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ACS News Service Weekly PressPac: June 09, 2006

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News Items in this Edition

New high-efficiency “plastic” solar cells

Nobel laureate Alan J. Heeger (Chemistry, 2000) and a group of colleagues including Kwanghee Lee say that new developments in "plastic" solar cells, particularly chemical modifications to titanium oxide layers, could provide efficiencies of up to 15 percent in the future.

Heeger already has developed plastic solar cells with efficiencies between 5 percent and 6 percent, considered among the highest to date for this type of solar cell. These developments could pave the way for wider use of plastic solar cells, a type of conducting polymer, which are increasingly seen as a low cost, efficient and long-lasting source of solar energy.

Nobel laureate Alan J. Heeger (Chemistry, 2000) and a group of colleagues including Kwanghee Lee say that new developments in "plastic" solar cells, particularly chemical modifications to titanium oxide layers, could provide efficiencies of up to 15 percent in the future.

Heeger already has developed plastic solar cells with efficiencies between 5 percent and 6 percent, considered among the highest to date for this type of solar cell. These developments could pave the way for wider use of plastic solar cells, a type of conducting polymer, which are increasingly seen as a low cost, efficient and long-lasting source of solar energy.

Ultrathin, dye-sensitized solar cells called most efficient to date

Researchers in Switzerland have developed dye-sensitized solar cells that have reached the highest efficiencies to date among a new generation of thin film photovoltaic devices that show promise as a low-cost energy source.

The new cells, composed of an ultrathin film of nano-sized semiconductor crystals such as titanium dioxide, have been shown in laboratory studies to produce efficiencies of 11 percent, whereas most new solar cells have efficiencies between 4 percent and 5 percent, according to Michael Graetzel, Ph.D., a chemist at the Swiss Federal Institute of Technology, Lausanne.

Graetzel’s cells, which can be engineered into inexpensive, flexible sheets, could be used as coatings on glass windows to supply electric power to homes and businesses or as coatings on tents to supply power for soldiers in the field. The cells could be used in consumer applications within two to three years, the researcher says.

‘Conversation stoppers’ fight deadly bacterial infections

NOTE: A press conference on this topic with call-in audio participation will be held at 10 a.m. Sept. 11. Reporters are asked to call five to ten minutes prior to the scheduled start time. Reporters will be asked to identify themselves, their affiliations and the topic of the briefing. Call 800-967-7140 (domestic); 719-457-2629 (international).

Bacterial infections are becoming more deadly worldwide due to increased resistance to antibiotics. Now Helen E. Blackwell and colleagues have developed a powerful strategy to fight these deadly infections: Instead of killing the bacteria directly, the scientists designed a group of compounds that can block the chemical signals that the bacteria use to communicate in an effort to stop their spread.

These compounds, small organic molecules that they call ‘conversation stoppers,’ could help deliver a powerful one-two punch to knock out deadly infections when combined with the killing power of antibiotics. In addition, these ‘conversation stoppers’ do not target bacterial growth, so the potential for the development of bacterial resistance is minimized.

So far, the researchers have identified at least two compounds that show particular promise at blocking biofilm formation in Pseudomonas aeruginosa, a bacterium that is a common cause of death in people with cystic fibrosis, AIDS and severe burns.

‘Crabby’ compound that skewers bacteria could prevent medical implant infections

A chemical compound found in crabs and shrimp long known to have certain medicinal value also can act like a “bed of nails,” fending off microbes seeking to colonize wound dressings, catheters and other implantable medical devices, Philip Stewart and colleagues report.

Using the compound to coat these medical devices, they say, could help prevent thousands of bacterial and yeast infections annually. In preliminary laboratory studies, chitosan ― a sugar in the cells of crabs and shrimp ― repelled bacteria and yeast, effectively preventing these microbes from forming slimy, glue-like layers of infectious cells, known as biofilms, Stewart said.

These biofilms account for up to 65 percent of the bacterial infections in the United States, according to the U. S. Centers for Disease Control and Prevention. The researchers say that while chitosan is well known for its antimicrobial activity, this is the first time its anti-biofilm activity has been described.

Biodegradable ‘napkin’ could help quickly detect, identify biohazards

Detecting bacteria, viruses and other dangerous substances could soon be as simple as wiping a napkin or paper towel across a table, according to Cornell University researchers. Once fully developed, the new absorbent wipe, embedded with nanofibers containing antibodies to numerous biohazards, could be used by virtually anyone to rapidly uncover pathogens in meat packing plants, hospitals, cruise ships, airplanes and other commonly contaminated areas, the researchers say.

The materials for this new process, which is still being tested in the laboratory, were described in a report by Margaret Frey and colleagues. It forms nanofibers with diameters between 100 nanometers and 2 microns (a human hair is about 80,000 nanometers wide). On these nanofibers, the researchers created platforms made of biotin, a B-vitamin and the protein streptavidin to hold the antibodies. The nanofibers, which are made of polyactide ― a polymer made from corn ― can be used to make non-woven wipers or swabs. To reduce costs, the nanofibers also could be incorporated into conventional paper products.

