Science looks to poplar trees for 'cool roof' technology

For as long as humans have been able to reason, they have mimicked nature in attempts to derive benefits for themselves; and just because we’ve become ultra-high tech in many ways, it doesn’t mean we’ve stopped looking to nature to help us solve some of the problems that continue to arise in our paths. As one example Yanlin Song and others on a team doing research for the Chinese Academy of Science, as described in their paper "Highly reflective superhydrophobic white coating inspired by poplar leaf hairs toward an effective 'cool roof'" in Energy & Environmental Science, are copying the way poplar trees protect themselves from harsh sunlight and believe it might lead to new ways to help control the heat that is produced when sunlight beats down on a roof.

The idea is simple, the poplar tree, over eons, has developed micro-fibers on the undersides of its leaves that can reflect both light and heat from the sun; thus, when the sun shines directly on the tree, it turns its leaves upside down to protect the insides of the leaves from extreme heat and the ensuing loss of moisture.

The Chinese team has been working on spinning polymers into long protective hollow fiber coatings that could in theory reflect sunlight, and thus reduce the amount of heat that is absorbed when sunlight shines on a roof. To test their results, they covered a swath of material with diarylethene, a compound that changes color when heated, then covered that with their polymer film, and then let the sun shine. They found that the more closely they could emulate the structure of the natural fibers on the poplar leaves, the less the diarylethene changed color.

And while the results the team has managed to show so far are promising, there is still a pretty serious obstacle standing in the way of developing a commercial product that could help homeowners or businesses cut their summer cooling costs; the polymers are just not resistant enough to stand up to the constant barrage of heat, cold, wind and other weather conditions.

Song says he and his team will continue to work with the polymers to see if they can come up with something stronger but will also continue with what they've developed thus far, perhaps even branching out in to other areas, such as lighting applications or in developing waterproofing substances since their polymer film turned out to be water resistant as well.

More information: Highly reflective superhydrophobic white coating inspired by poplar leaf hairs toward an effective "cool roof", Changqing Ye, Mingzhu Li, Junping Hu, Qunfeng Cheng, Lei Jiang and Yanlin Song, Energy Environ. Sci., 2011, Advance Article. DOI:10.1039/C0EE00686F

 

Only the weak survive? Pitt team adds more give for stronger self-healing materials

Conventional rules of survival tend to favor the strongest, but University of Pittsburgh-based researchers recently found that in the emerging world of self-healing materials, it is the somewhat frail that survive.

The team presents in the journal Langmuir a new model laying out the inner workings of self-healing materials made of nanoscale gel particles that can regenerate after taking damage and are being pursued as a coating or composite material. Moreover, the researchers discovered that an ideal amount of weak bonds actually make for an overall stronger material that can withstand more stress.

Although self-healing nanogel materials have already been realized in the lab, the exact mechanical nature and ideal structure had remained unknown, explained Anna Balazs, corresponding author and Distinguished Professor of Chemical Engineering in Pitt's Swanson School of Engineering. The team's findings not only reveal how self-healing nanogel materials work, but also provide a blueprint for creating more resilient designs, she said. Balazs worked with lead author and Pitt postdoctoral researcher Isaac Salib; Chet Gnegy, a Pitt chemical and petroleum engineering sophomore; German Kolmakov, a postdoctoral researcher in Balazs' lab; and Krzysztof Matyjaszewski, a chemistry professor at Carnegie Mellon University with a special appointment in Pitt's Department of Chemical and Petroleum Engineering.

The team worked from a computational model Gnegy, Kolmakov, and Salib created based on a self-healing material Matyjaszewski developed known as nanogel, a composition of spongy, microscopic polymer particles linked to one another by several tentacle-like bonds. The nanogel particles consist of stable bonds—which provide overall strength—and labile bonds, highly reactive bonds that can break and easily reform, that act as shock absorbers.

The computer model allowed the researchers to test the performance of various bond arrangements. The polymers were first laid out in an arrangement similar to that in the nanogel, with the tentacles linked end-to-end by a single strong bond. Simulated stress tests showed, however, that though these bonds could recover from short-lived stress, they could not withstand drawn out tension such as stretching or pulling. Instead, the team found that when particles were joined by several parallel bonds, the nanogel could absorb more stress and still self-repair.

The team then sought the most effective concentration of parallel labile bonds, Balazs said. According to the computational model, even a small number of labile bonds greatly increased resilience. For instance, a sample in which only 30 percent of the bonds were labile—with parallel labile bonds placed in groups of four—could withstand pressure up to 200 percent greater than what could fracture a sample comprised only of stable bonds.

On the other hand, too many labile linkages were so collectively strong that the self-healing ability was cancelled out and the nanogel became brittle, the researchers report.

