54 research outputs found
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Measuring large topographic change with InSAR: lava thicknesses, extrusion rate and subsidence rate at Santiaguito volcano, Guatemala
Lava flows can produce changes in topography on the order of 10s-100s of metres. A knowledge of the resulting volume
change provides evidence about the dynamics of an eruption. We present a method to measure topographic changes from the
differential InSAR phase delays caused by the height differences between the current topography and a Digital Elevation Model
(DEM). This does not require a pre-event SAR image, so it does not rely on interferometric phase remaining coherent during
eruption and emplacement. Synthetic tests predicts that we can estimate lava thickness of as little as �9 m, given a minimum of 5
interferograms with suitably large orbital baseine separations. In the case of continuous motion, such as lava flow subsidence, we
invert interferometric phase simultaneously for topographic change and displacement. We demonstrate the method using data from
Santiaguito volcano, Guatemala, and measure increases in lava thickness of up to 140 m between 2000 and 2009, largely associated
with activity between 2000 and 2005. We find a mean extrusion rate of 0.43 +/- 0.06 m3/s, which lies within the error bounds of
the longer term extrusion rate between 1922-2000. The thickest and youngest parts of the flow deposit were shown to be subsiding
at an average rate of �-6 cm/yr. This is the first time that flow thickness and subsidence have been measured simultaneously. We
expect this method to be suitable for measurment of landslides and other mass flow deposits as well as lava flows
The Kolmogorov-Smirnov test for the CMB
We investigate the statistics of the cosmic microwave background using the
Kolmogorov-Smirnov test. We show that, when we correctly de-correlate the data,
the partition function of the Kolmogorov stochasticity parameter is compatible
with the Kolmogorov distribution and, contrary to previous claims, the CMB data
are compatible with Gaussian fluctuations with the correlation function given
by standard Lambda-CDM. We then use the Kolmogorov-Smirnov test to derive upper
bounds on residual point source power in the CMB, and indicate the promise of
this statistics for further datasets, especially Planck, to search for
deviations from Gaussianity and for detecting point sources and Galactic
foregrounds.Comment: Improved significance of the results (which remain unchanged) by
using patches instead of ring segments in the analysis. Added sky maps of the
Kolmogorov-parameter for original and de-correlated CMB ma
Big Bang Baryogenesis
An overview of baryogenesis in the early Universe is presented. The standard
big bang model including big bang nucleosynthesis and inflation is breifly
reviewed. Three basic models for baryogenesis will be developed: The
``standard" out-of-equilibrium decay model; the decay of scalar consensates
along flat directions in supersymmetric models; and lepto-baryogenesis, which
is the conversion of a lepton asymmetry into a baryon asymmetry via
non-perturbative electroweak interactions.Comment: 36 pages, LaTeX, UMN-TH-1249, Lectures given at the 33rd
International Winter School on Nuclear and Particle Physics, ``Matter Under
Extreme Conditions", Feb. 27 - March 5 1994, Schladming Austri
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Applications of electrified dust and dust devil electrodynamics to Martian atmospheric electricity
Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kVm-1 to 100 kVm-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ measurements
Mouse Chromosome 11
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46996/1/335_2004_Article_BF00648429.pd
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