bluuebunny/crossref_metadata_2025 huggingface dataset:
A Fracture Toughness Data Bank
Authors: Kaufman JG , Collis SF
Published: February 2009

A data bank containing fully characterized plane-strain fracture toughness test data on aluminum products has been developed for The Metal Properties Council. Procedures were developed for computer storage, retrieval, and analysis of the data. Statistical tolerance limits were determined for two high-strength high-toughness plate products to demonstrate the system's capability. Regression analyses correlating plane-strain fracture toughness values with notch-yield ratios were performed on data for the same two products to generate critical notch-yield ratios. Such critical notch-yield ratios can be used for quality assurance purposes. The fully characterized test data provide system capability for validity criteria revision, although this was not done in the initial contract.
An Optimal Method for Determining Anisotropic Parameters Under Combined Stress Tests
Authors: Ikegami K
Published: February 2009

An optimal test method to determine the anisotropic parameters of the yield condition under a combined stress state is proposed. Because scattering of experimental values affects the calculated results, the combined stress tests should be conducted under conditions that minimize the scattering effect. Hill's anisotropic yield function is used to establish such a test condition.
Laser Scanner for Exoelectron Display and Measurement of Fatigue Damage
Authors: Baxter WJ
Published: February 2009

Fatigue damage in metals can be displayed and assessed by means of exoelectron emission. The surface of a fatigue sample is scanned by a focused ultraviolet laser and the spatial distribution of the exoelectron emission is displayed on an oscilloscope. The operation of the system is illustrated by torsional and reverse bending fatigue tests on two different types of steel. The local intensity of the emission is a quantitative measure of the local deformation and permits the accumulated damage to be expressed in terms of the fraction of fatigue life expended.
Results of Interlaboratory Test Programs to Evaluate the ⅝-in. (16-mm) Dynamic Tear Test Method
Authors: Heberling TG , Harris ES , Lange EA
Published: February 2009

An ASTM Task Group evaluated the “Proposed Method for ⅝-in. (16-mm) Dynamic Tear Test of Metallic Materials.” Effects of testing machine type, impact velocity, specimen geometry, and testing variables on dynamic tear test results were determined. The method was found to be useful in reproducibly determining fracture energy and transition temperature. Difficulties were encountered in pressing the notch tip to the specified depth range, and the method has been modified.

Dynamic tear absorbed energy was not significantly affected by testing machine type or impact velocity. Small but statistically significant energy differences were found among the participating laboratories as a result of specimen preparation and testing variables. Increasing experience with the test method should make possible the reduction or elimination of these differences.
A Modified Fourier Method of Shape and Surface Texture Analysis of Planar Sections of Particles
Authors: Czarnecka ET , Gillott JE
Published: February 2009

A mathematical model based on a Fourier series expansion has been used to represent the roughness of planar sections of particles, that is, the combined effect of shape and surface texture. A new coefficient T is introduced which more precisely expresses the total roughness of the projected two-dimensional profile. It also gives a measure of shape and texture contribution factors separately. The value of the total roughness coefficient depends on the Fourier amplitude coefficients Cn, the length of the perimeter of the profile, and the difference between the maximum and minimum radii. Therefore the value of the total roughness coefficient T is a better representation of grain morphology than is a coefficient derived only from Fourier terms to which shape makes a dominant contribution. This value is the sum of the shape contribution factor Pc and the texture contribution factor Tc.
The Effect of Hygrothermal History on Residual Strength of Glass Fiber Reinforced Plastic Laminates
Authors: Ishai O , Arnon U
Published: February 2009

Structural glass fabric/epoxy laminates were exposed to various periods of immersion in water at room and elevated temperatures and tested after oven drying. Changes in weight, dimensions, and mechanical characteristics with exposure indicated that immersion in hot water had a significant effect on residual weight loss and residual tensile strength. A correlation between these two variables could be derived which is independent of hygrothermal history. The observed deterioration of mechanical properties is attributable mainly to degradative processes to which the glass fiber reinforced plastic laminate is subjected as a result of water penetration processes that are accelerated at elevated temperature.
Fatigue Life and Crack Propagation Analyses of Welded Components Containing Residual Stresses
Authors: Smith KN , El Haddad M , Martin JF
Published: February 2009

This study deals with the fatigue of welded components emphasizing the use of small specimen data, a general stress-strain expression, the fatigue notch factor, and the effect of residual stresses. A computer-based fatigue damage analysis for welded structures is investigated; although accurate fatigue predictions have been made for notched structures, this type of analysis has not previously been applied to welded components. Fatigue crack propagation data are presented emphasizing the mean stress effect on the rate of cracking. Crack measurements have been made for both butt and fillet welded specimens in which the cracks commence from the toe of the weld.

