A numerical study on aerodynamic resonance in transonic separated flow

An ongoing numerical investigation of unsteady shock/boundary layer interaction on a 2-d supercritical airfoil in transonic flow is presented. Initially, the finitevolume URANS solver DLR-TAU is used to simulate self-sustained periodic shock oscillations well known as shock buffet. Next, emphasis is put on the fixed-point stability of the steady flow field below the shock buffet onset. Therefore the flow is perturbed in time with small sinusoidal deflections of the airfoil geometry and random impulses. With increasing angle of attack the mean flow is shown to develop a damped aerodynamic resonance, that degenerates finally towards self-amplification. The occurrence of the aerodynamic resonance is closely related to the development of shock-induced separation, accompanied by quasi-steady inverse shock motion

Aeroelastic analysis of a troposkien-type wind turbine blade

The linear aeroelastic equations for one curved blade of a vertical axis wind turbine in state vector form are presented. The method is based on a simple integrating matrix scheme together with the transfer matrix idea. The method is proposed as a convenient way of solving the associated eigenvalue problem for general support conditions

Jahn-Teller like origin of the tetragonal distortion in disordered Fe-Pd magnetic shape memory alloys

The electronic structure and magnetic properties of disordered Fe$_{x}$Pd$_{100-x}$ alloys $(50 < x < 85)$ are investigated in the framework of density functional theory using the full potential local orbital method (FPLO). Disorder is treated in the coherent potential approximation (CPA). Our calculations explain the experimental magnetization data. The origin of the tetragonal distortion in the Fe-Pd magnetic shape memory alloys is found to be a Jahn-Teller like effect which allows the system to reduce its band energy in a narrow composition range. Prospects for an optimization of the alloys' properties by adding third elements are discussed

Pressure to be Perfect: Eating Disorders in Sports

Eating disorders have become more prevalent in recent years as societal standards have gotten harsher. Typically, when people think about the type of people who develop eating disorders, the first thing that pops into their head is not athletes. There is an association between athletes and the need for great amounts of food to fuel their bodies. However, in sports such as wrestling and aesthetic sports, like gymnastics and figure skating, the emphasis of image and the pressure from their coaches can be extremely harmful to their mental health. This paper discusses specific statistics of the incidence of eating disorders in various sports, but mainly focuses on figure skating, gymnastics, and wrestling. The claim that the main driving force of eating disorders in these athletes is their coach’s comments is disputed. Rather, these disorders are caused by an internal struggle that is enhanced due to societal expectations and standards. I chose this topic because since I am going into nursing, I will have to treat many different patients with a wide range of disorders. Knowing the risk factors for these diseases and what type of living and training conditions cause these toxic thoughts and actions can help in the early detection and treatment of these diseases. In the future, health professionals, as well as the general public, should put more of an emphasis on acceptance of different body types and the prevention of eating disorders with the intention of saving many individuals from suffering

Pressure to be Perfect

Eating disorders have become more prevalent in recent years, as societal standards have gotten harsher. Typically, when non-athletes think about the type of people who develop eating disorders, they may not consider athletes to be among those that are most affected. However, in sports such as wrestling and aesthetic sports, like gymnastics and figure skating, the emphasis of image and the pressure from coaches can be extremely harmful to athletes’ mental health. This article discusses specific statistics of the incidence of eating disorders in various sports, but mainly focuses on figure skating, gymnastics, and wrestling. The claim that the main driving force of eating disorders in these athletes is their coach’s comments is disputed. Rather, these disorders are caused by an internal struggle that is enhanced due to societal expectations and standards. In the future, health professionals, as well as the general public, should put more of an emphasis on acceptance of different body types and the prevention of eating disorders with the intention of saving many individuals from suffering

Optical 3D-Nanometry to Study the Function of Biomolecular Motors in Nanotransport

