Search Results - (Author, Cooperation:T. M. Williams)

2014-10-04

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; *Carnivora ; *Energy Metabolism ; *Predatory Behavior ; Puma/*metabolism/*psychology ; Running

2018-02-03

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Geosciences

Computer Science

Medicine

Natural Sciences in General

Physics

Ecology, Physiology

1365-2044

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1748-7692

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Electronic Resource

1745-6584

Blackwell Publishing Journal Backfiles 1879-2005

Energy, Environment Protection, Nuclear Power Engineering

Geosciences

A two-well tracer experiment was conducted in a coastal, sandy aquifer in South Carolina to investigate tracer migration in ground-water systems. Chloride tracer was injected into the aquifer under a steady flow condition created by continuous injection and withdrawal of ground water at an injection and a withdrawal well dipole separated by a distance of 5 meters. Breakthrough data were collected at several depths from two multilevel sampling wells, 1.5 meters apart, between the injection well and the withdrawal well.A one-dimensional advection-dispersion model that considers the nonuniform velocity field of the two-well experiment was employed to estimate the hydrologic properties of the aquifer. The values of the porosity and dispersivity were estimated by fitting the model to the observed breakthrough data collected at three depths at one sampling well (Well A). These values were then used to predict the breakthroughs at the same depths in the other sampling well (Well B). A two-dimensional flow and transport model was also employed to simulate the tracer migration. Results of both one- and two-dimensional simulations show that these models fail to predict the tracer breakthrough at Well B using parameter values obtained from Well A.The failure of the model to predict breakthroughs at Well B suggests that a three-dimensional characterization of aquifer heterogeneities and a three-dimensional modeling effort may be needed in order to capture the complex flow pattern in the aquifer.

Electronic Resource

1436-3259

Key words: wetland, elevation, scaling, stochastic, multifractal, intermittency.

Springer Online Journal Archives 1860-2000

Architecture, Civil Engineering, Surveying

Energy, Environment Protection, Nuclear Power Engineering

Geography

Geosciences

Abstract. The land surface elevation distribution will serve as fundamental input data to any wetland flow model. As an alternative to the traditional smooth function approach to represent or interpolate elevation data, we explore the use of Levy monofractals and universal multifractals as a means for defining a statistically equivalent topography. The motivation behind this effort is that fractals, like natural topography, are irregular, they offer a way to relate elevation variations measured at different scales, and the relationships are of a statistical nature. The study site was a riparian wetland near Savannah, GA, that contained beavers, and a total of four elevation transects were examined. The elevation increments showed definite non-Gaussian behavior, with parameter values, such as the Hurst coefficient and Lévy index (α), depending on the question of presence of beaver activity. It was obvious that the data were highly irregular, especially the transects influenced by beavers. Significantly different α values were obtained depending on whether the entire data set or just the tails were examined, which demonstrated inability of the monofractal model to reflect fully the irregularity of wetland data. Further analysis confirmed definite multifractal scaling, and it is concluded that the multifractal model is superior for this data set. Universal multifractal parameters are calculated and compared to those obtained previously for more typical terrain. Although it is difficult to consider a unique universal multifractal parameter α for the entire wetland, multifractal-like scaling was evident in each transect as reflected by the nonlinear behaviors of the scaling functions. We demonstrate a good agreement between theory and measurements up to a critical order of statistical moments, q D , close to 3.5 and obtain realistic unconditioned simulations of multifractal wetland topography based on our parameter estimates. Future work should be devoted to conditioning multifractal realizations to data and to obtaining larger data sets so that the question of anisotropy may be studied.

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] To determine whether there is an energetic saving associated with wave-riding, we trained bottlenose dolphins to follow a moving boat (Fig. 1). Freely swimming dolphins remained at least 1 m below the water surface and were positioned outside the boat's wake. Wave-riding dolphins ...

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The samples were analysed by established methods22"24 and the results, presented in Table 1, show obvious discontinuities, both in the concentrations of the individual radionuclides and in the activity ratios, which suggest that the samples can (with the few exceptions discussed below) be grouped ...

