Sharif Digital Repository

Molecules acting as antioxidants capable of scavenging reactive oxygen species (ROS) are of upmost importance in the living cell. Thymol derivatives exhibit various antioxidant activities and potential health benefits. Exploration of structure-radical scavenging activity (SAR) was approached with a wide range of thymol derivatives. To accomplish this task, the DPPH experimental assay along with quantum-chemical calculations were also employed for these compounds. By comparing the structural properties of the derivatives of interest, their antioxidant activity was explained by the formation of an intramolecular hydrogen bond and the presence of unsaturated double bond (–CHdouble bond; length... 

Steel plate shear walls are lateral load resisting systems, especially against earthquake excitation. They are constructed with or without stiffeners. Stiffened walls are more ductile than those without stiffeners. In this research a numerical study using finite element analysis via a finite element program is conducted. Nine thin steel plate shear wall models were considered in three groups of 5-storey, 10-storey and 15-storey walls. In each group different yield point steel for the infill plate was used. The yield points of infill plates were assumed to be 160, 200 and 240 MPa. The results showed that using low yield point (LYP) steel will increase energy dissipation of models by up to... 

A numerical simulation is carried out to study flow-induced vibration of an elliptical cylinder equipped with a wake-mounted flat plate in a laminar flow regime at Re = 100. The objects are constrained to vibrate independently in the cross-flow direction. The Vortex-induced vibration of an upstream cylinder with four different aspect ratios (AR = 0.25, 0.5, 0.75, 1) is investigated in the presence of a plate mounted in different horizontal spacing of G = 0.5–3. Simulations are performed for a fixed mass ratio of 10 and negligible damping ratio across a range of reduced velocities (Ur = 2–12). The results demonstrate that the presence of the flat plate can amplify the vibration amplitude of... 

In This paper, a simple single-dimension Space Vector Modulation (SVM) technique is introduced to implement on three-phase thirteen-level Modified Packed U-Cell (MPUC) inverter for photo-voltaic system in which many DC sources are avail-able. The three-phase thirteen-level converter con-sists of three single-phase seven-level MPUCs that each phase has six switches and two isolated DC sources. One major advantage of proposed method is to produce an output voltage with nearly constant amplitude in desired range in case of input DC voltage fluctuations, which is common in renewable sources like Photovoltaic Systems (PV). On the other hand, the conventional Pulse Width Modulation (PWM)... 

The cation radicals of DNA constituents generated by the ionizing radiation initiate the alteration of the bases, which is one main type of cytotoxic DNA lesions. These cation radical spices are known for their role in producing nucleic acid strand break, and it is important to identify the cation radical formation at particular atomic site in these molecules so that the major pathway for the nucleic acid damage may be trapped. In the present study, we explored theoretically energetic, structural, and electronic properties of the possible radicals formed via proton atom abstraction at various sites of sugar part of deoxycytidine cation radical by employing density functional theory at... 

3g wireless communication is the next version of mobile networks. Load balancing in networks causes efficient using of network resources. In this paper, we propose an efficient algorithm for load balancing of Radio Network Controllers (RNCs) in Radio Access Networks (RANs). As the characteristics of connections between RNCs and BTSs in a RAN are similar to those of graphs, we make use of graphs to solve our problem. The algorithm is based on the finding a path by which the RNCs could exchange their overloads. By using these paths the algorithm load balances the RNCs in an efficient and fast way. By testing our algorithm on networks with different topology and comparing the results, the... 

Bromophenols are known as antioxidant radical scavengers for some biomolecules such as those in marine red alga. Full understanding of the role played by bromophenols requires detailed knowledge of the radical scavenging activities in probable pathways, a focus of ongoing research. To gain detailed insight into two suggested pathways, H-atom transfer and electron transfer, theoretical studies employing first principle quantum mechanical calculations have been carried out on selected bromophenols. Detailed investigation of the aforementioned routes revealed that upon H-atom abstraction or the electron transfer process, bromophenols cause an increase in radical species in which the unpaired... 

The morphological, physical and mechanical properties of polypropylene/clay nanocomposites (PPCNs) were prepared by in situ polymerization are investigated. Non-modified scmectite type clay (e.g. bentonite) was used to prepare bi-supported Ziegler-Natta catalyst of TiCl4/Mg(OEt)2/clay. Exfoliated PPCNs were obtained by in situ intercalative polymerization of propylene using produced bi-supported catalyst. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) micrograph were used to assess the clay morphology and dispersion of clay. The crystalline structures of PPCNs were characterized by differential scanning calorimetry (DSC). The mechanical properties of PPCNs were... 

Understanding the nature of interaction between metal nanoparticles and biomolecules such as amino acids is important in the development and design of biosensors. In this paper, binding of M3 clusters (M = Au, Ag and Cu) with neutral and anionic forms of histidine amino acid was studied using density functional theory (DFT-B3LYP). It was found that the interaction of histidine with M3 clusters is governed by two major bonding factors: (a) the anchoring N-M and O-M bonds and (b) the nonconventional N-H⋯M and O-H⋯M hydrogen bonds. The nature of these chemical bonds has been investigated based on quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. In the next... 

The relative stabilities and noncovalent interactions of the six low-lying energy tautomers of cytosine nucleobase with some biological anions (such as F-, Cl-, and CN-) have been investigated in gas phase by density functional theory (DFT) method in conjunction with 6-311++G (d,p) atomic basis set. Furthermore, to systematically investigate all possible tautomerisms from cytosine induced by proton transfer, we describe a study of structural tautomer interconversion in the gas phase and in a continuum solvent using DFT calculation. We carried out geometrical optimizations with the integral equation formalism of polarizable continuum (IEF-PCM) model to account for the solvent effect, and the... 

Understanding the nature of the interaction between metal nanoparticles and biomolecules has been important in the development and design of sensors. In this paper, structural, electronic, and bonding properties of the neutral and anionic forms of glutathione tripeptide (GSH) complexes with a Au 3 cluster were studied using the DFT-B3LYP with 6-31+G**-LANL2DZ mixed basis set. Binding of glutathione with the gold cluster is governed by two different kinds of interactions: Auâ€"X (X = N, O, and S) anchoring bond and Au··•·•H-X nonconventional hydrogen bonding. The influence of the intramolecular hydrogen bonding of glutathione on the interaction of this peptide with the gold cluster has been... 

Copper(II) efficiently catalyzes the aerobic oxidation of aryl thioacetamides into the corresponding α-keto aryl thioamides in moderate to high yields in the presence of K2CO3 under O 2 atmosphere. This protocol is simple, clean, and generates water as the only byproduct. A mechanism is proposed for the reaction course. © Georg Thieme Verlag Stuttgart