Determination of aflatoxins in animal feeds by HPLC with multifunctional column clean-up

A reversed-phase HPLC method with fluorescence detection for the determination of the aflatoxins B1, B2, G1 and G2 in 42 animal feeds, comprising corn (16), soya bean meal (8), mixed meal (13), sunflower, wheat, canola, palm kernel, copra meals (1 each) was carried out. The samples were first extracted using acetonitrile:water (9:1), and was further cleaned-up using a multifunctional column. Optimum conditions for the extraction and chromatographic separation were investigated. By adopting an isocratic chromatographic system using a mobile phase comprising acetonitrile:methanol:water (8:27:65, v/v/v), the separation of the four aflatoxins was possible within 30 min. Recoveries for aflatoxins B1, B2, G1 and G2 were 98 ± 0.7%, 95 ± 1.0%, 94 ± 3.6% and 97 ± 4.3%, respectively. The results show that eight samples (19%) were contaminated with aflatoxins, ranging from 6.5 to 101.9 ng g^?1. Total aflatoxin levels in three samples exceed the legal limits of many countries of 20 ng g^?1.     

Habituation as a mechanism of reduced aggression between neighboring territorial male bullfrogs (Rana catesbeiana).

Territorial animals often exhibit relatively lower levels of aggression toward familiar territorial neighbors than toward strangers. Habituation to a neighbor or its communication signals has been proposed to account for this reduced aggression between adjacent territorial neighbors. The authors asked whether discrimination between neighbors and strangers by territorial male bullfrogs (Rana catesbeiana) could result from habituation of the aggressive response to repeated presentations of the acoustic communication signals of a simulated new neighbor calling from an adjacent territory. In 3 field playback experiments, the authors found evidence for 5 response characteristics that operationally define habituation. Moreover, aggressive response decrements persisted between nights of chorusing and were specific to an individually distinct property of male advertisement calls. The authors suggest that reduced aggression between neighboring territorial male bullfrogs could result from long-term, stimulus-specific habituation to the advertisement calls of a new neighbor. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Micro powder injection moulding of alumina micro-channel part

A feedstock consisting of submicron alumina powder and a formulated binder, was developed to fabricate alumina micro-channel part by micro powder injection moulding. During small scale-mixing, the mixing torques of feedstocks with four different powder loadings were used to establish a suitable powder loading. The thermal and rheological properties of the selected feedstock were examined and used to establish conditions for large scale mixing, debinding and injection moulding. The micro-channel parts were pressureless sintered at different temperatures. The results showed that the moulded, debound and sintered micro-channel parts had good shape retention. The dimensions of the micro-channel part changed with the different processing steps. High densification of the micro-channel parts was achieved at sintering temperatures of 1350 °C and above. Above 1350 °C, the grain grew significantly with increasing the sintering temperatures and thus it led to a decrease in the microhardness.     

Ultrasound-assisted extraction of natural antioxidants from betel leaves (Piper betle): Extraction kinetics and modeling

Present study investigated the extraction kinetics of antioxidants from Piper betle by ultrasound-assisted extraction for three extraction variables: temperature, solute to solvent ratio and ethanol concentration. Based on the results of yield, total phenolic content and antioxidant activity, the optimum results were obtained at 50°C, 1:20 g/mL and 80% ethanol, respectively. Statistical coefficients of R² ≥ 0.961 and RMSE ≤ 0.508 for two-site kinetic model confirm the use of proposed models for simulation and prediction purpose. Comparison with ascorbic acid and butylated hydroxytoluene solidifies the use of Piper betle as feasible source of natural antioxidants. The presence of hydroxychavicol and eugenol was affirmed by high-performance liquid chromatography assay.     

Polyoxyethylene esters of fatty acids: an alternative synthetic route for high selectivity of monoesters

Esterification reaction of fatty acids with polyoxyethylenes has been studied in the presence of solid acid catalysts and the results are compared with those obtained with a classical homogeneous catalyst, p-toluene sulphonic acid. Solid acid catalysts showed very high selectivities for monoesters even under less favorable reaction conditions of 1:1 molar ratios of oleic acid to PEG. Excess amount of PEG is normally required to ensure high selectivity for monoesters in the presence of homogeneous catalysts. The yields for monoesters given by heterogeneous catalysts such as zeolites, HPA and nafion were comparable to that with p-toluene sulphonic acid after 24 h of reaction. Results suggest that solid acid catalysts are potential catalysts for selective synthesis of monoesters from oleic acids and PEG even under severe reaction conditions. A screening study of different solid acid catalysts showed ZSM-5, zeolite-β, and nafion to be better catalysts than zeolite USY and mordenite, the former giving higher selectivity and yield to monoesters. The results suggest that the most important parameters in optimization catalyst performance for monoesters production is the acid strength and less so on other properties such as shape selectivity and concentration of active sites.     

Poisson's ratio and volume change accompanying deformation of randomly oriented electrospun nanofibrous membranes

ABSTRACT

The present work focuses on the determination of volume change accompanying deformation and Poisson's ratio for electrospun nanofibrous membranes. For this purpose, polyurethane (PU) is considered for the fabrication of electrospun nanofibrous membranes. Three different sample thicknesses are fabricated. Following this, surface morphology analysis and fibre orientation analysis are conducted to investigate the variation of properties between electrospun PU membranes of different thicknesses. Subsequently, PU specimens are subjected to uniaxial extension test where the changes in sample width and thickness are recorded as a function of applied strain. Volume changes are computed while further analysis on the relationship between transverse strains and axial strain provided the values of Poisson's ratio. For all three electrospun PU samples investigated, significant volume changes are observed while the in-plane Poisson's ratio is found to be around 0.55. However, the out-of-plane Poisson's ratio of electrospun PU membranes are not classical and remains undetermined.     

Flow rate impact on the performance of immobilized nanoFeCu for sewage treatment and its reusability

Ammonia pollution is a global issue, and it endangers human and aquatic life. The role of nanoFeCu in oxidizing ammonia has been identified, but its practicality and performance on the pilot scale are still unclear. This study was conducted to investigate immobilized nanoFeCu's performance in terms of ammonia, nitrate, nitrite, biological oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solid (TSS) by using sewage as feed. The effect of sewage flow rate was studied to determine the optimum operating condition of a pilot-scale reactor. The reusability test was conducted to address sustainability concerns. The nanoFeCu was synthesized, immobilized in polymer clay, and placed into the reactor filled with sewage at a varied flow rate of from 210 to 1200 mL/min. Results showed that a higher sewage flow rate increased the ammonia removal rate within a shorter time but exhausted the immobilized nanoFeCu at a higher rate. Nitrate, nitrite, and TSS have a similar removal trend as ammonia. 800 mL/min was identified as the optimum flow rate with effluent ammonia concentration below 10 ppm in 9 h and maintained for 12 h. A reusability study showed that immobilized nanoFeCu could be reused for at least 10 successive cycles. The stability and performance of immobilized nanoFeCu suggested that it could be an alternative to treat sewage wastewater for real-life applications.