Radiologists differ markedly in the estimation of pneumothorax risk for a patient undergoing co-axial lung biopsy. Identifying individual patients developing pneumothorax was only possible when risk was estimated at > or =50%. Pulmonary haemorrhage was uncommon and difficult to predict accurately.

SynopsisPositron lifetime studies were performed on well-characterized annealed and quenched samples of isotactic polypropylene. The positron experiments were conducted from -20 to 110°C a s a function of both heating and cooling. Of the three decaying exponential components resolved from the lifetime spectra, only the long-lifetime ortho-positronium (o-Ps) pickofr component was affected by the changes in temperature. The behavior of both the lifetime and intensity of the o-Ps component was interpreted with the aid of x-ray diffraction, densitometry, and optical microscopy examinations and results from previously reported investigations of the thermal transition behavior of polypropylene. The present experiments demonstrate that 0-Ps lifetimes were similar for both the annealed and quenched samples, independent of thermal cycling, while the 0-Ps component intensity was significantly larger for the quenched material during heating, with both sample types exhibiting a significant hysteresis upon cooling. These results suggest that the mean free-volume cavity size is independent of prior thermal treatment, while the density of free-volume sites is a sensitive function of structure and prior thermal history. The variations of lifetime and of intensity with temperature have provided insight into polypropylene's glass transition phenomena.

Since Messner and Habeler climbed to the summit of Mount Everest (8,848 m) without oxygen in 1978, there has been controversy between scientists trying to explain this feat. Field studies have suggested better respiratory performance than that found during a simulated climb in a hypobaric chamber, but the lack of data at extreme altitude has hampered the debate.We measured arterial oxygen saturation (Sa,O 2 ) and alveolar partial pressure of oxygen (PA,O 2 ) in nine subjects as they climbed from 3,500 to 8,000 m. Four of the climbers reached 8,000 m and one reached the summit. We also tested the effects of breathing supplementary oxygen on Sa,O 2 at 6,550 and 8,000 m.At all altitudes tested, we found that both PA,O 2 and Sa,O 2 were higher than expected from low pressure chamber studies. We also found that standard rates of supplementary oxygen (2 L·min -1 ) were insufficient to restore Sa,O 2 above 90% at 8,000 m.The respiratory performance of climbers at extreme altitude is better than expected from sea-level chamber studies, which may, in part, explain why humans can reach the summit (8,848 m) without added oxygen. The better performance is likely to be due to more appropriate acclimatization.

It is shown that germanium is more rapidly etched than silicon in conventional fluorine-, chlorine-, and brominebased low-pressure plasmas and that a high Ge/Si etch rate ratio ERR can be readily obtained. The etching of Ge induced by plasma-generated fluorine atoms relies much less on ion bombardment than the etching of Si. A very high Ge/Si ERR (=40) may therefore be achieved for plasma etching conditions or for reactive ion etching at high pressure (250 mtorr)

SynopsisPositron annihilation lifetime spectroscopy has been used to study the isothermal relaxation response of compression molded bisphenol-A polycarbonate at temperatures of 263, 273, and 303 K. The temperature dependence of both the lifetime and intensity of the ortho-Positronium (0-Ps) pickoff component is discussed in terms of ductile-to-brittle transition behavior and free .volume theory. An additive exponential model and the Williams-Watt model were used to ;analyze the relaxation as a function of temperature and provided results consistent with the anticipated molecular mobility of polycarbonate at sub-2' ' temperatures.