Dynamics of an Intruder in Dense Granular Fluids

We investigate the dynamics of an intruder pulled by a constant force in a dense two-dimensional granular fluid by means of event-driven molecular dynamics simulations. In a first step, we show how a propagating momentum front develops and compactifies the system when reflected by the boundaries. To be closer to recent experiments \cite{candelier2010journey,candelier2009creep}, we then add a frictional force acting on each particle, proportional to the particle's velocity. We show how to implement frictional motion in an event-driven simulation. This allows us to carry out extensive numerical simulations aiming at the dependence of the intruder's velocity on packing fraction and pulling force. We identify a linear relation for small and a nonlinear regime for high pulling forces and investigate the dependence of these regimes on granular temperature

A Review of the fossil record of turtles of the clade Baenidae

The fossil record of the turtle clade Baenidae ranges from the Early Cretaceous (Aptian—Albian) to the Eocene. The group is present throughout North America during the Early Cretaceous, but is restricted to the western portions of the continents in the Late Cretaceous and Paleogene. No credible remains of the clade have been reported outside of North America to date. Baenids were warmadapted freshwater aquatic turtles that supported high levels of diversity at times through niche partitioning, particularly by adapting to a broad range of dietary preferences ranging from omnivorous to molluscivorous. Current phylogenies place Baenidae near the split of crown-group Testudines. Within Baenidae three more inclusive, named clades are recognized: Baenodda, Palatobaeninae and Eubaeninae. A taxonomic review of the group concludes that of 49 named taxa, 30 are nomina valida, 12 are nomina invalida and 7 are nomina dubia

Die biologische Wirkung des energiereichen kosmischen Strahlungsfeldes auf ein mehrzelliges Modellobjekt bei kurz- und langdauernden Weltraumfluegen Schlussbericht

Experiences with exemplary results of lasting radiobiological experiments for the duration of 8 to 2150 days in space are summarized. By the state of biophysical knowledge obtained from earlier experiments (BIOSTACK on Apollo-Soyuz, Spacelab-1 and accelerators UNILAC, BEVALAC), which demanded new evaluation of the dose concept, the suitability of detectors and bioobjects for heavy ions effect, new flight units (improved compartments for detectors and bioobjects) were built by inert structure material. They provided more exact differentiated microdosimetric data of particle hits. Thus, the significance of charge (Z) and linear energy transfer (LET) for the relative biological effect (RBE) of single and multiple particle hits of the mixed radiation in orbit inside potential targets of a multicellular model object (Arabidopsis seed empbryo) was indicated. Specialities of radiation damge (lethality, survival, sterility etc.) were interpreted as physiological stress (modification) and genetic risk (mutation). The role of orbit, duration and shielding in the composition of the particle radiation spectrum and, thus, its acute and interactive damage effect is recognized for the improvement of radiation protection during repeated, long lasting space flights. (orig.)SIGLEAvailable from TIB Hannover: F95B1581+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany); Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)DEGerman

EURECA - Advanced Free Flyer BIOSTACK mit einem pflanzlichen Modell- und Testobjekt

Available from TIB Hannover: D.Dt.F. AC1000(44,50) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman