Robustness of topologically sensitive harmonic generation in laser-driven linear chains

A huge difference in the harmonic yield from the two topological phases of finite, dimerizing linear chains in laser fields has recently been observed in all-electron time-dependent density functional simulations [D. Bauer, K.K. Hansen, Phys. Rev. Lett. 120, 177401 (2018)]. In this work, we explore the robustness of the effect concerning the size of the chains, a continuous transition between the two topological phases, and disorder. A high robustness of both the degeneracy of the edge states in the topologically non-trivial phase and of the pronounced destructive interference causing a dip in the harmonic spectra in the topologically trivial phase is observed.Comment: 7 pages, 7 figures, RevTeX 4.

Steering Edge Currents through a Floquet-Topological Insulator

Periodic driving may cause topologically protected, chiral transport along edges of a 2D lattice that, without driving, would be topologically trivial. We study what happens if one adds a different on-site potential along the diagonal of such a 2D grid. In addition to the usual bulk and edge states, the system then also exhibits doublon states, analogous to two interacting particles in one dimension. A particle initially located at an edge propagates along the system's boundary. Its wavefunction splits when it hits the diagonal and continues propagating simultaneously along the edge and the diagonal. The strength of the diagonal potential determines the ratio between both parts. We show that for specific values of the diagonal potential, hopping onto the diagonal is prohibited so that the system effectively separates into two triangular lattices. For other values of the diagonal potential, we find a temporal delay between the two contributions traveling around and through the system. This behavior could enable the steering of topologically protected transport of light along the edges and through the bulk of laser-inscribed photonic waveguide arrays

High-harmonic spectra of hexagonal nanoribbons from real-space time-dependent Schr\"odinger calculations

High-harmonic spectroscopy is a promising candidate for imaging electronic structures and dynamics in condensed matter by all-optical means and with unprecedented temporal resolution. We investigate harmonic spectra from finite, hexagonal nanoribbons, such as graphene and hexagonal boron nitride, in armchair and zig-zag configuration. The symmetry of the system explains the existence and intensity of the emitted harmonics

"Making Art, Making Media, Making Change!?" Prozesse des Queerings und des Empowerments in der Arbeit mit Jugendlichen

"Wie können soziale und kulturelle Ordnungen, die eine Gesellschaft strukturieren, in der Arbeit mit Jugendlichen thematisiert werden? Wie lassen sich Machtverhältnisse und hegemoniale Deutungen infrage stellen? Das in diesem Beitrag vorgestellte Wissenschaftskommunikationsprojekt greift solche Fragestellungen auf und eröffnet in der Zusammenarbeit mit Jugendlichen Möglichkeiten der Intervention in hegemoniale Deutungsmuster durch eigene kulturelle Produktionen. Den theoretischen Rahmen bildet eine Verbindung der Perspektive des Queerings mit Ansätzen der kritischen Kunst- und Kulturvermittlung. Anhand von durchgeführten Workshops mit Jugendlichen und den im Projekt entwickelten visuellen Materialien diskutieren wir, wie durch Bildkarten die Heteronormativität sowie Zweigeschlechtlichkeit infrage gestellt sowie dominante Blickregime und hegemoniale Bildpolitiken und Zuschreibungen kritisch reflektiert werden können. Ein Queering kann demnach Handlungsräume für Jugendliche eröffnen, in denen gemeinsam gesellschaftliche und soziale Normierungen dekonstruiert sowie (macht)kritische und ermächtigende Deutungen erarbeitet werden können." (Autorenreferat)"How can social and cultural regimes that structure society be addressed when working with young people? How can power structures and hegemonic constructions be called into question? The scientific communication project presented in this article addresses these questions. In collaboration with young people, the project opens up possible interventions in hegemonic interpretations through young people's active cultural productions. The theoretical outline is shaped by queer theories - in particular the queering perspective - linked to approaches in critical art and cultural education. Based on visual material developed within the research project (image cards that question heteronormativity and gender binary) we discuss a way to critically reflect dominant regimes of the gaze and hegemonic images. We suggest that queering can open a space of agency for young people in which societal and social norms can be deconstructed and new meanings developed and envisioned." (author's abstract

