bluuebunny/crossref_metadata_2025 huggingface dataset:
A Correlative Study Between Analysis and Experiment on the Fracture Behavior of Graphite/Epoxy Composites
Authors: Yeow YT , Morris DH , Brinson HF
Published: February 2009

Several of the current approaches to the analysis of the fracture behavior of notched fiber-reinforced composites are reviewed and discussed. Experimental results of fracture tests on uniaxial tensile strips containing center cracks are presented. Photoelastic coating photographs illustrate the regions of high stress gradient ahead of the crack for the various laminates investigated, namely, [0 deg]8s, [0 deg/90 deg]4s, [± 45 deg]4s, and [0 deg/±45 deg/0 deg]2s. A brief discussion of damage zones and fracture planes is given. Comparisons between several two-parameter fracture models and a new boundary integral equation approach of Cruse are made and comparisons between predictions of fracture strength using these models and experimental results are presented.
Evaluation of Erosion Resistance of Metallic Materials and the Role of Material Properties in Correlations
Authors: Syamala Rao BC , Veerabhadra Rao P , Lakshmana Rao NS
Published: February 2009

A study of the correlations between material properties and normalized erosion resistance (inverse of erosion rates) of various materials tested in the rotating disk and the flow venturi at various intensities indicates that different individual properties influence different stages of erosion. At high and low intensities of erosion, energy properties predominate the phenomenon, whereas at intermediate intensities strength and acoustic properties become more significant. However, both strength and energy properties are significant in the correlations for the entire spectrum of erosion when extensive cavitation and liquid impingement data from several laboratories involving different intensities and hydrodynamic conditions are considered. The use of true material properties improved the statistical parameters by 3 to 37%, depending on the intensity of erosion. It is possible to evaluate qualitatively the erosion resistances of materials based on the true stress-true strain curves.
Fundamentals of Combustion Toxicology in Fire Hazard Assessment
Authors: Packham SC , Hartzell GE
Published: February 2009

This paper discusses fundamental principles of combustion toxicology and the application of those principles in formulating test protocols and research strategies aimed ultimately toward smoke toxicity hazard assessment and the influence of materials thereupon. It offers a review of principles basic to combustion toxicology to serve as introductory reading for fire technology professionals not generally familiar with the biological aspects of applied fire research and testing. While some methods of contemporary significance are referred to or discussed, this paper is not intended to be an exhaustive review or analysis of laboratory methods that have been applied in evaluating toxicological properties of smoke.

This paper also addresses the basic issues of the assessment of toxic hazards to life and how laboratory methods may be applied in determining whether the choice of one material over another would significantly alter potential toxicological threats to life. Some approaches to laboratory assessments are given involving time-dependent bioassays of toxicological effects caused by allowing materials to perform as they would in a real fire. This paper is intended to open the way to the complex area of smoke toxicity hazard assessment in the laboratory in a relevant and practical manner.
Correlation of Fiber Composite Tensile Strength with the Ultrasonic Stress Wave Factor
Authors: Vary A , Lark RF
Published: February 2009

An acoustic-ultrasonic technique was used to indicate the strength variations of tensile specimens of a graphite/epoxy composite. A “stress wave factor” was determined and its value was found to depend on variations of the fiber-resin bonding as well as fiber orientation. The fiber orientations studied were 0 deg (longitudinal), 10 deg (off-axis), 90 deg (transverse), [0 deg/±45 deg/0 deg] symmetrical, and [±45 deg] symmetrical. Correlations indicated that the stress wave factor can predict variations of the tensile and shear strengths of composite materials. The method was also found to be sensitive to strength variations associated with microporosity and differences in fiber/resin ratio.
Optimization of the Electrical Potential Technique for Crack Growth Monitoring in Compact Test Pieces Using Finite Element Analysis
Authors: Aronson GH , Ritchie RO
Published: February 2009

Finite element procedures are used to optimize the efficiency of the electrical potential technique for monitoring the initiation and slow growth of cracks, as applied to the compact tension fracture test piece. An analysis of various configurations of current input and potential measurement lead placement is performed to optimize the accuracy, sensitivity, and reproducibility of measurement and to maximize output voltages. Numerical calibration curves are computed for selected configurations and are confirmed by experimental measurements.
Effects of Temperature on the Behavior of Metals Under Erosion by Particulate Matter
Authors: Gat N , Tabakoff W
Published: February 2009

The effect of temperature on the erosion of metals by solid particles is studied. Properties that, as the temperature increases, decrease the metals' resistance to erosion (Type I) are identified, as are other properties that increase their resistance to erosion (Type II). The removal of erosive material is accomplished through the simultaneous action of several mechanisms. Under given test conditions (such as angle of impact, particle shape, and hardness) one mechanism is likely to dominate. Whether erosion increases or decreases as the temperature increases depends on the dominant erosion mechanism because some mechanisms are affected by Type I factors while others are affected by Type II factors. This dependence may change, however, at various ranges of the temperature scale. At homologous temperatures (the ratio between the actual temperature of the material and its melting temperature, in absolute degrees) above 0.5, Type II factors dominate most erosion mechanisms. Of particular interest are the brittle-to-ductile transition temperature and the recrystallization temperature.
Concrete Core Strength—The Effect of Length to Diameter Ratio
Authors: Meininger RC , Wagner FT , Hall KW
Published: February 2009

