14,107 research outputs found

    Helicopter main-rotor speed effects: A comparison of predicted ranges of detection from the aural detection program ICHIN and the electronic detection program ARCAS

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    NASA LaRC personnel have conducted a strudy of the predicted acoustic detection ranges associated with reduced helicopter main rotor speeds. This was accomplished by providing identical input information to both the aural detection program ICHIN 6, (I Can Hear It Now, version 6) and the electronic acoustic detection program ARCAS (Assessment of Rotorcraft Detection by Acoustics Sensing). In this study, it was concluded that reducing the main rotor speed of the helicopter by 27 percent reduced both the predicted aural and electronic detection ranges by approximately 50 percent. Additionally, ARCAS was observed to function better with narrowband spectral input than with one-third octave band spectral inputs and the predicted electronic range of acoustic detection is greater than the predicted aural detection range

    Selection and static calibration of the Marsh J1678 pressure gauge

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    During the experimental testing of the ultralight, it was determined that a pressure gauge would be required to monitor the simulated flight loads. After analyzing several factors, which are indicated in the discussion section of this report, the Marsh J1678 pressure gauge appeared to be the prominent candidate for the task. However, prior to the final selection, the Marsh pressure gauge was calibrated twice by two different techniques. As a result of the calibration, the Marsh gauge was selected as the appropriate measuring device during the structural testing of the ultralight. Although, there are commerical pressure gauges available on the market that would have proven to be more efficient and accurate. However, in order to obtain these characteristics in a gauge, one has to pay the price on the price tag, and this value is an exponential function of the degree of accuracy efficiency, precision, and many other features that may be designed into the gauge. After analyzing the extent of precision and accuracy that would be required, a more expensive gauge wouldn't have proven to be a financial benefit towards the outcome of the experiment

    The systemic environment: at the interface of aging and adult neurogenesis.

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    Aging results in impaired neurogenesis in the two neurogenic niches of the adult mammalian brain, the dentate gyrus of the hippocampus and the subventricular zone of the lateral ventricle. While significant work has characterized intrinsic cellular changes that contribute to this decline, it is increasingly apparent that the systemic environment also represents a critical driver of brain aging. Indeed, emerging studies utilizing the model of heterochronic parabiosis have revealed that immune-related molecular and cellular changes in the aging systemic environment negatively regulate adult neurogenesis. Interestingly, these studies have also demonstrated that age-related decline in neurogenesis can be ameliorated by exposure to the young systemic environment. While this burgeoning field of research is increasingly garnering interest, as yet, the precise mechanisms driving either the pro-aging effects of aged blood or the rejuvenating effects of young blood remain to be thoroughly defined. Here, we review how age-related changes in blood, blood-borne factors, and peripheral immune cells contribute to the age-related decline in adult neurogenesis in the mammalian brain, and posit both direct neural stem cell and indirect neurogenic niche-mediated mechanisms

    More Power to You

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    "Anyone interested in the Bonneville Power project will find much valuable data in this folio volume.

    Early Catholic Missions in Old Oregon, Volume II. Edited by Clarence B. Bagley

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    "The present and concluding volume contains a translation into the English language of the rare Notice sur le Territoire et sur la Mission de l'Oregon (Bruxelles, 1847).

    Francis Parkman's The Oregon Trail. Edited by Harry G. Paul

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    "This classic was written just at the time that England had relinquished its title to the Oregon country and the full tide of American immigration had set in.

    Adventures in Alaska and Along the Trail

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    "Three new volumes received by this Quarterly since the last issue was printed indicates a continuing interest in Alaska and the Northland.

    Bibliography of American Historical Societies

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    "The work as now issued is easily the most important one volume bibliography in the field of American history.

    Handbook of Learned Societies and Institutions: America

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    "One of the first projects approved by the trustees of the Carnegie Institution was the publication of a handbook of learned societies, this being regarded as a necessary preparation to almost any kind of careful research.

    A Contribution Toward a Bibliography of Marcus Whitman

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    "The following list of references relating to Marcus Whitman has been prepared for the Reference Department of the University of Washington Library.
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