Showing papers by "University of Tabriz published in 2002"

Resistance-associated point mutations of organophosphate insensitive acetylcholinesterase, in the olive fruit fly Bactrocera oleae

Abstract: A 2.2-kb full length cDNA containing an ORF encoding a putative acetylcholinesterase (AChE) precursor of 673 amino acid residues was obtained by a combined degenerate PCR and RACE strategy from an organophosphate-susceptible Bactrocera oleae strain. A comparison of cDNA sequences of individual insects from susceptible and resistant strains, coupled with an enzyme inhibition assay with omethoate, indicated a novel glycine-serine substitution (G488S), at an amino acid residue which is highly conserved across species (13396 of Torpedo californica AChE), as a likely cause of AChE insensitivity. This mutation was also associated with a 35-40% reduction in AChE catalytic efficiency. The I199V substitution, which confers low levels of resistance in Drosophila, was also present in B. oleae (I214V) and in combination with G488S produced up to a 16-fold decrease in insecticide sensitivity. This is the first agricultural pest where resistance has been associated with an alteration in AChE, which arises from point mutations located within the active site gorge of the enzyme.

Cohomological dimension of certain algebraic varieties

Abstract: Let a be an ideal of a commutative Noetherian ring R. For finitely generated R-modules M and N with Supp N ⊆ Supp M, it is shown that cd(a, N) dim N - c(N/αN) -1. Here c(N) denotes the connectedness dimension of the topological space Supp N. Finally, as a consequence of this inequality, two previously known generalizations of Faltings' connectedness theorem are improved.

CEOs and development of the meaningful mission statement

Abstract: Developing a mission statement has been considered a crucial factor in the formulation of business strategy in organisations. The mission statement promotes a sense of shared expectations in employees and, not surprisingly, it has recently been regarded as increasingly important in small‐ and medium‐sized enterprises (SMEs) in the electronic industry. One major reasons for this is the growing complexity and dynamic competitive environments in which these enterprises have operated and managed to find themselves. Mission statements have become a management tool most commonly used by chief executive officers (CEOs) over the last decade. One exercise that both academics and practitioners have deemed strategically critical to the success of an enterprise is the development of a meaningful mission statement. This article explores the perceptions of CEOs of their mission statement in SMEs. It is based on the findings of recent research in 508 firms in the electrical and electronic industry in the UK. The study, amongst other things, investigated the existence and content of the mission statements and, accordingly, it determines the relationships (if any) between a SME’s development of a meaningful mission statement and selected performance outcomes of the firm.

Single-phase PQ theory

Abstract: The theory of instantaneous reactive power compensation of single-phase circuits is presented. This theory is a general case of well-known pq theory and it is usable in single-phase as well as three-phase circuits. A new definition of instantaneous active and reactive powers in single-phase circuits that is based on space vector concept is also presented. The principle of operation is explained using analytical analysis. The validity of the presented method and its comparison with original pq theory is studied through simulation results.

Sensorless direct torque control of induction motors used in electric vehicle

Abstract: A three-phase squirrel-cage induction motor is used as the propulsion system of an electric vehicle (EV) The motor is controlled at different operating conditions using a direct torque control (DTC) technique combined with a new switching pattem producing low harmonics The operating flux of the motor is chosen optimally for both loss minimization and good dynamic response Since speed estimation is sensitive to rotor resistance variations, the rotor resistance value is calculated and modified in real-time continuously Simulation and experimental results show that the proposed DTC is able to follow the reference speed (which may be only input reference of the system) with a reasonable dynamic and relatively low error

Nickel pentacyanonitrosylferrate film modified aluminum electrode for electrocatalytic oxidation of hydrazine

Abstract: The electrocatalytic oxidation of hydrazine at the aluminum electrode, modified by electroless deposition of nickel pentacyanonitrosylferrate (NiPCNF) on the surface of the electrode has been studied by cyclic voltammetry, chronoamperometry and rotating disk electrode voltammetry and the kinetics of the catalytic reaction were investigated. The results were explained using the theory of electrocatalytic reactions at chemically modified electrodes. It was found that a one-electron charge-transfer process is rate limiting and that the average values of the rate constant for the catalytic reaction and the diffusion coefficient, evaluated by different approaches, are 5.2×103 M–1s–1 and 8.5×10–6 cm2s–1, respectively. Further examinations of the modified electrodes show that the modifying layers (NiPCNF) on the aluminum substrate have reproducible behavior and a high level of stability, after exposing them in air and hydrazine solutions for a long time.

