Showing papers by "University of Tabriz published in 2004"

Photocatalytic degradation of azo dye acid red 14 in water on ZnO as an alternative catalyst to TiO2

Abstract: The degradation of acid red 14 (AR14), commonly used as a textile dye, can be photocatalysed by ZnO. Using advanced oxidation processes (AOPs), zinc oxide appears to be a suitable alternative to TiO2 for water treatment. In this study, a detailed investigation of photocatalytic degradation of acid red 14 is presented. Photodegradation efficiency was small when the photolysis was carried out in the absence of ZnO and it was also negligible in the absence of UV light. The semi-log plot of dye concentration versus time was linear, suggesting first order reaction (K=0.0548 min−1). The effects of some parameters such as pH, amount of photocatalyst, hydrogen peroxide and ethanol concentration were also examined. The addition of proper amount of hydrogen peroxide improved the decolorization, while the excess hydrogen peroxide could quenched the formation of hydroxyl radicals ( OH). As our results indicated that ethanol inhibited the photodegradation of dye, we concluded from the inhibitive effect of ethanol that hydroxyl radicals played a significant role in the photodegradation of dye. This should not undermine direct oxidation caused by positive holes.

Effect of coating time and heat treatment on structures and corrosion characteristics of electroless Ni-P alloy deposits

Abstract: Mild steel was electroless coated with nickel–phosphorus alloy from a bath containing sodium hypophosphite and glycin–citrate complexing agents. The effect of coating time on phosphorus content, thickness, structure and hardness of the deposits were analyzed. Corrosion parameters such as current density, corrosion potential and corrosion rate were obtained from tafel polarization curves and immersion corrosion tests in aerated 3.5% NaCl solution. The X-ray diffraction (XRD) patterns, anodic polarization curves and scanning electron microscopy (SEM) of heat-treated specimens obtained in various coating times were also studied. The X-ray diffraction patterns showed that by changing the coating times, amorphous or crystalline structure could be obtained. The coatings containing 11.1–13.1% phosphorous were amorphous, and showed better corrosion resistance than microcrystalline structure. The heat-treated specimens obtained in different coating time had more hardness and corrosion resistance than unheated samples. According to the polarization studies and scanning electron microscopy images, the heat-treated samples with 10.8 and 10.1% phosphorous show the intergranular corrosion, while the coatings with 11.7 and 12.2% of phosphorus have the least corrosion rate. Immersion corrosion test data at the 4-month interval had good agreement with electrochemical polarization results.

Kinetic modeling of photocatalytic degradation of Acid Red 27 in UV/TiO2 process

Abstract: The photocatalytic degradation of Acid Red 27 (AR27) was investigated using UV radiation in the presence of TiO2-P25 as a function of initial concentration of AR27 ([AR27]0), oxygen concentration ([O2]), TiO2-P25 amount, light intensity (Ia), pH and temperature. The activation energy of the photocatalytic degradation of AR27 was 8.24 kJ mol−1. The photocatalytic degradation rate follows pseudo-first order kinetic with respect to the AR27 concentration. The following rate of decolorization was achieved by kinetic modeling: r AR 27 =5.294 I a exp −8247 RT 0.79 O 2 1+0.79 O 2 4.23 AR 27 1+4.23 AR 27 0 The calculated results obtained from above equation were in good agreement with experimental data. This model predicts the concentration of AR27 during the photodegradation process at different temperatures, light intensities, AR27 and oxygen concentrations.

Tunable phase control for subluminal to superluminal light propagation

Abstract: We demonstrate tunable control of the group velocity of a weak probe pulse from subluminal to superluminal. The model is an extended $\ensuremath{\Lambda}$-type system with two extra control fields and an extra energy level. Phase variation of one of the control fields imparts the tunability in the group velocity along with other interesting spectral behavior in the absorption spectrum.

