Sharif Digital Repository

A large amount of the discovered oil reserves are reserved in carbonate formations, which are mostly naturally fractured oil-wet. Wettability alteration towards more water-wet state reduces the capillary barrier, hence improving the oil recovery efficiency in such reservoirs. In this study, wettability alteration towards favorable wetting state was investigated by combining modified low salinity brine with surfactant during water flooding. The diluted brine was modified by increasing the concentration of Mg2+ and SO4 2−, individually as well as both ions in combination. Different brine formulations were tested experimentally through the observations of contact angle measurements and... 

In this paper, we have proposed, designed, implemented, and characterized a low-cost camera-based microarray scanner which is capable of imaging fluorescently-labeled DNA or Protein microarrays. The proposed system is designed to simultaneously measure two different fluorescent dyes using two parallel channels which increase the overall scan speed. We have shown that the wide dynamic range of system makes it able to detect fluorophore densities from 100-106 molecule/μm2. In each capture, a 5.6 mm × 3.7 mm field is imaged on a 22.3 mm × 14.9 mm (18 megapixels) CMOS sensor. Therefore, the microarray can be scanned with ∼ 1μm2 spatial resolution which is high enough to distinguish borders of... 

The modification of the surface wetting characteristics in fractured oil-wet carbonate reservoirs, by reversing wettability from oil-wet to water-wet, leads to improved oil recovery. However, in order to obtain a successful oil recovery process, it is crucial to understand the active mechanisms of wettability alteration. This study looks at the effect of sulfate ions as one of the most promising wettability influencing ions on the wetting properties of oil-wet calcite; the effect is studied both with and without the presence of cationic surfactant and possible mechanisms of wettability alteration are explored. A number of analytical techniques were utilized to analyze the mineral surface... 

The concentration and temperature behaviors of the self-diffusion coefficient were analyzed in glycerol-water and methanol-water solutions using Diffusion-Ordered Spectroscopy (DOSY) experiment. Our results indicate that the self-diffusion coefficient dips with increasing concentration and decreasing temperature. The concentration behavior shows that there is hydrogen bond interaction between water and alcohol, which declines the self-diffusion coefficients of both in the aqueous binary mixtures. The self-diffusion activation energies were estimated 13.6, 29.4, and 32.8 (kJ/mol) for methanol and 24.8, 25.5, and 27.6 (kJ/mol) for water in the methanol-water solutions with 0.03, 0.10, and 0.20... 

The plasmonic effects of infiltrated silver (Ag) nanoparticles, with different contents, inside a nanostructured TiO2 film on the photovoltaic performance of dye-sensitized solar cells (DSSCs) are explored. The synthesized Ag nanoparticles are immobilized onto deposited TiO2 nanoparticles by a new strategy using 3-mercaptopropionic acid (MPA), a bifunctional linker molecule. Transmission electron microscope (TEM) images show that monodispersed Ag and polydispersed TiO2 nanoparticles have an average diameter of 12 ± 3 nm and 5 ± 1 nm, respectively. Moreover, Fourier transform infrared spectroscopy (FTIR) analysis reveals that Ag nanoparticles were successfully functionalized and capped with... 

A mixture of the platinum(0) complex [Pt(PtBu3)2] and tetrakis(acetonitrile)copper(i) hexafluorophosphate in acetone activated a water molecule and gave the hydride platinum(ii) complex [PtH(CH3CN)(PtBu3)2]PF6, 1, and the hydroxide Cu(i) species. The crystal structure of complex 1 was determined by X-ray crystallography, indicating a distorted square planar geometry around the platinum center. Although three possible mechanisms are proposed for this transformation, monitoring of the reaction using NMR spectroscopy at low temperature reveals that a cooperative pathway involving formation of a Pt0-CuI dative bond complex is the most probable pathway. The hydride platinum complex 1 is stable in... 

