@article{ReisertSchneiderGeissleretal.2013, author = {Reisert, Steffen and Schneider, Benno and Geissler, Hanno and Gompel, Matthias van and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Multi-sensor chip for the investigation of different types of metal oxides for the detection of H2O2 in the ppm range}, series = {physica status solidi (a)}, volume = {210}, journal = {physica status solidi (a)}, number = {5}, publisher = {Wiley}, address = {Weinheim}, issn = {1862-6319}, pages = {898 -- 904}, year = {2013}, abstract = {In this work, a multi-sensor chip for the investigation of the sensing properties of different types of metal oxides towards hydrogen peroxide in the ppm range is presented. The fabrication process and physical characterization of the multi-sensor chip are described. Pure SnO2 and WO3 as well as Pd- and Pt-doped SnO2 films are characterized in terms of their sensitivity to H2O2. The sensing films have been prepared by drop-coating of water-dispensed nano-powders. A physical characterization, including scanning electron microscopy and X-ray diffraction analysis of the deposited metal-oxide films, was done. From the measurements in hydrogen peroxide atmosphere, it could be shown, that all of the tested metal oxide films are suitable for the detection of H2O2 in the ppm range. The highest sensitivity and reproducibility was achieved using Pt-doped SnO2. Calibration plot of a SnO2, WO3, Pt-, and Pd-doped SnO2 gas sensor for H2O2 concentrations in the ppm range.}, language = {en} } @article{HennemannKohlReisertetal.2013, author = {Hennemann, J{\"o}rg and Kohl, Claus-Dieter and Reisert, Steffen and Kirchner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Copper oxide nanofibres for detection of hydrogen peroxide vapour at high concentrations}, series = {physica status solidi (a)}, volume = {210}, journal = {physica status solidi (a)}, number = {5}, publisher = {Wiley}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201200775}, pages = {859 -- 863}, year = {2013}, abstract = {We present a sensor concept based on copper(II)oxide (CuO) nanofibres for the detection of hydrogen peroxide (H2O2) vapour in the percent per volume (\% v/v) range. The fibres were produced by using the electrospinning technique. To avoid water condensation in the pores, the fibres were initially modified by an exposure to H2S to get an enclosed surface. By a thermal treatment at 350 °C the fibres were oxidised back to CuO. Thereby, the visible pores disappear which was verified by SEM analysis. The fibres show a decrease of resistance with increasing H2O2 concentration which is due to the fact that hydrogen peroxide is an oxidising gas and CuO a p-type semiconductor. The sensor shows a change of resistance within the minute range to the exposure until the maximum concentration of 6.9\% v/v H2O2. At operating temperatures below 450 °C the corresponding sensor response to a concentration of 4.1\% v/v increases. The sensor shows a good reproducibility of the signal at different measurements. CuO seems to be a suitable candidate for the detection of H2O2 vapour at high concentrations. Resistance behaviour of the sensor under exposure to H2O2 vapours between 2.3 and 6.9\% v/v at an operating temperature of 450 °C.}, language = {en} } @phdthesis{Schieffer2012, author = {Schieffer, Andre}, title = {Studies on diversity and coexistence in an experimental microbial community}, pages = {76 Bl. : Ill.}, year = {2012}, abstract = {Biodiversity and the coexistence of species have puzzled and fascinated biologists since decades and is a hotspot in todays' natural sciences. Preserving this biodiversity is a great challenge as habitats and environments underlying tremendous changes like climate change and the loss of natural habitats, which are mainly due to anthropogenic influences. The coexistence of numerous species even in homogeneous environments is a stunning feature of natural communities and has been summarized under the term 'paradox of plankton'. Up to now, there are several mechanisms discussed, which may contribute to local and global diversity of organisms. Several interspecific trade offs have been identified maintaining the coexistence of species like their abilities regarding competition and predator avoidance, their capability to disperse in space and time, and their ability to exploit variable resources. Further, micro-evolutionary dynamics supporting the coexistence of species have been added to our knowledge, and deriving from theoretical deterministic models, non-linear dynamics which describe the temporal fluctuation of abundances of organisms. Whereas competition and predation seem to be clue structural elements within interacting organisms, the intrinsic dynamic behavior - by means of temporal changes in abundance - plays an important role regarding coexistence within a community. The present work sheds light on different factors affecting the coexistence of species using experimental microbial model systems consisting of a bacterivorous ciliate as the predator and two bacteria strains as prey organism. Additionally, another experimental setup consisting of two up to five bacteria species competing for one limiting resource was investigated. Highly controllable chemostat systems were