A turn-key Concept for active cancellation of Global Positioning System L3 Signal

We present a concept, developed at the National Astronomy and Ionosphere Center (NAIC) at Arecibo, Puerto Rico, for active suppression of Global Positioning System (GPS) signals in the 305 m dish radio receiver path prior to backend processing. The subsystem does not require an auxiliary antenna and is intended for easy integration with radio telescope systems with a goal of being a turnkey addition to virtually any facility. Working with actual sampled signal data, we have focused on the detection and cancellation of the GPS L3 signal at 1381.05 MHz which, during periodic test modes and particularly during system-wide tests, interfere with observations of objects in a range of redshifts that includes the Coma supercluster, for example. This signal can dynamically change modulation modes and our scheme is capable of detecting these changes and applying cancellation or sending a blanking signal, as appropriate. The subsystem can also be adapted to GPS L1 (1575.42 MHz), L2C (1227.6 MHz), and others. A follow-up is underway to develop a prototype to deploy and evaluate at NAIC.Comment: Presented at the RFI mitigation workshop, 29-31 March 2010, Groningen, the Netherlands. Accepted for publication by the Proceedings of Scienc

The 200 Degree-Long Magellanic Stream System

We establish that the Magellanic Stream (MS) is some 40 degrees longer than previously known with certainty and that the entire MS and Leading Arm (LA) system is thus at least 200 degrees long. With the GBT, we conducted a ~200 square degree, 21-cm survey at the MS-tip to substantiate the continuity of the MS between the Hulsbosch & Wakker data and the MS-like emission reported by Braun & Thilker. Our survey, in combination with the Arecibo survey by Stanimirovic et al., shows that the MS gas is continuous in this region and that the MS is at least ~140 degrees long. We identify a new filament on the eastern side of the MS that significantly deviates from the equator of the MS coordinate system for more than ~45 degrees. Additionally, we find a previously unknown velocity inflection in the MS-tip near MS longitude L_MS=-120 degrees at which the velocity reaches a minimum and then starts to increase. We find that five compact high velocity clouds cataloged by de Heij et al. as well as Wright's Cloud are plausibly associated with the MS because they match the MS in position and velocity. The mass of the newly-confirmed ~40 degree extension of the MS-tip is ~2x10^7 Msun (d/120 kpc)^2 (including Wright's Cloud increases this by ~50%) and increases the total mass of the MS by ~4%. However, projected model distances of the MS at the tip are generally quite large and, if true, indicate that the mass of the extension might be as large as ~10^8 Msun. From our combined map of the entire MS, we find that the total column density (integrated transverse to the MS) drops markedly along the MS and follows an exponential decline with L_MS. We estimate that the age of the ~140 degree-long MS is ~2.5 Gyr which coincides with bursts of star formation in the Magellanic Clouds and a possible close encounter of these two galaxies with each other that could have triggered the formation of the MS. [Abridged]Comment: 15 pages, 12 figures. Accepted for publication in The Astrophysical Journa

Opportunities and Challenges for Dietary Arsenic Intervention

The diet is emerging as the dominant source of arsenic exposure for most of the U.S. population. Despite this, limited regulatory efforts have been aimed at mitigating exposure, and the role of diet in arsenic exposure and disease processes remains understudied. In this brief, we discuss the evidence linking dietary arsenic intake to human disease and discuss challenges associated with exposure characterization and efforts to quantify risks. In light of these challenges, and in recognition of the potential longer-term process of establishing regulation, we introduce a framework for shorter-term interventions that employs a field-to-plate food supply chain model to identify monitoring, intervention, and communication opportunities as part of a multisector, multiagency, science-informed, public health systems approach to mitigation of dietary arsenic exposure. Such an approach is dependent on coordination across commodity producers, the food industry, nongovernmental organizations, health professionals, researchers, and the regulatory community.Dartmouth College Toxic Metals Superfund Research Program from National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health (NIH) [1R13ES026493-01, P42ES007373]; Children's Environmental Health and Disease Prevention Research Center at Dartmouth from NIEHS of the NIH [P01ES022832]; U.S. Environmental Protection Agency [RD-83544201]Open access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]