Scientia Iranica
Volume:22 Issue: 3, 2015

Plasmonic mode propagation properties of a graphene strip placed on a substrate is studied in THz range. Based on propagation properties (phase constant), a design guide for a dipole-like antenna made of graphene strips is presented. The input impedance and the radiation properties of such graphene-based antenna are investigated through full-wave numerical simulations. Full-wave simulations show that graphene antennas can provide higher input impedance along with the tunability of the resonance frequency that are two important design requirements in high performance terahertz photoconductive antenna sources and detectors.

In this study, we intend to improve the mixing performance of a nanoscale mixer using the throttling idea. The study is conducted at a Knudsen number of 0.12, which corresponds to the transitional flow regime. Therefore, we have chosen the DSMC method to perform reliable numerical simulations. We consider a number of different throttles with various widths and shapes to enrich our study and to explore a wider range of their influences on the mixing evolution. We choose a linear converging-diverging nozzle profile, an arced converging-diverging nozzle profile, and a sudden contraction-expansion configuration as our throttle shapes. The results show that both the mixing length and the mass flow rate decrease as the throttle widths decrease.However, the throttle width decrease plays more effective role in reducing the mixing length than the mass flow rate decrease. Evaluating the results of three chosen throttle shapes, we conclude that the arced nozzle and sudden contraction-expansion shapes would result in less mixing length and mass flow rate magnitudes; although the reductions are more pronounced for the latter shape. We also conclude that the throttle shape affects the mixing length reduction more seriously than the mass flow rate reduction.

Undoped and copper doped nickel oxide films, prepared onto glass substrate by spray pyrolysis method, were studied from various physical view points including: morphological, structural, optical, electrical and thermo-electrical properties. The XRD patterns show the nano-sized grains have cubic polycrystalline nature (with no additional related Cu-content phase) and the data analysis revealed while the crystallite sizes are decreased (13-10.5 nm) the dislocation density are increased (5.92×10-3 - 9.07×10-3 nm-2) with increments in the doping density. The electrical and thermo-electrical data (Seebeck effect) confirmed more substitutions of Cu ions with Ni2+ ions and in turn more p-type conductivity in samples with higher doping. Optical measurements showed the direct and indirect band gaps of the transparent conductive layers are decreased. These variations are in good agreement with the variations of the crystallite sizes and carrier densities of the samples

In this research, in uences of intermolecular interactions on the behavior of nanobeams are studied. Suddenly applied voltages actuates the clamped-clamped nanobeam. The e ects of electrostatic actuation, intermolecular forces, midplane stretching, the fringing eld e ect and residual stress are considered. Initially, the governing equation is non-dimensionalized, and the partial di erential equation of motion is converted to a nonlinear ordinary di erential equation by means of the Galerkin method. Afterwards, the nonlinear ordinary di erential equation of motion is solved using the homotopy analysis method. To validate the model, the response of a sample beam was compared with that in the relevant literature. Finally, the e ects of various parameters on the nonlinear frequency of the response are studied. The results indicate that the nonlinear frequency of oscillations signi cantly decreases by increasing intermolecular e ects.

The aim of current study was the loading of ceftazidime onto the first generation of poly(propyleneimine) dendrimer (PPI-G1) to produce an effective drug delivery system against Pseudomonas aeruginosa.The mechanism of ceftazidime- PPI-G1 dendrimer complexes formation is based on interaction between amine groups of dendrimers and carboxylic groups of ceftazidime.PPI-G1 was dissolved in dry tetrahydrofuran (THF) and ceftazidimewas addedto the solution to prepare the nanodrug. The series of tests including size, zeta potential, drug release, stability and kinetic evaluations as well as scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy were performed for characterization of the ceftazidime-loaded PPI-G1. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the nanodrug was determined with respect to Pseudomonas aeruginosa asthe test microorganism. Ceftazidime-PPI-G1 complex was synthesized with the size of 156.6 nm and -10.2 mV zeta potential. The value of loaded ceftazidime was determined about 38.46 mol%. A gradual drug release was observed within three days up to 92% of the loaded ceftazidime The macrodilution assay demonstrated that PPI-G1 enhances the antibacterial activity of ceftazidime. A new drug delivery system was improved against P. aeruginosa with sustained release and enhanced antibacterial activity.

