Femoral lengthening with the Barnes device.

Twenty femoral lengthenings were performed with a staged lengthening technique with the Barnes device. After the plate is attached to the femur, the femur is lengthened 2 cm initially and at two or more subsequent stages. Average length gained was 5.4 cm (range 2.5-8.3 cm), and there were no malunions or nonunions. There were two transient peroneal palsies, but no permanent nerve injuries. There were no pin tract problems, no chronic infections, and no knee subluxations. The complication rate with this technique compares favorably with those of other methods.

Pharmacokinetic principles in relation to serum drug sample collections.

Pharmacokinetics is a relatively new field in the health sciences. It is receiving more interest and utilization as patients' serum drug levels are being correlated with clinical response and drug side effects and toxicities. Many variable factors influence serum drug levels, consequently affecting the interpretation of these levels and possibly altering therapy. We discuss some of these variables in relation to proper timing for serum sampling, and suggest times for peak level serum sampling of some commonly monitored drugs.

Hexagonal vs Triangular Core Lightweight Mirror Structures.

The higher rigidity of a lightweight mirror structure with core ribs that form hexagonal cells, as compared with triangular cells, is demonstrated by holographic deflection measurements on 75-cm diam acrylic structural models.

Optimal design of cored mirror structures.

The design and construction of lightweight mirror substrates has been the subject of considerable study in recent years. A consensus has been reached that the best design approach involves two plates connected by an array of ribs and consisting of a single material throughout. Although a single, rib reinforced plate has some advantage over a solid plate in efficient use of material, the two-plate sandwich is even more efficient, and our attention has been focused there. The consensus has not yet progressed to total agreement on preferred rib configurations, thickness, and spacing or preferred plate thicknesses and total thickness. This article attempts to demonstrate that some preferences can be established in general, although modifications may be appropriate for particular applications.

Some effects of aerospace thermal environments on high-acuity optical systems.

The effects of the major features of an aerospace thermal environment on the principal components of large-aperture photographic catadioptric systems are considered. First approximation solutions to the focal shift and on-axis wavefront aberration produced by heat fluxes in windows (or corrector plates) are presented. The effects of axial heat fluxes and uniform temperature changes on mirror structures representative of current practice in lightweight-mirror technology are examined, and first approximations to the deformations of simple slab mirrors, Kanigen-coated metal mirrors, and sandwich-plate construction are derived. Some conclusions on the comparative utility of Kanigen-coated beryllium mirrors and solid or egg-crate fused-silica mirrors are drawn.

Considerations in the use of beryllium for mirrors.

Some practical problems associated with the use of beryllium as a mirror substrate material are analyzed, with particular emphasis on nonelastic strains that may affect mirror performance. Present information on the nonelastic behavior of beryllium is summarized.