bluuebunny/crossref_metadata_2025 huggingface dataset:
Solution of a multiple Nevanlinna–Pick problem for Schur functions via orthogonal rational functions
Authors: Bultheel Adhemar , Lasarow Andreas
Published: February 2008

An interpolation problem of Nevanlinna–Pick type for complex-valued Schur functions in the open unit disk is considered. We prescribe the values of the function and its derivatives up to a certain order at finitely many points. Primarily, we study the case that there exist many Schur functions fulfilling the required conditions. For this situation, an application of the theory of orthogonal rational functions is used to characterize the set of all solutions of the problem in question. Moreover, we treat briefly the case of exactly one solution and present an explicit description of the unique solution in that case.
Thermodynamic and Structural Investigations of Condensates of Small Molecules in Mesopores
Authors: Knorr Klaus , Huber Patrick , Wallacher Dirk
Published: February 2008

Liquids and solids consisting of small, mainly van-der-Waals interacting building blocks, such as Ar, Kr, N2, O2, and CO, are among the most simple systems of condensed matter imaginable. As we shall demonstrate in this microreview on our work sponsored within the Sonderforschungsbereich 277, these cryoliquids condensed in mesoporous hosts with typical mean pore diameters of 7 to 10nm are also particularly suitable for the investigation of fundamental questions regarding the thermodynamics and structure of spatially mesoscale confined systems. An exploration of phase transitions like the vapour–liquid (capillary condensation), the vapour–solid (capillary sublimation), the liquid–solid (freezing and melting) and some solid–solid transformations of such pore condensates reveals a remarkably rich, sometimes perplexing phenomenology. We will show, however, that by experiments combining sorption isotherm, X-ray and neutron diffraction, calorimetric and optical transmission measurements, and by referring to concepts, intermediate between surface and bulk physics, a deeper understanding of the mesoscale mechanisms ultimatively responsible for this complex behaviour can indeed be accomplished, both on a qualitative and a quantitative level.
Precursorchemistry with Metalalkoxides and their Use for Nano-Scaled Materials
Authors: Veith Michael
Published: February 2008

The synthesis of nano-scaled materials using several variations of the single source precursor concept in sol–gel and chemical vapour deposition techniques is demonstrated. Mono- and biphasic ceramics and cermets (metallic phases incorporated in a metal oxide phase) are addressed. The materials prepared are all nanocrystalline in a range from 5 to 50nm. The ceramics belong inter alia to the spinel and perowskite-type. In the biphasic ceramic systems, especially NdAlO3 in Al2O3 is highlighted. In the cermet family Ge, Sn and Pb in either their oxide matrices or in perowskite matrices (M´MO3, M´ = Ca, Sr, Ba; M = Ge, Sn, Pb) and Al and Ga in Al2O3 or Ga2O3 matrices are discussed. Two general concepts are presented in more detail: 1) the arrangement of mutually dependent ligands in the precursor molecule, to facilitate intra-molecular cascade or domino reactions, and 2) the role of metastable phases for physical patterning. The temperature and pressure dependent formation of aluminum/aluminum oxide composites and their structural consequences leading to zero-dimensional ball-shape spheres or to one-dimensional nano-wires is shown as well as the core shell structures of such composites.
One-Dimensional Semiconductor Nanostructures: Growth, Characterization and Device Applications
Authors: Mathur Sanjay , Barth Sven
Published: February 2008

One dimensional (1D) inorganic materials are gaining increasing attention because of their unique structural features and interesting functional properties. Given the structural stability, they show promising application potential in vacuum as well as in oxidizing atmospheres, which provides them a competitive edge over their carbon-based counterparts. A number of synthetic procedures have been developed and demonstrated for 1D nanostructures that have led to intriguing morphological variations (wires, tubes, belts, rods, etc.), however the control over radial and axial dimensions remains a continuing challenge. In addition, the choice of material is rather limited. We have developed a generic approach for the size-selective and site-specific growth of nanowires by combining vapor–liquid–solid (VLS) approach with molecule-based chemical vapor deposition. The synthesis of nanowires (NWs) is based on the decomposition of discrete molecular species, which allows growing nanowires at low temperatures with a precise control over their diameter and length. The precursor chemistry can be tuned to facilitate the stripping of organic ligands and to achieve complete decomposition that is critical for maintaining the gas phase super-saturation necessary for 1D growth. High-yield synthesis of elemental (Ge) and compound semiconductors (SnO2, Fe3O4, V2O5, In2O3) was performed by the chemical vapor deposition of appropriate metal-organic precursors. Axial and radial dimensions of the NWs were varied by adjusting the precursor feedstock, deposition temperature, and catalyst size. Finally, the device potential of these building blocks as photo- and gas sensors was investigated by integrating individual nanowires in electrical circuits using focussed ion beam (FIB) assisted nano-lithography.
Investigation of Nanocrystalline Materials Using Radioactive Isotopes
Authors: Wichert Th. , Wolf H. , Guan Z. , Li X.
Published: February 2008

