Sharif Digital Repository

Atherosclerosis is a major cause of coronary artery disease leading to morbidity and mortality worldwide. Currently, coronary angiography is considered to be the most accurate technique to diagnose coronary artery disease (CAD). However, this technique is an invasive and expensive procedure with risks of serious complications. Since the symptoms of CAD are not noticed until advanced stages of the disease, early and effective diagnosis of CAD is considered a pertinent measure. In this paper, a non-invasive optical signal, the finger photoplethysmogram (PPG) obtained before and after reactive hyperemia is investigated to discriminate between subjects with different CAD conditions. To this end,... 

Regularities shown by different fluids along the contour of the ideal compressibility factor Z= PV/(RT)=1 in the temperature density plane was used to test the accuracy of the equations of state and derive temperature dependencies of their parameters. The contour, also known as the Zeno line, was empirically observed to be nearly linear. The precision of the van der Waals equation in predicting the Zeno line was evaluated. It was shown that the equation could predict a linear relation between temperature and density on the Z=1 contour, qualitatively  

A new hard-core potential model was recently used to calculate thermodynamic properties of some model fluids, including equilibrium properties, such as compressibility factor and internal energy. A Lennard-Jones (LJ) like potential has been used to modify the repulsive part of the potential. The modified potential contains five parameters, namely, R, and HS. The parameter is the tail of the attractive branch whose value changes from zero to one. In this work, we have chosen = 1 to make the potential continuous at separation r = R, where the parameter R is the well width. R lies in the range 1.2 to 2.5, and R = 1.3 was found to be the best value for all real gases studied. The parameter is... 

Metallic nanoparticles are interesting because of their use in catalysis and sensors. The surface energy of the FCC platinum nanoparticles are investigated via molecular dynamics simulation using Quantum Sutton-Chen (QSC) potential. We have calculated the Gibbs free energy for the FCC platinum bulk and also for its nanoparticle. All calculations have been carried out at zero pressure. We have used the thermodynamic integration method to obtain the Gibbs free energy. The total Gibbs free energy is taken as the sum of its central bulk and its surface free energy. We have calculated the free energy of a platinum nanoparticle as a function of temperature  

As the delay time and hence nuclei formation play a crucial role in the pathophysiology of sickle cell disease, MD simulation and molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) calculations have been performed on three systems of hemoglobin; namely dimer of hemoglobin with valine (Hb S), tryptophan (Hbβ6W), and phenylalanine (Hbβ6F) at β6 position. The structural changes due to these aromatic substitutions are investigated. It is shown that β subunits have significant impact on the differences between a dimer and other crystal structures. Transition from a dimer to polymer for Hb S system affects the donor molecule more than that of the acceptor. In the case of donor and... 

We investigate a one-dimensional (1-D) Ising model for finite-site systems. The finite-site free energy and the surface free energy are calculated via the transfer matrix method. We show that, at high magnetic fields, the surface free energy has an asymptotic limit. The absolute surface energy increases when the value of f (the ratio of magnetic field to nearest-neighbor interactions) increases, and for f ≥10 approaches a constant value. For the values of f ≥0.2, the finite-site free energy also increases, but slowly. The thermodynamic limit in which physical properties approach the bulk value is also explored  

The interaction energies of 3,5 di-methyl pyridine (A) and 2,4 di-methyl pyridine (B) on the (100) surface of body-centered cubic (bcc) iron were determined via a cluster model and ab initio quantum chemical calculations at density functional theory level. The obtained energies were used to compare the inhibition behavior of these molecules for iron corrosion in hydrochloric acid solution. The iron surface and its adsorption sites (on-top, bridge, hollow) were considered as some clusters taken from two-layered 〈100〉 planes, i.e. Fe1(1), Fe4(2,2), and Fe5(4,1). So, the process for which quantum chemical calculations was carried out consists of adsorption of molecule A (B) on these clusters.... 

Continuing an ongoing study, molecular dynamics (MD) simulations were performed to investigate the effects of methanol concentration on Nafion morphology, such as the size of solvent cluster, solvent location, and polymer structure via the sandwich model. Our survey shows that high methanol concentrations resulted in increment of solvent cluster size in Nafion membrane. The sulfonic acid clusters also befall much in order as subsequent layers of such ionic clusters are formed. The number of neighbouring hydronium ions around a sulfur atom is independent of methanol concentration, but the first shell of hydronium and water around sulfonic acid clusters is broader. Although methanol would... 

Molecular dynamics simulations are performed to obtain insight into the structural properties of hydrated Nafion using the sandwich model of the polymer membrane. It is shown that a larger distance between the sulfonate groups of a chain leads to the polymer forming a better inverted micelles structure. Water- and hydronium-polymer interfaces are investigated. Comparing our results with others indicates that, from the perspective of distance, the formation of shells of water and hydronium ions is independent of the model and monomer type, but depends on both if the coordination number is considered. The behaviour of water molecules and hydronium ions is also studied dynamically. Our survey... 

In the present work, several new thermodynamic linear isotherm regularities for the dense fluids have been derived for the first time. For this purpose, the thermodynamic perturbation theory (TPT) employing only the attractive effective pair potential (AEPP) as u(r) = - ϵeff (σeff / r)m was used, where σeff which is the effective hard core diameter, is temperature dependent and m > 0. Based on the derived regularities, the isotherm (Z - Z(0))v2 is a linear function of ρ2, ρ and 1/ρ, depends on the values of m = 12, 9 and 6, respectively where Z - Z(0) is the difference between the experimental compressibility factor of the real fluid (Z) and that of the reference fluid (Z(0)). Also, Z - Z(0)... 

