4,923 research outputs found

    A chromatin modifying enzyme, SDG8, is involved in morphological, gene expression, and epigenetic responses to mechanical stimulation

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    Thigmomorphogenesis is viewed as being a response process of acclimation to short repetitive bursts of mechanical stimulation or touch. The underlying molecular mechanisms that coordinate changes in how touch signals lead to long-term morphological changes are enigmatic. Touch responsive gene expression is rapid and transient, and no transcription factor or DNA regulatory motif has been reported that could confer a genome wide mechanical stimulus. We report here on a chromatin modifying enzyme, SDG8/ASHH2, which can regulate the expression of many touch responsive genes identified in Arabidopsis. SDG8 is required for the permissive expression of touch induced genes; and the loss of function of sdg8 perturbs the maximum levels of induction on selected touch gene targets. SDG8 is required to maintain permissive H3K4 trimethylation marks surrounding the Arabidopsis touch-inducible gene TOUCH 3 (TCH3), which encodes a calmodulin-like protein (CML12). The gene neighboring was also slightly down regulated, revealing a new target for SDG8 mediated chromatin modification. Finally, sdg8 mutants show perturbed morphological response to wind-agitated mechanical stimuli, implicating an epigenetic memory-forming process in the acclimation response of thigmomorphogenesis

    Automated Spacecraft Communications Service Demonstration Using NASA's SCaN Testbed

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    The traditional paradigm for space mission operations relies on inefficient, highly scripted pre-planned activities between space communications & navigation service providers and user ground mission operations centers. Typically there is limited or non-existent automation capabilities on the user spacecraft for requesting space communications services, and on the provider network for request dispositioning and service provisioning. In the past, using these processes for space networks was sufficient with the relatively small number of user spacecraft requesting services. However, with an ever increasing number of satellites being launched to orbit, more complex event-driven science objectives, exploration missions involving collaborative platforms, and more distant missions, approaches that improve automation, flexibility and efficiency are needed. This paper describes NASA's recently completed on-orbit demonstration results of a new space communications service concept called User Initiated Service, and a discussion for infusing this innovation into operations

    The Explanatory Visualization Framework: an active learning framework for teaching creative computing using explanatory visualizations

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    Visualizations are nowadays appearing in popular media and are used everyday in the workplace. This democratisation of visualization challenges educators to develop effective learning strategies, in order to train the next generation of creative visualization specialists. There is high demand for skilled individuals who can analyse a problem, consider alternative designs, develop new visualizations, and be creative and innovative. Our three-stage framework, leads the learner through a series of tasks, each designed to develop different skills necessary for coming up with creative, innovative, effective, and purposeful visualizations. For that, we get the learners to create an explanatory visualization of an algorithm of their choice. By making an algorithm choice, and by following an active-learning and project-based strategy, the learners take ownership of a particular visualization challenge. They become enthusiastic to develop good results and learn different creative skills on their learning journey

    A comparison of HPV DNA testing and liquid based cytology over three rounds of primary cervical screening: extended follow up in the ARTISTIC trial.

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    BACKGROUND: The additional sensitivity of HPV testing compared with cytology could permit extended cervical screening intervals. We wished to determine, through a further (third) round of screening in the ARTISTIC trial, the protection provided by a negative baseline HPV screen compared with that of cytology over a 6 year period. METHODS: Cumulative rates of CIN2 or worse (CIN2+) and CIN3 or worse (CIN3+) were correlated with baseline HPV status and cytology. HPV was detected using the Hybrid Capture 2 (Qiagen) assay for high risk types and genotyped using the Linear Array (Roche) and Papillocheck (Greiner) assays. LBC was performed using ThinPrep (Hologic). FINDINGS: Round 3 included 8,873 women of whom 6,337 had been screened in both rounds 1 and 2 and 2,536 had not been screened since round 1. The median duration of follow-up was 72.7 months. The cumulative rate of CIN2+ over three rounds was 3.88% (95%CI 3.59%, 4.17%) overall; 2.39% in round 1, 0.78% in round 2 and 0.74% in round 3. Cumulative rates by baseline status were 20.53% (95%CI 19.04%, 22.08%) for abnormal cytology, 20.12% (95%CI 18.68%, 21.61%) for HPV detection, 1.41% (95%CI 1.19%, 1.65%) for negative cytology and 0.87% (95%CI 0.70%, 1.06%) for a negative HPV test. In HPV negative women aged over 50 the cumulative rate was 0.16% (95%CI 0.07%, 0.34%). Women who were HPV positive/cytology negative at entry had a cumulative CIN2+ rate of 7.73% (95%CI 6.29%, 9.36%) over 6 years, twice the overall rate. INTERPRETATION: A negative HPV test was significantly more protective than normal cytology over three rounds. The findings of this extension of ARTISTIC suggest that the screening interval could be extended to 6 years if HPV testing replaced cytology as the primary screening test

