bluuebunny/crossref_metadata_2025 huggingface dataset:
Quenching of Photoluminescence in ZnO QDs Decorating Multiwalled Carbon Nanotubes
Authors: Dutta Mrinal , Jana Santanu , Basak Durga
Published: March 2010

We report the controlled growth of ZnO quantum dots (QDs) on the sidewalls of multiwalled carbon nanotubes (MWCNTs) by a one‐step process and study the effect on the photoluminescence (PL) properties of the ZnO QDs‐MWCNT composite. The PL intensity of the composite is quenched and the lifetime is reduced compared to the only ZnO QDs. The origin of the PL quenching is discussed in terms of energy transfer, which is examined by varying the density and size of ZnO QDs by changing the molar concentration of the precursor solution for ZnO and the amount of MWCNT.
Image differentiation with corporate environmental responsibility
Authors: Heikkurinen Pasi
Published: March 2010

This paper analyzes strategic implications of corporate responsibility (CR) and in particular how a firm can differentiate with an environmentally responsible image. A single case study was conducted in the Nordic hospitality industry with semi‐structured interviews as the main data collection method.

By adopting an environmentally responsible identity through shared values with the firm's key stakeholders, the firm can reflect an environmentally responsible image. This image can enhance the firm's strategic position through internal and external differentiators from competitors – as the firm becomes a more preferred employer, partner and supplier, it results in enhanced employee motivation, cost savings, better reputation, and greater guest loyalty. The amount of CR depends on the micro/meso/macro/global‐level drivers, and competitive aims of the firm. The emphasis on stakeholder communication becomes greater as the firm increases its CR‐aggressiveness. Copyright © 2010 John Wiley & Sons, Ltd and ERP Environment.
A Fluid Model of the Sheath Formation in Front of an Electron Emitting Electrode with Space Charge Limited Emission Immersed in a Plasma that Contains a One‐Dimensional Mono‐Energetic Electron Beam
Authors: Gyergyek T. , Kovačič J. , Čerček M.
Published: March 2010

Sheath formation in front of a large, planar, electron emitting electrode (collector) immersed in a plasma that contains a mono‐energetic, one‐dimensional electron beam is studied by a one‐dimensional fluid model. A current‐voltage characteristics of the collector is calculated. For certain beam parameters triple valued floating potentials of the collector are found. The calculated current‐voltage characteristics is qualitatively similar to experimental characteristics observed by [Nam et al J. Appl. Phys., 63, 5674 (1988)] and also by [M.C. Griskey and R.L. Stenzel, Phys. Rev. Letters, 82, 556 (1999)]. We suggest that the triple valued floating potential are a consequence of a non‐monotonic dependence of the space charge limited emission current on the collector potential, which is caused by the penetration of the electron beam in the collector sheath and does not depend on the physical mechanism (e.g. thermal or secondary) of the electron emission from the collector (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Comparative Study of Electron Heat Transport in a Stochastic and a Non‐Stochastic Magnetic Field
Authors: Gao Hong , Zha Xuejun
Published: March 2010

We studied the electron heat transport across a non‐local stochastic magnetic field and a non‐local non‐stochastic magnetic field in tokamak plasmas. Analytical results and numerical simulation results were compared with conditions of a stochastic and a non‐stochastic magnetic field respectively in this article. Parameter of stochasticity in perturbed magnetic field was found not tobe a key factor in influencing effective radial heat conductivity in radial direction of tokomak when Chirikov parameter is close to one (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Miniaturized XeCl Dielectric Barrier Discharge as a Source of Short Lived, Fast Decaying UV Radiation
Authors: Bussiahn R. , Pipa A.V. , Kindel E.
Published: March 2010

A dielectric barrier discharge (DBD) of coaxial geometry has been examined as source of intensive, short‐lived UV radiation. A binary gas mixture consisting of 98% Xe + 2% Cl2 and a ternary composition of 96% Ne + 6% Xe + 0.2% HCl were investigated in the pressure range between 10 and 750 mbar. The discharge was excited by unipolar high voltage square pulses with amplitudes of 3 to 7 kV at a repetition rate of 100 Hz. UV radiation intensity is increased by combining 5 square pulses with a period of 1 μs each in one train (burst). Radiation decay on three orders of magnitude within 10 μs was obtained for both gas mixtures in burst mode. Maximum energy of the light pulse was the same for both gas mixtures and estimated as 40 nJ. It is shown that the optimum gas pressure for highest radiation intensity depends not only on gas composition but also on applied voltage and number of pulses in the train. A variation of the spectral band shape of XeCl emission during the pulse is detected (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microfield Fluctuations and Spectral Line Shapes in Strongly Coupled Two–Component Plasmas
Authors: Nersisyan H. B. , Toepffer C. , Zwicknagel G.
Published: March 2010

The spectral line shapes for hydrogen–like heavy ion emitters embedded in strongly correlated two–component electron–ion plasmas are investigated with numerical simulations. For that purpose the microfield fluctuations are calculated by molecular dynamics simulations where short range quantum effects are taken into account by using a regularized Coulomb potential for the electron–ion interaction. The microfield fluctuations are used as input in a numerical solution of the time–dependent Schrödinger equation for the radiating electron. In distinction to the standard impact and quasistatic approximations the method presented here allows to account for the correlations between plasma ions and electrons. The shapes of the Lyα–line in Al are investigated in the intermediate regime. The calculations are in good agreement with experiments on the Lyα–line in laser generated plasmas (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flow cytometric analysis of circulating microparticles in plasma
Authors: Orozco Aaron F. , Lewis Dorothy E.
Published: March 2010

