Scientia Iranica
Volume:14 Issue: 4, 2007

In this study, the extracellular production of silver nanoparticles by the fungus Fusarium oxysporum was investigated. It was found that exposure of Fusarium oxysporum to silver ion leads to the formation of silver nanoparticles. The silver nanoparticles were in the range of 5-60 nm in dimension. The nanoparticles were examined using UV-Visible Spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Transmission Electron Microscopy (TEM) analyses. The formation of nanoparticles by this method is extremely rapid, undertaken in ambient conditions and the synthesized hydrosol is stable for several months in the absence of light.

Open Circuit Potential (OCP) is one of the electrochemical methods to evaluate the corrosion performance of organic coatings. Some authors have used OCP measurement data to confirm their results obtained with Electrochemical Impedance Spectroscopy (EIS). In this investigation, there is an attempt to utilize OCP measurements to estimate the CPVC (Critical Pigment Volume Concentration) of two anti-corrosive pigments, i.e., zinc phosphate and zinc chromate. OCP measurements showed two distinct behaviors in the PVCs lower than CPVC and one typical behavior at the PVCs higher than CPVC. The results showed that OCP measurement could be a highly reliable method for the evaluation of CPVC.

A simple Cloud Point Extraction (CPE) method has been proposed for the simultaneous preconcentration and determination of Zn(II), Co(II), Ni(II) and Pb(II). The pH of the sample solution was adjusted to 9 with buffer solution and the cations were complexed with 2-guanidinobenzimidazole. Triton X-114 was added as a non-ionic surfactant. After the phase separation at 4\pm1\degree C, the surfactant-rich phase was diluted to 1.5 ml using an ethanolic solution of HNO_3 and the analytes were determined by flame atomic absorption spectrometry. The influence of variables, such as pH, ligand concentration, surfactant concentration, etc. upon the complexation and extraction, was studied. Preconcentration of a 50 ml sample solution in the presence of Triton X-114 (0.05% V/V) provided detection limits of 8.8, 4.9, 7.8 and 11 ng ml^{-1} for Zn, Ni, Co and Pb, respectively. The dynamic linear range of concentration, relative standard deviation and enhancement factors are as follows: 8.8-80, 4.9-3000, 7.8-2000, 11-6000 ngmL^{-1}; 5.2%, 4.%, 7.8%, 3.2% and 13, 15.5, 15, 29.6 for Zn, Ni, Co and Pb, respectively.

In this research, a naturally occurring clay mineral, hectorite, was used as the support for several quaternary ammonium and phosphonium cations to measure and compare their catalytic activity in a triphase catalytic system. The intercalation of the catalysts in the clay has the advantage of easy catalyst recovery; the catalyst can be removed by a simple separation technique, such as filtration or centrifugation, upon completion of the reaction. The rate of conversion of $n$-butyl bromide to $n$-butyl chloride was measured in the presence of two classes of phase transfer catalyst: Quaternary ammonium and quaternary phosphonium cations. The rate of the reaction was measured for the biphase reactions (no supporting clay) and for the triphase catalytic system (with supporting clay). The results have shown that quaternary phosphonium catalysts are somewhat more reactive than the corresponding quaternary ammonium catalysts. It was also found that the intercalated catalysts could be used several times before losing their catalytic activity. Also, a remarkable increase in catalytic activity has been observed using a co solvent. However, it appears that there is a limit for the co-solvent concentration to be effective.

The aim of this work was to evaluate the possibilities of immobilization of lactoperoxidase (LPO) on concanavalin A-Sepharose 4B support. Significant biospecific interaction of this heme-containing glycoenzyme with Con A was established by using \alpha-D-mannopyranoside and \alpha-D glucopyranoside, which are involved in the linking of the carbohydrate moieties of the enzyme with lectin. The preparation obtained indicated improved kinetic parameters (K_m and V_{\max}) compared with the soluble form. No significant differences were observed between the optimal pH and temperature of the anchored and free enzymes. The thermal stability of the biospecifically immobilized preparation was substantially higher than that of the unbound enzyme. In addition, seven cycles of enzymatic conversion and washing of the column showed the remarkable operational stability of immobilized LPO.

