Sharif Digital Repository

Purpose: The prime end of this study was to design a novel pH-sensitive as well as a PEGylated dendritic nanocarrier for both controllable and traceable gemcitabine delivery to cancerous cells. To accomplish this goal, we took advantage of a hybrid of nanoparticles including: mesoporous silica, graphene oxide and magnetite. Methods: The nanocarrier was prepared in a multi-step synthesis route. First, magnetite mesoporous silica was deposited on the graphene oxide matrix. Then, polyamidoamine dendrimers (up to generation 1.5) with pentaethylene hexamine end groups were grafted on the surface of the nanoparticles. In order to enhance the biostability, and as the next step, the nanocarrier was... 

Due to the high activity of Au nanoparticles (NPs) for various reactions, many researchers have tried to develop heterogeneous catalysts in order to prevent irreversible agglomeration of Au NPs. Herein, magnetic graphene oxide modified with polyaniline (PANI) was used as a support for Au NPs that brings together advantages including: uniform dispersal of the catalyst in water,alarge surface area related to the graphene oxide; easy electron transfer in chemical reactions and good attachment of Au NPs to the support associated with PANI; and finally facile recovery in the presence of a magnetic field. Catalytic reduction of different analytes (Congo red, methylene blue, rhodamine B and 4-nitro... 

In this study, a new magnetic nanocomposite was synthesized via radical polymerization of methyl acrylate onto modified magnetic nanoparticles followed by the functionalization of the methyl ester groups with ethylenediamine and sodium chloroacetate. The generated magnetic nanocomposite was characterized by FT-IR, TEM, SEM, TGA, VSM, XRD and elemental analysis. Its key role as an adsorbent for the removal of typical cationic dyes, methyl violet and malachite green was investigated in terms of pH, contact time and initial dye concentration. The resulted adsorbent displays excellent adsorption capacities for cationic dyes which are more effective than most of the adsorbents reported so far.... 

A model has been proposed to capture the complex strain rate effect on dynamic precipitation of GP zones in an age-hardenable aluminum alloy. The contributions of vacancies and dislocations to dynamically formed GP zones have been specified in the model. It has been demonstrated that the proposed model is capable for predicting the contribution of each dynamic precipitation mechanisms, accurately, which are acting during deformation. Furthermore, the vacancy and dislocation evolutions during deformation have been considered in this modeling. The effect of strain rate by considering different mechanisms of dynamic precipitation of GP zones has been studied and confirmed by experimental data... 

Microstructure and mechanical properties of AA2024 after severe plastic deformation (SPD) and non-isothermal annealing were investigated. The non-isothermal treatment was carried out on the severely deformed AA2024, and the interaction between restoration and precipitation phenomena was investigated. Differential scanning calorimetry, hardness and shear punch tests illustrate that static recovery and dissolution of GPB zones/Cu–Mg co-clusters occur concurrently through non-isothermal annealing. Scanning electron microscope and electron backscatter diffraction illustrate that non-isothermal annealing of deformed AA2024 up to 250 °C promotes the particle-free regions and also particle... 

Let G be a graph whose each component has order at least 3. Let s: E(G) → Zk for some integer k≥ 2 be an improper edge coloring of G (where adjacent edges may be assigned the same color). If the induced vertex coloring c: V(G) → Zk defined by c(v)=∑e∈Evs(e)inZk, (where the indicated sum is computed in Zk and Ev denotes the set of all edges incident to v) results in a proper vertex coloring of G, then we refer to such a coloring as an improper twin k-edge coloring. The minimum k for which G has an improper twin k-edge coloring is called the improper twin chromatic index of G and is denoted by χit′(G). It is known that χit′(G)=χ(G), unless χ(G)≡2(mod4) and in this case χit′(G)∈{χ(G),χ(G)+1}.... 

A magnetic nanoparticle@starch-g-poly(vinyl sulfate) nanocomposite (MNP@St-g-PVS) as a new magnetic nano-adsorbent has been prepared based on graft copolymerization of vinyl acetate onto starch in the presence of magnetic nanoparticles, where the acetate groups were converted to hydroxyl groups followed by the sulfation of the hydroxyl groups using chlorosulfonic acid. Characterization of this magnetic nanocomposite was carried out by FTIR, TGA, XRD, VSM, SEM, TEM and elemental analysis. The resulting nanocomposite was used as an adsorbent for the removal of typical cationic dyes, methylene blue (MB) and malachite green (MG), from aqueous solutions. All experimental parameters that can... 

