Differential accumulation of polychlorinated biphenyl congeners in the terrestrial food web of the Kalamazoo River Superfund site, Michigan

A series of field studies was conducted to determine the bioaccumulation of polychlorinated biphenyl (PCB) congeners in the terrestrial food web of the Kalamazoo River flood plain. Samples included colocated soils, native plants likely to be consumed by wildlife, several taxa of terrestrial invertebrates, small mammals, passerine bird eggs, nestlings, and adults, and great horned owl plasma and eggs. Mean concentrations of total PCBs in samples from the former Trowbridge impoundment were 6.5 mg/kg dry weight for soils and 0.023, 0.13, 1.3, 1.3, 1.6, and 8.2 mg/kg wet weight for plants, small herbivorous mammals, depurated earthworms, shrews, great horned owl eggs, and house wren eggs, respectively. Historical data from the Kalamazoo River have reported Aroclor-equivalent total PCB concentrations in the terrestrial food web; however, the degree of environmental weathering of the parent PCB mixtures was unknown. In this study, earthworms and composite samples of coleoptera exhibited PCB congener patterns that were similar to patterns in colocated soils. However, in plants, less chlorinated PCBs (e.g., mono-, di-, tri-, and tetrachlorinated biphenyls) were predominant, and in small mammals, there was a notable enrichment of PCBs 153, 180, 138, 118, and 99. In general, concentrations of PCBs were lower in most biota than in soil from the Kalamazoo River Area of Concern (KRAOC) although there was a modest biomagnification of PCBs from lower trophic level biota to highertrophic levels. As a consequence of environmental weathering of PCBs in the terrestrial food web of the KRAOC, the relative potency of the PCBs (expressed as mg TEQs/kg PCBs) decreased from soil to most biota. While there was a general trend, as expected, in which concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) increased with total PCBs, this relationship was rather poor (R2 = 0.13). Taken together, these data suggest that the differential accumulation of PCB congeners in the terrestrial food web can be explained by congener-specific differences in bioavailability from soil, exposure pathways, and metabolic potential of each of the food web components.     

Extension to mixtures of two robust hard‐sphere equations of state satisfying the ordered close‐packed limit

Two new hard‐sphere EOS are proposed and tested using the same attractive potential terms used by the SAFT EOS. Generalized expressions for the pair RDF at contact value, the compressibility factor, and the excess chemical potentials have been derived. Extension to mixtures is tested using three mixing rules for multicomponent hard‐sphere fluids. The proposed EOS combined with the Santos et al. and the Barrio‐Solana mixing rules reproduced the compressibility factors and the excess chemical potentials more accurately than the Boublik‐Mansoori‐Camahan‐Starling‐Leland (BMCSL) EOS. However the pair RDF at contact value had larger deviations than those obtained with the BMCSL EOS. The combination of the proposed equations and the Barrio‐Solana mixing rule gave an accurate reproduction of the compressibility factor for binary hard‐sphere fluids with high diameter ratio even in the low concentration regions of the larger spheres.     

Thin film graphene oxide membrane: Challenges and gas separation potential

Graphene oxide membranes were prepared by vacuum and pressurized ultrafiltration methods on the 12% modified Polyacrylonitrile (12mPAN) substrate to specify challenges, salient features, future directions, and potential of GO membrane for separation fields using characterization techniques and gas separation test (studied gases are CO₂, He and N2), which is an efficient tool for better understanding of GO membrane behavior. GO membrane structure was examined over a wide range of parameters, such as pore size range of substrate and its surface properties, pH of GO dispersion, GO content, synthesis pressure, operating pressure and temperature. The results show that the GO content does not hold a linear relationship with the permeance and selectivity. Film thickness, aggregates, synthesis pressure defects and interlayer spacing have significant effects on the gas separation performance of GO membranes which originate from the synthesis method and its conditions.     

Novel CuO/polymethylenedisulfide nanocomposite for high performance electrocatalytic determination of hydrochlorothiazide in real samples

Journal of Porous Materials - Surface of a carbon paste electrode was modified by using copper oxide nanoparticles/polymethylenedisulfide (CuO NPs/PMDS) nanocomposite. X-ray diffraction...     

