bluuebunny/crossref_metadata_2025 huggingface dataset:
Perspective—Historical Roots of theA Behavioral Theory of the FirmModel at GSIA
Authors: Augier Mie , Prietula Michael
Published: June 2007

Richard Cyert and James March’s (1963) A Behavioral Theory of the Firm (ABTOF) is one of the most influential works in organization science. An important element of that work was a computational model of a duopoly, which was arguably the first computational model that instantiated organizational constructs within a substantial theoretical framework. We suggest that the academic environment within which this theory and model grew was instrumental in its emergence. Furthermore, an examination of the model itself (by triangulating on the verbal descriptions, the flow charts, and the code) reveals innovative embodiments of organizational attention, organizational learning, organizational memory, routines, metaroutines, aspiration level adjustments and computational experiments. In this paper we examine the historical roots of the model—the concepts, culture, and characters at Carnegie Tech and the Graduate School of Industrial Administration (GSIA). Although causality is difficult to assess historically, we suggest the significance of a strong research-based, interdisciplinary culture at a time when innovative (and often computational) concepts and theories were emerging within the contexts of computer science, economics, and psychology.
Perspective—Neo-Carnegie: The Carnegie School’s Past, Present, and Reconstructing for the Future
Authors: Gavetti Giovanni , Levinthal Daniel , Ocasio William
Published: June 2007

Cyert and March’s (1963) A Behavioral Theory of the Firm and the broader Carnegie School form critical theoretical underpinnings for modern organization studies. Despite its impact, however, we suggest that researchers who rely on the Carnegie School have progressively lost touch with its defining commitment to a decision-centered view of organizations. Decision making has given way to learning, routines, and an increased focus on change and adaptation; the organizational level of analysis, although frequently invoked, has been largely supplanted by either a more micro or a more macro focus. In this paper, we argue for restoring the School’s original mission and perspective. Our proposal for how this overarching goal can be achieved encompasses three central points. First, we believe the School needs to resurrect a few select ideas that, despite their fundamental importance, have been neglected over time. Second, we believe there is a need for greater paradigmatic closure amongst the School’s central theoretical pillars. Loose coupling among such pillars might keep key insights on organizational decision making from emerging. Finally, there is the need to incorporate major developments that have been generated post-Carnegie School, both within organization theory and in the behavioral and social sciences more broadly. In particular, we point to the shift to more open systems perspectives on organizations, the conceptions of organizations being embedded in larger social contexts, and recent developments in the study of individual cognition.
Perspective—On the Evolutionary and Behavioral Theories of Organizations: A Tentative Roadmap
Authors: Dosi Giovanni , Marengo Luigi
Published: June 2007

Cyert and March’s A Behavioral Theory of the Firm has been acknowledged as one of the most fundamental pillars on which evolutionary theorizing in economics is built. Nelson and Winter’s 1982 book is pervaded by the philosophy and concepts previously developed by Cyert, March, and Simon. Behavioral notions, such as bounded rationality are also at the heart of economic theories of institutions such as transaction costs economics. In this paper, after briefly reviewing the basic concepts of evolutionary economics, we discuss its implications for the theory of organizations (and business firms in particular), and we suggest that evolutionary theory should coherently embrace an “embeddedness” view of organizations, whereby the latter are not simply efficient solutions to informational problems arising from contract incompleteness and uncertainty, but also shape the “visions of the world,” interaction networks, behavioral patterns, and the identity of the agents. After outlining the basic features of this perspective, we analyze its consequences and empirical relevance.
Influence of targeted basic surgical training lists on SHO operative experience in the EWTD era
Authors: Beaton C , Morgan MA , Shute K , Hopper AN , Stephens MR , Lewis WG
Published: June 2007

Presented at the Association of Surgeons of Great Britain and Ireland, Edinburgh, May 2006.
A junior surgeon's year in Africa – Francis' Mission Hospital, Katete, Zambia
Authors: Bethune Rob
Published: June 2007

It is becoming more and more difficult for junior surgical trainees to get operative experience in this country and it will only get worse in the future. Africa is desperately short of medical professionals and particularly surgeons. To kill two birds with one stone why not work in Africa for a year? This is a report of one such adventure.
Silver Scalpel: recognising the trainers
Authors: Towell Elaine
Published: June 2007

In 2000 a new award was instituted to recognise surgical training. For two years it formed part of the Hospital Doctor awards and in its first year attracted more nominations for a new award than any in previous years, for any discipline. Since then, it has almost single-handedly been carried forward by its creator, David O'Regan, past president of the Association of Surgeons in Training (ASiT). The award is presented on an annual basis to the person deemed most worthy of the title of surgical trainer of the year. It is an award, he says, that should be given much wider recognition.
But orthodontics is always different…
Authors: Hunt Nigel
Published: June 2007

Rarely does a week go by without hearing the phrase 'Ah yes, but orthodontics is always different…' Frequently it is said with an air of criticism, but is almost always underwritten with slightly more than a touch of envy. Although it may be said in relation to a whole spectrum of matters, the cohesive ideology of the various groups that constitute the British Orthodontic Society (BOS) and the forward thinking of the teachers and trainers serve as two examples.
Manifolds with asymptotically nonnegative minimal radial curvature
Authors: Santos Newton L
Published: June 2007

