Predicting Chemical Properties with Neural Networks

ORNL researchers have developed a computerprogram that can predict physical properties of some classes of chemical compounds based ontheir chemical names. The inexpensive personal-computer software relies on a neural network,a "learning computer" that can be trained to recognize patterns and make associations. It is fast,accurate, and easy to use.

Already ORNL researchers have used the program, called MOLDESIGN, to address the recentban on the production and use of common Freon in heat pump compressors and car airconditioners. MOLDESIGN has the capability of evaluating numerous possible Freon substitutesand determining the best candidates that could be used in existing equipment without changingits design and parts. The best compounds would have the desirable properties of Freon but wouldnot destroy earth's protective ozone layer and increase the likelihood of skin cancer and cataractscaused by ultraviolet radiation from the sun.

The computational approach was developed by Andre Gakh (a postdoctoral scientist), BobbySumpter, and Don Noid, all of ORNL's Chemical and Analytical Sciences Division.

MOLDESIGN can screen present and predicted compounds to identify materials with desiredproperties. This capability could save U.S. industry millions of dollars in testing costs as itsearches for more effective drugs, explosives, and metallic alloys and plastics. "MOLDESIGN's ability to predict physical, chemical, and mechanical properties of compoundsbefore they are synthesized can be very useful" Sumpter says. "It can guide a material's designand processing to get the best product."

MOLDESIGN, Noid says, is particularly useful for polymers, the large molecules formed fromchains of smaller molecules that make up plastics. MOLDESIGN can be used to predict theproperties of different blends of polymers. Sumpter adds that it has the capability to identify thebest processing technologies for making polymers that have desired properties such as increasedhardness or stiffness.

"A neural network," Sumpter says, "can be constructed to predict correctly the properties ofchemical compounds based on structural features and elemental compositions. This capabilityprovides the foundation for designing new compounds or for predicting properties of existingcompounds that have not been previously characterized."

MOLDESIGN was developed at the Laboratory as part of a 1992 cooperative research anddevelopment agreement (CRADA) between Lockheed Martin Energy Systems, which managesORNL for the Department of Energy, andHoechst Celanese Corporation, an international manufacturer of fibers, chemicals, plastics, andpharmaceuticals, which is headquartered in Germany and has an office in Summit, New Jersey.The development was supported by Y-12 Plant funds obtained from DOE's Defense Programs.

This CRADA, called Atomistic Simulations of Materials: A Neural Network Approach, is partof a larger CRADA called Materials by Computational Design involving DOE's Oak Ridge Y-12Plant, Lawrence Livermore National Laboratory,Los Alamos National Laboratory, and Sandia National Laboratories.

Avoiding Car Crashes Subject of CRADA

ORNL is collaborating with Scientific-Atlanta, Inc., on research that could reduce the numberof deaths and injuries from vehicle collisions. The partners will develop a device to study bothdriver and vehicle behavior, and the information could aid in the design of crash avoidancesystems for cars and trucks.

ORNL and Scientific-Atlanta will develop a portable automotive data acquisition system forcrash-avoidance research (DASCAR). The goal is to apply technologies developed for defenseto the reduction of human suffering and financial losses resulting from vehicle collisions on U.S.highways.

The effort is receiving U.S. Department ofTransportation (DOT) funds designated for development of the Intelligent-VehicleHighway System (IVHS). The nation's first IVHS CRADA is supporting the crash-avoidanceresearch project.

Scientific-Atlanta is a communications company whose task is to develop and provide anautomotive data processing unit, compressed video digital storage and retrieval system, andcommunications equipment. ORNL's expertise in human factors research (e.g., identifying themost effective ways to display and communicate reactor control information to human operators),advanced technology, and instrumentation and controls will be called upon in the CRADA.

Richard J. Carter is ORNL's principal investigator for the CRADA and a psychologist in the Computing and Mathematical Sciences Division.Working with him on this project at ORNL is Frank Barickman, a senior at Gannon Universityin Erie, Pennsylvania, who is participating in a program sponsored by the Oak Ridge Institute for Science and Education and DOE.Another collaborator on the project at ORNL is Philip F. Spelt of the same division.

Carter says the key to developing crash-avoidance systems for cars and trucks is to understandthe detailed behavior of drivers and vehicles under a variety of road and traffic conditions.

