Monday, August 9, 2010


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Nanomaterials are poised for widespread use in the construction industry, where they can offer significant advantages for a variety of applications ranging from making more durable concrete to self-cleaning windows. But widespread use in building materials comes with potential environmental and health risks when those materials are thrown away. Those are the conclusions of a new study published by Rice University engineering researchers in ACS Nano.

"The advantages of using nanomaterials in construction are enormous," said study co-author Pedro Alvarez, Rice's George R. Brown Professor and chair of the Department of Civil and Environmental Engineering. "When you consider that 41 percent of all energy use in the U.S. is consumed by commercial and residential buildings, the potential benefits of energy-saving materials alone are vast.

"But there are reasonable concerns about unintended consequences as well," Alvarez said. "The time for responsible lifecycle engineering of man-made nanomaterials in the construction industry is now, before they are introduced in environmentally relevant concentrations."

Alvarez and co-authors Jaesang Lee, a postdoctoral researcher at Rice, and Shaily Mahendra, now an assistant professor at the University of California, Los Angeles, note that nanomaterials will likely have a greater impact on the construction industry than any other sector of the economy, after biomedical and electronics applications. They cite dozens of potential applications. For example, nanomaterials can strengthen both steel and concrete, keep dirt from sticking to windows, kill bacteria on hospital walls, make materials fire-resistant, drastically improve the efficiency of solar panels, boost the efficiency of indoor lighting and even allow bridges and buildings to "feel" the cracks, corrosion and stress that will eventually cause structural failures.
In compiling the report, Lee, Mahendra and Alvarez analyzed more than 140 scientific papers on the benefits and risks of nanomaterials. In addition to the myriad benefits for the construction industry, they also identified potential adverse health and environmental effects. In some cases, the very properties that make the nanomaterials useful can cause potential problems if the material is not disposed of properly. For example, titanium dioxide particles exposed to ultraviolet light can generate molecules called "reactive oxygen species" that prevent bacterial films from forming on windows or solar panels. This same property could endanger beneficial bacteria in the environment.

"There are ways to engineer materials in advance to make them environmentally benign," Alvarez said. "There are also methods that allow us to consider the entire lifecycle of a product and to ensure that it can be recycled or reused rather than thrown away. The key is to understand the specific risks and implications of the product before it is widely used."

Rice University


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Researchers have long known that humans lack a key enzyme -- one possessed by most of the animal kingdom and even plants -- that reverses severe sun damage.

For the first time, researchers have witnessed how this enzyme works at the atomic level to repair sun-damaged DNA.

The discovery holds promise for future sunburn remedies and skin cancer prevention.

In the early online edition of the journal Nature, Ohio State University physicist and chemist Dongping Zhong and his colleagues describe how they were able to observe the enzyme, called photolyase, inject a single electron and proton into an injured strand of DNA. The two subatomic particles healed the damage in a few billionths of a second.

“It sounds simple, but those two atomic particles actually initiated a very complex series of chemical reactions,” said Zhong, the Robert Smith Associate Professor of Physics, and associate professor in the departments of chemistry and biochemistry at Ohio State. “It all happened very fast, and the timing had to be just right.”

Exactly how photolyases repair the damage has remained a mystery until now.

“People have been working on this for years, but now that we’ve seen it, I don’t think anyone could have guessed exactly what was happening,” Zhong said.

He and his colleagues synthesized DNA in the lab and exposed it to ultraviolet light, producing damage similar to that of sunburn, then added photolyase enzymes. Using ultrafast light pulses, they took a series of “snapshots” to reveal how the enzyme repaired the DNA at the atomic level.

Ultraviolet (UV) light damages skin by causing chemical bonds to form in the wrong places along the DNA molecules in our cells.

This study has revealed that photolyase breaks up those errant bonds in just the right spots to cause the atoms in the DNA to move back into their original positions. The bonds are then arranged in such a way that the electron and proton are automatically ejected out of the DNA helix and back into the photolyase, presumably so it could start the cycle over again and go on to heal other sites.

All plants and most animals have photolyase to repair severe sun damage. Everything from trees to bacteria to insects enjoys this extra protection. Only mammals lack the enzyme.

