VOLUME 30, NO2, APR 2008

Anion of Quinocyanomethylene: Simulation of Dimerization

3,5-Bis(1,1-dimethylethyl)-4-oxo-2,5 cyclohexadienylideneacetonitrile, QM, is an electron acceptor. Simulation of cyclic voltammogram of QM, in acetonitrile at platinum electrode was carried out, and a scheme was suggested to obtain the heterogeneous rate constants for electron transfer. The results of simulations based on two shareware programs are generally consistent with theoretical and experimental work.read more

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INAM UL HAQUE ,ASIM KHAN ,SHUMAILA SADAF ,

Kinetics and Electrochemical Studies of Uranium in Perchlorate and Sulphate Media by Cyclic Voltammetry

The cyclic voltammetric behavior of uranyl ion was investigated at hanging mercury drop electrode in perchlorate supporting electrolyte.  The standard heterogeneous electrons transfer rate constant “ks” for the reduction of uranium from U(VI) to U(V) state was 2.72 x 10-3 cm sec-1 in simple perchlorate medium and in the presence of 0.40 mol L-1 sulphate ions the value of ks was 2.56 x 10-3 cm sec-1. The effect of temperature on the values of ks was investigated and different thermodynamic constants,  H*,  S* and  G298*, were calculated. The values of   H*,  S* and  G298* were 7.97 kJ mol-1, -23.80 J mol-1 K-1 and 15.06 kJ mol-1 in simple perchlorate medium and 3.99 kJ mol-1, -37.70 J mol-1 K-1, and 15.22 kJ mol-1 in sulphate medium. The stability constants of uranyl sulphate complexes were calculated from the analysis of shift in peak potential of uranyl ions with increasing concentration of sulphate ions. The values of logß1 and logß2 for 1: 1 and 1: 2 uranyl sulphate complexes were found to be 1.90 ? 0.01 and 2.92 ? 0.02 respectively, which are in close agreement with the literature values. read more

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ABDUL SATTARALI KHAN ,MUHAMMAD LATIF MIRZA ,RIAZ AHMED ,

Biological Removal of Hydrogen Sulfide from Various Distillates of Crude Oil with Pseudomonas putida

Removal of hydrogen sulfide (H2S) has been attempted from various distillation fractions with bacterium Pseudomonas putida. Biodesulfurization technique has been found to be more effective than conventional desulphurization methods. Tremendous amount of hydrogen sulfide (H2S) has been removed in all the distillation fractions under study i,e. 64.94 %, 65.83 % and 66.66 % has been reduced in case of  light (bp 200 0C), medium (bp 300 0C),  and heavy (bp 360 0C) distillate fractions, respectively. Because of the volatile nature, hydrogen sulfide (H2S) was found to be concentrated mostly in light distillate (0.0170 %) next in medium (0.0120 %) and then in heavy (0.0090 %) distillate fractionsread more

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MUHAMMAD SHAHKIRULLAH ,MUHAMMAD ISHAQ ,MUHAMMAD NAEEM ,IMTIAZ AHMED ,MUHAMMAD ARSALAN KHAN ,

A pHs Equation for Calcium Carbonate Scale Prediction in Cooling Water Systems

Cooling water systems contain a large number of potential scale and scale causing constituents and calcium carbonate is the chief ingredient of scale formed. Scale forming and/ or corrosive tendencies of water can be predicted qualitatively by using the saturation indices. Studies were conducted to introduce a pHs for simplicity . Some of the industrially used empirical indices for predicting CaCO3 scaling potential are reviewed and their shortcomings are discussed. The theoretically calculated results for pHs equation have been compared and validated with experimental values and with other commonly and industrially used indices. The results showed that pHs equation is a better predictive approach.  This equation is a measure of the scaling potential and provides a conservative measure. It is also important to point out that saturation pH (pHs) value calculated in the present study has shown the same result i.e. pHs = 7.68 as predicted by the literature. Increase in temperature accelerates the rates of both scaling and corrosion processes thus the values of [pKa2- pKsp] are inversely proportional to temperature and are directly proportional to the concentration of TDS.  Moreover, it was investigated that the pAlkalinity decreases as the concentration of bicarbonate increases. read more

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KHALID MAHMOOD ZAI ,RAKHSHANDA NAWAZ ,IJAZ AHMAD BHATTI ,HAQ NAWAZ BHATTI ,

Determination of Critical Micelle Concentration (Cmc) of Sodium Dodecyl Sulfate (SDS) and the Effect of Low Concentration of Pyrene on its Cmc Using ORIGIN Software

Critical micelle concentration of sodium dodecyl sulfate (SDS) was determined using condunctance and fluorescence method. Effect of low concentration of pyrene was checked on the Cmc of SDS conductometrically. The Cmc was determined from the data using two different methods. ORIGIN software shown up as a much better and easier way for the theoretical treatment of experimental data. It was observed that low concentration of pyrene has no effect on the Cmc of SDS.read more

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SYED SAKHAWAT SHAH ,ASAD MUHAHAMMAD KHAN ,

Dynamic Temperature X-ray Diffraction (DTXRD) Studies on Dolomite (MgCO3CaCO3) of Balochistan (Pakistan).

