Focus on Research
Penn State Intercom......March 20 , 2003

Friction fault

Angel-hair pasta helps explain
earthquake forcesRESEARCH_Marone

 

 

 

 

 

By A'ndrea Elyse Messer
Public Information

A popular brand of angel hair pasta is helping researchers experimentally to understand the friction forces that occur in an earthquake fault and providing better information than current numerical models, according to a Penn State geoscientist.

"Researchers creating numerical models of the micro-mechanics of debris movement in an earthquake fault often produce odd results that do not match laboratory experiments," said Chris Marone, associate professor of geosciences. "Very little has been done to look at how initial and boundary condRESEARCH_Marone05itions such as surface characteristics and particle dimensionality affect friction."

Angel hair pasta, glass rods, glass beads and sand have different sizes and surface finishes so researchers can explore the importance of these characteristics in earthquake faults. The researchers use stacks of pasta or glass rods to measure friction created by shear motion. For shear of a single plane or one-dimensional motion, they apply force to the rods so the motion is in the long direction. For two directions or two-dimensional motion, the force is applied across the stack of pasta. The spheres and sand are used to measure three-dimensional motion. One problem is that numericists model one- or two-dimensional smooth particles while experimentalists work with natural materials that have three dimensions and are irregular. Current computer capabilities cannot handle three-dimensional calculations or account for surface irregularities, but Marone, Kevin M. Frye, a former MIT student, and Karen Mair, former MIT postdoctoral fellow, experimented with all three types of motion and both smooth and rough surfaces.

Between the two sides of an earthquake fault lie the wear material that accrues from the two sides slipping past each other. This material, called gouge, can be smaller than sand particles or as large as boulders, although most of the material is small.

To simulate gouge in the laboratory, the researchers used smooth glass beads, quartz sand, quartz glass fiberoptic rods and angel hair pasta. They tested the materials in a test rig that allowed them to control the directions of motion applied.

"We began with the pasta because it had the same shape and size as the glass rods, which had not arrived yet," said Marone. "However, they worked not only to test the setup, but in the experiment as well, so we continued with them."

He notes that because the pasta was machine manufactured it was very uniform. Pasta does compress more than glass, but the researchers can easily account and correct for that.

"Our data show that discrepancies reported in recent (numerical) works are due to differences in initial conditions -- rough vs. smooth particles -- and particle dimensionality -- 2-D versus 3-D granulated particles," said Marone. "In this case the actual material does not have a significant effect because many rock types have a coefficient of friction of .60 to .62."

The researchers also found that smooth glass beads produce very different results than quartz sand with the sand producing more friction than the smooth beads. To ensure that the rougher surface of the sand caused the difference and not the size or some other characteristic of the sand, the researchers ran the experiment beginning with smooth glass beads. They gradually crushed the beads creating broken beads with rough surfaces, and the final friction recorded was equivalent to the quartz sand.

"Using spheres is not a good approximation of what occurs in the real world," said Marone. "However, their inability to model rough particles limits the numerical models."

The researcher is continuing this line of investigation with one of his students who will test a variety of pastas to see how rod diameter and layer thickness influences the two-dimensional friction measurements. He will test spaghetti, spaghettini, vermicelli, capellini and angel hair.


A'ndrea Elyse Messer can be reached at aem1@psu.edu.

Coral layers
reflect Atlantic
climate cycles

By A'ndrea Elyse Messer
Public Information RESEARCH_Greer04

Tree rings may tell how old a tree is, but the rings or annual bands in some skeletal coral may tell not only the age of the animal, but also something of the dynamics of the ocean in which it grew, according to Penn State and University of Miami researchers.

"Some coral grows like a tree; each year a complete layer with both a high and low-density skeletal calcium carbonate band is formed by the coral animal," said Lisa Greer, assistant professor of geosciences. "Not all corals create rings, but the massive corals like boulder star coral or pin cushion coral do."

Greer, and Peter Swart, professor at the Rosenstiel School of Marine and Atmospheric Science, University of Miami, looked at both modern and fossil corals to see if the calcium carbonate of the coral skeletons could shed light on the temperature and salinity of the tropical Atlantic Ocean.

