Friday, November 26, 2010


0 comentarios
Using particles that are 1/100,000 the width of a human hair to deliver drugs to cells or assist plants in fighting off pests may sound like something out of a science fiction movie, but these scenarios may be a common occurrence in the near future.

Carbon nanotubes, cylindrically shaped carbon molecules with a diameter of about 1 nanometer, have many potential applications in a variety of fields, such as biomedical engineering and medical chemistry. Proteins, nucleic acids, and drugs can be attached to these nanotubes and delivered to cells and organs. Carbon nanotubes can be used to recognize and fight viruses and other pathogens. However, results of studies in animals have also raised concerns about the potential toxicity of nanoparticles.

Recent research by a team of researchers from China, led by Dr. Nan Yao, explored the effects of nanoparticles on plant cells. The findings of Dr. Yao and his colleagues are published in the October issue of the American Journal of Botany (

Dr. Yao and his team of researchers isolated cells from rice as well as from the model plant species Arabidopsis. The researchers treated these cells with carbon nanotubes, and then assessed the cells for viability, damage to DNA, and the presence of reactive oxygen species.

The researchers found an increase in levels of the reactive oxygen species hydrogen peroxide. Reactive oxygen species cause oxidative stress to cells, and this stress can result in programmed cell death. Dr. Yao and his colleagues discovered that the effect of carbon nanotubes on cells was dosage dependent—the greater the dose, the greater the likelihood of cell death. In contrast, cells exposed to carbon particles that were not nanotubes did not suffer any ill effects, demonstrating that the size of the nanotubes is a factor in their toxicity.

"Nanotechnology has a large scope of potential applications in the agriculture industry, however, the impact of nanoparticles have rarely been studied in plants," Dr. Yao said. "We found that nanomaterials could induce programmed cell death in plant cells."

Despite the scientists' observations that carbon nanotubes had toxic effects on plant cells, the use of nanotechnology in the agriculture industry still has great promise. The scientists only observed programmed cell death as a temporary response following the injection of the nanotubes and did not observe further changes a day and a half after the nanotube treatments. Also, the researchers did not observe death at the tissue level, which indicates that injecting cells with carbon nanotubes caused only limited injury.

"The current study has provided evidence that certain carbon nanoparticles are not 100% safe and have side effects on plants, suggesting that potential risks of nanotoxicity on plants need to be assessed," Dr. Yao stated. In the future, Dr. Yao and colleagues are interested in investigating whether other types of nanoparticles may also have toxic effects on plant cells. "We would like to create a predictive toxicology model to track nanoparticles."

Only once scientists have critically examined the risks of nanoparticles can they take advantage of the tremendous potential benefits of this new technology.

American Journal of Botany


0 comentarios
Risø Energy Report 9 lists a wide range of energy technologies in the market with low or no emissions of greenhouse gases, describing how several of these will be made commercially available in the next decades.

However, it is not possible to make the world's energy supply CO2-free as cheaply as possible, using only technology development in the current energy systems. There must be room for technological leaps and there is a need for an integrated process to optimise the entire energy system, from energy production, through transformation into energy carriers, to energy transportation and distribution and efficient end use.

There is also a need for a smart grid, connecting production and end use at local level. End users should contribute to maintain balance in the future energy system and new technologies should be introduced to the end users, including houses with low and flexible consumption, smart electronic equipment, heat pumps, energy storage and local energy supplies such as solar cells and micro CHP. Information and communication technology (ICT) will determine how successful the integration of renewables into the grid actually will be.

Considering the security of supply in the short and long term, there is still a need for access to fossil fuels, but they must be continuously replaced with renewable energy sources. If we do not make efforts to promote renewable energy sources, coal and gas might easily be prevailing in the global energy supply for the rest of this century. For many countries, however, it could be advantageous to switch to renewable energy sources in order to reduce dependence on imported oil and gas. In addition, this transition can help the countries achieve their environmental policy goals.

Seen in isolation, Denmark has a great chance for achieving these goals and for phasing out fossil fuels at a rapid pace and thus reduce emissions of greenhouse gases at the required pace.

Danish wind and biomass resources in particular will make it possible to phase out fossil fuels in connection with power generation and heat production before 2040. It will take further 10 years to eliminate fossil fuels within the transport sector.

A future smart energy system requires that we start investments now. If we do not make these investments, future generations will look back on this period wondering how we could be satisfied with an outdated energy system, without taking advantage of the opportunities which we already were aware of.

