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  • 1
    Publication Date: 2007-02-03
    Description: Since the mid-1980s, our understanding of nutrient limitation of oceanic primary production has radically changed. Mesoscale iron addition experiments (FeAXs) have unequivocally shown that iron supply limits production in one-third of the world ocean, where surface macronutrient concentrations are perennially high. The findings of these 12 FeAXs also reveal that iron supply exerts controls on the dynamics of plankton blooms, which in turn affect the biogeochemical cycles of carbon, nitrogen, silicon, and sulfur and ultimately influence the Earth climate system. However, extrapolation of the key results of FeAXs to regional and seasonal scales in some cases is limited because of differing modes of iron supply in FeAXs and in the modern and paleo-oceans. New research directions include quantification of the coupling of oceanic iron and carbon biogeochemistry.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Boyd, P W -- Jickells, T -- Law, C S -- Blain, S -- Boyle, E A -- Buesseler, K O -- Coale, K H -- Cullen, J J -- de Baar, H J W -- Follows, M -- Harvey, M -- Lancelot, C -- Levasseur, M -- Owens, N P J -- Pollard, R -- Rivkin, R B -- Sarmiento, J -- Schoemann, V -- Smetacek, V -- Takeda, S -- Tsuda, A -- Turner, S -- Watson, A J -- New York, N.Y. -- Science. 2007 Feb 2;315(5812):612-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Institute for Water and Atmospheric Research (NIWA) Centre for Chemical and Physical Oceanography, Department of Chemistry, University of Otago, Dunedin, New Zealand. pboyd@alkali.otago.ac.nz〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17272712" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atmosphere ; Carbon/analysis/metabolism ; Carbon Dioxide ; Chlorophyll/analysis ; Climate ; Diatoms/growth & development ; *Ecosystem ; *Iron/analysis ; Oceans and Seas ; Phytoplankton/*growth & development/metabolism ; *Seawater ; Zooplankton/*growth & development
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2019-07-19
    Description: The ATIC balloon-born experiment measures the energy spectra of elements from H to Fe in primary cosmic rays from about 100 GeV to 100 TeV. ATIC is comprised of a fully active bismuth germinate calorimeter, a carbon target with embedded scintillator hodoscopes, and a silicon matrix that is used as a main charge detector. The silicon matrix produces good charge resolution for the protons and helium but only a partial resolution for heavier nuclei. In the present paper a charge resolution of ATIC device was improved and backgrounds were reduced in the region from Be to Si by means of the upper layer of the scintillator hodoscope that was used as charge detector together with silicon matrix. Relative fluxes of nuclei B, C, N, O in the energy region from about 20 GeV/nucleon to 200 GeV/nucleon that were obtained from new high-resolution and high-quality charge spectra of nuclei are presented.
    Keywords: Astrophysics
    Type: MSFC-386 , International Cosmic Ray Conference 2007; Jul 03, 2007 - Jul 11, 2007; Merida, Yucatan; Mexico
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  • 3
    Publication Date: 2019-07-19
    Description: The Advanced Thin Ionization Calorimeter (ATIC), a balloon-borne experiment, is designed to investigate the composition and energy spectra of cosmic rays of charge Z = 1 to 26 over the energy range - 10(exp 11) - 10(exp 14) ev. The instrument consists of a silicon matrix charge detector, plastic-scintillator strip hodoscopes interleaved with graphite interaction targets, and an 18 radiation length deep, fully active bismuth germanate (BGO) calorimeter. ATIC has had two successful long duration balloon (LDB) flights launched from McMurdo Station, Antarc't'ica in 2000 and 2002. In this paper, we present the all-particle spectrum extracted from data collected during the ATIC flights, and compare it with results from other experiments at both lower and higher energies.
    Keywords: Astrophysics
    Type: MSFC-381 , International Cosmic Ray Conference 2007; Jul 03, 2007 - Jul 11, 2007; Merida, Yucatan; Mexico
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  • 4
    Publication Date: 2019-07-19
    Description: The highest energy measurements of cosmic ray electrons extend just beyond 1 TeV. High energy electrons are of particular interest because energy losses during interstellar propagation insure that they arrive primarily from nearby sources. This may produce observable structure in their spectrum. Further, it is predicted that electrons and positrons result from the annihilation of many exotic particles deposited as dark matter candidates. These electrons may appear as excesses in the cosmic ray electron spectrum from 200 GeV to 1000 GeV. A new long duration balloon experiment, ECAL, is being planned to provide direct cosmic ray electron measurements from approx.50 GeV to 〉1 TeV. To make these measurements ECAL must discriminate strongly against showers from protons and heavier ions. One of the techniques used to make this discrimination may be based on measuring the secondary neutrons produced by events in the instrument. The neutron detector configuration and technique will be discussed along with its expected performance based on Monte Carlo simulations.
