Adsorption and diffusion of Pt, Cu, Ag and Au on missing row reconstructed Pt(110) surfaces: An ab initio investigation

We present density functional theory (DFT) calculations for the heterodiffusion and adsorption for Ag, Au and Cu adatoms on the Pt(110)(1 7 1) (1 7 2) and (1 7 3) surfaces. The adsorption energy shows an important variation as function of the reconstruction order for Pt/Pt and Au/Pt systems, while the adsorption energy varies slightly for Cu/Pt and Ag/Pt. Likewise, the activation energy is examined for different systems and geometries and the highest barrier was found for Pt adatom diffusion. In addition, the estimated diffusion barriers are found to be influenced by reconstruction order for all systems under consideration but with different magnitudes of variation as function of reconstruction order for each system. Indeed, we found that the activation energy varies as function of the reconstruction order but the magnitude of variation is important for Pt/Pt and Cu/Pt systems, whereas the diffusion barrier for Ag/Pt and Au/Pt systems has a slight dependence on the reconstruction order. The analysis of the adatom relaxation with its neighbor atoms as well as the variation of the bond length was provided to more deeply explain the observed trends for each system. The general trend of activation energies for these systems is consistent with available experimental and theoretical data

Large Malignant Pheochromocytoma: About Three Cases

Introduction: Malignant pheochromocytomas are rare tumors which carry a poor prognosis and their clinical presentation is variable. Malignancy is defined by the presence of local invasion and/or metastases. In this report, we describe three cases of large malignant pheochromocytomas.Cases Presentation: The three cases have presented abdominal masses. Two patients complained of hypochondrium pain, and the third one was asymptomatic. One of the patients experienced sweating for 2 years, while the two others had no symptoms suggesting the hyper secretion of catecholamines. Urinalysis revealed elevation of daily urinary excretion of catecholamine metabolites in two cases and the computed tomography (CT) revealed large adrenal masses in the three cases. The malignancy was confirmed by the presence of multiple liver, lung and bone metastases. Surgery was performed in one case, but the tumor resection was impossible because the mass was adherent to great vessels. Calcitonin, intact parathormone (PTH) and calcium were normal in the 3 cases, which ruled out multiple endocrine neoplasia syndrome type 2. Otherwise, there was no sign suggesting phacomatosis. Two patients died before starting therapy, while in the third case the treatment considered was surgery and chemotherapy regimen of cyclophosphamide, dacarbazine and vincristine (CVD). Follow-up, showed a progression of tumor size with no significant improvement of metastatic disease.Conclusion: Malignant pheochromocytomas are particularly rare and aggressive tumors. Despite advances in diagnosis and treatment of malignant pheochromocytomas, their management is still a real dilemma, especially in our context because of the lack of diagnostic tools such as genetic analysis and the cost of therapy