Sharif Digital Repository

The objective of this research was to fabricate nanocomposites based on reduced graphene oxide (rGO) and strontium titanate (SrTiO₃) and investigate their photovoltaic properties as charge transport platforms in dye-sensitized solar cells (DSSCs). Initially, graphene oxide was prepared using the Hummers method and combined with strontium titanate through a ex-situ approach. Subsequently, strontium titanate based on reduced graphene oxide nanocomposites were obtained using thermal and solvothermal methods. Structural and optical characterization of these nanocomposites was performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric... 

The goal of authenticated encryption is to ensure confidentiality, integrity and authenti-cation of the messages simultaneously. The anouncement of CAESAR comptetition has attracted esearchers’ attention to this branch of symmetric cryptography, since 2014. 57 schemes have been introduced as the first round candidates of this competition, from which 29 where selected as second round candidates. Cryptanalysis of these schemes needs a lot of collective effort. In this thesis after describing preliminaries of authen- ticated encryption, general structure of the schemes and their reported cryptanalysis is reviewed. Then, the details of Pr∅st family of authenticated encryption, which is one of... 

In this research, synthesis, structural and theoretical studies of rhnium(I) tricarbonyl complexes with general formula, fac-[Re(CO)3(NN)X] in which NN´ is chelating bidentate diimine ligand and X = Cl, Br, and OCOCF3 ligands were studied. The synthesized complexes were characterized by 1H-NMR and FTIR spectroscopic methods and their solid state structures were determined by X-ray diffraction analysis. Then, the reaction of the synthesized rhenium complexes were studied by copper(I) iodide. Crystal structure determination by single-crystal X-ray diffraction allows us to fully examine the intramolecular and intermolecular interactions. We also investigated the energy of different... 

Superparamagnetic Iron Oxide NPs (SPIONs) because of their multi-task capabilities (e.g. magnetic labeling, cell isolation, hyperthermiaand controlled drug release) have been recognized as one of the most promising NPs for theranosis applications.When NPs come in contact with a biological medium, the surfaces of them are covered by biomolecules (e.g., proteins, natural organic materials, and enzymes). Therefore, what a biological entity, such as cells, tissues, and organs, sees when interacting with NPs is different original pristine surface of the NPs and actually is hard protein corona. Shape of NPs has a great impact on proteins adsorb onto its surface and consequently on the way that... 

In this thesis, the copper oxide - zinc oxide nanocomposite was synthesized and functionalized using 3-aminopropyltrimethoxysilane. The functionalized nanocomposite was characterized using X-ray Diffraction spectroscopy (XRD), Fourier Transform Infrared (FT-IR), X-ray Fluorescence Spectroscopy (XRF), Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (BET). Dye removal from synthetic wastewater was done in a batch system using functionalized copper oxide - zinc oxide nanocomposite as adsorbent. Direct red 23, direct red 80 and direct red 81 were used for preparation of synthetic wastewaters. The effects of operational parameters such as adsorbent dosage, initial dye concentration,... 

Superparamagnetic iron oxide nanoparticles (SPION) with proper surface coatings are increasingly being evaluated for clinical applications such as hyperthermia, drug delivery, magnetic resonance imaging, transfection, and cell/protein separation. Since the particles with various sizes exhibit different flow rates in the same environment (same capillary size), it is essential to use particles of a desirable size for targeted drug delivery and imaging. Particles of different sizes may be exposed to different viscosities and behave differently, particularly with regard to their velocities as they move through capillaries. In the present work, SPION with different size, purity, shape and... 

In this research, nano composite MgH2-TiCr1.2 Fe0.6 nano crystalline was synthesized by mechanical alloying and Vacuum arc re-melting (VAR). the effect of Milling conditions and adding nano crystalline TiCr1.2 Fe0.6 as a catalyst on the structure and hydrogen desorption properties of MgH2 were studied. MgH2 powder grain size after 4 hours milling gained to 15nm and strain network reached to 0.8%. Determined that the increasing of accumulated lattice strain because of mechanical milling combined with adding nano crystalline alloy TiCr1.2 Fe0.6 significantly improve the properties of MgH2 hydrogen desorption. After an hour mill working, high pressure phase of γ-MgH2 was appeared in... 

Diabetes mellitus is a global endemic that is rapidly increasing prevalence in both developing and developed countries. Recently, the American Diabetes Association has recommended the hemoglobin A1c as a possible substitute to fasting blood glucose for diagnosis of diabetes because it is an indicator of long-term glycemic control. Also, centrifugal microfluidics systems have a good potential to be used in the point of care testing systems. In this study, two centrifugal microfluidic discs were designed and manufactured in order to separately measure the hemoglobin and hemoglobin A1c in the whole blood. In the first part of the study, the hemoglobin measurement disc consists of two chambers... 