How do Black Lives Matter? Zur visuellen Konstruktion von Protest in deutschsprachigen Tageszeitungen und auf Instagram

Der gewaltsame Tod von George Floyd Ende Mai 2020 löste eine globale Protestbewegung aus: Ausgehend von den USA fanden weltweit zahlreiche Kundgebungen, Demonstrationen und Mahnwachen statt, mit denen gegen Rassismus und Polizeigewalt Stellung bezogen wurde. Dieser Protest war und ist Gegenstand unterschiedlicher visueller Repräsentationen und medialer Formen, die einen wichtigen Anteil an den Bedeutungsproduktionen rund um die Protesthandlungen haben. Auf Basis einer Bildtypenanalyse der (Bild-)Berichterstattung über die Proteste in deutschsprachigen Tageszeitungen sowie der Darstellungsformen auf Instagram im Kontext von Demonstrationen im deutschsprachigen Raum setzt sich der Beitrag mit visuellen Konstruktionen von Protest auseinander und diskutiert deren Bedeutung vor dem Hintergrund gesellschaftlicher, medialer und politischer Kontexte. Es zeigen sich jeweils unterschiedlich dominierende Bildtypen: So sind in der Medienberichterstattung Bilder von Demonstrierenden als Masse vorherrschend, die die einzelnen Teilnehmer:innen nicht wahrnehmbar machen. Auf Instagram finden sich vor allem Innen-Perspektiven der Demonstrationen durch individuelle (Selbst-)Inszenierungen der Demonstrierenden. Deutlich wird zudem, dass die journalistischen Bilder die Proteste insbesondere im Hinblick auf spannungsreiche Konfliktsituationen im US-Kontext mit hohem Nachrichtenwert zeigen, während auf Instagram die Vergemeinschaftung über Gruppenbilder und damit die Inszenierung und Mobilisierung der Teilnehmenden in den Vordergrund rückt. The violent death of George Floyd at the end of May 2020 triggered a global protest movement: Starting in the US, numerous rallies, demonstrations, and vigils took place around the world, taking a stand against racism and police violence. This protest was and is subject to different visual representations and mediated expressions, which have an important share in the production of meaning around the protest actions. Based on a picture type analysis of the (image) coverage of the protests in Austrian, German and Swiss newspapers as well as on visual expressions on Instagram in the context of demonstrations in German-speaking cities, the article deals with visual constructions of protest and discusses their meaning against the background of social, media, and political contexts. Different dominant image types emerge in each case: In media coverage, for example, images of demonstrators as a mass are predominant, which make the individual participants imperceptible. On Instagram, there are mainly internal perspectives of the demonstrations through individual self-dramatizations of the demonstrators. It also becomes clear that journalistic images show protests with a high news value, especially with regard to tense conflict situations in the US context, while on Instagram the communalization via group images and thus the staging and mobilization of the participants comes to the fore

Parathyroid hormone, vitamin D, and cardiovascular disease in chronic renal failure

Parathyroid hormone, vitamin D, and cardiovascular disease in chronic renal failure.BackgroundParathyroid hormone and vitamin D have been shown to influence cardiac and vascular growth and function experimentally in human subjects with normal renal function. Because of the increased prevalence of hyperparathyroidism and altered vitamin D status in chronic renal failure, these alterations have been considered to contribute to the increased prevalence of cardiovascular disease and hypertension seen in this patient population.Methods and ResultsIn this article, we review experimental and clinical literature on the cardiovascular effects of parathyroid hormone and vitamin D and relate them to the development of cardiac and vascular dysfunction in uremia, such as: cardiomyopathy, myocardial hypertrophy, and fibrosis, as well as to myocardial ischemia; uremic glucose intolerance, dyslipidemia, and atherosclerosis; hypertension; and vascular and cardiac calcifications.ConclusionsThe hyperparathyroid state and altered vitamin D status found in uremia contribute to the cardiovascular pathology seen clinically in uremia and also to the excess mortality from cardiovascular causes found in this patient group. The therapeutic implications of these observations are also discussed