"We are primarily interested in the changes that occur right before an accident or near miss, suchas an increase in speed," Carter explains. "These specially equipped vehicles will be used on atest track and the open road to test the effects on driver performance of various conditionsranging from the weather to traffic congestion." Using high-speed digital data processing equipment and specially developed software,Scientific-Atlanta and ORNL will develop a prototype system that will consist of four videocameras, each the size of a thumb; sensors strewn along the car's bottom and under the hood;and an on-board computer system. The computer system, which is small enough to fit in thetrunk of almost any car, collects, records, processes, compresses, and transmits data from thesensors and cameras. The processed data will be transmitted to a control center by cellulartelephone and microwave communications with a satellite (for cars on the open road) and by radiotelemetry (for cars on a test track).

"Sensors will record all driver actions, such as braking, steering, turning on the wipers, andtuning the radio, as well as data on the driver, such as heart rate and brain waves," Carter says."DASCAR will gather near real-time information on the car's speed, pitch, roll, yaw, lateralposition within the lane, and distance from cars ahead and behind. DASCAR will also recordinformation on characteristics of the road, changes in the weather, and traffic and sign densitythat could affect driving."

ORNL has completed a study to determine the parameters and measures that should be recorded,identified available state-of-the-art hardware and software to record the parameters and measures,and estimated the costs of developing a DASCAR system.

"We were asked to conceive of an unobtrusive data recording system that wouldn't be noticedby the outside world," Carter says. "We couldn't have a satellite dish on the car roof, gadgetshanging from the bumper, or a fifth wheel behind the car. We will have electrodes on the driverbecause it is too expensive to sense driver physiology and behavior remotely."

The heart of the DASCAR system will be Scientific-Atlanta's data processing unit, which collectsdata from all the sensors and cameras. For this system, Scientific-Atlanta also will contribute aradio telemetry system and satellite link for two-way communications with the INMARSATsatellite. The Global Positioning System will help determine where the car is on the road andwithin its lane. In addition, the company will provide a compressed video digital storage andretrieval system, which rapidly retrieves and integrates compressed video data with other digitizedinformation for analysis and transmission by DASCAR.

ORNL's role in the CRADA will be to incorporate hardware supplied by Scientific-Atlanta intothe other components of the data acquisition system. ORNL will then install and calibrate theDASCAR within five vehicle types and will evaluate and pilot test the data acquisitionsystem.

"Our goals are to procure, develop, test, and validate this hardware and software on a car. Wewill put the first DASCAR system on a car driven by the director of ORNL's Robotics and Process Systems Division,"Carter says. "We will drive this car around the Oak Ridge area this year. In 1995 we will testsome DASCAR systems on cars on a 7.5-mile test track in East Liberty, Ohio. Then 15DASCAR cars will be tested by volunteers throughout the nation."

Carter says ORNL also has been asked to develop software for the data processing center to makesense out of data sent there from all the test cars. Such software will seek out meaningful datafrom the cars, such as a significant sequence of events occurring within one second of a carcrash. It will present the data as easy-to-interpret graphics on a display screen.

"Most vehicle crashes could be prevented if the correct action were taken within a half secondto a second before the collision," Carter says. "If the car can sense that it is too close to anothercar, it could be programmed to take over steering and braking from the driver at a certain pointto avert the collision. DASCAR should demonstrate that a car's lateral position in the lane anddistance from cars ahead and behind can be recorded. If so, an intelligent cruise control couldbe developed to respond instantly to shrinking distances between cars to avoid a potentially deadlycrash."

ORNL research for the CRADA will be supported by $205,000 from the National HighwayTraffic Safety Administration (part of DOT).

Medical Isotope Generator Licensed to California Firm

A new ORNL-developed device that produces an inexpensive radioisotope for treating patientswith cancerous tumors, cancer-induced bone pain, or arthritis may become a commercial productfor hospitals by the end of the decade.

Through a licensing agreement, Lockheed Martin Energy Systems, Inc., has granted exclusiverights to Isotope Products Laboratories, Inc. (IPL), in Burbank, California, to manufacture andmarket the tungsten-188/rhenium-188 generator. The device was developed by F. F. (Russ)Knapp and colleagues in the Nuclear Medicine Group in ORNL's Health Sciences Research Division.

IPL, which was founded in 1967, produces radioisotopes used in environmental measurements,analytical instruments, and nuclear medicine. IPL's new nuclear medicine subsidiary, IPLImaging and Therapeutics, Inc., will manufacture the generator and seek U.S. Food and Drug Administration approval to market it tohospitals.

Robotics and Process SystemsDivision "We hope to build upon the solid development work of Dr. Knapp's group," says LenHendrickson, IPL president. "Much clinical development work remains to be done before therhenium generator can benefit patients worldwide. We look forward to completing the worknecessary to bring the product to market. The rhenium generator is an important addition toIsotope Products' growing line of nuclear medicine products. Our new subsidiary will beresponsible for manufacturing and marketing the product."

