Engineering News 7628

Workplace advice: Adapt or fall by the wayside

Keeping up with workplace and technological trends is key to a successful engineering career

Newton, MA--Rapid technological changes and a shake-up in the corporate-worker relationship mean engineers must work harder than ever to advance their careers.

"Employment is changing and engineers must take control of their professional lives," says engineer and management consultant Ted Gautschi.

Gone are the days when engineers worked for one firm their whole lives, receiving the traditional gold watch at retirement. Today's tenures are shorter, and many of the faces in corporate corridors seem to change almost daily. "Companies are using part-time workers, freelancers, subcontractors, and independent professionals," Gautschi says. Others are creating virtual corporations by gathering groups to complete a project, then disbanding them when the project is done.

So how can engineers ensure that their careers are rewarding and long-term? "Keep learning new skills that the company needs," advises Norm Staller, systems engineer for Polaroid Corp. He has been at Polaroid 22 years, in a variety of engineering jobs. He is currently pursuing a master's degree in his latest specialty: plastics engineering.

For Paris Altidis, staff engineer at Borg Warner Automotive Inc., the trend toward concurrent engineering led him to broaden his experience in materials, manufacturing, and designing experiments. "More than ever, design engineers are being asked to specify components and materials across many different product lines," he says.

Today's engineers work on more projects (15.2 per year and 4.5 at a time) than they did even three years ago, according to a Design News-Simmons Research study. They also specify more components than ever before. The implication: They must dedicate themselves to life-long learning to keep up with their many and varied tasks. And, they must work both faster and smarter.

Engineers are turning to software tools such as 3-D modeling (51%), 2-D CAD (42%), and computerized FEA systems (24%) to help shorten design time, according to the Design News Annual Salary Survey. Others use rapid prototyping (35%), concurrent engineering teams (34%), or a combination of techniques to hasten time to market.

Formal training isn't always necessary to learn how to use new technologies. Engineer Victor Popp recently moved to a new company largely because of CAD skills acquired at his previous job. "By just plugging in the numbers from projects I was working on, I quickly learned what I needed to know," Popp says.

"Experience in AutoCAD, Pro/ENGINEER, or SDRC CAD systems is sought by most employers," reports Bill Stone, engineering manager for Baker Brothers, a capital-equipment manufacturer. While a B.S. degree is important for engineers wanting to get ahead, he prefers practical experience in modeling and CAD over an advanced degree.

"An advanced degree would benefit an engineer seeking a management position, along with good interpersonal skills and proficiency in the more mainstream software packages." But, he warns, "Engineers in management positions have a more difficult time keeping skills from getting rusty and maintaining an up-to-date tool bag."

"Overall opportunities continue for all levels of engineering professionals, and design engineers can look forward to another year of hiring and stable employment," according to Source Engineering, engineering recruiting specialists.

Most high-growth positions are at the small to mid-size firms that design and manufacture capital equipment and machined products, says Bruce Matthews of DiNisco Matthews Associates, a Burlington, MA-based employment agency that deals with manufacturing, technical, and engineering professionals. "The Midwest leads other regions in opportunities for more traditional mechanical-engineering functions," he adds.

Ultimately, today's competitive environment requires engineers to be flexible and adapt to market changes. "Engineers should drop their traditional focus on employment and instead focus on employability," Gautschi advises. "They must assume the responsibility for managing their own careers, continue to learn new skills, extend their education, and establish a professional network with others."

--John Lewis, Northeast Technical Editor

Dynamic splint helps broken wrists heal

Minneapolis, MN--A dynamic splint developed by Empi Inc. helps people regain range of motion in injured forearms by providing gentle, spring-loaded stress on the affected joint.

The Advance Dynamic ROM(R) orthosis consists of a wrist cradle, pads, struts, cuffs, and a torsion spring that applies torque to the patient's wrist and forearm. Adjustments by a physician or physical therapist can ensure consistent force at the end of the patient's range of motion.

