Footprints of the YORP effect in asteroid families

The YORP effect affects not only the rotation rate, but also the spin orientation of asteroids. For this reason, due to Yarkovsky effect, it influences also the evolution of the semimajor axis with time. In asteroid dynamical families, the combined outcome can be a depletion of objects in the central part of the family, shown by the absolute magnitude vs. semimajor axis so-called V-plot. A reclassification of asteroid families, extended to a very large database of proper elements, has recently been performed by Milani et al. [2014] (Icarus, 239, 46-73). Only some of the related V-plots, used to estimate the age of several families, exhibit the depletion predicted above. In this paper we discuss the problem, introducing the concept of the YORP-eye and a general method of analysis. We show that the effect may sometimes be located in the low H tail, and thus difficult to detect. Moreover, it may be hindered by several anomalous physical properties of the family (asymmetry, cratering origin, multiple collisions history and so on). With a new method of analysis, we identify the footprints of the effect for most of the analysed families, obtaining also an independent estimate of the age of the family. In spite of the uncertainties, we obtain a very good agreement between these ages and those estimated on the basis of the slope of the V-plot: a result which supports both methods and the underlying physics

Asteroid families classification: exploiting very large data sets

The number of asteroids with accurately determined orbits increases fast. The catalogs of asteroid physical observations have also increased, although the number of objects is still smaller than in the orbital catalogs. We developed a new approach to the asteroid family classification by combining the Hierarchical Clustering Method (HCM) with a method to add new members to existing families. This procedure makes use of the much larger amount of information contained in the proper elements catalogs, with respect to classifications using also physical observations for a smaller number of asteroids. Our work is based on the large catalog of the high accuracy synthetic proper elements (available from AstDyS). We first identify a number of core families; to these we attribute the next layer of smaller objects. Then, we remove all the family members from the catalog, and reapply the HCM to the rest. This gives both halo families which extend the core families and new independent families, consisting mainly of small asteroids. These two cases are discriminated by another step of attribution of new members and by merging intersecting families. By using information from absolute magnitudes, we take advantage of the larger size range in some families to analyze their shape in the proper semimajor axis vs. inverse diameter plane. This leads to a new method to estimate the family age (or ages). The results from the previous steps are then analyzed, using also auxiliary information on physical properties including WISE albedos and SDSS color indexes. This allows to solve some difficult cases of families overlapping in the proper elements space but generated by different collisional events. We analyze some examples of cratering families (Massalia, Vesta, Eunomia) which show internal structures, interpreted as multiple collisions. We also discuss why Ceres has no family

Ages of asteroid families estimated using the YORP-eye method

In the present paper we complete the analysis discussed in a previous work, using an improved algorithm and an extended database of families. We confirm that the analysis connected to the search for the YORP-eye can lead to an estimate of the age

Effectiveness of cyclosporine and mycophenolate mofetil in a child with refractory evans syndrome

Evans Syndrome is a rare autoimmune disease consisting of hemolytic anemia, thrombocytopenia and/or neutropenia. It may be associated with other autoimmune or lymphoproliferative diseases. Its course can be extremely serious and, rarely, even life-threatening; thus it represents a excellent treatment challenge for the pediatric hematologist. First line treatment consists of steroids and/or immunoglobulin; further therapy with rituximab, vincristine, cyclophosphamide and other immunosuppressive drugs can be considered in unresponsive patients. We describe a baby with refractory Evans Syndrome that was cured by prolonged administration of mycophenolate mofetil and remained disease-free for 4 years after the discontinuation of treatment

YORP-Yarkowski evolution of asteroid families: the effects of collisions

The depletion of objects in the central part of an asteroid family, which can be observed in the absolute magnitude vs. semimajor axis, can be explained in terms of a coupling of the YORP and Yarkovsky effects (Paolicchi and Knezevic, Icarus, 2016). In particular, it can be ascribed to the obliquity evolution caused by YORP and on how it influeces the Yarkovsky drift.With this work we intend to improve the modeling of YORP-Yarkovsky evolution of asteroid families exploiting a model which tracks the evolution of the spin vector of small asteroids, including also the effects of collisions on the YORP induced obliquity evolution. This allows a better modeling of the asteroid spin evolution.In these preliminary steps, we will first consider a few model families simulating their time evolution in the magnitude vs. semimajor axis plots. The obtained results will be then compared with observed families to determine and tune the intensity of the effect

Circulating gamma-glutamyltransferase fractions in cirrhosis.