The ASTM Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete (C 42–68) currently contains length to diameter ratio correction factors for soaked cores but not dried cores. However, it is widely recognized that for structures which will be substantially dry in service dried cores are more appropriate. It is sometimes difficult—because of constraints of aggregate size, reinforcing bar placement, and member dimensions—to obtain drilled cores of the preferred dimensions, with a length twice the diameter. Research performed in two laboratories involving the drilling and testing of a large number of 4-in. (102-mm) diameter soaked and dried cores with length to diameter ratios of 1.0, 1.25, 1.5, 1.75, and 2.0, taken from six structural-size members, indicates that the same correction factors can be used for both moisture conditions and that the factors now in ASTM Method C 42–68 should be lowered slightly. In addition, data were gathered on the effect of end preparation procedure on core strength. For the methods used (three capping procedures and grinding of the ends) no important differences in measured strength were noted.
A Simple Ductility Tester for Metal Films
Authors: Nakahara S , Okinaka Y , Turner DR
Published: February 2009

A simple apparatus for measuring the ductility of metal films is described. The specimen is held rigidly between two metal plates with circular openings while a metal ball is slowly pushed upwards until the metal film ruptures. The distance the metal ball travels between the point where it first makes contact with the film and that where the film ruptures is observed. The ductility is determined from a graph which relates this distance to elongation. Reproducibility of the measurement is better than ± 10%. The apparatus is compact, portable, and simple to operate. It is recommended where a simple, yet reproducible, technique for ductility measurement is needed on a routine basis.
Review of New Developments in Crack Propagation Studies
Authors: El Haddad MH , Topper TH , Mukherjee B
Published: February 2009

The application of fracture mechanics concepts to characterize crack growth at low and high temperatures under cyclic, creep, and creep-fatigue conditions is reviewed. The applicability and limitations of various fracture mechanics techniques in predicting cycle- and time-dependent crack growth are discussed. Also, applications of fracture mechanics to predict the fatigue life of various components and the behavior of cracks at near-threshold conditions are discussed with an emphasis given to the growth of small cracks.
Quenching, Tempering, and Aging Chromium-Molybdenum-Vanadium Cast Steels
Authors: Coulon PA , Leymonie C , Saisse H , Thauvin G
Published: February 2009

The usual specifications for Cr-Mo-V steel castings fix modest levels of yield strength (350 to 450 MPa) in the hope of obtaining acceptable toughness. But this optimism sometimes leads to disappointment when only the components themselves are considered and not the attached parts. Tests carried out on Cr-Mo steel casings that have 100 000 h or more of service life show that, if toughness is sufficiently high in the as-received condition, and if certain precautions are taken into account at start-up, one may accept service embrittlement and even allow casings that reveal cracks caused by creep or thermal fatigue to remain in service. The aim of the work discussed in this paper has been to compare different grades of Cr-Mo steel distinguished in particular by chromium and nickel contents. Two subjects have been dealt with: the influence of the chemical composition on the optimal conditions of hardening and tempering and the preliminary study of age embrittlement (evaluated by the translation of Charpy V-notch and ductile fracture toughness transition curves).
A Method for the Determination of the Surface Area of Fine Aggregate in Bituminous Mixtures
Authors: Craus J , Ishai I
Published: February 2009

The paper describes a basic analytical method for calculating the surface area of fine aggregate particles (sands and fillers). Equations were derived for direct determination of the specific surface using data of actual size distribution, fineness, and shape properties of the particles. Practical calculation examples are given and compared with other conventional methods and with experimental determination of the surface area. In general, the method is flexible and affords a desirable degree of accuracy according to a proper partitioning of the size range into fractions. Results of the calculated surface areas were very close to values obtained experimentally. This indicates the advantages of the suggested method over some other useful methods for surface area calculations. The suggested method is basic and general and can be applied to any technology where the surface area of fine particles is an important factor.
The Effect of Orientation on the Analysis of Shape and Texture of Concrete Aggregates by the Modified Fourier Method
Authors: Czarnecka ET , Gillott JE
Published: February 2009

Two sorts of concrete, one prism of each, were investigated. One concrete prism was made with natural partly crushed gravel aggregate and the other, with 2.5-cm long by 0.5-cm diameter glass rods as coarse aggregate. The glass rods were essentially smooth and elongated and adopted a preferred orientation approximately parallel to the base of the concrete prism. Several sections of each concrete prism were made by slicing both at the same angles with respect to this plane of preferred orientation. In the extreme case of long and very smooth glass rods results show that the orientation of the section has an important effect on the average values of the shape and roughness coefficients. When the shape of particles is such that preferred orientation is less apparent these values do not differ significantly for differently oriented sections provided the number of profiles is representative.
Liquid Metal Embrittlement of 4145 Steel by Lead-Tin and Lead-Antimony Alloys
Authors: Breyer NN , Johnson KL
Published: February 2009

