University Times

Stronger self-healing materials modeled

A Pitt and Carnegie Mellon team has developed a new model of how self-repairing materials function. In a report published in the journal Langmuir, they show that materials with a certain number of easily breakable bonds can absorb more stress.

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

The researchers discovered that an ideal amount of weak bonds actually makes for an overall stronger material that can withstand more stress.

Although self-healing nanogel materials already have been realized in the lab, the exact mechanical nature and ideal structure had remained unknown, explained corresponding author Anna Balazs, Distinguished Professor of Chemical 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’s lab; and Krzysztof Matyjaszewski, a chemistry faculty member 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 first were 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. They found that 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. But, too many labile linkages were so collectively strong that the self-healing ability was canceled out and the nanogel became brittle.

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.”

Generic meds programs could save billions

If all eligible patients filled their prescriptions through a $4 generic drug program, the societal savings could amount to nearly $6 billion, according to a Graduate School of Public Health (GSPH) study published in the March 14 issue of Archives of Internal Medicine.

The study examined a large group of people who used generic medications or their brand-name counterparts that also were available for $4 per 30-day supply through a discounted generic drug program available at many retail stores’ pharmacies.

The study found that fewer than 6 percent of the patients taking these medications used the $4 generic medication programs in 2007, even though prescription drug coverage plans, on average, ask patients to pay about $10 for a 30-day supply of generic drugs and about $25 per 30-day supply of brand-name medications.

Had all eligible patients used the discount programs in 2007, the societal savings would have been $5.8 billion.

The study’s lead author, Yuting Zhang, a faculty member in health policy and management, said: “Although just half of the potential users of the $4 programs would have saved more than $22 a year in out-of-pocket expenses, the societal savings are great. This suggests the majority of savings comes from a small proportion of individuals.”

The researchers examined a nationally representative sample of nearly 31,000 people in the 2007 Medical Expenditure Panel Survey (MEPS) and identified patients who could have saved money had they filled their medications through a discount generic drug program.

The researchers calculated potential savings as the difference between the actual prescription payments recorded in MEPS and the $4 the patients would have paid through a discount program.

“We are not promoting any specific pharmacy or any retail store’s discount generic medication program,” Zhang said. “However, if policy makers and clinicians direct patients to low-cost generic programs, patients and taxpayers could save tremendously.”

The study was funded by the RAND University of Pittsburgh Health Institute and the National Institutes of Health-funded Clinical and Translational Science Institute.

Co-authors included Lei Zhou of GSPH and Walid F. Gellad of the School of Medicine, the VA Pittsburgh Healthcare System and the RAND Corp.

Aortic valve implants tested

UPMC has performed its first patient implants in a Medtronic CoreValve clinical trial to evaluate a non-surgical, less-invasive procedure as a treatment alternative to open-heart surgery for patients who suffer from a serious narrowing of the heart’s aortic valve.

UPMC is one of 40 hospitals across the nation to participate in the trial for patients with severe aortic stenosis, which prevents the heart’s aortic valve from opening completely and in turn hampers healthy blood flow from the aorta to the rest of the body. Untreated, it can lead to serious heart problems.

Department of Medicine faculty members William Anderson, director of interventional cardiology at UPMC, and Thomas Gleason, director of the Center for Thoracic Aortic Disease, in January performed one of the first CoreValve implants on a 66-year-old man from New Alexandria who suffered from shortness of breath and required oxygen nearly around-the-clock because of his aortic stenosis.

The physicians channeled a catheter through a small opening in his femoral artery to reach the heart, then guided the CoreValve system to the aortic valve, where the valve self-expanded to replace the diseased aortic valve. The procedure was completed without open-heart surgery or surgical removal of the aortic valve.

Anderson said, “Aortic stenosis frequently occurs in elderly patients who have a higher risk of complications from standard valve-replacement surgery. This growing patient population may then have the most to gain from new, less invasive, catheter-based approaches to the implantation of a new aortic valve. The trial will allow us to explore this possibility.”

Gleason added, “Because open-heart surgery is currently the only available treatment option for these patients, and because the risks of surgery can be significant for many patients, the medical community is enthusiastic about the less-invasive option.”

CoreValve will not be commercially available in the United States until the successful completion of this clinical trial and approval by the Food and Drug Administration. The system received the CE (Conformité Européenne) Mark in Europe in 2007.

Information on the clinical trial can be found at www.aorticstenosistrial.com.

Engineers model expanded power grid

A research team at the Swanson School of Engineering has launched a large-scale project to integrate modern and efficient power-delivery technology into the rapidly growing American grid.

By employing the same simulation technology used to design and engineer electricity grids, the researchers will model an expanded power grid that delivers electricity from the power plant to homes and businesses with less infrastructure and a more reliable and efficient flow of electricity. This improved infrastructure would not only conserve electricity, but also make it easier to tap into renewable resources, particularly solar and wind power, which typically are generated in remote locations far from consumers.