Unlike a static splint used to hold a joint or limb in a fixed position, a dynamic splint uses a force-producing mechanism to gently urge a patient's joint through a desired motion. Such constant, low-load stress on the damaged area promotes new tissue growth or lengthening of tissue. Low-Load Prolonged Stretch (LLPS) with a dynamic splint reduces the risk of tissue trauma that can occur during the high-force stretching and vigorous exercise sometime used in therapy.

Engineers at Empi use an adjustable spiral eccentric torsion spring to load the Advance Dynamic ROM orthosis toward a position where the palm is open and facing up. Typically, patients wear the orthosis during periods of rest or sleep.

DEC speeds 'personal workstation'

Maynard, MA--Digital Equipment Corp. recently unveileved two "personal workstations" aimed at technical users seeking workstation-class speed.

The Alpha XL 300 and 366, priced at $8,495 and $9,995 respectively, run the Microsoft Windows NT operating system. Company officials say such Windows-NT systems offer high-powered computing of UNIX-based workstations at a fraction of the cost. In addition, these workstations offer the advantage of running thousands of off-the-shelf commercial packages written for the popular Windows environment.

Digital's XL workstations feature DEC's Alpha micrprocessors, but also offer the option of Intel Pentium and Pentium Pro CPUs.

Magnetic system may cut brain-surgery trauma

St. Louis--The skull protects the brain from trauma--and is one reason why brain surgery is so traumatic. In order for doctors to get at the gray matter, they often must remove a sizable portion of a patient's skull, result-ing in lengthy recovery times.

A minimally invasive technique employing superconducting magnets and digital image processing may be a promising alternative to conventionalneurosurgery. Engineers at Stereotaxis, Inc. are testing the Magnetic Stereotaxis System (MSS), designed to allow many procedures to be performed through an incision the size of a pencil eraser.

An array of electromagnets provides impetus for a magnetic seed, which is inserted into the brain through a small hole drilled in the skull. By controlling the magnets' output, surgeons can guide the seed through the brain to the desired location. Attach a catheter or other treatment device, and a wide range of brain therapies becomes possible.

According to Mike Lawson, chief engineer at Stereotaxis, the MSS posed a number of significant design challenges. First among them: finding magnets powerful enough to move the seed. "The prototype used water-cooled copper magnets," Lawson recalled. "We needed 500 amps to effect movement and a garden hose running at full blast to keep it cool." This wasn't practical for most operating rooms. Furthermore, the magnets were so large that the six required in the array could not fit together.

The design team switched to customized superconducting coils cooled by liquid helium. While powerful enough, the new magnets presented new problems. The application needed magnets whose intensities could quickly be adjusted up and down to permit fine control of the seed's motion. The MSS would quench--lose superconductivity--when power was added too quickly. Quenching occurred when heat-generating eddy currents developed in the coils, causing the temperature to rise above that required for superconductivity.

Limiting magnet ramp-up to 1 amp/sec avoided quenching. However, since the magnet was required to operate at 100 amps peak value, this resulted in frequent periods of inactivity, which would be unacceptable to surgeons in the OR. Designers found the solution in a pulse-width modultated servo for large dc motors developed by Glentek of El Segundo, CA.

Having magnets of sufficient power and responsiveness, designers then needed to develop an image processing system for monitoring the seed in the brain. A system involving paired Kevex KM125 microfocus X-ray sources from Kevex X-Ray, Inc. of Scotts Valley, CA creates 3-D images of the seed and the markers placed on the patient's skull for reference. The Kevex units are operated in a pulse mode at low current to limit patient dosage.

Standard X-ray flurorscopic intensifiers produce electrons and so cannot be used around magnets. Instead, the MSS receives X-rays on phosphor screens, producing photons which are focused onto microchannel plate intensifier-based CCD cameras manufactured by Stanford Photonics of Palo Alto, CA. Video output is sent to the workstation used by the surgeon and combined with a preoperative MRI image to show the seed's precise location.

Stereotaxis is assembling a second MSS unit for testing by its partner, Barnes Hospital at Washington University, also in St. Louis, which is evaluating the prototype.

Polymer housing surpasses tight connector tolerances

Harrisburg, PA--When it comes to high-density, high-performance I/O connector system housings, straightness and tight tolerances take on new meanings. That's why AMP Inc. specified a liquid-crystal polymer (LCP) for its Blindmate(R) connector system.

Part dimensions in the AMP system must be held within a few thousandths of an inch. Zydar(R) G-930 LCP from Amoco Polymer, Alpharetta, GA, offers nearly zero shrinkage in the mold. This made the LCP a natural for the application, according to Ronald Baker, AMP senior engineer.

AMP considered other materials, such as glass-filled nylon, PBT, and PPS for the connector. "These have much higher shrinkage and some variability in shrinkage," Baker explains. He also points out that the other materials are anisotropic, hence more subject to bowing and warpage.

AMP only permits 0.003 inch of fore-aft bow in the connector parts. "Any bowing or twisting in the vertical direction, viewing the mating face, would be intolerable to the functionality of the mated connector system," says Baker.

LCP materials generally cost more than other engineering thermoplastics commonly used for connectors on a pound-for-pound basis. "However, the consistent quality of results usually makes part costs effectively less expensive," Baker adds. "LCP materials are better suited for hot-runner molding, permitting the improved economies resulting from higher-volume production." Hot-runner molding avoids wasted runner material, which could prove more expensive than the material content of the part under production.

Xydar G-930 LCP is a 30% glass-reinforced UL94 V-O injection-molding grade. Amoco believes it has the highest flow of any commercially available LCP.

FEA determines duct assembly strength

Huntington Beach, CA--When Applied Analysis & Technology needed to examine a high-performance jet's engine duct assembly, the company turned to Algor software.

The assembly to be analyzed supports the duct that carries exhaust from the engine. The purpose of the transient heat- transfer analysis was to determine if the duct would weaken due to high temperatures from the jet exhaust.

"We started by placing the computer model of the duct at room temperature, 80F. Then we subjected the model to a rapid increase in temperature to 1,500F for 60 seconds," says David Dearth, president at Applied Analysis.

"This drastic leap in temperature represents the fiery blast from the jet exhaust that the duct assembly would experience during engine start-up field usage," Dearth adds.

After the 60-second simulated blast, engineers investigated the response of the computer model as the assembly's temperature returned to room temperature. Analysis results indicated that the part should not weaken below acceptable limits.

"The computer simulations generated by Algor software enabled us to analyze many designs at a fraction of the cost, and to select the optimal design to be physically tested."

RP system produces dense metal gears

Draper, UT--Beginning with proprietary metal tapes as raw material, Lone Peak Engineering Inc. has directly fabricated fully dense metal gears from CAD files using a Laminated Object Manufacturing (LOM) rapid-prototyping machine. Funded by a U.S. Navy Small Business Innovative Research program, the six-month Phase I project demonstrated that LOM can prepare bronze-infiltrated 316L stainless-steel parts without hard tooling.

Engineer Alair Griffin explains that Lone Peak used an approach originally developed for ceramic rapid-prototype parts to prepare 2-inch-diameter spur gears. "We use an LOM machine, and instead of employing the paper the machine normally uses, we use a green, unfired tape. It's basically stainless steel mixed with plasticizers, and almost seems like a plastic sheet," says Griffin. She emphasizes that the slightly modified RP machine, manufactured by Helisys Corp., Torrance, CA, is not exotic. In fact, Lone Peak has owned the machine for three years.

The company sells ceramic gears ranging from 1/4 inch to 6 inches in diameter. "We should be able to offer a similar range in steel," Griffin remarks. "But we won't know for sure until we've gone through more development."

Lone Peak makes its own tape for direct manufacture of metal parts. A laser cuts parts from the tape, just as in a standard LOM operation. After producing the green parts, Lone Peak sends them to United Technologies Research Center (UTRC) in East Hartford, CT, where engineers use furnaces to de-bind the unsupported parts, sinter them, and then infiltrate the parts with bronze. Personnel at UTRC then test the completed parts to determine their physical properties. "We can use tapes from 2 to 10 mils thick," says Griffin, adding that 2 to 5 mils is probably better for most purposes.

