17,159 research outputs found

    The Langley Research Center CSI phase-0 evolutionary model testbed-design and experimental results

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    A testbed for the development of Controls Structures Interaction (CSI) technology is described. The design philosophy, capabilities, and early experimental results are presented to introduce some of the ongoing CSI research at NASA-Langley. The testbed, referred to as the Phase 0 version of the CSI Evolutionary model (CEM), is the first stage of model complexity designed to show the benefits of CSI technology and to identify weaknesses in current capabilities. Early closed loop test results have shown non-model based controllers can provide an order of magnitude increase in damping in the first few flexible vibration modes. Model based controllers for higher performance will need to be robust to model uncertainty as verified by System ID tests. Data are presented that show finite element model predictions of frequency differ from those obtained from tests. Plans are also presented for evolution of the CEM to study integrated controller and structure design as well as multiple payload dynamics

    Atmospheric effects on remote sensing of non-uniform temperature sources

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    The equations of transfer, for a plane-parallel scattering atmosphere with a point source of energy on the lower bounding surface, were solved for various values of sensor/point source orientation and optical depths. Applications of this analysis to Skylab and ERTS mission are discussed, and requirements for atmospheric property data and radiation transfer properties are considered

    A synopsis of test results and knowledge gained from the Phase-0 CSI evolutionary model

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    The Phase-0 CSI Evolutionary Model (CEM) is a testbed for the study of space platform global line-of-sight (LOS) pointing. Now that the tests have been completed, a summary of hardware and closed-loop test experiences is necessary to insure a timely dissemination of the knowledge gained. The testbed is described and modeling experiences are presented followed by a summary of the research performed by various investigators. Some early lessons on implementing the closed-loop controllers are described with particular emphasis on real-time computing requirements. A summary of closed-loop studies and a synopsis of test results are presented. Plans for evolving the CEM from phase 0 to phases 1 and 2 are also described. Subsequently, a summary of knowledge gained from the design and testing of the Phase-0 CEM is made

    Parasitism, Adult Emergence, Sex Ratio, and Size of \u3ci\u3eAphidius Colemani\u3c/i\u3e (Hymenoptera: Aphidiidae) on Several Aphid Species

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    Aphidius colemani Viereck parasitizes several economically important aphid pests of small grain crops including the greenbug, Schizaphis graminum and the Russian wheat aphid, Diuraphis noxia. The ability of A. colemani to switch from S. graminum to several species of aphids common to agricultural and associated non-agricultural ecosystems in the Great Plains, and the effects of host-change on several biological parameters that influence population growth rate were determined. Female A. colemani parasitized and developed to adulthood in nine of 14 aphid species to which they were exposed in the laboratory. All small grain feeding aphids except Sipha flava were parasi­tized. Two sunflower feeding species (Aphis nerii and A. helianthi) and two crucifer feeding species (Lipaphis erysimi and Brevicoryne brassicae) were parasitized, as was the cotton aphid. Aphis gossypii. The average percentage of aphids parasitized differed significantly among host aphid species. as did the percentage of parasitoids surviving from the mummy to the adult stage and the time required for immature development. The sex ratio of adults that enclosed from the various hosts did not differ significantly among species. Dry weights of adult parasitoids differed significantly among host species. Adults from S. graminum weighed most (0.054 mg) while those emerging from A. helianthi weighed least (0.020 mg). Results are discussed in terms of strategies for classical biological control of aphid pests of cereals

    Structural characteristics of positionally-disordered lattices: relation to the first sharp diffraction peak in glasses

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    Positional disorder has been introduced into the atomic structure of certain crystalline lattices, and the orientationally-averaged structure factor S(k) and pair-correlation function g(r) of these disordered lattices have been studied. Analytical expressions for S(k) and g(r) for Gaussian positional disorder in 2D and 3D are confirmed with precise numerical simulations. These analytic results also have a bearing on the unsolved Gauss circle problem in mathematics. As the positional disorder increases, high-k peaks in S(k) are destroyed first, eventually leaving a single peak, that with the lowest-k value. The pair-correlation function for lattices with such high levels of positional disorder exhibits damped oscillations, with a period equal to the separation between the furthest-separated (lowest-k) lattice planes. The last surviving peak in S(k) is, for example for silicon and silica, at a wavevector nearly identical to that of the experimentally-observed first sharp diffraction peak (FSDP) in the amorphous phases of those materials. Thus, for these amorphous materials at least, the FSDP can be regarded as arising from scattering from atomic configurations equivalent to the single family of positionally-disordered local Bragg planes having the furthest separation.Comment: v2: changes in response to referees' comments: Figure 2 made more readable, improved discussion of height of peaks in S(k), other minor changes 4 pages, 3 figures, submitted to Physical Review

    Design characteristics of comparative effectiveness trials for the relief of symptomatic dyspepsia: A systematic review