Risø National Laboratory for Sustainable Energy


0 comentarios
Point spreads—the number of points by which a strong team can be expected to defeat a weaker team—are supposed to reflect the "wisdom of crowds." But a new study in the Journal of Consumer Research found that crowds don't have a clue.

"Point spread betting markets seem to offer an important example of crowd wisdom, because point spreads are very accurate and are widely believed to reflect the 'crowd's' prediction of upcoming sporting events," write authors Joseph P. Simmons (Yale University), Leif D. Nelson (University of California at Berkeley), Jeff Galak (Carnegie Mellon University), and Shane Frederick (Yale University). But previous research shows that bettors are biased in their predictions; their intuitions tend to favor "favorites" over "underdogs."

The authors conducted a season-long investigation of the betting habits of enthusiastic NFL football fans from diverse regions of the United States. Participants wagered more than $20,000 on football games against point spreads that were manipulated to favor the underdog.

The authors first tested a hypothesis that crowds will wisely choose underdogs against spreads that disadvantage favorites. The bettors failed this test, predicting vastly more favorites (89 percent) than underdogs. Next, they found that even when bettors were warned that the spreads had been increased they still predicted favorites only slightly less often (83 percent).

"In this context, the temptation to rely on one's intuition is so strong as to lead people to rely on what they intuitively feel to be true (this favorite will prevail against the spread) rather than on what they generally know to be true (the favorite will usually lose against the spread)" the authors write. And it seems people have trouble learning from their mistakes: the crowd's predictions worsened over time, rather than getting better.

Finally, the researchers hit upon a method of eliciting better choices. "Asking people to predict point differentials rather than make choices against point spreads decreased reliance on faulty intuitions and produced vastly different, and vastly wiser, predictions against the spread," the authors conclude.

University of Chicago Press


0 comentarios
Why would someone choose a credit card with a one percent interest rate over another with a zero percent rate? A new study in the Journal of Consumer Research finds that consumers are often flummoxed when it comes to zero.

"A reasonable assumption is that a product will be more attractive when it offers more of a good thing, such as free pictures (with a digital camera purchase), or less of a bad thing, like interest rates on a credit card," writes author Mauricio Palmeira (Monash University, Australia). But Palmeira's research found that consumer comparison methods tend to get confused when one of the comparison terms has a zero value.

For example, a consumer interested in a new credit card may need to choose between one with a $45 annual fee and a one percent interest rate and another with a $15 fee and a 20 percent interest rate. "One could view this decision as a choice between an extra $30 annually for a 19 percent reduction in interest rate. Alternately, it can be viewed in relative terms. In this sense, a $30 difference between $15 and $45 appears much bigger than the same difference between $115 and $145," writes Palmeira. Consumers tend to be more sensitive to relative rather than absolute differences, which is why a one percent interest rate looks good, since its interest rate is 20 times less than 20 percent.

But what if consumers compare a 20 percent interest rate to a zero percent one? "I argue that whereas a 20 percent interest rate may look very large compared to one percent (it is 20 times larger!), it may not look as large compared to zero percent. Zero eliminates the reference point we use to assess the size of things," Palmeira explains.

"This leads to a counterintuitive situation, in which a credit card can increase its likelihood of being selected when it has a small but non-zero interest rate," writes Palmeira. The same is true of other attributes that consumers want to minimize, like interest rates and fat content.

The inverse is true when consumers desire an attribute. For example, if a digital camera offers a promotion that adds 200 free pictures to a purchase, a competitor may be better off offering nothing rather than just a few free pictures. "This is because 200 will look larger compared to 10 or 20 than compared to zero," Palmeira writes.

Chicago Journals


0 comentarios
Tyrannosaurus rex was far from a plodding Cretaceous era scavenger whose long tail only served to counterbalance the up-front weight of its freakishly big head.

T. rex's athleticism (and its rear end) has been given a makeover by University of Alberta graduate student Scott Persons. His extensive research shows that powerful tail muscles made the giant carnivore one of the fastest moving hunters of its time.

As Persons says, "contrary to earlier theories, T. rex had more than just junk in its trunk."

The U of A paleontology student began his research by comparing the tails of modern-day reptiles like crocodiles and Komodo dragons to T.rex's tail. Persons found for that all animals in his study, the biggest muscles in the tail are attached to upper leg bones. These caudofemoralis muscles provide the power stroke allowing fast forward movement.

But Persons found T.rex had one crucial difference in its tail structure.

