Sharif Digital Repository

Herein, poly (acrylic acid) (PAA) microgels were synthesized via alcohol type cross-linked by a free radical precipitation polymerization approach. At the first time, 1,6-hexanediol (1–6 diol), trimethylolpropane (TMP), and pentaerythritol (PEN) were selected as multifunctional cross- linking agent to synthesize cross-linked poly(acrylic acid) microgels. Alcohol type cross-linking agents can connect the PAA chains. The cross-linking reaction takes place due to reaction between hydroxyl groups of various cross-linkers and carboxyl groups of PAA chains. All of the hydroxyl groups do not participate in the reaction with acid groups of polymer chains through the polymerization stage; therefore,... 

Ionic liquids (ILs) are a growing trend in Enhanced Oil Recovery (EOR) studies as alternatives to commercial surfactants due to their environmentally friendly nature, and their resistance in harsh temperatures and salinities. ILs are customizable and come in an immense variety, and therefore, it is vital that different combinations of cation/anion be investigated for use in the industry. In this work, experiments are designed and performed to evaluate novel ILs’ surface activity and performance in a lab-scale EOR set-up, compatible with Iranian oil reservoir conditions. Three imidazolium-based ionic liquids were used, namely, butyl-methylimidazolium nitrate, hexyl-methylimidazolium nitrate,... 

In this work, for the first time, different forms of nanocomposites based on rGO and MWCNT were prepared in conjoining with the bioactive glass (BioGlass). In the carbonic layers, a highly toxic nanoparticle, CoNi2S4, was intercalated, and the role of this nanoparticle in the alkaline phosphatase activity, relative cell viability on different cell lines, and also the effect on the cell walls and cell morphologies were investigated. From another perspective, the ability of the chemotherapy drug loading to the prepared nanocomposites was investigated, and the use of leaf extracts was thought of as a green method to lower the cytotoxicity and regulate the genotoxicity of the generated... 

Radiopacity is sometimes an essential characteristic of biomaterials that can help clinicians perform follow-ups during pre- and post-interventional radiological imaging. Due to their chemical composition and structure, most bioceramics are inherently radiopaque but can still be doped/mixed with radiopacifiers to increase their visualization during or after medical procedures. The radiopacifiers are frequently heavy elements of the periodic table, such as Bi, Zr, Sr, Ba, Ta, Zn, Y, etc., or their relevant compounds that can confer enhanced radiopacity. Radiopaque bioceramics are also intriguing additives for biopolymers and hybrids, which are extensively researched and developed nowadays for... 

In the bone tissue engineering field (BTE), it is of significant importance to develop bioactive multifunctional scaffolds with enhanced osteoconductivity, osteoinductivity, and antibacterial properties required for lost bone tissue regeneration. In this work, a bioactive glass-ceramic scaffold was manufactured via a novel polymer-derived ceramics (PDC) manufacturing method. To gain antibacterial properties, the silver ions were incorporated in controlled amount along with other precursors in the PDC processing stage. Microstructural and structural properties of the fabricated silicate-phosphate glass-ceramic scaffold were evaluated by scanning electron microscopy (SEM) equipped with energy... 

This paper deals with an experimental investigation into the mechanical performance and microstructure characteristics of the cementitious mortars containing recycled waste materials subjected to acidic, neutral and alkaline environments. The recycled waste materials include glass, eggshell, iron and rubber powder in various amounts, namely 7, 14 and 21% by volume, as the replacement for ordinary Portland cement (OPC). In this respect, to examine the mechanical performance of the specimens, the compressive, tensile and bending strength tests as well as water absorption test were carried out at the ages of 7, 28 and 90 days. Moreover, to study the microstructure of the specimens, the scanning... 