The potential of detecting the hyperfine interaction at the nuclear site of radioactive isotopes for the investigation of nanocrystalline (nc) materials is discussed. The subject is illustrated with help of different examples for characterizing nc samples. Using the perturbed γ
γ angular correlation technique (PAC) for detecting the hyperfine interaction at the site of the radioactive probe 111In/111Cd experiments regarding the doping of nc semiconductors ZnO and InP, the shift of the Néel temperature in nc antiferromagnetic NiO, the structure of grain boundaries in Ni, and the homogeneity of nc Ni-Cu alloys are presented. The resulting information is compared with that obtained by Mössbauer spectroscopy and by standard techniques used in materials science.
Theoretical Studies of Structural, Energetic, and Electronic Properties of Clusters
Authors: Springborg Michael , Dong Yi , Grigoryan Valeri G. , Tevekeliyska Violina , Alamanova Denitsa , Kasabova Elisaveta , Roy Sudip , Joswig Jan-Ole , Asaduzzaman Abu Md.
Published: February 2008

Size in combination with low symmetry makes theoretical studies of the properties of clusters a challenge. This is in particular the case when the studies also shall identify the structures of the lowest total energy. We discuss here various methods for calculating the structural, energetic, and electronic properties of nanoparticles, emphasizing that the computational method always should be chosen carefully according to the scientific questions that shall be addressed. Therefore, different approximate methods for calculating the total energy of a given structure are discussed, including the embedded-atom method and a parameterized density-functional method. Moreover, different approaches for choosing/determining the structures are presented, including an Aufbau/Abbau method and genetic algorithms. In order to illustrate the approaches we present results from calculations on metallic and semiconducting nanoparticles as well as on nanostructured HAlO.
Photoemission Investigation of the L¯-Gap Surface States on Clean and Rare Gas-Covered Noble Metal (111)-Surfaces
Authors: Hüfner Stefan , Reinert Friedrich , Schmidt Stefan , Nicolay Georg , Forster Frank
Published: February 2008

High resolution photoemission spectroscopy is used to investigate the linewidth and dispersion of the L¯-gap surface states on (111)-surfaces of noble metals. The effect of a coverage of rare gases is demonstrated.
Computer Simulations of Phase Transitions and Dynamics in Confined Systems
Authors: Rieger Heiko , Paul Raja , Noh Jae-Dong , Schehr Gregory
Published: February 2008

Results of theoretical studies of spatially confined systems via Monte Carlo simulations are reported. Three experimentally relevant systems are considered: 1) Ad- and desorption phenomena in nanoporous materials like Vycor glass; 2) Dipolar molecules on a graphite surface that undergo an orientational transition; 3) Non-equilibrium dynamics in two-dimensional disordered materials.
Mechanical Properties of Nanomaterials Examined with a NI-AFM
Authors: Vehoff H. , Yang B. , Barnoush A. , Natter Harald , Hempelmann Rolf
Published: February 2008

The mechanical properties and strain rate sensitivity of nanocrystalline nickel was studied as a function of grain size at different temperatures in tensile tests and with a nanoindenter in order to examine the different deformation mechanisms of nanocrystalline materials. The effect of lateral boundaries and hydrogen on the nucleation of dislocations was studied in detail. For the first time it was possible to observe the reduction of the dislocation nucleation stress on a nanoscale. In addition the experiments yielded, depending on temperature and strain rate, the strain rate sensitivity, the activation volume and the creep exponents as a function of stress and grain size. From the creep experiments the transition between grain boundary sliding and dislocation climb as a function of temperature was obtained. The strain rate jump tests gave extremely small activation volumes, nearly a factor of 100 smaller than in conventional nickel as a function of grain size. To help in understanding this behaviour the strain rate sensitivity of single grains was tested with a nanoindenter. The results clearly showed that the primary interaction of dislocations with grain boundaries is the reason for the observed strong rate effects and small activation volumes.
Equilibrium and Nonequilibrium Behaviour of Ferrofluids – Experiments and Theory
Authors: Embs Jan Peter , Huke Björn , Leschhorn Andreas , Lücke Manfred
Published: February 2008

Selected results on the spatiotemporal behaviour of equilibrium and nonequilibrium properties of ferrofluids in different magnetic fields are reviewed. They have been obtained in the project B13 Transport, response and instability behaviour of ferrofluids of the SFB 277 by experiments and by various theoretical methods ranging from purely analytical calculations to full numerical approaches.
Combinatorial Fabrication of Thin Film-Libraries and Evaluation of their Piezoelectricity by Ultrasonic Piezo-Mode Imaging
Authors: Rende Daniela , Schwarz Kerstin , Rabe Ute , Maier Wilhelm F. , Arnold Walter
Published: February 2008

