Explore Magazine Volume 5 Issue 1


UF Team Pioneering Super-Thin Solar Cells
By Aaron Hoover

University of Florida engineers are pioneering an inexpensive method for making a new breed of exceptionally thin and cheap solar cells expected to make solar power a more widespread source of electricity in the new millennium.

The cells, known as "thin-film solar cells," are 100 times thinner and potentially lighter than today’s silicon cells. They also require less semiconductor materials, an attribute that opens the door for the cells to be made cheaply and in great quantity.

"The material cost is very minimal," said Sheng Li, a UF professor of electrical and computer engineering and part of a four-member UF faculty team at work on the process. "This is a very promising technology for solar cells."

The UF research comes at a time when the market for solar cells is in a strong growth spurt. For the past several years, the industry has had an annual growth rate of 15 to 20 percent, similar to that of the booming semiconductor and computer industries. Total sales reached the $1 billion mark in 1998, according to industry publications.

Solar cells’ advantage is that they produce "green" power without harmful emissions. Also, they can generate power for a house or small business on site, reducing electrical demand on power plants and electrical grids.

Traditional silicon cells, however, require relatively large amounts of semiconducting materials, making them expensive to manufacture and driving up their cost in the marketplace. They also are heavy and unwieldy, limiting their potential applications, Li said.

The UF researchers hope to get around these problems through the thin-film cells, which can be created with "pennies’ worth" of materials on flexible surfaces such as plastic. Where traditional solar cells use wafers similar to computer chips, thin-film cells use thin layers of semiconductor material. Thin-film cells, however, have a far more complex chemical structure and are more difficult to make than traditional cells, attributes that have limited their production and commercialization to date.

Scientists and engineers at more than a dozen universities, government labs and corporations are exploring several different thin-film solar cell technologies as part of a major initiative sponsored by the National Renewable Energy Laboratory, a government lab that seeks to develop renewable energy technologies and improve energy efficiency.

The UF team, part of the Thin Film Partnership Program, is focusing on a technology that uses a compound semiconductor called copper indium diselenide, or CIS.

The technology involves depositing an extremely thin layer of CIS on a specially prepared material such as glass, Li said. Two to 3 microns thick, the semiconductor layer is thinner than a human hair and 100 times thinner than conventional solar cells, he said.

Researchers elsewhere have demonstrated CIS cells can convert as much as 18 percent of sunlight to electricity, about the efficiency of the most efficient traditional silicon cells, according to the National Renewable Energy Laboratory. But there still are major challenges to overcome in manufacturing the cells.

"They have a more complicated structure and require more complicated processing," said Tim Anderson, chairman of the UF chemical engineering department and member of the CIS team. "Our role is to better understand the processing and transfer the technology to industry."

The UF team also is experimenting with ways to simplify the manufacturing process, Li said. Three years into the six-year project, the team has used a simpler, cheaper process to make CIS cells with efficiencies in the range of 8 to 10 percent — good progress toward the team’s goal of 13- to 15-percent efficiency, Li said.

The National Renewable Energy Laboratory is providing about $1.6 million for the research. The other UF team members are Paul Holloway, a professor of materials science and engineering, and Oscar Crisalle, an associate professor of chemical engineering.

Sheng Li, shengli@eng.ufl.edu
Tim Anderson, tim@nersp.nerdc.ufl.edu

Astronomers Capture "Stellar Sonogram" Of Star
By Steve Orlando

A University of Florida astronomer is part of an international team that has captured the first images of the very earliest stages of a "dark cloud" — the coldest astronomical object in the universe — becoming a new star and planetary system.

The images, akin to a deep-space sonogram of a baby at the zygote stage, will give astronomers a new understanding of how stars begin to form and even what was happening when our own solar system began to come to life about 4.5 billion years ago, said team member Elizabeth Lada, an associate professor of astronomy at UF.

"Here we have an outstanding example of a cloud that appears to have just initiated collapse to form a star, and we can study the structure in detail," Lada said.

Lada is collaborating on the project with her brother, Charles, an astronomer at the Harvard-Smithsonian Center for Astrophysics; and Joao Alves, an astronomer with the European Southern Observatory.

