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| 2. |
- Dahl-Jensen, D., et al.
(författare)
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Eemian interglacial reconstructed from a Greenland folded ice core
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 493:7433, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
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| 3. |
- Steen-Larsen, H. C., et al.
(författare)
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Continuous monitoring of summer surface water vapor isotopic composition above the Greenland Ice Sheet
- 2013
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 13:9, s. 4815-4828
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Tidskriftsartikel (refereegranskat)abstract
- We present here surface water vapor isotopic measurements conducted from June to August 2010 at the NEEM (North Greenland Eemian Drilling Project) camp, NW Greenland (77.45 degrees N, 51.05 degrees W, 2484 m a.s.l.). Measurements were conducted at 9 different heights from 0.1m to 13.5m above the snow surface using two different types of cavity-enhanced near-infrared absorption spectroscopy analyzers. For each instrument specific protocols were developed for calibration and drift corrections. The inter-comparison of corrected results from different instruments reveals excellent reproducibility, stability, and precision with a standard deviations of similar to 0.23 parts per thousand for delta O-18 and similar to 1.4 parts per thousand for delta D. Diurnal and intraseasonal variations show strong relationships between changes in local surface humidity and water vapor isotopic composition, and with local and synoptic weather conditions. This variability probably results from the interplay between local moisture fluxes, linked with firn-air exchanges, boundary layer dynamics, and large-scale moisture advection. Particularly remarkable are several episodes characterized by high (> 40 parts per thousand) surface water vapor deuterium excess. Air mass back-trajectory calculations from atmospheric analyses and water tagging in the LMDZiso (Laboratory of Meteorology Dynamics Zoom-isotopic) atmospheric model reveal that these events are associated with predominant Arctic air mass origin. The analysis suggests that high deuterium excess levels are a result of strong kinetic fractionation during evaporation at the sea-ice margin.
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| 6. |
- Kaindl, H., et al.
(författare)
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Robot-Supported Cooperative Work : A Shared-Shopping Scenario
- 2011
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Ingår i: System Sciences (HICSS), 2011 44th Hawaii International Conference on. - 9780769542829 ; , s. 5718472-
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Konferensbidrag (refereegranskat)abstract
- Computer-support cooperative work has been studied extensively and achieved applications that are widely useful. However, there was not much emphasis on support through robots for cooperative work. So, there is no deep understanding of what is needed to support tasks that involve individually moving communication partners and for which the physical context is relevant. This work shows an example of robot-supported cooperative work, where two robots communicate with each other to indirectly support communication between their human users. This example is a shared-shopping scenario. For its realization, we make use of high-level discourse models both for specifying communication between a robot shopping cart and its human user, and between two robot carts. The emerging communication from such intertwined discourses supports a shared (shopping) task of their two human users, who collaborate based on the shopping list shared in this way. Such support is important in a setting where the physical context is relevant, e.g., the vicinity to products.
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| 7. |
- Smith, P., et al.
(författare)
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How much land-based greenhouse gas mitigation can be achieved without compromising food security and environmental goals?
