On the Thermoelastic Martensitic Transformation in Tetragonal Zirconia

Recent evidence is summarized showing that the tetragonal ( t ) → monoclinic ( m ) martensitic transformation in ZrO₂ can occur thermoelastically in certain ZrO₂-containing ceramics, and that microcracking accompanying the transformation is more common than had previously been recognized. The implications of these new data for the conditions under which the stress-induced transformation is irreversible, and for the particle size dependence of the transformation start ( M _s), temperature, are discussed.     

An outer shell of positively charged poly(ethyleneimine) strongly increases the transfection efficiency of calcium phosphate/DNA nanoparticles

Nanoparticles with an inner core of calcium phosphate, followed by layers of DNA and calcium phosphate and an outer layer of poly(ethyleneimine) (PEI) were prepared, characterized, and tested on different cell lines (HeLa, T24, and NIH3T3). A considerable increase in transfection efficiency was found for such nanoparticles, compared to the commercial reagent Polyfect^® (a cationic dendrimer). The DNA is incorporated into the nanoparticles and protected from the attack by enzymes (nucleases) inside the cytoplasm of cells. The outer layer of PEI leads to electrosteric colloidal stabilization and gives a positive charge to the nanoparticle, which is helpful for the penetration through the negatively charged cell membrane.     

Einige offene Fragen in der Rheologie der Polymerschmelzen

Limiting ourselves to the rheology of homogeneous, isotropic polymer melts, this contribution gives a summary of important steps in the development of a rheological equation of state and draws attention to two unsolved problems which are addressed by current research. These topics are firstly the relation of the linear-viscoelastic spectrum of relaxation times to molecular structure and secondly the formulation of a rheological equation of state for general biaxial elongations.     

History of geothermal exploration in Indonesia from 1970 to 2000

Reconnaissance surveys undertaken since the 1960s show that more than 200 geothermal prospects with significant active surface manifestations occur throughout Indonesia. Some 70 of these were identified by the mid-1980s as potential high-temperature systems using geochemical criteria of discharged thermal fluids. Between 1970 and 1995, about 40 of these were explored using geological mapping, geochemical and detailed geophysical surveys. Almost half of the surveyed prospects were tested by deep (0.5–3 km) exploratory drilling, which led to the discovery of 15 productive high-temperature reservoirs. Several types of reservoirs were encountered: liquid-dominated, vapour-dominated, and a vapour layer/liquid-saturated substratum type. All three may be modified by upflows (plumes) containing magmatic fluid components (volcanic geothermal systems). Large, concealed outflows are a common feature of liquid-dominated systems in mountainous terrain. All explored prospects are hosted by Quaternary volcanic rocks, associated with arc volcanism, and half occur beneath the slopes of active or dormant stratovolcanoes. By 1995, five fields had been developed by drilling of production wells; three of them supplied steam to plants with a total installed capacity of 305 MW_e. By 2000, with input from foreign investors, the installed capacity had reached 800 MWe in six fields, but geothermal developments had stalled because of the 1997–1998 financial crisis.     

Stationäres Kriechverhalten innendruckbelasteter dünnwandiger Kreiszylinderschalen unter Berücksichtigung des orthotropen Werkstoffverhaltens und des CSD-Effektes

Zusammenfassung In Hinblick auf eine verbesserte Werkstoffausnutzung und aufgrund experimenteller Daten hochtemperaturbeanspruchter Werkstoffe sind bei der Auslegung von z.B. zylindrischen Druckkesseln und Rohrleitungen der chemischen Industrie und des Kraftwerkbaus au?er dem orthotropen Werkstoffverhalten auch unterschiedliche Druck- und Zugkriechgrenzen (creep-strength-differential effect, kurz CSD-Effekt genannt) zu berücksichtigen. Hierzu wird im Rahmen der Darstellungstheorie tensorwertiger Funktionen eine Materialgleichung vorgeschlagen, die in Verbindung mit dem Norton-Baileyschen Kriechgesetz für die Berechnung des sekund?ren Kriechverhaltens axialysmmetrisch belasteter dünnwandiger Kreiszylinderschalen zugrunde gelegt wird, wobei die vielfach in der Literatur verwendete Sandwich-Konstruktion nicht benutzt wird. Vielmehr gehen die Untersuchungen von einer einheitlichen Vollwandschale aus, deren Kriechverformung dann mit Hilfe der finiten Differenzen-Methode zusammen mit dem erweiterten Newton-Verfahren ermittelt wird. Numerische Beispielrechnungen werden für die an den Enden eingespannte offene Kreiszylinderschale, die mit Innendruck belastet ist, durchgeführt. Es zeigt sich, da? sowohl orthotropes Werkstoffverhalten wie auch unterschiedliche Druck- und Zugkriechgrenzen gro?en Einflu? auf die Verschiebungen und Biegemomente haben. Die Untersuchung wurde von der Deutschen Forschungsgemeinschaft (DFG) finanziell unterstützt, wofür an dieser Stelle gedankt sei.     

Ein biometrisches Bezahlsystem für Kaufhäuser

Biometrische Bezahlsysteme auf Identifikationsbasis stellen h?chste Ansprüche an die biometrischen Algorithmen, den F?lschungsschutz, die Rechenleistung — und an den Datenschutz. Warum das so ist, soll hier an einem Beispielkonzept erl?utert werden.     

One Question,Multiple Answers: Biochemical and Biophysical Screening Methods Retrieve Deviating Fragment Hit Lists

Fragment‐based lead discovery is gaining momentum in drug development. Typically, a hierarchical cascade of several screening techniques is consulted to identify fragment hits which are then analyzed by crystallography. Because crystal structures with bound fragments are essential for the subsequent hit‐to‐lead‐to‐drug optimization, the screening process should distinguish reliably between binders and non‐binders. We therefore investigated whether different screening methods would reveal similar collections of putative binders. First we used a biochemical assay to identify fragments that bind to endothiapepsin, a surrogate for disease‐relevant aspartic proteases. In a comprehensive screening approach, we then evaluated our 361‐entry library by using a reporter‐displacement assay, saturation‐transfer difference NMR, native mass spectrometry, thermophoresis, and a thermal shift assay. While the combined results of these screening methods retrieve 10 of the 11 crystal structures originally predicted by the biochemical assay, the mutual overlap of individual hit lists is surprisingly low, highlighting that each technique operates on different biophysical principles and conditions.