Pure lead soldered to the gage section of 200-ksi (1379-MPa) 4145 steel tensile specimens tested at temperatures ranging from room temperature to 700°F (371°C) exhibit a severe loss in ductility between 400 and 680°F (204 and 360°C). The ductility, as measured by reduction of area, recovered at 695°F (368°C), the so-called brittle-to-ductile recovery temperature. This recovery temperature was shifted to higher temperatures in a sensitive manner by relatively small amounts of either tin or antimony added to alloy the externally applied lead.
An Analysis of the Influence of Mean Stress Intensity and Environment on Fatigue Crack Growth in a New High Strength Aluminum Alloy
Authors: Branco CM , Radon JC , Culver LE
Published: February 2009

The effects of the mean stress intensity factor Km and the range of the stress intensity ΔK on fatigue crack propagation during wholly tensile loading cycles in the aluminum (Al) alloy RR58 in laboratory air and in a 3.5% NaCl solution have been studied using contoured double-cantilever beam specimens. In general the fatigue crack growth rate in NaCl solution was greater than in air under similar conditions except for tests in which high values of the maximum stress intensity factor were used when no significant difference was observed.

Based on the experimental data a relation between the cyclic crack growth rate da/dN and the tensile loading levels has been proposed. The threshold value of ΔK, ΔKth, is approximately 12% higher in air than in the 3.5% NaCl solution, and its value decreases linearly with increasing values of Km.
Cumulative Fatigue Damage Analysis of a Light Truck Frame
Authors: Mitchell MR , Wetzel RM
Published: February 2009

A case study describes a fatigue damage analysis of a light truck frame. The objective of the analysis is to determine whether an existing frame design can safely accept a 10% increase in load. The analysis, completed in less than a month, incorporates an experimental stress-strain analysis, proving ground test data, and experimentally determined properties of the frame material. Three common methods of damage analysis and a relatively new procedure are compared and the advantages of the new method are demonstrated.
The Effect of Water Content on the Compressive Strength of Laterized Concrete
Authors: Adepegba D
Published: February 2009

Laterized concrete is defined as concrete in which laterite fines replace sand. A previous paper highlighted only the salient points of difference between laterized and normal concrete. The results reported in this paper are mainly on the effect of water content on the compressive strength of laterized concrete. Other properties such as durability, resistance to frost action, and creep need to be investigated to decide whether or not laterized concrete would be usable in all climates. It is the aim of the author that this paper and his earlier paper will generate research interest in other parts of the world where facilities and climatic conditions are more favorable for the investigations of properties which are not easily investigated in the tropics.

The mix design showed that laterized concrete mixes require more water than normal concrete for equal proportions and weights of dry normal concrete and of dry laterized concrete mix. The water/cement ratio recommended for structural laterized concrete mixes of 1:1:2 and 1:1½:3 by weight is 0.65. This water/cement ratio would yield compressive strength of about 23.59 MPa (3425 psi) for 1:1:2 and 21.45 MPa (3110 psi) for 1:1½:3 by weight in 28 days. The water/cement ratio recommended for 1:2:4 mix by weight is 0.75. This would yield about 18.50 MPa (2682 psi) in 28 days.

Graphs showing the variation of compressive strength with water/cement ratio and independently with age are presented.

A schematic map of the world showing laterite deposits is included. It is suggested that the paper may generate interest in reinforced laterized concrete structural elements and that laterized concrete may eventually be used for structural works in those parts of the world where suitable sharp sand is not available, just as lightweight concrete is now being slowly introduced into major construction works.
Variability in Fatigue Crack Growth Rate Testing
Authors: Clark WG , Hudak SJ
Published: February 2009

To provide the data necessary to develop a recommended practice for fatigue crack growth rate testing, an extensive interlaboratory (round robin) program was conducted and the variability and bias associated with the current state of the art of fatigue crack growth rate testing was determined. Fatigue crack growth rate data (expressed in terms of linear elastic fracture mechanics parameters) were generated for a 190-ksi (1310-MPa) yield strength 10 Ni-8Co-1Mo steel at 15 different laboratories with several test specimen geometries. The results were evaluated statistically and on the basis of a graphical comparison, and the variability and bias associated with both the experimental and analytical aspects of crack growth rate testing were determined. In general, the overall interlaboratory variability was found to be approximately 3 to 1 (on crack growth rate at a given stress intensity range). The intralaboratory variability was typically 2 to 1. No significant geometry or data processing bias was encountered. The results of this study show that the primary source of variability associated with fatigue crack growth rate testing is the experimental procedure used to obtain the raw test data (crack length versus elapsed cycles).
Women Leaders in the Davidian and Branch Davidian Traditions
Authors: Pitts William L.
Published: February 2009