  Dolomite (MgCO3CaCO3) is identified as the crystalline phase in the low temperature range,.i.e. at temperatures less than 816 K. At 816 K, the high temperature compound periclase (MgO) is produced, as a consequence of, phase transition.  This is confirmed from iso-intensity plot of DTXRD. For MgO at 1273 K, the cubic unit cell parameter is estimated to be about 4.26 Ao. We observe certain microscopic changes on dolomite at temperatures less than 816 K as is evidenced from diffraction patternsread more

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SALMA JABEEN ,SYED MOHSIN RAZA ,GEERT VANHOYLAND ,

Electrodeposition of Polypyrrole on Aluminium in Oxalic Acid

Adherent and homogenous polypyrrole films were electropolymerized onto aluminum from aqueous oxalic acid and oxalic acid containing different anions ( SO32- , SO42-, CO32- DBS- ,) by cyclic voltametry. The corrosion behavior of coated and uncoated aluminum with polypyrrole was investigated in 0.1 M HCl by potentiodynamic polarization method. Inhibition effect of anions onto uncoated aluminum was determined in 0.1 M HCl. The curves of anodic and cathodic polarization were obtained. The electrochemical parameters were determined from the polarization curves. The efficiency of polypyrrole coating on aluminum was calculated. It was shown that thin PPy film had provided good corrosion protection of aluminum in 0.1 M HCl.  Oxalate¦DBS-¦PPy system had showed the most superior corrosion protection properties than other anion systems.read more

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ELEM YAKAR ,SIBEL ZOR ,

Biorecovery of Manganese from Pyrolusite ore using Aspergillus niger PCSIR-06

Investigations were carried out for biotechnological leaching of manganese from pyrolusite ore using Aspergilus niger.Strian of Aspergilus niger PCSIR-06 was isolated from pyrolusite ore collected from wahd area of Khuzdar District, Balochistan, Pakistan. The growth characteristics were investigated in term of final pH, biomass and total acid produced by the fungus in both shaking and surface culturing conditions. Bioleaching of manganese from low grade pyrolusite ore was carried out in shake  cultures by applying Aspergilus niger PCSIR-06. Effects of various parameters in situ leaching of pyrolusite ore such as sucrose concentration, pulp density and inoculum size were investigated. Maxiu, leaching of manganese (85.39 %) was achieved at 19 % sucrose, 1 % pulp density and 10 % inoculum in a period of 12 days.read more

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SHEREEN GUL ,MUJEEB UR REHMAN ,MOHAMMAD ZAHOORUL HAQ ,S A KAYANI ,

Investigation of Resonance Effect, Inductive Effect, Solvation Energies and Electron Affinities of Some Thiosemicarbazides, Hydrazides and Carboxylic Acids through Linear Scan Voltammetry

Electrochemical measurements have been carried out for three sets of compounds. Set 1 comprising fourteen 4-(4-substitutedphenyl)-1-(isomericpyridoyl)thiosemicarbazides, Set 2 compri-sing three isomeric pyridine carboxylic acid hydrazides and Set 3 comprising three isomeric pyridine carboxylic acids. In all these compounds substituents on phenyl group are bromo, chloro, fluoro, methyl and methoxy group. All these compounds were studied in non-aqueous solvent DMF at 293K using linear scan voltammetry (LSV) as measuring techniques. LSV reveals a single reversible peak for all compounds. Effects of substituents on halfwave potential (E1/2) values were explained on the basis of resonance and inductive effects. E1/2 values were used for the evaluation of solvation energies (S) and electron affinities (A). Moreover, correlations of energies of lowest unoccupied molecular orbitals (ELUMO) and Hammett constants (s) with halfwave potentials (E1/2) and electron affinities (A) were also studied.read more

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RUMANA QURESHI ,MOHAMMAD SADIQ SUBHANI ,ANILA AKRAM ,ABDUR RAHMMAN ,

Comparative Changes in Growth and Seed Yield Characteristics of [Vigna Radiata (L.) Wilczek] Varieties under the Influence of Increased Levels of Cadmium (Cd+2)

A net house experiment was conducted to determine the effects of different levels of Cadmium application on growth, yield and Cadmium (Cd+2) in various Mungbean plant parts. The NM-98 variety produced higher biomass of different plant parts than NM-28. Significant differences in growth and yield of various plant parts were observed among the treatments. The significant interactions was found between Cadmium (Cd+2) treatments and varieties for yield in all the parts of plant. The NM-98 had much greater yield than other varietiesread more

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ABDUL GHANI ,AAMIR ALI ,