Showing papers by "University of Bremen published in 2015"
Beth Israel Deaconess Medical Center1, University of Pennsylvania2, UCL Institute of Neurology3, University of Bremen4, Utrecht University5, University of Michigan6, University of Texas Southwestern Medical Center7, University of Toronto8, Sunnybrook Research Institute9, University of Manchester10, Erasmus University Rotterdam11, Leiden University Medical Center12, University of California, Los Angeles13, University of California, San Diego14, Stanford University15
TL;DR: This review provides a summary statement of recommended implementations of arterial spin labeling (ASL) for clinical applications and describes the major considerations and trade‐offs in implementing an ASL protocol and provides specific recommendations for a standard approach.
Abstract: This review provides a summary statement of recommended implementations of arterial spin labeling (ASL) for clinical applications. It is a consensus of the ISMRM Perfusion Study Group and the European ASL in Dementia consortium, both of whom met to reach this consensus in October 2012 in Amsterdam. Although ASL continues to undergo rapid technical development, we believe that current ASL methods are robust and ready to provide useful clinical information, and that a consensus statement on recommended implementations will help the clinical community to adopt a standardized approach. In this review, we describe the major considerations and trade-offs in implementing an ASL protocol and provide specific recommendations for a standard approach. Our conclusion is that as an optimal default implementation, we recommend pseudo-continuous labeling, background suppression, a segmented three-dimensional readout without vascular crushing gradients, and calculation and presentation of both label/control difference images and cerebral blood flow in absolute units using a simplified model.
1,617 citations
Centre national de la recherche scientifique1, Pierre-and-Marie-Curie University2, Kaiserslautern University of Technology3, Spanish National Research Council4, École Normale Supérieure5, Commissariat à l'énergie atomique et aux énergies alternatives6, Katholieke Universiteit Leuven7, Vrije Universiteit Brussel8, Academy of Sciences of the Czech Republic9, Sewanee: The University of the South10, University of Évry Val d'Essonne11, Canadian Institute for Advanced Research12, University of Bremen13, Stazione Zoologica Anton Dohrn14, IFREMER15, European Bioinformatics Institute16, Kyoto University17, Max Delbrück Center for Molecular Medicine18, University of Paris19, Aix-Marseille University20, National Science Foundation21, Bigelow Laboratory For Ocean Sciences22, University of Western Brittany23
TL;DR: Diversity emerged at all taxonomic levels, both within the groups comprising the ~11,200 cataloged morphospecies of eukaryotic plankton and among twice as many other deep-branching lineages of unappreciated importance in plankton ecology studies.
Abstract: Marine plankton support global biological and geochemical processes. Surveys of their biodiversity have hitherto been geographically restricted and have not accounted for the full range of plankton size. We assessed eukaryotic diversity from 334 size-fractionated photic-zone plankton communities collected across tropical and temperate oceans during the circumglobal Tara Oceans expedition. We analyzed 18S ribosomal DNA sequences across the intermediate plankton-size spectrum from the smallest unicellular eukaryotes (protists, >0.8 micrometers) to small animals of a few millimeters. Eukaryotic ribosomal diversity saturated at ~150,000 operational taxonomic units, about one-third of which could not be assigned to known eukaryotic groups. Diversity emerged at all taxonomic levels, both within the groups comprising the ~11,200 cataloged morphospecies of eukaryotic plankton and among twice as many other deep-branching lineages of unappreciated importance in plankton ecology studies. Most eukaryotic plankton biodiversity belonged to heterotrophic protistan groups, particularly those known to be parasites or symbiotic hosts.
1,378 citations
Institut national de la recherche agronomique1, University of Lorraine2, United States Department of Energy3, Clark University4, Hungarian Academy of Sciences5, Helmholtz Centre for Environmental Research - UFZ6, Lund University7, University of Hasselt8, Universidade Federal de Viçosa9, University of Lyon10, University of Turin11, King Abdulaziz University12, Aix-Marseille University13, University of Oslo14, Swedish University of Agricultural Sciences15, Max Planck Society16, University of Bremen17, Harvard University18, Swiss Federal Institute for Forest, Snow and Landscape Research19, Pierre-and-Marie-Curie University20, University of Cologne21
TL;DR: Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of myCorrhiza-induced genes.