The team got the images in March at the European Southern Observatory at La Silla in the Chilean Andes, using the observatory’s 3.5-meter Very Large Telescope and a near-infrared detector known as SOFI.

The dark cloud, also known as a dark globule, is called Barnard 68 and is in front of a dense star field in the Milky Way. Barnard 68, also known as B68, is about 500 light years from Earth.

Dark clouds are made up of interstellar molecular gas and dust and are the coldest objects in the universe, with temperatures around -263 degrees Celsius, or 10 degrees above absolute zero. Astronomers have known for some time that such clouds contract and eventually turn into hydrogen-burning stars, but the details of exactly how that happened remain unclear.

Dark clouds appear dark because the dust within them is opaque to visible radiation, so they blot out the light of stars beyond them. Otherwise, they are invisible because they are made up almost entirely of molecular hydrogen, which is too cold to glow in visible light. But with the new work by Lada and her colleagues, the veil is beginning to lift.

Previously, radio telescopes were used to study dark clouds, but the interpretation of radio emission is not straightforward. With the near-infrared method they developed, Lada and her colleagues were able to, for the first time, "see" through the cloud and detect the stars behind it. By measuring the change in the color of the background stars caused by the presence of intervening dust in the cloud, they were able to directly map out the distribution of matter within the cloud itself.

"There are theories about how the formation of a star begins," Lada said, "but our observations of B68 give us some of the best evidence to test those theories."

The team caught the cloud just as it was beginning its collapse, a process that takes about 100,000 to 200,000 years. To get an idea of how early on in development B68 is, Lada said, it will be another 10 million years or so after the collapse before the star will burn hydrogen and shine like the sun.

"We’re looking at things that are very comparable to what our Sun would have looked like when it was forming," Lada said.

Elizabeth Lada, lada@astro.ufl.edu
UF Researchers Reverse Diabetes In Mice
By Melanie Fridl Ross

University of Florida researchers have reversed juvenile diabetes in mice with a simple injection of cells that soon produce enough insulin to regulate blood sugar effectively, they reported in March in the journal Nature Medicine.

To do so, they harvested pancreatic cells in their earliest stages of development from the mice themselves, then nurtured them in the laboratory until they evolved into small, insulin-secreting organs known as islets of Langerhans.

Researchers collected the cells into a syringe and injected them just beneath the surface of the animals’ skin. Within a few days they began to function like the pancreas’ islets of Langerhans, said UF immunologist Ammon B. Peck.

"This is very exciting, because the cells can be placed very simply into an individual in an area with no need for a complicated surgical procedure," he said.

People with diabetes lose their ability to regulate how the body uses and stores sugar and other nutrients for energy when their immune system launches a self-directed attack, destroying the insulin-producing cells in the pancreas. Researchers were encouraged to find that no such assault occurred on the implanted cells — known as stem cells — during the study period, which lasted more than three months.

The findings open up the possibility of someday permanently reversing Type-1 diabetes for the more than 750,000 Americans who battle the disease. Many suffer major side effects, including damage to blood vessels, which can lead to heart disease, stroke, blindness, kidney failure and poor circulation to the lower limbs.

"This indicates there is some mechanism, something about growing them from stem cells in culture, that tricks the autoimmune response, at least for some time," Peck said.

Stem cells have the ability to evolve into an array of cell types as they mature. After they were placed in the mice, the cells secreted insulin and thrived as new blood vessels grew toward them. Within a week to 10 days, all the mice were able to regulate levels of sugar, or glucose, in the bloodstream for the time of the study.

"If you eat a candy bar it raises the amount of glucose in the blood," explained Peck, a professor of pathology, immunology and laboratory medicine at UF’s College of Medicine. "The islets respond rapidly to that because they sense how much sugar is in the blood and produce insulin, and insulin allows for proper utilization of glucose for energy by other cells in the body."

The ability to control the growth and development of pancreatic stem cells potentially provides an unlimited resource for insulin-producing cells for people with diabetes, Peck and his co-authors, including UF pediatric endocrinologist Desmond A. Schatz wrote in the journal.

The study was supported by the National Institutes of Health; Vijayakumar Rimiya, of Ixion Biotechnology Inc. at UF’s Progress Park in Alachua, Fla.; and Karl Arfors, of
Q-Med, Scandinavia, in San Diego.

