NIEL Dose Dependence for Solar Cells Irradiated with Electrons and Protons

The investigation of solar cells degradation and the prediction of its end-of-life performance is of primary importance in the preparation of a space mission. In the present work, we investigate the reduction of solar-cells' maximum power resulting from irradiations with electrons and protons. Both GaAs single junction and GaInP/GaAs/Ge triple junction solar cells were studied. The results obtained indicate how i) the dominant radiation damaging mechanism is due to atomic displacements, ii) the relative maximum power degradation is almost independent of the type of incoming particle, i.e., iii) to a first approximation, the fitted semi-empirical function expressing the decrease of maximum power depends only on the absorbed NIEL dose, and iv) the actual displacement threshold energy value (Ed=21 eV) accounts for annealing treatments, mostly due to self-annealing induced effects. Thus, for a given type of solar cell, a unique maximum power degradation curve can be determined as a function of the absorbed NIEL dose. The latter expression allows one to predict the performance of those solar cells in space radiation environment.Comment: To appear on the Proceedings of the 13th ICATPP Conference on Astroparticle, Particle, Space Physics and Detectors for Physics Applications, Villa Olmo (Como, Italy), 23--27 October, 2013, to be published by World Scientific (Singapore

Landslide damming hazard susceptibility maps: a new GIS-based procedure for risk management

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Hubble Space Telescope H-Band Imaging Survey of Massive Gas-Rich Mergers

We report the results from a deep HST NICMOS H-band imaging survey of a carefully selected sample of 33 luminous, late-stage galactic mergers at z < 0.3. Signs of a recent galactic interaction are seen in all of the objects in the HST sample, including all 7 IR-excess Palomar-Green (PG) QSOs in the sample. Unsuspected double nuclei are detected in 5 ULIRGs. A detailed two-dimensional analysis of the surface brightness distributions in these objects indicates that the great majority (81%) of the single-nucleus systems show a prominent early-type morphology. However, low-surface-brightness exponential disks are detected on large scale in at least 4 of these sources. The hosts of 'warm' AGN-like systems are of early type and have less pronounced merger-induced morphological anomalies than the hosts of cool systems with LINER or HII region-like nuclear optical spectral types. The host sizes and luminosities of the 7 PG~QSOs in our sample are statistically indistinguishable from those of the ULIRG hosts. In comparison, highly luminous quasars, such as those studied by Dunlop et al. (2003), have hosts which are larger and more luminous. The hosts of ULIRGs and PG QSOs lie close to the locations of intermediate-size (about 1 -- 2 L*) spheroids in the photometric projection of the fundamental plane of ellipticals, although there is a tendency in our sample for the ULIRGs with small hosts to be brighter than normal spheroids. Excess emission from a young stellar population in the ULIRG/QSO hosts may be at the origin of this difference. Our results provide support for a possible merger-driven evolutionary connection between cool ULIRGs, warm ULIRGs, and PG~QSOs although this sequence may break down at low luminosity. (abridged)Comment: Paper to be published in the Astrophysical Journal; revised based on comments from referee. A PDF file combining both text and figures is available at http://www.astro.umd.edu/~veilleux/pubs/nicmos.pd

Low, Milky-Way like, Molecular Gas Excitation of Massive Disk Galaxies at z~1.5

We present evidence for Milky-Way-like, low-excitation molecular gas reservoirs in near-IR selected massive galaxies at z~1.5, based on IRAM Plateau de Bure Interferometer CO[3-2] and NRAO Very Large Array CO[1-0] line observations for two galaxies that had been previously detected in CO[2-1] emission. The CO[3-2] flux of BzK-21000 at z=1.522 is comparable within the errors to its CO[2-1] flux, implying that the CO[3-2] transition is significantly sub-thermally excited. The combined CO[1-0] observations of the two sources result in a detection at the 3 sigma level that is consistent with a higher CO[1-0] luminosity than that of CO[2-1]. Contrary to what is observed in submillimeter galaxies and QSOs, in which the CO transitions are thermally excited up to J>=3, these galaxies have low-excitation molecular gas, similar to that in the Milky Way and local spirals. This is the first time that such conditions have been observed at high redshift. A Large Velocity Gradient analysis suggests that molecular clouds with density and kinetic temperature comparable to local spirals can reproduce our observations. The similarity in the CO excitation properties suggests that a high, Milky-Way-like, CO to H_2 conversion factor could be appropriate for these systems. If such low-excitation properties are representative of ordinary galaxies at high redshift, centimeter telescopes such as the Expanded Very Large Array and the longest wavelength Atacama Large Millimeter Array bands will be the best tools for studying the molecular gas content in these systems through the observations of CO emission lines.Comment: 5 pages, 4 figures. ApJ Letters in pres

Correction to: Morphological analysis and features of the landslide dams in the Cordillera Blanca, Peru

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TDEM for Martian in situ resource prospecting missions

This paper presents a TDEM (Time Domain Electromagnetic Methods) application, addressed to the search for water on Mars. In this context, the opportunities for a TDEM system as payload in a future mission are investigated for different in situ exploration scenarios. The TDEM sounding capability is evaluated with respect to the expected Martian environment, and some considerations are made about the many unknown variables (above all the background EM noise and the subsoil composition) altogether with the limited resources availability (mission constraints in mass, time and power) and the way they could represent an obstacle for operations and measurements

Confirmation of two extended objects along the line of sight to PKS1830-211 with ESO-VLT adaptive optics imaging

We report on new high-resolution near-infrared images of the gravitationally lensed radio source PKS1830-211, a quasar at z=2.507. These adaptive optics observations, taken with the Very Large Telescope (VLT), are further improved through image deconvolution. They confirm the presence of a second object along the line of sight to the quasar, in addition to the previously known spiral galaxy. This additional object is clearly extended in our images. However, its faint luminosity does not allow to infer any photometric redshift. If this galaxy is located in the foreground of PKS1830-211, it complicates the modeling of this system and decreases the interest in using PKS1830-211 as a means to determine H0 via the time delay between the two lensed images of the quasar.Comment: Accepted in A&A Letter

The electrooxidation of CO: a test reaction in electrocatalysis

This review paper aims to show how the electrochemical behaviour of CO plays a key role in the understanding of the reaction mechanism of many electrocatalytic oxidations of small organic molecules. For that purpose, the adsorption of CO on noble metal electrodes, eventually modified by foreign metal adatoms, is reviewed, taking into account both experimental (electrochemical and spectroscopic techniques) and theoretical (Extended Hückel Model) approaches. Data from the gas phase-solid metal interface are also considered.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta