Statistical mechanics of strong and weak point vortices in a cylinder

The motion of one-hundred point vortices in a circular cylinder is simulated numerically and compared with theoretical predictions based on statistical mechanics. The novel aspect considered here is that the vortices have greatly different circulation strengths. As envisaged by Onsager, such an arrangement leads to a substantial amplification of statistical trends such as the preferred clustering of the strong vortices in either same-signed or oppositely-signed pairs, depending on the overall energy level. A microcanonical ensemble based on the conserved total energy E and angular momentum M for the whole vortex system is then used, in which the few strong vortices are treated as a subsystem in contact with a reservoir composed of the many weak vortices. It is shown that allowing for the finite size of this reservoir is essential in order to predict the statistics of the strong vortices accurately. Notably, this goes beyond the standard canonical ensemble with positive or negative temperature. A certain approximation is then shown to allow a single random sample of uniformly distributed vortex configurations to be used to predict the strong vortex statistics for all possible values of E and M. Detailed predictions for distribution functions are then made for comparison with three simulated cases of near-zero M and low, neutral, or high E. It is found that the statistical mechanics predictions compare remarkably well with the numerical results, including a prediction of vortex accumulation at the cylinder wall for low values of E.Comment: In press, Physics of Fluid

Uncertainty quantification in graph-based classification of high dimensional data

Classification of high dimensional data finds wide-ranging applications. In many of these applications equipping the resulting classification with a measure of uncertainty may be as important as the classification itself. In this paper we introduce, develop algorithms for, and investigate the properties of, a variety of Bayesian models for the task of binary classification; via the posterior distribution on the classification labels, these methods automatically give measures of uncertainty. The methods are all based around the graph formulation of semi-supervised learning. We provide a unified framework which brings together a variety of methods which have been introduced in different communities within the mathematical sciences. We study probit classification in the graph-based setting, generalize the level-set method for Bayesian inverse problems to the classification setting, and generalize the Ginzburg-Landau optimization-based classifier to a Bayesian setting; we also show that the probit and level set approaches are natural relaxations of the harmonic function approach introduced in [Zhu et al 2003]. We introduce efficient numerical methods, suited to large data-sets, for both MCMC-based sampling as well as gradient-based MAP estimation. Through numerical experiments we study classification accuracy and uncertainty quantification for our models; these experiments showcase a suite of datasets commonly used to evaluate graph-based semi-supervised learning algorithms.Comment: 33 pages, 14 figure

Der Duft der großen weiten Welt

Nach der «Freßwelle», der «Kleiderwelle», der «Einrichtungswelle» bringt das Wirtschaftswunder in Westdeutschland die «Reisewelle». Auf anderer Basis als zur KdF-Zeit wird der Urlaub im Ausland eine Selbstverständlichkeit. Der Slogan vom Duft der großen weiten "Welt ist weit über den Zusammenhang mit der Zigarettenwerbung hinaus ein Ausdruck dessen, was die Westdeutschen um 1960 schätzen.Digital imag

