The first instability in spherical Taylor-Couette flow

In this paper continuation methods are applied to the axisymmetric Navier-Stokes equations in order to investigate how the stability of spherical Couette flow depends on the gap size σ. We find that the flow loses its stability due to symmetry-breaking bifurcations and exhibits a transition with hysteresis into a flow with one pair of Taylor vortices if the gap size is sufficiently small, i.e. if σ ≤σ_B. In wider gaps, i.e. for σ_B σ_F. The numbers σ_B and σ_F are computed by calculating the instability region of the spherical Couette flow and the region of existence of the flow with one pair of Taylor vortices

Progress in linear stability methods for design applications

Despite recent developments in the understanding of boundary layer receptivity and non-linear stability, linear stability methods remain the state-of-the-art in industry for aerodynamic design and analysis. A conceptual model is presented to explain why the eN approach is used and the circumstances under which it might be expected to work. The paper reviews the latest results and conclusions from a series of recent collaborative projects, supported by the European Commission, which have contributed significantly to the confidence and ease with which linear stability methods can now be used for design. Recent experimental work has allowed local, linear stability N-factor correlations to be derived, for the first time in Europe, for HLF systems. A range of N-factor integration strategies have been evaluated during the analysis of these experiments. The use of non-local theory has demonstrated a significant effect on crossflow N-factors which warrants further, systematic correlation of these N-factors against experiment. The authors feel that the use of advanced non-linear transition prediction techniques can be used to provide guidance in the avoidance of pathological situations in the design of commercial HLF systems, but that linear stability theory is today's best tool for design purposes. Database methods derived from linear theory can considerably accelerate the design process provided that they are validated appropriately against stability computations

Detection of transient generalized and mutual phase synchronization by clustering and application by single brain signals

The present work introduces an analysis framework for the detection of metastable signal segments in multivariate time series. It is shown that in case of linear data these segments represent transient generalized synchronization, while metastable segments in circular data reflect transient mutual phase synchronization. We propose a single segmentation approach for both types of data considering the space-time structure of the data. Applications to both event-related potentials and single evoked potentials obtained from an auditory oddball experiment reveal the lack of the component P300 in an experimental condition, indicates attention effects in component N100 and shows dramatic latency jitters in single trials. A comparison of the proposed method to a conventional index of mutual phase synchronization demonstrates the superiority of considering space-time data structures

Progress Toward Efficient Laminar Flow Analysis and Design

A multi-fidelity system of computer codes for the analysis and design of vehicles having extensive areas of laminar flow is under development at the NASA Langley Research Center. The overall approach consists of the loose coupling of a flow solver, a transition prediction method and a design module using shell scripts, along with interface modules to prepare the input for each method. This approach allows the user to select the flow solver and transition prediction module, as well as run mode for each code, based on the fidelity most compatible with the problem and available resources. The design module can be any method that designs to a specified target pressure distribution. In addition to the interface modules, two new components have been developed: 1) an efficient, empirical transition prediction module (MATTC) that provides n-factor growth distributions without requiring boundary layer information; and 2) an automated target pressure generation code (ATPG) that develops a target pressure distribution that meets a variety of flow and geometry constraints. The ATPG code also includes empirical estimates of several drag components to allow the optimization of the target pressure distribution. The current system has been developed for the design of subsonic and transonic airfoils and wings, but may be extendable to other speed ranges and components. Several analysis and design examples are included to demonstrate the current capabilities of the system

Is multilingualism linked to a higher tolerance of ambiguity?

The present study investigates the link between multilingualism and the personality trait Tolerance of Ambiguity (TA) among 2158 mono-, bi- and multilinguals. Monolinguals and bilinguals scored significantly lower on TA compared to multilinguals. A high level of global proficiency of various languages was linked to higher TA scores. A stay abroad of more than three months was also linked to higher TA although the effect levelled off after one year. Growing up in a multilingual family had no effect on TA. These findings show that a high level of multilingualism makes individuals more at ease in dealing with ambiguity, but we acknowledge that a higher level of TA can also strengthen an individual’s inclination to become multilingual

High Speed Laser Micro Drilling for Aerospace Applications

AbstractTo realize a reduced fuel consumption of civil jet transport aircrafts, hybrid laminar flow control (HLFC) is a key technology in aerospace industry. For drag reduction caused by boundary layer suction, small holes at the leading edges of the aircraft wings and tail planes are needed. Much effort has been spend in drilling of small holes into different materials. Nevertheless, the economically drilling of small holes in the range of 50 to 100μm in diameter on large areas is up to date crucial. Apart from processing time this is also due to the demand of close tolerances in case of suction holes. Additionally, minimization of the thermal distortion when drilling large areas gets more challenging. This paper deals with the transfer of the laser drilling process to an adequate system technology for the fabrication of large suction inserts using a short pulsed fiber laser with a power of 200W at a pulse repetition rate of 200kHz. The laser combined with a galvanic scanner and a plane field optic leads to a precise and fast drilling over an area of 100mm x 100mm. Using a precise stage several of these drilling fields can be placed side by side to machine the complete panel area. The amount of drilled through-going holes and their roundness as well as the distortion of the panel is influenced by the applied drilling sequence and energy input. As a result, round micro holes down to 30μm in diameter can be produced with a drilling rate of more than 400 holes per second in 0.8mm thick titanium sheets

