Showing papers by "University of Bremen published in 2021"
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Evgeny Epifanovsky, Andrew T.B. Gilbert1, Andrew T.B. Gilbert2, Xintian Feng3 +235 more•Institutions (54)
TL;DR: The Q-Chem quantum chemistry program package as discussed by the authors provides a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, and methods for computing vibronic spectra, the nuclear-electronic orbital method, and several different energy decomposition analysis techniques.
Abstract: This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange-correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear-electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an "open teamware" model and an increasingly modular design.
360 citations
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TL;DR: An empirically grounded conceptualization is developed that sets these two phenomena apart, finding that there are two distinctive differences: digital transformation activities leverage digital technology in (re)defining an organization’s value proposition, while IT-enabled organizational transformation activities Leverage digitalTechnology in supporting the value proposition.
Abstract: Although digital transformation offers a number of opportunities for today’s organizations, information systems scholars and practitioners struggle to grasp what digital transformation really is, particularly in terms of how it differs from the well-established concept of information technology (IT)-enabled organizational transformation. By integrating literature from organization science and information systems research with two longitudinal case studies—one on digital transformation, the other on IT-enabled organizational transformation—we develop an empirically grounded conceptualization that sets these two phenomena apart. We find that there are two distinctive differences: (1) digital transformation activities leverage digital technology in (re)defining an organization’s value proposition, while IT-enabled organizational transformation activities leverage digital technology in supporting the value proposition, and (2) digital transformation involves the emergence of a new organizational identity, whereas IT-enabled organizational transformation involves the enhancement of an existing organizational identity. We synthesize these arguments in a process model to distinguish the different types of transformations and propose directions for future research.
218 citations
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Joint Global Change Research Institute1, German Aerospace Center2, University of Bremen3, ETH Zurich4, École Polytechnique5, University of Exeter6, Met Office7, University of Leeds8, University of Denver9, Centre national de la recherche scientifique10, Netherlands Environmental Assessment Agency11, International Institute for Applied Systems Analysis12, University of Melbourne13, University of Maryland, College Park14, Potsdam Institute for Climate Impact Research15, National Center for Atmospheric Research16, Goddard Institute for Space Studies17, University of Paris18, Max Planck Society19, University of Hamburg20, Korea Meteorological Administration21, Commonwealth Scientific and Industrial Research Organisation22, Central Maine Community College23, Geophysical Fluid Dynamics Laboratory24, Pukyong National University25, Korean Ocean Research and Development Institute26, Nanjing University of Information Science and Technology27, Norwegian Meteorological Institute28, Indian Institute of Tropical Meteorology29, Ontario Ministry of Natural Resources30, University of Toulouse31, Alfred Wegener Institute for Polar and Marine Research32, Oak Ridge National Laboratory33, Deutscher Wetterdienst34, University of Arizona35, Japan Agency for Marine-Earth Science and Technology36, Lawrence Livermore National Laboratory37, Swedish Meteorological and Hydrological Institute38, China Meteorological Administration39, Danish Meteorological Institute40, Chinese Academy of Sciences41
TL;DR: In this paper, the authors present a range of its outcomes by synthesizing results from the participating global coupled Earth system models for concentration driven simulations, focusing mainly on the analysis of strictly geophysical outcomes: mainly global averages and spatial patterns of change for surface air temperature and precipitation.
Abstract: . The Scenario Model Intercomparison Project (ScenarioMIP) defines and coordinates the primary future climate projections within the Coupled Model Intercomparison Project Phase 6 (CMIP6). This paper presents a range of its outcomes by synthesizing results from the participating global coupled Earth system models for concentration driven simulations. We limit our scope to the analysis of strictly geophysical outcomes: mainly global averages and spatial patterns of change for surface air temperature and precipitation. We also compare CMIP6 projections to CMIP5 results, especially for those scenarios that were designed to provide continuity across the CMIP phases, at the same time highlighting important differences in forcing composition, as well as in results. The range of future temperature and precipitation changes by the end of the century encompassing the Tier 1 experiments (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) and SSP1-1.9 spans a larger range of outcomes compared to CMIP5, due to higher warming (by 1.15 °C) reached at the upper end of the 5–95 % envelope of the highest scenario, SSP5-8.5. This is due to both the wider range of radiative forcing that the new scenarios cover and to higher climate sensitivities in some of the new models compared to their CMIP5 predecessors. Spatial patterns of change for temperature and precipitation averaged over models and scenarios have familiar features, and an analysis of their variations confirms model structural differences to be the dominant source of uncertainty. Models also differ with respect to the size and evolution of internal variability as measured by individual models' initial condition ensembles' spread, according to a set of initial condition ensemble simulations available under SSP3-7.0. The same experiments suggest a tendency for internal variability to decrease along the course of the century, a new result that will benefit from further analysis over a larger set of models. Benefits of mitigation, all else being equal in terms of societal drivers, appear clearly when comparing scenarios developed under the same SSP, but to which different degrees of mitigation have been applied. It is also found that a mild overshoot in temperature of a few decades in mid-century, as represented in SSP5-3.4OS, does not affect the end outcome in terms of temperature and precipitation changes by 2100, which return to the same level as those reached by the gradually increasing SSP4-3.4. Central estimates of the time at which the ensemble means of the different scenarios reach a given warming level show all scenarios reaching 1.5 °C of warming compared to the 1850–1900 baseline in the second half of the current decade, with the time span between slow and fast warming covering 20–28 years from present. 2 °C of warming is reached as early as the late '30s by the ensemble mean under SSP5-8.5, but as late as the late '50s under SSP1-2.6. The highest warming level considered, 5 °C, is reached only by the ensemble mean under SSP5-8.5, and not until the mid-90s.
