Institution
University of Bremen
Education•Bremen, Germany•
About: University of Bremen is a education organization based out in Bremen, Germany. It is known for research contribution in the topics: Population & Context (language use). The organization has 14563 authors who have published 37279 publications receiving 970381 citations. The organization is also known as: Universität Bremen.
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TL;DR: It is shown by atomistic simulations that a consistent part of the green gap in c-plane InGaN/GaN-based light emitting diodes may be attributed to a decrease in the radiative recombination coefficient with increasing indium content due to random fluctuations of the indium concentration naturally present in any In GaN alloy.
Abstract: White light emitting diodes (LEDs) based on III-nitride InGaN/GaN quantum wells currently offer the highest overall efficiency for solid state lighting applications. Although current phosphor-converted white LEDs have high electricity-to-light conversion efficiencies, it has been recently pointed out that the full potential of solid state lighting could be exploited only by color mixing approaches without employing phosphor-based wavelength conversion. Such an approach requires direct emitting LEDs of different colors, including, in particular, the green-yellow range of the visible spectrum. This range, however, suffers from a systematic drop in efficiency, known as the "green gap," whose physical origin has not been understood completely so far. In this work, we show by atomistic simulations that a consistent part of the green gap in c-plane InGaN/GaN-based light emitting diodes may be attributed to a decrease in the radiative recombination coefficient with increasing indium content due to random fluctuations of the indium concentration naturally present in any InGaN alloy.
364 citations
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01 Jan 2010
TL;DR: Weimer et al. as discussed by the authors showed that 30% of the World's population lives within 60 km of the coast, and the hazard posed by submarine landslides is expected to grow as global sea level rises.
Abstract: Submarine mass movements represent major offshore geohazards due to their destructive and tsunami-generation potential. This potential poses a threat to human life as well as to coastal, near shore and offshore engineering structures. Recent examples of catastrophic submarine landslide events that affected human populations (including tsunamis) are numerous; e.g., Nice airport in 1979 (Dan et al. 2007), Finneidfjord in 1996 (e.g., L’Heureux et al., this volume, Steiner et al., this volume), Papua-New Guinea in 1998 (Tappin et al. 2001), Stromboli in 2002 (Chiocci et al. 2008), and the 2006 and 2009 failures in the submarine cable network around Taiwan (Hsu et al. 2008). The Great East Japan Earthquake of March 2011 also generated submarine landslides that may have amplified effects of the devastating tsunami as shown in Fryer et al. (2004). Given that 30% of the World’s population lives within 60 km of the coast, the hazard posed by submarine landslides is expected to grow as global sea level rises. In addition, the deposits resulting from such processes provide-various types of constraints to offshore development (Shipp et al. 2004), and have significant implications for non-renewable energy resource exploration and production (Weimer and Shipp 2004; Beaubouef and Abreu 2010).
363 citations
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TL;DR: It is demonstrated that prokaryotic cell abundances on seafloor-exposed basalts are 3–4 orders of magnitude greater than in overlying deep sea water, with important implications for deep-sea carbon cycling and chemical exchange between basalt and sea water.
