36,311 research outputs found

    A preliminary look at control augmented dynamic response of structures

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    The augmentation of structural characteristics, mass, damping, and stiffness through the use of control theory in lieu of structural redesign or augmentation was reported. The standard single-degree-of-freedom system was followed by a treatment of the same system using control augmentation. The system was extended to elastic structures using single and multisensor approaches and concludes with a brief discussion of potential application to large orbiting space structures

    Estimates of body sizes at maturation and at sex change, and the spawning seasonality and sex ratio of the endemic Hawaiian grouper (Hyporthodus quernus, F. Epinephelidae)

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    A case study of the reproductive biology of the endemic Hawaiian grouper or hapu’upu’u (Hyporthodus quernus) is presented as a model for comprehensive future studies of economically important epinephelid groupers. Specimens were collected throughout multiple years (1978–81, 1992–93, and 2005–08) from most reefs and banks of the Northwestern Hawaiian Islands. The absence of small males, presence of atretic oocytes and brown bodies in testes of mature males, and both developed ovarian and testicular tissues in the gonads of five transitional fish provided evidence of protogynous hermaphroditism. No small mature males were collected, indicating that Hawaiian grouper are monandrous (all males are sex-changed females). Complementary microscopic criteria also were used to assign reproductive stage and estimate median body sizes (L50) at female sexual maturity and at adult sex change from female to male. The L50 at maturation and at sex change was 580 ±8 (95% confidence interval [CI]) mm total length (TL) and 895 ±20 mm TL, respectively. The adult sex ratio was strongly female biased (6:1). Spawning seasonality was described by using gonadosomatic indices. Females began ripening in the fall and remained ripe through April. A February–June main spawning period that followed peak ripening was deduced from the proportion of females whose ovaries contained hydrated oocytes, postovulatory follicles, or both. Testes weights were not affected by season; average testes weight was only about 0.2% of body weight—an order of magnitude smaller than that for ovaries that peaked at 1–3% of body weight. The species’ reproductive life history is discussed in relation to its management

    Structural control interaction

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    The basic guidance and control concepts that lead to structural control interaction and structural dynamic loads are identified. Space vehicle ascent flight load sources and the load relieving mechanism are discussed, along with the the characteristics and special problems of both present and future space vehicles including launch vehicles, orbiting vehicles, and the Space Shuttle flyback vehicle. The special dynamics and control analyses and test problems apparent at this time are summarized

    Higher physical fitness levels are associated with less language decline in healthy ageing

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    Healthy ageing is associated with decline in cognitive abilities such as language. Aerobic fitness has been shown to ameliorate decline in some cognitive domains, but the potential benefits for language have not been examined. In a cross-sectional sample, we investigated the relationship between aerobic fitness and tip-of-the-tongue states. These are among the most frequent cognitive failures in healthy older adults and occur when a speaker knows a word but is unable to produce it. We found that healthy older adults indeed experience more tip-of-the-tongue states than young adults. Importantly, higher aerobic fitness levels decrease the probability of experiencing tip-of-the-tongue states in healthy older adults. Fitness-related differences in word finding abilities are observed over and above effects of age. This is the first demonstration of a link between aerobic fitness and language functioning in healthy older adults

    A Catalog of MIPSGAL Disk and Ring Sources

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    We present a catalog of 416 extended, resolved, disk- and ring-like objects as detected in the MIPSGAL 24 micron survey of the Galactic plane. This catalog is the result of a search in the MIPSGAL image data for generally circularly symmetric, extended "bubbles" without prior knowledge or expectation of their physical nature. Most of the objects have no extended counterpart at 8 or 70 micron, with less than 20% detections at each wavelength. For the 54 objects with central point sources, the sources are nearly always seen in all IRAC bands. About 70 objects (16%) have been previously identified, with another 35 listed as IRAS sources. Among the identified objects, those with central sources are mostly listed as emission-line stars, but with other source types including supernova remnants, luminous blue variables, and planetary nebulae. The 57 identified objects (of 362) without central sources are nearly all PNe (~90%).which suggests that a large fraction of the 300+ unidentified objects in this category are also PNe. These identifications suggest that this is primarily a catalog of evolved stars. Also included in the catalog are two filamentary objects that are almost certainly SNRs, and ten unusual compact extended objects discovered in the search. Two of these show remarkable spiral structure at both 8 and 24 micron. These are likely background galaxies previously hidden by the intervening Galactic plane
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