Microparticles, which include exosomes, micro‐vesicles, apoptotic bodies and apoptotic microparticles, are small (0.05 ‐ 3 μm in diameter), membranous vesicles that can contain DNA, RNA, miRNA, intracellular proteins and express extracellular surface markers from the parental cells. They can be secreted from intracellular multivesicular bodies or released from the surface of blebbing membranes. Circulating microparticles are abundant in the plasma of normal individuals and can be derived from circulating blood cells such as platelets, red blood cells and leukocytes as well as from tissue sources, such as endothelial and placental tissues. Elevated levels of microparticles are associated with various diseases such as thrombosis (platelet microparticles), congestive heart failure (endothelial microparticles), breast cancer patients (leukocyte microparticles) and women with preeclampsia (syncytiotrophoblast microparticles). Although microparticles can be detected by microscopy, enzyme‐linked immunoassays and functional assays, flow cytometry is the preferred method because of the ability to quantitate (fluorescent bead‐ or flow rate‐based method) and because of polychromatic capabilities. However, standardization of pre‐analytical and analytical modus operandi for isolating, enumerating and fluorescent labeling of microparticles remains a challenge. The primary focus of this article is to review the preliminary steps required to optimally study circulating in vivo microparticles which include: 1) centrifugation speed used, 2) quantitation of microparticles before antibody labeling, 3) levels of fluorescence intensity of antibody‐labeled microparticles, 4) polychromatic flow cytometric analysis of microparticle sub‐populations and 5) use of polyclonal antibodies designed for Western blotting for flow cytometry. These studies determine a roadmap to develop microparticles as biomarkers for a variety of conditions. © 2010 International Society for Advancement of Cytometry
Use of the Ki67 promoter to label cell cycle entry in living cells
Authors: Zambon Alexander C.
Published: March 2010

Genetic based reporters have distinct advantages over classical immunocytochemical techniques for probing cellular functions. Most importantly, they enable dynamic real‐time visualization and quantification of cellular processes in living cells and tissue. This study was conducted to generate a genetic based reporter to label cells that transitioned from the G0 to G1/S phases of the cell cycle, hypothesizing that the proximal promoter of the Ki67 (Ki67p) gene, a commonly used cytology marker induced during this transition, would contain the suitable regulatory elements to drive marker gene expression. This study reports the cloning and characterization of the 1.5 kb proximal promoter (Ki67p) of the human Ki67 gene. Ki67p driven GFP expression colocalizes in cells with endogenous Ki67 expression and is correlated with cells transitioning through S/G2/M phases of the cell cycle. Treatment Ki67p‐GFP expressing HT1080 cells with mitomycin C, an antineoplastic agent, induces P21 and P27 expression, G1/S/G2M block and attenuates Ki67p activity. Attenuation of the Ki67p also occurs during cell‐density induced cell cycle arrest. Taken together, these results indicate that the Ki67p can be used to identify proliferating subpopulations of live cells in intact complex three‐dimensional cellular aggregates, such as embryoid bodies, thus providing some unique advantages over conventional immunohistochemical approaches. © 2010 International Society for Advancement of Cytometry
Direction finding receiver for UWB impulse radio signal in multipath environment
Authors: Lie Joni Polili , Ng Boon Poh , See Chong Meng Samson
Published: March 2010

In this paper, we propose a direction finding (DF) receiver for ultra wideband impulse radio (UWB‐IR) signal in a realistic multipath environment. The receiver uses an array of antenna, where each antenna is connected to a proposed propagation‐delay estimation structure. The advantage of the proposed structure is that it outputs a trapezoidal signal whose amplitude reflects the propagation delay and thus relaxes the sampling rate requirement of the analog‐to‐digital‐converter (ADC). The angle‐of‐arrival (AOA) is estimated from the vector of propagation delays measured with respect to reference antenna. Because these estimated delays contain outliers, we propose a simple AOA estimation algorithm based on minimum fractional‐distance search. Experimental results based on simulation show that the proposed DF receiver achieves better performance compared with the minimum ℓ1‐ and ℓ2‐based (least‐squares based) distance search. Copyright © 2010 John Wiley & Sons, Ltd.
Distinct roles for telethonin N‐versus C‐terminus in sarcomere assembly and maintenance
Authors: Sadikot Takrima , Hammond Courtney R. , Ferrari Michael B.
Published: March 2010

The N‐terminus of telethonin forms a unique structure linking two titin N‐termini at the Z‐disc. While a specific role for the C‐terminus has not been established, several studies indicate it may have a regulatory function. Using a morpholino approach in Xenopus, we show that telethonin knockdown leads to embryonic paralysis, myocyte defects, and sarcomeric disruption. These myopathic defects can be rescued by expressing full‐length telethonin mRNA in morpholino background, indicating that telethonin is required for myofibrillogenesis. However, a construct missing C‐terminal residues is incapable of rescuing motility or sarcomere assembly in cultured myocytes. We, therefore, tested two additional constructs: one where four C‐terminal phosphorylatable residues were mutated to alanines and another where terminal residues were randomly replaced. Data from these experiments support that the telethonin C‐terminus is required for assembly, but in a context‐dependent manner, indicating that factors and forces present in vivo can compensate for C‐terminal truncation or mutation. Developmental Dynamics 239:1124–1135, 2010. © 2010 Wiley‐Liss, Inc.
Expression analysis of TALE family transcription factors during avian development
Authors: Coy Sarah E. , Borycki Anne‐Gaëlle
Published: March 2010

