Journal of Sciences, Islamic Republic of Iran
Year:2002 | Volume:13 | Issue:3|Papers Count:19

 Based on the Randic suggestion of the resolution of a structure into shape, size, and function an index representing structure-catabolic fate relationships of amino acids is constructed. The index obtained by multiplying three factors; (nb2 + nr), nc and M; representing shape, size and function respectively, where nb2 = number of double bonds, nr = number of rings, nc = number of carbon atoms, and M = molecular weight. A systematics of amino acids is obtained and a correlation is observed between the index value and the catabolic fate.

Phosphatidate phosphohydrolase (PAP) from cytosolic fraction of rat liver was purified to homogeneity having specific activity of 5.14 U/mg proteins. An activity staining procedure was developed to determine molecular weight of the enzyme on polyacrylamide gel electrophoresis using Ferguson plot. Molecular Weight (M.W.) of the active PAP was 298 KDa. SDS-PAGE analysis showed a M.W. of 47 KDa for PAP subunits. Active multimer of the enzyme, therefore, was calculated to be hexamer. Gel filtration on Sephadex G-100 column showed a M.W. of 850 KDa for PAP due to the protein aggregation on the matrix. The purified enzyme was inhibited by divalent cations such as Fe2+, Cu2+ and Ca2+ but requires Mg 2+ for its activity. The activity loss of PAP inhibited by cations was restored by Mg2+ on polyacrylamide gel. The data suggest that the active form of cytosolic PAP is a hexamer of identical subunits and that charge density plays an important role in enzyme-substrate interaction. Magnesium ion is probably the only divalent cation capable of generating proper enzyme-metal-substrate complex necessary for the catalytic activity.

N-propylsalicylidene based on silica as ion exchanger (IE) was used for the separation by complexation of Mn2+, Co2+, Ni2+, Cu2+, Hg2+, Cr3+, Fe3+, and UO2 2+ from their parent solutions. IE and its metal complexes are characterized by elemental analysis, electronic and infrared spectra, in addition to thermal analysis in atmospheric pressure. The mode of chelation and the proposed geometric structures of the metal complexes of IE are suggested by infrared and electronic spectra, respectively. Elemental and thermal analysis indicate that the percentage of the organic content increased from IE-Cr (5.409) to IE-Hg (13.5) with respect to that of IE (13.655) owing to the catalytic effect of these metal ions. Three different stages of decomposition have been accompanied by the thermal degradation of IE and IE-metal complexes. These stages were found to be affected by the presence of the investigated metal ion. By application of non-isothermal kinetic equation, the activiation energy (Ea) for the IE and its complexes was calculated. Ea follows the order, IE-Fe < IE-Co < IE < IE-Mn < IE-UO2 < IE-Cr < IE-Ni < IE-Cu < IE-Hg. The thermodynamic parameters Ea, ΔH°, ΔS° and ΔG° of the obtained complexes were found to be largely dependant on the electronegativity of the studied metal ions.

Vanadium silicates such as V-Al-analcime, V-analcime, V-magediite and VZSM- 11 were synthesized using vanadium pentoxide or vanadyl sulfates. Vanadium silicates with analcime structure with and without aluminum (V-Alanalcime, V-analcime) were prepared as pure phase by hydrothermal crystallization from a gel with molar composition of (1 SiO2; 0.2 V2O5; 1 Na2O; 0.034 Al2O3; 35.7 H2O) and (1 SiO2; 1 Na2O; 5.3×10-3 V2O5; 34.7 H2O) at 130°C in 72 h respectively. XRD and SEM results showed that, although these two have similar XRD patterns, their morphologies were completely different. The new magediite with and without aluminum was also prepared as pure phase by hydrothermal crystallization. Vanadium silicate with ZSM-11 structure was synthesized by sodium silicate, tetrabutylammonium hydroxide (TBAOH) and V2O5 or VOSO4.nH2O. The structures obtained are stable up to 700°C. The role of tetrabutylammonium hydroxide (TBAOH), tetrabutylammonium bromide (TBABr), tetraethylammonium chloride (TEACl) and triethanolamine (TENA) were studied. The results showed that although TBAOH and TBABr had essential role on V-ZSM-11 formation, TEACl led to the formation of a mixture of VZSM- 11 and V-magediite. Effect of time and temperature were also studied.

