Sharif Digital Repository

Creating laser texture on dental implants is a novel method for accelerating osseointegration and prolongation of lifespan. The purpose of this research was twofold: (1) Creating intersecting lines pattern with different angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) on the surface of Ti6Al4V, using pulse Nd:YAG laser with a wavelength of 1064 nm and a pulse length of 170 ns and (2) comparing optical and SEM images, EDS analyses, contact angles (CAs), and surface free energies (FEs) for different intersecting lines angles. CA and FE depended on the intersecting lines angle according to Y = Y 0 + A sin (x B + C), where Y is the CA or FE; x is the intersecting lines angle; and Y0, A, B, and C... 

In the present study, bubble-driven magnesium-based micromotors were fabricated through a shading method, and the potential of magnetic guidance of magnesium-based Janus micro/nanomotors through functionalization with superparamagnetic iron oxide nanoparticles (SPIONs) was investigated for the first time. SPIONs had physical electrostatic attraction with the positively charged magnesium spheres due to negative charges on their surfaces. It was also found that upon applying a field gradient, the micromotors’ velocity increased by 13% unlike other magnetically navigated spherical magnesium-based micromotors which only show a change in direction. In this work the cytotoxicity of the moving... 

In this research, a series of numerical simulations were conducted utilizing computational fluid dynamics (CFD) software in order to predict the heat transfer performance of queues nanofluids containing clove-treated graphene nanoplatelets (CGNPs) flowing in a horizontal stainless steel heated pipe. The GNPs were covalently functionalized with clove buds using free radical grafting reaction using an eco-friendly process. The advantage of this synthesis method was that it did not use hazardous acids, which are typically used in traditional treatment methods of carbon nanostructures. The thermo-physical properties of the aqueous nanofluids obtained experimentally were used as inputs for the... 

Background & Objective: Aluminum (Al) is used in different industries to produce cosmetics, supplements, drugs, food packaging, toothpaste, kitchen utensils, and antiperspirants. Uterine fibroid (UF) is women's most prevalent benign tumor during the reproductive ages. Since Al can accumulate in the body's organs, it may play a role in the pathogenesis of UF. This study aimed to measure Al levels in serum and uterine samples (normal uterine tissue of control and UF patients, and leiomyoma of UF patients). Materials & Methods: In this descriptive study, we included ten women who underwent hysterectomy (five women due to UF and five women for a reason other than UF). Samples were obtained from... 

Unlike gold and silver, aluminum shows a localized surface plasmon resonance (LSPR) over a wide spectral range from ultraviolet (UV) to the visible region. Herein, we demonstrate a new process to optically couple TiO2 nanotubes (NTs) with a high-strength aluminum substrate, to achieve a synergistic enhancement of photocatalytic antibacterial effects through controlled LSPR of aluminum. The high-strength aluminum substrate was produced by tubular channel angular pressing (TCAP). Their LSPR was tailored through the formation of superficial nano-concave arrays (NCAs) with desired concave diameters. A layer of aligned TiO2 NTs was fabricated on the surface of aluminum nano-concave arrays (Al... 

Systemic chemotherapy has lost its position to treat cancer over the past years mainly due to drug resistance, side effects, and limited survival ratio. Among a plethora of local drug delivery systems to solve this issue, the combinatorial strategy of chemo-hyperthermia has recently received attention. Herein we developed a magneto-thermal nanocarrier consisted of superparamagnetic iron oxide nanoparticles (SPIONs) coated by a blend formulation of a three-block copolymer Pluronic F127 and F68 on the oleic acid (OA) in which Curcumin as a natural and chemical anti-cancer agent was loaded. The subsequent nanocarrier SPION@OA-F127/F68-Cur was designed with a controlled gelation temperature of... 

In this paper, the effect of various arrangements of displacement, velocity and acceleration related weighting matrices on the performance of active control systems on nonlinear frames has been studied. Different arrangements of weighting matrices and feedback combinations of the response have been considered to design the active controllers using a single actuator for reducing the response of an eight-storey bilinear hysteretic frame under white noise excitations. The nonlinear Newmark-based instantaneous optimal control algorithm has been used, where the distributed genetic algorithm (DGA) is employed to determine the proper set of weighting matrices. For each set of feedback and weighting... 

Targeting on the selenium free, pure sulfide kesterite compound (CZTS) allows retention of the higher band gap nontoxic absorber for a single-junction solar cell. In this work, CZTS thin films were deposited by the PLD method and the Structural/optical properties, as well as Mott–Schottky analysis, were studied at different substrate temperatures. Without undergoing the sulfurization process, the single-phase CZTS thin film is prepared at 300 ℃. In the second step, a numerical simulation is performed using the solar cell capacitance simulator to study the effect of the grading layer of MoS(Se)2 on the rear side of pure sulfide kesterite based solar cells. The device with a MoSe2 coated... 