In the present work, the thermodynamic of dense fluids, both compressed liquids and dense supercritical fluids, has been modeled, solely, based on the contribution of attraction of effective pair potential. The intermolecular interaction is modeled by the hard-core Yukawa potential (HCY) as an effective pair potential (EPP) with temperature dependent hard-core diameter. Using this EPP in the exact thermodynamic relations, an equation of state (EoS) for the compressibility factor of dense fluid has been derived. This EoS shows that (Z - ZCS) as function of ρ1/3 must be linear for each isotherm of fluid where ZCS is the compressibility factor of the reference fluid (Carnahan-Starling (CS) EoS)... 

The growing number of spine diseases and surgeries has resulted in advancements in equipment and implants. On the other hand, given the uniqueness of the anatomy of the spine, particularly in terms of mechanical characteristics, selecting the type of implant is critical. In addition to high biocompatibility and superelasticity, the implant utilized in the spine needs properties like strength, fatigue resistance, and elastic modulus close to the bone, which is found in nitinol. NiTi alloy lumbar-like samples were prepared by sintering and mechanical braiding method. The mechanical properties study revealed that the elastic modulus of the sample was 3.5 GPa, and the compressive strength at 6 %... 

Molecular dynamics, MD, simulation of calcite (CaCO3) is selected to compare the p-v-T behaviour of some universal equations of state, UEOS, for the temperature range 100 K ≤ T 800 ≤ K, and pressures up to 3000 kbar. The isothermal sets of p-v-T data generated by simulation were each fitted onto some three- and two-parameter EOSs including Parsafar and Mason (PM), Linear Isotherm Regularity (LIR), Birch-Murnaghan (BM), Shanker, Vinet, Baonza and Modified generalized Lennard-Jones (MGLJ) EOSs. It is found that the MD data satisfactorily fit these UEOS with reasonable precision. Some features for a good UEOS criteria such as temperature dependencies of coefficients, pressure deviation,... 

We present an approach for constant-pressure molecular dynamics simulations. This approach is especially designed for finite systems, for which no periodic boundary condition applies. A molecular dynamics (MD) simulation for Ni nanoclusters is used to calculate their pressurevolumetemperature (pvT) data for the temperature range 200 K≤T≤400 K, and pressures up to 600 kbar. Isothermal sets of pvT data were generated by the simulation; each set was fitted by three equations of state (EoSs): Linear Isotherm Regularity-II (LIRII), BirchMurnaghan (BM), and EOS III. It is found that the MD data are satisfactorily reproduced by the EoSs with reasonable precision. Some features of the EoSs criteria,... 

A simple functional form for a general equation of state based on an effective near-neighbor pair interaction of an extended Lennard-Jones (12,6,3) type is given and tested against experimental data for a wide variety of fluids and solids. Computer simulation results for ionic liquids are used for further evaluation. For fluids, there appears to be no upper density limitation on the equation of state. The lower density limit for isotherms near the critical temperature is the critical density. The equation of state gives a good description of all types of fluids, nonpolar (including long-chain hydrocarbons), polar, hydrogen-bonded, and metallic, at temperatures ranging from the triple point... 

A method is developed to calculate the critical line of two dimensional (2D) anisotropic Ising model including nearest-neighbor interactions. The method is based on the real-space renormalization group (RG) theory with increasing block sizes. The reduced temperatures, Ks (where K=J/kBT and J, kB, and T are the spin coupling interaction, the Boltzmann constant, and the absolute temperature, respectively), are calculated for different block sizes. By increasing the block size, the critical line for three types of lattice, namely: triangular, square, and honeycomb, is obtained and found to compare well with corresponding results reported by Onsager in the thermodynamic limit. Our results also... 

To solve the controversy, regarding the existence of an analytic solution to the 1-D Ising model with nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions in the presence of a magnetic field, we apply the transfer matrix method to solve the 1-D Ising model in the presence of a magnetic field, taking both NN and NNN interactions into account. We show that it is possible to write a transfer matrix only if the number of sites is even. Even in such a case, it is impossible to diagonalize the transfer matrix in an analytic form. Therefore, we employ a numerical method to obtain the eigenvalues of the transfer matrix. Moreover, the heat capacity, magnetization, and magnetic... 

Continuous and remote monitoring of vital health-related and physical activity signs of a patient is one of the most important technology-oriented applications to monitor the health-care of ill individuals. In this paper, an innovative framework for a wireless Body Area Network (BAN) system, based on the IEEE 802.15.6 standard, with three types of sensors is proposed and implemented. These include Electrocardiogram (ECG), Force Sensitive Resistor (FSR) and Gyroscope. The proposed design is a novel implementation of an embedded system for the real-time processing and analyzing of the ECG signal, gait phases, and detection of the respiration rate from the ECG signal, by means of small... 

Non-invasive measurement of flow-mediated dilation (FMD) in the brachial artery for assessing endothelial function is costly and operator-dependent, limiting its application to research cases. In this paper, an approach based on a physiological model between normalized central blood pressure and finger photoplethysmogram is presented. Baseline model parameters are estimated using a genetic algorithm in 30 subjects consisting of ten normal blood pressure (BP), ten high-BP and ten elderly volunteers. Beat-to-beat fitness values after reactive hyperaemia are calculated using baseline (before cuff occlusion) data. Results show that stimulus-induced changes are fairly described with a first order... 

We present in this paper a new method of modifying hard-core potentials to correctly predict the equilibrium and non-equilibrium properties of real fluids at low densities (specifically when ρ ≤ B/C where ρ is density, and B and C are the second and third virial coefficients) only by one set of potential parameters. Because the molecular diameter becomes smaller when temperature increases, we introduced a new expression for the variation of molecular diameter with temperature that incorporates this effect. The temperature dependence of the diameter was used in both Sutherland (ST) and square-well (SW) potential models to modify the second virial coefficient. Then we have shown that the...