Effects of porcelain/alloy interfacial diffusion zones on thermo-mechanical strain.

Chemical bonding between dental porcelains and alloys results from interdiffusion of porcelain and metal ions. An interfacial diffusion zone is created which, most likely, has properties different from those of bulk materials. The changed interface might affect experimental measurements of thermo-mechanical strain. To determine the magnitude and conditions under which this would occur, the interface was modeled as the intermediate layer of a three-layered porcelain-veneered split-metal ring. Layer thicknesses and coefficients of thermal expansion were varied, and the effects on gap change after cooling through 500 degrees C were calculated. Results are presented in a series of 14 Figs., ten curves each, which depict not only interfacial effects, but are extended for use in interpretation of the effects of properties of opaques and glazes as well. Under most conditions, the interface will not affect experimental measurements; some special exceptions are noted.

Intramuscular anatomy of the latissimus dorsi muscle.

Two recent articles in the British Journal of Plastic Surgery have served to explain the anatomy of the blood vessels serving the latissimus dorsi muscle. A theory was presented with a supporting case in which the superficial surface of the muscle was thinned acutely during a reconstruction, with full survival. A case complication is presented in which an unusual partial muscle loss in a latissimus dorsi free tissue transfer is explained by this theory.

New energy transfer dyes for DNA sequencing.

We have synthesized a set of four energy transfer dyes and demonstrated their use in automated DNA sequencing. The donor dyes are the 5- or 6-carboxy isomers of 4'-aminomethylfluorescein and the acceptor dyes are a novel set of four 4,7-dichloro-substituted rhodamine dyes which have narrower emission spectra than the standard, unsubstituted rhodamines. A rigid amino acid linker, 4-aminomethylbenzoic acid, was used to separate the dyes. The brightness of each dye in an automated sequencing instrument equipped with a dual line argon ion laser (488 and 514 nm excitation) was 2-2.5 times greater than the standard dye-primers with a 2 times reduction in multicomponent noise. The overall improvement in signal-to-noise was 4- to 5-fold. The utility of the new dye set was demonstrated by sequencing of a BAC DNA with an 80 kb insert. Measurement of the extinction coefficients and the relative quantum yields of the dichlororhodamine components of the energy transfer dyes showed their values were reduced by 20-25% compared with the dichlororhodamine dyes alone.