Stefan L. P. Wolf

Water Dynamics from THz Spectroscopy Reveal the Locus of a Liquid–Liquid Binodal Limit in Aqueous CaCO 3 Solutions

Many phenomena depend on CaCO3 nucleation where the role of water remains enigmatic. Changes in THz absorption during the early stages of CaCO3 nucleation evidence altered coupled motions of hydrated calcium and carbonate ions. The direct link between these changes and the continuous development of the ion activity product reveals the locus of a liquid-liquid binodal limit. The data strongly suggest that proto-structured amorphous CaCO3 forms through solidification of initially liquid precursors. Furthermore, polycarboxylates, which stabilize liquid precursors of CaCO3 , significantly enhance the kinetic stability of the metastable liquid-liquid state, but they do not affect the locus of the binodal limit. The importance of water network dynamics in phase separation mechanisms can be understood based on the notions of the pre-nucleation cluster pathway, and is likely to be more general for aqueous systems.

Synergy of Mg2+ and poly(aspartic acid) in additive-controlled calcium carbonate precipitation

Additive-controlled precipitation of calcium carbonate is central to various fields of research. Technically, scale formation is an important problem, where polycarboxylates are most commonly employed as inhibitors. Herein, we show that the combination of poly(aspartic acid) with magnesium ions leads to synergistic effects that bring about a dramatic increase in the efficiency towards inhibition of nucleation and growth of nanoscopic CaCO3 precursors. These effects can also be crucial in biomineralization processes, where polycarboxylates and magnesium ions are thought to play important roles.

Gel-Like Calcium Carbonate Precursors Observed by in situ AFM

The debate about crystallization processes is still ongoing and nonclassical crystallization mechanisms attract more and more attention. This work indicates that polymer induced liquid precursor (PILP) phases play a role for nonclassical calcium carbonate crystallization and growth processes. Here we report the observation of gel-like precursors for the crystal growth on a calcite surface by means of an in situ AFM study. These precursors spread out on the surface with time supporting their liquid character. This study will give new insights into biomineralization and crystallization processes in general.

Applications of Mathematical Models of Road Cycling

Abstract This contribution discusses several use cases of mathematical models for road cycling. A mechanical model for the pedaling forces is the basis for an accurate indoor ergometer simulation of road cycling on real-world tracks. Together with a simple physiological model for the exertion of the athlete as a function of his/her accumulated power output, an optimal riding strategy for time trials on mountain ascents is computed. A combination of the two models leads to a mathematical optimization problem that can be solved numerically by discretization. The physical model depends sensitively on an accurate estimation of the road slope on the course. For this purpose, we also present a new method that combines model-based slope estimations with noisy measurements from multiple GPS signals of differing quality. Altogether, we provide a means to simulate road cycling on real-world tracks, to analyze cyclist performance, to identify and quantify potential performance improvement, as well as to instruct the athlete exactly where and how to change his/her pacing strategy to achieve these gains.

How to Accurately Determine the Position on a Known Course in Road Cycling

With modern cycling computers it is possible to provide cyclists with complex feedback during rides. If the feedback is course-dependent, it is necessary to know the riders current position on the course. Different approaches to estimate the position on the course from common GPS and speed sensors were compared: the direct distance measure derived from the number of rotations of the wheel, GPS coordinates projected onto the course trajectory, and a Kalman filter incorporating speed as well as GPS measurements. To quantify the accuracy of the different methods, an experiment was conducted on a race track where a fixed point on the course was tagged during the ride. The Kalman filter approach was able to overcome certain shortcomings of the other two approaches and achieved a mean error of \({-0.13}\,{\text {m}}\) and a root mean square error of \({0.97}\,{\text {m}}\).

Business Process Orientation in Software Development

Abstract In this article experiences with applying business process orientation in software development are described. Based on the motivation of applying business process technology in a specific software development project, the activities to be carried out in a process oriented software development project are defined. The advantages of developing software by modeling, analyzing, specifying and implementing business processes are discussed. Finally, the experiences gained by applying the described approach in a real world project are described.