A major challenge in nanotechnology is the controlled transport of cargo on the nanometer scale. A promising approach to this problem is the use of molecular motors of the cellular cytoskeleton. The aim of this work was to develop a method to characterize the behavior of filamentous nanoshuttles – specifically of motor protein-driven microtubules – in three dimensions (3-D). The main requirements to meet were low impact on the nanotransport system, high spatial and temporal resolution, and versatility. Furthermore, this method was intended to be used to address open questions in the field of nanotransport. In particular, it was firstly attempted to characterize cargo transport in a system currently favored by most studies in the field, where nanoshuttles are powered by the microtubule motor best understood so far – the plus-end-directed kinesin-1. Secondly, the goal was to further the understanding of potential counter-players of kinesin-1 in nanotransport applications - the much less well understood microtubule minus-end-directed motor proteins 22S dynein and the kinesin-14 non-claret disjunctional (ncd). A novel method to study the linear forward motion as well as the axial motion of filamentous nanoshuttles, which are driven by motors of the cell cytoskeleton, has been introduced. The method uses fluorescence interference-based 3-D nanometer tracking of quantum dots as optical probes that are attached to the nanoshuttles. While other recently reported 3-D tracking techniques based on dual-focus imaging offer similar sensitivity, the method here can be easily performed on any standard epi-fluorescence microscope, even with arc lamp illumination, and additionally holds the potential to retrieve absolute height values. It is strongly suggested that the ease of use might help to spread this valuable and versatile tool for a variety of applications, including studies of interactions between single molecules or even intramolecular changes. Specifically, 3-D tracking has been used to visualize and analyze the rotation of microtubules around their longitudinal axis when they are propelled on a motor protein-coated surface. This geometry called gliding assay is currently favored for most proof-of-principle studies that investigate the use of biomolecular motors for transport of nanoscale cargo with the goal to assemble and manipulate nanostructures. The suitability of the method has been proven for kinesin-1 gliding assays, where knowledge of properties of both, microtubules and kinesin-1, allowed a very precise prediction of microtubule rotation, which was matching the actual measured values very well. The microtubule rotation in kinesin-1 gliding assays has turned out to be robust against the attachment of small cargo in the shape of quantum dots (diameter ∼20 nm), but also against the reduction of electrostatic interactions between microtubules and kinesin-1 by cleavage of the tubulin E-hook. The situation was dramatically different when large cargo (beads with diameter of ∼3 µm) was attached to microtubules. In this case, filament rotation was stopped, but otherwise the impact on motility was surprisingly low. In particular, the velocity of the gliding microtubules only decreased to a negligible degree. This shows that in principle microtubules driven by processive motors like kinesin-1 can make flexible, responsive and effective molecular shuttles for nanotransport applications. In addition, the results might indicate that in vivo kinesin-1 molecules, which transport cargo along microtubules, can likewise flexibly respond to an axial force by deviating from their path parallel to the protofilament axes. Two microtubule minus-end-directed motors that might be employed to counteract kinesin-1 in engineered nanotransport systems are dynein and ncd. Both motors have been found to be capable of generating torque causing short-pitched microtubule rotation in gliding motility assays. The results for 22S dynein helped to resolve controversial findings of earlier reports about the ability of 22S dynein to generate torque. However, it turned out difficult to establish conditions where the movement of the dynein-driven nanoshuttles was homogeneous and reproducible. In contrast, motility in ncd gliding assays looks much more promising. The obtained results supported previous reports of torque generation by ncd. Moreover, a strong dependence of rotational pitches of gliding microtubules on ATP concentration was found. The reason could be that ncd motors in the nucleotide-free microtubule-bound state impede the forward movement of gliding microtubules stronger than the axial motion. To fully understand the nature of this effect, further research is required. Most likely, this will substantially contribute to the understanding of ncd function in vivo. Furthermore, the possibility of tuning the rotation of microtubules acting as nanoshuttles might provide a means to increase control of processes like cargo-loading and unloading.Eine große Herausforderung auf dem Gebiet der Nanotechnologie ist der kontrollierte und präzise Transport von nanoskaligen Objekten. Der Einsatz von molekularen Motoren des zellulären Zytoskeletts hat sich dabei als vielversprechender Ansatz erwiesen. Ziel der hier vorgelegten Arbeit war die Entwicklung einer Methode, um das Verhalten von filamentartigen Nanotransportern - speziell von Mikrotubuli, die durch Motorproteine über Oberflächen bewegt werden - in drei Dimensionen (3-D) zu