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Notes: Abstract A typical, small encatchment (catena Bölkendorf) in the moraine, northeast German agricultural landscape Schorfheide-Chorin was studied with respect to summit, midslope, and foot-slope positions at northern and southern slope exposure, respectively, including a central noncultivated kettle hole position (pot hole). Across the sequence of seven distinct sampling positions, soil organic carbon and total nitrogen contents, soil gravimetric water content, and soil microbial biomass displayed maxima at the kettle hole position. Soil pH revealed a decreasing trend at the northern exposed slope and a minimum at the kettle hole position. Against this background, the population density of total culturable bacteria clearly displayed a minimum at the kettle hole position, whereas the population density of carboxymethylcellulose decomposing bacteria was not clearly differentiated in relation to sampling positions. To study the phylogenetic diversity of culturable cellulolytic bacteria, 311 isolates were obtained from the sampling positions across the entire encatchment and examined by restriction analysis of PCR-amplified 16S rDNA. Using the restriction enzyme ScrFI, isolates were classified into 31 pattern groups. Although the ratio of actinomycetes within total isolates ranged from 0.73 to 0.94, only 16 pattern groups originated from actinomycetes, but 15 from other bacteria. At all sampling positions, a dominant pattern group was identified, containing 38 to 65% of total isolates. Two site-specific pattern groups could be identified, representing significant parts of the total population, which were highly specific for the kettle hole (19% of total isolates) and for foot- and midslope positions (15–18% of total isolates), respectively. In general, the composition of cellulolytic isolates across the encatchment displayed differences with respect to slope positions, but was not significantly affected by soil properties. Based on 16S rDNA sequence analysis, isolates of the dominant as well as the specific pattern groups could be assigned to the genus Streptomyces. Furthermore, sequencing of 16S rDNA of isolates of another three pattern groups revealed a high phylogenetic diversity among these isolates, including cellulomonads and bacilli.

Notes: The vacuum ultraviolet emission of neon excited with a pulsed 100 MeV 32S9+ ion beam from the Munich Tandem van de Graaff accelerator was studied at pressures between 1.8 and 96.1 kPa. In the wavelength range between 70 and 110 nm the first, second, and third excimer continua were observed. From time- and pressure-dependent studies of the third continuum emission at a wavelength of 99 nm, rate coefficients k2=(3.6±0.3)×10−13 cm3/s for the bimolecular reaction Ne2++Ne→2Ne+ and k3=(2.84±0.09)×10−31 cm6/s for the termolecular reaction Ne2++2Ne→(Ne2+Ne)2++Ne were determined.

Notes: Abstract Organ shortage and suboptimal prosthetic or biological materials for repair or replacement of diseased or destroyed human organs and tissues are the main motivation for increasing research in the emerging field of tissue engineering. No organ or tissue is excluded from this multidisciplinary research field, which aims to provide vital tissues with the abilities to function, grow, repair, and remodel. There are several approaches to tissue engineering, including the use of cells, scaffolds, and the combination of the two. The most common approach is biodegradable or resorbable scaffolds configured to the shape of the new tissue (e.g. a heart valve). This scaffold is seeded with cells, potentially derived from either biopsies or stem cells. The seeded cells proliferate, organize, and produce cellular and extracellular matrix. During this matrix formation, the starter matrix is degraded, resorbed, or metabolized. First clinical trials using skin or cartilage substitutes are currently under way. Both the current state of the field and future prospects are discussed.

Notes: Amplified spontaneous emission on the second xenon excimer continuum at 172 nm wavelength was observed in dense gas evaporated from a solid xenon surface and pumped by heavy ions. A pulsed 3.78 MeV Kr+ beam from a radio-frequency quadrupole accelerator was used for the experiment. A series of 800 μJ particle pulses each 10 ns long was focused to a small, elliptical beam spot leading to a pump power density of the order of 1 GW/g. Optical gain in the target was deduced from the angular distribution of light emitted along the target axis, and from a variation of optical intensity with gain length. A maximum gain of 26%/cm was determined using a model calculation which reproduced the experimental data.

Notes: The use of low-energy ((approximate)15 keV) electron beams for pumping laser systems in dense gases with high specific power deposition is described. Thin (300 nm) SiNx ceramic foils used as entrance window in a transverse geometry for the electron beam allows pressure differentials of several atmospheres with low percentage energy loss in transmission. The 1.73 μm XeI (5d[3/2]1–6p[5/2]2) infrared laser was used for a first demonstration of this concept. The laser operated between 130 and 650 mbar. A threshold pumping power of 5.3 W and a maximum output power of 6 mW were observed. The system can be scaled to high pumping power ((approximate)MW/cm3) and short wavelength. © 1999 American Institute of Physics.

Notes: Beams of high-energy heavy ions (Ar and U) from the UNILAC accelerator have been used to excite rare gases at pressures near 1 bar. The dominant spectroscopic feature observed in Ar, Kr, and Xe gases was molecular excimer emission at the second excimer continuum at 130, 150, and 170 nm, respectively. The excimer radiation was studied as a function of time (with respect to the excitation pulse), ion-beam current, pressure, and excitation density. The efficiency of excimer production from heavy-ion-beam energy was found to be several percent. Details of spectral shape, especially the ratio of first-to-second continuum emission, were found to depend on pressure and exciting beam type.

Notes: Eleven rare-gas laser lines in the near infrared and the 1.45-μm line in carbon have been pumped with an intense 3.6-MeV He+ dc beam from the Stuttgart Dynamitron accelerator. In one experimental run a 40 Ar beam was also successfully tested. Laser action was observed in gas mixtures up to several hundred mbar total pressure using a differentially pumped gas target. A maximum output power of 170 mW was observed from He-Ar laser lines. This shows that ion beam accelerators which are widely used in nuclear physics can also be used as a versatile pumping source for lasers. The maximum power which can presently be provided by the Stuttgart accelerator is about 1 kW (dc). The observed laser lines in the infrared region between 1.15 and 3.07 μm are known from low-pressure electrical discharge lasers. The excitation scheme at the relatively high pressures used had been investigated in connection with nuclear pumped lasers by other authors. Ion beam pumping is found to be an interesting pumping method in itself and at present a suitable way to optimize the conditions relevant for nuclear-pumped lasers as the measurements do not have to be performed in the vicinity of a high flux nuclear reactor.