An N band interferometric survey of the disks around post-AGB binary stars

It is now well established that FGK post-AGB stars that are surrounded by both hot and cold dust (as derived from the spectral energy distribution), are almost always part of a binary system with $100 < P_{orb} < 5000$~days. The properties and long-term stability of the dust emission requires it to arise from a gas- and dust-rich, puffed-up and (semi-)stable circumbinary disk. This interpretation has been confirmed with spatially resolved observations at a range of wavelengths for various individual objects. Here I present the first results of the first mid-IR interferometric survey of this class of objects. Our sample comprises 18 sources, most of which are confirmed binaries and which cover a range in IR excess. Our analysis clearly shows the compactness of the dust structures in these systems. We perform a statistical comparison with radiative transfer disk models, showing that most objects are indeed continuous disks from the sublimation radius outwards.Comment: To appear in the proceedings of "Physics of evolved stars 2015 - A conference dedicated to the memory of Olivier Chesneau" (http://poe2015.sciencesconf.org/

Modelling the motion of a cell population in the extracellular matrix

The paper aims at describing the motion of cells in fibrous tissues taking into account of the interaction with the network fibers and among cells, of chemotaxis, and of contact guidance from network fibers. Both a kinetic model and its continuum limit are described

Modeling cell movement in anisotropic and heterogeneous network tissues

Cell motion and interaction with the extracellular matrix is studied deriving a kinetic model and considering its diffusive limit. The model takes into account of chemotactic and haptotactic effects, and obtains friction as a result of the interactions between cells and between cells and the fibrous environment. The evolution depends on the fibre distribution, as cells preferentially move along the fibre direction and tend to cleave and remodel the extracellular matrix when their direction of motion is not aligned with the fibre direction. Simulations are performed to describe the behavior of ensemble of cells under the action of a chemotactic field and in presence of heterogeneous and anisotropic fibre networks

Structure and function of SARS-CoV-2 polymerase

Coronaviruses use an RNA-dependent RNA polymerase (RdRp) to replicate and express their genome. The RdRp associates with additional non-structural proteins (nsps) to form a replication–transcription complex (RTC) that carries out RNA synthesis, capping and proofreading. However, the structure of the RdRp long remained elusive, thus limiting our understanding of coronavirus genome expression and replication. Recently, the cryo-electron microscopy structure of SARS-CoV-1 RdRp was reported. Driven by the ongoing COVID-19 pandemic, structural data on the SARS-CoV-2 polymerase and associated factors has since emerged at an unprecedented pace, with more than twenty structures released to date. This review provides an overview of the currently available coronavirus RdRp structures and outlines how they have, together with functional studies, led to a molecular understanding of the viral polymerase, its interactions with accessory factors and the mechanisms by which promising antivirals may inhibit coronavirus replication

A Classification of Musical Scales Using Binary Sequences

Every beginning music student has gone through the four main musical scales: major, natural minor, harmonic minor, and melodic minor. And some might wonder, why those four and not five, or six, or just three? Here we show that a mathematical classification can be used to identify these scales as representatives of certain scale families. Moreover, the classification reveals another scale family, which is much less known: the harmonic major scale. We find that each scale family contains exactly seven scales, which include the modes (dorian, phrygian,...) and other scales such as the Romanian, Gypsi or Hindu-scales. Besides of giving a complete classification of proper heptatonic scales, we also emphasize the pedagogical potential of these {0,1}-representations of scales, as these can help students to navigate and remember complicated scales