"When we started, we thought we could buy tape from tape manufacturers, but most manufacturers have a notion of what is a good tape based on tapes made for electronic packaging," she remarks. "That kind of tape won't work; it's too stiff and too thick." Starting with formulae used to make standard industrial ceramic tape, and working with UTRC, Lone Peak engineers developed their own proprietary tapes.

Lone Peak does not sell tape, but does accept contracts to do tape development work. During such projects, the Utah firm takes the customer's metal or ceramic powders and makes a special tape to carry the material. "We'll develop a binder system that will work with their powder so the customer can run it," Griffin explains. Tape design varies with the type of powder used, particle size, desired tape thickness, and what the customer intends to do with its rapid-prototyping machine. Lone Peak also develops ceramic filaments for fused deposition modeling systems and ceramic powder for selective laser sintering.

Researchers at UTRC are interested in the LOM process as a means of going directly from a computer model to a part, according to Richard Aubin, UTRC's manager of manufacturing processes. "It's an entirely new process," he points out, and not limited to the stainless steel and bronze now used by Lone Peak. "Whatever you can render into powder, you can process," says Aubin. "So this approach opens up a whole new opportunity window, so to speak, in the kind of materials you can use to make different parts."

In addition to the gears, other 316L stainless-steel parts prototyped by Lone Peak include tensile strength test specimens and the top and bottom of a 1.5- x 3-inch case.

Electro spotlights new products

Somerset, NJ--This spring's Electro--the annual East Coast electronics trade show--marked the debut of new products ranging from heat sinks to sensors.

Aavid Thermal Technologies, Laconia, NH, led the way with an augmented-fin heat sink. The design increases airflow turbulence in forced-air cooling systems because the fins aren't completely straight or continuous along the length of the heat sink. The units lower temperature rises by 15 to 25% compared with traditional flat-fin heat sinks, according to company engineers. The best part: no price premium over the flat-fin devices.

A photomicrosensor that detects both white paper and translucent objects was new from Omron Electronics, Schaumburg, IL. Miniature fresnel lenses and an angled emitter and detector provide a 7-mm-distant focused sensing area and prevent unwanted detection of background surfaces. Applications include edge detection in office-automation equipment and computer peripherals.

Instrument Specialties, Delaware Water Gap, PA, unveiled removable EMI/RFI shielding for pc boards. The metal "fences" enclose pc-board components and are held in place by spring force that can withstand shock and vibration. Notches provide clearance for traces and other components and the company can add access holes to allow for component adjustment.

Available in tin-plated phosphor bronze, tin-coated steel, and other materials, the fences range in height from 0.14 to 1.00 inch. They can be hand-formed or supplied preformed with assembled covers. Options include custom shapes, a variety of pin styles and locations, and fence height.

Software streamlines design process

Waukegan, IL--Computer tools recently helped Outboard Marine Corp. to optimize an engine-block design and cut development time by moving from sand casting to a "lost foam." process.

When designing the three-cylinder Mirage engine block, Outboard engineers actually modeled it twice: first as a rough prototype to get a running engine, and second as five individual lost-foam patterns needed to manufacture the cylinder block. Pro/ENGINEER CAD software helped designers produce the complexity of the block and the five separate pieces.

The lost-foam process begins with a polystyrene foam part made by molding or carving from a polystyrene block. Unlike the company's previous method of sand casting, the lost-foam process allows designers to test and prove the actual manufacturing process, Outboard engineers explain.

To avoid the extra time sand casting required, Outboard designed the prototype engine using a process called spray metal, which creates production-quality prototypes.

Used in conjunction with Pro/ENGINEER, Pro/MECH-ANICA structural-analysis software helped designers test the spray-metal block for structural and thermal variations at the earliest prototyping stages.

The Mirage's starter rope housing needed to be designed for optimal vibration noise and strength. Engineers developed a solid model of the Mirage housing in two days and performed an analysis. "We found that the housing for the Mirage was strong and it wouldn't fail," says Tim Truesdale, CAE project designer. "If we hadn't performed the analysis, we wouldn't have been sure about the part until three months down the road when we already had parts from the vendor."

Diaphragm boosts actuator reliability

Amherst, NH--Long life and reliability over millions of cycles are important to many applications. But they were especially critical in the design of an air-powered actuator for a cyanoacrylate adhesive applicator from Loctite Corp., Rocky Hill, CT.