Piezoelectric materials are used in an ever increasing number of technical products. The need for new and improved piezoelectric materials is growing rapidly. Conventional methods are too slow to explore the potential parameter spaces. A combinatorial workflow has been developed to produce mixed oxide thin film libraries and screen them for piezoelectric properties by atomic force microscopy in the ultrasonic piezo-mode. Validation and new findings are reported. Determination of piezoelectric properties in an automated fashion was only possible within the same class of materials.
Agricultural Exports and the Environment: A Cross‐National Study of Fertilizer and Pesticide Consumption*
Authors: Longo Stefano , York Richard
Published: February 2008

AbstractThe mass consumption of agrochemicals, including manufactured fertilizers and pesticides, by industrialized agricultural systems worldwide threatens human health and the health of ecosystems. The production of these agricultural inputs is a highly energy‐ and capital‐intensive process, and their application contributes to a variety of direct and indirect impacts on the environment. This study is an analysis of the relationships between international trade in agricultural products and the consumption of these synthetic compounds. Using OLS regression models and data from World Bank and UNFAO, we analyze cross‐national data to examine the relationship between structural factors, such as economic development and export intensity, and both fertilizer and pesticide consumption. The findings are considered from the opposing theoretical perspectives of international political economy (IPE) and neo‐liberal modernization (NLM). The results generally support the claims of IPE and contradict those of NLM, indicating that increases in exports of agricultural products contribute to increases in fertilizer and pesticide consumption within nations. These results call into question policies that promote increased trade liberalization in agricultural products.
The Use of Frames Analysis in Evaluating Capacity‐Building in Local Coastal Programs in Louisiana*
Authors: Norris‐Raynbird Carla
Published: February 2008

Abstract Frames theory has been widely used to explain the dynamics of group processes and decision‐making. Some researchers have applied frames theory to policy adoption and implementation. Following from this, my research applies frames analysis to a regulatory program in coastal Louisiana. The data derive from a pre‐Hurricane Katrina study of the effectiveness of Louisiana's Coastal Resources Program in building coastal zone management (CZM) capacity among local decision‐makers. In this paper, I examine the potential influence of three independent variables (Local Coastal Program development, type of respondent, and frequency of coastal zone management interaction) on the level of agreement with regulator frame ideology. The frames analysis shows that parishes with Local Coastal Programs (LCPs) have a significantly stronger presence of regulator framing than do parishes without LCPs. Among the three types of decision‐makers (CZM administrators/staff, CZM advisory panel members and parish council or police jury) regulator frame agreement is particularly strong among advisory panel members, while agreement with regulator frames is lowest among parish council or police jury officials. Respondents reporting more CZM interaction exhibit higher levels of regulator frame agreement. OLS regression shows that the conditions of having an LCP, or being a panel member and having greater frequency of CZM interactions significantly increase the likelihood of regulator framing. These findings demonstrate the importance of the LCP process in the shaping of frames congruent with lead agency ideology.
The Reflexive Producer: The Influence of Farmer Knowledge Upon the Use of Bt Corn*
Authors: Kaup Brent Z.
Published: February 2008

Abstract This paper examines the influence of farmer knowledge upon decision making processes. Drawing upon the sociological debates around the ideas of reflexive modernity and biotechnology as well as from classic adoption and diffusion studies, I explore the influences upon farmers' use of Bacillus thuringiensis (Bt) corn. Utilizing survey data gathered from corn farmers in Minnesota and Wisconsin, I argue that farmers are ‘reflexive’ actors who actively negotiate between ‘expert’ and ‘local’ knowledges when deciding to plant Bt corn. Furthermore, I hypothesize that farmers are more likely to be influenced by their first‐hand or local experiences than by state or expert observations.
Presidential Address Rural Sociology at the Crossroads*
Authors: Krannich Richard S.
Published: February 2008

Abstract A complex array of socio‐historical, demographic, and organizational factors have combined in recent years to threaten both the current status of and future prospects for the discipline of rural sociology, and for the Rural Sociological Society (RSS). This paper examines the somewhat problematic recent trajectories of the RSS as a professional organization and of rural sociology more generally and notes a degree of disciplinary and organizational inertia that have limited the pursuit of new directions. It also presents a discussion of selected factors that have contributed to these concerns, including both “external” factors that are largely beyond the organizational reach of RSS and “internal” factors that are more directly linked to organizational characteristics and actions. Drawing upon the distinctions between “red ocean” and “blue ocean” strategies outlined by market strategists Kim and Mauborgne, the discussion then shifts to a focus on action alternatives that, if pursued, could help to create an expanded set of opportunities and a brighter future for rural sociology, and for the Rural Sociological Society.
Fish Pathogen Screening and Its Influence on the Likelihood of Accidental Pathogen Introduction during Fish Translocations
Authors: Fenichel Eli P. , Tsao Jean I. , Jones Michael , Hickling Graham J.
Published: February 2008