The TALE family of homeodomain containing transcription factors consists of the Meis, Prep and Tgif, and the Pbx subfamily of proteins. Several TALE orthologues have been identified in amniotes, but no comprehensive analysis of their expression pattern during embryogenesis has been performed. Here, we report on TALE gene expression in the avian embryo. During embryonic development, Pbx genes are predominantly expressed in the neural ectoderm and paraxial mesoderm, although Pbx3 is restricted to the intermediate and lateral mesoderm, and anterior central nervous system. Members of the Meis, Prep, and Tgif subfamilies are expressed at high levels in the paraxial mesoderm, and display differential expression along the anterior–posterior and dorsoventral axes of the developing neural tube. Overall the expression patterns reported in this study are consistent with the known function of the TALE gene family in controlling early patterning of limb, neural tube and paraxial mesoderm tissues during embryogenesis. Developmental Dynamics 239:1234–1245, 2010. © 2010 Wiley‐Liss, Inc.
How does the tubular embryonic heart work? Looking for the physical mechanism generating unidirectional blood flow in the valveless embryonic heart tube
Authors: Männer Jörg , Wessel Armin , Yelbuz T. Mesud
Published: March 2010

The heart is the first organ to function in vertebrate embryos. The human heart, for example, starts beating around the 21st embryonic day. During the initial phase of its pumping action, the embryonic heart is seen as a pulsating blood vessel that is built up by (1) an inner endothelial tube lacking valves, (2) a middle layer of extracellular matrix, and (3) an outer myocardial tube. Despite the absence of valves, this tubular heart generates unidirectional blood flow. This fact poses the question how it works. Visual examination of the pulsating embryonic heart tube shows that its pumping action is characterized by traveling mechanical waves sweeping from its venous to its arterial end. These traveling waves were traditionally described as myocardial peristaltic waves. It has, therefore, been speculated that the tubular embryonic heart works as a technical peristaltic pump. Recent hemodynamic data from living embryos, however, have shown that the pumping function of the embryonic heart tube differs in several respects from that of a technical peristaltic pump. Some of these data suggest that embryonic heart tubes work as valveless “Liebau pumps.” In the present study, a review is given on the evolution of the two above‐mentioned theories of early cardiac pumping mechanics. We discuss pros and cons for both of these theories. We show that the tubular embryonic heart works neither as a technical peristaltic pump nor as a classic Liebau pump. The question regarding how the embryonic heart tube works still awaits an answer. Developmental Dynamics 239:1035–1046, 2010. © 2010 Wiley‐Liss, Inc.
Hepatocyte nuclear factor 4 alpha is related to survival of the condensed mesenchyme in the developing mouse kidney
Authors: Kanazawa Tomonori , Konno Akihiro , Hashimoto Yoshiharu , Kon Yasuhiro
Published: March 2010

Hepatocyte nuclear factor 4 alpha (Hnf4α) is a transcription factor required for embryogenesis and organogenesis. In the adult kidney, Hnf4α is expressed at a high level in proximal tubules. Although its expression begins from the embryonic period, its function in the developing kidney has remained almost unknown. In this study, we investigated the role of Hnf4α in the cultured embryonic mouse kidney by gene silencing using the RNA interference method. Additionally, we identified the dynamics of Hnf4α in the microenvironment of the developing kidney. As a result of gene silencing, the cellular organization in the condensed mesenchyme (CM) fell into disorder and many apoptotic cells appeared. In addition, laser microdissection‐reverse transcriptase‐polymerase chain reaction provided evidence that Hnf4α gene expression began first in the CM. These results suggest the possibility that Hnf4α plays an important role in the regulation of the cell survival at the CM stage in nephrogenesis. Developmental Dynamics 239:1145–1154, 2010. © 2010 Wiley‐Liss, Inc.
ETS family protein ETV2 is required for initiation of the endothelial lineage but not the hematopoietic lineage in the Xenopus embryo
Authors: Salanga Matthew C. , Meadows Stryder M. , Myers Candace T. , Krieg Paul A.
Published: March 2010

Transcription factors of the ETS family are important regulators of endothelial and hematopoietic development. We have characterized the Xenopus orthologue of the ETS transcription factor, ETV2. Expression analysis shows that etv2 is highly expressed in hematopoietic and endothelial precursor cells in the Xenopus embryo. In gain‐of‐function experiments, ETV2 is sufficient to activate ectopic expression of vascular endothelial markers. In addition, ETV2 activated expression of hematopoietic genes representing the myeloid but not the erythroid lineage. Loss‐of‐function studies indicate that ETV2 is required for expression of all endothelial markers examined. However, knockdown of ETV2 has no detectable effects on expression of either myeloid or erythroid markers. This contrasts with studies in mouse and zebrafish where ETV2 is required for development of the myeloid lineage. Our studies confirm an essential role for ETV2 in endothelial development, but also reveal important differences in hematopoietic development between organisms. Developmental Dynamics 239:1178–1187, 2010. © 2010 Wiley‐Liss, Inc.
Fusion of uniluminal vascular spheroids: A model for assembly of blood vessels
Authors: Fleming Paul A. , Argraves W. Scott , Gentile Carmine , Neagu Adrian , Forgacs Gabor , Drake Christopher J.
Published: March 2010