Two women, Florence Houteff and Lois Roden, attained positions of leadership in the Davidian and Branch Davidian traditions. This article examines how they achieved, maintained, and eventually lost power. Several factors, including money, visions, and legal strategies contributed to their successes, but marriage to the founders of the two movements and the precedent of the influential female Adventist leader, Ellen White, helped to legitimate Florence Houteff and Lois Roden as leaders of their religious communities. Once they had assumed leadership roles, they proved themselves by innovative, radical, and convincing teachings based on scripture. Florence Houteff's leadership foundered on failed prophecy. Lois Roden lost leadership in a succession struggle between her son, George Roden, and Vernon Howell/David Koresh. Both prevailed briefly as leaders because of the persuasiveness of their religious authority.
Generating River Bottom Profiles with a Dual-Frequency Identification Sonar (DIDSON)
Authors: Maxwell Suzanne L. , Smith April V.
Published: February 2009

Estimating fish passage in rivers with a side-looking sonar positioned near shore requires proper alignment of the transducer with the river bottom. To maximize fish detection, we developed a robust aiming protocol using river bottom profiles generated from standard and long-range dual-frequency identification sonars (DIDSONs). The DIDSON profiles compared well with those generated from range and depth measures or bathymetry methods when the river bottoms were linear or changed from a steeper slope near shore to a flatter slope offshore. If the offshore slope was steeper, the DIDSON profile displayed shallower depths. The actual differences in depth between the DIDSON profiles and those from other methods were often considerably less than the potential differences from beam-spreading error. The maximum depth differences between the same DIDSON profiles marked independently multiple times ranged from 0.08 m for the DIDSON's highest frequency to 0.5 m for the lowest. A model of the fish-counting transducer beam was plotted in the same coordinate system as the river bottom profile. Macros developed for Excel spreadsheets enabled us to “rotate” the beam and determine the optimal tilt angle for each river bottom profile.
Range‐wide reproductive consequences of ocean climate variability for the seabird Cassin's Auklet
Authors: Wolf Shaye G. , Sydeman William J. , Hipfner J. Mark , Abraham Christine L. , Tershy Bernie R. , Croll Donald A.
Published: February 2009

We examine how ocean climate variability influences the reproductive phenology and demography of the seabird Cassin's Auklet (Ptychoramphus aleuticus) across ∼2500 km of its breeding range in the oceanographically dynamic California Current System along the west coast of North America. Specifically, we determine the extent to which ocean climate conditions and Cassin's Auklet timing of breeding and breeding success covary across populations in British Columbia, central California, and northern Mexico over six years (2000–2005) and test whether auklet timing of breeding and breeding success are similarly related to local and large‐scale ocean climate indices across populations. Local ocean foraging environments ranged from seasonally variable, high‐productivity environments in the north to aseasonal, low‐productivity environments to the south, but covaried similarly due to the synchronizing effects of large‐scale climate processes. Auklet timing of breeding in the southern population did not covary with populations to the north and was not significantly related to local oceanographic conditions, in contrast to northern populations, where timing of breeding appears to be influenced by oceanographic cues that signal peaks in prey availability. Annual breeding success covaried similarly across populations and was consistently related to local ocean climate conditions across this system. Overall, local ocean climate indices, particularly sea surface height, better explained timing of breeding and breeding success than a large‐scale climate index by better representing heterogeneity in physical processes important to auklets and their prey. The significant, consistent relationships we detected between Cassin's Auklet breeding success and ocean climate conditions across widely spaced populations indicate that Cassin's Auklets are susceptible to climate change across the California Current System, especially by the strengthening of climate processes that synchronize oceanographic conditions. Auklet populations in the northern and central regions of this ecosystem may be more sensitive to changes in the timing and variability of ocean climate conditions since they appear to time breeding to take advantage of seasonal productivity peaks.
Experimental evidence for density‐dependent reproduction in a cooperatively breeding passerine
Authors: Brouwer Lyanne , Tinbergen Joost M. , Both Christiaan , Bristol Rachel , Richardson David S. , Komdeur Jan
Published: February 2009

Temporal variation in survival, fecundity, and dispersal rates is associated with density‐dependent and density‐independent processes. Stable natural populations are expected to be regulated by density‐dependent factors. However, detecting this by investigating natural variation in density is difficult because density‐dependent and independent factors affecting population dynamics may covary. Therefore, experiments are needed to assess the density dependence of demographic rates. In this study, we investigate the effect of density on demographic rates of the Seychelles Warbler (Acrocephalus sechellensis). This species, endemic to a few islands in the Indian Ocean, went through a severe population bottleneck in the middle of the last century, with only ∼30 individuals left on one small island, but has since recovered. Our monitoring shows that since reaching the island's carrying capacity, population density has remained stable. However, we detected neither density‐dependent reproduction nor survival on the basis of natural density variation during this stable period. For conservation reasons, new populations have been established by transferring birds to nearby suitable islands. Using the change of numbers during the process of saturation as a natural experiment, we investigated whether we can detect regulation of numbers via density‐dependent survival and reproduction within these new populations. We found that populations were mainly regulated by density‐dependent reproduction, and not survival. Variation in density between islands can be explained by food abundance, measured as insect density. Islands with the highest insect densities also had the highest bird densities and the largest breeding groups. Consequently, we suggest that the density‐dependent effect on reproduction is caused by competition for food.
Size‐spectra dynamics from stochastic predation and growth of individuals
Authors: Law Richard , Plank Michael J. , James Alex , Blanchard Julia L.
Published: February 2009

