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Showing papers by "University of Delaware published in 2019"



Journal ArticleDOI
TL;DR: Recent developments with InterPro (version 70.0) and its associated software are reported, including an 18% growth in the size of the database in terms on new InterPro entries, updates to content, the inclusion of an additional entry type, refined modelling of discontinuous domains, and the development of a new programmatic interface and website.
Abstract: The InterPro database (http://www.ebi.ac.uk/interpro/) classifies protein sequences into families and predicts the presence of functionally important domains and sites. Here, we report recent developments with InterPro (version 70.0) and its associated software, including an 18% growth in the size of the database in terms on new InterPro entries, updates to content, the inclusion of an additional entry type, refined modelling of discontinuous domains, and the development of a new programmatic interface and website. These developments extend and enrich the information provided by InterPro, and provide greater flexibility in terms of data access. We also show that InterPro's sequence coverage has kept pace with the growth of UniProtKB, and discuss how our evaluation of residue coverage may help guide future curation activities.

1,167 citations


Journal ArticleDOI
TL;DR: A catalyst that features two adjacent copper atoms that work together to carry out the critical bimolecular step in CO2 reduction is reported, which results in a Faradaic efficiency for CO generation above 92%, with the competing hydrogen evolution reaction almost completely suppressed.
Abstract: The electrochemical reduction of CO2 could play an important role in addressing climate-change issues and global energy demands as part of a carbon-neutral energy cycle. Single-atom catalysts can display outstanding electrocatalytic performance; however, given their single-site nature they are usually only amenable to reactions that involve single molecules. For processes that involve multiple molecules, improved catalytic properties could be achieved through the development of atomically dispersed catalysts with higher complexities. Here we report a catalyst that features two adjacent copper atoms, which we call an ‘atom-pair catalyst’, that work together to carry out the critical bimolecular step in CO2 reduction. The atom-pair catalyst features stable Cu10–Cu1x+ pair structures, with Cu1x+ adsorbing H2O and the neighbouring Cu10 adsorbing CO2, which thereby promotes CO2 activation. This results in a Faradaic efficiency for CO generation above 92%, with the competing hydrogen evolution reaction almost completely suppressed. Experimental characterization and density functional theory revealed that the adsorption configuration reduces the activation energy, which generates high selectivity, activity and stability under relatively low potentials. Anchored single-atom catalysts have recently been shown to be very active for various processes, however, a catalyst that features two adjacent copper atoms—which we call an atom-pair catalyst—is now reported. The Cu10–Cu1x+ pair structures work together to carry out the critical bimolecular step in CO2 reduction.

467 citations


Journal ArticleDOI
TL;DR: The Health Stigma and Discrimination Framework is proposed, which is a global, crosscutting framework based on theory, research, and practice, and its application to a range of health conditions, including leprosy, epilepsy, mental health, cancer, HIV, and obesity/overweight is demonstrated.
Abstract: Stigma is a well-documented barrier to health seeking behavior, engagement in care and adherence to treatment across a range of health conditions globally. In order to halt the stigmatization process and mitigate the harmful consequences of health-related stigma (i.e. stigma associated with health conditions), it is critical to have an explicit theoretical framework to guide intervention development, measurement, research, and policy. Existing stigma frameworks typically focus on one health condition in isolation and often concentrate on the psychological pathways occurring among individuals. This tendency has encouraged a siloed approach to research on health-related stigmas, focusing on individuals, impeding both comparisons across stigmatized conditions and research on innovations to reduce health-related stigma and improve health outcomes. We propose the Health Stigma and Discrimination Framework, which is a global, crosscutting framework based on theory, research, and practice, and demonstrate its application to a range of health conditions, including leprosy, epilepsy, mental health, cancer, HIV, and obesity/overweight. We also discuss how stigma related to race, gender, sexual orientation, class, and occupation intersects with health-related stigmas, and examine how the framework can be used to enhance research, programming, and policy efforts. Research and interventions inspired by a common framework will enable the field to identify similarities and differences in stigma processes across diseases and will amplify our collective ability to respond effectively and at-scale to a major driver of poor health outcomes globally.

