مجله پژوهش فیزیک ایران
سال بیست و یکم شماره 2 (تابستان 1400)

Spinel ferrites nanoparticles are among the most important magnetic materials and their applications in ‎different areas have increased significantly in the last two decades. The idea of using ferrites ‎nanoparticles in medical applications, caused attraction of attention of researchers in worldwide to this field ‎and increase number of studies on the subject. The increase of the magnetic resonance imaging (MRI) contrast is one ‎of the most important medical applications of spinel ferrite nanoparticles. The imaging results of ‎live organisms show that the spinel ferrite nanoparticles can increase the contrast of images of ‎cancerous cells and therefore help tumors diagnosis. Magnetic hyperthermia is another ‎application of spinel ferrite nanoparticles, in which several factors affect the specific adsorption ‎rate and efficiency of the method. However, this method has not yet been applied to human kind, ‎and it is being studied in laboratories on animals like mouse etc. Targeted drug delivery is the ‎third application of spinel ferrite nanoparticles in the field of medicine. This method is one of the ‎most advanced treatment routes. In this method, several parameters must be considered to ‎achieve the best results. Considering the importance of health and treatment, the main purpose of ‎this review is to give the latest results of studies on the three mentioned methods on using the ‎spinel ferrite nanoparticles for medical purposes‎.

In this research, the Fe-Sn alloy nanowires were made by AC electrodeposition method in anodic ‎aluminum oxide (AAO). The effect of different symmetrical voltages of electrodeposition (17.5-32.5 V) ‎and annealing temperature on magnetic and structural properties of Fe-Sn nanowires were investigated. ‎The magnetic properties, morphology, element composition of materials and crystal structure of the ‎nanowires were studied by AGFM, SEM, EDX and XRD, respectively. The results showed that, coercivity ‎field (Hc) and square ratio (Sq) increases by increasing deposition voltage and also, crystallinity of the ‎nanowires and resulting their crystalline magnetic anisotropy increased, but deposition percentage of Sn ‎to Fe reduced. The Hc and Sq of prepared nanowires were increased by annealing due to increases in their ‎crystalline structure and crystalline magnetic anisotropy. The most variation in Hc and Sq were achieved ‎for prepared nanowires at 30 V.‎

Porous silicon (PSi) biosensor based on reflectometric interference Fourier transform spectroscopy ‎‎(RIFTS) has received a lot of attention due to its applicability as a label-free biosensor. In this ‎approach, light is illuminated on the surface of a PSi layer and the interference pattern of all reflected ‎beams from all interfaces is recorded. After exposing the PSi surface to bioanalyte, depending on ‎analyte's size, it absorbs on the surface of PSi layer or penetrates to the pores and absorbs on the wall of ‎the pores. This phenomenon causes variation in the refractive index of the interface of PSi/environment ‎or in the refractive index of the layer respectively. As a consequence, decrease in peak intensity or shift ‎in the peak position of fast Fourier transform of the interference pattern is observable, which can then ‎be used as a key parameter for biosensing applications. In this work, theoretical foundations of RIFTS ‎method were discussed. Then the experimental details of using this method for biosensing applications ‎on modified porous silicon were described. Finally, experimental data for diagnosis of Osteocalcin ‎protein, a piece of VKORC1 gen and Escherichia coli bacteria by RIFTS methods were illustrated.‎

Due to their high efficiency and low ‎cost, electrostatic electron accelerators with a moderate energy,  are used in the industry. In an electrostatic accelerator, the acceleration tube plays the role of dividing ‎the potential of the high-voltage terminal so that it accelerates the beam incrementally in a straight line. In this ‎paper, an acceleration tube for a Dynamitron accelerator with a voltage of 500 kV is designed by CST Studio ‎Suite software. In this design, an electron gun with flat cathode, and a current of 50 mA was used.  In order to ‎extract the beam from the electron gun, two filters are used: electrodes and the lens electrode, with voltages of 495 and ‎‎481 kV, respectively; besides for electron acceleration, 13 electrodes with a potential step of 37 kV have been ‎designed. To hold the electrodes and prevent electrical discharges between the electrodes, insulating ‎sheets made of Pyrex are used. At the end of the acceleration tube, a 50mA beam current, a waist radius of less than 0.5 ‎mm, a 73nm radian emittance, and a 0.15μperv beam were obtained. The dimensions of the acceleration tube ‎and the results of investigating the change in the radius of the electrodes, the displacement and deviation of ‎the angles of the first electrode relative to the axis of the acceleration tube are presented in this paper‎.‎

