| 561. |
- Mizuno, T., et al.
(författare)
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High sensitivity balloon-borne hard X-ray/soft Gamma-Ray Polarimeter PoGOLite
- 2007
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Ingår i: Nuclear Science Symposium Conference Record, 2007. NSS ’07. IEEE. - : IEEE. - 9781424409228 ; , s. 2538-2544
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Konferensbidrag (refereegranskat)abstract
- The Polarized Gamma-ray Observer - Lightweight version (PoGOLite) is a new balloon experiment capable of detecting 10% polarization from a 200 mCrab source in the 25-80 keV energy range in a single 6-hour flight for the first time. Polarization measurements of hard X-rays and soft gamma-rays are expected to provide a powerful probe into high-energy emission mechanisms as well as source geometries. PoGOLite uses Compton scattering and photo-absorption to measure polarization in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators. The adoption of a well-type phoswich counter concept and a thick polyethylene neutron shield provides a narrow field-of-view (1.25 msr), a large effective area ( gt; 250 cm2 at 40-50 keV), a high modulation factor (more than 25%) and the low background ( 100 mCrab) required to conduct high-sensitivity polarization measurements. Through tests in laboratories and accelerator facilities of a scaled-down prototype with the front-end electronics of flight design and an extensive study by Monte Carlo simulation, we have demonstrated high instrument performance. PoGOLite will be ready for a first engineering flight in 2009 and a science flight in 2010, during which polarization signals from the Crab Nebula/pulsar, Cygnus X-1 and other objects will be observed.
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| 562. |
- Mocchiutti, E., et al.
(författare)
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The PAMELA electromagnetic calorimeter : performances
- 2006
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Ingår i: Calorimetry in High Energy Physics. - : American Institute of Physics (AIP). - 0735403643 ; , s. 159-166
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Konferensbidrag (refereegranskat)abstract
- A sampling silicon-tungsten imaging calorimeter has been designed and built for the PAMELA satellite-borne experiment. The calorimeter has been designed to identify antiprotons from an electron background and positrons in a background of protons with a high efficiency and rejection power. In this work we present the identification capabilities of the calorimeter obtained using both Monte Carlo and test beam data. We show that the calorimeter provides a proton rejection factor of at least 105 while keeping a high efficiency in selecting electrons and positrons. Hence, the calorimeter will fulfill the identification power needed to reach the primary scientific objectives of PAMELA, that are the measurement of the flux of antiprotons, positrons and light isotopes in the cosmic radiation.
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| 563. |
- Orsi, S., et al.
(författare)
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A second level trigger for the PAMELA satellite experiment
- 2006
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 25:1, s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- The PAMELA space experiment will be launched on-board of a Russian Resurs DK1 satellite towards the end of 2005. The main scientific goal is the study of the antimatter component of the cosmic radiation. Three years of data taking will provide unprecedented statistics for antiprotons (80 MeV-190 GeV) and positrons (50 MeV-270 GeV) and will set the upper limit for the ratio He/He below 10(-8). PAMELA is built around a permanent magnet silicon spectrometer, surrounded by a plastic scintillator anticoincidence shield. An electromagnetic calorimeter is used for particle identification and energy measurements. If PAMELA data exceed the storage allowance on the satellite or the daily downlink quota (20 GB), a second level trigger may be activated by uplink from ground. Information from the anticoincidence system and from the calorimeter will be included in the second level trigger condition, providing a selective reduction of data. The second level trigger condition provides a reduction of data of similar to 60%, with a maximum systematic uncertainty in the proton (electron) spectra of 10% (3%). This uncertainty will be assessed during flight measuring one event every 10 without the second level trigger condition.
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| 564. |
- Pearce, Mark, et al.
(författare)
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CLIMB : cosmic light isotopes and muons with balloons
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 525:02-jan, s. 114-117
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Tidskriftsartikel (refereegranskat)abstract
- A new balloon-borne experiment is proposed which will measure high-energy light isotopes at the top of the Earth's atmosphere and cosmic ray muons at fixed altitudes within the Earth's atmosphere.
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| 565. |
- Pearce, Mark, et al.
(författare)
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PoGOLite : A balloon-borne soft gamma-ray polarimeter
- 2007
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Ingår i: Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007. - : Universidad Nacional Autonoma de Mexico. ; , s. 479-482
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Konferensbidrag (refereegranskat)abstract
- Polarized gamma-rays are expected from a wide variety of sources including rotationpowered pulsars, accreting black holes and neutron stars, and jet-dominated active galaxies. Polarization measurements provide a powerful probe of the gamma-ray emission mechanism and the distribution of magnetic and radiation fields around the source. No measurements have been performed in the soft gamma-ray band where non-thermal processes are expected to produce high degrees of polarization. The PoGOLite experiment applies well-type phoswich detector technology to polarization measurements in the 25 - 80 keV energy range. The instrument uses Compton scattering and photoabsorption in an array of 217 phoswich detector cells made of plastic and BGO scintillators, and surrounded by active BGO shields. A prototype of the flight instrument has been tested with polarized gammarays and background generated with radioactive sources. The test results and computer simulations confirm that the instrument can detect 10% polarization of a 200 mCrab source in one 6 hour balloon observation. In flight, targets are constrained to within better than 5% of the field-of-view (~5 degrees squared) in order to maximize the effective detection area during observations. The pointing direction on the sky is determined by an attitude control system comprising star trackers, differential GPS receiver system, gyroscopes, accelerometers and magnetometers which provide correction signals to a reaction wheel and torque motor system. Additionally, the entire polarimeter assembly rotates around its viewing axis to minimize systematic bias during observations. Flights are foreseen to start in 2009- 2010 and will target northern sky sources including the Crab pulsar/nebula, Cygnus X-1, and Hercules X-1. These observations will provide valuable information about the pulsar emission mechanism, the geometry around the black hole, and photon transportation in the strongly magnetized neutron star surface, respectively. Future goals include a long duration balloon flight from the Esrange facility in Northern Sweden to Canada.
