Whirling skirts and rotating cones

Steady, dihedrally symmetric patterns with sharp peaks may be observed on a spinning skirt, lagging behind the material flow of the fabric. These qualitative features are captured with a minimal model of traveling waves on an inextensible, flexible, generalized-conical sheet rotating about a fixed axis. Conservation laws are used to reduce the dynamics to a quadrature describing a particle in a three-parameter family of potentials. One parameter is associated with the stress in the sheet, aNoether is the current associated with rotational invariance, and the third is a Rossby number which indicates the relative strength of Coriolis forces. Solutions are quantized by enforcing a topology appropriate to a skirt and a particular choice of dihedral symmetry. A perturbative analysis of nearly axisymmetric cones shows that Coriolis effects are essential in establishing skirt-like solutions. Fully non-linear solutions with three-fold symmetry are presented which bear a suggestive resemblance to the observed patterns.Comment: two additional figures, changes to text throughout. journal version will have a wordier abstrac

Higher wages or lower expectations? Adjustments of German firms in the hiring process

Labour shortages are a field of research that has been investigated quite thoroughly. The reactions of firms facing problems during the hiring process are, however, largely neglected in empirical literature. Our research will fill this empirical gap and shed light on the question of whether reactions according to the neoclassical theory or to the Reder Hypothesis are more common in reality. We make use of a unique dataset, the German Job Vacancy Survey, which allows us to observe the entire operational recruitment process including potential problems, concessions made by firms as well as characteristics of the hired candidate, the vacancy and the firm itself. Whether concessions are made mainly depends on the labour market situation and on the specific hiring problems of a firm. We also find that firms are rather flexible in their reactions in accordance with the specific hiring problem. Therefore, both theories seem to apply in reality.Das Thema Arbeitskräfteengpässe wurde bereits umfangreich erforscht, allerdings blieben dabei die Reaktionen von Betrieben mit Schwierigkeiten im Einstellungsprozess weitestgehend unberücksichtigt. Unsere Forschung soll diese Lücke schließen und Aufschluss darüber geben, ob auf dem deutschen Arbeitsmarkt eher die neoklassische Theorie oder aber die Reder-Hypothese Anwendung findet. Für unsere Analysen greifen wir auf die IAB-Stellenerhebung zurück. Dieser Datensatz ermöglicht es den gesamten Rekrutierungsprozess zu beobachten, einschließlich der Probleme die dabei auftreten können, mögliche Zugeständnisse seitens der Unternehmen als auch personen-, stellen- und firmenspezifische Charakteristika. Ob Zugeständnisse gemacht werden hängt vor allem von der Arbeitsmarktlage und den spezifischen Einstellungsproblemen eines Unternehmens ab. Die Ergebnisse zeigen auch, dass die Unternehmen entsprechend den spezifischen Einstellungsproblemen flexibel reagieren. Daraus lässt sich ableiten, dass beide Theorien Anwendung auf dem deutschen Arbeitsmarkt finden

Manage Your \u27Blind Flight\u27 - The Optimal Timing for IT Project Re-Evaluation

As the value of an IT project can change over time, management is in blind flight about the state of the project until the project has been re-evaluated. As each evaluation causes costs, continuous evaluation is economically unreasonable. Nevertheless, the blind flight should not take too long, because the project value can considerably deviate from its initial estimation and high losses can occur. To trade off costs of re-evaluation and potential loss of project value, this paper will elaborate upon an economic model that is able to determine the optimal time until re-evaluation considering the risky cash flows of a project. Based on a simulation, we find that it makes good economic sense to optimize the interval of re-evaluation. Therefore, companies are able to avoid financial loss caused by evaluating too early as well as hazarding project value caused by evaluating too late

Using New Camera-Based Technologies for Gait Analysis in Older Adults in Comparison to the Established GAITRite System

Various gait parameters can be used to assess the risk of falling in older adults. However, the state-of-the-art systems used to quantify gait parameters often come with high costs as well as training and space requirements. Gait analysis systems, which use mobile and commercially available cameras, can be an easily available, marker-free alternative. In a study with 44 participants (age ≥ 65 years), gait patterns were analyzed with three different systems: a pressure sensitive walkway system (GAITRite-System, GS) as gold standard, Motognosis Labs Software using a Microsoft Kinect Sensor (MKS), and a smartphone camera-based application (SCA). Intertrial repeatability showed moderate to excellent results for MKS (ICC(1,1) 0.574 to 0.962) for almost all measured gait parameters and moderate reliability in SCA measures for gait speed (ICC(1,1) 0.526 to 0.535). All gait parameters of MKS showed a high level of agreement with GS (ICC(2,k) 0.811 to 0.981). Gait parameters extracted with SCA showed poor reliability. The tested gait analysis systems based on different camera systems are currently only partially able to capture valid gait parameters. If the underlying algorithms are adapted and camera technology is advancing, it is conceivable that these comparatively simple methods could be used for gait analysis

Der Einfluss von Cortisol, Anandamid, Capsaicin, Nimesulid und IL-1β auf die IFN-γ-abhängige Aktivierung von STAT1, STAT3, p38 und ERK in synovialen Fibroblasten bei Rheumatoider Arthritis

Die Ergebnisse dieser Arbeit liefern Grundlagen für das Verständnis der Aktivierungskinetik von STATs und MAPKen durch IFN-γ und die Wirkungsweise von „small molecule“-Modulatoren in OASF und RASF. IFN-γ aktivierte STAT1 und STAT3. Während die IFN-γ induzierte Aktivierung von STAT1 nach 48 h weiterhin erhöht war, zeigte sich die STAT3-Aktivierung rückläufig. In geringerem Maße aktivierte IFN-γ zudem p38. IL-1β aktivierte MAPKen stark, nicht aber STAT1 und STAT3. Signifikante Modulation der STAT1-Aktivierung durch „small-molecule“-Modulatoren zeigte sich insbesondere nach 48-stündiger IFN-γ-Stimulation jeweils bei Kostimulation mit Nimesulid: Cortisol verstärkte die STAT1-Aktivierung in RASF. AEA hingegen verminderte die STAT1-Aktivierung in OASF. Capsaicin verminderte außerdem die STAT1-Aktivierung in RASF und OASF. Cortisol, AEA und Capsaicin hemmten zudem die durch 30-minütige IFN-γ-Stimulation getriggerte p38-Aktivierung in RASF

Fully Onboard Low-Power Localization with Semantic Sensor Fusion on a Nano-UAV using Floor Plans

Nano-sized unmanned aerial vehicles (UAVs) are well-fit for indoor applications and for close proximity to humans. To enable autonomy, the nano-UAV must be able to self-localize in its operating environment. This is a particularly-challenging task due to the limited sensing and compute resources on board. This work presents an online and onboard approach for localization in floor plans annotated with semantic information. Unlike sensor-based maps, floor plans are readily-available, and do not increase the cost and time of deployment. To overcome the difficulty of localizing in sparse maps, the proposed approach fuses geometric information from miniaturized time-of-flight sensors and semantic cues. The semantic information is extracted from images by deploying a state-of-the-art object detection model on a high-performance multi-core microcontroller onboard the drone, consuming only 2.5mJ per frame and executing in 38ms. In our evaluation, we globally localize in a real-world office environment, achieving 90% success rate. We also release an open-source implementation of our work.Comment: Under review for ICRA 2024, 7 page