190 citations
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Swedish Museum of Natural History1, Stockholm University2, Purdue University3, Met Office4, University of Exeter5, George Mason University6, University of Southern California7, University of Bristol8, Uppsala University9, University of Kiel10, Boise State University11, Alfred Wegener Institute for Polar and Marine Research12, University of Oslo13, Cardiff University14, University of Bremen15, Northumbria University16, ETH Zurich17, University of Washington18
TL;DR: A review of the state-of-the-art in Miocene climate, ocean circulation, biogeochemical cycling, ice sheet dynamics, and biotic adaptation research can be found in this article.
Abstract: The Miocene epoch (23.03–5.33 Ma) was a time interval of global warmth, relative to today. Continental configurations and mountain topography transitioned towards modern conditions, and many flora and fauna evolved into the same taxa that exist today. Miocene climate was dynamic: long periods of early and late glaciation bracketed a ∼2 Myr greenhouse interval – the Miocene Climatic Optimum (MCO). Floras, faunas, ice sheets, precipitation, pCO2, and ocean and atmospheric circulation mostly (but not ubiquitously) covaried with these large changes in climate. With higher temperatures and moderately higher pCO2 (∼400–600 ppm), the MCO has been suggested as a particularly appropriate analogue for future climate scenarios, and for assessing the predictive accuracy of numerical climate models – the same models that are used to simulate future climate. Yet, Miocene conditions have proved difficult to reconcile with models. This implies either missing positive feedbacks in the models, a lack of knowledge of past climate forcings, or the need for re‐interpretation of proxies, which might mitigate the model‐data discrepancy. Our understanding of Miocene climatic, biogeochemical, and oceanic changes on broad spatial and temporal scales is still developing. New records documenting the physical, chemical, and biotic aspects of the Earth system are emerging, and together provide a more comprehensive understanding of this important time interval. Here we review the state‐of‐the‐art in Miocene climate, ocean circulation, biogeochemical cycling, ice sheet dynamics, and biotic adaptation research as inferred through proxy observations and modelling studies.
165 citations
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TL;DR: In this paper, the authors show that Fe-Fe distributed on graphite carbon nitride (Fe2/g-CN) can manipulate the binding strength of the target reaction species (compromises the ability to adsorb N2H and NH2), therefore achieving the best NRR performance among 23 transition metal centers.
Abstract: Great enthusiasm in single-atom catalysts (SACs) for the nitrogen reduction reaction (NRR) has been aroused by the discovery of metal-Nx as a promising catalytic center. However, the poor activity and low selectivity of available SACs are far away from the industrial requirement. Through the first-principles high-throughput screening, we find that Fe-Fe distributed on graphite carbon nitride (Fe2/g-CN) can manipulate the binding strength of the target reaction species (compromises the ability to adsorb N2H and NH2), therefore achieving the best NRR performance among 23 transition metal (TM) centers. Our results show that Fe2/g-CN achieves a high theoretical Faradaic efficiency of 100% and, impressively, the lowest limiting potential of -0.13 V. Particularly, multiple-level descriptors shed light on the origin of NRR activity, achieving a fast prescreening among various candidates. Our predictions not only accelerate discovery of catalysts for ammonia synthesis but also contribute to further elucidate the structure-performance correlations.
161 citations
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Belgian Institute for Space Aeronomy1, Royal Netherlands Meteorological Institute2, University of Bremen3, Norwegian Institute for Air Research4, University of Innsbruck5, Goddard Space Flight Center6, Université Paris-Saclay7, Aristotle University of Thessaloniki8, Wageningen University and Research Centre9, University of Toronto10, European Space Agency11, Max Planck Society12, Russian Academy of Sciences13, National Autonomous University of Mexico14, Chiba University15, Danish Meteorological Institute16, Japan Agency for Marine-Earth Science and Technology17, Finnish Meteorological Institute18, University of Science and Technology of China19, Instituto Nacional de Técnica Aeroespacial20, University of La Réunion21, National Institute of Water and Atmospheric Research22, University of Manchester23, Kyrgyz National University24
TL;DR: In this article, ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite are compared to correlative measurements collected from, respectively, 19 Multi-Axis DOAS (MAX-DOAS), 26 NDACC Zenith-Scattered-Light DOAS, and 25 PGN/Pandora instruments distributed globally.
Abstract: This paper reports on consolidated ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite. Tropospheric, stratospheric, and total NO2 column data from S5p are compared to correlative measurements collected from, respectively, 19 Multi-Axis DOAS (MAX-DOAS), 26 NDACC Zenith-Scattered-Light DOAS (ZSL-DOAS), and 25 PGN/Pandora instruments distributed globally. The validation methodology gives special care to minimizing mismatch errors due to imperfect spatio-temporal co-location of the satellite and correlative data, e.g., by using tailored observation operators to account for differences in smoothing and in sampling of atmospheric structures and variability, and photochemical modelling to reduce diurnal cycle effects. Compared to the ground-based measurements, S5p data show, on an average: (i) a negative bias for the tropospheric column data, of typically −23 to −37 % in clean to slightly polluted conditions, but reaching values as high as −51 % over highly polluted areas; (ii) a slight negative bias for the stratospheric column data, of about −0.2 Pmolec/cm2, i.e. approx. −2 % in summer to −15 % in winter; and (iii) a bias ranging from zero to −50 % for the total column data, found to depend on the amplitude of the total NO2 column, with small to slightly positive bias values for columns below 6 Pmolec/cm2 and negative values above. The dispersion between S5p and correlative measurements contains mostly random components, which remain within mission requirements for the stratospheric column data (0.5 Pmolec/cm2), but exceed those for the tropospheric column data (0.7 Pmolec/cm2). While a part of the biases and dispersion may be due to representativeness differences, it is known that errors in the S5p tropospheric columns exist due to shortcomings in the (horizontally coarse) a-priori profile representation in the TM5-MP chemistry transport model used in the S5p retrieval, and to a lesser extent, to the treatment of cloud effects. Although considerable differences (up to 2 Pmolec/cm2 and more) are observed at single ground-pixel level, the near-real-time (NRTI) and off-line (OFFL) versions of the S5p NO2 operational data processor provide similar NO2 column values and validation results when globally averaged, with the NRTI values being on average 0.79 % larger than the OFFL values.
