Electrorheological properties of kaolinite,polyindole, and polyindole/kaolinite composite suspensions

In this study, polyindole (PIN) and polyindole/kaolinite (PIN/KAO) composite were synthesized by free radical polymerization using FeCl₃ as an initiator. Average particle sizes (d₅₀) of PIN and PIN/KAO composite were determined by dynamic light scattering (DLS) as 7.2 and 6.2 μm, respectively. The samples were characterized by FTIR, elemental analysis, DSC/TGA and SEM measurements. Suspensions of KAO, PIN, and PIN/KAO composite were prepared in silicone oil (SO) and the sedimentation stabilities were determined. Electrorheological (ER) properties of these suspensions were studied as a function of dispersed phase concentration, shear rate, shear stress, and temperature; and yield stresses and excess shear stresses determined. Further, dielectric properties of KAO, PIN, and PIN/KAO composite were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Separation of gas and organic/water mixtures by MFI type zeolite membranes synthesized in a flow system

MFI type zeolite membranes were synthesized in a recirculating flow system at 95 °C where the synthesis solution was flown over the tubular α-alumina supports. The performance of the membranes for the separation of binary gas mixtures and alcohol/water liquid mixtures was investigated. A membrane synthesized by two consecutive synthesis steps had a separation selectivity of 15 and 11 for equimolar mixtures of n-C₄H₁₀/CH₄ and n-C₄H₁₀/N₂ at 200 °C, respectively. The membrane selectively permeated large n-C₄H₁₀ over small CH₄ and N₂, suggesting that the separation is essentially adsorption-based and the membrane has few nonselective intercrystalline pores. The selectivities in the pervaporation separation of 5% ethanol/95% water mixture were 43 and 23 with permeate fluxes of 0.2 and 1.9 kg/m² h at 25 and 85 °C, respectively. The separation performance of membranes showed that MFI type membranes prepared in a recirculating flow system can be used both in the separation of gas and liquid mixtures.     

Effect of osmotic pretreatment and microwave frying on acrylamide formation in potato strips

BACKGROUND: The presence of acrylamide, a probable carcinogen, is currently a major concern relating to the consumption of fried products. Therefore, recent frying studies have focused on ways of reducing the acrylamide content. The main objective of the present study was to determine the effects of microwave frying and osmotic treatment prior to frying on acrylamide formation in potato strips. RESULTS: Potatoes fried using 400 W microwave power for 1.0 min had an 87.85% lower acrylamide content than potatoes fried conventionally for 4.5 min (i.e. an 81.82% reduction in frying time) but a comparable moisture content. The acrylamide content of fried potatoes treated osmotically prior to both microwave and conventional frying was found to be lower than that of fried potatoes not pretreated osmotically. However, the reduction in acrylamide content was lower when osmotic treatment was applied before microwave frying. CONCLUSION: As a result of this study, it was concluded that microwave frying can be an alternative to conventional frying. Copyright © 2007 Society of Chemical Industry     

Characterization of water distribution in xanthan-curdlan hydrogel complex using magnetic resonance imaging, nuclear magnetic resonance relaxometry, rheology, and scanning electron microscopy

