STUDY: WOMEN ARE PUTTING FAMILY BEFORE MATHEMATICS
By Alan S. Brown 

A new study suggests that twice as many women as men drop out of math-intensive careers, including engineering, and that the trend is more pronounced as women advance in their professions. The authors of the study believe that many women leave to devote time to families instead of careers.

The study was conducted by Stephen J. Ceci and Wendy M. Williams, two Cornell University professors of human development, and Susan Barnett, a visiting scholar at the university. They looked at more than 400 studies and analyses of women in math-related professions in order to draw broad conclusions. Their research is in a paper, “Women’s Underrepresentation in Science: Sociocultural and Biological Considerations,” published in the March 2009 issue of Psychological Bulletin.

In the United States, roughly twice as many men as women score in the top 1 percent on the quantitative reasoning sections of such “gatekeeper” tests as the SAT and Graduate Record Examination. Yet this gap has narrowed over time, and in some other countries, the gap either does not exist or its ratio is reversed.

“Women would comprise 33 percent of the professorships in math-intensive fields if it was based solely on being in the top 1 percent of math ability, but they currently comprise less than 10 percent,” Ceci said.

The authors believe that many women who fail to reach senior leadership positions in math-intensive and other fields do so because they choose to have families instead. “The timing of child rearing coincides with the most demanding periods of their career, such as trying to get tenure or working exorbitant hours to get promoted,” Ceci noted.

The demands of parenting and caregiving may also explain why more women than men drop out of math and physical sciences, Williams said.

They note that women have made enormous strides over the past 40 years. In 1976, for example, women accounted for only 7.5 percent of faculty in the physical sciences and less than 1 percent in engineering. By 2006, this had increased to 16 to 25 percent.

Instead, the attrition occurs as women progress in their careers. For example, women earned 31.3 percent of chemistry Ph.D. degrees between 1993 and 2003, but were hired for only 21.5 percent of assistant professorships in 2002.

Pressures, popularized as the “Mommy Track” in the early 1990s, affect women in a range of vocations.
Lisa Frehill, who studies the workforce as executive director of the Commission on Professionals in Science and Technology, found that men and women leave engineering for different reasons.

“The number one reason is that they are interested in another career. Men gave that answer 53 percent and women 47 percent of the time,” Frehill said.

Men left more often than women did for advancement opportunities, 35 percent to 20 percent. Women left more often than men for time and family related reasons, 18 percent to 3 percent, and because of negative work climate issues, 14 percent to 5 percent.

“Of those who left because they were bored or lacked challenges, 19 percent were men and 16 percent women,” Frehill said.

Ceci and Williams have written a book, The Mathematics of Sex: How Biology and Society Conspire to Limit Talented Women and Girls, which is due to be published in August by Oxford University Press.   

SMALL STEP ON NANO ENERGY
By Jeffrey Winters

In the assessment of the health of General Motors produced by the Obama administration in March, the company’s investment in electric vehicles received a failing mark. “While the [Chevrolet] Volt holds promise,” the report read, “it is currently projected to be much more expensive than its gasoline-fueled peers and will likely need substantial reductions in cost in order to become commercially viable.”

Electric vehicles have been hard-pressed to compete with gasoline-fueled cars thanks to one simple metric: energy density. The energy stored in 10 gallons of gasoline is equal to about 350 kWh. To hold that much energy in a standard lead-acid battery would require 14 metric tons of storage. And while batteries using lithium chemistry are more energy dense, they are far more expensive.

Aluminum oxide pores 30 nm wide, when covered by an insulating material and a metal, become powerful capacitors.

In a result that might one day upend that arithmetic, researchers at the University of Maryland’s NanoCenter have developed a way to store electric charge using nanoscale technology that can circumvent the limits of batteries. The promise of the breakthrough is that it can enable electricity to be stored and released as quickly and easily as gasoline, and at a comparable price.

Instead of a battery, which holds electricity in electrochemical form, the Maryland researchers have developed a new type of capacitor, which stores energy in the form of electric charge on a pair of opposing plates. Because the charge can be tapped directly, rather than through a chemical change, capacitors are able to supply large jolts of power, but for a limited time. In fact, the energy density of capacitors is lower than that of batteries.

To cram more energy into the same space, the research team started with a micrometer-thick slice of aluminum riddled with even smaller pores. Over that porous surface, the researchers deposited an ultrathin layer of an insulating material and then covered that with another layer of metal. The result was a contorted sandwich that could hold as much as 10 times the electric charge of conventional metal-insulator-metal capacitors.

The research team, led by Gary Rubloff, director of the Maryland NanoCenter, published their results in Nature Nanotechnology.

The experimental device has a power density of 1 MW per kilogram, which ought to be sufficient to give an electric vehicle enough zip to be attractive. The reported energy density—about 0.7 Wh per kilogram—still trails far, far behind that of gasoline. But, the researchers write, “it should be possible to scale devices fabricated with this approach to make viable energy storage systems that provide both high energy density and high power density.”

Whether this can be done quickly enough to save the Chevy Volt—or let alone GM—remains to be seen.

CO₂ SCRUBBER TO GET A TRIAL

Units of Alstom and Dow Chemical plan to build a pilot plant to test what they describe as an advanced amine-based technology for removing CO₂ from flue exhaust.

