411 research outputs found
A project for polarimetric observations in single dish with Medicina and Noto 32 m antennas
A project with multidisciplinary characteristics, aimed to implement the possibility of polarimetric measurements in single dish at the VLBI stations of Medicina and Noto, is presented. The project will open a new window on many
astrophysical items that may be approached using the already existing instrumentation and facilities of the two Italian radioastronomical stations. We report here some scientific backgrounds, together with some technical evaluations, on which the feasibility of the project is based
Trigonometric Parallaxes of Massive Star Forming Regions: IV. G35.20-0.74 and G35.20-1.74
We report trigonometric parallaxes for the high-mass star forming regions
G35.20-0.74 and G35.20-1.74, corresponding to distances of 2.19 (+0.24 -0.20)
kpc and 3.27 (+0.56 -0.42) kpc, respectively. The distances to both sources are
close to their near kinematic distances and place them in the
Carina-Sagittarius spiral arm. Combining the distances and proper motions with
observed radial velocities gives the locations and full space motions of the
star forming regions. Assuming a standard model of the Galaxy, G35.20-0.74 and
G35.20-1.74 have peculiar motions of ~13 km/s and ~16 km/s counter to Galactic
rotation and ~9 km/s toward the North Galactic Pole.Comment: 16 pages, 8 figure
Water maser variability over 20 years in a large sample of star-forming regions: the complete database
Context. Water vapor emission at 22 GHz from masers associated with
star-forming regions is highly variable. Aims. We present a database of up to
20 years of monitoring of a sample of 43 masers within star-forming regions.
The sample covers a large range of luminosities of the associated IRAS source
and is representative of the entire population of H2O masers of this type. The
database forms a good starting point for any further study of H2O maser
variability. Methods. The observations were obtained with the Medicina 32-m
radiotelescope, at a rate of 4-5 observations per year. Results. To provide a
database that can be easily accessed through the web, we give for each source:
plots of the calibrated spectra, the velocity-time-flux density plot, the light
curve of the integrated flux, the lower and upper envelopes of the maser
emission, the mean spectrum, and the rate of the maser occurrence as a function
of velocity. Figures for just one source are given in the text for
representative purposes. Figures for all the sources are given in electronic
form in the on-line appendix. A discussion of the main properties of the H2O
variability in our sample will be presented in a forthcoming paper.Comment: 11 pages, 9 figures, to be published in Astronomy and Astrophysics;
all plots in appendix (not included) can be downloaded from
http://www.arcetri.astro.it/~starform/water_maser_v2.html or
http://www.ira.inaf.it/papers/masers/water_maser_v2.htm
Supersonic water masers in 30 Doradus
We report on extremely high velocity molecular gas, up to -80 km/s relative
to the ambient medium, in the giant star-formation complex 30 Doradus in the
Large Magellanic Cloud (LMC), as observed in new 22 GHz H2O maser emission
spectra obtained with the Mopra radio telescope. The masers may trace the
velocities of protostars, and the observed morphology and kinematics indicate
that current star formation occurs near the interfaces of colliding
stellar-wind blown bubbles. The large space velocities of the protostars and
associated gas could result in efficient mixing of the LMC. A similar mechanism
in the Milky Way could seed the galactic halo with relatively young stars and
gas.Comment: 11 pages plus 1 PS and 1 EPS figure, uses AASTeX preprint style;
accepted for publication in Astrophysical Journal Letter
Molecular and supramolecular routes to enhance Gadolinium-based contrast agents relaxivity: How far are we from the theoretical optimal value?
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Highly parallel assays of tissue-specific enhancers in whole Drosophila embryos
Transcriptional enhancers are a primary mechanism by which tissue-specific gene expression is achieved. Despite the importance of these regulatory elements in development, responses to environmental stresses, and disease, testing enhancer activity in animals remains tedious, with a minority of enhancers having been characterized. Here, we have developed ‘enhancer-FACS-Seq’ (eFS) technology for highly parallel identification of active, tissue-specific enhancers in Drosophila embryos. Analysis of enhancers identified by eFS to be active in mesodermal tissues revealed enriched DNA binding site motifs of known and putative, novel mesodermal transcription factors (TFs). Naïve Bayes classifiers using TF binding site motifs accurately predicted mesodermal enhancer activity. Application of eFS to other cell types and organisms should accelerate the cataloging of enhancers and understanding how transcriptional regulation is encoded within them
Hard X-ray emission in the star-forming region ON2: discovery with XMM-Newton
We obtained X-ray XMM-Newton observations of the open cluster Berkeley 87 and
the massive star-forming region (SFR) ON 2. In addition, archival infrared
Spitzer Space Telescope observations were used. It is likely that the SFR ON 2
and Berkeley 87 are at the same distance, 1.23 kpc, and hence are associated.
The XMM-Newton observations detected X-rays from massive stars in Berkeley 87
as well as diffuse emission from the SFR ON 2. The two patches of diffuse X-ray
emission are encompassed in the shell-like H II region GAL 75.84+0.40 in the
northern part of ON 2 and in the ON 2S region in the southern part of ON 2. The
diffuse emission from GAL 75.84+0.40 suffers an absorption column equivalent to
A_V approx. 28 mag. Its spectrum can be fitted either with a thermal plasma
model at T < 30 MK or by an absorbed power-law model with gamma; approx. -2.6.