New Book Cites Rawlings' Influence With Top Authors
By Cathy Keen

Marjorie Kinnan Rawlings did more for literature than win the Pulitzer Prize. According to a new book published by University Press of Florida, she cheered up an ailing F. Scott Fitzgerald, encouraged Thomas Wolfe to be less wordy and went fishing with Ernest Hemingway.

The first published collection of the entire correspondence between Rawlings and Maxwell E. Perkins, recognized by many as the foremost 20th-century American editor, sheds new light on their relationship and on the major literary figures of the 1930s and ’40s, said Rodger L. Tarr, University Distinguished Professor at Illinois State University and author of the book Max and Marjorie: The Correspondence between Maxwell E. Perkins and Marjorie Kinnan Rawlings.

"Perkins is the renowned editor of Hemingway, Fitzgerald and Wolfe," Tarr said. "But few people know he found Rawlings if not in a professional sense their equal, certainly in a personal sense he treated her as their equal."

Tarr, who did his research at the University of Florida’s Smathers Library special collections and at Princeton University, said the 698 letters, notes and telegrams included in the book contain not only important new information about Fitzgerald, Wolfe and Hemingway but Perkins as well. Rawlings arranged in 1950 to donate her manuscripts and papers to UF.

When Perkins pressed Rawlings to visit and cheer up an ill and despondent Fitzgerald, she drove to the Asheville, N.C. inn where he was convalescing, Tarr said.

"They spent the whole day together — wined and dined and laughed and cried," Tarr said.

Perkins also summoned Rawlings to New York to persuade Wolfe — notorious for writing lengthy manuscripts — not to be so verbose. And it was through Perkins that Rawlings met Hemingway, becoming good friends and fishing with him in Bimini, Tarr said.

Perkins, the sophisticated, urbane editor, had little in common with Rawlings, the earthy, remote orange grower, but their partnership was the single most important influence on Rawlings’ literary life, Tarr said. In fact, Tarr’s book reveals how Perkins participated in the actual writing of Rawlings’ books.

It was Perkins’ idea that Rawlings write a "boy’s book" about life in rural Florida among the Crackers, which led to The Yearling, her 1939 Pulitzer Prize winner, Tarr said. And it was Perkins who supplied the unifying metaphor for her equally celebrated book Cross Creek.

"Perkins was more than an editor," Tarr said. "He was her second voice, one might almost say her silent voice. He supplied language, metaphors and plot, and he encouraged her to alter her works in a way that would make them suitable for Scribner’s (publishing)."

In The Yearling, she removed parts of the book he suggested were off-color, he said. In turn, Rawlings suggested writers to Perkins, including Zora Neale Hurston, who sent manuscripts to Perkins, he said.

After Perkins’ death, Rawlings struggled to finish her last novel The Sojourner, which finally was published six years later, never to receive the acclaim of her earlier novels. "When Perkins died suddenly in 1947, Rawlings’ literary lamp went out," Tarr said.

Rodger Tarr, rtarr@ilstu.edu

Study Finds House Arrest No Easy Out For Criminals
By Cathy Keen

Contrary to public perception, home becomes a prison and the entire family is punished when criminal offenders are sentenced to house arrest, a new University of Florida study finds.

Offenders say the guilt of having to see family members suffer and not be able to help them makes home confinement — a popular alternative to a jail sentence — worse than prison, said Sylvia Ansay, a UF graduate student in sociology who did the research for her doctoral dissertation.

"The public sees people out and about instead of in prison and may see this as an easy thing," Ansay said. "But for family members that I interviewed, it’s not a bit easy. It was clear that in some households all members were virtually on community control.

If a wife’s car breaks down at midnight, a child misses a school bus or a disabled grandmother needs a prescription, the family member in home confinement feels totally helpless, she said.

"One public defender said that if it were his son or daughter, he would advise them to take prison time and get it over,’" she said. "Many offenders expressed the same sentiment, that if they had to do it again, they would rather go to prison."

Community control, Florida’s version of home confinement and intensive supervision, is one of the nation’s most ambitious programs, said Ansay, whose study tracked 26 offenders and their families from one circuit court district during the last year.

