Glide-symmetric holey structures applied to waveguide technology: Design considerations

This article belongs to the Special Issue Antennas and PropagationRecently, there has been an increased interest in exploring periodic structures with higher symmetry due to various possibilities of utilizing them in novel electromagnetic applications. The aim of this paper is to discuss design issues related to the implementation of holey glide-symmetric periodic structures in waveguide-based components. In particular, one can implement periodic structures with glide symmetry in one or two directions, which we differentiate as 1D and 2D glide symmetry, respectively. The key differences in the dispersion and bandgap properties of these two realizations are presented and design guidelines are indicated, with special care devoted to practical issues. Focusing on the design of gap waveguide-based components, we demonstrate using simulated and measured results that in practice it is often sufficient to use 1D glide symmetry, which is also simpler to mechanically realize, and if larger attenuation of lateral waves is needed, a diagonally directed 2D glide symmetric structure should be implemented. Finally, an analysis of realistic holes with conical endings is performed using a developed effective hole depth method, which combined with the presented analysis and results can serve as a valuable tool in the process of designing novel electrically-large waveguide-based components.This work was supported by the Croatian Science Foundation (HRZZ) under the projects IP-2018-01-9753 and IP-2019-04-1064, by the Spanish Government under the projects PID2019-107688RB-C21 and TEC2016-79700-C2-R, and by the European COST Action CA18223-SYMAT

Ophthalmic Disorders in Posterior Reversible Encephalopathy Syndrome Associated with Preeclampsia

Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiological entity presented with different symptoms such as visual disturbances, headaches, seizures, severe hypertension and altered mental status. It has been recognized in a different pathological conditions, although preeclampsia/eclampsia is the most common cause of PRES. The pathogenesis of PRES is still not fully understood, but it seems that failure of cerebrovascular autoregulation causing vasogenic edema, cerebral vasoconstriction, and disruption of the blood brain barrier plays an important role. Cortical blindness, hypertensive retinopathy, serous retinal detachment (SRD), central retinal artery and vein occlusions, retinal or vitreous hemorrhages, anterior ischemic optic neuropathy (AION) and Purtscher’s retinopathy are ophthalmic disorders that may occur in PRES associated with preeclampsia. Among these, cortical blindness is the best documented complication of preeclampsia. Magnet resonance imaging (MRI) is a gold standard to establish the diagnosis of PRES because clinical findings are not sufficiently specific. Typically, there are bilateral cortical occipital lesions with hyperdensity on T2-weighted MRI. Blindness due to occipital lesions is reversible and the vision loss is usually regained within 4 h to 8 days