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Sökning: WFRF:(Wittmann B.)

  • Resultat 1-10 av 19
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  • Correa, D. F., et al. (författare)
  • Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates
  • 2023
  • Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 32:1, s. 49-69
  • Tidskriftsartikel (refereegranskat)abstract
    • Aim To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period Tree-inventory plots established between 1934 and 2019. Major taxa studied Trees with a diameter at breast height (DBH) >= 9.55 cm. Location Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types.
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  • Samreth, D., et al. (författare)
  • Geolocation with respect to persona privacy for the Allergy Diary app - a MASK study
  • 2018
  • Ingår i: World Allergy Organization Journal. - : BMC. - 1939-4551. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Collecting data on the localization of users is a key issue for the MASK (Mobile Airways Sentinel network: the Allergy Diary) App. Data anonymization is a method of sanitization for privacy. The European Commission's Article 29 Working Party stated that geolocation information is personal data. To assess geolocation using the MASK method and to compare two anonymization methods in the MASK database to find an optimal privacy method. Methods: Geolocation was studied for all people who used the Allergy Diary App from December 2015 to November 2017 and who reported medical outcomes. Two different anonymization methods have been evaluated: Noise addition (randomization) and k-anonymity (generalization). Results: Ninety-three thousand one hundred and sixteen days of VAS were collected from 8535 users and 54,500 (58. 5%) were geolocalized, corresponding to 5428 users. Noise addition was found to be less accurate than k-anonymity using MASK data to protect the users' life privacy. Discussion: k-anonymity is an acceptable method for the anonymization of MASK data and results can be used for other databases.
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  • Bralower, T, et al. (författare)
  • The Habitat of the Nascent Chicxulub Crater
  • 2020
  • Ingår i: AGU Advances. - : American Geophysical Union (AGU). ; 1
  • Tidskriftsartikel (refereegranskat)abstract
    • An expanded sedimentary section provides an opportunity to elucidate conditions in the nascent Chicxulub crater during the hours to millennia after the Cretaceous‐Paleogene (K‐Pg) boundary impact. The sediments were deposited by tsunami followed by seiche waves as energy in the crater declined, culminating in a thin hemipelagic marlstone unit that contains atmospheric fallout. Seiche deposits are predominantly composed of calcite formed by decarbonation of the target limestone during impact followed by carbonation in the water column. Temperatures recorded by clumped isotopes of these carbonates are in excess of 70°C, with heat likely derived from the central impact melt pool. Yet, despite the turbidity and heat, waters within the nascent crater basin soon became a viable habitat for a remarkably diverse cross section of the food chain. The earliest seiche layers deposited with days or weeks of the impact contain earliest Danian nannoplankton and dinocyst survivors. The hemipelagic marlstone representing the subsequent years to a few millennia contains a nearly monogeneric calcareous dinoflagellate resting cyst assemblage suggesting deteriorating environmental conditions, with one interpretation involving low light levels in the impact aftermath. At the same horizon, microbial fossils indicate a thriving bacterial community and unique phosphatic fossils including appendages of pelagic crustaceans, coprolites andbacteria‐tunneled fish bone, suggesting that this rapid recovery of the base of the food chain may have supported the survival of larger, higher trophic‐level organisms. The extraordinarily diverse fossil assemblage indicates that the crater was a unique habitat in the immediate impact aftermath, possibly as aresult of heat and nutrients supplied by hydrothermal activity.
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  • Peripato, Vinicius, et al. (författare)
  • More than 10,000 pre-Columbian earthworks are still hidden throughout Amazonia
  • 2023
  • Ingår i: Science (New York, N.Y.). - 1095-9203. ; 382:6666, s. 103-109
  • Tidskriftsartikel (refereegranskat)abstract
    • Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.
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  • Rivas, D. E., et al. (författare)
  • Next Generation Driver for Attosecond and Laser-plasma Physics
  • 2017
  • Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10(20)W/cm(2) with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.
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  • Witteveen, Anke B., et al. (författare)
  • Post-disaster psychosocial services across Europe : the TENTS project
  • 2012
  • Ingår i: Social Science and Medicine. - : Elsevier BV. - 0277-9536 .- 1873-5347. ; 75:9, s. 1708-1714
  • Tidskriftsartikel (refereegranskat)abstract
    • At present post-disaster activities and plans seem to vary widely. An adequate estimation of the availability of post-disaster psychosocial services across Europe is needed in order to compare them with recently developed evidence-informed psychosocial care guidelines. Here we report on the results of a cross-sectional web-based survey completed in 2008 by two hundred and eighty-six representatives of organizations involved in psychosocial responses to trauma and disaster from thirty-three different countries across Europe. The survey addressed planning and delivery of psychosocial care after disaster, methods of screening and diagnosis, types of interventions used, and other aspects of psychosocial care after trauma. The findings showed that planning and delivery of psychosocial care was inconsistent across Europe. Countries in East Europe seemed to have less central coordination of the post-disaster psychosocial response and fewer post-disaster guidelines that were integrated into specific disaster or contingency plans. Several forms of psychological debriefing, for which there is no evidence of efficacy to date, were still used in several areas particularly in North Europe. East European countries delivered evidence-based interventions for PTSD less frequently, whilst in South- and South-Eastern European countries anxiety suppressing medication such as benzodiazepines were prescribed more frequently to disaster victims than in other areas. Countries across Europe are currently providing sub-optimal psychosocial care for disaster victims. This short report shows that there is an urgent need for some countries to abandon non-effective interventions and others to develop more evidence based and effective services to facilitate the care of those involved in future disasters.
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