For fillet welded attachments and butt welds with substantial reinforcement, a residual stress adjustment was made based on the assumption that the maximum stress at the notch root is equal to yield stress. A fatigue damage analysis for welded specimens subjected to block loading using a computer-based damage model gave results close to experimental data. With a proposed stress function as the controlling stress parameter for crack growth, crack propagation data were successfully correlated.
Enhancement of Compressive Properties of Failed Concrete Cylinders with Polymer Impregnation
Authors: Blankenhorn PR , Kline DE
Published: February 2009

Compressive properties of concrete which was failed in compression and then impregnated were investigated. Specimens were impregnated with a vacuum-pressure technique. The two monomer systems used were epoxy and a methyl methacrylate prepolymer system. The mixing ratio of the methyl methacrylate prepolymer system was adjusted so that its viscosity was very close to that of the epoxy system just prior to impregnation. Control specimens (not failed) were also impregnated with the monomer systems and tested in compression to compare their data with the data of the failed-impregnated specimens. The specimens which were failed and then impregnated had compressive data, stress-strain curves, compressive modulus and compressive strength almost identical to the impregnated controls. The work suggests that the epoxy system used in the study fills the void volume of the specimens somewhat better than the methyl methacrylate prepolymer system.
An Apparatus for Two-Dimensional Measurement of the Shrinkage Resistance of Soils
Authors: Uzan J
Published: February 2009

This paper deals with the behavior of an Israeli fat clay under the combined action of shrinkage due to drying and tensile stresses which develop as a result of controlled shrinkage. Since the behavior is known to be nonlinear, an appropriate theoretical background which permits design of apparatuses and tests is presented. Two apparatuses are described which allow for the measurement of stress and strain in a two-dimensional state of stressing. Results of preliminary tests are presented and analyzed.
A Strain Gage Method for Determining the Mechanical Properties of Filaments
Authors: Swearengen JC , Ericksen RH
Published: February 2009

A test method has been established which permits utilization of strain gages to obtain mechanical properties of filaments. Uniaxial monotonic load-strain and creep measurements were made using several techniques to verify that the method measures properties representative of the flaments. The method eliminates the requirements of obtaining a compliance calibration of the testing machine and has the advantage of facilitating measurements of small strains in filaments having very high stiffness.
Tensile Creep of Angle-Plied Boron/Epoxy Laminates
Authors: Chwirut DJ
Published: February 2009

Tensile creep tests were performed at 75°F (24°C) and 300°F (149°C) on 26 specimens cut from ±30-deg and ±45-deg laminates of boron/epoxy composite material to characterize the creep behavior of these materials. A linear viscoelastic laminate theory proposed by McQuillen was compared with the experimental data for the tests run at 75°F (24°C). The predicted creep strains differed greatly from the measured values, indicating that the linear theory is not applicable to laminates with these filament orientations. A general creep equation of the form ε = kσmtn was fitted to the experimental data with excellent correlation. The stress exponents was fitted to the experimental data with excellent correlation. The stress exponents m varied from 1.79 to 5.17 for the four series of tests, thus characterizing the nonlinear behavior of boron/epoxy laminates with these filament orientations.
A Simple Technique for Determining Relative Strength of Aggregates
Authors: Rad PF
Published: February 2009

The performance of graded aggregate bases can normally be determined from the property indexes of the aggregate materials such as compressive strength, density, abrasion, hardness, and absorption. All these values can be systematically obtained through standardized laboratory operations.

A simple impact technique is advocated for characterization of base materials in the field. This technique, modified from one successfully used in fragmentation operations, uses a cylinder nearly 3 in. (76 mm) in diameter and 26 in. (660 mm) high. A sample of the material is placed on the bottom and impacted with a standard weight. The change in size distribution of the material as a result of several impacts is used to determine the impact strength index (ISI). The value of ISI correlates with unconfined compressive strength and specific energy. Progress is being made to determine correlation of the results of a multisize sample with compressive strength and the Los Angeles number.
Detection of Chrysotile Asbestos in Airborne Dust from Thermosetting Resin Grinding
Authors: Faulring GM , Forgeng WD , Kleber EJ , Rhodes HB
Published: February 2009

Airborne dust samples generated during grinding thermosetting resin plaques containing 0.8 to 18% chrysotile and reference samples were examined optically and on the electron microprobe up to magnifications of ×900.

Chrysotile in dust samples was analyzed by new methods using iodine in solution or as a vapor for selectively staining chrysotile and increasing its visibility and by the NIOSH phase contrast method. No free fibers of chrysotile were detected in dust collected from 0.8% chrysotile-polyester plaques. Only a low-level concentration was found in dust from 4–18% chrysotile-polyester plaques. The difference in texture of chrysotile and cellulose ester membrane (CEM) filters was emphasized by vacuum deposition of aluminum and carbon.

The importance of care in handling chrysotile-bearing CEM filters and the improvement in retention with carbon coating are described.

