Sharif Digital Repository

In this study, cellulose acetate (CA) fibers were prepared using different solvent systems in electrospinning. The recorded scanning electron microscopy micrographs indicated that the morphology of the prepared fibers is closely associated with the type of electrospinning solvents. The prepared CA fibers were used as an extractive phase for on–line micro–solid phase extraction (μ-SPE) of nonsteroidal–inflammatory drugs (NSAIDs) in biological samples pursued by HPLC–UV determination. Work conducted on this research ascertained that the use of dichloromethane:acetone (3:1, v/v) solvent system in the CA dissolution for electrospinning, leads to the formation of porous ribbon–like fibers and... 

Graphene nanoplatelets with different surface functional groups and polarity were prepared by Hummer's method and electrochemical exfoliation of graphite in two aqueous acids. The XRD, FTIR and sedimentation tests performed to characterize the polarity of the prepared graphenes. The highest polarity was associated with the sample prepared by Hummer's method and the sample synthesized by electrochemical exfoliation in nitric acid medium showed the moderate polarity. Meanwhile, the sample prepared in sulfuric acid medium showed the lowest polarity. Then thermoplastic polyurethane (TPU)/graphene nanocomposite films were fabricated with solvent exchange method. While the dispersion state and... 

The current investigation was to present composite membranes with strong interfacial adhesion between top polymeric selective layer and the bottom micro-porous support layer with appropriate gas permeation behavior and practically suitable processing characteristics. To this end, a series of acrylate-terminated polyurethanes (APUs) based on poly (ethylene glycol) (PEG) with different molecular weights (Mn) of 600, 1000, 1500, 2000 and 4000 g/mol, toluene diisocyanate (TDI), and 2-hydroxyethyl methacrylate (HEMA) were synthesized. Composite membranes were prepared with UV-curable acrylate-terminated polyurethane/acrylate diluent (APUAs) as selective layer and polyester/polysulfone (PS/PSF) as... 

It is known that Fluoride ions strongly affect bone mineralization and formation. In the present study, the engineered bone tissue scaffolds are fabricated using silk fibroin (SF) and flouridated TiO2 nanoparticles. TiO2 nanoparticles are modified by fluoride ions, and different levels (0, 5, 10, 15 and 20 wt%) of the fluoridated TiO2 nanoparticles (TiO2-F) were subsequently added to the SF matrix through phase separation method to prepare silk fibroin/flouridated TiO2 nanocomposite scaffolds (SF/TiO2-F). Phase structure, functional groups, morphology and mechanical properties of the obtained scaffolds were evaluated by X-ray diffraction method (XRD), Fourier transform infrared spectroscopy... 

For thousands of years, plants and their products have been used as the mainstay of medicinal therapy. In recent years, besides attempts to isolate the active ingredients of medicinal plants, other new applications of plant products, such as their use to prepare drug delivery vehicles, have been discovered. Nanobiotechnology is a branch of pharmacology that can provide new approaches for drug delivery by the preparation of biocompatible carrier nanoparticles (NPs). In this article, we review recent studies with four important plant proteins that have been used as carriers for targeted delivery of drugs and genes. Zein is a water-insoluble protein from maize; Gliadin is a 70% alcohol-soluble... 

Biodegradable acrylate-terminated polyurethane/acrylate (APUA) filled with 2-hydroxyethyl methacrylate functionalized carbon nanotube (CNT-HEMA) was prepared by in situ free radical crosslinking. CNT-HEMA enhanced crystallinity of soft domain and caused more phase separation between hard and soft domains of APUA. Tensile testing showed a considerable improvement in elastic modulus (∼160%) and tensile strength (∼30%) at 1 wt% loading. Morphological features of APUA induced by nanotubes were found to be dominant on mechanical properties of APUA/CNT-HEMA. CNT-HEMA increased water contact angle of APUA; however, wettability of APUA/CNT-HEMA maintained in acceptable range for biomedical... 