The Pitt model is corroborated by nature, which engineered the same principle into the famously tough abalone shell, Balazs said. An amalgamation of microscopic ceramic plates and a small percentage of soft protein, the abalone shell absorbs a blow by stretching and sliding rather than shattering.

"What we found is that if a material can easily break and reform, the overall strength is much better," she said. "In short, a little bit of weakness gives a material better mechanical properties. Nature knows this trick."

Provided by University of Pittsburgh

The science of spring: Plants rely on internal alarm clocks to tell them when to wake up from winter

Just in time for the birds and the bees to start buzzing, the flowers and the trees somehow know when to open their buds or start flowering. But the exact way that plants get their wake-up call has been something of a mystery.

"Why should plants care?" The general answer to that is that there are a lot of situations where it’s important not to do something developmentally until spring has arrived," said Richard Amasino, a professor of biochemistry at the University of Wisconsin Madison. "Trees want to make sure that their buds are protected until spring."

Sibum Sung, a molecular biologist at the University of Texas Austin has an idea of how this protective action works on a cellular level. He discovered a special molecule in plants that gives them the remarkable ability to recall winter and to bloom on schedule in the spring. Sung published his results last December in the journal Science Express.

While digging through the DNA of a small cabbage-like plant called Arabidopsis, Sung and a colleague discovered that the production of a special molecule could be turned on or off by a string of genetic material. When the plant gets cozy for the winter, this molecule is not produced, repressing a plant’s ability to create flowers. But after 20 days of consistently frigid weather, production of the molecule gets turned back on, signaling another gene to stop repressing flower production and start preparing for spring. The plant takes another 10-20 days to prime itself for warmer temperatures. Without the 20 days of freezing temperatures, the molecule wouldn't be produced -- even if there is a brief spike in the thermometer reading.

Sung hypothesized that over millions of evolutionary years, this molecule -- called COLDAIR -- has created a sort of cellular memory in generations of plants, letting them know that a month of winter has come and gone, and now they can start preparing for the spring.

Of course, mysteries remain. Sung admits that his team is still working on questions like how the plant knows that temperatures have been low for at least 20 days.

"Well, we know that there are several things done by cold -- but how? That we don't really know yet," Sung said.

The genetic pathways involved are different for each type of plant, said Amasino, but the kind of alarm clock memory is similar. The reason may have to do with the early evolution of plants.

"Flowering plants had already evolved and changed 150 million years ago, when the Earth was a pretty different place," Amasino said. At that time, the Earth was much warmer, and the Atlantic Ocean didn't even exist yet. "So it's relatively recently that plants had to contend with winter," he said.

The kind of responses that plants developed to cold over the past hundred million years happened independently, said Amasino -- and that is one reason that different plants have unique systems to deal with wintertime. "One aim of plant research for the future is to explore how these systems evolved in different plant species," Amasino said.

When the planet’s climate changes more rapidly, it can sometimes be difficult for plants to keep up. Researchers have been studying plants that are opening earlier in the season, according to Ove Nilsson, a professor at the Umea Plant Science Centre in Umea, Sweden. He said that another problem with early spring is that plants get out of sync with their insect pollinators.

"This could potentially be catastrophic for the plants since these flowers can freeze to death," said Nilsson.

But as long as there is winter, nature will keep the pressure on to set an alarm clock for springtime, and the plants will once more open up.

More information: Vernalization-Mediated Epigenetic Silencing by a Long Intronic Noncoding RNA, Science 7 January 2011: Vol. 331 no. 6013 pp. 76-79. DOI: 10.1126/science.1197349

Provided by Inside Science News Service (news : web)

Multitarget drugs against prion diseases

 

The central nervous systems of humans and cattle alike are attacked by prions (abnormal insoluble amyloidogenic proteins) when they suffer from Creutzfeldt–Jakob disease (CJD) or bovine spongiform encephalopathy (BSE).

This causes a steady deterioration of neurological function and ultimately leads to death. There is no currently approved treatment for prion diseases, and no drug candidates are expected to enter clinical trials soon. In ChemMedChem, Maria Laura Bolognesi (University of Bologna, Italy) and colleagues argue in support of a multitarget drug discovery strategy as an alternative way to develop effective anti-prion agents.

Under the dominant drug discovery paradigm "one disease, one target, one molecule," which ignores the polyetiological nature of prion diseases and similar maladies, developing anti-prion therapies is a particular challenge; indeed, this paradigm could be a factor in the ongoing failure of current neurotherapeutic drugs.