Abstract: To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.
799 citations
Vrije Universiteit Brussel1, Pierre-and-Marie-Curie University2, Université libre de Bruxelles3, University of Arizona4, Université catholique de Louvain5, École Normale Supérieure6, Katholieke Universiteit Leuven7, Spanish National Research Council8, University of Paris9, University of Bremen10, Centre national de la recherche scientifique11, Kyoto University12, University of Western Brittany13, French Alternative Energies and Atomic Energy Commission14
TL;DR: It is found that environmental factors are incomplete predictors of community structure and associations across plankton functional types and phylogenetic groups to be nonrandomly distributed on the network and driven by both local and global patterns.
Abstract: Species interaction networks are shaped by abiotic and biotic factors. Here, as part of the Tara Oceans project, we studied the photic zone interactome using environmental factors and organismal abundance profiles and found that environmental factors are incomplete predictors of community structure. We found associations across plankton functional types and phylogenetic groups to be nonrandomly distributed on the network and driven by both local and global patterns. We identified interactions among grazers, primary producers, viruses, and (mainly parasitic) symbionts and validated network-generated hypotheses using microscopy to confirm symbiotic relationships. We have thus provided a resource to support further research on ocean food webs and integrating biological components into ocean models.
717 citations
University of Arizona1, École Normale Supérieure2, Spanish National Research Council3, French Alternative Energies and Atomic Energy Commission4, Katholieke Universiteit Leuven5, Vrije Universiteit Brussel6, Centre national de la recherche scientifique7, Pierre-and-Marie-Curie University8, University of Paris9, Aix-Marseille University10, Stazione Zoologica Anton Dohrn11, Kyoto University12, University of Bremen13, University of Western Brittany14, Max Delbrück Center for Molecular Medicine15, University of Évry Val d'Essonne16
TL;DR: These investigations establish a global ocean dsDNA viromic data set with analyses supporting the seed-bank hypothesis to explain how oceanic viral communities maintain high local diversity.
Abstract: Viruses influence ecosystems by modulating microbial population size, diversity, metabolic outputs, and gene flow. Here, we use quantitative double-stranded DNA (dsDNA) viral-fraction metagenomes (viromes) and whole viral community morphological data sets from 43 Tara Oceans expedition samples to assess viral community patterns and structure in the upper ocean. Protein cluster cataloging defined pelagic upper-ocean viral community pan and core gene sets and suggested that this sequence space is well-sampled. Analyses of viral protein clusters, populations, and morphology revealed biogeographic patterns whereby viral communities were passively transported on oceanic currents and locally structured by environmental conditions that affect host community structure. Together, these investigations establish a global ocean dsDNA viromic data set with analyses supporting the seed-bank hypothesis to explain how oceanic viral communities maintain high local diversity.
588 citations
TL;DR: The potential impact of the corona for NM-microbiome-(human)host interactions and the novel concept of 'nanologicals', i.e., the nanomaterial-specific targeting of molecular machines are introduced.
Abstract: Besides the wide use of engineered nanomaterials (NMs) in technical products, their applications are not only increasing in biotechnology and biomedicine, but also in the environmental field. While the physico-chemical properties and behaviour of NMs can be characterized accurately under idealized conditions, this is no longer the case in complex physiological or natural environments. Herein, proteins and other biomolecules rapidly bind to NMs, forming a protein/biomolecule corona that critically affects the NMs' (patho)biological and technical identities. As the corona impacts the in vitro and/or in vivo NM applications in humans and ecosystems, a mechanistic understanding of its relevance and of the biophysical forces regulating corona formation is mandatory. Based on recent insights, we here critically review and present an updated concept of corona formation and evolution. We comment on how corona signatures may be linked to effects at the nano–bio interface in physiological and environmental systems. In order to comprehensively analyse corona profiles and to mechanistically understand the coronas' biological/ecological impact, we present a tiered multidisciplinary approach. To stimulate progress in this field, we introduce the potential impact of the corona for NM–microbiome–(human)host interactions and the novel concept of ‘nanologicals’, i.e., the nanomaterial-specific targeting of molecular machines. We conclude by discussing the relevant challenges that still need to be resolved in this field.