Enhancement of Dissolution Rate and Anti-inflammatory Effects of Piroxicam Using Solvent Deposition Technique

Abstract: Piroxicam solid depositions were prepared by means of the solvent deposition technique using different concentrations of microcrystalline cellulose as carrier material. The solvent deposition system (SDS) with drug to carrier ratio of 1:9 had a rapid dissolution rate in vitro. When this SDS was administered perorally to rats with a previous experimentally induced inflammation in their paws, it exhibited a pronounced anti-inflammatory action. X-ray diffraction and infrared (IR) spectroscopy showed no differences in the crystal state of piroxicam in SDS formulation and physical mixture of piroxicam and carrier. The increase in the dissolution rate and consequent enhancement of anti-inflammatory effect of piroxicam in SDS were attributed to the reduced particle size of drug deposited on the carrier and enhanced wettability of the particles brought about by the carrier.

Electrochemistry and Electrocatalytic Activity of Pyrocatechol Violet (PCV) Film on a Glassy Carbon Electrode Towards the Oxidation of Reduced Nicotinamide Adenine Dinucleotide(NADH)

Abstract: Electrocatalytic oxidation of nicotinamide adenine dinucleotied (NADH) at a glassy carbon electrode modified with electrodeposited film derived from pyrocatechol violet (PCV) has been studied. The PCV modified glassy carbon electrode shows excellent electrocatalytic activity toward NADH oxidation in phosphate buffer solution (pH 7.0) with an overpotential of about 447 mV lower than that of the bare electrode. The apparent charge transfer rate constant and charge transfer coefficient for electron transfer between the electrode surface and immobilized PCV were calculated as 5.3 s−1 and 0.49, respectively. The catalytic rate constant of the modified glassy carbon electrode for the oxidation of NADH is determined by cyclic voltammetry and rotating disk electrode measurements. Also, it has been shown that using the PCV modified electrode, NADH can be estimated by amperometry with high sensitivity and good limit of detection.

Amperometric Determination of Ascorbic Acid in Real Samples Using an Aluminum Electrode, Modified with Nickel Hexacyanoferrate Films by Simple Electroless Dipping Method

Abstract: Nickel hexacyanoferrate (NiHCNF) film modified Al electrode prepared by simple and rapid electroless dipping procedure was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic or linear sweep voltammetry was linearly dependent on the ascorbic acid concentration. At a fixed potential under hydrodynamic conditions (stirred solutions), the calibration plot was linear over the ascorbic acid concentration range 2×10−6–2×10−4 M. The detection limit of the method is 2×10−6 M, low enough for trace ascorbic acid determination in various real samples. The proposed method was used for determination of ascorbic acid in fresh fruit juices, vegetables, pharmaceutical preparations and blood plasma. The results obtained are in good agreement with those obtained by the official standard methods. The analysis with NiHCF-film-modified Al electrode was selective for ascorbic acid from the various concomitant reducing compounds in real samples.