Over the past four decades, interest in the physical and chemical properties of inclusion complexes has grown considerably. One of the most important reasons for this is the relevance that inclusion complexes have to enzyme substrate and drug-receptor interactions. Inclusion complexation between the drug piroxicam and $\beta$-cyclodextrin was investigated by using the simple and easily accessible UV-visible spectroscopy technique, and the stability constants of the inclusion complexes at two different concentrations of the guest molecule were calculated. The stability constant of the inclusion complex with a diluted solution of the piroxicam drug was \overline{K}=24.75\pm5.89 mol^{-1}.L at \lambda_{max}=352 nm and that of the saturated solution of piroxicam was calculated to be: K=69.35\pm5.65 mol^{-1}.L at \lambda_{max}=285 nm and K=56.34\pm8.34 mol^{-1}.L at \lambda_{max}=251 nm.

The essential oil of \Rosa damascena Mill cultivated in central Iran (Kashan region) from the petals and whole flower (petals and retals), were extracted using a Clevenger apparatus in aqueous and acidic (10% v/v)solutions. Depending on the conditions of the steam distillation, eighteen major components of the essential oil extracts were identified by GC-MS in a 0.4-1% yield. The volatile components obtained from the retals were compared with the volatile oil from whole flowers (retals and petals) in aqueous and acidic solutions. The major differences were, first, some of the effective component in the retals, like \beta-citronellol, which is responsible for the higher quality of the rose oil obtained in a better yield, and, secondly, some of the toxic components, like 2-octanamine (0.47% in E sample), which can reduce the quality of the rose oil and which are completely removed in the acidic solution. According to the GC-MS results, \beta-citronellol (14.5-47.5%), nonadecane (10.5-40.5%), geraniol (5.5-18%) and henicosane (7-14%), were the major components of the oil.

A convenient one-pot preparation of 2-(alkylamino) and 2(arylamino)-4(3H) quinazolinones in high yields has been developed by microwave induced heterocyclization of 2-aminobenzamide with isothiocyanates (or Isocyanates) in solvent-free conditions. In comparison, the reactions are faster under microwave irradiation and the yields are much higher than those by/of conventional heating (under reflux in toluene).

Theoretically, plants growing under stress conditions, such as in saline or waterlogged conditions, should behave with ^{13}CO_2 discrimination and have different \delta^{13}C values. Therefore, this experiment was conducted to evaluate the effect of factors such as salinity and hypoxia in affecting delta values of Puccinellia ciliata and Balansa clover (Trifolium michelianum Savi. Var balansae boiss). This study reveals that these two species (C_3 plants) behave differently and B. clover has more positive \delta^{13}C values (7.6\%) compared to P. ciliata. The overall average of \delta^{13}C were -28.85 and -26.66 ^0/_{00}, respectively, for P. ciliata and B. clover. The \delta^{13}C values for the shoots and roots of the two species also have different values (more positive values in roots compared to shoots). Waterlogging and salinity have a significant affect on {13}CO_2 discrimination and, statistically, these effects on \delta^{13}C values are significant (p<0.001). This means that environmental factors, such as salinity and waterlogging, create a situation for plants in which the discriminate rate against \delta^{13}C would be changed (less discrimination for hypoxia and more for salinity conditions). The combined effects on species and plant parts of waterlogging and salinity are not statistically insignificant on \delta^{13}C values, however, each factor separately has a significant effect on \delta^{13}C values. P. ciliata was grown in different seasons (summer and winter) and showed significant differences in \delta^{13}C values (by almost 4\%). The carbon content (\%) of the two species was different, but, were not related to \delta^{13}C, respectively.

An understanding of solid-liquid mixing, with many aspects of mixing, dispersing and contacting, is critical to the efficient preparation of brine from sodium formate and other processes, such as agitated leaching, in the mining industry, rubber crumb, crystallization and precipitations. Generally speaking, solids can be porous catalysts for catalytic reactions, active agents for adsorption, polymers and co-polymers for suspension polymerization or particles that need to be dissolved or coated. In the present attempt, large-eddy simulations of a turbulent flow of a mixture of solid liquid in a baffled, cylindrical mixing vessel, with a large number of solid particles, were formulated to obtain insight into the fundamental aspects of a solid-liquid mixing. The impeller-induced flow at the blade tip radius of an axial turbine was modeled using the dynamic-mesh Lagrangian method. The simulations were four-way coupled, which implies that both solid liquid and solid-solid interactions are taken into account. By using a phenomenological model, based on the modified Kelvin-Maxwell model, normal and tangential forces were calculated acting on a particle, due to viscoelastic contacts with other neighboring particles. Simulations were performed for the special case of dissolving solids, whose dissolution rate was assumed to be mass transfer controlled. The results suggest that the granulated form of dissolving solids, such as sodium formate, may provide a mixture that allows faster and easier preparation of formate brine in a mixing tank.

