Ab-initio simulation and experimental validation of beta-titanium alloys

In this progress report we present a new approach to the ab-initio guided bottom up design of beta-Ti alloys for biomedical applications using a quantum mechanical simulation method in conjunction with experiments. Parameter-free density functional theory calculations are used to provide theoretical guidance in selecting and optimizing Ti-based alloys with respect to three constraints: (i) the use of non-toxic alloy elements; (ii) the stabilization of the body centered cubic beta phase at room temperature; (iii) the reduction of the elastic stiffness compared to existing Ti-based alloys. Following the theoretical predictions, the alloys of interest are cast and characterized with respect to their crystallographic structure, microstructure, texture, and elastic stiffness. Due to the complexity of the ab initio calculations, the simulations have been focused on a set of binary systems of Ti with two different high melting bcc metals, namely, Nb and Mo. Various levels of model approximations to describe mechanical and thermodynamic properties are tested and critically evaluated. The experiments are conducted both, on some of the binary alloys and on two more complex engineering alloy variants, namely, Ti-35wt.%Nb-7wt.%Zr-5wt.%Ta and a Ti-20wt.%Mo-7wt.%Zr-5wt.%Ta.Comment: 23 pages, progress report on ab initio alloy desig

Tempo in Mahler as Recollected by Natalie Bauer-Lechner

There is no standard concert hall repertoire in which lack of sensitivity to tempo and Expression marks is more damaging than Mahler\u27s symphonies. Their coherence lies in a series of tonal relationships emphasized by thematic connections, and tempo provides the medium through which these connections are made. Drawing on the writings of Mahler\u27s friend Natalie Bauer-Lechner, the importance of tempo in Mahler\u27s works is illustrated by the composer\u27s own words

Industries and the bank lending effects of bank credit demand and monetary policy in Germany

This paper presents evidence on the industry effects of bank lending in Germany and identifies the industry effects of bank lending associated with changes in monetary policy and industryspecific bank credit demand. To this end, we estimate individual bank lending functions for 13 manufacturing and non-manufacturing industries and five banking groups using quarterly bank balance sheet and bank lending data for the period 1992:1-2002:4. The evidence from dynamic panel data models shows that industry-specific bank lending growth predominantly responds to changes in industry-specific bank credit demand rather than to changes in monetary policy. In fact, conclusions regarding the bank lending effects of monetary policy are very sensitive to the choice of industry. The empirical results lend strong support to the existence of industry effects of bank lending. Because industries are a prominent source of variation in the bank lending effects of bank credit demand and monetary policy, the paper concludes that the industry composition of bank credit portfolios is an important determinant of bank lending growth and monetary policy effectiveness. --Monetary policy transmission,credit channel,industry structure,dynamic panel data

Vertical Distribution of Meroplankton and Bivalve Competition in a Well-Mixed Estuary

If we want to understand how meroplankton utilize the water column and how their vertical distribution may influence horizontal advection, it is important to study their behavior in the various environments where they exist. In a well-mixed system with physical cues dampened, and no vertical layering, these organisms will have to depend on environmental cues such as light, tidal current, and tide cycle, as well as their own swimming ability to migrate vertically. Plankton and water samples were collected at three depths (near surface, midwater, near bottom) during the summers of 2013 and 2014 from sites within the main channel of the Intracoastal Waterway. Six taxonomic groups were collected including polychaetes, bivalves, gastropods, barnacles, tunicates, and crabs, and fell into one of three categories of vertical distribution. Certain preferences for vertical distribution, and habitat, of sessile invertebrates can increase, or provide refuge from, competition. To assess the potential competition for spatial resources between native and nonnative bivalves in the Guana Tolomato Matanzas estuary, settlement collectors with settlement plates at different depths were deployed for one month periods during the summers of 2013 and 2014 at two main channel sites and two feeder creek sites. Competition would likely be highest subtidally and within the main channel due to all species occurring in that habitat in higher numbers than the feeder creek

Diversity in the narrative-moralitas relationship of Robert Henryson\u27s The Morall Fabillis of Esope the Phyrgian

Most of the recent critical comment of Robert Henryson’s The Moral Fabillis of Esop The Phrygain has been directed toward the relation between the two parts of each fable: (1) the narrative itself and (2) the moralitas, an allegorical interpretation which follows each narrative. The moralitas interpretations do not always follow expected patterns and, in fact, may seem highly artificial and contrived when compared to the more natural and familiar animal stories which make up the fables themselves. It is probably this element of the unexpected in Henryson’s interpretations of the thirteen fables that has called attention to the fable-moralitas relationship

