Nickel Dynamics Switches the Selectivity of CO2 Hydrogenation.

The Reverse Water Gas-Shift reaction (CO2 + H2=CO + H2O) allows to balance syn-gas under industrial conditions. Nickel has been suggested as a potential catalyst but the temperature required is too high, more than 800ºC, limiting practical implementation but when lowering the temperature methanation occurs. Simulations via Density Functional Theory on well-defined surfaces have systematically failed to reproduce these experimental results. But under reaction conditions Ni surfaces are not static and DFT models coupled to microkinetics show that at high CO coverages drive the generation of Ni adatoms that are the active sites for methanation. At higher temperatures, the adatom population decreases, and the selectivity towards CO increases. Thus, the mechanism behind the selectivity switch is driven by the dynamics induced by reaction intermediates. Our work contributes to the inclusion of dynamic aspects of materials under reaction conditions in the understanding of complex catalytic behaviour.

[Prognostic value of clinical, histopathological and immunohistochemical features in medullary thyroid cancer]. / Valor pronóstico de las características clínicas, histopatológicas e inmunohistoquímicas en el carcinoma medular de tiroides.

BACKGROUND AND OBJECTIVE: To analyze the importance of various clinical, histopathological and immunohistochemical features in the prognosis of resected medullary thyroid carcinoma. PATIENTS AND METHODS: A total of 55 cases of medullary thyroid carcinoma consecutively operated were investigated. The data referring to clinical features were collected in the patient's clinical history. The histopathological and immunohistochemical features of the tumors were taken from their pathological anatomy report. RESULTS: Survival at one year was 96 ± 2%; at 5 years 91 ± 4%; at 10 years 88 ±6%; at 15 years 83 ± 7%; and at 20 years 61 ± 14%. Among epidemiological features, tumor type was significantly related with the disease (best familial prognosis; P=.035); among histopathological features, the presence of C cell hyperplasia and the presence of tumor necrosis had a significant relationship (P=.0005 and P=.039); among immunohistochemical features, positivity for p53 and for c-erb-b2 (P=.023 and P=.022); and finally, among staging data, TNM clinical staging (P=.015), size (P=.046) and the presence of distant metastases (P=.002). According to Cox's regression model, the only variables indicating a poor prognosis were: the existence of necrosis (P=.039; OR=6.513) and tumor size>4 cm (P=.027; OR=14.196). CONCLUSIONS: The survival rate was mainly determined by tumor size and the presence of tumor necrosis. None of the immunohistochemical markers had a significant influence on survival.

[Histological and immunohistochemical profile of sporadic and familial medullary thyroid carcinoma]. / Perfil histológico e inmuno-histoquímico del carcinoma medular de tiroides esporádico y familiar.

INTRODUCTION: The histological and immunohistochemical profile of medullary thyroid carcinoma is ill-defined. The objective of this study was to determine the epidemiological, histological, and immunohistochemical characteristics of medullary carcinoma and to analyze whether differences exist between sporadic and familial carcinomas. PATIENTS AND METHODS: Fifty-five histologically confirmed tumors were studied. Histological slides were reviewed and immunohistochemical staining of the archival paraffin blocks was performed. RESULTS: Nineteen of the 55 carcinomas (35%) were sporadic, and 36 (65%) familial. Sex distribution was similar, but familial carcinoma was more common in patients under 40 years of age (p<0.001). A solid growth pattern and plasmacytoid cells were found in most cases. C-cell hyperplasia and multicentricity were more frequent findings in familial carcinoma, while tumor necrosis, hemorrhagic foci, vascular invasion, and neovascularization were more common in the sporadic type. Immunohistochemical staining was positive for calcitonin, CEA, bcl-2, and p53 protein. With regard to staging, familial carcinomas were diagnosed in the earliest stages, when they were smaller and there were no lymph node metastases (p<0.01). CONCLUSIONS: Familial cases were more frequent when there was more C-cell hyperplasia and multicentricity. Sporadic cases more frequently showed foci of necrosis, hemorrhage, vascular invasion, and neovascularization. Neither histopathological nor immunohistochemical criteria are useful for differentiating between familial and sporadic forms.