@article{FeichtingerEilmannBuchmannetal.2014, author = {Feichtinger, Linda M. and Eilmann, Britta and Buchmann, Nina and Rigling, Andreas}, title = {Growth adjustments of conifers to drought and to century-long irrigation}, series = {Forest Ecology and Management}, volume = {2014}, journal = {Forest Ecology and Management}, number = {334}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1872-7042 (Online)}, doi = {10.1016/j.foreco.2014.08.008}, pages = {96 -- 105}, year = {2014}, abstract = {Our knowledge on tree responses to drought is mainly based on short-term manipulation experiments which do not capture any possible long-term adjustments in this response. Therefore, historical water channels in inner-Alpine dry valleys were used as century-long irrigation experiments to investigate adjustments in tree growth to contrasting water supply. This involved quantifying the tree-ring growth of irrigated and non-irrigated (control) Scots pine (Pinus sylvestris L.) in Valais (Switzerland), as well as European larch (Larix decidua Mill.) and black pine (Pinus nigra Arnold) in Vinschgau (Italy). Furthermore, the adjustments in radial growth of Scots pine and European larch to an abrupt stop in irrigation were analyzed. Irrigation promoted the radial growth of all tree species investigated compared to the control: (1) directly through increased soil water availability, and (2) indirectly through increased soil nutrients and humus contents in the irrigated plots. Irrigation led to a full elimination of growth responses to climate for European larch and black pine, but not for Scots pine, which might become more sensitive to drought with increasing tree size in Valais. For the control trees, the response of the latewood increment to water availability in July/August has decreased in recent decades for all species, but increased in May for Scots pine only. The sudden irrigation stop caused a drop in radial growth to a lower level for Scots pine or similar level for larch compared to the control for up to ten years. However, both tree species were then able to adjust to the new conditions and subsequently grew with similar (Scots pine) or even higher growth rates (larch) than the control. To estimate the impact of climate change on future forest development, the duration of manipulation experiments should be on longer time scales in order to capture adjustment processes and feedback mechanisms of forest ecosystems.}, language = {en} } @article{EilmannSterckWegneretal.2014, author = {Eilmann, Britta and Sterck, Frank J. and Wegner, L. and de Vries, Sven M. G. and von Arx, G. and Mohren, Godefridus M. J. and den Ouden, Jan and Sass-Klaassen, Ute G. W.}, title = {Wood structural differences between northern and southern beech provenances growing at a moderate site}, series = {Tree Physiology}, volume = {34}, journal = {Tree Physiology}, number = {8}, publisher = {Oxford University Press}, address = {Oxford}, issn = {1758-4469 (Online)}, doi = {10.1093/treephys/tpu069}, pages = {882 -- 893}, year = {2014}, language = {en} } @article{MuellerHirschfeldLambertzetal.2014, author = {M{\"u}ller, Martin and Hirschfeld, Julian and Lambertz, Rita and Schulze Lohoff, Andreas and Lustfeld, Hans and Pfeifer, Heinz and Reißel, Martin}, title = {Validation of a novel method for detecting and stabilizing malfunctioning areas in fuel cell stacks}, series = {Journal of power sources}, volume = {272}, journal = {Journal of power sources}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-2755 (E-Journal); 0378-7753 (Print)}, doi = {10.1016/j.jpowsour.2014.08.045}, pages = {225 -- 232}, year = {2014}, abstract = {In this paper a setup for detecting malfunctioning areas of MEAs in fuel cell stacks is described. Malfunctioning areas generate electric cross currents inside bipolar plates. To exploit this we suggest bipolar plates consisting not of two but of three layers. The third one is a highly conducting layer and segmented such that the cross currents move along the segments to the surface of the stack where they can be measured by an inductive sensor. With this information a realistic model can be used to detect the malfunctioning area. Furthermore the third layer will prevent any current inhomogeneity of a malfunctioning cell to spread to neighbouring cells in the stack. In this work the results of measurements in a realistic cell setup will be compared with the results obtained in simulation studies with the same configuration. The basis for the comparison is the reliable characterisation of the electrical properties of the cell components and the implication of these results into the simulation model. The experimental studies will also show the limits in the maximum number of segments, which can be used for a reliable detection of cross currents.