In this paper we extend results on the geometry of manifolds with asymptotically nonnegative curvature to manifolds with asymptotically nonnegative minimal radial curvature, showing that most of the results obtained by [U. Abresch, Lower curvature bounds, Toponogov's theorem, and bounded topology. Ann. Sci. École Norm. Sup. (4) 18 (1985), 651–670. MR839689 (87j:53058) Zbl 0595.53043], [A. Kasue, A compactification of a manifold with asymptotically nonnegative curvature. Ann. Sci. École Norm. Sup. (4) 21 (1988), 593–622. MR982335 (90d:53049) Zbl 0662.53032] and [S.-H. Zhu, A volume comparison theorem for manifolds with asymptotically nonnegative curvature and its applications. Amer. J. Math.
116 (1994), 669–682. MR1277451 (95c:53049) Zbl 0953.53027] hold in a more general context. Particularly, we show that there exists one and only one tangent cone at infinity to each such manifold, in contrast with the class of manifolds of nonnegative Ricci curvature.
Hermitian indicator sets
Authors: Cossidente A , Lunardon G , Marino G , Polverino O
Published: June 2007

Indicator sets arising from symplectic line-spreads of a 3-dimensional projective space are characterized. Moreover, locally Hermitian ovoids of a Hermitian surface

(3, q
2) are studied in terms of “non-equivalent” associated indicator sets. Translation locally Hermitian ovoids of

(3, q
2) arising from regular spreads of PG(3, q), Kantor semifield spreads of PG(3, q) and semifield spreads of PG(3, q) with center

are also investigated.
Intersection properties of polyhedral norms
Authors: Moreno José Pedro , Schneider Rolf
Published: June 2007

We investigate the family

of intersections of balls in a finite-dimensional vector space with a polyhedral norm. The spaces for which

is closed under Minkowski addition are completely determined. We characterize also the polyhedral norms for which

is closed under adding a ball. A subset

of

consists of the Mazur sets K, defined by the property that for any hyperplane H not meeting K there is a ball containing K and not meeting H. We characterize the Mazur sets in terms of their normal cones and also as summands of closed balls. As a consequence, we characterize the polyhedral spaces with only trivial Mazur sets as those whose unit ball is indecomposable.
Control of porosity in fluoride thin films prepared by vapor deposition
Authors: Kim Hakkwan , King Alexander H.
Published: June 2007

We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF2), and calcium fluoride (CaF2) as a function of the substrate temperature for films deposited by thermal evaporation onto glass substrates. The amount of porosity in the thin films was measured using an atomic force microscope and a quartz crystal thickness monitor. The porosity was very sensitive to the substrate temperature and decreased as the substrate temperature increased. Consistent behavior was observed among all of the materials in this study.
Low-temperature ultraviolet sol-gel photoannealing processing of multifunctional lead-titanate-based thin films
Authors: Calzada M.L. , Bretos I. , Jiménez R. , Guillon H. , Ricote J. , Pardo L.
Published: June 2007

(Pb1−xCax)TiO3 perovskite thin films with nominal compositions of (Pb0.76Ca.24)TiO3 (ferroelectric) and (Pb0.50Ca0.50)TiO3 (relaxor-ferroelectric) were prepared on silicon substrates at low temperatures compatible with those used in Si-technology. The technique used for the processing of these films was ultraviolet (UV) sol-gel photoannealing, using photo-sensitive precursor solutions and UV-assisted rapid thermal processing. The UV-irradiation and thermal treatment of the solution-derived films (gel films) were carried out in air or in oxygen. In both cases, the formation of the perovskite occurred at the same temperature, and this temperature increased as the Ca2+ content increased. Thus, full-perovskite films of (Pb0.76Ca.24)TiO3 were obtained at 723 K whereas those of (Pb0.50Ca0.50)TiO3 were formed at 773 K. Well-defined ferroelectric hysteresis loops were measured in the (Pb0.76Ca.24)TiO3 films, with values of remanent polarization of Pr ∼ 11 μC cm−2 and coercive fields for the films processed in oxygen lower than those of the films processed in air, Ec ∼ 164 and ∼226 kV.cm−1, respectively. These films showed a ferro-paraelectric transition at close temperatures of Tmax ∼ 605 K, although with higher values of the permittivity for the film processed in oxygen, k ∼ 567 at 10 kHz. The (Pb0.50Ca.50)TiO3 films had a diffuse ferro-paraelectric transition with a relaxor-like character, also with higher k values for the films prepared in oxygen, k ∼ 179 at Tmax ∼ 20 K. The possible use of these materials in silicon integrated multifunctional devices is discussed in this paper.
Electrical characterization of defect states in local conductivity domains in ZnO:N,As layers
Authors: Krtschil Andre , Dadgar Armin , Diez Annette , Krost Alois
Published: June 2007

P- and n-type conductivity domains in dual-doped ZnO:As+N layers grown by metal organic vapor phase epitaxy on GaN–sapphire templates were electrically microcharacterized by scanning capacitance microscopy (SCM) and scanning surface potential microscopy (SSPM) techniques with respect to their defect states. The p-type domains were found to be dominated by two acceptors with thermal activation energies of about 80 and 270 meV, as observed by transient SCM scans at different temperatures. Optically excited SSPM scans revealed defect-to-band transitions at 400, 459, and 505 nm omnipresent in both domain types as well as a shallower transition at 377 nm exclusively in the p-type regions. According to the similar energy levels, the optical transitions at 377 and 400 nm are assigned to acceptor states, whereby the 80-meV acceptor is probably responsible for the conversion from n- to p-type regions in the domains.
Preliminary investigation on the catalytic mechanism of TiF3 additive in MgH2–TiF3 H-storage system
Authors: Ma Lai-Peng , Wang Ping , Kang Xiang-Dong , Cheng Hui-Ming
Published: June 2007

