Dedication of the Palomar Observatory and the Hale Telescope

The dedication of the Palomar Observatory, if it were being held in England, would be accompanied by brilliant pageantry both of the state, with its knights, heralds, pursuivants, kings at arms, admirals and captains, and of the church with its bishops, priests and deacons, crucifiers and choirs; and I am sure that we feel the quality of religion in this ceremony. We would hear the choirs chanting in antiphony that great canticle which so delights the choir boys: Benedicite, omnia opera Domini

Revised timing of cenozoic atlantic incursions and changing hinterland sediment sources during southern patagonian orogenesis

New detrital zircon U-Pb geochronology data from the Cenozoic Magallanes-Austral Basin in Argentina and Chile ~51° S establish a revised chronostratigraphy of Paleocene-Miocene foreland synorogenic strata and document the rise and subsequent isolation of hinterland sources in the Patagonian Andes from the continental margin. The upsection loss of zircons derived from the hinterland Paleozoic and Late Jurassic sources between ca. 60 and 44Ma documents a major shift in sediment routing due to Paleogene orogenesis in the greater Patagonian-Fuegian Andes. Changes in the proportion of grains from hinterland thrust sheets, comprised of Jurassic volcanics and Paleozoic metasedimentary rocks, provide a trackable signal of long-term shifts in orogenic drainage divide and topographic isolation due to widening of the retroarc fold-thrust belt. The youngest detrital zircon U-Pb ages confirm timing of Maastrichtian-Eocene strata but require substantial age revisions for part of the overlying Cenozoic basinfill during the late Eocene and Oligocene. The upper Río Turbio Formation, previously mapped as middle to late Eocene in the published literature, records a newly recognized latest Eocene-Oligocene (37-27Ma) marine incursion along the basin margin. We suggest that these deposits could be genetically linked to the distally placed units along the Atlantic coast, including the El Huemul Formation and the younger San Julián Formation, via an eastward deepening within the foreland basin system that culminated in a basin-wide Oligocene marine incursion in the Southern Andes. The overlying Río Guillermo Formation records onset of tectonically generated coarse-grained detritus ca. 24.3Ma and a transition to the first fully nonmarine conditions on the proximal Patagonian platform since Late Cretaceous time, perhaps signaling a Cordilleran-scale upper plate response to increased plate convergence and tectonic plate reorganization.Fil: Fosdick, Julie C.. University of Connecticut; Estados UnidosFil: VanderLeest, R. A.. University of Connecticut; Estados UnidosFil: Bostelmann, J. E.. Universidad de Chile; ChileFil: Leonard, J. S.. Arizona State University; Estados UnidosFil: Ugalde, R.. Universidad Mayor; ChileFil: Oyarzún, J. L.. Parque Geo-paleontológico la Cumbre-baguales; ChileFil: Griffin, Miguel. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

The Northwestern Greenland Ice Sheet During The Early Pleistocene Was Similar To Today

The multi-million year history of the Greenland Ice Sheet remains poorly known. Ice-proximal glacial marine diamict provides a direct but discontinuous record of ice sheet behavior; it is underutilized as a climate archive. Here, we present a novel multiproxy analysis of an Early Pleistocene marine diamict from northwestern Greenland. Low cosmogenic nuclide concentrations indicate minimal near-surface exposure, similar to modern terrestrial sediment. Detrital apatite (U-Th-Sm)/He (AHe) ages all predate glaciation by \u3e150 million years, suggesting the northwestern Greenland Ice Sheet had, by 1.9 Ma, not yet incised fjords of sufficient depth to excavate grains with young AHe ages. The diamict contains terrestrial plant leaf wax, likely from land surfaces surrounding the ice sheet. These data indicate that a persistent, dynamic ice sheet existed in northwestern Greenland by 1.9 Ma and that diamict is a useful archive of ice sheet history and process

First normal stress difference and crystallization in a dense sheared granular fluid

The first normal stress difference (${\mathcal N}_1$) and the microstructure in a dense sheared granular fluid of smooth inelastic hard-disks are probed using event-driven simulations. While the anisotropy in the second moment of fluctuation velocity, which is a Burnett-order effect, is known to be the progenitor of normal stress differences in {\it dilute} granular fluids, we show here that the collisional anisotropies are responsible for the normal stress behaviour in the {\it dense} limit. As in the elastic hard-sphere fluids, ${\mathcal N}_1$ remains {\it positive} (if the stress is defined in the {\it compressive} sense) for dilute and moderately dense flows, but becomes {\it negative} above a critical density, depending on the restitution coefficient. This sign-reversal of ${\mathcal N}_1$ occurs due to the {\it microstructural} reorganization of the particles, which can be correlated with a preferred value of the {\it average} collision angle $\theta_{av}=\pi/4 \pm \pi/2$ in the direction opposing the shear. We also report on the shear-induced {\it crystal}-formation, signalling the onset of fluid-solid coexistence in dense granular fluids. Different approaches to take into account the normal stress differences are discussed in the framework of the relaxation-type rheological models.Comment: 21 pages, 13 figure

On general measures of deformation

Each particle of a continuum is assigned a second order tensor which is taken as a measure of the deformation of some neighborhood of the particle, and which is determined by a functional depending on the configurations of that neighborhood. Two invariance restrictions are imposed on the functional whose values are spatial strain tensors, that is, associated with the deformed configuration. The first requirement is that a time shift and rigid transformation of the deformed configuration leave the spatial deformation tensor unaltered relative to it. The second requires that if particles of distinct continua undergo the same deformation, the corresponding deformation tensors should be the same. For the special case in which the functional depends on the deformation in the smallest neighborhood of a particle, the restrictions imply that the deformation tensors associated with the deformed and reference configurations are isotropic functions of the left and right Cauchy-Green tensors, respectively. Jedem Teilchen eines Kontinuums wird ein Tensor zweiter Stufe als Maß für die Deformation einer gewissen Nachbarschaft dieses Teilchen zugeordnet, der durch ein Funktional bestimmt wird, das von der Konfiguration dieser Nachbarschaft abhängt. Zwei Invarianzbedingungen werden diesem Funktional, dessen Werte räumliche Verzerrungstensoren darstellen, auferlegt, und zwar im Hindblick auf die deformierte Konfiguration. Die erste Forderung besagt, daß eine Zeitverschiebung und eine starre Transformation der deformierten Konfiguration den räumlichen Verzerrungstensor im Hinblick auf diese ungeändert lassen. Die zweite Einschränkung besagt, daß entsprechende Deformationstensoren von Partikeln verschiedener Kontinua, die dieselbe Verformung erlitten haben, gleich sein sollen. Im Spezialfall, daß die Funktionale nur von der Deformation in der nächsten Umgebung des Partikels abhängen, beinhalten die Einschränkungen die Aussage, daß die mit dem deformierten und dem undeformierten Zustand verknüpften Deformationstensoren nur isotrope Funktionen des linken und des rechten Cauchy-Green Tensors sein können.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41717/1/707_2005_Article_BF01172146.pd

Thermomechanical couplings in shape memory alloy materials

In this work we address several theoretical and computational issues which are related to the thermomechanical modeling of shape memory alloy materials. More specifically, in this paper we revisit a non-isothermal version of the theory of large deformation generalized plasticity which is suitable for describing the multiple and complex mechanisms occurring in these materials during phase transformations. We also discuss the computational implementation of a generalized plasticity based constitutive model and we demonstrate the ability of the theory in simulating the basic patterns of the experimentally observed behavior by a set of representative numerical examples