454 citations


Journal ArticleDOI
TL;DR: In this article, a high-performance family of poly(aryl piperidinium) membranes was proposed for HEMFCs with high ionic conductivity, chemical stability, mechanical robustness, and selective solubility.
Abstract: One promising approach to reduce the cost of fuel cell systems is to develop hydroxide exchange membrane fuel cells (HEMFCs), which open up the possibility of platinum-group-metal-free catalysts and low-cost bipolar plates. However, scalable alkaline polyelectrolytes (hydroxide exchange membranes and hydroxide exchange ionomers), a key component of HEMFCs, with desired properties are currently unavailable, which presents a major barrier to the development of HEMFCs. Here we show hydroxide exchange membranes and hydroxide exchange ionomers based on poly(aryl piperidinium) (PAP) that simultaneously possess adequate ionic conductivity, chemical stability, mechanical robustness, gas separation and selective solubility. These properties originate from the combination of the piperidinium cation and the rigid ether-bond-free aryl backbone. A low-Pt membrane electrode assembly with a Ag-based cathode using PAP materials showed an excellent peak power density of 920 mW cm−2 and operated stably at a constant current density of 500 mA cm−2 for 300 h with H2/CO2-free air at 95 °C. A key challenge for hydroxide exchange membrane fuel cells is the development of membranes with both high ionic conductivity and mechanical strength. Here the authors report a high-performance family of poly(aryl piperidinium) membranes enabling promising durability and power density.

453 citations


Journal ArticleDOI
29 Mar 2019-Science
TL;DR: The sources and impacts of natural nanomaterials, which are not created directly through human actions; incidental nanom material, which form unintentionally during human activities; and engineered nanomMaterials,Which are created for specific applications are reviewed.
Abstract: BACKGROUND Natural nanomaterials have always been abundant during Earth’s formation and throughout its evolution over the past 4.54 billion years. Incidental nanomaterials, which arise as a by-product from human activity, have become unintentionally abundant since the beginning of the Industrial Revolution. Nanomaterials can also be engineered to have unusual, tunable properties that can be used to improve products in applications from human health to electronics, and in energy, water, and food production. Engineered nanomaterials are very much a recent phenomenon, not yet a century old, and are just a small mass fraction of the natural and incidental varieties. As with natural and incidental nanomaterials, engineered nanomaterials can have both positive and negative consequences in our environment. Despite the ubiquity of nanomaterials on Earth, only in the past 20 years or so have their impacts on the Earth system been studied intensively. This is mostly due to a much better understanding of the distinct behavior of materials at the nanoscale and to multiple advances in analytic techniques. This progress continues to expand rapidly as it becomes clear that nanomaterials are relevant from molecular to planetary dimensions and that they operate from the shortest to the longest time scales over the entire Earth system. ADVANCES Nanomaterials can be defined as any organic, inorganic, or organometallic material that present chemical, physical, and/or electrical properties that change as a function of the size and shape of the material. This behavior is most often observed in the size range between 1 nm up to a few to several tens of nanometers in at least one dimension. These materials have very high proportions of surface atoms relative to interior ones. Also, they are often subject to property variation as a function of size owing to quantum confinement effects. Nanomaterial growth, dissolution or evaporation, surface reactivity, and aggregation states play key roles in their lifetime, behaviors, and local interactions in both natural and engineered environments, often with global consequences. It is now possible to recognize and identify critical roles played by nanomaterials in vital Earth system components, including direct human impact. For example, nanomaterial surfaces may have been responsible for promoting the self-assembly of protocells in the origin of life and in the early evolution of bacterial cell walls. Also, weathering reactions on the continents produce various bioavailable iron (oxy)hydroxide natural and incidental nanomaterials, which are transported to the oceans via riverine and atmospheric pathways and which influence ocean surface primary productivity and thus the global carbon cycle. A third example involves nanomaterials in the atmosphere that travel locally, regionally, and globally. When inhaled, the smallest nanoparticles can pass through the alveolar membranes of the lungs and directly enter the bloodstream. From there, they enter vital organs, including the brain, with possible deleterious consequences. OUTLOOK Earth system nanoscience requires a convergent approach that combines physical, biological, and social sciences, as well as engineering and economic disciplines. This convergence will drive developments for all types of intelligent and anticipatory conceptual models assisted by new analytical techniques and computational simulations. Ultimately, scientists must learn how to recognize key roles of natural, incidental, and engineered nanomaterials in the complex Earth system, so that this understanding can be included in models of Earth processes and Earth history, as well as in ethical considerations regarding their positive and negative effects on present and predicted future environmental and human health issues.

