Area fraction quantification of ferroelectric domain orientations in BaTiO3 using piezoresponse force microscopy

Understanding the domain structure of ferroelectric ceramics is very important to develop sound knowledge of the influence of the microstructure on the macroscopic properties. To proceed in this direction, experimental tools are necessary in order to quantify the domain patterns in ferroelectrics. This study on BaTiO3 single crystals exemplifies how vector piezoresponse force microscopy can be used to obtain statistical information about domain directions

Sub-10-micrometer toughening and crack tip toughness of dental enamel

In previous studies, enamel showed indications to occlude small cracks in-vivo and exhibited R-curve behaviors for bigger cracks ex-vivo. This study quantifies the crack tip toughness (KI0, KIII0), the crack closure stress and the cohesive zone size at the crack tip of enamel and investigates the toughening mechanisms near the crack tip down to the length scale of a single enamel crystallite. The crack-opening-displacement (COD) profile of cracks induced by Vickers indents on mature bovine enamel was studied using atomic force microscopy (AFM). The mode I crack tip toughness KI0 of cracks along enamel rod boundaries and across enamel rods exhibit similar range of values: KI0,Ir=0.5-1.6MPa.m0.5 (based on Irwin’s ‘nearfield’ solution) and KI0,cz=0.8-1.5MPa.m0.5 (based on the cohesive zone solution of the Dugdale-Muskhelishvili (DM) crack model). The mode III crack tip toughness KIII0,Ir was computed as 0.02-0.15MPa.m0.5. The crack-closure stress at the crack tip was computed as 163-770MPa with a cohesive zone length and width 1.6-10.1μm and 24-44nm utilizing the cohesive zone solution. Toughening elements were observed under AFM and SEM: crack bridging due to protein ligament and hydroxyapatite fibres (micro- and nanometer scale) as well as microcracks were identified

Safety of Concomitant Potassium-sparing Diuretics in Angiotensin-converting Enzyme-inhibitor Therapy in Severe Congestive-heart-failure

The safety of concomitant use of angiotensin-converting enzyme (ACE) inhibitors and potassium-sparing diurectics (PSD) in severe heart failure remains a controversial issue. The database of the recently reported double-blind international trial, ''Xamoterol in Severe Heart Failure,'' was investigated to elucidate this question. Of 516 patients with New York Heart Association (NYHA) class III-IV, despite diuretics and ACE inhibitor therapy, 352 were randomized to xamoterol, a beta(1) partial agonist, and 164 were randomized to placebo. During the 13-week study, 28% of all patients (xamoterol, 104; placebo, 42) received potassium-sparing diuretics. All groups were comparable in hemodynamics and dose of other diuretics. At study end, patients with or without PSD showed no significant differences in serum K+ or creatinine, independent of xamoterol or placebo therapy

HRSC auf Mars Express - Photogrammetrische und kartographische Auswertungen

Die High Resolution Stereo Camera (HRSC) an Bord der europäischen Raumsonde Mars Express ist die erste Kamera einer Planetenmission, die speziell für photogrammetrische und kartographische Zwecke entwickelt wurde. Seit Januar 2004 liefert die Kamera hochaufgelöste Bilddaten der Marsoberfläche in Stereo und in Farbe. Die Bilddaten bergen ein immenses Potenzial zur Ableitung präziser Digitaler Geländemodelle (DGMs) und farbiger Orthophotos sowie zur Herstellung topographischer und thematischer Karten und weiterer Produkte. Die Arbeitsgruppe für Photogrammetrie und Kartographie des internationalen HRSC-Forscherteams beschäftigt sich mit der systematischen Erstellung von Standardprodukten aus den Bilddaten und der Verfeinerung dieser Produkte mit dem Ziel, eine höchstmögliche Qualität zu erzielen. Dieser Beitrag beschreibt einige zur Verfeinerung geeignete Arbeitsschritte und illustriert den erreichten Stand anhand einer Reihe von Beispielen