Sharif Digital Repository

In this study, the essential oil of aerial parts species of a plant called Spearmint was extracted by CO 2 to optimize the results of the supercritical extraction process. In order to achieve maximum total yield extraction and SF-CO 2 concentration, tests were done in a laboratorial pilot considering the Taguchi method under following condition: pressure. 90,100,140,170 bar, temperature. of 35, 40, 45, 50 °C, mean particles size: 250,500,710,1000 μm, flow rate 1,3,5,8 ml/s and dynamic time 30,50,90,120 min. The optimizing conditions for SCE and SF-CO 2 concentration are: 90 bar, 45 °C, 500 μm, 5 ml/s, 120 min and 90 bar, 35 °C, 250 μm, 1 ml/s, 30 min. SCE total yield and CO 2 concentration... 

The morphological manipulation, structural characterization, and optical properties of different CdSe nanocrystals were reported. Several different CdSe nanostructures, including nanowires, tetrapod crystals, and nanoparticles were grown by varying the volume ratio of triethylenetetraamine (TETA) and water (WA) in their mixed solution. By manipulating the growth driving force (i.e., the degree of supersaturation) and kinetics of the process (i.e., growth rate), the morphology and crystal structure of CdSe nanocrystals can be tailored. Growth driving force changed their morphology from nanowires to tetrapod structures and from the latter structure to nanoparticles. Moreover, kinetics of the... 

In this study, we have investigated the bioleaching potential of a native strain of Acidithiobacillus ferrooxidans isolated from zinc and lead sulfide mines under varied ambient conditions of growth and substrate consumption. The effects of intermittent irrigation, type of agglomeration, feed formulation in terms of acid, enriched salt solution, initial number of microorganism, and their interactions on the bioleaching of low-grade zinc sulfide ores (containing 5.78% zinc) on growth and biooxidation efficiency of the bacteria have been evaluated. Bioleaching capacities of the isolate were optimized by the utilization the Taguchi method (e-qualitic-4) for design of experiments. As a result,... 

A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe 3O 4 nanoparticles (NPs) as a sorbent. The unique properties of Fe 3O 4 NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe 3O 4 and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully... 

A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100-200nm for polyamide nanofibers with a homogeneous and porous surface... 

The properties of metallic nanorods vary due to changes in their composition, size and shape, which all depend on the aspect ratio of the nanorods. This work focuses on the optimization of the aspect ratio of silver nanorods using response surface methodology (RSM). Seed-mediated approach, which is the newest method with less difficulty, has been used for the synthesis of silver nanorods. First, silver ions were reduced with sodium borohydride in the presence of sodium citrate dehydrate, as stabilizer. Then, the prepared seeds were added to a solution containing more metal salts, a weak reducing agent (ascorbic acid) and a rod-like micellar template (cetyltrimethylammonium bromide, CTAB).... 

This study focuses on the mode classification of phones speaker modes using GMM 1. In this regard, speech data in both enabled and disabled speaker modes of cell phones and telephones were collected, processed and classified into two different categories. The different mixture numbers (1 to 4) of GMM and wave files sizes of 10, 20, 40 and 80 kb were tested in order to obtain an optimal condition for classification. The GMM method attained 87.99% correct classification rate on test data. This classification is important for speech enabled IVR 2 systems [1], dialog systems and many systems in speech processing in the sense that it could help to load an optimum model for increasing system... 

This article presents experimental results on the electrophoretic deposition (EPD) of bioresorbable chitosan/45S5 Bioglass® composite coatings for orthopaedic implants based on the Taguchi design of experiments (DOE) approach. The influence of EPD parameters including Bioglass® concentration, electric voltage and deposition time on deposition yield was studied by an orthogonal Taguchi array of L18 type. Multivariate analysis of variance (MANOVA) and regression analysis based on the partial least-square method were used to identify the significant factors affecting the deposition yield and its stability during constant-voltage EPD. The coatings were characterised by high resolution scanning... 

Statistically based experimental designs were applied to screen and optimize the bioleaching of spent hydrocracking catalyst by Penicillium simplicissimum. Eleven factors were examined for their significance on bioleaching using a Plackett-Burman factorial design. Four significant variables (pulp density, sucrose, NaNO3, and yeast extract concentrations) were selected for the optimization studies. The combined effect of these variables on metal bioleaching was studied using a central composite design (CCD). Second-order polynomials were established to identify the relationship between the recovery percent of the metals and the four significant variables. The optimal values of the variables... 

Nanocrystalline TiO2-AgO thin films and powders were prepared by an aqueous particulate sol-gel route at the low temperature of 573 K (300 °C). Titanium tetraisopropoxide and silver nitrate were used as precursors, hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the phase composition of the mixed oxide depends upon the annealing temperature, being a mixture of TiO2 and AgO in the range 573 K to 773 K (300 °C to 500 °C) and a mixture of TiO2, AgO, Ag2O at 973 K (700 °C). Furthermore, one of the smallest crystallite sizes was obtained for TiO... 

Novel unbreakable solid phase microextraction (SPME) fiber coatings were fabricated by electrospinning method in which the polymeric solution was converted to nanofibers using high voltages. Four different polymers, polyurethane (PU), polycarbonate (PC), polyamide (PA) and polyvinyl chloride (PVC) were prepared as the fiber coatings on thin stainless steel wires. The extraction efficiencies of new coatings were investigated by headspace solid-phase microextraction (HS-SPME) of some environmentally important chlorobenzenes from aqueous samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Among them, PU showed a prominent efficiency. Effects of coating time and polymer... 

