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September 2001

News about Science, Technology and Engineering at Iowa State University

Helping buildings withstand attacks
The twin towers of the World Trade Center acted admirably given the fact that each had withstood an impact greater than for what is was designed. What apparently made them fall was the intense internal heat generated by the ignition of thousands of gallons of jet fuel. All facts which mean designers and owners will need to rethink some future high-rise buildings to make them potentially safer in case of future attacks, says Max Porter, Iowa State professor of civil and construction engineering.

"The fact that those two buildings stood for an hour to an hour-and-a-half after being struck means they acted admirably in the face of the damage they incurred," says Porter, who is president of the Structural Engineering Institute, an engineering society group that is sending two teams of structural engineers to the crash sites. The teams will assess the performance of the buildings that were struck.

Porter said engineers now need to find ways of improving the safety of future tall buildings by looking into ways of curtailing the fireball or by containing it, and by possibly designing some sort of escape room into each building floor. He adds that Iowa State engineers have extensively tested the floor system used in the World Trade Center and they are testing new composite systems that bolster the strength of existing buildings. For more information call Porter at (515) 294-7456, or Skip Derra, ISU News Service, (515) 294-4917.

New methods of vaccine delivery
Balaji Narasimhan, an ISU assistant professor of chemical engineering, recently received a three-year $210,000 grant from the Whitaker Foundation, for research that could provide a method of administering vaccines in a single-dose to infants with deadly diseases such as tetanus and diphtheria. By eliminating multiple injections, a single-dose vaccine would reduce the cost of delivery and enlist greater patient compliance.

Narasimhan said infant mortality due to tetanus could be reduced by 50 percent if vaccines can be implemented in mass immunization programs. "The development of stable, single-dose, non-toxic vaccines that would protect against common childhood diseases such as diphtheria and tetanus is a crucial step towards effective immunization worldwide," he said.

Narasimhan's approach is to infuse the vaccine into plastic spheres so tiny that they can be suspended in a solution and injected into the body, where they slowly dissolve. The release of the active substances (antigens) in the vaccine is controlled by the properties of the spheres -- their size, elemental composition and length of the molecular chains that make up the plastic. To be effective, the antigen must remain active until it reaches the bloodstream. Specifically, the antigen must be degraded as little as possible by interactions with the plastic in which it is embedded or with the body's immune system.

Narasimhan believes that the composition of the plastic spheres and the antigens may change during dissolution of the spheres. He now is studying how the microstructure of the plastic spheres affects the antigen release mechanism, and he will determine ways to modify the microstructure to obtain the best possible delivery of the antigen. Information from the study will be used to design biodegradable plastic microspheres for further studies on antigen stability and release. For more information, contact Narasimhan, (515) 294-8019; Bridget Bailey, ISU News Service, (515) 294-4066; or Skip Derra, ISU News Service, (515) 294-4917.

Advanced CFD methods to reduce design time and cost of chemical reactors
The chemical processing industry is increasingly relying on computer simulations rather than traditional trial and error methods in an effort to save cost in predicting an engineering design. One such computer modeling technique, being investigated by Iowa State chemical engineering professor Rodney Fox, could improve the design and operation of multiphase reactors and save millions of dollars in operational costs for industry.

With a $400,000 National Science Foundation grant, Fox is examining "slurry bubble column reactors," which are critical to the production process that turns coal into liquid fuels and other chemical feedstocks. Current computational fluid dynamics (CFD) models employed to simulate multiphase reactors require high computational costs and have been limited by existing computer resources and algorithms, Fox said. Recent advances in the expanded memory, bandwidth and processing capabilities of multi-processor computers have made possible a more detailed analysis of the physics and chemistry of small and large scale processes occurring in multiphase flows.

Collaborating with scientists at the Scalable Computing Laboratory at the Department of Energy's Ames Laboratory, Fox will focus on improving multi-fluid CFD codes. This includes coupling interphase mass transport and chemical reactions to produce high-resolution simulations of the fluid dynamics of bubble columns. The detailed information generated will be used to develop engineering models for use in reactor design and scale up. "This is an investment in an important tool for industry that will provide fast turnaround and eliminate the unknowns before actually building new reactors," Fox said. For more information, contact Fox, (515) 294-9104, or Sunanda Vittal, Engineering Communications, (515) 294-6750.


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