Fish translocations are an important tool in fisheries management, yet translocating fish carries the risk of introducing unwanted pathogens. Although pathogen screening can be a useful tool for managing the risk associated with fish translocations, screening cannot eliminate this risk. This paper addresses these problems by demonstrating that two elements must be considered when designing efficient and effective aquatic pathogen screening programs: (1) how many fish to screen and (2) how long to continue screening programs when repeated testing detects zero infected individuals. The chance that infected fish are translocated despite screening is the joint probability of (1) the failure of the screening to detect infected fish in the sample and (2) the actual presence of infected fish in the translocation batch. Our analysis demonstrates that transfer of an infected fish is most likely to occur at moderately low levels of pathogen prevalence because the probability of detecting at least one infected fish through screening increases as pathogen prevalence increases. Small screening samples (i.e., with a low number of individuals) are most likely to detect infected fish when pathogen prevalence is relatively high (i.e., >5%). Screening programs should terminate after some number of successive screening events in which no infected individuals have been detected. The number of screening events is a function of the cost of the screening program, the cost of a pathogen translocation, and the probability that an infected fish will be transferred. Furthermore, our analysis indicates that the cost of a disease outbreak has relatively little effect on the length of time the screening program should continue. A more pronounced result is that screening programs that are inexpensive or allow a higher probability of pathogen translocation should be continued longer.
Effectiveness and Retention of Thiamine and Its Analogs Administered to Steelhead and Landlocked Atlantic Salmon
Authors: Ketola H. George , Isaacs Gary R. , Robins Jeffrey S. , Lloyd Russell C.
Published: February 2008

We investigated the feasibility of enhancing the reproduction of steelhead Oncorhynchus mykiss and landlocked Atlantic salmon Salmo salar in lakes where the consumption of alewives Alosa pseudoharengus and other forage fishes containing thiaminase can cause them to become thiamine deficient and thereby reduce the survival of their fry. We evaluated feeding fingerling steelhead excess thiamine hydrochloride (THCl) for 1 or 2 weeks or equimolar amounts of thiamine mononitrate, thiamine-tetrahydro-furfuryl-disulfide, benfotiamine, or dibenzoyl thiamine (DBT). We found minimal internal reserves of thiamine after 6 months. We also compared the ability of injections of thiamine and its analogs to prevent mortality in thiamine-deficient steelhead and Atlantic salmon sac fry and found all forms to be effective, although benfotiamine was the least effective on an equimolar basis. Further, we injected yearling steelhead and found that DBT was tolerated at approximately 11,200 nmol/g of body weight, about 10 times more than thiamine in any other form. When yearling steelhead were injected with near-maximal doses of thiamine hydrochloride and several analogs and then fed a thiamine-deficient diet, DBT was retained for approximately 2 years—in contrast to other forms, which were retained for less than about 6 months. Therefore, these results suggest that neither feeding nor injecting young hatchery salmonids with DBT is likely to enhance their reproduction for more than 2 years after stocking. However, injecting DBT in nearly mature fish (either cultured fish from hatcheries or wild fish captured in lakes) may provide them with enough thiamine to successfully spawn within 2 years even though they consume mainly thiaminase-containing forage fishes.
Contribution of Terrestrial Invertebrates to Yearly Brook Trout Prey Consumption and Growth
Authors: Sweka John A. , Hartman Kyle J.
Published: February 2008

Terrestrial invertebrates are an important component of stream fish diets, especially during the summer months, when aquatic invertebrates are limited. The seasonal diet composition of the brook trout Salvelinus fontinalis inhabiting two West Virginia streams was used in a bioenergetics model to simulate yearly prey consumption for two cohorts of age‐1 brook trout in each stream. Baseline simulations were run by fitting the model to observed growth from June 2000 to June 2001 for the first cohort and from June 2001 to June 2002 for the second cohort. Terrestrial invertebrate inputs can be negatively impacted by anthropogenic effects (e.g., timber harvest and pesticide application). To determine the degree to which growth would be suppressed by a reduction in terrestrial invertebrate consumption, we ran simulations in which the amount of terrestrial invertebrate consumption was reduced by 25, 50, 75, and 100%. Simulations were then run to determine the consumption of aquatic invertebrates that would be necessary to compensate for a reduction in terrestrial invertebrate consumption. The baseline simulations showed that terrestrial invertebrates accounted for 38‐47% of the biomass consumed annually and 51‐63% of the energy consumed. Reductions in the amount of terrestrial invertebrates in the diet of brook trout reduced growth; to maintain the same growth, brook trout would need to increase yearly consumption of aquatic invertebrates by more than 100% in the absence of terrestrial invertebrate input. These modeling results illustrate the importance of terrestrial invertebrates to headwater stream fish production, and managers need to recognize this energy source in assessing a stream's potential to support fish and in managing riparian forests.
An Overview of Methods for Developing Bioenergetic and Life History Models for Rare and Endangered Species
Authors: Petersen James H. , DeAngelis Donald L. , Paukert Craig P.
Published: February 2008