Price Transmission and Market Integration in Swiss Agricultural and Food Markets

Diese Dissertation umfasst drei Studien zu Preistransmission und Marktintegration in Schweizer Agrar- und Lebensmittelmärkten. Der Artikel "Protecting the Swiss milk market from foreign price shocks: Public border protection vs. quality differentiation" analysiert räumliche oder horizontale Preistransmission zwischen der Europäischen Union und der Schweiz am Beispiel des Milchmarkts. Milch ist das wichtigste Agrarprodukt der Schweiz und verschiedene Milchprodukte unterliegen unterschiedlichen Handelshemmnissen und Grenzschutz-Instrumenten. Während für Milchprodukte wie Butter und Milchpulver weiterhin Zölle und Zollkontingente gelten, ist der Käsehandel mit der EU vollständig liberalisiert. Um zu verstehen, wie sich solche unterschiedlichen Schutzniveaus auf die räumliche Preistransmission auswirken, analysieren wir die Preistransmission zwischen Deutschland und der Schweiz für mehrere Produkte auf Großhandelsebene und für Rohmilcherzeugerpreise. Wir stellen fest, dass nicht das Niveau des Grenzschutzes den Grad und die Geschwindigkeit der Preistransmission bestimmt, sondern die qualitative Differenzierung der Schweizer Produkte. Die Preise für zollgeschützte Milchprodukte werden von der deutschen Preisentwicklung beeinflusst, die Käsepreise jedoch nicht. Auch auf Erzeugerebene sind die Milchpreise für die Käseverarbeitung weniger stark an die ausländischen Preise gebunden als die Milchpreise für die industrielle Milchverarbeitung. Unsere Ergebnisse legen nahe, dass für kleine einkommensstarke Länder wie die Schweiz die Förderung hochwertiger Produkte und damit die Verringerung der internationalen Substituierbarkeit den internationalen Preisdruck mehr mindert als den Schutz durch Zölle. Der Artikel "Vertical Price Transmission in Swiss Dairy and Cheese Value Chains" ergänzt diese Analyse durch die Untersuchung der vertikalen Preistranmission innerhalb der Schweiz. In der Schweiz gibt es getrennte Wertschöpfungsketten für Milch- und Käseprodukte, die sich hinsichtlich Branchenkonzentration, Governanceform und Produkteigenschaften unterscheiden. Wir analysieren, wie Milchpreise entlang dieser verschiedenen Wertschöpfungsketten weitergegeben werden. Anhand detaillierter Preisdaten auf Produzenten-, Großhandels-, Export- und Einzelhandelsebene untersuchen wir die vertikale Preistransmission im Schweizer Milch- und Käsemarkt mithilfe von asymmetrischen Vektorautoregressiven und Fehlerkorrekturmodellen. Im Gegensatz zu einem Grossteil der vorhandenen Literatur finden wir fast keine langfristigen Preisbeziehungen und keine signifikanten Asymmetrien zwischen den verschiedenen Wertschöpfungsebenen und Produkten und diskutieren die möglichen Gründe. Die dritte Studie "Market Integration and Market Efficiency under Seasonal Tariff Rate Quotas" geht über die Analyse reiner Preisinformationen hinaus, indem Daten zu Preisen, Handelskosten und Handelsströmen kombiniert werden. Die Schweiz wendet saisonale Zollkontingente für den Import vieler Obst- und Gemüsesorten während der inländischen Erntezeit an. Es ist jedoch nicht bekannt, wie sich dieses System auf Preise, Handelsmuster und räumliche Effizienz mit seinen Handelspartnern auswirkt. Aus diesem Grund analysieren wir die Beziehung zwischen italienischen und schweizerischen Tomatenpreisen und testen die physische Marktintegration und die räumlichen Gleichgewichtsbedingungen im Zeitverlauf. Wir verwenden detaillierte, transaktionsbasierte Daten zu Handelsströmen und Handelskosten und schätzen ein erweitertes Parity Bounds Modell. Wir stellen fest, dass die Märkte in der Sommersaison, wenn Zollkontingente angewandt werden, ineffizient sind. Während Kontingentinhaber positive Renten erhalten, sind die marginalen Renten für Importeure ohne Kontingentanteile negativ. Dies verhindert Handelsströme oberhalb der von den Zollkontingenten zugelassenen Einfuhrmenge; das Instrument wirkt also während der administrierten Sommerperiode wie eine bindende Importquote. In der nicht-administrierten Periode, wenn keine einheimischen Produkte zu schützen sind, sind die Märkte dagegen in einem Wettbewerbsgleichgewicht und durch grosse Handelsströme räumlich integriert. Wir folgern, dass saisonale Zollkontingente ein wirksames Instrument sind, um die inländische Produktion gegen konkurrierende Importe zu schützen, und somit deren Absatz zu stabilen Preisen zu gewähren. Dies geschieht jedoch auch höchst ineffiziente Weise, da Importeure Renten abschöpfen können, und zwar zulasten von Konsumenten, die während der Schweizer Tomatensaison hohe Preise im Einzelhandel zahlen.This PhD thesis comprises three