established to exclude extrinsic disturbances. According to theoretical analyses I was able to show - experimentally and theoretically - that phenotypic plasticity of one species within a microbial one-predator-two-prey food web enlarges the range of possible coexistence of all species under different dynamic conditions, compared to a food web without phenotypic plasticity. This was accompanied by non-linear (chaotic) population dynamics within all experimental systems showing phenotypic plasticity. The experiments on the interplay of competition, predation and invasion showed that all aspects have an influence on species coexistence. Under undisturbed controlled conditions all aspects were analyzed in detail and in combination. Populations showed oscillations which were shown by quasi-chaotic attractors in phase space diagrams. Competition experiments with two up to five bacteria species competing for one limiting resource showed that all organisms were able to coexist which was mediated by species oscillations entering a regime of chaos. Besides that fact it was found, that the productivity (biomass) as well as the total cell numbers - under the same nutrition supply - increased by an increasing number of species in the experimental systems. Up to now, the occurrence of non-linear dynamics in well controlled experimental studies has been recognized several times and this phenomenon seemed to be more common in natural systems than generally assumed.}, language = {en} } @article{NomdedeuWillenSchiefferetal.2012, author = {Nomdedeu, Mar Monsonis and Willen, Christine and Schieffer, Andre and Arndt, Hartmut}, title = {Temperature-dependent ranges of coexistence in a model of a two-prey-one-predator microbial food web}, series = {Marine Biology}, volume = {159}, journal = {Marine Biology}, number = {11}, publisher = {Springer}, address = {Berlin}, issn = {1432-1793}, doi = {10.1007/s00227-012-1966-x}, pages = {2423 -- 2430}, year = {2012}, abstract = {The objective of our study was to analyze the effects of temperature on the population dynamics of a three-species food web consisting of two prey bacteria (Pedobacter sp. and Acinetobacter johnsonii) and a protozoan predator (Tetrahymena pyriformis) as model organisms. We assessed the effects of temperature on the growth rates of all three species with the objective of developing a model with four differential equations based on the experimental data. The following hypotheses were tested at a theoretical level: Firstly, temperature changes can affect the dynamic behavior of a system by temperature-dependent parameters and interactions and secondly, food web response to temperature cannot be derived from the single species temperature response. The main outcome of the study is that temperature changes affect the parameter range where coexistence is possible within all three species. This has significant consequences on our ideas regarding the evaluation of effects of global warming.}, language = {en} } @article{HeinzelSchaeferMuelleretal.2010, author = {Heinzel, Alexander and Sch{\"a}fer, Ralf and M{\"u}ller, Hans-Wilhelm and Schieffer, Andre and Ingenhag, Ariane and Northoff, Georg and Franz, Matthias and Hautzel, Hubertus}, title = {Differential modulation of valence and arousal in high-alexithymic and low-alexithymic individuals}, series = {Neuroreport}, volume = {21}, journal = {Neuroreport}, number = {15}, publisher = {Lippincott Williams \& Wilkins}, address = {London}, issn = {1473-558X}, doi = {10.1097/WNR.0b013e32833f38e0}, pages = {998 -- 1002}, year = {2010}, abstract = {High-alexithymic individuals are characterized by an impaired ability to identify and communicate emotions whereas low-alexithymic individuals have a wide-ranging ability to deal with emotions. This study examined the hypothesis that valence and arousal modifications of emotional stimuli differentially modulate cortical regions in high-alexithymic and low-alexithymic individuals. To this end, 28 high-alexithymic and 25 low-alexithymic individuals were investigated with event-related fMRI using visual emotional stimuli. We found differential neural activations in the dorsal anterior cingulate, the insula and the amygdala. We suggest that these differences may account for the impaired ability of high-alexithymic individuals to appropriately handle emotional stimuli.}, language = {en} } @article{HeinzelSchaeferMuelleretal.2010, author = {Heinzel, Alexander and Sch{\"a}fer, Ralf and M{\"u}ller, Hans-Wilhelm and Schieffer, Andre and Ingenhag, Ariane and Eickhoff, Simon B. and Northoff, Georg and Franz, Matthias and Hautzel, Hubertus}, title = {Increased Activation of the Supragenual Anterior Cingulate Cortex during Visual Emotional Processing in Male Subjects with High Degrees of Alexithymia: An Event-Related fMRI Study}, series = {Psychotherapy and Psychosomatics}, volume = {79}, journal = {Psychotherapy and Psychosomatics}, number = {6}, publisher = {Karger}, address = {Basel}, issn = {0033-3190}, doi = {10.1159/000320121}, pages = {363 -- 370}, year = {2010}, abstract = {Background: One of the most prominent neurobiological models of alexithymia assumes an altered function of the anterior cingulate cortex (ACC) as the crucial neural correlate of alexithymia. So far functional