Abstract: Xanthan‐curdlan hydrogel complex (XCHC) has been shown capable of retaining moisture up to 5 freeze‐thaw cycles (FTCs); however, moisture distribution in the complex in relation to the hydrogel composition and structure remains uncharacterized. In the present study, magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) relaxometry, rheology, and scanning electron microscopy (SEM) were used to examine the effect of water distribution and interaction with 2.0% aqueous solutions of xanthan, curdlan, and XCHC consisting of equal amounts of both polysaccharides. A gel structure with an indication of syneresis was clearly seen in the MR image of curdlan alone, whereas the distribution of protons throughout xanthan and XCHC samples remained homogeneous and showed no detectable syneresis. The three‐dimensional network, indicated by frequency sweeps, of curdlan was responsible for curdlan's gel structure. The frequency sweep and slope of the storage modulus (G′) of XCHC was significantly closer to curdlan with higher elasticity and less dependency upon angular frequency than xanthan alone. The reduction in XCHC dynamic moduli (G′ and G″) compared to curdlan could be attributed to the formation of wavy layers instead of a fully cured three‐dimensional structure. Addition of xanthan to curdlan restricted XCHC spin–spin relaxation time (T₂) to intermediate and slower exchange regimes, namely approximately 110 and 342 ms, respectively, promoting the polymer's interaction with water while inhibiting interpolymer interactions found in curdlan. A 3rd proton pool with the slowest T₂ seen in curdlan was not found in XCHC, correlating to the absence of syneresis. Practical Application: The combination of texture measurements and discrete noninvasive techniques was found capable of providing insightful understanding of water distribution in a gel system. These techniques may be applied to other hydrogel complexes. The XCHC system investigated has the potential to enhance freeze‐thaw stability in frozen food products by minimizing syneresis due to undesirable temperature fluctuations during distribution and consumer application.     

A novel indicator system for catalytic spectrophotometric determination and speciation of inorganic selenium species （Se（Ⅳ）, Se（Ⅵ）） at trace levels in natural lake and river water samples

A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI), and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of Celestine blue by sodium sulfide at pH 7.0 phosphate buffer. The fixed-time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the two calibration graphs are linear with a good correlation coefficient in the range 2–20 and 20–200 μg·L⁻¹ of Se(IV) for the fixed-time method at 30°C. The experimental and theoretical detection limits of the developed kinetic method were found to be 0.21 and 2.50 μg·L⁻¹ for the fixed-time method (3 min). All of the variables that affect the sensitivity at 645 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se(IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus as long as chelating agents of thiourea and thiosulphate. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The relative standard deviations (RSDs) for ten replicate measurements of 2, 10, and 20 μg·L⁻¹ of Se(IV) change between 0.35% and 5.58%, while the RSDs for ten replicate measurements of 3, 6, and 12 μg·L⁻¹ of Se(VI) change between 0.49% and 1.61%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. The Se(IV), Se(VI), and total inorganic selenium in lake and river water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).     

Annealing effect on the characteristics of La0.67Sr0.33MnO3 polycrystalline thin films produced by the sol–gel dip-coating process

The effect of annealing temperature on selected characteristics of polycrystalline La_0.67Sr_0.33MnO₃ films, which have been produced on quartz substrates, was investigated. X-Ray powder diffraction patterns showed that the phase formation started at 873 K and all the films had perovskite structure. By increasing the annealing temperature, the lattice parameters were decreased. Scanning electron microscope indicated that the film thicknesses were approximately 3 μm and the average grain size of the samples varied between 30–100, 50–110, 70–120, and 100–150 nm for films annealed at 873, 973, 1,073, and 1,173 K, respectively. All the films showed a paramagnetic–ferromagnetic (T_C) and metal–insulator (T_IM) phase transition. The T_C indicated a small variation [from 131 K (S4) to 124 K (S1)] as a function of annealing temperature, whereas the T_IM went down from 212 K (S4) to 110 K (S1), a strong decrease of 102 K. A colossal magneto resistance with magneto resistance ratios of 130, 139, 156, and 163% were observed near T_C and at 6 T magnetic field.     

Combined effect of gamma-irradiation and conventional cooking onAeromonas hydrophila in meatball

Irradiation combined with a conventional cooking procedure was applied to meatball and the effects on bacterial load and inoculatedAeromonas hydrophila were determined. Meatball samples were irradiated by using a⁶⁰Co source at the dose levels of 0, 0.30,0.75,1.50,2.50 kGy and cold stored at 4±1°C for 7 days. Bacterial load and the count ofA. hydrophila decreased when the irradiation dose level increased. A minimum inhibition effect was found at the dose of 0.30 kGy. Irradiation in combination with a conventional cooking procedure was found to be more effective in reducingA. hydrophila and the bacterial load in meatball. This study indicated that a dose of 0.75 kGy was sufficient to destroy approximately 10⁴ cfu/g ofA. hydrophila in meatball.     