Molecular analysis of pattern recognition receptors involved in sensing human rhinoviruses by dendritic cells

Infektionen durch humane Rhinoviren (HRV) sind die häufigste Ursache für Erkältungen. Sie bedingen aber auch eine Prädisposition für bakterielle Infektionen sowie Verschlimmerungen von Asthmaanfällen. Die pathogenen Mechanismen von HRV Infektionen, die jene Komplikationen verursachen, werden hingegen schlecht verstanden. Dendritische Zellen (DC) sind die wichtigsten Antigen-präsentierenden Zellen (APC) des Immunsystems. Mit Hilfe von viral pattern recognition Rezeptoren (VPRR) können DC evolutionär hoch konservierte molekulare Muster von Viren erkennen. Die nach solcher Aktivierung resultierenden reifen DC besitzen die Fähigkeit, eine adaptive Immunantwort einzuleiten. HRV sind kleine, ikosahedrische, nicht-Membran-umhüllte (+)-Strang Einzelstrang RNS (ssRNA) Viren. Wir haben kürzlich gezeigt, dass HRV14, ein Mitglied der major group HRV, die akzessorische Funktion von DC herunterreguliert. HRV14 behandelte DC reifen nicht und weisen durch die Expression inhibitorischer Oberflächenmoleküle eine stark herabgesetzte Kapazität zur T-Zell Proliferationsstimulation auf. HRV replizieren in DC nicht. DC sind aber mit unterschiedlichen VPRR ausgestattet, die virale ssRNA (vssRNA) erkennen. Aus diesem Grund war unsere Fragestellung, ob die genomische RNS von HRV alleine - als potentielles danger signal - die Kapazität hat, DC Reifung zu induzieren. Diese Studie zeigt, dass HRV ssvRNA durch DC erkannt wird, was zu einer starken Typ 1 Interferon (IFN) Antwort führt. Diese IFN Induktion wurde auch in einem Luciferase Reporter Assay unter Verwendung von RIG-I transfizierten HEK Zellen gefunden. Dieses Ergebnis identifiziert RIG-I als potentiellen VPRR für HRV RNA. Dennoch konnten wir in DC, im Gegensatz zu HEK Zellen, keine NFκB Aktivierung, die für die DC Reifung wesentlich ist, durch ssvRNA feststellen. Weiters wurden typische Reifungsmarker wie CD83, sowie die Freisetzung der proinflammatorischen Cytokine TNFα, IL-12 und IL6 nicht induziert. Letzlich konnte ssvRNA in einer allo-mixed leukocyte reaction keine erhöhte T-Zell stimulatorische Kapazität von DC bewirken. HRV ssvRNA ist also nur ein semi-danger Signal für DC: Trotz Erkennung, induziert ssvRNA keine DC Reifung.Human rhinovirus (HRV) infections are the most prevalent cause of the common cold but may also induce a predisposition for bacterial infections as well as exacerbations of asthma. The pathogenic mechanisms of HRV infections leading to such complications are still poorly understood. Dendritic cells (DC) are the main professional antigen presenting cells of the immune system. With the help of viral pattern recognition receptors (VPRR) DC can recognize evolutionary highly conserved molecular patterns of viruses. Once activated, the resulting mature DC are capable of inducing adaptive immune responses. HRV, are small, icosahedral, nonenveloped (+)-strand single-stranded RNA (ssRNA) viruses. We have previously shown that HRV14, a member of the major group rhinoviruses, specifically down-modulates the accessory function of monocyte-derived-DC (DC). HRV14-treated DC do not mature and show a strongly diminished T-cell stimulatory capacity due to the upregulation of inhibitory surface molecules. HRV do not replicate in DC. However, DC are well equipped with different single-stranded viral RNA (ssvRNA) detecting VPRR. Therefore, we wondered whether the genomic RNA of HRV alone, as a potential danger signal, has the capacity to induce DC maturation. This study shows that HRV ssvRNA is recognized by DC, causing a strong Type I interferon (IFN) response. A profound IFN induction was also observed in a luciferase reporter assay using RIG-I-transfected HEK cells, identifying RIG-I as a potential VPRR for HRV RNA. However, in DC, in contrast to HEK cells, ssvRNA failed to induce NFκB activation, which is required for proper maturation induction. Furthermore, markers of maturation like the surface molecule CD83 were absent, and the proinflammatory cytokines TNFα, IL-12 and IL-6 were not produced. In addition, HRV ssvRNA failed to induce an increased T-cell stimulatory capacity in an allo-mixed leukocyte reaction. Therefore, ssvRNA of HRV is only a semi-danger signal for DC: Despite recognition, ssvRNA fails to induce proper DC maturation

