Although it is a very rare condition, physicians should be aware that a pheochromocytoma can bleed and present acutely in the abdomen with shock; an accurate diagnosis and adequately prepared surgical removal are important for a good postoperative prognosis.

No abstract

No abstract

No abstract

No abstract

No abstract

The propagation characteristics of medium-latitude whistlers are studied on the basis of measurements with a new direction finder at Moshiri (geomag. lat. 34.5øN; L --1.6) during January and February 1978. Detailed analyses are made for two selected events: one with the highest daytime activity on January 22 and the other with the highest nighttime activity on February 20. Daytime whistlers are of multiflash or of an isolated type, and the dispersion remains constant during the event. The measured polarization is, on the average, close to exactly circular, indicating a negligible effect of multi-paths in the earth-ionosphere waveguide, implying that the ionospheric exit points are determined accurately. The characteristics on the direction finding results are compared with the properties expected for ducted and nonducted pro-longitudinal mode propagation and it is concluded that the whistlers may be attributed to ducted progagation. Just a single duct is present during the event. The dimension at the lower boundary of the ionosphere, illuminated by the duct which probably terminated' at the F•_, is found to be -• 100 km. The small apparent movement of the exit regions may be due to a temporal fluctuation of the propagation conditions between the duct endpoint and the lower boundary of the ionosphere. For the nighttime whistlers there are four distinct dispersions, but we concentrate ourselves on the main dispersion which remained constant during the event. The observed polarization is less circular than for the case of daytime whistlers for the measured incident angle •< 60 ø. For larger incident angles, 60 ø • i • 75 ø, we find a great variabilit• in the measured polarization. These indicate that multi-path propagation may have a significant effect on the propagation in the waveguide at night. Correspondingly, there is a great scatter in the estimated exit points during each time interval. The exit region also shows a large apparent drift. This may be interpreted in terms of a joint effect of the presence of four ducts at the nearly same L shell and the temporal variation of the activity of the lightning sources at the feet of the four ducts in the conjugate zone. The scale of nighttime ducts is difficult to determine due to the great scatter of the data.by Thomson and Dowden [1977]. Hence, the results of the direction finding measurements are used for the study of the propagation mechanism, i.e., ducted or non-ducted PL mode. If the whistlers are attributed to ducted propagation, we can study the properties of medium-latitude ducts and their stability, which would be a basis for comparison with those at high latitudes.The measurement was made during two months in whistler active January and February, 1978. One event was selected, for detailed analysis, from daytime and nighttime whistlers, respectively. Section 2 is concerned with the direction finding results for daytime whistlers and their propagation character-•On leave from Research Institute of Atmospherics, Nagoya Uni-istics. Then in section 3 the results...

The measurement of the wave normal direction of short whistlers is made in the ionosphere by means of a three-dimensional crossed loop antenna on a rocket. The results of the whistler wave normal direction are presented, and some relationships to the propagation characteristics in the magnetosphere and also to the penetration through the ionosphere are discussed. Since the proposal of trapped propagation by Smith [1961]there has never been any direct evidence for the presence of field-aligned ducts for whistler propagation. However, a steady accumulation of indirect evidence for ducted propagation of ground-based whistlers enables us to deduce the electron density profile of the magnetosphere [Helliwell, 1965]. Carpenter [1968] ha s obtained evidence for ducted prop-agation that is inferred from the fact that the phenomena are consistent with the half-gyrofrequency propagation effect predicted by Smith. Then Angerami [1970] found in situ evidence for the existence of ducts, 'using the simultaneous detection of ducted whistlers as well as the high-frequency leaked ones on board the Ogo 3 satellite, and also got information on duct properties, such as the enhancement factor, the width, and the interduct spacing. Furthermore, Scarf and Chappell [1973] have studied the association of whistler dispersions with ß ß eee ß ß ß ß ß ß ß ß