}, language = {en} } @article{KluczkaEcksteinAlexopoulosetal.2014, author = {Kluczka, Sven and Eckstein, Julian and Alexopoulos, Spiros and Vaeßen, Christiane and Roeb, Martin}, title = {Process simulation for solar steam and dry reforming}, series = {Energy procedia : Proceedings of the SolarPACES 2013 International Conference}, volume = {49}, journal = {Energy procedia : Proceedings of the SolarPACES 2013 International Conference}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102 (E-Journal)}, doi = {10.1016/j.egypro.2014.03.092}, pages = {850 -- 859}, year = {2014}, abstract = {In co-operation with the German Aerospace Center, the Solar-Institut J{\"u}lich has been analyzing the different technologies that are available for methanol production from CO2 using solar energy. The aim of the project is to extract CO2 from industrial exhaust gases or directly from the atmosphere to recycle it by use of solar energy. Part of the study was the modeling and simulating of a methane reformer for the production of synthesis gas, which can be operated by solar or hybrid heat sources. The reformer has been simplified in such a way that the model is accurate and enables fast calculations. The developed pseudo-homogeneous one- dimensional model can be regarded as a kind of counter-current heat exchanger and is able to incorporate a steam reforming reaction as well as a dry reforming reaction.}, language = {en} } @article{GuoSekiMiyamotoetal.2014, author = {Guo, Yuanyuan and Seki, Kosuke and Miyamoto, Ko-ichiro and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Device simulation of the light-addressable potentiometric sensor with a novel photoexcitation method for a higher spatial resolution}, series = {Procedia Engineering}, volume = {87}, journal = {Procedia Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2014.11.369}, pages = {456 -- 459}, year = {2014}, abstract = {A novel photoexcitation method for the light-addressable potentiometric sensor (LAPS) realized a higher spatial resolution of chemical imaging. In this method, a modulated light probe, which generates the alternating photocurrent signal, is surrounded by a ring of constant light, which suppresses the lateral diffusion of photocarriers by enhancing recombination. A device simulation verified that a higher spatial resolution could be obtained by adjusting the gap between the modulated and constant light. It was also found that a higher intensity and a longer wavelength of constant light was more effective. However, there exists a tradeoff between the spatial resolution and the amplitude of the photocurrent, and thus, the signal-to-noise ratio. A tilted incidence of constant light was applied, which could achieve even higher resolution with a smaller loss of photocurrent.}, language = {en} } @article{MiyamotoSekiWagneretal.2014, author = {Miyamoto, K. and Seki, K. and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Yoshinobu, T.}, title = {Enhancement of the spatial resolution of the chemical imaging sensor by a hybrid fiber-optic illumination}, series = {Procedia Engineering}, volume = {87}, journal = {Procedia Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2014.11.563}, pages = {612 -- 615}, year = {2014}, abstract = {The chemical imaging sensor, which is based on the principle of the light-addressable potentiometric sensor (LAPS), is a powerful tool to visualize the spatial distribution of chemical species on the sensor surface. The spatial resolution of this sensor depends on the diffusion of photocarriers excited by a modulated light. In this study, a novel hybrid fiber-optic illumination was developed to enhance the spatial resolution. It consists of a modulated light probe to generate a photocurrent signal and a ring of constant light, which suppresses the lateral diffusion of minority carriers excited by the modulated light. It is demonstrated that the spatial resolution was improved from 92 μm to 68 μm.