Significance of toxaphene in Great Lakes fish consumption advisories

Fish consumption advisories have been issued for the Great Lakes generally based on the most restrictive contaminant. For the Canadian waters of the Great Lakes, toxaphene causes minor restrictions only in Lake Superior, i.e., 3% of the total (restrictive + unrestrictive) advisories issued. However, the significance of the hazard posed by toxaphene in fish is not clear since more restrictive advisories due to other priority contaminants may be masking the less restrictive advisories. We simulated fish consumption advisories for the Toxaphene-only scenario by neglecting the presence of contaminants other than toxaphene, and compared with the issued advisories as well as with the published simulated Mercury-only scenario. Restrictive advisories under the Toxaphene-only scenario compared to the issued toxaphene related advisories would increase from 3% to 14%, < 1% to 4%, and 0% to 2% for Lakes Superior, Huron and Ontario, respectively, and remain at 0% for Lake Erie. For Lake Superior, most of the restrictive Toxaphene-only advisories would be for fatty fish. Overall, the Toxaphene-only advisories would be significantly less restrictive compared to the issued advisories, and also generally less restrictive compared to the Mercury-only scenario. These results suggest that toxaphene is less of a concern than PCBs (including dioxin-like PCBs), dioxins–furans and mercury from the perspective of health risk to humans consuming Great Lakes fish; elevated toxaphene is mainly a concern for human consumers of Lake Superior fatty fish. Our results suggest that the routine monitoring of toxaphene in other Canadian waters of the Great Lakes and Lake Superior lean/pan fish could be discontinued.     

Incremental communication for multilayer neural networks: erroranalysis

Artificial neural networks (ANNs) involve a large amount of internode communications. To reduce the communication cost as well as the time of learning process in ANNs, we earlier proposed (1995) an incremental internode communication method. In the incremental communication method, instead of communicating the full magnitude of the output value of a node, only the increment or decrement to its previous value is sent to a communication link. In this paper, the effects of the limited precision incremental communication method on the convergence behavior and performance of multilayer neural networks are investigated. The nonlinear aspects of representing the incremental values with reduced (limited) precision for the commonly used error backpropagation training algorithm are analyzed. It is shown that the nonlinear effect of small perturbations in the input(s)/output of a node does not cause instability. The analysis is supported by simulation studies of two problems. The simulation results demonstrate that the limited precision errors are bounded and do not seriously affect the convergence of multilayer neural networks.     

Silver and gold nanocluster catalyzed reduction of methylene blue by arsine in micellar medium

Arsenic can be determined in parts-per-million (ppm) level by absorbance measurement. This method is based on the quantitative colour bleaching of the dye, methylene blue by arsine catalyzed by nanoparticles in micellar medium. The arsine has been generated in situ from sodium arsenate by NaBH₄ reduction. The absorbance measurement was carried out at the λ_max of the dye at 660 nm. The calibration graph set-up for three linear dynamic ranges (LDR) are 0-8.63 ppm, 0-1.11 ppm and 0-0.11 ppm and limit of detections (LODs) are 1.3, 0.53 and 0.03 ppm, respectively. This method is simple, sensitive and easy to carry out. It is free from phosphate and silicate interference and applicable to real sample analysis.     

Computational fluid dynamics simulations of submicrometer and micrometer particle deposition in the nasal passages of a Sprague-Dawley rat

Computational fluid dynamics (CFD) simulations were conducted in a model of the complete nasal passages of an adult male Sprague-Dawley rat to predict regional deposition patterns of inhaled particles in the size range of 1 nm to 10 μm. Steady-state inspiratory airflow rates of 185, 369, and 738 ml/min (equal to 50%, 100%, and 200% of the estimated minute volume during resting breathing) were simulated using Fluent?. The Lagrangian particle tracking method was used to calculate trajectories of individual particles that were passively released from the nostrils. Computational predictions of total nasal deposition compared well with experimental data from the literature when deposition fractions were plotted against the Stokes and Peclet numbers for micro- and nanoparticles, respectively. Regional deposition was assessed by computing deposition efficiency curves for major nasal epithelial cell types. For micrometer particles, maximum olfactory deposition was 27% and occurred at the lowest flow rate with a particle diameter of 7 μm. Maximum deposition on mucus-coated non-olfactory epithelium was 27% for 3.25 μm particles at the highest flow rate. For submicrometer particles, olfactory deposition reached a maximum of 20% with a particle size of 5 nm at the highest flow rate, whereas deposition on mucus-coated non-olfactory epithelium reached a peak of approximately 60% for 1–4 nm particles at all flow rates. These simulations show that regional particle deposition patterns are highly dependent on particle size and flow rate, indicating the importance of accurate quantification of deposition in the rat for extrapolation of results to humans.     

Degradation and Metabolite Profiling of Benz (a) Anthracene,Dibenz (a,h) Anthracene and Indeno [1, 2, 3-cd] Pyrene by Aspergillus terricola

Mycoremediation of low molecular weight polycyclic aromatic hydrocarbons (PAH) is well studied. This study highlights the degradation of high molecular weight PAH (HMW-PAHs): Benz (a) anthracene (BAA), Dibenz (a, h) anthracene (DBA), and Indeno pyrene (IND) by Aspergillus terricola var americanus. The metabolism of the HMW-PAHs by this fungus was investigated in liquid submerged culture added with 60 mg/L of each compound. Depletion of BAA, DBA, and IND was 94.80, 90.16, and 93.80%, respectively, after 10 days of culture. Fungal broth solvent extracts were analyzed for the presence of metabolites by gas chromatography mass spectrometry and the extracellular enzymes produced were also assayed. The coexistence of two metabolic pathways, cytochrome P450 monooxygenase and ligninolytic pathway were identified. A high laccase activity was observed in BAA cultures on day 4 when compared to other PAH's studied. In conclusion, A. terricola might be a promising fungus for bioremediation of HMW-PAH mixtures co-metabolically.     