“Using this method we should, in theory, be able to quickly activate the fabric to detect whatever is the hazard of the week, whether it is bird flu, mad cow disease or anthrax,” Frey said.

Ingredient in Prozac increases risk of extinction for freshwater mussels

One of the first studies to examine the ecotoxicological effects of Prozac (fluoxetine) on native freshwater mussels finds that the drug causes females to prematurely release their larvae, essentially dooming them.

Prozac, one of the nation’s most prescribed anti-depressant medications, helps relieve depression by increasing the brain’s supply of a neurotransmitter called serotonin. But like many prescription drugs, some remnants of Prozac ultimately are mixed into wastewater that reaches rivers and streams.

In the new study, Rebecca Heltsley and colleagues placed female freshwater mussels carrying larvae into tanks containing laboratory water with varying concentrations of fluoxetine. They also exposed a similar set of mussels directly to serotonin. Within 48 hours, the mussels in both groups had released their larvae prematurely. When larvae are released too early, they are not viable, which only contributes to the problems faced by struggling populations of native freshwater mussels, Heltsley said.

Brown seaweed contains promising fat fighter, weight reducer

Chemists in Japan have found that brown seaweed, a flavor component used in many Asian soups and salads, contains a compound that appears in animal studies to promote weight loss by reducing the accumulation of fat. Called fucoxanthin, the compound achieved a 5 percent to 10 percent weight reduction in test animals and could be developed into a natural extract or drug to help fight obesity, the researchers say.

Kazuo Miyashita and colleagues report that the compound targets abdominal fat, in particular, and may help reduce oversized waistlines. The brown seaweed used in the current study was Undaria pinnatifida, a type of kelp also known as wakame, which is widely consumed in Japan. Human studies are planned, the researcher says, but adds that it may take three to five years before such an anti-obesity pill is available to consumers. Until then, people should continue to eat a well-balanced diet and get plenty of exercise, he says.

Of rice and hen: Fashions from the farm

In the future, it might be perfectly normal to wear suits and dresses made of chicken feathers or rice straw. But don’t worry: These clothes won’t resemble fluffy plumage or hairy door mats. Yiqi Yang and colleagues report that they plan to develop these agricultural waste products into conventional-looking fabrics as a way to reduce the use of petroleum-based synthetic fabrics.

The feather-based fabric will resemble wool, while the rice straw fabric will look and feel more like linen or cotton, according to the researchers. Both fabrics are still in early development and may not reach the consumer market for several years, the researchers say.

With millions of tons of chicken feathers and rice straw available worldwide each year, these agricultural wastes represent an abundant, cheap and renewable alternative to petroleum-based synthetic fibers. And unlike petroleum-based fibers, these agro-fibers are biodegradable. Chicken feathers and rice straw also could become “green” fabrics used in carpets, automobiles, building materials and a host of other everyday applications.

Black-Bone Silky Fowl: An odd bird with meat to crow about

Food scientists from the Peoples’ Republic of China report a biochemical explanation for the Black-Bone Silky Fowl’s 1,000-year-old reputation as a marvel of traditional Chinese medicine.

One odd bird, indeed, this chicken sports an abundance of snow-white feathers that feel as smooth as silk. Underneath is black-colored skin, black meat and — you guessed it — black bones. As a kind of folk invigorant and a source of traditional Chinese medicine, the chicken is used to boost immunity and diabetes, anemia, menstrual cramps and postpartum disorders, according to researchers.

Seeking an explanation for the bird’s reputed medical abilities, which date to at least the early 1000s A.D., Mingyong Xie and colleagues found that the fowl contains high levels of carnosine, a naturally occurring peptide most familiar in the West as a dietary supplement. It is used in an effort to increase muscle strength, ward off the effects of aging and alleviate diseases such as autism and diabetes.

Tiny fuel cell might replace batteries in laptop computers, portable electronics

If you’re frustrated by frequently losing battery power in your laptop computer, digital camera or portable music player, then take heart: A better source of “juice” is in the works. Don Gervasio and colleagues have created a tiny hydrogen-gas generator that they say can be developed into a compact fuel cell package that can power these and other electronic devices — from three to five times longer than conventional batteries of the same size and weight.

The generator uses a special solution containing borohydride, an alkaline compound that has an unusually high capacity for storing hydrogen, a key element that is used by fuel cells to generate electricity. In laboratory studies, a prototype fuel cell made from this generator was used to provide sustained power to light bulbs, radios and DVD players.

The fuel cell system can be packaged in containers of the same size and weight as conventional batteries and is recharged by refilling a fuel cartridge, they say. Research on these battery replacement fuel cells suggests they are safer for the environment than regular batteries.

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