2,236 research outputs found

    Mars Dust Storms: Interannual Variability and Chaos

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    The hypothesis is that the global climate system, consisting of atmospheric dust interacting with the circulation, produces its own interannual variability when forced at the annual frequency. The model has two time-dependent variables representing the amount of atmospheric dust in the northern and southern hemispheres, respectively. Absorption of sunlight by the dust drives a cross-equatorial Hadley cell that brings more dust into the heated hemisphere. The circulation decays when the dust storm covers the globe. Interannual variability manifests itself either as a periodic solution in which the period is a multiple of the Martian year, or as an aperiodic (chaotic) solution that never repeats. Both kinds of solution are found in the model, lending support to the idea that interannual variability is an intrinsic property of the global climate system. The next step is to develop a hierarchy of dust-circulation models capable of being integrated for many years

    A Nova Web Application for Population Viability and Sustainable Harvesting Analyses

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    Population viability analyses are used to assess the probability that a particular population of individuals will persist as a self-reproducing, ecologically viable entity for a specified period of time. Such models are typically cast as Markov processes that may inter alia include demographic structure (e.g. age, stage, sex), ecological processes through the incorporation of density-dependent reproduction or survival functions, viability thresholds that trigger remedial interventions when breached (e.g. removal of individuals to protect environments), metapopulation structure, stocking, harvesting or translocations of the population. These models can also be used to assess the impacts of harvesting strategies when they include population removal options. Here we present a general Nova modeling framework that integrates all of the above features and generates distributions of outcomes through repeated simulations. The framework incorporates the most relevant ecosystem structures, including metapopulation structure with associated connectivity and movement parameters, age/stage class structure with population-specific life history data, demographic and environmental stochasticity components, and management interventions including off-take, translocation, and stocking components. The NOVA PVA model is available as a responsively configured web application that can be run locally in a browser or on high performance computing systems controlled by a browser-based dashboard. In this talk the structure of the model will be discussed and the operation of the web application will be demonstrated

    Method and Apparatus for Non-Destructive Evaluation of Materials

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    Methods and apparatus for characterizing composite materials for manufacturing quality assurance (QA), periodic inspection during the useful life, or for forensic analysis/material testing. System are provided that relate eddy-current sensor responses to the fiber layup of a composite structure, the presence of impact damage on a composite structure with or without a metal liner, volumetric stress within the composite, fiber tow density, and other NDE inspection requirements. Also provided are systems that determine electromagnetic material properties and material dimensions of composite materials from capacitive sensor inspection measurements. These properties are related to the presence of buried defects in non-conductive composite materials, moisture ingress, aging of the material due to service or environmental/thermal exposure, or changes in manufacturing quality

    Source-to-sink magnetic properties of NE Saharan dust in Eastern Mediterranean marine sediments: review and paleoenvironmental implications

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    We present a review of the magnetic properties of NE Saharan dust that was conducted, following a source-to-sink approach, to unravel the paleoclimatic significance of environmental magnetic records from Eastern Mediterranean marine sediments. Our synthesis indicates that pedogenic hematite, which formed during past wetter Green Sahara periods (GSPs), is the most common magnetic mineral in Eastern Mediterranean marine sediments as a result of its eolian transportation, along with smaller amounts of lithogenic hematite, from the NE Sahara. Coupled with the limited impact of reductive sedimentary diagenesis on hematite abundances in Eastern Mediterranean Sea sediments, this indicates that hematite concentrations provide reliable quantitative estimates of NE Saharan dust supply. Our results indicate that variations in NE Saharan dust supply record an on-off mechanism in which a key control on eolian input is provided by the monsoon-driven spread and retreat of savannah vegetation through the Sahara. Magnetite/maghemite is also a common magnetic mineral in NE Saharan dust, and also formed mainly pedogenically during GSPs but in much smaller amounts compared to hematite. Limited production of magnetite/maghemite in the source area during GSPs, along with the later imprint of diagenetic processes, indicates that magnetite/maghemite abundances cannot be used to estimate dust inputs from the NE Sahara. Goethite cannot be used either to estimate variations in NE Saharan dust supply, because its occurrence in Eastern Mediterranean marine sediments also appears to be linked to fluvial inputs. Our results reinforce the view that a source-to-sink approach should be routinely conducted in environmental magnetic studies to understand the complex combination of processes involved in the production, transportation, sedimentation, and diagenetic evolution of magnetic minerals in sedimentary environments. © 2015 Larrasoaña, Roberts, Liu, Lyons, Oldfield, Rohling and Heslop.A Rand D H gratefully acknowledge support from Australian Research Council grant DP110105419 , and ER acknowledges support from 2012 Australia Laureate Fellowship FL120100050.Peer reviewe

    Method and Apparatus for Non-Destructive Evaluation of Materials

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    Methods and apparatus for characterizing composite materials for manufacturing quality assurance (QA), periodic inspection during the useful life, or for forensic analysis/material testing. System are provided that relate eddy-current sensor responses to the fiber layup of a composite structure, the presence of impact damage on a composite structure with or without a metal liner, volumetric stress within the composite, fiber tow density, and other NDE inspection requirements. Also provided are systems that determine electromagnetic material properties and material dimensions of composite materials from capacitive sensor inspection measurements. These properties are related to the presence of buried defects in non-conductive composite materials, moisture ingress, aging of the material due to service or environmental/thermal exposure, or changes in manufacturing quality