In aquatic ecosystems, where organisms typically feed and grow by eating smaller individuals, a characteristic size spectrum emerges, such that large organisms are much more rare than small ones. Here, a stochastic individual‐based model for the dynamics of size spectra is described, based on birth, growth, and death of individuals, using simple assumptions about feeding behavior. It is shown that the deterministic limit derived from the stochastic process is a partial differential equation previously used to describe the dynamics of size spectra. The equation has two classes of dynamics in the long term. The first is a steady state. A derivation under simple mass‐balance assumptions shows that, at steady state, the linear size spectrum relating log abundance to log mass has a slope of approximately −1, similar to that often observed in natural size spectra. The second class of dynamics, not previously described, is a traveling‐wave solution in which waves move along the size spectrum from small to large body size. Traveling waves become more likely when predators prefer prey much smaller than themselves and when they are specialized in the range of prey body sizes consumed. Wavelength depends on the size of prey relative to the size of predator, and wave speed depends on how fast mass moves through the spectrum.
Modeling species occurrence dynamics with multiple states and imperfect detection
Authors: MacKenzie Darryl I. , Nichols James D. , Seamans Mark E. , Gutiérrez R. J.
Published: February 2009

Recent extensions of occupancy modeling have focused not only on the distribution of species over space, but also on additional state variables (e.g., reproducing or not, with or without disease organisms, relative abundance categories) that provide extra information about occupied sites. These biologist‐driven extensions are characterized by ambiguity in both species presence and correct state classification, caused by imperfect detection. We first show the relationships between independently published approaches to the modeling of multistate occupancy. We then extend the pattern‐based modeling to the case of sampling over multiple seasons or years in order to estimate state transition probabilities associated with system dynamics. The methodology and its potential for addressing relevant ecological questions are demonstrated using both maximum likelihood (occupancy and successful reproduction dynamics of California Spotted Owl) and Markov chain Monte Carlo estimation approaches (changes in relative abundance of green frogs in Maryland). Just as multistate capture–recapture modeling has revolutionized the study of individual marked animals, we believe that multistate occupancy modeling will dramatically increase our ability to address interesting questions about ecological processes underlying population‐level dynamics.
Leaf traits capture the effects of land use changes and climate on litter decomposability of grasslands across Europe
Authors: Fortunel Claire , Garnier Eric , Joffre Richard , Kazakou Elena , Quested Helen , Grigulis Karl , Lavorel Sandra , Ansquer Pauline , Castro Helena , Cruz Pablo , DoleŽal JiŘí , Eriksson Ove , Freitas Helena , Golodets Carly , Jouany Claire , Kigel Jaime , Kleyer Michael , Lehsten Veiko , Lepš Jan , Meier Tonia , Pakeman Robin , Papadimitriou Maria , Papanastasis Vasilios P. , Quétier Fabien , Robson Matt , Sternberg Marcelo , Theau Jean-Pierre , Thébault Aurélie , Zarovali Maria
Published: February 2009

Land use and climate changes induce shifts in plant functional diversity and community structure, thereby modifying ecosystem processes. This is particularly true for litter decomposition, an essential process in the biogeochemical cycles of carbon and nutrients. In this study, we asked whether changes in functional traits of living leaves in response to changes in land use and climate were related to rates of litter potential decomposition, hereafter denoted litter decomposability, across a range of 10 contrasting sites.

To disentangle the different control factors on litter decomposition, we conducted a microcosm experiment to determine the decomposability under standard conditions of litters collected in herbaceous communities from Europe and Israel. We tested how environmental factors (disturbance and climate) affected functional traits of living leaves and how these traits then modified litter quality and subsequent litter decomposability.

Litter decomposability appeared proximately linked to initial litter quality, with particularly clear negative correlations with lignin‐dependent indices (litter lignin concentration, lignin : nitrogen ratio, and fiber component).

Litter quality was directly related to community‐weighted mean traits. Lignin‐dependent indices of litter quality were positively correlated with community‐weighted mean leaf dry matter content (LDMC), and negatively correlated with community‐weighted mean leaf nitrogen concentration (LNC). Consequently, litter decomposability was correlated negatively with community‐weighted mean LDMC, and positively with community‐weighted mean LNC.