Reasoning about weight in great apes (Pan troglodytes, Pan paniscus, Gorilla gorilla gorilla, Pongo pygmaeus abelii) and 3- to -4-year-old children

Im Laufe des letzten Jahrhunderts ist auf dem Gebiet der visuellen Fähigkeiten von Primaten viel Forschungsarbeit geleistet worden, von einer physiologischen (Kremers 2005) und kognitiven Perspektive (Tomasello & Call 1997). Im Gegensatz dazu ist über die Relevanz von nicht-visuellen Informationen bei Primaten wenig bekannt. Eine Vielzahl von Pflanzen und Früchten ändern ihre Farbe und andere visuelle Eigenschaften während des Reifungsprozesses nur wenig wenn überhaupt. In Anbetracht dessen, sollte die Verwendung anderer Sinne auch eine wichtige Rolle spielen um relevante Informationen zur Nahrungsmittelauswahl zu erlangen. Povinelli (2004) vertritt die Ansicht, dass Schimpansen auf sichtbare Eigenschaften von Objekten angewiesen sind und kein Verständnis von nicht sichtbaren Objekteigenschaften wie zum Beispiel Gewicht haben. Nach der Meinung des Autors ist die menschliche Sprache eine wesentliche Vorbedingung um die Wahrnehmung von Gewicht mit einem Konzept von Gewicht zu verbinden. Im Rahmen meiner Doktorarbeit habe ich untersucht, ob Menschenaffen und 3-4 jährige Kinder ein Verständnis von Gewicht als nichtvisuelle Objekteigenschaft besitzen. Desweiteren bin ich der Frage nachgegangen, ob sie in der Lage sind anhand von Gewichtsinformationen Schlussfolgerungen zu ziehen. In der ersten Studie wurde untersucht, ob andere Menschenaffen als Schimpansen eine Aufgabe zur Gewichtsdiskrimination lösen können. In der Folgestudie wurden alle Menschenaffenarten getestet. Konkret habe ich geprüft, ob Menschenaffen Gewichtsinformation in einer Situation verwenden können, in welcher Gewicht in einer kausalen Beziehung zur Lösung der Aufgabe steht. Abschließend wollte ich untersuchen, ob 3-4 jährige Kinder in der Lage sind die Relevanz von Gewicht als physikalische Kraft an einer Balkenwaage zu erkennen. Die Ergebnisse zeigen, dass Menschenaffen Gewichtsunterschiede von Objekten wahrnehmen können und Gewicht als Information zum Lösen einer kausalen Problemstellung verwenden können. Menschliche Kinder unter 4 Jahren haben noch keine klaren Erwartungen hinsichtlich der Rolle von Gewicht auf das Verhalten einer Balkenwaage entwickelt. Diese Resultate legen nahe, dass die menschliche Sprache nicht die Vorbedingung für ein abstraktes Verständnis von Gewicht ist.Over the last century much work has been done on the visual abilities of primates, both from a physiological (Kremers 2005) and cognitive perspective (Tomasello & Call 1997). In contrast, very little is known about the relevance of non-visual information in primates. Given that a variety of plants and fruits change color or other visual features only little if at all during maturation, other senses might also play an important role in acquiring relevant information for food selection. Povinelli (2004) suggested that chimpanzees rely strictly upon observable features and have no understanding of unobservable entities such as weight. In the authors opinion human language is essential to connect perception of weight with a concept of weight. My PhD centered on the study of great apes´ (orangutans, bonobos, gorillas and chimpanzees) and 3- to -4-year-old children’s understanding of weight as a non- visual- based object property and whether they are genuinely able to reason about weight. In the first experiment I evaluated how great apes, other than chimpanzees, perform in a weight discrimination task. In a next step I investigated whether these apes and a group of naive chimpanzees would be able to use weight information in a situation in which weight has a causal relation with the solution of the task. Finally, I wanted to assess whether 3-to-4-year-old children are able to correctly encode the relevance of weight as a physical force in influencing the behavior of a balance- scale. The results showed that great apes are sensitive to differences in weight and can use weight information in a problem-solving task. Human children younger than 4 years have not yet developed clear expectations regarding the role of weights on the movements of a balance-scale. These findings suggest that human language is not mandatory for an abstract understanding of weight

On allowable surface tolerances for laminar flow

The classical criteria on allowable surface imperfections for laminar flow are slightly modified and applied to an hybrid-laminar-flow-control (HLFC) wing