A combined structure/property investigation is performed to understand the catalytic effect of TiF3 additive on the absorption/desorption reactions of MgH2. It was found that both TiH2 and MgF2 phases identified by x-ray diffraction cannot explain the observed kinetic enhancement in the MgH2–TiF3 system, whether they are incorporated in a direct or an in situ manner. In combination with the comparative investigation on the catalytic activity of TiF3 and its analog TiCl3, as well as the samples milled under inert and reactive atmospheres, we propose that the catalytically active species is a multicomponent metastable phase composed of host Mg, transition metal Ti, and F anion, the catalytic activity of which is dependent on its interaction with the surrounding chemical environment.
Characteristics of hafnium oxide grown on silicon by atomic-layer deposition using tetrakis(ethylmethylamino)hafnium and water vapor as precursors
Authors: Chiou Yan-Kai , Chang Che-Hao , Wu Tai-Bor
Published: June 2007

The growth of HfO2 thin films on a HF-dipped p-Si(100) substrate at 200 °C by atomic-layer deposition (ALD) using Hf[N(C2H5)(CH3)]4 and H2O vapor as precursors is demonstrated. Uniform HfO2 thin films are obtained on a 4-in. silicon wafer, and the energy-band gap and band offset are determined by x-ray photoelectron spectroscopy analysis. The as-deposited HfO2 thin film is amorphous and able to crystallize at 500 ∼ 600 °C with only the monoclinic phase. As for the electrical performance of Au–Ti–HfO2–Si metal oxide semiconductor capacitors, a dielectric constant of ∼17.8 and an equivalent oxide thickness value of ∼1.39 nm are obtained from the 40-cycle ALD film after annealing at 500 °C. In addition, the breakdown field is in the range of 5 ∼ 5.5 MV/cm, and the fixed charge density is on the order of 1012 cm−2, depending on the annealing temperatures. The interface quality of HfO2 thin films on silicon is satisfactory with an interface-trap charge density of ∼3.7 × 1011 cm−2 eV−1.
Infrared luminescence properties of bismuth-doped barium silicate glasses
Authors: Ren Jinjun , Qiu Jianrong , Chen Danping , Wang Chen , Jiang Xiongwei , Zhu Congshan
Published: June 2007

Infrared (IR) luminescence covering 1.1 to ∼1.6 μm wavelength region was observed from bismuth-doped barium silicate glasses, excited by a laser diode at 808 nm wavelength region, at room temperature. The peak of the IR luminescence appears at 1325 nm. A full width half-maximum (FWHM) and the lifetime of the fluorescence is more than 200 nm and 400 μs, respectively. The fluorescence intensity increases with Al2O3 content, but decreases with BaO content. We suggest that the IR luminescence should be ascribed to the low valence state of bismuth Bi2+ or Bi+, and Al3+ ions play an indirect dispersing role for the infrared luminescent centers.
Phase and microstructural evolution in polymer-derived composite systems and coatings
Authors: Torrey Jessica D. , Bordia Rajendra K.
Published: June 2007

Polymer-derived ceramics have shown promise as a novel way to process low-dimensional ceramics such as environmental barrier coatings. Composite coatings have been developed as oxidation and carburization barriers on steel using poly(hydridomethylsiloxane) matrix and titanium disilicide as reactive fillers. A systematic study of the phase transformations and microstructural changes in the coatings and their components during pyrolysis in air is presented here. The system evolves from an amorphous polymer filled with a binary metal at room temperature to an inorganic amorphous network of oxidized silicon and titanium at the target temperature of 800 °C. Crystallization of the composite occurs at higher temperatures to reach cristobalite and rutile by 1600 °C. The polymer-to-ceramic conversion occurs between 200 and 600 °C. The oxidation of the expansion agent and the densification of the composite take place between 300 and 800 °C.
Thin-film synthesis and microstructure characterization of the poly(vinyl alcohol) matrix with functionalized carbon nanotubes
Authors: He Xiaoling , Xu Song , Sklyarov Andrey V. , Hardcastle Steven
Published: June 2007

We report on the synthesis and surface characterization of thin-film nanocomposites using functionalized single-walled carbon nanotubes (CNTs) with a diamine-terminated oligomeric poly(ethylene glycol) [poly(ethylene glycol) bis (3-aminopropyl)-terminated 1500]. The functionalized CNT samples are soluble in highly polar solvents. Their common solubility allows for the intimate mixing of the functionalized nanotubes with the matrix polymer–poly(vinyl alcohol) by dip coating and wet casting to form nanocomposite thin films. We demonstrate the alignment of the CNT bundles in the thin films that are formed without the external field forces. We present our results and discuss alignment reorientations from the characterizations of the nanocomposite thin films by using a Raman spectrometer, scanning electron microscopy, and atomic force microscopy.
Formation of nanocrystalline surface of a Cu–Zn alloy under electropulsing surface treatment
Authors: Du X.N. , Wang B.Q. , Guo J.D.
Published: June 2007

A nanocrystalline surface layer of a Cu–Zn alloy was developed by electropulsing (ECP) surface treatment. The average grain size was about 20 nm on the top surface layer and was gradually augmented with the increase in depth from the top surface. Nanoindentation measurements showed that the hardness was significantly enhanced on the top surface layer compared with the as-annealed Cu–Zn sample. The mechanism for the evolution of this structure and property was related not only to a solid-state phase transformation, but also to the effect of the enhancement of the nucleation rate and the skin effect during the ECP treatment. Therefore, the ECP surface treatment provides a promising method for obtaining surface self-nanocrystallization materials.
Particle size control of a monodisperse spherical Y2O3:Eu3+ phosphor and its photoluminescence properties
Authors: Yoo Hyoung Sun , Jang Ho Seong , Im Won Bin , Kang Jong Hyuk , Jeon Duk Young
Published: June 2007

