Showing papers by "Oak Ridge National Laboratory published in 1985"
TL;DR: In this paper, the effects of boron additions on grain-boundary chemistry and tensile properties of Ni3Al containing 24-26 at.% Al were studied, and the results suggest that alloy stoichiometry strongly influences grain-body chemistry, which in turn affects the grainboundary cohesion.
920 citations
TL;DR: In this paper, a thermodynamic model of boiling hydrothermal solutions is developed and applied over a wide range of physical and chemical conditions, and it is shown that boiling is the most generally effective ore depositional mechanism at the conditions operative in many natural boiling hydroglobal systems.
Abstract: A thermodynamic model of boiling hydrothermal solutions is developed and applied over a wide range of physical and chemical conditions. Within the range of conditions observed in natural boiling hydrothermal systems the processes of liquid-vapor partitioning and the resultant effects on mineral solubilities are highly varied and complex. Metals that are complexed by chloride are deposited largely as a result of the decreasing proton concentration associated with CO 2 exsolution during boiling. Metal bisulfide complexes are destabilized most when the decrease in proton concentration is sluggish relative to the loss of H 2 S.Vaporization of only a few percent of a solution can decrease the proton concentration by several orders of magnitude when the CO 2 /H (super +) and CO 2 /Sigma SO 4 concentration ratios are initially high. The relationship between the proton, CO 2 , and Sigma SO 4 concentrations prior to boiling to the proton concentration after boiling is defined explicitly by a few simple equations. These equations along with the solubilities of calcite and anhydrite constitute the chemical boundary conditions for significant mineral deposition by boiling. Typical hydrothermal fluids lose most of their volatile components to the vapor phase and most of their metals to mineral phases by the time boiling has proceeded to the point where the volumes of the vapor and liquid phases are equal.Physical variables such as the heat budget and the restrictions on the partitioning of mass between liquid and vapor, although significant, are subordinate to the compositional variables in determining the chemical evolution of a boiling hydrothermal solution. Mineral deposition is most vigorous when the volatile components partition from the solution to the vapor phase in a manner resembling perfect fractional (Rayleigh) distillation. As temperature decreases, the efficiency of boiling for depositing metals from solution increases, and the amount of metals in solution typically decreases such that the net effect of boiling is most favorable for ore formation at temperatures around 300 degrees C. Mineral and metal complex stoichiometries in combination with the relative volatilities of CO 2 and H 2 S determine the general sequence of mineral deposition during boiling. These major variables, many other minor variables, and the multiple interactions thereof are accounted for rigorously. The amount and paragenesis of ore and gangue minerals deposited by boiling are presented for numerous hypothetical hydrothermal systems. Analysis of these results suggests that boiling is perhaps the most generally effective ore depositional mechanism at the conditions operative in many boiling hydrothermal systems.
605 citations
TL;DR: In this article, a world map of the Holdridge Life Zone Classification, developed from approximately 8,000 meteorological records, is compared with a Holdridge Map with average temperature increments simulated by a model of climate under elevated atmospheric CO2 concentration.
Abstract: The broad-scale distribution of terrestrial ecosystem complexes is determined in large part by climate and can be altered by climatic change due to natural causes or due to human activities such as those leading to increasing atmospheric CO2 concentration. Classifications that recognize the dependence of natural vegetation on climate provide one means of constructing maps to display the impact of climatic change on the geography of major vegetation zones. A world map of the Holdridge Life-Zone Classification, developed from approximately 8,000 meteorological records, is compared with a Holdridge Map with average temperature increments simulated by a. model of climate under elevated atmospheric CO2 concentration. The largest changes are indicated at high latitudes, where the simulated temperature increase is largest and the temperature intervals defining life zones are smallest. Boreal Forest Zones are replaced by either Cool Temperate Forest or Cool Temperate Steppe, depending on average precipitation. Changes in the tropics are smaller; however, in some regions, Subtropical Moist Forest is replaced by Tropical Dry Forest.
593 citations
TL;DR: In this paper, the amount of nitrogen stored in soil is related to climate through biotic processes associated with productivity of vegetation and decomposition of organic matter, such as rainfall input, dry deposition input, nitrogen fixation and losses of inorganic nitrogen due to leaching contribute to the variability of nitrogen storage.
