Testing Gravity in the Outer Solar System: Results from Trans-Neptunian Objects

The inverse square law of gravity is poorly probed by experimental tests at distances of ~ 10 AUs. Recent analysis of the trajectory of the Pioneer 10 and 11 spacecraft have shown an unmodeled acceleration directed toward the Sun which was not explained by any obvious spacecraft systematics, and occurred when at distances greater than 20 AUs from the Sun. If this acceleration represents a departure from Newtonian gravity or is indicative of an additional mass distribution in the outer solar system, it should be detectable in the orbits of Trans-Neptunian Objects (TNOs). To place limits on deviations from Newtonian gravity, we have selected a well observed sample of TNOs found orbiting between 20 and 100 AU from the Sun. By examining their orbits with modified orbital fitting software, we place tight limits on the perturbations of gravity that could exist in this region of the solar system.Comment: 20 pages, 4 figures, 2 tables, uses AASTex v5.x macro

Shoreline Erosion in Virginia

Virginia has over 5,000 miles of tidal shoreline. Several different shore types occur in the Tidewater region including the low-lying barrier islands of the Eastern Shore, the ocean front headland-barrier spit of southeastern Virginia, and the shores of the Chesapeake Bay and other estuaries which range from high bluffs to tidal marshes. In order to put shore erosion in proper perspective as a natural phenomenon, one must examine the recent geologic history of the region. Much of shoreline erosion is a direct product of high energy storms like hurricanes and northeasters. The rate and amount of erosion along a specific shoreline may vary from year to year. The rate of erosion will depend upon the following factors: (1) storm frequency; (2} storm type and direction; (3) storm intensity and duration; and (4) resulting wind tides, currents, and waves. Also, the presence of man-made structures (bulkheads, groins, etc.) will modify the erosion process, increasing or decreasing it to a degree depending on the type, location, design, etc., of the structure (O\u27Connor, et al., 1978}. The problem of shoreline erosion is most acute when coastal property with improvements is threatened by a rapidly receding shore bank. Many waterfront properties are bought and developed each year with little or no consideration of the shoreline situation. Consequently, additional money must be spent for erosion protection structures. Shoreline protection structures must be adequately designed and correctly placed to be effective under the severest of storm conditions. Inadequate installation or design may result in failure or deleterious effects to adjacent waterfront properties. In many cases a structure is not needed and protection of a shore bank may be accomplished by vegetative means, such as the planting of appropriate grasses, shrubs or vines to stabilize the bank, beach or nearshore area. Virginia\u27s coast is a dynamic and active environment as well as a beautiful place to live. Sound judgement in coastal development is essential to effective control of shoreline erosion

Breaking and Seating of Rigid Pavements

Breaking and seating has been utilized extensively in Kentucky to rehabilitate portland cement concrete pavements. Experience over three or four years with this type of design and construction are summarized and reported. Breaking to a range of nominal fragments is evaluated. Evaluation of two roller weights for seating is reported. The use of dynamic deflections to evaluate the effectiveness of the breaking and seating process and to measure the appropriateness of the asphaltic concrete overlay

Propellant Chemistry for CFD Applications

Current concepts for reusable launch vehicle design have created renewed interest in the use of RP-1 fuels for high pressure and tri-propellant propulsion systems. Such designs require the use of an analytical technology that accurately accounts for the effects of real fluid properties, combustion of large hydrocarbon fuel modules, and the possibility of soot formation. These effects are inadequately treated in current computational fluid dynamic (CFD) codes used for propulsion system analyses. The objective of this investigation is to provide an accurate analytical description of hydrocarbon combustion thermodynamics and kinetics that is sufficiently computationally efficient to be a practical design tool when used with CFD codes such as the FDNS code. A rigorous description of real fluid properties for RP-1 and its combustion products will be derived from the literature and from experiments conducted in this investigation. Upon the establishment of such a description, the fluid description will be simplified by using the minimum of empiricism necessary to maintain accurate combustion analyses and including such empirical models into an appropriate CFD code. An additional benefit of this approach is that the real fluid properties analysis simplifies the introduction of the effects of droplet sprays into the combustion model. Typical species compositions of RP-1 have been identified, surrogate fuels have been established for analyses, and combustion and sooting reaction kinetics models have been developed. Methods for predicting the necessary real fluid properties have been developed and essential experiments have been designed. Verification studies are in progress, and preliminary results from these studies will be presented. The approach has been determined to be feasible, and upon its completion the required methodology for accurate performance and heat transfer CFD analyses for high pressure, tri-propellant propulsion systems will be available

Intramyocardial current flow in acute coronary occlusion in the canine heart

Data from numerous experimental infarction studies indicate that rapid myocardial cell depolarization following ischemia causes the flow of injury currents. These currents were measured in the canine myocardium by monitoring voltage gradients across infarct boundaries using silver chloride plunge electrodes, followed by placement of a 100 Ω resistor between the electrodes and again measuring the voltage gradients. Current flow was calculated from these measurements with the following results: 1) TQ currents developed within 15 seconds after occlusion and persisted for 120 to 150 minutes, often attaining a magnitude of 1μA. 2) ST currents also developed within 15 seconds and attained 2 to 3 μA within 15 to 30 minutes, then usually subsided to some degree. 3) T currents were biphasic and attained 2 to 5 μA. Initially, current flowed from normal to ischemic myocardium but usually reversed within 30 minutes after occlusion. 4) The current flow was often disproportionate to the voltage gradient between 120 and 180 minutes after occlusion, possibly indicating electrical uncoupling of the infarcting cells from normal cells.These data indicate that intramyocardial current flow develops early after acute coronary occlusion. These currents may be sufficient to induce reexcitation

