Iranian Journal of Physics Research
Year:2019 | Volume:18 | Issue:4 |Papers Count:23

In this study, the SrS nanopowder co-activated by Ce3+ and Sm3+ (SrS: Ce, Sm) was synthesized by the co-precipitation method. The transparent pellets were fabricated by mixing the SrS: Ce, Sm nanopowder and bisphenol-A epoxy resin as a crystal of the optically stimulated luminescence (OSL) dosimeter. The crystalline phase verification and also, the morphology of the synthesized nanopowder were investigated using the XRD patterns and FESEM images, respectively. The effects of Ce3+ and Sm3+ concentration and the Thioglycerol (as capping agent) concentration on the sensitivity of SrS: Ce, Sm OSL response were evaluated in the same exposure and measurement conditions. The obtained results demonstrated the optimum sensitivity of the OSL response of the samples to a test dose of approximately 0. 4 mGy by X-ray irradiation, which was related to 0. 02 and 0. 01 mol% concentrations of Ce and Sm, respectively; the 0. 1 M concentration of the Thioglycerol was associated with the nanocrystallite size of 24+2 nm as well.

In this paper, we have investigated the kaon-deuteron interaction at an incident momentum of 1 GeV/c using the relativistic and non-relativistic Faddeev method for different phenomenological and chiral potentials. By calculating the π ∑ invariant mass spectra on different particle channels, we have shown that the trace of Λ (1405) resonance is visible in such spectra. In the present work, the study of kaon-deuteron interaction is used to better understand of the KN-π ∑ interaction and the nature of the Λ (1405) resonance.

Calcium channels are cell membrane proteins that play an important role in control the Ca ion flux through the membrane. In this study, the effect of external constant electric field on the dynamics of calcium ions in a L-type channel, located within a stochastically fluctuating medium, is modeled via the application of the molecular dynamics (MD) simulation method. The obtained results show that application of constant field of 0. 03 V/nm did not show significant effect on the ions motion. On the other hand, when the channel is exposed to a constant electric field of strength 0. 3 V/nm, the ions directional motion along the applied field is observed. Furthermore, it is found that no net motion is observed when the field direction is changed.

In the present work, the scattering differential cross section has been investigated for ion-multi electron atoms collision in the charge transfer channel. For this purpose, an active electron model was implemented and the collision process was considered as a three-body impact in the high energy range. A semi-classical formalism was used with the eikonal distorted wave function to describe the system, and the first and second order scattering amplitude of the Brinkman-Kramers approximation was employed to calculate the differential cross section. In this work, the screening Coulomb Effect and the static potential were implemented to calculate the eikonal wave function. The differential cross section was calculated for Proton-Helium, Proton-Carbon, Proton-Neon and Proton-Argon impacts by using the static Brinkman-Kramers, screening Coulomb Brinkman-Kramers, the potential Brinkman-Kramers effect, and the second order static Brinkman-Kramers approximation. The findings were then compared with the available experimental and theoretical results.

The measurement of the polarization of cosmic microwave background (CMB) provides considerable useful information about different physical phenomena at the last scattering surface. The polarization of CMB is due to Compton scattering. In this work, we consider the parity violation of Compton scattering. Then we insert the new amplitude into the quantum Boltzmann equation and show that the forward scattering term can produce the B-mode polarization.

The optical properties and thermal conductivity of carbon nanotubes in the presence of Nitrogen doping and electric field investigated via the Green's function method and tight binding approximation. The doping and external fields lead to modifications in the density of state (DOS), optical properties, electrical and thermal conductivity. The band gap decreases by the electric field until reaches zero and nanotubes with larger radius are more sensitive than small ones. The number and energies of peaks in the in the DOS and optical spectra are dependent on the electric field strength and doping concentration. The electrical and thermal conductivity increases with temperature until reaches maximum value then decreases. The behaviors of these parameters in the external electric field are different for pure and doped systems. By increasing the doping concentration and electric field strength, they decreases in higher temperature.

In this paper, we study a new kind of multiphoton resonances in a strongly driven six-level quantum system, where one of its levels is coupled individually with the other two levels that have the constant energy separation E. Near the multiphoton resonance condition, a different behavior for the number of even or odd photons was found qualitatively, which could be explained by considering two certain interfering trajectories and computing the interference phase of system. In the regime of strong dephasing, we calculated the rates of interlevel transitions, showing that multilevel Landau-Zener (LZ) interferences between first and third order processes could lead to resonances with characteristics differing markedly from those of familiar two-level resonances that first arose at the fourth order in the couplings of the energy levels. The rates displayed resonant features at the number of integer photons. Finally, we could explicitly connect our model to the experiments, showing that it captured all relevant features of the experimental data. This paper can be relevant for a variety of solid state and atomic or molecular systems. In particular, it provides a clear mechanism to explain the puzzling experimental observations in strongly driven double quantum dots.

