Reactive scattering of rydberg atoms: H* + D2 --> HD + D*.

The scattering of highly excited hydrogen Rydberg atoms, H* (n = 36), with deuterium molecules in their rovibrational ground state, D2(v = 0, j = 0), has been investigated at a relative collision energy of 0.53 eV. Time-of-flight distributions of elastically/inelastically scattered H* Rydberg atoms and reactively scattered D* Rydberg atoms have been measured at different laboratory angles. The extracted rovibrationally resolved state distributions of the HD product molecules from reactive collisions resemble closely those reported for the corresponding ion-molecule reaction, H+ + D2 --> HD + D+. This similarity is rationalised using the free electron model which predicts that the Rydberg electron acts as a spectator while the ionic reaction takes place.

[Artifacts in MRT caused by instruments and implants]. / Artefakte in der MRT durch Instrumente und Implantate.

Metallic instruments and implants can cause severe image artifacts in magnetic resonance imaging (MRI). Besides the properties of the materials and the geometrical arrangement of the devices, the applied MRI sequence type and its parameters (echo time, voxel size, read-out bandwidth, orientations of encoding directions, etc.) play also an important role. These interactions are presented in a systematic survey. A detailed description of the basic physical mechanisms underlying the generation of artifacts is also provided.

Confocal laser scanning microscopy of urinary bladder after intravesical instillation of a fluorescent dye.

OBJECTIVES: To assess the potential of confocal laser scanning microscopy for imaging of the urinary bladder after intravesical instillation of a fluorescent dye. METHODS: The study was performed on the bladder of male Copenhagen rats. For confocal fluorescence microscopy (CFM), a standard confocal laser scanning microscope (Zeiss LSM 410) was used. Before measuring, the fluorescent marker SYTO 17 was instilled intravesically. After 2 hours of incubation, the rat was killed, the bladder excised and opened, and CFM was performed starting from the surface going through the urothelium and superficial layers of the lamina propria. Except for the opening incision, the bladder was left intact and no biopsies were taken. After imaging, the bladder was sent for conventional histologic studies. RESULTS: CFM allows imaging of cellular details of the entire urothelium (superficial umbrella cells, intermediate, and basal urothelial cells) and superficial layers of the lamina propria. CFM images are close to those obtained by standard microscopy after conventional hematoxylin-eosin staining. Cell structure (eg, shape, size, chromatin texture, nucleoli, mitotic figures, nuclear/cytoplasmic ratio), as well as the structure of the connective tissue (eg, collagen fibers, blood vessels, erythrocytes), can be studied, allowing a standard histologic evaluation. Furthermore, in contrast to conventional histologic evaluation, CFM provides three-dimensional information and allows the study of intact tissue representing the true in vivo situation. CONCLUSIONS: CFM enables the study of the microscopic anatomy of bladder mucosa in its in vivo state. In combination with optical fiber bundles, endoscopic microscopy of the bladder may be possible in the future.