The X-ray luminosity of GAL 75.84+0.40 is L_X approx. 6 10^31 erg/s. The
diffuse emission from ON 2S is adjacent to the ultra-compact H II (UCHII)
region Cygnus 2N, but does not coincide with it or with any other known UCHII
region. It has a luminosity of L_X approx. 4 10^31 erg/s. The spectrum can be
fitted with an absorbed power-law model with gamma; approx.-1.4. We adopt the
view of Turner and Forbes (1982) that the SFR ON 2 is physically associated
with the massive star cluster Berkeley 87 hosting the WO type star WR 142. We
discuss different explanations for the apparently diffuse X-ray emission in
these SFRs. These include synchrotron radiation, invoked by the co-existence of
strongly shocked stellar winds and turbulent magnetic fields in the
star-forming complex, cluster wind emission, or an unresolved population of
discrete sources.Comment: ApJ 2010, 712, 763. Reduced fig. resolution. Full resolution version
is at
http://www.astro.physik.uni-potsdam.de/research/abstracts/oskinova-ber87.htm
In Bonobos Yawn Contagion Is Higher among Kin and Friends
In humans, the distribution of yawn contagion is shaped by social closeness with strongly bonded pairs showing higher levels of contagion than weakly bonded pairs. This ethological finding led the authors to hypothesize that the phenomenon of yawn contagion may be the result of certain empathic abilities, although in their most basal form. Here, for the first time, we show the capacity of bonobos (Pan paniscus) to respond to yawns of conspecifics. Bonobos spontaneously yawned more frequently during resting/relaxing compared to social tension periods. The results show that yawn contagion was context independent suggesting that the probability of yawning after observing others\u27 yawns is not affected by the propensity to engage in spontaneous yawns. As it occurs in humans, in bonobos the yawing response mostly occurred within the first minute after the perception of the stimulus. Finally, via a Linear Mixed Model we tested the effect of different variables (e.g., sex, rank, relationship quality) on yawn contagion, which increased when subjects were strongly bonded and when the triggering subject was a female. The importance of social bonding in shaping yawn contagion in bonobos, as it occurs in humans, is consistent with the hypothesis that empathy may play a role in the modulation of this phenomenon in both species. The higher frequency of yawn contagion in presence of a female as a triggering subject supports the hypothesis that adult females not only represent the relational and decisional nucleus of the bonobo society, but also that they play a key role in affecting the emotional states of others
A convergent decomposition algorithm for support vector machines.
In this work we consider nonlinear minimization problems with a single linear equality constraint and box constraints. In particular we are interested in solving problems where the number of variables is so huge that traditional optimization methods cannot be directly applied. Many interesting real world problems lead to the solution of large scale constrained problems with this structure. For example, the special subclass of problems with convex quadratic objective function plays a fundamental role in the training of Support Vector Machine, which is a technique for machine learning problems. For this particular subclass of convex quadratic problem, some convergent decomposition methods, based on the solution of a sequence of smaller subproblems, have been proposed. In this paper we define a new globally convergent decomposition algorithm that differs from the previous methods in the rule for the choice of the subproblem variables and in the presence of a proximal point modification in the objective function of the subproblems. In particular, the new rule for sequentially selecting the subproblems appears to be suited to tackle large scale problems, while the introduction of the proximal point term allows us to ensure the global convergence of the algorithm for the general case of nonconvex objective function. Furthermore, we report some preliminary numerical results on support vector classification problems with up to 100 thousands variables
The interconnection of hierarchy, affiliative behaviours, and social play shapes social dynamics in Maremmana beef cattle
Dominance hierarchies can be interconnected with behaviours that are essential to manage social living, such as affiliative behaviours and social play, whose importance can already emerge in the early phases of life. Here, we carried out an observational study (all occurrences sampling) to investigate the possible interconnection between these three behavioural categories in a group of Maremmana beef cattle (n = 44, 6–21 months of age) in an extensive breeding system. We found that a clearly linear hierarchy is present in the group, and that the age of the animals positively correlated with their hierarchical ranks. Affiliative behaviours were directed up to the hierarchy: dominants received more affiliative behaviours and subordinates were generally starting the sessions, suggesting that affiliative behaviours may be used by subordinates to bond with dominants for possibly gaining some benefits. Social play mainly consisted of play fighting and dominant subjects played with the highest frequency. However, playful modality was independent from playmates’ relative rank position, with longer-lasting sessions being characterized by unbalanced and unreciprocated patterns. This indicates that play fighting in cattle has a competitive rather than cooperative nature and that it may be used as physical training to develop competitive skills in all groupmates. When play fighting was punctuated by affiliative behaviours, the playful sessions lasted longer. In this view, affiliative behaviours can have a communicative value useful in downgrading the competition emerging during play fighting. In conclusion, under naturalistic conditions young animals of beef cattle express all the behavioural repertoire typical of adulthood and their agonistic, affiliative, and playful behaviours are strongly interconnected in shaping social dynamics. Thus, our study suggests that extensive farming conditions are ideal to study the behavioural strategies domestic animals enact to form cohesive social groups. Such information is needed to enhance management and welfare of domestic ungulates
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