Design of a sca old with appropriate physical and mechanical properties for tissue engineering is a major challenge. In this research, the e ects of nano-titania (nTiO2) on the physical and mechanical properties of a nano-bioglass (nBG) sca old were evaluated. First, nBG powder with a grain size of 100-110 nm was prepared using the method of melting pure raw material at a temperature of 1400C. Then, a porous ceramic sca old of nBG/nTiO2, with 30 wt% of nBG, containing di erent weight ratios of nano-titania (3, 6 and 9 wt% nTiO2 with a grain size of 35-37 nm), was prepared using the polyurethane sponge replication method. XRD, XRF, SEM, FE-SEM and FTIR were used to study the phase and elemental structures, morphology, particle size, and determination of functional groups, respectively. XRD and XRF results showed that the type of produced bioglass was 45S5. he results of XRD and FT-IR showed that the best temperature to produce a bioglass sca old was 600C, because, at this temperature, the crystal was obtained, and the main sign of the obtained crystal was the presence of Na2Ca2Si3O9 crystal. The mechanical strength and modulus of the sca old improved by adding nTiO2 to the nBG sca old. The results showed that the sca olds have 80-88% porosity at the range of 200- 600 m; a compressive strength of 0.04-0.16 MPa, and a compressive modulus of 4-13.33 MPa, illustrating that they could be good candidates for bone tissue engineering.

In this study, the colloidal stability and mobility of Fe/Ni nano particles, concurrently synthesized and stabilized in the presence of starch (S-nZVI/Ni), were investigated. In particular, the in uence of pore velocity (ranging from 7 to 85 m/d) and injected particle concentrations (0.3 and 3 g/l) was evaluated in a one-dimensional column. Experimental results exposed the ne mobility of the S-nZVI/Ni particles in porous materials. According to the breakthrough curves and mass recovery, the S-nZVI travel distance was limited to the range of 0.2 to 0.4 m for low pore velocities (5 to 7 m/d), and in the order of 10 m at higher velocities (> 50 m/d). Moreover, increasing pore velocity enhanced the mobility of S-nZVI. Results also proposed that the mobility of SnZVI suspension in sand media should be lower than in glass beads media. The clogging phenomenon of the column and the pore pressure variations during the injection period were strongly a ected by media type and injected particle concentration. Clogging, due to the deposition of particles, was observed, in particular, for 3 g/l nZVI suspension, low velocities and sand media. Finally, the results indicated that starch stabilized iron nano particles have the potential to become an e ective reactive material for in-situ groundwater remediation. Keywords:

Neutron diffraction technique used to study structural characterization of water/ice in mesoporous SBA-15 silica with 86Å nanopore diameter. Different filling factors of the silica pores, considered over a wide temperature range. Neutron diffraction data for the almost-filled case with filling factor of 0.95 that undergoes a temperature change of 300-100K, shows a main asymmetric triplet peak ~1.74Å-1. Using five symmetric functions, we found an excellent fit with the whole range of data sets for the triplet. Interestingly each of these functions directly linked to the position of different ice components and show systematic variation of peak parameters. As a complementary experiment, data analysis of the partially-filled cases with filling factor of 0.6 (300-130K) and 0.4 (300-100K), show characteristics that markedly differ from those of the filling factor 0.95. The nucleation temperature for all cases is reduced and different ice structures along with their temporal order have been detected for confined water. Further investigations confirm that for the different filling factors, there are different amount of hexagonal, cubic and the disordered ice component. Surprisingly, data analysis proved the reversibility of the whole nucleation process, although the formation/melting of the ice in the main body of the pore show the expected hysteresis.