Sharif Digital Repository

In this paper, the elastic properties of monomeric actin (G-actin) and the trimer nucleus (G-actin trimer) in different states of nucleotide binding are estimated using steered molecular dynamic (SMD) simulations. Three nucleotide binding states are considered: ADP- and ATP-bound actin and nucleotide-free actin assemblies. Our results show that nucleotide binding and the corresponding changes in structure have significant effects on the mechanical behaviors of actin assemblies. Simulations reveal that the deformation behavior of G-actin monomers is generally elastic up to engineering strains of 16 and 40% in the tension and shear tests, respectively. In addition, the G-actin trimers react... 

A total of 6289 drug-like anticancer molecules were collected from Binding database and were analyzed by using the classification techniques. The collected molecules were encoded to a diverse set of descriptors, spanning different physical and chemical properties of the molecules. A combination of genetic algorithms and counterpropagation artificial neural networks was used for navigating the generated drug-like chemical space and selecting the most relevant molecular descriptors. The proposed method was used for the classification of the molecules according to their therapeutic targets and activities. The selected molecular descriptors in this work define discrete areas in chemical space,... 

A new micro-solid phase extraction method was developed by combining solid-phase extraction and stir bar sorptive extraction to benefit from the advantages of both techniques. A polypyrrole coating was electrochemically synthesized on the surface of an already used graphite furnace, employed in electro-thermal atomic absorption spectroscopy. The cylindrical geometry of the graphite tube provided a rather huge surface area, suitable for sorptive extraction. The novel sorbent coating was examined as an extracting medium to isolate malathion. Effects of different parameters such as extraction time, salt concentration, sample volume, desorption solvent and time were investigated and optimized.... 

In this work, the preparation of a new grafted nanosilica-based sorbent was extensively investigated. An inexpensive modifier, cis-9-octadecenoic acid (oleic acid) was selected to be grafted on the surface of the nanosilica particles as the support. The grafting process was accurately confirmed by Fourier transform infra-red spectrometry (FT-IR). Applicability of the prepared sorbent was thoroughly examined by needle trap extraction (NTE) method. The grafted sorbent was dispersed in the appropriate solvent and carefully packed inside a steel needle. Feasibility of the method was completely examined using polycyclic aromatic hydrocarbons (PAHs), as model compounds. For extraction of analytes... 

Experimental permeability and diffusivity values for CO2 and CH4 through imidazolium-based ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N]) were determined in the temperature range of 300-320K using temperature correction factor defined in our previous study. According to literature, experimental values of permeability and diffusivity obtained in this study for CO2 in [hmim][Tf2N], showed good agreement with predictive models reported by other researchers. In addition, experimental values of permeability and diffusivity for CH4 in [hmim][Tf2N] as a function of pressure have been reported in this study. Considering the results of present study and... 

The efficient synthesis of bridged polycyclic naphthooxazocines 3 via addition of naphthalenols 1 as a bis-nucleophile to N-alkylquinolinium salts 2 is described (Scheme 1 and Table 2). This new approach provides a powerful entry into polycyclic structures containing bicyclic N,O-acetals related to bioactive compounds  

A molybdate-based heterogeneous magnetic catalyst was synthesized and used in direct oxidation of various primary and secondary organic halides to the corresponding aldehydes and ketones using 30% H2O2 as an oxidant in ethanol. Various organic halides were oxidized to their corresponding aldehydes and ketones in good to excellent yields. The catalyst system can be easily separated by applying an external magnetic field and reused for 6 runs without any significant loss of catalytic activity. The catalyst was fully characterized by FT-IR, SEM, TEM, EDS, XRD, VSM, ICP-AES techniques, and elemental analysis (CHN)  

Network tools have been extensively applied to study the properties of brain functional and anatomical networks. In this paper, resiliency of Caenorhabditis elegans cortical networks against cascaded failures is studied. To this end, directed network formed by chemical connections and undirected network formed by electrical couplings through gap junctions are considered. Furthermore, two types of C. elegans networks are studied: the whole cortical network of the hermaphrodite type and the network of the posterior cortex in male C. elegans. The results show that resiliency of hermaphrodite and male networks is different. The male cortical network of chemical synapses shows extensively weaker... 

Objective: The purpose of this study was to compare the relative stiffness of four common external fixation (XF) configurations used to span and stabilize the knee after knee dislocation. Methods: Synthetic composite femora and tibiae connected with cords were used to simulate a knee. Four configurations of external fixation were tested: anterior femoral pins with monotube (XF1), anterolateral femoral pins with monotube (XF2), anterolateral femoral pins with two connecting rods (XF3), and hinged ring fixator (XF4). Six specimens of each configuration were loaded nondestructively in varus/valgus, anterior-to- posterior shear, flexion/extension, axial compression, internal/external torsion,... 

Several methods have been proposed to construct Statistical Shape Model (SSM) to aim image analysis using computer in field Computer Aided Diagnosis (CAD), Computer Assisted Surgery (CAS), and other medical applications by providing a prior knowledge. The major challenge for liver shape model is a high variation in geometry such as size, shape and volume between livers. In this paper, we have presented a new technique for the automatic Multi-Scale Statistical Shape Model (MS-SSM) of three-dimensional (3-D) liver from volumetric segmented images data. The procedure included both building of Spherical Harmonics shape description and the Wavelet transform. Principal Component Analysis (PCA) was... 

A rapid, environmental friendly and low-cost method to prepare hydroxyapatite nanoparticles is proposed. In this method, hydroxyapatite is produced in a sonicated pseudo-body solution. The sonication time was found effective in the formation of the crystalline phase of nanoparticles. In our experimental condition, 15 min sonication resulted in the most pure hydroxyapatite phase. Also it was shown that growth temperature is a crucial factor and hydroxyapatite crystallizes only at 37 °C. The particles formed by sonication were generally smaller and more spherical than those obtained without sonication. Sonication increased the hydroxyapatite crystal growth rate up to 5.5 times compared to... 