present study, twenty three catalysts for dimethylether (DME) synthesis were prepared, according to a pre-designed research program consisting of four phases. In each phase, by applying the Taguchi experimental design method, a number of catalysts was synthesized by the co-precipitation method, using different percentages of metal nitrate solution. The activities of the catalysts were determined by applying a laboratory scale continuous packed bed reactor. It was noted that the ZnO content of the catalyst, nature of precipitant agent, mass ratio of gamma-alumina to total metal oxides and calcination temperature, had the highest impact on the activity of the catalysts. ژ

PVT properties are important parameters in reservoir engineering. Correlations are used whenever experimentally derived PVT data are not available and data from local regions are expected to give better approximation to estimated PVT values. This paper evaluates the most frequently used empirical black oil PVT correlations for application in the Middle East. As will be discussed, Empirical PVT Correlations for Middle East crude oil have been compared as a function of commonly available PVT data. Correlations have been compared for: Bubble point pressure; solution gas oil ratio at bubble point pressure and oil formation volume factor at bubble point pressure. Often, these properties are required for oil field computations when there are no experimental or laboratory measurements available. For comparison of correlations, a wide range of data has been covered. Approximately, five hundred Pressure-Volume-Temperature (PVT) reports have been used in the comparison correlations. The PVT correlations can be ordered with respect to their accuracy: (a) Bubble point pressure: The result of Al-Marhoun and Standing are similar to Hanafy, Dindoruk; (b) Oil formation volume factor: Petrosky, Glaso and Dokla correlations produce similar results, while Al-Marhoun, Standing and Hanafy predictions are different and (c) Solution gas oil ratio: Standing and Al-Marhoun results are the same, however, Dindoruk, Glaso and Petrosky correlations are less accurate. Error bounds of the obtained correlations are calculated and compared to Middle East crude oil. All reservoir fluid property correlations available in the petroleum engineering literature were compared with this databas.

The aim of the present work was to examine the changeable relationship between antioxidant activity and the phenolic content of dried pistachio hulls during Solid-State Fermentation (SSF) by Phanerochaete chrysosporium. Recently, in the literature, mobilization of phenolic antioxidants from soybean powders by Lentinus edodes has been reported [1]. P. chrysosporium, a well-studied white-rot fungus, was capable of producing lignin peroxidase (LiP) and manganese peroxidase (MnP) during the fermentation of pistachio hulls. Phenolic content, in the aqueous extract of the SSF of pistachio hulls, increased during the first 4 days of fermentation by 11% and decreased during the next 2 days. An increasing trend was again seen, which became evident during days 8 to 16 and which reached the highest level of 63 mg caffeic acid equivalent (CAE)/g of dried pistachio hulls. The lowest amount of phenolics was 49.28 mg of CAE/g dried pistachio hulls. The antioxidant activity of the water extract tested in terms of 2,2 diphenyl-1-picrylhydrazl (DPPH) assay. Antioxidant activity fluctuated similar to the phenolics content during the SSF period. The lowest antioxidant activity, in terms of the scavenging of DPPH, was 77%, while the highest level measured was 88%. The culture did not show any LiP and MnP activity during the first 2 days of the SSF. However, activity increased during the next 2 days and, for MnP, activity reached its highest level by day 14 (56.9 U/l), while LiP activity, which was 4.4 U/l on day 6 of fermentation, reached its highest (60.72 U/l). This work includes important points regarding the potential use of pistachio hulls as agricultural waste and as an inexpensive source of production of fungal peroxidases, while the existence of the changeable relationship between phenolics and antioxidant activity may favor the use of fermented pistachio hulls as possible functional food.

The immobilization of cellulase onto non-porous ultrafine silica particles was studied. Cellulase was extracted from a Trichoderma reesei culture after partial purification with ammonium sulfate (pH = 5.0), which was then immobilized onto non-porous ultrafine silica particles, with or without the use of glutaraldehyde as a crosslinking agent. Cellulase was immobilized by adsorption onto ultrafine silica particles efficiently, as well as by covalent cross-linking with glutaraldehysde. Increasing the concentration of the free form of enzyme increased the amount of immobilized cellulase. The maximum enzyme immobilization happened at the free enzyme concentration of 0.48 mg/ml. In general, the optimum pH for immobilization was found to be 5.0, which is close to the pI of the enzyme. The relative activity of the immobilized enzyme was also increased as the amount of immobilized enzyme was increased. However, immobilization of the enzyme on the ultrafine silica particles, with or without the use of glutaraldehyde, showed almost the same enzyme activities. The immobilized cellulase showed a higher thermal stability, with respect to temperature, compared to the free cellulase.