Photoelectric Charging by Ultraviolet Light of a Lunar Dust Simulant in a Microgravity Environment

A microgravity experiment to test the electrostatic behavior of a lunar dust simulant being charged through the photoelectric effect will expand understanding of the charging characteristics of dust particles and may lead to a possible mitigation solution. With a design based upon Robert Milikan\u27s oil-drop experiment, this experiment is designed to observe the interactions of a lunar dust simulant without the conflicting effects of a dominant gravitational force. The dust particles will be charged by means of a lamp capable of photon energies necessary to emit electrons by the photoelectric effect. In the presence of an axial electric field, the photo-electrons and charged dust will be attracted to opposing sides of a capacitor and the net charge over time as well as physical trajectories of the particles can be determined

Surface Geometry and Heat Flux Effect on Thin Wire Nucleate Pool Boiling of Subcooled Water in Microgravity

In the summer of 2010, undergraduates from the USU Get Away Special team flew a nucleate pool boiling experiment on NASA’s Weightless Wonder to study nucleate boiling heat transfer in microgravity. The motivation of this research was to understand the effects of surface geometry and heat flux applied to a thin wire heater for the design and development of efficient thermal management systems for space applications. The specific objectives were to observe and characterize behaviors of boiling onset, steady state heat transfer, and bubble dynamics with respect to nucleate boiling of subcooled water.. Using three thin platinum wire geometries and five different constant power levels, free-floating boiling experiments were conducted for more than 30 parabolic flight trajectories to simulate microgravity. To represent the trends in bubbles behavior across hundreds of frames of video in a single graph, a new method for relative bubble area analysis was developed to analyze the recorded videos of the experiment. It was found that the efficiency of steady state heat transfer via nucleate boiling in microgravity was equal comparable to (and in some cases more efficient than) steady state heat transfer in terrestrial experiments. The three wire geometry reduced the heat flux necessary to initiate boiling. Bubble dynamics showed a transition from isolated bubbles to jets of small bubbles as heat flux increases, which was confirmed both visually and with the relative bubble area analysis. The implications of this research are that sustained convective heat transfer with subcooled water is possible in microgravity. There are surface geometries that enable boiling to be initiated at lower heat fluxes, which is beneficial because the high heat transfer rates associated with boiling can be achieved with minimal super heating of the surface

Guide to making time-lapse graphics using the facilities of the National Magnetic Fusion Energy Computing Center

The advent of large, fast computers has opened the way to modeling more complex physical processes and to handling very large quantities of experimental data. The amount of information that can be processed in a short period of time is so great that use of graphical displays assumes greater importance as a means of displaying this information. Information from dynamical processes can be displayed conveniently by use of animated graphics. This guide presents the basic techniques for generating black and white animated graphics, with consideration of aesthetic, mechanical, and computational problems. The guide is intended for use by someone who wants to make movies on the National Magnetic Fusion Energy Computing Center (NMFECC) CDC-7600. Problems encountered by a geographically remote user are given particular attention. Detailed information is given that will allow a remote user to do some file checking and diagnosis before giving graphics files to the system for processing into film in order to spot problems without having to wait for film to be delivered. Source listings of some useful software are given in appendices along with descriptions of how to use it. 3 figures, 5 tables

Capillary retraction of the edge of a stretched viscous sheet

Surface tension causes the edge of a fluid sheet to retract. If the sheet is also stretched along its edge then the flow and the rate of retraction are modified. A universal similarity solution for the Stokes flow in a stretched edge shows that the scaled shape of the edge is independent of the stretching rate, and that it decays exponentially to its far-field thickness. This solution justifies the use of a stress boundary condition in long-wavelength models of stretched viscous sheets, and gives the detailed shape of the edge of such a sheet, resolving the position of the sheet edge to the order of the thickness.</jats:p

