@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} } @article{ParlLarueStreunetal.2011, author = {Parl, C. and Larue, H. and Streun, M. and Ziemons, Karl}, title = {Double-side-readout technique for SiPM-matrices}, series = {2010 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, journal = {2010 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, publisher = {IEEE}, address = {New York}, issn = {1095-7863}, pages = {1486 -- 1487}, year = {2011}, abstract = {In our case the double-side-method is used to minimize the complexity of a matrix-readout. Here the number of channels is reduced to 2√N̅. It is also possible to benefit from the method in a single pixel readout system. One signal can be used to measure position and energy of the event, the other one can be applied to a fast trigger-circuit at the same time. In a next step we will investigate timing behavior and electrical crosstalk of the circuit.}, language = {en} } @article{HerzogPietrzykShahetal.2010, author = {Herzog, Hans and Pietrzyk, Uwe and Shah, N. Jon and Ziemons, Karl}, title = {The current state, challenges and perspectives of MR-PET}, series = {Neuroimage}, volume = {49}, journal = {Neuroimage}, number = {3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1053-8119}, doi = {10.1016/j.neuroimage.2009.10.036}, pages = {2072 -- 2082}, year = {2010}, abstract = {Following the success of PET/CT during the last decade and the recent increasing proliferation of SPECT/CT, another hybrid imaging instrument has been gaining more and more interest: MR-PET. First combined, simultaneous PET and MR studies carried out in small animals demonstrated the feasibility of the new approach. Concurrently, some prototypes of an MR-PET scanner for simultaneous human brain studies have been built, their performance is being tested and preliminary applications have already been shown. Through this pioneering work, it has become clear that advances in the detector design are necessary for further optimization. Recently, the different issues related to the present state and future prospects of MR-PET were presented and discussed during an international 2-day workshop at the Forschungszentrum J{\"u}lich, Germany, held after, and in conjunction with, the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference in Dresden, Germany on October 27-28, 2008. The topics ranged from small animal MR-PET imaging to human MR-BrainPET imaging, new detector developments, challenges/opportunities for ultra-high field MR-PET imaging and considerations of possible future research and clinical applications. This report presents a critical summary of the contributions made to the workshop.}, language = {en} } @article{BeerStreunHombachetal.2010, author = {Beer, S. and Streun, M. and Hombach, T. and Buehler, J. and Jahnke, S. and Khodaverdi, M. and Larue, H. and Minwuyelet, S. and Parl, C. and Roeb, G. and Schurr, U. and Ziemons, Karl}, title = {Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants}, series = {Physics in Medicine and Biology}, volume = {55}, journal = {Physics in Medicine and Biology}, number = {3}, publisher = {IOP}, address = {Bristol}, issn = {1361-6560}, doi = {10.1088/0031-9155/55/3/006}, pages = {635 -- 646}, year = {2010}, abstract = {Positron emitters such as 11C, 13N and 18F and their labelled compounds are widely used in clinical diagnosis and animal studies, but can also be used to study metabolic and physiological functions in plants dynamically and in vivo. A very particular tracer molecule is 11CO2 since it can be applied to a leaf as a gas. We have developed a Plant Tomographic Imaging System (PlanTIS), a high-resolution PET scanner for plant studies. Detectors, front-end electronics and data acquisition architecture of the scanner are based on the ClearPET™ system. The detectors consist of LSO and LuYAP crystals in phoswich configuration which are coupled to position-sensitive photomultiplier tubes. Signals are continuously sampled by free running ADCs, and data are stored in a list mode format. The detectors are arranged in a horizontal plane to allow the plants to be measured in the natural upright position. Two groups of four detector modules stand face-to-face and rotate around the field-of-view. This special system geometry requires dedicated image reconstruction and normalization procedures. We present the initial performance of the detector system and first phantom and plant measurements.