1,451 research outputs found

    Feasibility study of an Integrated Program for Aerospace vehicle Design (IPAD). Volume 3: Support of the design process

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    The user requirements for computer support of the IPAD design process are identified. The user-system interface, language, equipment, and computational requirements are considered

    Assessing landscape dust emission potential using combined ground‐based measurements and remote sensing data

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    Modeled estimates of aeolian dust emission can vary by an order of magnitude due to the spatiotemporal heterogeneity of emissions. To better constrain location and magnitude of emissions, a surface erodibility factor is typically employed in models. Several landscape-scale schemes representing surface dust-emission potential for use in models have recently been proposed, but validation of such schemes has only been attempted indirectly with medium-resolution remote sensing of mineral aerosol loadings and high-resolution land-surface mapping. In this study, we used dust-emission source points identified in Namibia with Landsat imagery together with field-based dust-emission measurements using a Portable In-situ Wind Erosion Laboratory (PI-SWERL) wind tunnel to assess the performance of schemes aiming to represent erodibility in global dust-cycle modeling. From analyses of the surface and samples taken at the time of wind tunnel testing, a Boosted Regression Tree analysis identified the significant factors controlling erodibility based on PI-SWERL dust flux measurements and various surface characteristics, such as soil moisture, particle size, crusting degree and mineralogy. Despite recent attention to improving the characterisation of surface dust-emission potential, our assessment indicates a high level of variability in the measured fluxes within similar geomorphologic classes. This variability poses challenges to dust modelling attempts based on geomorphology and/or spectral-defined classes. Our approach using high-resolution identification of dust sources to guide ground-based testing of emissivity offers a valuable means to help constrain and validate dust-emission schemes. Detailed determination of the relative strength of factors controlling emission can provide further improvement to regional and global dust-cycle modeling

    Report of Meeting for the Purpose of Obtaining the Views of the Three Affiliated Tribes of the Fort Berthold Reservation on the Lieu Lands Offered by the Secretary of War, 1946

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    Notice of meeting in the Secretary\u27s conference room to obtain the views of the Three Affiliated Tribes of the Fort Berthold Reservation of the lieu lands offered by the Secretary of War. Provides a copy of the transcript for the meeting and the exhibits explained during the meeting. Includes: Section 6 Public Law 374, 79th Congress 2d session, memorandum to Secretary of the interior from the acting commissioner of Indian Affairs on subject of Transmitting correspondence to Secretary, Letter from Chairman George Gillette accepting invitation to have representatives of the Three Affiliated Tribes at a special hearing. Also includes: notice to all members of the Three Affiliated Tribes of the Fort Berthold Reservation listing a schedule of meetings to be held to discuss offer and inform tribe of schedule; list of attendees and comments for meeting in Lucky Mound District on December 5, 1946; list of attendees and comments in Red Butte District on December 5, 1946; List of attendees and comments in Charging Eagle District on December 6, 1946; List of attendees and comments in Independence District on December 7, 1946; List of attendees and comments in Nishu District on December 8, 1946; List of attendees and comments in Shell Creek District on December 9, 1946; Resolution announcing rejection to offer for the lieu lands offered to the Three Affiliated Tribes; and Exhibit 4 - formal rejection of offer, and Exhibit 5 - letter from J.A. Krug, Secretary of the Intererior) warranted a restudy of the lands. See also: Report of Second Meeting for the Purpose of Obtaining the Views of the Three Affiliated Tribes of the Fort Berthold Reservation on the Lieu Lands Offered by the Secretary of War, 1946https://commons.und.edu/langer-papers/1144/thumbnail.jp

    Trapped in the darkness of the night: thermal and energetic constraints of daylight flight in bats

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    Bats are one of the most successful mammalian groups, even though their foraging activities are restricted to the hours of twilight and night-time. Some studies suggested that bats became nocturnal because of overheating when flying in daylight. This is because—in contrast to feathered wings of birds—dark and naked wing membranes of bats efficiently absorb short-wave solar radiation. We hypothesized that bats face elevated flight costs during daylight flights, since we expected them to alter wing-beat kinematics to reduce heat load by solar radiation. To test this assumption, we measured metabolic rate and body temperature during short flights in the tropical short-tailed fruit bat Carollia perspicillata at night and during the day. Core body temperature of flying bats differed by no more than 2°C between night and daytime flights, whereas mass-specific CO2 production rates were higher by 15 per cent during daytime. We conclude that increased flight costs only render diurnal bat flights profitable when the relative energy gain during daytime is high and risk of predation is low. Ancestral bats possibly have evolved dark-skinned wing membranes to reduce nocturnal predation, but a low degree of reflectance of wing membranes made them also prone to overheating and elevated energy costs during daylight flights. In consequence, bats may have become trapped in the darkness of the night once dark-skinned wing membranes had evolved

    Efficacy of Female Rat Models in Translational Cardiovascular Aging Research

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    Cardiovascular disease is the leading cause of death in women in the United States. Aging is a primary risk factor for the development of cardiovascular disease as well as cardiovascular-related morbidity and mortality. Aging is a universal process that all humans undergo; however, research in aging is limited by cost and time constraints. Therefore, most research in aging has been done in primates and rodents; however it is unknown how well the effects of aging in rat models translate into humans. To compound the complication of aging gender has also been indicated as a risk factor for various cardiovascular diseases. This review addresses the systemic pathophysiology of the cardiovascular system associated with aging and gender for aging research with regard to the applicability of rat derived data for translational application to human aging

    Hierarchically coupled ultradian oscillators generating robust circadian rhythms

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    Ensembles of mutually coupled ultradian cellular oscillators have been proposed by a number of authors to explain the generation of circadian rhythms in mammals. Most mathematical models using many coupled oscillators predict that the output period should vary as the square root of the number of participating units, thus being inconsistent with the well-established experimental result that ablation of substantial parts of the suprachiasmatic nuclei (SCN), the main circadian pacemaker in mammals, does not eliminate the overt circadian functions, which show no changes in the phases or periods of the rhythms. From these observations, we have developed a theoretical model that exhibits the robustness of the circadian clock to changes in the number of cells in the SCN, and that is readily adaptable to include the successful features of other known models of circadian regulation, such as the phase response curves and light resetting of the phase
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