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C Sanner

Publications and source records attributed to C Sanner.

9 recordsLinked to original sources
PubMed2005

Light scattering to determine the relative phase of two Bose-Einstein condensates.

We demonstrated an experimental technique based on stimulated light scattering to continuously sample the relative phase of two spatially separated Bose-Einstein condensates of atoms. The phase measurement process created a relative phase between two condensates with no initial phase relation, read out the phase, and monitored the phase evolution. This technique was used to realize interferometry between two trapped Bose-Einstein condensates without need for splitting or recombining the atom cloud.

Journal Article↗
PubMed2004

Quantum reflection from a solid surface at normal incidence.

We observed quantum reflection of ultracold atoms from the attractive potential of a solid surface. Extremely dilute Bose-Einstein condensates of 23Na, with peak density 10(11)-10(12) atoms/cm(3), confined in a weak gravitomagnetic trap were normally incident on a silicon surface. Reflection probabilities of up to 20% were observed for incident velocities of 1-8 mm/s. The velocity dependence agrees qualitatively with the prediction for quantum reflection from the attractive Casimir-Polder potential. Atoms confined in a harmonic trap divided in half by a solid surface exhibited extended lifetime due to quantum reflection from the surface, implying a reflection probability above 50%.

Journal Article↗
PubMed2004

Dynamical instability of a doubly quantized vortex in a Bose-Einstein condensate.

Doubly quantized vortices were topologically imprinted in /F=1> 23Na condensates, and their time evolution was observed using a tomographic imaging technique. The decay into two singly quantized vortices was characterized and attributed to dynamical instability. The time scale of the splitting process was found to be longer at higher atom density.

Journal Article↗
PubMed2003

An application framework for computer-aided patient positioning in radiation therapy.

The importance of exact patient positioning in radiation therapy increases with the ongoing improvements in irradiation planning and treatment. Therefore, new ways to overcome precision limitations of current positioning methods in fractionated treatment have to be found. The Department of Medical Physics at the German Cancer Research Centre (DKFZ) follows different video-based approaches to increase repositioning precision. In this context, the modular software framework FIVE (Fast Integrated Video-based Environment) has been designed and implemented. It is both hardware- and platform-independent and supports merging position data by integrating various computer-aided patient positioning methods. A highly precise optical tracking system and several subtraction imaging techniques have been realized as modules to supply basic video-based repositioning techniques. This paper describes the common framework architecture, the main software modules and their interfaces. An object-oriented software engineering process has been applied using the UML, C + + and the Qt library. The significance of the current framework prototype for the application in patient positioning as well as the extension to further application areas will be discussed. Particularly in experimental research, where special system adjustments are often necessary, the open design of the software allows problem-oriented extensions and adaptations.

Computer Terminals↗
PubMed1997

Medium-chain acyl CoA dehydrogenase: evidence for phosphorylation.

Mature medium chain acyl-CoA dehydrogenase isolated from pig kidney (pkMCADH) and originating from mitochondria carries a phosphate group as demonstrated by 31P-NMR-spectroscopy and chemical analysis. Two broad resonances at -6.3 and -8 ppm are observed and are assigned to the pyrophosphate group of the cofactor FAD. A third, narrow resonance at 4.65 ppm indicates the presence of a phosphomonoester residue. Chemical analysis of intact pkMCADH shows the presence of 3 +/- 0.3 phosphates, those of FAD and of an additional covalently attached phosphate. With recombinant, human wild type MCADH expressed in and purified from E. coli only the two FAD phosphates (2 +/- 0.35) are found. Similarly, pkMCADH which has been converted to the apoenzyme and reconstituted to holoenzyme also contains 2 +/- 0.4 phosphates. The covalently bound phosphate can be hydrolyzed by phosphatase and subsequently removed by dialysis. The phosphate group has no detectable effect on the catalytic activity of the MCADH measured with artificial and natural electron acceptors such as pig electron transferring flavoprotein. However, phosphorylation has a marked effect on protein solubility which is +5-fold lower for the dephosphorylated protein.

Acyl-CoA Dehydrogenase↗
PubMed1994

Upregulation of NMDARI mRNA induced by MK-801 is associated with massive death of axotomized motor neurones in adult rats.

Studies on the pathogenesis of human motor neurone disease have suffered from the absence of models of motor neurone degeneration in adult animals. Normally in adult rodents, transection of motor neurone axons results in only a modest degree of neuronal death. We reasoned that axotomy-induced motor neurone death might be enhanced by modulating glutamatergic transmission. By axotomizing the facial nerve in adult rats and then administering MK-801 for the first week of a 4-week or 8-week post-lesion survival period, we induced a 67% motor neurone loss by 8 weeks as compared with a 19% loss in controls. A possible explanation for the increased motor neurone loss after MK-801 treatment is that transient blockade of NMDA receptors may upregulate synthesis of NMDA receptor components. In order to test this idea, we employed quantitative in situ hybridization to determine the response of NMDAR1 mRNA to axotomy and axotomy + MK-801 treatment. Quantification of the percentage of area occupied by NMDAR1 silver grains per motor neurone somata indicated that axotomy alone did not provoke a change in NMDAR1 mRNA. However, axotomy and MK-801 combined treatment resulted in a highly significant upregulation of NMDAR1 mRNA when compared with controls or animals treated solely with axotomy. Our results suggest that motor neurone death in adult animals can be enhanced after axotomy in association with the upregulation of NMDA receptor mRNA. Thus, abnormalities in glutamate receptor signalling may lead to subacute motor neurone death in vivo. Furthermore these results indicate that transient treatment with MK-801 is a convenient method for enhancing the degree of motor neurone death after axotomy in adult animals.

Animals↗
PubMed1991

15N- and 13C-NMR investigations of glucose oxidase from Aspergillus niger.

The apoprotein of glucose oxidase from Aspergillus niger was reconstituted with specifically 15N- and 13C-enriched FAD derivatives and investigated by 15N- and 13C-NMR spectroscopy. On the basis of the 15N-NMR results it is suggested that, in the oxidized state of glucose oxidase, hydrogen bonds are formed to the N(3) and N(5) positions of the isoalloxazine system. The hydrogen bond to N(3) is more pronounced than that to N(5) as compared with the respective hydrogen bonds formed between FMN and water. The resonance position of N(10) indicates a small decrease in sp2 hybridization compared to free flavin in water. Apparently the isoalloxazine ring is not planar at this position in glucose oxidase. Additional hydrogen bonds at the carbonyl groups of the oxidized enzyme-bound FAD were derived from the 13C-NMR results. A strong downfield shift observed for the C(4a) resonance may be ascribed in part to the decrease in sp2 hybridization at the N(10) position and to the polarization of the carbonyl groups at C(2) and C(4). The polarization of the isoalloxazine ring in glucose oxidase is more similar to FMN in water than to that of tetraacetyl-riboflavin in apolar solvents. In the reduced enzyme the N(1) position is anionic at pH 5.6. The pKa is shifted to lower pH values by at least 1 owing to the interaction of the FAD with the apoprotein. As in the oxidized state of the enzyme, a hydrogen bond is also formed at the N(3) position of the reduced flavin. The N(5) and N(10) resonances of the enzyme-bound reduced FAD indicate a decrease in the sp2 character of these atoms as compared with that of reduced FMN in aqueous solution. Some of the 15N- and 13C-resonance positions of the enzyme-bound reduced cofactor are markedly pH-dependent. The pH dependence of the N(5) and C(10a) resonances indicates a decrease in sp2 hybridization of the N(5) atom with increasing pH of the enzyme solution.

Aspergillus niger↗