Packing Plane Spanning Trees and Paths in Complete Geometric Graphs

We consider the following question: How many edge-disjoint plane spanning trees are contained in a complete geometric graph $GK_n$ on any set $S$ of $n$ points in general position in the plane? We show that this number is in $\Omega(\sqrt{n})$. Further, we consider variants of this problem by bounding the diameter and the degree of the trees (in particular considering spanning paths).Comment: This work was presented at the 26th Canadian Conference on Computational Geometry (CCCG 2014), Halifax, Nova Scotia, Canada, 2014. The journal version appeared in Information Processing Letters, 124 (2017), 35--4

Entwicklung einer modellbasierten In-the-Loop-Testumgebung für Waschautomaten

Im Maschinenbau (z.B. Automotiv, Hausgeräte, Raumfahrt) werden neue Funktionen für mehr Sicherheit, geringere Umweltbelastung und mehr Komfort zunehmend durch elektronische Steuergeräte realisiert. Als Folge nimmt der Entwicklungs- und Testaufwand zu. Modellbasiertes Testen und die Zuhilfenahme von Echtzeitsimulationen (Hauptausprägung HiL-Simulationen) bieten die Möglichkeit, die Testtiefe und den -umfang zu erhöhen, um die Steuergerätequalität sicherzustellen und weiter zu verbessern. Ziel dieser Arbeit war die Entwicklung einer modellbasierten In-the-Loop-Testumgebung für Waschautomaten, im speziellen einer HiL-Simulation. Die Herausforderung beim Erstellen eines echtzeitfähigen Gesamtmodells des Waschautomaten liegt darin, das gesamte, implizit vorhandene domänenübergreifende Prozess- und Systemwissen explizit abzubilden. Für eine effektive Nutzung wurde die HiL-Simulation in bestehende Werkzeugketten und Entwicklungsprozesse integriert. Damit wurden die grundlegenden Rahmenbedingungen für eine Nutzung der In-the-Loop-Technologien geschaffen. Abschließend wurde exemplarisch der Nutzen einer MiL-Simulation anhand von zwei Bespielen verdeutlicht.In mechanical engineering (e.g. automotive, appliance, aerospace) new features for more safety, less pollution and greater comfort are more and more implemented with electronic control units. This increases the development and testing effort. Model-based testing and real-time simulations (mainly HiL simulation) offer the possibility to increase the test depth and scope to ensure and improve the quality of the control devices. The aim of this study was to develop a model-based in-the-loop test environment for washing machines, in particular a HiL simulation. The challenge in creating a real-time model of the washing machine is to extract the whole, implicit knowledge of the cross-domain process and system and to make it explicit. For an effective use, the HIL simulation has been integrated into existing tool chains and development processes. Thus, the basic framework for the use of the in-the-loop technologies was established. Finally, the advantages of MiL simulations were illustrated by means of two examples.von Dipl.-Ing. Alexander Löffler. Referent: Prof. Dr.-Ing. habil. Ansgar Trächtler, Korreferent: Prof. Dr.-Ing. Jürgen GausemeierTag der Verteidigung: 01.08.2016Universität Paderborn, Fakultät Maschinenbau, Univ., Dissertation, 201

Recognizing Stick Graphs with and without Length Constraints

Stick graphs are intersection graphs of horizontal and vertical line segments that all touch a line of slope -1 and lie above this line. De Luca et al. [GD'18] considered the recognition problem of stick graphs when no order is given (STICK), when the order of either one of the two sets is given (STICK_A), and when the order of both sets is given (STICK_AB). They showed how to solve STICK_AB efficiently. In this paper, we improve the running time of their algorithm, and we solve STICK_A efficiently. Further, we consider variants of these problems where the lengths of the sticks are given as input. We show that these variants of STICK, STICK_A, and STICK_AB are all NP-complete. On the positive side, we give an efficient solution for STICK_AB with fixed stick lengths if there are no isolated vertices

Teaching the Digital Transformation of Business Processes: Design of a Simulation Game for Information Systems Education

The ability to manage business processes in the context of the digital transformation is a key competency that should be addressed in Information Systems (IS) education. One possibility for teaching this competency is through simulation games, but the current ones lack a dynamic view on changing business processes induced by the digital transformation. In this paper, we present the design of a simulation game to teach the digital transformation of business processes within IS education. The game simulates the transformation of a bike manufacturing company to a bike-sharing provider, in which students have to manage changes in the production process in teams during different transformation phases. We argue how our game supports central learning objectives for teaching the aforementioned topic and show the benefit of our game design by running a pilot test with students from IS education using the Systems Usability Scale to evaluate the utility of our implementation

Assay validity of point-of-care platelet function tests in thrombocytopenic blood samples