}, language = {en} } @article{BronderWuPoghossianetal.2014, author = {Bronder, Thomas and Wu, Chunsheng and Poghossian, Arshak and Werner, Frederik and Keusgen, M. and Sch{\"o}ning, Michael Josef}, title = {Label-free detection of DNA hybridization with light-addressable potentiometric sensors: comparison of various DNA-immobilization strategies}, series = {Procedia Engineering}, volume = {87}, journal = {Procedia Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2014.11.647}, pages = {755 -- 758}, year = {2014}, abstract = {Light-addressable potentiometric sensors (LAPS) consisting of a p-Si-SiO2 and p-Si-SiO2-Au structure, respectively, have been tested for a label-free electrical detection of DNA (deoxyribonucleic acid) hybridization. Three different strategies for immobilizing single-stranded probe DNA (ssDNA) molecules on a LAPS surface have been studied and compared: (a) immobilization of thiol-modified ssDNA on the patterned Au surface via gold-thiol bond, (b) covalent immobilization of amino-modified ssDNA onto the SiO2 surface functionalized with 3-aminopropyltriethoxysilane and (c) layer-by-layer adsorption of negatively charged ssDNA on a positively charged weak polyelectrolyte layer of poly(allylamine hydrochloride).}, language = {en} } @article{HuckPoghossianBaeckeretal.2014, author = {Huck, Christina and Poghossian, Arshak and B{\"a}cker, Matthias and Reisert, Steffen and Schubert, J. and Zander, W. and Begoyan, V. K. and Buniatyan, V. V. and Sch{\"o}ning, Michael Josef}, title = {Chemical sensors based on a high-k perovskite oxide of barium strontium titanate}, series = {Procedia Engineering}, volume = {87}, journal = {Procedia Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2014.11.258}, pages = {28 -- 31}, year = {2014}, abstract = {High-k perovskite oxide of barium strontium titanate (BST) represents a very attractive multi-functional transducer material for the development of (bio-)chemical sensors for liquids. In this work, BST films have been applied as a sensitive transducer material for a label-free detection of adsorbed charged macromolecules (positively charged polyelectrolytes) and concentration of hydrogen peroxide vapor as well as protection insulator layer for a contactless electrolyte-conductivity sensor. The experimental results of characterization of individual sensors are presented. Special emphasis is devoted towards the development of a capacitively-coupled contactless electrolyte-conductivity sensor.}, language = {en} } @article{SchusserBaeckerKrischeretal.2014, author = {Schusser, Sebastian and B{\"a}cker, Matthias and Krischer, M. and Wenzel, L. and Leinhos, Marcel and Poghossian, Arshak and Biselli, Manfred and Wagner, P. and Sch{\"o}ning, Michael Josef}, title = {Enzymatically catalyzed degradation of biodegradable polymers investigated by means of a semiconductor-based field-effect sensor}, series = {Procedia Engineering}, volume = {87}, journal = {Procedia Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2014.11.689}, pages = {1314 -- 1317}, year = {2014}, abstract = {A semiconductor field-effect device has been used for an enzymatically catalyzed degradation of biopolymers for the first time. This novel technique is capable to monitor the degradation process of multiple samples in situ and in real-time. As model system, the degradation of the biopolymer poly(D, L-lactic acid) has been monitored in the degradation medium containing the enzyme lipase from Rhizomucor miehei. The obtained results demonstrate the potential of capacitive field-effect sensors for degradation studies of biodegradable polymers.}, language = {en} } @article{Stulpe2014, author = {Stulpe, Werner}, title = {From the attempt of certain classical reformulations of quantum mechanics to quasi-probability representations}, series = {Journal of Mathematical Physics}, volume = {55}, journal = {Journal of Mathematical Physics}, number = {1}, publisher = {AIP Publishing}, address = {College Park, Md.