519 citations
TL;DR: A three-step enrichment model for shifts in community structure from bulk soil toward roots, based on comparison of microbiome data for the different root-soil compartments and on knowledge of bacterial functions, is presented.
Abstract: Land plants interact with microbes primarily at roots. Despite the importance of root microbial communities for health and nutrient uptake, the current understanding of the complex plant-microbe interactions in the rhizosphere is still in its infancy. Roots provide different microhabitats at the soil-root interface: rhizosphere soil, rhizoplane, and endorhizosphere. We discuss technical aspects of their differentiation that are relevant for the functional analysis of their different microbiomes, and we assess PCR (polymerase chain reaction)-based methods to analyze plant-associated bacterial communities. Development of novel primers will allow a less biased and more quantitative view of these global hotspots of microbial activity. Based on comparison of microbiome data for the different root-soil compartments and on knowledge of bacterial functions, a three-step enrichment model for shifts in community structure from bulk soil toward roots is presented. To unravel how plants shape their microbiome, a major research field is likely to be the coupling of reductionist and molecular ecological approaches, particularly for specific plant genotypes and mutants, to clarify causal relationships in complex root communities.
457 citations
TL;DR: It is observed that under TAOM conditions, both ANME and the HotSeep-1 bacteria overexpress genes for extracellular cytochrome production and form cell-to-cell connections that resemble the nanowire structures responsible for interspecies electron transfer between syntrophic consortia of Geobacter.
Abstract: The anaerobic oxidation of methane (AOM) with sulfate controls the emission of the greenhouse gas methane from the ocean floor. In marine sediments, AOM is performed by dual-species consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) inhabiting the methane-sulfate transition zone. The biochemical pathways and biological adaptations enabling this globally relevant process are not fully understood. Here we study the syntrophic interaction in thermophilic AOM (TAOM) between ANME-1 archaea and their consortium partner SRB HotSeep-1 (ref. 6) at 60 °C to test the hypothesis of a direct interspecies exchange of electrons. The activity of TAOM consortia was compared to the first ANME-free culture of an AOM partner bacterium that grows using hydrogen as the sole electron donor. The thermophilic ANME-1 do not produce sufficient hydrogen to sustain the observed growth of the HotSeep-1 partner. Enhancing the growth of the HotSeep-1 partner by hydrogen addition represses methane oxidation and the metabolic activity of ANME-1. Further supporting the hypothesis of direct electron transfer between the partners, we observe that under TAOM conditions, both ANME and the HotSeep-1 bacteria overexpress genes for extracellular cytochrome production and form cell-to-cell connections that resemble the nanowire structures responsible for interspecies electron transfer between syntrophic consortia of Geobacter. HotSeep-1 highly expresses genes for pili production only during consortial growth using methane, and the nanowire-like structures are absent in HotSeep-1 cells isolated with hydrogen. These observations suggest that direct electron transfer is a principal mechanism in TAOM, which may also explain the enigmatic functioning and specificity of other methanotrophic ANME-SRB consortia.
399 citations
Max Planck Society1, University of Bremen2, Centre national de la recherche scientifique3, George Washington University4, Goddard Space Flight Center5, University of Bern6, University of Houston–Clear Lake7, Maynooth University8, Instituto Nacional de Técnica Aeroespacial9, Paris Diderot University10, Carnegie Institution for Science11, German Aerospace Center12
TL;DR: The evolved gas analyzer Cometary Sampling and Composition experiment aboard Rosetta’s Philae lander was designed for in situ analysis of organic molecules on comet 67P/Churyumov-Gerasimenko, and displayed a suite of 16 organic compounds that had not previously been reported in comets.
Abstract: Comets harbor the most pristine material in our solar system in the form of ice, dust, silicates, and refractory organic material with some interstellar heritage. The evolved gas analyzer Cometary Sampling and Composition (COSAC) experiment aboard Rosetta’s Philae lander was designed for in situ analysis of organic molecules on comet 67P/Churyumov-Gerasimenko. Twenty-five minutes after Philae’s initial comet touchdown, the COSAC mass spectrometer took a spectrum in sniffing mode, which displayed a suite of 16 organic compounds, including many nitrogen-bearing species but no sulfur-bearing species, and four compounds—methyl isocyanate, acetone, propionaldehyde, and acetamide—that had not previously been reported in comets.