Abstract: The amount of nitrogen stored in soil is related to climate through biotic processes associated with productivity of vegetation and decomposition of organic matter. Other factors, particularly rainfall input, dry deposition input, nitrogen fixation and losses of inorganic nitrogen due to leaching contribute to the variability of nitrogen storage. Here we report that soil nitrogen storage ranges from 0.2 kg m−3 in warm deserts to 2 kg m−3 in rain tundra, with a peak of 1.6 kg m−3 in subtropical wet forests. Soil carbon storage shows a similar pattern. The global nitrogen pool in the surface metre of soil comprises an estimated 9.5 × 1013 kg. Each soil profile examined was classified according to the Holdridge life zone1 in which it was found. Soil carbon/nitrogen ratios range from 20 in cool, wet forests or rain forests. We determined C/N ratios of 15–20 in cool life zones and 10–15 in warm life zones. These results indicate that: (1) relatively large amounts of soil nitrogen in wet tropical regions are associated with recalcitrant humic materials in an advanced state of decay, with low C/N ratios; (2) the seasonal climate contrast in temperate regions, combined with variable litter quality due to the mix of coniferous and deciduous species, results in moderate carbon and nitrogen storage in soil and variable C/N ratios; and (3) slow decomposition in wet tundra regions results in high carbon and nitrogen storage, with high C/N ratios.
428 citations
TL;DR: In this paper, the authors have shown that a dislocation is generated if the applied stress was sufficiently large that the force on the dislocation was repulsive down to the core distance from the crack tip.
397 citations
TL;DR: A fractal model is proposed for a rough interface between two materials of very different conductivities, e.g., an electrode and an electrolyte, which provides insight into the conducting properties of the percolating cluster and the source of the 1/f noise in electronic components.
Abstract: A fractal model is proposed for a rough interface between two materials of very different conductivities, e.g., an electrode and an electrolyte. The equivalent circuit of the model, which takes into consideration the resistance in the two substances and the capacitance of the interface, has the property of the so-called constant-phase-angle element, i.e., a passive circuit element whose complex impedance has a power-law singularity at low frequencies. The exponent of the frequency dependence is related to the fractal dimension. The model also provides insight into the conducting properties of the percolating cluster and the source of the 1/f noise in electronic components.
385 citations
TL;DR: In this paper, the potential impacts of short-term, recurring disturbances of aquatic systems below dams are important considerations in hydropower development, where water is typically stored in a reservoir at night and released through turbines to satisfy increased electrical demand during the day.
Abstract: Rapid changes in flow below hydroelectric facilities result from peaking operations, where water is typically stored in a reservoir at night and released through turbines to satisfy increased electrical demand during the day. Potential impacts of these short-term, recurring disturbances of aquatic systems below dams are important considerations in hydropower development. Reduced biotic productivity in tailwaters may be due directly to flow variations or indirectly to a variety of factors related to flow variations, such as changes in water depth or temperature, or scouring of sediments. Many riverine fish and invertebrate species have a limited range of conditions to which they are adapted. The relatively recent pattern of daily fluctuations in flow is not one to which most species are adapted; thus, such conditions can reduce the abundance, diversity, and productivity of these riverine organisms. Information needs for site-specific evaluations of potential impacts at hydroelectric peaking projec...
377 citations
TL;DR: The budgeting method predicts higher fine root turnover and productivity than the max-min method for systems with significant rates of nitrification, and by comparison of seasonal maxima and minima in biomess and by nitrogen budgeting.
Abstract: Two methods of estimating fine root production and turnover are compared for 13 forest ecosystems exhibiting a wide range in form (NH4+ vs. NO3-) and quantity of available nitrogen. The two methods are by comparison of seasonal maxima and minima in biomess and by nitrogen budgeting. Both methods give similar results for stands with low rates of nitrification. The budgeting method predicts higher fine root turnover and productivity than the max-min method for systems with significant rates of nitrification.
356 citations
TL;DR: The applications of Poisson regression analysis to problems of summarizing relative risk and disease rate modeling are illustrated with examples of cancer incidence and mortality data, including an example of a nonlinear model predicted by the multistage theory of carcinogenesis.
Abstract: Summarizing relative risk estimates across strata of a covariate is commonly done in comparative epidemiologic studies of incidence or mortality. Conventional Mantel-Haenszel and rate standardization techniques used for this purpose are strictly suitable only when there is no interaction between relative risk and the covariate, and tests for interaction typically are limited to examination for departures from linearity. Poisson regression modeling offers an alternative technique which can be used for summarizing relative risk and for evaluating complex interactions with covariates. A more general application of Poisson regression is its utility in modeling disease rates according to postulated etiologic mechanisms of exposures or according to disease expression characteristics in the population. The applications of Poisson regression analysis to problems of summarizing relative risk and disease rate modeling are illustrated with examples of cancer incidence and mortality data, including an example of a nonlinear model predicted by the multistage theory of carcinogenesis.