424 citations


Journal ArticleDOI
TL;DR: The synthesis of polyarylether-based covalent organic frameworks (PAE-COFs) with high crystallinity, porosity and chemical stability, as well as good stability against harsh chemical environments including boiling water and strong acids and bases are reported.
Abstract: The development of crystalline porous materials with high chemical stability is of paramount importance for their practical application. Here, we report the synthesis of polyarylether-based covalent organic frameworks (PAE-COFs) with high crystallinity, porosity and chemical stability, including towards water, owing to the inert nature of their polyarylether-based building blocks. The PAE-COFs are synthesized through nucleophilic aromatic substitution reactions between ortho-difluoro benzene and catechol building units, which form ether linkages. The resulting materials are shown to be stable against harsh chemical environments including boiling water, strong acids and bases, and oxidation and reduction conditions. Their stability surpasses the performance of other known crystalline porous materials such as zeolites, metal-organic frameworks and covalent organic frameworks. We also demonstrate the post-synthetic functionalization of these materials with carboxyl or amino functional groups. The functionalized PAE-COFs combine porosity, high stability and recyclability. A preliminary application of these materials is demonstrated with the removal of antibiotics from water over a wide pH range.

414 citations


Journal ArticleDOI
TL;DR: In this article, the authors explore critical technological advancements using a value co-creation lens to provide insights into service innovations that impact ecosystems, and identify three areas of likely future disruption in service experiences: extra-sensory experiences, hyper-personalized experiences and beyond-automation experiences.
Abstract: Technological disruptions such as the Internet of Things and autonomous devices, enhanced analytical capabilities (artificial intelligence) and rich media (virtual and augmented reality) are creating smart environments that are transforming industry structures, processes and practices. The purpose of this paper is to explore critical technological advancements using a value co-creation lens to provide insights into service innovations that impact ecosystems. The paper provides examples from tourism and hospitality industries as an information dependent service management context.,The research synthesizes prevailing theories of co-creation, service ecosystems, networks and technology disruption with emerging technological developments.,Findings highlight the need for research into service innovations in the tourism and hospitality sector at both macro-market and micro-firm levels, emanating from the rapid and radical nature of technological advancements. Specifically, the paper identifies three areas of likely future disruption in service experiences that may benefit from immediate attention: extra-sensory experiences, hyper-personalized experiences and beyond-automation experiences.,Tourism and hospitality services prevail under varying levels of infrastructure, organization and cultural constraints. This paper provides an overview of potential disruptions and developments and does not delve into individual destination types and settings. This will require future work that conceptualizes and examines how stakeholders may adapt within specific contexts.,Technological disruptions impact all facets of life. A comprehensive picture of developments here provides policymakers with nuanced perspectives to better prepare for impending change.,Guest experiences in tourism and hospitality by definition take place in hostile environments that are outside the safety and familiarity of one’s own surroundings. The emergence of smart environments will redefine how customers navigate their experiences. At a conceptual level, this requires a complete rethink of how stakeholders should leverage technologies, engage and reengineer services to remain competitive. The paper illustrates how technology disrupts industry structures and stimulates value co-creation at the micro and macro-societal level.

344 citations


Journal ArticleDOI
12 Dec 2019-Nature
TL;DR: Observations of solar-wind plasma at heliocentric distances of about 35 solar radii reveal an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second—considerably above the amplitude of the waves.
Abstract: The prediction of a supersonic solar wind1 was first confirmed by spacecraft near Earth2,3 and later by spacecraft at heliocentric distances as small as 62 solar radii4. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvenic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5–7. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9–11, well within the distance at which stream interactions become important. We find that Alfven waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second—considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12–14. Data collected by the Parker Solar Probe in the solar corona are used to determine the organization of Alfven waves, revealing an increasing flow velocity peaking at 35–50 km s−1.

