Microscopic characterization of pretransition oxide formed on Zr-Nb-Sn alloy under various Zn and dissolved hydrogen concentrations

Microstructure of oxide formed on Zr-Nb-Sn tube sample was intensively examined by scanning transmission electron microscopy after exposure to simulated primary water chemistry conditions of various concentrations of Zn (0 or 30 ppb) and dissolved hydrogen (H-2) (30 or 50 cc/kg) for various durations without applying desirable heat flux. Microstructural analysis indicated that there was no noticeable change in the microstructure of the oxide corresponding to water chemistry changes within the test duration of 100 days (pretransition stage) and no significant difference in the overall thickness of the oxide layer. Equiaxed grains with nano-size pores along the grain boundaries and microcracks were dominant near the water/oxide interface, regardless of water chemistry conditions. As the metal/oxide interface was approached, the number of pores tended to decrease. However, there was no significant effect of H-2 concentration between 30 cc/kg and 50 cc/kg on the corrosion of the oxide after free immersion in water at 360 degrees C. The adsorption of Zn on the cladding surface was observed by X-ray photoelectron spectroscopy and detected as ZnO on the outer oxide surface. From the perspective of OH - ion diffusion and porosity formation, the absence of noticeable effects was discussed further

Neuroendocrine tumors presenting with thyroid gland metastasis: a case series

<p>Abstract</p> <p>Introduction</p> <p>Autopsy series have shown that metastasis to the thyroid gland has occurred in up to 24% of patients who have died of cancer. Neuroendocrine tumors may metastasize to thyroid gland.</p> <p>Case presentations</p> <p>Case 1 was a 17-year-old Turkish woman who was referred from our Endocrinology Department for a thyroidectomy for treatment of neuroendocrine tumor metastasis. She was treated with a bilateral total thyroidectomy. Histopathological examination results were consistent with a neuroendocrine tumor; neoplastic cells showed strong immunoreactivity to chromogranin A and synaptophysin, but the immunohistochemical profile was inconsistent with medullary thyroid carcinoma in that the tumor was negative for calcitonin, carcinoembryonic antigen, and thyroid transcription factor-1.</p> <p>Case 2 was a 54-year-old Turkish woman who presented with a 3-cm nodule on her right thyroid lobe. She had undergone surgery for a right lung mass four years previously. After a right pneumonectomy, thymectomy and lymph node dissection, a typical carcinoid tumor was diagnosed. Under ultrasonographic guidance, fine needle aspiration biopsy of her right thyroid pole nodule was performed and the biopsy was compatible with a neuroendocrine tumor metastasis. She was treated with a bilateral total thyroidectomy. Histopathological examination indicated three nodular lesions, 5 cm and 0.4 cm in diameter in her right lobe and 0.1 cm in diameter in her left lobe. The tumors were consistent with a neuroendocrine phenotype, showing strong immunoreactivity to chromogranin A and synaptophysin.</p> <p>Conclusion</p> <p>Thyroid nodules detected during follow-up of neuroendocrine tumor patients should be thoroughly investigated. A fine needle aspiration biopsy of the thyroid confirms the diagnosis in most cases and leads to appropriate management of those patients and may prevent unnecessary treatment approaches.</p

Factors That Affect the False-Negative Outcomes of Fine-Needle Aspiration Biopsy in Thyroid Nodules

Background. The purpose of this study was to assess the factors that affect the false-negative outcomes of fine-needle aspiration biopsies (FNABs) in thyroid nodules. Methods. Thyroid nodules that underwent FNAB and surgery between August 2005 and January 2012 were analyzed. FNABs were taken from the suspicious nodules regardless of nodule size. Results. Nodules were analyzed in 2 different groups: Group 1 was the false-negatives (n=81) and Group 2 was the remaining true-positives, true-negatives, and false-positives (n=649). A cytopathologist attended in 559 (77%) of FNAB procedures. There was a positive correlation between the nodule size and false-negative rates, and the absence of an interpreting cytopathologist for the examination of the FNAB procedure was the most significant parameter with a 76-fold increased risk of false-negative results. Conclusion. The contribution of cytopathologists extends the time of the procedure, and this could be a difficult practice in centres with high patient turnovers. We currently request the contribution of a cytopathologist for selected patients whom should be followed up without surgery

