Sharif Digital Repository

A glassy carbon electrode (GCE) was modified with a thin layer of multiwalled carbon nanotubes (MWCNTs) and subsequently, electrochemically deposited poly-pyrrole. The electrochemical behavior of mesalazine was studied on the surface of the modified electrode by applying linear sweep voltammetry (LSV). The electropolymerization process and the electrochemical response toward mesalazine were investigated in the presence of different aromatic anion dopants including, benzenesulfonic acid (BSA), 1,3-benzenedisulfonic acid (1,3-BDSA), 1,5-naphthalenedisulfonic acid (1,5-NDSA) and new coccine (NC). By using 1,5-NDSA as dopant, a significant increase (~418 times) in the peak current of mesalazine... 

A glassy carbon electrode (GCE) is modified with platinum nanoparticle (PtNPs) decorated multiwalled carbon nanotube (MWCNT). The modified electrode is applied for the determination of ceftriaxone (CFX) in the presence of lidocaine. Different methods were used to characterize the surface morphology of the modified electrode. The electrochemical behavior of CFX was investigated at GCE, MWCNT/GCE and PtNPs/MWCNT/GCE. A factorial-based response-surface methodology was used to find out the optimum conditions with minimum number of experiments. Under the optimized conditions, oxidation peak currents increased linearly with CFX concentration in the range of 0.01-10.00 μM with a detection limit of... 

A composite surface coating is prepared by electropolymerization of a mixture of pyrrole and carbon nanoparticles onto a glassy carbon electrode (GCE). The microscopic structure and morphology of the composite film is characterized by scanning electron microscopy. The modified electrode offers a considerable improvement in voltammetric sensitivity toward methyldopa (m-dopa), compared to the bare and polypyrrole-coated GCEs. A significantly enhanced anodic peak current together with a remarkable increase in sharpness of the cyclic voltammetric (CV) signals are observed for the detection of m-dopa. The effect of experimental parameters, such as scan rate and pH, are investigated by monitoring... 

Pyrrole was electro-polymerized on the surface of the glassy carbon electrode (GCE) coated with a thin film of carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG) or graphite nanopowder (GNP). Morphology, thickness, stability and loading of the polypyrrole (PPY) film were significantly affected by the structure and morphology of the sub-layer of carbon nanomaterials. Electrochemical oxidation of atorvastatin (ATOR) was investigated. Under the optimized conditions, a significant increase in the peak current (compared to other modified electrodes and bare GCE) and a negative shift in the peak potential (compared to bare GCE) were... 

This paper describes the development and implementation of MCRC software, chemometric software for Multivariate Curve Resolution of two-way Chromatographic data. MCRC software is developed for chemometric analysis of chromatographic data; however, it may also be used for other types of multivariate data. It consists of five groups of techniques for preprocessing, chemical rank determination, local rank analysis, multivariate resolution and peak integration. This software has the ability of the analysis of complex multi-component chromatographic signals of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography-diode array detection (HPLC-DAD). The software... 

This article is focused on developing an Energy Service Company (ESCO) risk assessment model for use by energy savings certificates (ESC) market regulators. This model enables market regulators to determine the appropriate point in time for ESCOs to sell their certificates with the aim of minimizing risk as well as maximizing economic gain yet remain motivated for reducing the cost of energy efficiency technologies. To this end, the interactions between an ESCO and other parties (such as suppliers) in the market in addition to the principles of the energy efficiency performance contract are taken into consideration. Then, appropriate probability distributions have been fitted to the... 

According to Arthur (2006, p. 200), “Through the use of literature, a language learning experience might become at the same time a source of immediate pleasure and satisfaction for the student. This possibility makes literature an appealing teaching device for ESL teachers”. However, numerous factors may contribute to the teachers’ lack of interest in using literary texts as a teaching tool. This study was an attempt to investigate Iranian EFL teachers’ attitude toward using literature in language classes and their perception toward the probable reasons of some teachers’ lack of interest in doing so. Altogether forty-four language teachers (19 females and 25 males, with a mean age of 26)... 

In this study, the inclusion of multi-walled carbon nanotubes as the second phase in the hydroxyapatite matrix, in order to improve the mechanical strength, has been performed via the sol-gel process. The stability of carbon nanotube sol with the changes of pH and dispersant values (sodium dodecyl sulfate) was evaluated by zeta potential analysis. The results indicated that synthesis of hydroxyapatite particles in the presence of the carbon nanotubes had the best result in homogenization of the carbon nanotube dispersion and faster crystallization of hydroxyapatite. The crystallization of hydroxyapatite phase was investigated with differential scanning calorimetry (DSC) and X-ray diffraction... 