Zebrafish Intrahepatic Biliary System: Confocal projection through the liver of a 5 day post‐fertilization zebrafish larva immunostained with antibodies raised against the human multidrug resistance protein‐1 (red), also known as Pglcyoprotein, an ABC transporter in the hepatocyte canalicular membrane, and a novel zebrafish epitope 2F11 (green) that recognizes biliary epithelial cells. Hepatocytes secrete bile through their canaliculus into the intrahepatic biliary duct network. 10 μm z‐stack. From Lorent et al., Developmental Dynamics 239:398‐406, 2010.
Distribution and toxicity of sediment-associated pesticides in urban and agricultural waterways from Illinois, USA
Authors: Ding Yuping , Harwood Amanda D. , Foslund Heather M. , Lydy Michael J.
Published: March 2010

A statewide investigation of insecticide presence and sediment toxicity was conducted in Illinois, USA, from June to August 2008. Twenty sediment samples were collected from urban areas throughout Illinois, and 49 sediment samples were collected from 14 agriculture-dominated counties in central and southern Illinois. Ten-day sediment toxicity tests were conducted using the amphipod Hyalella azteca, and 59% of the urban sites and 2% of the agricultural locations sampled caused significant mortality in the amphipods. The field sediments were analyzed for 29 pesticides, including 19 organochlorines, one organophosphate, and nine pyrethroids. The detection frequencies of organochlorines, chlorpyrifos, and pyrethroids were 95, 65, and 95%, respectively, for urban sites, and 45, 6.1, and 47%, respectively, for agricultural sites. Based on toxic unit analysis, bifenthrin was the main contributor to the detected mortality in urban sediments. The present study provides the first broad assessment of pesticide prevalence in both urban and agriculture areas in Illinois. Environ. Toxicol. Chem. 2010;29:149–157. © 2009 SETAC
Human exposure to polybrominated diphenyl ethers at production area, China
Authors: Jin Jun , Wang Ying , Yang Congqiao , Hu Jicheng , Liu Weizhi , Cui Jian
Published: March 2010

The concentrations of polybrominated diphenyl ethers (PBDEs) were detected in air and aquatic products in PBDEs production areas which are located at the south coast area of Laizhou Bay, Shandong province, China in this study. Concentrations of ∑PBDEs in the air ranged from 0.47 ng/m3 to 161 ng/m3. In aquatic products, concentrations of ∑PBDEs ranged from 2.7 ng/g wet weight to 42 ng/g wet weight. The mean dietary intake of ∑PBDEs via aquatic products consumption in this study was 218 ng/day. Daily intake of ∑PBDEs via inhalation in this study was 612 ng for men and 455 ng for women. With a contribution of 80%, BDE-209 was predominant in the total intake. Dietary intake and breathing inhalation contributed 29 and 71%, respectively, to the total PBDEs intake. The results indicate that breathing inhalation also plays a very significant pathway for the population of the PBDEs production area. Compared with similar studies in other countries, human exposure to PBDEs via diet and inhalation in this study was the highest in the world. Environ. Toxicol. Chem. 2010;29:1031–1035. © 2010 SETAC
Comparing weighted and unweighted analyses applied to data with a mix of pooled and individual observations
Authors: Anderson Sarah G. , Bailer A. John
Published: March 2010

Smaller organisms may have too little tissue to allow assaying as individuals. To get a sufficient sample for assaying, a collection of smaller individual organisms is pooled together to produce a simple observation for modeling and analysis. When a dataset contains a mix of pooled and individual organisms, the variances of the observations are not equal. An unweighted regression method is no longer appropriate because it assumes equal precision among the observations. A weighted regression method is more appropriate and yields more precise estimates because it incorporates a weight to the pooled observations. To demonstrate the benefits of using a weighted analysis when some observations are pooled, the bias and confidence interval (CI) properties were compared using an ordinary least squares and a weighted least squares t-based confidence interval. The slope and intercept estimates were unbiased for both weighted and unweighted analyses. While CIs for the slope and intercept achieved nominal coverage, the CI lengths were smaller using a weighted analysis instead of an unweighted analysis, implying that a weighted analysis will yield greater precision. Environ. Toxicol. Chem. 2010;29:1168–1171. © 2010 SETAC
Cholinesterase and glutathione-S-transferase activities in freshwater invertebrates as biomarkers to assess pesticide contamination
Authors: Domingues Inês , Agra Ana Raquel , Monaghan Kieran , Soares Amadeu M.V.M. , Nogueira António J.A.
Published: March 2010