Bolognesi and colleagues now describe the discovery of rationally designed molecules endowed with various activities relevant for combating prion neurodegeneration. A new series of chimeric molecules were generated by linking the antioxidant fragment of lipoic acid to heteroaromatic prion-recognition motifs. These compounds effectively counter both prion fibril formation and oxidative stress in a cell culture model of prion replication.

The reported in vitro results make these compounds effective candidates for further in vivo investigations into their multiple biological properties against prion diseases.

More information: Maria Laura Bolognesi, Hybrid Lipoic Acid Derivatives to Attack Prion Disease on Multiple Fronts, ChemMedChem, http://dx.doi.org/ … dc.201100072

Provided by Wiley (news : web)

U of M researchers close in on technology for making renewable petroleum

University of Minnesota researchers are a key step closer to making renewable petroleum fuels using bacteria, sunlight and dioxide, a goal funded by a $2.2 million United States Department of Energy grant.

Graduate student Janice Frias, who earned her doctorate in January, made the critical step by figuring out how to use a protein to transform fatty acids produced by the bacteria into ketones, which can be cracked to make hydrocarbon fuels. The university is filing patents on the process.

The research is published in the April 1 issue of the Journal of Biological Chemistry. Frias, whose advisor was Larry Wackett, Distinguished McKnight Professor of Biochemistry, is lead author. Other team members include organic chemist Jack Richman, a researcher in the College of Biological Sciences' Department of Biochemistry, Molecular Biology and Biophysics, and undergraduate Jasmine Erickson, a junior in the College of Biological Sciences. Wackett, who is senior author, is a faculty member in the College of Biological Sciences and the university's BioTechnology Institute.

"Janice Frias is a very capable and hard-working young scientist," Wackett says. "She exemplifies the valuable role graduate students play at a public research university."

Aditya Bhan and Lanny Schmidt, chemical engineering professors in the College of Science and Engineering, are turning the ketones into diesel fuel using catalytic technology they have developed. The ability to produce ketones opens the door to making petroleum-like hydrocarbon fuels using only bacteria, sunlight and carbon dioxide.

"There is enormous interest in using carbon dioxide to make hydrocarbon fuels," Wackett says. "CO2 is the major greenhouse gas mediating global climate change, so removing it from the atmosphere is good for the environment. It's also free. And we can use the same infrastructure to process and transport this new hydrocarbon fuel that we use for fossil fuels."

The research is funded by a $2.2 million grant from the U.S. Department of Energy's Advanced Research Projects Agency-energy (ARPA-e) program, created to stimulate American leadership in renewable energy technology.

The U of M proposal was one of only 37 selected from 3,700 and one of only three featured in the New York Times when the grants were announced in October 2009. The University of Minnesota's Initiative for Renewable Energy and the Environment (IREE) and the College of Biological Sciences also provided funding.

Wackett is principal investigator for the ARPA-e grant. His team of co-investigators includes Jeffrey Gralnick, assistant professor of microbiology and Marc von Keitz, chief technical officer of BioCee, as well as Bhan and Schmidt. They are the only group using a photosynthetic bacterium and a hydrocarbon-producing bacterium together to make hydrocarbons from carbon dioxide.

The U of M team is using Synechococcus, a bacterium that fixes carbon dioxide in sunlight and converts CO2 to sugars. Next, they feed the sugars to Shewanella, a bacterium that produces hydrocarbons. This turns CO2, a greenhouse gas produced by combustion of fossil fuel petroleum, into hydrocarbons.

Hydrocarbons (made from carbon and hydrogen) are the main component of fossil fuels. It took hundreds of millions of years of heat and compression to produce fossil fuels, which experts expect to be largely depleted within 50 years.

Provided by University of Minnesota (news : web)

Researchers make advances in rechargeable solid hydrogen fuel storage tanks

Researchers have revealed a new single-stage method for recharging the hydrogen storage compound ammonia borane. The breakthrough makes hydrogen a more attractive fuel for vehicles and other transportation modes.

In an article appearing today in Science magazine, Los Alamos National Laboratory (LANL) and University of Alabama researchers working within the U.S. Department of Energy's Chemical Hydrogen Storage Center of Excellence describe a significant advance in hydrogen storage science.

Hydrogen is in many ways an ideal fuel. It possesses a high energy content per unit mass when compared to petroleum, and it can be used to run a fuel cell, which in turn can be used to power a very clean engine. On the down side, H2 has a low energy content per unit volume versus petroleum (it is very light and bulky). The crux of the hydrogen issue has been how to get enough of the element on board a vehicle to power it a reasonable distance.

Work at LANL and elsewhere has focused on chemical hydrides for storing hydrogen, with one material in particular, ammonia borane, taking center stage. Ammonia borane is attractive because its hydrogen storage capacity approaches a whopping 20 percent by weight—enough that it should, with appropriate engineering, permit hydrogen-fueled vehicles to go farther than 300 miles on a single "tank," a benchmark set by the U.S. Department of Energy.

