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Seismic, gravity, and electrical resistivity data, believed to be most relevent to development of earthquake premonitory models of the crust, are presented. Magnetotellurics (MT) are discussed. Radon investigations are reviewed.
The acoustic radiation of a randomly fluctuating source in motion is characterized analytically to determine the mutual coherence function (MCF). A far-field relation is derived via a series of invertible transformations, and a higher-dimension Radon transformation is performed to reconstruct the MCF; explicit formulas for computing the MCF from the transformed radiation data are provided. The technique is applied to the cases of an axisymmetric line source of finite extent moving at constant velocity along a line and a spatially incoherent line source. Applications to X-ray tomography and analysis of the noise emitted by a moving jet aircraft are suggested.
The feasibility of neutrino tomography of the earth's interior is discussed, taking the 80-GeV W-boson mass determined by Arnison (1983) and Banner (1983) into account. The opacity of earth zones is calculated on the basis of the preliminary reference earth model of Dziewonski and Anderson (1981), and the results are presented in tables and graphs. Proposed tomography schemes are evaluated in terms of the well-posedness of the inverse-Radon-transform problems involved, the neutrino generators and detectors required, and practical and economic factors. The ill-posed schemes are shown to be infeasible; the well-posed schemes (using Tevatrons or the neutrino sky as sources) are considered feasible but impractical.
An algorithm for computer tomography has been developed that is applicable to reconstruction from data having incomplete projections because an opaque object blocks some of the probing radiation as it passes through the object field. The algorithm is based on iteration between the object domain and the projection (Radon transform) domain. Reconstructions are computed during each iteration by the well-known convolution method. Although it is demonstrated that this algorithm does not converge, an empirically justified criterion for terminating the iteration when the most accurate estimate has been computed is presented. The algorithm has been studied by using it to reconstruct several different object fields with several different opaque regions. It also has been used to reconstruct aerodynamic density fields from interferometric data recorded in wind tunnel tests.
The piston velocity for the tropical Atlantic Ocean has been determined from 29 radon profiles measured during the TTO Tropical Atlantic Study. By combining these data with the pCO2 data measured in the surface water and air samples, the net flux of CO2 across the sea-air interface has been calculated for the tropical Atlantic. The dependence of the piston velocity on wind speed is discussed, and possible causes for the high sea-to-air CO2 flux observed in the equatorial zone are examined.
An overview is given of the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) which was designed to observe the spatial characteristics of total ozone that were not resolved by the nadir-viewing Nimbus BUV and SBUV instruments. At the wavelengths suitable for total ozone measurements, the radiance is large enough that the entire daytime atmosphere could be surveyed with about 50-km resolution from a polar orbiting satellite. The resulting high spatial resolution TOMS ozone images are found to reflect the internal dynamic structure of the lower atmosphere. Features which can be identified and tracked include: planetary wave scale troughs and ridges, mesoscale cutoff lows and rapidly moving troughs, jet stream confluence and difluence areas, hurricanes, and polar night lows. These features control the ozone above any given location and account for nearly all the variance in the total ozone. The instrument has been used to track the volcanic eruption clouds from El Chichon, Mount St. Helens, Alaid, and smaller eruptions such as Galunggung. It would be feasible to use a similar instrument on a geostationary platform to obtain half-hourly maps. Determination of the vertical ozone distribution in the lower stratosphere using Radon transform principles would be of importance in measuring jet stream folds and the related troposphere-stratosphere exchange.
The occurrence of high Rn-222 episodes (radonic storms) observed at three islands (Crozet, Kerguelen, and Amsterdam) in the subantarctic Indian Ocean is simulated using a three-dimensional chemical tracer model. The chemical tracer model is described and the simulated time series of Rn-222 concentrations at the three islands are compared to observations. The origin, seasonal frequencies, and periodicities of the storms are examined. It is found that the storms are due to fast boundary layer advection of air from South Africa, made possible by the conjunction of a subtropical high SE of Madagascar and a midlatitudes low off the southern tip of Africa. The implications of the results for the transport of continental air to the subantarctic Indian Ocean are discussed.
The production of X-ray fluxes in thunderstorms has been attributed to bremsstrahlung. Assuming this, another question arises. How can a thunderstorm modulate the number density of electrons which are sufficiently energetic to produce X-rays? As a partial answer to this question, the effects of typical thunderstorm electric fields on a background population of energetic electrons, such as produced by cosmic ray secondaries and their decays or the decay of airborne radionuclides, are considered. The observed variation of X-ray flux is shown to be accounted for by a simple model involving typical electric field strengths. A necessary background electron number density is found from the model and is determined to be more than 2 orders of magnitude higher than that available from radon decay and a factor of 8 higher than that available from cosmic ray secondaries. The ionization enhancement due to energetic electrons and X-rays is discussed.