Many fish species are at risk to some degree, and conservation efforts are planned or underway to preserve sensitive populations. For many imperiled species, models could serve as useful tools for researchers and managers as they seek to understand individual growth, quantify predator‐prey dynamics, and identify critical sources of mortality. Development and application of models for rare species however, has been constrained by small population sizes, difficulty in obtaining sampling permits, limited opportunities for funding, and regulations on how endangered species can be used in laboratory studies. Bioenergetic and life history models should help with endangered species‐recovery planning since these types of models have been used successfully in the last 25 years to address management problems for many commercially and recreationally important fish species. In this paper we discuss five approaches to developing models and parameters for rare species. Borrowing model functions and parameters from related species is simple, but uncorroborated results can be misleading. Directly estimating parameters with laboratory studies may be possible for rare species that have locally abundant populations. Monte Carlo filtering can be used to estimate several parameters by means of performing simple laboratory growth experiments to first determine test criteria. Pattern‐oriented modeling (POM) is a new and developing field of research that uses field‐observed patterns to build, test, and parameterize models. Models developed using the POM approach are closely linked to field data, produce testable hypotheses, and require a close working relationship between modelers and empiricists. Artificial evolution in individual‐based models can be used to gain insight into adaptive behaviors for poorly understood species and thus can fill in knowledge gaps.
Development and Evaluation of a Bioenergetics Model for the Inland Silverside in Freshwater Systems
Authors: Chizinski Christopher J. , Huber Caleb G. , Pope Kevin L.
Published: February 2008

Consumption and respiration parameters were fit for inclusion in a bioenergetics model developed to predict the growth of the inland silverside Menidia beryllina. Although this model accurately predicted inland silverside growth through the initiation of spawning, it failed to predict the growth of reproductively active inland silversides. Model simulations provided initial evidence that a single model cannot predict the lifetime growth patterns of this species. Instead, a two‐stage model is probably necessary to account for the physiological differences between the prespawning and active‐spawning stages. In addition, the bioenergetics models of short‐lived (life span, <2 years) fishes may need to include a better means for assessing the direct energy expenditure for reproduction.
A Bioenergetics Approach to Modeling Striped Bass and Threadfin Shad Predator‐Prey Dynamics in Lake Powell, Utah‐Arizona
Authors: Vatland Shane , Budy Phaedra , Thiede Gary P.
Published: February 2008

An understanding of the mechanisms driving the cyclic relationship between piscivorous sport fish and their food base is needed in systems where predator and prey are tightly coupled. To understand the dynamics between striped bass Morone saxatilis and threadfin shad Dorosoma petenense in Lake Powell, Utah‐Arizona, we (1) synthesized and evaluated 20 years of historical data on temperature, diet, growth, and abundance of these fish, (2) collected similar data on a finer scale in 2003‐2004, (3) used components of this data set to develop specific conversions between coarser historic data and present data, and (4) modeled striped bass and threadfin shad dynamics within a bioenergetics framework. We estimated the consumption of threadfin shad by age‐0, subadult, and adult striped bass in Lake Powell from 1985 to 2003. During this period, threadfin shad abundance peaked at approximately 5‐ to 7‐year intervals and striped bass growth, condition, and abundance corresponded closely to peaks in threadfin shad foraging. Individual consumption of threadfin shad by striped bass was highest for adults followed by subadult and age‐0 fish; scaling individual consumption up to the population level resulted in highly variable subadult consumption that fluctuated from highs of about 1.2 million kg (18.4 kg/ha) to lows of about 0.3 million kg (4.6 kg/ha) on a 1‐ to 2‐year cycle. Despite these fluctuations, the consumption of threadfin shad was dominated by subadult striped bass, which appeared to control threadfin shad numbers in all but the highest peak years of shad abundance. Based on bioenergetics output, striped bass demonstrate a type II functional feeding response; consumption rates reach an asymptote when the threadfin shad biomass index exceeds 10,000 kg/year. We demonstrate a modeling approach that allowed us to evaluate the large fluctuations in predator and prey populations, which often become evident only over long time periods. Our results increase our understanding of the Lake Powell ecosystem and highlight areas for future study.
Individual Variation in Bioenergetic Rates of Young‐of‐Year Rainbow Trout
Authors: Tyler Jeffrey A. , Bolduc Melanie B.
Published: February 2008