    The design and fabrication of an automated workstation for the manufacture of fiber optic gyroscopes

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    Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (leaf 105).by David C. Roberts.M.S

    Piezoelectric microvalve for high pressure, high frequency hydraulic applications

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references.A piezoelectrically-driven hydraulic amplification microvalve for use in high specific power hydraulic pumping applications was designed, fabricated, and experimentally characterized. High frequency, high force actuation capabilities were enabled through the incorporation of one or more bulk piezoelectric material elements beneath a micromachined annular tethered-piston structure. An hydraulic amplification mechanism was employed to amplify the limited stroke of this piezoelectrically-driven piston structure to a significantly larger motion (40-50x) of a micromachined valve membrane with attached valve cap. This valve cap was actuated through its stroke to open and close against a fluid orifice. These design features enabled the valve device to simultaneously meet a set of high frequency (1-10kHz), high pressure(0.1-IMPa), and large stroke (15-40,um) requirements that had not previously been satisfied by other microvalves presented in the literature. This research was carried out through a series of modeling, design, fabrication, assembly, and experimental testing tasks. Linear and non-linear modeling tools characterizing the structural deformations of the active valve sub-systems were developed. These tools enabled accurate prediction of real-time stresses along the micromachined valve membrane structure during deflection into its non-linear large-deflection regime. A systematic design procedure was developed to generate an active valve geometry to satisfy membrane stress limitations and valve power consumption requirements set forth by external hydraulic system performance goals.(cont.) Fabrication challenges, such as deep-reactive ion etching (DRIE) of the drive element and valve membrane structures, wafer-level silicon-to-silicon fusion bonding and silicon-to-glass anodic bonding operations, preparation and integration of piezoelectric material elements within the micromachined tethered piston structure, die-level assembly and bonding of silicon and glass dies, and filling of degassed fluid within the hydraulic amplification chamber were overcome. The active valve structural behavior and flow regulation capabilities were evaluated over a range of applied piezoelectric voltages, actuation frequencies, and differential pressures across the valve. For applied piezoelectric voltages up to 500Vpp at lkHz, the valve devices demonstrated amplification ratios of drive element deflection to valve cap deflection of 40-50x. These amplification ratios correlated within 5 - 10% of the model expectations. Flow regulation experiments proved that a peak average flow rate through the device of 0.21mL/s under a lkHz sinusoidal drive voltage of 500Vpp, with valve opening of 17pm, against a differential pressure of 260kPa could be obtained. Tests revealed that fluid-structural interactions between the valve cap and membrane components and flow instabilities (due to transition between the laminar and turbulent flow regimes through the valve orifice) limited the valve performance capabilities.by David C. Roberts.Ph.D

    Clinician-targeted interventions to reduce antibiotic prescribing for acute respiratory infections in primary care:An overview of systematic reviews

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    This is the protocol for a review and there is no abstract. The objectives are as follows: To systematically review the literature and appraise the existing evidence from systematic reviews regarding the effects of interventions, aimed at changing clinician behaviour, to reduce antibiotic prescribing for ARIs in primary care

    Clinician-targeted interventions to influence antibiotic prescribing behaviour for acute respiratory infections in primary care: An overview of systematic reviews