336 citations


Journal ArticleDOI
TL;DR: The MIUViG (Minimum Information about an Uncultivated Virus Genome) as mentioned in this paper standard was developed within the Genomic Standards Consortium framework and includes virus origin, genome quality, genome annotation, taxonomic classification, biogeographic distribution and in silico host prediction.
Abstract: We present an extension of the Minimum Information about any (x) Sequence (MIxS) standard for reporting sequences of uncultivated virus genomes. Minimum Information about an Uncultivated Virus Genome (MIUViG) standards were developed within the Genomic Standards Consortium framework and include virus origin, genome quality, genome annotation, taxonomic classification, biogeographic distribution and in silico host prediction. Community-wide adoption of MIUViG standards, which complement the Minimum Information about a Single Amplified Genome (MISAG) and Metagenome-Assembled Genome (MIMAG) standards for uncultivated bacteria and archaea, will improve the reporting of uncultivated virus genomes in public databases. In turn, this should enable more robust comparative studies and a systematic exploration of the global virosphere.

318 citations


Journal ArticleDOI
01 May 2019
TL;DR: In this article, a facile synthesis of freestanding triangular-shaped two-dimensional Cu nanosheets that selectively expose the (111) surface was reported, which exhibited an acetate Faradaic efficiency of 48% in a 2'M KOH electrolyte.
Abstract: Upgrading carbon dioxide to high-value multicarbon (C2+) products is one promising avenue for fuel and chemical production. Among all the monometallic catalysts, copper has attracted much attention because of its unique ability to convert CO2 or CO into C2+ products with an appreciable selectivity. Although numerous attempts have been made to synthesize Cu materials that expose the desired facets, it still remains a challenge to obtain high-quality nanostructured Cu catalysts for the electroreduction of CO2/CO. Here we report a facile synthesis of freestanding triangular-shaped two-dimensional Cu nanosheets that selectively expose the (111) surface. In a 2 M KOH electrolyte, the Cu nanosheets exhibit an acetate Faradaic efficiency of 48% with an acetate partial current density up to 131 mA cm−2 in electrochemical CO reduction. Further analysis suggest that the high acetate selectivity is attributed to the suppression of ethylene and ethanol formation, probably due to the reduction of exposed (100) and (110) surfaces. Upgrading CO to high-value multicarbon products is a promising avenue for fuel and chemical feedstock production. Here triangular Cu nanosheets that selectively expose the (111) surface exhibit a high acetate partial current density (131 mA cm–2) and Faradaic efficiency (48%) in CO electroreduction.

Journal ArticleDOI
TL;DR: In this paper, the combination of identities, forms, logics, or other core elements that would conventionally not go together is explored. Drawing on in-depth longitudinal data, the authors identify the core elements of an organization that need to be combined.
Abstract: Organizations increasingly grapple with hybridity—the combination of identities, forms, logics, or other core elements that would conventionally not go together. Drawing on in-depth longitudinal da...

Journal ArticleDOI
TL;DR: Why the 30-million-word gap should not be abandoned, and the importance of retaining focus on the vital ingredient to language learning-quality speech directed to children rather than overheard speech, are addressed.
Abstract: Sperry, Sperry, and Miller (2018) aim to debunk what is called the 30-million-word gap by claiming that children from lower income households hear more speech than Hart and Risley () reported. We address why the 30-million-word gap should not be abandoned, and the importance of retaining focus on the vital ingredient to language learning-quality speech directed to children rather than overheard speech, the focus of Sperry et al.'s argument. Three issues are addressed: Whether there is a language gap; the characteristics of speech that promote language development; and the importance of language in school achievement. There are serious risks to claims that low-income children, on average, hear sufficient, high-quality language relative to peers from higher income homes. [ABSTRACT FROM AUTHOR]

Journal ArticleDOI
Nuno Queiroz1, Nuno Queiroz2, Nicolas E. Humphries1, Ana Rita Couto2  +163 moreInstitutions (61)
22 Aug 2019-Nature
TL;DR: It is concluded that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas), demonstrating an urgent need for conservation and management measures at high-seas hotspots of shark space use.
Abstract: Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management.