135 citations
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TL;DR: In this article, the authors investigated the nutrient fluxes and physiological as well as molecular responses of the widespread coral Stylophora pistillata to heat stress prior to the onset of bleaching to identify processes involved in the breakdown of the coral-algal symbiosis.
Abstract: Recurrent mass bleaching events are pushing coral reefs worldwide to the brink of ecological collapse. While the symptoms and consequences of this breakdown of the coral-algal symbiosis have been extensively characterized, our understanding of the underlying causes remains incomplete. Here, we investigated the nutrient fluxes and the physiological as well as molecular responses of the widespread coral Stylophora pistillata to heat stress prior to the onset of bleaching to identify processes involved in the breakdown of the coral-algal symbiosis. We show that altered nutrient cycling during heat stress is a primary driver of the functional breakdown of the symbiosis. Heat stress increased the metabolic energy demand of the coral host, which was compensated by the catabolic degradation of amino acids. The resulting shift from net uptake to release of ammonium by the coral holobiont subsequently promoted the growth of algal symbionts and retention of photosynthates. Together, these processes form a feedback loop that will gradually lead to the decoupling of carbon translocation from the symbiont to the host. Energy limitation and altered symbiotic nutrient cycling are thus key factors in the early heat stress response, directly contributing to the breakdown of the coral-algal symbiosis. Interpreting the stability of the coral holobiont in light of its metabolic interactions provides a missing link in our understanding of the environmental drivers of bleaching and may ultimately help uncover fundamental processes underpinning the functioning of endosymbioses in general.
131 citations
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King's College London1, University at Buffalo2, Goddard Space Flight Center3, University of Bremen4, University of Oslo5, University of Alaska Fairbanks6, Bjerknes Centre for Climate Research7, Utrecht University8, Université libre de Bruxelles9, California Institute of Technology10, University of Grenoble11, University of Edinburgh12, University of California, San Diego13, University of St Andrews14, University of Leeds15, International Institute for Applied Systems Analysis16, University of Tokyo17, Met Office18, University of Reading19, National Center for Atmospheric Research20, University of Bristol21, Université Paris-Saclay22, Columbia University23, Goddard Institute for Space Studies24, Potsdam Institute for Climate Impact Research25, Victoria University of Wellington26, Los Alamos National Laboratory27, Colorado State University28, Hokkaido University29, University of California, Irvine30, Universities Space Research Association31, University of Liège32, Nagoya University33, Australian Antarctic Division34, University of Tasmania35, University of Lapland36, University of Tromsø37, Norwegian Polar Institute38, Alfred Wegener Institute for Polar and Marine Research39, University of Fribourg40, Swiss Federal Institute for Forest, Snow and Landscape Research41, ETH Zurich42, Vrije Universiteit Brussel43, GNS Science44, Lawrence Berkeley National Laboratory45, University of Innsbruck46, University of Liverpool47, University of British Columbia48, Carnegie Mellon University49, Memorial University of Newfoundland50, Pennsylvania State University51, University of Potsdam52, Beijing Normal University53, CSC – IT Center for Science54
TL;DR: In this article, the authors estimate probability distributions for these projections under the new scenarios using statistical emulation of the ice sheet and glacier models, and find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges.
Abstract: The land ice contribution to global mean sea level rise has not yet been predicted1 using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models2,3,4,5,6,7,8, but primarily used previous-generation scenarios9 and climate models10, and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios11,12 using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.
120 citations
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TL;DR: In this paper, the authors provide a tutorial on the fundamental properties of the RIS technology from a signal processing perspective, to complement the recent surveys of electromagnetic and hardware aspects, and exemplify how they can be utilized for improved communication, localization and sensing.
Abstract: A reconfigurable intelligent surface (RIS) is a two-dimensional surface of engineered material whose properties are reconfigurable rather than static [4]. For example, the scattering, absorption, reflection, and diffraction properties can be changed with time and controlled by software. In principle, the surface can be used to synthesize an arbitrarily-shaped object of the same size, when it comes to how electromagnetic waves interact with it [5].
The long-term vision of the RIS technology is to create smart radio environments [9], where the wireless propagation conditions are co-engineered with the physical-layer signaling, and investigate how to utilize this new capability. The common protocol stack consists of seven layers and wireless technology is chiefly focused on the first three layers (physical, link, and network) [10]. An RIS operates at what can be referred to as Layer 0, where the traditional design issue is the antennas of the transmitter/receivers; one can think of RIS as extending the antenna design towards the environment, commonly seen as uncontrollable and decided by "nature". This approach can profoundly change the wireless design beyond 5G.
This article provides a tutorial on the fundamental properties of the RIS technology from a signal processing perspective, to complement the recent surveys of electromagnetic and hardware aspects [4], [7], communication theory [11], and localization [8]. We will provide the formulas and derivations that are required to understand and analyze RIS-aided systems, and exemplify how they can be utilized for improved communication, localization, and sensing. We will also elaborate on the fundamentally new possibilities enabled by Layer 0 engineering and electromagnetic phenomena that remain to be modeled and utilized for improved signal processing.
