Preparation, analysis and release of simulated interplanetary grains into low Earth orbit

Astronomical observations which reflect the optical and dynamical properties of interstellar and interplanetary grains are the primary means of identifying the shape, size, and the chemistry of extraterrestrial grain materials. Except for recent samplings of extraterrestrial particles in near-Earth orbit and in the stratosphere observations were the only method of deducing the properties of extraterrestrial particles. In order to elucidate the detailed characteristics of observed dust, the observations must be compared with theoretical studies, some of which are discussed in this volume, or compared with terrestrial laboratory experiments. The formation and optical characterization of simulated interstellar and interplanetary dust with particular emphasis on studying the properties on irregularly shaped particles were discussed. Efforts to develop the techniques to allow dust experiments to be carried out in low-Earth orbit were discussed, thus extending the conditions under which dust experiments may be performed

Vibrational state dependence of ionic rotational branching ratios in resonance enhanced multiphoton ionization of CH

We show that rapid evolution of a Rydberg orbital with internuclear distance in a resonance enhanced multiphoton ionization (REMPI) process can have a profound influence on the production of molecular ions in alternative rotational states. This is illustrated by calculations of ionic rotational branching ratios for (2+1′) REMPI via the O11 (20.5) branch of the E′ ^2Σ^+(3pσ) Rydberg state of CH. The rotational propensity rule for ionization changes from ΔN=odd (ΔN=N_+−N_i) at lower vibrational excitation, as expected from the ΔN+l=odd selection rule, to ΔN=even at higher vibrational levels. This effect is expected to be quite general and should be most readily observable in diatomic hydrides

Microgravity nucleation and particle coagulation experiments support

This project is a part of a program at GSFC to study to formation and growth of cosmic dust grain analogs under terrestrial as well as microgravity conditions. Its primary scientific objective is to study the homogeneous nucleation of refractory metal vapors and a variety of their oxides among others, while the engineering, and perhaps a more immediate objective is to develop a system capable of producing mono-dispersed, homogeneous suspensions of well-characterized refractory particles for various particle interaction experiments aboard the Space Shuttle and Space Station Freedom. Both of these objectives are to be met by a judicious combination of laboratory experiments on the ground and aboard NASA's KC-135 experimental research aircraft. Major effort during the current reporting period was devoted to the evaluation of our very successful first series of microgravity test runs in Feb. 1990. Although the apparatus performed well, it was decided to 'repackage' the equipment for easier installation on the KC-135 and access to various components. It will now consist of three separate racks: one each for the nucleation chamber, the power subsystem, and the electronic packages. The racks were fabricated at the University of Virginia and the assembly of the repackaged units is proceeding well. Preliminary analysis of the video data from the first microgravity flight series was performed and the results appear to display some trends expected from Hale's Scaled Nucleation Theory of 1986. The data acquisition system is currently being refined

Mössbauer diffractometry on polycrystalline (57)Fe3Al

A Mossbauer powder diffractometer was used to measure diffraction patterns from polycrystalline foils of (Fe3Al)-Fe-57. The intensities of Bragg diffractions were measured as a function of the energy of the incident photon. The bee fundamental diffractions showed large changes in intensity as the incident energy was tuned through the nuclear resonances. These variations of diffraction intensity with incident energy were calculated with reasonable success using a kinematical theory of diffraction that included effects of coherent interference between x-ray Rayleigh scattering and, more importantly for these samples, Mossbauer scattering from nuclei having different hyperfine magnetic fields

A hierarchical Bayesian model for predicting ecological interactions using scaled evolutionary relationships

Identifying undocumented or potential future interactions among species is a challenge facing modern ecologists. Recent link prediction methods rely on trait data, however large species interaction databases are typically sparse and covariates are limited to only a fraction of species. On the other hand, evolutionary relationships, encoded as phylogenetic trees, can act as proxies for underlying traits and historical patterns of parasite sharing among hosts. We show that using a network-based conditional model, phylogenetic information provides strong predictive power in a recently published global database of host-parasite interactions. By scaling the phylogeny using an evolutionary model, our method allows for biological interpretation often missing from latent variable models. To further improve on the phylogeny-only model, we combine a hierarchical Bayesian latent score framework for bipartite graphs that accounts for the number of interactions per species with the host dependence informed by phylogeny. Combining the two information sources yields significant improvement in predictive accuracy over each of the submodels alone. As many interaction networks are constructed from presence-only data, we extend the model by integrating a correction mechanism for missing interactions, which proves valuable in reducing uncertainty in unobserved interactions.Comment: To appear in the Annals of Applied Statistic

Radiative properties of visible and subvisible Cirrus: Scattering on hexagonal ice crystals

One of the main objectives of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) is to provide a better understanding of the physics of upper level clouds. The focus is on just one specific aspect of cirrus physics, namely on characterizing the radiative properties of single, nonspherical ice particles. The basis for further more extensive studies of the radiative transfer through upper level clouds is provided. Radiation provides a potential mechanism for strong feedback between the divergence of in-cloud radiative flux and the cloud microphysics and ultimately on the dynamics of the cloud. Some aspects of ice cloud microphysics that are relevant to the radiation calculations are described. Next, the Discrete Dipole Approximation (DDA) is introduced and some new results of scattering by irregular crystals are presented. The Anomalous Diffraction Theory (ADT) was adopted to investigate the scattering properties of even larger crystals. In this way the scattering properties of nonspherical particles were determined over a range of particle sizes

Microgravity nucleation and particle coagulation experiments support

Modifications to the nucleation apparatus suggested by our first microgravity flight campaign are complete. These included a complete 'repackaging' of the equipment into three racks along with an improved vapor spout shutter mechanism and additional thermocouples for gas temperature measurements. The 'repackaged' apparatus was used in two KC-135 campaigns: one during the week of June 3, 1991 consisting of two flights with Mg and two with Zn, and another series consisting of three flights with Zn during the week of September 23, 1991. Our effort then was focused on the analysis of these data, including further development of the mathematical models to generate the values of temperature and supersaturation at the observed points of nucleation. The efforts to apply Hale's Scaled Nucleation Theory to our experimental data have met with only limited success, most likely due to still inadequate temperature field determination. Work on the development of a preliminary particle collector system designed to capture particles from the region of nucleation and condensation, as well as from other parts of the chamber, are discussed

Microgravity nucleation and particle coagulation experiments support

Researchers at NASA Goddard Space Flight Center have embarked on a program to study the formation and growth of cosmic grains. This includes experiments on the homogeneous nucleation of refractory vapors of materials such as magnesium, lead, tin, and silicon oxides. As part of this program, the Chemical Engineering Department of the University of Virginia has undertaken to develop a math model for these experiments, to assist in the design and construction of the apparatus, and to analyze the data once the experiments have begun. Status Reports 1 and 2 addressed the design of the apparatus and the development of math models for temperature and concentration fields. The bulk of this report discusses the continued refinement of these models, and the assembly and testing of the nucleation chamber along with its ancillary equipment, which began in the spring of 1988

Scaling parameters for the simulation of highly expanded rocket exhaust plumes and the resultant impingement forces on an immersed body

Scaling parameters for simulating highly expanded rocket exhaust plumes and resultant impingement forces on immersed bodie

Ride quality meter

A ride quality meter is disclosed that automatically transforms vibration and noise measurements into a single number index of passenger discomfort. The noise measurements are converted into a noise discomfort value. The vibrations are converted into single axis discomfort values which are then converted into a combined axis discomfort value. The combined axis discomfort value is corrected for time duration and then summed with the noise discomfort value to obtain a total discomfort value