Fabrication and structural analysis of ZnO coated fiber optic phase modulators

Fiber optic modulators were fabricated by coating optical fibers with electrode and piezoelectric ZnO layers. The techniques of piezoelectric fiber optic modulator (PFOM) fabrication are presented, and the microstructure and crystallographic texture of the coatings are analyzed. In order to produce thick (approximately 5 μm) ZnO coatings, it was necessary to study the reactive dc magnetron sputtering process in O2/Ar gas mixtures under conditions close to the transition between an oxidized and nonoxidized Zn target surface. In situ quartz crystal microbalance measurements of the deposition rate revealed thee distinct regions in the deposition rate (R) vs oxygen partial pressure behavior, at constant total pressure, for sputtering under conditions that provided an oxidized Zn target surface. Additionally, a transition between oxygen and argon dominated sputtering as observed by varying the sputtering pressure while maintaining a constant The transition between oxygen and argon dominated sputtering influences R to varying extents within the three R vs regions for an oxidized target surface. Correlations among the cathode current and voltage, deposition rate, and gas flow rate are presented to give a better understanding of the reactive sputtering processes occurring at the oxidized Zn target surface. Sputtering conditions optimized for a high ZnO deposition rate were used to produce 〈001〉 radially oriented ZnO fiber coatings for PFOM devices that can produce optical phase shifts as large as 0.38 rad/

Fabrication and structural analysis of ZnO coated fiber optic phase modulators

Fiber optic modulators were fabricated by coating optical fibers with electrode and piezoelectric ZnO layers. The techniques of piezoelectric fiber optic modulator (PFOM) fabrication are presented, and the microstructure and crystallographic texture of the coatings are analyzed, Ln order to produce thick (approximately 5 mu m) ZnO coatings, it was necessary to study the reactive de magnetron sputtering process in O-2/Ar gas mixtures under conditions close to the transition between an oxidized and nonoxidized Zn target surface. In situ quartz crystal microbalance measurements of the deposition rate revealed thee distinct regions in the deposition rate (R) vs oxygen partial pressure (P-o2) behavior, at constant total pressure, for sputtering under conditions that provided an oxidized Zn target surface. Additionally, a transition between oxygen and argon dominated sputtering as observed by varying the sputtering pressure while maintaining a constant P-o2. The transition between oxygen and argon dominated sputtering influences R to varying extents within the three R vs P-o2 regions for an oxidized target surface. Correlations among the cathode current and voltage, deposition rate, and gas flow rate are presented to give a better understanding of the reactive sputtering processes occurring at the oxidized Zn target surface. Sputtering conditions optimized for a high ZnO deposition rate were used to produce [001] radially oriented ZnO fiber coatings for PFOM devices that can produce optical phase shifts as large as 0.38 rad/V

Impactos do Carbon Dot Krill A32 na produtividade de biomassa da microalga Chlorella sorokiniana (LBA#39).

Há vários esforços para tornar o cultivo de microalgas economicamente viável. Isso porque esses organismos são fontes de diversas biomoléculas de valor econômico, como lipídios, proteínas e enzimas. Entretanto, há desafios na produção que dificultam a lucratividade da atividade. Alguns estudos indicam que tratamentos com carbon quantum dots podem incrementar a produtividade da biomassa microalgal produzida. Foram feitos três experimentos com diferentes concentrações do Carbon Dot Krill A32, que foram aplicadas em cultivos com a microalga Chlorella sorokiniana (LBA#39) para investigar os efeitos na produção de biomassa. Um teste inicial foi feito em biorreatores de 500 mL testando‑se 500 μg/L e 500 ng/L da nanopartícula. O segundo foi uma varredura em um volume de 1,5 L em que as concentrações investigadas foram 10 mg/L; 1 mg/L; 500 μg/L; 100 μg/L; 10 μg/L; 1 μg/L e 500 ng/L da nanopartícula. O terceiro foi uma validação em reatores de 2 L utilizando concentrações de 100 μg/L e 10 μg/L da nanopartícula. Os resultados da curva de crescimento dos cultivos não apresentaram diferenças estatisticamente significativas. Para os resultados de biomassa seca, com o aumento do volume de cultivo, os incrementos foram progressivamente menores e estatisticamente iguais ao controle. Os resultados sugerem que nas condições estudadas não há incremento na produtividade da biomassa. São necessárias análises sobre a qualidade da biomassa para melhor interpretação do observado

First results from stimulation assessment and monitoring of the 426°C geothermal well RN-15/IDDP-2 (H2020-DEEPEGS project)

The RN-15/IDDP-2 deep geothermal well of the DEEPEGS EU project on the Mid-Atlantic ridge at Reykjanes, Iceland, is a unique site for geothermal research. With a bottom hole temperature of approximately 426°C, it is one of the hottest geothermal wells ever drilled aiming for fluids at supercritical condition. Consequently, down-hole measurements are reliable to a depth of about 3.5 km, only. Pressure and temperature condition in the reservoir can be inferred using the newly developed wellbore simulator WellboreKit. Due to complete fluid loss, the well has been drilled at flow rates that reach hydraulic stimulation condition. After the drilling, the well was stimulated further by applying different concepts ranging from high flow rate hydraulic stimulation to long-term but low flow rate hydraulic stimulation to increase the reservoir performance at around 4.6 km depth. Thermo-hydro-mechanically coupled numerical modelling was performed to predict the performance response and thus, develop a well stimulation schedule. Processes related to drilling and stimulation are monitored using seismic and magnetotelluric methods to characterize and understand the processes ongoing during injection