Tissue engineering (TE) and regenerative medicine have held great promises for the repair and regeneration of damaged tissues and organs. Additive manufacturing has recently appeared as a versatile technology in TE strategies that enables the production of objects through layered printing. By applying 3D printing and bioprinting, it is now possible to make tissue-engineered constructs according to desired thickness, shape, and size that resemble the native structure of lost tissues. Up to now, several organic and inorganic materials were used as raw materials for 3D printing; bioactive glasses (BGs) are among the most hopeful substances regarding their excellent properties (e.g., bioactivity... 

Fluid flow in porous media is affected by surface characteristics such as roughness and topography. In this work, to simulate the surface of natural porous structures in transparent interconnected media like micromodels, various degrees of roughness have been artificially created on flat glass substrates via different methods of laser ablation, cream etching, combination of laser ablation and cream etching, and hydrofluoric acid (HF) etching. The obtained surfaces by each method were characterized in detail via field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX/EDS), and surface profilometry. The impact of high... 

Magnesium (Mg) and its alloys have proved promising as biodegradable candidates for the repair of bone tissue. Despite the encouraging bio-related properties of Mg, its high corrosion rate in contact with body fluids still presents a major challenge. An efficient approach to address this issue is to provide a protective coating on Mg. The present research evaluates, for the first time, in vitro bioactivity and biocompatibility of a novel multifunctional composite coating based on poly(methyl methacrylate) (PMMA) biopolymer and bioactive glass (BG) particles on Mg-based implant. Electrophoretic deposition (EPD) was utilized to obtain this coating from a bi-component suspension. Coatings’... 

Polylactic acid (PLA) scaffolds produced by the fused deposition modeling (FDM) method have biocompatibility, close Young's modulus to that of bone, and the ability to make complex shapes. However, PLA has some drawbacks like brittleness, inappropriate mechanical strength and hydrophobicity, and a low degradation rate. In this study, polyethylene glycol (PEG) (5 and 10 wt%) by solving method and titanium (Ti) particles (5 wt%) by two different methods were mixed with PLA to address the mentioned problems. Extruded filaments were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and fourier transform infrared (FTIR). Surface morphology of the produced filaments... 

This study aims at investigating the effect of the substrate material on growth mechanism and also microstructure of Ta2O5 thin films. For this purpose, atomic force microscopy, scanning electron microscopy, and interferometry analyses were implemented to reveal the influence of silicon wafer and amorphous BK7 glass substrates on the nucleation and growth mechanisms of Ta2O5 thin films deposited via the radio frequency magnetron sputtering technique. Results indicated that those films with finer morphologies had relatively higher nucleation densities. Compared with BK7 glass substrate, crystals formed on the silicon wafer were shown to be finer and had lower mean areas in more nucleation... 

In this study, a fixed-bed catalytic membrane reactor was used for the production of ethylene and cyclohexane from ethane and benzene. A two-dimensional non-isothermal mathematical model was used for estimating the performance of the membrane reactor. Furthermore, the effect of inlet temperature (720–1080 K), feed molar ratio (3–10) and the reactor spacetime (1–76 kgCat.s/mol) was studied on the conversion of ethane to ethylene and benzene to cyclohexane. The results of modeling showed that with the increase of inlet temperature the conversion of both (de)-hydrogenation reactions increased and the 95% of ethane conversion was achieved when the molar ratio of benzene/ethane was fixed on 3.... 

The exploitation of solar energy facilitates the renewable energy paradigm. In this regard, parabolic trough collectors (PTC) are considered as a useful set-up to absorb solar energy. Simultaneous study of thermal, thermodynamic, and exergoeconomic performance of PTC systems paves the way for designers and manufacturers to not only have a better insight into understanding the underlying concepts about the operation of PTC systems but also to find the most effective and cost-effective circumstances. This study aims at analyzing a practical PTC system by considering an evacuated absorber tube with glass cover, non-uniform heat flux, and taking into account the convective and radiative heat... 

