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41.
Belton MJ Gierasch PJ Smith MD Helfenstein P Schinder PJ Pollack JB Rages KA Ingersoll AP Klaasen KP Veverka J Anger CD Carr MH Chapman CR Davies ME Fanale FP Greeley R Greenberg R Head JW Morrison D Neukum G Pilcher CB 《Science (New York, N.Y.)》1991,253(5027):1531-1536
Images of Venus taken at 418 (violet) and 986 [near-infrared (NIR)] nanometers show that the morphology and motions of large-scale features change with depth in the cloud deck. Poleward meridional velocities, seen in both spectral regions, are much reduced in the NIR In the south polar region the markings in the two wavelength bands are strongly anticorrelated. The images follow the changing state of the upper cloud layer downwind of the subsolar point, and the zonal flow field shows a longitudinal periodicity that may be coupled to the formation of large-scale planetary waves. No optical lightning was detected. 相似文献
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First images of asteroid 243 ida 总被引:1,自引:0,他引:1
Belton MJ Chapman CR Veverka J Klaasen KP Harch A Greeley R Greenberg R Head JW McEwen A Morrison D Thomas PC Davies ME Carr MH Neukum G Fanale FP Davis DR Anger C Gierasch PJ Ingersoll AP Pilcher CB 《Science (New York, N.Y.)》1994,265(5178):1543-1547
The first images of the asteroid 243 Ida from Galileo show an irregular object measuring 56-kilometers by 24 kilometers by 21 kilometers. Its surface is rich in geologic features, including systems of grooves, blocks, chutes, albedo features, crater chains, and a full range of crater morphologies. The largest blocks may be distributed nonuniformly across the surface; lineaments and dark-floored craters also have preferential locations. Ida is interpreted to have a substantial regolith. The high crater density and size-frequency distribution (-3 differential power-law index) indicate a surface in equilibrium with saturated cratering. A minimum model crater age for Ida-and therefore for the Koronis family to which Ida belongs-is estimated at 1 billion years, older than expected. 相似文献
44.
A'Hearn MF Belton MJ Delamere WA Kissel J Klaasen KP McFadden LA Meech KJ Melosh HJ Schultz PH Sunshine JM Thomas PC Veverka J Yeomans DK Baca MW Busko I Crockett CJ Collins SM Desnoyer M Eberhardy CA Ernst CM Farnham TL Feaga L Groussin O Hampton D Ipatov SI Li JY Lindler D Lisse CM Mastrodemos N Owen WM Richardson JE Wellnitz DD White RL 《Science (New York, N.Y.)》2005,310(5746):258-264
Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity. The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength (<65 pascals). Local gravitational field and average nucleus density (600 kilograms per cubic meter) are estimated from ejecta fallback. Initial ejecta were hot (>1000 kelvins). A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water. On approach, the spacecraft observed frequent natural outbursts, a mean radius of 3.0 +/- 0.1 kilometers, smooth and rough terrain, scarps, and impact craters. A thermal map indicates a surface in equilibrium with sunlight. 相似文献
45.
A'Hearn MF Belton MJ Delamere WA Feaga LM Hampton D Kissel J Klaasen KP McFadden LA Meech KJ Melosh HJ Schultz PH Sunshine JM Thomas PC Veverka J Wellnitz DD Yeomans DK Besse S Bodewits D Bowling TJ Carcich BT Collins SM Farnham TL Groussin O Hermalyn B Kelley MS Kelley MS Li JY Lindler DJ Lisse CM McLaughlin SA Merlin F Protopapa S Richardson JE Williams JL 《Science (New York, N.Y.)》2011,332(6036):1396-1400
Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus. 相似文献
46.
Broadfoot AL Belton MJ Takacs PZ Sandel BR Shemansky DE Holberg JB Ajello JM Atreya SK Donahue TM Moos HW Bertaux JL Blamont JE Strobel DF McConnell JC Dalgarno A Goody R McElroy MB 《Science (New York, N.Y.)》1979,204(4396):979-982
Observations of the optical extreme ultraviolet spectrum of the Jupiter planetary system during the Voyager 1 encounter have revealed previously undetected physical processes of significant proportions. Bright emission lines of S III, S IV, and O III indicating an electron temperature of 10(5) K have been identified in preliminary analyses of the Io plasma torus spectrum. Strong auroral atomic and molecular hydrogen emissions have been observed in the polar regions of Jupiter near magnetic field lines that map the torus into the atmosphere of Jupiter. The observed resonance scattering of solar hydrogen Lyman alpha by the atmosphere of Jupiter and the solar occultation experiment suggest a hot thermosphere (>/= 1000 K) wvith a large atomic hydrogen abundance. A stellar occultation by Ganymede indicates that its atmosphere is at most an exosphere. 相似文献
47.
