RESUMO
An engineering research program has been conducted at the Advanced Photon Source (APS) in order to determine the thermomechanical conditions that lead to crack formation in GlidCop®, a material commonly used to fabricate X-ray absorbers at X-ray synchrotron facilities. This dispersion-strengthened copper alloy is a proprietary material and detailed technical data of interest to the synchrotron community is limited. The results from the research program have allowed new design criteria to be established for GlidCop® X-ray absorbers based upon the thermomechanically induced fatigue behavior of the material. X-ray power from APS insertion devices was used to expose 30 GlidCop® samples to 10000 thermal loading cycles each under various beam power conditions, and all of the samples were metallurgically examined for crack presence/geometry. In addition, an independent testing facility was hired to measure temperature-dependent mechanical data and uniaxial mechanical fatigue data for numerous GlidCop® samples. Data from these studies support finite element analysis (FEA) simulation and parametric models, allowing the development of a thermal fatigue model and the establishment of new design criteria so that the thermomechanically induced fatigue life of X-ray absorbers may be predicted. It is also demonstrated how the thermal fatigue model can be used as a tool to geometrically optimize X-ray absorber designs.
RESUMO
Schneiderian papilloma (SP) are uncommon tumors with malignant transformation even less common. The histologic criteria to define malignant transformation are not well developed nor is the immunohistochemical profile reported in a large series of carcinomas. 20 cases of malignant transformation of SP included 7 females and 13 males, aged 38-86 years (mean 60.7 years). Patients presented most frequently with a mass (n = 11) and obstructive symptoms (n = 7), present for 38.7 months (mean). Most patients had no previous history of SP (n = 13); metachronous carcinoma was identified in 7 patients an average of 34.4 months after the first diagnosis of SP, with 1-4 recurrences of SP. With a mean size of 4.1 cm, the majority of tumors involved a combination of more than one anatomic site (n = 10), followed by the maxillary sinus only (n = 5) or nasal cavity only (n = 3). Histologically, 17 were inverted and 3 exophytic type SP. There were 17 squamous cell carcinomas, 2 mucoepidermoid carcinomas and 1 sinonasal undifferentiated carcinoma, comprising from 10 to 95 % of the tumor volume. Malignant histologic features included atypical mitoses, necrosis, bone invasion, lymphovascular invasion, decreased transmigrating neutrophils, paradoxical maturation, dyskeratosis and/or perineural invasion (n = 3). Patients tended to present with advanced stage (n = 14, Stage III and IV). Immunohistochemical studies showed positive reactions in the malignancies for CK5/6 (86 %), p63 (86 %), CK7 (luminal, 50 %), p53 (83 %), and p16 (25 %). In situ hybridization detected human papillomavirus in 26 %. Surgery was often accompanied by radiation therapy (n = 13), with a mean of 2.4 years of follow-up. Five patients developed a recurrence between 0.8 and 3.3 years. Carcinomas ex-SP are less common and are associated with better outcome than previously reported. Patients tend to present with a synchronous carcinoma, developing in an inverted type SP, with squamous cell carcinoma the most common malignancy. Development of metachronous carcinomas ex-SP was always preceded by SP recurrence in this series.
