Active topolectrical circuits

The transfer of topological concepts from the quantum world to classical mechanical and electronic systems has opened fundamentally new approaches to protected information transmission and wave guidance. A particularly promising technology are recently discovered topolectrical circuits that achieve robust electric signal transduction by mimicking edge currents in quantum Hall systems. In parallel, modern active matter research has shown how autonomous units driven by internal energy reservoirs can spontaneously self-organize into collective coherent dynamics. Here, we unify key ideas from these two previously disparate fields to develop design principles for active topolectrical circuits (ATCs) that can self-excite topologically protected global signal patterns. Realizing autonomous active units through nonlinear Chua diode circuits, we theoretically predict and experimentally confirm the emergence of self-organized protected edge oscillations in one- and two-dimensional ATCs. The close agreement between theory, simulations and experiments implies that nonlinear ATCs provide a robust and versatile platform for developing high-dimensional autonomous electrical circuits with topologically protected functionalities.Comment: 10 pages, 4 figures, includes supplementary material. This version adds 2D experiment

Topolectrical circuits

Invented by Alessandro Volta and F\'elix Savary in the early 19th century, circuits consisting of resistor, inductor and capacitor (RLC) components are omnipresent in modern technology. The behavior of an RLC circuit is governed by its circuit Laplacian, which is analogous to the Hamiltonian describing the energetics of a physical system. We show that topological semimetal band structures can be realized as admittance bands in a periodic RLC circuit, where we employ the grounding to adjust the spectral position of the bands similar to the chemical potential in a material. Topological boundary resonances (TBRs) appear in the impedance read-out of a topolectrical circuit, providing a robust signal for the presence of topological admittance bands. For experimental illustration, we build the Su-Schrieffer-Heeger circuit, where our impedance measurement detects a TBR related to the midgap state. Due to the versatility of electronic circuits, our topological semimetal construction can be generalized to band structures with arbitrary lattice symmetry. Topolectrical circuits establish a bridge between electrical engineering and topological states of matter, where the accessibility, scalability, and operability of electronics synergizes with the intricate boundary properties of topological phases.Comment: 11 pages, 4 figure

Junctional adhesion molecule (JAM)-C deficient C57BL/6 mice develop a severe hydrocephalus

The junctional adhesion molecule (JAM)-C is a widely expressed adhesion molecule regulating cell adhesion, cell polarity and inflammation. JAM-C expression and function in the central nervous system (CNS) has been poorly characterized to date. Here we show that JAM-C−/− mice backcrossed onto the C57BL/6 genetic background developed a severe hydrocephalus. An in depth immunohistochemical study revealed specific immunostaining for JAM-C in vascular endothelial cells in the CNS parenchyma, the meninges and in the choroid plexus of healthy C57BL/6 mice. Additional JAM-C immunostaining was detected on ependymal cells lining the ventricles and on choroid plexus epithelial cells. Despite the presence of hemorrhages in the brains of JAM-C−/− mice, our study demonstrates that development of the hydrocephalus was not due to a vascular function of JAM-C as endothelial re-expression of JAM-C failed to rescue the hydrocephalus phenotype of JAM-C−/− C57BL/6 mice. Evaluation of cerebrospinal fluid (CSF) circulation within the ventricular system of JAM-C−/− mice excluded occlusion of the cerebral aqueduct as the cause of hydrocephalus development but showed the acquisition of a block or reduction of CSF drainage from the lateral to the 3rd ventricle in JAM-C−/− C57BL/6 mice. Taken together, our study suggests that JAM-C−/− C57BL/6 mice model the important role for JAM-C in brain development and CSF homeostasis as recently observed in humans with a loss-of-function mutation in JAM-C