The technology of using houseplant leaves for reducing volatile organics inside closed facilities has been demonstrated with formaldehyde and benzene. Philodendrons are among the most effective plants tested to date. Philodendron domesticum had demonstrated the ability to remove formaldehyde from small experimental chambers at a rate of 4.31 micro-g/sq cm leaf surface area with initial starting concentrations of 22 ppm. At initial starting concentrations of 2.3 ppm a formaldehyde removal rate of 0.57 micro-g/sq cm was achieved during a 24 hour test. Aleo vera demonstrated a much higher formaldehyde efficiency removal rate than Philodendron domesticum at low formaldehyde concentrations. During a 24 hour exposure period 5 ppm of formaldehyde were reduced to 0.5 ppm demonstrating a removal efficiency rate of 3.27 micro-g/sq cm. Removal efficiency rates can be expected to decrease with concentration levels because fewer molecules of chemicals come in contact with the leaf surface area. Several centimeters of small washed gravel should be used to cover the surface of pot plants when large numbers of plants are kept in the home. The reason for this is to reduce the exposed area of damp potting soil which encourages the growth of molds (fungi). The leaves of Philodendron domesticum and golden pothos (Scindapsus aureus) have also demonstrated their ability to remove benzene and carbon monoxide from closed chambers. A combination of activated carbon and plant roots have demonstrated the greatest potential for removing large volumes of volatile organics along with smoke and possible radon from closed systems. Although fewer plants are required for this concept a mechanical blower motor must be used to pull or push the air through the carbon-root filter. NASA studies on motor sizes and bioregeneration rates should be completed by 1988.
Air-conditioner provides ventilation designed to be used alone or incorporated into cooling or heating system operates efficiently only by recirculating stale air within building. Energy needed to operate overall ventilating cooling or heating system slightly greater than operating nonventilating cooling or heating system. Helps to preserve energy efficiency while satisfying need for increased forced ventilation to prevent accumulation of undesired gases like radon and formaldehyde. Provides fresh treated air to variety of confined spaces: hospital surgeries, laboratories, clean rooms, and printing shops and other places where solvents used. In mobile homes and portable classrooms, eliminates irritant chemicals exuded by carpets, panels, and other materials, ensuring healthy indoor environment for occupants.
The overall goal of this study was to provide a quantitative understanding of the cycling of carbon in the soils associated with deep-rooting Amazon forests. In particular, we wished to apply the understanding gained by answering two questions: (1) what changes will accompany the major land use change in this region, the conversion of forest to pasture? and (2) what is the role of carbon stored deeper than one meter in depth in these soils? To construct carbon budgets for pasture and forest soils we combined the following: measurements of carbon stocks in above-ground vegetation, root biomass, detritus, and soil organic matter; rates of carbon inputs to soil and detrital layers using litterfall collection and sequential coring to estimate fine root turnover; C-14 analyses of fractionated SOM and soil CO2 to estimate residence times; C-13 analyses to estimate C inputs to pasture soils from C-4 grasses; soil pCO2, volumetric water content, and radon gradients to estimate CO2 production as a function of soil depth; soil respiration to estimate total C outputs; and a model of soil C dynamics that defines SOM fractions cycling on annual, decadal, and millennial time scales.
The objective of this grant was to complete below-ground carbon budgets for pastures and forest soils in the Amazon. Profiles of radon and carbon dioxide were used to estimate depth distribution of CO2 production in soil. This information is necessary for determining the importance of deep roots as sources of carbon inputs. Samples were collected for measuring root biomass from new research sites at Santana de Araguaia and Trombetas. Soil gases will be analyzed for CO2 and (14)CO2, and soil organic matter will be analyzed for C-14. Estimates of soil texture from the RADAMBRASIL database were merged with climate data to calculate soil water extraction by forest canopies during the dry season. In addition, a preliminary map of areas where deep roots are needed for deep soil water was produced. A list of manuscripts and papers prepared during the reporting periods is given.
A method is proposed for analyzing an almost monochromatic train of waves propagating in a single direction in an inhomogeneous medium that is not otherwise changing in time. An effective phase is defined in terms of the Hilbert transform of the wave function, which is related, via the JWKB approximation, to the spatial variation of the background state against which the wave is propagating. The contaminating effect of interference between the truly monochromatic components of the train is eliminated using its propagation properties. Measurement errors, provided they are uncorrelated, are manifest as rapidly varying noise; although that noise can dominate the raw phase-processed signal, it can largely be removed by low-pass filtering. The intended purpose of the analysis is to determine the distortion of solar oscillations induced by horizontal structural variation and material flow. It should be possible to apply the method directly to sectoral modes. The horizontal phase distortion provides a measure of longitudinally averaged properties of the Sun in the vicinity of the equator, averaged also in radius down to the depth to which the modes penetrate. By combining such averages from different modes, the two-dimensional variation can be inferred by standard inversion techniques. After taking due account of horizontal refraction, it should be possible to apply the technique also to locally sectoral modes that propagate obliquely to the equator and thereby build a network of lateral averages at each radius, from which the full three-dimensional structure of the Sun can, in principle, be determined as an inverse Radon transform.