The source of the tungsten-188 for the generator is ORNL's High Flux Isotope Reactor. As the radioactivetungsten decays in the generator, it forms radioactive rhenium-188, which can be used formedical treatment. "Because half of tungsten-188's radioactivity disappears in 69 days," Knappsays, "the shelf life of the generator is at least two months. Rhenium is constantly being suppliedfor several weeks.

"The radioactive rhenium produced in the generator," he adds, "emits energetic electrons calledbeta radiation and short bursts of light called photons as half of its radioactivity decays in about17 hours. After injection into the patient, the distribution in the body of rhenium-188-labeledagents can be monitored with photon-sensitive cameras. More importantly, the beta radiation,which can kill cancer cells, can penetrate a third of an inch into tumor tissue, suggesting that itcan be used to reduce large tumors."

Researchers at the Center for Molecular Medicine and Immunology at the University of NewJersey developed a procedure for chemically linking rhenium-188 to an antibody that homes inon colon cancer cells. Studies of 12 patients with colon tumors showed the ability of thistherapeutic agent to concentrate in these cells.

Rhenium-188 is expected to play an important role in treating cancer-induced bone pain. Therhenium can be attached to certain compounds that tend to settle in bones. "The treatment isexpected to be considerably less costly than using strontium-89, rhenium-186, and otherradioisotopes that are currently used to treat bone pain," Knapp says, "and studies are in progressto verify this prediction. If the rhenium-188 treatment is found to be less expensive, it could helpreduce health care costs."

Patients having cancer of the breast or prostate often experience bone pain when cancer cellsmigrate from the primary tumor to the skeleton. The cancer cells can penetrate tissuessurrounding the bone. It is believed that increased pressure on nerves in this tissue from bothtumor cells and inflammation causes bone pain. The energy of the beta radiation reducesinflammation, thus relieving bone pain.

For treatment of arthritis, the rhenium can be attached to compounds that are injected into thefluid of inflamed knees and other fluid-filled joints. According to Knapp, the energy released asthe rhenium decays helps relieve the painful swelling and inflammation of arthritic joints.

"The use of radioisotopes for arthritis treatments is very common in Europe," Knapp says. "Suchtreatments are expected to be used more widely in the United States on an agingpopulation."

Superconducting Wire Technology CRADA

ORNL and Oxford Superconducting Technology of Carteret, New Jersey, are jointly developingtechnology needed to produce long lengths of bismuth-2212 wires that can carry useful amountsof electrical current when chilled to low temperatures. The wires will be made of silver tapescoated with thick bismuth films.

Superconducting films and wires of short lengths have been fabricated, but few long wires thathave high critical current density have been reliably reproduced. ORNL is collaborating withindustrial partners to develop reliable processes for fabricating long superconducting wires foruse in bulk electrical conductors and energy storage devices.

In a CRADA signed earlier this year, Oxford is developing a dip-coating process for coatingsilver tapes with long, thick films of bismuth. Oxford has the primary responsibility for allpowder and slurry preparation; for preparation, heat treatment, and evaluation of longer lengthsof prototype conductors; and for actual manufacturing of the wires.

Oxford is choosing appropriate powders, solvents, binders, and dispersants that make possibleuniform and homogeneous coatings over a long length. Oxford will also produce samples ofdip-coated bismuth-2212 wires.

In the CRADA, ORNL researchers led by Robert K. Williams of the Metals and CeramicsDivision evaluate the microstructure of powders and wires and perform other analyticalcharacterizations. For example, they will determine the sizes of crystalline grains making up thewire and the chemistry in the areas between the grains, known as grain boundaries. For thiswork, they are using X-ray diffraction, thermogravimetric and differential thermal analysis,metallography, and electron microscopy.

ORNL also is engaged in developing or selecting lower-cost alloys that could replace the silvernow used for tapes on which the bismuth is deposited. In addition, ORNL and Oxford will jointlymeasure wire performance such as critical current density, critical temperature, and magnetizationas a function of magnetic field.

The one-year CRADA is valued at $125,000; DOE will fund $50,000 of the project. All of thework at ORNL is funded by DOE's Office of Energy Management's Superconductivity Programfor Electric Power Systems. The program is developing with industry the technology necessaryfor commercial development of electric power applications of high-temperaturesuperconductors.

Oxford Superconducting Technology is a leading producer of low-temperature superconductorsused in magnets for magnetic resonance imaging (MRI) scanners, nuclear magnetic resonancespectroscopy, particle accelerators, and other applications. The company has recently completeddelivery of nearly two million feet of superconducting cable to DOE's Brookhaven National Laboratory for the RelativisticHeavy Ion Collider.

Where to?

[ Search | Mail | Contents ]