}, issn = {222-488}, doi = {10.1063/1.4861939}, pages = {Artikel 012109}, year = {2014}, abstract = {The concept of an injective affine embedding of the quantum states into a set of classical states, i.e., into the set of the probability measures on some measurable space, as well as its relation to statistically complete observables is revisited, and its limitation in view of a classical reformulation of the statistical scheme of quantum mechanics is discussed. In particular, on the basis of a theorem concerning a non-denseness property of a set of coexistent effects, it is shown that an injective classical embedding of the quantum states cannot be supplemented by an at least approximate classical description of the quantum mechanical effects. As an alternative approach, the concept of quasi-probability representations of quantum mechanics is considered.}, language = {en} } @article{DachwaldMikuckiTulaczyketal.2014, author = {Dachwald, Bernd and Mikucki, Jill and Tulaczyk, Slawek and Digel, Ilya and Espe, Clemens and Feldmann, Marco and Francke, Gero and Kowalski, Julia and Xu, Changsheng}, title = {IceMole : A maneuverable probe for clean in situ analysis and sampling of subsurface ice and subglacial aquatic ecosystems}, series = {Annals of Glaciology}, volume = {55}, journal = {Annals of Glaciology}, number = {65}, publisher = {Cambridge University Press}, address = {Cambridge}, issn = {1727-5644}, doi = {10.3189/2014AoG65A004}, pages = {14 -- 22}, year = {2014}, abstract = {There is significant interest in sampling subglacial environments for geobiological studies, but they are difficult to access. Existing ice-drilling technologies make it cumbersome to maintain microbiologically clean access for sample acquisition and environmental stewardship of potentially fragile subglacial aquatic ecosystems. The IceMole is a maneuverable subsurface ice probe for clean in situ analysis and sampling of glacial ice and subglacial materials. The design is based on the novel concept of combining melting and mechanical propulsion. It can change melting direction by differential heating of the melting head and optional side-wall heaters. The first two prototypes were successfully tested between 2010 and 2012 on glaciers in Switzerland and Iceland. They demonstrated downward, horizontal and upward melting, as well as curve driving and dirt layer penetration. A more advanced probe is currently under development as part of the Enceladus Explorer (EnEx) project. It offers systems for obstacle avoidance, target detection, and navigation in ice. For the EnEx-IceMole, we will pay particular attention to clean protocols for the sampling of subglacial materials for biogeochemical analysis. We plan to use this probe for clean access into a unique subglacial aquatic environment at Blood Falls, Antarctica, with return of a subglacial brine sample.}, language = {en} } @article{LevesqueSiegwolfEilmannetal.2014, author = {L{\´e}vesque, Mathieu and Siegwolf, Rolf and Eilmann, Britta and Saurer, Matthias and Rigling, Andreas}, title = {Increased water-use efficiency does not lead to enhanced tree growth under xeric and mesic conditions}, series = {New Phytologist}, volume = {203}, journal = {New Phytologist}, number = {1}, publisher = {Wiley-Blackwell}, address = {Oxford}, issn = {1469-8137 (Online)}, doi = {10.1111/nph.12772}, pages = {94 -- 109}, year = {2014}, language = {en} } @article{RaueWambachGloeggleretal.2014, author = {Raue, Markus and Wambach, M. and Gl{\"o}ggler, S. and Grefen, Dana and Kaufmann, R. and Abetz, C. and Georgopanos, P. and Handge, U. A. and Mang, Thomas and Bl{\"u}mich, B. and Abetz, V.}, title = {Investigation of historical hard rubber ornaments of Charles Goodyear}, series = {Macromolecular chemistry and physics}, volume = {Vol. 215}, journal = {Macromolecular chemistry and physics}, number = {No. 3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, pages = {245 -- 254}, year = {2014}, language = {en} } @article{HafnerDemetzWeickertetal.2014, author = {Hafner, David and Demetz, Oliver and Weickert, Joachim and Reißel, Martin}, title = {Mathematical Foundations and Generalisations of the Census Transform for Robust Optic Flow Computation}, series = {Journal of Mathematical Imaging and Vision}, journal = {Journal of Mathematical Imaging and Vision}, publisher = {Springer}, address = {New York}, issn = {1573-7683 (Online)}, doi = {10.1007/s10851-014-0529-9}, year = {2014}, language = {en} } @article{FredebeulKreinSteingroever2014, author = {Fredebeul-Krein, Markus and Steingr{\"o}ver, Markus}, title = {Wholesale broadband access to IPTV in an NGA environment : how to deal with it from a regulatory perspective?