Critical States Embedded in the Continuum

We introduce a class of critical states which are embedded in the continuum (CSC) of one-dimensional optical waveguide array with one non-Hermitian defect. These states are at the verge of being fractal and have real propagation constant. They emerge at a phase transition which is driven by the imaginary refractive index of the defect waveguide and it is accompanied by a mode segregation which reveals analogies with the Dicke super -radiance. Below this point the states are extended while above they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states to bound states in the continuum.Comment: 4.5 pages, 3 figures, 1 page of supplementary material including one figur

Experimental study on heat transfer from rectangular fins in combined convection

Combined natural and forced convective heat transfer arise in many transport processes in engineering devices and in nature, which is frequently encountered in industrial and technical processes, including electronic devices cooled by fans, heat exchangers placed in a low-velocity environment, and solar receivers exposed to winds. In this study, the effects of design parameters have been experimentally investigated for the air-side thermal performance under combined (natural and forced)convection of the rectangular plate heat sinks, and the values of optimum design parameters were sought. Many ideas for improving cooling methods have been proposed, one of which is the heat sink. In this work, the average Nusselt number (Nu) and thermal resistance of a simple base rectangular plate and five vertical rectangular plate heat sinks with different numbers of fins under natural and combined convection were experimentally investigated to obtain the maximum average Nu and minimum thermal resistance for various Reynolds numbers (Re) from 2300 to 40000, Rayleigh numbers (Ra) from 1300000 to 13000000, and Richardson numbers (Ri) from 0.4 to 3. Also, in this experiment, fin spacing (P) was varied from 2.8 mm to 14.6 mm and the dimensionless P/H ratio was varied from 0.1 to 0.49. The flow velocity varied in the range of 2 to 8 m/s under combined convection. Based on the effects of Ri and Re, two empirical equations for natural and also for combined convection heat transfer were derived to calculate the average Nu. The average deviation for these two equations is about 7%.The outcomes of this research can be beneficial for engineers who work on electronics cooling systems

Device-induced perforation of right atrium following interventional closure of Atrial Septal Defect (ASD)

This is a case presentation of a 26-year-old woman with a moderate-sized atrial septal secundum defect (17mm) who underwent catheterism, during which an Amplatzer Septal Occluder number 26 was inserted successfully. On the second postoperative day, she deteriorated and a clinical examination showed a typical tamponade. After a percutaneous aspiration of the pericardial cavity and transient improvement in vital signs, a pig-tail catheter was inserted percutaneously emergently, and the patient was transferred to the operating room in a preshock state. During the operation, an active bleeding point in the superoanterior aspect of the right atrium near the aortic root was detected, which was repaired by direct suture and pericardial patch reinforcement. The Amplatzer device was removed and the atrial septal defect was repaired with a pericardial patch. A lethal complication of the interventional closure of atrial septal defect, properly treated by an emergent intervention and operation, is presented and discussed herein

Light Localization Induced by a Random Imaginary Refractive Index

We show the emergence of light localization in arrays of coupled optical waveguides with randomness only in the imaginary part of their refractive index and develop a one-parameter scaling theory for the normalized participation number of Floquet-Bloch modes. This localization introduces a different length scale in the decay of the autocorrelation function of a paraxial beam propagation. Our results are relevant to a vast family of systems with randomness in the dissipative part of their impedance spatial profile

Virtual spatial diversity antenna for GNSS-based mobile positioning in the harsh environments

Global Navigation Satellite Systems (GNSS) is the most commonly used positioning technology for many Location Based Services (LBS) including navigation. However, GNSS applications are limited to outdoors as GNSS signals can get blocked and attenuated inside or between buildings, making positioning unreliable, inaccurate or impossible. Blockage of GNSS signals may result in the lack of availability of the minimum of four satellites in-view at each epoch, for a single constellation GNSS positioning, and consequently, lead to a failure in the continuity of the positioning service. This is a particularly common issue in urban canyon and indoors. This paper proposes and implements a framework to handle this challenge by virtually distribute the antenna in space and time and accumulate the measurements while adding some unknowns to solve the synchronization and the position solution. To test the proposed technique, Virtual Spatial Diversity Antenna (VSDA), raw GNSS measurements are captured using an Android 7.1.1. running smartphone over the period of forty-seven minutes. Then the observations are accumulated until the number of measurements outcounts the number of unknown, i.e. three position components plus the number of epochs. The results of the GPS-only measurements for a relatively limited period of 47 minutes, where satellite geometry may not significantly change, prove the feasibility of solving position solution in presence of fewer than four satellites at each epoch using VSDA scheme, and achieving the horizontal and vertical accuracy of 47.16 m and 68.45m, respectively

