Fractionation and analysis of fluorescent products of lipid peroxidation

The fluorescence excitation spectrum of model conjugated Schiff base compounds that arise from the reaction of malonaldehyde with amino acids was shown to contain a maximum at 260–280 nm in addition to the previously observed maximum at 350–390 nm. Excitation at either maximum results in emission at a single maximum at 440–480 nm. The excitation and emission maxima of the model fluorescent compounds, together with the characteristic reductions in fluorescence intensity caused by alkaline pH or heavy metal coordination, provide criteria with which to examine lipid peroxidation products for the presence of the conjugated Schiff base fluorophore. Silicic acid column chromatography and silica gel thin layer chromatography were employed to fractionate the fluorescent products of model lipid peroxidation systems and of rat testicular lipid soluble extracts. These products contained large families of compounds whose fluorescence characteristics were the same as those of the Schiff base floorophores. The fractionation methods used enabled more thorough fluorescence characterization of many of the products of lipid peroxidation, but the fluores-cence criteria available do not provide definitive proof of structure.     

Comparative analysis of mass transfer at vibrating electrodes

The application of oscillatory flows to electrochemical processes was found to increase the rate of mass transfer and improve the quality of deposit. Various mechanisms to which this phenomenon is attributable are discussed and expressions for the average rate of mass transfer, resulting thereof, are derived. Comparison with experimental data indicates that the stretched-film concept, although an oversimplification of the physical situation, is most successful in correlating the data.Nomenclature A Amplitude of oscillatory motion (cm) - c Concentration of the diffusing species (g mol cm^–3) - D Diffusivity (cm² s^–1) - F Frequency of oscillation (Hz) - k Instantaneous mass transfer coefficient (cm s^–1) - ¯k _vib Time-average vibratory mass transfer coefficient (cm s^–1) - L Length of active area (cm) - S Velocity gradient at solid-liquid interface (cm s^–1 cm^–1) - u Oscillatory velocity of fluid layers adjacent to the electrode (cm s^–1) - _u Rel Relative velocity between the electrode and the bulk of the fluid (cm s^–1) - v Relative velocity between the electrode and the fluid layers adjacent to it (cm s^–1) - W Width of active area (cm) - x Distance along the surface of the electrode (cm) - z Distance perpendicular to the surface of the electrode (cm) - Dimensionless distance=z(S/9Dx)^1/3 - Dimensionless distance=z ²/2 - Kinematic viscosity of the electroyte (cm² s^–1) - Angular frequency=2F     

Degradation of cyanobacteria toxin by advanced oxidation processes

Advanced oxidation processes (AOPs) using O(3), H(2)O(2), O(3)/H(2)O(2), O(3)/Fe(II), and Fenton treatment were investigated for the degradation of aqueous solutions of cyanobacteria. The effects of concentration of reactants, temperature, and pH on toxins degradation were monitored and the reaction kinetics was assessed. O(3) alone or combined with either H(2)O(2) or Fe(II) were efficient treatment for toxins elimination. A higher toxin oxidation tendency was observed with Fenton reaction; total toxins degradation (MC-LR and MC-RR) was achieved in only 60s. The ozonation treatment was successfully described by second-order kinetics model, with a first-order with respect to the concentration of either ozone or toxin. At 20 degrees C, with initial concentration of MC-LR of 1mg/L, the overall second-order reaction rate constant ranged from 6.79 x 10(4) to 3.49 x 10(3)M(-1)s(-1) as the solution pH increased from 2 to 11. The reaction kinetics of the other AOPs (O(3)/H(2)O(2), O(3)/Fe(II), and Fenton), were fitted to pseudo first-order kinetics. A rapid reaction was observed to took place at higher initial concentrations of O(3), H(2)O(2) and Fe(II), and higher temperatures. At pH 3, initial concentration of toxin of 1mg/L, the pseudo first-order rate constant, achieved by Fenton process, was in order of 8.76+/-0.7s(-1).     

Dehydration by Successive Pressure Drops for Drying Paddy Rice Treated by Instant Controlled Pressure Drop

The aim of the present work was to study the application of the dehydration by successive pressure drops (DDS) process to different varieties of paddy rice initially treated by the instantaneous controlled pressure drop (DIC), which is a high-temperature, short time postharvest treatment (moisture content about 20-25% dry basis) and takes less than 30 s. DIC paddy rice is dried by DDS in a relatively short time and a high milling quality is obtained (12-13% db in about 2 h). The final rice is white, easily distinguishing it from the standard parboiled one. Without a tempering period, DDS rice has less than 3% of broken grains, with a high organoleptic quality (preservation of the natural aroma with a firm and non-sticky texture), and the cooking time of both brown (whole) and white DIC rice is very short (15 and 7 min, respectively).     

Performance of feed‐forward linearizers of power amplifiers in OFDM systems under complex gain errors

Adaptive feed‐forward (FF) linearization schemes of power amplifiers provide high distortion cancelation and adjacent channel power ratio (ACPR) reduction. However, FF schemes are very sensitive to imbalances in the circuit parameters used to achieve signal cancelation. In this paper, an FF linearization circuit is analyzed using the orthogonalization of the nonlinear model and considering the effects of complex gain errors in the signal and distortion cancelation loops on the overall performance of the FF linearizer. The analysis enables the effective signal‐to‐distortion ratio (SDR) and ACPR to be estimated from FF circuit model. It is shown that complex gain errors in the distortion cancelation loop have a more significant effect on in‐band distortion than out‐of‐band distortion, which means that the design of FF linearizers based on ACPR improvement is not optimal. Copyright © 2015 John Wiley & Sons, Ltd.     

