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| 2. |
- Ahnen, M. L., et al.
(author)
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Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies
- 2016
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In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2
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Journal article (peer-reviewed)abstract
- We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.
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- Chazdon, Robin L., et al.
(author)
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Carbon sequestration potential of second-growth forest regeneration in the Latin American tropics
- 2016
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In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 2:5
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Journal article (peer-reviewed)abstract
- Regrowth of tropical secondary forests following complete or nearly complete removal of forest vegetation actively stores carbon in aboveground biomass, partially counterbalancing carbon emissions from deforestation, forest degradation, burning of fossil fuels, and other anthropogenic sources. We estimate the age and spatial extent of lowland second-growth forests in the Latin American tropics and model their potential aboveground carbon accumulation over four decades. Our model shows that, in 2008, second-growth forests (1 to 60 years old) covered 2.4 million km2 of land (28.1% of the total study area). Over 40 years, these lands can potentially accumulate a total aboveground carbon stock of 8.48 Pg C (petagrams of carbon) in aboveground biomass via low-cost natural regeneration or assisted regeneration, corresponding to a total CO2 sequestration of 31.09 Pg CO2. This total is equivalent to carbon emissions from fossil fuel use and industrial processes in all of Latin America and the Caribbean from 1993 to 2014. Ten countries account for 95% of this carbon storage potential, led by Brazil, Colombia, Mexico, and Venezuela. We model future land-use scenarios to guide national carbon mitigation policies. Permitting natural regeneration on 40% of lowland pastures potentially stores an additional 2.0 Pg C over 40 years. Our study provides information and maps to guide national-level forest-based carbon mitigation plans on the basis of estimated rates of natural regeneration and pasture abandonment. Coupled with avoided deforestation and sustainable forest management, natural regeneration of second-growth forests provides a low-cost mechanism that yields a high carbon sequestration potential with multiple benefits for biodiversity and ecosystem services.
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| 4. |
- Lindgren, Fredrik
(author)
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Si negative electrodes for Li-ion batteries : Aging mechanism studies by electrochemistry and photoelectron spectroscopy
- 2016
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Doctoral thesis (other academic/artistic)abstract
- This thesis is focusing on the challenges when using Si as a possible new negative electrode material in Li-ion batteries. The overall aim is to contribute to a general understanding of the processes in the Si electrode, to identify aging mechanisms, and to evaluate how they influence the cycling performance. Another objective is to investigate how photoelectron spectroscopy (PES) can be used to analyze these mechanisms.LiPF6 based electrolytes are aggressive towards the oxide layer present at the surface of the Si particles. With the use of fluoroethylene carbonate (FEC) as an electrolyte additive the cycling performance is improved, but the oxide layer is still affected. A recently developed salt, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), is shown not to have any detrimental effects on the oxide. The SEI with FEC and vinylene carbonate (VC) as contains a high concentration of LiF and polymeric carbonate species and this composition seems to be beneficial for the cycling performance, but the results indicate that additional aging mechanisms occur. Therefore, electrochemical analysis is performed and confirms a continuous SEI formation. However, it also reveals a self-discharge mechanism and that a considerable amount of Li is remaining in the Si material after standard cycling.PES is used in this work to analyze the SEI-layers as well as the surface and the bulk of the Si material. With this technique it is hence possible to distinguish changes in the Si material as a function of lithiation. To improve the data interpretation of PES spectra, a range of battery electrode model systems are investigated. These results show shifts of the SEI peaks relative to the electrode specific peaks as a result of the SEI thickness and the presence of a dipole layer. Also other electronically insulating composite electrode components show relative peak shifts as a function of the electrochemical potential.To summarize, these studies investigate a number of well recognized aging mechanisms in detail and also establish additional processes contributing to aging in Si electrodes. Furthermore, this work highlights phenomena that influence data interpretation of PES measurements from battery materials.
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| 5. |
- Munoz-Ruiz, Miguel Angel, et al.
