Sharif Digital Repository

The inhibition of mild steel corrosion in 0.5 M sulphuric acid by the symmetrical acetylenic alcohol 2- butyne-1,4-diol is investigated. Weight loss and electrochemical impedance data consistently indicate inhibition efficiencies up to 98%. Short-term impedance measurements reveal that the interfacial inhibition is a function of the exposure time, and that full performance is achieved faster as inhibitor concentration and temperature are higher. An infrared study of the surface film provides evidence that the film does not achieve its final state but after several hours. Atomic force Microscopy has been used for investigation the surface topography of metallic electrode. © 2009 by ESG  

In this article, we have used quantum and semiclassical models to analyse the electrical characteristics of gate all around silicon nanowire transistor (GAA SNWT). A quantum mechanical transport approach based on non-equilibrium Green's function (NEGF) method with the use of mode space approach in the frame work of effective mass theory has been employed for this analysis. Semiclassical drift diffusion mode space (DDMS) approach has also been used for the simulation of GAA SNWT. We have studied the short-channel effects on the performance of GAA SNWT and evaluated the variation of the threshold voltage, the subthreshold slope (SS), the leakage current and the drain-induced barrier lowering... 

A Gate All Around Nanowire Transistor (GAA NWT) which employs source heterojunction and strained channel is proposed which improves device characteristics. A quantum mechanical transport approach based on nonequilibrium Green's function (NEGF) method in the frame work of effective mass theory is employed in this analysis. We evaluate the variation of the threshold voltage, the subthreshold slope, ON and OFF state currents when channel length decreases. It is shown that the source heterojunction strained channel GAA NWT gives high performance transistors values of the scaled transconductance and ON current that are greater than conventional silicon GAA NWT. Furthermore, comparison of... 

Computational methods to understand interactions in bio-complex systems are however limited to time-scales typically much shorter than in Nature. For example, on the nanoscale level, interactions between nanoparticles (NPs)/molecules/peptides and membranes are central in complex biomolecular processes such as membrane-coated NPs or cellular uptake. This can be remedied by the application of e.g. Jarzynski's equality where thermodynamic properties are extracted from non-equilibrium simulations. Although, the out of equilibrium work leads to non-conservative forces. We here propose a correction Pair Forces method, that removes these forces. Our proposed method is based on the calculation of... 

Free-energy calculations are crucial for investigating biomolecular interactions. However, in theoretical studies, the neglect of electronic polarization can reduce predictive capabilities, specifically for free-energy calculations. To effectively mimick polarization, we explore a Charge Switching (CS) model, aiming to narrow the gap between computational and experimental results. The model requires quantum-level partial charge calculations of the molecule in different environments, combined with atomistic MD simulations. Studying three different anti-cancer drug molecules with three different phospholipid membranes, we show that the method significantly improves agreement with available... 

We present a new TiO2 morphology, featuring high surface area and open structure, synthesized by a two-step chemical route for the manufacture of dye-sensitized solar cells (DSSCs). This construct is sets of intertwined one-dimensional (1D) nanostructures (i.e., nanotubes), so-called skein-like nanotubes (NTs). Such morphology is produced by a combination of TiC oxidation and hydrothermal processes. The mesoporous TiO2 nanoparticles, as the product of TiC oxidation operation, is used as the precursor of hydrothermal process to grow the skein-like NTs. The effect of processing parameters of TiC oxidation and hydrothermal processes is studied. The skein-like morphology enables to eliminate the... 

Biocompatible nanostructured coating plays an important role in enhancement of osseointegration ability of metallic implants. This study sets out to obtain optimized SiC concentration in Hydroxyapatite (HA) coating on AISI 316L stainless steel alloy through electrophoretic deposition method. Effect of SiC concentrations (1, 2, and 3%.wt) on the morphology, corrosion behaviour, and mechanical properties of the HA coating is investigated. Results show that SiC could obstruct the formation and growth of micro cracks in the HA coating where HA-3%SiC is considered as a crack free coating. Electrochemical tests reveal that SiC has improved the corrosion resistance of HA coating, and HA-3%SiC... 

In this work, central composite design (CCD) as a statistical experimental design method is performed to prepare nickel nano-particle of different magnetic domain regimes by the modified polyol process. It is shown that not only the concentration of the different chemicals but also the injection rate is determining for the morphology and magnetic properties. The average diameter of the synthesized nickel NPs is smaller than the critical single domain size and thus the single domain or pseudo-single domain nickel nano-particles can be prepared based on Day's plot  

In this paper, an efficient dynamic simulation algorithm is developed for an Unmanned Underwater Vehicle (UUV) with a N degrees of freedom manipulator. In addition to the effects of mobile base, the various hydrodynamic forces exerted on these systems in an underwater environment are also incorporated into the simulation. The effects modeled in this work are added mass, viscous drag, fluid acceleration, and buoyancy forces. Also the dynamics of thrusters are developed, and an appropriate mapping matrix dependent on the position and orientation of the thrusters on the vehicle, is used to calculate resultant forces and moments of the thrusters on the center of gravity of the vehicle. It should... 

Superparamganetic iron oxide-based contrast agents in magnetic resonance imaging (MRI) have offered new possibility for early detection of lymph nodes and their metastases. According to important role of nanoparticle size in biodistribution, magnetite nanoparticles coated with different polyethylene glycol (PEG) concentrations up to 10/1 PEG/iron oxide weight ratio in an ex situ manner. To predict the PEG-coated nanoparticle behavior in biological media, such as blood stream or tissue, colloidal stability evaluation was performed to estimate the coating endurance in different conditions. Accordingly, optical absorbance measurements were conducted in solutions with different values of pH and... 

