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A Gaupp

Publications and source records attributed to A Gaupp.

6 recordsLinked to original sources
PubMed2001

Observation of the x-ray magneto-optical Voigt effect.

The existence of the x-ray magneto-optical Voigt effect is demonstrated. By means of polarization analysis the Voigt rotation and ellipticity of linearly polarized synchrotron radiation are measured at the Co L3 edge upon transmission through an amorphous Co film. The observed x-ray Voigt rotation is about 7.5 degrees /microm. On the basis of ab initio calculations it is shown that the x-ray Voigt effect follows sensitively the amount of spin polarization of the 2p core states. Therefore it provides a unique measure of the spin splitting of the core states.

Journal Article↗
PubMed2000

Tissue pH in human kidney transplants during hypothermic ischemia.

Ex vivo NMR spectroscopy was used to investigate pH in 67 human kidney transplants. (1)H and (31)P spectra were recorded at 1.5 T during regular hypothermic storage in histidine-tryptophane-alpha-ketoglutarate (HTK) solution. Estimations of cytosolic pH from chemical shift differences between inorganic phosphate and phosphodiesters and of extracellular pH from the varepsilon1 and delta2 protons of histidine were based upon systematic titration studies. The possibility to predict acute tubular necrosis (ATN) by measuring pH was compared to results obtained with peak area ratios of phosphomonoesters (PME) and Pi and of the gamma-phosphorus of nucleoside 5'-triphosphate (gamma-NTP) and Pi. Cytosolic pH was 6.86+/-0.10 in kidneys showing immediate post-transplant function and 6.84+/-0.10 in those with ATN. Time-dependent studies demonstrated a monoexponential pH decay (velocity constant: 0.14+/-0.07 h(-1)). Extracellular pH varied between 7.40 and 7.15. Grafts with immediate function showed higher PME/Pi (2.24+/-0.57 vs. 1.77+/-0.50, p<0.05) and gamma-NTP/Pi (0.33+/-0.16 vs. 0.16+/-0.08, p<0.001). Intra- and extracellular pH can be monitored non-invasively during hypothermic transplant storage. The pH gradient between both compartments provides quantitative information about the buffer capacity of the preservation medium. Acidification is not a primary cause of ATN during regular HTK storage. The total nucleotide pool is a determinant of the reversibility of ischemic injury.

Adolescent↗
PubMed1998

Insertion devices for BESSY II.

The high-brilliance synchrotron radiation source BESSY II will provide space for the installation of 14 insertion devices. At the time of writing (July 1997), eight insertion devices are funded. The first light for use by scientists will be available in January 1999. The undulators are designed for a scanning operation in parallel with the monochromator. This modus requires tight tolerances concerning the drive system. The first insertion device to be installed, a U-49 undulator, has been assembled and magnetically measured. The r.m.s. phase error is 2 degrees. An endpole configuration using coils with less than 64 amp-turns makes the angular kick smaller than +/-3 micro rad over a gap range 15-50 mm.

Journal Article↗
PubMed1998

A plane-grating monochromator for circularly polarized undulator radiation at BESSY II.

At BESSY II, a third-generation 1.7 GeV storage ring is under construction. A planar elliptical undulator will be installed as a source of X-rays that have a high degree of circular polarization. Radiation in the first, third and fifth harmonics will cover the energy range 87-1330 eV. The beamline will essentially consist of a plane-grating monochromator working with collimated light in the dispersion plane. A single set of optical elements can be used to handle the two angularly separated beams of opposite helicity from the double undulator. The degree of circular polarization ranges from 73 to 100%, and a flux of up to 5 x 10(13) photons s(-1) (100 mA)(-1) can be achieved. A maximum spectral resolution of about 13 000 will be possible at 100 eV using a 20 micro m slit.

Journal Article↗
PubMedDate not supplied

Kinetics of metabolism in human kidney transplants measured by dynamic 31P NMR spectroscopy.

The technique of ex vivo 31P NMR spectroscopy has been used for the investigation of metabolic turnover in 15 cadaveric human kidneys obtained from brain-dead donors for transplantation. Measurements were carried out at 1.5 T time-dependently during regular hypothermic storage in histidine-tryptophan-alpha-ketoglutarate solution. The minimum delay between explanation and spectroscopy was 2 h 41 min. In one case of a discarded organ the measurements could be extended over a period of 161 h 35 min. A detailed kinetic model describing monoexponential ischemic phosphate turnover, which accounts for various interrelations of the NMR visible metabolites, has been derived. Averaged velocity constants of the decays of nucleotides and phosphomono- and -diesters ranged from 0.0047 to 0.294h-1 at approximately 4 degrees C. Intracellular pH decreased monoexponentially with an averaged velocity constant of 0.31 h-1.

Brain Death↗