Cross-species amplification of microsatellite loci in aphids: assessment and application

Abstract: Despite the relative ease of isolating microsatellites, their development still requires substantial inputs of time, money and expertise For this reason there is considerable interest in using existing microsatellites on species from which markers were not cloned We tested cross-species amplification of 48 existing aphid loci in species of the following genera: Aphidinae: Aphidini: Aphis and Rhopalosiphum ; Aphidinae: Macrosiphini: Acyrthosiphum , Brevicoryne , Diuraphis , Illinoia , Macrosiphoniella , Macrosiphum , Metopeurum , Metapolophium , Myzus , Phorodon , Sitobion and Uroleucon and Neuquenaphidinae: Neuquenaphis Our results show cross-species application of known microsatellite loci is a highly promising source of codominant markers for population genetic and evolutionary studies in aphids

Modified Polypyrrole with Tetrasulfonated Nickel Phthalocyanine as a Fiber for Solid-Phase Microextraction. Application to the Extraction of BTEX Compounds from Water Samples

Abstract: Gold wire was coated with polypyrrole (PPY) by electropolymerization and used as a solid-phase microextraction (SPME) fiber. The adsorptive property of the coating was modified by doping with tetrasulfonated nickel phthalocyanine (NiPcTS). The efficiency and reliability of this fiber was investigated for the extraction of BTEX compounds from the headspace of water samples. Monitoring of extraction efficiency was performed by capillary GC-FID. Effects of several factors such as electropolymerization time, salt addition, exposure time and stirring speed on extraction efficiency were studied. The calibration graphs were linear in the range of 0.06 to 50 ng mL−1 and the detection limits for BTEX compounds were 20–50 pg mL−1. Comparing the results obtained using these fibers with results reported in the literature with polydimethylsiloxane (PDMS) fibers shows that under optimum conditions, the detection limits are comparable.

A novel method for synthesis of water-soluble polypyrrole with horseradish peroxidase enzyme

Abstract: A novel water-soluble, conducting polypyr- role was synthesized by horseradish peroxidase (HRP), in the presence of sulfonated polystyrene, as a polyanionic template. The HRP is an effective catalyst for the oxidative polymerization of pyrrole in the presence of hydrogen per- oxide at room temperature. The reaction is sensitive to so- lution pH and it is performed in pH 2 aqueous solutions. Polymerization of pyrrole by this biological route produced a conducting water-soluble polypyrrole for the first time. The reaction is benign and in one pot, and the product requires minimal purification. The reversible redox activity of the polypyrrole displays a hystersis loop with pH changes. FT-IR, UV-vis absorption spectroscopy ,and cyclic voltammetry are used in the characterization of the synthe- sized polypyrrole. These studies confirm the electroactive and conducting form of polypyrrole, similar to that which has been traditionally synthesized, chemically and electro- chemically. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 254 -258, 2004

Modified Pencil Lead as a New Fiber for Solid-Phase Microextraction

Abstract: The efficiency of modified pencil lead as a new fiber for solid-phase microextraction (SPME) has been investigated. Modified pencil lead fibers have been prepared by use of several activation processes, for example heating at 600 °C in the stream of inert gas (He), heating under reflux with concentrated H2SO4 , fusing with NaOH at 400 °C, and activation at 600 °C with water vapor for 60 min. The fibers were used for extraction of trace amounts of polycyclic aromatic hydrocarbons (PAH) from aqueous samples. Monitoring of extracted compounds and quantitative analysis of model samples were performed by capillary GC–FID. The results obtained prove the suitability of the proposed fibers for sampling organic compounds from water. Effects on extraction efficiency of factors such as temperature, salting out, stirring speed, and exposure time were studied. Under optimum conditions and using one fiber for extraction of naphthalene as a typical compound, a relative standard deviation of 5.3% (n=7) was achieved. The calibration plot was linear in the range 50–10,000 pg mL−1 (r=0.9997) and the detection limit was 25 pg mL−1 (S/N=3). This fiber is very stable at high temperature, inexpensive, and can be prepared simply.

A novel method of cold expansion which creates near-uniform compressive tangential residual stress around a fastener hole

Abstract: A recognized way of improving the fatigue resistance of a fastener hole is to introduce compressive tangential residual stress around it. This can be achieved by using a cold expansion method in which an oversized pin or ball is forced through the hole to produce a local plastic region surrounded by an elastic one. Once the pin or ball is removed allowing the elastic region to spring back it results in compressive tangential residual stress around the hole. In practise, however, it is found that such a cold expansion method creates a non-uniform residual stress distribution through the plate thickness and even tensile residual stress can be created at the entrance and exit faces. In this paper a new method of cold expansion is proposed. It uses a tapered pin with a mating tapered split sleeve and creates an almost uniform compressive residual stress around the hole as shown by FE method. Also, fatigue tests were carried out to verify that the method does significantly improve fatigue life. Finally the tangential residual stress distribution and fatigue life improvement of this new method were compared with those of a well-established cold expansion method and it was shown that the new method is more efficient in improving fatigue life.

