1,855 research outputs found

    Effects of decision-making on the transport costs across complex networks

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    We analyze the effects of agents' decisions on the creation of congestion on a centralized network with ring-and-hub topology. We show that there are two classes of agents each displaying a distinct set of behaviours. The dynamics of the system are driven by an interplay between the formation of, and transition between, unique stable states that arise as the network is varied. We show how the flow of objects across the network can be understood in terms of the ordering and allocation of strategies. Our results show that the existence of congestion in a network is a dynamic process that is as much dependent on the agents' decisions as it is on the structure of the network itself.Comment: Special Issue on Complex Networks, edited by Dirk Helbin

    Expression of active human sialyltransferase ST6GalNAcI in Escherichia coli

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    Georgios Skretas, Sean Carroll, and George Georgiou are with the Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712, USA -- George Georgiou is with the Department of Biomedical Engineering, University of Texas at Austin and the Section of Microbiology and Molecular Genetics, University of Texas at Austin, Austin, TX 78712, USA -- Georgios Skretas and George Georgiou are with the Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA -- Shawn DeFrees, Karl F. Johnson, and Marc F. Schwartz are with Neose Technologies Inc, 102 Rock Road, Horsham, PA, 19044, USABackground: The presence of terminal, surface-exposed sialic acid moieties can greatly enhance the in vivo half-life of glycosylated biopharmaceuticals and improve their therapeutic efficacy. Complete and homogeneous sialylation of glycoproteins can be efficiently performed enzymically in vitro but this process requires large amounts of catalytically active sialyltransferases. Furthermore, standard microbial hosts used for large-scale production of recombinant enzymes can only produce small quantities of glycosyltransferases of animal origin, which lack catalytic activity. Results and conclusion: In this work, we have expressed the human sialyltransferase ST6GalNAc I (ST6), an enzyme that sialylates O-linked glycoproteins, in Escherichia coli cells. We observed that wild-type bacterial cells are able to produce only very small amounts of soluble ST6 enzyme. We have found, however, that engineered bacterial strains which possess certain types of oxidative cytoplasm or which co-express the molecular chaperones/co-chaperones trigger factor, DnaK/DnaJ, GroEL/GroES, and Skp, can produce greatly enhanced amounts of soluble ST6. Furthermore, we have developed a novel high-throughput assay for the detection of sialyltransferase activity and used it to demonstrate that the bacterially expressed ST6 enzyme is active and able to transfer sialic acid onto a desialylated O-glycoprotein, bovine submaxillary mucin. To the best of our knowledge, this is the first example of expression of active human sialyltransferase in bacteria. This system may be used as a starting point for the evolution of sialyltransferases with better expression characteristics or altered donor/acceptor specificities.Chemical EngineeringBiomedical EngineeringInstitute for Cellular and Molecular [email protected]

    Ongoing initiatives within the Scottish National Health Service to affect the prescribing of selective serotonin reuptake inhibitors and their influence

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    Aim: Increasing use of selective serotonin-reuptake inhibitors (SSRIs) in Scotland, coupled with safety concerns with some SSRIs, and the increasing availability of generic SSRIs, have resulted in multiple initiatives to improve the quality and efficiency of their prescribing in Scotland. Our aim is to assess their influence to provide future direction. Materials & methods: The prescription costs analysis database was used to document utilization and expenditure on SSRIs between 2001 and 2017 alongside documenting the initiatives. Results: Multiple interventions over the years increased international nonproprietary name prescribing up to 99.9% lowering overall costs. This, coupled with initiatives to limit escitalopram prescribing due to concerns with its value, resulted in a 73.7% reduction in SSRI expenditure between 2001 and 2017 despite a 2.34-fold increase in utilization. Safety warnings resulted in a significant reduction in the prescribing of paroxetine, citalopram and escitalopram alongside a significant increase in sertraline Conclusion: Multiple initiatives have increased the quality and efficiency of SSRI prescribing in Scotland providing direction to others