A monodisperse spherical Y2O3:Eu3+ phosphor was prepared by a homogeneous precipitation method. The mean size of the phosphor particles (MSPP) was successfully controlled by changing the volume ratio of normal alcohol (RA) (propanol) in the solvents mixed between deionized water and normal propanol. When the RA was increased from 0 to 0.7, the MSPP decreased while maintaining a high yield of >95%. Although the prepared phosphor samples were fired at the same temperature, the thermal energy was delivered more efficiently into the inner side of the phosphor particles with the decrease of the MSPP. Therefore, the crystallinity and also the photoluminescence (PL) intensity of the phosphor increased with the decrease in the MSPP. In addition, because the numbers of Eu3+ ions located near the particle surfaces increased with the decrease of particle size, the ratio of PL intensity caused by the 5D0–7F2 transition to that caused by 5D0–7F1 transition increased from 10.8 to 12.7 with the decrease in MSPP.
Shell Strength and Appearance in Cultured Blue Mussels Mytilus edulis, M. trossulus, and M. edulis × M. trossulus Hybrids
Authors: Penney Randy W , Hart M Jeanne , Templeman Nadine D
Published: June 2007

We studied shell strength and appearance in six mixed-species cultured populations of blue mussels (Mytilus edulis, M. trossulus, and their hybrids) from Newfoundland, Canada. Shell strength (defined as the force causing shell breakage) and shell thickness both increased with shell length. Strength and thickness varied significantly among sites and among genotypes within sites; M. edulis had stronger and thicker shells than M. trossulus. Shell strength was related to shell thickness and shell width, both of which were greater in M. edulis than in M. trossulus. Hybrids tended to be intermediate. Appearance was studied on the basis of shell color and shape. The frequency of brown-shelled mussels varied considerably among sites and was higher in M. trossulus than in M. edulis. Shell width, depth, width-length ratio, and depth-length ratio all varied significantly among sites. Within sites, M. edulis had a greater shell width, width-length ratio, and width-depth ratio than M. trossulus, whereas hybrids were intermediate. Intrasite variability in shell shape characteristics, expressed as total population variance, was greater in the mixed-species populations from Newfoundland than in a unispecific M. edulis population from Prince Edward Island. In a reciprocal seed transfer experiment, shell width, width-length ratio, and width-depth ratio were greater in M. edulis than in M. trossulus of similar age. Width-length and width-depth ratios decreased with increasing age. Fourteen months after transfer, shell width and depth differed between transferred and nontransferred stocks. Interspecific relationships between M. edulis and M. trossulus in shell width and width-length ratio were similar in transferred and nontransferred stocks, while the other shell dimensions and their ratios differed. We infer that genotype-related differences in shell shape may change after stock transfer owing to site-related effects on shell growth. We discuss these results in terms of their potential impact on future industry development, particularly expansion of the seed supply for further industry growth.
Efficiency of Trout Raceway Quiescent Zones in Controlling Suspended Solids
Authors: Soderberg Richard W
Published: June 2007

Best management practice for effluent control of trout hatchery discharges calls for separation of cleaning waste by collection in quiescent zones (QZs) at the end of each raceway. The efficiency of QZs in trapping solid waste over a range of fish densities, water velocities, and QZ areas, measured by overflow rate (OFR), were studied. Solids retention in the QZs was negligible at velocities of 2.0 and 4.4 cm/s (regardless of fish density) and at a fish density of 40 kg/m3 (regardless of velocity). Solids collection efficiency was affected more by OFR and fish density than by velocity. At OFRs of 0.5 and 1.0 cm/s, solids collection was significantly better at a fish density of 160 kg/m3 than at a density of 80 kg/m3. At a density of 80 kg/m3, solids retention was better at an OFR of 0.5 cm/s than at an OFR of 1.0 cm/s. Solids retention was not affected by OFR at a fish density of 160 kg/m3. Velocities in the range of 2.4–3.4 cm/s did not affect solids collection efficiency at either fish density. Thus, optimum conditions for solids collection in trout raceway QZs were 2.4–3.4-cm/s velocity and (1) a fish density of 160 kg/m3 at an OFR of 0.5 or 1.0 cm/s or (2) a density of 80 kg/m3 at an OFR of 0.5 cm/s. Under these conditions, up to 20% of the total solids load was collected in the raceway QZs. Although this value is lower than expected based on the literature, actual solids levels were less than 5 mg/L and solids concentrations in the effluents of downstream units of serial raceways were not additive.
Status of an Introgressed Guadalupe Bass Population in a Central Texas Stream
Authors: Littrell Bradley M. , Lutz-Carrillo Dijar J. , Bonner Timothy H. , Fries Loraine T.
Published: June 2007

