Treatment of metal‐containing wastewaters with a novel extractive membrane reactor using sulfate‐reducing bacteria

This work reports a novel system for the treatment of acidic metal‐containing wastewaters, the Extractive Membrane Bioreactor–Sulfate‐Reducing Bacteria (EMB‐SRB) system. In this system, hydrogen sulfide is produced in the bioreactor by the sulfate‐reducing bacteria, transfers through a dense phase membrane, and precipitates metal ions in the wastewater. The non‐porous membrane prevents the SRB from having direct contact with the toxic metals, extremes of pH, or high salinity in the wastewater. Silicone rubber, which is permeable to H₂S but virtually impermeable to ionic species in the system, was used as a membrane. The rate of mass transfer of H₂S across the membrane was studied and found to be well described by a resistances‐in‐series model. k_ov values vary in the range 5 × 10⁻⁶ –10 × 10⁻⁶ ms⁻¹ 1 depending on the membrane thickness. A continuous EMB–SRB system was operated and more than 90% (w/v) of the Zn²⁺ present in a wastewater was removed. A film of metal precipitate was found to build up on the inside (wastewater) side of the membrane, and became the dominant resistance contributing to the overall mass transfer coefficient during operation. © 2001 Society of Chemical Industry     

Direct Correlation Between Adhesion Promotion and Coupling Reaction at Immiscible Polymer-Polymer Interfaces

Hugh Brown has shown that interfacial entanglements govern adhesion between two polymers. We demonstrate this for three systems by adding interfacial chains via chemical coupling. The adhesion between polypropylene (PP)/amorphous polyamide (aPA) was reinforced by the coupling reaction of maleic anhydride grafted PP (PP-g-MA) and the primary amine groups on aPA; huge increases in adhesion were observed. A good correlation between critical fracture toughness, G_c, and PP-g-MA concentration squared follows Brown's crazing mechanism. For a polystyrene (PS)/aPA interface reinforced by the coupling reaction of poly(styrene-r-maleic anhydride) (PS-r-MA)/aPA only modest adhesion increases in G_c were observed through the whole PS-r-MA concentration range. This different behavior of G_c vs. functional polymer concentration is believed to be caused by segregation of the formed graft copolymers at the interface. The relationship between G_c and the extent of coupling was studied quantitatively with a model PS/PMMA system. The interface was reinforced by the coupling reaction of 0-10% PS-NH₂/PMMA-anh. G_c was measured with the asymmetric dual cantilever beam test (ADCB) and the amount of copolymer formed at the interface was determined by a fluorescence labeling technique. G_c is low and is linear in block copolymer interfacial coverage (Σ), indicating a chain scission mechanism. Reasonable agreement was achieved between experiment and theoretical prediction based on the energy to break C-C bonds.     

Effect of dynamic crosslinking on crystallization and thermal degradation of polypropylene in polypropylene (PP)/ethylene-propylene DIENE (EPDM) rubber blends

Blends of isotactic polypropylene and ethylene propylene diene (EPDM) rubber were dynamically vulcanized using the dimethylol phenolic resin/stannous chloride crosslinking system. The EPDM blends are thermally more stable than polypropylene (PP). Dynamic curing rendered the vulcanizate thermally more stable than unvulcanized blends. The variations in degree of crosslinking and degree of crystallinity are the main factors for observed increase in thermal stability of vulcanized blends. Degree of crosslinking increases the interfacial adhesion between the PP and EPDM phases. Dimethylol phenolic resin used as a compatibilizer also enhanced the thermal stability of the PP/EPDM blends. Crystallization of PP in the blends of PP/EPDM was also studied through modulated differential scanning calorimetry. Other detailed analyses of endotherm peaks obtained after first and second melts in terms of heat of enthalpy, degree of undercooling, and degree of crystallinity were also evaluated. Kinetic parameters were also determined.     

