Electrochemical biosensor for detection of formaldehyde in rain water

BACKGROUD: This study describes the construction of an electrochemical formaldehyde biosensor based on poly(glycidyl methacrylate‐co‐3‐methylthienyl methacrylate)/formaldehyde dehydrogenase/polypyrrole [poly(GMA‐co‐MTM)/FDH/PPy] composite film electrode. Formaldehyde dehydrogenase (FDH) was chemically immobilized via the epoxy groups of the glycidyl methacrylate (GMA) side chain of the polymer. Formaldehyde measurements were conducted in 0.1 mol L^?1, pH 8 phosphate buffer solution (PBS) including 0.1 mol L^?1 KCl, 0.5 mmol L^?1 of NAD⁺ (cofactor of the enzyme) and 1 mmol L^?1 of 1,2‐napthoquinone‐4‐sulfonic acid sodium salt (NQS) as mediator with an applied potential of ? 0.23 V (vs. Ag/AgCl, 3 mol L^?1 NaCl). Analytical parameters of the biosensor were calculated and discussed. The biosensor was tested in rain water samples. RESULTS: Sensitivity was found to be 15 000 per mmol L^?1 (500 nA ppm^?1) in a linear range between 0.1 ppm and 3 ppm (3.3–100 µmol L^?1). A minimum detectable concentration of 4.5 ppb (0.15 µmol L^?1) (S/N = 3) with a relative standard deviation (RSD) of 0.73% (n = 5) was obtained from the biosensor. Response time of the biosensor was very short, reaching 99% of its maximum response in about 4 s. The biosensor was also tested for formaldehyde measurements in rain water samples. Formaldehyde concentrations in samples were calculated using the proposed biosensor with recovery values ranged between 92.2 and 97.7% in comparison with the colorimetric Nash method. CONCLUSION: The poly(GMA‐co‐MTM)/FDH/PPy) electrode showed excellent measurement sensitivity in comparison with other formaldehyde biosensor studies. Strong chemical bonding between the enzyme and the copolymer was created via the epoxy groups of the composite film. The proposed biosensor could be used successfully in rain waters without a pretreatment step. © 2012 Society of Chemical Industry     

A robust integrator algorithm with genetic based fuzzy controller feedback for direct vector control

The voltage model used for direct vector control has in the flux calculation process an open integration problem, which is generally solved with a feedback loop. In this paper, a new design method is developed for the feedback loop of the integrator. The method, as apart from standards in the literature, uses a fuzzy controller. Fuzzy controllers are knowledge-based systems that include fuzzy rules and fuzzy membership functions to incorporate human knowledge into their knowledge base. The determination of these rules and membership functions is one the key problems when designing fuzzy controllers, and is generally affected by subjective decisions. In this study, a fuzzy controller with rules and membership functions determined by genetic algorithms (GAs) in this study is designed and tested on various motors of different power ratings. The proposed method is simulated by using MATLAB/SIMULINK and implemented on an experimental system using a TMS320C31 digital signal processor.     

Atomic force microscopy tips (cantilevers) as molecular nucleic acid sensors

A model single strand DNA (ssDNA) was covalently immobilized onto AFM tips (cantilevers) as specific ligand. These tips were interacted with the buffer solutions with or without free ssDNA molecules as the target strands to be detected. Immobilization and hybridization onto the cantilever surfaces were observed by optical and fluorescence microscopies. Interactions between the AFM tip (cantilever) and the aqueous medium (therefore with the target ssDNAs) were quantified by obtaining the "percent separation distance" ("PSD") as the main variable. The PSD values obtained for the buffer solutions were between -2.07 and +4.91%. There were slight increases in the negative values when non-complementary ssDNA molecules were introduced into the buffer. However, after hybridization with its complementary ssDNA, the PSD values were significantly increased (between -32.24 and -43.47%). There was a correlation between the concentration of the complementary target ssDNA in the medium and the PSD value. As a result of these promising results it was concluded that this approach may be further developed to create AFM-based molecular sensors for diverse applications.     