strongSwan Android 4 Client with Endpoint Assessment

Zielsetzung „Bring your own device“ (BYOD), ein grosses Thema der modernen Computerzeit. Smartphones sind nicht mehr nur für Businessleute wichtig, vielmehr ist das Smartphone zu einem Alltagsgegenstand geworden. Klar ist auch, dass die Funktionalitäten des intelligenten Telefons genutzt werden wollen. So gibt es viele Firmennetze, welche die Benutzer mit ihren eigenen Geräten ins Netz lassen. Das Ziel dieser Studienarbeit ist, die bestehende Implementation der strongSwan – Android App so zu erweitern, dass eine Validierung der Endgeräte möglich wird. Zu diesem Zweck sollen die Implementationsteile in C und Java dahingehend erweitert werden, dass eine dynamische Validierung ermöglicht wird. Der Server sendet dem Client sogenannte Attribute-Requests, welche vom Client verarbeitet und beantwortet werden. Sollte ein Gerät gewisse Kriterien nur zum Teil oder gar nicht erfüllen, so wird die Verbindung geschlossen oder in eine Quarantänezone verschoben, wo nur eingeschränkter Zugriff möglich ist. Dies erlaubt Benutzern den Zugriff auf ein Firmennetzwerk mit ihren eigenen Geräten, ohne die Sicherheit des Netzwerks zu gefährden. Ergebnis Mittels des Trusted Network Connect Protokolls (PA-TNC [1]) kommuniziert der Android Client mit einem Server. Der Server selbst dient als Zertifizierungsstelle und hält die „Integrity Measurement Verifier“ (IMV) bereit, welche die Resultate des Clients überprüfen. Der Client selbst hat einen „Integrity Measurement Collector“ (IMC) welcher die Messung im Auftrag des Servers vornimmt. Ein Teil der Implementation erfolgte in Java, ein anderer in C. Die native (C) Implementation ist zuständig für die Kommunikation mit dem Server (IMVs) und die Weiterleitung von Nachrichten an die Java- Implementation. Mit dem AndroidIMC ist ein generischer Java-Manager entstanden, welcher die einzelnen Messungen im Auftrag des nativen Codes durchführt. Dieser kann nach Belieben erweitert werden. Werden die Messungen durchgeführt, so wird vom Server zum Schluss des Verbindungsvorganges und nach den verschiedensten Abklärungen ein Resultat zum Client gesandt. Ist dieses Positiv, so darf der Client die Verbindung aufbauen. Ein neues GUI-Element zeigt dem Benutzer den Status der Validierung an. Dieser ändert sich nach jedem Verbindungsversuch und widerspiegelt die letzte Messung. Der Benutzer kann diese Resultate stets anzeigen und sich darüber informieren, wie diese Fehler zu beseitigen sind