A microprocessor-based multilingual terminal for a computerized information handling system

Conclusion The technical feasibility of the proposed microprocessor-based multilingual terminal is apparent. The lower cost of the microprocessor family components makes the system economically viable. The addition and deletion of languages are very flexible. Including any new language requires only the following three steps: (1) assign a unique number to the language, (2) assign to the terminal keys the symbols necessary to generate the characters of the language and (3) develop software routines (preferably microcoded) to generate the characters of the language using the appropriate algorithm indicated and integrate these routines with the rest of the system. Similarly an existing language could be easily removed from the system. Finally, it should be mentioned that as of now a full hardware unit suitable for marketing is not yet ready. The algorithms explained have already been tested and the output shown in this paper generated by software through keyboard simulation using an existing terminal; the ‘CTRL’ control shift is used to accommodate the excess keys required in the multilingual terminal. The hardware development is in progress.     

Preparation of conducting fibers via the electrochemical polymerization of pyrrole

Cyclic voltammograms of pyrrole monomer and polypyrrole films prepared potentiostatically at 1.0 V versus an Ag/AgCl electrode have been examined. The insulating natural fibers, such as cotton, silk, and wool become electrically conducting when they are subjected to electrical treatment in the polymerizing solution of pyrrole in acetonitrile containing p-toluenesulfonic acid as a supporting electrolyte. The weight gain and the electrical conductivity of the fibers increase with the time of electrolysis and impressed current levels. The conductivities are in the range of 0.2 to 15 s/cm and dependent on the nature of the fibers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1073–1077, 1997     

Sol–gel derived multiwalled carbon nanotubes ceramic electrode modified with molecularly imprinted polymer for ultra trace sensing of dopamine in real samples

A new class of composite electrodes made of sol–gel derived ceramic-multiwalled carbon nanotubes is used for the growth of a nanometer thin film adopting “surface grafting-from approach”. For this the multiwalled carbon nanotubes-ceramic electrode surface is first modified with an iniferter (benzyl N,N-diethyldithiocarbamate) and then dopamine imprinted polymer, under UV irradiation, for differential pulse anodic stripping voltammetric sensing of dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples (detection limit 0.143–0.154 ng mL⁻¹, 3σ), without any cross reactivity, interferences and false-positive contributions. Such composite electrodes offer higher stability, electron kinetics, and renewable porous surface of larger electroactive area (with insignificant capacitance) than carbon ceramic electrodes. Additional cyclic voltammetry (stripping mode) and chronocoulometry experiments were performed to explore electrodics and kinetics of electro-oxidation of dopamine.     

Effects of sintering temperature on structural and electromagnetic properties of MgCuZn ferrite prepared by microwave sintering

Nanocrystalline magnesium–copper–zinc (Mg_0.30Cu_0.20Zn_0.50Fe₂O₄) ferrites were prepared by microwave sintering technique. The effects of the sintering temperature on particle size and magnetic properties were investigated. In this article, optimum sintering temperature required for MgCuZn ferrite system for obtaining good electromagnetic properties, suitable for applications in low temperature co-fired ceramics (LTCC) chip components was studied. The grain size, initial permeability, dielectric constant and saturation magnetisations were found to increase, and dielectric loss was found to decrease with the increasing sintering temperature. Mg–Cu–Zn ferrites with a permeability of μ?=?1110 (at 1?MHz) were fully densified at the standard LTCC sintering temperature of 950°C.     

Is it safe to eat fish from the Great Lakes? An adaptive modelling-monitoring framework to assess compliance with consumption advisories

In this study, we conducted a retrospective analysis of the spatio-temporal trends of fish contamination in the Canadian Great Lakes. We subsequently formulated consumption advisories that explicitly account for all sources of uncertainty, such as model error, sampling bias, and natural variability of fish assemblages. Our analysis generated exceedance frequency maps of the tolerable daily intakes (TDIs), which showed that mercury (Hg) concentrations are generally at a safer level for consumption, whilst polychlorinated biphenyls (PCBs) continue to result in restrictive advisories. Specifically, the initial decline in PCBs has transitioned into a steady state, possibly due to the combined effects of external contamination sources and internal abiotic and biotic factors. Our assessment of the PCB decline rates required to comply with TDI thresholds over the next twenty years suggest that a small degree of reduction is needed for Walleye (Sander vitreus) across all sampled sites, whereas much faster decay rates are needed for Lake Trout (Salvelinus namaycush), especially in lower Lake Huron, Lake Erie, and Lake Ontario. We also detected a distinct Hg gradient whereby the southernmost waterbody, Lake Erie, had the lowest average concentrations, whereas the highest levels amongst the fish species sampled were registered in St. Lawrence River. Finally, we show the ability of our Bayesian approach to fish consumption advisories to produce time-specific, highly customizable, risk-assessment statements that account for the inherent variability in natural fish communities and the variant degree of empirical evidence about the contamination history in different locations around the Great Lakes.