Journal ArticleDOI
TL;DR: In this article, the authors review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory and emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of solar wind.
Abstract: The solar wind is a magnetized plasma and as such exhibits collective plasma behavior associated with its characteristic spatial and temporal scales. The characteristic length scales include the size of the heliosphere, the collisional mean free paths of all species, their inertial lengths, their gyration radii, and their Debye lengths. The characteristic timescales include the expansion time, the collision times, and the periods associated with gyration, waves, and oscillations. We review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory. We emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of the solar wind. We describe methods to measure in-situ properties of particles and fields. We then discuss the role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution.

Journal ArticleDOI
01 Dec 2019
TL;DR: In this paper, the progress towards high-rate CO conversion is shown alongside mechanistic insights and device designs that can improve performance even further, and a techno-economic analysis of the two-step conversion process and cradle-to-gate lifecycle assessment is presented.
Abstract: The electrochemical conversion of carbon dioxide to value-added chemical products has been heavily explored as a promising strategy for carbon utilization. However, the direct synthesis of multi-carbon (C2+) products suffers from undesired side reactions and relatively low selectivity. Electrochemically converting CO2 to single-carbon products is much more effective and being commercially deployed. Recent studies have shown that CO can be electrochemically transformed further to C2+ at high reaction rates, high C2+ selectivity and inherently improved electrolyte stability, raising the prospect of a two-step pathway to transform CO2. In this Perspective, the progress towards high-rate CO conversion is shown alongside mechanistic insights and device designs that can improve performance even further. A techno-economic analysis of the two-step conversion process and cradle-to-gate lifecycle assessment shows the economic feasibility and improved environmental impact of a high-volume commercial process generating acetic acid and ethylene compared to the current state of the art. Carbon monoxide can be electrochemically transformed to multi-carbon products selectively at high rates, raising the prospect of a two-step pathway to transform CO2 into value-added chemical products. This Perspective highlights recent progress complemented by a techno-economic analysis of the two-step conversion process and cradle-to-gate lifecycle assessment.

Journal ArticleDOI
TL;DR: In this paper, the authors present a systematic trade-off between material use in the production of buildings, vehicles, and appliances and energy use in their operation, requiring a careful life cycle assessment of ME strategies.
Abstract: As one quarter of global energy use serves the production of materials, the more efficient use of these materials presents a significant opportunity for the mitigation of greenhouse gas (GHG) emissions. With the renewed interest of policy makers in the circular economy, material efficiency (ME) strategies such as light-weighting and downsizing of and lifetime extension for products, reuse and recycling of materials, and appropriate material choice are being promoted. Yet, the emissions savings from ME remain poorly understood, owing in part to the multitude of material uses and diversity of circumstances and in part to a lack of analytical effort. We have reviewed emissions reductions from ME strategies applied to buildings, cars, and electronics. We find that there can be a systematic trade-off between material use in the production of buildings, vehicles, and appliances and energy use in their operation, requiring a careful life cycle assessment of ME strategies. We find that the largest potential emission reductions quantified in the literature result from more intensive use of and lifetime extension for buildings and the light-weighting and reduced size of vehicles. Replacing metals and concrete with timber in construction can result in significant GHG benefits, but trade-offs and limitations to the potential supply of timber need to be recognized. Repair and remanufacturing of products can also result in emission reductions, which have been quantified only on a case-by-case basis and are difficult to generalize. The recovery of steel, aluminum, and copper from building demolition waste and the end-of-life vehicles and appliances already results in the recycling of base metals, which achieves significant emission reductions. Higher collection rates, sorting efficiencies, and the alloy-specific sorting of metals to preserve the function of alloying elements while avoiding the contamination of base metals are important steps to further reduce emissions.

Journal ArticleDOI
16 Oct 2019-Joule
TL;DR: In this paper, the authors analyzed the economics of hydrogen-, nitrogen-, and carbon-based fuels made by carbon-neutral pathways in a post-fossil world where only water, air, and renewable electricity are available for fuel synthesis.