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    Background: Dyspepsia represents a symptom domain rather than a diagnostic condition and covers a wide range of complex, underlying pathophysiologies that are not well understood. The review explores comparative effectiveness interventions for the treatment of symptomatic dyspepsia along a pragmatic-explanatory continuum. The aim is to identify relevant design characteristics applicable to future upper gastrointestinal comparative effectiveness research employing integrative medicine. Methods: Medline, CINAHL, Scopus, Cochrane Central Register of Controlled Trials (CENTRAL) and WHO Clinical Trials were systematically searched until January 2019. Included articles were original research with two or more comparative intervention arms for the primary outcome; relief of symptomatic dyspepsia. Evaluation of the studies was conducted using the pragmatic-explanatory continuum indicator summary (PRECIS-2) tool. Results: Thirty-six articles were included in the review. A total of 68 Patient Reported Outcome Measurements (PROMs), utilizing 50 different formats were deployed across the studies. The appraisal process revealed eligibility, flexibility in adherence, flexibility in delivery and organization domains further aligned towards an explanatory design. Conclusion: This review identified three design characteristics relevant for future comparative effectiveness research for the treatment of upper gastrointestinal disorders in a community setting. Extensive exclusion eligibility criteria limited the generalization of comparative effectiveness study results by removing sub-groups of the target populations more at risk of dyspeptic symptoms. The requirement for entry endoscopy was found to be common and not always pragmatically justifiable. Development of validated PROMs appropriate for a generic application to upper gastrointestinal disorders would be advantageous for future comparative effectiveness research within integrative medicine

    Assessing the Effect of Stellar Companions from High-Resolution Imaging of Kepler Objects of Interest

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    We report on 176 close (<2") stellar companions detected with high-resolution imaging near 170 hosts of Kepler Objects of Interest. These Kepler targets were prioritized for imaging follow-up based on the presence of small planets, so most of the KOIs in these systems (176 out of 204) have nominal radii <6 R_E . Each KOI in our sample was observed in at least 2 filters with adaptive optics, speckle imaging, lucky imaging, or HST. Multi-filter photometry provides color information on the companions, allowing us to constrain their stellar properties and assess the probability that the companions are physically bound. We find that 60 -- 80% of companions within 1" are bound, and the bound fraction is >90% for companions within 0.5"; the bound fraction decreases with increasing angular separation. This picture is consistent with simulations of the binary and background stellar populations in the Kepler field. We also reassess the planet radii in these systems, converting the observed differential magnitudes to a contamination in the Kepler bandpass and calculating the planet radius correction factor, XR=Rp(true)/Rp(single)X_R = R_p (true) / R_p (single). Under the assumption that planets in bound binaries are equally likely to orbit the primary or secondary, we find a mean radius correction factor for planets in stellar multiples of XR=1.65X_R = 1.65. If stellar multiplicity in the Kepler field is similar to the solar neighborhood, then nearly half of all Kepler planets may have radii underestimated by an average of 65%, unless vetted using high resolution imaging or spectroscopy.Comment: 23 pages, 12 figures. Accepted for publication in The Astronomical Journa

    Nambu-Goldstone Modes in Gravitational Theories with Spontaneous Lorentz Breaking

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    Spontaneous breaking of Lorentz symmetry has been suggested as a possible mechanism that might occur in the context of a fundamental Planck-scale theory, such as string theory or a quantum theory of gravity. However, if Lorentz symmetry is spontaneously broken, two sets of questions immediately arise: what is the fate of the Nambu-Goldstone modes, and can a Higgs mechanism occur? A brief summary of some recent work looking at these questions is presented here.Comment: 6 pages. Presented at the meeting "From Quantum to Cosmos," Washington, D.C., May 2006; published in Int. J. Mod. Phys. D16:2357-2363, 200

    White blood cell count and risk of incident lung cancer in the UK Biobank

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    Background The contribution of measurable immunological/inflammatory parameters to lung cancer development remains unclear, particularly among never-smokers. We investigated the relationship between total and differential white blood cell (WBC) counts and incident lung cancer risk overall and among subgroups defined by smoking status and sex in the United Kingdom (UK). Methods We evaluated 424,407 adults aged 37-73 years from the UK Biobank. Questionnaires, physical measurements, and blood were administered/collected at baseline in 2006-2010. Complete blood cell counts were measured using standard methods. Lung cancer diagnoses and histological classifications were obtained from cancer registries. Multivariable Cox regression models were used to estimate the hazard ratio (HR) and 95% confidence intervals (CI) of incident lung cancer in relation to quartiles (Q) of total WBC and subtype-specific counts, with Q1 as the reference. Results There were 1,493 incident cases diagnosed over an average 7-year follow-up. Overall, the highest quartile of total WBC count was significantly associated with elevated lung cancer risk (HRQ4=1.67, 95% CI:1.41-1.98). Among women, increased risks were found in current-smokers (ncases/n=244/19,464, HRQ4=2.15, 95% CI:1.46-3.16), former-smokers (ncases/n=280/69,198, HRQ4=1.75, 95% CI:1.24-2.47), and never-smokers without environmental tobacco smoke exposure (ncases/n=108/111,294, HRQ4=1.93, 95% CI:1.11-3.35). Among men, stronger associations were identified in current-smokers (ncases/n=329/22,934, HRQ4=2.95, 95% CI:2.04-4.26) and former-smokers (ncases/n= 358/71,616, HRQ4=2.38, 95% CI:1.74-3.27) but not in never-smokers. Findings were similar for lung adenocarcinoma and squamous cell carcinoma and were driven primarily by elevated neutrophil fractions. Conclusions Elevated WBCs could potentially be one of many important markers for increased lung cancer risk, especially among never-smoking women and ever-smoking men
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