Electronic Resource

1432-0428

Cognitive impairment ; hypoglycaemia ; hyperglycaemia ; adults

Springer Online Journal Archives 1860-2000

Medicine

Summary To examine the long-term effects of recurrent severe hypoglycaemia and other biomedical complications on mental efficiency, a battery of cognitive tests was administered to 142 Type 1 (insulin-dependent) diabetic adult patients (age 33.5±5.6 years; mean ±SD) and 100 demographically similar non-diabetic control subjects. All diabetic subjects had been diagnosed before the age of 17 years. Diabetic subjects with one or more complications (distal symmetrical polyneuropathy; advanced background or proliferative retinopathy; overt nephropathy; one or more episodes of severe hypoglycaemia) performed significantly (p〈0.001) more poorly than non-diabetic control subjects on tests requiring sustained attention, rapid analysis of visuospatial detail, and hand eye co-ordination. Regression analyses indicated that the best biomedical predictor of cognitive test performance was a diagnosis of polyneuropathy. Although severe recurrent hypoglycaemia was not associated with performance on any test, the neuropathy × recurrent hypoglycaemia interaction term was significant. These results suggest that in adults with Type 1 diabetes of long duration, recurrent hypoglycaemia does not appear to influence cognitive performance directly, but may interact with neuropathy to exaggerate or otherwise magnify the extent of neurobehavioural dysfunction.

Electronic Resource

1432-0495

Springer Online Journal Archives 1860-2000

Geosciences

Abstract Integrated total elemental, phase-specific, and pore-water analyses of sediment cores from Loch Ba, Scotland, show that early diagenetic processes have promoted extensive metal enrichment immediately beneath the sediment-water interface. The accumulation of Mn, Pb, Zn, Cu, and Co in sedimentary solids upward of 3 cm depth is accompanied by an increasing residence of these elements in adsorbed and hydrous oxide phases. Such phases are formed through oxidative precipitation from the interstitial pore fluids, following the upward migration of metals from more deeply buried, anaerobic sectors of the sediment pile. There is good evidence that Fe and Ni are subject to similar influences, although their total abundances near the sediment surface are less conspicuously modified. In the Loch Ba sediments, the oxic conditions promoting metal precipitation are entirely confined to strata of postindustrial age. In the absence of fully diagnostic pore-water and sequential chemical data, similar diagenetic profiles could plausibly be misinterpreted as the product of anthropogenic contamination.

Electronic Resource

1432-0495

Metal speciation ; Surficial sediments ; Scotland

Springer Online Journal Archives 1860-2000

Geosciences

Abstract The geochemical partitioning of ten elements in stratified Holocene sediments from Loch Dee, southwest Scotland, has been established by use of a five-stage sequential extraction procedure. Samples from below 15 cm sediment depth show minimal evidence of modification by anthropogenic contamination or active diagenesis and hold Fe, Mg, Cu, Cd, Co, Pb, and Ni primarily in detrital silicates or organic complexes, while Mn, Ca, and Zn reside largely in adsorbed and reducible oxide phases. In the uppermost ca 15 cm of sediment, enhanced total concentrations of Zn, Cu, and Pb reflect increased atmospheric deposition during the postindustrial period. Of these metals, only Pb displays any notable adjustment of partitioning in the enriched zone, showing disproportionate accumulation in labile oxides and organic-Pb phases. The lack of Pb and Zn carbonates in the “contaminated” horizon may reflect inherent thermodynamic instability under the acid surface and pore-water conditions of Loch Dee. Increments to total Mn and Co in the surficial ca 5 cm of sediment are attributable to the accumulation of secondary oxides and adsorbed species, consistent with precipitation from the interstitial pore-waters across a sedimentary redox front. The presence of metals such as Zn and Cd in soluble or acid-volatile phases in the interfacial sediment has implications for the future management of the Loch Dee basin, with leaching into the overlying waters likely, given the continuation of current trends of lake acidification.

Electronic Resource

1432-0495

Key words Acid mine drainage ; Hydrochemistry ; Modelling ; Zimbabwe

Springer Online Journal Archives 1860-2000

Geosciences

Abstract  Acid mine drainage (AMD) with a minimum pH of 0.52 was recorded at Iron Duke mine near Mazowe, Zimbabwe during an investigation of the environmental geochemistry of mine waters in the Greenstone Belts of Zimbabwe. Hydrochemical data for waters emanating from the Iron Duke waste-rock pile indicate their super-saturation with respect to Fe and SO4 2–. Extremely high dissolved concentrations of Al, Zn, Cu, Co, Ni, V, Cr, Cd and As also prevail. Substantial losses of metals from solution occur within 400 m of the AMD source through the precipitation of crystalline sulphates, principally melanterite. Further downstream, hydrous oxide precipitation forms the dominant mechanism of metal attenuation in waters characteristically under-saturated with respect to Fe sulphates. Speciation and saturation index data generated using the equilibrium model WATEQ4F, suggest that such codes have broad utility for generic prediction of the mineralogical contraints on metal mobility in acute AMD systems. Major discrepancies between modelled and empirical hydrochemistries are, however, evident for super-saturated waters in which the kinetics of Fe precipitation are slow, and in which total ionic strengths markedly exceed their theoretical maximum.