This master’s thesis has two major parts. The first part which includes chapters 1 to 8, describes the article A. Pfister, Quadratische Formen in beliebigen Körpern, Invent. Math. 1, (1966)pp. 116-132, and expresses important facts about the Witt ring W(K) of quadratic forms over an arbitrary field K of characteristic unequal to 2. Among those, it is shown that the order of each element in the additive group of W(K) is a power of 2, the Witt ring doesn’t have any zero divisor of odd dimension and a necessary and sufficient condition for W(K) to be an integral domain is given. The connections between the square class number of a field and the cardinality of its Witt ring and, providing some... 

This thesis contains four chapters. In first chapter the role of water in organic reactions as a ecofriendly solvent, computational chemistry and dynamic nuclear magnetic resonance were studied. In the second chapter synthesis of new 4-hydroxy pyrrole derivatives in water were reported. For the synthesis of these compounds arylglyoxal derivatives, 1,3-dicarbonyl compounds and ammonium acetate were used. The reaction conditions are very mild. The third chapter contains the synthesis of new (4 or 5)-Aryl-2-aryloeil-(1H)-imidazole compounds in aqueous media. We also investigated the tauto-isomerisation of isomeric imidazoles during this reaction using DNMR technique. In forth chapter a... 

This thesis contains two parts .In the first part a catalyst such as AlCl3/Al20 has been demonstrated to catalyze Michael addition reaction of amines to a,�- unsaturated compounds with high yields , short reaction time and under solvent-free condition.The Michael addition to a,�- unsaturated compounds produces quantitively the mono addition products.The next part is about olefins epoxidation . Alkene epoxidation is a useful reaction in organic synthesis. Epoxides play an important role in industrial intermediates for the production of fine chemicals as well as pharmaceuticals .The hydrogen peroxide has been used as an oxidant because it is considered as an economical and appropriate reagent... 

Enanthioselective synthesis of biological molecules are so important in synthetic chemistry, and because of their biological activities, β-amino carbonyl compounds have earned so much attention in this area of chemistry. Mannich reaction is a classical method for synthesis of these molecules. The Mannich reaction is a three-component reaction between an enolizable CH-acidic carbonyl compound, an amine, and an aldehyde producing β-amino carbonyl compounds. But acidic or basic difficult circumstances, long reaction time, low yield and enantioselectivity, are the drawbacks of classical methods. In this project, we used titania-based solid acid as an enantioselective catalyst to overcome these... 

Biological processes are accompanied by changes in free energy. Therefore, an accurate understanding of molecular mechanisms requires precise computation of free energy differences. Various methods have been developed since 1935 to calculate free energy using the principles of classical physics and statistical mechanics. Although many biological simulations provide qualitatively good complements to experimental results, in many cases, there still exists a gap between simulation and experimental data. Due to the complexity of biological environments, more realistic molecular modeling approaches are required to improve prediction accuracy and interpretation of results. Different intrinsic and... 

In this thesis, which is based on an article of Claus Scheiderer (Reference [21]), the relation between positive semi-definite elements of a semilocal ring, called psd, and elements of the ring which can be written as a sum of square elements of the ring and are called sos will be evaluated. In Chapter One, the concepts of prime cones, real spectrum of a ring and real ideals will be defined and then the relation between psd and sos elements in the total rings of quotients will be assessed. The Krull Valuation of an element which is a sum of squares will also be determined. In Chapter Two, the concept of totally positive elements in a ring will be defined and their properties will be... 

For a field of characteristic not two, the classical u-invariant is defined as the maximal dimension of anisotropic quadratic forms over F. Initially Kaplansky conjectured that u(F), when finite, is always a 2-power. Later Merkurjev constructed a field F such that u(F) = 6. This dissertation examines in detail the article: R. Elman, T. Y. Lam, Quadratic forms and the u-invariant. I. Math. Z. 131, 283-304 (1973). in which the notion of ”generalized u-invariant” (motivated by Pfister’s Local-Global Principle) was defined as the maximal dimension of anisotropic torsion quadratic forms over F. This is indeed a right generalization of the definition of the classical u-invariant since it not only... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Purification of waste water containing metal ions, is one of major environmental problems which have threaten human’s life, other creatures and even agricultural products by means of polluting suberranean water. Copper ion is one of dangerous heavy metals that exists in potable water and agricultural uses, due to serious problems in health of humans and aquatic. In recent years, different methods for purification of waste water containing heavy metal ions have been published. Right now, thorough these methods such as: filtration, coagulation, precipitation and adsorption are being used, which have their own advantages and disadvantages.In this research, new method for purification of waste... 

Albert proposed the cyclic algebraof the degree 4 in1934. After that more studies were conducted on thecyclic algebras on F in conditions in which L = F(µ )nis an extention of F, for in the Albert’s example it wasmanifest that 2|[F(µ ) : F]. In a paper in the same yearnAlbert proposed a condition for an F-division algebrato be cyclic. In this thesis, a theorem will be proposedin which for the condition (n=1) the Albert’s theoremwill be the result. Moreover, F-division rings of the pndegree are investigated. the required means is modularspectral factorization which was for the ?rst time de?nedin clusters by Merkuryev. Finally a condition will beproposed for the fact that F-division...