Although most offenders appreciate being with their families while serving their sentences, the stress of continuing family obligations frequently breaks down the roles and rituals that hold the family together, Ansay said.

"This research is of major significance because it takes a rare look at the everyday experience for families of having a member of the household on house arrest," said Jaber F. Gubrium, a UF sociology professor who supervised Ansay’s research.

Sylvia Ansay, ansay@nersp.nerdc.ufl.edu

Rising Seas Killing Trees On Florida’s West Coast
By Aaron Hoover

When University of Florida researchers first looked into Florida west-coast residents’ complaints of dying palms, they thought the cause was a disease.

But in a landmark study recently published in the journal Ecology, a team of UF and U.S. Geological Survey researchers concluded the cabbage palms and many other coastal trees are falling victim to saltwater exposure tied to global sea-level rise. The phenomenon may be a more immediate threat to coastal forests on Florida’s west coast than commonly recognized, partly because small increases in sea level can affect large areas of extremely flat coastline on the west coast, and partly because development and farms impede forests from growing anew on higher ground farther inland, the researchers say.

"What this does for me is bring home the global problem of sea-level rise," said Francis Putz, a UF professor of botany and member of the team that worked on the project.

The research team launched the project seven years ago at the Waccasassa Bay State Preserve south of Cedar Key in Levy County, dividing forested islands with differing elevations into 400-square-meter plots. They tagged and counted all the trees and seedlings and monitored groundwater salinity and tidal flooding. Over the next three years, they returned to the sites periodically to note changes to the tree populations and correlate them with measurements of tidal flooding and changes in groundwater salinity.

Despite the relatively short duration of the study, many trees died by the end of the field research. Although some of the deaths were attributed to the 1993 Storm of the Century, some occurred before the storm.

"Trees died during the course of the study in several island plots, changing community composition ... Southern red cedars were lost from two of the four most frequently flooded stands, leaving cabbage palms as the only tree species in three plots," the study said, noting that the cabbage palms were usually the last trees to die.

Perhaps more worrisome, the researchers also found that even when older trees and palms survived, they often failed to produce new seedlings, effectively making them the last generation of trees on the once densely forested islands.

"Elimination of tree regeneration may precede the death of established trees by many decades," the study says. "For cabbage palms ... the stand with fewest surviving trees is estimated to have suffered complete regeneration failure around 80 years ago."

Kimberlyn Williams, a member of the research team and former assistant professor of botany at UF, said researchers do not have enough information yet to determine whether the tree die-off rate and forest retreat are faster now than in the past. She noted that sea levels have been rising for the past 10,000 years, but that many scientists fear global warming has sped up the process in recent years. She added that rising sea levels may not be the only contributor to the demise of the coastal forest.

"Things such as drought and a reduction in freshwater flow to the coast may have accelerated the process — we can’t tell yet, but it’s definitely a possibility," she said.

Whatever the case, the process is happening relatively quickly, especially by the standards of geologic time. Sea levels are rising an average of about 1.5 millimeters each year globally, a seemingly small increase. But on the large areas of Florida’s west coast that have little or no slope, this small increase is converting as much as 2 meters of forest to salt marsh annually, Williams said.

The forest retreat threatens many coastal parks and nature reserves, such as Waccasassa Bay State Preserve, because the reserves are sandwiched between the ocean on one side and residential areas or farms on the other, Putz said. If Florida wants to have coastal forests, it should plan ahead and buy forested areas inland of the reserves now, he and Williams said. Putz added that sea-level rise also is likely to be killing trees on Florida’s east coast, but that the area is harder to study because of tidal fluctuation.

Francis Putz, fep@botany.ufl.edu

Homosexual Behavior In Beetles Tied To Evolution
By Aaron Hoover

In a new hypothesis for a behavior observed in a number of species, two researchers say the process of natural selection may explain homosexual behavior in a beetle that preys on citrus in South Florida.

An article about the research co-authored by an Israeli researcher and a University of Florida professor appeared in the Oct. 21, 1999 edition of the journal Nature.

Ally R. Harari, a researcher at the Volcani Center at Ben-Gurion University in Israel, and Jane Brockmann, professor and chair of UF’s Department of Zoology, studied the behavior of Diaprepes abbreviatus, an inch-long black beetle commonly known as the sugarcane rootstalk borer weevil. The research began in 1996 at UF when Harari was a post-doctoral researcher in UF’s Department of Entomology and Nematology.

