Journal of Sciences, Islamic Republic of Iran
Volume:25 Issue: 2, Spring 2014

Heavy metal pollution all around the world has become a major environmental concern and the bioremediation of polluted environments is an increasingly popular strategy due to both its efficiency and safety. In this study، a bacterial strain resistant to heavy metal was isolated from metal contaminated sites. Strain MKH2 was removed Pb (II) with 95. 06%. This isolate was also resistant to zinc، copper، nickel and cadmium. The results of morphological and physiological characteristics showed that MKH2 was belonging to Citrobacter sp. Moreover، 16S rRNA sequencing and phylogenetic analysis indicated that MKH2 was similar to Citrobacter freundii with 99% homology. Investigation to determine if the gene resistance to heavy metal is located exclusively on a plasmid، curing was achieved. The results suggested that the resistance to heavy metal in the MKH2 is possibly conferred chromosomally. The isolated heavy metal resistant bacterium could be useful for the bioremediation of heavy metal contaminated sites.

Hydrothermal synthesis of nickel-chitosan hybrid has been accomplished using Ni (CH3COO) 2،4H2O، chitosan and water as starting material، template and solvent respectively، followed by calcination at 800 and 900˚C to provide nanoporous NiO800 and NiO900. The solid products were characterized by X-ray diffraction (XRD)، nitrogen adsorption-desorption، scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) techniques. NiO800 proved to be active for adsorption of Congo red with pseudo-second order kinetic model and adsorption isotherms، respectively fitted by Freundlich equation. NiO900 was also found to successfully catalyze the photodegradation of organic dye pollutants such as Congo red and methylene blue. The kinetic of photocatalytic behavior of NiO900 have proven to obey the first order and Langmuir–Hinshelwood model.

A two-dimensional nanolayered polyoxomolybdate، [4،4´-H2bipy] [Mo7O22]. H2O (1)، where 4،4´-bipy = 4،4´-bipyridine، was prepared and characterized by FT-IR and atomic absorption spectroscopies، transmission electron microscopy (TEM)، X-ray single crystal and powder diffraction (XRD)، and thermogravimetric analysis. The catalytic performance of 1 was assessed in the epoxidation of some olefins employing tert-butyl hydroperoxide (TBHP) as oxidant and acetonitrile as solvent. Compound 1 showed moderate to excellent activity and selectivity towards the epoxidation of the olefins. Thermal، structural and catalytic stability of 1 as well as its reusability were examined. The effect of the catalyst amount and the nature of solvent on the activity of 1 were also investigated.

A simple and efficient method for the chemoselective 1,1-diacetate protection of aromatic aldehydes with acetic anhydride by using Ni2+ supported on hydroxyapatite-core-shell magnetic γ-Fe2O3 nanoparticles (γ-Fe2O3@HAp-Ni2+) under solvent free conditions. This method has several advantages, including high yield, short reaction time, simple work-up and recyclable property of the catalyst. The catalyst can be readily isolated by using an external magnet and no obvious loss of activity was observed when the catalyst was reused in five consecutive runs.

Uniaxial compressive strength (UCS) and elastic properties of rocks play a major and vital role for the design of any engineering structure. The specimen diameter size is one of the main factors that influencing on UCS، elasticity modulus and Poisson’s ratio (E and υ). Here، an attempt has been made to investigate the effect of specimen diameter size on UCS، E and υ. Moreover، we studied the correlation between E and υ with UCS together with the effect of specimen diameter size on them. For this purpose، 9 different travertine samples were selected and core specimens with a diameters size of 38، 44، 54، 64 and 74 mm were prepared. Then، UCS، E and υ of samples in different diameter were determined. The test results were statistically analyzed using the method of least squares regression between the different specimen diameters with UCS، E and υ. The data analysis results showed that specimen diameter size significantly affects on UCS، E and υ. Moreover، it was found that the best correlation between E and UCS was for the specimen diameter of 38 mm، whereas there is not meaningful correlation between υ and UCS.

Mard-abad calc-alkaline granite formed along the margin of active pull-apart or intra-continental plates، and it is post-collision granite type. Granophyric، perthitic and myrmekitic are main textures that could form from crystallization of hypersolvus source magma، which occurred under water vapor pressure of approximately 2 kb. During this study the temperature of formation of these granites has been estimated as high as 750 to 800 C° based on mineralogical and geochemical evidences. However، the thermometric measurement on zircon crystals has also been applied to achieve this goal. Zircon is of great importance because of its certain features such as resistance to chemical and mechanical processes، high melting point، and the ability of recording various geological events in its external structure as well as its internal texture. Crystallization of zircon is a function of temperature، chemical composition and the amount of water of the magma. The morphology of zircon crystals in Mard-abad granite points hybrid origin of granitic magma، which is in accordance with the geochemical evidence of the associated rocks. Such morphology also indicates to calc-alkaline and dry nature of the magma. The calculated crystallization temperature of these granite bodies is 700 to 800 C° based on morphology of zircons، 772. 2 to 792 C° according to zircon saturation thermometry، and 760 to 800 C° based on the results from chemical analyses.

This paper is concerned with the problem of designing discrete-time control systems with closed-loop eigenvalues in a prescribed region of stability. First، we obtain a state feedback matrix which assigns all the eigenvalues to zero، and then by elementary similarity operations we find a state feedback which assigns the eigenvalues inside a circle with center and radius. This new algorithm can also be used for the placement of closed-loop eigenvalues in a specified disc in z-plane for discrete-time linear systems. Some illustrative examples are presented to show the advantages of this new technique.

We consider Gabor systems generated by a Gaussian function and prove certain classical results of Paley and Wiener on nonharmonic Fourier series of complex exponentials for the Gabor expansion. In particular، we prove a version of Plancherel-Po lya theorem for entire functions with finite order of growth and use the Hadamard factorization theorem to study regularity، exactness and deficiency of Gabor systems.

Nanocomposites made of Carbon Nanotube (CNT) bundles have attracted researchers’ attention due to their unusual properties such as: light weight, flexibility and stiffness. In this paper, the effects of straight and rope-shaped bundles on nanocomposite effective mechanical properties are investigated. First, FEA models are created consisting of CNTs with different shapes of straight and rope-shaped bundles to investigate the effects of straight and rope-shaped bundles dimensions. Next, the reinforcing efficiency of CNTs in different matrices is investigated using models consisting of matrices with different moduli of elasticity. The results show that the increases of Young’s modulus of matrix and straight bundle and rope-shaped bundle diameter can significantly reduce the stiffening effect of the nanotubes in longitudinal fiber and increase the stiffening effect of the nanotubes in transverse fiber. Also, Young’s modulus prediction for carbon nanotube in a poly (ethylene terephthalate) matrix is compared to experimental data investigated by Gómez-del Río et al. (2010), and good agreement is observed.