Jun 2011, Volume 6 Issue 2
    

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  • RESEARCH ARTICLE
    Ruizhou ZHANG, Zhenguo LI, Xiaohong LI, Xianzhou ZHANG

    Theoretical study of several O-nitrosyl carboxylate compounds have been performed using quantum computational ab initio RHF and density functional B3LYP and B3PW91 methods with 6-31G** basis set. Geometries obtained from DFT calculations were used to perform the natural bond orbital (NBO) analysis. It is noted that weakness in the O3-N2 bond is due to nO1σO3-N2* delocalization and is responsible for the longer O3-N2 bond lengths in O-nitrosyl carboxylate compounds. It is also noted that decreased occupancy of the localized σO3-N2 orbital in the idealized Lewis structure, or increased occupancy of σO3-N2* of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are related with the resulting BoldItalic character of the corresponding sulfur natural hybrid orbital (NHO) of σO3-N2 bond orbital. In addition, the charge transfer energy decreases with the increase of the Hammett constants of subsitutent groups.

  • RESEARCH ARTICLE
    Chun-mei YANG, Xian-chun CHEN, Xiao-ming LIAO, Zhong-bing HUANG, Ya-dong YAO, Guang-fu YIN

    ZrO2 toughened Al2O3 (Al2O3/ZrO2) ceramic layers with required thickness were prepared by electrophoretic deposition (EPD) method using ethanol suspensions with stabilizing agent of polyethyleneimine (PEI) under constant-voltage mode in this paper. The deposition of Al2O3/ZrO2 ceramic powders occurred on the titanium alloy cathode. A stable suspension with 1wt% PEI in ethanol at pH 5 was prepared in terms of the zeta potential and sedimentation of the suspension. The effects of the suspension concentration, applied voltage, deposition time and processing method of titanium alloy cathode on the coating thickness and morphology were investigated. The deposition layers on titanium alloys with smooth surfaces and thickness of 0.35–1.2 mm could be obtained by adjusting the aforementioned parameters. In addition, after being sintered at 1500°C for 3 h in air atmosphere, ZrO2 toughened Al2O3 ceramic layers became smooth and dense.

  • RESEARCH ARTICLE
    Rafia AZMAT, Faryal Vali MOHAMMED, Tehseen AHMED, Qurat-ul-Ain TANWIR

    This article describes the potential of KMnO4 for oxidation of the thiazine dye (Toluidine blue TB) in an acidic medium. The effect of different operational parameters like initial concentration of dye, potassium permanganate, pH, ionic strength, catalyst, acids and temperature were investigated spectrophotometrically at λmax = 613 nm. The results showed a complete removal of the TB with mineralization of the dye solution. Smooth and complete decoloration was observed in the presence of monobasic acid (HCl) as compared to the H2SO4 where little color removal was observed. Pb was found to be an effective catalyst in oxidation for complete and fast decolorization with mineralization. No significant change at elevated temperatures showed that an intermediate complex degraded with slight change in the temperature. UV/visible spectrophotometry and GC mass analysis showed an intermediate activated complex demethylated sulophooxide of TB which later on degraded into smaller fragments.

  • RESEARCH ARTICLE
    Saeed-UR-REHMAN, Muhammad IKRAM, Sadia REHMAN, Shah NAWAZ

    Coordination compounds of modified diamine, the basic unit of which are ethylenediamine, with that of Co (II) are prepared. The modified diamines are ethylenediaceticacid (EDDA) and N,N,N,N-tetaraethylene-1,2-diamine (TEEDA). These diamines are characterized through 1H-NMR, 13C-NMR, elemental analysis and IR techniques. Cobalt (II) complexes of these two ligands were prepared and characterized by physical measurements including elemental analysis, IR, UV-Visible, magnetic susceptibilities and conductance measurements. Antibacterial activities are also carried out in order to investigate the biological activity upon complexation. They were screened against four pathogenic bacteria like BoldItalic and BoldItalic. The results showed significant enhancement in activities.

  • RESEARCH ARTICLE
    Muhammad SULTAN, Hajira TAHIR, Khalid AHMED, Qazi JAHANZEB

    The kinetics of the reaction of Fast Green dye (FG) with cetylpyridinum chloride was studied in alkaline medium by UV-Visible spectrophotometer. Reduction of Fast Green dye was carried out by varying the fast green dye concentration, cetylpyridinum chloride concentration and concentration of sodium hydroxide. In the present study the reduction of dye was carried out in order to reduce the color content. The interaction of dye was carried out with reducing analyte (cetylpyridinum chloride). The rate of the reaction was determined by varying the above parameters at different temperatures. It was observed that the reduction followed pseudo first-order kinetics with respect to dye, surfactant, OH- ion concentration according to the following reaction pathway.

    The mechanism for the photo bleaching of the dye has been?proposed and well confirmed by the data simulation procedure. The activation parameters of the reaction like entropy of activation (ΔBoldItalic) and free energy of activation (ΔBoldItalic) showed the extremely solvated states of transient complex which was less disorderly arranged than the oxidized form of dye, whereas BoldItalicBoldItalic values reflects a high amount of energy required for the reduction of dye with cetylpyridinum chloride.

