Development of silicon carbide substrates for aerospace applications

Payload and high-tech are important characteristics when the goals are aerospace applications. The development of the technologies associated to these applications has interests that transcend national boundaries and are of strategic importance to the nations. Ultra lightweight mirrors, supports and structures for optical systems are important part of this subject. This paper reports the development of SiC substrates, obtained by pressing, to be applied on embedded precision reflective optics. Different SiC granulometries, having YAG as sintering additive, were processed by: ball milling, drying and deagglomeration, sift, uniaxial and isostatic pressing, and, finally, argon atmosphere sintering at 1900°C. Different porosities were obtained according to the amount of organic material added. Into one side of the samples pellets of organic material were introduced to generate voids to reduce the weight of samples as a whole. The substrates were grinding and polished, looking for a SiC surface having low porosity, as porosity is directly related to light scattering that should be avoided on optical surfaces. Laser surface treatments were applied (using or not SiC barbotine) as a method to improve the surface quality. The samples were characterized by optical and laser confocal microscopy, roughness measurements and mechanical tests. The results are very promissory for future applications. © 2012 Materials Research Society.

Osseointegration assessment of chairside argon-based nonthermal plasma-treated Ca-P coated dental implants

This study investigated the effect of an Argon-based nonthermal plasma (NTP) surface treatment-operated chairside at atmospheric pressure conditions applied immediately prior to dental implant placement in a canine model. Surfaces investigated comprised: Calcium-Phosphate (CaP) and CaP + NTP (CaP-Plasma). Surface energy was characterized by the Owens-Wendt-Rabel-Kaelble method and chemistry by X-ray photoelectron spectroscopy (XPS). Six adult beagles dogs received 2 plateau-root form implants (n = 1 each surface) in each radii, providing implants that remained 1 and 3 weeks in vivo. Histometric parameters assessed were bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed by Kruskall-Wallis (95% level of significance) and Dunn's post-hoc test. The XPS analysis showed peaks of Ca, C, O, and P for the CaP and CaP-Plasma surfaces. Both surfaces presented carbon primarily as hydro-carbon (CAC, CAH) with lower levels of oxidized carbon forms. The CaP surface presented atomic percent values of 38, 42, 11, and 7 for C, O, Ca, and P, respectively, and the CaPPlasma presented increases in O, Ca, and P atomic percent levels at 53, 12, and 13, respectively, in addition to a decrease in C content at 18 atomic percent. At 1 week no difference was found in histometric parameters between groups. At 3 weeks significantly higher BIC and BAFO were observed for CaPPlasma treated surfaces. Surface elemental chemistry was modified by the Ar-based NTP. Ar-based NTP improved bone formation around plateau-root form implants at 3 weeks compared with CaP treatment alone. © 2012 Wiley Periodicals, Inc.

Estudo das propriedades de barreira de filmes depositados a plasma sobre a liga de alumínio 2024

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Eficiência do protocolo superestimulatório P-36, associado à administração de eCG ou LH, em animais da raça Angus

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tratamento de polímeros com jato de plasma em pressão atmosférica

Pós-graduação em Física - FEG

Densidade mineral óssea de vértebras de ratos wistar suspensos pela cauda por 15 e 36 dias

Pós-graduação em Ciência Animal - FMVA

Influência da atmosfera protetora no cordão de solda obtido através dos processos de soldagem GMAW e FCAW

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Disponibilidade de minerais, germinação e vigor de sementes de milho

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

ECLAC Notes Nº 36

Latin America and the Caribbean's Economies Turn in Stronger Performances this Year To Invest More - but also Better - in Education Opinion: An Opportunity to Consolidate Growth, by José Luis Machinea Highlights: Valuable Experiences that Improve Gender Equity Indicators The Region's Energy Resources Should Guarantee Secure Supply at Reasonable Prices Recent Titles Calendar

Notas de la CEPAL Nº 36

Auge económico en América Latina y el Caribe para 2004 Invertir más pero también mejor en educación Columna de opinión de José Luis Machinea:Una oportunidad para consolidar el crecimiento Precisiones: Experiencias valiosas que mejoran la equidad de género Indicadores Recursos energéticos de la región permitirían abastecimiento económico y seguro Publicaciones Recientes Calendario de Eventos

Notas de Población Vol.36 N° 89

La generación de información sociodemográfica de inicios del siglo XXI enfrenta retos significativos producto de la variedad de temas y enfoques a abordar que, a su vez, derivan de los cambios sociales y políticos y de las nuevas demandas que imponen diferentes sectores de la población. En la actualidad, la información no solo constituye una herramienta técnica, sino también un recurso político en pro de la realización de derechos, que contribuye a la democracia y al buen gobierno. Por este motivo, las instituciones del Estado, los organismos internacionales y las organizaciones de la sociedad civil plantean demandas crecientes de información tendiente a visualizar, por ejemplo, la situación de la mujer y los problemas de género o las condiciones de vida de grupos históricamente excluidos, como los pueblos indígenas y los afrodescendientes. Además de contribuir a la definición de políticas más efectivas y pertinentes, la disponibilidad de más y mejor información también pone a disposición de los diferentes usuarios un instrumento de utilidad para que puedan ejercer grados crecientes de participación y control respecto de las acciones que llevan a cabo los Estados y sus organismos. . En este contexto, Notas de población No. 89 presenta siete artículos que dan respuestas concretas a las nuevas demandas de información, como la identificación de grupos étnicos en los censos de población, las potencialidades de los registros vitales para realizar perfiles epidemiológicos diferenciados o para evaluar políticas públicas y aplicaciones novedosas para el análisis longitudinal mediante el uso de encuestas de hogares que, en principio, fueron diseñadas para el análisis de corte transversal.