Nanotecnologia e nanociência em livros didáticos de física do nível médio: discursos sobre a tecnologia e a educação científica e tecnológica

Na presente investigação, analisamos as abordagens sobre a nanotecnologia e a nanociência em edições recentes de livros didáticos de Física, do nível médio da educação brasileira. A amostra inicial foi constituída por quinze coleções de livros didáticos de Física de edições recentes, porém, apenas dois livros, pertencentes a coleções distintas incorporam considerações sobre a nanotecnologia e a nanociência em suas abordagens. Focamos a análise em três aspectos, a saber: o lugar dedicado às abordagens sobre a nanociência e a nanotecnologia, as noções sobre a tecnologia e suas contribuições para uma educação científica crítica. Trata-se de uma pesquisa qualitativa, e usamos como referencial teórico da filosofia da tecnologia, da analise de discurso da escola francesa e referenciais ciência, tecnologia, sociedade e ambiente. Constatamos nos dois livros didáticos analisados que as abordagens sobre a nanociência e nanotecnologia encontram-se contempladas como Física Moderna e Contemporânea, associadas à teoria quântica. O teor das abordagens sobre a nanociência e a nanotecnologia foca superficialmente a gênese do campo de estudo, algumas possíveis áreas de aplicações e em um dos livros, possibilidades futuras bastante fantasiosas. Não identificamos nas abordagens dos livros didáticos alertas quanto aos possíveis riscos à saúde humana e ao meio ambiente, decorrentes da utilização da nanotecnologia e da nanociência. Interpretamos que as abordagens dos livros didáticos sobre a nanotecnologia e a nanociência aproximam-se de uma perspectiva tecnológica instrumental e que e distanciam-se de uma perspectiva de educação científica e tecnológica crítica

Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering

Oxygen-deficient TiO2 films with enhanced visible and near-infrared optical absorption have been deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is observed that the increase in the absorption coefficient is more effective when the O2 gas supply is periodically interrupted rather than by a decrease of the partial O2 gas pressure in the deposition plasma. The optical absorption coefficient at 1.5 eV increases from about 1 102 cm 1 to more than 4 103 cm 1 as a result of the gas flow discontinuity. A red-shift of 0.24 eV in the optical absorption edge is also observed. High resolution transmission electron microscopy with composition analysis shows that the films present a dense columnar morphology, with estimated mean column width of 40 nm. Moreover, the interruptions of the O2 gas flow do not produce detectable variations in the film composition along its growing direction. X-ray diffraction and micro-Raman experiments indicate the presence of the TiO2 anatase, rutile, and brookite phases. The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films deposited under discontinued O2 gas flow. The increase of optical absorption in the visible and near-infrared regions has been attributed to a high density of defects in the TiO2 films, which is consistent with density functional theory calculations that place oxygen-related vacancy states in the upper third of the optical bandgap. The electronic structure calculation results, along with the adopted deposition method and experimental data, have been used to propose a mechanism to explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic structure are potentially useful concerning the optimization of efficiency of the photocatalytic activity and the magnetic doping of TiO2 films

Exposure effects of endotoxin-free titanium-based wear particles to human osteoblasts

Titanium-based materials are widely employed by the biomedical industry in orthopedic and dental implants. However, when placed into the human body, these materials are highly susceptible to degradation processes, such as corrosion, wear, and tribocorrosion. As a consequence, metallic ions or particles (debris) may be released, and although several studies have been conducted in recent years to better understand the effects of their exposure to living cells, a consensual opinion has not yet been obtained. In this work, we produced metallic based wear particles by tribological tests carried out on Ti-6Al-4V and Ti-15Zr-15Mo alloys. They were posteriorly physicochemically characterized according to their crystal structure, size, morphology, and chemical composition and compared to Ti-6Al-4V commercially available particles. Finally, adsorbed endotoxins were removed (by applying a specific thermal treatment) and endotoxin-free particles were used in cell experiments to evaluate effects of their exposure to human osteoblasts (MG-63 and HOb), namely cell viability/metabolism, proinflammatory cytokine production (IL-6 and PGE2), and susceptibility to internalization processes. Our results indicate that tribologically-obtained wear particles exhibit fundamental differences in terms of size (smaller) and morphology (irregular shapes and rough surfaces) when compared to the commercial ones. Consequently, both Ti-6Al-4V and Ti-15Zr-15Mo particles were able to induce more pronounced effects on cell viability (decrease) and cytokine production (increase) than did Ti-6Al-4V commercial particles. Furthermore, both types of wear particles penetrated osteoblast membranes and were internalized by the cells. Influences on cytokine production by endotoxins were also demonstrated.This work was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP (2015/50280-5 and 2017/24300-4), Fundacao para a Ciencia e Tecnologia - FCT (UID/EEA/04436/2013), Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior - CAPES (Finance Code 0001), FCT/CAPES Joint Research Project (99999.008666/2014-08), FCT COMPETE 2020 (POCI-01-0145-FEDER-006941 and POCI-01-0145-FEDER-007265) and M-ERA-NET (0001/2015)

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

NANOTECNOLOGIA E NANOCIÊNCIA EM LIVROS DIDÁTICOS DE FÍSICA DO NÍVEL MÉDIO: DISCURSOS SOBRE A TECNOLOGIA E A EDUCAÇÃO CIENTÍFICA E TECNOLÓGICA

Na presente investigação, analisamos as abordagens sobre a nanotecnologia e a nanociência em edições recentes de livros didáticos de Física, do nível médio da educação brasileira. A amostra inicial foi constituída por quinze coleções de livros didáticos de Física de edições recentes, porém, apenas dois livros, pertencentes a coleções distintas incorporam considerações sobre a nanotecnologia e a nanociência em suas abordagens. Focamos a análise em três aspectos, a saber: o lugar dedicado às abordagens sobre a nanociência e a nanotecnologia, as noções sobre a tecnologia e suas contribuições para uma educação científica crítica. Trata-se de uma pesquisa qualitativa, e usamos como referencial teórico da filosofia da tecnologia, da analise de discurso da escola francesa e referenciais ciência, tecnologia, sociedade e ambiente. Constatamos nos dois livros didáticos analisados que as abordagens sobre a nanociência e nanotecnologia encontram-se contempladas como Física Moderna e Contemporânea, associadas à teoria quântica. O teor das abordagens sobre a nanociência e a nanotecnologia foca superficialmente a gênese do campo de estudo, algumas possíveis áreas de aplicações e em um dos livros, possibilidades futuras bastante fantasiosas. Não identificamos nas abordagens dos livros didáticos alertas quanto aos possíveis riscos à saúde humana e ao meio ambiente, decorrentes da utilização da nanotecnologia e da nanociência. Interpretamos que as abordagens dos livros didáticos sobre a nanotecnologia e a nanociência aproximam-se de uma perspectiva tecnológica instrumental e que e distanciam-se de uma perspectiva de educação científica e tecnológica crítica

ANALYSIS OF NANOSCIENCE AND NANOTECHNOLOGY A PERSPECTIVE OF SCIENCE, TECHNOLOGY AND SOCIETY – CTS

In this contribution, we discuss and analyze some aspects of nanoscience and nanotechnology, based on the approach kwon as Science, Technology and Society (STS), as well as the prospects of Philosophy of Technology. In this context, we specify the constitute the nanoscience and nanotechnology analytic research field. I is also reported its genesis and limits, emphasizing the impacts of nanotechnology in the development of the contemporary society, such as the possible benefits and problems associated to the use of nanotechnology, as well as environmental impacts, doubts and uncertainties that permeate this areas, in addition some ethical questions and public policies for the sector are analyzed