98 citations
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TL;DR: In this paper, the authors examine which banks typically collaborate with fintechs, how intensely they do so, and which form of alliance they prefer, and provide detailed evidence on the different forms of alliances occurring in practice.
Abstract: The increasing pervasiveness of technology-driven firms that offer financial services has led to growing pressure on traditional banks to modernize their core business activities and services. Many banks tackle the challenges of digitalization by cooperating with startup firms that offer technology-driven financial services and novel service packages (fintechs). In this article, we examine which banks typically collaborate with fintechs, how intensely they do so, and which form of alliance they prefer. Using hand-collected data covering the largest banks from Canada, France, Germany, and the United Kingdom, we provide detailed evidence on the different forms of alliances occurring in practice. We show that banks are significantly more likely to form alliances with fintechs when they pursue a well-defined digital strategy and/or employ a chief digital officer. Moreover, in line with incomplete contract theory, we find that banks more frequently invest in small fintechs but often build product-related collaborations with larger fintechs.
97 citations
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Netherlands Institute for Space Research1, Heidelberg University2, Karlsruhe Institute of Technology3, Finnish Meteorological Institute4, University of Toronto5, National Institute of Water and Atmospheric Research6, Japan Aerospace Exploration Agency7, University of Wollongong8, California Institute of Technology9, University of Bremen10
TL;DR: In this paper, the authors describe the improvements that have been implemented to retrieve CH 4 from TROPOMI using the RemoTeC full-physics algorithm, which features a constant regularization scheme of the inversion that stabilizes the retrieval and yields less scatter in the data and includes a higher resolution surface altitude database.
Abstract: . The TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor (S5-P) satellite provides methane (CH 4 ) measurements with high accuracy and exceptional temporal and spatial resolution and sampling. TROPOMI CH 4 measurements are highly valuable to constrain emissions inventories and for trend analysis, with strict requirements on the data quality. This study describes the improvements that we have implemented to retrieve CH 4 from TROPOMI using the RemoTeC full-physics algorithm. The updated retrieval algorithm features a constant regularization scheme of the inversion that stabilizes the retrieval and yields less scatter in the data and includes a higher resolution surface altitude database. We have tested the impact of three state-of-the-art molecular spectroscopic databases (HITRAN 2008, HITRAN 2016 and Scientific Exploitation of Operational Missions – Improved Atmospheric Spectroscopy Databases SEOM-IAS) and found that SEOM-IAS provides the best fitting results. The most relevant update in the TROPOMI XCH 4 data product is the implementation of an a posteriori correction fully independent of any reference data that is more accurate and corrects for the underestimation at low surface albedo scenes and the overestimation at high surface albedo scenes. After applying the correction, the albedo dependence is removed to a large extent in the TROPOMI versus satellite (Greenhouse gases Observing SATellite – GOSAT) and TROPOMI versus ground-based observations (Total Carbon Column Observing Network – TCCON) comparison, which is an independent verification of the correction scheme. We validate 2 years of TROPOMI CH 4 data that show the good agreement of the updated TROPOMI CH 4 with TCCON ( − 3.4 ± 5.6 ppb) and GOSAT ( − 10.3 ± 16.8 ppb) (mean bias and standard deviation). Low- and high-albedo scenes as well as snow-covered scenes are the most challenging for the CH 4 retrieval algorithm, and although the a posteriori correction accounts for most of the bias, there is a need to further investigate the underlying cause.
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RWTH Aachen University1, University of Bern2, University of Wrocław3, University of Paris4, Dresden University of Technology5, University of Milan6, Charles University in Prague7, University of Novi Sad8, University of Bremen9, University of Szeged10, Romanian Academy11, Leibniz Association12, University of Bayreuth13
TL;DR: In this paper, a map of the distribution of aeolian sediments (mainly loess) and major potential source areas for Europe is presented, combining geodata of different mapping approaches.
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TL;DR: In this article, a nonmagnetic hexavalent molybdenum (Mo6+) atomically dispersed within oxide lattice steers the intrinsic activity of catalytically active sites by entrapping extrinsic electrons at their 3D orbitals, without the occurrence of lattice symmetry breaking and magnetic perturbation.
Abstract: Complexity in strongly correlated oxides such as perovskite strictly dominates their performance for oxygen reduction reaction (ORR). Precise control of the physical correlations among spin, charge, orbital, and lattice degrees of freedom in these oxides can exercise considerable enhancement of ORR activity, but has until now remained elusive. Here, we show that nonmagnetic hexavalent molybdenum (Mo6+) atomically dispersed within oxide lattice steers the intrinsic activity of catalytically active sites by entrapping extrinsic electrons at their 3d orbitals, without the occurrence of lattice symmetry breaking and magnetic perturbation. With double perovskite La2Co2+Mn4+O6 as a model catalyst, the atomic-scale electron trap generates additional high-spin, catalytically active Mn3+(t32ge1g) sites and highly conductive Co2+(e2g)–O–Mn3+(e1g) double exchange channels, leading to five-fold improvement in ORR activity. First-principles calculations reveal a substantial increase of the spin density on Mn sites caused by electron trapping, and unambiguously confirm a more exothermic reaction pathway as well as a lower barrier of the rate-limiting surface hydroxide regeneration on Mo1/La2CoMnO6. We can also extend this strategy with atomic precision easily to other four oxide catalysts and achieve large enhancement in their ORR activities as anticipated, indicating its broad utility. This work embodies the theories of condensed matter physics in rational design of ORR catalysts, and may inspire further development of the control of electron correlation in strongly correlated electron systems.