Polyvinylidene fluoride (PVDF) is one of the well-known polymers in different types of ‎membranes for water treatment applications, because of its unique chemical, mechanical and ‎thermal properties. Because of the presence of fluorine groups in polymer chain, the PVDF has ‎a negative electrostatic surface charge that makes the PVDF a suitable adsorbing material for ‎cationic dyes such as Rhodamine B (RB) and Methylene Blue (MB). The presence of two-‎dimensional graphene oxide sheets with negative electrostatic surface charge in the PVDF ‎matrix, can improve the adsorption of the dyes on PVDF/graphene oxide (PGO) composite ‎membranes due to increasing of negative electrostatic charge. In this study, we aimed to ‎explore synthesis and characterization of the PGO composite membranes by Scanning Electron ‎Microscopy (SEM), Atomic Force Microscopy (AFM), Raman spectroscopy, X-Ray diffraction ‎‎(XRD), to confirm the effective presence of the GO sheets in PVDF matrix.  In continue, the ‎mechanisms of physical adsorption of the dyes on PGO membranes have been investigated‎‎.‎

One of the advantages of observations of gravitational microlensing is stellar spots detection.  Our aim ‎in this paper is to study and characterize the perturbations due to stellar spots on the microlensing ‎light curves. Considering a suitable formalism for the stellar spots, we simulate the microlensing of ‎spotted source stars. One of the effects of a spot on stellar light curve is the local demagnification (where ‎the lens is crossing the stellar spot) and it causes asymmetric perturbations on the light curve. The ‎spots that locate at the source center after projection make larger and deeper perturbations than the ‎spots locate the stellar limbs. In caustic crossing binary microlensing events, the typical-size spot-‎induced perturbations mostly make (more than 40‏‎ percent) the relative deviations larger than ‎‏5‏‎. This ‎fraction is bigger for single lensing events‎‎‎.‎

The Jaynes-Cummings model is the canonical model for atom-light interactions, describing ‎a single confined bosonic mode interacting with a two-level system (qubit). This is ‎sufficient to describe a wide range of phenomena in quantum optics and quantum ‎computing. We simulate the dynamics of this model using the hybrid quantum-classical ‎algorithm (HQCA) consisting of quantum and classical computers. The parametric quantum ‎state preparations and quantum measurements are performed on the quantum computer ‎and parameters optimization employ on the classic computer. For implement of hybrid ‎quantum-classical algorithms, the Noisy Intermediate Scale Quantum (NISQ) computer is ‎used. In Noisy Intermediate Scale Quantum computers, we don’t need to error correction.  ‎For this purpose, we transform Hamiltonian to qubit form and using an algorithm to obtain ‎the dynamic of the Jaynes-Cummings model. We obtain occupation probability and ‎transition probability in the Jaynes-Cummings model using the hybrid quantum-classical ‎algorithm. The output of the algorithm is compatible with the exact calculation‎‎‎‎.‎

In the framework of quantum mechanics and based on the non-commutativity between the ‎coordinates in Minkowski space-time, we generalize the geometric non-commutative relation ‎to a space-time other than Minkowski. Using the authority of inserting the unit operator, we ‎exploit the translation operator to derive the Wyle-Moyal star product operator. Up to the first ‎order of translation parameters and by employing the Wyle-Moyal star operator, we find the ‎modified non-commutativity of coordinates relation in terms of geometric structure. The basic ‎premise of this article is that pseudo-Riemannian local homomorphic with Minkowski space-‎time‎‎ are equivalent.

In this paper, relying on the clustering of complex networks that can determine large scale features of ‎the network, we study 48 financial markets across the world. To this end, we develop a modularity ‎maximization method for directed and weighted networks. According to the linear correlation measure, ‎we construct the adjacency matrix, and by using the theory of random matrices, we divide the space of ‎eigenvalues of our matrix into two irrelevant and relevant fragments. By considering the temporal ‎window and its evolution over time series, our results demonstrate that in the vicinity of so-called ‎financial crisis clusters, which are often affected by geographical characteristics, are formed and from the ‎perspective of complex networks, they show more random behavior‎.‎‎

