Comparative theoretical study of the Ag-MgO (100) and (110) interfaces

We have calculated the atomic and electronic structures of Ag-MgO(100) and (110) interfaces using a periodic (slab) model and an ab initio Hartree-Fock approach with a posteriori electron correlation corrections. The electronic structure information includes interatomic bond populations, effective charges, and multipole moments of ions. This information is analyzed in conjunction with the interface binding energy and the equilibrium distances for both interfaces for various coverages. There are significant differences between partly covered surfaces and surfaces with several layers of metal, and these can be understood in terms of electrostatics and the electron density changes.For complete monolayer (1:1) coverage of the perfect MgO(100) surface, the most favorable adsorption site energetically for the Ag atom is above the surface oxygen. However, for partial (1:4) coverage of the same surface, the binding energies are very close for all the three likely adsorption positions (Ag over O, Ag over Mg, Ag over a gap position),For a complete (1:1) Ag monolayer coverage of the perfect MgO(110) interface, the preferable Ag adsorption site is over the interatomic gap position, whereas for an Ag bilayer coverage the preferred Ag site is above the subsurface Mg2+ ion (the bridge site between two nearest surface O2- ions). In the case of 1:2 layer coverage, both sites are energetically equivalent. These two adhesion energies for the (110) substrate are by a factor of two to three larger than over other possible adsorption sites on perfect(110) or (100) surfaces.We compare our atomistic calculations for one to three Ag planes with those obtained by the shell model for 10 Ag planes and the Image Interaction Model addressing the case of thick metal layers. Qualitatively, our ab initio results agree well with many features of these models. The main charge redistributions are well in line with those expected from the Image Model. There is also broad agreement in regard to orders of magnitude of energies. (C) 1999 Elsevier Science B.V. All rights reserved

Ethical issues in autologous stem cell transplantation (ASCT) in advanced breast cancer: A systematic literature review

BACKGROUND: An effectiveness assessment on ASCT in locally advanced and metastatic breast cancer identified serious ethical issues associated with this intervention. Our objective was to systematically review these aspects by means of a literature analysis. METHODS: We chose the reflexive Socratic approach as the review method using Hofmann's question list, conducted a comprehensive literature search in biomedical, psychological and ethics bibliographic databases and screened the resulting hits in a 2-step selection process. Relevant arguments were assembled from the included articles, and were assessed and assigned to the question list. Hofmann's questions were addressed by synthesizing these arguments. RESULTS: Of the identified 879 documents 102 included arguments related to one or more questions from Hofmann's question list. The most important ethical issues were the implementation of ASCT in clinical practice on the basis of phase-II trials in the 1990s and the publication of falsified data in the first randomized controlled trials (Bezwoda fraud), which caused significant negative effects on recruiting patients for further clinical trials and the doctor-patient relationship. Recent meta-analyses report a marginal effect in prolonging disease-free survival, accompanied by severe harms, including death. ASCT in breast cancer remains a stigmatized technology. Reported health-related-quality-of-life data are often at high risk of bias in favor of the survivors. Furthermore little attention has been paid to those patients who were dying. CONCLUSIONS: The questions were addressed in different degrees of completeness. All arguments were assignable to the questions. The central ethical dimensions of ASCT could be discussed by reviewing the published literature