The measurement of stress and phase fraction distributions in pre and post-transition Zircaloy oxides using nano-beam synchrotron X-ray diffraction

Zircaloy-4 oxide stress profiles and tetragonal:monoclinic oxide phase fraction distributions were studied using nano-beam transmission X-ray diffraction. Continuous stress relief and phase transformation during the first cycle of oxide growth was observed. The in-plane monoclinic stress was shown to relax strongly up to each transition, whereas in-plane tetragonal stress-relief (near the metal-oxide interface) was only observed post transition. The research demonstrates that plasticity in the metal and the development of a band of in-plane cracking both relax the monoclinic in-plane stress.The observations are consistent with a model of transition in which in-plane cracking becomes interlinked prior to transition. These cracks, combined with the development of cracks with a through-thickness component (driven primarily by plasticity in the metal) and/or a porous network of fine cracks (associated with phase transformation), form a percolation path through the oxide layer. The oxidising species can then percolate from the oxide surface to the metal/oxide interface, at which stage transition then ensues

Cell proliferation rate and telomerase activity in the differential diagnosis between benign and malignant mesothelial proliferations

Aims: The differential diagnosis of malignant mesothelioma ( MM) from benign mesothelial lesions ( BML) based on histopathological criteria is sometimes not satisfying and causes diagnostic problems for histopathologists. We aimed to investigate whether the immunohistochemically determined cell proliferation rate and telomerase activity, using Ki-67 and human telomerase reverse transcriptase ( hTERT) immunohistochemistry, respectively, are useful in the differential diagnosis of MM from BML

Effect of Sn on Corrosion Mechanisms in Advanced Zr-Cladding for Pressurised Water Reactors

The desire to improve the corrosion resistance of Zr cladding material to allow high burnup has resulted in a general trend among fuel manufacturers to develop alloys with reduced levels of Sn. Whereas the detrimental effect of Sn on high-temperature aqueous corrosion performance is widely accepted, the reason for it remains unclear. High-energy synchrotron x-ray diffraction was used to characterise the oxides formed by autoclave exposure on Zr-Sn-Nb alloys with tin concentrations ranging from 0.01 to 0.92 wt. %. The alloys studied included the commercial alloy ZIRLO and two variants of ZIRLO with significantly lower tin levels, referred to here as A-0.6Sn and A-0.0Sn. The nature of the oxide grown on tube samples from each alloy during autoclave testing at 360°C was investigated by cross-sectional scanning and transmission electron microscopy (SEM and TEM). Non-destructive synchrotron x-ray diffraction analysis on the oxides revealed that the monoclinic and tetragonal oxide phases display highly compressive in-plane residual stresses with the magnitudes dependent on both phase and alloy. Additional in situ synchrotron x-ray diffraction experiments during oxidation at 550°C provided further confirmation of the trends seen for autoclave-tested samples and demonstrated the presence of elevated levels of tetragonal phase in the initial stages of oxidation. In situ and ex situ measurements demonstrate unambiguously that the amount of tetragonal phase present and, more importantly, the degree of transformation from tetragonal to monoclinic oxide both decrease with decreasing tin levels, suggesting that tin stabilises the tetragonal phase. It is proposed that in Zr-Nb-Sn alloys with low Sn, the tetragonal phase is mainly stabilised by very small grain size and, therefore, remains stable throughout the corrosion process. By contrast, in alloys with higher tin levels, larger, stress stabilised, tetragonal grains can form initially, but then transform as the corrosion front progresses inward and stresses in the existing oxide relax