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that they would be willing to prescribe 17Pfor women with a history of prematurebirths. However, although the drug isapproved for fertility treatment, it isn’tcommercially available.

Others are less sure about giving 17P.Jeffrey C. King of New York Medical Col-lege in New York says that although thenew research is well done, it needs to bereplicated. “I would hate to see [17P]blindly adopted by lots of practitionersbecause they have nothing else to offerpatients,” he says.

“Obstetrics has a somewhat dark historyof rapidly adopting technologies and treat-ments that are subsequently shown to benot effective and in some cases dangerous,”says King.

Consider the synthetic estrogen calleddiethylstilbestrol (DES). It was prescribedfrom 1940 to 1971 to prevent complicationsin pregnancies but turned out to increasecancer risk. Meis acknowledges that thisoutcome may have discouraged researchinto 17P over the past 3 decades, even thoughthe hormones differ chemically. —N. SEPPA

Super FibersNanotubes make toughthreads

The superior mechanical and electricalproperties of carbon nanotubes haveintrigued materials scientists for a decade.But they’ve struggled to take advantage ofthe hollow tubes, just nanometers wide, formacroscopic projects.

Now, researchers have spun the tubesinto composite fibers that are tougher thansteel, Kevlar, or spider silk. The new fibersappear to be tougher than any other syn-thetic or natural material, says Ray Baugh-man of the University of Texas at Dallas inRichardson. Toughness indicates howmuch energy a material can absorb beforebreaking.

By modifying a process developed byFrench researchers (SN: 12/16/00, p. 398),Baughman’s team spins fibers made of car-bon nanotubes and polyvinyl alcohol, acommon industrial polymer. In the June 12Nature, Baughman and his colleaguesdescribe the finished threads, which are thewidth of a human hair and 100 to 200meters long.

The achievement is “very good news forthe field of nanotubes,” says Philippe Poulin

of the Paul Pascal Research Center in Pas-sac, France, one of the researchers whodeveloped the technique that Baughman’steam modified.

The Texas researchers tested their fibers’mechanical properties and compared themwith known values for 3,000 other mate-rials. The fibers are 20 times as tough assteel wire, 17 times as tough as the Kevlarused in bulletproof vests, and 4 times astough as spider silk—a natural materialwhose renowned toughness researchershave long tried to mimic (SN: 08/17/02, p.100). The nanotube fibers are also strongerthan spider silk and Kevlar, meaning theycan support more weight.

“The results are the best I have seen fromnanotube-composite materials,” commentsOtto Zhou of theUniversity of NorthCarolina at ChapelHill. “This is a bigstep toward eventualutilization of carbonnanotubes . . . incomposites, whichhas been envisionedsince the discovery ofcarbon nanotubesmore than 10 yearsago.”

“This fiber willprovide for a newgeneration of high-strength fabrics andenergy-absorbingmaterials, such as vehicle armor,” suggestsKen Smith of Carbon Nanotechnologies,a Houston company that supplies Baugh-man with carbon nanotubes.

The fibers’ extraordinary properties couldalso make them candidates for safety har-nesses, explosion-proof blankets, or bullet-proof vests, suggests Baughman. He cau-tions, however, that the fibers haven’t yetbeen tested for antiballistic capabilities.

Baughman and his coworkers havealready fashioned the fibers into electric-ity-storage devices called supercapacitors,which they incorporated into ordinarycloth. This exercise demonstrates the fibers’potential for electronic textiles, such as mil-itary uniforms with built-in antennas, sen-sors, or tiny batteries for powering com-munications equipment, he says.

The most exciting thing about the newnanotube work is that the supertough fiberscan now be made available to manyresearchers, says James Von Ehr, thefounder of Zyvex, a firm based in Richard-son, Texas, that’s developing carbon nan-otube composites and other nanotechnol-ogy products. Ehr personally donated theseed money that established the NanoTechInstitute at the University of Texas whereBaughman and his colleagues work.

Right now, nanotube researchers agree,the biggest hurdle to exploiting the new fibers

is the cost and limited availability of the nan-otubes Baughman uses, known as the single-walled carbon nanotubes. — J. GORMAN

Lease on LifeOld mice live longer when given young ovaries

Here’s one more reason to be obsessed withreproduction. A new study with aging micesuggests that the reproductive system playsa role in determining how long animals live.

James Carey and his colleagues at theUniversity of California, Davis trans-planted ovaries from 2-month-old mice

into mice whoseovaries had beenremoved a few weeksafter birth. The pro-cedure extendedsome of the animals’lives. It proved equiv-alent to enabling a50-year-old womanto live to age 92instead of 80, her current lifeexpectancy, Careyexplains.

“The gonads arecommunicating withthe body to stayyoung for reproduc-

tion,” he says. In the June Aging Cell, Carey and his

coworkers describe their experiments withfive groups of female mice. One groupretained its original ovaries. In four groups,the researchers removed the animals’ovaries when the mice were only 3 weeksold and thumbnail size. Of those mice, onegroup remained without ovaries. Theresearchers transplanted 2-month-oldovaries into the other groups when the ani-mals reached 5, 8, or 11 months of age.

Carey compared the remaining lifeexpectancies of each group when the micewere 11 months old, an age at which they’renormally no longer capable of reproduc-tion. The mouse group that had their orig-inal ovaries had about a month more to livethan the group that had their ovariesremoved and not replaced.

A mouse’s age when it received its ovarytransplant influenced its life expectancy.The mice that received new ovaries at 11months of age benefited most, living 60percent longer than those that had theirovaries removed but not replaced and 40percent longer than those still with theiroriginal ovaries.

The mice that had received ovaries at 8months had 24 percent longer to live thanthe mice with no ovaries did, and the groupthat received ovaries at 5 months lived

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SCIENCENEWSThis Week

FUTURISTIC FIBERS Materials scientistsused carbon nanotubes to make two electricity-storing supercapacitors (black threads) thatthey inserted into cloth. The woven area is alittle more than 2 centimeters long.

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