A new electrochemical biosensor for hydrogen peroxide using HRP/AgNPs/cysteamine/p-ABSA/GCE self-assembly modified electrode

An electrochemical hydrogen peroxide biosensor was designed by immobilizing horseradish peroxidase (HRP) on Ag nanoparticles/cysteamine/p-aminobenzene sulfonic acid/glassy carbon (GC) electrode. Ag nanoparticles can act as tiny conduction centers on electrodes that adsorb redox enzymes, facilitating the transfer of electrons with no requiring any loss of biological activity. The forerunner film was first electropolymerized on the glassy carbon electrode with p-aminobenzene sulfonic acid (p-ABSA) by cyclic voltammetry. The cysteamine (CA) was bound on the surface of the film by electrostatic force, then Ag nanoparticles were immobilized on the cysteamine monolayer, and lastly HRP was adsorbed onto the surfaces of the Ag nanoparticles. A dramatic decrease in the overvoltage of H₂O₂ was observed with improved sensitivity, which makes the modified electrodes of great promise for oxidase-based amperometric biosensors. The biosensor responded to H₂O₂ in the linear range from 1.2×10⁶ mol/L to 9.8×10³ mol/L with a detection limit of 1.1×10⁸ mol/L. Moreover, the obtained biosensor exhibited good accuracy and high sensitivity.     

Development of an algorithm for optimum control process to compensate the nozzle wear effect in cutting the hard and tough material using abrasive water jet cutting process

In the process of abrasive water jet cutting, the change of nozzle diameter, due to nozzle wearing throughout cutting process, causes a decrease in surface quality and an increase in kerf width. In this paper, a series of experiments have been done to determine the effect of process parameters and the results show that traverse speed and nozzle diameter are significant parameters on the kerf quality and geometry, and a control program algorithm is suggested to compensate the effect of nozzle diameter increase on cut surface quality and kerf width and the control program creates an offset with required amount in nozzle path.     

Optimisation of a chromatographic procedure for determining biogenic amine concentrations in meat and meat products employing a cation-exchange column with a post-column system

The aim of this study was to optimise and validate a chromatographic method for determining biogenic amine (BA) in meat and meat products separated by a cation-exchange column with a post-column system, using o-phthalaldehyde as a derivatising reagent. A perfect separation of nine BA (tyramine, histamine, β-phenylethylamine, putrescine, cadaverine, tryptamine, agmatine, spermidine and spermine) was obtained in 22 min. The conditions were: column Tª 40 °C and coil Tª 45 °C, pump flow rate 0.8 mL/min, pH phase A 6.33, B 5.63 and C 13.00. The method was adjusted linearly in a range of 0.10–12 mg/L with a correlation coefficient superior to 0.998. Detection and quantification limits were between 0.03–0.10 mg/L and 0.10–0.20 mg/L, respectively. Precision studies were satisfactory, with RSD less than 2% and meat extracts recovering over 98%. This method showed an appropriate, precise, fast and versatile procedure for determining nine BA simultaneously in different meat product matrices.     

The effect of Na+ montmorillonite (NaMMT) nanoclay on thermal properties of medium density fiberboard (MDF)

In this study, the potential use of nanotechnology was evaluated to improve the thermal properties of medium density fiberboard (MDF). For this, Na⁺ montmorillonite (NaMMT) nanoclay was added to urea formaldehyde resin to produce MDF. In order to characterize the structure of the MDF, X-ray diffraction (XRD) and SEM observation were performed, and the thermal properties were examined using thermogravimetric analysis (TGA), differential thermal analysis (DTA), thermal conductivity test and fire test. Characterization of the MDFs shows that dispersed and exfoliated structures were generated by the hot press. The X-ray diffraction confirmed the suitable exfoliation of NaMMT in the MDFs containing NaMMT. The SEM images of NaMMT-added boards showed a suitable dispersion of NaMMT through the MDF. The results of thermal tests indicated a desirable effect of NaMMT on thermal-oxidative stability and thermal conductivity of MDF.     

Chemical compositions of the marine algae Gracilaria salicornia (Rhodophyta) and Ulva lactuca (Chlorophyta) as a potential food source

