Force-dependent unbinding rate of molecular motors from stationary optical trap data

Molecular motors walk along filaments until they detach stochastically with a force-dependent unbinding rate. Here, we show that this unbinding rate can be obtained from the analysis of experimental data of molecular motors moving in stationary optical traps. Two complementary methods are presented, based on the analysis of the distribution for the unbinding forces and of the motor's force traces. In the first method, analytically derived force distributions for slip bonds, slip-ideal bonds, and catch bonds are used to fit the cumulative distributions of the unbinding forces. The second method is based on the statistical analysis of the observed force traces. We validate both methods with stochastic simulations and apply them to experimental data for kinesin-1

All-orders resummation for diphoton production at hadron colliders

We present a QCD calculation of the transverse momentum distribution of photon pairs produced at hadron colliders, including all-orders soft-gluon resummation valid at next-to-next-to-leading logarithmic accuracy. We specify the region of phase space in which the calculation is most reliable, compare our results with data from the Fermilab Tevatron, and make predictions for the Large Hadron Collider. The uncertainty of predictions for production of diphotons from fragmentation of final-state quarks is examined.Comment: 16 pages, 6 figures; minor change

Volterra-series approach to stochastic nonlinear dynamics: linear response of the Van der Pol oscillator driven by white noise

The Van der Pol equation is a paradigmatic model of relaxation oscillations. This remarkable nonlinear phenomenon of self-sustained oscillatory motion underlies important rhythmic processes in nature and electrical engineering. Relaxation oscillations in a real system are usually coupled to environmental noise, which further enriches their dynamics, but makes theoretical analysis of such systems and determination of the equation's parameter values a difficult task. In a companion paper we have proposed an analytic approach to a similar problem for another classical nonlinear model, the bistable Duffing oscillator. Here we extend our techniques to the case of the Van der Pol equation driven by white noise. We analyze the statistics of solutions and propose a method to estimate parameter values from the oscillator's time series. We use experimental data of active oscillations in a biological system to demonstrate how our method applies to real observations and how it can be generalized for more complex models.Comment: 12 pages, 6 figures, 1 tabl

Somatodendritic integration under increased network activity in layer 5 pyramidal cells of the somatosensory cortex

Integrative properties of single neurons have been extensively studied in acute brain slices. However, these preparations are characterized by extremely low levels of synaptic and action potential activity. In comparison to in vivo, reduced intracortical input and lack of subcortical modulation increase the effective difference between mean membrane potential and spiking threshold, preventing self-sustained network activity in vitro. To elicit an increased and stable network activity (INA) in vitro comparable to that found in awake animals, we mimicked subcortical cholinergic and serotoninergic inputs using carbachol or barium alone or in combination with serotonin in layer 5 pyramidal cells in slices of mouse somatosensory cortex. INA is primarily induced by a modulation of intrinsic conductances resulting in a depolarization of the membrane potential. We studied the impact of INA on synaptic and somatodendritic integration using extracellular stimulation and dendritic calcium imaging. Synaptic inhibition is strengthened due to an increased driving force for chloride. The critical frequency at which somatic action potentials induce a dendritic calcium action potential is lowered. Simultaneous inhibitory synaptic input is powerful enough to suppress dendritic calcium action potential generation. Pharmacologically induced INA enables the study of neuronal integration in well-accessible cortical slices within an active networ

Erkundungen im Spannungsfeld von Pädagogik, Spielspass und technischer Machbarkeit. Gedanken zur Konzeption und Entwicklung spielbasierter digitaler Lernumgebung

Computerspiele sind heute aus der digitalen Medienwelt nicht mehr wegzudenken. Ihre rasante technische Entwicklung sowie ihre hohe Akzeptanz in der Jugendkultur werfen Fragen nach pädagogischer Verwertbarkeit dieses Mediums auf. Auf diesem Gebiet besteht Forschungsbedarf: Für den Einsatz aktueller Spielkonzepte als Lehrmittel existieren keine fundierten Theorien oder Konzepte. Der schöpferische Umgang mit Spielen durch Anwender («Emergent Gameplay») bietet hier durch sein hohes Motivationspotential einen vielversprechenden Ansatz. Die oft wenig beachtete Rolle der digitalen Spielen zugrunde liegenden Softwaretechnik sollte stärkere Berücksichtigung finden: Es existiert einerseits ein für die Akzeptanz beim Anwender notwendiges Minimum, andererseits ist der Einsatz des aktuellen technischen «state of the art» für die Umsetzung pädagogischer und didaktischer Ambitionen durch seine enormen Anforderungen wenig zielführend. Im Ergebnis sind Idee und Spielspass das Mass auch für Anwendungen des Game Based Learn­ing

Aggregate Confusion: The Divergence of ESG Ratings

This paper investigates the divergence of environmental, social, and governance (ESG) ratings based on data from six prominent ESG rating agencies: Kinder, Lydenberg, and Domini (KLD), Sustainalytics, Moody’s ESG (Vigeo-Eiris), S&P Global (RobecoSAM), Refinitiv (Asset4), and MSCI. We document the rating divergence and map the different methodologies onto a common taxonomy of categories. Using this taxonomy, we decompose the divergence into contributions of scope, measurement, and weight. Measurement contributes 56% of the divergence, scope 38%, and weight 6%. Further analyzing the reasons for measurement divergence, we detect a rater effect where a rater’s overall view of a firm influences the measurement of specific categories. The results call for greater attention to how the data underlying ESG ratings are generated