Introductions of nonnative smallmouth bass Micropterus dolomieu into central Texas streams resulted in introgressive hybridization with an endemic allopatric congener, the Guadalupe bass M. treculii. The objectives of this study were to use the variation at 14 microsatellite DNA loci to examine the frequencies of Guadalupe bass, smallmouth bass, and their hybrids 10 years after supplemental stockings of Guadalupe bass in the Blanco River. Genetic analysis identified 40% of individuals as smallmouth bass, 51% as smallmouth bass × Guadalupe bass hybrids, and 9% as other Micropterus hybrids. Pure Guadalupe bass were not collected. Despite supplemental stocking, the frequency of pure Guadalupe bass appears to have declined in the Blanco River in the past 10 years. These results emphasize the need for a current survey of the genetic status of the species throughout its native range.
Diel Behavior of Adult Striped Bass Using Tailwater Habitat as Summer Refuge
Authors: Young Shawn P. , Isely J. Jeffery
Published: June 2007

General patterns of summer diel distribution and movement were identified for adult striped bass Morone saxatilis using tailwater habitat influenced by the diel operation cycle of a hydroelectric dam during the summers of 2003 and 2004. Striped bass distribution within the tailwater was similar during each diel‐tracking event and across both summers. The majority of fish remained within the tailwater the entire summer; however, some made periodic excursions to and from the tailwater throughout the summer. Further, most striped bass were located within 0.5 km of Richard B. Russell Dam during all stages of operation on all occasions—probably because of the constant availability of optimal habitat during all three stages of operation on all diel‐tracking events. The diel cycle of dam operation, which included pumped storage during each summer, did not degrade tailwater habitat below optimal conditions, according to summer habitat suitability index values for inland adult striped bass. Movement was significantly higher during hydroelectric generation operations than during no‐generation and pumped storage periods in summer 2003; this difference was not apparent during summer 2004. Mean absolute movement peaked during hydroelectric generation on six of eight diel‐tracking events. During both summers, movement was directed up‐reservoir during no‐generation and generation periods and down‐reservoir during pumped storage. Mean total daily movement rates ranged from 0.59 to 4.04 km/d and were greater than those previously estimated from bimonthly sampling for this population. Total daily movement rate peaked during the first tracking event each summer and then declined as summer progressed. These findings suggest that hydroelectric discharges affect adult striped bass behavior, but the effects are not adverse as long as habitat is not degraded by hydroelectric facility operations.
Low‐temperature amorphous‐silicon backplane technology development for flexible displays in a manufacturing pilot‐line environment
Authors: Raupp Gregory B. , O'Rourke Shawn M. , Moyer Curt , O'Brien Barry P. , Ageno Scott K. , Loy Douglas E. , Bawolek Edward J. , Allee David R. , Venugopal Sameer M. , Kaminski Jann , Bottesch Dirk , Dailey Jeff , Long Ke , Marrs Michael , Munizza Nick R. , Haverinen Hanna , Colaneri Nicholas
Published: June 2007

Abstract—A low‐temperature amorphous‐silicon (a‐Si:H) thin‐film‐transistor (TFT) backplane technology for high‐information‐content flexible displays has been developed. Backplanes were integrated with frontplane technologies to produce high‐performance active‐matrix reflective electrophoretic ink, reflective cholesteric liquid crystal and emissive OLED flexible‐display technology demonstrators (TDs). Backplanes up to 4 in. on the diagonal have been fabricated on a 6‐in. wafer‐scale pilot line. The critical steps in the evolution of backplane technology, from qualification of baseline low‐temperature (180°C) a‐Si:H process on the 6‐in. line with rigid substrates, to transferring the process to flexible plastic and flexible stainless‐steel substrates, to form factor scale‐up of the TFT arrays, and finally manufacturing scale‐up to a Gen 2 (370 × 470 mm) display‐scale pilot line, will be reviewed.
The use of coarse, separable, condensed-phase organic carbon particles to characterize desorption resistance of polycyclic aromatic hydrocarbons in contaminated sediments
Authors: Chai Yunzhou , Kochetkov Alexander , Reible Danny D.
Published: June 2007

Physical separations were employed to characterize the source of desorption-resistant behavior for polycyclic aromatic hydrocarbons (PAHs) in laboratory- and field-contaminated sediments. Size and density separation of laboratory-contaminated sediments did not effectively separate the amorphous-phase (volatile) and condensed-phase (nonvolatile) organic carbon as measured by thermal oxidation at 375°C. These separations also did not result in sediment fractions with significantly different desorption characteristics as measured by apparent partition coefficients. Coarse particles from a field-contaminated sediment from Utica Harbor (UH; Utica, NY, USA), however, could be directly separated into sandy fractions and organic fractions that were composed of woody organic matter, charcoal or charred vegetative matter, and coal-like and coal-cinder particles. Chemical analysis showed that coal-like (glassy, nonporous) and coal-cinder (porous, sintered) particles exhibited very high PAH concentrations and high apparent partition coefficients. These particles also exhibited significantly higher condensed-phase (nonvolatile) organic carbon contents as defined by thermal oxidation at 375°C. The apparent partition coefficients of PAHs in the coal-cinder particles were a good indication of the apparent partition coefficients in the desorption-resistant fraction of UH sediment, indicating that the coarse particles provided a reasonable characterization of the desorption-resistance phenomena in these sediments even though the coarse fractions represented less than 25% of the organic carbon in the whole sediment.
Deterministic and probabilistic acute-based environmental risk assessment for naproxen for Western Europe
Authors: Straub Jürg Oliver , Stewart Kathleen M.
Published: June 2007