For the actuator's diaphragm, Loctite engineers consulted Dia-com Corp. "They had unique challenges," recalls Dutch Schwab, Dia-com product engineering manager. "They had a very small diameter to fit the diaphragm and a relatively large effective pressure area, and they needed ease of assembly for volume production."

Dia-com and Loctite settled on a molded elastomeric diaphragm. The design offers low friction and an expected life of about two years, say Dia-com engineers. The component uses a d-bead--like a half o-ring--vulcanized to the outside edge of the diaphragm to create a permanent seal.

For the diaphragm's fabric specification, engineers performed peel tests and evaluated fabrics that resisted "blousing," or uneven stretching under pressure. "The fabric selection is the most critical step," says Schwab. In the end, they chose a square-woven polyester joined with an elastomer.

"The user is metering adhesive in this application," explains Dia-com Marketing Manager Bud Comstock. "You need precise application when the piston is pushed--the same amount on the first stroke as the three millionth." Adds Schwab: "This is the first time that anything has been designed to go that fast and that precisely for a displacement pump."

Scope ruggedized for oil drilling rigs

Houston, TX--Most oscilloscopes sit quietly on a bench top. The worst they encounter is dust, constant use, and maybe some rough handling.

Western Atlas puts scopes in trucks and skids outfitted for logging and sending data from oil- and gas-drilling operations. The trucks bounce along nonexistent roads in deserts and jungles; the skids are self-contained units that get shipped to offshore platforms and other remote locations not accessible by trucks. A crash frame minimizes damage due to shipping. Needless to say, it's not a smooth ride.

Off-the-shelf scopes aren't designed to withstand this abuse. So Western Atlas turned to Fluke Corp., Everett, WA, to ruggedize its CombiScope.

The model PM 3380A CombiScope features two channels, 100-MHz bandwidth, and 100-Msample/sec sampling rate. It can operate as both an analog scope and a digital storage oscilloscope, and an autoranging capability lets the scope automatically and continuously adjust the timebase and attenuators to keep signals on screen.

Western Atlas uses the CombiScope to monitor the quality of signals from the down-hole telemetry sensors. Such devices use acoustic techniques, gamma rays, or bore-hole imaging, for example, to measure the density of rock formation or determine whether a fluid is gas or oil.

In the field, vibration sources include not only drilling and bumpy roads, but also the running of such equipment as the truck's engine, hydraulic pumps, generator, and air-conditioning system.

Fluke engineers did the first round of toughening up the scope in their Holland factory. "We took care of what we thought would fail," says Fluke Product Marketing Manager Charles Holtom, "and, in fact, shook several scopes to pieces in the factory during the ruggedization trials."

The first unit Fluke delivered to Western Atlas had 15 loose parts after Western Atlas put it through multiaxis random-vibration life testing. The test involves shaking a scope at multiple amplitudes and frequencies for six hours while it isn't operating. Amplitudes and frequencies are those the scope would see in the field.

Back at the Fluke factory, one strategy engineers used was to put capacitors in groups of four so they couldn't move and shake off the pc board. Another tact was using Dow Corning sealing glue to keep wires from moving and causing wear to the insulation.

"I was impressed by how quickly they came back with the second unit," says Zeinoun A. Klink, Western Atlas's environmental test supervisor, after Fluke delivered a revised unit four weeks after the first.

The second scope passed random-vibration and shock testing and then went on to survive thermal cycling. The two together are called the "shake-and-bake" test. Now the scopes are being installed in the truck and skid instrumentation racks and are ready to rock and roll.

--Julie Anne Schofield, Associate Editor

Receiver pulls in U.S., Russian satellite data

Sunnyvale, CA--Glasnost has come to global positioning.

Ashtech engineers in Moscow and Silicon Valley have developed a single-board receiver that reads signals from both U.S. and Russian satellites. The company says its GG24 is the first commercial product to use data from both systems.

