Selective recognition of chloroacetic acids by imprinted polyaniline film

A novel conductive imprinted polyaniline (PAN) film is prepared by adding template during the PAN film preparation. Monochloroacetic acid (MCA) and trichloroacetic acid (TCA) were used as templates. The conductivity of imprinted PAN films was measured by the four‐point probe method. The conductivity changes of imprinted PAN films were compared to reference PAN reflecting the MCA and TCA specific sites on the surface of PAN films. The conductivities were linearly dependent on the template concentrations, and linear calibration curves were obtained in the range 1–30 and 1–40 ppm of the MCA and TCA, respectively. Excellent method reproducibility (standard deviation 0.04 S/cm⁻¹) was observed for the determination of 15 ppm MCA. The effect of various factors on preparation, properties, and recognition effects of the imprinted PAN films was investigated. The best electrical and mechanical properties were obtained with 7 × 10⁻⁴ mmol MCA as a template and doping agent. The measurements are carried out under room temperature, and the maximum conductivities are reached after about 10 and 20 min for reference and imprinted PAN film, respectively. Selectivity experiments were carried out with standard MCA, TCA, and five analogs (dichloro‐, dibromo‐, and monobromoacetic acid) in water. The results exhibited a good selectivity for the templates compared to structurally related compounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A hierarchy of models for analysing sensory data

We propose a hierarchy of models for averaging sensory profile data. The models follow from formulating the data from each assessor in terms of association matrices and considering different strategies for weighted averaging of these matrices. It turns out that two forms of weighting contained within the hierarchy are very close to Generalised Procrustes Analysis (GPA) and Individual Differences Scaling (INDSCAL). The advantage of the current approach is that the methods are not iterative. The methods are illustrated using data based on perception of yoghurts.     

Comparison of cigarette and water pipe smoking among female university students in Egypt.

This study investigated behavioral and sociodemographic factors associated with tobacco use among female university students patronizing water pipe cafes in Cairo, Egypt. We interviewed two groups of female university student smokers (100 and 96 students from a public and a private university, respectively). The interviews took place in nine water pipe cafes near the two universities. A logistic regression model was developed to analyze the relationship between tobacco-related knowledge and beliefs and the choice between smoking water pipe or cigarettes. Among these smokers, 27% smoked cigarettes only, 37.8% smoked water pipe only, and 35.2% smoked both types of tobacco. Most of the water pipe smokers (74.1%) preferred this method because they believe it to be less harmful than smoking cigarettes. More than half of the subjects were encouraged to start smoking by other females (56.6%). Curiosity was a significant factor for initiation (OR = 2.8, 95% CI = 1.3-6.2, p<.01). We found no significant differences between water pipe and cigarette smokers regarding current age, age at initiation, quit attempts, knowledge about the hazards of smoking, wanting to be fashionable, or smoking with friends. About one in four (23.7%) attempted to quit, with health cited as a major reason. An urgent need exists for correction of the misperception among this study population that water pipe smoking is safe and less harmful than cigarette smoking.     

A Simple Control Scheme for the High Performance Z-Source Inverter

In the past decade, the Z-source inverter (ZSI) is successfully developed for many applications. This paper proposes a simple integrated control scheme for the high performance ZSI. A proportional-integral PI controller is used to regulate the voltage of the Z-network capacitor. Moreover, the peak value of the DC-link voltage is controlled by limiting the shoot-through duty ratio. Furthermore, the instantaneous voltage control technique is utilized to retain the sinusoidal shape of the output voltage. A feed-forward signal of the AC voltage is employed to smooth the output voltage. To generate the PWM signals for the ZSI switches, the simple boost control method is utilized which coordinates the operation of different controllers. Extensive digital simulations are conducted to evaluate the dynamic behavior of the proposed control scheme. Moreover, an experimental setup is built to verify the performance of the proposed control scheme for the high performance ZSI.     

