Sharif Digital Repository

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

With current memory scalability challenges, Phase-Change Memory (PCM) is viewed as an attractive replacement to DRAM. The preliminary concern for PCM applicability is its limited write endurance that results in fast wear-out of memory cells. Worse, process variation in the deep-nanometer regime increases the variation in cell lifetime, resulting in an early and sudden reduction in main memory capacity due to the wear-out of a few cells. Recent studies have proposed redirection or correction schemes to alleviate this problem, but all suffer poor throughput or latency. In this article, we show that one of the inefficiency sources in current schemes, even when wear-leveling algorithms are used,... 

Using density functional theory combined with non-equilibrium Green's function method, we have investigated the electronic and transport properties of graphenes defected by one and two carbon ad-dimers (CADs), placed parallel to the graphene lattice. Addition of these CADs to graphenes creates 3D paired pentagon-heptagon defects (3D-PPHDs). The band structure, density of states (DOS), quantum conductance, projected DOS, as well as the current-voltage characteristic per graphene super-cells containing each type of 3D-PPHD are calculated. The local strain introduced to graphene by 3D-PPHDs forces the C-bonds in the dimers to hybridize in sp 3-like rather than sp 2-like orbitals, creating... 

Graphene nanogrids (crossed graphene nanoribbons synthesized by the oxidative unzipping of multi-walled carbon nanotubes) on a SiO2 matrix containing TiO2 nanoparticles (NPs) were applied as a photocatalytic stimulator in the accelerated differentiation of human neural stem cells (hNSCs) into two-dimensional neural networks. The hydrophilic graphene nanogrids exhibited patterned proliferations of hNSCs (consistent with patterns of the nanogrids), in contrast with the usual random growths occurring on quartz substrates. The number of cell nuclei differentiated on reduced graphene oxide nanoribbon (rGONR) grid/TiO2 NPs/SiO2 increased ∼5.9 and 26.8 fold compared to the number of cells on quartz... 

Design and operation of an opto-mechanical system employing a double-cell is reported here for the color liquid reflection studies. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected from the sample to a photodetector. By scanning the double-fiber assembly in one-direction reflection properties of different color liquids are investigated. Reflection signals depend on the cell surface structure and the cell filled material. Two sets of flat/cylindrical cells made of almost similar glass materials are used for this... 

In recent years there has been potential increase in the use of alkaline protease as industrial catalysts. Many major industrial and commercial applications, such as food and textile industries, and medical diagnoses, are highly dependent on the protease enzyme. In the cell immobilization technique, the free movement of microorganisms is restricted in the process, and a continuous system of fermentation can be used. In the present work, this technique has been used for alkaline protease production using different carriers, such as chitosan, corn cob and corn tassel. Enzyme activity before immobilization (72 h) was 78.3 U/ml. Corn cob, with 65% immobilization capacity and the highest enzyme... 

Analysis and investigation of the relation between different parts of biological cells such as biomembrane, cytoplasm and nucleus can help to better understand their behaviors and material properties. In this paper, first, the whole elastic properties of mouse oocyte and embryo cells have been computed by inverse finite element and Levenberg-Marquardt optimization algorithm and second, using the derived mechanical properties and the mechanical properties of its bio membrane from the literature, the mechanical properties of its cytoplasm has been characterized. It has been assumed that the cell behavior is as continues, isotropic, nonlinear and homogenous material for modeling. Matching the... 

Evaluation of the reaction force on a tool which is used for exertion of force on biomaterials such as biological cells or soft tissues has applications in virtual reality based medical simulators or haptic tools. In this study, two least square based support vector machine (SVM) models have been constructed to predict the indentation or reaction force on mouse oocyte and embryo cells in cell injection experiment. Inputs of these two models are geometrical parameters of indented cell, namely dimple radius (a), dimple depth (w) and radius of the semicircular curve (R). Experimental data for calibration and prediction of the models have been captured from literatures. The performance of the... 

In nano-scaled CMOS technology, the reduction of soft error rate and leakage current are the most important challenges in designing Field Programmable Gate Arrays (FPGA). To overcome these challenges, based on the observations that most configuration bit-streams of FPGA are zeros across different designs and that configuration memory cells are not directly involved with signal propagation delays in FPGA, this paper presents three new low-leakage and hardened configuration memory cells for nano-scaled CMOS technology. These cells are completely hardened when zeros are stored in the cells and cannot flip from particle strikes at the sensitive cell nodes. These cells retain their data with... 

Curcumin (as a natural reductant material) was utilized for green reduction and functionalization of chemically exfoliated graphene oxide (GO) sheets. The π-π attachment of the curcumin molecules onto the curcumin-reduced graphene oxide (rGO) sheets was confirmed by Raman and Fourier transform infrared spectroscopies. Zeta potential of the GO sheets decreased from about - 40 mV to - 20 mV, after the green reduction and functionalization. The probable cytotoxicity of the curcumin-rGO sheets was studied through their interactions with two human breast cancer cell lines (MDA-MB-231 and SKBR3 cell lines) and a normal cell line (mouse fibroblast L929 cell line). The curcumin-rGO sheet with... 