  • RESEARCH ARTCILE
    A. Rasheed KHAN, Fahim UDDIN, Rehana SAEED, Mahjabeen MUKHTAR

    The effects of CuCl2 and ZnCl2 on the viscosity in aqueous ethanol mixtures (10%–50% v/v) were studied in the concentration range 1.0×10-2–8.0×10-2 mol·dm-3 at different temperatures. It was found that the viscosities increased with an increase in the concentration of the salts and percent composition of ethanol content, whereas it decreased with an increase in temperature. Ion-ion and ion-solvent interactions are determined with the help of BoldItalic- and BoldItalic-coefficients of Jones-Dole equation. The values of BoldItalic- and BoldItalic-coefficients are irregular and increase with a rise in temperature and also with an increase in ethanol contents for both salts. Negative values of BoldItalic-coefficients show that ion solvent interactions is comparatively small and suggest that CuCl2 and ZnCl2 behave as structure breakers in aqueous ethanol mixtures. Thermodynamic parameters like the energy of activation (BoldItalicη) and change in entropy of activation (ΔBoldItalic*) were also evaluated which confirm the structure breaker behavior of salts in aqueous ethanol mixtures.

  • RESEARCH ARTICLE
    Rafia AZMAT, Nida SALEEM

    An investigation of the thionine sensitized aerobic photooxidation of thiourea was observed spectrophotometrically at a wavelength of 598 nm. Articles reported two types of reactions which generally occur in the presence of oxygen: 1) Singlet oxygen, produced by dye sensitization due to the hydrolysis that reacts with thiourea to form oxidative products like urea and other sulfur-containing fragments and 2) bleaching of dye, which leads to the reduction. The rate of reaction in all studied parameters followed first order kinetics with respect to maximum absorption of the dye in the visible band region. Reaction kinetics was significantly dependent upon the medium and the reaction accelerated more rapidly at low pH. A direct relation was exhibited between the thiourea concentration and dye sensitizer, which was not pragmatic with the concentration of dye. The reaction was effected by the temperature, and the values of energy parameters suggested that the energy of activation was low while the entropy of activation increases with the rise in temperature, which indicated a highly solvated state of intermediate complex. Lower value of ΔBoldItalic* and ΔBoldItalic* at elevated temperature showed that free energy is the driving force for the completion of reaction. A mechanism based on the above findings has been suggested.

  • RESEARCH ARTICLE
    Aditya M. VORA

    The well recognized model potential is used to investigate the vibrational properties of four Fe-based binary glassy alloys viz. Fe90Zr10, Fe80B20, Fe83B17 and Fe80P20. The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves (PDC). Three theoretical approaches given by Hubbard-Beeby (HB), Takeno-Goda (TG) and Bhatia-Singh (BS) are used in the present study to compute the PDC. Six local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) and Sarkar et al.’s local field factor (SLFF) based excgange and correlation function are employed to see the effect of exchange and correlation in the aforesaid properties.

  • RESEARCH ARTICLE
    Asadollah FARHADI, Mohammad Ali TAKASSI

    In the present study, the density functional theory (DFT) and Gibbs free energy calculations were performed to investigate the stability and tautomerism of C4-substituted-3,4-dihydropyrimidin-2(1BoldItalic)-ones. Three different forms are possible for the ethyl 3,4-dihydropyrimidinones (ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1BoldItalic)-one-5-carboxylates, ethyl 4-aryl-2-hydroxy-6-methyl-1,4-dihydropyrimidine-5-carboxylates and ethyl 4-aryl-2-hydroxy-6-methyl-3,4-dihydropyrimidine-5-carboxylates) forms that the most stable form is ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1BoldItalic)-one-5-carboxylates (keto-form). The obtained data showed that the substitution on the C4-substitut position can be effective on the equilibrium constant (BoldItaliceq).

  • RESEARCH ARTICLE
    S. NITHIYANANTHAM, L. PALANIAPPAN, D. Raja

    Starch metabolism due to adsorption of enzyme amylase on the starch substrate is outlined briefly. To explore the necessary conditions required for effective adsorption in biological media, ultrasonic techniques have been applied to elucidate the structural variations and component destruction in the considered systems. The ability of the enzyme amylase to break the linkages in starch (substrate) was determined from the observed ultrasonic velocity, which highlights the deciding factors of metabolism. It is concluded that the phenomenon of adsorption is decided by the surface area, the number of subunits held by the substrate, and the structure existing in the adsorbent, and above all, a relatively higher quantity of enzyme and the substrate.

  • RESEARCH ARTICLE
    K. R. Vishnu MAHESH, H. N. Narasimha MURTHY, B. E. KUMARASWAMY, N. RAGHAVENDRA, R. SRIDHAR, M. KRISHNA, Niranjan PATTAR, Ratna PAL, B. S. Sherigara

    The Sodium Montmorillonite (Na-MMT) is not susceptible to polymer due to its organophilic character and low basal spacing. The primary objective of this study was to improve Na-MMT platelets separation by organically modifying it with cation and anion exchanges using Cetyl trimethyl ammonium bromide (CTAB) and Sodium dodecyl sulfate (SDS) respectively. Basal spacing, presence of functional groups, Zeta-potential with particle size analysis and thermal stability of the Organomodified Na-MMT (OMMT) were characterized using XRD, FTIR, zeta-potential analyzer and TGA respectively. The basal spacing of CTAB modified OMMT increased to 19.5 ? from 11.0 ? which corresponds to the basal spacing of Na-MMT. The SDS modified OMMT did not show any increase in the basal spacing. FTIR spectra of CTAB modified Na-MMT illustrated the attachment of CTAB functional groups to Na-MMT, while the same was absent in the case of SDS modified Na-MMT. The zeta-potential of Na-MMT shifted from -24.88 mV to 15.66 mV in the case of CTAB modified Na-MMT and 12.49 mV for SDS modified Na-MMT, indicating a greater surface potential of the modified nanoclay. The TGA showed greater weight loss for CTAB modified Na-MMT than that for Na-MMT, indicating the effective Na+ ion exchange with alkyl amines.