Comparative study of unsharp masking methods for image enhancement

Abstract: Contrast enhancement by the unsharp masking (UM) approaches are computationally and conceptually the simplest methods. In this paper, the different methods of UM for image enhancement are compared. These algorithms have been tested and compared for the same conditions. The results show that majority of these algorithms are very sensitive to the enhancement factor and are good for sharpening. This factor must be estimated recursively by considering the statistics of neighboring pixel values.

Inverse correlation of secreted frizzled-related protein 4 and beta-catenin expression in endometrial stromal sarcomas.

Abstract: Endometrial stromal sarcomas are rare uterine tumours. Whereas the histology and immunohistochemistry of these tumours are well documented, almost nothing is known about the molecular mechanisms involved in their pathogenesis. To characterize the genes altered in these malignancies, a genome-wide cDNA library was generated by suppression subtractive hybridization and a set of differentially expressed clones was isolated. These were then used to produce custom-spotted cDNA arrays. Genes deregulated in endometrial stromal sarcomas were identified by cDNA array hybridization and were confirmed by quantitative real-time PCR analyses and in situ hybridization. Following cDNA array analysis, more than 300 genes deregulated in endometrial stromal sarcoma were selected and sequenced. Among the most significantly deregulated genes were those of secreted frizzled-related proteins (SFRPs), in particular secreted frizzled-related protein 4 (SFRP4). SFRPs are putative modulators of the Wnt-signalling pathway and play a role in different cellular events including cell proliferation. Compared with normal endometrium, the expression of SFRP4 was decreased in both low-grade endometrial stromal sarcoma (ESS; n = 10) and undifferentiated endometrial sarcoma (UES; n = 4), being lower in the latter more aggressive form. These results were verified on paraffin wax-embedded tissue by quantitative real-time PCR analysis and in situ hybridization. Furthermore, the expression of beta-catenin, an important component of the Wnt-signalling pathway, was regulated in an opposite manner to SFRP4, being particularly increased in undifferentiated sarcomas. The activation of the Wnt-signalling pathway was additionally supported by the immunohistochemical demonstration that beta-catenin was translocated to the nucleus in UES. SFRP4 may therefore be a putative tumour suppressor involved in deregulation of the Wnt pathway and in the pathogenesis of ESS and UES.

Electrocatalytic Oxidation of Methanol on a Nickel-Porphyrin IX Complex Modified Glassy Carbon Electrode in Alkaline Medium

Abstract: Electrocatalytic oxidation of methanol on a glassy carbon disc electrode modified with Ni(II)-hematoporphyrin IX, complex and conditioned by potential recycling in a limited range (between 100 and 600 mV vs. SCE) in 0.10 M NaOH solution, abbreviated as NiOHPME(A), was studied by cyclic voltammetry in alkaline medium. The results were compared with those obtained for a NiO modified glassy carbon electrode, NiOME, prepared in similar conditions. The findings show that the NiOHP film at NiOHPME(A) behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium via Ni(III) species with the cross-exchange reaction occurring throughout the layer at a low concentration of methanol and for a thin film of modifier. A plausible mechanism was proposed for catalytic oxidation of methanol at NiOHP modified electrode. Moreover, the effects of various parameters such as the scan rate, methanol concentration, thickness of NiOHP film and the real surface area of modified electrode on the oxidation of methanol were investigated. Finally, it has been shown that the NiOHPME(A) has a long-term stability toward the oxidation of methanol.

