Jupiter as a Giant Cosmic Ray Detector

We explore the feasibility of using the atmosphere of Jupiter to detect Ultra-High-Energy Cosmic Rays (UHECR's). The large surface area of Jupiter allows us to probe cosmic rays of higher energies than previously accessible. Cosmic ray extensive air showers in Jupiter's atmosphere could in principle be detected by the Large Area Telescope (LAT) on the Fermi observatory. In order to be observed, these air showers would need to be oriented toward the Earth, and would need to occur sufficiently high in the atmosphere that the gamma rays can penetrate. We demonstrate that, under these assumptions, Jupiter provides an effective cosmic ray "detector" area of $3.3 \times 10^7$ km$^2$. We predict that Fermi-LAT should be able to detect events of energy $>10^{21}$ eV with fluence $10^{-7}$ erg cm$^{-2}$ at a rate of about one per month. The observed number of air showers may provide an indirect measure of the flux of cosmic rays $\gtrsim 10^{20}$ eV. Extensive air showers also produce a synchrotron signature that may be measurable by ALMA. Simultaneous observations of Jupiter with ALMA and Fermi-LAT could be used to provide broad constraints on the energies of the initiating cosmic rays.Comment: 8 pages, 5 figures. Accepted for publication in the Astrophysical Journal Letter

Non-Maximal Definites in Romance

Mainly based on data from Old Spanish and Modern Francoprovençal, this paper discusses a hitherto underresearched use of the Romance definite article that cannot straightforwardly be explained by recurring to any of the standard analyses of semantic definiteness, i.e., maximality and/or familiarity. We show that such weakly referential definites are definites with representative object interpretations licensed by the kind-oriented mode of talk and not short weak definites. They denote inherently non-specific, semantically number neutral regular objects whose only co(n)textual relevance is their being typical instantiations of their corresponding kind. Representative object definites are shown to be favored by ‘habitual’ readings of the predicate (and text genres like recipes, treatises, narratives about what people used to do in former times, etc.). In Francoprovençal, this is the case especially in the scope of non-perfective verb tenses in prepositional or presentational complements and sometimes in direct objects. In Old Spanish, non-maximal definites often occur in the scope of non-assertive mood (imperative/subjunctive, due to the genre of recipes), while, at the same time, introducing important discourse referents. In addition, in the latter language such definites are demonstrated to be positively susceptible to priming by preceding non-maximal definites

Discovery of a possibly old galaxy at z=6.027z=6.027, multiply imaged by the massive cluster Abell 383

We report the discovery of a unique $z=6.027$ galaxy, multiply imaged by the cluster Abell 383 and detected in new Hubble Space Telescope ACS and WFC3 imaging, as well as in Warm Spitzer observations. This galaxy was selected as a pair of i-dropouts; its suspected high redshift was confirmed by the measurement of a strong Lyman-alpha line in both images using Keck/DEIMOS. Combining Hubble and Spitzer photometry after correcting for contamination by line emission (estimated to be a small effect), we identify a strong Balmer break of 1.5 magnitudes. Taking into account the magnification factor of 11.4+/-1.9 (2.65+/-0.17 mag) for the brightest image, the unlensed AB magnitude for the source is 27.2+/-0.05 in the H band, corresponding to a 0.4 L* galaxy, and 25.7+/-0.08 at 3.6 um. The UV slope is consistent with beta~2.0, and from the rest-frame UV continuum we measure a current star formation rate of 2.4+/-1.1 Msol/yr. The unlensed half-light radius is measured to be 300 pc, from which we deduce a star-forming surface density of ~10 Msol/yr/kpc2. The Lyman-alpha emission is found to be extended over ~3" along the slit, corresponding to ~5 kpc in the source plane. This can be explained by the presence of a much larger envelope of neutral hydrogen around the star-forming region. Finally, fitting the spectral energy distribution using 7 photometric data points with simple SED models, we derive the following properties: very little reddening, an inferred stellar mass of M*=6e9 Msol, and an inferred age of ~800 Myrs (corresponding to a redshift of formation of ~18). The star-formation rate of this object was likely much stronger in the past than at the time of observation, suggesting that we may be missing a fraction of galaxies at z~6 which have already faded in rest-frame UV wavelengths.Comment: 6 pages, 3 figures, MNRAS in press, replaced with accepted version including minor comment

Prozesssimulation der Bauteil-Abschreckung in flüssigen Medien: Zur Analyse des mehrphasigen Strömungs- und Wärmetransports in Siedeprozessen

The quenching process during heat treatment of steel parts is significantly influenced by boiling phenomena. At wall temperatures above the liquid boiling point, the vapour formation and the interaction of the vapour phase with the liquid flow field is determining the local cooling conditions of the workpiece. High temperature gradients can result in an inhomogeneous distribution of the final material properties (e.g. hardness). A multiphase flow and heat transfer model is utilized to simulate the local flow field and the resulting cooling conditions during quenching. The applied bubble-crowding approach is able to investigate the different boiling phases within one single numerical model. Simulation results of the transient cooling of cylindrical specimens in an axial water flow are discussed for various flow velocities and liquid subcoolings and are compared to experimental results. The determined heat transfer coefficients are utilized to calculate the phase transformation and the surface hardness within a material simulation approach, so that the result of the quenching process with respect to the initial liquid flow conditions can be predicted

Quantitative scattering of melanin solutions

The optical scattering coefficient of a dilute, well solubilised eumelanin solution has been accurately measured as a function of incident wavelength, and found to contribute less than 6% of the total optical attenuation between 210 and 325nm. At longer wavelengths (325nm to 800nm) the scattering was less than the minimum sensitivity of our instrument. This indicates that UV and visible optical density spectra can be interpreted as true absorption with a high degree of confidence. The scattering coefficient vs wavelength was found to be consistent with Rayleigh Theory for a particle radius of 38+-1nm.Comment: 23 pages, 5 figure

Electrodynamics of Media

Contains reports on two research projects.Joint Services Electronics Programs (U.S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-0300U.S. Air Force Cambridge Research Laboratories Contract Fl9628-70-C-0064M. I. T. Sloan Fund for Basic Research (Grant 616

Quantitative photoluminescence of broad band absorbing melanins: A procedure to correct for inner filter and re-absorption effects

We report methods for correcting the photoluminescence emission and excitation spectra of highly absorbing samples for re-absorption and inner filter effects. We derive the general form of the correction, and investigate various methods for determining the parameters. Additionally, the correction methods are tested with highly absorbing fluorescein and melanin (broadband absorption) solutions; the expected linear relationships between absorption and emission are recovered upon application of the correction, indicating that the methods are valid. These procedures allow accurate quantitative analysis of the emission of low quantum yield samples (such as melanin) at concentrations where absorption is significant.Comment: 20 pages, 13 figure

Master of Science

thesisThe author is deelpy indebted to Dr. Norman C. Williams, at whose suggestion the problem was undertaken, for his invaluable counsel in the field and in the preparation of the manuscript; to Dr. A. J. Eardley for much valuable information and for his aid in editing the manuscript ; to Dr. W. L. Stokes for helping edit the manuscript and for identifying the fossil collection; and finally to Mr. W. J. Wood for his help in measuring the stratigraphic section