}, series = {Telecommunications Policy}, volume = {38}, journal = {Telecommunications Policy}, number = {3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0308-5961 (Print)}, doi = {doi:10.1016/j.telpol.2013.04.002}, pages = {264 -- 277}, year = {2014}, language = {en} } @article{MartinGonzalezKotliarRiosMartinezetal.2014, author = {Martin-Gonzalez, Anabel and Kotliar, Konstantin and Rios-Martinez, Jorge and Lanzl, Ines and Navab, Nassir}, title = {Mediated-reality magnification for macular degeneration rehabilitation}, series = {Journal of Modern Optics}, volume = {61}, journal = {Journal of Modern Optics}, number = {17}, publisher = {Taylor \& Francis}, address = {London}, issn = {1362-3044}, doi = {10.1080/09500340.2014.936110}, pages = {1400 -- 1408}, year = {2014}, language = {en} } @article{VogtMottaghyRathetal.2014, author = {Vogt, C. and Mottaghy, Darius and Rath, V. and Marquart, G. and Dijkshoorn, L. and Wolf, A. and Clauser, C.}, title = {Vertical variation in heat flow on the Kola Peninsula: palaeoclimate or fluid flow?}, series = {Geophysical Journal International}, volume = {199}, journal = {Geophysical Journal International}, number = {2}, publisher = {Oxford University Press}, address = {Oxford}, issn = {1365-246X}, doi = {10.1093/gji/ggu282}, pages = {829 -- 843}, year = {2014}, abstract = {Following earlier studies, we present forward and inverse simulations of heat and fluid transport of the upper crust using a local 3-D model of the Kola area. We provide best estimates for palaeotemperatures and permeabilities, their errors and their dependencies. Our results allow discriminating between the two mentioned processes to a certain extent, partly resolving the non-uniqueness of the problem. We find clear indications for a significant contribution of advective heat transport, which, in turn, imply only slightly lower ground surface temperatures during the last glacial maximum relative to the present value. These findings are consistent with the general background knowledge of (i) the fracture zones and the corresponding fluid movements in the bedrock and (ii) the glacial history of the Kola area.}, language = {en} } @article{HaagZontarSchleupenetal.2014, author = {Haag, S. and Zontar, D. and Schleupen, Josef and M{\"u}ller, T. and Brecher, C.}, title = {Chain of refined perception in self-optimizing assembly of micro-optical systems}, series = {Journal of sensors and sensor systems}, volume = {3}, journal = {Journal of sensors and sensor systems}, number = {1}, publisher = {Copernicus Publ.}, address = {G{\"o}ttingen}, issn = {2194-878X}, doi = {10.5194/jsss-3-87-2014}, pages = {87 -- 95}, year = {2014}, abstract = {Today, the assembly of laser systems requires a large share of manual operations due to its complexity regarding the optimal alignment of optics. Although the feasibility of automated alignment of laser optics has been shown in research labs, the development effort for the automation of assembly does not meet economic requirements - especially for low-volume laser production. This paper presents a model-based and sensor-integrated assembly execution approach for flexible assembly cells consisting of a macro-positioner covering a large workspace and a compact micromanipulator with camera attached to the positioner. In order to make full use of available models from computer-aided design (CAD) and optical simulation, sensor systems at different levels of accuracy are used for matching perceived information with model data. This approach is named "chain of refined perception", and it allows for automated planning of complex assembly tasks along all major phases of assembly such as collision-free path planning, part feeding, and active and passive alignment. The focus of the paper is put on the in-process image-based metrology and information extraction used for identifying and calibrating local coordinate systems as well as the exploitation of that information for a part feeding process for micro-optics. Results will be presented regarding the processes of automated calibration of the robot camera as well as the local coordinate systems of part feeding area and robot base.}, language = {en} } @article{VosLagemaatBarentszetal.2014, author = {Vos, E. K. and Lagemaat, M. W. and Barentsz, J. O. and F{\"u}tterer, J. J. and Zamecnik, P. and Roozen, H. and Orzada, S. and Bitz, Andreas and Maas, M. C. and Scheenen, T. W. J.