The tails of both T.rex and modern animals are given their shape and strength by rib bones attached to the vertebrae. Persons found that the ribs in the tail of T. rex are located much higher on the tail. That leaves much more room along the lower end of the tail for the caudofemoralis muscles to bulk-up and expand. Without rib bones to limit the size of the caudofemoralis muscles, they became a robust power-plant enabling T.rex to run.

Persons’ extensive measurements of T.rex bones and computer modeling shows previous estimates of the muscle mass in the dinosaur's tall were underestimated by as much as 45 per cent.

That led many earlier T. rex researchers to believe the animal lacked the necessary muscle mass for running which in turn limited its hunting skills. That lack of speed cast T. rex in the role of a scavenger only able to survive by feeding on animals killed by other predators.

As for an T. rex's exact speed, researchers say that is hard to measure, but Persons says it could likely run down any other animal in its ecosystem.

University of Alberta


0 comentarios

Engineers from Harvard University have designed and demonstrated ice-free nanostructured materials that literally repel water droplets before they even have the chance to freeze.

The finding, reported online in ACS Nano on November 9th, could lead to a new way to keep airplane wings, buildings, powerlines, and even entire highways free of ice during the worst winter weather. Moreover, integrating anti-ice technology right into a material is more efficient and sustainable than conventional solutions like chemical sprays, salt, and heating.

A team led by Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science at the Harvard School of Engineering and Applied Sciences (SEAS) and a Core Member of the Wyss Institute for Biologically Inspired Engineering at Harvard, focused on preventing rather than fighting ice buildup.

"We wanted to take a completely different tact and design materials that inherently prevent ice formation by repelling the water droplets," says Aizenberg. "From past studies, we also realized that the formation of ice is not a static event. The crucial approach was to investigate the entire dynamic process of how droplets impact and freeze on a supercooled surface."

For initial inspiration, the researchers turned to some elegant solutions seen in nature. For example, mosquitos can defog their eyes, and water striders can keep their legs dry thanks to an array of tiny bristles that repel droplets by reducing the surface area each one encounters.

"Freezing starts with droplets colliding with a surface," explains Aizenberg. "But very little is known about what happens when droplets hit surfaces at low temperatures."

To gain a detailed understanding of the process, the researchers watched high-speed videos of supercooled droplets hitting surfaces that were modeled after those found in nature. They saw that when a cold droplet hits the nanostructured surface, it first spreads out, but then the process runs in reverse: the droplet retracts to a spherical shape and bounces back off the surface before ever having a chance to freeze.

By contrast, on a smooth surface without the structured properties, a droplet remains spread out and eventually freezes.

"We fabricated surfaces with various geometries and feature sizes—bristles, blades, and interconnected patterns such as honeycombs and bricks—to test and understand parameters critical for optimization," says Lidiya Mishchenko, a graduate student in Aizenberg's lab and first author of the paper.

The use of such precisely engineered materials enabled the researchers to model the dynamic behavior of impacting droplets at an amazing level of detail, leading them to create a better design for ice-preventing materials.

Another important benefit of testing a wide variety of structures, Mishchenko adds, was that it allowed the team to optimize for pressure-stability. They discovered that the structures composed of interconnected patterns were ideally suited for stable, liquid-repelling surfaces that can withstand high-impact droplet collisions, such as those encountered in driving rain or by planes in flight.

The nanostructured materials prevent the formation of ice even down to temperatures as low as -25 to -30 degrees Celsius. Below that, due to the reduced contact area that prevents the droplets from fully wetting the surface, any ice that forms does not adhere well and is much easier to remove than the stubborn sheets that can form on flat surfaces.

"We see this approach as a radical and much needed shift in anti-ice technologies," says Aizenberg. "The concept of friction-free surfaces that deflect supercooled water droplets before ice nucleation can even occur is more than just a theory or a proof-of-principle experiments. We have begun to test this promising technology in real-world settings to provide a comprehensive framework for optimizing these robust ice-free surfaces for a wide range of applications, each of which may have a specific set of performance requirements."

In comparison with traditional ice prevention or removal methods like salting or heating, the nanostructured materials approach is efficient, non-toxic, and environmentally friendly. Further, when chemicals are used to de-ice a plane, for example, they can be washed away into the environment and their disposal must be carefully monitored. Similarly, salt on roads can lead to corrosion and run-off problems in local water sources.

The researchers anticipate that with their improved understanding of the ice forming process, a new type of coating integrated directly into a variety of materials could soon be developed and commercialized.

(Photo: Mike Oliveri, Flickr)

Harvard University




Selected Science News. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com