Zielnetzplanung CH light: Schlussbericht

Zielnetzplanung (ZNP) ist ein wichtiges Hilfsmittel für die kosteneffiziente Weiterentwicklung der Verteilnetze im Zeithorizont der Nutzungsdauer der Betriebsmittel. Insbesondere für die Integration von dezentralen, erneuerbaren Energien, Speichertechnologien und der Elektromobilität in Verteilnetzen wird die ZNP ein wichtiger Baustein für die Umsetzung der Energiewende sein. Die derzeit bei grösseren Netzbetreibern angewendete ZNP-Methodik benötigt Grundlagendaten und Berechnungs tools, welche für kleinere und mittlere Verteilnetzbetreiber (VNB) zu aufwendig sind. Im Projekt «Zielnetzplanung CH light» wurden Hilfsmittel für die Zielnetzplanung auf den Netzebenen 5 bis 7 entwickelt. Sie stehen allen Verteilnetzbetreibern unentgeltlich zur Verfügung. Ein wesentlicher Output des Projektes ist das anwenderfreundliche, auf Excel basierte Software-Tool «ZNP light». Es erlaubt anhand der beschriebenen Methodiken eine einfache technische und betriebswirtschaftliche Bewertung verschiedener Zielnetzvarianten. Ein zweites Excel-Tool namens «ZNP-Profile» liefert, basierend auf vordefinierten Szenarien, Leistungsprofile für die Lastflussberechnungen. Die bei Projektende vorhandenen Anleitungen und Werkzeuge bieten eine wertvolle Grundlage zur Durchführung einer effizienten und effektiven Zielnetzplanung bei kleinen und mittelgrossen Verteilnetzbetreibern.Le plan directeur est un outil important pour un développement efficient et durable des réseaux de distribution, ainsi que pour la durée d'utilisation de l'équipement. En particulier, pour l'intégration des technologies décentralisées, renouvelables, du stockage d'énergie et de la mobilité électrique. Dans les réseaux de distribution, le plan directeur est un élément important pour la mise en œuvre de la transition énergétique. La méthodologie qui est appliquée par les grands opérateurs exige des données de base et des outils de calcul qui sont malheureusement trop coûteux pour des petits et moyens opérateurs de réseaux de distribution. Le projet «Zielnetzplanung CH light» a permis de développer des outils pour la planification à des niveaux de réseau 5 à 7. Ces outils sont gratuitement disponibles pour tous les opérateurs de réseaux de distribution. Un des outputs clé est l'outil logiciel «ZNP light». Avec la méthodologie décrite, il permet d'appliquer une évaluation technique et économique simple pour différents réseaux. Basé sur des scenarios prédéfinis, un second outil logiciel avec le nom «ZNP-Profile» fournit des profils de puissance pour les calculs de flux de charge. Les instructions et outils qui sont disponibles à la fin du projet forment une base précieuse pour la mise en œuvre d'un plan directeur efficace et effectif chez des petits et moyens opérateurs de réseaux de distribution.Target grid planning is an important concept for a cost-efficient development of distribution grids within the time horizon of the equipment life time. Taking into account the integration of distributed renewables, storage technology and e-mobility into the future distribution grids, target grid planning will be an important element for an efficient implementation of the Swiss energy strategy 2050 on the lower voltage levels. The methods used by large grid companies for target grid planning today require data sets and calculation tools, which are too costly and not adequate for small- and medium-sized distribution grid operators. During the project «Target grid planning CH light», different aids for the target grid planning on the grid levels 5 to 7 were developed. They are available free of charge for all distribution grid operators. A key output of the project is the user-friendly, Excel-based software tool «ZNP light». Using the methods described, it allows a simple technical and economic evaluation of different target grid variants. Based on predefined scenarios, a second Excel tool named «ZNP-Profile» provides power profiles for the load flow calculations. The manuals and tools established during the project are a valuable basis for efficient and effective target grid planning for small and medium-sized distribution grid operators

Intracellular hemin is a potent inhibitor of the voltage-gated potassium channel Kv10.1

Heme, an iron-protoporphyrin IX complex, is a cofactor bound to various hemoproteins and supports a broad range of functions, such as electron transfer, oxygen transport, signal transduction, and drug metabolism. In recent years, there has been a growing recognition of heme as a non-genomic modulator of ion channel functions. Here, we show that intracellular free heme and hemin modulate human ether à go-go (hEAG1, Kv10.1) voltage-gated potassium channels. Application of hemin to the intracellular side potently inhibits Kv10.1 channels with an IC50 of about 4 nM under ambient and 63 nM under reducing conditions in a weakly voltage-dependent manner, favoring inhibition at resting potential. Functional studies on channel mutants and biochemical analysis of synthetic and recombinant channel fragments identified a heme-binding motif CxHx8H in the C-linker region of the Kv10.1 C terminus, with cysteine 541 and histidines 543 and 552 being important for hemin binding. Binding of hemin to the C linker may induce a conformational constraint that interferes with channel gating. Our results demonstrate that heme and hemin are endogenous modulators of Kv10.1 channels and could be exploited to modulate Kv10.1-mediated cellular functions