Influence of sn‐1,3‐lipase‐catalysed interesterification on the oxidative stability of soybean oil‐based structured lipids

The oxidative stability of structured lipids (SLs) synthesised by specific sn‐1,3‐lipase catalysed interesterification of soybean oil (SBO) with caprylic acid (CA) in a stirred batch reactor was studied. SLs contained considerable amounts of tocopherol (TOH) isomers, although they lost almost 25% of endogenous TOHs during production. The effects of the addition of different TOH homologues (α, β, γ, δ), ascorbyl palmitate (AP, 200 ppm), lecithin (Le, 1000 ppm), butylated hydroxytoluene (BHT, 100 ppm) and butylated hydroxyanisole (BHA, 100 ppm) on the oxidative stability of SLs were investigated. Induction time (IT) of SBO, determined by the Rancimat method, decreased from 8.4 to 5.8 h at 110 °C after the modification. On the other hand, purified SLs and purified SBO had the same IT due to the tocopherol reduction during silica purification. No significant difference was observed between IT of SLs and SLs plus different α‐tocopherol concentrations (50, 100, 150, 200, 300, 500 and 1000 ppm) (P > 0.05). However, the addition of Le and/or AP significantly improved oxidative stability of purified SLs and SBO. The ternary blend containing δ‐TOH, AP and Le had higher IT than ternary blends of α‐TOH, β‐TOH or γ‐TOH. Furthermore, ternary blend containing BHA, AP and Le had higher IT than ternary blends of BHT, AP and Le. In addition, there was an increase in peroxide value (PV), conjugated diene (CD) content and p‐anisidine value (AV) during oxidation of oils at 60 °C. Antioxidant mixtures of α‐TOH (50 ppm) and δ‐TOH (500 ppm) with AP and Le decreased PV, CD and AV effectively. Copyright © 2006 Society of Chemical Industry     

Application of differential evolution algorithm and comparing its performance with literature to predict rock brittleness for excavatability

ABSTRACT

The aim of this study was to estimate brittleness of intact rock by applying differential evolution (DE) algorithm and then to compare the results obtained from the optimum model with literature. For this aim, several models including linear and nonlinear were developed for predicting the brittleness via DE algorithm using the dataset obtained from 48 tunnel cases around the world. Each model were developed using 80% of the dataset as training and 20% of the dataset as testing in random. After that, developed models are compared according to the coefficient of correlations (r ²), computer process unit (CPU), mean-squared error (MSE) and number of function evaluation (NFE) values to choose the best accurate one among them. It is found that the values r ², MSE, NFE and CPU ranged between 0.9385–0.9501, 8.2616–9.938, 7217–11,176 and 4.91–36.22, respectively, with the quadratic model (QM) indicating the best performance. It is concluded that the DE algorithm is itself very powerful tool for estimating the brittleness; however, the QM is superior especially for simulations in which computational time and optimisation is a critical.     

Synthesis and Electrochemical Properties of Carbon-Mixed LiEr_(0.02)Fe_(0.98)PO_4 Cathode Material for Lithium-ion Batteries

LiEr0.02Fe0.98PO4/C composite cathode was synthesized by a simple solution method with polyethylene glycol (PEG) as the reductive agent and carbon source. The effect of erbium doping on the electrochemical behavior of LiFePO4 was studied in this paper. The samples were characterized by X-ray powder diffraction and scanning electron microscopy and the electrochemical properties were investigated by the charge-discharge test. An initial discharge capacity of 149 mAh·g-1 was achieved for the LiEr0.02Fe0.98PO4/C composite cathode with a rate of 0.1 C. The electronic conductivity of Er doped LiFePO4/C was measured as 10-2 S·cm-1. The results indicated that erbium doping did not destroy the lattice structure of LiFePO4 and enlarge the lattice volume. These changes are beneficial to the improvement of the electrochemical performance of the LiFePO4 cathode.