Predator Dispersal Determines the Effect of Connectivity on Prey Diversity

Linking local communities to a metacommunity can positively affect diversity by enabling immigration of dispersal-limited species and maintenance of sink populations. However, connectivity can also negatively affect diversity by allowing the spread of strong competitors or predators. In a microcosm experiment with five ciliate species as prey and a copepod as an efficient generalist predator, we analysed the effect of connectivity on prey species richness in metacommunities that were either unconnected, connected for the prey, or connected for both prey and predator. Presence and absence of predator dispersal was cross-classified with low and high connectivity. The effect of connectivity on local and regional richness strongly depended on whether corridors were open for the predator. Local richness was initially positively affected by connectivity through rescue of species from stochastic extinctions. With predator dispersal, however, this positive effect soon turned negative as the predator spread over the metacommunity. Regional richness was unaffected by connectivity when local communities were connected only for the prey, while predator dispersal resulted in a pronounced decrease of regional richness. The level of connectivity influenced the speed of richness decline, with regional species extinctions being delayed for one week in weakly connected metacommunities. While connectivity enabled rescue of prey species from stochastic extinctions, deterministic extinctions due to predation were not overcome through reimmigration from predator-free refuges. Prey reimmigrating into these sink habitats appeared to be directly converted into increased predator abundance. Connectivity thus had a positive effect on the predator, even when the predator was not dispersing itself. Our study illustrates that dispersal of a species with strong negative effects on other community members shapes the dispersal-diversity relationship. When connections enable the spread of a generalist predator, positive effects of connectivity on prey species richness are outweighed by regional extinctions through predation

Photoelasticity of crystalline and amorphous silica from first principles

Based on density-functional perturbation theory we have computed from first principles the photoelastic tensor of few crystalline phases of silica at normal conditions and high pressure (quartz, $\alpha$-cristobalite, $\beta$-cristobalite) and of models of amorphous silica (containig up to 162 atoms), obtained by quenching from the melt in combined classical and Car-Parrinello molecular dynamics simulations. The computational framework has also been checked on the photoelastic tensor of crystalline silicon and MgO as prototypes of covalent and ionic systems. The agreement with available experimental data is good. A phenomenological model suitable to describe the photoelastic properties of different silica polymorphs is devised by fitting on the ab-initio data.Comment: ten figure

Influência da iluminação e da aeração sobre o crescimento de Chlorella sorokiniana em meio BG11.

Representando uns dos principais objetos de estudos atualmente, microalgas são, em geral, microrganismos fotossintetizantes altamente capazes de retirar CO2 atmosférico e gerar biomassa rica em biomoléculas de interesse industrial e comercial. No entanto, para obtenção de altos valores de rendimento e produtividade, condições ideais de crescimento são muito importantes. Diante disso, o objetivo deste trabalho foi comparar a influência de biorreatores, ou modelos utilizados para o cultivo, sobre o crescimento e o rendimento de biomassa de Chlorella sorokiniana em meio BG11 e, também, verificar os resultados que o uso de diferentes luzes pode gerar. Para tanto, foram realizados dois experimentos não simultâneos em que, primeiramente, a cepa foi cultivada em dois módulos de cultivos diferentes: módulo novo (MN), com biorreatores e sistema de aeração novos da sala de microalgas; e módulo antigo (MA), utilizando Erlenmeyers, pipeta estéril para passagem de ar e outros componentes. Em um segundo momento, com o intuito de analisar quais luzes e combinações geram maiores crescimentos e, por conseguinte, maiores biomassas secas finais, as microalgas foram cultivadas sob três condições de iluminação diferentes: luz branca (B), luz branca + luz colorida (B+C) e luz colorida (C). Para os dois módulos, temperatura, aeração e pH também foram por espectrofotometria, contagem de células, leitura de turbidez por OD manual e centrifugação e liofilização das biomassas, para saber o peso de massa seca final, foram feitas. Com isso, as análises e os testes mostraram rendimento de biomassa bem maior em MN em comparação com MA e maior crescimento dos cultivos crescidos sob luz B+C, havendo diferenças significativas em ambos os experimentos. Esses resultados permitiram demonstrar a maior eficiência dos novos módulos de cultivo de microalgas da Embrapa Agroenergia e quais luzes utilizadas geram maiores crescimentos, destacando‑se também a importância de se ter condições de cultivo adequadas

Sistema automatizado de monitoramento para fotobiorreatores de microalgas.

O presente artigo apresenta e discute a construção de um sistema de monitoramento e gerenciamento de dados automatizado para fotobiorreatores de microalgas destinados à produção de biomassa. A montagem do projeto de automação fez uso de hardware de baixo custo destinado à prototipagem rápida, adaptado para atender às condições do ambiente laboratorial no intuito de monitorar inicialmente o pH dentro do sistema fechado, porém criando bases sólidas para a integração de monitoramento de outros parâmetros de interesse à produção, como temperatura, iluminação e oxigenação. O presente trabalho explora aspectos dessa implementação, como os protocolos de comunicação, implementação de datalogger, instalação de calibração de sensores e desenvolvimento de código para microcontrolador Arduino. Os resultados obtidos neste trabalho permitem concluir que o emprego do sistema automatizado fornece previsões otimistas em relação ao uso desse tipo de tecnologia no ambiente de cultivo de microalgas, reduzindo a carga de trabalho repetitivo e manual do operador, aumentando a produtividade e contribuindo para a viabilização dos processos industriais que envolvem a produção da biomassa de microalgas