The Cutting Edge: COMPUTING / TECHNOLOGY / INNOVATION : New Method Turns Complex Math Into Solid Model

Scientific computer visualization is a dramatic way to take complex mathematics and turn it into something you can see on a computer screen. Meteorologists, for example, can study the inner workings of thunderstorms or tornadoes without leaving the lab.

But sometimes a solid model gives researchers a different perspective on a scientific 3-D set of data that complements the insights made possible from a computer graphics display. For several years, manufacturing companies have had access to technology called rapid prototyping, which allows them to generate solid models of mechanical parts from computer designs. Now two researchers at the San Diego Supercomputer Center have found a way to combine scientific visualization with rapid prototyping technology to produce solid models from digital geometry data.

The first experiment consisted of constructing a model of San Diego Bay from data supplied by an SDSC computational biologist and a visualization researcher. The data set consisted of 125,000 polygons that were converted into a solid prototype to serve as a study tool for ecologists and oceanographers. The plan is to test the technology for applications in areas such as medical imaging, mapping, surgical planning and cell and protein structure research.

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Eliminating Body’s Black Holes: Outer space isn’t the only place where black holes exist. The scans performed by magnetic resonance imaging, or MRI--which use magnetic fields and radio waves to create high-resolution images of the inside of the body--also come up with “black holes.”

Unlike X-rays, which show only dense tissue such as bone, MRI scans can detect nerves and other soft tissues and thus are an invaluable tool in diagnosing disease and injury. But because the technology depends on the magnetic fields of hydrogen nuclei in water, the MRI scanner, which reads radio signals transmitted by the hydrogen nuclei, has difficulties when those fields are distorted.

Air, which may interfere with the scanner’s magnetic field and is present in the mouth, throat, ears, nose and sinus cavities, is usually to blame. The biggest problem occurs when the MRI loses the area behind the nose, which is near the brain’s neurocognitive centers. This problem is exacerbated by new high-speed imaging techniques, particularly those that can show the brain working.

Researchers at Pennsylvania State University’s Milton S. Hershey Medical Center have developed computer models that detail the magnetic distortions and will allow radiologists to correct them. According to Michael Smith, associate professor of radiology, because the magnetic field in the head varies so much, the computer models need to be extremely detailed.

With the help of Viewpoint, a special effects company that had already created detailed models of the body, Smith divided the model of the head into 80,000 tetrahedron-shaped regions, each only a few millimeters across. The researchers then calculated the magnetic field in each region, and of the entire head, point by point. The models allow Smith to determine magnetic field distortions caused by the air-tissue surface and to filter out the black hole in front of the brain after the scan is completed.

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Ink Zapper: The laser printer has been a boon to business communications, but it’s been a bear for paper recyclers. That’s because all recycled paper must de-inked, and the heat used in laser processing makes that ink, which is electronically deposited on the fibers of the paper, particularly hard to remove.

Traditional recycling processes rely on chemical and mechanical actions to remove ink. But these processes also reduce fiber strength, a weakness compensated for by adding fortifying chemicals. These operations increase the cost of recycling and make it less economical compared to making paper from virgin pulp.

Now researchers at the Georgia Institute of Technology have developed a way to apply a direct-current electric field to the recycled fiber slurry, which removes twice as many of the ink specks from office paper as de-inking without the electric field.

The patented process is based on a reactor consisting of a central anode and a cathode, which can be retrofitted to existing recycled paper-processing equipment. Ink particles carry charges ranging from high positive to weak negative; paper fibers usually carry a weak negative charge. Applying the direct current field to a reactor full of fiber slurry attracts the ink particles away from the fibers and causes the ink to coagulate. The coagulated ink is floated to the surface and skimmed off. The resulting paper made from these fibers is strong and white.