Environmental factors (disturbance and climate) influenced community‐weighted mean traits. Plant communities experiencing less frequent or less intense disturbance exhibited higher community‐weighted mean LDMC, and therefore higher litter lignin content and slower litter decomposability. LDMC therefore appears as a powerful marker of both changes in land use and of the pace of nutrient cycling across 10 contrasting sites.
Evaluating accuracy and precision of species–area relationships for multiple estimators and different marine assemblages
Authors: Chapman M. G. , Underwood A. J.
Published: February 2009

This paper evaluates the accuracy and precision of six nonparametric estimators and six regression models for predicting the number of species in an area using random subsamples of that area. Such extrapolations are important for increased understanding of species–area relationships in different assemblages of species to inform ecological theories, and because they have direct implications in many conservation issues. Often, such extrapolations are evaluated by considering how well they fit existing data, rather than the actual number of species in the larger area. Also, many studies have focused on larger species in terrestrial habitats, where numbers of species are quite well known. Assemblages of invertebrates and smaller plants, especially in marine habitats, are less well known, and their distributions are dominated by small‐scale variability. We examined species–area relations for two assemblages on boulders from six locations, for rocky shore assemblages in three locations, and for gastropods colonizing artificial habitat. Changing the focus of subsampling relative to the extent of the study and changing the size of the subsamples was also evaluated for subsets of data. Most estimators fitted the number of species poorly, with the second‐order Jackknife consistently the best of the nonparametric measures, and the Negative Exponential the best of the regression models. Increasing the number of replicates improved most models, but some only slightly, and others considerably. Changing focus had little effect, probably because marine assemblages such as these vary at small scales as much as at many larger scales. These extensive analyses provide clear evidence about which estimators should not be used for measuring species–area relationships in assemblages such as these, and which will consistently over‐ or underestimate the number of species. The findings are applicable to many assemblages dominated by small organisms with strong stochastic variation.
Improved estimation of neutral model parameters for multiple samples with different degrees of dispersal limitation
Authors: Etienne Rampal S.
Published: February 2009

The standard neutral model of biodiversity, as introduced by S. P. Hubbell, is currently increasingly used as a null model for the structure of ecological communities. In such applications, estimation of the model parameters is essential. An exact maximum likelihood approach has been developed for data sets consisting of multiple, spatially separated, samples of species abundances. This approach is only computationally tractable when it is assumed that all these samples have the same amount of dispersal limitation. Recently, an approximate approach has been proposed that does not require this assumption. However, this approach cannot estimate the fundamental biodiversity number θ when there are only a few samples or many, very different, samples. In this note, I present a modification of this approximate approach that does not suffer from this shortcoming. I illustrate it with simulated and real data sets.
Friendly competition: evidence for a dilution effect among competitors in a planktonic host–parasite system
Authors: Hall Spencer R. , Becker Claes R. , Simonis Juniper L. , Duffy Meghan A. , Tessier Alan J. , Cáceres Carla E.
Published: February 2009

The “dilution effect” concept in disease ecology offers the intriguing possibility that clever manipulation of less competent hosts could reduce disease prevalence in populations of more competent hosts. The basic concept is straightforward: host species vary in suitability (competence) for parasites, and disease transmission decreases when there are more incompetent hosts interacting with vectors or removing free‐living stages of a parasite. However, host species also often interact with each other in other ecological ways, e.g., as competitors for resources. The net result of these simultaneous, multiple interactions (disease dilution and resource competition) is challenging to predict. Nonetheless, we see the signature of both roles operating concurrently in a planktonic host–parasite system. We document pronounced spatiotemporal variation in the size of epidemics of a virulent fungus (Metschnikowia bicuspidata) in Midwestern U.S. lake populations of a dominant crustacean grazer (Daphnia dentifera). We show that some of this variation is captured by changes in structure of Daphnia assemblages. Lake‐years with smaller epidemics were characterized by assemblages dominated by less suitable hosts (“diluters,” D. pulicaria and D. retrocurva, whose suitabilties were determined in lab experiments and field surveys) at the start of epidemics. Furthermore, within a season, less suitable hosts increased as epidemics declined. These observations are consistent with a dilution effect. However, more detailed time series analysis (using multivariate autoregressive models) of three intensively sampled epidemics show the signature of a likely interaction between dilution and resource competition between these Daphnia species. The net outcome of this interaction likely promoted termination of these fungal outbreaks. Should this outcome always arise in “friendly competition” systems where diluting hosts compete with more competent hosts? The answers to this question lie at a frontier of disease ecology.
Evolutionary ecology of endocrine‐mediated life‐history variation in the garter snake Thamnophis elegans
Authors: Sparkman Amanda M. , Vleck Carol M. , Bronikowski Anne M.
Published: February 2009

