Sharif Digital Repository

The authors describe an impedimetric method for the quantitation of the DNA of the human papilloma virus (HPV) type 16. A glassy carbon electrode (GCE) was modified with gold nanosheets and is shown to be superior to a common gold disk electrode. A single-stranded 25mer oligonucleotide (ssDNA) acting as the probe DNA was immobilized via its thiolated 5′ end on both electrodes. After hybridization with target (analyte) DNA, electrochemical impedance spectra were acquired in the presence of hexacyanoferrate as a redox marker. The sensor can distinguish between complementary, non-complementary and single base pair mismatches of HPV ssDNA. At a 1 mM hexacyanoferrate concentration, the biosensors... 

Investigation of non-covalent interaction of hydrophobic surfaces with the protein G (PrG) is necessary due to their frequent utilization in immunosensors and ELISA. It has been confirmed that surfaces, including carbonous-nanostructures (CNS) could orient proteins for a better activation. Herein, PrG interaction with single-walled carbon nanotube (SWCNT) and graphene (Gra) nanostructures was studied by employing experimental and MD simulation techniques. It is confirmed that the PrG could adequately interact with both SWCNT and Gra and therefore fine dispersion for them was achieved in the media. Results indicated that even though SWCNT was loaded with more content of PrG in comparison with... 

Background: Study of nanostructure-protein interaction for development of various types of nano-devices is very essential. Among carbon nanostructures, carbon nanotube (CNT) provides a suitable platform for functionalization by proteins. Previous studies have confirmed that the CNT induces changes in the protein structure. Methods: Molecular dynamics (MD) simulation study was employed to illustrate the changes occurring in the protein G (PGB) in the presence of a CNT. In order to predict the PGB surface patches for the CNT, Autodock tools were utilized. Results: Docking results indicate the presence of two different surface patches with diverse amino acids: the dominant polar residues in the... 

The main aim of this article is to find the optimum positions of the stabilizers that reduces the vibration and leads to the largest weight on bit (WOB) in drill strings. In this work, the potential energy of drill strings has been derived by considering the drill string weight and WOB. The potential energy of this continuous system is considered as a multi-degree-of-freedom system by the mode summation method. The equilibrium position of the system and its stability is determined by finding the roots of the first derivative and the sign of the second derivative of the potential energy, respectively. Using this formulation, the best positions of stabilizers that lead to the largest WOB can... 

Afacile, seed-less and one-pot method was developed for synthesis of gold nanoflowers with multiple tips through reduction of HAuCl4 with deep eutectic solvent at room temperature. This solvent is ecofriendly, low-cost, non-toxic and biodegradable and can act as both reducing and shape-controlling agent. In this protocol, highly branched and stable gold nanoflowers were obtained without using any capping agent. The obtained products were characterized by different techniques including, field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction andUV-vis spectroscopy. The as-prepared gold nanoflowers exhibit efficient surface-enhanced Raman scattering... 

Due to high surface to volume ratio and tunable band gap, two dimensional (2D) layered materials such as MoS2, is good candidate for gas sensing applications. This research mainly focuses on variation of Density of States (DOS) of MoS2 monolayes caused by ethanol adsorption. The nanosheets are synthesized by liquid exfoliation, and then using Scanning Tunneling Spectroscopy (STS) and Density Functional Theory (DFT), local electronic characteristic such as DOS and band gap in non-vacuum condition are analyzed. The results show that ethanol adsorption enhances DOS and deform orbitals near the valence and conduction bands that increase transport of carriers on the sheet. © 2018 IOP Publishing... 

Direct Simulation Monte Carlo (DSMC) method is applied to evaluate the performance of a new micro gas sensor (MIKRA) for mass analysis of ammonia in the rarefied gas. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equation is applied to obtain high precision results. This study performed comprehensive studies to reveal the main mechanism of force generation and applied this for the analysis of the gas mixture. Our findings show that value of generated Knudsen force significantly varies when the percentage of the NH3 varies in the mixture. According to obtained results, the maximum Knudsen force increases when the fraction of the ammonia decreases. Our findings... 

The artificial neural network-group contribution (ANN-GC) method is applied to estimate the standard enthalpy of combustion of pure chemical compounds. A total of 4590 pure compounds from various chemical families are investigated to propose a comprehensive and predictive model. The obtained results show the squared correlation coefficient (R 2) of 0.999 99, root mean square error of 12.57 kJ/mol, and average absolute deviation lower than 0.16% for the estimated properties from existing experimental values  

A highly efficient and simple procedure for the synthesis of quinazolin-4(3H)-ones from the condensation of 2-aminobenzamide with triethylorthoesters in presence of a catalytic amounts of heteropolyacids in various solvents is reported  

Introduction: Research evidence indicates that maladaptive reorganization of the brain plays a critical role in amplifying pain experiences and pain chronification; however, no clear evidence of change exists in brain wave activity among patients with chronic low back pain (CLBP). The objective of this study was to assess brain wave activity in patients with CLBP, compared to healthy controls. Methods: Twenty-five patients with CLBP and twenty-four healthy controls participated in the study. A quantitative electroencephalography device was used to assess brain wave activity in eyes-open and eyes-closed (EO and EC) conditions. The regional absolute and relative power of brain waves were... 

