Silicon Carbide as Base Material for MEMS Sensors of Aerospace Use: An Overview

This paper discusses the use of silicon carbide (SiC), in bulk and thin-film form, in MEMS (Micro-Electro-Mechanical Systems) sensors for extreme environment applications, especially in aerospace. The physical and chemical properties of SiC that make it a suitable material for electronic devices and sensors are described. Concepts, developments and applications of MEMS technology are presented. An overview of the current stage of development of SiC-based MEMS sensors and an analysis of research conducted in this area in Brazil and abroad, both in universities and industries are also presented. The recent progress made, difficulties encountered and the impact of these investigations are discussed as well as the outlook for the near future.Este artigo discute o emprego do carbeto de silício (SiC), na forma de substrato e filme fino, em sensores MEMS (Micro-Electro-Mechanical Systems) para aplicações em ambientes sujeitos a condições extremas, especialmente no setor aeroespacial. As propriedades físicas e químicas do SiC que o tornam um material adequado para dispositivos eletrônicos e sensores são descritas. Os conceitos, evolução e aplicações da tecnologia MEMS são apresentados. Uma visão geral sobre o estágio atual de desenvolvimento de sensores MEMS baseados em SiC e uma análise das pesquisas realizadas nesta área no exterior e no Brasil, tanto nas universidades quanto nas indústrias, são também apresentadas. Os recentes avanços alcançados, as dificuldades encontradas e o impacto dessas pesquisas são discutidos, bem como as perspectivas para um futuro próximo.FATEC CEETEPS Departamento de Ensino GeralUNIVAP Instituto de Pesquisa e DesenvolvimentoUNIFESP Instituto de Ciência e TecnologiaUNIFESP, Instituto de Ciência e TecnologiaSciEL

A HPLC‐DAD method for identifying and estimating the content of fucoxanthin, β‐carotene and chlorophyll a in brown algal extracts

Seaweeds are photosynthetic organisms that have high contents of pigments. The coloration of each alga is defined by the content and combination of pigments synthesized, which varies among species and environmental conditions. The most abundant pigments in algae are chlorophylls and carotenoids, lipophilic molecules that can be used as natural colorants and have high acceptance by consumers. In this work, a simple and short hands-on time HPLC-DAD method for identifying and estimating the pigment content of algal extracts, specifically fucoxanthin, β-carotene and chlorophyll a was carried out. Using this optimized method, a pigment screening was performed on the ethanolic extracts obtained by ultrasound-assisted extraction from nine brown algal from the Atlantic coastline: Ascophyllum nodosum, Bifurcaria bifurcata, Fucus spiralis, Himanthalia elongata, Laminaria saccharina, Laminaria ochroleuca, Pelvetia canaliculata, Sargassum muticum and Undaria pinnatifida. HPLC results permitted to highlight L. saccharina and U. pinnatifida as promising sources of these three target pigments containing a total amount of 10.5 – 11.5 mg per gram of dry weight. Among them, the most abundant one was fucoxanthin, an added-value compound with a high potential to be commercially exploited by different industries, such as the food, cosmetic, and pharmaceutical sectors.The research leading to these results was supported by MICINN sup- porting the Ramón y Cajal grant for M.A. Prieto (RYC-2017-22891), the FPU grant for A. Carreira-Casais (FPU2016/06135); and by Xunta de Galicia for supporting the post-doctoral grant of M. Fraga-Corral (ED481B-2019/096). The research leading to these results was sup- ported by the European Union through the “NextGenerationEU ”pro- gram supporting the “Margarita Salas ”grant awarded to P. Garcia- Perez. Authors are grateful to AlgaMar company ( www.algamar.com ) for the collaboration and algal material provision. This research was funded by the Ibero-American Program on Science and Technology (CYTED —AQUA-CIBUS, P317RT0003), the Bio Based Industries Joint Undertaking (JU) under grant agreement No 888003 UP4HEALTH Project (H2020-BBI-JTI-2019) that supports the work of C. Lourenço- Lopes. The JU receives support from the European Union’s Horizon 2020 research and innovation program and the Bio Based Industries Consor- tium. The project SYSTEMIC Knowledge hub on Nutrition and Food Se- curity, has received funding from national research funding parties in Belgium (FWO), France (INRA), Germany (BLE), Italy (MIPAAF), Latvia (IZM), Norway (RCN), Portugal (FCT), and Spain (AEI) in a joint ac- tion of JPI HDHL, JPI-OCEANS and FACCE-JPI launched in 2019 un- der the ERA-NET ERA-HDHL (n°696295). The authors would like to thank the EU and FCT for funding through the project PTDC/OCE- ETA/30240/2017- SilverBrain - From sea to brain: Green neuropro- tective extracts for nanoencapsulation and functional food production (POCI-01-0145-FEDER-030240).info:eu-repo/semantics/publishedVersio