BACKGROUND: The nutritional compositions of two edible red (Gracilaria salicornia) and green (Ulva lactuca) seaweeds were determined to evaluate their possible uses as potential food ingredients. RESULTS: In general, these species contained limited amounts of lipids ranging between 0.99 and 2.00 g 100 g^?1 dry weight) and considerably high amount of minerals, especially in G. salicornia (38.91 g 100 g^?1 d.w.). The crude protein values varied between 9.58 and 10.69 g 100 g^?1 d.w. Amounts for total amino acids were 889.78 ± 22.64 mg g^?1 protein d.w. in G. salicornia and 543.3 ± 15.14 mg g^?1 protein d.w. in U. lactuca. The most abundant fatty acids were C12:0, C16:0, C20:4 ω6 and C22:5 ω3, in addition to C18:1 in G. salicornia. Both seaweed species were balanced sources of ω3 and ω6 fatty acids with a ratio of ω6/ω3 that varied between 1.2 and 1.17. Between the seaweeds investigated, high levels of K (2414.02‐11 380.06 mg 100 g^?1 d.w.) were observed and the amounts of Ca, Na and Fe were higher than those reported for land plants. CONCLUSIONS: Thus, G. salicornia and U. lactuca may be utilised as value‐added products for human nutrition purposes. Copyright © 2012 Society of Chemical Industry     

Seasonal prevalence of Vibrio species in retail shrimps with an emphasis on Vibrio parahaemolyticus

Seasonal prevalence of Vibrio species in shrimp samples from retail outlets in the South-western part of Iran was studied. A total of 300 samples were analyzed (75 samples in each season). Special attention was paid to the prevalence of total and pathogenic Vibrio parahaemolyticus. All the TCBS isolates were first identified to the genus level with PCR and then identified to the species level using a battery of biochemical reactions and tests. To investigate the pathogenicity of the isolated V. parahaemolyticus, multiplex PCR (tl, tdh and trh genes) was performed. Vibrios were detected during the whole investigation period, depending on the sampling season. They were detected in 18.6% of the winter samples, 64% of the spring samples, 70.6% of the summer samples and 41.3% of the autumn samples. Vibrio calviensis and Vibrio alginolyticus were dominant in samples of different seasons, with the average prevalence of 18.6% and 17.6%, respectively. V. parahaemolyticus was found in 4.0% of the winter samples, 13.3% of the spring samples, 18.6% of the summer samples and 8% of the autumn samples. During the period of this study, two tdh-positive strains were isolated, while no trh-positive V. parahaemolyticus strain was detected in samples of different seasons.     

Effect of Geometry, Joule Heating, and Critical Current on the Responsivity of MOD Superconducting Transition Edge Sensors

By fabrication of several bolometric detectors on the YBCO film made of Metal-Organic Deposition (MOD) and the effect of pattering and film parameters on the optical responsivity of transition edge sensors is investigated. The low cost nonfluorine (MOD) method has been applied to fabricate YBCO thin films with different patterning parameters. The measurement results of the optical responsivity versus modulation frequency up to 100 KHz for these devices are reported.     

Preparation and antibacterial activity of Ag/SiO2 thin film on glazed ceramic tiles by sol–gel method

In the present study, silver-doped silica thin films on glazed surface of ceramic tiles were well prepared by sol–gel method to achieve antibacterial activity. Thermal treatment was done in the air at 1100 °C for two hours. The Ag/SiO₂ thin films were investigated through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and wavelength dispersive spectrometry (WDS). Atomic absorption spectroscopy (AAS) was used for the quantitative determination of the silver ion concentration being released from Ag/SiO₂ films over a 24 day period. The antibacterial effects of Ag/SiO₂ thin films against Escherichia coli and Staphylococcus aureus were also examined. From the analysis results, it was found that high temperature treated coating consists of two phases of SiO₂ and Ag based on the trapping of the Ag phase in the silica matrix. The presence of Ag elements on the surface of the coated tiles, were also observed. Thermal treatment at high temperatures caused sharp XRD peaks and high crystallinity in this system. Ag⁺ ions were released constantly and the mean release rate (±SD) was 0.104 ±0.01 μg/ml during 24 days. Coating films exhibited an excellent antibacterial performance against both bacterium.     

A case study on suspended particles in a natural gas urban transmission and distribution network

Suspended particles in the natural gas transmission and distribution network of the city of Kerman, Iran were investigated. Particle concentration and size distribution were measured in different locations of the natural gas pipeline network. Particle samplings were carried out in two seasons: summer, when there is the lowest consumption, and winter, when there is the highest consumption of natural gas. Additional particle characterization was carried out by scanning electron microscopy coupled with energy dispersion X-ray (SEM/EDX) and X-ray diffraction(XRD) analyses. Particle concentration was found to be significantly higher in winter as compared to summer. The range of particle concentrations in summer was from 0.12 mg/Nm³ at the end of the pipeline to 4.7 mg/Nm³ at the network entrance, and from 0.30 mg/Nm³ to 22.1 mg/Nm³ in winter. Particle size distribution showed a higher frequency of smaller particles in winter than in summer. Larger particles were more likely to exist at the network entrance as compared to the exit. The average particle size ranged from 181 μm at the network end to 253 μm at the entrance in summer, and from 74 μm to 209 μm in winter. Particle characterization confirmed the presence of corrosion products in the suspended particles.