Sharif Digital Repository

In this paper, photonic cavities made of point defects in 2-D photonic crystals are modeled by finite-size transmission lines terminated at both ends by appropriate scalar impedances. The proposed model forms a simple transmission line resonator and is demonstrated to be quite beneficial in fast extraction of resonant frequency, quality factor, and mode profile of such photonic cavities. In this manner, an approximate yet quite accurate approach is introduced to characterize the electromagnetic properties of photonic crystal cavities. This method is successfully applied to different structures for both major polarizations and is shown to be as accurate as rigorous numerical methods, viz. the... 

An approximate circuit model is proposed for mode extraction in two-dimensional photonic crystal waveguides. The dispersion equation governing the complex propagation constant of the photonic crystal waveguide is then related to the resonance condition in the proposed circuit model. In this fashion, a scalar complex transcendental equation is given for mode extraction. To avoid searching for the complex roots of the derived scalar dispersion equation, however, the real and imaginary parts of the sought-after propagation constant are extracted by using the physical resonance condition and its corresponding quality factor in the here-proposed circuit model, respectively. All the necessary... 

The transmission-line analogy of the planar electromagnetic reflection problem is exploited to obtain a transmission-line model that can be used to design effective, robust, and wideband interference-based matching stages. The proposed model based on a new definition for a scalar impedance is obtained by using the reflection coefficient of the zeroth-order diffracted plane wave outside the photonic crystal. It is shown to be accurate for in-band applications, where the normalized frequency is low enough to ensure that the zeroth-order diffracted plane wave is the most important factor in determining the overall reflection. The frequency limitation of employing the proposed approach is... 

We present a new method for modeling and design of photonic crystal nano-beam resonators (PCNBRs) based on cascaded transmission lines. The proposed model provides an accurate estimate of the PCNBRs properties such as resonance wavelength and quality factor (Q) with much smaller computation cost as compared to the brute-force numerical methods. Furthermore, we have developed a straightforward technique for the design of high-Q PCNBRs based on resonance modes with Gaussian electromagnetic field profiles. The results obtained by using the proposed transmission line model are compared against numerical and experimental results and the accuracy of the model is verified. The proposed model... 

We present a wideband tunable optical cavity based on electrostatic actuation. Over 60nm shift in wavelength is achieved by applying less than 1 Volt corresponds to a mechanical displacement of 30nm  

In this paper, enhanced spatial and temporal shifts in the reflection of Gaussian wave packets from twodimensional photonic crystal waveguides supporting above-the-light-line leaky modes are studied, for the first time to our best knowledge. Particular attention is given to two important special cases, namely, harmonic Gaussian beams and Gaussian-pulse uniform plane waves. Analytical expressions are given for enhanced spatial and temporal shifts when the stationary phase approximation holds and the incident wave excites above-the-light-line leaky modes. The enhanced spatial and temporal shifts of Gaussian wave packets are thereby related to each other via the group velocity of the excited... 

The Goos-Haenchen shift of a totally reflected beam at the planar interface of two dielectric media, as if the incident beam is reflected from beneath the interface between the incident and transmitted media, has been geometrically associated with the penetration of the incident photons in the less-dense forbidden transmission region. This geometrical approach is here generalized to analytically calculate the Goos-Haenchen shift in one- and two-dimensional periodic structures. Several numerical examples are presented, and the obtained results are successfully tested against the well-known Artman's formula. The proposed approach is shown to be a fast, simple, and efficient method that can... 

Many authors simply use band structure of infinite photonic crystals to predict the beam's direction in a finite structure. The validity of this approximation for high frequencies has been questioned by Felbacq (PRL 92, 193902) and instead a dressed (by evanescent waves) transfer matrix has been suggested. In this work, we show through numerical examples that the direction obtained by conventional band structure is more accurate than that of dressed transfer matrix of Felbacq et. al. We also demonstrate that this approximation can be improved by taking the effect of evanescent Bloch modes into consideration. The effect of these modes leads to a constant shift of beam's center inside and far... 

Boundary-layer effects in lengthy cross-ply laminated circular cylindrical shell panels under uniform axial extension are investigated by two analytical solutions. First, Reddy's layerwise theory with state-space approach is utilized to determine the local interlaminar stresses. In this method, the general displacement field is discretized through the shell thickness by a linear shape function. When the shell panel is subjected to an axial force, the axial strain is estimated by an equivalent single-layer theory. Second, the stress-function approach along with Fourier series expansion is applied to develop a novel elasticity solution. The elasticity solution, which is based on simply-support... 