Insights into corrosion behaviour of uncoated Mg alloys for biomedical applications in different aqueous media

MgCa and MgGd series of alloys are often reported as promising candidates for biomedical applications. In the present study, cytotoxicity and corrosion behavior of Mg1Ca and Mg10Gd alloys in different electrolytes (NaCl, PBS, MEM) have been investigated in order to make a direct comparison and understand the mechanisms behind their performance. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were employed to analyze corrosion processes depending on media composition, whereas X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate crystalline structure, phase composition and surface morphology of the corroded substrates after immersion in the different electrolytes. Moreover, cytotoxicity of the Mg alloys was assessed using the WST-1 reduction and lactate dehydrogenase (LDH) release assays in L929 mouse fibroblasts. The electrochemical results showed that Mg1Ca has a lower degradation rate when compared to Mg10Gd, due to the lower microgalvanic effects and the presence of Ca as an alloying element. Furthermore, the corrosion activity is reduced in MEM, for both alloys, when compared to NaCl and PBS. The cytotoxicity assays revealed that Mg10Gd was cytotoxic in all the conditions tested, while the toxicity of Mg1Ca was low. Overall, these findings show that Mg1Ca alloy presents a higher corrosion resistance and biocompatibility and is a promising material to be used in biomedical implants.This work was financed by Portugal 2020 through European Regional Development Fund (ERDF) in the frame of Operational Competitiveness and Internationalization Programme (POCI), in the scope of the project MAGICOAT POCI-01-0145-FEDER016597/PTDC/CTM-BIO/2170/2014 and in the scope of the project CICECO - Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/ MCTES. Furthermore, thanks are due to Portuguese Foundation for Science and Technology/MCTES for the financial support through national funds to EPI Unit (UIDB/04750/2020).info:eu-repo/semantics/publishedVersio

Optimisation of reverse osmosis based wastewater treatment system for the removal of chlorophenol using genetic algorithms

YesReverse osmosis (RO) has found extensive applications in industry as an efficient separation process in comparison with thermal process. In this study, a one-dimensional distributed model based on a wastewater treatment spiral-wound RO system is developed to simulate the transport phenomena of solute and water through the membrane and describe the variation of operating parameters along the x-axis of membrane. The distributed model is tested against experimental data available in the literature derived from a chlorophenol rejection system implemented on a pilot-scale cross-flow RO filtration system with an individual spiral-wound membrane at different operating conditions. The proposed model is then used to carry out an optimisation study using a genetic algorithm (GA). The GA is developed to solve a formulated optimisation problem involving two objective functions of RO wastewater system performance. The model code is written in MATLAB, and the optimisation problem is solved using an optimisation platform written in C++. The objective function is to maximize the solute rejection at different cases of feed concentration and minimize the operating pressure to improve economic aspects. The operating feed flow rate, pressure and temperature are considered as decision variables. The optimisation problem is subjected to a number of upper and lower limits of decision variables, as recommended by the module’s manufacturer, and the constraint of the pressure loss along the membrane length to be within the allowable value. The algorithm developed has yielded a low optimisation execution time and resulted in improved unit performance based on a set of optimal operating conditions

