Sharif Digital Repository

Herein, we present a novel, simple, and ultrasensitive electrochemical DNA (E-DNA) sensor based on hollow carbon spheres (HCS) decorated with polyaniline (PANI). A thiolated 21-mer oligonucleotide, characteristic of HBV DNA, is immobilized via electrodeposited gold nanoparticles on HCS-PANI. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) are used to characterize the electrochemical properties of the prepared nanocomposite. Scanning electron microscopy is employed to investigate the morphological texture of the fabricated modifier. An enhanced intrinsic signal of PANI is probed to evaluate the biosensing ability of the prepared... 

A sensitive voltammetric sensor is fabricated by the electrochemical oxidation of polypyrrole (PPy) on a glassy carbon electrode surface covered with a thin film of single-walled carbon nanotubes (SWCNT/GCE). Ponceau4R (P4R) used as an anionic dopant controlled the structure, stability, conductivity, and electrochemical properties of the PPy. The porosity and oxygen-containing active sites on the P4R-PPy/SWCNT/GCE were increased by over-oxidation of the PPy layer to achieve P4R-oPPY/SWCNT/GCE. Morphology features of the P4R-oPPY/SWCNT layer are thoroughly characterized using microscopy instruments. The salbutamol (SAL) voltammetric behavior is evaluated by P4R-oPPY/SWCNT/GCE and a mechanism... 

In this research, the IFT behavior of two different specimens of W/O emulsion with distinctive soluble ingredients of water in contact with CO2 and N2 was examined. The Minimum Miscibility Pressure (MMP) of the mentioned gases with emulsion specimens were measured and compared with the case of the original crude oil with no water content. This study focuses on the quantity of water in the W/O emulsion specimens and its effects on IFT and MMP values. The IFT behavior of W/O emulsions was surveyed for two different cases of distinctive water soluble ingredients, i.e. sea water and reservoir brine. The tests were performed under high pressure-high temperature (HPHT) conditions utilizing... 

Solid oxide fuel cells (SOFCs) are rapidly becoming recognized as a new alternative to traditional energy conversion systems because of their high energy efficiency. From an ecological perspective, this environmentally friendly technology, which produces clean energy, is likely to be implemented more frequently in the future. However, the current SOFC technology still cannot meet the demands of commercial applications due to temperature constraints and high cost. To develop a marketable SOFC, suppliers have tended to reduce the operating temperatures by a few hundred degrees. The overall trend for SOFC materials is to reduce their service temperature of electrolyte. Meanwhile, it is... 

A numerical simulation algorithm based on the finite volume discretisation is presented for analyzing ship motions. The algorithm employs a fractional step method to deal with the coupling between the pressure and velocity fields. The free surface capturing is fulfilled by using a volume of fluid method in which the interface between the liquid (water) and gas (air) phases are computed by solving a scalar transport equation for the volume fraction of the liquid phase. The computed velocity field is employed to evaluate the acting forces and moments on the vessel. Using the strategy of boundary-fitted body-attached mesh and calculating all six degrees-of-freedom of motion in each time step,... 

Numerical simulation of floating or submerged body motions is presented based on a Volume of Fluid (VoF)-fractional step coupling. Solving a scalar transport equation for volume fraction of two phases results in a single continuum with a fluid property jump at the interface. In addition, velocity and pressure fields are coupled using the fractional step method. Based on integration of stresses over a body, acting forces and moments are calculated. Using the strategy of non-orthogonal body-attached mesh and calculation of motions in each time step result in time history of hydrodynamic motions. To verify the accuracy of the numerical procedure in simulation of two-phase flow, sloshing and dam... 

In two phase flow investigation, there is a need for robust methods capable of predicting interfaces, in addition to treating the traditional governing equations of fluid mechanics (Navier-Stokes Eqs.). Such methods in a finite volume approach can be classified into two typical categories called interface tracking and interface capturing methods. According to their abilities, interface capturing methods are of more interest in free surface modeling, especially when complex interface topologies such as wave breaking are included. These methods solve a scalar transport equation in order to find the distribution of two phases all over the computational domain. That is, all properties of the... 