Studies investigating the use of biomarkers in pesticide risk assessment have greatly increased in recent years; however, issues concerning the ecological meaning of enzymatic responses have proved controversial. Ideally a good biomarker response should be modulated by the environmental contaminants alone and demonstrate a predictable behavior towards certain types of toxins. As these premises are rarely observed, the present study aims to outline research that has contributed to an understanding of the behavior of two widely used biomarkers, cholinesterase and glutathione-S-transferase, describing environmental and biotic factors that affect their response in freshwater invertebrates. Studies were performed in the main classes of aquatic invertebrates with these biomarkers and conclusions were reached concerning their behavior towards the main classes of pesticides. Links between biomarker responses and conventional endpoints were evaluated so that ecological relevance could be attributed to enzymatic responses. Toxicity of mixtures was investigated, and cases of synergism and antagonism were pointed out as factors changing the expected toxicity of aquatic systems and leading to misinterpretations of biomarker responses. Finally, the use of biomarkers as a tool for biomonitoring and in situ assays was investigated, with discussion of advantages and disadvantages of their use. Environ. Toxicol. Chem. 2010;29:5–18. © 2009 SETAC
Antidepressants and their metabolites in municipal wastewater, and downstream exposure in an urban watershed
Authors: Metcalfe Chris D. , Chu Shaogang , Judt Colin , Li Hongxia , Oakes Ken D. , Servos Mark R. , Andrews David M.
Published: March 2010

Antidepressants are a widely prescribed group of pharmaceuticals that can be biotransformed in humans to biologically active metabolites. In the present study, the distribution of six antidepressants (venlafaxine, bupropion, fluoxetine, sertraline, citalopram, and paroxetine) and five of their metabolites was determined in a municipal wastewater treatment plant (WWTP) and at sites downstream of two WWTPs in the Grand River watershed in southern Ontario, Canada. Fathead minnows (Pimephales promelas) caged in the Grand River downstream of a WWTP were also evaluated for accumulated antidepressants. Finally, drinking water was analyzed from a treatment plant that takes its water from the Grand River 17 km downstream of a WWTP. In municipal wastewater, the antidepressant compounds present in the highest concentrations (i.e., >0.5 µg/L) were venlafaxine and its two demethylation products, O- and N-desmethyl venlafaxine. Removal rates of the target analytes in a WWTP were approximately 40%. These compounds persisted in river water samples collected at sites up to several kilometers downstream of discharges from WWTPs. Venlafaxine, citalopram, and sertraline, and demethylated metabolites were detected in fathead minnows caged 10 m below the discharge from a WWTP, but concentrations were all <7 µg/kg wet weight. Venlafaxine and bupropion were detected at very low (<0.005 µg/L) concentrations in untreated drinking water, but these compounds were not detected in treated drinking water. The present study illustrates that data are needed on the distribution in the aquatic environment of both the parent compound and the biologically active metabolites of pharmaceuticals. Environ. Toxicol. Chem. 2010;29:79–89. © 2009 SETAC
Reconcilable differences: The use of reference material to reduce methodological artifacts in the reporting of organochlorine pesticides and polychlorinated biphenyls
Authors: de Solla Shane R. , Weseloh D.V. Chip , Letcher Robert J. , Hebert Craig E.
Published: March 2010

Numerous long-term monitoring programs have assessed spatial and temporal trends of organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs). Changes in analytical approaches (e.g., gas chromatography coupled with electron capture detection [GC-ECD] versus mass spectrometric detection [GC-MSD]) can reveal artifacts in the reported concentrations. In-house reference material (RM) was used to determine the analytical artifacts in the measurement of OCs and PCBs in Great Lake herring gull eggs previously analyzed from 1994 to 1996 (GC-ECD) and 1997 to 1999 (GC-MSD). Approximately 19.0% of the variability of PCB congeners in gull eggs was associated with analytical artifacts, and differences among colonies were obscured. Although the discrepancy in sum PCBs (ΣPCBs) was fairly small (2.1%), some congeners varied considerably between methods (>60%). After statistically removing the artifacts, only 1.4% of the variability in PCBs of herring gull eggs was associated with artifacts, and differences among gull colonies became apparent. After excluding OCs near the detection limit in the RM, statistically removing the artifacts reduced some of the differences between methods for OCs. Analytical artifacts may potentially render inferences difficult, confounded, and erroneous. When combining contaminant data obtained using different methods, the methods should be assumed to give different results unless demonstrated otherwise. Assessments of the compatibility of analytical methodologies should be made using an appropriate RM. Environ. Toxicol. Chem. 2010;29:19–26. © 2009 SETAC
Measuring variability in phytotoxicity testing using crop and wild plant species
Authors: Boutin Céline , White Andrea L. , Carpenter David
Published: March 2010

A series of experiments was conducted to assess the level of variability in phytotoxicity testing and to investigate factors that may explain some of the observed uncertainties and inconsistencies. The work was conducted in greenhouse or growth chamber environments with plants growing individually in pots and harvested 28 d after spraying with two herbicides, glyphosate and atrazine, as formulated products. Between six and 10 doses were used on five or six replicates, necessitating over 4,500 individually growing plants. In the first set of experiments, several ecotypes (originating from different areas of the world) of eight wild plant species were tested. Significant differences in sensitivity to atrazine and glyphosate were found among ecotypes of most species tested. In the second suite of experiments, the reproducibility of results during different seasons (when growing conditions vary) was investigated using three crops and four wild plant species. Results showed that seasonal variability elicited a pronounced discrepancy in response between plants tested at different times of the year. It was found that no consistent effects could be attributed to the biotic or abiotic factors investigated. Several ecotypes of the same species differed in their seed size, percentage germination, or germination requirements, as well as in growth patterns, but these differences could not explain differences in herbicide sensitivity. Likewise, differences in phytotoxicity could not be attributed to factors such as temperature, light intensity, and sunlight duration. The present study supports the inclusion of an uncertainty factor in risk assessments to account for the intrinsic variability in plant sensitivity to herbicides. Environ. Toxicol. Chem. 2010;29:327–337. © 2009 SETAC
Polybrominated diphenyl ethers, toxaphenes, and other halogenated organic pollutants in great blue heron eggs
Authors: Champoux Louise , Moisey John , Muir Derek C.G.
Published: March 2010

