Teenage scientists show off projects.

More than 900 high school students displayed their experiments at the 45th International Science and Engineering Fair, competing or schlorships, awards, prizes, and trips valued at competing for scholarships, awards, prizes, and trips valued at nearlky $400,000. Their projects covered 14 categories and ranged from homemdade cyclotrons to self-cooling lunch packs. Science Service, which publishes SCIENCE NEWS, sponsors the annual event. Somne examples of projects:

* Reed L. Levine, 16, of John F. Kennedy High School in Bellmore, N.Y., examined whether magnetic resonance imaging (MRI) alters the spatial-learning abilities of mice and the concentrations of melatonin in their blood. Other studies show that the brains of mice, humans, and turtles contain magnetized particles and that magnetic fields in the environment affect melatonin concentrations, he writes in an abstract.

Mice that underwent MRI failed to learn how to negotiate a maze as well as mice not exposed to a magnetic field, but their melatonin concentrations remained unchanged. The MRI's effect on the brain's magnetized particles may have impaired the animals' spatial skills, Levine suggests.

* Robert D. Smith, 18, of Poplarville (Miss.) Senior High School, sought to develop hardier strawberries. Among small fruits, strawberries rank as teh most prone to disease. They are quite susceptible to Colletotrichum, a fungus, Smith says.

He exposed small pieces of strawberry and strawberry seedlings to different concentrations of a toxin released by the fungus. He is now using the surviving cells and seedlings to grow what he hopes will become disease-resistant plants. the usual test for fungal resistance involves sprying plants with the fungus, which is more dangerous to plants than the toxin.

* Yvonne Ou, 17, of Lexington (Mass.) High School, went in search of a "low-cost, environmentally safe, interim road deicer," she explains. Researchers have developed a good replacement for the corrosove and environmentally unfriendly rock salt (NaCl). But that alternative, calcium magniesium acetate (CMA), is too expensive for wide use. So Ou decided to test the effectiveness of a misture of the two compounds.

She measured how various blends influenced ice melt and grass growth and how much they corroded metal. To find the best combination of the two ingredients, she developed a computer model of the different blends' effects.

"Results or laboratory experiments indicated that DMA/NaCI deicer mixtures are an attractive alternative," Ou writes in her project abstract. The mixtures' ice-melting abilities requalted those of rock salt. In some cases, the blends proved less likely than rock salt to suppress vegetation. Her results on the mixtures' corrosiveness proved inconclusive, but other studies suggest it rivals CMA in this category, she says.

For states in New England and the Midwest, the cost of uisng CMA by itself would amount to $8.3 billion annually, while the tab for rock salt runs to a mere $2.4 billion. the mixture would come in with a $4 billion price tag, she calculates. It should be used in environmentally sensitive areas and on bridges, whe argues.

* Eddie Chon-wai Wu, 17 of Los Gatos (Calif.) H.S. examined the accumulation of vanadium, a metallic element found in tunicates, also called sea squirts. Certain types of tunicates have a high concentration of vanadium in their blood cells, says Wu. In fact, its much higher thanthe concentration of vanadium in the seawater where they live.

He found that a previously unknown, sideophore-like compound accumulates trhe vanadium in tunicates. Sideroiphores are molecules that concentrate metals in a bacterium. Wu detected the compound using a variety of approaches, including dissecting the tunicate and filtering its cells. He analyzed it using MRI, among other methods, and compared it to known siderophores, he writes.