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TL;DR: In this article, a comparison of the two market segments is made, focusing on the stakeholders, microstructures, regulatory environments, and development of the markets, concluding with suggestions for future ICO and crowdfunding research.
Abstract: Entrepreneurial finance markets are in a dynamic state. New market niches and players have developed and continue to emerge. The rules of the game and the methods for receiving financial backing have changed in many ways. This editorial and the special issue of Small Business Economics focus on crowdfunding (CF) and initial coin offerings (ICOs), which are two distinct but important entrepreneurial finance market segments of the future. Although the two market segments initially appear to be similar, we identify differences between them. Our comparison focuses on the stakeholders, microstructures, regulatory environments, and development of the markets. We conclude with suggestions for future ICO and CF research.
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Université Paris-Saclay1, University of Reading2, Max Planck Society3, University of Arizona4, Yale University5, University of Tokyo6, University of Toronto7, University of Leeds8, University of Bristol9, Goddard Institute for Space Studies10, Russian Academy of Sciences11, Japan Agency for Marine-Earth Science and Technology12, University of Bremen13, VU University Amsterdam14, National Center for Atmospheric Research15
TL;DR: In this article, a new generation of climate models has been used to generate LGM simulations as part of the PMIP contribution to the Coupled model intercomparison project (CMIP).
Abstract: The Last Glacial Maximum (LGM, ∼ 21 000 years ago) has been a major focus for evaluating how well state-of-the-art climate models simulate climate changes as large as those expected in the future using paleoclimate reconstructions. A new generation of climate models has been used to generate LGM simulations as part of the Paleoclimate Modelling Intercomparison Project (PMIP) contribution to the Coupled Model Intercomparison Project (CMIP). Here, we provide a preliminary analysis and evaluation of the results of these LGM experiments (PMIP4, most of which are PMIP4-CMIP6) and compare them with the previous generation of simulations (PMIP3, most of which are PMIP3-CMIP5). We show that the global averages of the PMIP4 simulations span a larger range in terms of mean annual surface air temperature and mean annual precipitation compared to the PMIP3-CMIP5 simulations, with some PMIP4 simulations reaching a globally colder and drier state. However, the multi-model global cooling average is similar for the PMIP4 and PMIP3 ensembles, while the multi-model PMIP4 mean annual precipitation average is drier than the PMIP3 one. There are important differences in both atmospheric and oceanic circulations between the two sets of experiments, with the northern and southern jet streams being more poleward and the changes in the Atlantic Meridional Overturning Circulation being less pronounced in the PMIP4-CMIP6 simulations than in the PMIP3-CMIP5 simulations. Changes in simulated precipitation patterns are influenced by both temperature and circulation changes. Differences in simulated climate between individual models remain large. Therefore, although there are differences in the average behaviour across the two ensembles, the new simulation results are not fundamentally different from the PMIP3-CMIP5 results. Evaluation of large-scale climate features, such as land–sea contrast and polar amplification, confirms that the models capture these well and within the uncertainty of the paleoclimate reconstructions. Nevertheless, regional climate changes are less well simulated: the models underestimate extratropical cooling, particularly in winter, and precipitation changes. These results point to the utility of using paleoclimate simulations to understand the mechanisms of climate change and evaluate model performance.
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TL;DR: A systematic search of the PubMed, MEDLINE and Web of Science (January 2015 to October 2020) was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines as discussed by the authors.
Abstract: Introduction Oxidative stress and inflammation are known to play a critical role in ageing and chronic disease development and could therefore represent important targets for developing dietary strategies for disease prevention. We aimed to systematically review the results from observational studies and intervention trials published in the last 5 years on the associations between dietary patterns and biomarkers of oxidative stress and inflammation. Methods A systematic search of the PubMed, MEDLINE and Web of Science (January 2015 to October 2020) was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Methodological quality of selected studies was evaluated based on the NUTRIGRADE and BIOCROSS assessment tools. Results In total, 29 studies among which 16 observational studies and 13 intervention studies were found eligible for review. Overall, results indicated an inverse association between plant-based diets - the Mediterranean and Dietary Approaches to Stop Hypertension (DASH) diet - and oxidative stress and proinflammatory biomarkers. In observational studies, inverse associations were further revealed for the vegetarian diet, the USDA Healthy Eating Index (HEI) - based diet and the paleolithic diet, whereas a positive association was seen for western and fast food diets. Quality assessment suggested that majority of dietary intervention studies (n = 12) were of low to moderate quality. Conclusions This study provides evidence that the plant-based dietary patterns are associated with lowered levels of oxidative stress and inflammation and may provide valid means for chronic disease prevention. Future large-scale intervention trials using validated biomarkers are warranted to confirm these findings.
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TL;DR: In this paper, the authors conceptualize outwelling in mangrove, saltmarsh, seagrass and macroalgae ecosystems, diagnose key challenges preventing robust quantification, and pave the way for future work integrating mobile carbon in the blue carbon framework.