    Winding effects on brane/anti-brane pairs

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    We study a brane/anti-brane configuration which is separated along a compact direction by constructing a tachyon effective action which takes into account transverse scalars. Such an action is relevant in the study of HQCD model of Sakai and Sugimoto of chiral symmetry breaking, where the size of the compact circle sets the confinement scale. Our approach is motivated by string theory orbifold constructions and gives a route to model inhomogeneous tachyon decay. We illustrate the techniques involved with a relatively simple example of a harmonic oscillator on a circle. We will then repeat the analysis for the Sakai-Sugimoto model and show that by integrating out the winding modes will provide us with a renormalized action with a lower energy than that of truncating to zero winding sector.Comment: 21 pages, 3 figures. v3: discussion and references added, published versio

    The fables of pity: Rousseau, Mandeville and the animal-fable

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    Copyright @ 2012 Edinburgh University PressPrompted by Derrida’s work on the animal-fable in eighteenth-century debates about political power, this article examines the role played by the fiction of the animal in thinking of pity as either a natural virtue (in Rousseau’s Second Discourse) or as a natural passion (in Mandeville’s The Fable of the Bees). The war of fables between Rousseau and Mandeville – and their hostile reception by Samuel Johnson and Adam Smith – reinforce that the animal-fable illustrates not so much the proper of man as the possibilities and limitations of a moral philosophy that is unable to address the political realities of the state

    Shallow seafloor gas emissions near Heard and McDonald Islands on the Kerguelen Plateau, Southern Indian Ocean

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    © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Spain, E. A., Johnson, S. C., Hutton, B., Whittaker, J. M., Lucieer, V., Watson, S. J., Fox, J. M., Lupton, J., Arculus, R., Bradney, A., & Coffin, M. F. Shallow seafloor gas emissions near Heard and McDonald Islands on the Kerguelen Plateau, Southern Indian Ocean. Earth and Space Science, 7(3), (2020): e2019EA000695, doi:10.1029/2019EA000695.Bubble emission mechanisms from submerged large igneous provinces remains enigmatic. The Kerguelen Plateau, a large igneous province in the southern Indian Ocean, has a long sustained history of active volcanism and glacial/interglacial cycles of sedimentation, both of which may cause seafloor bubble production. We present the results of hydroacoustic flare observations around the underexplored volcanically active Heard Island and McDonald Islands on the Central Kerguelen Plateau. Flares were observed with a split‐beam echosounder and characterized using multifrequency decibel differencing. Deep‐tow camera footage, water properties, water column ÎŽ3He, subbottom profile, and sediment ÎŽ13C and ÎŽ34S data were analyzed to consider flare mechanisms. Excess ÎŽ3He near McDonald Islands seeps, indicating mantle‐derived input, suggests proximal hydrothermal activity; McDonald Islands flares may thus indicate CO2, methane, and other minor gas bubbles associated with shallow diffuse hydrothermal venting. The Heard Island seep environment, with subbottom acoustic blanking in thick sediment, muted 3He signal, and ÎŽ13C and ÎŽ34S fractionation factors, suggest that Heard Island seeps may either be methane gas (possibly both shallow biogenic methane and deeper‐sourced thermogenic methane related to geothermal heat from onshore volcanism) or a combination of methane and CO2, such as seen in sediment‐hosted geothermal systems. These data provide the first evidence of submarine gas escape on the Central Kerguelen Plateau and expand our understanding of seafloor processes and carbon cycling in the data‐poor southern Indian Ocean. Extensive sedimentation of the Kerguelen Plateau and additional zones of submarine volcanic activity mean additional seeps or vents may lie outside the small survey area proximal to the islands.We thank the Australian Marine National Facility (MNF) for its support in the form of sea time on RV Investigator , support personnel, scientific equipment, and data management. We also thank the captain, crew, and fellow scientists of RV Investigator voyage IN2016_V01. We also thank specifically the following: T. Martin, F. Cooke, S. L. Sow, N. Bax, J. Ford, and F. Althaus, CSIRO (Commonwealth Scientific and Industrial Research Organisation); Echoview Software Pty. Ltd. (Hobart, Australia); C. Dietz and C. Cook, Central Science Laboratory, University of Tasmania; C. Wilkinson and T. Baumberger, National Oceanic and Atmospheric Administration; R. Carey, University of Tasmania; T. Holmes, Institute for Marine and Antarctic Studies, University of Tasmania; N. Polmear; and A. Post, Geoscience Australia. The overall science of the project is supported by Australian Antarctic Science Program (AASP) grant 4338. E.S.' PhD research is supported by the Australian Research Council's Special Research Initiative Antarctic Gateway Partnership (Project ID SR140300001) and by an Australian Government Research Training Program Scholarship. S.C.J. is supported by iCRAG under SFI, European Regional Development Fund, and industry partners, as well as ANZIC‐IODP. J.M.W. is supported by ARC grant DE140100376 and DP180102280. This is PMEL publication number 4910. All IN2016_V01 data and samples acquired on IN2016_V01 are made publicly available in accordance with MNF policy

