ABSTRACT
Lead-free piezoelectric powders (K0.44Na0.52Li0.04)(Nb0.82Ta0.10Sb0.04)O3 were obtained by conventional and microwave-assisted reactive heating. Firstly, the synthesis of the material was carried out following the mixed oxide route and employing both traditional methods and microwave technology. Thermogravimetry, X-ray diffraction, field emission scanning electron microscopy and electrical properties analyses were evaluated. X-ray diffraction of the powders calcined by the microwave process shows the formation of perovskite structure with orthorhombic geometry, but it is possible to observe the presence of other phases. The presence of the secondary phases found can have a great influence on the heating rate during the synthesis on which the kinetics of the reaction of formation of the piezoelectric compound depend. The calcined powder was sintered at different temperatures by conventional and non-conventional processes. The microstructure of the ceramics sintered by microwave at 1050 °C for 10 min shows perovskite cubes with regular geometry, of size close to 2-5 µm. However, the observed porosity (~8%), the presence of liquid phase and secondary phases in the microstructure of the microwave sintered materials lead to a decrease of the piezoelectric constant. The highest d33 value of 146 pC/N was obtained for samples obtained by conventional at 1100 °C 2 h compared to samples sintered by microwave at 1050 °C 10 min (~15 pC/N).
ABSTRACT
The choice of the right material is essential in microwave processing. The carbon materials are good microwave absorbers, which allows them to be transformed by microwave heating into new carbon materials with adapted properties, capable of heating other materials indirectly. In this paper, the microwave heating of graphene as reinforcement of the lithium aluminosilicate (LAS) ceramics has been explored. LAS ceramics have a near-zero coefficient of thermal expansion and exhibit an effective and efficient heating by microwave. Nevertheless, we have found that the graphene did not show any significant response to the microwave radiation and, hence, the interaction as mechanical reinforcement with the LAS material is harmful. The possible benefits of graphene materials to microwave technology are widely known; however, the mechanism involved in the interaction of microwave radiation with ceramic-graphene composites with high dielectric loss factors has not been addressed earlier.
Subject(s)
Trigeminal Nerve Diseases/pathology , Trigeminal Nerve/pathology , Ulcer/pathology , Aged , Biopsy , Face , Female , Follow-Up Studies , HumansABSTRACT
Introducción: la enfermedad de Alzheimer (EA) es uno de los problemas sociosanitarios más importantes actualmente. Se considera la toxicidad del péptido beta-amiloide la clave de su patogenia. Cada vez es más importante conseguir marcadores periféricos de la enfermedad para avanzar en su conocimiento y de sus posibles dianas terapéuticas. Con este estudio pretendemos valorar la idoneidad de los linfocitos como modelo en el que estudiar la toxicidad del beta-amiloide. Material y métodos: se reclutó a 6 voluntarios sanos, 3 varones y 3 mujeres, con edades comprendidas entre los 25 y 35 años, sin antecedentes familiares de EA. Se les realizó una extracción sanguínea de donde se aislaron los linfocitos que posteriormente se incubaron con beta-amiloide 1-42 durante 6 h. Se utilizó la microscopia confocal y la citometría de flujo para estudiar, como marcadores de toxicidad celular, la apoptosis, el potencial de membrana mitocondrial y el número de mitocondrias. Resultados: encontramos un aumento de muerte celular en sus distintos estadios (apoptosis temprana y tardía) así como una disminución de mitocondrias en los linfocitos incubados con el péptido beta-amiloide. Observamos un mayor daño celular en los linfocitos de los varones que en las mujeres, probablemente por el efecto protector de los estrógenos. Conclusiones: los linfocitos son un buen modelo para estudiar la toxicidad celular del péptido beta-amiloide
Introduction: Alzheimer's disease is a major health concern. The toxicity of the beta amyloid peptide is a key pathogenic event in the development of this disease. Finding peripheral markers for Alzheimer's disease is an important step for the early detection and treatment of this disease. The aim of the present study was to evaluate the utility of lymphocytes as a peripheral model for the study of beta amyloid toxicity. Material and methods: six healthy volunteers (three men and three women), aged 25-35 years, without a family history of Alzheimer's disease were recruited. Peripheral blood lymphocytes were obtained and incubated with 10 micromolar beta amyloid peptide for 6 hours. Confocal microscopy and flow cytometry were used to determine the rate of apoptosis, mitochondrial membrane potential, and the number of mitochondria. Results: incubation of lymphocytes with beta amyloid peptide caused an increase in cell death (apoptosis plus necrosis) as well as a decrease in the number of mitochondria. The peptide caused more damage to cells from men than to those from women, probably due to the protective effect of estrogens. Conclusions: lymphocytes are a good model for studying cellular susceptibility to beta amyloid peptide