An approach for eliminating unnecessary portions of a volume when producing a direct volume rendering is described. This reduction in volume size sacrifices some image quality in the interest of rendering speed. Since volume visualization is often used as an exploratory visualization technique, it is important to reduce rendering times, so the user can effectively explore the volume. The methods presented can speed up rendering by factors of 2 to 3 with minor image degradation. A family of decimation algorithms to reduce the number of primitives in the volume without altering the volume's grid in any way is introduced. This allows the decimation to be computed rapidly, making it easier to change decimation levels on the fly. Further, because very little extra space is required, this method is suitable for the very large volumes that are becoming common. The method is also grid-independent, so it is suitable for multiple overlapping curvilinear and unstructured, as well as regular, grids. The decimation process can proceed automatically, or can be guided by the user so that important regions of the volume are decimated less than unimportant regions. A formal error measure is described based on a three-dimensional analog of the Radon transform. Decimation methods are evaluated based on this metric and on direct comparison with reference images.
The discovery of new transient or persistent sources in the hard X-ray regime with the BATSE Earth occultation Technique has been limited previously to bright sources of about 200 mCrab or more. While monitoring known source locations is not a problem to a daily limiting sensitivity of about 75 mCrab, the lack of a reliable background model forces us to use more intensive computer techniques to find weak, previously unknown emission from hard X-ray/gamma sources. The combination of Radon transform imaging of the galactic plane in 10 by 10 degree fields and the Harvard/CFA-developed Image Search (CBIS) allows us to straightforwardly search the sky for candidate sources in a +/- 20 degree latitude band along the plane. This procedure has been operating routinely on a weekly basis since spring 1997. We briefly describe the procedure, then concentrate on the performance aspects of the technique and candidate source results from the search.
The rare-gas atoms are chemically inert, to an extent unique among all elements. This is due to the stable electronic structure of the atoms. Stable molecules with chemically bound rare-gas atoms are, however, known. A first such compound, XePtF6, W2S prepared in 1962 and since then a range of molecules containing radon, xenon and krypton have been obtained. Most recently, a first stable chemically bound compound of argon was prepared, leaving neon and helium as the only elements for which stable chemically bound molecules are not yet known. Electronic structure calculations predict that a metastable species HHeF exists, but significance of the result depends on the unknown lifetime. Here we report quantum dynamics calculations of the lifetime of HHeF, using accurate interactions computed from electronic structure theory. HHeF is shown to disintegrate by tunneling through energy barriers into He + HF and H + He + F the first channel greatly dominating. The lifetime of HHeF is more than 120 picoseconds, that of DHeF is 14 nanoseconds. The relatively long lifetimes are encouraging for the preparation prospects of this first chemically bound helium compound.
We have investigated the importance of intercontinental transport using source-receptor relationship. A global radon-like and seven regional tracers were used in three-dimensional model simulations to quantify their contributions to column burdens and vertical profiles at world-wide receptors. Sensitivity of these contributions to meteorological input was examined using different years of meteorology in two atmospheric simulations. Results show that Asian emission influences tracer distributions in its eastern downwind regions extending as far as Europe with major contributions in mid- and upper troposphere. On the western and eastern sides of the US, Asian contribution to annual average column burdens are 37% and 5% respectively with strong monthly variations. At an altitude of 10 km, these contributions are 75% and 25% respectively. North American emissions contribute more than 15% to annual average column burden and about 50% at 8 km altitude over the European region. Contributions from tropical African emissions are wide-spread in both the hemispheres. Differences in meteorological input cause non-uniform redistribution of tracer mass throughout the troposphere at all receptors. We also show that in model-model and model-data comparison, correlation analysis of tracer's spatial gradients provides an added measure of model's performance.
Accelerated helium ions with mean energies at the target location of 3-7 MeV were used to simulate alpha-particle radiation from radon daughters. The experimental setup and calibration procedure allowed determination of the helium-ion energy distribution and dose in the nuclei of irradiated cells. Using this system, the induction of DNA double-strand breaks and their spatial distributions along DNA were studied in irradiated human fibroblasts. It was found that the apparent number of double-strand breaks as measured by a standard pulsed-field gel assay (FAR assay) decreased with increasing LET in the range 67-120 keV/microm (corresponding to the energy of 7-3 MeV). On the other hand, the generation of small and intermediate-size DNA fragments (0.1-100 kbp) increased with LET, indicating an increased intratrack long-range clustering of breaks. The fragment size distribution was measured in several size classes down to the smallest class of 0.1-2 kbp. When the clustering was taken into account, the actual number of DNA double-strand breaks (separated by at least 0.1 kbp) could be calculated and was found to be in the range 0.010-0.012 breaks/Mbp Gy(-1). This is two- to threefold higher than the apparent yield obtained by the FAR assay. The measured yield of double-strand breaks as a function of LET is compared with theoretical Monte Carlo calculations that simulate the track structure of energy depositions from helium ions as they interact with the 30-nm chromatin fiber. When the calculation is performed to include fragments larger than 0.1 kbp (to correspond to the experimental measurements), there is good agreement between experiment and theory.