Laparoscopic repair of iatrogenic long ureteral injury

Introduction: Transection of the ureter in laparoscopic retroperitoneal lymph node dissection (RPLND) is a rare iatrogenic complication. Its repair is possible by end-to-end anastomosis when the defect is short, but if there is a long defect, laparoscopic repair is a challenge. Methods: A 30-year-old man underwent modified RPLND of a clinically stage-A mixed germ cell of the left testis. While cutting the gonadal vein, 1.5 cm of the ureter was transected 2 cm below the renal pelvis and clipped by one of our residents. The injury was diagnosed immediately. After the completion of the modified RPLND, the clips were removed and a 20-mm defect of the ureter was seen precluding anastomosis. The kidney was dissected and pulled down 35 mm. The lower pole of the kidney was then fixed to the psoas muscle by a 2-0 vicryl, making anastomosis possible after an 8-mm spatulation of both sides. Anastomosis was done over a stent by interrupted sutures using 4-0 vicryl. Results: Leakage was 400 mL at the first postoperative day and ceased at the 4th day. On the control excretion urography, the kidney function was normal and a fullness of the caliceal system was seen. Conclusion: Long defect of the ureter that may occur in laparoscopic urological surgeries could be manageable laparoscopically using methods for shortening of the interval such as relocation of the kidney. Thus, a same approach as open surgeries can yield acceptable results in laparoscopic surgeries

Tunable Non-Hermitian Acoustic Filter

We propose, design, and experimentally test a non-Hermitian acoustic superlattice that acts as a tunable precise filter. The superlattice is composed of two concatenated sublattices. The first sublattice is Hermitian, while the other can be adjusted to be Hermitian or non-Hermitian. The existence of non-Hermiticity, in terms of an induced loss in the second sublattice, results in the generation of absorption resonances that appear in the reflected spectrum. This provides us with a powerful knob to absorb or reflect several frequencies at will with high accuracy. The number of filtered frequencies can be controlled by designing the resonances in the first sublattice. Our proposed tunable acoustic filter can be extended to higher-frequency ranges, such as ultrasound, and other areas, such as photonics

A rare presentation of late right coronary artery spasm following aortic valve replacement

BACKGROUND: Coronary artery spasm (CAS) is defined as a reversible, sudden epicardial coronary artery stenosis that causes vessel occlusion or near occlusion. CASE REPORT: In this article, we present a clinical case of CAS in a 48-year-old woman undergoing elective aortic valve replacement surgery for aortic stenosis. On the 3rd post-operative day, the patient suffered from chest pain and dyspnea. Emergent coronary angiography demonstrated a significant spasm of the ostium portion of the right coronary artery. CONCLUSION: This case shows that delayed coronary spasm should be considered as a cause of hemodynamic instability after valvular surgery. © 2015, Isfahan University of Medical Sciences(IUMS). All rights reserved

Identifying Urban Functional Areas and Their Dynamic Changes in Beijing: Using Multiyear Transit Smart Card Data

A growing number of megacities have been experiencing changes to their landscape due to rapid urbanisation trajectories and travel behaviour dynamics. Therefore, it is of great significance to investigate the distribution and evolution of a city’s urban functional areas over different periods of time. Although the smart card automated fare collection system (SCAFC) is already widely used, few studies have used smart card data to infer information about changes in urban functional areas, particularly in developing countries. Thus, this research aims to delineate the dynamic changes that have occurred in urban functional areas based on passengers’ travel patterns, using Beijing as a case study. We established a Bayesian framework and applied a Gaussian mixture model (GMM) derived from transit smart card data in order to gain insight into passengers’ travel patterns at station level and then identify the dynamic changes in their corresponding urban functional areas. Our results show that Beijing can be clustered into five different functional areas based on the analysis of corresponding transit station functions, namely: multimodal interchange hub and leisure area; residential area; employment area; mixed but mainly residential area; and a mixed residential and employment area. In addition, we found that urban functional areas have experienced slight changes between 2014 and 2017. The findings can be used to inform urban planning strategies designed to tackle urban spatial structure issues, as well as guiding future policy evaluation of urban landscape pattern use