Abstract: The term ‘Blue Carbon’ was coined about a decade ago to highlight the important carbon sequestration capacity of coastal vegetated ecosystems. The term has paved the way for the development of programs and policies that preserve and restore these threatened coastal ecosystems for climate change mitigation. Blue carbon research has focused on quantifying carbon stocks and burial rates in sediments or accumulating as biomass. This focus on habitat-bound carbon led us to losing sight of the mobile blue carbon fraction. Oceans, the largest active reservoir of carbon, have become somewhat of a blind spot. Multiple recent investigations have revealed high outwelling (i.e., lateral fluxes or horizontal exports) of dissolved inorganic (DIC) and organic (DOC) carbon, as well as particulate organic carbon (POC) from blue carbon habitats. In this paper, we conceptualize outwelling in mangrove, saltmarsh, seagrass and macroalgae ecosystems, diagnose key challenges preventing robust quantification, and pave the way for future work integrating mobile carbon in the blue carbon framework. Outwelling in mangroves and saltmarshes is usually dominated by DIC (mostly as bicarbonate), while POC seems to be the major carbon species exported from seagrass meadows and macroalgae forests. Carbon outwelling science is still in its infancy, and estimates remain limited spatially and temporally. Nevertheless, the existing datasets imply that carbon outwelling followed by ocean storage is relevant and may exceed local sediment burial as a long-term (>centuries) blue carbon sequestration mechanism. If this proves correct as more data emerge, ignoring carbon outwelling may underestimate the perceived sequestration capacity of blue carbon ecosystems.
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TL;DR: The role of the twist angle in a vdW TBL can be used in controlling the dynamics of optically excited states is explored, thus, expanding the conceptual applications of "twistronics".
Abstract: In van der Waals (vdW) heterostructures formed by stacking two monolayers of transition metal dichalcogenides, multiple exciton resonances with highly tunable properties are formed and subject to both vertical and lateral confinement. We investigate how a unique control knob, the twist angle between the two monolayers, can be used to control the exciton dynamics. We observe that the interlayer exciton lifetimes in MoSe_{2}/WSe_{2} twisted bilayers (TBLs) change by one order of magnitude when the twist angle is varied from 1° to 3.5°. Using a low-energy continuum model, we theoretically separate two leading mechanisms that influence interlayer exciton radiative lifetimes. The shift to indirect transitions in the momentum space with an increasing twist angle and the energy modulation from the moire potential both have a significant impact on interlayer exciton lifetimes. We further predict distinct temperature dependence of interlayer exciton lifetimes in TBLs with different twist angles, which is partially validated by experiments. While many recent studies have highlighted how the twist angle in a vdW TBL can be used to engineer the ground states and quantum phases due to many-body interaction, our studies explore its role in controlling the dynamics of optically excited states, thus, expanding the conceptual applications of "twistronics".
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Maria Lc Iurilli1, Bin Zhou1, James E. Bennett1, Rodrigo M. Carrillo-Larco1 +1399 more•Institutions (374)
TL;DR: In this article, the authors investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants.
Abstract: From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions.
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TL;DR: PaleoMIST 1.0 as discussed by the authors provides a global reconstruction of ice sheets for the past 80,000 years that allows to test proxy-based sea level reconstructions and helps to reconcile disagreements with sea level changes inferred from models.
Abstract: The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed. The configuration of past ice sheets, and therefore sea level, is highly uncertain. Here, the authors provide a global reconstruction of ice sheets for the past 80,000 years that allows to test proxy based sea level reconstructions and helps to reconcile disagreements with sea level changes inferred from models.
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Bjerknes Centre for Climate Research1, Leibniz Institute of Marine Sciences2, Leibniz Institute for Baltic Sea Research3, Geophysical Institute, University of Bergen4, Silver Spring Networks5, Spanish National Research Council6, Scripps Institution of Oceanography7, National Oceanography Centre, Southampton8, National Oceanic and Atmospheric Administration9, University of Washington10, Rio de Janeiro State University11, University of Groningen12, Alfred Wegener Institute for Polar and Marine Research13, Japan Meteorological Agency14, University of Paris15, Japan Agency for Marine-Earth Science and Technology16, University of Bremen17, University of Tasmania18, Atlantic Oceanographic and Meteorological Laboratory19, Massachusetts Institute of Technology20, Princeton University21
TL;DR: The Global Ocean Data Analysis Project (GLODAPv2.2021) as mentioned in this paper is the most recent version of GLODAP and includes data from 43 new cruises, data coverage extended until 2020, removal of all data with missing temperatures, and the inclusion of a digital object identifier for each cruise in the product files.
Abstract: . The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface-to-bottom ocean biogeochemical bottle data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of seawater samples. GLODAPv2.2021 is an update of the previous version, GLODAPv2.2020. The major changes are: data from 43 new cruises were added, data coverage extended until 2020, removal of all data with missing temperatures, and the inclusion of a digital object identifier (doi) for each cruise in the product files. In addition, a number of minor corrections to GLODAPv2.2020 data were performed. GLODAPv2.2021 includes measurements from more than 1.3 million water samples from the global oceans collected on 989 cruises. The data for the 12 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have undergone extensive quality control with a focus on systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but updated to WOCE exchange format and (ii) as a merged data product with adjustments applied to minimize bias. For this annual update, adjustments for the 43 new cruises were derived by comparing those data with the data from the 946 quality-controlled cruises in the GLODAPv2.2020 data product using crossover analysis. Comparisons to estimates of nutrients and ocean CO2 chemistry based on empirical algorithms provided additional context for adjustment decisions in this version. The adjustments are intended to remove potential biases from errors related to measurement, calibration, and data handling practices without removing known or likely time trends or variations in the variables evaluated. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µmol kg-1 in dissolved inorganic carbon, 4 µmol kg-1 in total alkalinity, 0.01–0.02 in pH (depending on region), and 5 % in the halogenated transient tracers. The other variables included in the compilation, such as isotopic tracers and discrete CO2 fugacity (fCO2), were not subjected to bias comparison or adjustments. The original data, their documentation and doi codes are available at the Ocean Carbon Data System of NOAA NCEI ( https://www.ncei.noaa.gov/access/ocean-carbon-data-system/oceans/GLODAPv2_2021/ , last access: 07 July 2021). This site also provides access to the merged data product, which is provided as a single global file and as four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under https://doi.org/10.25921/ttgq-n825 (Lauvset et al., 2021). These bias-adjusted product files also include significant ancillary and approximated data, and can be accessed via www.glodap.info (last access: 29 June 2021). These were obtained by interpolation of, or calculation from, measured data. This living data update documents the GLODAPv2.2021 methods and provides a broad overview of the secondary quality control procedures and results.