Point-of-care (POC) platelet function tests are faster and easier to perform than in-depth assessment by flow cytometry. At low platelet counts, however, POC tests are prone to assess platelet function incorrectly. Lower limits of platelet count required to obtain valid test results were defined and a testing method to facilitate comparability between different tests was established. We assessed platelet function in whole blood samples of healthy volunteers at decreasing platelet counts (> 100, 80-100, 50-80, 30-50 and < 30 x109/L) using two POC tests: impedance aggregometry and in-vitro bleeding time. Flow cytometry served as the gold standard. The number of platelets needed to reach 50% of the maximum function (ED50) and the lower reference limit (EDref) were calculated to define limits of test validity. The minimal platelet count required for reliable test results was 100 x109/L for impedance aggregometry and in-vitro bleeding time but only 30 x109/L for flow cytometry. Comparison of ED50 and EDref showed significantly lower values for flow cytometry than either POC test (P value < 0.05) but no difference between POC tests nor between the used platelet agonists within a test method. Calculating the ED50 and EDref provides an effective way to compare values from different platelet function assays. Flow cytometry enables correct platelet function testing as long as platelet count is > 30 x109/L whereas impedance aggregometry and in-vitro bleeding time are inconsistent unless platelet count is > 100 x109/L

Compromised Bone Healing in Aged Rats Is Associated With Impaired M2 Macrophage Function

Fracture repair is initiated by a multitude of immune cells and induction of an inflammatory cascade. Alterations in the early healing response due to an aged adaptive immune system leads to impaired bone repair, delayed healing or even formation of non-union. However, immuno-senescence is not limited to the adaptive immunity, but is also described for macrophages, main effector cells from the innate immune system. Beside regulation of pro- and anti-inflammatory signaling, macrophages contribute to angiogenesis and granulation tissue maturation. Thus, it seems likely that an altered macrophage function due to aging may affect bone repair at various stages and contribute to age related deficiencies in bone regeneration. To prove this hypothesis, we analyzed the expression of macrophage markers and angiogenic factors in the early bone hematoma derived from young and aged osteotomized Spraque Dawley rats. We detected an overall reduced expression of the monocyte/pan-macrophage markers CD14 and CD68 in aged rats. Furthermore, the analysis revealed an impaired expression of anti-inflammatory M2 macrophage markers in hematoma from aged animals that was connected to a diminished revascularization of the bone callus. To verify that the age related disturbed bone regeneration was due to a compromised macrophage function, CD14+ macrophage precursors were transplanted locally into the osteotomy gap of aged rats. Transplantation rescued bone regeneration partially after 6 weeks, demonstrated by a significantly induced deposition of new bone tissue, reduced fibrosis and significantly improved callus vascularization

Ökologien der Erde: zur Wissensgeschichte und Aktualität der Gaia-Hypothese

Ökologien der Erde bestimmen die Gegenwart. Dabei gewinnt die in den 1970er Jahren von James Lovelock gemeinsam mit Lynn Margulis entwickelte Gaia-Theorie heute neue Erklärungskraft. Wenn Gaia bei Bruno Latour sogar zum allgemeinen Modell der Welterklärung im 21. Jahrhundert wird, gilt es, nach der Plausibilität zu fragen, die die Rede von Gaia aktuell entwickelt. Die vier Beiträge des Bandes geben hierauf eine Antwort, indem sie die metaphorologischen und begriffshistorischen Linien der Gaia-Theorie nachzeichnen und ihren Bezug auf zeitgenössische Computersimulationen in den Blick nehmen. So wird der gegenwärtige Ort des Wiederauflebens Gaias deutlich - und damit die Verschränkung von kybernetischen und organizistischen Ökologien mit der Annahme einer Programmierbarkeit von Umgebungen

Anisotropy-induced spin disorder in intergrown, ferrimagnetic Fe7_7 S8_8 polytypes

The monosulfides of the pyrrhotite omission series (Fe$_{1−}$S, 0<≤0.125) are important remanence carriers for paleomagnetic reconstruction of the Earth\u27s crust and extraterrestrial materials. The ferrimagnetic Fe$_7$S$_8$ polytypes are the endmembers, and their stacking modulations of full and vacant layers generate different magnetic anisotropy properties due to the cation-vacancy configurations. In this study, intergrown long-range ordered polytypes with four- and threefold modulation, i.e., 4C and 3C pyrrhotite, were prepared in a diffusion-driven process by quenching of a natural pyrrhotite crystal with randomized vacancies. In addition, a third constituent with coherence lengths of a few nanometers, denoted 3C*, was found that exhibits spin-glass behavior at about 10 K due to local magnetic anisotropies arising from vacancy-density variations. The concomitant occurrence of this nano-scale constituent with spin disorder and the long-range ordered polytypes indicate competitive diffusion-driven processes during Fe$_7$S$_8$ formation. Such information provides insight into the provenance and genesis of ferrimagnetic pyrrhotite in Earth and extraterrestrial systems and in a broader sense into vacancy-induced materials