Sharif Digital Repository

In the present work, synthesis and swellability of acrylatedstarch-based hydrogels was investigated. Acrylic groups were introduced onto starch backbone by a homogeneous synthesis to produce starch monomers with three different degree of substitution (DS). The radical copolymerization of acrylatedstarch (AST) with acrylic acid (AA) and acrylamide (AAm) was carried out in aqueous solution using ammonium persulfate (APS) as an initiator. Infrared spectroscopy (FT-IR) and TGA thermal analysis were carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was examined by scanning electron microscopy (SEM). Their equilibrium swelling degree was evaluated... 

Partial purification of plant peroxidase from turnip (Brassica rapa) was optimized. Aqueous two phase system and precipitation by ammonium sulfate (as two parallel purification methods) were used. Polyethylene glycol/ammonium sulfate/NaCl (25:7:3%, w/v) system followed by gel-filtration chromatography gave a purification factor of about 36 fold. On the other hand, ammonium sulfate precipitation (60-80% deg) followed by gel filtration gave only about 13 purification fold. Hence, the aqueous two-phase system was more efficient and useful method as a primary purification step since it was less laborious, less time-consuming, and led to more purification factor. The partially purified turnip... 

Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3-(methacrylamido)propyl)]dimethyl(3- sulfopropyl)ammonium hydroxide were synthesized through in situ polymerization in aqueous solution with different contents of an organo-modified clay (OMMT, Cloisite 30B). Structural and thermomechanical properties of hydrogels were characterized by FT-IR, XRD, and DMTA, respectively. Swollen gel strength of hydrogels was determined by a rheological method. Storage modulus of the hydrogels was considerably improved in comparison with its the clay-free counterpart. The nanocomposite hydrogel containing 15% OMMT possessed the highest gel strength. The glass... 

Hydroxyapatite (HAp) nanorods with uniform morphology and controllable size were successfully synthesized by precipitating Ca(NO3) 24H2O and (NH4)2HPO4 in the presence of cetyltrimethylammonium bromide (CTAB) and polyethylene glycol 400 (PEG 400) as cationic surfactant and non-ionic cosurfactant, respectively, under hydrothermal conditions. The effect of hydrothermal temperature on the composition, morphology and size of HAp particles was studied using X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR) and scanning electron microscopy (SEM). Results revealed that the morphology and size of HAp particles can be effectively controlled by the presence of CTAB and PEG... 

A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in southern Iran. It was affiliated with Pseudomonas. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, MR01, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. Compositional analysis revealed that the extracted biosurfactant was composed of high percentages lipid (∼65%, w/w) and carbohydrate (∼30%, w/w) in addition to a minor fraction of protein (∼4%, w/w). The best production of 2.1 g/l was obtained when the cells were grown on... 

Buoyancy-induced fluid flow, which is responsible for most forms of macro-segregation and channel-type segregates in castings, is not directly controllable. If left uncontrolled, natural convection will contribute to non-uniform distribution of alloy constituents and grain structure during solidification of a casting. Non-uniform distribution of chemical composition and physical structure in an alloy casting can significantly affect the reliability of mechanical components. Therefore, materials with acceptable defects can be produced only by trial-and-error and their acceptability is determined by costly inspections. We present a novel technique to control the formation of chimneys and... 

A series of biopolymer-based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free-radical graft copolymerization of acrylamide and 2-acrylamido-2-methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT-IR spectroscopy and scanning electron microscope analysis were used to confirm... 

Oxygen evolution was observed upon mixing solid manganese(III) bidentate Schiff base complexes with aqueous solutions of cerium(IV) ammonium nitrate. However, oxygen evolution was not observed upon mixing solutions of the complexes (in acetonitrile) with Ce(IV). Electron-withdrawing substituents on the Schiff base ligands (NO2, Br) enhanced the reactivity of the manganese complexes toward oxygen evolution. Oxygen evolution was also affected by R groups on the ligands, in the order Me > Et Bz. © 2009 Springer Science+Business Media B.V  

In this article, a new group contribution model is suggested for obtaining the thermodynamic properties of biomolecules in aqueous solutions. Accordingly, a Freed-FV model has been applied for the combinatorial free-volume term. The activity coefficients, solubilities, densities, and vapor pressures of amino acids and simple peptides in aqueous solutions were correlated, using the proposed group contribution model. Group interaction parameters of the proposed model were obtained by use of experimental data from amino acids available in the literature. The results demonstrate that the group contribution model can accurately correlate activity coefficient, solubility, density, and vapor... 

A template-directed synthetic method, using surfactant cetyltrimethylammonium bromide (CTAB) as a template and co-surfactant polyethylene glycol (PEG600) as a co-template under hydrothermal conditions, has been applied to obtain dandelion-like HAp. The morphology, size, crystalline phase, chemical composition, physical characteristics, and thermal behavior of the product were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier ransform infrared spectroscopy (FTIR), induced coupled plasma spectroscopy (ICP), BET (Brunauer, Emmett, and Teller) method, and simultaneous thermal analysis (STA). SEM and TEM... 

A mild and practically-convenient one-pot procedure for the direct Mannich reaction has been developed using a condensation of amines, aldehydes and unmodified ketones under solvent free conditions in the presence of Znl 2 with good to excellent yields. The present methodology offers several advantages, such as excellent yields, simple procedures, short reaction times and milder conditions with very small amounts of catalyst. Furthermore, it is the first time that the catalytic activity of several catalysts under solvent free conditions has been studied. It was found that both the diastereoselectivity and the rate of reaction were improved with various Lewis acids and metal oxides. However,... 