Rough particle swarm optimization and its applications in data mining

This paper proposes a novel particle swarm optimization algorithm, rough particle swarm optimization algorithm (RPSOA), based on the notion of rough patterns that use rough values defined with upper and lower intervals that represent a range or set of values. In this paper, various operators and evaluation measures that can be used in RPSOA have been described and efficiently utilized in data mining applications, especially in automatic mining of numeric association rules which is a hard problem.     

An adaptive artificial immune system for fault classification

Fault diagnosis is very important in ensuring safe and reliable operation in manufacturing systems. This paper presents an adaptive artificial immune classification approach for diagnosis of induction motor faults. The proposed algorithm uses memory cells tuned using the magnitude of the standard deviation obtained with average affinity variation in each generation. The algorithm consists of three steps. First, three-phase induction motor currents are measured with three current sensors and transferred to a computer by means of a data acquisition board. Then feature patterns are obtained to identify the fault using current signals. Second, the fault related features are extracted from three-phase currents. Finally, an adaptive artificial immune system (AAIS) is applied to detect the broken rotor bar and stator faults. The proposed method was experimentally implemented on a 0.37?kW induction motor, and the experimental results show the applicability and effectiveness of the proposed method to the diagnosis of broken bar and stator faults in induction motors.     

Thermo-oxidative stability studies on some new generation API group II and III base oils

Due to the increasing demand for highly saturated (group II and III) base oils for use in specialty lubricant application, it is necessary to obtain a clear picture of the base oil molecular distribution. These oils are more stable to oxidation and exhibit superior performance-based characteristics as compared with group I type base oils. With the aromatic content reaching a minimum value, saturated molecules control most of the physical properties in these oils. Molecular structure based characterization developed for conventionally refined base oils will be inadequate to address all the structural diversities of these base fluids. In this study, results from thin film micro oxidation (TFMO) and pressure differential scanning calorimetry (PDSC) were discussed in terms of the quantitative ¹³C NMR (inverse gated, CSE, GASPE) data. Correlations obtained with physical properties (e.g. viscosity), oxidation (evaporation, insoluble deposit) and structural data indicate the significance of base oil's saturate hydrocarbon structures in influencing most of the performance properties.     

Properties of rubberized concretes containing silica fume

A test program was carried out to develop information about the mechanical properties of rubberized concretes with and without silica fume. Two types of tire rubber, crumb rubber and tire chips, were used as fine and coarse aggregate, respectively, in the production of rubberized concrete mixtures which were obtained by partially replacing the aggregate with rubber. Six designated rubber contents varying from 2.5% to 50% by total aggregate volume were used. The concretes with silica fume were produced by partial substitution of cement with silica fume at varying amounts of 5–20%. Totally, 70 concrete mixtures were cast and tested for compressive and splitting tensile strengths, and static modulus of elasticity in accordance to ASTM standards. The design strength level ranging from 54 to 86 MPa was achieved using water–cementitious material (w/cm) ratios of 0.60 and 0.40. Test results indicated that there was a large reduction in the strength and modulus values with the increase in rubber content. However, the addition of silica fume into the matrix improved the mechanical properties of the rubberized concretes and diminished the rate of strength loss. Results also revealed that a rubber content of as high as 25% by total aggregate volume might be practically used to produce rubberized concretes with compressive strength of 16–32 MPa.     

A potential biodegradable rubber—Viscoelastic properties of a soybean oil-based composite

Scientists are more and more interested in biodegradable materials owing to their environmental advantage. We investigated viscoelastic properties of a newly developed biomaterial made from epoxidized soybean oil (ESO). ESO cross-linked by triethylene glycol diamine exhibited viscoelastic solid properties. The storage modulus (G′) was 2×10⁴ Pa over four frequency decades. The phase angles were 14–18°. Stress relaxation measurements showed that there was no relaxation up to 500 s. From the plateau modulus we estimated that the M.W. of this cross-linked soybean oil was on the order of 10⁵. The composites of cross-linked ESO with three different fibers had 50 times higher elasticity (G′) than those without fiber. Phase shifts were the same as those of cross-linked oil without fibers, but the linear range of rheological properties was much narrower than that of the material without fibers. All these results indicated that this new biopolymer made from soybean oil exhibited strong viscoelastic solid properties similar to synthetic rubbers. These rheological properties implied that this biomaterial has high potential to replace some of the synthetic rubber and/or plastics.