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13 pages, 9090 KiB

Open AccessArticle

Design and Simulation of Tunneling Diodes with 2D Insulators for Rectenna Switches

by Evelyn Li, Parameswari Raju and Erhai Zhao

Materials 2024, 17(4), 953; https://doi.org/10.3390/ma17040953 - 19 Feb 2024

Cited by 2 | Viewed by 2347

Rectenna is the key component in radio-frequency circuits for receiving and converting electromagnetic waves into direct current. However, it is very challenging for the conventional semiconductor diode switches to rectify high-frequency signals for 6G telecommunication (>100 GHz), medical detection (>THz), and rectenna solar cells (optical frequencies). Such a major challenge can be resolved by replacing the conventional semiconductor diodes with tunneling diodes as the rectenna switches. In this work, metal–insulator–metal (MIM) tunneling diodes based on 2D insulating materials were designed, and their performance was evaluated using a comprehensive simulation approach which includes a density-function theory simulation of 2D insulator materials, the modeling of the electrical characteristics of tunneling diodes, and circuit simulation for rectifiers. It is found that novel 2D insulators such as monolayer TiO₂ can be obtained by oxidizing sulfur-metal layered materials. The MIM diodes based on such insulators exhibit fast tunneling and excellent current rectifying properties. Such tunneling diodes effectively convert the received high-frequency electromagnetic waves into direct current. Full article

(This article belongs to the Special Issue Novel Semiconductor Devices and Nanomaterials for Energy, Power and High-Frequency Applications)

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14 pages, 1901 KiB

Open AccessEditor’s ChoiceArticle

Blood–Brain Barrier Integrity Is Perturbed in a Mecp2-Null Mouse Model of Rett Syndrome

by Giuseppe Pepe, Salvatore Fioriniello, Federico Marracino, Luca Capocci, Vittorio Maglione, Maurizio D’Esposito, Alba Di Pardo and Floriana Della Ragione

Biomolecules 2023, 13(4), 606; https://doi.org/10.3390/biom13040606 - 28 Mar 2023

Cited by 9 | Viewed by 4100

Abstract

Rett syndrome (RTT, online MIM 312750) is a devastating neurodevelopmental disorder characterized by motor and cognitive disabilities. It is mainly caused by pathogenetic variants in the X-linked MECP2 gene, encoding an epigenetic factor crucial for brain functioning. Despite intensive studies, the RTT pathogenetic mechanism remains to be fully elucidated. Impaired vascular function has been previously reported in RTT mouse models; however, whether an altered brain vascular homeostasis and the subsequent blood–brain barrier (BBB) breakdown occur in RTT and contribute to the disease-related cognitive impairment is still unknown. Interestingly, in symptomatic Mecp2-null (Mecp2^-/y, Mecp2^tm1.1Bird) mice, we found enhanced BBB permeability associated with an aberrant expression of the tight junction proteins Ocln and Cldn-5 in different brain areas, in terms of both transcript and protein levels. Additionally, Mecp2-null mice showed an altered expression of different genes encoding factors with a role in the BBB structure and function, such as Cldn3, Cldn12, Mpdz, Jam2, and Aqp4. With this study, we provide the first evidence of impaired BBB integrity in RTT and highlight a potential new molecular hallmark of the disease that might open new perspectives for the setting-up of novel therapeutic strategies. Full article

(This article belongs to the Special Issue Neurodevelopmental Disorders: Linking Genetics and Epigenetics to Disease-Related Pathways)

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8 pages, 1628 KiB

Open AccessCase Report

The First Case of Congenital Myasthenic Syndrome Caused by a Large Homozygous Deletion in the C-Terminal Region of COLQ (Collagen Like Tail Subunit of Asymmetric Acetylcholinesterase) Protein

by Nicola Laforgia, Lucrezia De Cosmo, Orazio Palumbo, Carlotta Ranieri, Michela Sesta, Donatella Capodiferro, Antonino Pantaleo, Pierluigi Iapicca, Patrizia Lastella, Manuela Capozza, Federico Schettini, Nenad Bukvic, Rosanna Bagnulo and Nicoletta Resta

Genes 2020, 11(12), 1519; https://doi.org/10.3390/genes11121519 - 18 Dec 2020

Cited by 9 | Viewed by 3429

Abstract

Congenital myasthenic syndromes (CMSs) are caused by mutations in genes that encode proteins involved in the organization, maintenance, function, or modification of the neuromuscular junction. Among these, the collagenic tail of endplate acetylcholinesterase protein (COLQ; MIM 603033) has a crucial role in anchoring the enzyme into the synaptic basal lamina. Here, we report on the first case of a patient with a homozygous deletion affecting the last exons of the COLQ gene in a CMS patient born to consanguineous parents of Pakistani origin. Electromyography (EMG), electroencephalography (EEG), clinical exome sequencing (CES), and single nucleotide polymorphism (SNP) array analyses were performed. The subject was born at term after an uneventful pregnancy and developed significant hypotonia and dystonia, clinical pseudoseizures, and recurring respiratory insufficiency with a need for mechanical ventilation. CES analysis of the patient revealed a homozygous deletion of the COLQ gene located on the 3p25.1 chromosome region. The SNP-array confirmed the presence of deletion that extended from exon 11 to the last exon 17 with a size of 19.5 Kb. Our results add new insights about the underlying pathogenetic mechanisms expanding the spectrum of causative COLQ mutations. It is relevant, considering the therapeutic implications, to apply suitable molecular approaches so that no type of mutation is missed: “each lost mutation means a baby treated improperly”. Full article

(This article belongs to the Special Issue Genetic Basis of Sensory and Neurological Disorders)

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12 pages, 4166 KiB

Open AccessArticle

Extension of an FFT-Based Beam Propagation Method to Plasmonic and Dielectric Waveguide Discontinuities and Junctions

by Adel Shaaban, Yi-Chun Du and Lotfy Rabeh Gomaa

Appl. Sci. 2019, 9(20), 4362; https://doi.org/10.3390/app9204362 - 16 Oct 2019

Cited by 5 | Viewed by 3659

Abstract

We adapted a fast Fourier transform-based Beam Propagation Method (FFT-BPM) to investigate waveguide discontinuities in plasmonic waveguides. The adaptation of the FFT-BPM to treat transverse magnetic (TM) fields requires the circumvention of two major difficulties: the mixed derivatives of the magnetic field and waveguide refractive index profile in the TM wave equation and the step-like index change at the transverse metal-dielectric boundary of the plasmonic guide and the transverse boundaries of the dielectric waveguide as well. An equivalent-index method is adopted to transform TM fields to transverse electric (TE) ones, thus enabling the benefit of the full power and simplicity of the FFT-BPM. Moreover, an appropriate smoothing function is used to approximate the step-like refractive index profile in the transverse direction. At the junction plane, we used an accurate combined spatial-spectral reflection operator to calculate the reflected field. To validate our proposed scheme, we investigated the modal propagation in a silicon waveguide terminated by air (like a laser facet in two cases: with and without a coating layer). Then we considered a subwavelength plasmonic waveguide (metal-insulator-metal MIM) butt-coupled with a dielectric waveguide, where the power transmission efficiency has been calculated and compared with other numerical methods. The comparison reveals good agreement. Full article

(This article belongs to the Special Issue Recent Advances in Plasmonics and Nanophotonics)

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