Why two? America's Global Positioning System (GPS) and Russia's Global Navigation Satellite System (GLO-NASS) each use signals from a network of 24 orbiting satellites to pinpoint locations anywhere on Earth. Between 5 and 12 of the 24 are likely to be over a specific location at any one time and signals from at least 4 satellites are needed for a good position reading. However, because the signals are line-of-sight, receivers in a city or near a mountain could be blocked from adequate coverage during certain orbiting times.

"This technology doubles the number of satellites a receiver can see at any one time," explains Todd V. Townsend, vice president of product and new-business development at Ashtech. In the case of a truck driving down a skyscraper-lined street, he says, this can boost coverage from 33 to 86% using GPS alone to 100% with a GPS-GLONASS system.

Another advantage of adding GLONASS, he says: Unlike GPS, the Russians have not deliberately incorporated errors into their satellite transmissions. The U.S. government did so for civilian usage of GPS signals because the system was initially developed for sensitive military applications.

Project engineers first had to design a receiver that could simultaneously pull two sets of 24 spread-spectrum signals "out of the noise," Townsend says. Then came the biggest hurdle: developing algorithms for simultaneously processing each system's different way of pinpointing coordinates, so signals from GPS and GLONASS satellites could produce meaningful information to find something on the ground. Much of this processing goes on in proprietary software; the system also uses a Texas Instruments DSP.

Prices begin at $5,995 for a Eurocard-form OEM board and $9,994 for a package that includes sensors, a power supply, and a data memory card.

High-tech toilet cuts water use--quietly

Troy, MI--A federal law limits the amount of water that new toilets can discharge to no more than 1.6 gallons (6 liters) per flush cycle (gpf). Unfortunately, consumers complain that double-flushes are too common with only 1.6 gpf. Many times, there isn't enough energy to properly evacuate the bowl and avoid drainline clogs.

To solve this problem, builders and homeowners have increasingly turned to pressure-assisted toilets, developed and first introduced in the late 1970s. While pressure-assisted toilets provide superior extraction and drainline carry capability, they are also noisier and more expensive than gravity-fed types.

A new type of pressure-assisted toilet should overcome these concerns. Scheduled to enter the market shortly, the breakthrough design comes from Bruce Martin, the man who invented the first pressure-assisted water closet flush technology. His PF/2^(TM) Energizer^(TM) flushometer tank is smaller, quieter, and more efficient than previous pressure-assisted products.

The vessel containing pressurized water is made of a high-performance plastic material, Ultradur(R) thermoplastic polyester, from BASF Corp. Plastic Materials, Mt. Olive, NJ. "We selected Ultradur because it is strong, durable, dimensionally stable, and water resistant," says Martin, who formed W/C Technology Corp. (WCTC) for the express purpose of exploiting the new flush technology.

The pressurized water vessel consists of two injection-molded halves joined by vibration welding. Ultradur B is used to make the vessel halves, plus several other components. The thermoplastic polyester has excellent cold-water resistance, including water containing chlorine. It also can handle the high pressures required for the application.

"BASF Plastic Materials played a key role in the successful development of the unit," Martin adds. "We were assisted by BASF's engineers from the nearby Wyandotte (MI) Plastics Application Center. This included finite element analysis, production assistance, mold-flow analysis, and material tests."

WCTC tested initial production units for over 200,000 cycles--equal to about 25 years of normal use--without any loss of efficiency or part failure.

Plastic lures give fishermen an edge

Eufaula, AL--Fishing lures from Mann's Bait Co. sport the clear advantage of a see-through lip for the life-like look of a forage fish, coupled with the tensile strength to withstand the rigors of fresh and saltwater casting. The durable, injection-molded lures, made for Mann's by the Eufaula Manufacturing Co., are elaborately painted to simulate live bait.

Mann's uses Tenite(R) butyrate from the Eastman Chemical Co., Kingsport, TN, for crank baits that require a clear lip. This includes everything from the "Depth Plus" deep-diving series to rattling crank baits that skim along on or beneath the water's surface.

"You want to make a lure that mimics, as closely as possible, the appearance and behavior of the bait fish that game fish, like bass, look for and key on," explains Mark Fisher, Mann's marketing manager. "We have developed a variety of innovative lip designs that make our lures dive or wobble, simulating the behavior of these natural forage fish. However, it was always a challenge to come up with a clear material for the lip."