394 citations
TL;DR: It is concluded that disturbance of microbial nitrogen cycling may be tightly linked to coral bleaching and disease.
374 citations
TL;DR: In this article, a multidisciplinary approach is proposed to establish a varve chronology, which can be applied to precisely date events like volcanic ash layers, earthquakes or human impact, as well as short and long-term climate (temperature, precipitation, wind, hydroclimatic conditions or flooding) and environmental changes (eutrophication, pollution).
Japan Agency for Marine-Earth Science and Technology1, University of Bremen2, Oregon State University3, Aarhus University4, J. Craig Venter Institute5, National Institute of Advanced Industrial Science and Technology6, University of Aberdeen7, University of Leoben8, University of Birmingham9, Nanjing University10, Kōchi University11, Massachusetts Institute of Technology12, University of New Hampshire13, University of Nebraska–Lincoln14, University of California, Riverside15, University of Rhode Island16, Rice University17, University of Queensland18, Chiba University19, California Institute of Technology20, Kyoto University21
TL;DR: Evidence is provided for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan, which suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed.
Abstract: Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10^4 cells cm^(−3). Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed.
TL;DR: Tara Oceans Data as discussed by the authors is a collection of seawater and plankton collected during the 2009-2013 Tara Oceans Expedition (2009-2013) in 20 biogeographic provinces of the world.
Abstract: The Tara Oceans expedition (2009–2013) sampled contrasting ecosystems of the world oceans, collecting environmental data and plankton, from viruses to metazoans, for later analysis using modern sequencing and state-of-the-art imaging technologies. It surveyed 210 ecosystems in 20 biogeographic provinces, collecting over 35,000 samples of seawater and plankton. The interpretation of such an extensive collection of samples in their ecological context requires means to explore, assess and access raw and validated data sets. To address this challenge, the Tara Oceans Consortium offers open science resources, including the use of open access archives for nucleotides (ENA) and for environmental, biogeochemical, taxonomic and morphological data (PANGAEA), and the development of on line discovery tools and collaborative annotation tools for sequences and images. Here, we present an overview of Tara Oceans Data, and we provide detailed registries (data sets) of all campaigns (from port-to-port), stations and sampling events.
TL;DR: An overview of the sequencing technologies and how they are uniquely suited to various types of metagenomic studies is provided and future trends in the field are provided with respect to tools and technologies currently under development.
Abstract: Advances in next-generation sequencing (NGS) have allowed significant breakthroughs in microbial ecology studies. This has led to the rapid expansion of research in the field and the establishment of “metagenomics”, often defined as the analysis of DNA from microbial communities in environmental samples without prior need for culturing. Many metagenomics statistical/computational tools and databases have been developed in order to allow the exploitation of the huge influx of data. In this review article, we provide an overview of the sequencing technologies and how they are uniquely suited to various types of metagenomic studies. We focus on the currently available bioinformatics techniques, tools, and methodologies for performing each individual step of a typical metagenomic dataset analysis. We also provide future trends in the field with respect to tools and technologies currently under development. Moreover, we discuss data management, distribution, and integration tools that are capable of performing comparative metagenomic analyses of multiple datasets using well-established databases, as well as commonly used annotation standards.
TL;DR: A review of existing attempts to define and classify SoS is used to identify several dimensions that characterise SoS applications and the state of the art for SoS modelling, architectural description, simulation, verification, and testing is reviewed.
Abstract: The term “System of Systems” (SoS) has been used since the 1950s to describe systems that are composed of independent constituent systems, which act jointly towards a common goal through the synergism between them. Examples of SoS arise in areas such as power grid technology, transport, production, and military enterprises. SoS engineering is challenged by the independence, heterogeneity, evolution, and emergence properties found in SoS. This article focuses on the role of model-based techniques within the SoS engineering field. A review of existing attempts to define and classify SoS is used to identify several dimensions that characterise SoS applications. The SoS field is exemplified by a series of representative systems selected from the literature on SoS applications. Within the area of model-based techniques the survey specifically reviews the state of the art for SoS modelling, architectural description, simulation, verification, and testing. Finally, the identified dimensions of SoS characteristics are used to identify research challenges and future research areas of model-based SoS engineering.
