4,002 research outputs found
The WINGS Survey: a progress report
A two-band (B and V) wide-field imaging survey of a complete, all-sky X-ray
selected sample of 78 clusters in the redshift range z=0.04-0.07 is presented.
The aim of this survey is to provide the astronomical community with a complete
set of homogeneous, CCD-based surface photometry and morphological data of
nearby cluster galaxies located within 1.5 Mpc from the cluster center. The
data collection has been completed in seven observing runs at the INT and
ESO-2.2m telescopes. For each cluster, photometric data of about 2500 galaxies
(down to V~23) and detailed morphological information of about 600 galaxies
(down to V~21) are obtained by using specially designed automatic tools.
As a natural follow up of the photometric survey, we also illustrate a long
term spectroscopic program we are carrying out with the WHT-WYFFOS and AAT-2dF
multifiber spectrographs. Star formation rates and histories, as well as
metallicity estimates will be derived for about 350 galaxies per cluster from
the line indices and equivalent widths measurements, allowing us to explore the
link between the spectral properties and the morphological evolution in high-
to low-density environments, and across a wide range in cluster X-ray
luminosities and optical properties.Comment: 12 pages, 10 eps figures, Proceedings of the SAIt Conference 200
GASP XVIII: Star formation quenching due to AGN feedback in the central region of a jellyfish galaxy
We report evidence for star formation quenching in the central 8.6 kpc region
of the jellyfish galaxy JO201 which hosts an active galactic nucleus, while
undergoing strong ram pressure stripping. The ultraviolet imaging data of the
galaxy disk reveal a region with reduced flux around the center of the galaxy
and a horse shoe shaped region with enhanced flux in the outer disk. The
characterization of the ionization regions based on emission line diagnostic
diagrams shows that the region of reduced flux seen in the ultraviolet is
within the AGN-dominated area. The CO J map of the galaxy disk reveals
a cavity in the central region. The image of the galaxy disk at redder
wavelengths (9050-9250 \overset{\lower.5em\circ}{\mathrm{A}}) reveals the
presence of a stellar bar. The star formation rate map of the galaxy disk shows
that the star formation suppression in the cavity occurred in the last few
10 yr. We present several lines of evidence supporting the scenario that
suppression of star formation in the central region of the disk is most likely
due to the feedback from the AGN. The observations reported here make JO201 a
unique case of AGN feedback and environmental effects suppressing star
formation in a spiral galaxy.Comment: Author's accepted manuscrip
Interaction in Assistive Robotics: A Radical Constructivist Design Framework
Despite decades of research, muscle-based control of assistive devices (myocontrol) is still unreliable; for instance upper-limb prostheses, each year more and more dexterous and human-like, still provide hardly enough functionality to justify their cost and the effort required to use them. In order to try and close this gap, we propose to shift the goal of myocontrol from guessing intended movements to creating new circular reactions in the constructivist sense defined by Piaget. To this aim, the myocontrol system must be able to acquire new knowledge and forget past one, and knowledge acquisition/forgetting must happen on demand, requested either by the user or by the system itself. We propose a unifying framework based upon Radical Constructivism for the design of such a myocontrol system, including its user interface and user-device interaction strategy
Cryopreservation of grapevine (Vitis spp.) shoot tips from growth chamber-sourced plants and histological observations
Many genebanks rely on cryopreservation as a method to preserve vulnerable field collections of vegetatively propagated crops. Effective cryopreservation procedures have been identified for Vitis; however, they usually use in vitro plantlets as the shoot tip source materials. It is costly to establish Vitis collections in vitro prior to cryopreservation. We sought to determine if growth chamber derived Vitis plants could serve as the source of shoot tips for cryopreservation. Nodal sections from growth chamber derived plants were surface-disinfected and placed in tissue culture on pre-treatment medium for 2 weeks. Uniform apical shoot tips (1 mm) were first obtained from the nodal sections and then precultured for 3 days on medium containing 0.3 M sucrose, salicylic acid, glutathione (reduced form), ascorbic acid and plant preservative mixture. Half-strength PVS2 was applied for 30 min at 22 °C, prior to full-strength PVS2 treatment at 0 °C. Cryopreserved shoot tips had the highest average regrowth of 50 and 55 % without and with cold-acclimation followed with a full-strength PVS2 exposure duration of 40 and 30 min at 0 °C, respectively. This cryopreservation protocol achieved high percentages of regrowth in V. vinifera 'Chardonnay' and 'Riesling' and V. hybrid 'Oppenheim'. Histological observations revealed that shoot tips from growth chamber plants had apical as well as multiple lateral meristems that survived LN immersion. The preservation of multiple meristems in each shoot tip may increase the capacity of shoot tip regeneration in cryopreserved Vitis that originates from ex vitro sources. The high percentage of regrowth after shoot tip cryopreservation using Vitis shoot tips derived from growth chamber source plants suggest that it may be possible to cryopreserve Vitis shoot tips without first introducing each accession into tissue culture
GASP IV: A muse view of extreme ram-pressure stripping in the plane of the sky: the case of jellyfish galaxy JO204
In the context of the GAs Stripping Phenomena in galaxies with Muse (GASP)
survey, we present the characterization of JO204, a jellyfish galaxy in A957, a
relatively low-mass cluster with . This galaxy
shows a tail of ionized gas that extends up to 30 kpc from the main body in the
opposite direction of the cluster center. No gas emission is detected in the
galaxy outer disk, suggesting that gas stripping is proceeding outside-in. The
stellar component is distributed as a regular disk galaxy; the stellar
kinematics shows a symmetric rotation curve with a maximum radial velocity of
200km/s out to 20 kpc from the galaxy center. The radial velocity of the gas
component in the central part of the disk follows the distribution of the
stellar component; the gas kinematics in the tail retains the rotation of the