The great blue heron (Ardea herodias) has been used as a bioindicator of the state of the St. Lawrence River (Québec, Canada) since 1996. At 5-year intervals, selected breeding colonies along the River and its estuary are visited to estimate reproductive success and determine levels of contamination. Brominated flame retardants are found in many ecosystems and are increasing in concentration in the Great Lakes, which is the source of much of the water for the St. Lawrence River. In 2001 and 2002, in addition to polychlorinated biphenyls (PCBs) and chlorinated pesticides, the levels of polybrominated diphenyl ethers (PBDEs), polychlorinated bornanes (toxaphene) congeners and non-ortho-substituted PCBs were measured for the first time in pools of great blue heron eggs. The PBDE levels in great blue heron eggs (70–1,377 ng/g wet wt) were comparable to those measured in herring gull (Larus argentatus) eggs from the Great Lakes. Toxaphene was detected in great blue heron eggs at levels comparable to those of other major chlorinated pesticides. Major toxaphene congeners were octachlorobornane P44 and the nonachlorobornane P50. Environ. Toxicol. Chem. 2010;29:243–249. © 2009 SETAC
The effects of continuous and pulsed exposures of suspended clay on the survival, growth, and reproduction ofDaphnia magna
Authors: Robinson Sarah E. , Capper Neil A. , Klaine Stephen J.
Published: March 2010

Suspended sediments are a natural component of aquatic ecosystems, but anthropogenic activity such as land development can result in significant increases, especially after rain events. Continuous exposures of suspended clay and silt have been shown to affect growth and reproduction of Cladocera, leading to a decrease in population growth rate. The mechanism of clay toxicity in these filter-feeding organisms is clogging of the gut tract, resulting in decreased food uptake and assimilation. When placed in clean water, daphnids can purge clay from their gut and recover. In many surface waters, aquatic organisms experience episodic exposures of high concentrations of suspended solids driven by rain events. However, little is known about the consequences of pulsed exposures on individuals and populations. The objective of the present study was to characterize the effects of continuous and pulsed exposures of natural and defined clays on survival, growth, and reproduction of Daphnia magna. Two defined clays, montmorillonite and kaolinite, as well as clay isolated from the Piedmont region of South Carolina, USA, were used. Continuous exposures of clays elicited a dose dependent decrease in survival. Toxicity varied depending on clay source with montmorillonite > natural clay > kaolinite. Pulsed exposures caused a decrease in survival in a 24 h exposure of 734 mg/L kaolinite. Exposure to 73.9 mg/L also caused an increase in the time to gravidity, although there was not a corresponding decrease in neonate production over 21 d. No significant effects resulted from 12 h exposures even at 730 mg/L, almost 10 times the 24-h reproductive effects concentration. This suggests that exposure duration impacted toxicity more than exposure concentration in these pulsed exposures. Environ. Toxicol. Chem. 2010;29:168–175. © 2009 SETAC
Sulfate reduction, molecular diversity, and copper amendment effects in bacterial communities enriched from sediments exposed to copper mining residues
Authors: Pavissich Juan P. , Silva Macarena , González Bernardo
Published: March 2010

Sulfate-reducing bacterial communities from coastal sediments with a long-term exposure to copper (Cu)-mining residues were studied in lactate enrichments. The toxicity of excess copper may affect sulfate-reducing bacterial communities. Sulfate reduction was monitored by sulfate and organic acid measurements. Molecular diversity was analyzed by 16S rRNA, dissimilatory sulfate reduction dsrAB, and Cu translocating phospho-type adenosine triphosphatases (P-ATPases) cop-like gene sequence profiling. The influence of Cu amendment was tested in these enrichments. Results showed fast sulfate reduction mostly coupled to incomplete organic carbon oxidation and partial sulfate reduction inhibition due to copper amendment. The 16S rRNA clonal libraries analysis indicated that δ- and γ-Proteobacteria and Cytophaga–Flexibacter–Bacteroides dominated the enrichments. The dsrAB libraries revealed the presence of Desulfobacteraceae and Desulfovibrionaceae families-related sequences. Copper produced significant shifts (i.e., a decrease in the relative abundance of sulfate-reducing microorganisms) in the enriched bacterial community structure as determined by terminal-restriction fragment length polymorphism (T-RFLP) profiling and multivariate analyses. Clonal libraries of cop-like sequences showed low richness in the enriched microbial communities, and a strong effect of copper on its relative abundance. Novel Cu-PIB-ATPase sequences encoding Cu resistance were detected. The present study indicates that Cu does not significantly affect sulfate reduction and genetic diversity of taxonomic and dissimilatory sulfate-reduction molecular markers. However, the diversity of Cu resistance genetic determinants was strongly modified by this toxic metal. Environ. Toxicol. Chem. 2010;29:256–264. © 2009 SETAC
The influence of diet on the assimilation efficiency of 47 polychlorinated biphenyl congeners in Japanese koi (Cyprinus carpio)
Authors: Liu Jian , Haffner G. Douglas , Drouillard Ken G.
Published: March 2010