Two electrochemical sensors based on modified glassy carbon electrodes with carbon nanostructures as graphene (GCE–EG) and carbon nanotubes (GCE–CNT) were evaluated for morpholine analysis. The carbon nanostructures were obtained and characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and cyclic voltammetry. All spectroscopic and microscopic techniques confirmed the procurement of graphene and CNT. The electrochemical studies proved the efficient behaviour of both electrodes GCE–EG and GCE–CNT in sensing and detection of morpholine via differential pulse voltammetry.... 

Methicillin resistance Staphylococcus aureus bacteria (MRSA) are serious hazards of bone implants. The present study was aimed to use the potential synergistic effects of Melittin and tetracycline to prevent MRSA associated bone implant infection. Chitosan/bioactive glass nanoparticles/tetracycline composite coatings were deposited on hydrothermally etched titanium substrate. Melittin was then coated on composite coatings by drop casting method. The surfaces were analyzed by FTIR, XRD, and SEM instruments. Tetracycline in coatings revealed multifunctional behaviors include bone regeneration and antibacterial activity. Releasing ALP enzyme from MC3T3 cells increased by tetracycline, so it is... 

Surface-Enhanced Raman Spectroscopy (SERS) is a sensitive vibration spectroscopy method applied to analyze a variety of analytes, including toxins and pesticides. The SERS method is an accurate method for detecting significantly low concentrations of biomaterials and chemicals. In the present study, in order to detect atrazine pesticide, the glass fiber substrates coated with silver nanoparticles have been used as SERS plasmonic nanosensors. First, silver nanoparticles were prepared by applying a chemical approach named the Tollens' method, and the SERS plasmonic substrates (SPS) were fabricated by depositing the colloidal silver solution on a glass fiber substrate. The SERS plasmonic... 

In this research, the atomic scale local structures in (Zr0.5Cu0.5)100−xAlx (x = 0,2,4,6,8,10,12) bulk metallic glass was studied using molecular dynamics simulation method. The pair distribution function, Voronoi analysis and mean squared displacement (MSD) were adopted for investigation of the local structures. It was found that Cu- and Al-centered full icosahedra possess the most frequency accompanied by the most changes during the glass transition process in the supercooled liquid region temperature. Moreover, it was observed that the Al-centered full icosahedra (Al-FI) and Cu-centered full icosahedra (Cu-FI) clusters with 2.5% and 1.9% increase (relative to total atoms), respectively,... 

The biodegradation behavior of Mg, coated by polymethyl methacrylate as well as polymethyl methacrylate (PMMA)−bioactive glass (BG) composite was investigated. Electrophoretic deposition and dip coating techniques were adopted to prepare composite coating using a suspension of different percentages of the above two chemical materials. The deposited coatings were characterized using SEM, EDS, FTIR, and water contact angle measurements. Biodegradation behavior study of the coated Mg was performed using linear polarization, impedance spectroscopy, and immersion tests in simulated body fluid. The compact and homogeneous composite coating was developed as evidenced by electron microscopy results.... 

Introduction. Dental caries is the most common cause of tooth loss. However, it can be stopped by enhancing remineralization. Fluoride and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) are among the most important remineralizing agents. Recent studies have used bioactive glass as a remineralizing agent in different forms. This study aimed to assess the efficacy of a composite paste (prepared by mixing urethane polypropylene glycol oligomer with bioactive glass powder for easier application). Materials and Methods. Enamel disks were cut out of the buccal surface of extracted sound third molars. The samples were randomly divided into 3 groups of 15 and underwent Vickers... 

One of the most arduous challenges in tissue engineering is neovascularization, without which there is a lack of nutrients delivered to a target tissue. Angiogenesis should be completed at an optimal density and within an appropriate period of time to prevent cell necrosis. Failure to meet this challenge brings about poor functionality for the tissue in comparison with the native tissue, extensively reducing cell viability. Prior studies devoted to angiogenesis have provided researchers with some biomaterial scaffolds and cell choices for angiogenesis. For example, while most current angiogenesis approaches require a variety of stimulatory factors ranging from biomechanical to biomolecular...