galaxy disk, indicating that JO204 is moving at high speed in the intracluster
medium. Both the emission and radial velocity maps of the gas and stellar
components indicate ram-pressure as the most likely primary mechanism for gas
stripping, as expected given that JO204 is close to the cluster center and it
is likely at the first infall in the cluster. The spatially resolved star
formation history of JO204 provides evidence that the onset of ram-pressure
stripping occurred in the last 500 Myr, quenching the star formation activity
in the outer disk, where the gas has been already completely stripped. Our
conclusions are supported by a set of hydrodynamic simulations.Comment: accepted for publication in Ap
GASP II. A MUSE view of extreme ram-pressure stripping along the line of sight: kinematics of the jellyfish galaxy JO201
This paper presents a spatially-resolved kinematic study of the jellyfish
galaxy JO201, one of the most spectacular cases of ram-pressure stripping (RPS)
in the GASP (GAs Stripping Phenomena in Galaxies with MUSE) survey. By studying
the environment of JO201, we find that it is moving through the dense
intra-cluster medium of Abell 85 at supersonic speeds along our line of sight,
and that it is likely accompanied by a small group of galaxies. Given the
density of the intra-cluster medium and the galaxy's mass, projected position
and velocity within the cluster, we estimate that JO201 must so far have lost
~50% of its gas during infall via RPS. The MUSE data indeed reveal a smooth
stellar disk, accompanied by large projected tails of ionised (Halpha) gas,
composed of kinematically cold (velocity dispersion <40km/s) star-forming knots
and very warm (>100km/s) diffuse emission which extend out to at least ~50 kpc
from the galaxy centre. The ionised Halpha-emitting gas in the disk rotates
with the stars out to ~6 kpc but in the disk outskirts becomes increasingly
redshifted with respect to the (undisturbed) stellar disk. The observed
disturbances are consistent with the presence of gas trailing behind the
stellar component, resulting from intense face-on RPS happening along the line
of sight. Our kinematic analysis is consistent with the estimated fraction of
lost gas, and reveals that stripping of the disk happens outside-in, causing
shock heating and gas compression in the stripped tails.Comment: ApJ, revised version after referee comments, 15 pages, 16 figures.
The interactive version of Figure 9 can be viewed at
web.oapd.inaf.it/gasp/publications.htm
Undergraduate module on nutrition education and communication for Africa: Profiles of potential students
To be adequately nourished, individuals need to have access to sufficient and good quality food. They also need to have an understanding of what constitutes a good diet for health, and have the skills and motivation to make good food choices. Nutrition education equips people to make such choices. Building countriesâ capacities to provide effective nutrition education and promote healthy diets is part of the work carried out by the Nutrition Division of the Food and Agriculture Organization (FAO) of the United Nations. The FAO Effective Education for Nutrition in Action (ENACT) project is assisting countries to develop institutional and professional capacities in nutrition education in Africa by producing a basic module on nutrition education at undergraduate level for use by national universities and other training institutions. The course materials will be available for online, face-to-face or blended use and are being piloted and revised to improve and adapt them to local context and consumer need. Creating a learner profile is an accepted step in course design, particularly important in situations where course developers do not have close contact with the students, as in this case. The ENACT learner profile was compiled from replies to a short questionnaire of 32 questions administered to a sample of students. The respondents were the actual piloting students, or were representative of those who would be piloting the course. One hundred and twenty eight responses were received from universities in Ethiopia, Ghana, Kenya, Nigeria, Tanzania and Uganda, approximately 20 per university. On average, respondents answered 96% of the questions in the questionnaire. Information was obtained on areas such as studentsâ social/cultural interests; food and nutrition experience and expertise; food and eating habits; ideas of nutrition education and training in nutrition education; and study preferences. In addition, the profile of a typical learner in each country (including age, gender and information on socio-economic background, urban/rural background and English proficiency) was compiled from the questionnaires and from additional information supplied by the tutors. The study findings have helped the course developers to select course content and structure learning activities to meet studentsâ needs and circumstances.Key words: professional training, nutrition education, Afric
The GALEX UV emission in shell galaxies
Shell galaxies are widely considered the debris of recent accretion/merging
episodes. Their high frequency in low density environment suggests that such
episodes could be among the driver of the early-type galaxy secular evolution.
We present far and near UV (FUV and NUV respectively hereafter) GALEX
photometric properties of a sample of shell galaxies.Comment: 2 pages, Proceedings of the Conference 'Formation and evolution of
galaxies disks', Rome 200
Experimental Studies on Drive Beam Generation in CTF3
The objective of the CLIC Test Facility CTF3, built at CERN by an international collaboration, is to demonstrate the main feasibility issues of the CLIC two-beam technology by 2010. CTF3 consists of a 150 MeV electron linac followed by a 42 m long delay loop, an 84 m combiner ring and a two-beam test area. One keyissue studied in CTF3 is the efficient generation of a very high current drive beam, used in CLIC as the power source for the acceleration of the main beam to multi-TeV energies. The beam current is first doubled in the delay loop and then multiplied again by a factor four in the combiner ring by interleaving bunches using transverse deflecting RF cavities. The combiner ring and the connecting transfer line have been installed and put into operation in 2007. In this paper we give the status of the commissioning, illustrate the beam optics measurements, discuss the main issues and present the results of the combination tests
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