Sharif Digital Repository

Nowadays, there is no doubt about the importance of investigation of physicochemical properties of nucleosides in order to determine the structure of these biopolymers. Nucleotides have a variety of roles in cellular metabolism. They are the constituents of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), the molecular repositories of genetic information. The metal ions play a significant role in several biological processes. Synthesis, replication, and cleavage of DNA and RNA as well as their structure integrity are affected by the presence of these ionized metals in the cell nucleus. To understand the role of cations in the biophysics of DNA, it is necessary first to... 

In this work, carbon nanotubes (CNTs) were synthesized via arc discharge in an aqueous solution. The role of iron catalyst in CNTs formation was investigated utilizing arc discharge in iron salts solution (Fe2(SO4)3 and FeCl3). Thermogarvimetric (TG) analysis showed the presence of multi-layered structures including multi-walled carbon nanotubes (MWCNTs) and multi-shelled graphite particles when processing was performed in DI-water. In the presence of iron ions, single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were formed. The effect of iron ions (Fe3+) concentration on CNTs yield was investigated by Raman spectroscopy. The highest yield was obtained when... 

The heavy ion collision experiments are in progress in order to investigate how the Universe has evolved after the Big Bang. The recent observations show that a nearly perfect fluid is produced after heavy ion collisions. An appropriate incorporation of the relativistic hydrodynamics and the field theory would help us to describe the dynamics of QCD (Quantum Chromodynamics) matter under extreme conditions, and to survey the expected phase transitions. The majority of efforts to investigate the characteristics of the QCD plasma are devoted to an ideal, non-dissipative one. To get the results which are highly in accordance with the experiment, it is necessary to bring also in mind the role of... 

Polyampholyte hydrogels are hydrophilic networks that contain both positively- and negatively-charged functional groups on their structure. Polysulfobetaines are the most important type of polyampholytes, which have been extensively studied. However, these hydrogels exhibited poor gel strength causing limitation of their applications. Consequently, much attention has been focused on the preparation of nanocomposite hydrogels with high gel strength and lower cost using organomodified clays. In this project, Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3-(methacrylamido)propyl)]dimethyl(3-sulfopropyl) ammonium hydroxide (MPDSAH) were... 

In this work, sulfonated polycarbonate (SPC ) membranes with different acid contents have been prepared by conducting sulfonation reaction at room temperature using Chlorosulfonic acid (CSA) as sulfonating agent at different concentration of acid in reacting solution. The SPC membranes were obtained by casting from 10% solution of SPC in chloroform at room temperature. The prepared membranes were characterized using Ion exchange capacity (IEC), and degree of sulfonation (DS), Fourier Transform Infrared (FTIR), NMR spectra, Thermal Gravimetric Analysis (TGA) and Water uptake. The obtained results showed that with increaseing in Chlorosulfonic acid content in sulfonation reaction IEC and DS of... 

During the various stages of uranium processing in Uranium Conversion Facility (UCF) in Isfahan, significant amounts of liquid waste stream is produced which is sent to evaporation ponds. In addition to environmental considerations, uranium recovery from existing pools is also economically feasible due to high concentration uranium in liquid waste. Several methods have been evolved over the years to remove dissolved uranium from uranium bearing solution. These methods are: chemical precipitation, liquid-liquid extraction, ion exchange and membrane processes. The purpose of this study is recovery of uranium from liquid waste of Isfahan UCF plant by using ion exchange method. Although this... 

During various stages of processing uranium in Uranium conversion facility (UCF) in Isfahan, significant amounts of liquid waste is produced which leads to evaporation ponds. Since the concentration of uranium in evaporation ponds is relatively high, it seems to addition to environmental issues with recycled uranium from existing pools is also economically. Various physical and chemical methods for removal of uranium waste is used such as solvent extraction, ion exchange, chemical precipitation, membrane processes, etc. Each method has advantages and disadvantages. The ion exchange method, The due to lower cost, less acid pollution with organic copmpounds, convenience and high selectivity... 

One of the basic resources for lithium extraction is brine which is very abundance in Iran. It is important to characterize these brines and their compositions to select a suitable method for lithium recovery from them. By investigation of the local brines and determining lithium and other alkali metals composition in them, the ion exchange process using titanium dioxide ion-sieve with nanotube morphology is suggested as highly effective method for lithium extraction from Iranian brines. Due to high advantages of hydrothermal process, TiO2 nanotubes were produced by this method and the optimum parameters of hydrothermal reactions were reported. In this way, hydrogen titanate nanotubes with... 

The transport behavior of water molecules inside a model carbon nanotube is investigated by using nonequilibrium molecular dynamics simulations. The shearing stress between the nanotube wall and the water molecules is identified as a key factor in determining the nanofluidic properties. Due to the effect of nanoscale confinement, the effective shearing stress is not only size sensitive but also strongly dependent on the fluid flow rate. Consequently, the nominal viscosity of the confined water decreases rapidly as the tube radius is reduced or when a faster flow rate is maintained. The effect of ion concentration and temperature rise on fluid flow and shearing stress is also investigated.... 

Ion channels are present in all cell membranes which are the important part of the performances in regulating the flow across the membrane as well as the signaling. We have investigated the water permeation through carbon nanotube (CNT) membranes as a model for the synthetic ion channels, i.e. peptide nanotube channels (PNCs). The effect of different charge configured CNTs which tailored based on these ion channels on the water permeation has been studied. In addition, the temperature dependence of the permeation using statistical models such as continuous time random walk model (CTRW) via molecular dynamics simulation has been investigated. We have found that there is a jump in the... 