A precise and compact tubular ultrasonic motor driven by a single-phase source is proposed and tested in this study. The motor is designed by modeling a motor stator in FEM software. The motor fabricated according to the design is tested experimentally and its working characteristics including speed and torque are measured and presented. The maximum speed and torque of the motor are 59 rpm and 0.28 mN m at 80 Vpp of applied voltage. The proposed motor possesses advantages such as a simple and compact structure with application in the fields of robotics, space, medical devices and high-resolution stages, among others. The proposed motor is a good candidate for applications where accurate... 

Ultrasonic motor working with coupled in-plane and out-of-plane vibration modes of rectangular plate is proposed and experimentally investigated. Thanks to its unique configuration, proposed motor provides large contact area between stator and rotor of motor which can reduce wear and enhance motor life-time. The proposed motor is designed using finite element method and according to the design, a prototype is fabricated and its working characteristics such as speed, normal and driving force and working frequency are measured. Overall dimension of designed prototype is 49 × 14 × 2 mm, working frequency of motor is 49.6 kHz, no-load speed and stall force of motor are 122 rpm and 0.32 mN m at... 

In the present study, the structural features, corrosion behavior, and in vitro bioactivity of TiO 2 nanotubular arrays coated on Ti–6Al–4V (Ti64) alloy were investigated. For this reason, Ti64 plates were anodized in an ammonium fluoride electrolyte dissolved in a 90:10 ethylene glycol and water solvent mixture at room temperature under a constant potential of 60 V for 1 h. Subsequently, the anodized specimens were annealed in an argon gas furnace at 500 and 700 °C for 1.5 h with a heating and cooling rate of 5 °C min −1 . From XRD analysis and Raman spectroscopy, a highly crystalline anatase phase with tetragonal symmetry was formed from the thermally induced crystallization at 500 °C.... 

This study aimed to prepare nanoporous anodic alumina on AA3003-H14 aluminum alloy using a mild anodization process with minimal working voltage and treatment time. The microstructural features, mechanical properties, and tribocorrosion behavior of the coatings were assessed to determine the optimum conditions for the fabrication of nanoporous anodic alumina on AA3003-H14 alloy. The microstructural analysis showed both uniform and nonuniform pore nucleations during anodization in H2SO4/C2H2O4, H2SO4/H2CrO4, and EG/H2O/NH4F electrolytes, where the optimal nanoporous structure with an average thickness, porosity, pore diameter, and interpore distance of 382 nm, 19%, 16 nm, and 35 nm,... 

Purpose: Although magnetite nanoparticles (MNPs) are promising agents for hyperthermia therapy, insufficient drug encapsulation efficacies inhibit their application as nanocarriers in the targeted drug delivery systems. In this study, porous magnetite nanoparticles (PMNPs) were synthesized and coated with a thermosensitive polymeric shell to obtain a synergistic effect of hyperthermia and chemotherapy. Materials and methods: PMNPs were produced using cetyltrimethyl ammonium bromide template and then coated by a polyethylene glycol layer with molecular weight of 1500 Da (PEG1500) and phase transition temperature of 48 ± 2 °C to endow a thermosensitive behavior. The profile of drug release... 

In this paper we consider a cooperative communication systems over Rayleigh fading channels. The system utilizes a combination of incremental and selective decode-and-forward (ISDF) relaying protocols. The symbol error rate (SER) of M-PSK modulation for the ISDF protocol is derived. Using an approximation of the SER expression, the optimal power allocation is investigated. In order to reduce the complexity of the receiver, we used a modified version of the ISDF protocol which does not use the storage or retransmission of the first phase signal. We also derived optimal power allocation coefficient for modified ISDF. It has been noted that for the optimal power allocation in the ISDF protocol,... 

In this paper we consider a relaying communication system over Rician fading channels. In this system we assume simple Incremental-Selective Decode-and-Forward (ISDF) protocol, which is jointly combining incremental and selective DF relaying protocols. In this protocol, storage or retransmission of the first phase signal are not allowed. We analyze the symbol error rate (SER) performance of the recommended protocol with M-PSK modulation. We evaluate the performance of the protocol in the frequency nonselective slow Rician fading channels. Using the approximation of the SER expression, the optimal power allocation is investigated. Our results show that at least 50% of total power must be used... 

The catalytic activity of potassium salts of phthalimide (PPI) and succinimide (PSI), as organonucleophilic catalysts, has been investigated for the cyclotrimerization of isocyanates under solvent-free conditions. PPI showed better catalytic activity in comparison with PSI. Diverse and challenging isocyanates afforded the respective symmetrical isocyanurates in good to quantitative yields in an atom economic reaction without any phase transfer catalyst. © 2005 Bentham Science Publishers Ltd  

Combination of sodium saccharin and tetrabutylammonium iodide as a novel anionic catalyst system promotes selectively the trimerization of isocyanates to give symmetrical isocyanurates under solvent-free conditions. © Springer-Verlag 2004