STUDY DESIGN.: An experimental design to investigate activation patterns of trunk muscles during multidirectional exertions. OBJECTIVES.: To evaluate trunk muscle activation patterns in varying directions and moment magnitudes during an isometric task, and to investigate the effects of angle and level of isometric exertion on the electromyography (EMG) variability of trunk muscles in upright posture. SUMMARY OF BACKGROUND DATA.: Few studies have investigated trunk muscle activation patterns in multidirectional exertions with different moment magnitudes. METHODS.: A total of 12 asymptomatic male subjects were participated in the study. The EMG activity of 10 selected trunk muscles was... 

Novel organic-inorganic hybrid heterogeneous nanocatalysts were obtained by covalent anchoring of a molybdenum(vi) complex of salicylidene 2-picoloyl hydrazine, MoO2(sal-phz)(CH3OH), (1) on the surface of magnetic nanoparticles functionalized by one of two routes: in the first method, the surface of magnetic nanoparticles is directly modified with 3-chloropropyltrimethoxysilane yielding 1A. In the second method, magnetic nanoparticles were silica-coated with tetraethoxysilane and then with 3-chloropropyltrimethoxysilane yielding the intermediate 2B. Then complex 1 was grafted on the surface of 1A or 2B through covalent interaction yielding 2A or 3B, respectively. The nanocatalysts 2A and 3B... 

Neural tissue engineering aims at developing novel approaches for the treatment of diseases of the nervous system, by providing a permissive environment for the growth and differentiation of neural cells. Three-dimensional (3D) cell culture systems provide a closer biomimetic environment, and promote better cell differentiation and improved cell function, than could be achieved by conventional two-dimensional (2D) culture systems. With the recent advances in the discovery and introduction of different types of stem cells for tissue engineering, microfluidic platforms have provided an improved microenvironment for the 3D-culture of stem cells. Microfluidic systems can provide more precise... 

One crucial part of an image registration algorithm is utilization of an appropriate similarity metric. For common similarity metrics such as CC or MI, it is assumed that the intensities of image pixels are independent from each other and stationary. Accepting these assumptions, one will have difficulty doing image registration in the presence of spatially varying intensity distortion. In Myronenko et al. [5] a solution based on minimization of residual complexity is introduced to solve this problem. In this work, the weakness of RC method is investigated for more complex spatially varying intensity distortions and a modification of this method is presented to improve its performance in such... 

In this study, AgxNi100-x, and CoxNi100-x (x = 0, 20, 40, 60, 80, and 100) bimetallic nanoparticles were successfully decorated on the surface of CeO2 nanorods derived from Ce-metal organic frameworks (Ce-MOF). The as-synthesized products were characterized using different techniques including XRD, FE-SEM, EDX, TEM, ICP, and BET. The as-prepared nanocomposites showed remarkable catalytic activity towards the reduction of organic pollutants such as 4-nitrophenol (4-NP), and rhodamine-B dye (RhB) by NaBH4 solution, with high stability and reusability for five consecutive cycles. The obtained results indicated that among these nanocomposites, Ag80Ni20@CeO2, and Co60Ni40@CeO2 exhibited the best... 

In this study, MoS2/reduced graphene oxide (rGO) was used as a cocatalyst to synthesize very highly efficient Cu2O/MoS2/rGO for cooperative catalytic applications. The resulting nanocomposite was characterized by various analytical techniques and applied for catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol and photocatalytic degradation of Acid blue 92. Cu2O/MoS2/rGO composite presents superior performance to pure Cu2O particles in both catalytic and photocatalytic reactions. This excellent activity demonstrates synergistic effect of MoS2/rGO as a cocatalyst in the nanocomposite. The role of the active sites in the reduction of 4-NP and degradation of dye was discussed and... 

Herein, we report the impact of chromium doping on the physical properties, electronic band structure and photovoltaic characteristics of their corresponding devices based on dye-sensitized solar cells (DSCs). Different DSCs with various compositions of the photoanode electrodes are fabricated to study their optical, structural, conduction band edge, donor density, depth of trap states and photoelectrochemical properties using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), Mott-Schottky capacitance analysis, chemical capacitance and electrochemical impedance spectroscopy (EIS) measurements. For such studies, the Cr-doped... 

The main aim of this research is to improve the photocatalytic activity of TiO2 nanotubes by co-doping with copper and sodium for application in the water splitting process as a photoanode. The doping was performed simultaneously to the anodizing process through a single-step treatment. The synthesized TiO2 nanotube array (TNA) was characterized by applying FESEM (Field Emission Scanning Electron Microscopy), XRD (X-ray Diffraction), DRS (Diffraction Reflection Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy) analyses. The results of XPS analysis proved the presence of copper with valence (2+) and carbon and sodium with valence (1+). Moreover, DRS tests showed a reduction in the band... 

Kinetic modeling of CO hydrogenation over Fe-Co-Mn catalyst was investigated; a ternary catalyst was prepared using incipient wetness impregnation. The kinetic parameters were determined from experiments carried out in a fixed bed micro-reactor under the following process conditions: T = 523.15-533.15 K, P = 1-10 bar, H2/CO = 1/1-3/1 and space velocity = 4500 h-1. Seventeen rate expressions were derived from five different mechanisms according to Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (ER) mechanisms and were tested against the experimental data. Non-linear regression method was used to estimate different kinetic parameters; according to the obtained experimental results...