charakterisieren. Die Hauptkriterien waren dabei eine geringe Störung des zu untersuchenden Systems, hohe räumliche und zeitliche Auflösungen sowie die generelle Anwendbarkeit für Einzelmolekülstudien. Ein weiteres Ziel war es, die entwickelte Methode zur Beantwortung offener Fragen bezüglich des Nanotransports mittels Zytoskelett-basierter Motoren einzusetzen. Insbesondere sollte das System aus Mikrotubuli und dem Motorprotein Kinesin-1, welches für die meisten aktuellen Studien zum Thema Nanotransport herangezogen wird, untersucht werden. Schließlich sollten neue Erkenntnisse über weniger gut erforschte Motorproteine, speziell über 22S Dynein und das Kinesin-14 „Non-claret disjunctional“ (Ncd), gewonnen werden. Beide Motoren könnten in Nanotransportsystemen als Gegenspieler von Kinesin-1 agieren. In der vorliegenden Arbeit wird eine neuartige, auf Fluoreszenz-Interferenz basierende 3-D Nanometertrackingmethode beschrieben. Auf deren Grundlage wird es möglich, die Bewegung von einzelnen fluoreszenten Partikeln nahe einer reflektierenden Oberfläche mit einer Genauigkeit im Nanometerbereich zu verfolgen. Im Vergleich zu anderen kürzlich vorgestellten 3-D Techniken, welche auf bifokaler optischer Mikroskopie basieren und ähnliche Genauigkeiten zulassen, ist die hier vorgestellte Methode mit deutlich geringerem Aufwand auf der Basis eines herkömmlichen Epi-Fluoreszenzmikroskops umsetzbar. Dabei kann die Fluoreszenzanregung wahlweise mit einer Bogenlampe oder einem Laser erfolgen. Weiterhin besteht die Möglichkeit, nicht nur Differenzwerte (wie bei bifokaler Mikroskopie), sondern absolute Werte in der Höhendimension zu messen. Im Ergebnis wurde ein mit geringem Aufwand umsetzbares, gleichwohl hochgradig genaues und vielseitig einsetzbares Werkzeug geschaffen, welches ideal für Studien der Interaktionen von Einzelmolekülen oder auch intramolekularer Dynamik geeignet ist. Mit Hilfe der hier vorgestellten 3-D Trackingmethode wurden die Rotationen von Mikrotubuli um ihre Längsachse während des Gleitens auf mit Motorproteinen besetzten Oberflächen analysiert. Diese Geometrie wird derzeit bevorzugt in Studien eingesetzt, welche den Einsatz von biomolekularen Motoren für den Transport von nanoskaligen Objekten untersuchen und das Ziel verfolgen, Nanostrukturen zu erzeugen und zu manipulieren. Die Ergebnisse zu Rotationen von Mikrotubuli, welche über mit Kinesin-1 besetzte Oberflächen bewegt werden, sind konsistent mit (i) der Eigenschaft von Kinesin-1 sich entlang der Protofilamente von Mikrotubuli zu bewegen und (ii) der Superhelixstruktur von in vitro rekonstituierten Mikrotubuli. Dies belegt die Eignung der Methode für die Charakterisierung von Nanotransportsystemen. Die Rotation von Mikrotubuli, welche durch Kinesin-1 angetrieben werden, hat sich sowohl beim Transport von kleinen Objekten in Form von Quantum Dots (Durchmesser ca. 20 nm) als auch bei der Reduktion elektrostatischer Wechselwirkungen zwischen Kinesin-1 und Mikrotubuli durch Verdau der Tubulin-C-Termini als stabil erwiesen. Ein vollkommen anderes Bild ergab sich für den Transport von großen Objekten (Durchmesser ca. 3 µm). In diesem Fall wurde die Rotation der Filamente angehalten. Unerwarteterweise war jedoch die Vorwärtsbewegung der Mikrotubuli und insbesondere deren Geschwindigkeit kaum betroffen. Dies zeigt, daß Mikrotubuli, welche von prozessiven Motoren wie Kinesin-1 angetrieben werden, das Potential zu responsiven, flexiblen und effektiven molekularen Shuttles besitzen. Außerdem weisen die Ergebnisse darauf hin, daß Kinesin-1-Moleküle, welche in vivo Frachten entlang von Mikrotubuli transportieren, auf seitwärts gerichtete Kräfte reagieren können, indem sie von ihrem intrinsisch vorgegebenen Pfad parallel zur Protofilamentachse des Mikrotubulus abweichen. Zwei Motoren, die sich im Gegensatz zu Kinesin-1 in Richtung des Minus-Endes von Mikrotubuli bewegen, sind 22S Dynein und Ncd. Sie sind somit als Gegenspieler von Kinesin-1 in Nanotransportsystemen prädestiniert. Beide Motoren können, ebenso wie Kinesin-1, die Translokation von Mikrotubuli über Oberflächen sowie damit verbundene Rotationen von Mikrotubuli verursachen. Im Gegensatz zu Kinesin-1 tritt die Rotation unabhängig von einer Superhelixstruktur der Mikrotubuli auf. Die Ergebnisse für 22S Dynein lösen Widersprüche zwischen früheren Studien auf, indem sie belegen, daß dieser Motor Rotationen von Mikrotubuli erzeugen kann. Jedoch scheint es unter Verwendung von 22S Dynein nicht möglich zu sein, Bedingungen zu schaffen, unter welchen sich Mikrotubuli in geeigneter Weise als Nanoshuttles homogen und reproduzierbar bewegen. Der Einsatz von Ncd ist hier deutlich erfolgversprechender. Die in diesem Falle erlangten Erkenntnisse bezüglich der Erzeugung von Rotationen von Mikrotubuli decken sich mit früheren Studien. Ein bislang unbekannter, bemerkenswerter Effekt ist dabei ein Rückgang in der Länge der Rotationsperioden mit sinkender ATP-Konzentration. Die mit dem heutigen Wissensstand über den mechanochemischen Zyklus von Ncd konsistente Erklärung ist, daß Ncd-Motoren im nukleotidfrei an Mikrotubuli gebundenen Zustand die Vorwärtskomponente der Bewegung von gleitenden Mikrotubuli stärker hemmen als die Rotationskomponente. Möglicherweise kann die sich hieraus ergebende Möglichkeit der Regulierung der Rotation von Mikrotubuli dazu eingesetzt werden, das Be- und Entladen von Nanoshuttles zu steuern

"Isadora Icarus": The Mythic Unity of Erica Jong's Fear of Flying

Paper by Jane Chance Nitzsch