An environmental risk assessment (ERA) was made for the common nonsteroidal anti-inflammatory drug naproxen. The ERA was performed according to deterministic and probabilistic methods, based on different predicted environmental concentrations (PECs) and measured environmental concentrations (MECs) on the exposure side as well as on published and newly elaborated acute ecotoxicity data on the effects side. Compilation of a large set of MECs allowed a qualification of the various PEC derivations. The European Medicines Evaluation Authority (EMEA) phase I PEC was shown to be far above realistic values, while the refined EMEA phase II (A and B) PECs were not too far from the 95th percentile MEC, in agreement with their nature as local PECs. The western European continental and regional PECs extrapolated based on actual use data, using the European Union system for the evaluation of substances, with the region reconfigured for Germany where most of the available European MECs are from, were in good to very close agreement with the median MECs. No risk to surface waters is apparent by any of the methodologies applied from the current use of naproxen; however, because only insufficient chronic ecotoxicity data are available, this is a preliminary conclusion.
Assessment of the toxicity of mixtures of nickel or cadmium with 9,10-phenanthrenequinone toDaphnia magna: Impact of a reactive oxygen-mediated mechanism with different redox-active metals
Authors: Xie Fangli , Lampi Mark A. , Dixon D. George , Greenberg Bruce M.
Published: June 2007

Recently, we showed that reactive oxygen species (ROS) formation was involved in the toxicity of the redox-active metal Cu and mixtures of Cu plus a photomodified polycyclic aromatic hydrocarbon (PAH), phenanthrenequinone (PHQ), to Daphnia magna. It is unknown, however, if similar results can be observed for metals with lower or no redox activity and their mixtures with PHQ. In the present study using D. magna, the toxicity of Ni, a weakly redox-active metal, and of Cd, a non-redox active metal, was examined with or without PHQ. The abilities of Ni, Cd, PHQ, and binary mixtures of metal plus PHQ to generate ROS were measured using a 2′,7′-dichlorofluorescein fluorescence assay. The results were compared with the results of Cu and mixtures of Cu plus PHQ from a recent study by our group. The order of metal toxicity to D. magna was found to be Cd ≥ Cu > Ni. As with Cu/PHQ mixtures, synergistic toxicity was observed for mixtures of Ni and PHQ, whereas additive toxicity was observed for mixtures of Cd and PHQ. Alone, PHQ had no impact on ROS levels in D. magna. Nickel alone caused elevated ROS, which was further enhanced in the presence of PHQ. Neither Cd nor Cd/PHQ mixtures increased ROS production. Attenuation of toxicity and ROS production was observed in response to treatment with low concentrations of L-ascorbic acid. These results indicate potential toxic interactions between metals and modified PAHs. With redox-active metals, such as Cu and Ni, and modified PAHs, such as PHQ, these interactions can involve ROS formation.
Bioenergetic and pharmacokinetic model for exposure of common loon (Gavia Immer) chicks to methylmercury
Authors: Karasov William H. , Kenow Kevin P. , Meyer Michael W. , Fournier Francois
Published: June 2007

A bioenergetics model was used to predict food intake of common loon (Gavia immer) chicks as a function of body mass during development, and a pharmacokinetics model, based on first-order kinetics in a single compartment, was used to predict blood Hg level as a function of food intake rate, food Hg content, body mass, and Hg absorption and elimination. Predictions were tested in captive growing chicks fed trout (Salmo gairdneri) with average MeHg concentrations of 0.02 (control), 0.4, and 1.2 μg/g wet mass (delivered as CH3HgCl). Predicted food intake matched observed intake through 50 d of age but then exceeded observed intake by an amount that grew progressively larger with age, reaching a significant overestimate of 28% by the end of the trial. Respiration in older, nongrowing birds probably was overestimated by using rates measured in younger, growing birds. Close agreement was found between simulations and measured blood Hg, which varied significantly with dietary Hg and age. Although chicks may hatch with different blood Hg levels, their blood level is determined mainly by dietary Hg level beyond approximately two weeks of age. The model also may be useful for predicting Hg levels in adults and in the eggs that they lay, but its accuracy in both chicks and adults needs to be tested in free-living birds.
Removal of cadmium ions during stationary growth phase by an extremely cadmium-resistant strain of Stenotrophomonas sp.
Authors: Chien Chih-Ching , Hung Chun-Wei , Han Chu-Ting
Published: June 2007

Stenotrophomonas sp. CD02 was isolated from a site that previously had been contaminated with high concentrations of the heavy metals cadmium (3 mg kg−1) and chromium (115 mg kg−1). This strain was able to grow on complex (Luria Bertani) medium containing high concentrations of cadmium ion (up to 4 mM). Additionally, it could remove up to 80% of the dissolved ions but only after reaching stationary growth phase. Strain CD02 also tolerated high concentrations of other heavy metals such as chromium, zinc, copper, nickel, and lead at levels more than 2 mM. Although strain CD02 can tolerate much higher cadmium concentrations than the three Stenotrophomonas maltophilia strains tested, they all possess resistance to the same range of antibiotics. This suggests that strain CD02 possesses a mechanism that allows it to tolerate and remove cadmium differently from those conferring resistance to antibiotics. Strain CD02 can be a suitable candidate for heavy metal bioremediation in contaminated environment because it is able to tolerate high concentration of heavy metals and remove cadmium aerobically.
Hazard characterization and identification of a former ammunition site using microarrays, bioassays, and chemical analysis
Authors: Eisentraeger Adolf , Reifferscheid Georg , Dardenne Freddy , Blust Ronny , Schofer Andrea
Published: June 2007