Titania nanoparticles with high photocatalytic activity were prepared from titanium alkoxide dissolved in alcohol and water under acidic conditions. The effects of the key parameters including (alkoxide/water) ratio, (alkoxide/alcohol) ratio, precursor type, solvent type, type and concentration of stabilizer, calcination temperature, presence of methylcellulose (MC) and hydrothermal treatment were studied. The optimal conditions were obtained through an experimental design technique. This technique is also used to find the main factors influencing the degradation of methylene blue (MB) and mass percent of anatase phase. The powders characteristics were investigated by XRD and... 

In this paper, the effect of different parameters on the thermal operation of a Closed Loop Pulsating Heat Pipe (CLPHP) has been investigated. These parameters include the working fluid, the inclination angle, the filling ratio, and the input heat flux. The effect of nanoparticle mass concentrations has been analyzed as well. It was observed that the CLPHP can decrease thermal resistance up to 11.5 times compared to the same empty copper tube with thermal resistance of 9.4 K/W. Optimum thermal operation for a system with the water-silver nanofluid was achieved at conditions of the 50% filling ratio with thermal resistance of 0.9 K/W, and for the water-titanium oxide system, the optimal... 

A spent processing catalyst from an Iranian oil refinery was initially characterized physically and chemically. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were used to mobilize Al, Co, Mo and Ni from the spent catalysts under optimized conditions in batch cultures. The characteristics of the bioleach solution (pH, Eh, cell concentration and Fe(II)/Fe(III) concentration) were determined along with the concentration of metal values extracted from the catalyst. The results showed that after bioleaching using A. ferrooxidans in the presence of ferrous sulfate, maximum extractions of 63% Al, 96% Co, 84% Mo and 99% Ni were achieved after 30 days at pH 1.8-2.0. However, the... 

Novel high capacity swelling nanoporous hydrogel (NPH) was synthesized via graft copolymerization of acrylamide (AAm) onto kappa-carrageenan (kC, as a polysaccharide) and gelatin (as a protein) hybrid backbone, after hydrolysis of this system. The Taguchi method as a strong experimental design tool was used for its optimized synthesis. The Taguchi method was applied for the experimental and standard 9 orthogonal array (OA) with four factors and three levels for each factor. A series of NPHs were synthesized by proposed conditions of Qualitek-4 Software. Considering the results of 9 trials according to analysis of variance (ANOVA), optimum conditions were proposed. The swelling behavior of... 

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry-selective ion monitoring (GC-MS-SIM) was applied to the determination of methyl tert-butyl ether (MTBE) in water samples. The effect of main parameters affecting the extraction efficiency was studied simultaneously. From selected parameters, volume of extraction solvent, volume of dispersive solvent, and salt concentration were optimized by means of experimental design. The statistical parameters of the derived model were R 2=0.9987 and F=17.83. The optimal conditions were 42.0μL for extraction solvent, 0.30mL for disperser solvent and 5% (w/v) for sodium chloride. The calibration linear range... 

In this study, we have investigated the potential of a native bacterial strain isolated from an Iranian oil field for the production of biosurfactant. The bacterium was identified to be Bacillus mycoides by biochemical tests and 16S ribotyping. The biosurfactant, which was produced by this bacterium, was able to reduce the surface tension of media to 34. mN/m. Compositional analysis of the produced biosurfactant has been carried out by thin layer chromatography (TLC) and FT-IR. The biosurfactant produced by the isolate was characterized as lipopeptide derivative. Biosurfactant production was optimized by the combination of central composite design (CCD) and response surface methodology... 

Enzymatic decolorization of the monoazo dye, acid orange 7 (AO7) by the fungal peroxidase from Coprinus cinereus NBRC 30628 is a complex system, which is greatly affected by temperature, pH, enzyme activity and the concentrations of H2O2 and dye concentration. The study of these factors and investigating the combined interactions between them by applying one-factor-at-a-time (OFAT) method and two other statistical methods including 2-factorial method and response surface methodology (RSM) were aimed in this work. Through OFAT analysis the optimized conditions were a temperature of 25 °C, pH 9.0 with H2O2 concentration of about 3.9 mM and AO7 concentration of 40 mg/l. A complete... 

The synthesis of amoxicillin with immobilized penicillin G acylase (PGA) in aqueous medium was investigated. The parameters studied were: time course of amoxicillin production, concentration of substrates: hydroxyphenylglycine methyl ester (HPGM) and 6-aminopeicillanic acid (6-APA) and the. effect of enzyme (PGA) content and pH, under variable and constant conditions and temperature variations. In the study of two substrate concentration on amoxicillin production, impressive results were obtained for a 1/3 ratio of 6-amino penicillanic acid (6-APA) and hydroxyl-phenylglycine methyl ester (HPGM). The. synthesis of amoxicillin was preferable at constant pH rather than a variable one. Other... 

A carbon paste electrode (CPE) chemically modified with TiO2 nanoparticles and quinizarine (QZ) was used as a selective electrochemical sensor for the simultaneous determination of minor amounts of d-penicillamine (D-PA) and tryptophan (Trp). This modified electrode showed very efficient electrocatalytic activity for anodic oxidation of both d-PA and Trp. Substantial decreases of anodic overpotentials for both compounds made this analysis possible. Results of square wave voltammetry (SWV) using this modified electrode showed two well-resolved anodic waves for the oxidation of d-PA and Trp, which makes the simultaneous determination of both compounds possible. The peak potential for the...