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George Mason University1, Met Office2, University of Exeter3, Stockholm University4, Department of Planning and Environment5, Purdue University6, Northumbria University7, Aix-Marseille University8, University of Bristol9, University of Bremen10, Utrecht University11, Alfred Wegener Institute for Polar and Marine Research12, Lafayette College13, Cardiff University14, China University of Geosciences (Wuhan)15, National Oceanography Centre, Southampton16, Princeton University17, Oregon State University18, Bjerknes Centre for Climate Research19
TL;DR: In this article, the authors synthesize several Miocene climate modeling efforts together with available terrestrial and ocean surface temperature reconstructions and evaluate the range of model-data agreement, highlight robust mechanisms operating across Miocene modeling efforts and highlight regions where differences across experiments result in a large spread in warming responses.
Abstract: The Miocene epoch, spanning 23.03–5.33 Ma, was a dynamic climate of sustained, polar amplified warmth. Miocene atmospheric CO2 concentrations are typically reconstructed between 300 and 600 ppm and were potentially higher during the Miocene Climatic Optimum (16.75–14.5 Ma). With surface temperature reconstructions pointing to substantial midlatitude and polar warmth, it is unclear what processes maintained the much weaker-than-modern equator-to-pole temperature difference. Here, we synthesize several Miocene climate modeling efforts together with available terrestrial and ocean surface temperature reconstructions. We evaluate the range of model-data agreement, highlight robust mechanisms operating across Miocene modeling efforts and regions where differences across experiments result in a large spread in warming responses. Prescribed CO2 is the primary factor controlling global warming across the ensemble. On average, elements other than CO2, such as Miocene paleogeography and ice sheets, raise global mean temperature by ∼2°C, with the spread in warming under a given CO2 concentration (due to a combination of the spread in imposed boundary conditions and climate feedback strengths) equivalent to ∼1.2 times a CO2 doubling. This study uses an ensemble of opportunity: models, boundary conditions, and reference data sets represent the state-of-art for the Miocene, but are inhomogeneous and not ideal for a formal intermodel comparison effort. Acknowledging this caveat, this study is nevertheless the first Miocene multi-model, multi-proxy comparison attempted so far. This study serves to take stock of the current progress toward simulating Miocene warmth while isolating remaining challenges that may be well served by community-led efforts to coordinate modeling and data activities within a common analytical framework.
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TL;DR: In this paper, a novel assembly of cobalt-doped interface-and defect-rich molybdenum disulfide (MoS2)/Ni3 S2 hetero-nanosheet anchoring on hierarchical carbon framework for alkaline HER is reported by directly vulcanizing NiMoO4 nanosheets.
Abstract: Molybdenum disulfide (MoS2 ) is a promising alternative to Pt-based catalysts for electrocatalytic hydrogen evolution reaction (HER) in an acidic environment. However, alkaline HER activity for molybdenum disulfide is limited by its slow water dissociation kinetics. Interface engineering is an effective strategy for the design of alkaline HER catalysts. However, the restricted heterointerfaces of current catalysts have significantly limited their alkaline HER performance. Herein, a novel assembly of cobalt-doped interface- and defect-rich MoS2 /Ni3 S2 hetero-nanosheet anchoring on hierarchical carbon framework for alkaline HER is reported by directly vulcanizing NiMoO4 nanosheets. In the heterostructure nanosheet, Ni3 S2 acts as a water dissociation promoter and MoS2 acts as a hydrogen acceptor. Density functional theory calculations find that redistribution of charges at the heterointerface can reduce hydrogen adsorption Gibbs free energy (∆GH* ) and water decomposition energy barrier. The resulting hierarchical electrode with the synergistic effect of both hybrid components shows a low overpotential of 89 mV at -10 mA cm-2 in 1 m KOH, a Tafel slope as low as 62 mV dec-1 , and can run at -100 mA cm-2 for at least 50 h without obvious voltage change. This study provides a potentially feasible strategy for the design of heterostructure-based electrocatalysts with abundant active interfaces.
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TL;DR: The literature search reveals that the epidemiology of mental disorders in children younger than 7 years is still a neglected area of research and indicates that there are a significant number of young children suffering from mental disorders who need appropriate age-adapted treatment.
Abstract: Background Children younger than 7 years can develop mental disorders that might manifest differently than in older children or adolescents. However, little is known about the prevalence of mental disorders at this early age. Methods We systematically searched the literature in the databases Web of Science, PsycINFO, PSYNDEX, MEDLINE, and Embase to identify epidemiological studies of community samples published between 2006 and 2020. A series of meta-analyses was conducted to estimate the pooled worldwide prevalence of mental disorders in general, specific mental disorders, and comorbidity in young children. Results A total of ten epidemiological studies reporting data on N = 18,282 children (12-83 months old) from eight countries met the inclusion criteria. The pooled prevalence of mental disorders in general was 20.1%, 95% CI [15.7, 25.4]. Most common disorders were oppositional defiant disorder (4.9%, 95% CI [2.5, 9.5]) and attention-deficit hyperactivity disorder (4.3%, 95% CI [2.5, 7.2]). The prevalence of any anxiety disorders was 8.5%, 95% CI [5.2, 13.5], and of any depressive disorders was 1.1%, 95% CI [0.8, 1.6]. Comorbidity was estimated at 6.4%, 95% CI [1.3, 54.0]. Conclusions The literature search reveals that the epidemiology of mental disorders in children younger than 7 years is still a neglected area of research. The findings also indicate that there are a significant number of young children suffering from mental disorders who need appropriate age-adapted treatment.
