Sharif Digital Repository

Myocardial infarction is a major cause of death worldwide and remains a social and healthcare burden. Injectable hydrogels with the ability to locally deliver drugs or cells to the damaged area can revolutionize the treatment of heart diseases. Herein, we formulate a thermo-responsive and injectable hydrogel based on conjugated chitosan/poloxamers for cardiac repair. To tailor the mechanical properties and electrical signal transmission, gold nanoparticles (AuNPs) with an average diameter of 50 nm were physically bonded to oxidized bacterial nanocellulose fibers (OBC) and added to the thermosensitive hydrogel at the ratio of 1% w/v. The prepared hydrogels have a porous structure with open... 

It is known that no quantum process can produce a predetermined superposition of unknown arbitrary states. It has already been shown that with some partial information about the states, one can produce with some probability such superpositions. In general the success probability of these machines, even for orthogonal states, are less than unity. Here we show that there are specific machines that can produce superpositions of orthogonal qubit states with unit probability. © 2017 American Physical Society  

We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I–V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal–interface–semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100–40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration... 

For more than a decade, stent implantation has been strategically used for solving gastrointestinal dilemmas such as biliary stenosis. Predicaments like insufficient radial strength, low twisting ability, inappropriate dynamic behaviour and restenosis are expected to be solved by the introduction of new designs. Superelastic Nitinol stent is an interesting alternative for minimising these tight spots. The application of finite element method to predict metallurgical and geometric behaviour of superelastic Nitinol stents for biliary duct dilatation is supported by conventional crimp tests. Model calculations show that all stents encounter the highest stress in their intersegment curvature.... 

Nitinol stents are used to minimize improper dynamic behavior, low twistability, and inadequate radial mechanical strength of femoral artery stents. In this study, finite element method is used to investigate the effect of crimping and Austenite finish temperature (A f) of Nitinol on mechanical performance of Z-shaped open-cell femoral stent under crimping conditions. Results show that low A f Nitinol has better mechanical and clinical performance due to small chronic outward force, large radial resistive force, and appropriate superelastic behavior  

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... 

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  

The energetics and kinetic energy barriers of vacancy/atom exchange in a 37-atom truncated octahedron Ag-Pt binary cluster in the Ag-rich range of compositions are investigated via a first-principles atomistic approach. The energy of the local minima obtained considering various distributions of a single vacancy and a few Pt atoms within the cluster and the energy barriers connecting them are evaluated using accurate density-functional calculations. The effects of the simultaneous presence of a vacancy and Pt atoms are found to be simply additive when their distances are larger than first-neighbors, whereas when they can be stabilizing at low Pt content due to the release of strain by the... 

This research aimed at finding the factors with more impact on the bioleaching of a spent hydrocracking catalyst by thermophilic acidophilic archaea called Acidianus brierleyi and determining the optimal condition in order to reach the maximum metals recovery. Initially, four more significant factors affecting the bioleaching efficiency including pH, pulp density, inoculation and elemental sulfur concentration, were screened and identified among ten key factors using Plackett-Burman factorial design. Next, a central composite design was applied to obtain the optimum conditions for achieving the maximum efficiency of the bioleaching process. pH 1.6, pulp density 0.6% (w/v), inoculation 4%... 

We provide a characterization of energy in the form of exchanged heat and work between two interacting constituents of a closed, bipartite, correlated quantum system. By defining a binding energy we derive a consistent quantum formulation of the first law of thermodynamics, in which the role of correlations becomes evident, and this formulation reduces to the standard classical picture in relevant systems. We next discuss the emergence of the second law of thermodynamics under certain-but fairly general-conditions such as the Markovian assumption. We illustrate the role of correlations and interactions in thermodynamics through two examples  

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... 

Nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) prepared by galvanostatic deposition were examined for their redox processes and electro-catalytic activities towards the oxidation of glucose in alkaline solutions. The methods of cyclic voltammetry (CV) and chronoamperometry (CA) 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. It is also observed that the overpotential for O 2 evolution increases for NiCu alloy modified electrode. In CV studies, NiCu alloy modified electrode yields significantly higher... 

Objective: The advent of telehealth applications and remote patient monitoring has led to an increasing need for continuous signal quality monitoring to ensure high diagnostic accuracy of the recordings. Cardiovascular diseases often manifest electrophysiological anomalies, therefore the electrocardiogram (ECG) is one of the most used signals for diagnostic applications. Various types of noise and artifacts are not uncommon in ECG recordings and assessing the quality of the signal is essential prior to any clinical interpretation. In this study, a dynamic signal quality index (dSQI) is introduced using a new time-frequency template-based approach. Approach: A smoothed pseudo Wigner-Ville... 

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... 

The expected lifetime of a power electronic converter is limited by its fragile components such as semiconductor devices and capacitors. These components are prone to wear-out failures depending on the converter mission profile and component thermal characteristics. This paper explores the wear-out failure of the power converter semiconductor devices in inverting and rectifying modes of the converter using different power factors. The obtained results show the different wear-out characteristics of a converter under rectification, inversion, and also partial-inversion/rectification modes as well as when provides reactive power support. Moreover, this paper proposes B10 lifetime curves to... 

Determination of soil shear modulus is one of the most controversial topics in unsaturated soil dynamics. Due to the fact that soils have an anisotropic response, the shear strength and stiffness of geological materials are greatly dependent on the principal stress direction and the intermediate principal stress. In this study, the effects of principal stress direction on shear modulus of unsaturated medium-dense sand have been investigated using cyclic hollow cylinder apparatus. Three series of stress-controlled cyclic tests with different fixed principal stress directions were carried out on the sand sample under different values of suction. Results reveal that shear modulus of unsaturated... 

Herniation in the lumbar area is one of the most common diseases which results in lower back pain (LBP) causing discomfort and inconvenience in the patients' daily lives. A computer aided diagnosis (CAD) system can be of immense benefit as it generates diagnostic results within a short time while increasing precision of diagnosis and eliminating human errors. We have proposed a new method for automatic diagnosis of lumbar disc herniation based on clinical MRI data. We use T2-W sagittal and myelograph images. The presented method has been applied on 30 clinical cases, each containing 7 discs (210 lumbar discs) for the herniation diagnosis. We employ Otsu thresholding method to extract the... 

Determination of soil shear modulus is one of the most controversial topics in unsaturated soil dynamics. Due to the fact that soils have an anisotropic response, the shear strength and stiffness of geological materials are greatly dependent on the principal stress direction and the intermediate principal stress. In this study, the effects of principal stress direction on shear modulus of unsaturated medium-dense sand have been investigated using cyclic hollow cylinder apparatus. Three series of stress-controlled cyclic tests with different fixed principal stress directions were carried out on the sand sample under different values of suction. Results reveal that shear modulus of unsaturated... 

Nowadays, there is a growing interest in synthesizing electrodes used in zinc electrowinning, increasing active surface area, decreasing specific energy consumption, and the oxygen evolution reaction (OER) overpotential. In this study, modified nanocomposite anodes were synthesized by applying pulsed and constant direct current electrodeposition to improve the catalytic activity of the electrodes toward the oxygen evolution reaction (OER) and reduce energy consumption in zinc electrowinning. By decreasing particle size, the active surface area of PbO2-RuO2 nano-mixed composite electrode was 2.88 and 14.22 times greater than PbO2-RuO2 microcomposite and pure PbO2 electrodes, respectively....