Optimization of process parameters for friction stir lap welding of carbon fibre reinforced thermoplastic composites by Taguchi method

Friction stir welding process parameters such as welding speed, rotational speed and tilt angle affect the strength of the weld joint. For maximizing the weld strength, these process parameters must therefore be properly selected and optimized. This study presents an application of Taguchi method to optimize process parameters like welding speed, rotational speed and tilt angle to maximize lap weld tensile-shear strength in 4 mm thick polypropylene composite sheets with 20 wt% carbon fiber. To this end, a L9 orthogonal array of Taguchi method using three factors at three levels was used. Analysis of variance and confirmation tests were conducted. The results indicated that welding speed, rotational speed and tilt angle are respectively the significant parameters affecting the lap weld strength. Optimization results also showed that tensile-shear strength of 6.06 MPa was obtained when welding speed, rotational speed and tilt angle were 25 mm/min, 1250 rpm and 1 degree, respectively.     

A Novel Precursor for Preparation of Silver Nanoparticles: Synthesis, Characterization and Crystal Structure of Ag(PPh3)2(2-pyCOO)

A novel silver complex, Ag(PPh₃)₂(2-pyCOO)·0.5H₂O·0.5C₂H₆O, was prepared from Ag(CH₃COO)(PPh₃)₂ and 2-pyridinecarboxylic acid and after characterization by elemental analysis, infrared, ¹H and ³¹P NMR spectroscopes, and X-ray crystallography, was used as a precursor for the preparation of silver nanoparticles. The silver nanoparticles were obtained by thermolysis of the silver complex at 350 °C in the presence of oleic acid as a surfactant. Resulting silver nanoparticles were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The formation of silver nanoparticles with an average size of 60 nm and spherical morphology was confirmed by SEM. Bulk silver particles were obtained instead of silver nanoparticles when thermolysis of the silver complex was carried out in the absence of oleic acid.     

HYDROMAGNETIC STAGNATION POINT FLOW TOWARDS A POROUS STRETCHING SHEET WITH VARIABLE SURFACE HEAT FLUX IN THE PRESENCE OF HEAT GENERATION

The influence of heat generation or absorption on the steady, two-dimensional flow of an electrically conducting fluid near a stagnation point on a stretching permeable surface with variable surface heat flux in the presence of a magnetic field is investigated. The governing system of partial differential equations describing the problem are converted into highly non-linear ordinary differential equations using similarity transformation. Numerical solutions of these equations are obtained using the fourth-order Runge-Kutta integration scheme with the shooting method. The effects of the heat generation or absorption parameter and the velocity ratio parameter on the velocity and the temperature are displayed graphically and discussed. The numerical values of the local skin-friction coefficient and the local Nusselt number for various values of physical parameters are presented through tables and discussed.     

MHD FLOW AND HEAT TRANSFER IN A VISCOUS FLUID OVER A NON-ISOTHERMAL STRETCHING SURFACE WITH THERMAL RADIATION IN SLIP-FLOW REGIME

The present work is concerned with the effects of surface slip conditions and thermal radiation on an electrically conducting fluid over a non-isothermal stretching surface in the presence of a uniform transverse magnetic field. Similarity transformation is used to transform the partial differential equations describing the problem into a system of nonlinear ordinary differential equations, which is solved analytically. The effects of various parameters on the velocity and temperature profiles as well as on the local skin-friction and the local Nusselt number are discussed in detail and displayed through graphs.     

Evaluation of solvent dearomatization effect in heavy feedstock thermal cracking to light olefin: An optimization study

Response surface method was used to study the effect of aromatic extraction of heavy feedstock in thermal cracking. N-methylpyrrolidone as the solvent performing dearomatization of feedstock was at different temperature and molar solvent to oil ratios. Temperature, flow rate and steam-to-hydrocarbon ratio were in the range of 1,053–1,143 K, 1–2 g/g, and 0.75–1.2 g/min, respectively. From the CCD studies, the effects of flow rate and coil outlet temperature were the key factors influencing the yield of light olefins. Ethylene and propylene yields increased more than 10% by dearomatization. C ₅ ⁺ decreased by 13% on average. Finally, we obtained the single maximum yield of ethylene, propylene, and simultaneous maximum yields for untreated and raffinate.