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Regensburg, Germany

Atamanchuk D.,Gothenburg University | Tengberg A.,Gothenburg University | Tengberg A.,Aanderaa Data Instruments AS | Thomas P.J.,Christian Michelsen Research | And 4 more authors.
Limnology and Oceanography: Methods | Year: 2014

This article reports the performance of an improved, newly developed, compact, low power, lifetime-based optical sensor (optode) for measuring partial pressure of dissolved CO2 gas (pCO2) in natural waters. The results suggest that after preconditioning, these sensors are stable in water for time periods longer than 7 months. The wide dynamic range of about 0-50000 μatm opens possibilities for numerous applications of which some are presented. In normal marine environments with pCO2 levels of 200-1000 μatm, the best-obtained precision was about ±2 μatm, and the absolute accuracy was between 2-75 μatm, depending on the deployment and the quality of the collected reference water samples. One limitation is that these sensors will become irreversibly poisoned by H2S and should thus not be deployed in sulphidic environments. © 2014, by the American Society of Limnology and Oceanography, Inc. Source


Hofmann J.,Friedrich - Alexander - University, Erlangen - Nuremberg | Meier R.J.,University of Regensburg | Mahnke A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schatz V.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 7 more authors.
Methods and Applications in Fluorescence | Year: 2013

Tissue oxygenation plays a critical role in the pathogenesis of various diseases, but non-invasive, robust and user-friendly methods for its measurement in vivo still need to be established. Here, we are presenting an in vivo oxygen-detection system that uses ratiometric luminescence imaging (RLI) as a readout scheme to determine the skin oxygen tension of mouse hind footpads via side-by-side comparison with more established techniques including luminescence-lifetime imaging using planar sensor films and the polarographic electrode as the gold standard. We also demonstrate that this technology allows the detection of changes in mouse skin tissue oxygenation induced by subjecting mice to systemic hypoxia. The data demonstrate oxygen imaging based on RLI to be a most useful tool for reliably and easily analyzing and monitoring skin tissue oxygenation in vivo. This technology will advance our understanding of local regulation of skin tissue oxygenation in various disease conditions. © 2013 IOP Publishing Ltd. Source


Meier J.K.,University of Regensburg | Prantl L.,University of Regensburg | Geis S.,University of Regensburg | Mueller S.,University of Regensburg | And 3 more authors.
Clinical Hemorheology and Microcirculation | Year: 2013

BACKGROUND: In a preliminary trial, we were able to show first promising results in the analysis of perioperative and postoperative perfusion of free flaps by means of a new monitoring system for detecting thrombotic vessel occlusion before clinical signs become evident. OBJECTIVE: We investigated whether flap monitoring by measuring perfusion-dependent parameters differs between radial forearm and fibular free flaps and whether a threshold value requiring anastomosis revision could be determined. METHODS: 37 radial forearm flaps (RF) and 15 fibular flaps (FF) were harvested and transplanted. Perfusion was determined by measuring a fluorescent oxygen sensor foil covering a flap's skin surface with a handheld fluorescence microscope. The sensor contained an oxygen reservoir, which was consumed by the tissue corresponding to the perfusion status of the flap. Measurements were done before explantation, after successful anastomosis and one day after surgery. RESULTS: We found a significant difference (p < 0.005) in the relative transdermal oxygen consumption (RTOC) between clinically well-perfused grafts (RF: mean: 0.13 ± 0.08; FF: mean: 0.15 ± 0.07) and clinically poorly perfused grafts (RF: mean: 0.40 ± 0.09; FF: mean: 0.55 ± 0.28). A threshold RTOC value of 0.3 for differentiating between well-perfused and poorly perfused flaps was confirmed for both RF and FF. © 2013 - IOS Press and the authors. All rights reserved. Source


Meier J.K.,University Medical CentreRegensburg | Prantl L.,University of Regensburg | Geis S.,University of Regensburg | Mueller S.,University Medical CentreRegensburg | And 3 more authors.
Clinical Hemorheology and Microcirculation | Year: 2014

A threshold RTOC value of 0.3 for differentiating between well-perfused and poorly perfused flaps was confirmed for both RF and FF. © 2014 - IOS Press and the authors. All rights reserved.Background: In a preliminary trial, we were able to show first promising results in the analysis of perioperative and postoperative perfusion of free flaps by means of a new monitoring system for detecting thrombotic vessel occlusion before clinical signs become evident.Objective: We investigated whether flap monitoring by measuring perfusion-dependent parameters differs between radial forearm and fibular free flaps and whether a threshold value requiring anastomosis revision could be determined.Methods: 37 radial forearm flaps (RF) and 15 fibular flaps (FF) were harvested and transplanted. Perfusion was determined by measuring a fluorescent oxygen sensor foil covering a flap's skin surface with a handheld fluorescence microscope. The sensor contained an oxygen reservoir, which was consumed by the tissue corresponding to the perfusion status of the flap. Measurements were done before explantation, after successful anastomosis and one day after surgery.Results: We found a significant difference (p < 0.005) in the relative transdermal oxygen consumption (RTOC) between clinically well-perfused grafts (RF: mean: 0.13 ± 0.08; FF: mean: 0.15 ± 0.07) and clinically poorly perfused grafts (RF: mean: 0.40 ± 0.09; FF: mean: 0.55 ± 0.28). Source


Thomas P.J.,Christian Michelsen Research | Pedersen G.,Christian Michelsen Research | Hide A.,MMC Tendos AS | Apostolidis A.,PreSens GmbH | And 7 more authors.
OCEANS 2013 MTS/IEEE Bergen: The Challenges of the Northern Dimension | Year: 2013

This paper describes our progress towards the development of field deployable pCO2 and NH3 in water measurement technologies. The fluorescence lifetime based pCO2 technology described here has a wide dynamic range of 102-5×104 microatmospheres and has undergone numerous field trials that indicate suitability to a wide range of short and long term monitoring applications. The spectrophotometric NH 3 technology described is in an earlier stage of development, and the characterization experiments performed to date show that the technology responds reversibly to ammonia concentrations at the low ppb level and could therefore be applicable to a wide range of applications within aquaculture and oceanography. The pCO2 and NH3 sensor prototypes used in these investigations are based on the same mechanical platform, that in future could also form the basis for other water quality monitoring technologies. © 2013 IEEE. Source

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