[en] Stress and its effect on the body remain an omnipresent topic in the field of health and social sciences. Despite the high interest a robust marker for the analysis of stress has yet not been identified. In this thesis a murine full-body analysis with 2-[18F]FDG µPET/µCT was used to establish suitable stress models for this method and evaluate whether it can be used as a robust marker for preclinical observation of the stress response in mice. Mice (C57BL/6) were stressed in three different ways: acute cooling, acute restrain and chronic cooling. Acute stress was conducted once for 1h in isolation (cooled or restraint) while chronic stress lasted over the course of 1 week. To observe the influence of obesity on stress response a high-fat diet obese mice model was also employed. Handling and imaging protocols were all optimized to improve the quality and reproducibility of results, since successful 2-[18F]FDG imaging is highly dependent on a multitude of factors such as consideration of circadian rhythm when monitoring stress (experiments from 8-12a.m.). Mice were anesthetized with Isoflurane for BGL and 2-[18F]FDG application as well as during the imaging procedure and scanned for 10min (static) or 70min (dynamic). Afterwards, serum samples were taken via cardiac puncture and animals sacrificed under anesthesia by cervical dislocation for subsequent dissection and harvesting of organs for ex-vivo biodistribution studies. Other methods were also used to gain further insight into the underlying mechanisms and additionally validate the newly established stress models. For this, corticosterone levels were quantified, as usually practiced, in serum samples via ELISA assay, but also in feces samples, representing a non-invasive less stress-inducing method. This work successfully showed the establishment of murine stress models including proper handling and imaging protocols, to be used for 2-[18F]FDG µPET/µCT analysis. Successful activation of stress response was identified by increased corticosterone levels via ELISA assay in serum and feces samples and activation of stress-related brain regions like hypothalamus, amygdala, and brain stem via 2-[18F]FDG µPET/µCT. Furthermore, we report for the first time that 2-[18F]FDG uptake in BAT is independent of the stress type or cold exposure and an increased uptake occurs in lean mice upon restrain. We were able to observe a number of trends in BAT uptake: a significantly reduced uptake in obese mice, no change in uptake upon stress in obese mice and a significantly higher BAT uptake in female mice. Obesity and sex also revealed to play a role in alteration of 2-[18F]FDG uptake in the heart. Lean mice do not show any significant changes in heart uptake after stress exposure whereas obese mice have a significantly increased uptake upon acute and chronic cooling. This trend is inverse to the changes in BAT uptake and suggests a difference in effects on target organs of the stress response, depending on the body type. All in all, 2-[18F]FDG-µPET/µCT imaging as conducted in this thesis proofed to be a suitable method for the evaluation of stress response activation and subsequent effects on the body. It was successfully used to observe changes depending on stress type, sex, and morphology. In the future it may be used to study stress and its outcome in multiple diseases and health conditions to gain further inside into this complex topic. (author)

[en] In order to shed light on the intriguing, and not yet fully understood fcc-isostructural γ → α transition in cerium, we have begun an experimental program aimed at the determination of the pressure evolution of the transverse acoustic (TA) and longitudinal acoustic (LA) phonon dispersions up to and above the transition. γ-Ce Crystals of 60-80 mm diameter and 20 mm thickness were prepared from a large ingot, obtained from Ames Lab, using laser cutting, micro-mechanical and chemical polishing techniques. Three samples with a surface normal approximately oriented along the [110] direction were loaded into diamond anvil cells (DAC), using neon as a pressure transmitting medium. The crystalline quality was checked by rocking curve scans and typical values obtained ranged between one and two degrees. Only a slight degradation in the sample quality was observed when the pressure was increased to reach the α-phase, and data could be therefore recorded in this phase as well. The spectrometer was operated at 17794 eV in Kirkpatrick-Baez focusing geometry, providing an energy resolution of 3 meV and a focal spot size at the sample position of 30 x 60 mm² (horizontal x vertical, FWHM). Eight to ten IXS spectra were typically recorded per phonon branch. Figure 1 reports the pressure dependence of the LA[100] branch in the γ-phase for pressures of 1, 4 and 6 kbar, together with previous inelastic neutron scattering (INS) results [1] at ambient pressure. A clear decrease of the phonon energies with increasing pressure is observed for 1 and 4 kbar, whereas the phonon energies increase again at 6 kbar, still well within the stability field of the γ-phase. Figure 2 reports the LA dispersion along all three main symmetry directions at 6 kbar (γ-phase) and 8 kbar (α-phase), together with the INS results at ambient conditions. Besides the already discussed unusual behavior along the [100] direction, the pressure evolution of the two other longitudinal branches in the γ-phase is quite different. The LA [110] branch displays a downward bending near the zone boundary (ZB), whereas the phonon energies at low reduced momentum transfer remain close to the ones at room pressure. In contrast to this, the LA [111] branch does not display any pressure dependence. The LA phonon energies in the α-phase at 8 kbar are systematically higher than the corresponding lower pressure phonon energies, consistent with the higher density of the α-phase and the expected larger elastic constants. We note, however, substantial changes in the lattice dynamics along the [110] direction. While the phonons between ζ = 0.4 and 0.6 show a large energy increase with pressure, the phonon energy decreases at the zone boundary, thus leading to a pronounced overbending of the branch. The shape of the LA phonon branches in the α-phase are close to those measured in thorium at ambient conditions [2] while the γ-phase phonon dispersion resembles fcc metastable lanthanum [3]. This behavior might be a signature of substantial changes in the Fermi surface topology, leading to significant changes in the electron-phonon coupling mechanism. A Born-von Karman fit to the phonon dispersion is currently being performed in order to quantify the changes in the force constant matrix