A laboratory-scale multistage anaerobic biofilm reactor of three compartments with a working volume of 54-L was used for treating a synthetic medium-strength wastewater containing molasses as a carbon source at different influent conditions. The start-up period, stability and performance of this reactor were assessed at mesophilic temperature (35 °C). During the start-up period, pH fluctuations were observed because there was no microbial selection or zoning, but as the experiment progressed, results showed that phase separation had occurred inside the reactor. COD removal percentages of 91.6, 91.6, 90.0 and 88.3 were achieved at organic loading rates of 3.0, 4.5, 6.75 and 9.0 kg COD/m3 day,... 

In this study, EVAc/PLA/organo clay nanocomposites were prepared via solution mixing method. The SEM images were used to investigate the morphology of nanocomposites revealing no phase separation or agglomeration of disperse phase in EVAc/PLA blends and nanocomposites. SAXS spectra confirmed the intercalated morphology of nanocomposites. Soil burial test were carried out and the rate of degradation of the samples were measured indirectly. Oxygen gas permeability of EVAc was slightly decreased by adding PLA to the matrix, when small loads of clay caused dramatic improvement in barrier properties. Melt rheological frequency sweep test illustrated the compatibility of EVAc with low contents of... 

We study the competition between spin and charge fluctuations of the extended Hubbard model with on-site and dipole-dipole interactions in a one-dimensional lattice. Using the extended two-particle self consistent (ETPSC) method, we find the corresponding expressions for spin and charge response functions. In this approach, the irreducible spin and charge vertices are a function of inter-particle distance (r) and wave-number (q). This theory allows us to determine the crossover temperatures and the dominant instability as a function of U and V. The phase diagrams are obtained for several effective particle densities: n = 0.5, n = 1 and n = 4/3. Each phase diagram (U − V − T space)... 

Smart bio-based shape memory polymers with high performance and fast response have the exciting potential to meet the growing need in biomedical applications. In this study, novel fast response UV-curable shape memory polyurethane acrylates (SMPUAs) comprising polycaprolactone diols (PCL-Diol), hexamethylene diisocyanate (HDI) and hydroxy-methyl methacrylate (HEMA) were synthesized by two-step bulk polymerization. Two series of PUAs with almost the same amount of hard segment content (HSC) were prepared with varying soft-segment molecular weight (2000, 3000, and 4000 g/mol) and different molar ratios of constituents. A mono-functional reactive diluent was used to control HSC and reduce the... 

Sample preparation for non-target analysis is challenging due to the difficulty in the extraction of polar and non-polar analytes simultaneously. Most commercial solid sorbents lack the proper comprehensiveness for extraction of analytes with different physiochemical properties. A possible key is the combination of hydrophobic polymer and hydrophilic surface functional groups in solid based extraction methods in order to generate the susceptibility for retaining both polar and non-polar analytes. To pursue this goal, in this study, four polar groups including [sbnd]NH 2 , [sbnd]NO 2 , [sbnd]COOH, and [sbnd]COCH 3 were chemically bound to Amberlite XAD-4 substrate in order to prepare a... 

In this study, a method was described for the extraction of three antibiotic residues from cow milk samples using a graphene oxide–starch–based nanocomposite. The prepared nanocomposites were employed as an extractive phase for micro-solid phase extraction of antibiotics from cow milk samples. The extracted antibiotics, i.e. amoxicillin, ampicillin and cloxacillin, were subsequently analyzed by high-performance liquid chromatography–ultraviolet detection (HPLC–UV). Important variables associated with the extraction and desorption efficiency were optimized. High extraction efficiencies for the selected antibiotics were conveniently achieved using the starch–based nanocomposite as the... 

In the present experimental study, the effect of operating parameters such as inlet and outlet pressure as well as inlet temperature on the mass separation capability of vortex tubes (VTs) for a gas mixture is investigated. Specifically, concentrating heavier components of a gas mixture in the hot outlet stream is considered. Proposing a semi-empirical index from the experimental study, the simulation of different arrangements of VTs, and the effect of recycling a portion of the hot outlet stream on its mass separation performance are investigated. Moreover, the proposed separation method by VTs is economically compared with commonly used methods by distillation columns and two-phase... 