In this research project, It has been investigated the ability of thenoyltrifluoroacetone (HTTA) as a carrier for selective separation of yttrium ions from aqueous media using bulk liquid membrane (BLM) system as a simple model for selective separation of 90Y from radioactive liquid wastes by the mentioned technique. Thus, a study has been made on carrier-mediated transport of yttrium(III) using a bulk liquid membrane prepared by dissolving thenoyltrifluoroacetone (HTTA) in dichloromethane. It has been observed that the use of n-propylamine (n-PA) in source phase as a synergistic reagent showed a marked enhancement of transport of yttrium ion. The source phase comprised of a solution of ... 

In the present work, interaction of high power and ultra short laser pulse with plasma in both under relativistic and relativistic regimes is investigated. The accelerated ions and electron are studied. The effect of pulse laser shapes on generating of the optimum wakefield is studied to find the maximum generated wakefield amplitude. It is found that similar to the wakefield amplitude generated by single pulse, the wakefield amplitude produced by dual trailing depends on the pulse shape and their permutation. Furthermore, the interaction of sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in... 

Water treatment from industrial and domestic pollutants is one of the most important issues in recent decades. In the present research, simulation of water purification using single-layer graphene membrane were studied. The effects of nanopores diameter, applied pressure, concentration of contaminant ions, and functional groups on the amount of filtered water and ion rejection through the membrane were quantified. Contaminant ions including Na+, K+, Mg2+, Ca2+, and Cl- were dissolved in water. Based on the results, by increasing the pore diameter and applied pressure, more water would pass through the membrane. Also it was concluded that pores with functional groups have better performance... 

In this study, polyoxometalate (POM) intercalated in the layered double hydroxide (LDH) was synthesized by a selective ion-exchange method. For this purpose, the nanocluster [VW12O40]3- was immobilized on the Mg2+/A13+/Cl–LDH support. The heterogeneous catalyst was characterized by FT-IR, XRD, SEM and analysis of ICP. The LDH-POM was applied as a catalyst in efficient oxidation of sulfides to sulfoxides using UHP as oxidant and CH3OH/ CH¬2¬Cl¬2 ¬as a solvent at room temperature, as well as epoxidation of olefins using TBHP as an oxidants and C¬2H4Cl2 as a solvent in 84°C. This catalyst showed excellent catalytic activities for a substrate/catalyst ratio (200:1). For example, this catalytic... 

In this research, we focus on reduction of solutes in left out water from reverse osmosis membranous units (brine) with reduction of scaling factors of membrane. This research is important from that perspective that the out put brine from reverse osmosis membranous unit After purification by this method, enter into membranous system in order to increase in recovered water volume and also minimization of out put waste from membranous system and decrease the environmental damages. The method used in this research, is three processes of cooling, chemical desalination and seeding by crystal material. In this research is investigated the type and amount of matter for chemical desalination and... 

Boric acid (H3BO3) is a weak monobasic acid that exist as a white powder in the standard conditions. In industry, it is used in manufacturing of fiberglas filaments, precious metals soldering and production of flat panel LCD displays. In all of these applications, normal grade boric acid is used, but nuclear industry demands an ultrapure boric acid (UPA) for controlling of the reactivity and power levels in pressurized water reactors. Annual consumption of UPA in Bushehr Power Plant (BPP) is around 60 metric tons. Currently, this amount is imported from Russia, but atomic energy organization of Iran plans to displace it by the acid made inside the country. Domestic production of UPA in... 

Using a Lithium Selective Ion Sieve is one of the most advanced processes for Extraction of lithium from Brines. The ability to Extract Lithium selectively from brines make the ion sieve suitable for brines with low concentrations of lithium. In this study brines samples from Urmia Lake with lithium concentration of 30 ppm was used. The main objective of this study was to find the best condition for lithium adsorption and desorption using the synthesized titanium dioxide ion sieve. In this study lithium selective ion sieve with nanotube morphology and Diameter of 81 nm was synthesized. Study on pH of synthesized solution containing lithium ions was carried out and pH=12 was concluded the... 

In this study, uranium removal from phosphoric acid with doulite resin was examined. Different uptake properties of the doulite resin were examined using batch, stirred and column methods. Langmuier, freundlich and dubinin equation was fitted the isotherm data and freundlich equation showed the best fitting. Adsorption kinetics was controlled by slow intraparticle diffusion of UO22+ ions in resin, and it obeyed a shrinking core model. Also a pseudo-second order chemical reaction fairly fitted the kinetics data  

As one of the main features of Li-Ion batteries, internal resistance severely affects performance and characteristics of these batteries e.g. output power and working voltage. In this study, we tried to understand role of internal resistance on microstructure development and provide a correlative relation between microstructural features and performance of lithium-ion batteries. To catch this target, four types of Li-Ion battery chose, varying cathode type. These batteries were exposed to both normal and severe cycling conditions. Regarding to the key role of current rate on the performance of Li-ion batteries, an extensive research on different types of batteries at various current rates... 

Ion exchange resins are widely used in nuclear industries. These spent resins result in the production of a large amount of low and intermediate level radioactive wastes, therefore, the treatment and immobilization of spent ion exchange resins are the major problems in the development of nuclear power plants.In this research, in a laboratory scale, we tried to find the suitable procedure and formulation to immobilize a specific group of cation-exchange resins which is used in Bushehr nuclear power plant (AMBERLITE IRN-97H) in the cement matrix. The solidification matrix consists of five constituents: anti sulfate slag type portland cement, cation-exchange resins, diatomite, sodium hydroxide...