Preparation and properties of polybenzidine film-coated electrode as an H2O2 selective polymeric material

By means of electrochemical polymerization, polybenzidine-modified electrodes were prepared in an aqueous monomer solution at a potential of 0.7 V versus Ag/AgCl. The permselective character of the polybenzidine electrode prepared in a one-step procedure was examined for electroactive (ascorbic acid, oxalic acid, and hydrogen peroxide) and nonelectroactive (lactose, sucrose, and urea) species. Influence of the various parameters on the permselective properties of the polybenzidine membrane was systematically investigated and the optimal values for these parameters were determined. It has been found that polybenzidine membrane showed selective permeation for hydrogen peroxide while blocking the permeation of electroactive and nonelectroactive interferents through film. In brief, it is claimed that this polybenzidine film can be used as a coating material to prevent interferences in electrochemical biosensor applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2227–2234, 1998     

Transient liquid phase (tlp) diffusion bonding of Ti45Ni49Cu6 P/M components using Cu interlayer

In this study, transient liquid phase diffusion bonding parameters of Ti₄₅Ni₄₉Cu₆ P/M components using copper interlayer were experimentally investigated in a protective (argon) atmosphere. Bonding processes of sintered Ti₄₅Ni₄₉Cu₆ P/M compacts were carried out at various temperatures and bonding periods while bonding pressure was kept unchanged. The process pressure, 20 MPa, was selected just below those which would cause macro deformations. Optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy were employed for microstructure examinations. Shear strength and hardness (HB) of bonded specimens were measured at bond interface and parent materials for mechanical property evaluations. Along the bond interface, copper, titanium, and nickel atom mutual migration was observed. Structural tests, metallographic analysis have shown the integrity of the diffusion bonded hardware, bonded between 940 and 970°C process temperatures, for 40–60-min bonding periods.     

Hot boning of intact carcasses: a procedure to avoid central nervous system self-contamination in beef and beef products

Compared with traditional boning of split refrigerated carcasses, hot boning of intact carcasses (the removal of meat from the skeleton prerigor) provides several commercially important cuts, may improve quality and reduce refrigeration costs, and may reduce the contamination of carcasses with central nervous system (CNS) tissue. In a comparative study of hot boning of intact and split carcasses, the CNS tissue contamination of intact carcasses was negligible (as measured with the CNS-related proteins glial fibrillary acidic protein and S-100 protein), but split carcasses were highly contaminated. The same trends were observed for dissection worktables used during the boning process. Most current boning plants have processing lines that are organized for boning carcass quarters, where the carcasses, in addition to transversal division, also are split horizontally. This part of the boning process was incorporated in the design of our study. Nine of the 18 intact carcasses were split horizontally between thoracic vertebrae 10 and 11 before they were hot boned. CNS tissue contamination was not detected on the carcass site related to this procedure. The amount of CNS tissue contamination was similar in boned cuts and minced meat from split and intact carcasses, except in the forerib. Boning of split carcasses appears to reduce CNS tissue contamination significantly to a level comparable to that of intact hot-boned carcasses.     

Microscale geochemical gradients in Hanford 300 Area sediment biofilms and influence of uranium

The presence and importance of microenvironments in the subsurface at contaminated sites were suggested by previous geochemical studies. However, no direct quantitative characterization of the geochemical microenvironments had been reported. We quantitatively characterized microscale geochemical gradients (dissolved oxygen (DO), H₂, pH, and redox potential) in Hanford 300A subsurface sediment biofilms. Our results revealed significant differences in geochemical parameters across the sediment biofilm/water interface in the presence and absence of U(VI) under oxic and anoxic conditions. While the pH was relatively constant within the sediment biofilm, the redox potential and the DO and H₂ concentrations were heterogeneous at the microscale (<500-1000 μm). We found microenvironments with high DO levels (DO hotspots) when the sediment biofilm was exposed to U(VI). On the other hand, we found hotspots (high concentrations) of H₂ under anoxic conditions both in the presence and in the absence of U(VI). The presence of anoxic microenvironments inside the sediment biofilms suggests that U(VI) reduction proceeds under bulk oxic conditions. To test this, we operated our biofilm reactor under air-saturated conditions in the presence of U(VI) and characterized U speciation in the sediment biofilm. U L_III-edge X-ray absorption spectroscopy (XANES and EXAFS) showed that 80-85% of the U was in the U(IV) valence state.     