The endocrine system plays an integral role in the regulation of key life‐history traits. Insulin‐like growth factor‐1 (IGF‐1) is a hormone that promotes growth and reproduction, and it has been implicated in the reduction of lifespan. IGF‐1 is also capable of responding plastically to environmental stimuli such as resource availability and temperature. Thus pleiotropic control of life‐history traits by IGF‐1 could provide a mechanism for the evolution of correlated life‐history traits in a new or changing environment. An ideal system in which to investigate the role of IGF‐1 in life‐history evolution exists in two ecotypes of the garter snake Thamnophis elegans, which derive from a single recent ancestral source but have evolved genetically divergent life‐history characteristics. Snakes from meadow populations near Eagle Lake, California (USA) exhibit slower growth rates, lower annual reproductive output, and longer median adult lifespans relative to populations along the lakeshore. We hypothesized that the IGF‐1 system has differentiated between these ecotypes and can account for increased growth and reproduction and reduced survival in lakeshore vs. meadow snakes. We tested for a difference in plasma IGF‐1 levels in free‐ranging snakes from replicate populations of each ecotype over three years. IGF‐1 levels were significantly associated with adult body size, reproductive output, and season in a manner that reflects established differences in prey ecology and age/size‐specific reproduction between the ecotypes. These findings are discussed in the context of theoretical expectations for a trade‐off between reproduction and lifespan that is mediated by pleiotropic endocrine mechanisms.
The effects of plant defensive chemistry on nutrient availability predict reproductive success in a mammal
Authors: DeGabriel Jane L. , Moore Ben D. , Foley William J. , Johnson Christopher N.
Published: February 2009

Plants contain a variety of chemical defenses that strongly affect feeding rates in captive mammals, but their effects on the fitness of wild herbivores are largely unknown. This is because the complexity of defensive compounds, and herbivores' counteradaptations to them, make their effects in the wild difficult to measure. We show how tannins interact with protein to produce spatial variation in the nutritional quality of eucalypt foliage, which is related to demography in a wild population of a marsupial folivore, the common brushtail possum (Trichosurus vulpecula Kerr). Tannins reduced the digestibility of nitrogen (N) in vitro, creating variation in available N concentrations among the home ranges of individual possums in an otherwise homogeneous habitat. This was strongly correlated with reproductive success: females with better quality trees in their home range reproduced more often and had faster‐growing offspring. These results demonstrate a powerful mechanism by which spatial variation in plant chemistry may control herbivore population dynamics in nature.
Still Dying After All These Years: A Classical Library for Contemporary Controversies
Authors: Kapp Marshall B.
Published: February 2009

A review and discussion of Death, Dying and the Ending of Life, edited by Margaret P. Battin, Leslie P. Francis, and Bruce M. Landesman. Ashgate Publishing, 2007. The many philosophical, ethical, legal, and social aspects of death and the dying process remain deeply controversial despite substantial and continuous public discussion and debate about them. Springing from an in-depth review of a newly-published compilation of some of the most seminal writings in this area, the author in this essay reflects on and systematically analyzes how the classical literature of the past millennium has set the intellectual stage and in many respects established the rules of engagement for modern discourse on end-of-life decisions and decision-making.
Cultural Responsiveness in Long-Term-Care Case Management: Moving Beyond Competence
Authors: Werkmeister-Rozas Lisa , Klein Waldo C.
Published: February 2009

Case mangers must deal with the ever-changing makeup of their client population as well as those who provide managed services to these clients. There is great ethnocultural diversity in the elder population, and statistics contend that it will only increase with time. Similarly, the majority of long-term-care providers have been consistently female and of color. Providing culturally competent services becomes more complex when long-term-care providers and clients possess different identities, countries of origins, and social statuses. This article examines a framework that addresses the complex, multidimensional, and bidirectional process that occurs between providers and consumers of any cultural makeup called cultural responsiveness.
Ecology of Sulfate‐Reducing Bacteria in an Iron‐Dominated, Mining‐Impacted Freshwater Sediment
Authors: Ramamoorthy Srividhya , Piotrowski Jeffrey S. , Langner Heiko W. , Holben William E. , Morra Matthew J. , Rosenzweig R. Frank
Published: February 2009

A legacy of lead and silver mining in its headwaters left Lake Coeur d'Alene, Idaho with a sediment body that is highly reduced and contains up to 100 g kg−1 iron and a smaller fraction of chemically active sulfide phases. The dynamic character of these sulfides and their importance for the sequestering of contaminating trace elements prompted this study of the sulfate‐reducing bacteria (SRB) involved in their production. We estimated parameters indicative of the distribution and activity of SRB in relation to season, site, and depth. Most probable number estimates and quantitative PCR assays of an SRB‐specific functional gene, α‐adenosine 5′‐phosphosulfate reductase, indicated 103 to 106 cultivable cells and 105 to 107 gene copy numbers g−1 dry wt sediment, respectively. Although culture‐based estimates of SRB abundance correlated poorly with site, season, depth, total S, or pore water SO4, non–culture‐based estimates of SRB abundance were markedly higher at contaminated sites and positively correlated with pore water SO4 Ex situ estimates of 35SO4 respiration and acid volatile sulfides abundance also showed strong among‐site effects, indicating elevated sulfidogenesis at contaminated sites. These observations support the view that biogenic sulfides may act in concert with reduced iron to retain soluble metal(loid)s in the solid phase.
Effect of Water Seal on Reducing 1,3‐Dichloropropene Emissions from Different Soil Textures
Authors: McDonald Jason A. , Gao Suduan , Qin Ruijun , Hanson Bradley D. , Trout Thomas J. , Wang Dong
Published: February 2009