"In contrast to research in the tropical Pacific, there have been few definitive studies utilizing proxy records within Atlantic coral skeletons to provide information on the climate dynamics in this region," Greer said.

Information on the climate dynamics of the Atlantic is necessary as input to global and regional climate models. Not only are the current dynamic patterns important, but patterns from the past, which may differ from today, are important as well. Greer uses a dental X-ray to locate the coral layers in a very thin slice taken from the core. In modern coral, she then counts down from the top to associate the layers with actual years. The sample she reported on was taken in 1994 and went back to 1935. Once the layers are located, Greer takes very small samples of the coral in a line running up the coral section. She averages about 22 samples per year covering the 59-year span.

Greer and Swart were investigating the relationship between non-radioactive or stable isotopes of oxygen in the calcium carbonate of the coral. The ratio of normal to heavier oxygen depends on the temperature of the water the coral grew in and its salinity. In warmer water, the coral incorporates more of the normal oxygen into its structure, but if the water is cooler, the coral will incorporate a higher percentage of the heavier oxygen isotope. The salinity effect has more to do with what is available. Fresh water has relatively less of the heavier isotope of oxygen. The saltier the water, the more of the heavier isotope is in the water and the more that is available for incorporation into the coral skeleton.

"When we look at the averaged annual data from 1935 to about 1994, we see it has the shape of a sine wave," Greer said. "It is periodic and has a significant pattern of oxygen isotope composition that has a peak at about every 12 to 15 years." Many people have measured the sea surface temperature in the subtropical Atlantic. They find that peak warming comes about every 12.5 years. "The recorded temperature data shows an important node at 12 to 15 years, but there is no way to pick it up except for the last 50 years when sea surface temperatures were recorded," she said.

Because temperature data only exists for the last 50 years, Greer also is looking at fossil corals taken from the western portion of the Dominican Republic. She can date these corals to an accuracy of up to plus or minus 44 years using an uranium/thorium method.


A'ndrea Elyse Messer can be reached at aem1@psu.edu.

NEWS IN BRIEF

Survey: Patients rate quality time first

Patients place far greater priority on quality and quantity of time spent with their physical therapist than on sophisticated equipment, easy parking and convenience of location, researchers said.

In the medical field, just as in business, service is the key, according to a research team from Penn State, University of South Carolina, Franklin and Marshall College, and Lebanon Valley College. According to the study, patients rate first in importance the amount of time the therapist spends with them, along with the therapist's listening and communication skills, and willingness to give clear explanations of treatment. The quality of patient-therapist interaction counts for much more than high-tech medical hardware, convenient location and office hours, and accessible parking.

"Maximizing patient satisfaction is a sound philosophy from both a clinical and business perspective," noted Mary Beth Pinto, associate professor of marketing at Penn State Erie. "Satisfied patients are more likely to comply with treatment and to continue to seek health care at a given facility."

Software creates dictionary molecule
for retrieving images

New software that responds to written questions by retrieving digital images has potentially broad application, ranging from helping radiologists compare mammograms to streamlining museum curators' archiving of artwork, say the Penn State researchers who developed the technology.

James Z. Wang, assistant professor in Penn State's School of Information Sciences and Technology and principal investigator, says the Automatic Linguistic Indexing of Pictures (ALIP) system first builds a pictorial dictionary, and then uses it for associating images with keywords. The new technology functions like a human expert who annotates or classifies terms.

"While the prototype is in its infancy, it has demonstrated great potential for use in biomedicine by reading X-rays and CT scans as well as in digital libraries, business, Web searches and the military," said Wang.

PENN STATE'S RESEARCH HERITAGE

Pennsylvania's first pure food laws were largely founded on the work of Penn State chemist William Frear (1860-1922), whose pioneer analyses of foods enabled the state to enforce truth-in-labeling laws. Frear also helped organize the first national pure-food congress, and the federal government's landmark Pure Food and Drug Act of 1906 was based on guidelines devised by an expert committee he headed.

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