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    Background: Antibiotic resistance is a worldwide health threat. Interventions that reduce antibiotic prescribing by clinicians are expected to reduce antibiotic resistance. Disparate interventions to change antibiotic prescribing behaviour for acute respiratory infections (ARIs) have been trialled and meta-analysed, but not yet synthesised in an overview. This overview synthesises evidence from systematic reviews, rather than individual trials. Objectives: To systematically review the existing evidence from systematic reviews on the effects of interventions aimed at influencing clinician antibiotic prescribing behaviour for ARIs in primary care. Methods: We searched the Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects (DARE), MEDLINE, Embase, CINAHL, PsycINFO, and Science Citation Index to June 2016. We also searched the reference lists of all included reviews. We ran a pre-publication search in May 2017 and placed additional studies in 'awaiting classification'. We included both Cochrane and non-Cochrane reviews of randomised controlled trials evaluating the effect of any clinician-focussed intervention on antibiotic prescribing behaviour in primary care. Two overview authors independently extracted data and assessed the methodological quality of included reviews using the ROBIS tool, with disagreements reached by consensus or by discussion with a third overview author. We used the GRADE system to assess the quality of evidence in included reviews. The results are presented as a narrative overview. Main results: We included eight reviews in this overview: five Cochrane Reviews (33 included trials) and three non-Cochrane reviews (11 included trials). Three reviews (all Cochrane Reviews) scored low risk across all the ROBIS domains in Phase 2 and low risk of bias overall. The remaining five reviews scored high risk on Domain 4 of Phase 2 because the 'Risk of bias' assessment had not been specifically considered and discussed in the review Results and Conclusions. The trials included in the reviews varied in both size and risk of bias. Interventions were compared to usual care. Moderate-quality evidence indicated that C-reactive protein (CRP) point-of-care testing (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.66 to 0.92, 3284 participants, 6 trials), shared decision making (odds ratio (OR) 0.44, 95% CI 0.26 to 0.75, 3274 participants, 3 trials; RR 0.64, 95% CI 0.49 to 0.84, 4623 participants, 2 trials; risk difference -18.44, 95% CI -27.24 to -9.65, 481,807 participants, 4 trials), and procalcitonin-guided management (adjusted OR 0.10, 95% CI 0.07 to 0.14, 1008 participants, 2 trials) probably reduce antibiotic prescribing in general practice. We found moderate-quality evidence that procalcitonin-guided management probably reduces antibiotic prescribing in emergency departments (adjusted OR 0.34, 95% CI 0.28 to 0.43, 2605 participants, 7 trials). The overall effect of these interventions was small (few achieving greater than 50% reduction in antibiotic prescribing, most about a quarter or less), but likely to be clinically important. Compared to usual care, shared decision making probably makes little or no difference to reconsultation for the same illness (RR 0.87, 95% CI 0.74 to 1.03, 1860 participants, 4 trials, moderate-quality evidence), and may make little or no difference to patient satisfaction (RR 0.86, 95% CI 0.57 to 1.30, 1110 participants, 2 trials, low-quality evidence). Similarly, CRP testing probably has little or no effect on patient satisfaction (RR 0.79, 95% CI 0.57 to 1.08, 689 participants, 2 trials, moderate-quality evidence) or reconsultation (RR 1.08, 95% CI 0.93 to 1.27, 5132 participants, 4 trials, moderate-quality evidence). Procalcitonin-guided management probably results in little or no difference in treatment failure in general practice compared to normal care (adjusted OR 0.95, 95% CI 0.73 to 1.24, 1008 participants, 2 trials, moderate-quality evidence), however it probably reduces treatment failure in the emergency department compared to usual care (adjusted OR 0.76, 95% CI 0.61 to 0.95, 2605 participants, 7 trials, moderate-quality evidence). The quality of evidence for interventions focused on clinician educational materials and decision support in reducing antibiotic prescribing in general practice was either low or very low (no pooled result reported) and trial results were highly heterogeneous, therefore we were unable draw conclusions about the effects of these interventions. The use of rapid viral diagnostics in emergency departments may have little or no effect on antibiotic prescribing (RR 0.86, 95% CI 0.61 to 1.22, 891 participants, 3 trials, low-quality evidence) and may result in little to no difference in reconsultation (RR 0.86, 95% CI 0.59 to 1.25, 200 participants, 1 trial, low-quality evidence). None of the trials in the included reviews reported on management costs for the treatment of an ARI or any associated complications. Authors' conclusions: We found evidence that CRP testing, shared decision making, and procalcitonin-guided management reduce antibiotic prescribing for patients with ARIs in primary care. These interventions may therefore reduce overall antibiotic consumption and consequently antibiotic resistance. There do not appear to be negative effects of these interventions on the outcomes of patient satisfaction and reconsultation, although there was limited measurement of these outcomes in the trials. This should be rectified in future trials. We could gather no information about the costs of management, and this along with the paucity of measurements meant that it was difficult to weigh the benefits and costs of implementing these interventions in practice. Most of this research was undertaken in high-income countries, and it may not generalise to other settings. The quality of evidence for the interventions of educational materials and tools for patients and clinicians was either low or very low, which prevented us from drawing any conclusions. High-quality trials are needed to further investigate these interventions. </p
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