Comparison of Biomarkers in Blood and Saliva in Healthy Adults

Researchers measure biomarkers as a reflection of patient health status or intervention outcomes. While blood is generally regarded as the best body fluid for evaluation of systemic processes, substitution of saliva samples for blood would be less invasive and more convenient. The concentration of specific biomarkers may differ between blood and saliva. The objective of this study was to compare multiple biomarkers (27 cytokines) in plasma samples, passive drool saliva samples, and filter paper saliva samples in 50 healthy adults. Demographic data and three samples were obtained from each subject: saliva collected on filter paper over 1 minute, saliva collected by passive drool over 30 seconds, and venous blood (3 mL) collected by venipuncture. Cytokines were assayed using Bio-Rad multiplex suspension array technology. Descriptive statistics and pairwise correlations were used for data analysis. The sample was 52% male and 74% white. Mean age was 26 (range = 19–63 years, sd = 9.7). The most consistent and highest correlations were between the passive drool and filter paper saliva samples, although relationships were dependent on the specific biomarker. Correlations were not robust enough to support substitution of one collection method for another. There was little correlation between the plasma and passive drool saliva samples. Caution should be used in substituting saliva for blood, and relationships differ by biomarker

Scaling laws and dynamics of bubble coalescence

The coalescence of bubbles and drops plays a central role in nature and industry. During coalescence, two bubbles or drops touch and merge into one as the neck connecting them grows from microscopic to macroscopic scales. The hydrodynamic singularity that arises when two bubbles or drops have just touched and the flows that ensue have been studied thoroughly when two drops coalesce in a dynamically passive outer fluid. In this paper, the coalescence of two identical and initially spherical bubbles, which are idealized as voids, that are surrounded by an incompressible Newtonian liquid is analyzed by numerical simulation. This problem has recently been studied (a) experimentally using high-speed imaging and (b) by asymptotic analysis in which the dynamics is analyzed by determining the growth of a hole in the thin liquid sheet separating the two bubbles. In the latter, advantage is taken of the fact that the flow in the thin sheet of non-constant thickness is governed by a set of one-dimensional, radial extensional flow equations. While these studies agree on the power law scaling of the variation of the minimum neck radius with time, they disagree with respect to the numerical value of the prefactors in the scaling laws. In order to reconcile these differences and also provide insights into the dynamics that are difficult to probe by either of the aforementioned approaches, simulations are used to access both earlier times than it has been possible in the experiments and also later times when asymptotic analysis is no longer applicable. Early times and extremely small length scales are attained in the new simulations through the use of a truncated domain approach. Furthermore, it is shown by direct numerical simulations in which the flow within the bubbles is also determined along with the flow exterior to them that idealizing the bubbles as passive voids has virtually no effect on the scaling laws relating minimum neck radius and time.This research was sponsored by the Petroleum Research Fund of the American Chemical Society, the Basic Energy Sciences Program of the United States Department of Energy, and the Engineering and Physical Sciences Research Council

White matter changes and confrontation naming in retired aging national football league athletes

Using diffusion tensor imaging (DTI), we assessed the relationship of white matter integrity and performance on the Boston Naming Test (BNT) in a group of retired professional football players and a control group. We examined correlations between fractional anisotropy (FA) and mean diffusivity (MD) with BNT T-scores in an unbiased voxelwise analysis processed with tract-based spatial statistics (TBSS). We also analyzed the DTI data by grouping voxels together as white matter tracts and testing each tract's association with BNT T-scores. Significant voxelwise correlations between FA and BNT performance were only seen in the retired football players (p < 0.02). Two tracts had mean FA values that significantly correlated with BNT performance: forceps minor and forceps major. White matter integrity is important for distributed cognitive processes, and disruption correlates with diminished performance in athletes exposed to concussive and subconcussive brain injuries, but not in controls without such exposure

Attenuation technique for measuring sediment displacement levels

A technique for obtaining accurate, high (spatial) resolution measurements of sediment redeposition levels is described. In certain regimes, the method may also be employed to provide measurements of sediment layer thickness as a function of time. The method uses a uniform light source placed beneath the layer, consisting of transparent particles, so that the intensity of light at a point on the surface of the layer can be related to the depth of particles at that point. A set of experiments, using the impact of a vortex ring with a glass ballotini particle layer as the resuspension mechanism, are described to test and illustrate the technique