Showing papers by "University of Tabriz published in 1996"

Preconcentration and Spectrophotometric Determination of Chromium (VI) and Total Chromium in Drinking Water by the Sorption of Chromium Diphenylcarbazone with Surfactant Coated Alumina

Abstract: A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO4. The relative standard deviation (10 replicate analyses) at the 10 μg l−1 of chromium (VI) and 10 μg l−1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l−1 and 0.033 μg l−1, respectively.

Determination of low molecular weight aliphatic amines by HPLC in environmental water samples

Abstract: A high resolution liquid chromatographic method is described for determination of low molecular weight (LMW) aliphatic amines in environmental waters. The analytes after isolation are derivatized by fluram and separated with isocratic elution on octyl (C8) column, followed by fluorimetric detection in 395/495 nm. Different isolation procedures such as octadecylsilane (ODS) and strong cation exchanger (SCX) solid phase extraction (SPE) cartridges and Amberlite CG-120 resin were evaluated. The quantitative characteristics such as recovery, linear dynamic range, correlation coefficient, limit of detection (LOD), and relative standard deviation (RSD) are presented. Using this method, aliphatic amines were analyzed in rain and tap water as well as in waste water.

Efficacy of sodium hypochlorite treatments for control of Xanthomonas campestris pv. campestris in Brassica seeds

Abstract: Twelve brassica seed lots, naturally infected with Xanthomonas campestris pv. campestris (Xcc), were immersed in a 0.525 % NaClO (1:10 clorox) aqueous solution at 5 ml/g seed at 50-53 deg C for up to 15 min. In eight lots, with pathogen counts of less or equal 5.3 x 10** (6) CFU per 10,000 seeds, Xcc was not detected in liquid assay or direct plating of seeds following a 5 min soak treatment. In three more highly infected seed lots a soak time of 15 min was necessary to control Xcc. As a follow up, in one additional heavily infected seed lot (3.4 % seed infection) the 15 min treatment reduced infection considerably but did not eliminate Xcc. The 5 min treatment did not significantly reduce germination in seed lots with 76 % or higher germination before treatment. Germination was reduced in three lots after 10 min, and in four lots after 15 min treatment. Average seed germination following all of the NaClO treatments was significantly higher than seed germination after hot water treatment at 50 deg C for 20 min

Liquid Chromatographic Determination of Nitroaromatics in Water following Solid Phase Extraction, Pre-column Reduction and Derivatization

Abstract: A selective and sensitive method for determination of nitroaromatics is described. The analytes were reduced to corresponding primary amines with iron powder and then derivatized with fluram in citrate buffer to form pyrrolinones. The highly fluorescent pyrrolinones were isolated and preconcentrated by octadecylsilane solid phase extraction cartridge followed by reversed-phase, high-performance liquid chromatographic analysis. Detection was at 395–495 nm. Various aspects such as the reduction process, derivatization, solid phase extraction and chromatographic separation were optimized. Analysis time was relatively short due to a special design for successive reduction and preconcentration. Limits of detection for 3-nitrophenol, nitrobenzene, 4 and 2-nitrotoluene were less than 60, 12, 60 and 280 ng L−1 respectively.

The effect of Al and Mn on growth and mineral composition of Casuarina equisetifolia Forst

Abstract: In pot experiments (perlite) with Casuarina equisetifolia a strong growth depression and clear Al and Mn toxicity symptoms were found with higher treatment levels of Al and Mn In nutrient solution dry matter yields at the highest Al treatment (2000 /µM) were 37,5% for shoot and 49,5% for root biomass compared to the control With the highest Mn treatment (3200 /µM) the yield was 49% of control for both shoot and root dry matter The lowest levels of Al and Mn treatments (250 µM Al and 400 /µM Mn) resulted in a dry weight production of 78,6% for shoots and 99,3% for roots in the case of Al and 80,7% for shoots and 89,8% for roots in the case of Mn compared with the dry weight produced by control plants The Al accumulation was relatively higher in roots than in shoots and increased with increasing Al concetrations in the nutrient solution Also, Mn content in roots under low Mn treatments was as high as in shoots High Al and Mn concentrations had a negative effect on the uptake of cations (Ca, Mg and Na) Aluminium had no effect on K uptake A high decrease in the phosphorus concentrations in shoots and roots occurred in the higher treatments of Mn and especially Al The uptake of NO3-N from the nutrient solution was positively influenced only by the lower Al and Mn treatments Higher concentrations of Al and Mn had no effect on the N uptake The principal toxicity symptoms shown by the plants were the blue-green colour with brown-necrotic spots on their shoots for Al and white-chlorotic spots in the upper parts of the shoots for Mn

Analysis of Genetic Distance among Nine Medicago Species by Using DNA Polymorphisms.

Abstract: The relationship of 9 Medicago species belonging to 4 subgenera was analyzed by using restriction fragment length polymorphism (RFLP) methodologies. We analyzed 85-132 RFLP band patterns, which were caused by chloroplast DNA variations, to estimate the genetic distance among the species. These species were clustered together at around 0.1 to 0.4 Ievel of distance for marker, indicating that the Medicago species have a large genetic similarity. The most similar species were M. Iittoralis and M. truncatula and the most dissimilar one was M. Iupulina. The cluster analysis based on RFLP band patterns differentiated 9 species in another 4 groups: a) M. Iittoralis. M. truncatula, M. scutellata and M. sativa ; b) M. orbicularis and M. radiata ; c) M. rigidula and M. minima ; d) M. Iupulina. Comparing the previous classification of Medicago species with that in this study, there are two discrepancies; M. Iupulina is the most distant species from others and M. sativa (subgenus M:edicago) was closely clustered with M. scutellata. M. Iittoralis and M. truncatula classified in subgenus Spirocarpos.

