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[en] The contribution under consideration reports on a gamma denitometric measurement of gas concentrations in a vertical heated tube bundle which is flowed around by a fluid. Two measurement positions, two flow rates of the circulating fluid, two subcooling values and eleven heat fluxes were selected for the measurement. The authors of this contribution describe the test facility, measurement methodology, results and their interpretation. The measurement uncertainty is described in detail.
[en] It is shown that β-rhombohedral boron has different states of thermal equilibrium at T < approximately 150 and < approximately 180 K. These states can be distinguished by their optical absorption spectra showing electronic transitions into a bound state at 0.4 eV at low temperatures, and transitions into an energy continuum at higher temperatures. By steady state optical excitation the transition temperature is lowered indicating a kind of Mott transition. This phase transition is assumed to be the reason for the discontinuity of numerous physical properties of β-rhombohedral boron in this range of temperature. (author)
[en] 70 patients subjected to orthopedic treatment and radiotherapy for skeletal tumors have been examined. It was found that serious radiation injuries frequently occurred. Above all there were contractures, disordered healing of wounds, ulcerations, and scolioses and kyphoses of the growing skeleton. Therefore, in the case of diseases of the skeleton, it is recommended to restrain radiotherapy. It has to be rejected in child's age
[en] To study the onset of the osteoarthrotic process, an osteoarthrosis model was used on the knee joint in adult rabbits by a valgus deformity of the proximal tibia of 300 in conformity with Reimann 1973. The synthesis capacity of the chondrocytes was investigated by using 35S-sulfate autoradiographies. Already prior to the affection of the superficial integrity of the cartilage it was possible to observe an enhanced glycosaminoglycan synthesis, but with progressing fibrillation the sulfate incorporation was found to be diminished. Thanks to autoradiography with 3H-thymidine the replication of the chondrocytes was already found at very early stages of osteoarthrosis that is likely to occur mitotically. The osteotomy itself induces mitoses and an enhanced glycosaminoglycan synthesis. (author)
[en] Tests have shown that ionizing radiation induces a characteristic smell in the packaging laminates which also affects the simulated foods used, which however were relatively neutral in flavour, so that the tests represent the worst case. The paper explains that due to the various additives used in the production of the plastic packaging materials, the same types of polymers may react differently to the ionizing radiation, so that the results obtained from the tests are not suitable for general application. It is recommended to very carefully select the suitable packaging material for given foods and intended irradiation processes. Aspects of particular importance are discusses. (orig./CB)
[de]Bei den bestrahlten Verpackungsfolien trat ein typischer 'Bestrahlungsgeruch' auf, der auch auf Lebensmittelsimulantien ueberging. Hierbei ist jedoch zu beachten, dass die verwendeten Prueflebensmittel Schokolade, Lactose und Wasser relativ geschmacksneutral sind und sich die Aenderungen der sensorischen Eigenschaften sehr empfindlich bestimmen lassen. Es handelt sich somit um den 'worst case' Fall. Weiterhin zeigen die Ergebnisse, dass sich gleiche Polymertypen aufgrund der unterschiedlichen herstellungsbedingten Additivzusaetze in den Kunststoffen dennoch unterschiedlich verhalten koennen. Dies macht eine Verallgemeinerung der gefundenen Effekte der ionisierenden Strahlung auf Kunststoffe sehr schwierig. In Anbetracht der sehr unterschiedlichen Strahlenbestaendigkeit von Kunststoffmaterialien ist es daher zu empfehlen, den Packstoff im Einzelfall unter Beruecksichtigung des realen Lebensmittels und der angewandten Bestrahlungsbedingungen zu pruefen. Grosses Augenmerk ist dabei auf moegliche Veraenderungen der Migration im leichtfluechtigen Bereich und auf die sensorischen Eigenschaften zu richten. (orig.)