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TL;DR: In this article, a mixed-integer linear program is proposed to find the optimal number of electrolyzers and production schedules for a power-to-x power plant with a large data set of intermittent energy and electricity prices.
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TL;DR: In this article, the authors correlate different fabrication processes, optical spectroscopy and electron microscopy to identify the optical signatures of chalcogen vacancies in monolayer MoS2.
Abstract: For two-dimensional (2D) layered semiconductors, control over atomic defects and understanding of their electronic and optical functionality represent major challenges towards developing a mature semiconductor technology using such materials. Here, we correlate generation, optical spectroscopy, atomic resolution imaging, and ab initio theory of chalcogen vacancies in monolayer MoS2. Chalcogen vacancies are selectively generated by in-vacuo annealing, but also focused ion beam exposure. The defect generation rate, atomic imaging and the optical signatures support this claim. We discriminate the narrow linewidth photoluminescence signatures of vacancies, resulting predominantly from localized defect orbitals, from broad luminescence features in the same spectral range, resulting from adsorbates. Vacancies can be patterned with a precision below 10 nm by ion beams, show single photon emission, and open the possibility for advanced defect engineering of 2D semiconductors at the ultimate scale. The relation between the microscopic structure and the optical properties of atomic defects in 2D semiconductors is still debated. Here, the authors correlate different fabrication processes, optical spectroscopy and electron microscopy to identify the optical signatures of chalcogen vacancies in monolayer MoS2.
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Spanish National Research Council1, Swiss Institute of Bioinformatics2, University of California, Santa Cruz3, University of Las Palmas de Gran Canaria4, Aix-Marseille University5, Kyoto University6, Université libre de Bruxelles7, Ohio State University8, United States Department of Energy9, University of La Laguna10, King Abdullah University of Science and Technology11, École Normale Supérieure12, Katholieke Universiteit Leuven13, European Bioinformatics Institute14, University of Bremen15, Edith Cowan University16
TL;DR: The Malaspina Gene Database as mentioned in this paper was used to analyze 58 metagenomes from tropical and subtropical deep oceans to generate a deep metagenome-assembled Genomes.
Abstract: The deep sea, the largest ocean’s compartment, drives planetary-scale biogeochemical cycling. Yet, the functional exploration of its microbial communities lags far behind other environments. Here we analyze 58 metagenomes from tropical and subtropical deep oceans to generate the Malaspina Gene Database. Free-living or particle-attached lifestyles drive functional differences in bathypelagic prokaryotic communities, regardless of their biogeography. Ammonia and CO oxidation pathways are enriched in the free-living microbial communities and dissimilatory nitrate reduction to ammonium and H 2 oxidation pathways in the particle-attached, while the Calvin Benson-Bassham cycle is the most prevalent inorganic carbon fixation pathway in both size fractions. Reconstruction of the Malaspina Deep Metagenome-Assembled Genomes reveals unique non-cyanobacterial diazotrophic bacteria and chemolithoautotrophic prokaryotes. The widespread potential to grow both autotrophically and heterotrophically suggests that mixotrophy is an ecologically relevant trait in the deep ocean. These results expand our understanding of the functional microbial structure and metabolic capabilities of the largest Earth aquatic ecosystem.
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Deutscher Wetterdienst1, Environment Canada2, Alfred Wegener Institute for Polar and Marine Research3, Danish Meteorological Institute4, Finnish Meteorological Institute5, Met Office6, University of Bremen7, Royal Netherlands Meteorological Institute8, Royal Meteorological Institute9, MeteoSwiss10, University of Toronto11, Cooperative Institute for Research in Environmental Sciences12, National Center for Atmospheric Research13, Agencia Estatal de Meteorología14, Jet Propulsion Laboratory15, Bureau of Meteorology16, University of Wollongong17, National Institute of Water and Atmospheric Research18, Goddard Space Flight Center19, European Centre for Medium-Range Weather Forecasts20, National Oceanic and Atmospheric Administration21
TL;DR: In this article, the COVID-19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020, over several months, and at so many stations, has not been observed in any previous year since at least 2000.
Abstract: Throughout spring and summer 2020, ozone stations in the northern extratropics recorded unusually low ozone in the free troposphere. From April to August, and from 1 to 8 kilometers altitude, ozone was on average 7% (≈4 nmol/mol) below the 2000 to 2020 climatological mean. Such low ozone, over several months, and at so many stations, has not been observed in any previous year since at least 2000. Atmospheric composition analyses from the Copernicus Atmosphere Monitoring Service and simulations from the NASA GMI model indicate that the large 2020 springtime ozone depletion in the Arctic stratosphere contributed less than one quarter of the observed tropospheric anomaly. The observed anomaly is consistent with recent chemistry‐climate model simulations, which assume emissions reductions similar to those caused by the COVID‐19 crisis. COVID‐19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020.
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TL;DR: In this article, how to integrate artificial intelligence (AI) technologies in the functioning and structures of our society has become a concern of contemporary politics and public debates, and the authors inves...
Abstract: How to integrate artificial intelligence (AI) technologies in the functioning and structures of our society has become a concern of contemporary politics and public debates. In this paper, we inves...
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TL;DR: The gas synthesis of nanoparticles has gained major interest by different industries and research groups for the development of new materials and their subsequent implementation in numerous devices as discussed by the authors, which can be found in the literature.
Abstract: The gas synthesis of nanoparticles has gained major interest by different industries and research groups for the development of new materials and their subsequent implementation in numerous devices...