The effect of electrostatic field on the aggregation rate and aggregate size of asphaltene particles precipitated from three different crude oil samples suspended in a mixture of toluene and n-heptane (a model oil) was investigated. An electrode-embedded glass micro-model utilizing a high-voltage direct current power supply was utilized in this study. The asphaltene particle size and the rate of aggregation under the electric field were monitored using a high-resolution optical microscope and the average aggregate size for asphaltene particles was estimated using image processing software. To investigate the effects of structural parameters on asphaltene aggregation rate, aggregate size and... 

The influence of Fe3O4 nanoparticles (NPs) on dielectric properties of planar and homeotropic oriented nematic liquid crystals (NLCs) were studied during the temperature interval of 298–322 °K. It was found that the dielectric permittivity was considerably increased by adding NPs mass percentages. The structural characterization of the synthesized NPs with the scale 14–18 nm has been analyzed by the X-ray diffraction and field-emission scanning electron microscopy results. The obtained dielectric anisotropy ((Formula presented.)) and mean dielectric ((Formula presented.)) have shown an immense increment in the value of 1% and 10% wt. NPs doped NLCs, respectively. These results were assigned... 

CO2 injection has proved to be the most common and efficient enhanced oil recovery techniques which leads to more residual oil recovery. Unfavorable sweep efficiency which results in fingering propagation and causes early gas breakthrough is the most challenging issue of gas flooding process. The aim of this work is to study foam stability and analyze the mobility of CO2 foam stabilized by mixture of raw silica nanoparticles and ethyl hexadecyl dimethyl ammonium bromide (cationic surfactant). The result is obtained through both dynamic and static techniques using a new adsorption index.NPS-stabilized foams are generated using Ross-Miles method. A novel index for the adsorption of surfactant... 

Classical molecular dynamics simulations are used to compute the solvation free energy of two pharmaceutical solids, namely ibuprofen and acetaminophen in carbon dioxide (CO2), over the density range of interest in supercritical processes. In order to examine the influence of the solvent model on the resulting free energies, three popular CO2 models (Zhang, EPM2, and TraPPE) are studied. Relatively large discrepancies for the solvation free energy exist between these CO2 models, suggesting that the former is sensitive to the different balances between dispersive and electrostatic forces used in these models. In particular, for the solvation of the highly polar (dipole moment of ∼5.2 Debye)... 

In radio channels modelings, the phases and amplitudes of the rays undergo some modifications when they are reflected from or transmitted through a particular material. These reflection and transmission coefficients make use of the electrical properties of the materials, thus, it is essential to know the values of the relative dielectric constant and of the conductivity or the loss tangent of the materials that appear in the propagation environments. In this paper, a theoretical model based on the inter-molecule interactions, has been developed and used to estimate the dielectric parameters of glass. ©2009 IEEE  

The objective of this paper is to investigate dynamical pull-in behavior of an electrostatic actuated nano-device based on Eringen's nonlocal elasticity theory. The Euler–Bernoulli beam model is used to establish the dynamic equation of motion of the nano-device subjected to both electrostatic and intermolecular forces. The nanobeam is considered with axially immovable ends and the geometrically nonlinearity due to mid-plane stretching is incorporated to the model as well. A new intermolecular attractive force model based on the macroscopic interactions of a circular cross section nanobeam and a flat surface is presented for the carbon nanotube based nano-device. The nonlinear static... 

The multielectron dissociative ionization of CH4 and CH2O molecules has been investigated using optimum convolution of different dual tailored short laser pulses. Based on three dimensional molecular dynamics simulations and TDDFT approach, the dissociation probability is enhanced by designing the dual chirped-chirped laser pulses and chirped-ordinary laser pulses for formaldehyde molecule. However, it is interesting to notice that the sensitivity of enhanced dissociation probability into different tailored laser pulses is not significant for methane molecule. In this presented modifications, time variation of bond length, velocity, time dependent electron localization function and evolution... 