The recrystallization behavior of an Al-Cu-Mg alloy is investigated in multi-directionally forged over-aged and solution treated alloys, during non-isothermal annealing. Deformation and non-isothermal annealing are performed with a Gleeble 3800 thermo-mechanical simulator. The hardness measurements show that there is a thermal stability in mechanical properties during non-isothermal annealing up to 250 °C with heating rate of 10 K·min− 1. Differential scanning calorimetry curves of deformed over-aged and solution treated alloys describe the related precipitation phenomena. EBSD maps demonstrate that partially recrystallized and fully recrystallized microstructures appear in deformed... 

Concurrent precipitation in an age hardenable aluminum alloy determines recrystallization behavior especially grains structure and recrystallization texture during continuous heating. In this study, to investigate the effect of concurrent precipitation on the recrystallization texture and grains structure, a solution treated Al-Cu-Mg alloy has been multi-directionally forged at room temperature and continuously heated with different heating rates (800, 1600 and 2500 K·min− 1) up to 450 °C using Gleeble 3800 thermo-mechanical simulator. At lower heating rates (800 K·min− 1), Goss texture component {110} 〈001〉 (Φ1 = 90°/0°, Φ = 90°/45°, Φ2 = 45°/90°) is developed during continuous heating and... 

Particle stimulated nucleation (PSN) is one of the important mechanisms of recrystallization which is investigated in this research during non-isothermal annealing of multi-directionally forged solution treated aluminum alloy 2024. Non-isothermal annealing is performed up to temperatures of 380 °C and 450 °C at heating rates of 10, 100 and 200 K·min− 1 using a Gleeble 3800 thermo-mechanical simulator. In order to investigate the microstructure, field emission gun scanning electron microscope (FEG-SEM) equipped with electron backscatter diffractometer (EBSD) and differential scanning calorimetry (DSC) are utilized. The results show that the heating rate has a significant effect on the PSN and... 

The effects of initial heat treatments, i.e. solution treating and over ageing, on deformation behavior of an age hardenable Al-Cu-Mg alloy, including mechanical properties and texture evolution, during multi-directional forging (MDF) are investigated. Hardness measurements, electron back scatter diffraction (EBSD) maps, and differential scanning calorimetry (DSC) are carried out. Mechanical behaviors of the alloy in terms of compressive stress and hardness test after MDF are investigated. In both solution treated and over-aged alloys, the compressive stress during MDF shows an increase up to the second pass, and by further straining the flow stress is decreased. However, shear and... 

The effects of severe plastic deformation on properties of AA1100 and AA2024 including the ultrasound velocity and the shear strength during multi-axial compression (MAC) are studied. Additionally, optical microscopy, scanning electron microscopy, and X-ray energy-dispersive spectroscopy are utilized. For both AA1100 and AA2024, an opposite trend is reported in the shear strength and the sound velocity versus deformation strain of MAC. At high strain range, AA1100 and AA2024 samples reach a plateau in the strength due to the occurrence of dynamic recovery. On the other hand, the sound velocity is shown to decrease 11% and 15% for AA1100 and AA2024, respectively. Furthermore, the... 

Poly(amidoamine)-graft-poly(methyl acrylate) magnetic nanocomposite was synthesized via radical polymerization of methyl acrylate onto modified magnetic nanoparticles followed by the functionalization of the methyl ester groups with poly(amidoamine) dendrimer. The resulting poly(amidoamine)-graft-poly(methyl acrylate) magnetic nanocomposite was then characterized by infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, scanning electron microscope and X-ray diffraction analysis. Its application as an adsorbent for the removal of Pb(II) ions was studied. The removal capability of the adsorbent was investigated in different pH values, contact time (kinetics) and... 

A new magnetic nano-adsorbent was synthesized via the radical polymerization of methyl acrylate on modified Fe3O4 nanoparticles, followed by its functionalization by amidation of the methyl ester groups using pentaethylenehexamine, to create active adsorption sites for removing anionic dyes from aqueous media. Physicochemical properties of the adsorbent were then characterized by SEM, TEM, XRD, FTIR, TGA and CHN analysis. The prepared nanocomposite was used as adsorbent for the removal of anionic dyes, naphthol green B and chromeazurol S, from aqueous solution and assessed in view of the kinetics and isotherm adsorption, and the effect of solution pH, contact time and initial dye... 

Post-uniform deformation energy of materials is defined as absorbed energy per unit area after necking. The energy is constant for a material type and its experienced specific processing history and also depends on its mechanical parameters as workhardening exponent, strain rate sensitivity, post-necking extension and inhomogeneity factor. Different methods such as single and multiple tensile testing had been proposed in the literature to calculate tearing energy, but the effect of post-necking extension had not been expressed explicitly. A new model by implementing uniform and failure elongations with the combination of Unwin theory is introduced. Based on the model, it was shown that...