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| 566. |
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| 567. |
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| 568. |
- Pearce, T. R., et al.
(författare)
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International collaboration between collections-based institutes for halting biodiversity loss and unlocking the useful properties of plants and fungi
- 2020
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Ingår i: Plants People Planet. - : Wiley. - 2572-2611. ; 2:5, s. 515-534
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Tidskriftsartikel (refereegranskat)abstract
- Societal Impact Statement The United Nations' Sustainable Development Goal (SDG) 17 calls for "strong global partnerships and cooperation" to support the other SDGs. The collections-based science community offers many examples of conservation of plant and fungal biodiversity, sharing, repatriation and aggregation of data, access to new technologies, supply of plant and fungal material, strengthening capacity of practitioners, and benefit sharing with the providers of biodiversity and genetic resources. Collaboration framed by workable multilateral treaties will increase our understanding of plant and fungal diversity, help halt biodiversity loss, and accelerate our sustainable use of plants and fungi and the exploration of their useful traits. SummaryCollections-based institutes are at the forefront of generating knowledge and understanding of plant and fungal biodiversity. Through the analysis of occurrence data, the use of modern technologies to better understand the evolutionary relationships between species and documentation of their useful properties, the work of collections-based institutes provides good models for conservation; addressing species loss and improving sustainable use of plants and fungi. Nevertheless, the pressure on the planet's plant and fungal diversity is relentless. We argue that a massive increase in the accessibility of preserved and living collections of plants and fungi is required. An increased scale of responsible exploration to both conserve and unlock the useful properties of plants and fungi is needed to deliver solutions to the many global challenges facing humanity and the planet. This article explores the role of collaborations between collections-based institutes and their partners in preventing biodiversity loss and delivering sustainable development. Drawing on examples from herbaria, agricultural and wild species genebanks, mycological collections, an international NGO, and the botanic garden community, we demonstrate how collaboration improves efficiency and impact. Collaborations can be peer to peer, institutional, governmental, national, or international, they may involve work with local communities and are frequently a combination of these. We suggest the five key benefits to collaboration and show that with trust, understanding, and mutual respect, powerful and sustainable partnerships develop. Such trust and respect are hard won, but once established, sustain a high level of commitment, enable development of shared long-term visions of success, and attract diverse funding streams.
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| 569. |
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| 570. |
- Sheldon, C. M., et al.
(författare)
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Variable influx of West Greenland Current water into the Labrador Current through the last 7200 years : a multiproxy record from Trinity Bay (NE Newfoundland)
- 2015
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Ingår i: arktos. - : Springer Science and Business Media LLC. - 2364-9453 .- 2364-9461. ; 1:8
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Tidskriftsartikel (refereegranskat)abstract
- A multiproxy study of marine sediment gravity core AI07-06G from Trinity Bay, Newfoundland, recorded changes in the strength of the Labrador Current (LC) during the Holocene. From ca. 7.2–5.7 cal kyr BP, Trinity Bay’s seafloor was influenced by cooled Atlantic water derived from the West Greenland Current (WGC) Davis Strait branch, merging into the relatively cold LC. This Atlantic water influence gradually decreased after ca. 5.7 cal kyr BP, reaching a minimum at ca. 4.9 cal kyr BP. In contrast, surface temperatures were relatively low due to cold surface water dominated by sea ice and meltwater carried south by the LC. Icebergs from outlet glaciers around Baffin Bay were abundant in the LC prior to ca. 5.5 cal kyr BP. From ca. 4.9–2.9 cal kyr BP, bottom waters became slightly colder and salinity decreased, as increased mixing of the water column brought less saline surface waters towards the seafloor. This may be explained by a weaker North Atlantic subpolar gyre, transporting less Atlantic water from the WGC to the (outer) LC. Arctic meltwater transport was reduced as glacial melting decreased at the end of the Holocene Thermal Optimum. At ca. 2.9 cal kyr BP, bottom waters returned to colder, more stable conditions, indicating a slight decrease in bottom-water ventilation. After ca. 2.1 cal kyr BP, surface water temperatures dropped and sea ice flux increased. The seafloor of Trinity Bay saw warmer conditions, consistent with a stronger subpolar gyre and increased influx of Atlantic-sourced water.
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