Reviews the Hafele-Keating experiment on relativistic changes in eastward and westward moving cesium atomic clocks. Recommends the use of the Sagnac effect to remove the east-west time asymmetry and of the general-relativistic effect to elucidate the clock-rate changes. (CC)

Discusses research activities conducted by scientists from the United State of America, Canada, and the United Kingdom to determine the long-term effects on natural marine ecosystems, especially plankton communities, of such pollutants as heavy metals, synthetic hydrocarbons, and petroleum hydrocarbons. (CC)

Describes a microbiological experiment designed to study the competition between two species of bacteria. Experimental procedures and data obtained in conducting this experiment are provided, together with a discussion of the results. (JR)

Describes the commercial applications of hydroponics, and then outlines ways in which this soilless plant culture method can be used in the science classroom and laboratory. Gives directions for making a suitable growth solution, and suggests appropriate student experiments involving hydroponics. (JR)

Provides description of an activity in which students synthesized sulfanilamide or sulfathiazole, II. The drug was then used as a chemotherapeutic agent. (RH)

A practical magnetotropism experiment with seeds is presented. The procedures, needed controls, and observations of results are described. (DF)

The ratio of electronic charge to Boltzmann's constant can be easily determined by measuring the short-circuit collector current versus the emitter-base voltage characteristic of a silicon transistor connected in the common-base mode. (Author/DF)