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On complete reducibility for infinite-dimensional Lie algebras
No full textIn this paper we study the complete reducibility of representations of infinite-
dimensional Lie algebras from the perspective of representation theory of vertex algebras.Israel Science Foundation (grant No. 1142/07)National Science Foundation (U.S.) (Grant No. DMS-0501395
On the cost of electrodialysis for the desalination of high salinity feeds
Full text linkWe propose the use of electrodialysis to desalinate produced waters from shale formations in order to facilitate water reuse in subsequent hydraulic fracturing processes. We focus on establishing the energy and equipment size required for the desalination of feed waters containing total dissolved solids of up to 192,000 ppm, and we do this by experimentally replicating the performance of a 10-stage electrodialysis system. We find that energy requirements are similar to current vapour compression desalination processes for feedwaters ranging between roughly 40,000-90,000 ppm TDS, but we project water costs to potentially be lower. We also find that the cost per unit salt removed is significantly lower when removed from a high salinity stream as opposed to a low salinity stream, pointing towards the potential of ED to operate as a partial desalination process for high salinity waters. We then develop a numerical model for the system, validate it against experimental results and use this model to minimise salt removal costs by optimising the stack voltage. We find that the higher the salinity of the water from which salt is removed the smaller should be the ratio of the electrical current to its limiting value. We conclude, on the basis of energy and equipment costs, that electrodialysis processes are potentially feasible for the desalination of high salinity waters but require further investigation of robustness to fouling under field conditions.Massachusetts Institute of Technology. Office of the Dean for Graduate Education (Hugh Hampton Young Memorial Fellowship)MIT Energy Initiativ
Persistent hepatitis C virus infection in microscale primary human hepatocyte cultures
No full textHepatitis C virus (HCV) remains a major public health problem, affecting approximately 130 million people worldwide. HCV infection can lead to cirrhosis, hepatocellular carcinoma, and end-stage liver disease, as well as extrahepatic complications such as cryoglobulinemia and lymphoma. Preventative and therapeutic options are severely limited; there is no HCV vaccine available, and nonspecific, IFN-based treatments are frequently ineffective. Development of targeted antivirals has been hampered by the lack of robust HCV cell culture systems that reliably predict human responses. Here, we show the entire HCV life cycle recapitulated in micropatterned cocultures (MPCCs) of primary human hepatocytes and supportive stroma in a multiwell format. MPCCs form polarized cell layers expressing all known HCV entry factors and sustain viral replication for several weeks. When coupled with highly sensitive fluorescence- and luminescence-based reporter systems, MPCCs have potential as a high-throughput platform for simultaneous assessment of in vitro efficacy and toxicity profiles of anti-HCV therapeutics.National Institutes of Health (U.S.) (Grant R01 DK56966)National Institutes of Health (U.S.) (NIH Roadmap for Medical Research Grant 1 R01 DK085713-01
Public health impacts of excess NOx emissions from Volkswagen diesel passenger vehicles in Germany
No full textIn September 2015, the Volkswagen Group (VW) admitted the use of 'defeat devices' designed to lower emissions measured during VW vehicle testing for regulatory purposes. Globally, 11 million cars sold between 2008 and 2015 are affected, including about 2.6 million in Germany. On-road emissions tests have yielded mean on-road NO[subscript x] emissions for these cars of 0.85 g km[superscript −1], over four times the applicable European limit of 0.18 g km[superscript −1]. This study estimates the human health impacts and costs associated with excess emissions from VW cars driven in Germany. A distribution of on-road emissions factors is derived from existing measurements and combined with sales data and a vehicle fleet model to estimate total excess NO[subscript x] emissions. These emissions are distributed on a 25 by 28 km grid covering Europe, using the German Federal Environmental Protection Agency's (UBA) estimate of the spatial distribution of NO[subscript x] emissions from passenger cars in Germany. We use the GEOS-Chem chemistry-transport model to predict the corresponding increase in population exposure to fine particulate matter and ozone in the European Union, Switzerland, and Norway, and a set of concentration-response functions to estimate mortality outcomes in terms of early deaths and of life-years lost. Integrated over the sales period (2008–2015), we estimate median mortality impacts from VW excess emissions in Germany to be 1200 premature deaths in Europe, corresponding to 13 000 life-years lost and 1.9 billion EUR in costs associated with life-years lost. Approximately 60% of mortality costs occur outside Germany. For the current fleet, we estimate that if on-road emissions for all affected VW vehicles in Germany are reduced to the applicable European emission standard by the end of 2017, this would avert 29 000 life-years lost and 4.1 billion 2015 EUR in health costs (median estimates) relative to a counterfactual case with no recall.Germany. Umweltbundesamt (UBA
The American Institute for Manufacturing Integrated Photonics: advancing the ecosystem
Full text linkThe American Institute for Manufacturing Integrated Photonics (AIM Photonics) is focused on developing an end-to-end integrated photonics ecosystem in the U.S., including domestic foundry access, integrated design tools, automated packaging, assembly and test, and workforce development. This paper describes how the institute has been structured to achieve these goals, with an emphasis on advancing the integrated photonics ecosystem. Additionally, it briefly highlights several of the technological development targets that have been identified to provide enabling advances in the manufacture and application of integrated photonics
