Caltech Authors
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Repository of works by Caltech published authors.
Mostrando recursos 1 - 4 de 4
1.
Chaotic motions of Prometheus and Pandora - Goldreich, Peter; Rappaport, Nicole
We demonstrate that the chaotic orbits of Prometheus and Pandora are due to interactions associated with the 121:118 mean motion resonance. Differential precession splits this resonance into a quartet of components equally spaced in frequency. Libration widths of the individual components exceed the splitting resulting in resonance overlap which causes the chaos. A single degree of freedom model captures the essential features of the chaotic dynamics. Mean motions of Prometheus and Pandora wander chaotically in zones of width 1.8 deg yr^?1 and 3.1 deg yr^?1, respectively.
(application/pdf) - 18-abr-2006
2.
Chaotic motions of [F-Ring Shepherds] Prometheus and Pandora - Goldreich, Peter; Rappaport, Nicole
Recent HST images of the Saturnian satellites Prometheus and Pandora show that their longitudes deviate from predictions of ephemerides based on Voyager images. Currently Prometheus is lagging and Pandora leading these predictions by somewhat more than 20?. We show that these discrepancies are fully accounted for by gravitational interactions between the two satellites. These peak every 24.8 d at conjunctions and excite chaotic perturbations. The Lyapunov exponent for the Prometheus-Pandora system is of order 0.35 yr^?1 for satellite masses based on a nominal density of 1.3 g cm^?3. Interactions are strongest when the orbits come closest together. This happens at...
(application/pdf) - 18-abr-2006
3.
Understanding the Behavior of Prometheus and Pandora - Farmer, Alison J.; Goldreich, Peter
We revisit the dynamics of Prometheus and Pandora, two small moons flanking Saturn's F ring. Departures of their orbits from freely precessing ellipses result from mutual interactions via their 121:118 mean motion resonance. Motions are chaotic because the resonance is split into four overlapping components. Orbital longitudes were observed to drift away from predictions based on Voyager ephemerides. A sudden jump in mean motions took place close to the time at which the orbits' apses were antialigned in 2000. Numerical integrations reproduce both the longitude drifts and the jumps. The latter have been attributed to the greater strength of interactions...
(application/pdf) - 18-abr-2006
4.
Idiosyncratic evolution of conserved eukaryote proteins that are similar in sequence to archaeal or bacterial proteins - Britten, Roy J.
Sequence comparisons have been made between the proteins of 571 prokaryote species including 46 archaea and 525 bacteria and the set of human proteins. Highly conserved eukaryotic proteins are often strikingly similar in sequence to archaeal and bacterial proteins. Yet in many cases similarity to archaeal proteins is not correlated to the similarity to bacterial proteins. In these comparisons there are hundreds of eukaryote
proteins that match well archeal proteins, but do not match recognizably to bacterial
proteins, while thousands of proteins match well to bacterial proteins but not
recognizably to archeal proteins. Forty percent of the 21,440 human proteins that
significantly match prokaryote...
(application/pdf) - 15-jul-2009
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