Sharif Digital Repository

The present article deals with super-swelling behavior of crosslinked homopolymer of 2-acrylamido-2-methylpropane sulfonic acid, poly(AMPS), in binary mixtures of dimethyl sulfoxide (DMSO) and various polar solvents including water, mono-, and polyhydric alcohols, and amide solvents such as N-methyl pyrrolidone. Extraordinary phase transition sequences including a new unusual swelling phenomenon, referred to as "overentrant" swelling, was observed for this polymeric organogel in the solvent/DMSO mixtures. The swelling behaviors were preliminarily explained based on the major interactions involved in the solvation process and dielectric constant of the swelling media. It was established that... 

In this article, a multiscale modeling procedure is implemented to study the effect of interphase on the Young's modulus of CNT/polymer composites. For this purpose, a three-phase RVE is introduced which consists of three components, i.e., a carbon nanotube, an interphase layer, and an outer polymer matrix. The nanotube is modeled at the atomistic scale using molecular structural mechanics. Moreover, three-dimensional elements are employed to model the interphase layer and polymer matrix. The nanotube and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones potential at the interface. Using this Molecular Structural Mechanics/Finite Element... 

The condition known as a water-hammer problem is a transient condition that may occur as a result of worst-case loadings, such as pump failures, valve closures, etc. in pipeline systems. The pressure in the water hammer can vary in such a way that in some cases it may increase and cause destruction to the hydraulic systems. The pressure in the water hammer can also be decreased to the extent that it can fall under the saturation pressure, where cavitation appears. Therefore, the liquid is vaporized, thus, making a two-phase flow. This pressure decrease can be as dangerous as the pressure rise. As a result of the pressure drop and vaporization of the liquid, two liquid regions are separated,... 

In this study, a multivariate-based strategy was developed for simultaneous determination of thirteen carcinogenic polycyclic aromatic hydrocarbons (PAHs) in water samples using gold nanoparticles (AuNPs) as solid-phase extraction (SPE) sorbent combined with gas chromatography (GC). The extraction technique is based on the strong affinity between citrate-capped AuNPs and PAHs. Furthermore, characterization of AuNPs was performed by UV-vis spectroscopy and transmission electron microscopy (TEM) techniques. A rotatable central composite design (CCD) combined with multiple linear regression (MLR) was used for designing the extraction procedure and developing models using the GC peak areas of 13... 

A dispersive micro-solid-phase extraction (D-μ-SPE) procedure coupled with surfactant-enhanced spectrofluorimetric detection was developed for determination of ofloxacin and lomefloxacin from biological and environmental samples. The D-μ-SPE procedure was performed using magnetic Fe3O4 nanoparticle grafted multi-walled carbon nanotube as an efficient adsorbent. The main factors affecting the signal enhancement (including surfactant concentration and pH) and extraction efficiency (including pH, extraction time, sample volume, amount of magnetic adsorbent, and desorption conditions) were investigated in detail. Under the optimized conditions, the calibration curves were linear (R2 0.9995) over... 

In this study, a dielectrophoresis field-flow fractionation device was analyzed using a numerical simulation method and the behaviors of a set of different cells were investigated. By reducing the alternating current frequency of the electrodes from the value used in the original setup configuration and increasing the number of exit channels, total discrimination in cell trajectories and subsequent separation of four cell types were achieved. Cells were differentiated based on their size and dielectric response that are represented in their real part of Clausius–Mossotti factor at different frequencies. A number of novel designs were also proposed based on the original setup configuration.... 

Natural silk fibroin (SF) polymer has biomedical and mechanical properties as a biomaterial for bone tissue engineering scaffolds. Freeze-dried porous nanocomposite scaffolds were prepared from silk fibroin and titanium dioxide (TiO2) nanoparticles as a bioactive reinforcing agent by a phase separation method. In order to fabricate SF/TiO2 scaffolds, 5, 10, 15 and 20 wt% of the TiO2 were added to the SF. The phase structure, functional groups and morphology of the scaffolds were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques, respectively. Porosity of the scaffolds was measured by Archimedes' Principle. In addition,... 

Comprehensive structural/molecular simulations have been undertaken to study the poly(benzimidazoles) (PBI) membrane combined with four different nano-oxide materials (ZnO, Al2O3, SiO2 and TiO2) for purification and production of hydrogen from natural gases. Composite membranes were built with different amounts of nano-oxide materials to investigate the influence of nano-oxide content on the PBI membrane performance. Several structural characterizations such as FFV, WAXD and also a thermal one (glass transition temperature) were done to study the structural properties of all simulated membrane cells. Moreover, MSD and adsorption isotherms tasks were used to estimate the diffusivity and... 

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... 

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,... 

A novel second-order-statistics-based sequential blind extraction algorithm for blind extraction of quasi-periodic signals, with time-varying period, is introduced in this paper. Source extraction is performed by sequentially converging to a solution that effectively diagonalizes autocorrelation matrices at lags corresponding to the time-varying period, which thereby explicitly exploits a key statistical nonstationary characteristic of the desired source. The algorithm is shown to have fast convergence and yields significant improvement in signal-to-interference ratio as compared to when the algorithm assumes a fixed period. The algorithm is further evaluated on the problem of separation of... 

