Focus on Research
Penn State Intercom......January 31, 2002

Analyzing marksmen's aim
may aid tremor patients

By Barbara Hale
Public Information

A new approach to analyzing the steadiness of a marksman's aim, developed by researchers from Penn State and the University of Verona, Italy, eventually may be useful in diagnosing and monitoring tremors in patients with neuro-muscular disorders. RESEARCH_Cusumano

Joseph P. Cusumano, associate professor of engineering science and mechanics, said, "The analyses that we are developing, with cooperation from the members of an Italian air pistol team, may enable us to develop a sort of steadiness profile or body tremor 'finger print' for any individual. Such a 'fingerprint' can be useful in a clinical setting to diagnose and track the progression of a neuro-muscular disorder or injury, or the recovery from such a disorder or injury."

He added, "The key thing -- and what is new about our approach -- is that the profile we generate is based on an analysis of an individual's movement while they are accomplishing a specific task, namely, aiming. Most previous work, for example, with Parkinson's patients, has looked at tremor independent of any task -- without, as it were, any context."

The new procedure allows the researchers to evaluate an individual athlete and understand the specific configurations in which they hold their limbs to maximize the way in which the natural tremor in their body is controlled when they aim at a target. Cusumano worked on the project with his co-investigator, Paola Cesari, director of the Movement Science Laboratory, University of Verona, Italy.

Cusumano explained that everyone, even the steadiest marksman, experiences unavoidable, inherent body tremor. People can minimize or amplify the way this natural movement affects their pointing accuracy by positioning their limbs in a variety of ways -- some positions being more or less effective than others. The new analysis technique, developed by Cusumano and Cesari, allows the researchers to use video cameras to co llect movement data from a person shooting at a target, reduce the person's movements to their basic elements and then explain how and why tremor varies as the person adjusts his or her joint angles to try to maintain a steady aim.

In their approach, Cusumano and Cesari have combined a method of statistical data analysis, called Principal Component Analysis, with stability analysis which relates tremor in the body joint positions to tremor of the target point.

The researchers found that all shooters, expert and non-expert alike, had one dominant pattern of movement which corresponded, at the target, to relatively large movements left to right and relatively small movement vertically. "Since even nonexperts, such as me, did pretty much the same thing, this suggests that these basic movements are related to our bio-mechanical nature, not to skill per se," Cusumano said.

However, higher scoring marksmen tended to hold their limbs in one of only a few consistent, coordinated patterns. These favored positions were such that the natural tremor in the body was strongly decreased in its effect on motion at the target. "While the number of coordinated movement patterns needed to accomplish a given task indicates an individual's level of coordination, increased stability or control at the target is related to a subject's ability to couple his or her motor coordination with the perception of the target," he added.  

Barbara Hale can be reached at


Survival of quaking aspen groves
remains complex problem in West

Quaking aspen groves in the American West have been on the decline since the beginning of serious settlement and exploitation, but recent studies of California aspen by University geographers suggest that the aspen decrease is more complicated than previously thought.

Quaking aspen, the most widely distributed tree in the northern hemisphere, is found from coast to coast in a band that includes northern California, the Rocky Mountains, Wisconsin, upstate New York and New England. Beside being noted for their shimmering leaves and the golden color they turn in the fall, aspen are unusual because they grow as clones, putting out vegetative shoots rather than forming seeds.

Assumptions for the decline of the intermountain aspen stands include the suppression of frequent fires, increased livestock grazing, and increased and concentrated herds of native herbivores.

Dong Ko, a recent University graduate with a master's degree in geography, and Alan Taylor, professor of geography, studied 20 aspen groves on the California side of the Lake Tahoe Basin. The researchers identified the ages of the trees in the stands and the types of trees found.

"Because aspen are clones and regenerate vegetatively, some of the groves are 8,000 years old," Taylor said. "Aspen have rarely been observed to regenerate from seed, however they did after the recent Yellowstone National Park fires."

The researchers suggest that it may take a major event, such as a massive fire, to force the trees to reproduce sexually.

Powerful mini motor
is size of rice grain

By A'ndrea Messer
Public Information

While the age of nanobots is not with us yet, a tiny, inexpensive motor with simple circuitry and easy manufacture, may become the motive force in micromedical applications in the near future, according to a University engineer.

The smallest of these ultrasonic, piezoelectric motors developed by researchers at the Materials Research Institute is about the size of a grain of rice. They are RESEARCH_Motor 1.8 millimeters in diameter and 4 millimeters long. Tiny, but powerful, the smallest motor's rotation can just be stopped with the pressure of thumb and forefinger, but those only slightly larger will tear the skin and draw blood.

"Initially, our applications for these motors are aimed at medical uses," said Kenji Uchino, professor of electrical engineering. "Because the motors are so small, and can be manufactured so cheaply, they appear ideal for applications where small diameter, disposable instruments are required." Some of these applications include specialized urinary catheters and endoscopic instruments.

Besides medical applications, they could function in appliances, computers and even wrist watches.

The researchers have fabricated the prototype motors from readily available materials, because they want to be able to mass produce the motors inexpensively. Each motor consists of a hollow metal tube, two sides flattened at 90 or more degrees. Two strips of PZT, a lead zirconate titanate that is piezoelectric, are fastened to the flattened areas. This tube becomes the motor's stator. Inside the tube, the rotor consists of a rod held down with a spring or just a spring. Piezoelectric materials deform when an electrical voltage is applied to them. By deforming the strips on the outside of the stator, the tube wobbles. This wobble causes the rotor to spin and the motor to move.

Uchino; Burhanettin Koc, Kirkkale University, Turkey and Serra Cagatay, graduate student in the University's intercollege program in materials, have applied for a provisional patent on the smaller motor. Uchino and IMRE-Singapore National Institute hold the patent for an earlier piezoelectric motor design.

A'ndrea Messer can be reached at