161 research outputs found

    Macroalgal Monitoring in the Great Bay Estuary: 2018 Annual Report

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    Since 2013, the abundance and taxa of intertidal macroalgae have been assessed at fixed locations throughout the Great Bay Estuary in New Hampshire. Algal abundance may be influenced by environmental conditions such as nutrient levels, water temperature, light and invasive species. Therefore, abundance of different algal groups can provide insights into the overall health of the estuary and signal ecological change. In 2018, intertidal abundance data for percentage cover and biomass were collected, as planned, from five of the eight sites. For the first time, subtidal sampling arrays were also incorporated at all four sites in Great Bay proper to monitor macroalgae at lower elevations and to collect data on eelgrass communities coexisting with the algae

    The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later

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    We have used the VLA FIRST survey and the APM catalog of the POSS-I plates as the basis for constructing a new radio-selected sample of optically bright quasars. This is the first radio-selected sample that is competitive in size with current optically selected quasar surveys. Using only two basic criteria, radio-optical positional coincidence and optical morphology, quasars and BL Lacs can be identified with 60% selection efficiency; the efficiency increases to 70% for objects fainter than magnitude 17. We show that a more sophisticated selection scheme can predict with better than 85% reliability which candidates will turn out to be quasars. This paper presents the second installment of the FIRST Bright Quasar Survey with a catalog of 636 quasars distributed over 2682 square degrees. The quasar sample is characterized and all spectra are displayed. The FBQS detects both radio-loud and radio-quiet quasars out to a redshift z>3. We find a large population of objects of intermediate radio-loudness; there is no evidence in our sample for a bimodal distribution of radio characteristics. The sample includes ~29 broad absorption line quasars, both high and low ionization, and a number of new objects with remarkable optical spectra.Comment: 41 pages plus 39 gifs which contain all quasar spectra. Accepted for publication in the Astrophysical Journal Supplement Serie

    Tormentas de ceniza volcĂĄnica en Patagonia : un peligro latente y subestimado

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    Foro Internacional: Los volcanes y su impacto. Arequipa, Peru, 26 y 27 de abril de 2018.Una tormenta de ceniza volcĂĄnica puede definirse como un evento de remobilizaciĂłn masiva de ceniza volcĂĄnica (<2mm) a partir de la acciĂłn eĂłlica (via suspensiĂłn, saltaciĂłn y reptaje). Pero, Âża quĂ© nos referimos exactamente cuando hablamos de resuspensiĂłn de ceniza volcĂĄnica? Bajo determinadas condiciones meteorolĂłgicas y ambientales, como vientos intensos, baja humedad de suelos y falta de cobertura vegetal, las partĂ­culas volcĂĄnicas pueden ser desprendidas de la superficie y puestas nuevamente en suspensiĂłn en la atmĂłsfera.Estacion Experimental Agropecuaria Bariloche. Laboratorio de TeledetecciĂłnFil: Forte, Pablo.Instituto de Geociencias, Universidad Johannes Gutenberg; AlemaniaFil: Dominguez, LucĂ­a. UniversitĂ© de GenĂšve. Department of Earth Sciences; SuizaFil: Bonadonna, Constanza. Departamento de Ciencias de la Tierra. Universidad de Ginebra; SuizaFil: Lamberti, MarĂ­a Clara. Departamento de Ciencias de la Tierra. Universidad de Ginebra; SuizaFil: Gregg, Chris E.East Tennessee State University. Department of Geosciences; Estados UnidosFil: Bran, Donaldo Eduardo. Instituto Nacional de TecnologĂ­a Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria Bariloche. Laboratorio de TeledetecciĂłn; ArgentinaFil: Castro, Jonathan M. Institut fĂŒr Geowissenschaften Johannes Gutenberg-UniversitĂ€t Mainz ; Alemani

    Managing Tsunami Risk: Social Context Influences on Preparedness

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    This article describes the testing of a model that proposes that people's beliefs regarding the effectiveness of hazard preparedness interact with social context factors (community participation, collective efficacy, empowerment and trust) to influence levels of hazard preparedness. Using data obtained from people living in coastal communities in Alaska and Oregon that are susceptible to experiencing tsunami, structural equation modelling analyses confirmed the ability of the model to help account for differences in levels of tsunami preparedness. Analysis revealed that community members and civic agencies influence preparedness in ways that are independent of the information provided per se. The model suggests that, to encourage people to prepare, outreach strategies must (a) encourage community members to discuss tsunami hazard issues and to identify the resources and information they need to deal with the consequences a tsunami would pose for them and (b) ensure that the community-agency relationship is complementary and empowering

