سال:1395 | دوره: | شماره: |تعداد مقالات:10

Several MRI contrast agents (CAs) are used in medical diagnosis that gadolinium (Gd3+) is the most widely used as contrast agents. Unfortunately, its toxicity is due to its inefficiency. In this review, we discuss about the ability of SPIONs in MRI and application in Multiple Sclerosis diagnosis. Superparamagnetic iron oxide nanoparticles (SPIONs) such as magnetite nanoparticles are used as good CAs in recent years because of biocompatibility, low level of toxicity, magnetic properties, simple synthesis and coating to use in medical diagnosis. Uncoated magnetite nanonoparticles are insoluble in water. Hydrophilic coatings result water solubility of nanoparticles and prolonged circulation half-lives of SPION and reduce recognition by RES.SPIONs have an important role in diagnosis of multiple sclerosis (MS) by MRI. SPIONs are MRI contrast agents better than gadolinium because, SPIONs taken up by macrophages but not Gd-nanoparticles.

Scanning Impedance Microscopy (SIM) is one of the novel scanning probe microscopy (SPM) techniques, which has been developed to taking image from sample surface, providing quantitative information with high lateral resolution on the interface capacitance, and investigating the local capacitance–voltage (C–V) behavior of the interface and AC transport properties. The SIM is an ordinary AFM equipped with a conductive tip (C-AFM), which is imaged by non-contact mode with harmonic detection. This method is based on the local detection of surface potential or the amplitude and phase of local voltage oscillations induced by a lateral periodic bias applied across the sample. SIM can simultaneously collect the amplitude and phase signals and image the morphology of the surfaces, afterward, calculate the corresponding histogram for each map. Hence, the amplitude and phase signals of the surface potential oscillations are related to the sample impedance. SIM can also be integrated with Surface Potential Microscopy (SSPM).The combination of these techniques provides an approach for the quantitative analysis of local DC and AC transport properties. These advantages give SIM a higher resolution than other SPM techniques and indicate its immense potential for vast applications. The combination of SSPM and SIM were demonstrated for a Schottky diode, but can be applied to any semiconductor device.

Stabilizations and atomic level quadrupole coupling constant (CQ) properties have been investigated for grapheme-like monolayers (G–monolayers) of boron nitride (BN), boron phosphide (BP), aluminum nitride (AlN), and aluminum phosphide (AlP) structures. To this aim, density functional theory (DFT) calculations have been performed to optimize the model structures and also to evaluate the CQ parameters. The results of optimizations indicated that the formations, polarities, and semiconducting properties of BN G–monolayer are more favorable than other investigated G–monolayers. Moreover, the atomic level CQ parameters also indicated that the atoms at the tips of monolayers have the most activities among other atoms and different properties have been seen for the atoms at different positions of monolayers. Differences of electronegativities are also important for the magnitudes of CQ properties as could be seen by larger values of CQ parameters for B and Al atoms in the BN and AlN G–monolayers in comparison with BP and AlP G–monolayers.

In this study, B12N12 Nano ring has been selected because it consist of four 6-side rings and polar bonds B-N which in comparison with non-polar bonds C-C, is more suitable for the study of the absorption of other compounds. So reactivity and stability of Benzene alone and in the presence B12N12 nano ring field checked.To determine the non-bonded interaction energies between Benzene and B12N12 nano ring in different orientations and distances, geometry of molecules with density functional theory B3LYP method and 6-31g *basis set optimized. Then calculated the natural bond orbital (NBO), nuclear independent chemical shift (NICS) and muliken charge of Benzene atoms alone and in the presence B12N12 done. The results of any order explains reduce the reactivity and increase stability of Benzene in the presence B12N12 nano ring and electron transfer from the nano ring to Benzene. The gaussian quantum chemistry package is used for all calculations.

In this study, removal of Acid blue 62 from aqueous solution by mesoporous silicate MCM-41 modified by Aminopropyltriethoxysilane (APTES) composite was studied. Properties of synthesized composite were analyzed and confirmed by SEM, EDX and FTIR. Results show that Langmuir adsorption isotherm has the best compatibility with the results of experiments. Kinetic analysis using pseudo-first-order model, pseudo second-order and the intra-particle diffusion model was carried out. Results also confirmed that adsorption process is compatible with the pseudo-second-order kinetic model. Thermodynamic parameters such as Gibbs free energy changes (DGo), Enthalpy changes (DHo) and Entropy changes (DSo) were calculated.Negative value of DGo and positive value of DHo show that adsorption of Acid blue 62 on aminated nanocomposite is a spontaneous process also endothermic.