Electronic Resource

1432-0495

Key words Mercury ; Mining ; Contamination ; Philippines

Springer Online Journal Archives 1860-2000

Geosciences

Abstract  An integrated geochemical and toxicological assessment of environmental mercury contamination and attendant human exposure in Honda Bay, Palawan was undertaken in 1995 following a nationally reported pollution scare centered on a coastal jetty, Sitio Honda Bay, constructed using approximately 1 million tons of tailings and beneficiation waste from a cinnabar mine. Mercury (Hg) data for marine and fluvial sediments, fish tissues and human hair indicate that the toxicological hazard is considerably lower than initially reported by state environment and health officials. Typical Hg concentrations in surficial Honda Bay sediments were found to lie within the global background range (〈60 μg/kg). Downcore profiles provide no evidence of enhanced Hg fluxes coincident with the onset of mining and/or coastal tailings disposal. The mean and median Hg concentrations recorded in tissues of six species of Honda Bay fish are compliant with thresholds established by the US Environmental Protection Agency (US-EPA) for marketable stocks. Earlier reports of 'Minamata range' Hg concentrations in fish and shellfish from Honda Bay remain unsubstantiated. Geochemical analyses of samples of the Sitio Honda Bay substrate have confirmed the prevalence of solid-phase Hg concentrations to ca. 340 mg/kg. The speciation of Hg is, however, dominated by secondary oxides of low bioavailability. The mean Hg concentration in hair from Sitio Honda Bay residents (4.41 mg/kg) was found to be statistically analogous to that for a neighbouring coastal community unimpacted by the coastal disposal of mine waste. A negligible residential exposure factor is thus inferred for the former. Relatively high hair Hg burdens prevail throughout the coastal Honda Bay population, consistent with significant methyl Hg ingestion through daily fish consumption. The data presented provide no environmental or toxicological justification for immediate remedial action.

Electronic Resource

1432-1211

Springer Online Journal Archives 1860-2000

Biology

Medicine

Electronic Resource

1573-2932

Overbank flooding ; redox potentials ; wetland criteria ; hydrologic modeling ; hydrogeomorphology

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract A four hectare mixed bottomland hardwood site on Ninety Six Creek in the Piedmont of South Carolina near Ninety Six, SC was studied for two years to characterize wetland traits. The soils were thermic Fluventic or Fluvaquentic Dystrochrepts predominantly Shellbluff series and well drained. Overbank flooding occurred on the average of 4 times per year and 1.5 times during the growing season for a 13 year period. High water table levels during the early growing season were related to rainfall events. A hydrologic model (WATRCOM-2D), soils, water table levels, and GIS techniques were used to estimate the portion of the bottom that met wetland criteria similar to those defined in the 1987 and 1989 federal wetland delineation manuals. Less than one hectare met these criteria. The wetland “status” of the vegetation within the bottom and adjacent slope was not correlated with water table levels, predicted wetland areas, or landforms. Wetland traits of the site were closely related to hydric soil traits within the upper 25 cm of the Chewacla and Chenneby soils and landform characteristics. Wetlands in this bottom were primarily driven by local precipitation and not by overbank flooding as originally suspected. Songbirds and small mammals were relatively abundant in the small bottom during the spring and summer of 1992. Protection of only the jurisdictional wetlands in this bottom would not be adequate to sustain riverine functions (conveyor) and to provide wildlife travel corridors between adjacent forested areas.

