1,279 research outputs found

    Impulsive Injection for Compressor Stator Separation Control

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    Flow control using impulsive injection from the suction surface of a stator vane has been applied in a low speed axial compressor. Impulsive injection is shown to significantly reduce separation relative to steady injection for vanes that were induced to separate by an increase in vane stagger angle of 4 degrees. Injected flow was applied to the airfoil suction surface using spanwise slots pitched in the streamwise direction. Injection was limited to the near-hub region, from 10 to 36 percent of span, to affect the dominant loss due to hub leakage flow. Actuation was provided externally using high-speed solenoid valves closely coupled to the vane tip. Variations in injected mass, frequency, and duty cycle are explored. The local corrected total pressure loss across the vane at the lower span region was reduced by over 20 percent. Additionally, low momentum fluid migrating from the hub region toward the tip was effectively suppressed resulting in an overall benefit which reduced corrected area averaged loss through the passage by 4 percent. The injection mass fraction used for impulsive actuation was typically less than 0.1 percent of the compressor through flow

    Active Closed-Loop Stator Vane Flow Control Demonstrated in a Low-Speed Multistage Compressor

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    Closed-loop flow control was successfully demonstrated on the surface of stator vanes in NASA Glenn Research Center's Low-Speed Axial Compressor (LSAC) facility. This facility provides a flow field that accurately duplicates the aerodynamics of modern highly loaded compressors. Closed-loop active flow control uses sensors and actuators embedded within engine components to dynamically alter the internal flow path during off-nominal operation in order to optimize engine performance and maintain stable operation

    Psychometric characteristics of the short form 36 health survey and functional assessment of chronic illness Therapy-Fatigue subscale for patients with ankylosing spondylitis

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    <p>Abstract</p> <p>Background</p> <p>We evaluated the psychometric characteristics of the Short Form 36 (SF-36) Health Survey and the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue subscale in patients with ankylosing spondylitis (AS).</p> <p>Methods</p> <p>We analyzed clinical and patient-reported outcome (PRO) data collected during 12-week, double-blind, placebo-controlled periods of two randomized controlled trials comparing adalimumab and placebo for the treatment of active AS. The Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, and other clinical measures were collected during the clinical trial. We evaluated internal consistency/reliability, construct validity, and responsiveness to change for the SF-36 and FACIT-Fatigue.</p> <p>Results</p> <p>The SF-36 (Cronbach alpha, 0.74-0.92) and FACIT-Fatigue (Cronbach alpha, 0.82-0.86) both had good internal consistency/reliability. At baseline, SF-36 and FACIT-Fatigue scores correlated significantly with Ankylosing Spondylitis Quality of Life scores (r = -0.36 to -0.66 and r = -0.70, respectively; all p < 0.0001). SF-36 scores varied by indicators of clinical severity, with greater impairment observed for more severe degrees of clinical activity (all p < 0.0001). FACIT-Fatigue scores correlated significantly with SF-36 scores (r = 0.42 to 0.74; all p < 0.0001) and varied by clinical severity (p < 0.05 to p < 0.0001).</p> <p>Conclusions</p> <p>The SF-36 is a reliable, valid, and responsive measure of health-related quality of life and the FACIT-Fatigue is a brief and psychometrically sound measure of the effects of fatigue on patients with AS. These PROs may be useful in evaluating effectiveness of new treatments for AS.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00085644">NCT00085644</a> and <a href="http://www.clinicaltrials.gov/ct2/show/NCT00195819">NCT00195819</a></p

    Closed Loop Active Flow Separation Detection and Control in a Multistage Compressor

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    Active closed loop flow control was successfully demonstrated on a full annulus of stator vanes in a low speed axial compressor. Two independent methods of detecting separated flow conditions on the vane suction surface were developed. The first technique detects changes in static pressure along the vane suction surface, while the second method monitors variation in the potential field of the downstream rotor. Both methods may feasibly be used in future engines employing embedded flow control technology. In response to the detection of separated conditions, injection along the suction surface of each vane was used. Injected mass flow on the suction surface of stator vanes is known to reduce separation and the resulting limitation on static pressure rise due to lowered diffusion in the vane passage. A control algorithm was developed which provided a proportional response of the injected mass flow to the degree of separation, thereby minimizing the performance penalty on the compressor system