Electron microprobe methods are presented that distinguish between chrysotile completely encapsulated in resin and chrysotile with a free surface. The airborne chrysotile in the grinding dust was usually nonfibrous, encapsulated in resin, and closely associated with other materials. In the samples analyzed, the number of chrysotile fibers with a free surface varied from zero to two per thousand dust particles.
Climate and soil‐age constraints on nutrient uplift and retention by plants
Authors: Porder Stephen , Chadwick Oliver A.
Published: February 2009

Plants and soils represent coevolving components of ecosystems, and while the effects of soils (e.g., nutrient availability) on plants have been extensively documented, the effect of plants on soils has received less attention. Furthermore there has been no systematic investigation of how plant effects vary across important ecological gradients in climate or soil age, which leaves a substantial gap in our understanding of how plant–soil systems develop. In this context, we analyzed changes in nutrient availability and elemental losses from the entire weathering zone at 35 sites arrayed across climatic and soil‐age gradients on the island of Hawai‘i. The sites are located on three basaltic lava flows (ages 10, 170, and 350 kyr) each of which crosses a precipitation gradient from ∼500 to 2500 mm/yr. By comparing the loss of nutrient (potassium, phosphorus) and non‐nutrient (e.g., sodium) rock‐derived elements, we identify a climatic zone at intermediate rainfall where the retention of plant nutrients in the upper soil is most pronounced. We further show that there are several abiotic constraints on plant‐driven retention of nutrients. At the dry sites (≤750 mm/yr on all three flows), plants slow the loss of nutrients, but the effect (as measured by the difference between K and Na losses) is small, perhaps because of low plant cover and productivity. At intermediate rainfall (750–1400 mm/yr) but negative water balance, plants substantially enrich both nutrient cations and P relative to Na in the surface horizons, an effect that remains strong even after 350 kyr of soil development. In contrast, at high rainfall (≥1500 mm/yr) and positive water balance, the effect of plants on nutrient distributions diminishes with soil age as leaching losses overwhelm the uplift and retention of nutrients by plants after 350 kyr of soil development. The effect of plants on soil nutrient distributions can also be mediated by the movement of iron (Fe), and substantial Fe losses at high rainfall on the older flows are highly correlated with P losses. Thus redox‐driven redistribution of Fe may place a further abiotic constraint on nutrient retention by plants. In combination, these data indicate that the effects of soil aging on plant uplift and retention of nutrients differ markedly with precipitation, and we view this as a potentially fruitful area for future research.
Defining fundamental niche dimensions of corals: synergistic effects of colony size, light, and flow
Authors: Hoogenboom Mia O. , Connolly Sean R.
Published: February 2009

The “fundamental niche” is the range of conditions under which an organism can survive and reproduce, measured in the absence of biotic interactions. Niche measurements are often based on statistical relationships between species presence and measured environmental variables, or inferred from measured responses of species along hypothesized niche axes. In this study, we use novel, process‐based models of how irradiance and gas diffusion influence photosynthesis and respiration to predict niche dimensions for three coral species: Acropora nasuta, Montipora foliosa, and Leptoria phrygia. We use a combination of mathematical modeling, laboratory experiments, and field observations to establish the link between energy acquisition and the dominant environmental gradients on reefs: light intensity and water flow velocity. Our approach allows us to quantify how the shape of the niche varies in response to light and flow conditions. The model predicts that, due to its higher photosynthetic capacity, the branching coral A. nasuta has a positive energy balance over a wider range of conditions than both a massive species (L. phrygia) and a foliose species (M. foliosa). Moreover, colony size influences niche width, with larger colonies of all three species achieving a positive energy balance over a broader range of conditions than small colonies. Comparison of model predictions with field data demonstrated that tissue biomass and reproductive output are significantly and positively correlated with predicted energy acquisition. These results show how interactions between light and flow determine organism performance along environmental gradients on coral reefs. In addition, this study demonstrates the utility of process‐based models for quantifying how physiology influences ecology, and for predicting the ecological consequences of varying environmental conditions.
Functional differences within a guild of tropical mammalian frugivores
Authors: Brodie Jedediah F. , Helmy Olga E. , Brockelman Warren Y. , Maron John L.
Published: February 2009

Many plants interact with groups of mutualist pollinators and seed dispersers. A key issue for both basic ecology and conservation is whether the different species within these guilds of mutualist animals are functionally equivalent. Comparing the relative effects of sympatric mutualists is important for understanding the evolution of multispecies mutualisms and for predicting mutualism stability in the face of anthropogenic change. However, empirical comparisons of the population‐level impacts of mutualist animals on their host plant are rare, particularly for seed dispersal mutualisms in species‐rich ecosystems. We compared the influence of three seed‐dispersing tropical mammals, lar gibbons (Hylobates lar), sambar deer (Rusa unicolor), and red muntjac deer (Muntiacus muntjak), on the demography of a shared host tree in Thailand,Choerospondias axillaris(Anacardiaceae). Sambar and muntjac dispersed far moreC. axillarisseeds than did gibbons. While sambar deposited many seeds under female tree canopies, muntjac were the only disperser to move seeds to open microhabitats, whereC. axillarisseed germination, seedling survival, and initial growth are enhanced. Using stage‐based population models, we assessed how disperser‐specific seed dispersal, variation in the frequency of canopy gap formation, and their interaction influenced the potential population growth ofC. axillaris. Large differences in dispersal quantity and small differences in dispersal quality among sambar and gibbons resulted in similar and negligible impacts on the tree's population dynamics. Muntjac, by taking some of the seeds to open microhabitats, are projected to have a greater positive impact onC. axillarisdemography than either sambar or gibbons. Model comparisons of population‐level species impacts may allow us to predict which ecological interactions are at risk from loss of critical species.
Modeling the sampling effect in the species–time–area relationship
Authors: McGlinn Daniel J. , Palmer Michael W.
Published: February 2009