Lead researcher Gregory Reed, a faculty member in electrical and computer engineering and director of the engineering school’s Power and Energy Initiative, explained that the problem with power delivery is one of consistency.

Electricity in the United States is generated, transported and delivered by alternating current (AC). But modern devices — from renewable power resources and electric vehicles to high-definition televisions, data centers, computers and many other electrical devices — take a direct current (DC) input, hence the AC/DC converter most consumer electronics need. The more practical choice before the electronic age, AC allows electricity to be delivered over long distances from a central generator such as a power plant; it also was more compatible with early industrial motors and other equipment, Reed said.

But AC transmission requires more infrastructure than DC, and because electricity flows on the surface of an AC power line, it results in greater energy loss. DC delivers electricity directly via electronic circuitry without the need for AC’s power-leeching transformers and iconic triple-wire steel towers. Plus, DC can be transferred over long distances with far less loss and at higher capacities, significant benefits in an increasingly spread-out society, Reed said.

Reed and his team are working to merge DC into the nation’s AC-dominated grid at the transport stage, he said. The team has received government and industry support, including a recent $600,000 grant from the state’s Ben Franklin Technology Development Authority.

“We have to expand our electric-power delivery network anyway as our nation becomes more digitized, and people live and work farther from power sources,” Reed said. “It makes sense to take advantage of this time and upgrade to a new, better way to deliver power, instead of just building onto the infrastructure developed nearly 100 years ago. A DC infrastructure is better for taking full advantage of renewable energy resources and more compatible with the ubiquitous DC devices and systems at the consumer level.”

Because Reed’s research group cannot reconstruct an actual power grid, it has acquired through a partnership with Siemens Energy the same simulator programs that are the industry-standard tools for designing and analyzing power transmission systems.

“By using the same tools used for daily utility operations, long-term planning and design and development, we can engineer a better electric power system that is realistic in both performance and implementation,” Reed said.

“Like the few projects similar to ours, the work we’ve undertaken is very ambitious because of its scale,” Reed continued, “but if we as a nation want to not only conserve energy but also get more out of the power we use, a DC-based infrastructure is an essential step forward.”

More information on the project is available at www.power.pitt.edu.

Tax choice touted

In the spring 2011 issue of the journal Democracy, Pitt business faculty member Cait Lamberton explores ways of getting Americans to look more favorably on paying taxes and suggests offering U.S. residents a greater hand in how their tax dollars are spent.

In the article, Lamberton, Fryrear Faculty Fellow and marketing faculty member in the Joseph M. Katz Graduate School of Business and College of Business Administration, collaborated with Charles A. Lamberton, a Pittsburgh civil rights attorney, to suggest offering tax choice, which would allow taxpayers to allocate a percentage of their income taxes to any portion of the discretionary federal budget.

Results of Cait Lamberton’s behavioral research on the efficacy of tax choice suggest that permitting taxpayers to allocate even a small percentage of their income taxes to the programs of their choice generates significant increases in taxpayer satisfaction.

The authors wrote, “In a tax choice program, a taxpayer who wishes to support public education, for example, could send some of her income tax dollars specifically to that part of the federal budget, while a taxpayer who feels strongly about the military could allocate a portion of his income tax payment accordingly.”

The idea of allowing tax choice would address one of the biggest reasons that Americans psychologically hate paying taxes, according to the authors — when making their payments, taxpayers don’t see what they are getting in return. Tax choice also addresses a second major psychological objection to taxes — Americans generally do not like being told what to do, they said.

PSC gets teaching grant

The Pittsburgh Supercomputing Center (PSC) has received a $100,000 grant from the DSF Charitable Foundation to develop a pilot program to prepare high-school math and science teachers to use computational modeling effectively as part of K-12 learning. The grant extends Computation and Science for Teachers, which introduced many local science and math teachers to easy-to-use modeling and simulation as powerful tools for classroom learning.

The DSF grant funds a three-way effort among PSC and the Maryland Virtual High School Project, which helped to pioneer the use of computational thinking in high school learning, along with the Math & Science Collaborative of the Allegheny Intermediate Unit, which provides specialized educational services to Allegheny County’s 42 suburban school districts and five vocational/technical schools.

Educators from these three organizations will plan and design a well-defined professional development program for STEM (science, technology, engineering and math) teachers in western Pennsylvania to become leaders in integrating computational modeling and simulations in classroom learning.

PSC director of education and outreach Cheryl Begandy said the pilot program’s objectives include increasing use of computational reasoning; improving the learning experience and engagement of students in math and science, and building local capacity for wider and sustained use of computational reasoning and tools.

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