An easy-to-design single-stub nano-coupler is proposed to increase the direct coupling efficiency between metal-insulator-metal (MIM) plasmonic and high-index dielectric waveguides. The modal reflection and transmission from the junction are exploited to provide a circuit description for the structure. The return loss of direct coupling is then minimized by loading the MIM waveguide with a single stub. Numerical examples are given, and the accuracy of the model is examined via finite-difference time-domain method  

A transmission line model is developed for coupled plasmonic metal-insulator-metal (MIM) waveguides. In the proposed model coupling between electric fields of two plasmonic waveguides is modeled by distributed mutual capacitor while distributed mutual inductor accounts for magnetic field coupling. These mutual elements are determined using propagation constants of supermodes of coupled waveguides. The model is applied to analyze coupled line directional coupler and side-coupled rectangular resonators. The effectiveness of the model is assessed using fully numerical finite-difference time-domain (FDTD) technique. The results have excellent agreement with the numerical methods  

We substitute different types of photonic crystal waveguide components by approximate transmission line circuits. The proposed distributed circuits exploit the analogy of wave propagation in photonic crystal waveguides and transmission lines. They are either cascaded to each other or inserted like stubs to imitate wave propagation within the photonic structure. Notable examples, e.g. coupled waveguide-cavity systems, sharp 90° bends, and T-junctions, are studied in detail. It is shown that analysis of the proposed circuits here can yield accurate enough results and thus substitute the brute-force numerical methods. The privilege of having analytical models is exploited to improve the... 

Insulated rail joints (IRJs) are widely used in signaling and broken rail identification systems. Track deterioration adjacent to IRJ is frequent due to excessive dynamic forces generated at IRJs by the repetitive passage of the ongoing traffic. Hence, they exhibit low service life and are considered high-risk elements and maintained through high standards. With a view to increase operational speed and the annual operational throughput, many improved structural designs have been proposed, of which inclined IRJs are the focus of this paper. To compare noise, vibration, and adjacent sleepers' vertical displacement of square and 30° and 45° cut joints, a series of field tests have been carried... 

Aim: Hepatitis E is a form of acute viral hepatitis, which is caused by hepatitis E virus (HEV). The study objective was to evaluate the prevalence of HEV to provide an overall relative frequency in Iran. Methods: In this study, databases such as PubMed and Scopus were searched using the following keywords according to MeSH, "Hepatitis E virus", "Epidemiology", "Enzyme-linked immunosorbent assay (ELISA)" and "Iran". Then studies which had reported prevalence of HEV were selected. Results: We selected 36 researches out of 9246 for our study. From all the samples, the pooled estimated prevalence of HEV positive was 9.7%. It should be noted that HEV infection's relative frequency varied from... 

Aims: Due to large sized genetic database of population in a given society, researchers face serious problem to analyze genetic data and provide accurate genetic identification. Variation in molecular markers such as SNPs, mtDNAs, STRs and Y-chromosome are utilized for different purposes, including genetic identification. In our country due to natural disasters and imposed war, the use of this technology was considered and according to the requirements, an optimal database was designed that has the capability of analyzing genetic data. Methods: After obtaining individual genetic information, a software was designed for the analysis of genetic information as well as to serve as a common... 

Compared with conventional cancer treatments, the main advantage of oncolytic virotherapy is its tumor-selective replication followed by the destruction of malignant cells without damaging healthy cells. Accordingly, this kind of biological therapy can potentially be used as a promising approach in the field of cancer management. Given the failure of traditional monitoring strategies (such as immunohistochemical analysis (in providing sufficient safety and efficacy necessary for virotherapy and continual pharmacologic monitoring to track pharmacokinetics in real-time, the development of alternative strategies for ongoing monitoring of oncolytic treatment in a live animal model seems... 

After publication of this article [1], it was brought to our attention that there are some errors in the section of 'Authors' contributions'. The correct Authors' contributions should be: MK, FS, and AG collected literature, designed and wrote the manuscript. FS and MM edited and prepared the manuscript for submission. All authors read and approved the final manuscript. © 2019 The Author(s)  

Oncolytic virotherapy has currently emerged as a promising approach upon which scientists have been able to induce tumor-specific cell death in a broad spectrum of malignancies. Paramyxoviruses represent intrinsic oncolytic capability, which makes them excellent candidates to be widely used in oncolytic virotherapy. The mechanisms through which these viruses destroy the cancerous cells involve triggering the autophagic machinery and apoptosis in target cells. Interestingly, oncolytic paramyxoviruses have been found to induce autophagy and lead to tumor cells death rather than their survival. Indeed, the induction of autophagy has been revealed to enhance the immunogenicity of tumor cells via...