Recent empirical work in numerous systems has demonstrated the interdependence of spatial and temporal accumulation of species in the species–time–area relationship (STAR). The purpose of this study was to develop a process‐based stochastic model for the STAR that assumes species neutrality and to compare the model's expectations to data collected on plant species in a tallgrass prairie. We varied two important aspects of the neutral species assemblage: evenness in the species pool and individual replacement rate (R). When R is larger than ∼0.5 and evenness is intermediate to high, the neutral STAR generates patterns qualitatively similar to the empirical STAR. Our model also indicates that space and time were not symmetrical in their effects on species accumulation, except in the special case of R = 1.0. We observed both positive and negative time‐by‐area interactions in the sampling model, which indicates that nonzero interactions are not necessarily evidence of ecological processes. Furthermore, as accumulated richness approaches the size of the species pool, the time‐by‐area interaction becomes increasingly negative in our model. This suggests that negative time‐by‐area interactions should be expected a priori in empirical systems if rates of species accumulation decrease due to increasing rarity of unique species. Given the wide range of STARs that the sampling model generated, the difficulty in estimating key parameters, and the complexity of assessing the relative abundance distribution and scale of the species pool, we cannot refute the sampling effect, and we suggest caution in accepting ecologically oriented explanations of empirical STARs.
Establishment of parallel altitudinal clines in traits of native and introduced forbs
Authors: Alexander Jake M. , Edwards Peter J. , Poll Myriam , Parks Catherine G. , Dietz Hansjörg
Published: February 2009

Due to altered ecological and evolutionary contexts, we might expect the responses of alien plants to environmental gradients, as revealed through patterns of trait variation, to differ from those of the same species in their native range. In particular, the spread of alien plant species along such gradients might be limited by their ability to establish clinal patterns of trait variation. We investigated trends in growth and reproductive traits in natural populations of eight invasive Asteraceae forbs along altitudinal gradients in their native and introduced ranges (Valais, Switzerland, and Wallowa Mountains, Oregon, USA). Plants showed similar responses to altitude in both ranges, being generally smaller and having fewer inflorescences but larger seeds at higher altitudes. However, these trends were modified by region‐specific effects that were independent of species status (native or introduced), suggesting that any differential performance of alien species in the introduced range cannot be interpreted without a fully reciprocal approach to test the basis of these differences. Furthermore, we found differences in patterns of resource allocation to capitula among species in the native and the introduced areas. These suggest that the mechanisms underlying trait variation, for example, increasing seed size with altitude, might differ between ranges. The rapid establishment of clinal patterns of trait variation in the new range indicates that the need to respond to altitudinal gradients, possibly by local adaptation, has not limited the ability of these species to invade mountain regions. Studies are now needed to test the underlying mechanisms of altitudinal clines in traits of alien species.
Behavioral correlations provide a mechanism for explaining high invader densities and increased impacts on native prey
Authors: Pintor Lauren M. , Sih Andrew , Kerby Jacob L.
Published: February 2009

The fact that superabundant invasive pests are also sometimes highly aggressive represents an interesting paradox. Strong intraspecific aggression should result in high intraspecific competition and limit the densities reached by exotic species. One mechanism that can allow invaders to attain high densities despite high intraspecific aggression, involves positive correlations between aggression and other behaviors such as foraging activity. We conducted a mesocosm experiment to quantify the ecological implications of correlations between aggressiveness and foraging activity among groups of exotic signal crayfish (Pacifastacus leniusculus) at low and high densities. Our results showed that high invader densities increased intraspecific aggression and per capita interactions between crayfish, but also increased foraging activity and impacts on preferred prey. As a result, exotic crayfish did not show density‐dependent reductions in per capita feeding or growth rates. We suggest that the positive correlation between aggression and activity is part of an aggression syndrome whereby some individuals are generally more aggressive/active than others across situations. An aggression syndrome can couple aggressive behaviors important to population establishment of invasive species with foraging activity that enhances the ability of invaders to attain high densities and have large impacts on invaded communities.
Projected climate‐induced faunal change in the Western Hemisphere
Authors: Lawler Joshua J. , Shafer Sarah L. , White Denis , Kareiva Peter , Maurer Edwin P. , Blaustein Andrew R. , Bartlein Patrick J.
Published: February 2009