More than 100,000 tons of 2,4,6-trinitrotoluene were produced at the former ammunition site Werk Tanne in Clausthal-Zellerfeld, Germany. The production of explosives and consequent detonation in approximately 1944 by the Allies caused great pollution in this area. Four soil samples and three water samples were taken from this site and characterized by applying chemical-analytical methods and several bioassays. Ecotoxicological test systems, such as the algal growth inhibition assay with Desmodesmus subspicatus, and genotoxicity tests, such as the umu and NM2009 tests, were performed. Also applied were the Ames test, according to International Organization for Standardization 16240, and an Ames fluctuation test. The toxic mode of action was examined using bacterial gene profiling assays with a battery of Escherichia coli strains and with the human liver cell line hepG2 using the PIQOR™ Toxicology cDNA microarray. Additionally, the molecular mechanism of 2,4,6-trinitrotoluene in hepG2 cells was analyzed. The present assessment indicates a danger of pollutant leaching for the soil-groundwater path. A possible impact for human health is discussed, because the groundwater in this area serves as drinking water.
Soil factors controlling the toxicity of copper and zinc to microbial processes in Australian soils
Authors: Broos Kris , Warne Michael St. J. , Heemsbergen Diane A. , Stevens Daryl , Barnes Mary B. , Correll Raymond L. , McLaughlin Mike J.
Published: June 2007

Two soil microbial processes, substrate-induced nitrification (SIN) and substrate-induced respiration (SIR), were measured in the topsoils of 12 Australian field trials that were amended separately with increasing concentrations of ZnSO4 or CuSO4. The median effect concentration (EC50) values for Zn and Cu based on total metal concentrations varied between 107 and 8,298 mg kg−1 for Zn and 108 and 2,155 mg kg−1 Cu among soils. The differences in both Zn and Cu toxicity across the 12 soils were not explained by either the soil solution metal concentrations or CaCl2-extractable metal concentrations, because the variation in the EC50 values was larger than those using total concentrations. Toxicity of Zn and Cu decreased with increasing soil pH for SIN. For Cu, also increasing cation exchange capacity (CEC) and percent clay decreased the toxicity towards SIN. In contrast to SIN, soil pH had no significant effect on toxicity values of SIR. Significant relationships were found between the EC50 values for SIR and background Zn and CEC for Zn, and percent clay and log CEC for Cu. Relationships such as those developed in this study will permit Australian environmental regulation to move from single-value national soil quality guidelines to soil-specific quality guidelines and permit soil-specific risk assessments to be undertaken.
Polybrominated diphenyl ethers in biota and sediments of the Pearl River Estuary, South China
Authors: Xiang Cai-Hong , Luo Xiao-Jun , Chen She-Jun , Yu Mei , Mai Bi-Xian , Zeng Eddy Y.
Published: June 2007

Polybrominated diphenyl ethers (PBDEs) were analyzed in three invertebrate species, five fish species with different living and feeding habits, and surface sediments collected from the Pearl River Estuary, South China. The concentrations of 10 PBDE congeners (BDEs 28, 47, 66, 99, 100, 85, 154, 153, 138, and 183) ranged from 34.1 to 444.5 ng/g lipid and from 9.88 to 39.0 ng/g organic carbon in biota and sediment samples, respectively. In sediments and some biota samples, BDE 209 was found as the major congener, ranging from nondetectable to 623.5 ng/g lipid in biota samples and from 792 to 4,137 ng/g organic carbon in sediment samples. Different levels of PBDEs in various biota species were attributed to the different feeding habits of the aquatic species or their ability to metabolize PBDE. Different congener profiles between the biota and sediment samples were observed and attributed to the bioaccumulation potential or the ability to metabolize individual BDE congeners. Polybrominated diphenyl ether levels in the biota from the Pearl River Estuary correlated well with lipid contents but did not correlate with the biota lengths. The distribution of biota-sediment accumulation factors for individual PBDE congeners was consistent with the general pattern predicted from a widely used bioaccumulation model.
Influence of dissolved organic matter on the complexation of mercury under sulfidic conditions
Authors: Miller Carrie L. , Mason Robert P. , Gilmour Cynthia C. , Heyes Andrew
Published: June 2007

The complexation of Hg under sulfidic conditions influences its bioavailability for microbial methylation. Neutral dissolved Hg-sulfide complexes are readily available to Hg-methylating bacteria in culture, and thermodynamic models predict that inorganic Hg-sulfide complexes dominate dissolved Hg speciation under natural sulfidic conditions. However, these models have not been validated in the field. To examine the complexation of Hg in natural sulfidic waters, octanol/water partitioning methods were modified for use under environmentally relevant conditions, and a centrifuge ultrafiltration technique was developed. These techniques demonstrated much lower concentrations of dissolved Hg-sulfide complexes than predicted. Furthermore, the study revealed an interaction between Hg, dissolved organic matter (DOM), and sulfide that is not captured by current thermodynamic models. Whereas Hg forms strong complexes with DOM under oxic conditions, these complexes had not been expected to form in the presence of sulfide because of the stronger affinity of Hg for sulfide relative to its affinity for DOM. The observed interaction between Hg and DOM in the presence of sulfide likely involves the formation of a DOM-Hg-sulfide complex or results from the hydrophobic partitioning of neutral Hg-sulfide complexes into the higher-molecular-weight DOM. An understanding of the mechanism of this interaction and determination of complexation coefficients for the Hg-sulfide-DOM complex are needed to adequately assess how our new finding affects Hg bioavailability, sorption, and flux.
Risk of weathered residual Exxon Valdez oil to pink salmon embryos in Prince William Sound
Authors: Brannon Ernest L. , Collins Keya M. , Cronin Mathew A. , Moulton Lawrence L. , Parker Keith R. , Wilson William
Published: June 2007

