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排序方式: 共有128条查询结果,搜索用时 20 毫秒
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Nielsen C Stover SM Schulz KS Hubbard M Hawkins DA 《American journal of veterinary research》2003,64(5):609-617
OBJECTIVE: To calculate normative joint angle, intersegmental forces, moment of force, and mechanical power at elbow, antebrachiocarpal, and metacarpophalangeal joints of dogs at a walk. ANIMALS: 6 clinically normal mixed-breed dogs. PROCEDURE: Kinetic data were collected via a force platform, and kinematic data were collected from forelimbs by use of 3-dimensional videography. Length, location of the center of mass, total mass, and mass moment of inertia about the center of mass were determined for each of 4 segments of the forelimb. Kinematic data and inertial properties were combined with vertical and craniocaudal ground reaction forces to calculate sagittal plane forces and moments across joints of interest throughout stance phase. Mechanical power was calculated as the product of net joint moment and the angular velocity. Joint angles were calculated directly from kinematic data. RESULTS: All joint intersegmental forces were similar to ground reaction forces, with a decrease in magnitude the more proximal the location of each joint. Flexor moments were observed at metacarpophalangeal and antebrachiocarpal joints, and extensor moments were observed at elbow and shoulder joints, which provided a net extensor support moment for the forelimb. Typical profiles of work existed for each joint. CONCLUSIONS AND CLINICAL RELEVANCE: For clinically normal dogs of a similar size at a walk, inverse dynamic calculation of intersegmental forces, moments of force, and mechanical power for forelimb joints yielded values of consistent patterns and magnitudes. These values may be used for comparison in evaluations of gait in other studies and in treatment of dogs with forelimb musculoskeletal disease. 相似文献
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Hubbard GG 《Science (New York, N.Y.)》1885,5(117):356-360
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Nathan?C.?HealeyEmail author Ayse?Irmak Timothy?J.?Arkebauer David?P.?Billesbach John?D.?Lenters Kenneth?G.?Hubbard Richard?G.?Allen Jeppe?Kjaersgaard 《Irrigation and Drainage Systems》2011,25(3):151-178
Water consumed through evapotranspiration (ET) impacts local and regional hydrologic regimes on various spatial and temporal
scales. Estimating ET in the Great Plains is a prerequisite for effective regional water resource management of the Ogallala
(High Plains) Aquifer, which supplies vital water resources in the form of irrigation for extensive agricultural production.
The Sand Hills region of Nebraska is one of the largest grass-stabilized eolian (windblown) sand dune formations in the world,
with an area of roughly 50,000–60,000 km2 that supports a system of five major land cover types: (1) lakes, (2) wetlands (with lakes, ~5%), (3) subirrigated meadows
(water table is within ~1 m of surface; ~10%), (4) dry valleys (water table is 1–10 m below surface; ~20%), and (5) upland
dunes (water table is more than 10 m below surface; ~65%). Fully understanding the hydrologic regime of these different ecosystems
is a fundamental challenge in regional water resource assessment. The surface energy and water balances were analyzed using
Bowen Ratio Energy Balance Systems (BREBS) at three locations: (1) a meadow, (2) a valley, and (3) an upland dune. Measurement
of the energy budget by BREBS, in concert with Landsat remote sensing image processing for 2004 reveals strong spatial gradients
between sites in latent heat flux that are associated with undulating topographic relief. We find that daily estimates of
ET from BREBS measurements and remote sensing agree well, with an uncertainty within 1 mm, which is encouraging when applying
remote sensing results across such a broad spatial scale and undulating topography. 相似文献
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Klein HP Horowitz NH Levin GV Oyama VI Lederberg J Rich A Hubbard JS Hobby GL Straat PA Berdahl BJ Carle GC Brown FS Johnson RD 《Science (New York, N.Y.)》1976,194(4260):99-105
Three different types of biological experiments on samples of martian surface material ("soil") were conducted inside the Viking lander. In the carbon assimilation or pyrolytic release experiment, (14)CO(2) and (14)CO were exposed to soil in the presence of light. A small amount of gas was found to be converted into organic material. Heat treatment of a duplicate sample prevented such conversion. In the gas exchange experiment, soil was first humidified (exposed to water vapor) for 6 sols and then wet with a complex aqueous solution of metabolites. The gas above the soil was monitored by gas chromatography. A substantial amount of O(2) was detected in the first chromatogram taken 2.8 hours after humidification. Subsequent analyses revealed that significant increases in CO(2) and only small changes in N(2) had also occurred. In the labeled release experiment, soil was moistened with a solution containing several (14)C-labeled organic compounds. A substantial evolution of radioactive gas was registered but did not occur with a duplicate heat-treated sample. Alternative chemical and biological interpretations are possible for these preliminary data. The experiments are still in process, and these results so far do not allow a decision regarding the existence of life on the plonet Mars. 相似文献
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A synthesis of organic matter from atmospheric carbon monoxide or carbon dioxide, or both, appears to take place in the surface material of Mars at a low rate. The synthesis appears to be thermolabile and to be inhibited by moisture. 相似文献
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