    Keywords: Astrophysics
    Type: MSFC-380 , International Cosmic Ray Conference 2007; Jul 03, 2007 - Jul 11, 2007; Merida, Yucatan; Mexico
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  • 5
    Publication Date: 2019-07-19
    Description: The Advanced Thin Ionization Calorimeter (ATIC) long duration balloon experiment had a successful science flight accumulating 18 days of data (12/02 - 1/03) during a single circumnavigation in Antarctica. ATIC measures the energy spectra of elements from H to Fe in primary cosmic rays using a fully active Bismuth Germanate calorimeter preceded by a carbon target, with embedded scintillator hodoscopes, and a silicon matrix charge detector at the top. Preliminary results from ATIC have been reported in previous conferences. The revised results reported here are derived from a new analysis of the data with improved charge resolution, lower background and revised energy calibration. The raw energy deposit spectra are de-convolved into primary energy spectra and extrapolated to the top of the atmosphere. We compare these revised results to previous data and comment upon the astrophysical interpretation of the results.
    Keywords: Astrophysics
    Type: MSFC-379 , International Cosmic Ray Conference 2007; Jul 03, 2007 - Jul 11, 2007; Merida, Yucatan; Mexico
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  • 6
    Publication Date: 2019-07-19
    Description: Electromagnetic ion cyclotron (EMIC) waves are an important magnetospheric emission, which is excited near the magnetic equator with frequencies below the proton gyro-frequency. The source of bee energy for wave growth is provided by temperature anisotropy of ring current (RC) ions, which develops naturally during inward convection from the plasma sheet These waves strongly affect the dynamic s of resonant RC ions, thermal electrons and ions, and the outer radiation belt relativistic electrons, leading to non-adiabatic particle heating and/or pitch-angle scattering and loss to the atmosphere. The rate of ion and electron scattering/heating is strongly controlled by the Wave power spectral and spatial distributions, but unfortunately, the currently available observational information regarding EMIC wave power spectral density is poor. So combinations of reliable data and theoretical models should be utilized in order to obtain the power spectral density of EMIC waves over the entire magnetosphere throughout the different storm phases. In this study, we present the simulation results, which are based on two coupled RC models that our group has developed. The first model deals with the large-scale magnetosphere-ionosphere electrodynamic coupling, and provides a self-consistent description of RC ions/electrons and the magnetospheric electric field. The second model is based on a coupled system of two kinetic equations, one equation describes the RC ion dynamics and another equation describes the power spectral density evolution of EMIC waves, and self-consistently treats a micro-scale electrodynamic coupling of RC and EMIC waves. So far, these two models have been applied independently. However, the large-scale magnetosphere-ionosphere electrodynamics controls the convective patterns of both the RC ions and plasmasphere altering conditions for EMIC wave-particle interaction. In turn, the wave induced RC precipitation Changes the local field-aligned current distributions and the ionospheric conductances, which are crucial for a large-scale electrodynamics. The initial results from this new self-consistent model of the magnetospheric electric field, RC and EMIC waves will be shown in this presentation.
    Keywords: Astrophysics
    Type: American Geophysical Union Fall Meeting; Dec 10, 2007 - Dec 14, 2007; San Francisco, CA; United States
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  • 7
    Publication Date: 2007-07-07
    Description: It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2694912/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2694912/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Willerslev, Eske -- Cappellini, Enrico -- Boomsma, Wouter -- Nielsen, Rasmus -- Hebsgaard, Martin B -- Brand, Tina B -- Hofreiter, Michael -- Bunce, Michael -- Poinar, Hendrik N -- Dahl-Jensen, Dorthe -- Johnsen, Sigfus -- Steffensen, Jorgen Peder -- Bennike, Ole -- Schwenninger, Jean-Luc -- Nathan, Roger -- Armitage, Simon -- de Hoog, Cees-Jan -- Alfimov, Vasily -- Christl, Marcus -- Beer, Juerg -- Muscheler, Raimund -- Barker, Joel -- Sharp, Martin -- Penkman, Kirsty E H -- Haile, James -- Taberlet, Pierre -- Gilbert, M Thomas P -- Casoli, Antonella -- Campani, Elisa -- Collins, Matthew J -- 076905/Wellcome Trust/United Kingdom -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 2007 Jul 6;317(5834):111-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Ancient Genetics, University of Copenhagen, Denmark. ewillerslev@bi.ku.dk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17615355" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acids/*analysis/history/isolation & purification ; Animals ; Bayes Theorem ; Climate ; DNA/*analysis/history/isolation & purification ; *Ecosystem ; Fossils ; Geography ; Greenland ; History, Ancient ; Ice Cover/*chemistry ; *Invertebrates/classification/genetics ; *Plants/classification/genetics ; Polymerase Chain Reaction ; Time ; *Trees