It has been hypothesized that pink salmon eggs incubating in intertidal streams transecting Prince William Sound (PWS) beaches oiled by the Exxon Valdez oil spill were exposed to lethal doses of dissolved hydrocarbons. Since polycyclic aromatic hydrocarbon (PAH) levels in the incubation gravel were too low to cause mortality, the allegation is that dissolved high-molecular-weight hydrocarbons (HPAH) leaching from oil deposits on the beach adjacent to the streams were the source of toxicity. To evaluate this hypothesis, we placed pink salmon eggs in PWS beach sediments containing residual oil from the Exxon Valdez oil spill and in control areas without oil. We quantified the hydrocarbon concentrations in the eggs after three weeks of incubation. Tissue PAH concentrations of eggs in oiled sediments were generally <100 ppb and similar to background levels on nonoiled beaches. Even eggs in direct contact with oil in the sediment resulted in tissue PAH loads well below the lethal threshold concentrations established in laboratory bioassays, and very low concentrations of HPAH compounds were present. These results indicate that petroleum hydrocarbons dissolved from oil deposits on intertidal beaches are not at concentrations that pose toxic risk to incubating pink salmon eggs. The evidence does not support the hypothesis that interstitial pore water in previously oiled beaches is highly toxic.
Adverse effects of chronic copper exposure in larval northern leopard frogs (Rana pipiens)
Authors: Chen Te-Hao , Gross Jackson A. , Karasov William H.
Published: June 2007

Northern leopard frogs (Rana pipiens) were exposed to environmentally relevant concentrations of copper in water (control and 5, 25, and 100 μg/L, as CuSO4) in a static renewal system for 154 d from posthatch stage to metamorphosis. After 10 d of copper exposure (from Gosner stages 19–25), survival of tadpoles was not significantly different between treatments (averages range from 96.7 to 99.3%), but a significantly higher incidence of deformities (p < 0.05) was observed in the 100-μg/L treatment. Tadpole growth rate was decreased in the 25- and 100-μg/L treatments relative to controls. Tadpole survival, swimming performance, percent metamorphosis, time to metamorphosis, and survival during and time required for tail resorption were also negatively affected in the 100-μg/L treatment. Copper concentrations in tadpole tissues ranged from 46.5 to 769.5 mg/kg dry mass and were positively related to copper concentrations in the water. In conclusion, copper was shown to affect development, growth, survival, and behavior in larval northern leopard frogs at ecologically relevant concentrations. The existing U.S. Environmental Protection Agency freshwater-quality chronic criterion for copper appears to be protective for larval Rana pipiens.
Effect of dichlorvos on the acetylcholinesterase from tambaqui (Colossoma macropomum) brain
Authors: Assis Caio Rodrigo Dias , Amaral Ian Porto Gurgel , Castro Patrícia Fernandes , Carvalho Luiz Bezerra , Bezerra Ranilson Souza
Published: June 2007

Dichlorvos is an acutely toxic organophosphorous pesticide that is known as a classical acetylcholinesterase (AChE; EC 3.1.1.7) inhibitor. Here, the brain AChE from the important Amazonian fish tambaqui (Colossoma macropomum) was assayed in the presence of this insecticide and also of deltamethrin, a classical sodium and potassium channel inhibitor (negative control). Four tissue homogenates were analyzed in triplicate for AChE activity using acetylthiocholine as the substrate and 5,5′-dithiobis(2-nitrobenzoic) acid (DTNB) as the color-developing agent. Each tissue homogenate represented pooled brains from five fish. The inhibitory effect of dichlorvos on AChE activities was determined at concentrations from 0.001 to 10 ppm and compared to controls. This effect followed an exponential decay model (y = 9.420 + 26.192e(–x/5.380); r2 = 0.989), presenting IC50 (the concentration of dichlorvos that is required for 50% of AChE inhibition) of 0.081 ppm (0.368 μmol/L). No effect was observed for the deltamethrin, and the concentration 0.0452 μmol/L of dichlorvos was significantly different from this control. These results suggest that tambaqui brain AChE can be proposed as a biomarker for dichlorvos and can be used as a tool for aquatic environment monitoring.
Development and validation of a 2,000-gene microarray for the fathead minnow (Pimephales promelas)
Authors: Larkin Patrick , Villeneuve Daniel L. , Knoebl Iris , Miracle Ann L. , Carter Barbara J. , Liu Li , Denslow Nancy D. , Ankley Gerald T.
Published: June 2007

Gene microarrays provide the field of ecotoxicology new tools to identify mechanisms of action of chemicals and chemical mixtures. Herein we describe the development and application of a 2,000-gene oligonucleotide microarray for the fathead minnow Pimephales promelas, a species commonly used in ecological risk assessments in North America. The microarrays were developed from various cDNA and subtraction libraries that we constructed. Consistency and reproducibility of the microarrays were documented by examining multiple technical replicates. To test application of the fathead minnow microarrays, gene expression profiles of fish exposed to 17β-estradiol, a well-characterized estrogen receptor (ER) agonist, were examined. For these experiments, adult male fathead minnows were exposed for 24 h to waterborne 17β-estradiol (40 or 100 ng/L) in a flow-through system, and gene expression in liver samples was characterized. Seventy-one genes were identified as differentially regulated by estradiol exposure. Examination of the gene ontology designations of these genes revealed patterns consistent with estradiol's expected mechanisms of action and also provided novel insights as to molecular effects of the estrogen. Our studies indicate the feasibility and utility of microarrays as a basis for understanding biological responses to chemical exposure in a model ecotoxicology test species.