    The GALEX Arecibo SDSS Survey II: The Star Formation Efficiency of Massive Galaxies

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    We use measurements of the HI content, stellar mass and star formation rates in ~190 massive galaxies with stellar masses greater than 10^10 Msun, obtained from the Galex Arecibo SDSS Survey (GASS) described in Paper I (Catinella et al. 2010) to explore the global scaling relations associated with the bin-averaged ratio of the star formation rate over the HI mass, which we call the HI-based star formation efficiency (SFE). Unlike the mean specific star formation rate, which decreases with stellar mass and stellar mass surface density, the star formation efficiency remains relatively constant across the sample with a value close to SFE = 10^-9.5 yr^-1 (or an equivalent gas consumption timescale of ~3 Gyr). Specifically, we find little variation in SFE with stellar mass, stellar mass surface density, NUV-r color and concentration. We interpret these results as an indication that external processes or feedback mechanisms that control the gas supply are important for regulating star formation in massive galaxies. An investigation into the detailed distribution of SFEs reveals that approximately 5% of the sample shows high efficiencies with SFE > 10^-9 yr^-1, and we suggest that this is very likely due to a deficiency of cold gas rather than an excess star formation rate. Conversely, we also find a similar fraction of galaxies that appear to be gas-rich for their given specific star-formation rate, although these galaxies show both a higher than average gas fraction and lower than average specific star formation rate. Both of these populations are plausible candidates for "transition" galaxies, showing potential for a change (either decrease or increase) in their specific star formation rate in the near future. We also find that 36+/-5% of the total HI mass density and 47+/-5% of the total SFR density is found in galaxies with stellar mass greater than 10^10 Msun. [abridged]Comment: 18 pages, 11 figures. Accepted for publication in MNRAS. GASS publications and released data can be found at http://www.mpa-garching.mpg.de/GASS/index.ph

    Importance of Driving and Potential Impact of Driving Cessation for Rural and Urban Older Adults

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    PurposeAnalyses compared older drivers from urban, suburban, and rural areas on perceived importance of continuing to drive and potential impact that driving cessation would have on what they want and need to do.MethodsThe AAA LongROAD Study is a prospective study of driving behaviors, patterns, and outcomes of older adults. A cohort of 2,990 women and men 65‐79 years of age was recruited during 2015‐2017 from health systems or primary care practices near 5 study sites in different parts of the United States. Participants were classified as living in urban, surburban, or rural areas and were asked to rate the importance of driving and potential impact of driving cessation. Logistic regression models adjusted for sociodemographic and driving‐related characteristics.FindingsThe percentages of older drivers rating driving as “completely important” were 76.9%, 79.0%, and 83.8% for urban, suburban, and rural drivers, respectively (P = .009). The rural drivers were also most likely to indicate driving cessation would have a high impact on what they want or need to do (P < .001). After adjustment for sociodemographic and driving‐related characteristics, there was a 2‐fold difference for rural versus urban older drivers in odds that driving cessation would have a high impact on what they need to do (OR = 2.03; 95% CI: 1.60‐2.58).ConclusionsOlder drivers from rural areas were more likely to rate driving as highly important and the prospect of driving cessation as very impactful. Strategies to enhance both the ability to drive safely and the accessibility of alternative sources of transportation may be especially important for older rural adults.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153160/1/jrh12369_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153160/2/jrh12369.pd
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