Journal ArticleDOI
TL;DR: N2 electrolysis, plasma-enabled N2 activation, and electro-thermochemical looping are three potential approaches for electrochemical ammonia synthesis; however, achieving high selectivity and energy efficiency remains challenging.
Abstract: Ammonia is a promising platform molecule for the future renewable energy infrastructure owing to its high energy density (when liquefied) and carbon-free nature. In particular, the interconversion between the chemical and electrical energies leveraging the nitrogen cycle could be an effective approach in mitigating the intermittency of renewable electricity production. However, efficient methods to store and release energy into and from ammonia, respectively, are still under development. Here, the latest developments in electrochemical ammonia synthesis and ammonia fuel cells are presented, and perspectives in the technical challenges and possible remedies are outlined. N2 electrolysis, plasma-enabled N2 activation, and electro-thermochemical looping are three potential approaches for electrochemical ammonia synthesis; however, achieving high selectivity and energy efficiency remains challenging. Direct ammonia fuel cells are suitable for a broad range of mobile and transportation applications but are limited by the lack of active catalysts for ammonia oxidation.

Journal ArticleDOI
TL;DR: Results clearly demonstrate the excellent visible-light-sensitive photocatalytic degradation of BPA over ZnFe2O4-TiO2 composite which has a great application potential for the decomposition of emerging contaminants in impaired waters.

Journal ArticleDOI
TL;DR: In this paper, the authors use a version of the American Customer Satisfaction Index (ACSI) model to demonstrate several important purchase-channel differences in the antecedents of customer satisfaction and its subsequent effect on customer loyalty.

Journal ArticleDOI
TL;DR: Numerical simulations of the Anak Krakatau tsunami highlight the significant hazard posed by relatively small-scale lateral volcanic collapses, which can occur en-masse, without any precursory signals, and are an efficient and unpredictable tsunami source.
Abstract: On Dec. 22, 2018, at approximately 20:55–57 local time, Anak Krakatau volcano, located in the Sunda Straits of Indonesia, experienced a major lateral collapse during a period of eruptive activity that began in June. The collapse discharged volcaniclastic material into the 250 m deep caldera southwest of the volcano, which generated a tsunami with runups of up to 13 m on the adjacent coasts of Sumatra and Java. The tsunami caused at least 437 fatalities, the greatest number from a volcanically-induced tsunami since the catastrophic explosive eruption of Krakatau in 1883 and the sector collapse of Ritter Island in 1888. For the first time in over 100 years, the 2018 Anak Krakatau event provides an opportunity to study a major volcanically-generated tsunami that caused widespread loss of life and significant damage. Here, we present numerical simulations of the tsunami, with state-of the-art numerical models, based on a combined landslide-source and bathymetric dataset. We constrain the geometry and magnitude of the landslide source through analyses of pre- and post-event satellite images and aerial photography, which demonstrate that the primary landslide scar bisected the Anak Krakatau volcano, cutting behind the central vent and removing 50% of its subaerial extent. Estimated submarine collapse geometries result in a primary landslide volume range of 0.22–0.30 km3, which is used to initialize a tsunami generation and propagation model with two different landslide rheologies (granular and fluid). Observations of a single tsunami, with no subsequent waves, are consistent with our interpretation of landslide failure in a rapid, single phase of movement rather than a more piecemeal process, generating a tsunami which reached nearby coastlines within ~30 minutes. Both modelled rheologies successfully reproduce observed tsunami characteristics from post-event field survey results, tide gauge records, and eyewitness reports, suggesting our estimated landslide volume range is appropriate. This event highlights the significant hazard posed by relatively small-scale lateral volcanic collapses, which can occur en-masse, without any precursory signals, and are an efficient and unpredictable tsunami source. Our successful simulations demonstrate that current numerical models can accurately forecast tsunami hazards from these events. In cases such as Anak Krakatau’s, the absence of precursory warning signals together with the short travel time following tsunami initiation present a major challenge for mitigating tsunami coastal impact.

Journal ArticleDOI
TL;DR: The role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution are discussed.
Abstract: The solar wind is a magnetized plasma and as such exhibits collective plasma behavior associated with its characteristic spatial and temporal scales. The characteristic length scales include the size of the heliosphere, the collisional mean free paths of all species, their inertial lengths, their gyration radii, and their Debye lengths. The characteristic timescales include the expansion time, the collision times, and the periods associated with gyration, waves, and oscillations. We review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory. We emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of the solar wind. We describe methods to measure in-situ properties of particles and fields. We then discuss the role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution.