Studies collecting data on bioenergetic rates in fish typically measure the rates of a large number of individuals once and then fit parameters to those data sets. Such data commonly have large amounts of variation around the mean, which is left unexplained because the study aims to address population‐level or ecosystem‐level questions. We addressed the question of whether individual fish have detectably different rates of maximum consumption and respiration rates by repeatedly measuring those rates in individually identified young‐of‐year (age‐0) rainbow trout Oncorhynchus mykiss over a range of temperatures. In experiment 1 we measured the respiration rates of two size‐classes of age‐0 rainbow trout five times at five different temperatures (9‐19°C). In experiment 2 we measured the respiration and maximum feed consumption rates of one size‐class of rainbow trout five times at four different temperatures (7‐19°C). We also use these data to develop a new parameter set for a Wisconsin bioenergetics model of maximum consumption and respiration rates for age‐0 rainbow trout. The results show that individual differences have a significant effect on their respiration and maximum feed consumption rates. The new bioenergetics parameter set differs considerably from the parameter sets developed for adult rainbow trout. The new bioenergetics model may prove useful for studies examining the growth and feed consumption of age‐0 rainbow trout. The finding of significant differences between individuals in measured rates of respiration and maximum consumption may be important in individual‐based models (IBMs) of fish populations. Specifically, IBMs have not included individual‐level differences in bioenergetic rates, but such differences may have an important effect on their predictions of fish growth, production, and population number.
Effects of Age‐1 Striped Bass Predation on Juvenile Fish in Western Albemarle Sound
Authors: Tuomikoski Jack E. , Rudershausen Paul J. , Buckel Jeffrey A. , Hightower Joseph E.
Published: February 2008

Historically, the fisheries for adult river herring (i.e., alewife Alosa pseudoharengus and blueback herring A. aestivalis) and American shad A. sapidissima were economically important in Albemarle Sound, North Carolina. Stocks of these species are in decline, while stocks of striped bass Morone saxatilis have increased roughly 10‐fold in the Albemarle Sound‐Roanoke River since the early 1990s. The goal of this study was to quantify the predatory impact of age‐1 striped bass on age‐0 prey fishes by estimating striped bass consumption rates and comparing loss rates from predation with total prey loss rates using catch curves. Age‐1 striped bass and their potential prey were collected with beach and purse seines from western Albemarle Sound from spring to fall, 2002 and 2003. Commercially and ecologically important prey in one or both years included river herring, American shad, Atlantic menhaden Brevoortia tyrannus, and yellow perch Perca flavescens. Predation by age‐1 striped bass had a marked effect on juvenile American shad densities in 2002 but little effect in 2003. Conversely, predation by age‐1 striped bass explained none of the loss in juvenile yellow perch in 2002 but accounted for nearly all of the loss early in 2003. In most cases, predation by age‐1 striped bass did not greatly influence juvenile alewife numbers. Juvenile blueback herring were preyed on during late summer and fall, but the predatory impact could not be confirmed because of apparent downstream emigration into the study area. Thus, for some species, these predator‐prey linkages are important in determining year‐class strength and should be incorporated into multispecies population models.
Effect of binary cement replacement materials on sulfuric acid resistance of dense concretes
Authors: Rahmani H. , Ramazanianpour A. A.
Published: February 2008

Biogenic sulfuric acid corrosion is often a problem in sewer environments. Also in certain industrial activities sulfuric acid is used during the production process. It can lead to a fast degradation of the concrete structures. There is therefore a substantial need for construction of durable concrete structures in such environments. The porosity of concretes plays an important role in harsh environments. For production of low-porosity concretes, optimisation of aggregate and cement grading and their proportions is necessary. A research programme was conducted to investigate concrete resistance in a sulfuric acid environment. Four concrete groups were investigated. The first group contains type II Portland cement as a control mix and the second group contains cement and super-fine quartz powder as a filler with particle size less than 16 μm. The third group includes three different mixtures containing cement and cement material replacements including 8% silica fume, 20% trass and pumice as natural pozzolans and a super-fine filler. Finally three mixtures were designed in the last group based on binary cement replacement materials containing cement with 15% natural pozzolans and 8% silica fume or 10% trass and 10% pumice and super-fine filler. The dense packing of siliceous aggregates and cementitious materials was used to achieve the highest density of concretes. Cementitious material content and water–binder (w/b) ratio were varied in this investigation. In the experiment, specimens were immersed in sulfuric acid with pH = 1·0. They were periodically examined for appearance, measured for mass change and tested in compression and flexure up to 180 days. Results show that the mass loss of mortar specimens immersed in sulfuric acid solutions increased as the w/b ratio decreased. There is, however, an optimum cementitious material content for each mixture. The performance of mortar and concretes containing trass and ultra-fine filler was better than the other mixes. Contradictory results were obtained for the concretes containing silica fume in sulfuric acid environments.
Strategic slab–column joint details for improved transmission of HSC column loads
Authors: Lee J.-H. , Yang J.-M. , Yoon Y.-S.
Published: February 2008

In typical construction, the slab is made of normal-strength concrete (NSC) and is cast in a continuous fashion through the slab–column joint. For the case of high-strength concrete (HSC) columns, this results in a layer of lower-strength concrete between the upper and lower columns at the floor levels. Since this lower-strength concrete layer can limit the capacity of the column, it is necessary to provide alternative design or construction strategies for the transmission of column loads through slab–column connections. The current paper presents the structural characteristics of slab–column connections by using full-scale tests and non-linear three-dimensional finite-element analyses. Finite-element analyses considering material non-linearity were performed to investigate the axial load plotted against average column strain responses, the type of failure, the principal stress distribution and the reinforcement yielding conditions for various slab–column members. The puddled HSC in the joint, the HSC core, the use of high-strength steel for the column longitudinal reinforcement, and the additional vertical compression reinforcement through the joint were investigated. The alternative reinforcement methods in the slab–column joints significantly improved the performance of the joints—that is, higher axial compressive strength, greater loading stiffness and higher ductility.
Deformability prediction model for self-compacting concrete
Authors: Kasemchaisiri R. , Tangtermsirikul S.
Published: February 2008