    \u3ci\u3eScaphanocephalus\u3c/i\u3e-Associated Dermatitis as the Basis for Black Spot Disease in Acanthuridae of St. Kitts, West Indies

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    Acanthurus spp. of St. Kitts and other Caribbean islands, including ocean surgeonfish A. bahianus, doctorfish A. chirurgus, and blue tang A. coeruleus, frequently show multifocal cutaneous pigmentation. Initial reports from the Leeward Antilles raised suspicion of a parasitic etiology. The aim of this study was to quantify the prevalence of the disease in St. Kitts’ Acanthuridae and describe its pathology and etiology. Visual surveys demonstrated consistently high adjusted mean prevalence at 3 shallow reefs in St. Kitts in 2017 (38.9%, 95% CI: 33.8−43.9) and 2018 (51.5%; 95% CI: 46.2−56.9). There were no differences in prevalence across species or reefs, but juvenile fish were less commonly affected than adults. A total of 29 dermatopathy-affected acanthurids were sampled by spearfishing for comprehensive postmortem examination. Digenean metacercariae were dissected from \u3c1 mm cysts within pigmented lesions. Using partial 28S rDNA sequence data they were classified as Family Heterophyidae, members of which are commonly implicated in black spot disease of other fishes. Morphological features of the parasite were most typical of Scaphanocephalus spp. (Creplin, 1842), and 2 genetic profiles were obtained suggesting more than 1 digenean species. Histologically, pigmented lesions had mild chronic perivascular dermatitis and increased melanophores and melanin density, often centered on encysted digenean metacercariae. In 1 affected A. chirurgus, similar metacercariae were histologically identified in skeletal and cardiac muscle. Further research is needed to clarify impact on host fitness, establish the number of heterophyid digenean species that cause black spots on Caribbean fishes and to determine the intermediate and definitive host species

    The Melanocortin 3 Receptor: A Novel Mediator of Exercise-Induced Inflammation Reduction in Postmenopausal Women?

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    The purpose of this study was to determine whether resistance exercise training-induced reductions in inflammation are mediated via melanocortin 3 receptor expression in obese (BMI 32.7 ± 3.7) women (65.6 ± 2.8 yrs) randomized to either a control (N = 11) or resistance training group (N = 12). The resistance trained group performed resistance training 3 days/week for 12 weeks. Resting blood samples were collected before and after the training intervention in both resistance trained and control groups. Resistance training upregulated melanocortin 3 receptor mRNA by 16-fold (P = .035) and decreased monocyte count, without changing leukocyte number, body composition, or body weight. Resistance trained individuals exhibited increased sensitivity to inflammatory stimuli, whereas control individuals exhibited no change. While there was no change in whole blood tumor necrosis factor alpha mRNA between the groups, whole blood interleukin 10 mRNA was higher in the resistance trained group following the intervention period. In summary, it appears that resistance training may modulate melanocortin 3 receptor expression, providing a possible mechanism for the anti-inflammatory effects of exercise training

    Piloted Evaluation of an Integrated Methodology for Propulsion and Airframe Control Design

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    An integrated methodology for propulsion and airframe control has been developed and evaluated for a Short Take-Off Vertical Landing (STOVL) aircraft using a fixed base flight simulator at NASA Lewis Research Center. For this evaluation the flight simulator is configured for transition flight using a STOVL aircraft model, a full nonlinear turbofan engine model, simulated cockpit and displays, and pilot effectors. The paper provides a brief description of the simulation models, the flight simulation environment, the displays and symbology, the integrated control design, and the piloted tasks used for control design evaluation. In the simulation, the pilots successfully completed typical transition phase tasks such as combined constant deceleration with flight path tracking, and constant acceleration wave-off maneuvers. The pilot comments of the integrated system performance and the display symbology are discussed and analyzed to identify potential areas of improvement

    Retraction: Psychometric characteristics of the ankylosing spondylitis quality of life questionnaire, short form 36 health survey, and functional assessment of chronic illness therapy-fatigue subscale

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    Retraction of Revicki DA, Rentz AM, Luo MP, Wong RL, Doward LC, McKenna SP: Psychometric characteristics of the ankylosing spondylitis quality of life questionnaire, short form 36 health survey, and functional assessment of chronic illness therapy-fatigue subscale. Health and Quality of Life Outcomes 2009, 7: 6
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