Kinematical studies of the glass transition in glassy Se80 ? xTe20Sbx

The present paper reports kinematic studies of the glass transition in glassy Se_80-xTe₂₀Sb_x alloys using the differential scanning calorimetric technique. The glass transition temperature (T_g) is found to increase monotonically with the heating rate. T_g also increases with the increase of Sb concentration in ternary Se_80-xTe₂₀Sb_x system. From the heating rate dependence of glass transition temperature, the activation energy ( E_t) for the relaxation time controlling the structural enthalpy, is calculated. The composition dependence of T_g and E_t is discussed in terms of the structure of the Se-Te-Sb glassy system.     

Study of Josephson effects in microbridges of Bi-Sr-Ca-Cu-O films made by spray pyrolysis

Superconducting Bi-Sr-Ca-Cu-O (2212) films were prepared by spraying stoichiometric aqueous solutions of nitrates of bismuth, strontium, calcium and copper on heated MgO (100) substrates and subsequent annealing in air. TheR-T curves of the films show metallic behaviour above the superconducting transition temperature.T _c (R=0) is observed between 80 and 85 K. Annealing temperature has a profound effect onT _c (R=0) and on the orientation of the film. Annealing in air in near-melting region yields highly oriented films withc-axis perpendicular to the substrate. These films show a sharp superconducting transition with zero resistance at 85 K. Microbridges of the dimensions of 50 μm × 50 μm have been patterned photolithographically followed with chemical etching. The 1 V characteristics of the microbridges show Josephson effects due to the presence of grain boundary weaklinks. The temperature dependence of the critical current for these microbridges suggest formation of superconductor-normal-superconductor type weaklinks.     

Design, implementation and testing of a microprocessor-basedhigh-speed relay for detecting transformer winding faults

The authors present the design, implementation and testing of a microprocessor-based high-speed relay that correctly detects transformer winding faults. Instead of relying on the presence of harmonics to identify magnetizing inrush, it uses a nonlinear model of the transformer to determine the state of its health. One version of the relay is suitable for protecting single-phase transformers, whereas another version is for protecting three-phase transformers. A three-phase delta-wye 15 kVA transformer was used to test the relay for a variety of operating conditions. The results show that the relay performs well     

A time-domain approach to model validation

In this paper we offer a novel approach to control-oriented model validation problems. The problem is to decide whether a postulated nominal model with bounded uncertainty is consistent with measured input-output data. Our approach directly uses time-domain input-output data to validate uncertainty models. The algorithms we develop are computationally tractable and reduce to (generally nondifferentiable) convex feasibility problems or to linear programming problems. In special cases, we give analytical solutions to these problems     

H∞ control and filtering for sampled-datasystems

H_∞ control and filtering problems for sampled-data systems are studied. Necessary and sufficient conditions are obtained for the existence of controllers and filters that satisfy a specified H_∞ performance bound. When these conditions hold, explicit formulas for a controller and a filter satisfying the H_∞ performance bound are also given     

Electrospray quadrupole mass spectrometry analysis of model oligonucleotides and polymerase chain reaction products: determination of base substitutions, nucleotide additions/deletions, and chemical modifications.

ESI FTICR mass spectrometry is the only technique currently used for accurate molecular weight analysis of PCR products above 100 bp in size. This is important in demonstrating the potential for MS in making major contributions in the molecular biology and genomics areas. In the near future, it is more likely that less expensive, more user friendly MS techniques will be used for high-throughput analyses (including MALDI TOF and ESI quadrupole). There have been numerous reports on the use of MALDI TOF. The current report is to the first to evaluate the use of ESI-quadrupole analysis of PCR products. Synthetic oligonucleotides (30 and 89 mers) and polymerase chain reaction products of varying molecular weight (62, 88, 89, and 114 bp) were analyzed by ESI using a quadrupole MS. The mass accuracy for nucleic acids in the 30-62 bp range was shown to allow determination of nucleotide substitutions and additions/deletions. For higher molecular weight PCR products (88-114 bp), the mass accuracy of ESI-MS distinguishes single or multiple nucleotide insertions/deletions. In addition, ESI quadrupole MS allows determination of molecular weight of both strands of higher molecular weight ds PCR products and can distinguish nucleotide modifications (e.g., with biotin). In conclusion, it is demonstrated that ESI-MS occupies an intermediate position (as compared to MALDI TOF and ESI FTICR) with regard to mass accuracy and resolution in analysis of nucleic acids.