In this paper an analytical approach to study the effect of the substrate physical properties on the kinetics of adhesion and motility behavior of cells is presented. Cell adhesion is mediated by the binding of cell wall receptors and substrate's complementary ligands, and tight adhesion is accomplished by the recruitment of the cell wall binders to the adhesion zone. The binders' movement is modeled as their axisymmetric diffusion in the fluid-like cell membrane. In order to preserve the thermodynamic consistency, the energy balance for the cell-substrate interaction is imposed on the diffusion equation. Solving the axisymmetric diffusion-energy balance coupled equations, it turns out that... 

In this study, cell-centered (CC) and cell-vertex (CV) finite volume (FV) approaches are applied and assessed for the simulation of two-dimensional structural dynamics on arbitrary quadrilateral grids. For the calculation of boundary nodes displacement in the CC FV approach, three methods are employed. The first method is a simple linear regression of displacement of boundary nodes from the displacement of interior cell centers. In the second method, an extrapolation technique is applied for this purpose and, in the third method; the line boundary cell technique is incorporated into the solution algorithm in an explicit manner. To study the effects of grid irregularity on the results of CC... 

In the recent years a great attention of research deals with different physical and biological aspects of the BBB structure, a robust shield that separates the blood and brain, a recent research held by the authors of this paper has focused on figuring out computing the diffusion coefficient of endothelial cell membrane. In this study, the major efforts have been concentrated on calculating a standardized measure for the amount of permeability and diffusion of this barrier. As a result, this work is dedicated to molecular dynamics (MD) simulation of calculating the interaction force between nano-particle and BBB membrane. data is recorded by using steered molecular dynamics simulation and... 

With current memory scalability challenges, Phase-Change Memory (PCM) is viewed as an attractive replacement to DRAM. The preliminary concern for PCM applicability is its limited write endurance that results in fast wear-out of memory cells. Worse, process variation in the deep-nanometer regime increases the variation in cell lifetime, resulting in an early and sudden reduction in main memory capacity due to the wear-out of a few cells. Recent studies have proposed redirection or correction schemes to alleviate this problem, but all suffer poor throughput or latency. In this article, we show that one of the inefficiency sources in current schemes, even when wear-leveling algorithms are used,... 

Optical tweezers provide an accurate measurement technique for evaluating mechanical properties of the living cells and many experimental studies have been done to understand the behavior of cells due to external forces. Numerical studies such as finite element methods have been used in order to simulate mechanical behavior of the Red Blood Cells (RBCs). Recent studies have shown that the particle methods are useful tools to simulate the mechanical behavior of living cells. Since in microscopic scales, using discrete models are preferred than continuum methods, a particle-based method is used to simulate the deformation of RBC which is stretched by optical tweezers. The cytoplasm of RBC is... 

Embryogenesis, regeneration and cell differentiation in microbiological entities are influenced by mechanical forces. Therefore, development of mechanical properties of these materials is important. Neural network technique is a useful method which can be used to obtain cell deformation by the means of force-geometric deformation data or vice versa. Prior to insertion in the needle injection process, deformation and geometry of cell under external point-load is a key element to understand the interaction between cell and needle. In this paper the goal is the prediction of cell membrane deformation under a certain force, and to visually estimate the force of indentation on the membrane from... 

The advent of microfluidics as suitable environments for culturing cells is associated with some challenges as shear stresses applied on the cells. Moreover, among all factors needed for cell viability, feeding hepatocytes with adequate oxygen is of great importance due to their high demand for oxygen compared the other cell types. In this paper three kinds of geometries has been studied in order that shear stresses would be in allowed range and provision of hepatocytes with sufficient oxygen concentrations has been ensured as well. In addition to supplying hepatocytes with oxygen, the range of its concentration has been adjusted in physiologic value so that it would be practical for further... 

Cell dynamics and motion stages are very important issues in the biological cell investigation in this novel method, we propose a novel method based on Kalman filter and second momentum for tracking cells on Sequential Microscopic Images. In proposed manner at first, we select a cell and cut covering rectangle. in the next step, we predict rectangle center of the cell in Next frame based on a modeling of velocity-acceleration using Kalman filter. The rectangle with triple covering area of previous cell rectangle and predicting center by Kalman filter is considered as a searching area. So, if all objects in the search areas have second momentum error less than threshold, it is selected as a... 

Graphene oxide foam (GOF) layers with thicknesses of ∼15-50 μm and density of ∼10 graphene oxide (GO) sheets/μm were fabricated by precipitation of chemically exfoliated GO sheets in an aqueous suspension at ∼80 °C under UV irradiation. Then, rolled GOFs with desirable scales were developed as electrically conductive 3D-scaffolds and applied in directional growth of neural fibers, through differentiation of human neural stem cells (hNSCs) into neurons under an electrical stimulation. X-ray photoelectron spectroscopy indicated that the UV irradiation resulted in partial deoxygenation of the layers. Scanning electron microscopy and Raman spectroscopy confirmed the presence of multilayer GO... 

The function and morphology of Endothelial Cells (ECs) play a key role in atherosclerosis. The mechanical stimuli of ECs, such as Wall Shear Stress (WSS) and arterial wall strain, greatly inuence the function and morphology of these cells. The present article deals with computations of these stimuli for a 3D model of a healthy coronary artery bifurcation. The focus of the study is to propose an accurate method for computations of WSS and strains. Two approaches are considered: Coupled simultaneous simulation of arterial wall and blood flow, called fluid-Structure Interaction (FSI) simulation, and decoupled, which simulates each domain (fluid and solid domain) separately. The study...