Background: Four GGT fractions (b-, m-, s-, and f-GGT) have been identified in human plasma and their concentrations and ratios vary in different pathological conditions. Aim: To assess the behavior of fractional GGT in cirrhotic patients evaluated for liver transplantation. Methods: This was a single-center, cross-sectional study; GGT fractions were determined by gel-filtration chromatography. Results: 264 cirrhotic patients (215 males; median age 54.5 years) were included and compared against a group of 200 healthy individuals (100 males; median age 41.5). Median (25th-75th percentile) total and fractional GGT were higher in cirrhotics, with s-GGT showing the greatest increase [36.6 U/L (21.0-81.4) vs. 5.6 U/L (3.2-10.2), (p<0.0001)], while the median b-GGT/s-GGT ratio was lower in cirrhotics than in healthy controls [0.06 (0.04-0.10)] vs. 0.28 (0.20-0.40), p<0.0001]. The ratio showed higher diagnostic accuracy (ROC-AUC, 95% CI: 0.951, 0.927-0.969) then either s-GGT (0.924, 0.897-0.947; p<0.05) or total GGT (0.900, 0.869-0.925; p<0.001). The diagnostic accuracy of the ratio was maintained (0.940, 0.907-0.963) in cirrhotic patients (n=113) with total GGT values within the reference range. The s-GGT fraction consisted of two components, with one (s2-GGT) showing a significant positive correlation with serum AST, ALT, LDH, ALP and bilirubin, and negative with albumin. The b-GGT fraction showed a positive correlation with albumin, fibrinogen, and platelet counts, and negative with INR, bilirubin and LDH. Conclusions: The ratio performs as a sensitive biomarker of the liver parenchymal rearrangement, irrespective of etiology of cirrhosis and presence of hepatocellular carcinoma, even in patients with total GGT values within the reference range

Rushing to equilibrium: A simple model for the collisional evolution of asteroids

A simple mathematical model for the evolution of a system of collisionally interacting bodies -- such as the asteroid population -- consists of two coupled, nonlinear, first-order differential equations for the abundances of 'small' and 'big' bodies. The model easily allows us to recover Dohnanyi's value (11/6) for the exponent of the equilibrium mass distribution. Moreover, the model shows that any initial value for the ratio of 'big' to 'small' bodies rapidly relaxes to the equilibrium ratio, corresponding to the 11/6 experiment, and that integrating the evolution equations backward in time -- an attractive possibility to investigate the mass distribution of primordial planetesimals -- leads to strong numerical instability

The origin of planetary systems in the scenario of star formation

Theoretical models of the formation of the solar system are examined critically in a review focusing on the problems of specific angular momentum (j) and mass depletion. The values of j for the present solar system, a low-mass binary system, a twin binary, and a typical interstellar cloud are estimated as 1, 120, 170, and 10 to the 6th, respectively, and hypotheses advanced to explain the j gap between the solar system and its possible precursors are considered. Two general types of disk models are identified, one which assumes that the primeval solar nebula had mass 0.01-0.1 solar mass and experienced some mass depletion (e.g., Safronov, 1969) and one which assumes a very large nebula of 1 solar mass and strong mass depletion (e.g., Cameron, 1978). It is concluded that the uncertainties in both types of models make a choice between them impossible at present, but that the unresolved problems of the low-mass models appear less critical

RUSHING TO EQUILIBRIUM - A SIMPLE-MODEL FOR THE COLLISIONAL EVOLUTION OF ASTEROIDS

A simple mathematical model for the evolution of a system of collisionally interacting bodies-such as the asteroid population-consists of two coupled, nonlinear, first-order differential equations for the abundances of ''small'' and ''big'' bodies. The model easily allows us to recover Dohnanyi's value (11/6) for the exponent of the equilibrium mass distribution. Moreover, the model shows that any initial value for the ratio of ''big'' to ''small'' bodies rapidly relaxes to the equilibrium ratio, corresponding to the 11/6 exponent, and that integrating the evolution equations backward in time-an attractive possibility to investigate the mass distribution of primordial plan-etesimals-leads to strong numerical instability