Pay What You Want as a Pricing Model for Open Access Publishing?

We analyze 'Pay What You Want' as a business model for Open Access publishing by discussing motives leading authors to make voluntary contributions, potential benefits for publishers and present results from a field experiment at one publisher. Data from the field experiment indicate authors' willingness to voluntarily contribute

Control of spatiotemporal chaos in catalytic CO oxidation by laser-induced pacemakers

Control of spatiotemporal chaos is achieved in the catalytic oxidation of CO on Pt(110) by localized modification of the kinetic properties of the surface chemical reaction. In the experiment, a small temperature heterogeneity is created on the surface by a focused laser beam. This heterogeneity constitutes a pacemaker and starts to emit target waves. These waves slowly entrain the medium and suppress the spatiotemporal chaos that is present in the absence of control. We compare this experimental result with a numerical study of the Krischer–Eiswirth–Ertl model for CO oxidation on Pt(110). We confirm the experimental findings and identify regimes where complete and partial controls are possible

Target patterns and pacemakers in reaction-diffusion systems

Pattern formation in systems far from thermal equilibrium is a fascinating phenomenon. Reaction-diffusion systems are an important type of system where pattern formation is observed. The target pattern and the associated wave source called pacemaker are typical patterns in such systems. This thesis studies pacemakers and target patterns systematically by analytical and numerical means. The underlying dynamics of the system may be oscillatory or excitable and the pacemakers may either consist of spatial heterogeneities of the medium or be self-organized, i.e. result of intrinsic processes. The investigation of heterogeneous pacemakers in oscillatory systems in the framework of the complex Ginzburg-Landau equation focuses on two aspects. First, the conditions of the creation of pacemakers and extended target patterns versus the creation of wave sinks and localized target patterns are derived systematically. In particular, inward traveling target patterns and large heterogeneities are discussed. Then, pacemakers which emit target waves with high frequencies are considered. In this case, the waves become Eckhaus unstable, causing ring-shaped amplitude defects or other complex patterns. For even larger frequencies, the amplitude defects already take place at the boundary of the heterogeneity, giving rise to a localized desynchronization phenomenon. Moreover, wave sinks can have a significant impact on the spatio-temporal dynamics of the system by breaking the waves arriving from other wave sources. It is well known that oscillatory media close to a Hopf bifurcation are not able to give rise to stable self-organized pacemakers. Therefore, to model such pacemakers, a system close to a pitchfork-Hopf bifurcation is proposed. The normal form and amplitude equations of the pitchfork-Hopf bifurcation are derived. Such a system displays birhythmicity, i.e. bistability of limit cycles, and it is demonstrated analytically that stable self-organized pacemakers are possible. Simulations confirm the existence of stable self-organized pacemakers. In the presence of a parameter gradient, such patterns drift, as shown analytically and numerically. The interaction between pacemakers is studied numerically, giving rise either to coexisting pacemakers or to a new phenomenon called global inhibition: Established pacemakers suppress new cores or merge with them. When the frequencies of the limit cycles differ strongly, the waves may become Eckhaus unstable and the pacemaker may destabilize. Furthermore, kinetic instabilities of the pacemakers are possible, creating breathing and swinging pacemakers. Self-organized pacemakers in excitable media are usually unstable. In this thesis, a three-component activator-inhibitor system on the basis of the FitzHugh-Nagumo model is proposed that gives rise to stable self-organized pacemakers in the excitable regime. The formation of such patterns is demonstrated if several conditions are fulfilled: The system is close to relaxational oscillations, the additional component is strongly diffusive, and the additional component inhibits the inhibitor. Moreover, bistability of pulse solutions is observed in such a system. Different pulses can interact and may create pacemakers. Alternatively, other complex spatio-temporal dynamics is observed. If the diffusion of the activator vanishes, the waves emitted by the wave source are unstable and spatio-temporal chaos appears. Thus, this thesis presents new results on the dynamics of pacemakers with large frequencies and demonstrates for the first time the possibility of stable self-organized pacemakers in birhythmic and excitable systems