High-Performance Liquid Chromatography Analysis and Assessment of Benzoic Acid in Yogurt, Ayran, and Cheese in Turkey

Among food sources, particular attention is paid to milk and dairy products, due to its nutritional importance. Benzoic acid is extensively used in the preservation of foods. A reliable method for the determination of benzoic acid in some dairy products, such as yogurt, ayran, and cheese using high-performance liquid chromatography and UV detection was validated. The peak of benzoic acid was measured at a wavelenght of 226 nm. Samples were purchased from supermarkets in Turkey in the period 2009–2010. All dairy product samples were produced from cow’s milk. The levels of benzoic acid in cheese, yogurt, and ayran samples were in the range of 3.17 to 56.77 mg kg⁻¹, 8.94 to 28.30 mg kg⁻¹, and 1.54 to 16.57 mg L⁻¹, respectively. The results show that benzoic acid widely occurs in milk products in Turkey at the low levels.     

Effects of Ozone Treatment on Microbiological Quality and Physicochemical Properties of Turkey Breast Meat

ABSTRACT

The effects of ozone treatment (1 × 10^?2 kg m^?3, for up to 8 h) on quality parameters of turkey meat were investigated. Ozone was effective in inactivating microorganisms. Approximately 2.9, 2.3 and 1.9 log reductions were achieved in the counts of total aerobic mesophilic bacteria, Enterobacteriaceae and yeast-mold, respectively. Ozone caused significant changes in carbonyl contents, thiobarbituric acid reactive substances, color and pH values of the samples. Water holding capacity and cooking yield of treated samples increased significantly (p < .05). This is the first report demonstrating that quality parameters of turkey breast meat are markedly affected by ozone treatment.     

Bioengineering functional copolymers. XI. Copper(II)-poly(N-vinyl-2-pyrrolidone-co-N-isopropylacrylamide) macrocomplexes

A series of poly(N-vinyl-2-pyrrolidone-co-N-isopropylacrylamide)s, poly(VP-co-NIPA) copolymers with different compositions were prepared by radical copolymerization of VP and NIPA in N,N′-dimethylformamide at 65°C using 2,2′-azobisisobutyronitrile as initiator. Cu(II)-copolymer macrocomplexes were prepared by complexation of the copolymers with copper sulfate in aqueous solution at 40°C. The structure and composition of the copolymers, and the formation of coordinated Cu(II)-complexes between amide VP units and Cu²⁺ ions, were studied by FTIR spectroscopy, DSC and TGA-DTG in addition to electrical conductivity. Studies on the relationship between composition and thermal behavior showed that the values of T_g and T_d of the copolymers and their coordinated macrocomplexes increased with increasing VP content. The copolymers predominantly show amorphous structure while their Cu(II)-macrocomplexes show the presence of a crystalline phase. The conductive properties of the synthesized Cu(II)-poly(VP-co-NIPA) complexes are also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Immobilization of urease and estimation of effective diffusion coefficients of urea in HEMA and VP copolymer matrices

Enzyme urease was immobilized in copolymer matrices of 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (VP). The activities of immobilized urease stored in phosphate buffer solution of pH 7.0 at 4°C were examined periodically for up to 90 days. For the matrices of higher VP/HEMA mole ratio in the structure, a higher volume increase and enhanced apparent activity were observed, while HEMA polymer alone proved to have the most stable matrix for prolonged activity. No appreciable amount of enzyme leakage was experienced for any of the matrices prepared. The effective diffusion coefficients of urea through these polymer matrices were calculated with a ‘diffusion and reaction’ model and the highest effective diffusion coefficient was found with pure HEMA matrix, possibly due to its laminated structure.