In this paper, ZrO2 thin films were grown on glass substrates using RF magnetic sputtering method. In ‎three separate experiments, three samples of ZrO2 film were prepared at various temperatures. Three ‎temperatures of  25 ̊C (laboratory temperature), 150 ̊C and 250 ̊C were selected for three samples, respectively. Except for temperature, other parameters ‎such as pressure, film growth rate, substrate to target distance and deposition time were the same for all ‎three samples. Optical properties and morphology of the samples were investigated. The morphology of ‎the samples was determined by atomic force microscopy (AFM) images and the ‎transmittance was measured using optical spectroscopy. The optical constants of the films were also ‎calculated using their spectrum. The results show that the effect of temperature is especially evident on ‎the optical properties of the films. As the temperature increases from the ambient temperature to ‎‎250 ̊C, the refractive index changes from n = 2.11 to n = 2.18. Moreover, increasing the ‎temperature, causes the absorption of the layer to increase. The morphology of the films also changes slightly ‎by changing temperature. The average roughness of all three samples is less than half a nanometer.‎.‎‎

This paper addresses a unimorph cantilevered piezoelectric nanogenerator having high ‎output power through vibrational energy harvesting that is simulated using finite element ‎method (FEM). The simulations are done for three types of perovskite piezoelectric ‎materials including PZT, PMN-PT and MAPbI3. The interdigitated electrodes were ‎exploited‏ ‏to obtain longitudinal vibration mode using d33 mode of piezoelectric layer during ‎the bending of nanogenerator structure. The presented structure consists of a piezoelectric ‎nanolayer with gold interdigitated electrodes on it, which is placed on a flexible PET ‎polymeric substrate. To encapsulate the piezoelectric layer, an SU-8 epoxy is placed over ‎the surface. The poling process is also simulated by applying high voltage through IDs to ‎piezoelectric layer. Generally, the electric potential distribution of the piezoelectric layer ‎must be performed by applying mechanical loadings. Then the output voltage, ‎power for free vibrations and base excitation (0.25-2g) of the nanogenerator at resonance ‎frequency are investigated. The resonance frequency of the PZT, PMN-PT, and MAPbI3 were ‎calculated to be 549 Hz, 560.5 Hz and 631 Hz, respectively. We found that PZT ‎piezoelectric materials yields maximum output voltage and electrical power values of 91.69 ‎V and 350 mW which shows better performance in vibrational energy harvesting ‎application. In comparison, the results of the simulation implied a good agreement with ‎other experimental studies. The unimorph piezoelectric energy harvester system generates ‎high voltage and output power in response to sub-kilohertz ambient vibration‎.‎‎

Interior design, engineering, and the configuration of materials used in photo‏-‏anode systems play ‎key roles in the photovoltaic performance of dye solar cells.‎‏ ‏In this study, the photo-anodes of dye sensitized ‎solar cells were fabricated based on TiO2, ZnO and SnO2 nanoparticles separately using doctor Blade method ‎on the transparent conductive oxide as substrates, then sensitized with N719 dye. Due to the fact that the dye ‎plays the role of photon absorption, different photo‏-‏anode oxides were placed in a N719 dye solution over a ‎different time period.‎‏ ‏Based on current-voltage curve, efficiency parameter, short-circuit current density, ‎open circuit voltage, and fill factor of the cells were obtained. The results of current-voltage characterization ‎indicate that the best time for the N719 dye loading for the TiO2 and SnO2 layers is 20 h and for the ZnO layer ‎is 1 h.‎‎

We study excitation transfer in a spin chain in presence of noise. To model noise, we assume that each ‎qubit of the spin chain is interacting with a Bosonic environment and has Markovian evolution. ‎We derive the explicit form of master equation both in global and local approaches. Comparing the ‎results of each approach, we discuss the noise effect on excitation transfer and in addition to that we ‎show that the results of local approach are not a limiting case of global approach‎.‎‎

In this paper, palladium doped-tungsten oxide thin films have been prepared by sol-gel deposition method. In this way, tungstic ‎acid obtained by Kudo method was doped by different amounts of palladium chloride and were deposited on transparent ‎conductive oxide of ITO/glass by dip-coating method. The effect of Pd doping on morphology and optical properties as well as ‎electrochemical characteristics were investigated using scanning electron microscopic (SEM), UV-Vis spectroscopy, cyclic ‎voltammetry (CV) and optical transmission at 632.8 nm constant wavelength. SEM revealed that the WO3 layers have a thickness ‎of 450-500 nm were obtained with smooth and uniform surfaces. Also, the transparency of layers was above 85%, for which the ‎optical gap was decreased by increasing Pd content. The voltammetry results showed that the doped palladium reduces the ‎catholic potential, increases the chemical stability of tungsten oxide thin films, stabilizing the electrochemical performance of ‎these layers. Finally, we measured the electrochromic response time and the corresponding electrochemical efficiencies