Electronic Resource

1573-2983

Springer Online Journal Archives 1860-2000

Geosciences

Medicine

Electronic Resource

1573-2983

Springer Online Journal Archives 1860-2000

Geosciences

Medicine

Electronic Resource

1573-2983

hair analysis ; mercury ; mining ; Philippines

Springer Online Journal Archives 1860-2000

Geosciences

Medicine

Abstract Human mercury (Hg) exposure in two contrasting areas of mining and mineral processing activity on the Philippine islands of Mindanao and Palawan was evaluated using hair analysis. On Mindanao, samples were collected from residents of Apokon, a major regional centre for gold beneficiation. On Palawan, a former cinnabar mine and mine-waste disposal site in Honda Bay formed the focus of investigation. Relatively high hair Hg burdens (up to 13 mg Hg kg−1 at Apokon and 18.5 mg Hg kg−1 in Honda Bay) were observed in both populations, with occupational factors apparently constituting a first-order exposure control. At Apokon, hair burdens in excess 2 mg Hg kg−1 were recorded in 90% of Au processing plant workers, compared with 21% of other sectors of the population. In Bay, ex-mineworkers, although possibly subject to occupational Hg exposure in the past, now display no evidence of this influence. Fishermen, however, systematically yielded hair Hg concentrations a factor of 2.5 higher than those of the remaining population. Approximately 7% of the Apokon and Honda Bay residents sampled presented hair Hg concentrations equal to or in excess of the World Health Organisation (WHO) reference dose. There is little evidence to indicate that residential factors significantly influence Hg exposure in either area. Hazard mitigation strategies involving the isolation of resident populations from perceived contaminant sources such as ore processing plant and sites of mine-waste disposal are, therefore, unlikely to prove beneficial.

Electronic Resource

1432-136X

Phoca vitulina ; Swimming ; Metabolism ; Fuel

Springer Online Journal Archives 1860-2000

Biology

Medicine

Summary 1. The turnover rates and oxidation rates of plasma glucose, lactate, and free fatty acids (FFA) were measured in three harbor seals (average mass=40 kg) at rest or during voluntary submerged swimming in a water flume at 35% (1.3 m·s-1) and 50% (2 m·s-1) of maximum oxygen consumption (MO2max). 2. For seals resting in water, the total turnover rates for glucose, lactate, and FFA were 23.2, 26.2, and 7.5 μmol·min-1·kg-1, respectively. Direct oxidation of these metabolites accounted for approximately 7%, 27%, and 33% of their turnover and 3%, 7%, and 18% of the total ATP production, respectively. 3. For swimming seals,MO2max was achieved at a drag load equivalent to a speed of 3 m·s-1 and averaged 1.85 mmol O2·min-1·kg-1, which is 9-fold greater than resting metabolism in water at 18°C. 4. At 35% and 50%MO2max, glucose turnover and oxidation rates did not change from resting levels. Glucose oxidation contributed about 1% of the total ATP production during swimming. 5. At 50%MO2max, lactate turnover and anaerobic ATP production doubled, but the steady state plasma lactate concentration remained low at 1.1 mM. Lactate oxidation increased 63% but still contributed only 4% of the total ATP production. Anaerobic metabolism contributed about 1% of the total ATP production at rest and during swimming. 6. The plasma FFA concentration and turnover rate inereased only 24% and 37% over resting levels, respectively, at 50%MO2max. However, the oxidation rate increased almost 3.5-fold and accounted for 85% of the turnover. The percentage of total ATP produced (21%) from FFA oxidation at 35% and 50%MO2max did not increase greatly over that at rest. 7. Dive duration decreased from 78 s while resting in water to 28 s at 50%MO2max. 8. The RQ ranged from 0.78 at rest to 0.74 at 50%MO2max, indicating that fat was an important source of energy during submerged swimming. 9. By adjusting breath-hold duration during strenuous underwater swimming, harbor seals are able to maintain an aerobic, fat-based metabolism.

Electronic Resource

1432-136X

Heart rate ; Oxygen consumption ; Harbor seal ; Sea lion

Springer Online Journal Archives 1860-2000

Biology

Medicine

Summary Respiratory, metabolic, and cardiovascular responses to swimming were examined in two species of pinniped, the harbor seal (Phoca vitulina) and the California sea lion(Zalophus californianus). 1. Harbor seals remained submerged for 82–92% of the time at swimming speeds below 1.2 m·s-1. At higher speeds, including simulated speeds above 1.4 m·s-1, the percentage of time spent submerged decreased, and was inversely related to body weight. In contrast, the percentage of time spent submerged did not change with speed for sea lions swimming from 0.5 m·s-1 to 4.0 m·s-1. 2. During swimming, harbor seals showed a distinct breathhold bradycardia and ventilatory tachycardia that were independent of swimming speed. Average heart rate was 137 beats·min-1 when swimming on the water surface and 50 beats·min-1 when submerged. A bimodal pattern of heart rate also occurred in sea lions, but was not as pronounced as in the seals. 3. The weighted average heart rate (WAHR), calculated from measured heart rate and the percentage time spent on the water surface or submerged, increased linearly with swimming speed for both species. The graded increase in heart rate with exercise load is similar to the response observed for terrestrial mammals. 4. The rate of oxygen consumption increased exponentially with swimming speed in both seals and sea lions. The minimum cost of transport calculated from these rates ranged from 2.3 to 3.6 J · m-1 · kg-1, and was 2.5–4.0 times the level predicted for similarly-sized salmonids. Despite different modes of propulsion and physiological responses to swimming, these pinnipeds demonstrate similar transport costs.

Electronic Resource