Cryogen-Free dissolution Dynamic Nuclear Polarization polarizer operating at 3.35 T, 6.70 T and 10.1 T

Purpose: A novel dissolution dynamic nuclear polarization (dDNP) polarizer platform is presented. The polarizer meets a number of key requirements for in vitro, pre-clinical and clinical applications. Method: It uses no liquid cryogens, operates in continuous mode, accommodates a wide range of sample sizes up to and including those required for human studies, and is fully automated. Results: It offers a wide operational window both in terms of magnetic field, up to 10.1 T, and temperature, from room temperature down to 1.3 K. The polarizer delivers a 13C liquid state polarization for [1-13C]pyruvate of 70%. The build-up time constant in the solid state is approx. 1200 s (20 min), allowing a sample throughput of at least one sample per hour including sample loading and dissolution. Conclusion: We confirm the previously reported strong field dependence in the range 3.35 to 6.7 T, but see no further increase in polarization when increasing the magnetic field strength to 10.1 T for [1-13C]pyruvate and trityl. Using a custom dry magnet, cold head and recondensing, closed-cycle cooling system, combined with a modular DNP probe, automation and fluid handling systems; we have designed a unique dDNP system with unrivalled flexibility and performance.Comment: 16 pages, 8 figure

Анализ результатов распознавания патологий на рентгенологических изображениях грудной клетки с помощью карт активации классов

International audienceAntibiotics are secondary metabolites, generally produced during stationary phase of growth under different nutritional and hydrodynamic stresses. However, the exact mechanisms of the induction of antibiotics production are still not clearly established. In a previous study, the induction of pristinamycins production by Streptomyces pristinaespiralis as well as product concentrations were correlated with power dissipation per unit of volume (P/V) in shaking flasks. In this study, detailed kinetics of growth, substrate consumption, oxygen transfer rate and pristinamycins production under varying P/V conditions have been obtained and analyzed. Our results showed that higher P/V resulted in a higher concentration of biomass and promoted an earlier nutrient limitation and ultimately an earlier induction of pristinamycins production. The maximal specific growth rate, specific oxygen consumption rate and specific consumption rate of glutamate increased with P/V while influence was less marked with specific consumption rate of glucose, arginine, ammonium ions and phosphate. When oxygen uptake rate (OUR) was limited by free-surface oxygen transfer, pristinamycins production was not detected despite the occurrence of nitrogen and/or phosphate sources limitation. The threshold value for OUR observed was around 25 mmol L(-1) h(-1). This suggested that a limitation in nitrogen and/or phosphate alone was not sufficient to induce pristinamycins production by S. pristinaespiralis pr11. To induce this production, the oxygen transfer had to be non-limiting

MR-Based PET Motion Correction Procedure for Simultaneous MR-PET Neuroimaging of Human Brain

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A fundamental research of growth, metabolism and product formation of tobacco suspension cells at different scales

