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This paper reviews the effect of organic and inorganic coatings on magnetic nanoparticles. The ferromagnetic-like behaviour observed in nanoparticles constituted by materials which are non-magnetic in bulk is analysed for two cases: (a) Pd and Pt nanoparticles, formed by substances close to the onset of ferromagnetism, and (b) Au and ZnO nanoparticles, which were found to be surprisingly magnetic at the nanoscale when coated by organic surfactants. An overview of theories accounting for this unexpected magnetism, induced by the nanosize influence, is presented. In addition, the effect of coating magnetic nanoparticles with biocompatible metals, oxides or organic molecules is also reviewed, focusing on their applications.
Assuntos
Fenômenos Magnéticos , Nanopartículas/química , Materiais Biocompatíveis/química , Nanopartículas Metálicas/química , Compostos Orgânicos/químicaRESUMO
Two new oxides of the Ruddlesden-Popper series have been isolated and structurally characterized in the Sr-Co-Ta-O system. X-ray and electron diffraction and high-resolution electron microscopy show that polycrystalline Sr(3)CoTaO(7) constitutes the n=2 member of a new Sr(n+1)(CoTa)(n)O(3n+1) homologous series, the essential feature of which is the existence of two connected Co/Ta octahedral layers, separated by Sr atoms. Sr(2)CoTaO(6), the n=infinity member of the series, shows a particular short-range ordering of Co and Ta at the octahedral sites leading, as shown by high-resolution electron microscopy, to the disordered intergrowth of simple and double perovskite type domains. Strategies to stabilize new oxides of this series are discussed.
RESUMO
AIM: To analyze the results of surgical treatment of left ventricular free wall rupture after acute myocardial infarct in a case series. METHOD: From 1984 to 2001, 25 patients (10 women and 15 men) were surgically treated in our Center for left ventricular free wall rupture after acute myocardial infarction. Their mean age was 62 years (range, 42-80). Cardiac symptoms (chest pain and/or dyspnea) prior to admission were recorded in 4 patients. One patient had acute myocardial infarction of the anterolateral wall, 6 patients of the lateral wall, 13 patients of the anterior wall, 4 patients of the inferior wall, and one patient had a right ventricle infarction. Thrombolytic therapy was administered in 10 patients, according to the criteria of the American Heart Association and Spanish Society of Cardiology criteria. In all patients, the final diagnosis was established echocardiographically before the surgery. RESULTS: All patients underwent surgical intervention on an emergency basis. Extracorporeal circulation was used in the first 9 cases, whereas the next 16 patients had off-pump surgery. Two patients had heart arrest during off-pump surgery, which required extracorporeal circulation support. One patient was found false positive for rupture only at surgery. In the first 4 cases, we performed a direct suture after excising necrotic tissue, in the next 15 cases we sutured a patch over the infarction zone, and in the last 5 patients we used Teflon patch fixed with fibrin glue and polypropylene and stitched to the epicardium with a continuous suture. Out of 24 patients, 8 died: one in the surgical room from uncontrollable bleeding and another 7 between 30 and 90 days after the surgery in the intensive care unit. All of them underwent surgery with extracorporeal circulation. There were no deaths among the patients undergoing off-pump surgery. Three out of 4 patients in whom direct suture and necrotic tissue excision was performed died in the hospital. Five out of 19 patients in whom patch correction with direct suture was done died in the hospital. CONCLUSION: The left ventricle free wall rupture, as a complication of acute myocardial infarction, can be diagnosed early and treated on time. Rapid diagnosis and emergency surgery are crucial for successful treatment of patients with impending heart rupture. Off-pump surgery and patch with glue technique seem to yield best results.