On Galois coverings and tilting modules

Let A be a basic connected finite dimensional algebra over an algebraically closed field, let G be a group, let T be a basic tilting A-module and let B the endomorphism algebra of T. Under a hypothesis on T, we establish a correspondence between the Galois coverings with group G of A and the Galois coverings with group G of B. The hypothesis on T is expressed using the Hasse diagram of basic tilting A-modules and is always verified if A is of finite representation type. Then, we use the above correspondence to prove that A is simply connected if and only if B is simply connected, under the same hypothesis on T. Finally, we prove that if a tilted algebra B of type Q is simply connected, then Q is a tree and the first Hochschild cohomology group of B vanishesComment: Fourth version. A result on the simple connectedness of tilted algebras was adde

Galois coverings of weakly shod algebras

We investigate the Galois coverings of weakly shod algebras. For a weakly shod algebra not quasi-tilted of canonical type, we establish a correspondence between its Galois coverings and the Galois coverings of its connecting component. As a consequence, we show that a weakly shod algebra is simply connected if and only if its first Hochschild cohomology group vanishes.Comment: Some references were added. The proof of Lemma 6.5 was modifie

Analysis and development of a sensor concept for multistable actuators with passive magnetic shape memory alloy

Based on the current state of research, the aim of this paper is to develop a position sensor for actuators using passive magnetic shape memory alloys. The presented sensor concept converts the strain dependent permeability of the magnetic shape memory alloy into an inductance change by using a sensor coil arrangement. The change in inductance of the sensor coil is converted into a change in the resonant frequency of a parallel oscillating circuit. A microcontroller detects the resonant frequency of the circuit and converts it into a position sensor signal. To evaluate the functionality of the sensor, a test rig is developed that deforms the magnetic shape memory element under realistic application conditions. Experimental measurements in a climate chamber are used to evaluate the performance and characteristics of the sensor. The characteristic, temperature drift and hysteresis behavior are analyzed. It is proven that the presented sensor concept can be used to determine the position of passive magnetic shape memory alloy actuators

Coverings of Laura Algebras: the Standard Case

In this paper, we study the covering theory of laura algebras. We prove that if a connected laura algebra is standard (that is, it is not quasi-tilted of canonical type and its connecting components are standard), then this algebra has nice Galois coverings associated to the coverings of the connecting component. As a consequence, we show that the first Hochschild cohomology group of a standard laura algebra vanishes if and only if it has no proper Galois coverings.Comment: The main result on the non-standard case was reformulated due to an inaccuracy in the previous version. Lemma 6.1 was removed due to a simplification. The last section on the special biserial case was removed. Typos corrected and bibliography updated. Final version to appear in Journal of Algebr

Assessing extraterrestrial regolith material simulants for in-situ resource utilization based 3D printing

This research paper investigates the suitability of ceramic multi-component materials, which are found on the Martian and Lunar surfaces, for 3D printing (aka Additive Manufacturing) of solid structures. 3D printing is a promising solution as part of the cutting edge field of future in situ space manufacturing applications. 3D printing of physical assets from simulated Martian and Lunar regolith was successfully performed during this work by utilising laser-based powder bed fusion equipment. Extensive evaluation of the raw regolith simulants was conducted via Optical and Electron Microscopy (SEM), Visible–Near Infrared/Infrared (Vis–NIR/IR) Spectroscopy and thermal characterisation via Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The analysis results led to the characterisation of key properties of these multi-component ceramic materials with regard to their processability via powder bed fusion 3D printing. The Lunar and Martian simulant regolith analogues demonstrated spectral absorbance values of up to 92% within the Vis–NIR spectra. Thermal analysis demonstrated that these materials respond very differently to laser processing, with a high volatility (30% weight change) for the Martian analogue as opposed to its less volatile Lunar counterpart (<1% weight change). Results also showed a range of multiple thermal occurrences associated with melting, glass transition and crystallisation reactions. The morphological features of the powder particles are identified as contributing to densification limitations for powder bed fusion processing. This investigation has shown that – provided that the simulants are good matches for the actual regoliths – the lunar material is a viable candidate material for powder bed fusion 3D printing, whereas Martian regolith is not

Lokale Volumenänderungen migrierender Oligodendrocyten-Vorläuferzellen bestimmt mithilfe der Raster-Ionenleitfähigkeitsmikroskopie

Die Migration von Zellen ist ein Prozess, der im Verlauf der gesamten Lebensspanne in nahezu allen Zelltypen auftritt. Zellmigration ist notwendig für viele unterschiedliche physiologische Prozesse, von der Wundheilung bis hin zur Bildung von Tumor-Metastasen. Bisher ist der Mechanismus der Zellmigration nicht vollständig aufgeklärt. Diese Arbeit zeigt zum ersten Mal einen seit einigen Jahren postulierten Teilaspekt des Mechanismus der Zellwanderung: Das Auftreten einer lokalen Zellschwellung in Bewegungsrichtung vor einer Bewegung des Zellkerns und des hinteren Zellteils.Cell migration occurs in nearly every cell type during a life-span of an organism. It is crucial for a wide variety of physiological processes, from wound healing to tumor metastases formation. The mechanism of cell migration is yet not understood completely. Here I show one aspect of the mechanism proposed for some years for the first time: A local cell swelling occurs at the leading edge of a cell prior to dislocation of the nucleus

Backstep scanning ion conductance microscopy as a tool for long term investigation of single living cells

Scanning ion conductance microscopy (SICM) is a suitable tool for imaging surfaces of living cells in a contact-free manner. We have shown previously that SICM in backstep mode allows one to trace the outlines of entire cell somata and to detect changes in cellular shape and volume. Here we report that SICM can be employed to quantitatively observe cellular structures such as cell processes of living cells as well as cell somata of motile cells in the range of hours