}, title = {Image quality and cancer visibility of T2-weighted Magnetic Resonance Imaging of the prostate at 7 Tesla}, series = {European Radiology}, volume = {24}, journal = {European Radiology}, number = {8}, publisher = {Springer}, address = {Cham}, issn = {1432-1084}, doi = {10.1007/s00330-014-3234-6}, pages = {1950 -- 1958}, year = {2014}, abstract = {Objectives To assess the image quality of T2-weighted (T2w) magnetic resonance imaging of the prostate and the visibility of prostate cancer at 7 Tesla (T). Materials \& methods Seventeen prostate cancer patients underwent T2w imaging at 7T with only an external transmit/receive array coil. Three radiologists independently scored images for image quality, visibility of anatomical structures, and presence of artefacts. Krippendorff's alpha and weighted kappa statistics were used to assess inter-observer agreement. Visibility of prostate cancer lesions was assessed by directly linking the T2w images to the confirmed location of prostate cancer on histopathology. Results T2w imaging at 7T was achievable with 'satisfactory' (3/5) to 'good' (4/5) quality. Visibility of anatomical structures was predominantly scored as 'satisfactory' (3/5) and 'good' (4/5). If artefacts were present, they were mostly motion artefacts and, to a lesser extent, aliasing artefacts and noise. Krippendorff's analysis revealed an α = 0.44 between three readers for the overall image quality scores. Clinically significant cancer lesions in both peripheral zone and transition zone were visible at 7T. Conclusion T2w imaging with satisfactory to good quality can be routinely acquired, and cancer lesions were visible in patients with prostate cancer at 7T using only an external transmit/receive body array coil.}, language = {en} } @article{LagemaatVosMaasetal.2014, author = {Lagemaat, Miriam W. and Vos, Eline K. and Maas, Marnix C. and Bitz, Andreas and Orzada, Stephan and Uden, Mark J. van and Kobus, Thiele and Heerschap, Arend and Scheenen, Tom W. J.}, title = {Phosphorus magnetic resonance spectroscopic imaging at 7 T in patients with prostate cancer}, series = {Investigative Radiology}, volume = {49}, journal = {Investigative Radiology}, number = {5}, publisher = {Lippincott Williams \& Wilkins}, address = {Philadelphia, Pa.}, issn = {1536-0210}, doi = {10.1097/RLI.0000000000000012}, pages = {363 -- 372}, year = {2014}, abstract = {Objectives The aim of this study was to identify characteristics of phosphorus (³¹P) spectra of the human prostate and to investigate changes of individual phospholipid metabolites in prostate cancer through in vivo ³¹P magnetic resonance spectroscopic imaging (MRSI) at 7 T. Materials and Methods In this institutional review board-approved study, 15 patients with biopsy-proven prostate cancer underwent T₂-weighted magnetic resonance imaging and 3-dimensional ³¹P MRSI at 7 T. Voxels were selected at the tumor location, in normal-appearing peripheral zone tissue, normal-appearing transition zone tissue, and in the base of the prostate close to the seminal vesicles. Phosphorus metabolite ratios were determined and compared between tissue types. Results Signals of phosphoethanolamine (PE) and phosphocholine (PC) were present and well resolved in most ³¹P spectra in the prostate. Glycerophosphocholine signals were observable in 43\% of the voxels in malignant tissue, but in only 10\% of the voxels in normal-appearing tissue away from the seminal vesicles. In many spectra, independent of tissue type, 2 peaks resonated in the chemical shift range of inorganic phosphate, possibly representing 2 separate pH compartments. The PC/PE ratio in the seminal vesicles was highly elevated compared with the prostate in 5 patients. A considerable overlap of ³¹P metabolite ratios was found between prostate cancer and normal-appearing prostate tissue, preventing direct discrimination of these tissues. The only 2 patients with high Gleason scores tumors (≥4+5) presented with high PC and glycerophosphocholine levels in their cancer lesions. Conclusions Phosphorus MRSI at 7 T shows distinct features of phospholipid metabolites in the prostate gland and its surrounding structures. In this exploratory study, no differences in ³¹P metabolite ratios were observed between prostate cancer and normal-appearing prostate tissue possibly because of the partial volume effects of small tumor foci in large MRSI voxels.}, language = {en} }