Climate change is predicted to be one of the greatest drivers of ecological change in the coming century. Increases in temperature over the last century have clearly been linked to shifts in species distributions. Given the magnitude of projected future climatic changes, we can expect even larger range shifts in the coming century. These changes will, in turn, alter ecological communities and the functioning of ecosystems. Despite the seriousness of predicted climate change, the uncertainty in climate‐change projections makes it difficult for conservation managers and planners to proactively respond to climate stresses. To address one aspect of this uncertainty, we identified predictions of faunal change for which a high level of consensus was exhibited by different climate models. Specifically, we assessed the potential effects of 30 coupled atmosphere–ocean general circulation model (AOGCM) future‐climate simulations on the geographic ranges of 2954 species of birds, mammals, and amphibians in the Western Hemisphere. Eighty percent of the climate projections based on a relatively low greenhouse‐gas emissions scenario result in the local loss of at least 10% of the vertebrate fauna over much of North and South America. The largest changes in fauna are predicted for the tundra, Central America, and the Andes Mountains where, assuming no dispersal constraints, specific areas are likely to experience over 90% turnover, so that faunal distributions in the future will bear little resemblance to those of today.
From Socially Weak to Potential Consumer: Changing Discourses on Elder Status in South Korea
Authors: Kim Heekyoung , Traphagan John W.
Published: February 2009

This article explores social and political dimensions associated with providing care for elders in South Korea. We look at changes in welfare policy since the 1980s and discuss the emergence of a long-term care insurance program in Korea similar to the program promulgated in Japan in 2000. We argue that while the status of South Korean elderly is undergoing change as new policies provide opportunities for elders to move from positions of dependency to increased independence as consumers of health care services, there are some reasons for concern. The capacity of elders to function as consumers remains tied to the fact family members or elders themselves must pay supplements to their health insurance premiums as well as significant co-payments for services rendered, and government policies retain a strong bias toward requiring in-home, family-centered care of frail and bedfast elders.
Family Medical Leave as a Resilience Resource for Family Caregivers
Authors: Swanke Jayme , Zeman Laura Dreuth
Published: February 2009

Case managers mobilize family networks to care for patients. Family medical leave can be a resource for case managers who seek to enhance resilience among family caregivers. The Family Medical Leave Act, passed in 1993, was the first U.S. policy to regulate employee leaves from work for family care purposes (29 CFR 825.102). This policy offers family caregivers increased flexibility and equality. Current and emerging policies also can reduce financial strain. The discussion examines how case managers can integrate family medical leave into best-practice models to support patients and family caregivers.
Methods for estimating the bioconcentration factor of ionizable organic chemicals
Authors: Fu Wenjing , Franco Antonio , Trapp Stefan
Published: February 2009

The bioaccumulation potential is an important criterion in risk assessment of chemicals. Several regressions between bioconcentration factor (BCF) in fish and octanol-water partition coefficient (KOW) have been developed for neutral organic compounds, but very few approaches address the BCF of ionizable compounds. A database with BCFs of 73 acids and 65 bases was collected from the literature. The BCF estimation method recommended by the Technical Guidance Document (TGD) for chemical risk assessment in the European Union was tested for ionizing substances using log KOW (corrected for the neutral species, log[fn·KOW]) and log D (sum of log KOW of neutral and ionic molecule, apparent log KOW) as predictors. In addition, the method of Meylan et al. (Environ Toxicol Chem 1999; 18:664–672) for ionizable compounds and a dynamic cell model based on the Fick-Nernst-Planck equation were tested. Moreover, our own regressions for the BCF were established from log KOW and pKa. The bioaccumulation of lipophilic compounds depends mainly on their lipophilicity, and the best predictor is log D. Dissociation, the pH-dependent ion trap, and electrical attraction of cations impact the BCF. Several methods showed acceptable results. The TGD regressions gave good predictions when log(fn·KOW) or log D were used as a predictor instead of log KOW. The new regressions to log KOW and pKa performed similarly, with mean errors of approximately 0.4. The method of Meylan et al. did not perform as well. The cell model showed weak results for acids but was among the best methods for bases.
Technical basis for polar and nonpolar narcotic chemicals and polycyclic aromatic hydrocarbon criteria. III. A polyparameter model for target lipid partitioning
Authors: Kipka Undine , Di Toro Dominic M.
Published: February 2009

A method is presented for extending the target lipid model (TLM) of narcotic toxicity to polar narcotic chemicals. The proposed polyparameter TLM extends the applicability of the TLM by including polar compounds and removing explicit chemical class corrections. The validity of the model is tested using a data set of 1,687 acute toxicity tests for 42 aquatic species, including fish, amphibians, arthropods, mollusks, polychaetes, coelenterates, protozoans, and algae, and 398 chemicals. The target lipid-water partition coefficient is computed using the Abraham polyparameter model. This replaces use of the octanol-water partition coefficient so that the partitioning of polar narcotic chemicals can be described correctly. The model predicts the log median lethal concentration with a root mean square error of 0.460 for nonpolar and polar chemicals and 0.501 for only polar chemicals.
Tropical Spiderwort (Commelina benghalensis L.) Increases Growth under Elevated Atmospheric Carbon Dioxide
Authors: Price Andrew J. , Runion G. Brett , Prior Stephen A. , Rogers Hugo H. , Torbert H. Allen
Published: February 2009