Modeling fate of nitrogen in unsaturated and saturated zone is a complex process, which requires detailed geochemical data. Complexities of the process as well as data insufficiencies are two major issues, which make quantitative assessment of the problem more complicated. In this work, a lumped-parameter model (LPM) is proposed that has been evaluated for a data-limited case to study temporal and steady-state behavior of Nitrate and Ammonium in unsaturated zone. The concentration of components in the model are assumed as the depth-averaged concentrations, and dispersive fluxes have been neglected. The case study area is Tehran City aquifer, which is highly contaminated by domestic... 

In this paper, a bottom-up hydrothermal route is reported for the synthesis of oxygen and nitrogen co-decorated carbon quantum dots (CQDs) using ammonium hydrogen citrate (AHC) as a single precursor. DLS data approved the formation of 4.0 nm (average size) CQDs. XRD pattern shows the interlayer spacing (002) of 3.5 Å for CQDs, which is exactly the same as that of crystalline graphite. XPS and FTIR spectra verified the formation of oxygen and nitrogen functional groups on the CQDs surface. Co-decorated carboxyl, hydroxyl and amine groups on the CQDs surfaces make them as promising polyelectrolyte for gene delivery. Toxicity assay showed a survival rate of 70% under different incubation times... 

Hydrogels of poly(acrylic acid) grafted onto salep with excellent water absorption and water retention abilities under neutral conditions were successfully synthesized for the first time and employed for different applications. The effect of reaction variables to achieve maximum swelling capacity was investigated. In our procedure, ammonium persulfate (APS) as a water-soluble initiator and methylenebisacrylamide (MBA) as a suitable crosslinking agent were used and the best synthesis conditions described. The structure of the final product was confirmed by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy SEM and TGA analysis and a mechanism for superabsorbent... 

Graft copolymerization of methyl methacrylate (MMA) was carried out on bagasse fibers in an aqueous medium using eerie ammonium nitrate (CAN) as initiator under a neutral atmosphere. In order to obtain the optimum condition for graft copolymerization, the effects of initiator concentration, temperature, time of reaction, and monomer concentration were studied. The maximum grafting percent was found to be 122%. The bagasse grafted poly(methyl methacrylate) was characterized by FTIR and its thermal behavior was characterized by TGA. Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA  

The interaction of n-dodecyl trimethylammonium bromide (DTAB) with oxyhemoglobin A and oxyhemoglobin S is investigated using UV-visible absorption spectra and chemometric resolution techniques. Oxyhemoglobins (A and S) induced to partial oxidized form (ferrihemoglobin) by DTAB and finally transform to fully oxidized hemichrome. Hemichrome mole fractions of HbS are more than HbA because of more hydrophobic interaction of DTAB-HbS in second set of binding site relative to DTAB-HbA. The visible spectra between 500 and 650 nm are used for identifying the present components in solution because each species of hemoglobin has a specific spectrum in this region. The number of components and mole... 

(Chemical Equation Presented) New 2-alkyl-5-aryl-(1H)-pyrrole-4-ol derivatives were synthesized via three-component reaction of β-dicarbonyl compounds with arylglyoxals in the presence of ammonium acetate in water at room temperature. © 2008 American Chemical Society  

Hydroxyapatite nanorods aligned with ultrahigh crystallinity and high-yield were successfully synthesized through a hydrothermal approach. In this experiment, a new composition of cetyltrimethylammonium bromide ((CH 3(CH2)15N+(CH3) 3Br-) was designated as CTAP)/Ca(NO3) 2/ (NH4)2HPO4/NaOH and distilled water under hydrothermal condition, to synthesize single crystal HAp nanorods with diameter of 20 ± 10 nm and length of 80 ± 20 nm, was introduced. Crystal phases were determined by X-ray diffraction (XRD). Scanning electron microscope (SEM) was applied to investigate the morphology. The microstructure of the HAp products were further observed by transmission electron microscope (TEM) and high... 

A carbon-paste electrode (CPE) is modified by incorporating cobalt-5-nitrosalophen (CoNSal) and tetraoctylammonium bromide (TOAB). The mechanism of electrocatalytic oxidation of dopamine (DA) and ascorbic acid (AA) at the surface of the CoNSal-modified CPE containing various percents of TOAB is thoroughly investigated by cyclic and differential pulse voltammetry. In solutions of pH 5.0, in which all studies are performed, DA exists as the positively charged species whereas AA is mainly as the neutral form. Therefore, the favorable ionic interaction (electrostatic repulsion) between the cationic form of DA and the cationic surfactant (TOA+) caused increasing the overvoltage for DA and... 

Polyacrylonitrile (PAN) was grafted onto carboxymethyl cellulose (CMC) sodium salt backbones by using cerie ammonium nitrate (CAN) as an initiator. The graft co-polymer, CMC-g-PAN, was hydrolyzed by NaOH solution to yield hydrogel, H-CMC-g-PAN. The nitrile groups of CMC-g-PAN were completely converted to a mixture of hydrophilic carboxamide and carboxylate groups during alkaline hydrolysis, followed by in situ crosslinking of the grafted PAN chains. The structure of the products was confirmed by FTIR spectroscopy. The synthetic parameters affecting the swelling capacity of the hydrogel (i.e., CMC-g-PAN add-on value, the hydrolysis time and temperature, and concentration of NaOH) were...