Acute Respiratory Distress Syndrome and COVID-19: A Scoping Review and Meta-analysis.

Acute respiratory distress syndrome (ARDS) is a fatal complication of the new severe acute respiratory syndrome coronavirus (SARS-CoV-2), which causes COVID-19 disease. This scoping review was carried out with international, peer-reviewed research studies and gray literature published up to July 2020 in Persian and English languages. Using keywords derived from MESH, databases including Magiran, IranMedex, SID, Web of Sciences, PubMed, Embase via Ovid, Science Direct, and Google Scholar were searched. After screening titles and abstracts, the full texts of selected articles were evaluated, and those which passed the criteria were analyzed and synthesized with inductive thematic analysis. Study quality was also evaluated using a standard tool. The overall prevalence of ARDS was estimated using a random-effects model. This led to identification of 23 primary studies involving 2880 COVID-19 patients. All articles were observational with a cross-sectional, retrospective, case report, and cohort design with moderate to strong quality. The main findings showed that COVID-19-related ARDS has a high prevalence and is different to ARDS due to other etiologies. Elderly and patients with comorbidities and organ failure should be closely surveyed for respiratory organ indications for several weeks after the onset of respiratory symptoms. There is currently no definitive treatment for ARDS in COVID-19 disease, and supportive therapies and their effects are somewhat controversial.

All-silicon reconfigurable metasurfaces for multifunction and tunable performance at optical frequencies based on glide symmetry.

Dielectric metasurfaces have opened promising possibilities to enable a versatile platform in the miniaturization of optical elements at visible and infrared frequencies. Due to high efficiency and compatibility with CMOS fabrication technology, silicon-based metasurfaces have a remarkable potential for a wide variety of optical devices. Adding tunability mechanisms to metasurfaces could be beneficial for their application in areas such as communications, imaging and sensing. In this paper, we propose an all-silicon reconfigurable metasurface based on the concept of glide symmetry. The reconfigurability is achieved by a phase modulation of the transmitted wave activated by a lateral displacement of the layers. The misalignment between the layers creates a new inner periodicity which leads to the formation of a metamolecule with a new sort of near-field interaction. The proposed approach is highly versatile for developing multifunctional and tunable metadevices at optical frequencies. As a proof of concept, in this paper, we design a bifunctional metadevice, as well as a tunable lens and a controllable beam deflector operating at 1.55 µm.

Twist and Polar Glide Symmetries: an Additional Degree of Freedom to Control the Propagation Characteristics of Periodic Structures.

New high-frequency 5G and satellite communication systems require fully-metallic antennas and electromagnetic components. These components can be implemented with truncated versions of periodic structures. In order to achieve the desired performance of these future devices, it is of crucial importance to have a precise control of the propagation properties, i.e. the frequency dispersion behavior and stop-bands. Here, we demonstrate the potential use of higher symmetries to diminish the frequency dispersion of periodic structures and control the width of stop-bands with a new type of fully-metallic transmission line, which is loaded with holes on a twist-symmetric configuration. Simulated and experimental results confirm the intrinsic link between the propagation characteristics and the symmetries of a periodic structure. Additionally, we provide a definitive explanation of the recently discovered polar glide symmetry and its potential combination with twist symmetries to produce low-dispersive materials and reconfigurable stop-bands. The promising properties of these structures are demonstrated with a fully-metallic reconfigurable filter, which could be used for future high-frequency 5G and satellite communication systems.