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1365-2486 .- 1354-1013. ; 19:8, s. 2285-2302
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Forskningsöversikt (refereegranskat)abstract
- Feeding 9-10billion people by 2050 and preventing dangerous climate change are two of the greatest challenges facing humanity. Both challenges must be met while reducing the impact of land management on ecosystem services that deliver vital goods and services, and support human health and well-being. Few studies to date have considered the interactions between these challenges. In this study we briefly outline the challenges, review the supply- and demand-side climate mitigation potential available in the Agriculture, Forestry and Other Land Use AFOLU sector and options for delivering food security. We briefly outline some of the synergies and trade-offs afforded by mitigation practices, before presenting an assessment of the mitigation potential possible in the AFOLU sector under possible future scenarios in which demand-side measures codeliver to aid food security. We conclude that while supply-side mitigation measures, such as changes in land management, might either enhance or negatively impact food security, demand-side mitigation measures, such as reduced waste or demand for livestock products, should benefit both food security and greenhouse gas (GHG) mitigation. Demand-side measures offer a greater potential (1.5-15.6Gt CO2-eq. yr(-1)) in meeting both challenges than do supply-side measures (1.5-4.3Gt CO2-eq. yr(-1) at carbon prices between 20 and 100US$ tCO(2)-eq. yr(-1)), but given the enormity of challenges, all options need to be considered. Supply-side measures should be implemented immediately, focussing on those that allow the production of more agricultural product per unit of input. For demand-side measures, given the difficulties in their implementation and lag in their effectiveness, policy should be introduced quickly, and should aim to codeliver to other policy agenda, such as improving environmental quality or improving dietary health. These problems facing humanity in the 21st Century are extremely challenging, and policy that addresses multiple objectives is required now more than ever.
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| 8. |
- Umrao, Sima, et al.
(författare)
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A possible mechanism for the emergence of an additional band gap due to a Ti-O-C bond in the TiO2-graphene hybrid system for enhanced photodegradation of methylene blue under visible light
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:104, s. 59890-59901
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Tidskriftsartikel (refereegranskat)abstract
- Here we report the experimental and theoretical study of two TiO2-graphene oxide (TG) and TiO2-reduced graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light (similar to 470 nm) photocatalytic degradation of Methylene Blue (MB) (99% efficiency), with high rate constant values (1800% over bare TiO2). TG couples TiO2 nanopowder with Graphene Oxide (GO) while TR couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses never-before-reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR (3.42 eV and 2.39 eV) composites, which represents the reason behind feasible visible light (2.56 eV) induced photocatalysis. TiO2 domains in the composites dominate the higher band edge, while GO/RGO domains explain the lower band edge. Formation of Ti-O-C bonds in both TG and TR drives the shifting upwards of the valence band edge and reduction in band gap. Further, these bonds provide a conductive pathway for charge carriers from TiO2 nanopowder to the degraded species via the GO/RGO matrix, resulting in decreased charge carrier recombination in TiO2 and enhanced efficiency. To attest that the developed theory is correct, density function theory (DFT) calculations were performed. DFT obtained energetics and electronic structures support experimental findings by demonstrating the role of the Ti-O-C bond, which results in double band edge phenomenon in composites. Finally, the mechanism behind MB degradation is discussed comprehensively and the effect of the weight percent of GO/RGO in the composite on the rate constant and photodegradation efficiency has been studied experimentally and explained by developing analytical equations.
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| 10. |
- Zaborowska, Magdalena, 1984, et al.
(författare)
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Microporous bacterial cellulose as a potential scaffold for bone regeneration
- 2010
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 6:7, s. 2540-2547
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Tidskriftsartikel (refereegranskat)abstract
- Nanoporous cellulose biosynthesized by bacteria is an attractive biomaterial scaffold for tissue engineering due to its biocompatibility and good mechanical properties. However, for bone applications a microscopic pore structure is needed to facilitate osteoblast ingrowth and formation of a mineralized tissue. Therefore, in this study microporous bacterial cellulose (BC) scaffolds were prepared by incorporating 300-500 mu m paraffin wax microspheres into the fermentation process. The paraffin wax microspheres were subsequently removed, and scanning electron microscopy confirmed a microporous surface of the scaffolds while Fourier transform infrared spectroscopy verified the elimination of paraffin and tensile measurements showed a Young's modulus of approximately 1.6 MPa. Microporous BC and nanoporous (control) BC scaffolds were seeded with MC3T3-E1 osteoprogenitor cells, and examined by confocal microscopy and histology for cell distribution and mineral deposition. Cells clustered within the pores of microporous BC, and formed denser mineral deposits than cells grown on control BC surfaces. This work shows that microporous BC is a promising biomaterial for bone tissue engineering applications. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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