An accurate examination of deformability of rock samples in response to any change in stresses is deeply dependent on the reliable determination of properties of the rock as analysis inputs. Although Young’s modulus (E) can provide valuable characteristics of the rock material deformation, the direct determination of E is considered a time-consuming and complicated analysis. The present study is aimed to introduce a new hybrid intelligent model to predict the E of granitic rock samples. Hence, a series of granitic block samples were collected from the face of a water transfer tunnel excavated in Malaysia and transferred to laboratory to conduct rock index tests for E prediction. Rock index... 

An accurate examination of deformability of rock samples in response to any change in stresses is deeply dependent on the reliable determination of properties of the rock as analysis inputs. Although Young’s modulus (E) can provide valuable characteristics of the rock material deformation, the direct determination of E is considered a time-consuming and complicated analysis. The present study is aimed to introduce a new hybrid intelligent model to predict the E of granitic rock samples. Hence, a series of granitic block samples were collected from the face of a water transfer tunnel excavated in Malaysia and transferred to laboratory to conduct rock index tests for E prediction. Rock index... 

The transfer of pyridinium ion across the water/nitrobenzene interface has been studied by the methods of cyclic voltammetry and ac-impedance measurements. The diffusion coefficients of these species in both media, Dw,pyH+ = 4.4 × 10-5 and DNB,pyH+ = 2.16 × 10-5 cm2 s-1, as well as the diffusion coefficient of pyridine in the organic phase, DNB,py, 3.05 × 10-7 cm2 s-1, have been calculated. The standard potential of pyridinium ion transfer, and the corresponding free energy change and its distribution coefficient between the two phases, have been reported by means of cyclic voltammetry. Impedance measurements resulted in an arc in Nyquist diagrams representing the transfer of pyridinium ion... 

Over recent years, frequent involvements in claims have been inevitable due to unpredictable economic changes and increasing complexities in construction industry. Therefore, even appropriately made contracts are not exempted from claims. On the other hand, construction contract claims are time-consuming, expense-involving and most likely leading to unsatisfactory results. However, there may be some positive outcomes, such as time extension or compensation of damages. To launch investigations, a list of important and frequent claims in oil and gas industry projects of Iran was extracted after a succinct documents review. Further, the most important claim causes were identified through... 

Signed graphs are graphs whose edges get signs ±1 and, as for unsigned graphs, they can be studied by means of graph matrices. Here we focus our attention to the largest eigenvalue, also known as the index of the adjacency matrix of signed graphs. Firstly we give some general results on the index variation when the corresponding signed graph is perturbed. Also, we determine signed graphs achieving the minimal or the maximal index in the class of unbalanced unicyclic graphs of order n≥3. © 2019  

Using a parallel mechanism in the wear test simulators of prosthetic knees provides an easy access to the femoral and tibial components during tests. Moreover, because of its higher accuracy and load capacity, in comparison with serial mechanisms, it allows simulation of heavier tasks, such as climbing stairs, to be performed. This paper describes a new 3 Degree of freedom (DoF) spatial 2T1R (T: Translational DoF; R: Rotational DoF) parallel mechanism, for reproducing the force and motion of the tibial component of the knee prostheses in a wear test simulator. Kinematics and dynamics analysis of the mechanism indicated that it can satisfy the required DoFs, workspace and load capacity... 

Fluxgate magnetometers with different design and core materials have been made. The sensors have been characterized and the frequency responses of the sensors have been measured. The fluxgate magnetometer based on orthogonal design and amorphous wire core working in fundamental mode reaches 30pT/Hz noise level and 40μV/nT sensitivity. Finally an active magnetic shield constructed based on the amorphous core fluxgate magnetometer reaches more than 60dB field attenuation for DC field and has a good response for frequencies below 100Hz  

Nickel-copper alloy modified glassy carbon electrodes (GC/NiCu) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol and glucose in alkaline solutions. The methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were employed. The cyclic voltammogram of NiCu alloy demonstrates the formation of β/β crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline solution. In CV studies, in the presence of methanol NiCu alloy modified electrode shows a significantly higher response in oxidation reaction. The peak current of the... 

The electro-oxidation of methanol on nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in a 1 M NaOH solution at different concentrations of methanol was studied by the method of ac-impedance spectroscopy. Two semicircles in the first quadrant of a Nyquist diagram were observed for electro-oxidation of methanol on GC/Ni corresponding to charge transfer resistance and adsorption of intermediates. Electro-oxidation of methanol on GC/NiCu shows negative resistance in impedance plots as signified by semi-circles terminating in the second quadrant. The impedance behavior shows different patterns at different applied anodic potential. The influence of the... 

In the present study, the behavior of fin pile under lateral loading was investigated by ABAQUS software. First, the generated model was verified against an available experimental small-scale test in the literature. Having conducted verification, a study was carried out on the fin pile dimensions under lateral loading. Different parameters, such as pile diameter, fin’s length, and width, were studied. Moreover, a study on the fin’s aspect ratio by setting fin’s area constant was conducted, and then, optimum fin’s ratio was obtained. The results indicated that both fin’s length and width could improve pile efficiency under lateral loading, yet fin’s length had a more critical impact, and...