The aim of the current study is to propose a model for predicting deformability of powder-type self-compacting concrete (SCC) based on theoretical and empirical approaches. Deformability, one of the essential functions for SCC's filling ability, was defined and determined in this study to include deformation capacity, indicated by slump flow value, and velocity of deformation, measured by 500 mm slump flow time (T500). In the process of mix proportioning, both deformation properties should be considered to achieve good deformability. Prediction models for deformation capacity and velocity of deformation were developed based on the concepts of free water content, water retainability of solid particles and inter-particle forces in the concrete. It was found that slump flow and T500 varied mainly with free water content in mixtures and were also affected by various factors, such as ratio of paste volume to void content of compacted aggregate phase, surface area, shape and water retainability of powder materials and aggregates and efficiency and dosage of superplasticiser. Experimental results from the current authors and other researchers were used in the verification of the proposed models. It was evident that the proposed models could be used to predict the slump flow and T500 with satisfactory accuracy.
Occurrences and ecological risks of roxithromycin, trimethoprim, and chloramphenicol in the Han River, Korea
Authors: Choi Kyungho , Kim Younghee , Jung Jinyong , Kim Myung-Hyun , Kim Chang-Soo , Kim Nam-Hee , Park Jeongim
Published: February 2008

We evaluated the occurrence of three antibiotics (roxithromycin, trimethoprim, and chloramphenicol) in surface water and effluents from several sewage treatment plants (STPs) on the Han River, Korea. In addition, standard acute toxicity tests were conducted using the microbe Vibrio fischeri, freshwater macroinvertebrates Daphnia magna and Moina macrocopa, and fish (Oryzias latipes) for these antibiotics. Antibiotics were more frequently detected at higher amounts in effluent samples and in samples collected during the low-flow season. For trimethoprim and chloramphenicol, the levels observed in surface water during low flow were, on average, 108 and 31 ng/L, respectively. These levels were comparable to those measured in the municipal effluents (average, 80 and 37 ng/L, respectively), suggesting the presence of other sources upstream (e.g., livestock wastes). For roxithromycin, surface water levels were approximately an order of magnitude lower than effluent levels. Adverse effects of roxithromycin, trimethoprim, and chloramphenicol were observed at mg/L levels in standard acute aquatic ecotoxicity tests. Based on hazard quotients calculated for the three antibiotics, minimal risks to aquatic systems are suggested. To further increase scientific understanding about the potential impacts of these pharmaceuticals in the environment, however, chronic ecotoxicology studies, with more subtle but ecologically meaningful end points or in combination with other mechanistically related contaminants, may be beneficial.
Assessment of exposure risk of polychlorinated biphenyls to interior least terns (Sterna antillarum)
Authors: Sanchez Brian C , Caldwell Colleen A
Published: February 2008

Risk of polychlorinated biphenyl (PCB) exposure and effects were assessed for a colony of federally endangered interior least terns (Sterna antillarum) nesting on the Bitter Lake National Wildlife Refuge (NM, USA). The colony feeds from an area on the Refuge (Hunter Marsh/Oxbow Complex) wherein fish with elevated concentrations of total PCBs have been documented. Concentrations of total PCBs in whole fish averaged 0.94 mg/kg with a maximum concentration of 2.77 mg/kg, wet weight. Estimated daily PCB intake rates by adult birds throughout their 180-d breeding season ranged from <0.01 mg/kg/d to 0.98 mg/kg/d, yielding hazard quotients that ranged from 0.01 to 21.68. Polychlorinated biphenyls pose a moderate risk to the colony of interior least terns that breed at the Bitter Lake National Wildlife Refuge, but the exposure rate is not likely to threaten their overall breeding success.
DNA Microarray-based ecotoxicological biomarker discovery in a small fish model species
Authors: Wang Rong-Lin , Bencic David , Biales Adam , Lattier David , Kostich Mitch , Villeneuve Dan , Ankley Gerald T , Lazorchak Jim , Toth Greg
Published: February 2008