348 citations
TL;DR: Striped bass Morone saxatilis has a paradoxical record of distribution and abundance, including population declines in coastal waters and variable success of freshwater introductions, and the thermal niche-dissolved oxygen hypothesis is proposed as a unified perspective of the habitat requirements of the species.
Abstract: Striped bass Morone saxatilis has a paradoxical record of distribution and abundance, including population declines in coastal waters and variable success of freshwater introductions. This record is analyzed for consistency with a hypothesis that striped bass are “squeezed” between their thermal and dissolved oxygen preferences or requirements. A commonality among diverse field and laboratory observations supports an inherent thermal niche for the species that changes to lower temperatures as fish age. This shift can cause local conditions, especially warm surface strata and deoxygenated deep water, to be incompatible with the success of large fish. Crowding due to temperature preferences alone or coupled with avoidance of low oxygen concentrations can lead to pathology and overfishing, which may contribute to population declines. Through a mixture of evidence and conjecture, the thermal niche-dissolved oxygen hypothesis is proposed as a unified perspective of the habitat requirements of the spec...
318 citations
TL;DR: Charcoal is common in the soils of mature rain forests within 75 kilometers of San Carlos de Rio Negro in the north central Amazon Basin and carbon-14 dates indicate that numerous fires have occurred since the mid-Holocene epoch.
Abstract: Charcoal is common in the soils of mature rain forests within 75 kilometers of San Carlos de Rio Negro in the north central Amazon Basin. Carbon-14 dates of soil charcoal from this region indicate that numerous fires have occurred since the mid-Holocene epoch. Charcoal is most common in tierra firme forest Oxisols and Ultisols and less common in caatinga and igapo forest soils. Climatic changes or human activities, or both, have caused rain-forest fires.
TL;DR: The Korringa-Kohn-Rostoker coherent-potential approximation is extended to transport properties and the structure of the formalism is displayed by applying it to a one-dimensional muffin-tin model alloy.
Abstract: The Korringa-Kohn-Rostoker coherent-potential approximation is a powerful and versatile tool for calculating the single-particle properties of disordered alloys. Here this technique is extended to transport properties. The formalism is based on the one-electron Kubo formula. It yields correct results in the limits of weak scattering or low concentration, i.e., the solution to the Boltzmann equation including vertex corrections. Transport coefficients can also be easily evaluated in the strong-scattering, high-concentration regime where the Boltzmann equation is not valid. The structure of the formalism is displayed by applying it to a one-dimensional muffin-tin model alloy.
TL;DR: In this paper, a modification of Debye's distance-dependent dielectric function was proposed, which more closely approximates physical reality at small interatomic separations and yields a dielectrics function that gives reasonable agreement with experimental data in preliminary calculations.
Abstract: Electrostatic effects are believed to determine the molecular structure and function of macromolecules in many ways. In metallo-based enzymes and in metal-macromolecule interactions in solution, these effects may predominate. In order to tackle metal ion-nucleic acid interactions theoretically, a modification of Debye's distance-dependent dielectric function first proposed more than 50 years ago is proposed. This function more closely approximates physical reality at small interatomic separations. The theory proposed here yields a dielectric function that gives reasonable agreement with experimental data in preliminary calculations. 39 references, 4 figures, 6 tables.
TL;DR: A personal history of the development of molten salt reactors in the United States is presented in this article, where the initial goal was an aircraft propulsion reactor, and a molten fluoride-fueled Aircraft Reactor E...
Abstract: A personal history of the development of molten salt reactors in the United States is presented. The initial goal was an aircraft propulsion reactor, and a molten fluoride-fueled Aircraft Reactor E...
TL;DR: A compilation of available growth data for Atlantic and Pacific corals shows a strong pattern of highest growth rates a short distance below the surface and a decrease with depth.
Abstract: Growth rates, determined by X-radiographic measurement of skeletal extension, decreased with depth for four of six species of coral examined at Discovery Bay, Jamaica. Growth of Porites astreoides, Montastrea annularis, Colpophyllia natans, and Siderastrea siderea decreased significantly with depth over a 1- to 30-m depth range. In Montastrea cavernosa, the highest growth rate occurred in the middle of the sampled depth range. Agaricia agaricites had no measurable change in growth rate with depth. A compilation of available growth data for Atlantic and Pacific corals shows a strong pattern of highest growth rates a short distance below the surface and a decrease with depth.
TL;DR: The average daily flux required to support these inventories range from 0.013 to 0.026 pCi cm−2 d−1 as discussed by the authors, with the highest inventories generally occurring in the spring and the lowest in the fall.