Quantum-dot cellular automata (QCA) are a promising nanotechnology to implement digital circuits at the nano scale. Devices based on QCA have the advantages of faster speed, lower power consumption, and greatly reduced sizes. In this paper, we are presented the circuits, which generate random numbers in QCA.Random numbers have many uses in science, art, statistics, cryptography, gaming, gambling, and other fields.The base of these circuits is the linear feedback shift register (LFSR). In this paper, an optimized QCA LFSR is designed, and then different random number generators (RNGs) using XOR and adder are presented. These circuits generate different random numbers in each simulation. The results show that our QCA designs are really fast and optimized in comparison with the previous CMOS and QCA designs.

Drilling fluid is the most important lifeline of the drilling operation, that main task is facilitate the cuttings removal of the drilling. There are varieties of drilling fluids such as sodium bentonite based-drilling fluid is called “mud” and drilling foam or surfactant based-drilling fluid is called “soap”. The present work aims are study on the modified drilling mud properties by using the TiO2/ Polyacrylamide (PAM) as a nanocomposite additive. This additive was obtained through the aqueous solution polymerization of acrylamide monomer in the presence of TiO2 nanoparticles and high hydrophilic-lipophilic balance (HLB) surfactants such as sodium dodecyl sulfate (SDS) and polyoxyethylene sorbitan mono-oleate (Tween 80). At first, the TiO2/ PAM nanocomposite was characterized by XRD, UV-Vis, FTIR, DLS and SEM. Then the viscosity, density-specific gravity- and filtration properties of the modified drilling mud were investigated in different amount of nanocomposite compounds. The results indicated that the density, fluid loss and filter cake thickness of the modified drilling mud were decreased with the increase of the surfactant concentration, whereas the viscosity was increased. With the increasing amount of SDS from 0.1 to 1.2 g in the synthesis process, the viscosity was increased approximately 4 cP and the density was decreased about 0.1 specific gravity. The nanoparticle and HLB value were affected in the filtration properties, but in general, that improved the fluid loss and filter cake thickness about 28 and 38% compared the based drilling mud, respectively.

In this study we investigate the effect of atoms such as B, N, Ge and Sn on the optical and the electrical properties of capped (5, 0) zigzag carbon nanotube, using DFT calculation method. These elements were attached to the one end of the carbon nanotube. We considered four different structure designs as possible candidates for a p-n junction device. The electrical properties of these structures were investigated using the quantum chemical information analysis which leads to the energy band gap, dipole moments, electrical charges and the DOS of these structures. Further TD-DFT calculations were performed to obtain the optical properties of the structure designs to investigate the electron mobility, indicating higher conductivity and higher rectifying voltage in the CNT terminated by Sn.

PEGylated polypropyleneimine (PPI) dendritic scaffold was used for the delivery of an anti-leukemic drug, Imatinib. The current study evolves and emerges the use PEGylated PPI dendritic scaffold for the delivery of this drug. In this Imatinib was synthesized and loaded with PEGylated PPI dendritic scaffold. Parameters such as FT-IR, NMR, SEM, drug release, DSC and hemolytictoxicity are required. Other parameters such as drug entrapment of both PEGylated and non-PEGylated systems were comparatively determined. Drugloading capacity was found to be increased with the PEGylation and reduces the haemolytic toxicity as well as drug release rate. By this, prolonged delivery of Imatinib was found to be suitable with this system. By delivering the drug for a prolonged period of time at a controlled rate, we expect that this approach will improve the management of drug therapy in leukemic patients.

We have performed density functional theory investigations on the adsorption properties of ammonia molecule on the undoped and N-doped TiO2 anatase nanoparticles. We have geometrically optimized the constructed undoped and N-doped nanoparticles in order to fully understand the adsorption behaviors of ammonia molecule. For TiO2 anatase nanoparticles, the binding site is preferentially located on the fivefold coordinated titanium sites. However, we have mainly studied the interaction of NH3 molecule over the fivefold coordinated titanium sites including the bond lengths, bond angles, adsorption energies, density of states (DOSs) and molecular orbitals. The results indicated that the adsorption of NH3 molecule on the N-doped nanoparticles is energetically more favorable than the adsorption on the undoped one, suggesting the strong adsorption of NH3 molecule on the N-doped nanoparticles. Adsorption on the N-doped nanoparticles leads to the more stable and favorable complexes. Our theoretical work represents that the N-doped nanoparticles have higher sensing capability than the pristine ones to remove the hazardous NH3 molecules from the environment.