papers on price transmission and market integration in Swiss agricultural and food markets. In the paper "Protecting the Swiss milk market from foreign price shocks: Public border protection vs. quality differentiation" we focus on spatial price transmission between the European Union and Switzerland. The milk market is of strategic importance for Switzerland, and the country applies a number of different border protection policies for milk products. While dairy products such as butter and milk powder are still subject to tariffs and tariff rate quotas, cheese trade with the EU is fully liberalized. To understand how such different levels of protection affect spatial price transmission, we analyze price transmission between Germany and Switzerland for several products at the wholesale level, and for raw milk producer prices. We find that not the level of border protection determines the degree and speed of price transmission, but rather the qualitative differentiation of the Swiss products. While prices of tariff-protected dairy products are influenced by German price developments, cheese prices are not. Also at the producer level, milk prices for cheese processing are less strongly linked to foreign prices than milk prices for industrial dairy production. Our results suggest that for small high-income countries such as Switzerland, promoting high-quality products and hence reducing international substitutability alleviates international price pressure more than protection via tariffs. The paper "Vertical Price Transmission in Swiss Dairy and Cheese Value Chains" complements this analysis by investigating vertical price transmission within Switzerland. In Switzerland, there are separated value chains for dairy and cheese products, which differ in terms of industry concentration, value chain governance, and product characteristics. We analyze how milk prices are passed on along these different value chains. Using detailed price data on farm-gate, wholesale, export, and retail levels, we apply asymmetric Vector Autoregressive and Vector Error Correction Models to study vertical price transmission in Swiss dairy and cheese chains. Contrary to most existing literature, we find almost no long-run price relationships and no significant asymmetries between the different stages and products and discuss the potential reasons. Finally, the paper "Market Integration and Market Efficiency under Seasonal Tariff Rate Quotas" goes beyond the analysis of price information by combining data on prices, trade costs and trade flows. Switzerland applies seasonal tariff rate quotas (TRQs) for the import of many fruits and vegetables during the domestic harvest season. Yet, it is not well understood how this system affects prices, trade patterns and spatial efficiency with its trade partners. Therefore, we analyse the relationship between Italian and Swiss tomato prices and test for physical market integration and spatial equilibrium conditions over time. We use detailed, transaction-based data on trade flows and trade costs and estimate an extended parity bounds model. We find that in the summer season, when TRQs are in place, markets are inefficient. While quota holders receive positive rents, the marginal rents for importers without quota shares are negative. This inhibits trade flows above the in-quota import quantity allowed by TRQs. Hence, despite leading to inefficiencies and creating rents for importers, seasonal TRQs are an effective policy instrument to protect domestic production against competing imports

Discourse and Cooperative Learning in the Math Classroom

In this action research study of my 6th grade math classroom I investigated the effects of increased student discourse and cooperative learning on the students’ ability to explain and understand math concepts and problem solving, as well as its effects on their use of vocabulary and written explanations. I also investigated how it affected students’ attitudes. I discovered that increased student discourse and cooperative learning resulted in positive changes in students’ attitudes about their ability to explain and understand math, as well as their actual ability to explain and understand math concepts. Evidence in regard to use of vocabulary and written explanations generally showed little change, but this may have been related to insufficient data. As a result of this research, I plan to continue to use cooperative learning groups and increased student discourse as a teaching practice in all of my math classes. I also plan to include training on cooperative learning strategies as well as more emphasis on vocabulary and writing in my math classroom