[en] To get information on the electronic states in the band gap of beta-rhombohedral boron, optical and photoelectric properties of samples with C contents up to 3250 ppm were investigated. The low-temperature phase transition is shown to be independent of the C content. Carbon acts as donor and evokes occupied electronic ground states in the energy range of the hole trapping level near the valence band edge, and excited states in the band gap. Simultaneous measurements of optical absorption and electrical conductivity yield valuable information on the transport process, and indicate diffusion processes of trapped carriers even at low temperatures
[en] The FORTE satellite, launched on August 29, 1997, carries both radio-frequency-receiver and optical (imaging and photometric) payloads for the study of lightning. The radio-frequency (RF) data for the first 7 months of operation are described, both to illustrate the satellite close-quote s capabilities and to explain the basic statistical findings so far. FORTE close-quote s multichannel RF trigger system represents a significant advance in space-based monitoring of lightning emissions. We are able to observe even rather weak and diffuse RF emissions from lightning and are no longer limited to the brightest known events, open-quotes transionospheric pulse pairs,close quotes or TIPPs. We do see TIPPs, and we show that the FORTE observations of TIPPs are consistent only with the second pulse close-quote s being due to a ground reflection. We find that TIPPs are basically bimodal in character, one type having a steep roll-off of power from 38 to 130 MHz and the other being essentially flat-spectrum in that range. The steep-spectrum TIPPs cluster together in the manner of most RF emissions from lightning, while the flat-spectrum events tend to maintain a wider spacing (>0.1 s) between recurrent emissions. copyright 1999 American Geophysical Union
[en] Preliminary observations of simultaneous RF and optical emissions from lightning as seen by the FORTE spacecraft are presented. RF/optical pairs of waveforms are routinely collected both as individual lightning events and as sequences of events associated with cloud-to-ground (CG) and intra-cloud (IC) flashes. CG pulses can be distinguished from IC pulses based on the properties of the RF and optical waveforms, but mostly based on the associated RF spectrograms. The RF spectrograms are very similar to previous ground-based VHF observations of lightning and show signatures associated with return strokes, stepped and dart leaders, and attachment processes,. RF emissions are observed to precede the arrival of optical emissions at the satellite by a mean value of 280 microseconds. The dual phenomenology nature of these observations are discussed in terms of their ability to contribute to a satellite-based lightning monitoring mission
[en] We aimed at assessing stent geometry and in-stent contrast attenuation with 64-slice CT in patients with various coronary stents. Twenty-nine patients (mean age 60 ± 11 years; 24 men) with 50 stents underwent CT within 2 weeks after stent placement. Mean in-stent luminal diameter and reference vessel diameter proximal and distal to the stent were assessed with CT, and compared to quantitative coronary angiography (QCA). Stent length was also compared to the manufacturer's values. Images were reconstructed using a medium-smooth (B30f) and sharp (B46f) kernel. All 50 stents could be visualized with CT. Mean in-stent luminal diameter was systematically underestimated with CT compared to QCA (1.60 ± 0.39 mm versus 2.49 ± 0.45 mm; P < 0.0001), resulting in a modest correlation of QCA versus CT (r 0.49; P < 0.0001). Stent length as given by the manufacturer was 18.2 ± 6.2 mm, correlating well with CT (18.5 ± 5.7 mm; r = 0.95; P < 0.0001) and QCA (17.4 ± 5.6 mm; r = 0.87; P < 0.0001). Proximal and distal reference vessel diameters were similar with CT and QCA (P = 0.06 and P = 0.03). B46f kernel images showed higher image noise (P < 0.05) and lower in-stent CT attenuation values (P < 0.001) than images reconstructed with the B30f kernel. 64-slice CT allows measurement of coronary artery in-stent density, and significantly underestimates the true in-stent diameter compared to QCA. (orig.)
[en] HfAlN hard coatings were synthesized by cathodic arc evaporation from Hf0.75Al0.25 targets at different bias voltages and N2 pressures. Structural investigations by x-ray diffraction (XRD) revealed the formation of a face-centered cubic (fcc) structure with a change in the preferred orientation depending on the energetic growth conditions. This change in the crystal structure did not significantly influence the mechanical properties, e.g., hardness, where values ranging from 24 to 26 GPa were measured. The obtained fcc phase is stable up to 1000 deg. C as no significant changes in the crystal structure could be observed after annealing in vacuum. Similar experiments in ambient air and subsequent analysis of the coatings by XRD and Raman spectroscopy revealed an onset temperature for oxidation in the range of 700-800 deg. C and the formation of monoclinic HfO2 as the dominating oxide phase. Ball-on-disk tests at different temperatures were performed in order to evaluate the tribological properties. The coefficient of friction ranged from 0.8 to 1.2 depending on the testing temperature while the best wear performance was obtained in the temperature range of 300-500 deg. C.