TL;DR: In this paper, the authors present an overview of German energy cooperatives in terms of organization, financing, and membership, and discuss how these theories could be applied to create a better understanding of energy cooperators, and derive a preliminary research agenda for their analysis.
Abstract: The transformation of energy systems is influencing economic policy agendas all over the world, particularly in industrialized countries. In this process, Germany has taken a pioneering role, and hence the technical innovations, legal frameworks, and business models established there are also of interest for other countries trying to achieve broader use of renewable energies. Energy cooperatives have been an important building block in the energy transition in Germany, although their practical importance is neither quantitatively nor qualitatively reflected in the academic literature. Drawing on recently collected data, this paper presents an overview of German energy cooperatives in terms of organization, financing, and membership. We then review literature from economics and the social sciences that has been used to analyze cooperatives on various levels in other fields. We discuss how these theories could be applied to create a better understanding of energy cooperatives, and we derive a preliminary research agenda for their analysis. We also assess the scope for interdisciplinary work among economists, sociologists, and other disciplines.
TL;DR: This work finds that the planar hypercoordinate two-dimensional monolayer system is quite stable during short annealing simulations up to 900 K, and predicts that it is a nonmagnetic metal.
Abstract: Two-dimensional (2D) materials with planar hypercoordinate motifs are extremely rare due to the difficulty in stabilizing the planar hypercoordinate configurations in extended systems. Furthermore, such exotic motifs are often unstable. We predict a novel Cu2Si 2D monolayer featuring planar hexacoordinate copper and planar hexacoordinate silicon. This is a global minimum in 2D space which displays reduced dimensionality and rule-breaking chemical bonding. This system has been studied with density functional theory, including molecular dynamics simulations and electronic structure calculations. Bond order analysis and partitioning reveals 4c–2e σ bonds that stabilize the two-dimensional structure. We find that the system is quite stable during short annealing simulations up to 900 K, and predict that it is a nonmagnetic metal. This work opens up a new branch of hypercoordinate two-dimensional materials for study.
TL;DR: In this article, Baur and Lucey (2010) augmentation of their model to a smooth transition regression (STR) using an exponential transition function which splits the regression model into two extreme regimes: periods in which stock returns are on average and therefore allowing to test whether gold acts as a hedge for stocks, the other one accounts for extreme market conditions where the volatility of the stock returns is high.
TL;DR: In this article, the authors argue that Deacon and Stanyer's article "Mediatization: Key Concept or Conceptual Bandwagon?" does not capture the complex relationship between changes in media and communication, on the one hand, and changes in various fields of culture and society on the other.
Abstract: In response to Deacon and Stanyer’s article ‘Mediatization: Key Concept or Conceptual Bandwagon?’ we argue that they build their criticism on a simplified methodology. They mistake a media-centered approach for a media-centric one, and they do not capture how mediatization research engages with the complex relationship between changes in media and communication, on the one hand, and changes in various fields of culture and society on the other. We conclude that the emergence of the concept of mediatization is part of a paradigmatic shift within media and communication research.
TL;DR: This dataset was able to chart the flow of carbon and nutrients through the multiple geochemical layers of bacterial processing and reveal potential ecological interactions within the communities.
Abstract: Estuaries are among the most productive habitats on the planet. Bacteria in estuary sediments control the turnover of organic carbon and the cycling of nitrogen and sulfur. These communities are complex and primarily made up of uncultured lineages, thus little is known about how ecological and metabolic processes are partitioned in sediments. De novo assembly and binning resulted in the reconstruction of 82 bacterial genomes from different redox regimes of estuary sediments. These genomes belong to 23 bacterial groups, including uncultured candidate phyla (for example, KSB1, TA06, and KD3-62) and three newly described phyla (White Oak River (WOR)-1, WOR-2, and WOR-3). The uncultured phyla are generally most abundant in the sulfate-methane transition (SMTZ) and methane-rich zones, and genomic data predict that they mediate essential biogeochemical processes of the estuarine environment, including organic carbon degradation and fermentation. Among the most abundant organisms in the sulfate-rich layer are novel Gammaproteobacteria that have genes for the oxidation of sulfur and the reduction of nitrate and nitrite. Interestingly, the terminal steps of denitrification (NO3 to N2O and then N2O to N2) are present in distinct bacterial populations. This dataset extends our knowledge of the metabolic potential of several uncultured phyla. Within the sediments, there is redundancy in the genomic potential in different lineages, often distinct phyla, for essential biogeochemical processes. We were able to chart the flow of carbon and nutrients through the multiple geochemical layers of bacterial processing and reveal potential ecological interactions within the communities.