Although considerable effort is being spent studying exotic plant pests, little consideration has been given as to how invasive plants might react to the increasing concentration of CO2 in the atmosphere. Tropical spiderwort (Commelina benghalensis L.) is considered one the world's worst weeds and is becoming more of a problem in agricultural settings of the southeastern USA. Growth responses of tropical spiderwort were evaluated using plants grown in containers with a soilless potting medium under ambient and elevated (ambient + 200 μmol mol−1) levels of CO2 in open‐top field chambers. Although plant height was unaffected by CO2, leaf and flower number tended to increase (approximately 23%) when exposed to elevated CO2 Aboveground plant parts exhibited significant increases in dry weight when exposed to high CO2; leaf, flower, stem, and total shoot dry weights were increased by 36, 30, 48, and 44%, respectively. Total plant dry weight was increased by 41% for plants grown under high CO2 Root dry weight and root length were unaffected by CO2 concentration. Tropical spiderwort allocated more biomass to stems and tended to allocate less to roots when plants were exposed to high CO2 Plant carbon concentration and content tended to be higher in CO2–enriched plants, whereas plant nitrogen concentration tended to be lower; thus, elevated CO2–grown plants had higher C/N ratios. Also, the amount of biomass produced per unit nitrogen was higher for plants exposed to elevated CO2 The growth response of this plant is in the upper range typical for C3 plants.
The Effects of Season and Agriculture on Nitrous Oxide Production in Headwater Streams
Authors: Beaulieu J. J. , Arango C. P. , Tank J. L.
Published: February 2009

Streams and rivers are a globally significant source of nitrous oxide (N2O), a potent greenhouse gas. However, there remains much uncertainty in the magnitude of N2O emissions from these sources, partly due to an incomplete understanding of the factors that control microbial N2O production in lotic sediments. During 2004–2005 we measured sediment N2O production in 12 headwater streams across an agricultural land use gradient. Stream water nitrate (NO3−) concentrations were positively related to the proportion of agricultural land use in the basin and frequently exceeded 20 mg N L−1 in the stream draining the most agricultural basin. Stream sediments were nearly always a net source of N2O, and production rates were positively related to stream water NO3− concentrations and sediment carbon content. There were no seasonal patterns in N2O production rates during 2004, but stream water NO3− and N2O production both peaked during the winter of 2005. The spike in NO3− concentrations likely resulted from winter rain and snowmelt that flushed NO3− from the soils following a dry summer and fall. In turn, the elevated stream water NO3− concentrations stimulated in‐stream N2O production rates. Overall, we were only able to explain 29% of the variation in N2O production rates on a log scale. The unexplained variation may be due to differences in the fraction of denitrified NO3− that is converted to N2O among the study sites, or that our measures of substrate availability in the water column were not reflective of substrate availability in the porewater used by denitrifiers.
Impact of Sedimentation on Wetland Carbon Sequestration in an Agricultural Watershed
Authors: McCarty Gregory , Pachepsky Yakov , Ritchie Jerry
Published: February 2009

Landscape redistribution of soil C is common within agricultural ecosystems. Little is known about the effects of upland sediment deposition on C dynamics within riparian wetlands. To assess sedimentation impact, we obtained profile samples of wetland soil and used the combination of 137Cs, 210Pb, and 14C chronological markers to determine rates of C sequestration and mineral deposition over the history of a wetland within a first‐order catchment under agricultural management in the coastal plains of the United States. Substantial post settlement deposition in the wetland soil was evidenced in places by a 20‐ to 40‐cm layer of mineral soil that buried the original histosol. Soil profiles contained a minimum in C content within the top 35 cm of the profile which originated from a rapid deposition from low C upland soils. Radiocarbon and radioisotope dating showed that increases in C above this minimum were the result of C sequestered in the past ∼50 yr. Modeling the kinetics of modern C dynamics using the 137Cs and 210Pb markers within these surface profiles provides strong evidence for accelerated C sequestration associated with mineral sediment deposition in the ecosystem. These findings indicate that at the landscape scale, dilution of ecosystem C by import of low C upland sediment into wetlands stimulates C sequestration by pulling soil C content below some pedogenic equilibrium value for the ecosystem. They also indicate that over the history of the wetland, rates of C accretion may be linked to mineral soil deposition.
Variability in the Mobilization of Sediment and Phosphorus across 13 European Soils
Authors: Miller Nicola , Quinton John N. , Barberis Elisabetta , Presta Manuela
Published: February 2009