Abstract: The atmospheric flux of 7Be over a 2-year period at a coastal site (Norfolk, Virginia) and at an inland site (Oak Ridge, Tennessee) typically supports inventories ranging from 1.0 to 2.0 pCi/cm2 (1 pCi = 0.037 Bq), with the highest inventories generally occurring in the spring and the lowest occurring in the fall. The calculated average daily fluxes required to support these inventories range from 0.013 to 0.026 pCi cm−2 d−1. Despite the different production-source terms for 7Be and 210Pb, there is a high degree of correlation between their measured total monthly deposition reflecting the importance of washout in removing both radionuclides from the atmosphere. Beryllium 7 inventories in soil and vegetated marsh cores compare favorably with inventories calculated from the atmospheric deposition data. Lead 210 inventories in soil and vegetated marsh cores may be enriched (by 20–30%) in relation to inventories calculated from its depositional flux to bucket samplers. Possible explanations for this enrichment are that above-ground vegetation is more efficient at collecting dry aerosols (containing short-lived radon daughters) than buckets or that foliage is an effective trap for particles containing sorbed 210Pb which may be eroded from unvegetated surfaces by wind or water. The vertical distribution and inventory of both 7Be and 210Pb in marsh cores are affected by the presence of vegetation and the location of the groundwater table.
TL;DR: The data indicate that collagen in fully mineralized bovine bone is considerably more closely packed than had been assumed previously, with a packing density similar to that of the relatively crystalline collagens such as wet rat tail tendon.
TL;DR: A dispersion relation is used to show that the ''anomalous'' behavior of the real part of the optical potential for /sup 16/O+ /sup 208/Pb scattering at low energies is an example of a general property of heavy-ion optical potentials at energies approaching the top of the Coulomb barrier, where the flux into nonelastic channels is drastically reduced.
Abstract: A dispersion relation is used to show that the "anomalous" behavior of the real part of the optical potential for $^{16}\mathrm{O}$ + $^{208}\mathrm{Pb}$ scattering at low energies is an example of a general property of heavy-ion optical potentials at energies approaching the top of the Coulomb barrier, where the flux into nonelastic channels is drastically reduced.
TL;DR: Because more hydrophobic PAH, such as BaP, have a high affinity for binding to DHM and rapid rates of biotransformation, these interactions may act to mitigate the biological impact of those very hydrophilic PAH having the greatest potential for bioaccumulation and transfer to humans via food chains.
Abstract: The uptake, depuration, metabolic fate and bioaccumulation of two polycyclic aromatic hydrocarbons (PAH), [14C]naphthalene (NPH) and [14C]benzo(α)pyrene (BaP), by bluegill sunfish were determined in the presence and absence of dissolved humic material (DHM) (20 mg C/L) The effect of binding to DHM on the bioavailability of PAH was analyzed by multicompartment kinetic models to determine the relative rates of uptake of PAH dissolved in water versus that bound to DHM. DHM reduced the accumulation of BaP by 90% (97% of BaP bound to DHM) but had little effect on uptake of NPH (2% bound to DHM). The rate coefficients for uptake of bound PAH were only 0 to 10% of the uptake of dissolved PAH. The potential for biotransformation has an important role in bioaccumulation by fish. Although accumulation of total radioactivity (PAH and metabolites) is 10-fold greater in fish exposed to BaP than in fish exposed to NPH, BaP is extensively metabolized whereas NPH is not. Consequently, the bioconcentration of the parent NPH greatly exceeds that of the parent BaP. Because more hydrophobic PAH, such as BaP, have a high affinity for binding to DHM and rapid rates of biotransformation, these interactions may act to mitigate the biological impact of those very hydrophobic PAH having the greatest potential for bioaccumulation and transfer to humans via food chains.
TL;DR: In this article, the dependence of the nonstoichiometry, x, on temperature and chemical potential of oxygen (oxygen potential) was represented by least-squares analysis using equations derived from the classical thermodynamic theory for the solid solution of a solute in a solvent.
TL;DR: The results indicate that diffusional and metabolic processes are intimately involved in the percutaneous fate of surface-applied chemicals and suggest that meaningful in vitro studies on skin absorption should consider both diffusion and cutaneous biotransformation of the applied compound.
TL;DR: Results from a LEED analysis of NiAl demonstrate that it possesses a large rippled relaxation away from its hypothetical truncated bulk surface, with the Al sites of the top composite Ni-Al layer being displaced approximately 0.22 \AA{} above the Ni sites.