TL;DR: In this paper, the authors investigate how trust moderates the impact of ad personalization on consumers' internal and external responses in the lab and propose a two-dimensional conceptualization of ad personalizedization: First, a banner's personalization depth defines how closely the ad reflects a consumer's interests.
TL;DR: A conceptual model, called Activity Theory-based Model of Serious Games (ATMSG), that aims to fill the gap in models, frameworks and methodologies for serious games analysis and design, and depicts how the combination of serious games elements supports pedagogical goals.
Abstract: There are currently a number of models, frameworks and methodologies for serious games analysis and design that provide useful interpretations of the possibilities and limitations offered by serious games. However, these tools focus mostly on high-level aspects and requirements and do not help understand how such high-level requirements can be concretely satisfied. In this paper, we present a conceptual model, called Activity Theory-based Model of Serious Games (ATMSG), that aims to fill this gap. ATMSG supports a systematic and detailed representation of educational serious games, depicting the ways that game elements are connected to each other throughout the game, and how these elements contribute to the achievement of the desired pedagogical goals. Three evaluation studies indicate that ATMSG helped participants, particularly those with gaming experience, identify and understand the roles of each component in the game and recognize the game's educational objectives. We present a model for serious games analysis and conceptual design, called ATMSG.Activity theory is used as the underlying theoretical framework.ATMSG supports a systematic and detailed representation of educational serious games.ATMSG depicts how the combination of serious games elements supports pedagogical goals.A taxonomy of serious games elements is presented to assist the analysis of SGs.
TL;DR: A high-resolution seawater pH record is presented across this interval, using boron isotope data combined with a quantitative modeling approach, to present a possible kill mechanism for the Permo-Triassic Boundary mass extinction.
Abstract: Ocean acidification triggered by Siberian Trap volcanism was a possible kill mechanism for the Permo-Triassic Boundary mass extinction, but direct evidence for an acidification event is lacking. We present a high-resolution seawater pH record across this interval, using boron isotope data combined with a quantitative modeling approach. In the latest Permian, increased ocean alkalinity primed the Earth system with a low level of atmospheric CO2 and a high ocean buffering capacity. The first phase of extinction was coincident with a slow injection of carbon into the atmosphere, and ocean pH remained stable. During the second extinction pulse, however, a rapid and large injection of carbon caused an abrupt acidification event that drove the preferential loss of heavily calcified marine biota.
TL;DR: In this paper, the influence of a plasma on the shadow of a supermassive black hole was analyzed. But the authors restricted their analysis to spherically symmetric and static situations, where the shadow is circular and the plasma is assumed to be nonmagnetized and pressureless.
Abstract: We analytically calculate the influence of a plasma on the shadow of a black hole (or of another compact object). We restrict to spherically symmetric and static situations, where the shadow is circular. The plasma is assumed to be nonmagnetized and pressureless. We derive the general formulas for a spherically symmetric plasma density on an unspecified spherically symmetric and static spacetime. Our main result is an analytical formula for the angular size of the shadow. As a plasma is a dispersive medium, the radius of the shadow depends on the photon frequency. The effect of the plasma is significant only in the radio regime. The formalism applies not only to black holes but also, e.g., to wormholes. As examples for the underlying spacetime model, we consider the Schwarzschild spacetime and the Ellis wormhole. In particular, we treat the case that the plasma is in radial free fall from infinity onto a Schwarzschild black hole. We find that for an observer far away from a Schwarzschild black hole, the plasma has a decreasing effect on the size of the shadow. The perspectives of actually observing the influence of a plasma on the shadows of supermassive black holes are discussed.