The influence of Fe3O4 nanoparticles (NPs) on dielectric properties of planar and homeotropic oriented nematic liquid crystals (NLCs) were studied during the temperature interval of 298–322 °K. It was found that the dielectric permittivity was considerably increased by adding NPs mass percentages. The structural characterization of the synthesized NPs with the scale 14–18 nm has been analyzed by the X-ray diffraction and field-emission scanning electron microscopy results. The obtained dielectric anisotropy (Δε) and mean dielectric (Formula presented.) have shown an immense increment in the value of 1% and 10% wt. NPs doped NLCs, respectively. These results were assigned to the strong... 

According to current researches, graphene oxide (GO) membranes show promising desalination properties due to ease of synthesis, low production cost, and high efficiency. There are several experimental works to study ionic sieving properties of GO membranes. However, it is difficult to characterize atomistic mechanism of water permeation and ion rejection by experimental approaches. On the other hand, there exist a few reports in which the atomistic picture of water permeation across GO membranes is investigated by means of molecular dynamics (MD) simulation. In the present work, in addition to water desalination, the atomic scale mechanism of ion rejection is studied using large scale MD... 

Anticancer character of gold cluster has been indicated through its free radical scavenging properties. This is in contrast to its free radical promoting ability suggested by other workers. Here, we address this controversy by probing the stabilizing effects of Au3 cluster on RO• vs its impacts on RO-H bond dissociation enthalpy, at B3LYP/ LACVP+* level (RH, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, and phenyl). In the presence of Au3 cluster, bond dissociation enthalpy of O-H bond and the spin density at the RO• oxygen are reduced dramatically. These are clear evidences for both the Au3 facilitation of the RO-H bond breakage and its scavenging of RO• radical. Since O-Au anchoring... 

Chemical reactions are a prominent feature of molecular communication (MC) systems, with no direct parallels in wireless communications. While chemical reactions may be used inside the transmitter nodes, receiver nodes or the communication medium, we focus on its utility in the medium in this paper. Such chemical reactions can be used to perform computation over the medium as molecules diffuse and react with each other (physical-layer computation). We propose the use of chemical reactions for the following purposes: (i) to reduce signal-dependent observation noise of receivers by reducing the signal density, (ii) to realize molecular physical-layer network coding (molecular PNC) by... 

In this study, high harmonic generation from a multi-atomic nitrous oxide molecule was investigated. A comprehensive three-dimensional calculation of the molecular dynamics and electron trajectories through an accurate time-dependent density functional theory was conducted to efficiently explore a broad harmonic plateau. The effects of multi-electron and inner orbitals on the harmonic spectrum and generated coherent attosecond pulses were analyzed. The role of the valence electrons in controlling the process and extending the harmonic plateau was investigated. The main issue of producing a super-continuum harmonic spectrum via a frequency shift was considered. The time-frequency... 

In this study, the structural and electronic properties of a carbohydrate-based (6-amino-6-deoxy hexopyranose [ADHP]) ionic liquid were explored. The interactions among 3 anions (BF4 ¯, PF6 ¯, and ClO4 ¯) and ADHP as cation were investigated at B3LYP/6-311++G(d,p) level. Based on the calculated interaction energy, it was found that PF6 ¯ anion has the highest interaction energy with ADHP. It was found that the hydrogen bonds play an important role in the interaction of ion pairs. The nature of hydrogen bonds in the optimized ion pars was analyzed by using natural bond orbital analysis and the quantum theory of atoms in molecules. The linear relationship between electron density at the bond... 

Calcium release-activated calcium (CRAC) channels open upon depletion of Ca2+ from the endoplasmic reticulum, and when open, they are permeable to a selective flux of calcium ions. The atomic structure of Orai, the pore domain of CRAC channels, from Drosophila melanogaster has revealed many details about conduction and selectivity in this family of ion channels. However, it is still unclear how residues on the third transmembrane helix can affect the conduction properties of the channel. Here, molecular dynamics and Brownian dynamics simulations were employed to analyze how a conserved glutamate residue on the third transmembrane helix (E262) contributes to selectivity. The comparison...