The objectives of this study were to examine the variability in mobilization and transport of primary particles and associated total phosphorus (TP) in sediments eroded by overland flow from 13 European arable soils and to consider the empirical support for more process‐based alternatives to modeling phosphorus (P) transfers. The 13 soils were subjected to simulated rainfall in laboratory experiments. Rainfall was applied to a soil flume (0.5 × 0.25 m) for 30 min at intensity of 60 mm h−1, and all overland flow generated during this period was collected. Two simulations were performed 5 d apart. The soils generated a wide range of overland flow (13.3–26.9 mm) and sediment (1.1–16.9 g). The sediments from the experiments were enriched with medium silt particles (6–20 μm). Except for one soil in the second simulation, all of the study soils produced overland flow sediments (OFS) that were enriched with P (TP 976–3884 mg kg−1, P enrichment ratio 0.92–4.42). Sediment TP was positively correlated (P < 0.05) with the sediment clay contents for both simulation events, and sediment total P enrichment was negatively correlated with soil TP. Attempts to reconstruct the TP content of sediments from TP analysis of the soil particle size fractions yielded significant (P < 0.05) relationships between reconstructed and measured TP values. However, the reconstructed TP values were consistently lower than the measured sediment TP contents, indicating that further improvements to measurement techniques are required if physically based modeling of P transport in overland flow is to be successful at small scales.
Effect of Urban Waste Compost Application on Soil Near‐Saturated Hydraulic Conductivity
Authors: Schneider S. , Coquet Y. , Vachier P. , Labat C. , Roger‐Estrade J. , Benoit P. , Pot V. , Houot S.
Published: February 2009

Compost application tends to increase soil fertility and is likely to modify soil hydrodynamic properties by acting on soil structural porosity. Two composts, a municipal solid waste compost (MSW) and a co‐compost of green wastes and sewage sludge (SGW), have been applied every other year for 6 yr to cultivated plots located on a silt loam soil in the Parisian Basin, France. Four soil zones were defined in the topsoil after plowing: the plowpan located at the base of the plowed layer, compacted (Δ) or noncompacted (Γ) zones located within the plowed layer, and interfurrows created by plowing and containing a large quantity of crop residues together with the recently‐applied compost. To assess the effect of compost application on the near‐saturated soil hydraulic conductivity, infiltration rates were measured using a tension disc infiltrometer at three water pressure potentials −0.6, −0.2, and −0.05 kPa in the various zones of the soil profile. Compost addition decreased K(sat) in the interfurrows after plowing by almost one order of magnitude with average values of 5.6 × 10−5 m.s−1 in the MSW plot and 4.1 × 10−5 m.s−1 in the SGW plot, against 2.2 × 10−4 m.s−1 in the control plot. This effect had disappeared 6 mo after plowing when the average K(sat) in the control plot had decreased to 1.9 × 10−5 m.s−1 while that in the compost‐amended plots remained stable.
Establishment and Growth of Two Willow Species in a Riparian Zone Impacted by Mine Tailings
Authors: Bourret Melody M. , Brummer Joe E. , Leininger Wayne C.
Published: February 2009

A field study was initiated to determine survival, growth characteristics, and metal uptake of two montane riparian willow species, Geyer (Salix geyeriana Andersson) and mountain (S. monticola Bebb) willow, grown in amended fluvial mine tailing deposits. Revegetation was done with staked and previously rooted cuttings to determine if planting method had an effect on successful establishment of willows. A second planting was done the following growing season which tested cuttings of different ages. The addition of lime increased the soil pH from 5.0 to 6.5 and effectively reduced bioavailability of most heavy metals below phytotoxic levels. However, both willow species, regardless of planting method, concentrated Cd, Mn, Pb, and Zn in their leaf tissue above levels considered toxic to agronomic plants. Over the course of four growing seasons, prerooted mountain willows had a consistently higher survival rate compared to staked willows. At the end of the fourth growing season, mountain willow had a higher survival rate and produced greater aboveground growth for both planting methods, irrespective of year planted, compared with Geyer willow. Based on growth characteristics, the use of prerooted mountain willows would be recommended for successful revegetation of amended fluvial mine tailing deposits in riparian zones. However, because of the high Cd uptake into aboveground tissues, care should be taken in restoration efforts where wildlife and domestic livestock are likely to browse on the willows.
Effectiveness of Vegetative Filter Strips in Reducing Pesticide Loading: Quantifying Pesticide Trapping Efficiency
Authors: Sabbagh G. J. , Fox G. A. , Kamanzi A. , Roepke B. , Tang J.‐Z.
Published: February 2009