For over two decades, plant cell cultures have been promising hosts for the expression of recombinant proteins such as hormones, growth factors, full-size antibodies and antigens. So far, over 700 different plant cell cultures are stored in the German Collection of Microorganisms and Cell Cultures (DSMZ) in Braunschweig. Among these plant cell cultures, the tobacco cell line Nicotiana tabacum Bright Yellow 2 (BY-2) was chosen as a good host cell line for the production of recombinant proteins, as this cell line is well characterized – showing high growth rates and high cell synchrony. Up to now, individual studies have only handled one or two parameters (i.e. biomass, osmolality or conductivity) for studying BY-2 cell growth. Such limited studies, however, do not provide a comprehensive insight into BY-2 cell metabolism. A first objective of this thesis, is to identify the optimal growth conditions for tobacco suspension cultures in shake flasks and to comprehensively characterize the growth of a transgenic BY-2 cell line. Hereby, multiple growth parameters were analyzed offline and online by using a Respiration Activity MOnitoring System (RAMOS). A faster shaking frequency resulted in clearly higher oxygen transfer rates and biomass concentrations. Moreover, a reproducibly observed shift of the oxygen transfer rate (OTR) could be identified to indicate ammonium depletion in the medium. Today, the MS-medium is the preferred medium for the cultivation of tobacco suspension cells, even though it was formulated for an optimal growth and not for the production of recombinant proteins. Here, the fluorescent proteins GFP and YFP are used as model proteins and their expression was elucidated in detail. Based on the correlations between nutrient consumption, cell growth and product formation, it is the intention to improve the standard MS-medium to enhance the expression of the recombinant proteins. The initial ammonium concentration was found to have significant influence on either cell growth and played a pregnant role in protein synthesis. After the MS-medium was improved, the GFP concentration nearly doubled. When this improved ammonium enriched medium was applied to another transgenic tobacco cell line similar improvements to the amount of the glycoprotein influenza hemagglutinin (HA) produced by Nicotiana tabacum NT-1 cells could be achieved. Furthermore, a controlled-release system was successfully applied to plant suspension cultures. Using this controlled-release system where additional ammonium was supplied to the plant cells, an increase of 40% GFP intensity was observed. Plant cells are maintained in suspension by pipetting a certain volume of grown culture into fresh medium. Applying this subcultivation method, results in non-defined growth conditions of plant cells. Due to that problem, plant suspension cultures always have to compete with animal cultures for the production of therapeutically relevant proteins as they have the advantage of an established cell banking system. Moreover, researchers are facing the huge problem of genetic instability of plant cells where growth and recombinant protein production tremendously vary. This well-known problem has been poorly documented so far. This growth variability of plant suspension cells was identified by relating the measured values of 22 oxygen transfer rates in a period of over two years. After the implementation of a new subculturing method a significantly better reproducibility of plant cell growth was obtained. However, the productivity, detected by fluorescence and Western blot, decreased by 80% in the same period. Besides the cultivation of plant cells in shake flasks, in this work, plant suspension cells were also cultivated in stirred tank reactors and microtiter plates (MTPs). As there are no geometric similarities between shake flasks and stirred tank reactors, a scale-up is not a trivial process. Here, the scale-up was carried out under the assumption of a constant volumetric power input. It could be shown, that an increasing viscosity was the key parameter influencing cell growth in the fermenter. According to literature there is only one publication dealing with plant cell cultivation in small scale. In this thesis BY-2 cell growth as well as GFP expression was monitored online using the BioLector technology. In addition, it was demonstrated that medium modifications influenced plant cell growth and the GFP production in the same way as shown in shake flasks. Ultimately, this thesis provides a deep insight into tobacco cultivations in shake flasks, fermenters and MTPs. The combined offline and online analysis of tobacco suspension cultures was used for a detailed growth characterization and media optimization to improve growth and boost target product formation. In conclusion, the RAMOS technology allows the online analysis of oxygen consumption and has been proven to be a useful analytical tool investigating plant suspension cultures

A navigator based rigid body motion correction for magnetic Resonance imaging

A novel three-dimensional navigator k-space trajectory for rigid body motion detection for Magnetic Resonance Imaging (MRI) – the Lissajous navigator – was developed and quantitatively compared to the existing spherical navigator trajectory [1]. The spherical navigator cannot sample the complete spherical surface due to slew rate limitations of the scanner hardware. By utilizing a two dimensional Lissajous figure which is projected onto the spherical surface, the Lissajous navigator overcomes this limitation. The complete sampling of the sphere consequently leads to rotation estimates with higher and more isotropic accuracy. Simulations and phantom measurements were performed for both navigators. Both simulations and measurements show a significantly higher overall accuracy of the Lissajous navigator and a higher isotropy of the rotation estimates. Measured under identical conditions with identical postprocessing, the measured mean absolute error of the rotation estimates for the Lissajous navigator was 38% lower (0.3°) than for the spherical navigator (0.5°). The maximum error of the Lissajous navigator was reduced by 48% relative to the spherical navigator. The Lissajous navigator delivers higher accuracy of rotation estimation and a higher degree of isotropy than the spherical navigator with no evident drawbacks; these are two decisive advantages, especially for high-resolution anatomical imaging

Auswärtiges Amt ; KFW: „Der Global Compact: public responsibility oder public relations?" <2003, Berlin> / [Tagungsbericht]

Tagungsbericht: Auswärtiges Amt ; KFW: „Der Global Compact: public responsibility oder public relations?" / veranstaltet vom Auswärtigen Amt und der Kreditanstalt für Wiederaufbau (KfW) am 9. September 2003

A navigator based rigid body motion correction for magnetic Resonance imaging

A novel three-dimensional navigator k-space trajectory for rigid body motion detection for Magnetic Resonance Imaging (MRI) – the Lissajous navigator – was developed and quantitatively compared to the existing spherical navigator trajectory [1]. The spherical navigator cannot sample the complete spherical surface due to slew rate limitations of the scanner hardware. By utilizing a two dimensional Lissajous figure which is projected onto the spherical surface, the Lissajous navigator overcomes this limitation. The complete sampling of the sphere consequently leads to rotation estimates with higher and more isotropic accuracy. Simulations and phantom measurements were performed for both navigators. Both simulations and measurements show a significantly higher overall accuracy of the Lissajous navigator and a higher isotropy of the rotation estimates. Measured under identical conditions with identical postprocessing, the measured mean absolute error of the rotation estimates for the Lissajous navigator was 38% lower (0.3°) than for the spherical navigator (0.5°). The maximum error of the Lissajous navigator was reduced by 48% relative to the spherical navigator. The Lissajous navigator delivers higher accuracy of rotation estimation and a higher degree of isotropy than the spherical navigator with no evident drawbacks; these are two decisive advantages, especially for high-resolution anatomical imaging