Abstract: Oceanic lithosphere exposed at the sea floor undergoes seawater– rock alteration reactions involving the oxidation and hydration of glassy basalt. Basalt alteration reactions are theoretically capable ofsupplyingsufficientenergyforchemolithoautotrophicgrowth 1 . Such reactions have been shown to generate microbial biomass in the laboratory 2 , but field-based support for the existence of microbes that are supported by basalt alteration is lacking. Here, using quantitative polymerase chain reaction, in situ hybridization and microscopy, we demonstrate that prokaryotic cell abundances on seafloor-exposed basalts are 3–4 orders of magnitude greater than in overlying deep sea water. Phylogenetic analyses of basaltic lavas from the East Pacific Rise (96 N) and around Hawaii reveal that the basalt-hosted biosphere harbours high bacterial community richness and that community membership is shared between these sites. We hypothesize that alteration reactions fuel chemolithoautotrophic microorganisms, which constitute a trophic base of the basalt habitat, with important implications for deep-sea carbon cycling andchemical exchange between basalt and sea water. We assessed the abundance, species richness and phylogenetic
363 citations
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University of Bristol1, University of Oregon2, Macquarie University3, Imperial College London4, University of Wyoming5, Centre national de la recherche scientifique6, University of Exeter7, Osaka City University8, University of Wisconsin-Madison9, University of New South Wales10, American Museum of Natural History11, Australian National University12, University of Bern13, Slovenian Academy of Sciences and Arts14, Sofia University15, University of Göttingen16, University of Montpellier17, Geological Survey of Denmark and Greenland18, Canadian Forest Service19, University of Newcastle20, École Polytechnique Fédérale de Lausanne21, Monash University22, Australian Nuclear Science and Technology Organisation23, University of Bremen24, UPRRP College of Natural Sciences25, University of Calgary26, University of Tennessee27, University of Cologne28, Virginia Tech29, Russian Academy of Sciences30, University of Wisconsin–Oshkosh31, Sapienza University of Rome32, Katholieke Universiteit Leuven33, University of Chile34, University of Queensland35, University of the Witwatersrand36, University of Münster37, Stockholm University38, Laval University39, Geode40, University of Franche-Comté41, University of Plymouth42, Fordham University43, University of the Free State44, Kyoto Prefectural University45, University of Kansas46, University of Orléans47, University of Geneva48, Central Washington University49, Chinese Academy of Sciences50
TL;DR: This article analyzed sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates and showed that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels.
Abstract: Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo- fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.
362 citations
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TL;DR: In this paper, a set of coupled ocean-atmosphere-vegetation simulations using state-of-the-art climate models is available for the Last Glacial Maximum (LGM) and the Mid-Holocene (MH) through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2).
Abstract: A set of coupled ocean-atmosphere(-vegetation) simulations using state of the art climate models is now available for the Last Glacial Maximum (LGM) and the Mid-Holocene (MH) through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2). Here we quantify the latitudinal shift of the location of the Intertropical Convergence Zone (ITCZ) in the tropical regions during boreal summer and the change in precipitation in the northern part of the ITCZ. For both periods the shift is more pronounced over the continents and East Asia. The maritime continent is the region where the largest spread is found between models. We also clearly establish that the larger the increase in the meridional temperature gradient in the tropical Atlantic during summer at the MH, the larger the change in precipitation over West Africa. The vegetation feedback is however not as large as found in previous studies, probably due to model differences in the control simulation. Finally, we show that the feedback from snow and sea-ice at mid and high latitudes contributes for half of the cooling in the Northern Hemisphere for the LGM, with the remaining being achieved by the reduced CO2 and water vapour in the atmosphere. For the MH the snow and albedo feedbacks strengthen the spring cooling and enhance the boreal summer warming, whereas water vapour reinforces the late summer warming. These feedbacks are modest in the Southern Hemisphere. For the LGM most of the surface cooling is due to CO2 and water vapour.
361 citations
Authors
Showing all 14961 results
Name | H-index | Papers | Citations |
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Roger Y. Tsien | 163 | 441 | 138267 |
Klaus-Robert Müller | 129 | 764 | 79391 |
Ron Kikinis | 126 | 684 | 63398 |
Ulrich S. Schubert | 122 | 2229 | 85604 |
Andreas Richter | 110 | 769 | 48262 |
Michael Böhm | 108 | 755 | 66103 |
Juan Bisquert | 107 | 450 | 46267 |
John P. Sumpter | 101 | 266 | 46184 |
Jos Lelieveld | 100 | 570 | 37657 |
Michael Schulz | 100 | 759 | 50719 |
Peter Singer | 94 | 702 | 37128 |
Charles R. Tyler | 92 | 325 | 31724 |
John P. Burrows | 90 | 815 | 36169 |
Hans-Peter Kriegel | 89 | 444 | 73932 |
Harald Haas | 85 | 750 | 34927 |