In this study, lamination as extrinsic mechanism was considered to enhance damage tolerance of three-layer Al6061-5%vol. SiCp/Al1050/Al6061-5%vol. SiCp composites. To fabricate laminates of dissimilar interfacial adhesion, different rolling strains were applied during hot roll-bonding. The discrepancy in interfacial strength of laminates was examined by shear test while toughness values were studied using three-point bending test. It was revealed that both interfacial adhesion and damage tolerance were influenced by rolling strain. Interfacial bonding played the major role in the energy absorption during fracture which was quantified as initiation, propagation and total toughness. The... 

Developing a simple, cost effective and accurate detection method for L-lysine (Lys), L-leucine (Leu) and glycine (Gly) as the important analytes in clinical diagnostics, biological processes and food industries is of great significance. Herein, we prepared spin-coated TEMPO-oxidized cellulose nanofibrils (TOCNFs) on Quartz Crystal Microbalance (QCM) chip to achieve QCM biodetectors. The coated QCMs were carefully characterized before and after interaction with amino acids (AA) using water contact angle (WCA), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and scanning electron microscopy (SEM). In addition, to study the response of... 

In this research, FINEMET alloy with composition of Fe73.5Si13.5B9Nb3Cu1 was produced by mechanical alloying from elemental powders. The effect of milling time on the magnetic and structural properties of alloy has been investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometery. The results showed that milling for 53 hr leads to the formation of Fe supersaturated solid solution which includes Si, B and Nb atoms with mean crystallite size of ~30 nm. The shift of the main peak of Fe to the higher angles indicated that Si and B atoms dissolve in the Fe solid solution, at primary stage of mechanical alloying, up to the... 

We theoretically demonstrate the tunabiltiy of terahertz random lasers composed of high temperature superconductor YBCO and ruby layers as active medium. The considered system is a one-dimensional disordered medium made of ruby grain and YBCO. Finite-difference time domain method is used to calculate the emission spectrum and spatial distribution of electric field at different temperatures. Our numerical results reveal that the superconductor based random lasers exhibit large temperature tunability in the terahertz domain. The emission spectrum is significantly temperature dependent, the number of lasing modes and their intensities increase with decreasing temperature. Also, we make some... 

In this work1, we consider the problem of secure multi-party computation (MPC), consisting of F sources, each has access to a large private matrix, N processing nodes or workers, and one master. The master is interested in the result of a polynomial function of the input matrices. Each source sends a randomized functions of its matrix, called as its share, to each server. The workers process their shares in interaction with each other, and send some results to the master such that it can derive the final results. There are several constraints: (1) each worker has a constraint on its storage, such that it can store equivalent of displaystyle rac{1}{m} fraction of size of each input matrices... 

Two newly synthesised Schiff bases [H2A3, N,N′-ortho-phenylene(salicylaldimine-acetylacetone imine) and H2A4, N,N′-ortho-phenylene(salicylaldimine-2-hydroxy-1-naphthaldimine)] were studied as inhibitors for the corrosion of mild steel in 0.5 mol dm-3 sulphuric acid. Results of weight loss, electrochemical impedance and Tafel polarisation measurements consistently identify both compounds as good inhibitors, with efficiencies of around 95% at a concentration of 400 ppm. The inhibition is in both cases of a mixed anodic-cathodic nature. Differences in inhibition efficiency between H2A3 and H2A4 are correlated with their chemical structures. Several adsorption isotherms are assessed, and the... 

Herein, we report a double-layer photoanode electrode composed of TiO2 nanoparticles active layer and a mixture of nanoparticles and newly proposed skein-like nanotubes (NTs) top layer. Such structure performs well in solar light harvesting due to first, the top layer exhibits superior light scattering and second, the active layer with high dye-loading can make better use of the back-scattered light. The results reveal that 30-40 nm nanoparticles have anatase structure, whereas 5-7 μm skein-like NTs show a mixture of anatase and rutile phases. Photovoltaic measurements demonstrate that by tuning mass ratio between nanoparticles and skein-like NTs, the cells based on single-layer photoanode... 

Clinical assessment of capsuloligamentous structures of the glenohumeral joint has been qualitative and subjective in nature, as demonstrated by limited intra- and inter-rater reliability. Robotic devices were utilized to develop a clinically objective measurement technique for glenohumeral joint stiffness. The purpose of this study was to quantify the amount of inferior-direction stiffness of the glenohumeral joint using a safe clinical device in the asymptomatic individuals, and to determine between trial and between session reliability of the robotic device. Twenty healthy subjects were recruited via convenience sampling. Inferior-directed translation and applying force were measured... 

Background For decades, contrast agents have been used to reduce longitudinal (T1) or transverse (T2) relaxation times. High toxicity of gadolinium-based contrast agents leads researchers to new T1 contrast agents. Manganese oxide (MnO) nanoparticle (NP) with the lower peril and good enough signal change ability has been offered as a new possibility for magnetic resonance imaging (MRI). Methods The synthesized NPs were investigated for physicochemical and biological properties by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscope, dynamic light scattering (DLS), inductively coupled plasma, enzyme-linked immunosorbent assay, and 3 T magnetic resonance... 

In order to provide sufficient heat without overheating healthy tissue in magnetic fluid hyperthermia (MFH), a careful design of the magnetic properties of nanoparticles is essential. We perform a systematic calculation of magnetic properties of Ni-alloy nanoparticles. Stoner-Wohlfarth model based theories (SWMBTs) are considered and the linear response theory (LRT) is used to extract the hysteresis loop of nickel alloy nanoparticles in alternating magnetic fields. It is demonstrated that in the safe range of magnetic field intensity and frequency the LRT cannot be used for the calculation of the area in the hysteresis for magnetic fields relevant for hyperthermia. The best composition and...