The influence of diet on polychlorinated biphenyl (PCB) assimilation was investigated by measuring dietary assimilation efficiencies (AEs) for 47 PCB congeners in juvenile koi (Cyprinus carpio) fed five experimental diets. Two of the diets were naturally contaminated and were obtained by collecting mayflies from Lake Erie (ON, Canada) and emerald shiners from the Detroit River (MI, USA). The remaining diets consisted of commercial fish pellets (lipid contents from 6.7 to 24%) that were contaminated by spiking with a PCB mixture. Experimental fish were held individually to quantify the amount of food consumed per fish and, following a 48-h fasting period to facilitate food digestion and assimilation; AEs were determined by mass balance. Fish fed the benthic invertebrate food exhibited the highest PCB AEs (70–101%) and were significantly elevated compared to the other diet treatments (AEs ranging from 23 to 87%). The PCB AEs for fish fed emerald shiners did not differ from those fed pellet formulations. Variation among PCB AEs was not related to diet lipid content. For all diet treatments, PCB AEs were significantly related to chemical hydrophobicity. The relationship between chemical AE and n-octanol/water partition coefficient (KOW) was best explained by a linear model compared to a two-phase resistance model. Overall, PCB AEs were observed to be dependent on both diet type and chemical hydrophobicity, with both factors contributing nearly equally to the variation measured in this toxicokinetic parameter. Environ. Toxicol. Chem. 2010;29:401–409. © 2009 SETAC
Exchange of polycyclic aromatic hydrocarbons among the atmosphere, water, and sediment in coastal embayments of southern California, USA
Authors: Sabin Lisa D. , Maruya Keith A. , Lao Wenjian , Diehl Dario , Tsukada David , Stolzenbach Keith D. , Schiff Kenneth C.
Published: March 2010

The present study investigated cross-media transport between both the sediment and the water column and between the water column and the atmosphere, to understand the role of each compartment as a source or a sink of polycyclic aromatic hydrocarbons (PAH) in southern California, USA, coastal waters. Concentrations of PAH were measured in the atmosphere, water column, and sediment at four water-quality-impaired sites in southern California: Ballona Creek Estuary, Los Angeles Harbor, Upper Newport Bay, and San Diego Bay. These concentrations were used to calculate site-specific sediment–water and atmosphere–water exchange fluxes. The net sediment–water exchange of total PAH (t-PAH) was positive, indicating that sediments were a source to the overlying water column. Furthermore, the net atmosphere–water exchange (gas exchange + dry particle deposition) of t-PAH was typically positive also, indicating the water column was a net source of PAH to the surrounding atmosphere through gas exchange. However, in all cases, the magnitude of the diffusive flux of PAH out of the sediments and into the water column far exceeded input or output of PAH through air/water exchange processes. These results demonstrate the potential importance of contaminated sediments as a source of PAH to the water column in coastal waters of southern California. Environ. Toxicol. Chem. 2010;29:265–274. © 2009 SETAC
The biodegradation of hydroquinone
Authors: Harbison Kenneth G. , Belly Robert T.
Published: March 2010

Hydroquinone is readily degraded by an acclimated activated sludge unit when present at concentrations of 100 mg/L in synthetic photographic or synthetic domestic wastes. A number of pure cultures of yeasts, fungi, and bacteria were isolated from soil and sludges which can utilize hydroquinone as a sole carbon source.

1,4-Benzoquinone, 2-hydroxy-1,4-benzoquinone, and β-ketoadipic acid were detected as minor components during the biodegradation of hydroquinone by pure cultures, but they did not persist. The total organic carbon during biodegradation was accounted for within experimental error by hydroxylated aromatic compounds. At pH 7 or below, biodegradation by pure cultures or sludges leaves only ca. 2.1% of the total organic carbon in solution after 3–5 days. This value is comparable to values observed for easily assimilated substrates under similar conditions.

At higher pH and in the absence of sulfite, some humic acids may be formed by chemical oxidation if the inoculum is low; these materials resist biodegradation.
Review: Behavior of organic chemicals at soil, air, water interfaces as related to predicting the transport and volatilization of organic pollutants
Authors: Spencer William F. , Farmer Walter J. , Jury William A.
Published: March 2010

The transfer of organic pollutants into the atmosphere is discussed from the standpoint of mechanisms involved, factors influencing rates of volatilization, and progress in developing models for predicting transfer rates. The volatilization rate of soil-incorporated chemicals is controlled by vapor pressure of the chemical in soil and by its rate of movement to the soil surface by diffusion or by a combination of diffusion and convection in evaporating water. Vapor pressures of organic chemicals are greatly decreased by their interaction with soil mainly due to adsorption. The magnitude of the adsorption effect depends upon the nature of the chemical, its concentration, the soil water content and soil properties, such as organic matter and clay content. Vaporization of chemicals in soil or from disposal sites covered with soil can be estimated from considerations of the physical and chemical factors controlling concentrations at the soil surface and most models developed to estimate volatilization rates are based upon equations describing the rate of movement of the chemical to the soil surface by diffusion and/or convection. Considerable progress has been made in developing laboratory based models for predicting volatilization from soil. Since volatilization of soil-incorporated chemicals is controlled mainly by factors within the soil, predictions from laboratory based mathematical models should be sufficiently accurate for many purposes.
Modeling effects of pesticides on populations of soil/litter invertebrates in an orchard ecosystem
Authors: Goodman Erik D.
Published: March 2010

