Threshold intensity factors as lower boundaries for crack propagation in ceramics

BACKGROUND: Slow crack growth can be described in a v (crack velocity) versus K(I )(stress intensity factor) diagram. Slow crack growth in ceramics is attributed to corrosion assisted stress at the crack tip or at any pre-existing defect in the ceramic. The combined effect of high stresses at the crack tip and the presence of water or body fluid molecules (reducing surface energy at the crack tip) induces crack propagation, which eventually may result in fatigue. The presence of a threshold in the stress intensity factor, below which no crack propagation occurs, has been the subject of important research in the last years. The higher this threshold, the higher the reliability of the ceramic, and consequently the longer its lifetime. METHODS: We utilize the Irwin K-field displacement relation to deduce crack tip stress intensity factors from the near crack tip profile. Cracks are initiated by indentation impressions. The threshold stress intensity factor is determined as the time limit of the tip stress intensity when the residual stresses have (nearly) disappeared. RESULTS: We determined the threshold stress intensity factors for most of the all ceramic materials presently important for dental restorations in Europe. Of special significance is the finding that alumina ceramic has a threshold limit nearly identical with that of zirconia. CONCLUSION: The intention of the present paper is to stress the point that the threshold stress intensity factor represents a more intrinsic property for a given ceramic material than the widely used toughness (bend strength or fracture toughness), which refers only to fast crack growth. Considering two ceramics with identical threshold limits, although with different critical stress intensity limits, means that both ceramics have identical starting points for slow crack growth. Fast catastrophic crack growth leading to spontaneous fatigue, however, is different. This growth starts later in those ceramic materials that have larger critical stress intensity factors

Carrier dependent ferromagnetism in chromium doped topological insulator Cr0.2BixSb1.8−xTe3Cr_{0.2}Bi_xSb_{1.8-x}Te_3

Carrier-independent ferromagnetism of chromium doped topological insulator $Bi_xSb_{2-x}Te_3$ thin films,which cannot be explained by current theory of dilute magnetic semiconductor, has been reported recently. To study if it is related to the distinctive surface state of topological insulator, we studied the structural, magnetic and transport characters of $Cr_{0.2}Bi_xSb_{1.8-x}Te_3$ single crystals. The Curie temperature $T_c$, which is determined from magnetization and anomalous Hall effect measurements by Arrott plots, is found to be proportional to $p^{1/3}$, where p is the hole density. This fact supports a scenario of RKKY interaction with mean-field approximation. This carrier density dependent nature enables tuning and controlling of the magnetic properties by applying a gate voltage in the future science researches and spintronics applications.Comment: 6 pages, 3 figure

Erfüllung der Instruktionspflicht durch Gebrauchsinformation zu Arzneimitteln

eingereicht von Mag. Dipl.Ing. Dr. Horst Franz JungwirthLiteraturverzeichnis: Blatt XII-XIIIAbstract in deutscher und englischer SpracheParis-Lodron-Universität Salzburg, Diplomarbeit, 2019(VLID)506714

Detektion von Apnoeereignissen aus Schnarchsignalen

Zur ambulanten Differenzierung zwischen primärem Schnarchen und obstruktiver Schlafapnoe wird eine kostengünstige und einfach durchführbare Diagnostik benötigt. Eine Quantifizierung der Schnarchlautstärke ist bisher nicht zufriedenstellend möglich, führt jedoch typischerweise den Patienten zum HNO-Arzt. Das Ziel dieser Studie war es, anhand von während des Schlafes aufgezeichneten Atemgeräuschen eine Software zu entwickeln, die Schnarchgeräusche quantifiziert und Atempausen detektiert.Auf der Basis von 89 Ganz-Nacht-Datensätzen von 49 Personen wurde ein Algorithmus entwickelt, der das gesamte Audiosignal mit speziellen Filtersystemen nach charakteristischen Atemgeräuschen durchsucht. Folgt auf eine Geräuschpause von mindestens 10 sec Länge ein typisches Öffnungsgeräusch, so wird diese Stelle als Apnoe-ähnliches Ereignis erkannt. Zur Ermittlung von Sensitivität und Spezifität der Software wurden die Ergebnisse dann mit den in der simultanen Polysomnographie gefundenen Atempausen verglichen. Das Ausmaß der Schnarchgeräusche wurde bezüglich ihrer Intensität und Häufigkeit quantifiziert.Zur Erzielung einer optimalen Apnoeerkennung waren Bandpassfilter und adaptive Schwellenwertbestimmung erforderlich. Bei einem Filterwert von 11 Sekunden wurde eine Sensitivität von 81,5% und eine Spezifität von 48,5% erreicht. Vereinfachte Hochpassfilter ergaben eine deutlich schlechtere Genauigkeit. Für die Beurteilung des Schnarchens wurde ein Index aus mittlerer Intensität und Schnarchhäufigkeit errechnet.Die Analyse von Atemgeräuschen im Schlaf kann erfolgreich zum Apnoescreening und zur Quantifizierung der Schnarchlautstärke genutzt werden. Weitere Modifikationen sind erforderlich, um die Genauigkeit des Systems noch zu verbessern.Supported by: teilweise unterstützt durch IFU GmbH, Lichtena

Single-dose psilocybin-assisted therapy in major depressive disorder: a placebo-controlled, double-blind, randomised clinical trialResearch in context

Summary: Background: Psilocybin has been suggested as a novel, rapid-acting treatment for depression. Two consecutive doses have been shown to markedly decrease symptom severity in an open-label setting or when compared to a waiting list group. To date, to our knowledge, no other trial compared a single, moderate dose of psilocybin to a placebo condition. Methods: In this double-blind, randomised clinical trial, 52 participants diagnosed with major depressive disorder and no unstable somatic conditions were allocated to receive either a single, moderate dose (0.215 mg/kg body weight) of psilocybin or placebo in conjunction with psychological support. MADRS and BDI scores were assessed to estimate depression severity, while changes from baseline to 14 days after the intervention were defined as primary endpoints. The trial took place between April 11th, 2019 and October 12th, 2021 at the psychiatric university hospital in Zürich, Switzerland and was registered with clinicaltrials.gov (NCT03715127). Findings: The psilocybin condition showed an absolute decrease in symptom severity of −13.0 points compared to baseline and were significantly larger than those in the placebo condition (95% CI −15.0 to −1.3; Cohens' d = 0.97; P = 0.0011; MADRS) and −13.2 points (95% CI; −13.4 to −1.3; Cohens’ d = 0.67; P = 0.019; BDI) 14 days after the intervention. 14/26 (54%) participants met the MADRS remission criteria in the psilocybin condition. Interpretation: These results suggest that a single, moderate dose of psilocybin significantly reduces depressive symptoms compared to a placebo condition for at least two weeks. No serious adverse events were recorded. Larger, multi-centric trials with longer follow-up periods are needed to inform further optimisation of this novel treatment paradigm. Funding: The study was funded by the Swiss National Science Foundation, Crowdfunding, the Swiss Neuromatrix Foundation, and the Heffter Research Institute