Soil physical conditions can affect diffusion, environmental fate, and efficacy of fumigants in soil disinfestation treatments. Water seals (applying water using sprinklers to soil following fumigation) can effectively reduce fumigant emissions from sandy loam soils. Soil column studies compared the effectiveness of water seals in reducing cis‐1,3‐dichloropropene (1,3‐D) emissions from three different textured soils (loamy sand, sandy loam, and loam). Treatments included an untreated control, an initial water seal (9 mm water applied immediately before fumigant injection), and intermittent water seals (initial 9 mm water seal followed by 3 mm at 12 and 24 h). For the loamy sand, instead of the initial water seal treatment, a reduced‐amount intermittent water seal (initial 3 mm water followed by 1 mm at 12 and 24 h) treatment was tested. Overall emission loss of 1,3‐D from the control over 2 wk was 56% for the loamy sand, 51% for the sandy loam, and 43% for the loam. The initial water seal reduced total 1,3‐D emissions to 46% in the sandy loam and 31% in the loam. The intermittent water seals reduced emission loss to 26% for the loamy sand, 41% for the sandy loam, and 21% for the loam. The reduced‐amount intermittent water seal for loamy sand had little effect. Low emission loss was associated with high surface soil water content. None of the water applications reduced gaseous fumigant concentrations. Results indicate that water seal techniques may be able to effectively reduce emissions for different soil textures without reducing fumigant concentration in the soil.
Physicochemical Study of the Sorption of Pesticides by Wood Components
Authors: Rodríguez‐Cruz M. Sonia , Valderrábano Marta , del Hoyo Carmen , Sánchez‐Martín M. Jesús
Published: February 2009

The sorption–desorption and interaction mechanisms of three non‐ionic (linuron, alachlor, and metalaxyl) and two ionic (paraquat and dicamba) pesticides by three commercial lignins (hydrophobic macromolecule) and cellulose (hydrophilic macromolecule) as wood components were studied. Wood is a low‐cost and environmentally friendly material proposed in recent years to immobilize pesticides in soils. The influence of sorbent and pesticide properties and the identification of the functional groups of the organic molecules involved in sorption were evaluated by a statistical approach and by Fourier transform infrared spectroscopy. The sorption isotherms of non‐ionic pesticides by the lignins and cellulose fit the Freundlich model, and those of the ionic pesticides also fit the Langmuir model. The sorption constants of pesticides by cellulose were 62‐, 9‐, 24‐, 119‐, and 3‐fold lower than those for the sorption by lignins. A predictive model of pesticide sorption indicated that 88.5% of the variability in the sorption coefficient normalized to the organic carbon content could be explained in terms of the variability of the polarity index and the octanol–water partition coefficient of sorbent and sorbate. The greater irreversibility observed for ionic pesticides was attributed to the involvement of simultaneous interaction mechanisms. The results obtained contribute the knowledge of sorption capacity of pesticides by lignin/cellulose, the main components of woods and ubiquitous materials in the environment.
Comparison of Hollow‐Fiber Ultrafiltration to the USEPA VIRADEL Technique and USEPA Method 1623
Authors: Hill Vincent R. , Polaczyk Amy L. , Kahler Amy M. , Cromeans Theresa L. , Hahn Donghyun , Amburgey James E.
Published: February 2009

Hollow‐fiber ultrafiltration (UF) is a technique that is increasingly viewed as an effective alternative for simultaneously recovering diverse microbes (e.g., viruses, bacteria, parasites) from large volumes of drinking water. The USEPA has organism‐specific methods, including Method 1623 for Cryptosporidium and Giardia and the virus adsorption–elution (VIRADEL) technique using 1MDS electropositive filters. In this study, we directly compare the performance of a previously published UF method to that of the USEPA Method 1623 (for recovering Cryptosporidium parvum and Giardia intestinalis) and the 1MDS VIRADEL method (for bacteriophages and echovirus) using 100‐L dechlorinated tap water samples. The UF method produced significantly higher recoveries of C. parvum versus Method 1623 (83% mean recovery for UF versus 46% mean recovery for Method 1623), while recoveries for G. intestinalis were similar for both methods. Results of the virus method comparison showed the UF method (including secondary concentration using microconcentrators) to be very effective for the recovery of echovirus 1, bacteriophage MS2, and bacteriophage phi X174, with mean recovery efficiencies of 58, 100, and 77%, respectively. The VIRADEL technique (including secondary concentration by organic flocculation) recovered significantly less echovirus 1, and the bacteriophages could not be quantified by the method due to phage inactivation and/or assay inhibition. The results of this study demonstrate that the UF technique can be as effective, or more effective, than established USEPA methods for recovery of viruses and protozoan parasites from 100‐L tap water samples.