Detection and determination of CrVI in solution using polyaniline modified quartz crystal electrode

Abstract: Conducting polymers such as polyaniline and polypyrrole exhibit novel sensoric properties and are able to interact chemically or electrochemically with the species of interest for detection. In the current investigation, construction of a sensor based on an electrochemical reaction between CrVI and a thin layer of polyaniline, coated at the surface of quartz crystal electrode, is reported. Polyaniline was synthesized, electrochemically, at the surface of quartz crystal electrode. It was then reduced at −0.1 V versus Ag/AgCl. The modified electrode was exposed to various concentrations of CrVI solutions ranging from 10−7 to 10−1M. Mass changes of the polymer-modified electrode due to the reaction between CrVI and polyaniline was found to be linear, corresponding to the concentration of CrVI. The experiments in both acidic and nonacidic conditions were performed. In both conditions, linear double-loga thmic calibration curves of mass change of the polymer film versus CrVI concentration were obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2772–2780, 2002

Implementation of single-phase pq theory

Abstract: Instantaneous reactive power compensation in a single-phase scheme is implemented. The analytical analysis is presented. The proposed single phase based theory can be successfully used for reactive power compensation of single phase as well as three phase systems. This method generates a sinusoidal reference current waveform in the utility side in the imbalanced utility voltage and/or imbalanced load current cases. The validity of the presented method and its comparison with original pq theory is studied through simulation results.

Modified copper wire as solid-phase microextraction fiber, selective extraction of some amines

Abstract: This paper presents results obtained using modified copper wire as a solid-phase microextraction (SPME) fiber. Modified copper fibers were prepared by dipping cleaned copper wires (350 μm o.d.) in a solution of CuCl2. Scanning electron microscopy experiments suggested the formation of a thin layer of CuCl microcrystals (d.p.<1 μm) on the metal surface. These fibers were used for the extraction of some volatile amines from gaseous samples. Extracted analytes were transferred to a GC injector using a homemade SPME device. Results obtained show that the proposed fiber has high selectivity and good recovery for extraction of amines. More than 83% of primary amines were extracted in 5 min from 50 mL gas sample with a relative standard deviation (RSD) <0.5% (n=5). Calibration graphs were linear in the range 0.3–15 ng mL−1 for primary amines. The detection limit was 0.1–0.3 ng mL−1 (S/N=3) using a flame ionization detector.

Electrochemically Controlled Binding and Release of Dexamethasone from Conducting Polymer Bilayer Films

Abstract: Conducting polymer bilayer films containing polypyrrole/ dexamethasone sodium phosphate as an inner film and poly(N-methylpyrrole)/ polystyrenesulfonate or self-doped polyanilinesulfonate as an outer film were prepared byelectrochemical and chemical methods. The controlled release of dexamethasone sodium phosphate (DMP) from the inner film was carried out by applying a cathodic potential. The amount of DMP released was investigated by UV-Vis spectrophotometry and electrochemical quartz crystal microbalance. Repeatedly DMP was reincorporated into the inner film, by applying an anodic potential, and then released. The results show that the outer film can act as a barrier to ion and solvent transport between the inner film and the electrolyte which provided a more balanced counter-directional movement of the anions.

New Features in Karyotype Structure and Origin of Saffron, Crocus sativus L.

Abstract: Karyotype analyses of saffron, Crocus sativus L., was made using improved routine and C-banding techniques on metaphase plates in root tip cells of 2 accessions from Republic of Azerbaijan and Iran. In the routine technique fixative of Lewitsky and aceto-iron-hematoxylin stain were used. It was established that metaphase chromosomes can be arranged according to their size and morphological features in 8 triplets ranging in size from 11.58±0.13 μm (triplet 1) to 4.57±0.05 μm (triplet 8). Triplets 1 and 2 include subacrocentric, triplets 3, 4 and 8 metacentric and triplets 6 and 7 submetacentric chromosomes. Three chromosomes in each triplet, as a rule, are similar although in some triplets one of them is infrequently distinguishable from the 2 others. Triplet 5 shows an extreme difference so that it always contains 2 kinds of chromosomes: chromosome 5(1) and chromosomes 5(2, 3). Chromosome 5(1) is metacentric (r=1.40) and 6.04±0.13 μm in length, but chromosomes 5(2, 3) are subacrocentric (r=3.49) and noticeably smaller (5.41±0.09 μm). Application of the C-banding technique revealed heterochromatin segments: the sharpest, sharp and week. The sharpest heterochromatin was on telomere of the short arm of chromosome type (triplet) 3 and on proximal part of the long arm of chromosome type 1; a sharp heterochromatin on telomere of the short arms of chromosome types 1, 4 and on the satellites, and a weak heterochromatin on a centromeric region all of 24 chromosomes. Chromosome type 5(1) had a heterochromatin that was a little stronger on the centromeric and, considerably weaker on telomeric regions comparing to those of chromosome type 4. Accessions of saffron from Republic of Azerbaijan and Iran were not significantly distinguishable in karyotype structure. The species C. sativus in its places of cultivation is obviously a clone of one triploid plant originated spontaneously in the nature through crossing between 2 closely related species with participation of n and 2n gametes. Results from statistic analysis and appropriate photographic evidences are provided.

