Periodic migration in a physical model of cells on micropatterns

We extend a model for the morphology and dynamics of a crawling eukaryotic cell to describe cells on micropatterned substrates. This model couples cell morphology, adhesion, and cytoskeletal flow in response to active stresses induced by actin and myosin. We propose that protrusive stresses are only generated where the cell adheres, leading to the cell's effective confinement to the pattern. Consistent with experimental results, simulated cells exhibit a broad range of behaviors, including steady motion, turning, bipedal motion, and periodic migration, in which the cell crawls persistently in one direction before reversing periodically. We show that periodic motion emerges naturally from the coupling of cell polarization to cell shape by reducing the model to a simplified one-dimensional form that can be understood analytically.Comment: 15 pages (includes supplementary material as an appendix). Recently accepted to Physical Review Letter

John Y. Templeton III: Pioneer of modern cardiothoracic surgery.

John Young Templeton III was born in 1917 in Portsmouth, Virginia, and graduated from Jefferson Medical College in 1941. He completed his residency training under Dr. John H. Gibbon, Jr., and was the first resident who worked on Gibbon\u27s heart-lung machine. After his training, he remained at Jefferson as an American Cancer Society fellow and Damon Runyon fellow and went on to become the fourth Samuel D. Gross Professor and Chair of the Department of Surgery in 1967. Dr. Templeton was the recipient of numerous grants and published over 80 papers in the field of cardiothoracic surgery. As a teacher and mentor, he was a beloved figure who placed great faith in his residents. He participated in over 60 professional societies, serving as president to many such as the Philadelphia Academy of Surgery and the Pennsylvania Association of Thoracic Surgery. He was also recognized through his many awards, in particular the John Y. Templeton III lectureship established in 1980 at Jefferson of whom Denton Cooley was the first lecturer. Dr. Templeton retired from practice in 1987. He is forever remembered as an important model of a modern surgeon evident in numerous academic achievements, the admiration and affection of his trainees, and the lives of patients that he had touched

Normalized Radiated Seismic Energy From Laboratory Fracture Experiments on Opalinus Clayshale and Barre Granite

We evaluate the radiated seismic energy normalized by external work for hydraulic fracturing, beam bending, and uniaxial compression experiments conducted on Opalinus clayshale and Barre granite specimens. Results suggest that normalized radiated seismic energy is highest for the beam bending, followed by uniaxial compression, and, finally, that the hydraulic fracturing experiments radiate the least seismic energy when normalized by external work. We also find that the normalized radiated energy during tests on Opalinus clayshale is 3% to 22% of that in Barre granite across multiple loading mechanisms

Safe Returning FaSTrack with Robust Control Lyapunov-Value Functions

Real-time navigation in a priori unknown environment remains a challenging task, especially when an unexpected (unmodeled) disturbance occurs. In this paper, we propose the framework Safe Returning Fast and Safe Tracking (SR-F) that merges concepts from 1) Robust Control Lyapunov-Value Functions (R-CLVF), and 2) the Fast and Safe Tracking (FaSTrack) framework. The SR-F computes an R-CLVF offline between a model of the true system and a simplified planning model. Online, a planning algorithm is used to generate a trajectory in the simplified planning space, and the R-CLVF is used to provide a tracking controller that exponentially stabilizes to the planning model. When an unexpected disturbance occurs, the proposed SR-F algorithm provides a means for the true system to recover to the planning model. We take advantage of this mechanism to induce an artificial disturbance by ``jumping'' the planning model in open environments, forcing faster navigation. Therefore, this algorithm can both reject unexpected true disturbances and accelerate navigation speed. We validate our framework using a 10D quadrotor system and show that SR-F is empirically 20\% faster than the original FaSTrack while maintaining safety.Comment: 6 pages, 4 figures, 1 table, 2 algorithms. Submitted to LCSS on 03/0

Normalized Radiated Seismic Energy From Laboratory Fracture Experiments on Opalinus Clayshale and Barre Granite

We evaluate the radiated seismic energy normalized by external work for hydraulic fracturing, beam bending, and uniaxial compression experiments conducted on Opalinus clayshale and Barre granite specimens. Results suggest that normalized radiated seismic energy is highest for the beam bending, followed by uniaxial compression, and, finally, that the hydraulic fracturing experiments radiate the least seismic energy when normalized by external work. We also find that the normalized radiated energy during tests on Opalinus clayshale is 3% to 22% of that in Barre granite across multiple loading mechanisms

The Amnesiac Lookback Option: Selectively Monitored Lookback Options and Cryptocurrencies

This study proposes a strategy to make the lookback option cheaper and more practical, and suggests the use of its properties to reduce risk exposure in cryptocurrency markets through blockchain enforced smart contracts and correct for informational inefficiencies surrounding prices and volatility. This paper generalizes partial, discretely-monitored lookback options that dilute premiums by selecting a subset of specified periods to determine payoff, which we call amnesiac lookback options. Prior literature on discretely-monitored lookback options considers the number of periods and assumes equidistant lookback periods in pricing partial lookback options. This study by contrast considers random sampling of lookback periods and compares resulting payoff of the call, put and spread options under floating and fixed strikes. Amnesiac lookbacks are priced with Monte Carlo simulations of Gaussian random walks under equidistant and random periods. Results are compared to analytic and binomial pricing models for the same derivatives. Simulations show diminishing marginal increases to the fair price as the number of selected periods is increased. The returns correspond to a Hill curve whose parameters are set by interest rate and volatility. We demonstrate over-pricing under equidistant monitoring assumptions with error increasing as the lookback periods decrease. An example of a direct implication for event trading is when shock is forecasted but its timing uncertain, equidistant sampling produces a lower error on the true maximum than random choice. We conclude that the instrument provides an ideal space for investors to balance their risk, and as a prime candidate to hedge extreme volatility. We discuss the application of the amnesiac lookback option and path-dependent options to cryptocurrencies and blockchain commodities in the context of smart contracts