imaging studies have yielded inconclusive results. Therefore, we tested this hypothesis in healthy alexithymics and nonalexithymics in an event-related fMRI study. Methods: Thirty high- and 30 low-alexithymic right-handed male subjects (selected by the 20-item Toronto Alexithymia Scale, TAS-20) were investigated with event-related fMRI using a picture viewing paradigm. The stimuli consisted of happy, fearful and neutral facial expressions (Ekman-Friesen) as well as positive, negative and neutral pictures from the International Affective Picture System. Results: Contrasting the high-alexithymic with the low-alexithymic group we observed increased activation of the supragenual ACC for different emotional valences as well as for different emotional stimuli. Moreover, there was a positive correlation of the ACC with the individual TAS-20 scores but no correlations with the individual Beck Depression Inventory scores. Additionally, there was no difference in activity of the amygdala. Conclusions: We demonstrated that the supragenual ACC is constantly activated more strongly in alexithymic subjects and that this activation is related to the symptoms of alexithymia and not to associated symptoms such as depression. Therefore, our findings support the hypothesis of an altered function of the ACC in alexithymia.}, language = {en} } @article{KirchnerOberlaenderSusoetal.2013, author = {Kirchner, Patrick and Oberl{\"a}nder, Jan and Suso, Henri-Pierre and Rysstad, Gunnar and Keusgen, Michael and Sch{\"o}ning, Michael Josef}, title = {Towards a wireless sensor system for real-time H2O2 monitoring in aseptic food processes}, series = {Physica status solidi (a)}, volume = {210}, journal = {Physica status solidi (a)}, number = {5}, publisher = {Wiley}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201200920}, pages = {877 -- 883}, year = {2013}, abstract = {A wireless sensor system based on the industrial ZigBee standard for low-rate wireless networking was developed that enables real-time monitoring of gaseous H2O2 during the package sterilization in aseptic food processes. The sensor system consists of a remote unit connected to a calorimetric gas sensor, which was already established in former works, and an external base unit connected to a laptop computer. The remote unit was built up by an XBee radio frequency (RF) module for data communication and a programmable system-on-chip controller to read out the sensor signal and process the sensor data, whereas the base unit is a second XBee RF module. For the rapid H2O2 detection on various locations inside the package that has to be sterilized, a novel read-out strategy of the calorimetric gas sensor was established, wherein the sensor response is measured within the short sterilization time and correlated with the present H2O2 concentration. In an exemplary measurement application in an aseptic filling machinery, the suitability of the new, wireless sensor system was demonstrated, wherein the influence of the gas velocity on the H2O2 distribution inside a package was determined and verified with microbiological tests.}, language = {en} } @inproceedings{DuongNguyenStaat2012, author = {Duong, Minh Tuan and Nguyen, Nhu Hunyh and Staat, Manfred}, title = {Finite Element Implementation of a 3D Fung-type Model}, series = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}, booktitle = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}, publisher = {Verlag d. Technischen Universit{\"a}t Graz}, address = {Graz}, isbn = {978-3-85125-223-1}, year = {2012}, language = {en} } @inproceedings{FrotscherRaatschenStaat2012, author = {Frotscher, Ralf and Raatschen, Hans-J{\"u}rgen and Staat, Manfred}, title = {Effectiveness of the edge-based smoothed finite element method applied to soft biological tissues}, series = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}, booktitle = {ESMC-2012 - 8th European Solid Mechanics Conference, Graz, Austria, July 9-13, 2012}, editor = {Holzapfel, Gerhard A.}, publisher = {Verlag d. Technischen Universit{\"a}t Graz}, address = {Graz}, isbn = {978-3-85125-223-1}, year = {2012}, language = {en} } @inproceedings{StreunAlKaddoumParletal.2012, author = {Streun, M. and Al-Kaddoum, R. and Parl, C. and Pietrzyk, U. and Ziemons, Karl and Waasen, S. van}, title = {Simulation studies of optical photons in monolithic block scintillators}, series = {2011 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, booktitle = {2011 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-4673-0120-6 (electronic ISBN)}, doi = {10.1109/NSSMIC.2011.6154621}, pages = {1380 -- 1382}, year = {2012}, abstract = {The interest in PET detectors with monolithic block scintillators is growing. In order to obtain high spatial resolutions dedicated positioning algorithms are required. But even an ideal algorithm can only deliver information which is provided by the detector. In this simulation study we investigated the light distribution on one surface of cuboid LSO scintillators of different size. Scintillators with a large aspect ratio (small footprint and large height) showed significant position information only for a minimum interaction depth of the gamma particle. The results allow a quantitative estimate for a useful aspect ratio.}, language = {en} }