Dual‐fuelling of an industrial indirect injection diesel engine by diesel and liquid petroleum gas

Abstract: For partial substitution of conventional diesel fuel with liquified-petroleum gas (LPG) fuel, in an indirect-injection, (IDI) diesel engine, the so-called ‘mixed diesel gas’ approach has been applied. For this purpose, a carburetted LPG fuel system has been designed and fitted on the inlet manifold of the engine. Extensive performance tests have been carried out at full load conditions of both the pure diesel and diesel-LPG engines. The results show that, at the rated speed, and at equal power of both engines, increasing the LPG proportion in the dual fuel decreases specific fuel consumption, exhaust gas temperature and black smoke but increase pollutants such as UHC and CO, cylinder peak pressure and the rate of pressure rise.

Estimation of pole position of an inverter fed permanent-magnet synchronous machine by the extended Kalman filter

Abstract: It is necessary to know exactly the pole position and the speed of a synchronous motor controlled by the field oriented concept. It is a common practice to measure these variables using conventional electro-mechanical devices such as angle encoder and tachogenerator. This makes the drive to become bulky and expensive and has considerable measurement errors. To overcome these disadvantages the pole position as well as the motor speed of a permanent-magnet synchronous motor (PMSM) can be estimated by measuring motor's currents and voltages. Since there are modeling and measurement errors, extended Kalman filter (EM7) algorithm used in this paper to minimize these errors. Finally discussion of problems encountered during modeling along with the results of the simulation are presented.

Analysis of Shaded Pole Induction Motors Considering Asymmetrical Flux Distribution and Saturation Effects

Abstract: Several methods are available for performance prediction of single phase shaded pole induction motors. A simple model, in conjunction with a more complicated and accurate model, which considers the asymmetrical windings and core loss, is used to compare the prediction methods against experimental results. Saturation is incorporated in the model. Fundamental and harmonic flux density wave distributions under the pole are determined by employing the accurate mathematical model of the motor and the influence of the shading angle upon this distribution is shown. The effect of airgap length upon the torque speed characteristic of the motor is also investigated.

Hypopigmented skin lesions associated with atopic dermatitis in asthma

Abstract: The association of vitiligo and other skin pigmentary disorders has been well shown with autoimmune diseases, i.e., systemic lupus erythematosus, rheumatoid arthritis. Furthermore, in certain diseases such as diabetes mellitus and adrenal insufficiency the incidence of pigmentation disorders is higher than in the general population. A total of 53 male and 46 female patients with a diagnosis of asthma, based on clinical findings and pulmonary function tests (PFT), were thoroughly examined for the presence of hypopigmented skin lesions and compared with 100 nonasthmatic controls with a similar demographic distribution. The patients were questioned regarding the history of steroid treatment in the past and present and subdivided into five groups based on the duration of therapy. Adrenal gland function was tested by 8:00 A.M. serum cortisol concentration in the group of patients with a history of steroid use as well as in some patients without this history. These patients were also tested for absolute lymphocyte and eosinophil count. Hypopigmented lesions were noted in 36.4% of asthmatic patients and in 11% nonasthmatic controls (p-value < 0.01). There were no differences in the location, but the size of lesions per patient was larger in the asthmatic than the control group. Twenty of 55 patients who had a history of steroid treatment in the past had hypopigmented skin lesions as compared to 16 of 42 patients who had no history of steroid treatment. We conclude that there is a higher coincidence of hypopigmented skin lesions, mainly vitiligo-type in asthmatic patients, compared to the general population, which is not related to a history of steroid treatment or incidence of adrenal insufficiency in these patients.

Calculation of madelung constant of various ionic structures based on the semisimple lie algebras

Abstract: Periodic structures are constructed by using semisimple Lie algebras. Then these structures are generalized to ionic structures. Finally Madelung constant of these structures are calculated by solving Poisson equation in the fundamental domain of corresponding Lie algebras with Dirichlet boundary conditions. The obtained results are consistent with data of the ionic crystals with the same coordination numbers as our structures.

Exact solution of indefinitely growing self‐avoiding and Hamiltonian walk on fractals in four dimensions

Abstract: The exponent ν and the connectivity constant μ of an indefinitely growing self-avoiding walk and the μ H for Hamiltonian walk in five simplex fractal have been calculated. We show that ν is a decreasing function of d and that d = 4 is not the critical dimension.

Simulation of a Variable Reluctance Steping Motor for Sinusoidal and Step Exitations

Abstract: Steady-state dynamic simulation of a variable reluctance stepping motor is carried out by applying two different excitation voltages. First a single-step voltage is applied to the motor, and a sinusoidal voltage, as the first term of Fourier series of the single-step voltage, is then used as the input voltage of the motor. In both cases plots of machine torque, current and speed are presented. A comparison between the results of the two cases shows that a sinusoidal input voltage cannot predict the real performance of the motor, and in critical dynamic conditions, a single-step response is far from the reality. Reasons for these discrepancies arising from the various factors are discussed in the paper.