Priors in Bayesian Estimation under the Rasch Model.

A review of various priors used in Bayesian estimation under the Rasch model is presented together with clear mathematical definitions of the hierarchical prior distributions. A Bayesian estimation method, Gibbs sampling, was compared with conditional, marginal, and joint maximum likelihood estimation methods using the Knox Cube Test data under the Rasch model. The shrinkage effect of the priors on item and ability parameter estimates was also investigated using the Knox Cube Test data. In addition, item response data for a mathematics test with 14 items by 765 examinees were analyzed with the joint maximum likelihood estimation method and Gibbs sampling under the Rasch model. Both methods yielded nearly identical item parameter estimates. The shrinkage effect was observed in the ability estimates from Gibbs sampling. The computer program OpenBUGS that implemented the rejection sampling method of Gibbs sampling was the main program employed in the study.

Static Langer's line and wound contraction rates according to anatomical regions in a porcine model.

This study investigated wound contraction rates according to anatomical regions and wound morphology according to skin tension line in a micropig porcine model. Of the four animals used, skin tension morphology was determined in one pig. In the remaining three pigs, six pairs of full-thickness skin excisions were created on the dorsum (six square and six circular). The wounds were grouped, Wounds #1 through #5, according to the skin tension line and anatomical regions: Wounds #1 and #2, cephalic; Wounds #4 and #5, caudal; and Wound #3, center. Wound sizes and contraction rates were calculated for 28 days. A static tension topography of the micropig dorsum was obtained. Excisional wounds deformed along the local tension vector and healed in this fashion. Wound contraction rates were significantly higher for cephalic wounds (p = 0.004). No significant difference in wound contraction rates were observed between square and circular wounds. Final wound morphology was related to the local tension vector and initial wound shape. Cephalic wounds contracted more quickly. Further studies are needed to characterize scar formation after primarily closed surgical wounds in relation to the newly established skin tension topography and to elucidate the mechanism behind the variable wound contraction rates in the cephalocaudal gradient.

Large auricular chondrocutaneous composite graft for nasal alar and columellar reconstruction.

BACKGROUND: Among the various methods for correcting nasal deformity, the composite graft is suitable for the inner and outer reconstruction of the nose in a single stage. In this article, we present our technique for reconstructing the ala and columella using the auricular chondrocutaneous composite graft. METHODS: From 2004 to 2011, 15 cases of alar and 2 cases of columellar reconstruction employing the chondrocutaneous composite graft were studied, all followed up for 3 to 24 months (average, 13.5 months). All of the patients were reviewed retrospectively for the demographics, graft size, selection of the donor site and outcomes including morbidity and complications. RESULTS: The reasons for the deformity were burn scar (n=7), traumatic scar (n=4), smallpox scar (n=4), basal cell carcinoma defect (n=1), and scar contracture (n=1) from implant induced infection. In 5 cases of nostril stricture and 6 cases of alar defect and notching, composite grafts from the helix were used (8.9×12.5 mm). In 4 cases of retracted ala, grafts from the posterior surface of the concha were matched (5×15 mm). For the reconstruction of the columella, we harvested the graft from the posterior scapha (9×13.5 mm). Except one case with partial necrosis and delayed healing due to smoking, the grafts were successful in all of the cases and there was no deformity of the donor site. CONCLUSIONS: An alar and columellar defect can be reconstructed successfully with a relatively large composite graft without donor site morbidity. The selection of the donor site should be individualized according to the 3-dimensional configuration of the defect.