Nondestructive Evaluation of Rigid Pavements Using Road Rater Deflections [1986]

Dynamic deflections have been used to determine in-place structural conditions of rigid pavements, based on modifications of principles and experience with the structural evaluation of flexible pavements. Details of the use of elastic layer theory to simulate deflection measurements associated with loadings for the Kentucky Road Rater are presented. Included is an illustration of the use of field deflection measurements to back calculate in-place moduli. The procedures are generally iterative and involve matching measured deflections with theoretical deflections. Elastic layer principles have been used to simulate deflections only at the mid slab position. Relationships regarding deflections at other locations on the slab currently involve empirical analyses. Evaluations involving the effects of pavement temperature, time of day, season, etc. are still empirical. In summary, major aspects of this report will be twofold. One will be related to procedures and principles applied to the use of deflections and layer elastic theory to estimate effective parameters representative of existing in-place pavement conditions. The second will be related to the application of deflection measurements and evaluation methodologies to determine appropriate recommendations of rehabilitation strategies and scheduling for rigid pavements

Nondestructive Evaluation of Rigid Pavements Using Road Rater Deflections [1984]

Road Rater deflections have been used to determine in-place structural conditions of rigid and composite pavements, based on modifications of principles and experience with the structural evaluation of flexible pavements. Details of the use of elastic layer theory to simulate deflection measurements associated with loadings for the Kentucky Road Rater are presented. Included is an illustration of the use of field deflection measurements to back calculate\u27 in-place moduli. The procedures are generally iterative and involve matching measured deflections with theoretical deflections. Elastic layer principles have been used to simulate deflections only at the midslab position. Relationships regarding deflections at other locations on the slab currently involve empirical analyses. Evaluations involving the effects of pavement temperature, time of day, season, etc. are still empirical. In summary, major aspects of this paper will be twofold. One will be related to procedures and principles applied to the use of deflections and layer elastic theory to estimate effective parameters representative of existing in-place pavement conditions. The second will be related to the application of deflection measurements and evaluation methodologies to determine appropriate recommendations of rehabilitation strategies and scheduling for rigid pavements

Pavement Thickness Designs Utilizing Low-Strength (Pozzolanic) Base and Subbase Materials

This paper presents information whereby laboratory test data for pozzolanic base and subbase materials may be combined with elastic layer theory and a limiting strain criterion to determine thickness designs equivalent to conventional asphaltic concrete and crushed stone pavement structures. A summary of laboratory testing in Kentucky also is presented. An example thickness design determination is presented and includes an economic comparison of alternative designs with the conventional asphaltic – crushed stone thickness design

Evaluation of Full-Depth Asphaltic Concrete Pavements

This study was initiated to verify a newly-developed set of design curves for full-depth asphaltic concrete pavements. Quality control during construction was checked using nuclear density testers, Benkelman beams, and a Road Rater. During the course of this study, an analysis system was developed to interpret the dynamic deflections as measured by the Road Rater and was confirmed by elastic theory. The thickness design curves were verified within the accuracy of construction variations. Rut depths measured in 1979 were analyzed in terms of potential rut depth resulting from consolidation under traffic due to lack of obtaining 100-percent of Marshall density during compaction immediately after paving. Potential rutting was calculated as the decimal equivalent of the quantity of 100 percent minus percent compaction times the layer thickness and the results accumulated from the surface downward. Advances in technology under this study have led to greater advances under succeeding studies. Traffic was monitored using automatic traffic counters, manual classification/volume counts, and weigh-in-motion scales installed in the pavement

The nature and extent of trace element contamination associated with fly-ash disposal sites in the Chisman Creek Watershed

This study was conducted by the Virginia Institute of Marine Science (VIMS) and the Virginia Associated Research Campus (VARC), both branches of the College of William and Mary, to document the nature, extent, and severity of environmental contamination by trace elements from the landfill disposal of fly-ash within the Chisman Creek watershed. Previous work in the area demonstrated that some metals were apparently mobile in the groundwater, and that two nearby household wells were contaminated (Va. SWCB, 1981). These short term studies were limited to the testing of only a few selected contaminants in wells near the fly-ash pits. The goal of our study was to provide a more comprehensive sampling of the basin to delineate the geographical extent of trace element contamination, and to assess whether the levels found there pose a hazard to man or to the terrestrial and aquatic ecosystem. An important aspect of the program is the use of an analytical technique which provides simultaneous measurement of a large number of elements, thereby obviating the need to speculate which elements would be found before the field work was begun. Proton Induced X-ray Emission (PIXE) is such a technique and provided data on 70 elements from each sample collected during this study