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Curve sketching is a typical problem in elementary as well as in advanced mathematics. It is even more complex to implement in computer-aided assessment when instant sketches on demand should be possible. This paper introduces an approach using STACK and JSXGraph based on Hermite splines that faces this problem. In addition to central aspects of both the implementation in JavaScript and the evaluation in Maxima, it will point out the didactical potential of the approach including experiences from a first trial.

Although STACK was developed to enable student-provided answers in computer aided assessment of mathematics, the system also offers a wide range of opportunities for different types of multiple choice questions (MCQ). The article points out reasons for both the use of MCQ in the assessment of STEM subjects and the use of STACK instead of other LMS question types to realize this. Scenarios of usage are illustrated by examples from mathematical bridging courses.

Das studienvorbereitende Angebot BeVorStudium der OTH Amberg-Weiden richtet sich an Studieninteressierte ohne Abitur und vermittelt die für ein WiMINT-Studium notwendigen Mathematik-Vorkenntnisse. Wesentlicher Baustein der Selbstlernphasen sind regelmäßige Online-Tests mit STACK-Fragen. Im Artikel wird auf die didaktische Konzeption sowie auf Erfahrungen aus der Umsetzung eingegangen. Dabei werden Besonderheiten im Zusammenhang mit der nicht zuletzt von der beruflichen Bildung geprägten Zielgruppe aufgezeigt.

Proteins in the venom of the fire ant Solenopsis invicta have been suggested to function in pheromone binding. Venom from queens and workers contains different isoforms of these proteins, consistent with the differing pheromones they secrete, but questions remain about the venom protein composition and glandular source. We found that the queen venom contains a previously uncharacterized pheromone-binding protein paralogue known as Sol i 2X1. Using imaging mass spectrometry, we located the main venom proteins in the poison sac, implying that pheromones might have to compete with venom alkaloids for binding. Using the known structure of the worker venom protein Sol i 2w, we generated three-dimensional homology models of the worker venom protein Sol i 4.02, and of the two main venom proteins in queens and female alates, Sol i 2q and Sol i 2X1. Surprisingly, the models show that the proteins have relatively small internal hydrophobic binding pockets that are blocked by about 10 amino acids of the C-terminal region. For these proteins to function as carriers of hydrophobic ligands, a conformational change would be required to displace the C-terminal region, somewhat like the mechanism known to occur in the silk moth pheromone-binding protein.

Within the scope of the optimization of the gas diffusion layer production process, 12 materials were made using the Design of Experiments method. The 12 cathode gas diffusion layers have the same carbon fiber substrate and only differ in terms of process parameters for impregnation and micro porous layer coating. During short stack testing at 40°C three of the materials unexpectedly lead to a loss of power of over 50 %, although standard ex-situ characterization showed no significant difference between the 12 materials. The aim of this work was to study the production process induced material variation and to develop new characterization methods to understand the cause of the power loss. In a first step an optical high-resolution method was developed which characterizes the gas diffusion layer roughness under compression as well as the camber of carbon fiber substrate into the channel and the behavior of irregularities with increasing compression. Afterwards a method for measuring the oxygen transport resistance was validated and applied on current gas diffusion layers. The results show that this method offers a costefficient way to forecast the performance of fuel cell stacks in normal operating points. Beside the known dry and wet oxygen transport resistance plateaus, an additional state of unexpected high resistances was found. Further testing by means of kryo-SEM and laser perforation showed the presence of excessive liquid water in the CCM-MPL-interface at low temperature operating points. The application of these findings on the initial problem show that the GDL induced power loss in short stacks at 40°C can be assigned to CCM-MPL interface flooding, which can be predicted with the method for measuring the oxygen transport resistance