    A systematic review of the energy and climate impacts of teleworking

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    Information and communication technologies (ICTs) increasingly enable employees to work from home and other locations (‘teleworking’). This study explores the extent to which teleworking reduces the need to travel to work and the consequent impacts on economy-wide energy consumption. Methods/Design: The paper provides a systematic review of the current state of knowledge of the energy impacts of teleworking. This includes the energy savings from reduced commuter travel and the indirect impacts on energy consumption associated with changes in non-work travel and home energy consumption. The aim is to identify the conditions under which teleworking leads to a net reduction in economy-wide energy consumption, and the circumstances where benefits may be outweighed by unintended impacts. The paper synthesises the results of 39 empirical studies, identified through a comprehensive search of 9,000 published articles. Review results/Synthesis: Twenty six of the 39 studies suggest that teleworking reduces energy use, and only eight studies suggest that teleworking increases, or has a neutral impact on energy use. However, differences in the methodology, scope and assumptions of the different studies make it difficult to estimate ‘average’ energy savings. The main source of savings is the reduced distance travelled for commuting, potentially with an additional contribution from lower office energy consumption. However, the more rigorous studies that include a wider range of impacts (e.g. non-work travel or home energy use) generally find smaller savings. Discussion: Despite the generally positive verdict on teleworking as an energy-saving practice, there are numerous uncertainties and ambiguities about its actual or potential benefits. These relate to the extent to which teleworking may lead to unpredictable increases in non-work travel and home energy use that may outweigh the gains from reduced work travel. The available evidence suggests that economy-wide energy savings are typically modest, and in many circumstances could be negative or non-existent

    Sepsis prediction for the general ward setting

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    OBJECTIVE: To develop and evaluate a sepsis prediction model for the general ward setting and extend the evaluation through a novel pseudo-prospective trial design. DESIGN: Retrospective analysis of data extracted from electronic health records (EHR). SETTING: Single, tertiary-care academic medical center in St. Louis, MO, USA. PATIENTS: Adult, non-surgical inpatients admitted between January 1, 2012 and June 1, 2019. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of the 70,034 included patient encounters, 3.1% were septic based on the Sepsis-3 criteria. Features were generated from the EHR data and were used to develop a machine learning model to predict sepsis 6-h ahead of onset. The best performing model had an Area Under the Receiver Operating Characteristic curve (AUROC or c-statistic) of 0.862 ± 0.011 and Area Under the Precision-Recall Curve (AUPRC) of 0.294 ± 0.021 compared to that of Logistic Regression (0.857 ± 0.008 and 0.256 ± 0.024) and NEWS 2 (0.699 ± 0.012 and 0.092 ± 0.009). In the pseudo-prospective trial, 388 (69.7%) septic patients were alerted on with a specificity of 81.4%. Within 24 h of crossing the alert threshold, 20.9% had a sepsis-related event occur. CONCLUSIONS: A machine learning model capable of predicting sepsis in the general ward setting was developed using the EHR data. The pseudo-prospective trial provided a more realistic estimation of implemented performance and demonstrated a 29.1% Positive Predictive Value (PPV) for sepsis-related intervention or outcome within 48 h

    Material condition assessment with eddy current sensors

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    Eddy current sensors and sensor arrays are used for process quality and material condition assessment of conducting materials. In an embodiment, changes in spatially registered high resolution images taken before and after cold work processing reflect the quality of the process, such as intensity and coverage. These images also permit the suppression or removal of local outlier variations. Anisotropy in a material property, such as magnetic permeability or electrical conductivity, can be intentionally introduced and used to assess material condition resulting from an operation, such as a cold work or heat treatment. The anisotropy is determined by sensors that provide directional property measurements. The sensor directionality arises from constructs that use a linear conducting drive segment to impose the magnetic field in a test material. Maintaining the orientation of this drive segment, and associated sense elements, relative to a material edge provides enhanced sensitivity for crack detection at edges

    Healthcare-associated infections (HAIs) during the coronavirus disease 2019 (COVID-19) pandemic: A time-series analysis

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    OBJECTIVE: To use interrupted time-series analyses to investigate the impact of the coronavirus disease 2019 (COVID-19) pandemic on healthcare-associated infections (HAIs). We hypothesized that the pandemic would be associated with higher rates of HAIs after adjustment for confounders. DESIGN: We conducted a cross-sectional study of HAIs in 3 hospitals in Missouri from January 1, 2017, through August 31, 2020, using interrupted time-series analysis with 2 counterfactual scenarios. SETTING: The study was conducted at 1 large quaternary-care referral hospital and 2 community hospitals. PARTICIPANTS: All adults ≥18 years of age hospitalized at a study hospital for ≥48 hours were included in the study. RESULTS: In total, 254,792 admissions for ≥48 hours occurred during the study period. The average age of these patients was 57.6 (±19.0) years, and 141,107 (55.6%) were female. At hospital 1, 78 CLABSIs, 33 CAUTIs, and 88 VAEs were documented during the pandemic period. Hospital 2 had 13 CLABSIs, 6 CAUTIs, and 17 VAEs. Hospital 3 recorded 11 CLABSIs, 8 CAUTIs, and 11 VAEs. Point estimates for hypothetical excess HAIs suggested an increase in all infection types across facilities, except for CLABSIs and CAUTIs at hospital 1 under the no pandemic scenario. CONCLUSIONS: The COVID-19 era was associated with increases in CLABSIs, CAUTIs, and VAEs at 3 hospitals in Missouri, with variations in significance by hospital and infection type. Continued vigilance in maintaining optimal infection prevention practices to minimize HAIs is warranted
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