51 research outputs found
Effect of superatmospheric pressures on nucleate boiling of organic liquids
Superatmospheric pressures greatly reduce the temperature differences in nucleate boiling of or ganic liquids. Since nucleate boiling is characterized by bubble formation at the heating surface, it seems logical to investigate the pressure difference that causes bubble formation. It has been found that for organic liquids the difference in vapor pressure corresponding to the temperature difference behaves in a regular manner with pressure but does not vary greatly. This regular behavior permits prediction of temperature differences at higher pressures with a knowledge of only vapor-pressure and boiling data at one pressure. New boiling data have been obtained in the investigation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37297/1/690040119_ftp.pd
VLBI and Archival VLA and WSRT Observations of the GRB 030329 Radio Afterglow
We present VLBI and archival Karl G. Jansky Very Large Array (VLA) and
Westerbork Synthesis Radio Telescope (WSRT) observations of the radio afterglow
from the gamma-ray burst (GRB) of 2003 March 29 (GRB 030329) taken between 672
and 2032 days after the burst. The EVLA and WSRT data suggest a simple power
law decay in the flux at 5 GHz, with no clear signature of any rebrightening
from the counter jet. We report an unresolved source at day 2032 of size
mas, which we use in conjunction with the expansion rate of the
burst to argue for the presence of a uniform, ISM-like circumburst medium.
We develop a semi-analytic method to model gamma-ray burst afterglows, and
apply it to the 5 GHz light curve to perform burst calorimetry. A limit of mas yr is placed on the proper motion, supporting the standard
afterglow model for gamma-ray bursts.Comment: 24 pages, 5 figure
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Exploring nanomagnetism with soft x-ray microscopy
Magnetic soft X-ray microscopy images magnetism in nanoscale systems with a spatial resolution down to 15nm provided by state-of-the-art Fresnel zone plate optics. X-ray magnetic circular dichroism (X-MCD) is used as element-specific magnetic contrast mechanism similar to photoemission electron microscopy (PEEM), however, with volume sensitivity and the ability to record the images in varying applied magnetic fields which allows to study magnetization reversal processes at fundamental length scales. Utilizing a stroboscopic pump-probe scheme one can investigate fast spin dynamics with a time resolution down to 70 ps which gives access to precessional and relaxation phenomena as well as spin torque driven domain wall dynamics in nanoscale systems. Current developments in zone plate optics aim for a spatial resolution towards 10nm and at next generation X-ray sources a time resolution in the fsec regime can be envisioned
A Parametrization of Cosmic Ray Shower Profiles Based on Shower Width
Cosmic ray (CR) air showers, detected via the air fluorescence technique, are
reconstructed in part using functions that parameterize the longitudinal
profile of each shower. The profile parameterization yields the position of
shower maximum, X_max, which is sensitive to the incident CR particle type:
e.g. p, C/N/O, Fe or photons. The integral of the profile is directly related
to the shower energy. The Pierre Auger fluorescence reconstruction uses the
Gaisser-Hillas 4-parameter form. The HiRes group has used both the
Gaisser-Hillas form and a 3-parameter Gaussian in Age form. Historically
analytic shower theory suggested yet other forms; the best known is a
3-parameter form popularized by Greisen. Our work now uses the shower full
width half-maximum, "fwhm", and shower asymmetry parameter, "f", to unify the
parameterization of all three profile functions. Furthermore shower profiles
expressed in terms of the new parameters: (fwhm, f) have correlations greatly
reduced over Gaisser-Hillas parameters (X_0, lambda). This allows shower
profile reconstructions to add constraints (if needed) on the mostly
uncorrelated parameters (fwhm, f).Comment: 12 pages, 6 figures, to be published in J. Phys G: Nucl. & Part. Phy
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Soft X-ray Imaging of Vortex Dynamics in Trilayer Pattered Magnetic Elements
Survival analysis using Medicare data: example and methods.
OBJECTIVE: To describe key methods and issues in conducting survival analyses, especially using Medicare (and other) administrative data. PRINCIPAL FINDINGS: Survival analyses are rich , informative, and underutilized methods for examining out comes whose timing is important . Medicare files contain the necessary information for conducting such analyses, including identification of cohorts, definition of events, censoring of observations, and adjustment for covariates. CONCLUSION: Survival analyses can readily be conducted using the information contained in administrative data files
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