past collisions such as faint stellar tidal tails as well as the very extended stellar halos which keep the memory of the last episodes of galactic accretion. Images and preliminary results from this on-going survey are presented, in particular a possible correlation between the fine structure index (which parametrizes the amount of tidal perturbation) of the ETGs, their stellar mass, effective radius and gas content.
Recently, massive early-type galaxies have shed their red-and-dead moniker, thanks to the discovery that many host residual star formation. As part of the ATLAS-3D project, we have conducted a complete, volume-limited survey of the molecular gas in 260 local early-type galaxies with the IRAM-30m telescope and the CARMA interferometer, in an attempt to understand the fuel powering this star formation. We find that around 22% of early-type galaxies in the local volume host molecular gas reservoirs. This detection rate is independent of galaxy luminosity and environment. Here we focus on how kinematic misalignment measurements and gas-to-dust ratios can be used to put constraints on the origin of the cold ISM in these systems. The origin of the cold ISM seems to depend strongly on environment, with misaligned, dust poor gas (indicative of externally acquired material) being common in the field but completely absent in rich groups and in the Virgo cluster. Very massive galaxies also appear to be devoid of accreted gas. This suggests that in the field mergers and/or cold gas accretion dominate the gas supply, while in clusters internal secular processes become more important. This implies that environment has a strong impact on the cold gas properties of ETGs.
We analysed the Spitzer maps of Stephan's Quintet in order to investigate the nature of the dust emission associated with the X-ray emitting regions of the large scale intergalactic shock and of the group halo. This emission can in principle be powered by dust-gas particle collisions, thus providing efficient cooling of the hot gas. However the results of our analysis suggest that the dust emission from those regions is mostly powered by photons. Nonetheless dust collisional heating could be important in determining the cooling of the IGM gas and the large scale star formation morphology observed in SQ.
The NGVS is mapping the Virgo Cluster with a depth making possible to detect very low surface brightness (LSB) structures, such as faint dwarf galaxies. To extract these from just above the sky noise and make statistical studies of their properties, we use the software MARSIAA (MARkovian Software for Image Analysis in Astronomy). This segmentation software uses a Markovian approach to classify pixels and identify low-surface brightness structures.
The Next Generation Virgo Cluster Survey (NGVS) is a CFHT Large Program that is using the wide field of view capabilities of the MegaCam camera to map the entire Virgo Cluster from its core to virial radius. The observing strategy has been optimized to detect very low surface brightness structures in the cluster, including intracluster stellar streams and faint dwarf spheroidal galaxies. We present here the current status of this ongoing survey, with an emphasis on the detection and analysis of the very low-mass galaxies in the cluster that have been revealed by the NGVS.
The structural changes induced in single crystal silicon implanted with Krypton above the amorphisation threshold were studied by X-ray reflectivity together with Grazing Incidence Small Angle X-ray Scattering technique. Silicon samples were implanted with Krypton with two different ion energies. A well-defined layer, 220 nm thick of amorphous silicon, rich in Krypton, was formed below the top, undisturbed layer. A series of samples consist of as-implanted, relaxed, and a number of samples with increased level of defects induced by additional Kr implantation. Additional implantation caused changes in the films composition and thickness, which was well evidenced in reflectivity curve, while only minor changes of surface roughness and critical angle were detected in GISAXS spectra.
We consider a tight binding model for magnetic systems, in which we allow atoms to become charged and to interact via the long ranged Coulomb interaction to a published tight binding model; this is then applied to the study defects in ferromagnetic iron. We encounter several problems with achieving self consistency with existing schemes. To address the issue of instability and slow convergency we developed a robust, efficient scheme for charge and spin self consistency. This is based on minimizing an extended form of the Harris-Foulkes functional which includes spin, leading to a Newton-Raphson iterative procedure. We then apply this to both bulk and defect calculations for iron.
Microstructural characterization (Focused Ion Beam and Transmission Electron Microscopy imaging) was performed on cross-sections of contacts in thick Electro Chemical Deposition copper metallization of System In Package Integrated Circuits. It was shown that the lower growth rate of ECD-Cu in the AlSiCu – barrier Ti – PVD-Cu – ECD-Cu layer stacking is related to a local higher resistivity induced by the presence of a great number of almost planar grain boundaries in the PVD-Cu layer, which are perpendicular to the growth axis. This morphology is a consequence of the almost heteroepitaxial growth of Ti layer on AlSiCu layer.
We describe magnetic field sensors based on a recently discovered magnetoresistance (MR) effect in nonmagnetic organic semiconductor sandwich devices. The MR effect reaches up to 10% in a magnetic field of 10 mT at room temperature. We perform an extensive experimental characterization of this effect. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. We also measured the device response to alternating magnetic fields up to 100 kHz. To the best of our knowledge, the discovered MR effect is not adequately described by any of the MR mechanisms known to date.