As potential biomarkers, gene classifiers are gene expression signatures or patterns capable of distinguishing biological samples belonging to different classes or conditions. This is the second of two papers on profiling gene expression in zebrafish (Danio rerio) treated with endocrine-disrupting chemicals of different modes of action, with a focus on comparative analysis of microarray data for gene classifier discovery. Various combinations of gene feature selection/class prediction algorithms were evaluated, with the use of microarray data organized by a chemical stressor or tissue type, for their accuracy in determining the class memberships of independent test samples. Two-way clustering of gene classifiers and treatment conditions offered another alternative to assess the performance of these potential biomarkers. Both gene feature selection methods and class prediction algorithms were shown to be important in identifying successful gene classifiers. The genetic algorithm and support vector machine yielded classifiers with the best prediction accuracy, regardless of sample size, nature of class prediction, and data complexity. A chemical stressor significantly altering the expression of a greater number of genes tended to generate gene classifiers with better performance. All combinations of gene feature selection/class prediction algorithms performed similarly well with data of high signal to noise ratio. Gene classifier discovery and application on the basis of individual sampling and sample data pooling, respectively, were found to enhance class predictions. Gene expression profiles of the top gene classifiers, identified from both microarray and quantitative polymerase chain reaction assays, displayed greater similarity between fadrozole and 17β-trenbolone than either one to 17α-ethinylestradiol. These gene classifiers could serve as potential biomarkers of exposure to specific classes of endocrine disruptors.
Altered reproduction in fish exposed to pulp and paper mill effluents: Roles of individual compounds and mill operating conditions
Authors: Hewitt L. Mark , Kovacs Tibor G , Dubé Monique G , MacLatchy Deborah L , Martel Pierre H , McMaster Mark E , Paice Michael G , Parrott Joanne L , van den Heuvel Michael R , van der Kraak Glen J
Published: February 2008

For the last 20 years, studies conducted in North America, Scandinavia, and New Zealand have shown that pulp and paper mill effluents affect fish reproduction. Despite the level of effort applied, few leads are available regarding the factors responsible. Effluents affect reproduction in multiple fish species, as evidenced by decreased gonad size, decreased circulating and gonadal production of reproductive steroids, altered expression of secondary sex characteristics, and decreased egg production. Several studies also have shown that effluent constituents are capable of accumulating in fish and binding to sex steroid receptors/binding proteins. Studies aimed at isolating biologically active substances within the pulping and papermaking process have provided clues about their source, and work has progressed in identifying opportunities for in-mill treatment technologies. Following comparisons of manufacturing processes and fish responses before and after process changes, it can be concluded that effluent from all types of mill processes are capable of affecting fish reproduction and that any improvements could not be attributed to a specific process modification (because mills normally performed multiple modifications simultaneously). Improved reproductive performance in fish generally was associated with reduced use of molecular chlorine, improved condensate handling, and liquor spill control. Effluent biotreatment has been effective in reducing some effects, but biotreated effluents also have shown no difference or an exacerbation of effects. The role of biotreatment in relation to effects on fish reproduction remains unclear and needs to be resolved.
Net trophic transfer efficiencies of polychlorinated biphenyl congeners to lake whitefish (Coregonus clupeaformis) from their food
Authors: Madenjian Charles P , O'Connor Daniel V , Rediske Richard R , O'Keefe James P , Pothoven Steven A
Published: February 2008

Lake whitefish (Coregonus clupeaformis) were fed rainbow smelt (Osmerus mordax) in four laboratory tanks over a 133-d experiment. At the start of the experiment, 10 to 14 of the fish in each tank were sacrificed, and the concentrations of 40 polychlorinated biphenyl (PCB) congeners within these fish were determined. Polychlorinated biphenyl congener concentrations were also determined in the 15 lake whitefish remaining in each of the four tanks at the end of the experiment as well as in the rainbow smelt fed to the lake whitefish. Each lake whitefish was weighed at the start and the end of the experiment, and the amount of food eaten by the lake whitefish during the experiment was tracked. Using these measurements, net trophic transfer efficiency (γ) from the rainbow smelt to the lake whitefish in each of the four tanks was calculated for each of the 40 PCB congeners. Results showed that γ decreased exponentially as log KOW for the congeners increased from 6 to 8. Further, γ averaged 0.70 for the tetrachloro congeners but averaged only 0.45 for the higher chlorinated congeners.
Electron-microscopic localization of lipophilic chemicals by an antibody-based detection system using the blue mussel Mytilus edulis as a model system
Authors: Einsporn Sonja , Koehler Angela
Published: February 2008

Identification of lipophilic chemicals requires the development of new techniques to detect these compounds at the cellular and subcellular levels. To address this issue, we have developed a combinational protocol using antibodies directed against chemicals together with a multiple signal amplification system (catalyzed signal amplification/gold-substituted silver-intensified peroxidase) to detect the lipophilic compounds at their subcellular sites of accumulation by transmission electron microscopy. As a model organism, we exposed the blue mussel Mytilus edulis to the polycyclic aromatic hydrocarbon phenanthrene and the polychlorinated biphenyl mixture Aroclor 1254 for up to 10 d. The aim of these exposure experiments was to analyze the cellular targets and sites of accumulation in the digestive system by transmission electron microscopy. The endo-lysosomal system of digestive cells and mitochondria of epithelial cells appeared to be the preferred accumulation sites for the lipophilic compounds studied. The antibody-based approach to detect lipophilic chemicals provides an important insight into the pathways of uptake and accumulation as well as mechanisms of toxicity.