Circulating Klotho levels: clinical relevance and relationship with tissue Klotho expression

Klotho is a protein that exerts paracrine and endocrine functions. In chronic kidney disease (CKD), its expression is decreased in several tissues. This decrease probably plays important roles in various complications associated with CKD, in both a fibroblast growth factor-23 (FGF23)-dependent and an FGF23-independent manner. The clinical diagnosis of Klotho deficiency is not easy. The relevance of circulating Klotho levels, if any, needs to be adequately defined. Serum Klotho may not reflect tissue Klotho concentration

Perfusion of an isolated jejunal loop in uremic rats: Effect of sodium deoxycholate

Perfusion of an isolated jejunal loop in uremic rats: Effect of sodium deoxycholate. The effect of sodium deoxycholate (NaDC) on net transintestinal movement of electrolytes, nitrogenous substances and water was studied in anesthetized uremic rats. A jejunal loop isolated in vivo was perfused for three hours using a closed circuit. When 2 mM NaDC was present in the lumen, a significant increase (P < 0.001) in the net transfer of sodium, potassium and calcium from blood to lumen was observed when compared to control perfusion without NaDC. The net fluxes of urea, creatinine, uric acid and phosphorus from blood to lumen were expresssed in terms of intestinal clearances. Mean clearances were increased by a factor of 2.5 for urea, 6.8 for creatinine, 6.6 for uric acid and 9.7 for phosphorus. Net water flow which was directed from lumen to blood with control was near zero when 2 mM NaDC was added to the perfusate; the difference, however, was not statistically significant. The effect of NaDC on net solute transfer was reproducible in the same animal and it could be reversed by the replacement of NaDC solution with control perfusate. Gross and histological examination of the isolated loops revealed no significant alterations. The data show that NaDC increases jejunal permeability to nitrogenous substances and electrolytes in the blood-to-lumen direction along a concentration gradient.Perfusion d'une anse jéjunale isolée chez le rat urémique: Effet du désoxycholate de sodium. L'action du désoxycholate de sodium (NaDC) sur les transports de substances azotées, d'eau et d'électrolytes à travers la paroi intestinale est étudiée chez le rat urémique par perfusion, en circuit fermé, d'une anse jéjunale isolée. Chaque expérience a une durée de 3 heures et est réalisée sous anesthésie générale à l'éther. L'addition de 2 mM de NaDC au liquide perfusé augmente de façon significative (P < 0.001) le transfert net du sang vers la lumière, du sodium, du potassium et du calcium. Les flux nets d'urée, de créatinine, d'acide urique et de phosphore, exprimés sous forme de clearances intestinales, sont également augmentés de façon hautement significative (P< 0.001). Les valeurs moyennes des clearances observées chez les témoins sont multipliérs par 2.5 pour l'urée, par 6.8 pour la créatinine, par 6.6 pour l'acide urique et par 9.7 pour le phosphore. Le transfert net d'eau dirigé de la lumière vers le sang lors de la perfusion de la solution témoin, tend à s'annuler après addition de 2 mM de NaDC; toutefois la différence n'est pas significative. L'action du NaDC sur les transferts transjéjunaux est reproductible chez le même animal. Elle est réversible par substitution de la solution témoin à la solution contenant le NaDC. L'étude histologique des anses perfusées ne découvre aucune altération significative. Ces résultats montrent que le NaDC exerce un effet sur la perméabilité de la paroi jéjunale aux substances azotées et aux électrolytes et augmente leur transfert du sang vers la lumière le long d'un gradient de concentration