At the Arizona-Sonora Desert Museum''s paleontology lab, the air scribe has become the workhorse of fossil preparation. The discovery of a large sauropod dinosaur in the highly indurated sandstones of the Mid-Cretaceous Turney Ranch Formation southeast of the museum posed numerous technical problems for our lab staff. Most troubling was the removal of vast amounts of sedimentary rock, which was both very tough and firmly cemented by silica to the softer, calcite-replaced bones. Experimenting with a number of hand tools, grinders, hardware-store engravers, and rotary devices, we happened upon a Chicago Pneumatic Air Scribe (see supplier''s address on page 421), and it has since become our primary lab tool on this project. We now have five Chicago air scribes, and progress on our dinosaur has been extraordinary. One large and complex midback vertebra, which had been crushed during fossilization, took seven months to prepare drillpressguides with the scribe, but it was in the middle of a 150-pound block of sandstone. Not only was museum preparator Yolaikia Sciole able to remove this complex and fragile drillpressguides vertebra without damage, but ultimately it was prepared from the inside out, exposing most of the internal bone structures, including arterial and nerve canals and never-before-seen pneumatic structures that lightened the bone in life. Most of the bones in this vertebra are no more than 0.25-inch thick and are replaced by easily cleaved, fragile calcite. The air scribe, and a light touch by the preparator, did the trick.

Nagel''s wife, Cindy, and her sister-in-law, Angela Nagel (both pictured on page 34), are trained technicians who go on the road with the equipment, scanning more than 15,000 cattle a year for producers across the Midwest and West. Their business, Midwest Sonatech, Inc. (605/369-2628) works with Iowa State University (ISU) to analyze the data. Business is booming."Ultrasound body composition data is the greatest tool a seedstock producers can use to make genetic improvement," says Cindy. "Customers are now demanding the data. Ultrasound results can make or break a bull."The Nagels use two Aloka 500V machines to collect measurements on fat thickness, ribeye area and marbling, and rump fat. The stored images are analyzed by ISU with computer software. The Nagels can scan 20 cattle an hour. They charge $14 a head, which includes $4 for image analysis.

Low-hydrogen types. These basic-coated electrodes, EXX15, drillpressguides EXX16, EXX18, EXX28, and EXX48, are formulated with low moisture-retaining drillpressguides coatings and manufactured to contain low levels of hydrogen. Hydrogen-controlled electrodes minimize risk of hydrogen-induced cold cracking when welding high-tensile steels on restrained structures. Fabricators use these electrodes to reduce or avoid the need for pre- or postweld heat treatment to drive hydrogen from weld metal. Weldmetal diffusible hydrogen content varies from 1 to 16 ml/100 g. Optional designators H16, H8, and H4 set decreasing limits on hydrogen content in deposited weld metal. An optional electrode drillpressguides designator, ''R'', indicates an electrode that is moisture resistant; it will not absorb water in excess of a specified limit after exposure to humidity. Low-hydrogen electrodes should be used in dry condition and may require baking after exposure to the atmosphere.

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