Simultaneous gains tuning in boiler/turbine PID-based controller clusters using iterative feedback tuning methodology

Tuning a complex multi-loop PID based control system requires considerable experience. In today's power industry the number of available qualified tuners is dwindling and there is a great need for better tuning tools to maintain and improve the performance of complex multivariable processes. Multi-loop PID tuning is the procedure for the online tuning of a cluster of PID controllers operating in a closed loop with a multivariable process. This paper presents the first application of the simultaneous tuning technique to the multi-input-multi-output (MIMO) PID based nonlinear controller in the power plant control context, with the closed-loop system consisting of a MIMO nonlinear boiler/turbine model and a nonlinear cluster of six PID-type controllers. Although simplified, the dynamics and cross-coupling of the process and the PID cluster are similar to those used in a real power plant. The particular technique selected, iterative feedback tuning (IFT), utilizes the linearized version of the PID cluster for signal conditioning, but the data collection and tuning is carried out on the full nonlinear closed-loop system. Based on the figure of merit for the control system performance, the IFT is shown to deliver performance favorably comparable to that attained through the empirical tuning carried out by an experienced control engineer.     

Nanocasting Synthesis of Ultrafine WO<Subscript>3</Subscript> Nanoparticles for Gas Sensing Applications

Ultrafine WO₃ nanoparticles were synthesized by nanocasting route, using mesoporous SiO₂ as a template. BET measurements showed a specific surface area of 700 m²/gr for synthesized SiO_2, while after impregnation and template removal, this area was reduced to 43 m²/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO₃ nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO₂ at 250°C and 300°C.     

Evaluation of bonding effectiveness of a self-etch and an etch-and-rinse adhesive resin to un-treated and Er:Yag laser treated dentin using mini-interfacial fracture toughness test

The aim of current study was to assess interfacial bonding effectiveness of self-etch and etch-and-rinse dental adhesives to untreated and Er:YAG laser-treated dentine using mini-interfacial fracture toughness (mini-iFT) test. 32 selected non-carious third molars were divided into two groups: untreated and Er:YAG laser treated. The laser-treated specimens were subjected to Er:YAG laser with energy density of 25.82?J/cm². Both groups were further assigned to two groups based on adhesive systems: self-etch and etch-and-rinse. The teeth were sectioned perpendicular to the adhesive/dentine interface to obtain 1.5?×?2?mm wide longitudinal rectangular sections. A single notch then was prepared at the adhesive-dentine interface. The mini-iFT test was done via a 4-point bend testing until failure and the KIC was calculated. All specimens were observed using a, scanning electron microscope (SEM). The data were analysed using two-way analysis of variance (ANOVA) at a significant level of 0.05. Weibull parameters including Weibull modulus and characteristic strength also were calculated for each experimental group. Two-way ANOVA showed both variables (the type of adhesive system and laser treatment) significantly influenced the mini-iFT values of specimens (p?≤?0.001). The self-etch and laser-treated group showed lower mini-iFT than the etch-and-rinse and untreated samples. SEM observations revealed that the fracture region was located at the adhesive-dentine interface in most of the specimens. The Er:YAG laser treatment may adversely affects the bonding effectiveness of the dentine/adhesive interface. The mini-iFT method can be used as a discriminative and valid method for the evaluation of bonding effectiveness at the adhesive-dentine interface.     

On the integration schemes for Drucker–Prager's elastoplastic models based on exponential maps

Rate plasticity equations for the case of Drucker–Prager's model in small strain regime are considered. By defining an augmented stress vector, the formulations convert the original problem into a quasi‐linear differential equation system. Two new exponential mapping schemes for integrating model equations are proposed. In addition, two traditional schemes for solving the dynamical system in an explicit manner are discussed. The two semi‐implicit schemes developed pose higher accuracy and better convergency. Error contours are provided for all four methods to display the accuracy of each scheme. In order to compare the results, these contours for the classical one‐step backward Euler integration method are also displayed. Accuracy and efficiency along with the rate of convergency of the existing and the proposed methods are examined by numerical examples. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of parameters on deposition pattern of ceramic nanoparticles in non-uniform AC electric field

In electrophoretic deposition (EPD), it is assumed that net movement of particles is zero under the influence of alternating current (AC) electric field. For this reason, AC electric field is not used for deposition of ceramic particles while in other areas scientists take the advantage of AC electric field for their purpose. By imposing some modifications on electric field, it is possible to use AC electric fields in processes such as fabrication of miniature ceramic parts. In this paper, non-uniform AC electric field was used to deposit TiO₂ nanoparticles on gold electrodes. Acetone was used as dispersing medium to avoid bubble formation at low frequencies. Effect of different parameters such as applied voltage and frequency, time and concentration on deposition pattern was studied and proper factors for optimization of the process were determined.