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This is Science in the News, in VOA Special English. I'm BobDoughty.

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And I'm Sarah Long. This week -- a study of antibiotics andbreast cancer ... plus, findings that a way to protect babies fromAIDS may not be so good for their mothers.

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Also ... an explosion laboratorywith a burst of creativity ... and a possible sign of recovery formountain gorillas in Africa.

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A study suggests a possible connection between use of antibioticdrugs and increased risk of breast cancer. However, the study doesnot answer the question if antibiotics are a cause of breast cancer.The study appeared last week in the Journal of the American MedicalAssociation.

Researchers in the American Northwest studied more than tenthousand women. The study involved members of Group HealthCooperative, a health plan based in Seattle, Washington.

Antibiotics are used to fight many different kinds of infectionscaused by bacteria. The study found that women who took moreantibiotics compared to other women had higher rates of breastcancer. Some women had taken antibiotics for more than five-hundreddays over an average period of seventeen years. These women had morethan two times the risk of breast cancer as women who had not takenany antibiotics.

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The study found that women who took antibiotics for fewer dayshad less risk. Yet even these women had one-and-one-half times therisk of those who took none.

Doctor Stephen Taplin of the National Cancer Institute was amongthe leaders of the study. Doctor Taplin says the risk increased withall the kinds of antibiotics they studied.

Some cancer experts suggested that antibiotics could suppress"good" bacteria in the intestinal system. They say these bacteriahelp the body process foods that may help defend against disease.Or, they say, antibiotics might damage the immune system thatprotects the body against infection.

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But Doctor Taplin and others say women who need more antibioticsmay already have weakened immune systems. Another possibility isthat the infections being treated may increase the risk of breastcancer. So the experts say more studies are needed before any directlink is made between antibiotics and breast cancer.

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In many poor countries, pregnant women infected with the AIDSvirus are given the drug nevirapine one time. This is during labor.Their babies also receive nevirapine once, during the first threedays after they are born. Such treatment can cut in half the riskthat the AIDS virus will spread from mother to baby.

But two studies have found that a single use of nevirapine maycause pregnant women to develop a resistance to it later. Scientistspresented the studies in San Francisco, California, during aconference on anti-AIDS drugs.

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In South Africa, scientists found that about forty percent ofinfected women who took the drug while giving birth later becameresistant to it. Researchers in Thailand also found that mothers whoreceived nevirapine were less likely to be helped by the drug ifthey developed AIDS. Researchers from France and the United Stateshelped carry out the studies.

In richer countries, pregnant women with H-I-V receive acombination of anti-AIDS drugs throughout their pregnancies. Healthofficials say this lowers the chance that the mother will develop aresistance.

In developing nations, however, this method may not beeconomically possible. Combinations of anti-retroviral drugs tosuppress the infection cost a lot. So the World Health Organizationsuggests the use of nevirapine alone. It says the two studies willnot change this advice, at least for now.

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Engineers are building a laboratory at the University ofCalifornia at San Diego to study the effects of explosions. Thereare other blast simulators in the world that study the effects ofexplosions on buildings and other structures. But the engineers saythis will be the first where scientists do not have to create realexplosions.

The Jacobs School of Engineering is building the new laboratoryat a field station several kilometers from the university. The blastsimulator is expected to be in operation by early next year.

It will use a computer to control devices called hydraulicactuators. These are a series of heavy metal tubes. Water flowsthrough them under pressure. The tubes are designed to extendquickly and strike an object with great force. This will recreatethe shock waves produced by a bomb explosion.

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The blast simulator will be connected to recording devices. Thescientists will measure the effects of different size explosions ondifferent kinds of structural materials. Bomb explosions move airwith such force and speed that it pushes and pulls walls and otherbuilding supports.

The United States government is providing support for the projectas part of anti-terrorism efforts. The structural engineers in SanDiego have been researching ways to harden buildings against bombattacks since nineteen-ninety-eight. That was the year bombs wreckedthe American embassies in Tanzania and Kenya.

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The Jacobs School of Engineering has done much work in the areaof design to protect buildings against earthquakes. In fact, theblast simulator laboratory will be connected to another newlaboratory.

The school has almost completed what it calls the world's firstoutdoor "shake table." Imagine a table that shakes -- and yet is bigenough to hold a building several floors high. It will helpscientists measure how buildings react to earthquakes.

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For years, experts have been concerned about the future of themountain gorillas of Africa. Disease, hunting, development and civilconflict all greatly reduced the population of these great apes. Butresearchers say the number of mountain gorillas in three nationalparks have increased by about seventeen-percent in recent years.

Mountain gorillas are one of the most endangered species in theworld.

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The International Gorilla Conservation Program led a studybetween September and October of last year. Teams of researchersstudied mountain gorilla environments across the three nationalparks in the Virunga forests. The forests are on the borders of theDemocratic Republic of Congo, Rwanda and Uganda.

The researchers recorded information about gorilla sleepingplaces and the gorillas they saw. They used that information toestimate the current population in those parks atthree-hundred-eighty gorillas. That is fifty-six gorillas more thanscientists had recorded in the last count in nineteen-eighty-nine.

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War and hunting reduced the Virunga population to abouttwo-hundred-sixty in the late nineteen-seventies. But national parkofficials and non-governmental organizations in the three countrieshave increased efforts in recent years to protect the great apes.

Researchers say three-hundred-twenty other mountain gorillas livein Uganda, in the Bwindi Impenetrable National Park. That is theonly other place they are found. This means there at leastseven-hundred mountain gorillas left in the wild.

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Thirteen villages in northern Cambodia now have e-mail through aproject that organizers hope other countries will copy. Energy fromthe sun powers computers in a group of schools and a medical centerin Ratanakiri Province. Electronic mail is sent over the Internet,but with the help of what are called "motomen."

Each day, five people ride motorcycles into the villages tocollect outgoing messages and bring incoming mail. The motorcyclesare equipped with a computer to store the messages. The "motomen"return to the local capital where the information is sent bysatellite to the Internet.

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Students write to other villages. Local citizens can communicatewith government officials, and receive newspaper stories by e-mail.Local doctors can get medical advice from far away. Organizers hopethe system will also help local farmers sell their products onlineto the world market.

The group American Assistance for Cambodia organized the project.The technology is from a company in Massachusetts called First MileSolutions.

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SCIENCE IN THE NEWS was written by Caty Weaver, Jill Moss,Jerilyn Watson and Cynthia Kirk, who was also our producer. We hadrecording assistance from _________. I'm Bob Doughty.

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And I'm Sarah Long. Join us again next week for more news aboutscience, in Special English, on the Voice of America.