Decomposition of anionic sodium dodecylbenzene sulfonate by uv/tio2 and uv/h202 processes a- comparison of reaction rates

Abstract: Anionic DBS surfactant can be photodegraded in a TiO2 dispersion and H2O2 solution under an Hg-lamp (15 W) UV illumination or solar exposure. Degradation process has been monitored through cleavage of aromatic moiety. Degradation of the detergent was small when the photolysis was carried out in the absence of TiO2 and H2O2 and it was negligible in the absence of light. Most of the curves representing the semi-log of pollutant concentration versus time were nearly linear, suggesting first order reactions. In the UV/TiO2 process, the extent of surfactant degradation was found to be influenced by the TiO2 loading, initial detergent concentration, agitation rate, temperature and initial pH. The UV peroxide degradation of the anionic detergent (DBS) by the UV/H2O2 process is more effective the UV/TiO2 process making it a promissable method for destroying the aquatic pollutants. A combination of UV and Solar light is used, degradation of DBS it is more effective than UV/H2O2 process.

Level Crossing Analysis of Growing surfaces

Abstract: We investigate the average frequency of positive slope $ u_{\alpha}^{+} $, crossing the height $\alpha = h- \bar h$ in the surface growing processes. The exact level crossing analysis of the random deposition model and the Kardar-Parisi-Zhang equation in the strong coupling limit before creation of singularities are given.

Klauder–perelomov and gazeau–klauder coherent states for some shape invariant potentials

Abstract: Firstly, the solvability of some quantum models like Eckart and Rosen–Morse II are explained on the basis of the shape invariance theory. Then, two generalized types of the Klauder–Perelomov and Gazeau–Klauder coherent states are calculated for the models. By means of calculating the Mandel parameter, it is shown that the weight distribution function of the first type coherent states obeys the Poissonian and super-Poissonian statistics, however, the weight distribution function of the second type coherent states obeys the Poissonian and sub-Poissonian statistics.

Hierarchy of Chaotic Maps with an Invariant Measure and their Compositions

Abstract: We give a hierarchy of many-parameter families of maps of the interval [0, 1] with an invariant measure and using the measure, we calculate Kolmogorov–Sinai entropy of these maps analytically. In contrary to the usual one-dimensional maps these maps do not possess period doubling or period-n-tupling cascade bifurcation to chaos, but they have single fixed point attractor at certain region of parameters space, where they bifurcate directly to chaos without having period-n-tupling scenario exactly at certain values of the parameters.

A novel control strategy for unified power quality conditioner (UPQC)

Abstract: This paper presents a novel and easy to implement control strategy for unified power quality conditioner (UPQC). This control strategy is usable in three-phase three-wire utilities. The control strategy of parallel active filter (PAF) is based on combination of extended p-q theory and instantaneous symmetrical components theory while the control circuit of series active filter (SAF) is based on instantaneous symmetrical components theory. The problem of generating three phase imbalance reference currents of extended p-q theory has been solved. Operation of PAF using this method compensates for reactive power, current harmonics and imbalance currents while operation of SAF compensates for voltage imbalance and voltage harmonics. The operation of control circuit is explained using analytical analysis. The validity of operation of control strategy is studied through simulation results.