Single-Cell Analysis Reveals Functionally Distinct Classes within the Planarian Stem Cell Compartment
Full text linkPlanarians are flatworms capable of regenerating any missing body region. This capacity is mediated by neoblasts, a proliferative cell population that contains pluripotent stem cells. Although population-based studies have revealed many neoblast characteristics, whether functionally distinct classes exist within this population is unclear. Here, we used high-dimensional single-cell transcriptional profiling from over a thousand individual neoblasts to directly compare gene expression fingerprints during homeostasis and regeneration. We identified two prominent neoblast classes that we named ζ (zeta) and σ (sigma). Zeta-neoblasts encompass
specified cells that give rise to an abundant postmitotic lineage including epidermal cells, and are
not required for regeneration. By contrast, sigma-neoblasts proliferate in response to injury,
possess broad lineage capacity, and can give rise to zeta-neoblasts. These findings present a new
view of planarian neoblasts, in which the population is comprised of two major and functionally
distinct cellular compartments.Human Frontier Science Program (Strasbourg, France)National Institutes of Health (U.S.) (Grant R01GM080639
"Data comes from the real world": A Constructionist Approach to Mainstreaming K12 Data Science Education
No full textSIGCSE Virtual 2024, December 5–8, 2024, Virtual Event, NC, USAData science is emerging as a crucial 21st-century competence, influencing professional practices from citing evidence when advocating for social change to developing artificial intelligence (AI) models. For middle and high school students, data science can put formerly decontextualized subjects into real-world scenarios. Many existing curricula, however, lack authenticity and personal relevance for students. A critique of data science courseware cites the lack of "author proximity," in which students do not contribute to the data's production or see their personal experiences reflected in the data. This paper introduces a novel data science curriculum to scaffold middle and high school students in undertaking real-world data science practices. Through project-based learning modules, the curriculum engages students in investigating solutions to community-based problems through visualization and analysis of live sensor data and public data sets. Materials include formative assessments to help educators (especially those from non-math and computing backgrounds) measure their students' abilities to identify statistical patterns, critically evaluate data biases, and make predictions. As we pilot and co-design with teachers, we will look closely at whether the curriculum's resources can successfully support non-technical practitioners engaging in an integrated curriculum
An abundant bacterial phylum with nitrite-oxidizing potential in oligotrophic marine sediments
No full textNitrite-oxidizing bacteria (NOB) are important nitrifiers whose activity regulates the availability of nitrite and dictates the magnitude of nitrogen loss in ecosystems. In oxic marine sediments, ammonia-oxidizing archaea (AOA) and NOB together catalyze the oxidation of ammonium to nitrate, but the abundance ratios of AOA to canonical NOB in some cores are significantly higher than the theoretical ratio range predicted from physiological traits of AOA and NOB characterized under realistic ocean conditions, indicating that some NOBs are yet to be discovered. Here we report a bacterial phylum Candidatus Nitrosediminicolota, members of which are more abundant than canonical NOBs and are widespread across global oligotrophic sediments. Ca. Nitrosediminicolota members have the functional potential to oxidize nitrite, in addition to other accessory functions such as urea hydrolysis and thiosulfate reduction. While one recovered species (Ca. Nitrosediminicola aerophilus) is generally confined within the oxic zone, another (Ca. Nitrosediminicola anaerotolerans) additionally appears in anoxic sediments. Counting Ca. Nitrosediminicolota as a nitrite-oxidizer helps to resolve the apparent abundance imbalance between AOA and NOB in oxic marine sediments, and thus its activity may exert controls on the nitrite budget
An empirical design theory for compact drip irrigation emitters
No full textWith freshwater reserves rapidly diminishing, sustainable irrigation technologies such as drip irrigation must be widely adopted to meet the food demand of a growing global population. Drip irrigation uses a network of pressurized tubes with flow-regulating devices called emitters to minimize conveyance losses, saving up to 65% water compared to flood and furrow irrigation. However, its widespread adoption remains limited due to its high initial capital costs, up to 55% of which are driven by the emitters and tubes. The plastic material consumed by the emitters and tubes is a major driver of their cost. To directly address this cost barrier, this paper details a hydraulic design theory for compact emitters having a common commercial architecture: uniform depth labyrinths with symmetric, triangular teeth. The theory uses geometric symmetry, manufacturing considerations, and clogging constraints to identify three design parameters in emitters that can be used to tune their hydraulic performance without significantly affecting their material volume: the tooth tip gap, labyrinth depth, and the number of tooth pairs. This knowledge allows designers to minimize emitter volume and set architecture a priori, and then use an empirically derived hydraulic model that uses the selected parameters as input arguments to tune flow rate independently. This ensures faster and simpler design iterations. The theory enabled a reduction in emitter material consumption by 67% compared to at least one commercial emitter, potentially cutting the initial capital cost of drip irrigation by up to 10%, making this already sustainable irrigation technology more globally accessible