TL;DR: In this article, the authors summarized the most recent studies on the modification of G with polymers and the subsequent synthesis and applications of high quality G-polymer nanocomposites.
TL;DR: The results indicate that the seep microbiome is structured according to metacommunity processes and that few cosmopolitan microbial taxa mediate the bulk of methane oxidation, with global relevance to methane emission in the ocean.
Abstract: Methane seeps are widespread seafloor ecosystems shaped by the emission of gas from seabed reservoirs. The microorganisms inhabiting methane seeps transform the chemical energy in methane to products that sustain rich benthic communities around the gas leaks. Despite the biogeochemical relevance of microbial methane removal at seeps, the global diversity and dispersion of seep microbiota remain unknown. Here we determined the microbial diversity and community structure of 23 globally distributed methane seeps and compared these to the microbial communities of 54 other seafloor ecosystems, including sulfate–methane transition zones, hydrothermal vents, coastal sediments, and deep-sea surface and subsurface sediments. We found that methane seep communities show moderate levels of microbial richness compared with other seafloor ecosystems and harbor distinct bacterial and archaeal taxa with cosmopolitan distribution and key biogeochemical functions. The high relative sequence abundance of ANME (anaerobic methanotrophic archaea), as well as aerobic Methylococcales, sulfate-reducing Desulfobacterales, and sulfide-oxidizing Thiotrichales, matches the most favorable microbial metabolisms at methane seeps in terms of substrate supply and distinguishes the seep microbiome from other seafloor microbiomes. The key functional taxa varied in relative sequence abundance between different seeps due to the environmental factors, sediment depth and seafloor temperature. The degree of endemism of the methane seep microbiome suggests a high local diversification in these heterogeneous but long-lived ecosystems. Our results indicate that the seep microbiome is structured according to metacommunity processes and that few cosmopolitan microbial taxa mediate the bulk of methane oxidation, with global relevance to methane emission in the ocean.
Harvard University1, Earth System Research Laboratory2, Lawrence Berkeley National Laboratory3, University of Leicester4, California Institute of Technology5, University of Bremen6, University of Wollongong7, Los Alamos National Laboratory8, Karlsruhe Institute of Technology9, Japan Aerospace Exploration Agency10, Nagoya University11, Cooperative Institute for Research in Environmental Sciences12
TL;DR: In this article, the authors use space-borne methane observations from the Greenhouse Gases Observing SATellite (GOSAT) to estimate global and North American methane emissions with up to 50 km × 50 km spatial resolution, respectively.
Abstract: . We use 2009–2011 space-borne methane observations from the Greenhouse Gases Observing SATellite (GOSAT) to estimate global and North American methane emissions with 4° × 5° and up to 50 km × 50 km spatial resolution, respectively. GEOS-Chem and GOSAT data are first evaluated with atmospheric methane observations from surface and tower networks (NOAA/ESRL, TCCON) and aircraft (NOAA/ESRL, HIPPO), using the GEOS-Chem chemical transport model as a platform to facilitate comparison of GOSAT with in situ data. This identifies a high-latitude bias between the GOSAT data and GEOS-Chem that we correct via quadratic regression. Our global adjoint-based inversion yields a total methane source of 539 Tg a−1 with some important regional corrections to the EDGARv4.2 inventory used as a prior. Results serve as dynamic boundary conditions for an analytical inversion of North American methane emissions using radial basis functions to achieve high resolution of large sources and provide error characterization. We infer a US anthropogenic methane source of 40.2–42.7 Tg a−1, as compared to 24.9–27.0 Tg a−1 in the EDGAR and EPA bottom-up inventories, and 30.0–44.5 Tg a−1 in recent inverse studies. Our estimate is supported by independent surface and aircraft data and by previous inverse studies for California. We find that the emissions are highest in the southern–central US, the Central Valley of California, and Florida wetlands; large isolated point sources such as the US Four Corners also contribute. Using prior information on source locations, we attribute 29–44 % of US anthropogenic methane emissions to livestock, 22–31 % to oil/gas, 20 % to landfills/wastewater, and 11–15 % to coal. Wetlands contribute an additional 9.0–10.1 Tg a−1.
