NEWS OF THE WEEK
SUPERCONDUCTIVITY: Doubts cast on claims above 200 Κ A purposeful but unsuccessful search for higher-temperature supercon ductors by IBM scientists has cast further doubt on the validity of re cent sightings by many groups of transient "superconductivity" at temperatures around 250 K. The IBM findings suggest that some, if not all, of these sightings may be arti facts of the measurement process, rather than indications of highertemperature superconductive phas es, as others have claimed. The IBM results were presented at last week's American Chemical Society meeting in New Orleans at the Inorganic Chemistry Division's symposium on the new ceramic superconductors. They reinforce growing skepticism among scien tists about the meaning of these widely reported high-temperature events. Researchers have grown in creasingly suspicious of late because they haven't been able to repro duce these transient anomalies, which have been seen in multiphase samples of yttrium-barium-copper oxide (Y-Ba-Cu-O). The IBM team, consisting of Jerry B. Torrance, Edward M. Engler, Paul M. Grant, and six other coworkers,
was searching for high-temperature superconductivity in a broad range of copper oxide compositions pre pared at different temperatures. A few samples of Y-Ba-Cu-O made at higher-than-normal temperatures (1050 and 1200 °C versus 950 °C) showed a resistance drop around 200 K. Other workers have inter preted such anomalies as signals of the presence of small amounts of a higher-temperature superconduc tive phase. But careful electrical measure ments made at the IBM Almaden Research Center in San Jose, Calif., convinced the IBM workers that the resistance drops in their samples are spurious. Two causes have been identified: First, they found that changes in the resistance of the con tacts between the electrical leads and the sample can masquerade as a re sistance drop in the sample. And second, the ceramic samples are ex tremely heterogeneous on a micro scopic scale, and this also can pro duce misleading electrical signals. Other researchers at the sympo sium were receptive to the IBM find ings. At a press conference, Arthur W. Sleight of Du Pont noted that
Superconducting materials made in useful bulk forms Researchers in Oregon and Washington apparently have taken an important step toward fabricating high-tempera ture superconducting materials into forms that can be useful in applica tions. Using a shock compression tech nique, they claim to have made sam ples of these normally brittle super conducting materials up to 24 cm in diameter. Lawrence E. Murr and Nicholas G. Eror Jr., both professors of materials science at the Oregon Graduate Cen
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ter in Beaverton, and Alan W. Hare, president of Northwest Technical In dustries in Sequim, Wash., used am monium nitrate explosives to create a shock wave that compresses a "sand wich" of superconducting YBa2Cu307 powder in a large channel between base and cover plates made of copper or aluminum. The explosion creates a continuous solid mass that the re searchers refer to as a monolith. The monolith encapsulates and supports the ceramic.
Torrance: apparent wrong answers scientists have arrived at a consen sus that the evidence for supercon ductivity above 200 Κ is "pretty slim/' and months of effort have failed to solidify it. In marked con trast, the initial announcement last February of a new record-high su perconductive temperature of about 90 Κ was confirmed in several labs in a matter of days. Today, more than six months after that historic milestone, 95 Κ remains the high est confirmed temperature for su perconductive behavior, Sleight says. Many researchers remain optimis tic that higher superconductive tem peratures will be achieved, but there's no way to predict when that will h a p p e n . And it's possible, Torrance says, that some of the pre viously reported anomalies may in deed be due to higher-temperature superconductivity. To avoid falling prey to artifacts,
Grant urges workers to adhere to several technical guidelines for making resistance measurements in the future. These guidelines are listed in the IBM group's paper, which has just been published in the latest volume (No. 351) of the ACS Symposium Series. Commenting on the recent flurry of news reports of "superconductivity" above 200 K, Torrance likens the situation to a TV game show whose contestants, in their haste to be the first to answer the prizewinning question, are sounding the buzzer before they're even sure of the answer. So far, he says, it appears they've all been coming up with the wrong answers. D
