11,656 research outputs found
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How Useful are High-Precision Delta ?17O Data in Defining the Asteroidal Sources of Meteorites?: Evidence from Main-Group Pallasites, Primitive and Differentiated Achondrites
High-precision oxygen isotope analysis is capable of revealing important information about the relationship between different meteorite groups. New data confirm that the main-group pallasites are from a distinct source to either the HEDs or mesosiderites
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Mineralogy and Geochemistry of Shergottite RBT 04262
This abstract presents mineralogical and geochemical data on newly discovered shergottite RBT 04262 and compares it with other known shergottites
Study of high altitude plume impingement
Computer program has been developed as analytical tool to predict severity of effects of exhaust of rocket engines on adjacent spacecraft surfaces. Program computes forces, moments, pressures, and heating rates on surfaces immersed in or subjected to exhaust plume environments. Predictions will be useful in design of systems where such problems are anticipated
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Tafassasset: The Saga Continues
In this study, we compare data for two separate Tafassasset stones and supply new oxygen isotope data for our sample. We include a discussion of the debate surrounding the classification of Tafassasset and offer a hypothesis for its origin based upon new information
Colligative properties of solutions: II. Vanishing concentrations
We continue our study of colligative properties of solutions initiated in
math-ph/0407034. We focus on the situations where, in a system of linear size
, the concentration and the chemical potential scale like and
, respectively. We find that there exists a critical value \xit such
that no phase separation occurs for \xi\le\xit while, for \xi>\xit, the two
phases of the solvent coexist for an interval of values of . Moreover, phase
separation begins abruptly in the sense that a macroscopic fraction of the
system suddenly freezes (or melts) forming a crystal (or droplet) of the
complementary phase when reaches a critical value. For certain values of
system parameters, under ``frozen'' boundary conditions, phase separation also
ends abruptly in the sense that the equilibrium droplet grows continuously with
increasing and then suddenly jumps in size to subsume the entire system.
Our findings indicate that the onset of freezing-point depression is in fact a
surface phenomenon.Comment: 27 pages, 1 fig; see also math-ph/0407034 (both to appear in JSP
Irreversibility in response to forces acting on graphene sheets
The amount of rippling in graphene sheets is related to the interactions with
the substrate or with the suspending structure. Here, we report on an
irreversibility in the response to forces that act on suspended graphene
sheets. This may explain why one always observes a ripple structure on
suspended graphene. We show that a compression-relaxation mechanism produces
static ripples on graphene sheets and determine a peculiar temperature ,
such that for the free-energy of the rippled graphene is smaller than
that of roughened graphene. We also show that depends on the structural
parameters and increases with increasing sample size.Comment: 4 pages, 4 Figure
Optical and dc transport properties of a strongly correlated charge density wave system: exact solution in the ordered phase of the spinless Falicov-Kimball model with dynamical mean-field theory
We derive the dynamical mean-field theory equations for transport in an
ordered charge-density-wave phase on a bipartite lattice. The formalism is
applied to the spinless Falicov-Kimball model on a hypercubic lattice at half
filling. We determine the many-body density of states, the dc charge and heat
conductivities, and the optical conductivity. Vertex corrections continue to
vanish within the ordered phase, but the density of states and the transport
coefficients show anomalous behavior due to the rapid development of thermally
activated subgap states. We also examine the optical sum rule and sum rules for
the first three moments of the Green's functions within the ordered phase and
see that the total optical spectral weight in the ordered phase either
decreases or increases depending on the strength of the interactions.Comment: 14 pages, 14 figures, submitted to Phys. Rev.
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Paris: The slightly altered, slightly metamorphosed CM that bridges the gap between CMs and Cos
A fresh, 1.3 kilo stone was found in Paris. It is a CM chondrite with metal, Fe-sulfide, FeS-rich PCPs and relict mesostasis and is ~3.0 ± 0.1. Petrographic and oxygen isotope evidence indicates that it has affinities with the CO chondrites
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