TL;DR: Initial symptomatic treatment with ibuprofen is a possible approach to be discussed with women willing to avoid immediate antibiotics and to accept a somewhat higher burden of symptoms.
Abstract: Study question Can treatment of the symptoms of uncomplicated urinary tract infection (UTI) with ibuprofen reduce the rate of antibiotic prescriptions without a significant increase in symptoms, recurrences, or complications? Methods Women aged 18-65 with typical symptoms of UTI and without risk factors or complications were recruited in 42 German general practices and randomly assigned to treatment with a single dose of fosfomycin 3 g (n=246; 243 analysed) or ibuprofen 3×400 mg (n=248; 241 analysed) for three days (and the respective placebo dummies in both groups). In both groups additional antibiotic treatment was subsequently prescribed as necessary for persistent, worsening, or recurrent symptoms. The primary endpoints were the number of all courses of antibiotic treatment on days 0-28 (for UTI or other conditions) and burden of symptoms on days 0-7. The symptom score included dysuria, frequency/urgency, and low abdominal pain. Study answer and limitations The 248 women in the ibuprofen group received significantly fewer course of antibiotics, had a significantly higher total burden of symptoms, and more had pyelonephritis. Four serious adverse events occurred that lead to hospital referrals; one of these was potentially related to the trial drug. Results have to be interpreted carefully as they might apply to women with mild to moderate symptoms rather than to all those with an uncomplicated UTI. What this paper adds Two thirds of women with uncomplicated UTI treated symptomatically with ibuprofen recovered without any antibiotics. Initial symptomatic treatment is a possible approach to be discussed with women willing to avoid immediate antibiotics and to accept a somewhat higher burden of symptoms. Funding, competing interests, data sharing German Federal Ministry of Education and Research (BMBF) No 01KG1105. Patient level data are available from the corresponding author. Patient consent was not obtained but the data are anonymised and risk of identification is low. Trial registration No ClinicalTrialGov Identifier NCT01488955.
TL;DR: It is shown that, although personalization can substantially enhance banner effectiveness, its impact hinges on its interplay with timing and placement factors, and click-through increases at an early information state of the purchase decision process and ad effectiveness on motive congruent or incongruent display websites.
Abstract: Firms track consumers' shopping behaviors in their online stores to provide individually personalized banners through a method called retargeting. We use data from two large-scale field experiments and two lab experiments to show that, although personalization can substantially enhance banner effectiveness, its impact hinges on its interplay with timing and placement factors. First, personalization increases click-through especially at an early information state of the purchase decision process. Here, banners with a high degree of content personalization DCP are most effective when a consumer has just visited the advertiser's online store, but quickly lose effectiveness as time passes since that last visit. We call this phenomenon overpersonalization. Medium DCP banners, on the other hand, are initially less effective, but more persistent, so that they outperform high DCP banners over time. Second, personalization increases click-through irrespective of whether banners appear on motive congruent or incongruent display websites. In terms of view-through, however, personalization increases ad effectiveness only on motive congruent websites, but decreases it on incongruent websites. We demonstrate in the lab how perceptions of ad informativeness and intrusiveness drive these results depending on consumers' experiential or goal-directed Web browsing modes.
TL;DR: In this paper, the structural and electronic properties of two 2D layered arsenic materials, namely, arsenic and its alloy AsSb, were characterized using phonon and binding energy calculations.
Abstract: Layered materials exhibit intriguing electronic characteristics and the search for new types of two-dimensional (2D) structures is of importance for future device fabrication. Using state-of-art first principle calculations, we identify and characterize the structural and electronic properties of two 2D layered arsenic materials, namely, arsenic and its alloy AsSb. The stable 2D structural configuration of arsenic is confirmed to be the low-buckled two-dimensional hexagonal structure by phonon and binding energy calculations. The monolayer exhibits indirect semiconducting properties with gap around 1.5 eV (corrected to 2.2 eV by hybrid function), which can be modulated into a direct semiconductor within a small amount of tensile strain. These semiconducting properties are preserved when cutting into 1D nanoribbons, but the band gap is edge dependent. It is interesting to find that an indirect to direct gap transition can be achieved under strain modulation of the armchair ribbon. Essentially the same phen...