Pesticide trapping efficiency of vegetated filter strips (VFS) is commonly predicted with low success using empirical equations based solely on physical characteristics such as width and slope. The objective of this research was to develop and evaluate an empirical model with a foundation of VFS hydrological, sedimentological, and chemical specific parameters. The literature was reviewed to pool data from five studies with hypothesized significant parameters: pesticide and soil properties, percent reduction in runoff volume (i.e., infiltration) and sedimentation, and filter strip width. The empirical model was constructed using a phase distribution parameter, defined as the ratio of pesticide mass in dissolved form to pesticide mass sorbed to sediment, along with the percent infiltration, percent sedimentation, and the percent clay content (R2 = 0.86 and standard deviation of differences [STDD] of 7.8%). Filter strip width was not a statistically significant parameter in the empirical model. For low to moderately sorbing pesticides, the phase distribution factor became statistically insignificant; for highly sorbing pesticides, the phase distribution factor became the most statistically significant parameter. For independent model evaluation datasets, the empirical model based on infiltration and sediment reduction, the phase distribution factor, and the percent clay content (STDD of 14.5%) outperformed existing filter strip width equations (STDD of 38.7%). This research proposed a procedure linking a VFS hydrologic simulation model with the proposed empirical trapping efficiency equation. For datasets with sufficient information for the VFS modeling, the linked numerical and empirical models significantly (R2 = 0.74) improved predictions of pesticide trapping over empirical equations based solely on physical VFS characteristics.
DNA-based real-time detection and quantification of aeromonads from fresh water beaches on Lake Ontario
Authors: Khan Izhar U. H. , Loughborough Alyssa , Edge Thomas A.
Published: February 2009

The present study was designed to develop a novel, rapid, direct DNA-based protocol to enumerate aeromonads in recreational waters. An Aeromonas genus-specific real-time quantitative polymerase chain reaction (Q-PCR) protocol was developed and optimized using newly designed genus-specific oligonucleotide primers derived from the gyrase B subunit (GyrB) gene. A standard curve was developed based on the PCR protocol with a minimum quantification limit of 10 cell equivalents ml−1 achieved using an autoclaved water sample from recreational water spiked with known quantities of an Aeromonas ATCC strain. The Q-PCR protocol was validated and applied to detect and quantify the total number of aeromonads in water samples collected from two fresh water beaches on Lake Ontario. The Q-PCR protocol revealed significantly higher numbers of aeromonads in all water samples than a culture-based assay at both beaches. Foreshore sand was found to serve as a reservoir of high concentrations of Aeromonas similar to this phenomenon noted for enteric bacteria like Eschershia coli. The new real-time Q-PCR protocol facilitated the rapid quantification of total numbers of Aeromonas cells present in recreational water samples in <3 hours without culturing.
Bacteriological quality and risk assessment of the imported and domestic bottled mineral water sold in Fiji
Authors: Zeenat A. , Hatha A. A. M. , Viola L. , Vipra K.
Published: February 2009

Considering the popularity of bottled mineral water among indigenous Fijians and tourists alike, a study was carried out to determine the bacteriological quality of different bottled waters. A risk assessment was also carried out. Seventy-five samples of bottled mineral water belonging to three domestic brands and 25 samples of one imported brand were analysed for heterotrophic plate count (HPC) bacteria and faecal coliforms. HPC counts were determined at 22°C and 37°C using R2A medium and a membrane filtration technique was used to determine the faecal coliform (FC) load in 100 ml of water on mFC agar. Between 28 and 68% of the samples of the various domestic brands failed to meet the WHO standard of 100 colony forming units (cfu) per 100 ml at 22°C and 7% of these also tested positive for faecal coliforms. All imported bottled mineral water samples were within WHO standards. A risk assessment of the HPC bacteria was carried out in terms of beta haemolytic activity and antibiotic resistance. More than 50% of the isolates showed beta haemolytic activity and were multi-drug resistant. While the overall quality of the product was generally good, there is a need to enforce stringent quality standards for the domestic bottlers to ensure the safety of consumers.
Development of a coarse membrane bioreactor for two-stage anaerobic digestion of biodegradable municipal solid waste
Authors: Walker M. , Banks C. J. , Heaven S.
Published: February 2009

A laboratory-scale coarse membrane bioreactor was developed to test its potential for the enhanced degradation of biodegradable municipal (solid) waste. The purpose of the mesh was to retain solid substrate and biomass in the reactor, promoting optimal degradation while also allowing intermediate soluble compounds to be removed and degraded in a second reactor. Three reactors with nylon woven mesh membranes of pore sizes 30, 100 and 140 μm were operated at a solid and liquid retention time of 20 and 1.5 days respectively and fed at an organic loading rate of 3.75 gVS l−1 d−1. Liquid effluent was fed to an anaerobic filter reactor. The total methane production for the two stage systems was very similar at 0.21–0.22 l g−1 VS added (c.f. 0.26 l g−1 VS added for BMP). The effect of increasing the pore size of the mesh was to reduce the methane production in the first stage and transfer more of this to the filter reactor, with the proportion of the total methane produced in the first stage changing from 72% to 49% between 30 and 140 μm meshes. The VS content of the first stage effluent also increased with pore size so it is likely that the mechanism for the differences in methane production is one of solids/biomass retention. The 30 μm pore size is recommended for further work since it transmitted a lower solid and soluble loading to the anaerobic filter. Solids accumulation in the second stage, although causing no problems in the 85-day operational period of this trial, could lead to blocking of the anaerobic filter, which is undesirable on a large scale.