Both male and female beetles mount each other, Brockmann said. When she and Harari studied the females’ behavior in laboratory experiments, they discovered the sight of a pair of mounted females attracts large males, who are equally likely to mate with either of the two females. Small males, by contrast, stay away, apparently dissuaded by the size of the top female.

"We are hypothesizing that by mounting each other, the females are able to attract more attention from larger males than if they were seeking males alone," Brockmann said, adding that bottom females are capable of pushing top ones off but do not do so.

Homosexual behavior is observed in a number of insects and other animal species, Brockmann said. The standard explanation for the behavior in domesticated animals such as cows is that mounting is a display of dominance, she said. The beetle’s behavior, by contrast, appears to suggest a different explanation.

"By mounting other females, females are improving their reproductive success because they are able to mate with larger males," Brockmann said. "Larger males are advantageous because their large size may indicate their ability to find food, or large males may transfer valuable resources to the female."

Some insects attract mates by emitting certain chemicals, but Harari found that in the rootstalk borer weevil, these cues are unreliable, Brockmann said. Instead, males appear to rely on sight.

"Males are attracted by the sight of heterosexual couples," she said. "The males and females are almost indistinguishable, so when the males see the mounted females they mistake them for a male mounting a female."

The female beetles are challenging to study in nature because they mount each other for an average of 17 minutes, which makes it difficult to examine the phenomenon experimentally, Brockmann said. To get around this problem, she and Harari glued dead female beetles to the backs of other females, then observed the males’ behavior.

"We created natural situations, but we created them more often so we could examine the effect," Brockmann said.

Brockmann said she and Harari are still studying male-male mounting in the species.

Jane Brockmann, hjb@zoo.ufl.edu

UF Team Wins $2.2 Million For Molecular Modeling
By Aaron Hoover

A University of Florida-based research team has received a $2.2 million federal grant to create powerful new computer simulations for use in probing how stress affects atoms and molecules in materials.

The three-year National Science Foundation grant is expected to improve researchers’ understanding of the chemical changes that occur at the atomic level when, for example, a material cracks under pressure. It also may one day help engineers develop stronger, lighter materials.

"The questions are basic, but the applications are enormous," said Rod Bartlett, a UF graduate research professor of chemistry and physics and the lead investigator on the team. "You always want materials that are lighter, stronger and that can stand up under more duress, and what we do will have impact in all of those areas in time."

The grant is part of a high-profile NSF initiative, the Knowledge and Distributed Intelligence Program, which seeks to "achieve the next generation of human capability to generate, model and represent more complex and cross-disciplinary scientific data from new sources and at enormously varying scales."

The UF team is composed of seven UF researchers as well as researchers at the Massachusetts Institute of Technology, the University of Arizona in Jackson and Washington State University. It is centered at UF’s Quantum Theory Project, a research group that explores the structure and dynamics of molecular, solid and layered systems.

Hai-Ping Cheng, a UF professor of physics and member of the research team, said surprisingly little is known about chemical changes at the atomic level when a material is strained or cracks under pressure. Scientists also know little about the fundamentals of how lubricants or polishes work, all areas the UF research will delve into, Cheng said.

"People in ancient Egypt knew how to use water as a lubricant, but the fundamental process at the atomic level we still don’t understand as completely as we would like," Cheng said.

Bartlett said the UF team plans to use quantum mechanical theories developed over many years at the Quantum Theory Project to study and describe how molecules and atoms interact, then apply the findings to the larger scale using the computer simulations.

"We want to take the core of information about how these molecules and atoms interact and insert that into simulation methods that might be applicable to thousands or tens of thousands of atoms, which is the real-world material," he said.

The result will be software that, when run on powerful parallel computers at UF and elsewhere, could open the door to designing better materials.

"It’s a tool that should be able to transcend experimental work," Bartlett said. "We want to create a seamless treatment of materials from the molecular all the way to the macroscopic."

Rod Bartlett, bartlett@qtp.ufl.edu
Hai-Ping Cheng, cheng@qtp.ufl.edu