Analysis of data obtained by the ultraviolet experiment on Mariner 10 indicates that Mercury is surrounded by a thin atmosphere consisting in part of helium. The partial pressure of helium at the terminator is about 5 x 10(-12) millibar. The total surface pressure of the atmosphere is less than about 2 x 10(-9) millibar. Upper limits are set for the abundance of various gases, including hydrogen, oxygen, carbon, argon, neon, and xenon. The wavelength dependence of Mercury's surface albedo is similar to that of the moon over a broad range of wavelengths from 500 to 1600 angstroms. Strong signals were recorded by the airglow instrument as Mariner 10 passed through the cavity behind Mercury. They are as yet unexplained but may provide information on the properties of the local plasma. 相似文献
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49.
Andrea S Rudolff Yves PS Moens Bernd Driessen Tamas D Ambrisko 《Veterinary anaesthesia and analgesia》2014,41(4):386-392
ObjectiveTo assess agreement between infrared (IR) analysers and a refractometer for measurements of isoflurane, sevoflurane and desflurane concentrations and to demonstrate the effect of customized calibration of IR analysers.Study designIn vitro experiment.SubjectsSix IR anaesthetic monitors (Datex-Ohmeda) and a single portable refractometer (Riken).MethodsBoth devices were calibrated following the manufacturer’s recommendations. Gas samples were collected at common gas outlets of anaesthesia machines. A range of agent concentrations was produced by stepwise changes in dial settings: isoflurane (0–5% in 0.5% increments), sevoflurane (0–8% in 1% increments), or desflurane (0–18% in 2% increments). Oxygen flow was 2 L minute?1. The orders of testing IR analysers, agents and dial settings were randomized. Duplicate measurements were performed at each setting. The entire procedure was repeated 24 hours later. Bland–Altman analysis was performed. Measurements on day-1 were used to yield calibration equations (IR measurements as dependent and refractometry measurements as independent variables), which were used to modify the IR measurements on day-2.ResultsBias ± limits of agreement for isoflurane, sevoflurane and desflurane were 0.2 ± 0.3, 0.1 ± 0.4 and 0.7 ± 0.9 volume%, respectively. There were significant linear relationships between differences and means for all agents. The IR analysers became less accurate at higher gas concentrations. After customized calibration, the bias became almost zero and the limits of agreement became narrower.Conclusions and clinical relevanceIf similar IR analysers are used in research studies, they need to be calibrated against a reference method using the agent in question at multiple calibration points overlapping the range of interest. 相似文献
50.
Thais M Menegheti Juliana T Wagatsuma Acácio D Pacheco Beatriz Perez Cynara M Pacheco Caio JX Abimussi Paulo PS dos Santos Valéria NL de Souza Oliva 《Veterinary anaesthesia and analgesia》2014,41(1):97-104
ObjectiveThe present study aimed to investigate the influence of methadone on cardiorespiratory parameters, electrocardiogram and clinical sedation in dogs. Further possible side effects are reported.Study designProspective experimental cross-over study.DogsEight, 1–4-year-old, various breeds of dogs of both genders weighing 9–36 kg.MethodsEach dog was treated three times: methadone 0.3 mg kg?1 (M0.3), 0.5 mg kg?1 (M0.5) and 1.0 mg kg?1 (M1.0) intramuscularly. Respiratory rate, heart rate and arterial blood pressure were recorded as well as electrocardiographic evaluation of lead II. Clinical sedation in each treatment received a score (0–3) after drug administration and at 30 minute intervals until scores and measurements returned to baseline values.ResultsA significant decrease in heart rate was seen with each dose of methadone and bradycardia (HR<60 bpm) was noted in a few dogs at each dose. A clinically significant arrhythmia occurred in one dog at 1 mg kg?1 that required reversal with butorphanol. There was no significant difference in SAP, MAP and DAP between treatments. Some side effects such as salivation, defecation, vocalization and panting, after administration of methadone were observed. There were no differences in mean values of heart rate, P-wave and QRS complex duration and QT interval between treatments.Conclusion and clinical relevanceMethadone administration was associated with panting and a decrease in heart rate at all doses tested in this study. The cardiac rhythm should be monitored carefully in dogs when methadone is administered on its own, especially at higher doses. 相似文献