In this study, we consider a composed system consisting of two identical non-interacting subsystems. Each sub-system is made of a moving qubit into a leaky cavity. The study of the dynamic of the composed system revealed that compared with the stationary qubits, entanglement, quantum discord and coherence between two moving qubits remained close to their initial values as time went by. In particular, we show that the entanglement, quantum discord and the initial coherence between the two qubits could be strongly protected from decay by increasing the velocity of the qubits. Furthermore, based on such results, we have drawn a comparison between the three quantum resources (entanglement, quantum discord and coherence), demonstrating that the coherence of a bipartite system could be more robust than the two other quantum resources.

The static structure of a turbulent self-gravitational disk is investigated based on the effect of cooling due to the presence of dust particles. In agreement with the numerical simulations of self-gravitational disks that have been done so far, the cumulative parameter is assumed to be on the threshold of its critical value; however, the coefficient of turbulence is obtained from the system's cooling rate. The physical quantities of the disk are obtained as a function of the radial amplitude. We show that the overall structure of the disk is divided into two regions, such that the inner part is optically a thick one and the outer part is an optically thin one. On the other hand, the model we present shows that as the mass increase speed is raised, the role of dust becomes more important. We show that the turbulent viscosity coefficient increases with the distance, but this coefficient decreases in the inner region due to the cooling of the dust. We then determine the mass of gravitational instability particles in the self-gravitational radius. We show that cooling dust particles increases the self-gravitational radius in the high accretion, while in the low accretion, the cooling of dust reduces the self-gravitational radius.

In this paper, we report on the design and fabrication of a low-cost phase shifter for application in phase shifting interferometry. Phase shifting interferometry is a powerful method for surface characterization. It uses interference data recorded during a series of predetermined phase shifts to recover the induced phase by the object surface. These controlled phase shifts are typically performed by putting a piezo-electric ceramic behind one of interferometer mirrors. Applying the controlled voltage to this ceramic provides the desired phase shifts. The piezo-electric positioners are very expensive. Phase shifting interferometry has different algorithms. One of the most effective algorithms is the four step phase shifting interferometry. In this algorithm, four interferograms are taken; then the unknown phase term due to surface is extracted by combining these interferograms. Here, we have proposed a low-cost alternative for piezo-electric positioners. Firstly, using the Fresnel diffraction from the phase step, we have measured etch rate of glass by HF acid. Then, a phase step with a quarter wavelength phase shift has been fabricated on a glass plate. The step height has been measured using Fresnel diffraction (phase step diffractometer) and interferometry. Then a stepwise structure has been fabricated on glass, providing phase shifts needed in the four step phase shifting interferometry.

Cancer is commonly known as a disease of the genes. Almost all the studies about cancers are based on finding the effective genes for each cancer and most of the efforts for diagnosing or curing cancer have faced several challenges. From the point of view of complexity, collective behaviors that have emerged from the interactions of many-body systems are not solely describable by knowing about the system’ s building blocks (genes) and we cannot understand what happens at a higher level of organization by just knowing how each element works at a lower scale! We know, each gene’ s expression affects other genes expression levels and this correlation causes a collective behavior which that alters the expression levels of the genes. In this study, instead of following the common reductionist view, we use the techniques of inverse statistical physics and infer the interaction matrix of the genes. Then, by applying the balance theory, we show the differences between the social behavior of cancer genes and normal genes as a whole. Our results show that the energy distribution of triads formed in the interaction networks behaves in a power-law manner and the energy of the normal network is higher than the cancer network.

In this paper, we study the decorated graphene oxide with titanium dioxide nanoparticles. In order to produce this nanomaterial, the titanium dioxide nanoparticles were produced and anchored simultaneously on graphene oxide sheets by arc current. The morphology of the prepared samples was studied by scanning and tunneling electron microscopy, showing that nanoparticles were stabilized on the graphene oxide sheets. Investigating the optical band gap by the Tauc plot of the UV-visible spectrum showed that the band gap energy of the nanomaterials was first reduced and then increased by raising the annealing temperature; the lowest band gap with a value of 2. 2 eV was related to the samples annealed at 600 ° C. In addition, the X-ray diffraction patterns showed the crystalline structure of nanoparticles was a mixture of anatase and rutile phase, in which the ratio of two phase changed for different annealing temperatures. In addition, the crystallite size of the anatase phase was always smaller than the rutile one.

Half lives alpha decay is the one of the most important parameters used for describing nuclear structure in nuclear dynamics; over the years, many studies have been done in this area. In this study, by using semi-empirical methods such as Viola-Seaborg (VSS), Royer, Parkhomenko and Sobiczewski (PSM), Brown, New Geiger-Nuttall (NGN), Poenaru et al. (UNIV) and Universal Decay Law (UDL), the half lives alpha decay of Thorium chain isotopes were considered and compared with the experimental data. The Viola-Seaborg method served as the best approach among the semi-empirical methods introduced above for studying Thorium chain isotopes.