}, language = {en} } @article{StreunLarueParletal.2009, author = {Streun, M. and Larue, H. and Parl, C. and Ziemons, Karl}, title = {A compact PET detector readout using charge-to-time conversion}, series = {2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, journal = {2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, publisher = {IEEE}, address = {New York}, isbn = {1082-3654}, pages = {1868 -- 1870}, year = {2009}, abstract = {The readout of gamma detectors is considerably simplified when the event intensity is encoded as a pulse width (Pulse Width Modulation, PWM). Time-to-Digital-Converters (TDC) replace the conventional ADCs and multiple TDCs can be realized easily in one PLD chip (Programmable Logic Device). The output of a PWM stage is only one digital signal per channel which is well suited for transport so that further processing can be performed apart from the detector. This is particularly interesting for large systems with high channel density (e.g. high resolution scanners). In this work we present a circuit with a linear transfer function that requires a minimum of components by performing the PWM already in the preamp stage. This allows a very compact and also cost-efficient implementation of the front-end electronics.}, language = {en} } @article{WedrowskiBruyndonckxTavernieretal.2009, author = {Wedrowski, M. and Bruyndonckx, P. and Tavernier, S. and Zhi, L. and Dang, J. and Mendes, P. R. and Perez, J. M. and Ziemons, Karl}, title = {Robustness of neural networks algorithm for gamma detection in monolithic block detector, positron emission tomography}, series = {2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, journal = {2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, isbn = {1082-3654}, pages = {2625 -- 2628}, year = {2009}, abstract = {The monolithic scintillator block approach for gamma detection in the Positron Emission Tomography (PET) avoids estimating Depth of Interaction (DOI), reduces dead zones in detector and diminishes costs of detector production. Neural Networks (NN) are very efficient to determine the entrance point of a gamma incident on a scintillator block. This paper presents results on the robustness of the spatial resolution as a function of the random fraction in the data, temperature and HV fluctuations. This is important when implementing the method in a real scanner. Measurements were done with two Hamamatsu S8550 APD arrays, glued on a 20 {\~A}— 20 {\~A}— 10 mm3 monolithic LSO crystal block.}, language = {en} } @article{JahnkeMenzelDusschotenetal.2009, author = {Jahnke, Siegfried and Menzel, Marion I. and Dusschoten, Dagmar van and Roeb, Gerhard W. and B{\"u}hler, Jonas and Minwuyelet, Senay and Bl{\"u}mler, Peter and Temperton, Vicky M. and Hombach, Thomas and Streun, Matthias and Beer, Simone and Khodaverdi, Maryam and Ziemons, Karl and Coenen, Heinz H. and Schurr, Ulrich}, title = {Combined MRI-PET dissects dynamic changes in plant structures and functions}, series = {The Plant Journal}, volume = {59}, journal = {The Plant Journal}, number = {4}, publisher = {Wiley}, address = {Weinheim}, isbn = {1365-313X}, pages = {634 -- 644}, year = {2009}, abstract = {Unravelling the factors determining the allocation of carbon to various plant organs is one of the great challenges of modern plant biology. Studying allocation under close to natural conditions requires non-invasive methods, which are now becoming available for measuring plants on a par with those developed for humans. By combining magnetic resonance imaging (MRI) and positron emission tomography (PET), we investigated three contrasting root/shoot systems growing in sand or soil, with respect to their structures, transport routes and the translocation dynamics of recently fixed photoassimilates labelled with the short-lived radioactive carbon isotope 11C. Storage organs of sugar beet (Beta vulgaris) and radish plants (Raphanus sativus) were assessed using MRI, providing images of the internal structures of the organs with high spatial resolution, and while species-specific transport sectoralities, properties of assimilate allocation and unloading characteristics were measured using PET. Growth and carbon allocation within complex root systems were monitored in maize plants (Zea mays), and the results may be used to identify factors affecting root growth in natural substrates or in competition with roots of other plants. MRI-PET co-registration opens the door for non-invasive analysis of plant structures and transport processes that may change in response to genomic, developmental or environmental challenges. It is our aim to make the methods applicable for quantitative analyses of plant traits in phenotyping as well as in understanding the dynamics of key processes that are essential to plant performance.}, language = {en} }