Site-selective protein modification via disulfide rebridging for fast tetrazine/trans-cyclooctene bioconjugation

An inverse electron demand Diels–Alder reaction between tetrazine and trans-cyclooctene (TCO) holds great promise for protein modification and manipulation. Herein, we report the design and synthesis of a tetrazine-based disulfide rebridging reagent, which allows the site-selective installation of a tetrazine group into disulfide-containing peptides and proteins such as the hormone somatostatin (SST) and the antigen binding fragment (Fab) of human immunoglobulin G (IgG). The fast and efficient conjugation of the tetrazine modified proteins with three different TCO-containing substrates to form a set of bioconjugates in a site-selective manner was successfully demonstrated for the first time. Homogeneous, well-defined bioconjugates were obtained underlining the great potential of our method for fast bioconjugation in emerging protein therapeutics. The formed bioconjugates were stable against glutathione and in serum, and they maintained their secondary structure. With this work, we broaden the scope of tetrazine chemistry for site-selective protein modification to prepare well-defined SST and Fab conjugates with preserved structures and good stability under biologically relevant conditions

Kristallmechanik in Vielkristallen - Crystal Mechanics in Polycrystals

Bei der plastischen Verformung von Polykristallen ändern die Kristallite zumeist ihre Orientierung. Auch bei homogener gradientenfreier äußerer Krafteinwirkung kommt es aufgrund des anisotropen Verhaltens des Materials und aufgrund von Reibung zumeist zu Orientierungsänderungen und Kornfragmentierungen. Heterogenitäten bezüglich Spannung, Dehnung und kristallographischer Orientierung auf Kornebene sind die Folge. Neben dem grundlegenden Erkenntnisgewinn bei der Untersuchung lokaler Kornmechanik ist die Aufklärung des Auftretens und die Systematik solcher Heterogenitäten aus verschiedenen Gründen von Interesse: Erstens, strukturelle und funktionelle Bauelemente werden zunehmend miniaturisiert. Mit der Verkleinerung solcher metallischen Bauteile verringert sich das homogenisierende Zusammenwirken mehrerer Kristalle und somit die Möglichkeit zur gezielten Einstellung einer texturbedingten Quasi–Isotropie. Bei kleinen Abmessungen wird der einkristalline Anisotropieeinfluss dominant und somit auch Gradienten innerhalb einzelner Kristallite. Zweitens, in Bauteilen sehr geringer Abmessungen zumindest in einer Richtung, wie beispielsweise Drähte und dünne Folien, können solche Heterogenitäten zu Schädigungsoder Versagensursachen werden. Drittens, die Quantifizierung der elastisch-plastischen Kornwechselwirkung bei der Polykristallverformung ist ein wichtiger Baustein zur Verbesserung und Verifizierung von kristallplastischen Homogenisierungstheorien. Solche Theorien dienen zur statistischen Vorhersage der plastischen Anisotropie (Fließort-Theorie) und von Verformungstexturen nach der Taylor-Bishop-Hill-Theorie. Viertens, mikromechanische Untersuchungsmethoden, wie die Nano-Härteprüfung, werden zunehmend zur Charakterisierung von mikromechanischer Effekte verwendet. Solche Untersuchungsverfahren werden allerdings derzeit in der Regel ohne Berücksichtigung der Kristallkinematik des betroffenen Korns durchgeführt. Die Orientierungsabhängigkeit dieser Messung bleibt dabei unberücksichtigt. Allein der kinematische Anteil an der Einzelkristallhärte kann aber durchaus einen Faktor zwei ausmachen (z.B. durch Variation des Taylorfaktors) und verdient daher nähere Berücksichtigung. Ähnliche Argumente gelten für alle Werkstoffprüfungen, bei denen Mikrostrukturelemente in einer ähnlichen Größenordnung wie die Probenabmessungen vorliegen. Fünftens, Bereiche lokaler Heterogenitäten bezüglich Spannung und Dehnung sind stets auch Gebiete hoher Keimdichte bei homogenen und heterogenen Phasenumwandlungen

Preconditions to ground based GPS water vapour tomography

The GPS water vapour tomography is a new technique which provides spatially resolved water vapour distributions in the atmosphere under all weather conditions. This work investigates the information contained in a given set of GPS signals as a precondition to an optimal tomographic reconstruction. The spatial distribution of the geometric intersection points between different ray paths is used to estimate the information density. Different distributions of intersection points obtained from hypothetical GPS networks with varying densities of GPS stations are compared with respect to the horizontal and vertical resolution of a subsequent tomographic reconstruction. As a result some minimum requirements for continuously operating extensive GPS networks for meteorological applications are given