Solid-Phase Microextraction of Aliphatic Alcohols Based on Polyaniline Coated Fibers

Abstract: The efficiency of polyaniline (PANI), coated gold wire was investigated for use as a fiber for solid-phase microextraction (SPME). Aniline monomers were electropolymerized on gold wires by applying a constant current to an acetate buffer containing NaClO4 as supporting electrolyte for 30 min. These fibers were used for the extraction of some aliphatic alcohols from gaseous samples. The results obtained proved the ability of PANI fiber for sampling organic compounds from gaseous samples. From this work, optimum conditions for preparation and conditioning of fibers and for the extraction of analytes from gaseous samples were obtained. Under optimum conditions, one fiber was used for several equivalent analyses and the relative standard deviations (RSD) were <7% (n=6). However, fiber to fiber reproducibility was <9% (n=6). This fiber is firm and durable and is simply prepared. Calibration graphs were linear in the range: 0.1–10 g mL−1 for aliphatic alcohols; the detection limit range was 15–75 ng mL−1 (S/N=3) using a flame ionization detector.

Photocatalytic Degradation of an Organophosphorus Pesticide Phosalone in Aqueous Suspensions of Titanium Dioxide

Abstract: The present work deals with photocatalytic degradation of an organophosphorus pesticide, phosalone, in water in the presence of TiO2 particles under UV light illumination (1000 W). The influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO2, irradiation time, stirring rate, and distance from UV source, on the photodegradation efficiency of phosalone was investigated. The degradation rate of phosalone was not high when the photolysis was carried out in the absence of TiO2 and it was negligible in the absence of UV light. The half-life (DT50) of a 20 ppm aqueous solution of phosalone was 15 min in optimized conditions. The plot of lnC (phosalone) vs. time was linear, suggesting first order reaction (K = 0.0532 min−1). The half-life time of photomineralization in the concentration range of 7.5–20 ppm was 13.02 min. The efficiency of the method was also determined by measuring the reduction of Chemical Oxygen Demand (COD). During the mineralization under optimized ...

Supersymmetry approaches to the bound states of the generalized woods–saxon potential

Abstract: Using the associated Jacobi differential equation, we obtain exactly bound states of the generalization of Woods–Saxon potential with the negative energy levels based on the analytic approach. According to the supersymmetry approaches in quantum mechanics, we show that these bound states by four pairs of the first-order differential operators, represent four types of the laddering equations. Two types of these supersymmetry structures, suggest the derivation of algebraic solutions by two different approaches for the bound states.

A New Method to Study Simple Shear Processing of Wheat Gluten‐Starch Mixtures

Abstract: This article introduces a new method that uses a shearing device to study the effect of simple shear on the overall properties of pasta-like products made from commercial wheat gluten-starch (GS) blends. The shear-processed GS samples had a lower cooking loss (CL) and a higher swelling index (SI) than unprocessed materials, suggesting the presence of a gluten phase surrounding starch granules. Pictures of dough micro-structure by confocal scanning laser microscopy (CSLM) showed the distribution of proteins in the shear-processed samples. This study revealed that simple shear processing could result in a product with relevant cooking properties as compared with those of commercial pasta. Increasing gluten content in GS mixtures led to a decrease in CL and an increase in maximum cutting stress of processed samples, whereas no clear correlation was found for SI values of sheared products. It was concluded that the new shearing device is unique in its capability to study the effect of pure shear defo...

Effects of azadirachtin/Neemazal on different stages and adult life table parameters of Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae).

Abstract: The effects of azadirachtin/Neemazal on adults, emergence, and life table parameters of Trichogramma cacoeciae Marchal were studied. The adults were exposed to fresh residues of the insecticide applied on glass plates. Based on the dose–response study, the LC50 value was 1,330 ppm or 13.3 μg (AI)/ml. The effect of Neemazal on three developmental stages of the parasitoid was tested by dipping parasitized Sitotroga cerealella (Olivier) and Cydia pomonella (L.) eggs at the field-recommended concentration 3, 6, and 9 d after parasitization corresponding to larval, prepupal, and pupal stages. The emergence of adult parasitoids was adversely affected in both hosts, but the adverse effect was more in S. cerealella eggs compared with C. pomonella. The adult emergence was reduced by 73.3 and 33.76% in Sitotroga and Cydia eggs compared with controls, respectively. Longevity and progeny production of the emergent adults did not differ significantly from control. Neemazal affected stable population parameter...