Weakly Conjugated Hybrid Zinc Porphyrin Sensitizers for Solid‐State Dye‐Sensitized Solar Cells

Molecularly engineered weakly conjugated hybrid porphyrin systems are presented as efficient sensitizers for solid‐state dye‐sensitized solar cells. By incorporating the quinolizino acridine and triazatruxene based unit as the secondary light‐harvester as well as electron‐donating group at the meso‐position of the porphyrin core, the power conversion efficiencies of 4.5% and 5.1% are demonstrated in the solid‐state devices containing 2,2′,7,7′‐tetrakis (N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spiro bifluorene as hole transporting material. The photovoltaic performance of the triazatruxene donor based porphyrin sensitizer is better than that of the previously published porphyrin molecules exhibiting strongly conjugated push–pull structure. The effect of molecular structure on the optical and electrochemical properties, the dynamics of charge extraction, as well as the photovoltaic performance are systematically investigated, which offers a new design strategy for further refinement of porphyrin molecules.     

Wadi natural aggregates in Western Saudi Arabia for use in Concrete

The engineering properties (physical and mechanical) of Wadi Al-Yamanyah natural aggregate were determined. In addition, correlations between these properties have been made. This Wadi is located in the central part of the western province of Saudi Arabia between Makkah and Taif. The aggregate along the Wadi was studied and five major rock units were identified namely granite, granodiorite, gneiss amphibole schist and andesite. These rocks were classified into three aggregate groups: basalt, granite and schist. Ninety aggregate samples were carefully collected and tested. The results of overall aggregate properties pointed out that Wadi Al-Yamanyah natural mixed aggregate is within the international and local specification limits and it is suitable for use in concrete. The estimated volume of natural aggregate in the Wadi is about 2 million m³. The engineering properties of individual aggregate groups were also determined. Basalt and schist groups, which represent about 65% of the Wadi natural aggregate, were of higher quality and low degree of alterations than the granite group. Direct and inverse relationships were found between some physical and mechanical properties for mixed natural aggregate of Wadi Al-Yamanyah with the exception of elongation index (I_E). It is recommended to use the derived equations, representing the best fit between the aggregate properties, with care and for rough estimation only.     

Synthesis and properties of starch-graft-acrylic acid/Na-montmorillonite superabsorbent nanocomposite hydrogels

The graft copolymerization of acrylic acid (AA) onto starch was carried out with monomer/starch weight ratio = 1.5. Cerium ammonium nitrate (CAN) and N,N′-methylenebis acrylamide (NMBA) were used as initiator and crosslink agent, respectively. Na-montmorillonite was used as nanoparticles. Starch-graft-acrylic acid/Na-MMT (S-g-AA/MMT) nanocomposite hydrogels were characterized by X-ray diffraction (XRD) and FTIR analysis. The effect of Na-MMT content in nanocomposite hydrogels on the swelling behavior was investigated. Increasing the Na-MMT/monomers ratio up to 1% causes an increment in water absorbency, which indicates that Na-MMT can improve the ability of water absorbency but further increase of Na-MMT causes a decrease in water absorbency. In addition, we describe the removal of safranine T from aqueous solutions using S-g-AA/MMT nanocomposite hydrogels. Effects of various parameters such as treatment time, initial dye concentration, and amount of the Na-MMT were investigated. The Freundlich equations were used to fit the equilibrium isotherms. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,viscosity behavior,and interactions with a surfactant of some amphiphilic copolymers of diallyldimethylammonium chloride and diallyldodecyl‐ or diallyloctadecyl‐ammonium chloride

The compatibilization of an immiscible polymer system polystyrene/poly(4-vinylpyridine) has been induced by the introduction of carboxylic acid groups within the polystyrene chains. Poly(styrene-co-cinnamic acid), PSCA, copolymers were used to prepare blends and complexes with poly(4-vinylpyridine), P4VP, and in a second time with poly(styrene-co-4-vinylpyridine), PS4VP, copolymer in order to reduce the density of the interacting groups. The miscibility of the systems has been ascertained by DSC, which revealed that both blends and complexes exhibit a single glass transition temperature indicating their single phase nature. The T_gs of the complexes of PS4VP with PSCA15, containing 15 mol % of cinnamic acid content, were higher than those of the corresponding blends indicating that stronger interpolymer interactions were developed in the complexes. Furthermore, the application of the Kwei equation suggested that P4VP interacts more strongly with PSCA15 than does PS4VP. FTIR spectra revealed the development of hydrogen bonding within the PS4VP/PSCA system and both hydrogen bonding and ionic interaction in the P4VP/PSCA blends whereas the same interactions were expected in both systems. This observation confirmed the stronger ability of P4VP to interact with PSCA copolymer. The viscosimetric study showed both positive and negative deviations of the reduced viscosity of the blends from the additivity law confirming the presence of specific interactions within the blend solutions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Differential recurrent neural network based predictive control

In this paper an efficient algorithm to train general differential recurrent neural network (DRNN) is developed. The trained network can be directly used in the nonlinear model predictive control (NMPC) context. The neural network is represented in a general nonlinear state-space form and used to predict the future dynamic behavior of the nonlinear process in real time. In the new training algorithms, the ODEs of the model and the dynamic sensitivity are solved simultaneously using Taylor series expansion and automatic differentiation (AD) techniques. The same approach is also used to solve the online optimization problem in the predictive controller. The efficiency and effectiveness of the DRNN training algorithm and the NMPC approach are demonstrated through a two-CSTR case study. A good model fitting for the nonlinear plant at different sampling rates is obtained using the new method. A comparison with other approaches shows that the new algorithm can considerably reduce network training time and improve solution accuracy. The DRNN based NMPC approach results in good control performance under different operating conditions.