Filtering the Tau method with Frobenius-Pad\'e Approximants

In this work, we use rational approximation to improve the accuracy of spectral solutions of differential equations. When working in the vicinity of solutions with singularities, spectral methods may fail their propagated spectral rate of convergence and even they may fail their convergence at all. We describe a Pad\'e approximation based method to improve the approximation in the Tau method solution of ordinary differential equations. This process is suitable to build rational approximations to solutions of differential problems when their exact solutions have singularities close to their domain

Biofilm technology : from support design to reactor operation

The aim of this work was to assess the feasibility of a Sequential Batch Biofilm Reactor (SBBR) to perform carbon and nitrogen removal: from support design to reactor operation. The experimental part was conducted in two phases. In the first phase, different supports were tested to select the most suitable one for SBBR operation. In the second phase, the most appropriate support was used in a SBBR to perform carbon and nitrogen removal. The results demonstrate that the support with the highest internal surface area presented a higher biomass accumulation. Time profiles of nitrogen ions and acetate concentration showed the typical behaviour of a SBBR performing carbon and nitrogen removal. Poly-bhydroxybutyrate (PHB) was formed immediately after acetate depletion and was subsequently consumed for biomass growth, owing to the high oxygen concentration in the reactor

Synthesis and degradation of poly-β-hydroxybutyrate in a sequencing batch biofilm reactor

The aim of this work was the study of poly-β-hydroxybutyrate (PHB) formation and degradation in a sequencing batch biofilm reactor (SBBR). The SBBR was operated in cycles comprising three individual phases: mixed fill, aeration and draw. A synthetic substrate solution with acetate and ammonium was used. PHB was formed during the aeration phase immediately after acetate depletion, and was subsequently consumed for biomass growth, owing to the high oxygen concentration in the reactor. It was observed a combination of suspended and biofilm growth in the SBBR with predominance of the fixed form of biomass (506 Cmmol and 2102 Cmmol, respectively). Maximum PHB fraction of suspended biomass (0.13 Cmol/Cmol) was considerably higher than that of biofilm (0.01 Cmol/Cmol). This may possibly be explained by a combination of two factors: lower mass transfer limitation of acetate and higher fraction of heterotrophs in suspended biomass compared to the ones of biofilm.Fundo Europeu de Desenvolvimento Regional (FEDER) - POCI 2010 (POCI/AMB/61155/2004)Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI BD/19687/9

Impact of biofilm growth in the microbial community composition of a sequencing batch reactor

Conventional activated sludge wastewater treatment plants (WWTP) for carbon and nutrient removal operate at high sludge retention time and, consequently, at a low food to microorganisms ratio. While the first condition is favourable for nitrifying bacteria growth, an excessive growth of certain species of filamentous bacteria often occurs in the presence of the second one. Interestingly, no problems with excessive growth of filamentous bacteria have been reported for the activated sludge process when combined with biofilm growth more than a decade ago. In this context, the present work aims to compare the microbial community composition of two sequencing batch reactors (SBRs) operating in the presence and in the absence of biofilm growth, and to correlate microbial composition with the performance of the reactors. Two SBRs with a working volume of 1.5 L were operated in parallel with a constant cycle time of 4 h, a volume exchange ratio of 0.5 L/L and a resulting hydraulic retention time of 8 h. The duration of the individual operating phases was: 5 min fill, 225 min aerated, 5 min settle and 5 min draw. During the aerated phase airflow was applied through membrane diffusers, causing the reactor contents including the carrier bed to circulate. The SBRs were operated with synthetic water containing acetate as the only carbon source and ammonium as nitrogen source. One SBR was operated just with suspended biomass while the second one combined suspended biomass with biofilm cultivation. The biofilm was formed on a new type of polyethylene support developed by University of Minho, consisting of hollow, star-shaped, carriers with 17 mm external diameter and a height of 10 mm. The bed formed by these carriers had a specific surface area of 407 m2/m3, an average porosity of 0.74 and occupied 20 % of the reactor volume. Grab samples were taken and analyzed for acetate using a HPLC system. Observation of the filamentous microbial and microfauna communities was accomplished by microscope inspection at 100 to 1000X magnification, in fresh samples and after Gram and Neisser staining. The microbial community of the SBR operating just with suspended growth was dominated by fungi micelar growth, while in the other reactor the communities were clearly more complex. The incorporation of carriers for biofilm growth in the other SBR apparently suppressed the excessive growth of fungi. Differences in the microfaunas community were also observed, the SBR operating just with suspended growth showing clearly a delay in the microfauna succession comparing to the other reactor. Despite this, acetate was completely removed in both SBRs