Journal ArticleDOI
TL;DR: These Salphen-based COFs exhibit high crystallinity and specific surface area in addition to excellent chemical stability and the Cu(II)-Salphen COF displays high activity in the removal of superoxide radicals.
Abstract: The development of three-dimensional (3D) functionalized covalent–organic frameworks (COFs) is of critical importance for expanding their potential applications. However, the introduction of functional groups in 3D COFs remains largely unexplored. Herein, we report the first example of 3D Salphen-based COFs (3D-Salphen-COFs) and their metal-containing counterparts (3D-M-Salphen-COFs). These Salphen-based COFs exhibit high crystallinity and specific surface area in addition to excellent chemical stability. Furthermore, the Cu(II)-Salphen COF displays high activity in the removal of superoxide radicals. This study not only presents a new pathway to construct 3D functionalized COFs but also promotes their applications in biology and medicine.

Journal ArticleDOI
TL;DR: Overall, the results indicate that intraspecific adjustments along the water availability gradient relied primarily on changes in resource allocation between sapwood and leaf area and in leaf water relations.
Abstract: Trait variability in space and time allows plants to adjust to changing environmental conditions. However, we know little about how this variability is distributed and coordinated at different organizational levels. For six dominant tree species in northeastern Spain (three Fagaceae and three Pinaceae) we quantified the inter- and intraspecific variability of a set of traits along a water availability gradient. We measured leaf mass per area (LMA), leaf nitrogen (N) concentration, carbon isotope composition in leaves (δ13 C), stem wood density, the Huber value (Hv, the ratio of cross-sectional sapwood area to leaf area), sapwood-specific and leaf-specific stem hydraulic conductivity, vulnerability to xylem embolism (P50 ) and the turgor loss point (Ptlp ). Differences between families explained the largest amount of variability for most traits, although intraspecific variability was also relevant. Species occupying wetter sites showed higher N, P50 and Ptlp , and lower LMA, δ13 C and Hv. However, when trait relationships with water availability were assessed within species they held only for Hv and Ptlp . Overall, our results indicate that intraspecific adjustments along the water availability gradient relied primarily on changes in resource allocation between sapwood and leaf area and in leaf water relations.

Journal ArticleDOI
TL;DR: In this article, an ideal triangular lattice of effective Jeff's = 1/2 moments with no inherent site disorder was investigated, and it was shown that an external magnetic field strongly perturbs the quantum disordered ground state and induces a clear transition into a collinear ordered state, consistent with a long predicted up-up-down structure for a triangular-lattice XXZ Hamiltonian driven by quantum fluctuations.
Abstract: Antiferromagnetically coupled S = 1/2 spins on an isotropic triangular lattice are the paradigm of frustrated quantum magnetism, but structurally ideal realizations are rare. Here, we investigate NaYbO2, which hosts an ideal triangular lattice of effective Jeff = 1/2 moments with no inherent site disorder. No signatures of conventional magnetic order appear down to 50 mK, strongly suggesting a quantum spin liquid ground state. We observe a two-peak specific heat and a nearly quadratic temperature dependence, in agreement with expectations for a two-dimensional Dirac spin liquid. Application of a magnetic field strongly perturbs the quantum disordered ground state and induces a clear transition into a collinear ordered state, consistent with a long-predicted up–up–down structure for a triangular-lattice XXZ Hamiltonian driven by quantum fluctuations. The observation of spin liquid signatures in zero field and quantum-induced ordering in intermediate fields in the same compound demonstrates an intrinsically quantum disordered ground state. We conclude that NaYbO2 is a model, versatile platform for exploring spin liquid physics with full tunability of field and temperature. At zero magnetic field, the triangular-lattice antiferromagnet NaYbO2 shows the absence of long-range magnetic order down to 50 mK, consistent with quantum spin liquid behaviour. An external field renders the system a collinear ordered phase.