(author)
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Using the Disease State Fingerprint Tool for Differential Diagnosis of Frontotemporal Dementia and Alzheimer's Disease
- 2016
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In: Dementia and Geriatric Cognitive Disorders Extra. - : S. Karger AG. - 1664-5464. ; 6:2, s. 313-329
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Journal article (peer-reviewed)abstract
- Background: Disease State Index (DSI) and its visualization, Disease State Fingerprint (DSF), form a computer-assisted clinical decision making tool that combines patient data and compares them with cases with known outcomes. Aims: To investigate the ability of the DSI to diagnose frontotemporal dementia (FTD) and Alzheimer's disease (AD). Methods: The study cohort consisted of 38 patients with FTD, 57 with AD and 22 controls. Autopsy verification of FTD with TDP-43 positive pathology was available for 14 and AD pathology for 12 cases. We utilized data from neuropsychological tests, volumetric magnetic resonance imaging, single-photon emission tomography, cerebrospinal fluid biomarkers and the APOE genotype. The DSI classification results were calculated with a combination of leave-one-out cross-validation and bootstrapping. A DSF visualization of a FTD patient is presented as an example. Results: The DSI distinguishes controls from FTD (area under the receiver-operator curve, AUC = 0.99) and AD (AUC = 1.00) very well and achieves a good differential diagnosis between AD and FTD (AUC = 0.89). In subsamples of autopsy-confirmed cases (AUC = 0.97) and clinically diagnosed cases (AUC = 0.94), differential diagnosis of AD and FTD performs very well. Conclusions: DSI is a promising computer-assisted biomarker approach for aiding in the diagnostic process of dementing diseases. Here, DSI separates controls from dementia and differentiates between AD and FTD.
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- Varenius, Eskil, 1986, et al.
(author)
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Subarcsecond international LOFAR radio images of Arp 220 at 150 MHz: A kpc-scale star forming disk surrounding nuclei with shocked outflows
- 2016
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593, s. A86-
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Journal article (peer-reviewed)abstract
- Context. Arp 220 is the prototypical ultra luminous infrared galaxy (ULIRG). Despite extensive studies, the structure at MHz-frequencies has remained unknown because of limits in spatial resolution.Aims: This work aims to constrain the flux and shape of radio emission from Arp 220 at MHz frequencies.Methods: We analyse new observations with the International Low Frequency Array (LOFAR) telescope, and archival data from the Multi-Element Radio Linked Interferometer Network (MERLIN) and the Karl G. Jansky Very Large Array (VLA). We model the spatially resolved radio spectrum of Arp 220 from 150 MHz to 33 GHz.Results: We present an image of Arp 220 at 150 MHz with resolution 0.̋65 × 0.̋35, sensitivity 0.15 mJy beam-1, and integrated flux density 394 ± 59 mJy. More than 80% of the detected flux comes from extended (6''≈ 2.2 kpc) steep spectrum (α = -0.7) emission, likely from star formation in the molecular disk surrounding the two nuclei. We find elongated features extending 0.3'' (110 pc) and 0.9'' (330 pc) from the eastern and western nucleus respectively, which we interpret as evidence for outflows. The extent of radio emission requires acceleration of cosmic rays far outside the nuclei. We find that a simple three component model can explain most of the observed radio spectrum of the galaxy. When accounting for absorption at 1.4 GHz, Arp 220 follows the FIR/radio correlation with q = 2.36, and we estimate a star formation rate of 220 M⊙ yr-1. We derive thermal fractions at 1 GHz of less than 1% for the nuclei, which indicates that a major part of the UV-photons are absorbed by dust.Conclusions: International LOFAR observations shows great promise to detect steep spectrum outflows and probe regions of thermal absorption. However, in LIRGs the emission detected at 150 MHz does not necessarily come from the main regions of star formation. This implies that high spatial resolution is crucial for accurate estimates of star formation rates for such galaxies at 150 MHz.
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