Long-delayed benzene levels set by OSHA Ending a decade of legal wrangling, the Occupational Safety & Health Administration last week ordered a 90% reduction in workplace exposure to benzene in an effort to reduce the risk of leukemia and other blood disorders for some 240,000 workers nationwide. Affected industries will have five months to comply with most provisions of the rule to cut on-the-job exposure to benzene fumes from 10 ppm to 1 ppm averaged over eight hours. However, they will have up to two years to install new engin e e r i n g controls. According to OSHA Administrator John A. Pendergrass, the tighter standard will prevent at least 326 deaths from leukemia and other blood disorders over a working lifetime of 45 years. Pendergrass termed the standard "a landmark rule" that incorporates new risk analysis requirements. He says he feels confident the new benzene standard will stand. "It has been proven beyond a doubt that benzene poses a significant risk of leukemia and other blood diseases to those exposed." However, other OSHA spokesmen who ask not to be named say they expect an immediate court challenge. The stricter standard is expected to cost industries, including the chemical and petrochemical industries, $24 million a year. The cost of
compliance will provide for engineering controls, respirators and other personal protective gear, and medical surveillance. It amounts to less than 0.2% of the annual revenues of affected industries, OSHA estimates. Additionally, the standard contains a 5-ppm limit averaged over 15 minutes to cut benzene health risks for pipefitters and maintenance workers who are faced with intermittent or peak exposures. Also, employers will be exempt from complying with the short-term or eighthour limits if they can show that benzene fumes are less than 0.5 ppm. For example, Edward Stein, OSHA benzene project officer, says bulk gasoline storage facilities will be exempt from the standard "if their loading and unloading operations use vapor control systems." If not, these facilities will have to monitor loading and unloading operations and conduct medical surveillance of their workers. Stein says there are about 15,000 such facilities, employing about 61,000 workers. OSHA first issued a 1-ppm temporary emergency standard in 1977, but, because of various legal maneuvers, it never took effect. In 1978 the agency proposed this low limit as a permanent standard, which the American Petroleum Institute (API) challenged in a federal appellate court. That same year, the appellate court set aside the standard because it said OSHA failed to do a costbenefit analysis. In 1980, the Sup r e m e Court u p h e l d the lower court's decision, but on slightly different grounds. The higher court ruled that OSHA had to show that a significant risk exists, and that a new standard would significantly reduce it. Since then OSHA has been collecting and analyzing data. API spokesman Reinhold G. Ensz says his trade association still contends that a lower benzene exposure level is not necessary. He says, "API is still studying the 598-page standard, and has no judgment on litigation at this time." The unions also are reviewing it for a possible legal challenge. Margaret Seminario, AFL-CIO deputy director for occupational safety and health, says the unions "may take legal action to
sustain the standard or to improve it. If there is no other serious challenge to the standard from other parties, then obviously we would be less inclined to proceed with litigation." Carol R. Stack, program manager of the Chemical Manufacturers Association benzene panel, says the panel will be reviewing the standard this month. "I don't think we will mount an aggressive challenge, but we will take protective measures if someone else mounts a challenge." D
FDA okays potent drug to lower cholesterol A new, potent drug capable of lowering levels of total cholesterol in blood 18 to 34% has been approved by the Food & Drug Administration. Called lovastatin, the drug is expected to be used especially for persons who are genetically inclined to very high cholesterol levels. Announcing the drug approval, FDA Commissioner Frank E. Young called the drug "a really major advance." Lovastatin, which was developed by Merck Sharp & Dohme, is expected to be on the market within a month under the trade name Mevacor. With a molecular weight of 404, lovastatin is one of a group of fungal metabolites that competitively inhibit the action of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase, a key component in the body's own production of cholesterol. The enzyme catalyzes conversion of hydroxymethylglutaryl-coenzyme A to mevalonate, an early and rate-limiting step in cholesterol synthesis. Merck scientist Jonathan A. Tobert told C&EN that lovastatin "would be almost impossible to synthesize—it has seven chiral centers—so it will be produced microbiologically." Clinical testing of lovastatin indicates that it reduces levels of lowdensity lipoprotein cholesterol 19 to 39%. Low-density lipoprotein is the form of cholesterol most often implicated in formation of arterial plaques that lead to atherosclerosis and coronary heart disease. Blood serum concentrations of high-density lipoprotein cholesterol, considSeptember 7, 1987 C&EN
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