Im Fokus: Armut in den Staaten der EU

Dass Armut in den meisten Staaten der EU ein immer dringlicher werdendes Problem darstellt, darauf verweisen nicht nur die entsprechenden sozialen Einrichtungen und Sozialverbände, sondern auch offizielle Berichte von Regierungen (z. B. der dritte Armuts- und Reichtumsbericht der deutschen Bundesregierung), Forschungsprogramme der EU zur Armut und ihrer Messung bzw. Messbarkeit (AMELI und die so genannten Laeken-Kriterien zur Messung relativer Armut) sowie der Tatbestand, dass die EU das Jahr 2010 als Jahr zur Bekämpfung von Armut und sozialer Ausgrenzung ausgerufen hat. Der vorliegende Beitrag gibt einen Überblick über verschiedene Maße zur Messung von Armut bzw. Ungleichheit der Einkommensverteilung in den einzelnen Staaten der EU für die Jahre 2000 und 2008. Die hier vorgestellten Indikatoren gehören zu den Laeken-Maßen und sind von allen Staaten der EU zu ermitteln und zu veröffentlichen. Hierdurch kann einerseits die deutsche Situation in einen europäischen Kontext eingebettet und andererseits ein Bewusstsein geweckt werden für ein zukünftig verstärkt auftretendes gesellschaftliches Problem

Soziale Armut im Alter

Relative Armut in unterschiedlichen Bevölkerungsschichten rückt seit einigen Jahren verstärkt in die öffentliche Diskussion – sei es als Armut von Kindern, Langzeitarbeitslosen oder Geringverdienern, Alleinerziehenden oder Rentnern. Bei der Festlegung, wer arm ist, hat das persönliche Einkommen einen sehr hohen Stellenwert. Materielle Armut ist aber nur eine Seite der Medaille; die andere Seite besteht darin, dass von Armut betroffene oder bedrohte Personen häufig auch nur eingeschränkt am gesellschaftlichen Leben teilhaben können – sei es, dass sie ausgegrenzt werden, sei es, dass sie sich selbst vom gesellschaftlichen Leben zurückziehen. Andererseits muss ein niedriges Einkommen nicht zwangsläufig mit Armut gleichgesetzt werden. Es ist ebenso gut denkbar, dass aktive soziale Teilhabe in unterschiedlichster Form einen Mangel an Einkommen durch „Zufriedenheit mit dem Leben“ teilweise kompensieren kann. Der Beitrag untersucht für Deutschland und die Jahre 2003 und 2008 auf der Grundlage der Daten des Sozio-oekonomischen Panels (SOEP), ob insbesondere ältere Menschen, die von Armut betroffen sind, durch zusätzliche gesundheitliche Probleme betroffen sind bzw. weniger als nicht arme Ältere am gesellschaftlichen Leben teilhaben können. Erwartungsgemäß sind ältere Menschen zu einem höheren Anteil mit ihrem Gesundheitszustand unzufrieden als jüngere. Unter den Personen, deren Einkommen unterhalb der einkommensbezogenen Armutsgefährdungsschwelle liegt, ist ebenfalls ein signifikant höherer Anteil mit ihrer Gesundheit unzufrieden. Dass Einkommensarmut auch ein Gesundheitsrisiko darstellt, wird dadurch bestätigt. Entsprechende Befunde lassen sich für die Zufriedenheit mit der Freizeit nicht finden: Unter den älteren Menschen sind signifikant mehr mit ihrer Freizeit zufrieden als unter den Befragten im Erwerbsalter. Auch Einkommensarmut geht danach nicht mit größerer Unzufriedenheit mit der Freizeit einher

Quantifying cancer epithelial-mesenchymal plasticity and its association with stemness and immune response

Cancer cells can acquire a spectrum of stable hybrid epithelial/mesenchymal (E/M) states during epithelial-mesenchymal transition (EMT). Cells in these hybrid E/M phenotypes often combine epithelial and mesenchymal features and tend to migrate collectively commonly as small clusters. Such collectively migrating cancer cells play a pivotal role in seeding metastases and their presence in cancer patients indicates an adverse prognostic factor. Moreover, cancer cells in hybrid E/M phenotypes tend to be more associated with stemness which endows them with tumor-initiation ability and therapy resistance. Most recently, cells undergoing EMT have been shown to promote immune suppression for better survival. A systematic understanding of the emergence of hybrid E/M phenotypes and the connection of EMT with stemness and immune suppression would contribute to more effective therapeutic strategies. In this review, we first discuss recent efforts combining theoretical and experimental approaches to elucidate mechanisms underlying EMT multi-stability (i.e. the existence of multiple stable phenotypes during EMT) and the properties of hybrid E/M phenotypes. Following we discuss non-cell-autonomous regulation of EMT by cell cooperation and extracellular matrix. Afterwards, we discuss various metrics that can be used to quantify EMT spectrum. We further describe possible mechanisms underlying the formation of clusters of circulating tumor cells. Last but not least, we summarize recent systems biology analysis of the role of EMT in the acquisition of stemness and immune suppression.Comment: 50 pages, 6 figure