Dow Oil and Gas developed the technology. Alstom Power will build and operate the test facility, which is expected to capture 1,800 tons of CO₂ a year from the exhaust of a 25 MW coal-fired plant that provides process steam for a Dow chemical complex at South Charleston, W.Va.

Amine strips the CO₂ from the flue gas and holds onto it, letting the remainder of the flue gas escape. The amine is regenerated by boiling off the CO2. The result is a nearly pure CO₂2 stream and amine ready to return to the scrubber.

Oxygen in flue gas can degrade most amines, but the companies say their amine technology is more resistant to oxygen.

The new technology is expected to use less energy than other CO₂ scrubbers. A Dow spokesman told us, “The advanced amine process jointly developed by Alstom and Dow is focused on capturing CO₂ in an energy-efficient manner. More details on this will be available at a later date.”

The pilot plant is intended to prove the scrubbing technology, and no specific plans have been announced for the concentrated CO₂ stream that will be isolated there. For now, the plan is to recombine the CO₂ with the flue gas to vent a stream very similar to the original.

On an industrial scale CO₂ would be sequestered or put to use. CO₂ can be injected into oilfields to enhance oil recovery. An Alstom spokesman said, “We are currently exploring other options on what to do with the CO₂.”

The test plant is expected to be in operation in the third quarter this year.

Alstom joined Dow early last year to develop a commercial version of the amine-based scrubbing technology.

FISH INSPIRATION
By Jean Thilmany

One of the species of  blind fish that thrive in the waters of the world’s deep caves has evolved a technique for sensing motion and inspired researchers at the Georgia Institute of Technology. They are at work to develop a new generation of sensors that may outperform today’s sonar.

Members of the fish species that the researchers are studying—Astyanax fasciatus—do not see their environment, but they can navigate by the sense of touch. They sense the movement of water around them through a system of gel-covered hairs that extend from their bodies.

The ability of these blind cavefish to detect objects and navigate inspired the research group to mimic the hairs in the laboratory, said Vladimir Tsukruk, a professor in Georgia Tech’s School of Materials Science and Engineering.

“These hair cells are like well-engineered mechanical sensors, similar to those that we use for balance and hearing in the human ear, where the deflection of the jelly-encapsulated hair cell measures important flow information,” he said.

“The hairs are better than active sonar, which requires a lot of space, sends out strong acoustic signals that can have a detrimental effect on the environment, and is inappropriate for stealth applications,” he added.

The fish use their specialized hair cells to detect obstacles, avoid predators, and find prey. Tsukruk said similar engineered sensors could have a variety of underwater applications, such as port security, surveillance, early tsunami detection, and underwater vehicle navigation.

Tiny hairs guide a blind fish. Georgia Tech is trying to engineer them for human use.

Tsukruk and two graduate students, Michael McConney and Kyle Anderson, conducted preliminary experiments with a simple artificial hair cell microsensor made of a common epoxy-based polymer capable of solidifying. They built it by using conventional microfabrication technology.

They found that the cell by itself could not achieve high sensitivity or long-range detection of hydrodynamic disturbances created by moving or stationary bodies in a flow field. The hair cell needed the gel-like capsule—called the cupula—to overcome these challenges.

“After covering the hair cell with a synthetic cupula, our bio-inspired microsensor had the ability to detect flow better than the blind fish,” Tsukruk said. “The fish can detect flow slower than 100 micrometers per second, but our system demonstrated flow detection of several micrometers per second.”

“Adding the cupula allowed us to detect a much smaller amount of flow and expand the dynamic range because it suppressed the background noise,” he added.

To date, the researchers have fabricated an array of eight microsensors and shown that the array is able to detect an oscillating object underwater.

They’re currently looking for industrial partners to efficiently scale up the research by fabricating arrays of thousands of the sensors and testing them in real marine environments.

The group presented its findings at a meeting of the American Physical Society in March. Their research was sponsored by the Defense Advanced Research Projects Agency.

BRIEFLY NOTED

The U.S. Department of Energy has announced that National Nuclear Security Administration has certified the completion of the National Ignition Facility, which is the world’s largest laser, at the Lawrence Livermore National Laboratory. Developed for the nuclear weapons stewardship program, the facility  will allow scientists to achieve fusion ignition. /// Michigan Metrology will host a one-day class, “3D Surface MicroTexture Measurement, Analysis, and Inspection” on May 7 at Radisson Hotel - Livonia in Livonia, Mich. Registration information can be requested online at www.michmet.com/ReqSemInfo.htm. /// AutoForm Engineering GmbH of Zurich, Switzerland, a supplier of software for the sheet metal forming industry, is shipping a new product line called AutoFormplus, which the company says covers the entire process chain and brings together the important aspects of sheet metal forming. /// ICONE 17, the 17th International Conference on Nuclear Engineering, will be held July 12–16 at the Sheraton Brussels Hotel in Brussels, Belgium. The event is sponsored by ASME, the Chinese Nuclear Society, and the Japan Society of Mechanical Engineers. Details are available at http://www.asmeconferences.org/ICONE17/. /// Metris of Leuven, Belgium, has launched Focus Scan 5.2, software that speeds up the preparation and execution of coordinate measuring machine laser scanning inspection.