Probabilistic assessment of fatigue initiation data on highly crosslinked ultrahigh molecular weight polyethylenes.

Ultrahigh molecular weight polyethylenes (UHMWPE) showing wear resistance, oxidative stability and good mechanical performance go on being a relevant research area in biomaterials for total joint replacements, where fatigue happens to be a recurrent damage mode that needs to be investigated. While crack propagation lifetime has been extensively studied, fatigue initiation data are scarcely offered in the literature, often due to the higher costs implied in the experimental programs. Moreover, their analysis is not always suitable to obtain reliable guidance. Different deterministic and probabilistic methods, generally resting on empirical bases have been previously used to analyze the fatigue initiation data. In this work, the probabilistic Weibull regression model of Castillo et al., based on both physical and statistical conditions, such as weakest link principle and the necessary compatibility between life-time and stress range distributions, is applied for the first time in the assessment of fatigue results of polymers, particularly to highly crosslinked UHMWPEs (HXLPEs). Accordingly, different published experimental data corresponding to HXLPE stabilized by thermal treatments and with α-tocopherol (vitamin E) are re-analyzed. Additional data are incorporated to assess the influence of notched HXLPE on fatigue performance. New conclusions are drawn from this revision.

[Bronchial cancers with morphologic and immunohistochemically diversely differentiated metastases]. / Uber Bronchialkarzinome mit morphologisch und immunhistochemisch abweichend differenzierten Metastasen.

We report on two unusual adenocarcinomas of the lung. The primary of the first case could be classified as a "solid adenocarcinoma" of the lung, whereas the metastases were undifferentiated and contained syncytiotrophoblast-like tumor cells. The primary of the second case consisted of diversely differentiated cells including adenocarcinomatous and syncytiotrophoblast-like cells, while the metastases were either adenocarcinomatous or syncytiotrophoblastic-like differentiated. Immunohistochemically, both primaries showed abundant CEA and little beta-HCG, while the metastases exhibited little CEA and abundant beta-HCG. The implications of such differences between the primaries and their metastases for tumor-cell heterogeneity and tumor classification are discussed.