Abstract: Results from a LEED analysis of NiAl(110) demonstrate that it possesses a large rippled relaxation away from its hypothetical truncated bulk surface, with the Al sites of the top composite Ni-Al layer being displaced approximately 0.22 \AA{} above the Ni sites. The evidence for this rippling is strong, since the agreement achieved between calculated and experimental $I\ensuremath{-}V$ profiles is of the same quality obtained in better LEED analyses of monatomic surfaces.
TL;DR: In this paper, two uncertainty analysis techniques were applied to a mathematical model that estimates the dose-equivalent to man from the concentration of radioactivity in air, water, and food.
Abstract: Two techniques of uncertainty analysis were applied to a mathematical model that estimates the dose-equivalent to man from the concentration of radioactivity in air, water, and food. The response-surface method involved screening of the model to determine the important parameters, development of the response-surface equation, calculating the moments using the response-surface model, and fitting a Pearson or Johnson distribution using the calculated moments. The second method sampled model inputs by Latin hypercube methods and iteratively simulated the model to obtain an empirical estimation of the cdf. Comparison of the two methods indicates that it is often difftcult to ascertain the adequacy or reliability of the response-surface method. The empirical method is simpler to implement and, because all model inputs are included in the analysis, it is also a more reliable estimator of the cumulative distribution function of the model output than the response-surface method.
TL;DR: It is suggested that severe hypertension is associated with uniform myocardial perfusion and focal alterations in the substrates used for the performance of myocardIAL work.
Abstract: Severe hypertension causes global and regional changes in myocardial perfusion and substrate utilization. Regional perfusion and fatty acid utilization were evaluated by dual-tracer autoradiography in normotensive and hypertensive rats of the Dahl strain. The regional distributions of perfusion and fatty acid utilization were homogeneous in normotensive rats. Severe hypertension was associated with a homogeneous pattern of regional perfusion, but fatty acid utilization was focally decreased in the free wall of the left ventricle. The decrease in fatty acid uptake was associated with a concomitant increase in glucose utilization. These findings suggest that severe hypertension is associated with uniform myocardial perfusion and focal alterations in the substrates used for the performance of myocardial work.
TL;DR: Stepwise regression models utilizing five easily-measured condition indices, two physiological variables and two environmental variables were developed for estimating the monthly growth of age-I and II largemouth bass sampled during 1980 and 1982 and the liver-somatic index and standard metabolism were the most significant variables.
Abstract: Stepwise regression models utilizing five easily-measured condition indices, two physiological variables and two environmental variables were developed for estimating the monthly growth of age-I and II largemouth bass sampled during 1980 and 1982. The liver-somatic index (LSI) and standard metabolism at surface and thermocline temperatures were the most significant variables for estimating growth. Determination of monthly growth using the LSI requires 50% fewer samples than the usual method of following changes in monthly mean weight. Because the LSI responds relatively rapidly to levels of energy intake and temperature, this index can be used to signal possible adverse effects on fish before changes in growth can be observed. This approach could be a useful management tool because, once validated for a particular aquatic system, frequent cost-effective growth estimates could be used to identify the presence of ecological perturbations and to quantify their effect.
TL;DR: The energy loss and differential probability of energy losses is calculated to all multipole orders for a charged particle moved uniformly past a sphere.
Abstract: The energy loss and differential probability of energy losses is calculated to all multipole orders for a charged particle moved uniformly past a sphere. The sphere's response is characterized by use of a local dielectric function.
TL;DR: In this paper, the real optical potentials for heavy ion scattering were calculated in a folding model using a density and energy-dependent generalization of the M3Y interaction that was calibrated against a realistic reaction matrix.
Patent•
22 Apr 1985TL;DR: In this paper, a mobile robot remotely controlled and/or powered through a cable from a stationary console is provided, which carries a cable management arrangement which stores the cable and dispenses and retracts it as needed.
Abstract: A mobile robot remotely controlled and/or powered through a cable from a stationary console is provided. The robot carries a cable management arrangement which stores the cable and dispenses and retracts it as needed. The arrangement lays down the cable under zero tension when the robot is outbound and reels it in as the robot returns to allow the robot to follow a tortuous path without entangling the cable under or around obstacles. The robot can have numerous configurations such as a simple configuration for use as a transporter for mail in an office and parts in a factory, to a complex configuration with robotic arms and sensors for use in remote surveillance and security work. The robot is especially usable in hostile environments such as nuclear power plants and has a containment box permitting it to be moved to numerous locations without contaminating other areas.
TL;DR: In this paper, the effect of binding polycyclic aromatic hydrocarbons (PAHs) to dissolved humic material (DHM) on the uptake and bioaccumulation of PAHs is examined in the cladoceran Daphnia magna.