In this study, thermal Casimir-Polder potential is calculated for an atom in the presence of a dielectric sphere using the formula given in terms of the Green’ s function. Then, the limiting cases of large and small sphere are investigated. In the limiting case of a large sphere, the formula of thermal potential for an excited atom in the presence of a dielectric half-space and then a perfectly conducting plate is obtained. The limiting case of the small sphere together with the proper replacement of its electric response by the polarizability of a second atom results in the thermal van der Waals interaction potential between the two atoms.

In this paper the propagation characteristics of the gaussian laser beam and the rippled laser beam in collisionless plasma were investigated, and their effects on and the excitation of the electron plasma wave were addressed by considering the ponderomotive and relativistic nonlinearity. Analytical expressions for the growth rate of the laser spike in plasma, the beam width of the rippled laser beam and excited electron plasma wave were obtained using paraxial ray approximation. These second-order differential equations of dimensionless beam width parameter were solved numerically. The results showed that increasing the density of plasma improved the self – focusing of the laser beam, the ripple laser beam and the electron wave plasma. Moreover, increasing the self-focusing of ripple beam laser enhanced the electrostatic potential of the electron plasma wave.

In this Research, the transition from equilibrium ignition to non-equilibrium burn was studied by DEIRA4 code for simple spherical targets with the dimensions of several mm. It consisted of inner DT fuel and outer Au layers driven by the 209Bi heavy ions beam. Because of their higher plasma opacity, it was expected that they could trap much of the produced charged particles, radiation or even fast neutrons. Therefore, fuel ignited in the volume ignition regime with the low ignition temperatures of 1-2 keV. In order to decrease the confinement time and, the driver energy, the equilibrium ignition must be developed into a non-equilibrium burn phase. To get a non-equilibrium burning stage, we have examined all the important gains and losses processes, as well as competition among them. In these calculations, the individual and total contributions of all physical heating processes such as the contribution of alpha particles generated by DT fusion, neutron heating due to the first elastic scattering and the secondary fusion reactions have been considered at the ignition and burn time scale of DT fuel. It has been shown that the role of secondary DD and D3He fusion reactions as well as the first elastic scattering contribution in the energy deposition of fast 2. 45 and 14. 06 MeV neutrons cannot be forgotten. Transition temperature to the non-equilibrium burn phase in these targets was reduced to 3. 24 keV, as compared to the ideal non-equilibrium transition temperature of 3. 6 keV; it was much lower than the ideal ignition temperature of 4. 3 keV. In order to investigate the effects of the driver parameters on the transition conditions, calculations were done for various configurations of simple spherical targets, showing that multiplier reduction in the pulse duration and multiplier increase in the beam power could reduce transition temperature and in such targets.

In this paper, slow light in a composite consisting of core-shell nanoparticles doped in a dielectric is studied. The light-velocity slowing factor as a function of the incident light frequency is discussed and analyzed. The influence of the thickness of shell, the composition of core and shell and the geometrical shape of nanoparticles on the slowing factor is investigated. The effect of the plasmon-exciton on the slow light is addressed too.

In this work, the stability and electronic structure of zigzag double-walled silicon carbide nanotubes (DWSiCNTs) (6, 0)@(n, 0) (with n=11-17) were investigated by using ab initio Van der Waals density functional. By calculating the formation energy and the binding energy of each double walled nanotube, the best interwall distance for the outer nanotube was indicated. The results revealed that (13, 0) nanotube could be the best external nanotube for the (6, 0) internal nanotube with 3. 53 Å interwall distance to make (6, 0)@(13, 0) DWSiCNT. The structural calculations also revealed that all studied silicon carbide nanotubes were semiconductors and their energy gap decreased from the single one to the double-walled one. Moreover, with raising the nanotube diameter, the energy gap increased, such that at the most stable double-walled nanotube, its value was about 0. 216 eV.

In this paper, Density Functional Theory (DFT) was utilized for the calculation of the hyperfine coupling constant and the g tensor alanine radicals at different crystal temperatures. The cluster approach was used for considering the effects of crystal environment. In the cluster approach, the careful selection of the cluster size is very important for the geometry structure of alanine and the EPR parameters of alanine radicals. The geometry structure of alanine and the EPR parameters of alanine radicals showed a good agreement with the experiment data when 6 alanine molecules had hydrogen bonds with the central alanine or alanine radicals. Further, bigger clusters could even lead to an incorrect description of the geometry structure of alanine and EPR parameters of alanine radicals in the condensed phase.

Surface plasmon resonance sensors have been widely considered due to their sensitivity, accuracy and response speed. In order to stimulate surface plasmons, a crisman structure is used in which the metal layer (mainly gold or silver) is placed on the surface of the prism. Due to temperature changes, various factors such as optical properties of the metal, the prism and the surrounding environment can change, which can, in turn, change the response of the plasmonic sensors. In this paper, the thermal effects on the optical response of a surface plasmon resonance sensor were theoretically evaluated. The results showed that the change in temperature led to significant changes in the reflectivity and phase. The greatest effect was due to the changes in the optical properties of the metal layer (gold here) due to temperature changes.