Making fibrous plant meat with less refined, starch-rich crops

The reduction of meat consumption is considered an effective way to increase the sustainability of one’s diet. Meat analogues can help consumers to eat less meat and more plant-based foods. It is suggested that meat analogues should mimic the texture and taste of real meat as much as possible. The texture, specifically the fibrous structure of meat, can be re-created from plant-based ingredients in thermo-mechanical processes such as High Moisture Extrusion (HME) or High Temperature Shear Cell (HTSC). Currently, mainly proteins from soy, wheat and to a lesser extent pea are used in meat analogues, which are obtained after intense fractionation processes. However, it is now recognized that new and less processed ingredients have to be incorporated to prevent monocultures and to increase the sustainability of meat analogues. In this dissertation, we aim to explore the potential of faba beans as a new ingredient for fibrous meat analogues and unveil the effect of using less refined ingredients. The latter introduces more starch to the final product.In Chapter 2, we described the suitability of Faba bean Protein Isolate (FPI) as an ingredient in gluten-containing fibrous meat analogues and compared it to Soy Protein Isolate (SPI) and Pea Protein Isolate (PPI). Swelling experiments revealed a universal interaction of gluten and the legume proteins, where the gluten formed a continuous network and exerted a pressure on the legume phase, which prevented it from swelling. Furthermore, we found that gluten formed fibrous structures on its own, while SPI, PPI and FPI did not. We concluded that gluten was responsible for the formation of fibrous structures and the non-gluten protein acted as a filler. A gluten content of 50% (d.b.) was necessary to form fibrous structures, which confirmed that gluten needs to form a continuous network to form a fibrous structure.To increase sustainability of the ingredients, we moved from isolates to concentrates. However, less refined raw ingredients sometimes lack the alleged functional properties for making fibrous food products. A high water holding capacity (WHC) is considered one of the functional properties relevant for fiber formation in the HTSC. In Chapter 3, we therefore studied the WHC of Faba bean Protein Concentrate (FPC), a mildly refined faba bean product. We found that the WHC of FPC was lower than that of Soy Protein Concentrate, but could be increased via a dry heat treatment. The dry heat treatment partially denatured the native protein in FPC and thereby increased the hydrophobicity of the protein. This led to aggregation, a lower protein solubility in water and finally an increased WHC of FPC.Faba beans contain a significant amount of starch. In Chapter 4 we reviewed the literature on the use of starch in meat and meat analogues. We discovered that purified starch is used as a functional ingredient in meat and meat analogues, often in modified form. We called this exogenous starch, because it is added to the recipe. Starch that is endogenously present in the original matrix of less refined or whole crop ingredients is rarely added deliberately, minimizing the reviewable literature findings in this regard. We proposed a new approach in which endogenous starch can be modified ‘in-situ”, using conventional starch modification processes as a route to obtain functional ingredients. The effect of starch on textural properties such as hardness and springiness of fibrous products has been investigated empirically, while deductive studies on the effect of starch on the mechanism of fibre formation are still lacking.This gap in the literature was taken as motivation for the work described in Chapter 5, where we explored the effect of starch on the formation of fibrous structures in the HTSC when mixed with gluten. We found that low amylose content starch (Amioca Starch - AS) disrupted fibre formation due to its inability to form a gel, while intermediate amylose content starch (Maize Starch – MS) and high amylose content starch (Hylon VII) could be applied in the same way as protein isolates. Pre-gelatinizing MS improved its structuring potential and resulted in remarkable textural properties, most notably a large anisotropy of the Young’s modulus that was previously not seen with protein ingredients.Chapters 2, 3 & 5 revealed that the interaction of the ingredients with water played a large role in the formation of fibrous structures. In Chapter 6 we therefore quantified the water content of the protein and the starch phase of doughs at room temperature and gels at high temperatures. The samples were made from air-classified faba bean fractions, but we modelled the water content of the individual starch and protein water phases. For the doughs, data for modelling was extracted from the partial sorption isotherms of doughs containing different amounts of starch, protein and water. The water content of the protein phase in the gels was modelled using the denaturation temperature of legumin. We found that starch takes up less water than protein at room temperature. The often described swelling of starch before initial gelatinization did not increase the water content of the starch. However, upon protein gelation, the starch had absorbed more water, thereby lowering the water content in the protein. We concluded that the water had migrated from the protein to the starch phase after the initial gelatinization of starch but before or during the gelation of protein.The dissertation was concluded with a general discussion of the results in Chapter 7. We reviewed the role of gluten as an agent of the formation of fibrous structures and revealed new insights regarding zein as a possible alternative. We discussed the use of faba beans as novel ingredient, as well as the opportunities and challenges that stem from using less refined ingredients. A list of ingredient requirements for fillers in fibrous structures was presented, along with a list of desirable properties. We highlighted the importance of water distribution in protein-starch blends and suggested thermal pre-treatments as a tool to improve the functionality of ingredients. To round out the dissertation, a new approach in the search for suitable new ingredients for fiber formation was proposed

Banking on Participation. Exploring the Co-production of Population and Public in Swiss Biobanking

This paper explores enactments of participation in two Swiss biobanking configurations, a cohort biobank and a general biobank. It sheds light on the role of Personalized Health endeavours, in which biobanks play a crucial role. In order to contribute to the understanding of the role of participation in biomedical research dynamics, the analysis focuses on the processes of co-production of identity and biobanks (Tupasela et al. 2015). It documents the overlaps between the population – providers of biological samples – and the public, the collective who is expected to give its opinion on issues raised by the reconfiguration of the research/healthcare interface. It shows that modalities of participation impact the potential scientific value derived from the biobank’s population, but also that the reconfiguration of the research/healthcare interface at the core of biobanking contributes to the current blooming of discourses and practices of participation. It argues that the forms of collective identity shaped through participation as population and/or public, exceed formal strategies of participatory governance and may play an even more important role in the shaping of biobanking configurations