Reexamination of data from the asteroid/meteoroid detector

The discovery of the existence of cosmoids, a class of meteoroid in near hyperbolic orbits, was made in a reevaluation of the Sisyphus Experiment on Pioneer 10 and 11. This experiment measured the spontaneous jetting of cosmoids and showed that the dispersion and increase in brightness occurs in microseconds and lasts only briefly. Cosmoid jetting caused multiple telescope thresholds to be exceeded simultaneously which explains the earlier inabilty to compute trajectories from the measured times in the fields of view. A new calculation correlated the Sisyphus individual event measurements with the zodiacal light. That the meteoroid population is dominated by cosmoids is demonstrated. Reported telescopic small comets, measured by a similar optical technique, appear consistent with the Sisyphus results. Characteristic jetting times measured by Sisyphus also show that the volatile cosmoids could not survive in short period orbits

Reexamination of data from the asteroid/meteoroid detector

A reexamination of the results of the Pioneer 10 and 11 Asteroid Meteoroid Detector, or Sisyphus, was carried out in the light of a recently derived theory characterizing interplanetary matter and the Zodiacal Light (ZL). Sisyphus measured individual meteoroids from reflected sunlight and ZL between meteoroid events. The results were questioned because meteoroid orbits could not be calculated as intended and the ZL as computed from individual meteoroids did not agree with values determined from the ZL mode and from the other ZL sensor on the spacecraft. It is first shown that, independent of any explanation, the measurements are, with high probability, valid and strongly correlated with the ZL. The model which explains the strange behavior of the Sisyphus instrument also resolves the enigma why the three dust experiments on the Pioneer 10 and 11 spacecraft produced extreme disparate results for the distribution and orbits of meteoric particles and the ZL. The theory based primarily on these measurements requires a population in the inner solar system of cold meteoroid material composed mainly of volatile molecules. These meteoroids in orbits of high eccentricity are called cosmoids. They are impulsively disrupted from solar heating, resulting in order of magnitude increases in optical cross section. The dispersed particles, predominantly micron sized, scatter most of the ZL and supply the polarization. The sublimation time in sunlight for micron sized particles of volatile composition opposes the gravitational flux increase expected in approaching the sun. The other two Pioneer 10/11 dust experiments were: the Imaging Photopolarimeter for the ZL, and the Meteoroid Detection Experiment that measured penetration of 25 micron (Pioneer 10) and 50 micron (Pioneer 11) thick walls of pressurized gas cells

Adapting the Phylogenetic Program FITCH for Distributed Processing

The ability to reconstruct optimal phylogenies (evolutionary trees) based on objective criteria impacts directly on our understanding the relationships among organisms, including human evolution, as well as the spread of infectious disease. Numerous tree construction methods have been implemented for execution on single processors, however inferring large phylogenies using computationally intense algorithms can be beyond the practical capacity of a single processor. Distributed and parallel processing provides a means for overcoming this hurdle. FITCH is a freely available, single-processor implementation of a distance-based, tree-building algorithm commonly used by the biological community. Through an alternating least squares approach to branch length optimization and tree comparison, FITCH iteratively builds up evolutionary trees through species addition and branch rearrangement. To extend the utility of this program, I describe the design, implementation, and performance of mpiFITCH, a parallel processing version of FITCH developed using the Message Passing Interface for message exchange. Balanced load distribution required the conversion of tree generation from recursive linked list traversal to iterative, array-based traversal. Execution of mpiFITCH on a Beowulf cluster running 64 processors revealed maximum performance enhancement of up to ~28 fold with an efficiency of ~ 40%

Computer-aided Interactive Classification: Applications of VIBE

Tools like the VIBE visualization system permit human analysts to use both an understanding of a data set's content and a recognition of structure that the visualization reveals. But what happens when a database's semantics are hidden from the analyst? What guidelines or heuristics can he or she use to reveal the "correct" underlying structure? Results of two experiments conducted at the University of Pittsburgh support the claim that VIBE analysts can uncover a meaningful clustering even without semantic clues. In one experiment artificial data sets were created in which some of the variables discriminate one or more clusters and the other half contribute only random noise. Variable selection guidelines based on computed discrimination value were used in an attempt to distinguish between the signal and noise variables. In a second experiment, a human analyst's encoding of 714 short phrases to 23 overlapping and inter-related categories was stripped of meaningful titles and relabeled with integers. A VIBE analyst was able to highlight relationships among the 23 categories solely on the basisof co-assignment of the phrases

Coarse-grained distributions and superstatistics

We show an interesting connexion between the coarse-grained distribution function arising in the theory of violent relaxation for collisionless stellar systems (Lynden-Bell 1967) and the notion of superstatistics introduced recently by Beck & Cohen (2003). We also discuss the analogies and differences between the statistical equilibrium state of a multi-components self-gravitating system and the metaequilibrium state of a collisionless stellar system. Finally, we stress the important distinction between mixing entropies, generalized entropies, H-functions, generalized mixing entropies and relative entropies