Hydrogen release from ammonia borane has been well demonstrated, and its chief drawback to use has been the lack of energy-efficient methods to reintroduce hydrogen into the spent fuel once burned. In other words, until now, after hydrogen release, the ammonia borane couldn't be recycled efficiently enough.

The Science paper describes a simple scheme that regenerates ammonia borane from a hydrogen depleted "spent fuel" form (called polyborazylene) back into usable fuel via reactions taking place in a single container. This "one pot" method represents a significant step toward the practical use of hydrogen in vehicles by potentially reducing the expense and complexity of the recycle stage. Regeneration takes place in a sealed pressure vessel using hydrazine and liquid ammonia at 40 degrees Celsius and necessarily takes place off-board a vehicle. The researchers envision vehicles with interchangeable hydrogen storage "tanks " containing ammonia borane that are used, and sent back to a factory for recharge.

The Chemical Hydrogen Storage Center of Excellence was one of three Center efforts funded by DOE. The other two focused on hydrogen sorption technologies and storage in metal hydrides. The Center of Excellence was a collaboration between Los Alamos, Pacific Northwest National Laboratory, and academic and industrial partners.

LANL researcher Dr. John Gordon, a corresponding author for the paper, credits collaboration encouraged by the Center model with the breakthrough.

"Crucial predictive calculations carried out by University of Alabama Professor Dave Dixon's group guided the experimental work of the Los Alamos team, which included researchers from both the Chemistry Division and the Materials Physics and Applications Division at LANL," Gordon said.

The success of this particular advance built on earlier work by this team (see: Angew. Chem. Int. Ed. 2009, 37, 6812). Input from colleagues at Dow Chemical (also a Center Partner), indicated that an alternative approach to the work in the Angew. Chem. paper would be required if ammonia borane recycle were to be feasible on a large scale. Armed with this information, it was "the insight, creativity and hard work of Dr. Andrew Sutton of Chemistry Division at LANL that provided the key to unlocking the 'one-pot' chemistry," Gordon said.

Provided by Los Alamos National Laboratory (news : web)

New adhesive earns patent, may find place in space

A recently patented adhesive made by Kansas State University researchers could become a staple in every astronaut's toolbox.

The patent, "pH dependent adhesive peptides," was issued to the Kansas State University Research Foundation, a nonprofit corporation responsible for managing technology transfer activities of K-State. The patent covers an adhesive made from peptides -- a compound containing two or more amino acids that link together -- that increases in strength as moisture is removed.

It was created by John Tomich, professor of biochemistry, and Xiuzhi "Susan" Sun, professor of grain science and industry. Assisting in the research was Takeo Iwamoto, an adjunct professor in biochemistry, and Xinchun Shen, a former postdoctoral researcher.

"The adhesive we ended up developing was one that formed nanoscale fibrils that become entangled, sort of like Velcro. It has all these little hooks that come together," Tomich said. "It's a mechanical type of adhesion, though, not a chemical type like most commercial adhesives."

Because of its unusual properties, applications will most likely be outside the commercial sector, Tomich said.

For example, unlike most adhesives that become brittle as moisture levels decrease, the K-State adhesive's bond only becomes stronger. Because of this, it could be useful in low-moisture environments like outer space, where astronauts could use it to reattach tiles to a space shuttle.

Conversely, its deterioration from water could also serve a purpose.

"It could be used as a timing device or as a moisture detection device," Tomich said. "There could be a circuit or something that when the moisture got to a certain level, the adhesive would fail and break the circuit, sounding an alarm."

The project began nearly a decade ago as Sun and a postdoctal researcher were studying the adhesive properties of soybean proteins. Needing an instrument to synthesize protein peptides, Sun contacted Tomich.

Serendipitously, Tomich's lab had developed a peptide some time ago that had cement-like properties. Tomich said he knew it was unusual but had set it aside to pursue other interests.

"When Dr. Sun and I resurrected this protein, we didn't use the whole thing -- just a segment of it," Tomich said. "We isolated a certain segment where the cells are highly attracted to each other and form these fibrils."

Since their collaboration Tomich has taken the same sequence and changed the way it was designed. The new peptide, he said, will have an eye toward gene therapy.

Sun's lab is trying to optimize the sequence against adhesion, as well as study how peptide sequences influence adhesion properties and surface energy.

"I continue studying protein structures and functional properties in terms of adhesion -- folding, aggregation, surface energy and gelling properties -- so we can rationally design and develop biobased adhesives using plant proteins," she said.

Provided by Kansas State University (news : web)