Superparamagnetic iron oxide nanoparticles (SPION) are being increasingly used in various biomedical applications such as hyperthermia, cell and protein separation, enhancing resolution of magnetic resonance imaging, and drug delivery. However, the toxicity data for SPION are limited. In this study, uncoated and single polyvinyl alcohol coated SPION with high chemical reactivity (due to the bigger surface area) were synthesized using a coprecipitation method. Cytotoxicity of these magnetic nanoparticles and their ability to cause arrest in cell life-cycles was investigated. Interaction of these nanoparticles with adhesive mouse fibroblast cell line (L929) was probed using MTT assay. High... 

Generally, in most areas, groundwater level is deep and heat sources (e.g., energy piles)are embedded in unsaturated soil media. Therefore, in order to accurately analyze the soil response close to heat sources, both heat and moisture transport in unsaturated soil domain should be considered. Thermal loading changes the moisture content in the porous media. In this study, the energy conservation and mass fluid continuity equations derived from hydrothermal analysis of a partially saturated soil medium are considered in cylindrical coordinate system. To make the analytical solution possible, partial differential equations (PDEs)are turned into ordinary differential equations (ODEs), through... 

Brain Computer Interface (BCI) systems, which are based on motor imagery, enable humans to command artificial peripherals by merely thinking about the task. There is a tremendous interest in implementing BCIs on portable platforms, such as Field Programmable Gate Arrays (FPGAS) due to their low-cost, low-power and portability characteristics. This article presents the design and implementation of a Brain Computer Interface (BCI) system based on motor imagery on a Virtex-6 FPGA. In order to design an accurate algorithm, the proposed method avails statistical learning methods such as Mutual Information (MI), Linear Discriminant Analysis (LDA), and Support Vector Machine (SVM). It also uses... 

Convective heat transfer plays a significant role in numerous industrial cooling and heating applications. This method of heat transfer can be passively improved by reconfiguring flow passage, fluid thermophysical properties, or boundary conditions. The broader scope of nanotechnology introduced several studies of thermal engineering and heat transfer. Nano-fluids are one of such technology which can be thought of engineered colloidal fluids with nano-sized particles. In the present study, turbulent forced convection heat transfer to nanofluids in an axisymmetric abrupt expansion heat exchanger was investigated experimentally. During heat transfer investigation, the functionalized... 

Pt@Bi-TiO2 photocatalysts with different Bi (0–5 wt%) and Pt (0–2 wt%) contents were prepared by a two-step sol-gel and photo-deposition technique and were used in photo-reduction of CO2. The synthesized catalysts were characterized by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning and transmission electron microscopy (SEM and TEM), nitrogen sorption measurement (BET), Raman spectroscopy, Electron paramagnetic resonance (EPR) spectroscopy and photoluminescence spectroscopy (PL). CO2 photo-reduction results revealed that the introduction of Bi into TiO2 structure and subsequent loading of Pt on its surface significantly increased the methane yield.... 

An automated technique based on purge-and-trap coupled to gas chromatography with mass spectrometric detection has been developed and optimized for the trace determination of five of the most important water odorants; 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2,4,6-trichloroanisole and geosmin. The extraction method was absolutely solvent-free. Analytes were purged from 20 ml of water sample containing sodium chloride at room temperature by a flow of He and trapped on a Tenax sorbent. The desorption step was performed with helium and temperature programming and desorbed analytes were directly transferred to a gas chromatograph coupled to a mass... 

Separating produced water is a key part of production processing for most crude oils. It is required for quality reasons, and to avoid unnecessary transportation costs and prevent pipework corrosion rates caused by soluble salts present in the water. A complicating factor is that water is often present in crude oil in the form of emulsions. Experiments were performed to evaluate the performance of ultrasonic fields in demulsifying crude oil emulsions using novel pipe-form equipment. A horn-type piezoelectric ultrasonic transducer with a frequency of 20 kHz and power ranging from 80 W to 1000 W was used for experimental purposes. The influences of the intensity of ultrasonic fields,... 

Isolation and characterization of circulating tumor cells (CTCs) found in blood samples of cancer patients have been considered as a reliable source for cancer prognosis and diagnosis. A new continuous microfluidic platform has been designed in this investigation for simultaneous capture and characterization of CTCs based on their deformability. The deformability-based chip (D-Chip) consists of two sections of separation and characterization where slanted weirs with a gap of 7 μm were considered. Although sometimes CTCs and leukocytes have the same size, the deformability differs in such a way that can be exploited for enrichment purposes. MCF7 and MDA-MB-231 cell lines were used for the... 

An efficient and selective drug delivery vehicle for cancer cells can remarkably improve therapeutic approaches. In this study, we focused on the synthesis and characterization of magnetic Ni1−x Cox Fe2 O4 nanoparticles (NPs) coated with two layers of methionine and polyethylene glycol to increase the loading capacity and lower toxicity to serve as an efficient drug car-rier. Ni1−x Cox Fe2 O4 @Methionine@PEG NPs were synthesized by a reflux method then charac-terized by FTIR, XRD, FESEM, TEM, and VSM. Naproxen was used as a model drug and its loading and release in the vehicles were evaluated. The results for loading efficiency showed 1 mg of Ni1−x Cox Fe2 O4 @Methionine@PEG NPs could load...