Spring 2011 Colloquia

January 10: First day of classes, no colloquium

January 17: Martin Luther King Day, no colloquium

January 24: Chris McKay, NASA Ames. Title: Perchlorate and organics in mid-latitudes on Mars and implications for the search for life.

January 31: Kevin Mandernack, Earth Sciences, IUPUI. Title: Experimental studies of microbial sulfide oxidation: stable isotope systematics of sulfate

February 7: Ursel Schuette, SPEA, Indiana University. Title: Bacterial diversity in a high arctic glacier foreland.

February 14: Kaj Johnson, Geological Sciences, Indiana University. Title: Potential for Earthquakes On and Off Major Faults in California

February 21: Peter Wilf, Geosciences, Pennsylvania State University. Title: Fossil Rainforests of Patagonian Fire Lakes and Their Australasian Legacy.

February 28: Bill Brown, Director Office of Sustainability, Indiana University. Title: Vision 2020: Indiana University's Sustainability Vision and Goals for a Decade of Sustainability

March 7: Jim Brophy, Department of Geological Sciences, Indiana University. Title: Silicic magma generation in oceanic environments: an up-date on theoretical, experimental and field-based studies

March 14: Spring Break, no colloquium

March 21: David Shelly, U.S. Geological Survey. Title: Tremor, slow slip, and earthquakes: Interacting modes of fault slip.

Dave is going to talk about perhaps the most exciting new discovery of the last decade in seismology and tectonics – so called low frequency earthquakes that occur deep on faults (in the lower crust) at depths where earthquakes were not previously known to occur. The identification of these new earthquakes and the rich new data sets emerging are providing a new way to study the behavior of faults. There will also be a brown bag seminar in G416 on Monday at noon.

Professor Kaj Johnson

March 28: Juergen Schieber, Department of Geological Sciences, Indiana University. Title: Reverse Engineering Mother Nature: The significance of experimental mudstone sedimentology for understanding shale successions and shale properties.

April 4: David Dilcher, IU Department of Biology. Title: Coevolution of land plants, flowers and people.

April 11: Lindsay Leighton, University of Alberta Canada. Title: The Influence of Predation on Community Composition and Evenness: A case-study of Eocene Molluscs.

April 18: Thomas Proffen, Neutron Scattering Science Division, Oak Ridge National Laboratory. Title: Structural Characterization of Complex Materials using Total Scattering

Abstract Structural characterization is mainly based on the measurement of Bragg intensities and yields the average structure of the crystalline material. However, this approach ignores any defects or local structural deviations that manifest themselves as diffuse scattering. It also fails in case of disordered materials, badly crystalline such as many nano-materials, or not crystalline at all, such as glasses. In some cases crystalline and amorphous phases coexist making the traditional crystallographic structure refinement difficult or incomplete. The total scattering pattern, however, contains structural information over all length scales [1] and can be used to obtain a complete structural picture of complex materials.

Suddenly one has access to a new parameter, the real-space range of the refinement and structures can be analyzed as function of length scale straight forwardly. A classic example is LaMnO3, here the average structure shows that the MnO6 octahedra in become regular when the material is heated above 1000°K, but total scattering measurement show [2], the octahedra stay regular up to the highest temperatures. The reason is the fact that the MnO6 octahedra stay distorted, and only the cooperative orientation of the Mn-O long bonds disappears. Since the atomic Pair Distribution Function (PDF) extracted from total scattering data contains structural information as function of length scale r, one can study the transition from the local to the average structure.

In this presentation an overview of experimental advances in neutron and x-ray total scattering measurements as well as the current state-of-the-art in modeling of disordered materials will be presented. Examples include local disorder in exotic oxides, hydrogen storage materials, nano-particles and their ligand structure as well as complex systems such as 'green' geopolymer concrete. Experiments were perfomed at the Advanded Photon Source at Argonne National Laboratory and at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. New opportunities for total scattering experiments under development at the Spallation Neutron Source at Oak Ridge National Laboratory will also be discussed.

April 28: Greg Hirth, Brown University. Title: The Role of Serpentine Deformation On the Spectrum of Fault Slip Behavior Observed in Subduction Zones