[en] The quantum efficiencies of a Si pnn/sup +/ and a GaAsP Schottky photodiode have been measured in the photon energy range from 5 to 1000 eV. The efficiency is generally much higher than that of photoemissive detectors. The performance of the Si diode is affected by soft X-ray exposure, but for the Schottky diode a stable quantum efficiency is observed over the entire spectral range making this device attractive for many applications

[en] The investigation of phonon dispersion in crystalline materials and collective atom motions in disordered matter such as liquids and glasses by inelastic X-ray scattering has attracted a diversified user community with the advent of 3"r"d generation synchrotron sources. The present article provides a short historical account of the research field and discusses selected highlights of research performed on the ESRF inelastic scattering beamlines ID16 and ID28 in the past ten years.

[en] The phonon dispersion of fcc argon under high pressure to 20 GPa has been measured along the (100) direction by inelastic x-ray scattering. First, this shows a novel possibility to investigate the single crystal dynamical properties under very high pressure in a diamond anvil cell. Second, the comparison between experiment and phonon calculations, using pair potentials (either the pure two-body potential or an effective pair potential) and a Slater-Kirkwood form for the three-body interaction, clearly demonstrates that phonon energies can be strongly influenced under high pressure by the nonadditive part of the interaction

[en] The calculation of the spherical aberration, which has been given only in the case of a point source up to now, is extended to the case of source of finite size. It is shown that the real size of the image can be well described by a convolution of the ideal size of the image and the aberrations involved. The expression for an optimum magnification is developed yielding the smallest possible image size for a given optical system in the case of a cylindrical mirror. Calculations are presented for different ESRF sources and the results are compared to simulations performed by the ray-tracing code SHADOW

[en] We report the first measurement of the Cu-O bond stretching phonon dispersion in optimally doped Bi2Sr1.6La0.4Cu2O6+delta using inelastic x-ray scattering. We found a softening of this phonon at q=(0.25,0,0) from 76 to 60 meV, similar to the one reported in other cuprates. A comparison with angle-resolved photoemission data on the same sample revealed an excellent agreement in terms of energy and momentum between the angle-resolved photoemission nodal kink and the soft part of the bond stretching phonon. Indeed, we find that the momentum space where a 63+-5 meV kink is observed can be connected with a vector q=(xi,0,0) with xi (ge) 0.22, corresponding exactly to the soft part of the bond stretching phonon

[en] Using insertion devices as intense light sources in the new, third generation storage rings leads to considerable heat load at the first optical element in the beamline. To minimize the thermal slope of these elements it is proposed to cool them cryogenically. In this article we present first tests of liquid nitrogen cooling of silicon and germanium crystals exposed to high intensity synchrotron radiation. The test were performed with white radiation from the HARWI wiggler at the Hamburger Synchrotronstrahlungslabor (HASYLAB). During the experiment the DORIS ring was running at 3.7 GeV electron energy and up to ∝ 100 mA current. The maximum power at the sample surface was ∝ 100 W with power densities of up to 0.4 W/mm². The minimization of thermal deteriorations by cryogenic cooling is demonstrated unambiguously by optical interferometry. (orig.)

[en] We report measurements of the phonon density of states as measured with inelastic x-ray scattering in SmFeAsO_1-xF_y powders. An unexpected strong renormalization of phonon branches around 23 meV is observed as fluorine is substituted for oxygen. Phonon dispersion measurements on SmFeAsO_1-xF_y single crystals allow us to identify the 21 meV A_1g in-phase (Sm,As) and the 26 meV B_1g (Fe,O) modes to be responsible for this renormalization, and may reaveal unusual electron-phonon coupling through the spin channel in iron-based superconductors.

[en] We report inelastic x-ray scattering experiments on the lattice dynamics in SmFeAsO and superconducting SmFeAsO_0.60F_0.35 single crystals. Particular attention was paid to the dispersions along the [100] direction of three optical modes close to 23 meV, polarized out of the FeAs planes. Remarkably, two of these modes are strongly renormalized upon fluorine doping. These results provide significant insight into the energy and momentum dependence of the coupling of the lattice to the electron system and underline the importance of spin-phonon coupling in the superconducting iron pnictides.