The rigors of fishing, where a cast lure often hits against a rock rather than the water, also demanded a material with exceptional tensile strength. "We have found that there are definite buoyancy and performance characteristics that differ from one material to another," says Fisher. "Tenite butyrate is preferred for its clarity, impact resistance, and paintability."

Mann's recently introduced a "sparkle" color finish designed to represent the realistic "flash" of a swimming bait fish, found on crank baits for bass, walleye, and white bass. Here, again, the butyrate material excelled. "Paint and decorations adhere easily to Tenite butyrate without surface treatment," explains Bob Burggrabe, vice president, Eufaula Manufacturing Co.

Automation system quickens gene mapping

Cambridge, MA--A ma-chine that speeds experimental procedures twenty-fold helped scientists create the most detailed map ever of the human genome. The Genomatron, a highly parallel robotic system developed by Intelligent Automation Systems (IAS), assisted in completing the map's first phase ahead of schedule and under budget.

The map pinpoints the physical location of 15,000 critical "landmarks" along human genetic material. Landmarks, or "molecular signatures," make it much less cumbersome to work with DNA.

The mapping project calls for locating 30,000 landmarks, a task that involves performing the same experiment on approximately 30 million samples. By applying factory-automation techniques to the process, IAS engineers, working in collaboration with Whitehead Institute of Biomedical Research scientists, achieved a throughput of almost 150,000 analyses every three hours. Prior to the development of the Genomatron, scientists were limited to 6,144 analyses every three hours.

The Genomatron consists of three machines that work independently of each other: a liquid-handling and card-assembly station; a massively parallel thermocycler; and a vacuum-spotting station that transfers the reactions onto a Nylon hybridization membrane.

"The Genomatron greatly accelerated the speed at which we could generate DNA landmarks to navigate the human genome, enabling us to do in a few months what would have taken years to achieve in the early 1980s," says Dr. Thomas Hudson, head of the Whitehead Institute's human genome mapping group. "In the coming years, we will complete the physical map of the mouseand rat genomes, conduct studies comparing human pop-ulations, and find human disease genes."

--John Lewis, Northeast Technical Editor

Electrical stimulation combats tremors

Minneapolis, MN--Physicians have discovered that nerve stimulation equipment originally developed to suppress intractable pain via spinal-cord stimulation can also stop trembling caused by illnesses such as Parkinson's disease.

The fully implantable system, developed by Medtronic Corp., consists of three components: the Model 3387 DBS(TM) lead, the Itrel(R) II implantable pulse generator, and the Model 7495 extension.

Physicians can use testing equipment before surgery to determine whether or not neurostimulation will reduce or stop tremor. If tests indicate that the therapy can help a patient, a neurosurgeon implants the lead in the patient's thalamus--the brain's message relay center--under local anesthesia. (It's necessary to use local anesthesia so the patient can answer questions about tremor suppression.) After implantation of the lead, the patient goes under general anesthesia, and the surgeon implants the pulse generator and extension.

Each of the Model 3387 leads has four electrodes at its tip; after positioning the electrodes in the thalamus, the neurosurgeon anchors the lead to the patient's skull. Next, the physician implants the 49-gram, 55- by 60- by 10-mm Itrel II pulse generator under the patient's skin, near the collarbone. To connect the lead to the implanted pulse generator, the Model 7495 extension is surgically tunneled under the skin of the patient's head, neck, and shoulder. During operation, the Itrel II generates pulse trains that are delivered to the thalamus by the extension and lead.

Patients can use a magnet to start and stop the stimulator. Many patients stop the stimulator at bedtime to extend battery life. Batteries typically last three to five years.

The Itrel(R) Spinal Cord Stimulation (SCS) system was introduced by Medtronic in 1982. Physicians use this implantable device and its successor, the Itrel(R) II, introduced in 1989, to control chronic, intractable pain.

Medtronic reports that perhaps 5 to 10% of patients suffering from Parkinson's disease or essential termor might be candidates for implantable neurostimulation. Among those, the company would estimate a success rate of 60 to 80%.