The International Monitoring System being installed to support monitoring compliance with the Comprehensive Nuclear Test Ban Treaty provides scientists with a unique opportunity for research. There are still a number of problems which limit the full exploitation of the system. These include limitations on signal-to-noise imposed by wind noise and the absence of well defined, internationally accepted calibration standards for sensors. But perhaps the major research challenges lie in the area of source characterization and definition. Most of the signals recorded at the few sites now operating come from unidentified sources. There has been some effort devoted to identifying local and regional sources but the unidentified category still exceeds 50% of all distinct events. There are a number of infrasound sources that occur naturally. These include volcanic eruptions, bolides, microbaroms, mountaintop/wind interactions, severe storms, and earthquakes. Manmade sources include most any energetic activity. After sorting out all these sources, there may remain more exotic sources of infrasound not yet identified. Therein lies a major source of excitement.

A new global network is breathing life into a dormant branch of geophysics. The study of infrasound, or long‐period acoustic signals in the atmosphere was bustling in the 1950s and 1960s. Prior to 1963, almost all nuclear tests occurred in the atmosphere. After 1963, the USSR and U.S. signed the Limited Test Ban Treaty (LTBT), which eliminated all atmospheric nuclear tests. During the era of atmospheric nuclear testing, infrasound research was in demand, since the massive explosions produced strong, long‐period acoustic waves that were globally observed and could be used to locate and describe the nuclear tests. Interest in this branch of geophysics waned with the end of atmospheric testing.

An infrasonic event with a 10to 15-minute duration was detected by multiple infrasonic arrays on April 23, 2001. Data from infrasound arrays IS59 (Hawaii), FAI (Fairbanks), and IS57 (California) are selected for the determination of the origin time and the location of the infrasonic source. The bolide was not observed by infrasonic stations operating in South America or the South Pacific. There were also no confirmed detections from ocean-bottom seismometers and hydroacoustic sensors near the epicenter. A preliminary location was obtained from array back azimuths, and this location was used as a seed for the source iteration process. We compare the estimates obtained for the source location and origin time using different atmospheric models and different stations. The tau-p method is used to estimate theoretical travel times, and we estimate the source position by reducing the time residuals. The variability in the locations may be due to errors in the atmospheric models, the propagation mo dels, or the array estimates. We outline the algorithm used for the location of infrasonic sources, and assess the accuracy of twoand three-station epicentral determinations.

Infection of sweet corn by MDMV and drought stress imposed during vegetative (early-stress) or reproductive (late-stress) growth stages were additive in their effects on ear and plant caracteristics. Weight of ears was reduced 16% by MDMV in 1984 and 22% in 1985. Butt blanking of ears was increased by early stress in 1984 and by MDMV in both years. Leaf area was reduced 15 and 37% by early stress in 1984 and 1985 respectively. Early stress reduced plant height by 7% in 1984 and by 22% in 1985. Reductions in plant height due to MDMV were 4% in 1984 and 23% in 1985. Sugar content of kernels was not affected by drought stress or MDMV. Titer of MDMV was not affected by drought stress

J. H. Burckhalter, H. N. Abramson, J. G. MacConnell, R. J. Thill, A. J. Olson, J. C. Hanson and C. E. Nordman, Chem. Commun. (London), 1968, 1274 DOI: 10.1039/C19680001274