Afternoon radio aurora was observed on 26 days out of 54 during the period May 1965 to January 1966, with the Millstone Hill, Massachusetts, radar. The completely steerable 84‐foot‐diameter antenna provided a 0.6° half‐power beamwidth at 1295 MHz. Echoes were obtained at azimuths within ±30° of the magnetic meridian (345°T) and at elevation angles up to 13°. They were returned from a layer‐like region having a thickness of 5–20 km and located at an average height near 110 km. The echoes are strongly aspect sensitive, and none were obtained from regions where the aspect angle was greater than about 3°. Both the occurrence of auroral echoes and the southernmost limit of the echo region were found to correlate with the magnetic index Kp. The Doppler spectra of the echoes show predominantly approaching velocities to the east of the magnetic meridian and receding velocities to the west. The magnitude of the Doppler offset and the variation of offset with azimuth favor the two‐stream plasma instability theory of Farley as an explanation of auroral echoes. The direction of plasma wave motion together with the variation of electrojet current with altitude may explain the presence of echoes at the magnetic meridian (not expected from the Farley theory for an east‐west current).

To test the hypothesis that there is an early stage of cholesterol gallstone formation in man characterized by symptoms of chronic cholecystitis, poor gallbladder emptying, and biliary cholesterol crystals, we studied cholecystokinin-stimulated gallbladder emptying by DISIDA scintigraphy and examined bile for cholesterol crystals in symptomatic patients with normal oral cholecystography and gallbladder sonography. Of 36 patients studied, 16 had biliary cholesterol crystals; their mean 30-min gallbladder ejection fraction was 25.9 +/- 14.8%. Among the 20 patients without crystals, the mean ejection fraction was 60.3 +/- 23.3%. Fifteen patients, 11 with crystals and four without, had cholecystectomy because of persistent symptoms. All with crystals preoperatively and three without had chronic cholecystitis histologically. One patient without crystals had normal histology. We conclude that poor gallbladder contractility, well-established as an etiologic factor in animal models of cholesterol cholelithiasis, is now linked to acalculous cholecystitis, an early stage of human cholesterol cholelithiasis.

The reflection of VHF radio waves from the sun has been observed regularly over the period April 19 to July 7, 1961, in a series of radar experiments conducted by the M.I.T. Lincoln Laboratory, Lexington, Massachusetts. The VHF radar system, designed for radio studies of the solar corona and other associated propagation research, is located near El Campo, Texas, at 29.00° north latitude and 96.25° west longitude. The radar was operated at a frequency of 38.25 Mc/s with a transmitted power of 500 kw, CW.

No abstract