In order to efficiently determine safe levels for introduction of toxic chemicals into the environment, regulators need to understand: (1) the environmental chemistry of the chemical, (2) the time-course of its distribution in the environment, (3) the exposure of key organisms to the chemical, and (4) the effects of the chemical on the exposed biota. It is not practical to determine all of these in field studies for each new chemical; thus, some generalizations must be made based on more limited laboratory determinations. To map from these determinations to a prediction of fate and effects in the field, regulators must implicitly or explicity employ some sort of model.

This paper presents one component of a modeling effort directed toward this goal. This model attempts to represent the effects of azinphosmethyl, an example chemical, on an example population of soil/litter invertebrates, based on extensive studies in a field situation and in the laboratory. Exposure of soil/litter-resident invertebrates is based on the time-course of toxicant distribution and the activity patterns of the organisms as represented by other models developed in the author's laboratory. Examples of these predicted toxicant distributions and comparable field-determined values are presented here.

A model is proposed here to represent temporally distributed mortality of an invertebrate population caused by repeated toxicant dosing. Detailed toxicological studies on the isopod Trachelipus rathkei have allowed the best model parameterization, but models for spiders, earthworms, and springtails have also been developed. Model outputs based on laboratory data are compared with field observations of isopod populations. Results indicate some areas in which further model development is required.
Fate of 2,3,7,8-tetrachlorodibenzo-P-dioxin (TCDD) in an outdoor pond and in model aquatic ecosystems
Authors: Tsushimoto Gen , Matsumura Fumio , Sago Ryuichi
Published: March 2010

Environmental fate of TCDD was studied in an aquatic ecosystem, using an outdoor pond which had been dosed initially with 53.7 ppt of14C-TCDD. The levels of radiocarbon reached an equilibrium in pondweeds after one month, in fish after two months and in the sediment after six months. Using the identical components from the outdoor pond, roughly comparable data were obtained in the laboratory for short-term distribution of radiocarbon. The largest source of variance and discrepancy between the outdoor and the laboratory data was pondweeds. This material produced the largest shift in biomass due to rapid growth and subsequent massive death, causing a drastic change in distribution of radiocarbon in the second year in the outdoor ecosystem. The amounts of the total TCDD remaining in the pond after 12 and 25 months were 49.7 and 29.4%, respectively. The bulk of metabolites was detected in water and pondweeds.
Comparison of laboratory and field results for prediction of the environmental behavior of phosphate esters
Authors: Muir D. C. G. , Grift N. P. , Lockhart W. L.
Published: March 2010

Two phosphate ester flame retardants, triphenyl phosphate (TPP) and 2-ethylhexyldi-phenyl phosphate (EHDPP) (both 14C-labelled) were added to two small artificial ponds (3 m3 volume) to give water concentrations of 60 μg/L for each compound. Both phosphate esters had half-lives of about 15 h in the water column and showed rapid sorption to bottom sediment. At 24 h posttreatment an estimated 28% of EHDPP and 9% of TPP added could not be accounted for by measurements of radioactivity in water, sediment and biota. Calculations of volatilization rates from water of the two compounds suggested that losses of EHDPP may have been due in part to volatilization. Bioconcentration of TPP by fathead minnows (Pimephales promelas) was similar to that predicted from laboratory studies on the uptake and clearance of TPP by rainbow trout (Salmo gairdneri). Prediction of the bioconcentration of EHDPP by duckweed (Lemna minor) from laboratory studies underestimated the rapid uptake of this compound observed in the ponds.
A screening procedure for assessing the transport and degradation of solid waste constituents in subsurface and surface waters
Authors: Falco J. W. , Mulkey L. A. , Swank R. R. , Lipcsei R. E. , Brown S. M.
Published: March 2010

An evaluation procedure was developed to rapidly screen chemicals for their potential to contaminate both subsurface and surface waters after disposal and subsequent release from landfills and lagoons. The procedure estimates movement and degradation of chemicals based on the physical and chemical properties of the compound and a defined range of environmental conditions that the compound potentially experiences in groundwater and in rivers, ponds, and reservoirs.

After high and low estimates are established, qualitative descriptors are assigned to describe the transport and persistence of the compound in subsurface and surface waters.

This procedure has been used to evaluate 193 compounds that were projected to be constituents of solid wastes from 75 manufacturing operations. The results of a sensitivity analysis indicate that where individual environmental process descriptions are defined, changes in rates of degradation of an order of magnitude are required to cause a significant number of changes in qualitative descriptors that define the transport and persistence of the compounds assessed.

The results of this application indicate that the procedure provides a means of qualitatively screening organic chemicals when specified process rate data are available. The evaluation of the small number of metals included in this assessment are speculative. Further research is required to adequately screen metals.