Journal ArticleDOI
Zi Wang1, Tiantian Li1, Anishkumar Soman1, Dun Mao1, Thomas Kananen1, Tingyi Gu1 
TL;DR: A one-dimensional high-contrast transmitarray metasurface-based lens defined on a standard silicon-on-insulator substrate and functionalities of Fourier transformation and differentiation are demonstrated.
Abstract: Metasurfaces can be programmed for a spatial transformation of the wavefront, thus allowing parallel optical signal processing on-chip within an ultracompact dimension. On-chip metasurfaces have been implemented with two-dimensional periodic structures, however, their inherent scattering loss limits their large-scale implementation. The scattering can be minimized in single layer high-contrast transmitarray (HCTA) metasurface. Here we demonstrate a one-dimensional HCTA based lens defined on a standard silicon-on-insulator substrate, with its high transmission (<1 dB loss) maintained over a 200 nm bandwidth. Three layers of the HCTAs are cascaded for demonstrating meta-system functionalities of Fourier transformation and differentiation. The meta-system design holds potential for realizing on-chip transformation optics, mathematical operations and spectrometers, with applications in areas of imaging, sensing and quantum information processing. Metasurfaces can be programmed for a spatial transformation of the wavefront, allowing on-chip optical signal processing. Here, the authors demonstrate a one-dimensional high-contrast transmitarray metasurface-based lens on SOI substrate and demonstrate functionalities of Fourier transformation and differentiation.

Journal ArticleDOI
TL;DR: In this article, the authors examined a set of readiness indicators in kindergarten and identified which domains were stronger predictors of academic and social trajectories through grade 3 and from grades 3 to 5.

Journal ArticleDOI
TL;DR: It is demonstrated that C–N bonds can be formed through co-electrolysis of CO and NH3 with acetamide selectivity of nearly 40% at industrially relevant reaction rates.
Abstract: The electroreduction of CO2 is a promising technology for carbon utilization. Although electrolysis of CO2 or CO2-derived CO can generate important industrial multicarbon feedstocks such as ethylene, ethanol, n-propanol and acetate, most efforts have been devoted to promoting C–C bond formation. Here, we demonstrate that C–N bonds can be formed through co-electrolysis of CO and NH3 with acetamide selectivity of nearly 40% at industrially relevant reaction rates. Full-solvent quantum mechanical calculations show that acetamide forms through nucleophilic addition of NH3 to a surface-bound ketene intermediate, a step that is in competition with OH– addition, which leads to acetate. The C–N formation mechanism was successfully extended to a series of amide products through amine nucleophilic attack on the ketene intermediate. This strategy enables us to form carbon–heteroatom bonds through the electroreduction of CO, expanding the scope of products available from CO2 reduction. The electroreduction of CO2-derived CO is a promising technology for the sustainable production of value-added chemicals. Now, it is shown how C–N bonds can be formed electrochemically through CO electroreduction on a Cu surface in the presence of amines. The formation of acetamides is observed through nucleophilic addition to a ketene intermediate.

Journal ArticleDOI
TL;DR: The state-of-the-art AELs and PemELs along with the current status of HEMELs are discussed in terms of their positive and negative aspects and electrocatalyst, membrane, and ionomer development needs for HEMels and benchmark electrocatalysts interms of the cost-performance tradeoff.
Abstract: Hydrogen is an ideal alternative energy carrier to generate power for all of society's energy demands including grid, industrial, and transportation sectors. Among the hydrogen production methods, water electrolysis is a promising method because of its zero greenhouse gas emission and its compatibility with all types of electricity sources. Alkaline electrolyzers (AELs) and proton exchange membrane electrolyzers (PEMELs) are currently used to produce hydrogen. AELs are commercially mature and are used in a variety of industrial applications, while PEMELs are still being developed and find limited application. In comparison with AELs, PEMELs have more compact structure and can achieve higher current densities. Recently, however, an alternative technology to PEMELs, hydroxide exchange membrane electrolyzers (HEMELs), has gained considerable attention due to the possibility to use platinum group metal (PGM)-free electrocatalysts and cheaper membranes, ionomers, and construction materials and its potential to achieve performance parity with PEMELs. Here, the state-of-the-art AELs and PEMELs along with the current status of HEMELs are discussed in terms of their positive and negative aspects. Additionally discussed are electrocatalyst, membrane, and ionomer development needs for HEMELs and benchmark electrocatalysts in terms of the cost-performance tradeoff.