Spin rate of asteroid (54509) 2000 PH5 increasing due to the YORP effect     

Taylor PA  Margot JL  Vokrouhlicky D  Scheeres DJ  Pravec P  Lowry SC  Fitzsimmons A  Nolan MC  Ostro SJ  Benner LA  Giorgini JD  Magri C 《Science (New York, N.Y.)》2007,316(5822):274-277

Radar and optical observations reveal that the continuous increase in the spin rate of near-Earth asteroid (54509) 2000 PH5 can be attributed to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, a torque due to sunlight. The change in spin rate is in reasonable agreement with theoretical predictions for the YORP acceleration of a body with the radar-determined size, shape, and spin state of 2000 PH5. The detection of asteroid spin-up supports the YORP effect as an explanation for the anomalous distribution of spin rates for asteroids under 10 kilometers in diameter and as a binary formation mechanism.  相似文献   

Diffusing-Wave Spectroscopy of Dynamics in a Three-Dimensional Granular Flow   总被引：1，自引：0，他引：1  

N Menon  DJ Durian 《Science (New York, N.Y.)》1997,275(5308):1920-1922

Diffusing-wave spectroscopy was used to measure the microscopic dynamics of grains in the interior of a three-dimensional flow of sand. The correlation functions show that minutely separated grains fly from collision to collision with large random velocities. On a time scale 10(3) to 10(4) times longer than the average time between collisions, the grains displayed slow, collective rearrangements, which, at the long-time limit, produced diffusive dynamics.  相似文献   

Freezing equine semen: the effect of combinations of semen extenders and glycerol on post-thaw motility   总被引：1，自引：1，他引：0  

J Scherzer  RA Fayrer-Hosken  M Aceves  DJ Hurley  LE Ray  L Jones  GL Heusner 《Australian veterinary journal》2009,87(7):275-279

Objective   We evaluated combinations of two commercial semen extenders and three concentrations of glycerol to determine the combination that yielded the highest post-thaw sperm motility.
Design   A randomised 2 × 3 block design was used.
Procedure   Semen was collected from four stallions (6 collections per stallion). The sample was diluted with either a dried skim-milk glucose extender (EZ Mixin Original Formula) or a chemically defined, milk-free diluent (INRA 96), and each was used in combination with 2%, 3% or 4% glycerol in standard commercial freezing medium. Sperm motility was assessed by microscopy in fresh and post-thaw semen.
Results   There was a significant difference between the two extenders in the motility of spermatozoa after cryopreservation (48.9% for INRA 96; 38.6% for EZ Mixin OF; P < 0.0001). Glycerol at 4% in freezing medium yielded the highest post-thaw motility, significantly better than 2% ( P < 0.05). Three of four stallions had significantly higher post-thaw motility using INRA 96 relative to EZ Mixin OF ( P < 0.01), and two of four stallions had significantly higher post-thaw motility using 4% glycerol ( P < 0.05). The combination of INRA 96 and 4% glycerol in freezing medium gave the highest average post-thaw motility of 51.5%.
Conclusion   In this study, INRA 96 combined with 4% glycerol yielded an average recovery of progressively motile sperm consistently above the 35% target.  相似文献   

Porcine β1,4-Galactosyltransferase-I Sequence and Expression     

EA Landers  HR Burkin  GT Bleck  L Howell-Skalla  DJ Miller 《Reproduction in domestic animals》2009,44(2):228-234

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