The unwanted effects of diffraction and defocus aberration in three-dimensional integral imaging are taken into account by using the Fourier optics approach. The concepts of point spread function and optical transfer function widely in use for conventional two-dimensional imaging are generalized and applied to three-dimensional integral imaging systems. The effects of diffraction and defocus aberration are then studied and the performance of the conventional single lens imaging system is compared against that of the integral imaging  

High temperature shape memory NiTiHf thin films with varying hafnium contents up to 28.7 at.% were fabricated by DC magnetron sputtering using simultaneous sputter deposition from separate elemental targets. The required film composition was achieved by adjusting the power ratio to the targets. The as-deposited films were amorphous; a post deposition annealing was performed at 550 °C to crystallize the films. Two-micron thick films were characterized by energy dispersive spectroscopy in a scanning electron microscope, temperature controlled X-ray diffraction, differential scanning calorimetry, and atomic force microscopy. The results showed that above 10 at.% Hf additions the transformation... 

Consider Myerson's optimal auction with respect to an inaccurate prior, e.g., estimated from data, which is an underestimation of the true value distribution. Can the auctioneer expect getting at least the optimal revenue w.r.t. the inaccurate prior since the true value distribution is larger? This so-called strong revenue monotonicity is known to be true for single-parameter auctions when the feasible allocations form a matroid. We find that strong revenue monotonicity fails to generalize beyond the matroid setting, and further show that auctions in the matroid setting are the only downward-closed auctions that satisfy strong revenue monotonicity. On the flip side, we recover an approximate... 

In recent years, subsidy payment has been made a main challenge for governments due to growth of population and energy price in global markets. Targeted subsidy plan has been implemented in Iran since last year, and this article discusses its effects on costs and revenues of Tehran Electricity Company as one of the major subdivisions of Iran's electricity industry. In the new system, structural changes have been made in electricity tariffs, so it is not possible to predict the future trends in electricity consumption only based on the past consumptions. In order to model the decision making structure in the recent conditions, a system dynamics method is applied. In addition to modeling the... 

Understanding the nature of interaction between metal nanoparticles and biomolecules such as amino acids is important in the development and design of biosensors. In this paper, binding of M3 clusters (M = Au, Ag and Cu) with neutral and anionic forms of histidine amino acid was studied using density functional theory (DFT-B3LYP). It was found that the interaction of histidine with M3 clusters is governed by two major bonding factors: (a) the anchoring N-M and O-M bonds and (b) the nonconventional N-H⋯M and O-H⋯M hydrogen bonds. The nature of these chemical bonds has been investigated based on quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. In the next... 

The relative stabilities and noncovalent interactions of the six low-lying energy tautomers of cytosine nucleobase with some biological anions (such as F-, Cl-, and CN-) have been investigated in gas phase by density functional theory (DFT) method in conjunction with 6-311++G (d,p) atomic basis set. Furthermore, to systematically investigate all possible tautomerisms from cytosine induced by proton transfer, we describe a study of structural tautomer interconversion in the gas phase and in a continuum solvent using DFT calculation. We carried out geometrical optimizations with the integral equation formalism of polarizable continuum (IEF-PCM) model to account for the solvent effect, and the... 

Understanding the nature of the interaction between metal nanoparticles and biomolecules has been important in the development and design of sensors. In this paper, structural, electronic, and bonding properties of the neutral and anionic forms of glutathione tripeptide (GSH) complexes with a Au 3 cluster were studied using the DFT-B3LYP with 6-31+G**-LANL2DZ mixed basis set. Binding of glutathione with the gold cluster is governed by two different kinds of interactions: Auâ€"X (X = N, O, and S) anchoring bond and Au··•·•H-X nonconventional hydrogen bonding. The influence of the intramolecular hydrogen bonding of glutathione on the interaction of this peptide with the gold cluster has been... 

As digital technology has developed, relays have evolved from simple electro-mechanical devices into robust microprocessor-embedded intelligent electronic devices (IEDs). Distance protection, one of the most important and sophisticated forms of substation protection, quickly and selectively detects and clears phase faults in sub-transmission and transmission lines. The installation of a substation automation system (SAS) involves implementing control, monitoring, and protection logic by programming the IEDs and providing an appropriate communication network. IEC61850 has gradually satisfied the need for a standard communication protocol so that IEDs from different manufacturers can... 

The first asymmetric synthesis of α,β-disubstituted γ-phosphono sulfonates is reported. The key step is the Michael addition of a lithiated enantiopure sulfonate bearing an inexpensive chiral sugar auxiliary to α,β-unsaturated phosphonates in good diastereoselectivities. After chromatographic purification, the cleavage of the chiral sugar auxiliary proceeds without any epimerization or racemization to form the corresponding isopropyl sulfonate in very good overall yield (75%) and excellent diastereomeric and enantiomeric excess (de, ee ≥ 95%). © 2009 Elsevier Ltd. All rights reserved  

In this study, UV‐Vis-NIR photodetectors based on decorated ZnO nanofibers (NFs) with optimized coverage of Au nanoparticles (NPs) fabricated via combined simple electrospinning and sputtering techniques are introduced. The effect of different coverages of Au NPs resulted from different Au nominal layer thicknesses on the morphology and optical properties of the ZnO fibers are investigated through various characterization methods. It is discovered that 4 nm Au nominal thickness provides the highest UV on/off ratio (~460), responsivity (~332 A/W), detectivity (~2.93×10 11 Jones) as well as faster rise and decay times as compared to pure ZnO nanofibers. A broad spectral response from UV to NIR...