The role of space, time and sociability in predicting social encounters

Space, time and the social realm are intrinsically linked. While an array of studies have tried to untangle these factors and their influence on human behaviour, hardly any have taken their effects into account at the same time. To disentangle these factors, we try to predict future encounters between students and assess how important social, spatial and temporal features are for prediction. We phrase our problem of predicting future encounters as a link-prediction problem and utilise set of Random Forest predictors for the prediction task. We use data collected by the Copenhagen network study; a study unique in scope and scale and tracks 847 students via mobile phones over the course of a whole academic year. We find that network and social features hold the highest discriminatory power for predicting future encounters

Accelerated Stochastic Matrix Inversion: General Theory and Speeding up BFGS Rules for Faster Second-Order Optimization

We present the first accelerated randomized algorithm for solving linear systems in Euclidean spaces. One essential problem of this type is the matrix inversion problem. In particular, our algorithm can be specialized to invert positive definite matrices in such a way that all iterates (approximate solutions) generated by the algorithm are positive definite matrices themselves. This opens the way for many applications in the field of optimization and machine learning. As an application of our general theory, we develop the {\em first accelerated (deterministic and stochastic) quasi-Newton updates}. Our updates lead to provably more aggressive approximations of the inverse Hessian, and lead to speed-ups over classical non-accelerated rules in numerical experiments. Experiments with empirical risk minimization show that our rules can accelerate training of machine learning models.Comment: 37 pages, 32 figures, 3 algorithm

Empirical competence-testing: A psychometric examination of the German version of the Emotional Competence Inventory

The “Emotional Competence Inventory“ (ECI 2.0) by Goleman and Boyatzis assesses emotional intelligence (EI) in organizational context by means of 72 items in 4 clusters (self-awareness, self- management, social awareness, social skills) which at large consist of 18 competencies. Our study examines the psychometric properties of the first German translation of this instrument in two different surveys (N = 236). If all items are included in reliability analysis the ECI is reliable (Cronbach’s Alpha = .90), whereas the reliability of the four sub dimensions is much smaller (Alpha = .62 - .81). For 43 items the corrected item-total correlation with its own scale is higher than correlations with the other three clusters. Convergent validity was examined by using another EI instrument (Wong & Law, 2002). We found a significant correlation between the two instruments (r = .41). The German version of the ECI seems to be quite useful, although the high reliability is achieved by a large number of items. Possibilities of improvement are discussed

Delegating Pricing Power to Customers: Pay What You Want or Name Your Own Price?

Pay What You Want (PWYW) and Name Your Own Price (NYOP) are customer driven pricing mechanisms that give customers (some) pricing power. Both have been used in service industries with high fixed costs to price discriminate without setting a reference price. Their participatory and innovative nature gives rise to promotional benefits that do not accrue to posted-price sellers. We explore the nature and effects of these benefits and compare PWYW and NYOP using controlled lab experiments. We show that PWYW is a very aggressive strategy that achieves almost full market penetration. It can be profitable if there are promotional benefits and if marginal costs are low. In contrast, NYOP can be used profitably also if marginal costs are high and if there are no such benefits. It reduces price competition and segments the market. In a second experiment, we generate promotional benefits endogenously. We show that PWYW monopolizes the follow-up market but fails to be profitable. NYOP is less successful in penetrating the market but yields much higher profits

Emotional Intelligence and its consequences for occupational and life satisfaction - Emotional Intelligence in the context of irrational beliefs

According to Albert Ellis' theory of Rational Emotive Behavior Therapy irrational beliefs (IB) lead to maladaptive emotions. A central component of irrationality is the denial of one's own possibilities to control important aspects of life. A specific IB is that one cannot control and thus cannot avoid certain emotion states. Emotion research considers regulative emotion control a pivotal component of the concept of emotional intelligence (EI). A negative association between IB and EI can thus be theoretically derived from both concepts. Furthermore both should be related to life satisfaction. We examined the relationship between IB and EI using standardized questionnaire instruments and the predictive value of both concepts regarding life satisfaction. We found a significant negative correlation between both conceptions (r = -.21). Life satisfaction and occupational satisfaction are better predicted by IB. R² increases from .04 to .12 when both concepts are incorporated in regression analysis