NEWS OF THE WEEK

sq cm, transmittance begins to decrease markedly, Tutt and Kost say.

The transmitted fluence effectively be­comes clamped at about 65 mj per sq cm. That is, when incident light with a fluence of about 200 mj per sq cm shines on the C60 solution, about 65 mj per sq cm is transmitted through the solution. As the incident fluence is increased to 1500 mj per sq cm, the transmitted flu­ence remains at 65 mj per sq cm.

Because the absorption spectrum for the C60 triplet parallels that of the ground state, the optical limiting action of C60 is likely to be effective across a broad spectrum of wavelengths of light. Since solid films are desirable for many optical limiting applications, Tutt and Kost are investigating the response of fullerene films to optical pulses.

In the other fullerene development, a team of chemists headed by C. N. R. Rao at the Indian Institute of Science, Bangalore, has produced C60 with the single iron atom inside its carbon cage [/. Am. Chem. Soc, 114, 2272, (1992)].

This is one of the first reports of incor­poration of a transition-metal atom into a fullerene cage.

This "endohedral" iron-fullerene complex, which can be denoted Fe@C60

according to a symbolism suggested last year by Rice University chemistry pro­fessor Richard E. Smalley, has a number of properties that distinguish it from sol­id FeC60 in which the iron is bound ex­ternally to the fullerene. For example, Rao and his coworkers report that in the newly produced complex, the iron is in a near-zero oxidation state. By contrast, FeC60 contains iron(III).

The Indian chemists produce Fe@C60

by vaporizing graphite in an atmosphere of Fe(CO)5. Other researchers who have produced endohedral fullerene com­plexes containing lanthanum or yttrium, for example, have vaporized graphite impregnated with the metal species. Rao's approach opens up new avenues for the production of endohedral metal-lofullerenes.

Rudy Baum

Dow Corning to quit making breast implants

government's capacity to fill its top sci­ence and technology-related positions. The nation can ill afford the conse­quences of leaving unattended this problem of executive recruitment."

But solving this recruitment problem will apparently involve much more than just better mechanics. At a press confer­ence discussing the NRC report as well as a related study by the Council for Ex­cellence in Government, Pendleton James, the head of the recruitment office in the Reagan White House, recalled some appointees who were thought to be first class and ideal for the job but turned out to be disasters. Others, deemed to be marginal at best, worked out splendidly.

Michael Heylin

C60 displays intriguing optical properties Two new contributions to the rapidly evolving exploration of the properties and chemistry of buckminsterfullerene, C60, came to light last week. One was discovery of some unusual and poten­tially useful optical properties. The other was the preparation of C60 with a single iron atom trapped in its carbon cage.

Last week's issue of Nature carries a paper reporting that a toluene solution of C60 transmits relatively low-intensity light but blocks the passage of light above a critical intensity. Solutions of C60's close cousin, C70, display similar behavior. This discovery suggests that fullerenes may be useful in optical lim­iting, a technique for protecting optical sensors against bright pulses of light.

Earlier studies of the optical proper­ties of buckminsterfullerene revealed that photoexcited C60 is a better light absorber than C60 in its ground state. Lee W. Tutt and Alan Kost of Hughes Research Laboratories, Malibu, Calif., realized that, because of this property, C60 might exhibit a nonlinear optical response of the sort that could be har­nessed to produce optical limiters.

The two scientists characterized the optical response of a toluene solution of C60 to 532-nm laser light [Nature, 356, 225 (1992)]. At low fluences, or light intensity, the C60 solution obeys Beer's law—that is, transmittance is constant with increasing light intensity. However, at an incident intensity of light of about 100 millijoules (mj) per

Dow Corning, the largest manufacturer of silicone gel breast implants, disclosed last week that it was quitting the busi­ness. In making the announcement, chief executive officer Keith R. McKennon said the company would set up a $10 million fund to carry out research on the implant's safety, and would offer up to $1200 to any woman whose physician recommends implant removal but who cannot afford the surgery.

On Jan. 6, Dow Corning and then three other manufacturers voluntarily stopped making these implants after the Food & Drug Administration called for a temporary ban until safety issues could be resolved. In February an FDA adviso­ry panel recommended that availability of silicone implants be sharply limited, and all women receiving them be part of clinical safety studies. FDA Commis­sioner David A. Kessler has until April 20 to act on the advisory panel's recom­mendation.

After the February advisory panel hearings, Dow Corning officials broad­ly hinted that the company would sell off its gel breast implant unit, which had long been unprofitable. Last week, McKennon said the reasons for not re­suming production and sales of the im­plants were "not related to issues of

science or safety but to the existing condition of the marketplace."

Dow Corning continues to believe that the implants "do not represent an unreasonable risk." However, these med­ical devices never represented more than 1% of Dow Coming's revenues, and McKennon sees no prospect for business improving. Based on the advisory pan­el's recommendation, he believes the market will shrink even further in the future. Additionally, Dow Corning is facing hundreds of lawsuits filed by women who believe their implants have caused them health problems.

Two companies, Mentor and McGhan Medical, also make silicone gel implants and have not said they would discontin­ue their manufacture. The two also make saline breast implants, whose use and sales were not affected by FDA's Jan. 6 ban. A fourth manufacturer of sil­icone gel implants, Bioplasty, last month announced it would no longer make them.

The $10 million funding set aside for breast implant research was included in the $25 million charge Dow Corning previously took against its 1991 earn­ings. Dow Corning is a joint venture of Dow Chemical and Corning.

Lois Ember

6 MARCH 23,1992 C&EN