    Multi-Messenger Astronomy with Extremely Large Telescopes

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    The field of time-domain astrophysics has entered the era of Multi-messenger Astronomy (MMA). One key science goal for the next decade (and beyond) will be to characterize gravitational wave (GW) and neutrino sources using the next generation of Extremely Large Telescopes (ELTs). These studies will have a broad impact across astrophysics, informing our knowledge of the production and enrichment history of the heaviest chemical elements, constrain the dense matter equation of state, provide independent constraints on cosmology, increase our understanding of particle acceleration in shocks and jets, and study the lives of black holes in the universe. Future GW detectors will greatly improve their sensitivity during the coming decade, as will near-infrared telescopes capable of independently finding kilonovae from neutron star mergers. However, the electromagnetic counterparts to high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus demand ELT capabilities for characterization. ELTs will be important and necessary contributors to an advanced and complete multi-messenger network.Comment: White paper submitted to the Astro2020 Decadal Surve

    Effects of variable magma supply on mid-ocean ridge eruptions : constraints from mapped lava flow fields along the GalĂĄpagos Spreading Center

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    Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q08014, doi:10.1029/2012GC004163.Mapping and sampling of 18 eruptive units in two study areas along the GalĂĄpagos Spreading Center (GSC) provide insight into how magma supply affects mid-ocean ridge (MOR) volcanic eruptions. The two study areas have similar spreading rates (53 versus 55 mm/yr), but differ by 30% in the time-averaged rate of magma supply (0.3 × 106 versus 0.4 × 106 m3/yr/km). Detailed geologic maps of each study area incorporate observations of flow contacts and sediment thickness, in addition to sample petrology, geomagnetic paleointensity, and inferences from high-resolution bathymetry data. At the lower-magma-supply study area, eruptions typically produce irregularly shaped clusters of pillow mounds with total eruptive volumes ranging from 0.09 to 1.3 km3. At the higher-magma-supply study area, lava morphologies characteristic of higher effusion rates are more common, eruptions typically occur along elongated fissures, and eruptive volumes are an order of magnitude smaller (0.002–0.13 km3). At this site, glass MgO contents (2.7–8.4 wt. %) and corresponding liquidus temperatures are lower on average, and more variable, than those at the lower-magma-supply study area (6.2–9.1 wt. % MgO). The differences in eruptive volume, lava temperature, morphology, and inferred eruption rates observed between the two areas along the GSC are similar to those that have previously been related to variable spreading rates on the global MOR system. Importantly, the documentation of multiple sequences of eruptions at each study area, representing hundreds to thousands of years, provides constraints on the variability in eruptive style at a given magma supply and spreading rate.This work was supported by the National Science Foundation grants OCE08–49813, OCE08–50052, and OCE08– 49711.2013-02-2

    LSST: from Science Drivers to Reference Design and Anticipated Data Products

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    (Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2^2 field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5σ\sigma point-source depth in a single visit in rr will be ∌24.5\sim 24.5 (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg2^2 with ÎŽ<+34.5∘\delta<+34.5^\circ, and will be imaged multiple times in six bands, ugrizyugrizy, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg2^2 region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to r∌27.5r\sim27.5. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

    Trends in the sources and sinks of carbon dioxide

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    Efforts to control climate change require the stabilization of atmospheric CO2 concentrations. This can only be achieved through a drastic reduction of global CO2 emissions. Yet fossil fuel emissions increased by 29% between 2000 and 2008, in conjunction with increased contributions from emerging economies, from the production and international trade of goods and services, and from the use of coal as a fuel source. In contrast, emissions from land-use changes were nearly constant. Between 1959 and 2008, 43% of each year's CO2 emissions remained in the atmosphere on average; the rest was absorbed by carbon sinks on land and in the oceans. In the past 50 years, the fraction of CO2 emissions that remains in the atmosphere each year has likely increased, from about 40% to 45%, and models suggest that this trend was caused by a decrease in the uptake of CO2 by the carbon sinks in response to climate change and variability. Changes in the CO2 sinks are highly uncertain, but they could have a significant influence on future atmospheric CO2 levels. It is therefore crucial to reduce the uncertainties
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