Humans do possess some enzymes that can undo damage with less efficiency. But we become sunburned when our DNA is too damaged for those enzymes to repair, and our skin cells die. Scientists have linked chronic sun damage to DNA mutations that lead to diseases such as skin cancer.

“People have been working on this for years, but now that we’ve seen it, I don’t think anyone could have guessed exactly what was happening,” Zhong said.

Now that researchers know the mechanism by which photolyase works, they might use that information to design drugs or lotions that heal sun damage, Zhong said.

Normal sunscreen lotions convert UV light to heat, or reflect it away from our skin. A sunscreen containing photolyase could potentially heal some of the damage from UV rays that get through.

Perhaps ironically, photolyase captures light of a different wavelength -- visible light, in the form of photons -- to obtain enough energy to launch the healing electron and proton into the DNA that has been damaged by UV light.

Researchers knew that visible light played a role in the process -- hence the term “photo” in the enzyme’s name -- but nobody knew exactly how, until now.

(Photo: OSU)

Ohio State University


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A UA team is working to build a surveillance system that, in addition to capturing video, would be able to detect suspicious behavior.

A surveillance video capturing a man removing his sweater near an SUV packed with explosives during the Times Square bomb scare in May swiftly resulted in a multi-agency search.

But as soon as news hit that the man was not connected to the threat, questions were brought to the forefront about the reliability of surveillance.

The challenge with surveillance is that it is costly and not always reliable, said Paul Cohen, the University of Arizona computer science department head.

"The cost of knowing what is going on is very, very high," Cohen said. "The problem right now is not that we cannot put more cameras up, the problem is that monitoring those cameras is very, very expensive and error-prone."

To help remedy some of these issues, Cohen and his collaborators are working to build an intuitive system not merely to capture video, but to detect suspicious human behaviors.

The team has received a $2 million grant for the project's first two years from the Defense Advanced Research Projects Agency, or DARPA, with Cohen serving as the principal investigator.

After the initial period, the team will have a chance to qualify for an additional $3 million for a three-year period, Cohen said.

Drawing on ways the human brain processes visual information, the research team plans to build a visual detection and tracking system, models of human behaviors and simulators to generate possible future scenes.

Another challenge with modern-day surveillance is that it must be monitored, said Kobus Barnard, an associate professor of computer science and member of the research team.

What is required, and what the team intends to utilize, is high-level semantics. "We have to bring in a lot of information and pull together these hypotheses," Barnard said.

Others involved at the UA are Ian Fasel, an assistant research professor of computer science, and Wesley Kerr, a doctoral degree candidate in the computer science department.

The team also is collaborating with Deva Ramanan, an assistant professor of computer science at the University of California, Irvine, and Clay Morrison, an assistant research professor in the computer science department.

One of the project's major components is the incorporation of visual imagination, a process by which the brain decodes what the eyes see while also guessing what should occur next.

"The same parts of the brain are involved in vision and visual imagination. To some extent the brain is telling the eyes what they should be seeing. So we want to model this sort of heavy involvement of the brain," Cohen said.

The researchers are taking on a highly complex and difficult challenge in training a system to do just that.

"It has been done before in small pilot demonstrations. But as the number of activities grows, the technology might not scale up," Cohen said. He also noted that "getting from seeing to understanding" actions is somewhat difficult.

To start, the team will focus on 48 specific verbs or commands, developing a multi-level system that can differentiate actions such as "carry," "escape," "run" and "climb."

But the system is not being designed merely to detect such behaviors, but to understand them in the context of interactivity – people interacting with people and people interacting with objects.

Given that goal, the team is figuring out ways to involve the three parts of the system simultaneously so that it will be able to make guesses and deductions, Barnard said.

"The goal of the system is to really take the next step forward in the semantics of actions that are a little bit extended in time and more complex than what has been achieved so far, which is still in the research domain," Barnard said.

In addition to a range of different scientific disciplines, such as computer science and geometry, the project has implications for a several branches, including law enforcement and military personnel, Cohen said.

"We researchers have always been interested in unsophisticated things any human can do while funding agencies are often interested in things that only a tiny portion of the population can do," Cohen said, adding that the initial proposal was one of the best DARPA programs he's come across.

"You learn most about intelligence by studying what everyone can do," he added. "Any 3-year-old can look at a movie and tell you what she sees. No machine can."

(Photo: U. Arizona)

University of Arizona




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