Group VIII B metal oxides supported on gamma-alumina were investigated as catalysts and promoters of MoO3 hydrodesulfurization catalysis. Superior promotion was observed in PbO promoted catalyst compared to that of CoO, the typically accepted promoter. Other metal oxides, SnO and Ho2O3 exhibited reasonable hydrodesulfurization catalysis promotion but lower than for CoO promoted catalyst.

Adsorption of p-Nitrophenol by three different activated carbons (F100, S.E.I. and B.D.H.) was carried out at 301 K and at controlled pH conditions. Two different adsorption models (Langmuir model and Freundlich model) were studied and compared. The adsorption capacity of the carbons depends on the Point of Zero Charge (PZC) and surface area of the carbons. Adsorption of the solute at higher pH was found to be dependent on the concentration of anionic form of the solutes. The isotherm data were fitted to the Langmuir and Freundlich isotherm equations to obtain the relative parameters.

In the area SW of Arak, intrusives are emplaced into metasediments of early Mesozoic age. The intrusive rocks vary in morphology, structure and mineralogy, and exhibit various degrees of alterations; Rb-Sr geochronological data have been obtained to constrain their timing. There are three different groups of granitic rocks in the area: (a) the Astaneh intrusion, consisting of granite, biotite granite and granodiorite, intersected by abundant veins of quartz and aplite; (b) the Tavandasht-Gosheh intrusions, occurring as separate, small outcrops and (c) the Borujerd complex, composed of granitic intrusions with a wide range of late magmatic products including pegmatites and quartz veins, and with a welldeveloped aureole in pelitic country rocks. Rb-Sr data indicate that the first intrusive activity, which postdated low grade regional metamorphism, occurred during early Alpine tectonic movements, in lower Cretaceous times (about 120 Ma). A large elongate granitic intrusion (Older Granites), which occupies most of the Borujerd complex, and the first group of pegmatites (Older Pegmatites) were formed during this stage. Syntectonic intrusive activity associated with continuing Alpine movements, is represented by the Astaneh intrusion, emplaced at 99 Ma. Following this, a series of post-tectonic intrusions (Younger Granites) and pegmatitic veins (Younger pegmatites) were formed during the late Cretaceousearly Paleocene (70-52 Ma).

 In the following work we present a proof for the strong law of large numbers for pairwise negatively dependent random variables which relaxes the usual assumption of pairwise independence. Let {Xij} be a double sequence of pairwise negatively dependent random variables. If p {│Xij│≥t}≤ p{│X│≥t} for all non-negative real numbers t and E│X│p log+ │X│<∞, for 1 < p < 2, then we prove that  Σ i-1 m  Σ j-1 n (Xij-EXij)/ (mn)1/p → 0 a.e  as m,n  →∞ . In addition, it also converges to 0 in L1. The results can be generalized to an r-dimensional array of random variables under condition E │X│p (log+ │X│r-1  < ∞, thus, extending Choi and Sung’s result [7] of one dimensional case for negatively dependent random variables.  

In this short note, we have given a short proof for the existence of the Haar measure on commutative locally compact hypergroups based on functional analysis methods by using Markov-Kakutani fixed point theorem.

The improved estimator of the variance in the general linear model is presented under an asymmetric linex loss function.

The effects of including incoherent (bound-electron) and coherent (Rayleigh) scattering in exposure buildup factor calculations for point isotropic gamma ray sources, penetrating a two-layer water-lead shield have been investigated in the gamma ray energy (Eγ) range of 40 keV to 3 MeV. Incoherent scattering decreases the values of these factors in both layers up to Eγ ~ 200 keV and the effect is more significant in the water layer. Coherent scattering increases the factor values and is more effective in the lead layer. This effect vanishes in the water layer at Eγ ~ 200 keV but is present in the lead layer up to Eγ ~ 1,000 keV. The combined effects of both incoherent and coherent scattering have also been investigated. The combined effect increases the exposure buildup factor values. These factors are presented for different thicknesses of water and lead layers.