Constraining the cometary flux through the asteroid belt during the late heavy bombardment

In the Nice model, the late heavy bombardment (LHB) is related to an orbital instability of giant planets which causes a fast dynamical dispersion of a transneptunian cometary disk. We study effects produced by these hypothetical cometary projectiles on main-belt asteroids. In particular, we want to check whether the observed collisional families provide a lower or an upper limit for the cometary flux during the LHB. We present an updated list of observed asteroid families as identified in the space of synthetic proper elements by the hierarchical clustering method, colour data, albedo data and dynamical considerations and we estimate their physical parameters. We selected 12 families which may be related to the LHB according to their dynamical ages. We then used collisional models and N-body orbital simulations to gain insight into the long-term dynamical evolution of synthetic LHB families over 4 Gyr. We account for the mutual collisions, the physical disruptions of comets, the Yarkovsky/YORP drift, chaotic diffusion, or possible perturbations by the giant-planet migration. Assuming a "standard" size-frequency distribution of primordial comets, we predict the number of families with parent-body sizes D_PB >= 200 km which seems consistent with observations. However, more than 100 asteroid families with D_PB >= 100 km should be created at the same time which are not observed. This discrepancy can be nevertheless explained by the following processes: i) asteroid families are efficiently destroyed by comminution (via collisional cascade), ii) disruptions of comets below some critical perihelion distance (q <~ 1.5 AU) are common. Given the freedom in the cometary-disruption law, we cannot provide stringent limits on the cometary flux, but we can conclude that the observed distribution of asteroid families does not contradict with a cometary LHB.Comment: accepted in Astronomy and Astrophysic

Ussing Chamber

The Ussing chamber system is named after the Danish zoologist Hans Ussing, who invented the device in the 1950s to measure the short-circuit current as an indicator of net ion transport taking place across frog skin (Ussing and Zerahn, Acta Physiol Scand 23:110-127, 1951). Ussing chambers are increasingly being used to measure ion transport in native tissue, like gut mucosa, and in a monolayer of cells grown on permeable supports. However, the Ussing chamber system is, to date, not often applied for the investigation of the impact of food bioactives (proteins, sugars, lipids) on health. An Ussing system is generally comprised of a chamber and a perfusion system, and if needed, an amplifier and data acquisition system. The heart of the system lies in the chamber with the other components performing supporting roles. The classic chamber design is still in wide use today. However, several newer designs are now available that optimize for convenience and for diffusion- or electrophysiology-based measurements. A well designed Ussing chamber supports an epithelia membrane or cell monolayer in such a way that each side of the membrane is isolated and faces a separate chamber-half. The chambers are then filled with a physiologically relevant solution, such as Ringer’s solution. This configuration allows the researcher to make unique chemical and electrical adjustments to either side of the membrane with complete control. The Ussing chamber technique has its strengths and limitations, which will be explained in more detail in this chapter

B.R.N.O. Contributions #38 Times of minima

This paper presents observations of eclipsing binaries acquired by members and cooperating observers of the Variable Star and Exoplanet Section of Czech Astronomical Society (B.R.N.O. observing project). Paper contains 3417 times of minima for 969 objects. It was obtained by 80 observers during 2011 – 2013 period. Some neglected southern eclipsing binaries and newly discovered stars by the observers of project B.R.N.O. are included in the list. New accurate ephemerides have been found for 447 binary systems. Time of primary minimum of long period variable eps Aur is presented as wellFil: Hoňková, K. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. Observatory and Planetarium of Johann Palisa; República ChecaFil: Juryšek, J. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. Observatory and Planetarium of Johann Palisa; República ChecaFil: Lehký, M. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. Astronomical Society at Hradec Kralove; República ChecaFil: Šmelcer, L. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. Valašské Meziříčí Observatory; República ChecaFil: Trnka, J. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. City Observatory Slaný; República ChecaFil: Colazo, C. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Estación Astrofísica Bosque Alegre; ArgentinaFil: Guzzo, P. Estación Astrofísica Bosque Alegre; ArgentinaFil: Mina, Federico Daniel. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Quinones, C. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Taormina, M. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Melia, R. Observatorio Remoto Bosque Alegre; ArgentinaFil: Schneiter, Ernesto Matías. Estación Astrofísica Bosque Alegre; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Scavuzzo, Alan Martin. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Marcionni, M. Estación Astrofísica Bosque Alegre; ArgentinaFil: Tapia, L. Estación Astrofísica Bosque Alegre; ArgentinaFil: Fasseta, G. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Suarez, N. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Vilášek, M. Observatory and Planetarium of Johann Palisa; República ChecaFil: Rozehnal, J.. Štefánik Observatory; República ChecaFil: Kalisch, T. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. Observatory and Planetarium of Johann Palisa; República ChecaFil: Lang, K.. Klokkerholm; DinamarcaFil: Gorková, S. ALTAN.Observatory; República ChecaFil: Novysedlák, R. Námestie sv. Martina; EslovaquiaFil: Salvaggio, F. Gruppo Astrofili Catanesi; ItaliaFil: Smyčka, T. Variable Star and Exoplanet Section of Czech Astronomical Society; República Checa. City Observatory Slaný; República ChecaFil: Spurný, M. Nejdlova 16; República ChecaFil: Wikander, T. Ornäs Backyard; República ChecaFil: Mravik, J. Slobodana Jajića 16; República ChecaFil: Šuchaň, J. Kraskova 12; EslovaquiaFil: Čaloud, J.. V Dolině 211; República Chec