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
    Publication Date: 2007-03-03
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Settele, Josef -- Kuhn, Ingolf -- Klotz, Stefan -- Hammen, Volker -- Spangenberg, Joachim -- New York, N.Y. -- Science. 2007 Mar 2;315(5816):1220.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17332393" target="_blank"〉PubMed〈/a〉
    Keywords: Biodiversity ; Economics ; *Ecosystem ; Environment ; *European Union ; *Interdisciplinary Communication ; *Research
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
    Publication Date: 2007-05-19
    Description: Episodic eddy-driven upwelling may supply a significant fraction of the nutrients required to sustain primary productivity of the subtropical ocean. New observations in the northwest Atlantic reveal that, although plankton blooms occur in both cyclones and mode-water eddies, the biological responses differ. Mode-water eddies can generate extraordinary diatom biomass and primary production at depth, relative to the time series near Bermuda. These blooms are sustained by eddy/wind interactions, which amplify the eddy-induced upwelling. In contrast, eddy/wind interactions dampen eddy-induced upwelling in cyclones. Carbon export inferred from oxygen anomalies in eddy cores is one to three times as much as annual new production for the region.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGillicuddy, Dennis J Jr -- Anderson, Laurence A -- Bates, Nicholas R -- Bibby, Thomas -- Buesseler, Ken O -- Carlson, Craig A -- Davis, Cabell S -- Ewart, Courtney -- Falkowski, Paul G -- Goldthwait, Sarah A -- Hansell, Dennis A -- Jenkins, William J -- Johnson, Rodney -- Kosnyrev, Valery K -- Ledwell, James R -- Li, Qian P -- Siegel, David A -- Steinberg, Deborah K -- New York, N.Y. -- Science. 2007 May 18;316(5827):1021-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1541, USA. dmcgillicuddy@whoi.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17510363" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atlantic Ocean ; Biomass ; Carbon/analysis ; Chlorophyll/analysis ; Cyanobacteria/growth & development/physiology ; Diatoms/growth & development ; *Ecosystem ; Geologic Sediments ; Oxygen/analysis ; Photosynthesis ; Phytoplankton/growth & development/physiology ; Plankton/*growth & development/physiology ; Seasons ; *Seawater/chemistry ; *Water Movements ; *Wind ; Zooplankton/growth & development/physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2007-05-19
    Description: Mesoscale eddies may play a critical role in ocean biogeochemistry by increasing nutrient supply, primary production, and efficiency of the biological pump, that is, the ratio of carbon export to primary production in otherwise nutrient-deficient waters. We examined a diatom bloom within a cold-core cyclonic eddy off Hawaii. Eddy primary production, community biomass, and size composition were markedly enhanced but had little effect on the carbon export ratio. Instead, the system functioned as a selective silica pump. Strong trophic coupling and inefficient organic export may be general characteristics of community perturbation responses in the warm waters of the Pacific Ocean.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Benitez-Nelson, Claudia R -- Bidigare, Robert R -- Dickey, Tommy D -- Landry, Michael R -- Leonard, Carrie L -- Brown, Susan L -- Nencioli, Francesco -- Rii, Yoshimi M -- Maiti, Kanchan -- Becker, Jamie W -- Bibby, Thomas S -- Black, Wil -- Cai, Wei-Jun -- Carlson, Craig A -- Chen, Feizhou -- Kuwahara, Victor S -- Mahaffey, Claire -- McAndrew, Patricia M -- Quay, Paul D -- Rappe, Michael S -- Selph, Karen E -- Simmons, Melinda P -- Yang, Eun Jin -- New York, N.Y. -- Science. 2007 May 18;316(5827):1017-21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences and Marine Science Program, University of South Carolina, Columbia, SC 29208, USA. cbnelson@geol.sc.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17510362" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bacteria/growth & development ; Biomass ; Carbon/analysis ; Chlorophyll/analysis ; Diatoms/*growth & development/physiology ; *Ecosystem ; Hawaii ; Nitrates ; Nitrites/analysis ; Pacific Ocean ; Photosynthesis ; Phytoplankton/growth & development/physiology ; *Seawater/chemistry ; Silicic Acid/analysis ; Silicon Dioxide/*analysis ; Temperature ; *Water Movements ; Zooplankton/growth & development/physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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