We used two digital methods—rise time discrimination (RTD) and an artificial neural network (ANN)—to simultaneously discriminate alpha particles and gamma rays detected by a phoswich detector (50 μm BC-400 coupled to 3 mm CsI(Tl)). The results for 10,000 pulses discriminated by the RTD method showed that the rise time distribution of the pulses is rather vast (between 200 and 800 ns for gamma rays and less than 40 ns for alpha particles). The same result was also observed in the dual-parameter diagram (pulse rise time versus area under the pulse) for an 241Am source. Then, as another approach, three pulse features—rise time, pulse height ratio, and charge ratio—were extracted from 2000... 

This study focused on the synthesis of TiO2-Zeolite nanocomposite through a sol-gel approach. The decrease in the size of the nanocomposite is considered a primary parameter to improve photocatalytic activity. In this regard, fabricated samples were exposed to laser irradiation (532 nm) for four different time intervals in order to investigate the size variation of the nanocomposite. FTIR, UV-Vis, XRD, DLS, SEM and EDX analyses were applied to characterize and determine the size of the products. An optimized nanocomposite sample, in term of the particle size, was used for photodegradation of 2,4-D herbicide from aqueous solution. Photodegradation was carried out under UV irradiation (12 W)... 

Zinc oxide nanoparticles were synthesized and modified by a three-stage method. Elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy, and Brunauer–Emmett–Teller method were applied to characterize the nanoparticles. These nanoparticles were evaluated for toluene adsorption from aqueous solutions as a representative of petroleum hydrocarbon removal. The optimum adsorption condition achieved at pH of 6 and contact time of 30 min. The adsorption isotherms were fitted to the Langmuir model. The measured adsorption capacity was 12.8 mg g−1. This study demonstrated that these nanoparticles could be used as an... 

In this study, magnetic nanoparticles (MNPs) modified with poly amidoamine (PAMAM) dendrimers - by adding methyl acrylate and ethylenediamine continuously till 10th generation- which further anchored to benzaldehyde ligand through polymeric bonding and studied as a novel method for synthesizing a nano sorbent for removing naphthalene (NAP) from aqueous environments. Synthesized nanopolymer was characterized by Fourier transform infrared spectroscopy (FTIR), Field-Emission Scanning Electron Microscopy (FE-SEM) equipped with EDS, X-ray Diffraction (XRD), Vibrating Sample Magnetometry (VSM), thermal gravimetric analysis (TGA). Based on the obtained analysis results synthesized average... 

This paper presents an online highly accurate system for automatic number plate recognition (ANPR) that can be used as a basis for many real-world ITS applications. The system is designed to deal with unclear vehicle plates, variations in weather and lighting conditions, different traffic situations, and high-speed vehicles. This paper addresses various issues by presenting proper hardware platforms along with real-Time, robust, and innovative algorithms. We have collected huge and highly inclusive data sets of Persian license plates for evaluations, comparisons, and improvement of various involved algorithms. The data sets include images that were captured from crossroads, streets, and... 

In this paper we present experimental results describing electrical readout of the mechanical vibratory response of graphene-doped fibers by employing electrical actuation. For a fiber resonator with an approximate radius of 850 nm and length of 100 m, we observed a resonance frequency around 580 kHz with a quality factor (Q) of about 2511 in air at ambient conditions. Through the use of finite element simulations, we show that the reported frequency of resonance is relevant. We also show that the resonance frequency of the fiber resonators decreases as the bias potential is increased due to the electrostatic spring-softening effect  

An efficient heterogeneous palladium catalyst system has been developed based on immobilization of Pd nanoparticles on silica-bonded N-propylpiperazine (SBNPP) substrate. SBNPP substrate can stabilize the Pd nanoparticles effectively so that it can improve their stability against aggregation. Also, grafted piperazine species onto the silica backbone prevents the removing of Pd nanoparticles from the substrate surface. It seems that the high recyclable capability of Pd-SBNPP catalysts is resulted from these two characteristics. Transmission electron microscopy (TEM) of catalyst is shown the size of Pd nanoparticles in Pd-SBNPP average of 20 nm. Furthermore, X-ray photoelectron spectroscopy... 

The paper presents an upgraded size-dependent formulation for micro-rotating shaft–disks system to study their nonlinear forced vibration behavior. The novel formulation is based on the nonlocal strain gradient theory (NSGT). To achieve this goal, first of all, by incorporating the geometrical nonlinearity within the Rayleigh beam theory, the governing equations of the lateral motion of the system are derived by the Hamilton principle and then converted into a complex form. By defining some dimensionless parameters, the normalized form of the complex governing equation is also extracted. In the next step, the Galerkin method is implemented to establish an infinite set of ordinary...