The potential utilization of encapsulation techniques in food, pharmaceutical and agricultural products preparation, presents a new alternative for complementary technologies such as targeting delivery vehicles and carriers for active food ingredients. Encapsulation could be accomplished by different techniques like: simple or complex coacervation, emulsification technique, phase separation, spray drying, spray chilling or spray cooling, extrusion coating, freeze drying, fluidized-bed coating, liposomal entrapment, centrifugal suspension separation, co-crystallization and molecular inclusion complexation. Encapsulation is a method by which one bioactive material or mixture of materials is... 

A cryogel–based semi–interpenetrating polymer network (Cryo–SIPN) was prepared in which conductive polymers such as polyaniline (PANI) and polypyrrole (PPy) were formed within the super porous network of acrylic acid cryogel. For completion of cryo-polymerization, all the constituent solutions were severely mixed and placed into the plastic straws and kept at -20°C and then the synthesized cyrogels were cut into the 1-cm length and freeze dried after washing with water. The Cryo–SIPN polymeric composite was applied in micro solid phase extraction (µSPE) of some selected antibiotic residues from various samples. The µSPE method combined with a high performance liquid... 

An efficient, green, novel and rapid vortex-assisted dispersive solid-phase extraction (VADSPE) technique was used for the preconcentration and determination of trace levels of Cu2+ followed by flame atomic absorption spectrometry. Graphene oxide (GO) was synthesized from graphite and then modified by pectic acid (poly-d-galacturonic acid, PA) to synthesize the pectic acid–graphene oxide (PA-GO) nanocomposite. The Fourier transform infrared spectrophotometry, field emission scanning electron microcopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis were used to characterize the synthesized GO-PA nanocomposite. By using VADSPE technique, PA-GO was used as an adsorbent for... 

In this study, we numerically determined the performance of a microscale separator comprising a lateral and a main channel to separate a two-phase flow. It was aimed to conduct continuous phase through the lateral channel and dispersed phase through the main channel. The continuous and dispersed phases were modeled as incompressible Newtonian fluids with the corresponding interface tracked by the phase-field model. The dynamics, including pressure fluctuations in the separator, were further examined. It was mechanistically demonstrated how the geometry of the separator modulates the phase separation. Further examined were the influences of various geometrical parameters on the performance of... 

In this study, the effects of the type and content of reactive diluents on the permeation/separation of carbon dioxide/nitrogen (CO2/N2) through acrylate-terminated polyurethane (APU)-acrylate/acrylic diluent (APUA) composite membranes was investigated. A series of APUs based on poly(ethylene glycol) (PEG)-1000 g mol−1, toluene diisocyanate, and 2-hydroxyethyl methacrylate was synthesized and then diluted with several reactive diluents. The results obtained from differential scanning calorimetry (DSC) and Fourier transform infrared analyses showed that the microphase interference of hard and soft segments increased with increasing reactive diluent content. Furthermore, with increasing alkene... 

The in vitro endothelial response of human umbilical vein endothelial cells was investigated on a poly (caprolactone)-based polyurethane surface vs an in situ TiO2-polyurethane nanocomposite surface, which has been produced as scaffolds for artificial vascular graft. The in situ synthesis of TiO2 nanoparticles in polyurethane provided surface properties that facilitated cellular adhesion, cell sensing, cell probing and especially cell migration. Cells on the nanocomposite surface have elongated morphology and were able to produce more extracellular matrix. All of these advantages led to an increase in the rate of endothelialization of the nanocomposite scaffold surface vs pure polyurethane.... 

Gas chromatography-mass spectrometry (GC-MS) combined with Chemometric resolution techniques were proposed as a method for the analysis of volatile components of Iranian damask rose oil. The essential oil of damask rose was extracted using hydrodistillation method and analyzed with GC-MS in optimized conditions. A total of 70 components were identified using similarity searches between mass spectra and MS database. This number was extended to 95 components with concentrations higher than 0.01% accounting for 94.75% of the total relative content using Chemometric techniques. For the first time in this work, an approach based upon subspace comparison is used for determination of the chemical...