15,890 research outputs found
Tridactyl tracks from the Lavini di Marco dinosaur ichnosite (Hettangian, Southern Alps, NE Italy). Ichnotaxonomical review and palaeobiogeography
The use of aerial- and close-range photogrammetry for the mapping of the Lavini di Marco tracksite (Hettangian, Southern Alps, NE Italy)
(EXCERPT FROM ABSTRACT) Close-range photogrammetry was executed following the procedure proposed by Mallison & Wings (2014). More than seventy 3D models were obtained and interpreted by means of color-coded and contour line images, which allow to improve the ichno- logical knowledge of the tracksite. The 3D models of the best-preserved tracks were used for the osteological reconstruction of the trackmakers’ autopodia, supposing the arthral position of the phalangeal pads. Three indirect methods were used to correlate tracks and their trackmakers: (i) synapomorphy-based approach; (ii) phenetic correlation; (iii) coincidence correlation (see Carrano & Wilson, 2001)
The final map was produced with different level of knowledge due to the distribution of tracks and current state of site preservation. Furthermore, it represents a complete documentation that will be used for future work of enhancement, preservation and valorization of the tracksite.
The ichnotaxonomical review of the quadrupedal trackways led us to emend the diagnosis of Lavinipes cheminii Avanzini et al. (2003) and to assign several other sparse tracks and trackways to L. chemini. The skeletal reconstruction of fore and hind limbs points towards Gongxianosaurus sp. as the most suitable trackmaker of L. cheminii. The herein supposed Laurasian affinity of the Lavini di Marco dinosaur assemblage clashes with the previous hypotheses that always link the Southern Alps sector with the Gondwana mainland
Selection bias in dynamically-measured super-massive black hole samples: consequences for pulsar timing arrays
Supermassive black hole -- host galaxy relations are key to the computation
of the expected gravitational wave background (GWB) in the pulsar timing array
(PTA) frequency band. It has been recently pointed out that standard relations
adopted in GWB computations are in fact biased-high. We show that when this
selection bias is taken into account, the expected GWB in the PTA band is a
factor of about three smaller than previously estimated. Compared to other
scaling relations recently published in the literature, the median amplitude of
the signal at yr drops from to
. Although this solves any potential tension between
theoretical predictions and recent PTA limits without invoking other dynamical
effects (such as stalling, eccentricity or strong coupling with the galactic
environment), it also makes the GWB detection more challenging.Comment: 6 pages 4 figures, submitted to MNRAS letter
A Statistical Semi-Empirical Model: Satellite galaxies in Groups and Clusters
We present STEEL a STatistical sEmi-Empirical modeL designed to probe the
distribution of satellite galaxies in groups and clusters. Our fast statistical
methodology relies on tracing the abundances of central and satellite haloes
via their mass functions at all cosmic epochs with virtually no limitation on
cosmic volume and mass resolution. From mean halo accretion histories and
subhalo mass functions the satellite mass function is progressively built in
time via abundance matching techniques constrained by number densities of
centrals in the local Universe. By enforcing dynamical merging timescales as
predicted by high-resolution N-body simulations, we obtain satellite
distributions as a function of stellar mass and halo mass consistent with
current data. We show that stellar stripping, star formation, and quenching
play all a secondary role in setting the number densities of massive satellites
above . We further show that observed
star formation rates used in our empirical model over predict low-mass
satellites below , whereas, star
formation rates derived from a continuity equation approach yield the correct
abundances similar to previous results for centrals.Comment: 21 pages, 17 Figures. MNRAS, in pres
Allocation of risk capital in a cost cooperative game induced by a modified expected shortfall
The standard theory of coherent risk measures fails to consider individual institutions as part of a system which might itself experience instability and spread new sources of risk to the market participants. This paper fills this gap and proposes a cooperative market game where agents and institutions play the same role. We take into account a multiple institutions framework where some institutions jointly experience distress, and evaluate their individual and collective impact on the remaining institutions in the market. To carry out the analysis, we define a new risk measure (SCoES) which is a generalization of the Expected Shortfall of and we characterize the riskiness profile as the outcome of a cost cooperative game played by institutions in distress. Each institution’s marginal contribution to the spread of riskiness towards the safe institutions in then evaluated by calculating suitable solution concepts of the game such as the Banzhaf–Coleman and the Shapley–Shubik values.
This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of the Operational Research Society on 16/12/2019, available online: http://www.tandfonline.com/10.1080/01605682.2019.168695
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