In this manuscript we consider the normal branch of DGP brane cosmological model in the presence of a ‎scalar field on the brane as the dark energy component. Using dynamical system approach we investigate ‎the stability properties of the system. We will see that one of the defined new variables lambda, that ‎depends on the potential function of the scalar field has a significant role in the evolution of the universe. ‎Therefore, we divide our discussion into two parts, the constant and the varying lambda. With a good ‎approximation we consider all the obtained critical points in the case of the constant lambda, as the ‎instantaneous critical points for the case of a varying lambda. We investigate two special scalar field ‎potential function: a double exponential potential and an inverse power law potential. In both of the cases we ‎study the evolution of the system and discuss the fate of the universe. We find that the inverse power law ‎potential function is in a good agreement with the current universe, but the double exponential potential ‎function can predict different future for the universe.‎

In this paper a new method in design and modeling of infrared detector HgCdTe in photoconductive mode ‎is presented. In this method after scrutiny mechanical, optical, electrical properties of semiconductor ‎HgCdTe and solving the photoconductive equations, software of equations is programmed and with initial ‎value and repeat cycle, their changes to key parameters such as thickness, wavelength and amount of ‎impurities are calculated and finally, performance of detector is optimized.‎ Modeling of photoconductive detector has been done in temperature of 300K and 2-6 µm wavelength range‎‎, according to obtained results, optimal specific detectivity  is 3×109 cmHz1/2W-1‎‏ ‏in 5.77 µm wavelength.‎

In this paper, we study the  modified gravity theory, where  and  represent the scalar-torsion and trace of energy-momentum tensor, respectively. According to our cosmological study, we show that the  gravity theory has a good agreement with observations. Function type for  can be determined by several factors. The most important motivation for determining  is that the Lagrangian of model follows the Noether continues symmetry; therefore, according to the Noether approach, we try to determine the function of . Moreover, the proposed model should behave in agreement with observations in terms of phenomenology. As a result, we compared the predictions of the model with observation constrains, for example, the cosmic microwave background and Hubble diagram can be mentioned. In this paper, we study the  gravity in the FRW space-time. So, we achieved the effective Lagrangian with respect to independent variables, scale factor , scalar-torsion  and trace of energy-momentum tensor . After imposing the Noether symmetry to Lagrangian, we can introduce the suitable form for the function. . Then, we calculated the Noether conservative quantity for the model.

In this paper we propose a dark energy-dark matter interaction model in which an early dark energy phase ‎emerges. This model is unique since the usual interacting dark matter-energy models affect the late time ‎cosmology and not the early phase. Although it sounds to be a solution for Hubble tension, but CMB dataset ‎prefers , which is inconsistent with local measurements. We will discuss the reasons ‎behind these results.

In this study, the thermoluminescece (TL) behavior of potassium chloride dosimeter doped with dysprosium impurity (KCl:Dy)  was studied. Evaluation of the morphology, shape and size of prepared crystal were done by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Potassium chloride was prepared by co-precipitation with different percentages of dysprosium impurities and the best TL response was determined for gamma rays in 0.5 mol% of impurity. The optimum annealing regime was obtained at 700  for 30 minutes. Using a general order kinetic based on computer simulator, the glow curve and corresponding kinetics parameters were calculated. The TL glow curve of synthesized dosimeter shows two peaks at 393 and 415 K. Also, other dosimetric properties such as fading and TL dose response were studied

The thickness of silicon oxide gate dielectric for field effect transistors is 1 to 2 nm. Therefore, reducing the thickness of gate to 1 nm for future products will increase the tunelling and leakage currents. The hybrid nano composites are good candidates as dielectric gates with high dielectric constant, wide band gap, and in thermal equilibrium in contact with silicon substrate. In the present work, we synthesized NiO/PVC hybrids as suitable dielectric materials by sol-gel method and tried to test the loss weight of samples against heat by using the thermogravimetric analysis (TGA) and its derivative. To measure the mobility, dielectric constant and conductivity of the samples at different annealing temperatures, we used A132GPS to calculate the activation energy in the logarithmic diagram in terms of temperature inverse. Results show that NiO/PVC:2 has less leakage current due to higher dielectric constant. The behavior of these samples is roughly the same rise up to 400 K. Differences between samples occur at higher temperatures so that the NiO/PVC:2 sample has a higher mobility at temperatures above 400 K.