Electromagnetic superconductivity of vacuum induced by strong magnetic field

The quantum vacuum may become an electromagnetic superconductor in the presence of a strong external magnetic field of the order of 10^{16} Tesla. The magnetic field of the required strength (and even stronger) is expected to be generated for a short time in ultraperipheral collisions of heavy ions at the Large Hadron Collider. The superconducting properties of the new phase appear as a result of a magnetic-field-assisted condensation of quark-antiquark pairs with quantum numbers of electrically charged rho mesons. We discuss similarities and differences between the suggested superconducting state of the quantum vacuum, a conventional superconductivity and the Schwinger pair creation. We argue qualitatively and quantitatively why the superconducting state should be a natural ground state of the vacuum at the sufficiently strong magnetic field. We demonstrate the existence of the superconducting phase using both the Nambu-Jona-Lasinio model and an effective bosonic model based on the vector meson dominance (the rho-meson electrodynamics). We discuss various properties of the new phase such as absence of the Meissner effect, anisotropy of superconductivity, spatial inhomogeneity of ground state, emergence of a neutral superfluid component in the ground state and presence of new topological vortices in the quark-antiquark condensates.Comment: 37 pages, 14 figures, to appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye

Small, Dense Quark Stars from Perturbative QCD

As a model for nonideal behavior in the equation of state of QCD at high density, we consider cold quark matter in perturbation theory. To second order in the strong coupling constant, $\alpha_s$, the results depend sensitively on the choice of the renormalization mass scale. Certain choices of this scale correspond to a strongly first order chiral transition, and generate quark stars with maximum masses and radii approximately half that of ordinary neutron stars. At the center of these stars, quarks are essentially massless.Comment: ReVTeX, 5 pages, 3 figure

A new set of relativistic screening constants for the screened hydrogenic model

AnewRelativisticScreenedHydrogenicModel has been developed to calculate atomic data needed to compute the optical and thermodynamic properties of high energy density plasmas. The model is based on anewset of universal screeningconstants, including nlj-splitting that has been obtained by fitting to a large database of ionization potentials and excitation energies. This database was built with energies compiled from the National Institute of Standards and Technology (NIST) database of experimental atomic energy levels, and energies calculated with the Flexible Atomic Code (FAC). The screeningconstants have been computed up to the 5p3/2 subshell using a Genetic Algorithm technique with an objective function designed to minimize both the relative error and the maximum error. To select the best set of screeningconstants some additional physical criteria has been applied, which are based on the reproduction of the filling order of the shells and on obtaining the best ground state configuration. A statistical error analysis has been performed to test the model, which indicated that approximately 88% of the data lie within a ±10% error interval. We validate the model by comparing the results with ionization energies, transition energies, and wave functions computed using sophisticated self-consistent codes and experimental data

Effects of parity order and reproductive management on the efficiency of rabbit productive systems.

The aim of this work was to study the effect of parity order and reproductive management systems on rabbit production performance. A total of 73 rabbit does (I group) were submitted to a 35-day intensive rhythm [artificial insemination (AI) on day 4 post-partum (pp) and weaning at 25 days of lactation], and 108 rabbit does (SI group) were submitted to a 42-day semi-intensive rhythm (AI on day 11 pp and weaning at 35 days of lactation) during 9 months. Primiparous does had the lowest live body weight at parturition (P < 0.0001) and at 21 days of lactation (P < 0.0001). They also had lower milk production (P < 0.0001) than does with later parities. I group animals needed a higher number of AI than SI group to become pregnant (1.70 ± 0.03 vs. 1.39 ± 0.03; P < 0.0001: especially after the third). Prolificacy was not affected by the management system. Parturition interval (PI) was longer than expected in both groups [56.0 ± 1.4 and 50.9 ± 1.38 days in I and SI groups, respectively (P < 0.05)]. Mean productivity, estimated as number of weaned rabbits per female and year, was 12 kits higher in rabbit does of the SI group (P < 0.05). From the third parturition onward, an increase in live body weight of kits at different ages was observed. At 21 (P < 0.05) and 25 days of age (P < 0.01), kits from the I group rabbit does weighed more than those from the SI group; however, the latter showed a higher weight at 35 (P < 0.05) and 60 days of age (P < 0.05). Rabbit does with two or three parturitions had higher litter size at 21 and 25 days of age (P < 0.0001 and P < 0.001, respectively). Kit mortality between 21 and 25 days of age and between 35 and 60 days of age was not affected by treatments but was higher in the I group between 25 and 35 days (18.2 vs. 5.03% in the I and SI groups, respectively; P < 0.0001) and as age of does increased (P < 0.05). In light of these results, we could conclude that long term doe reproductive performance is negatively affected and litter viability decreased when using intensive compared to a semi-intensive reproductive management