High-performance electrochemical immunomagnetic assay for breast cancer analysis

Despite the evolution of targeted therapies in oncology, some challenges such as screening and early diagnosis of cancer-related biomarkers still remain. The analysis of the Human Epidermal growth factor Receptor 2 (HER2) in biological fluids provides essential information for effective treatments. In this work we report the development of an electrochemical immunomagnetic bioassay for the analysis of the extracellular domain of HER2 (HER2-ECD) in human serum and cancer cells. Biomodified carboxylic acid functionalized magnetic beads (COOH-MBs) were used as the capture probe and an antibody labelled with alkaline phosphatase (AP) as the signalling probe. In the presence of HER2-ECD a sandwich complex was formed on the MBs, which were magnetically attracted to the surface of a screen-printed carbon electrode (SPCE). After the addition of 3-indoxyl phosphate and silver ions, used as the enzymatic substrate, the immunological interaction was detected by linear sweep voltammetry. Two linear concentration ranges were established: one between 5.0 and 50 ng/mL and another between 50 and 100 ng/mL. The developed assay provided a clinically useful detection limit (2.8 ng/mL) and has an adequate precision (Vx0 < 5%). The assay provided accurate results and was selective towards the target biomarker. Additionally, CTCs were analysed in human serum and a detection limit of 3 cells/mL was achieved for the HER+ breast cancer cell line SK-BR-3.The authors are grateful for the financial support from the Fundação para a Ciência e a Tecnologia (FCT) / the Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds (Portugal) (LAQV - UID/QUI/50006/2019 and CINTESIS - UID/IC/4255/2019). Maria Freitas is grateful to FCT for her PhD grant (SFRH/BD/111942/2015), financed by POPH- QREN-Tipologia 4.1-Formação Avançada, subsidized by Fundo Social Europeu and the MCTES. The authors are also thankful to Rui Rocha and CEMUP “Centro de Materiais da Universidade do Porto” for the SEM workinfo:eu-repo/semantics/publishedVersio

Implementation of robust multi-objective optimization in the build orientation problem

Additive manufacturing (AM) is an emerging technology to create 3D objects layer-by-layer directly from a 3D CAD model. The build orientation is a critical issue in AM and its optimization will significantly reduce the building costs and improve object accuracy. This paper aims to optimize the build orientation problem of a 3D CAD model using a robust multi-objective approach, taking into account the staircase effect and the support area characteristics. Thus, themain objective is to obtain a robust Pareto optimal front, composed of solutions that are not quite sensitive to perturbations in the variables. In this manner, a set of robust solutions is presented as alternatives and the decision-maker can identify the compromise solutions and choose according to his/her preferences.This work has been developed under the FIBR3D project - Hybrid processes based on additive manufacturing of composites with long or short fibers reinforced thermoplastic matrix (POCI-01-0145-FEDER-016414), supported by the Lisbon Regional Operational Programme 2020, under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work has been supported by FCT - Fundacao para a Ciencia e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020

A genetic algorithm for forest firefighting optimization

In recent years, a large number of fires have ravaged planet Earth. A forest fire is a natural phenomenon that destroys the forest ecosystem in a given area. There are many factors that cause forest fires, for example, weather conditions, the increase of global warming and human action. Currently, there has been a growing focus on determining the ignition sources responsible for forest fires. Optimization has been widely applied in forest firefighting problems, allowing improvements in the effectiveness and speed of firefighters’ actions. The better and faster the firefighting team performs, the less damage is done. In this work, a forest firefighting resource scheduling problem is formulated in order to obtain the best ordered sequence of actions to be taken by a single firefighting resource in combating multiple ignitions. The objective is to maximize the unburned area, i.e., to minimize the burned area caused by the ignitions. A problem with 10 fire ignitions located in the district of Braga, in Portugal, was solved using a genetic algorithm. The results obtained demonstrate the usefulness and validity of this approach.This work has been supported by FCT Fundação para a Ciência e Tecnologia within the R &D Units Project Scope UIDB/00319/2020 and PCIF/GRF/0141/2019: “O3F - An Optimization Framework to reduce Forest Fire” and the PhD grant reference UI/BD/150936/2021

Build orientation optimization of car hoodvent with additive manufacturing

Additive manufacturing is a widely used process consisting in the building of a three-dimensional (3D) object from a model projected on a computer, adding the material layer-by-layer. This technology allows the printing of complex shape objects and is being increasingly adopted by the aircraft industry, medical implants, jewelry, footwear, automotive, fashion products, among others. The build orientation optimization of 3D models has a great influence on costs and surface quality when printing three-dimensional objects. In this work, three build orientation optimization problems are studied: single objective problem, bi-objective problem and many-objective problem. To this end, three quality measures are applied: the support area, the build time and the surface roughness, for the Car Hoodvent model. First, a single-objective optimization problem is presented and solved by the genetic algorithm, obtaining optimal solutions for each objective function. Then, the study of the bi-objective optimization problem is carried out for each pair of two objectives and some representative trade-off solutions are identified. Finally, the study of the many objective optimization problem, considering the three measures optimized simultaneously, is presented with some more optimal solutions found. The bi-objective and many-objective problems are solved by a multi-objective genetic algorithm. For a better analysis and comparison of the solutions found, the Pareto fronts are used, enabling a better visualization of the solutions between the objectives. This study aims to assist the decision-maker in choosing the best part print orientation angles according to his/her preferences. The optimal solutions found confirmed the effectiveness of the proposed approach.info:eu-repo/semantics/publishedVersio

Chromatographic techniques for the determination of free phenol in foundry resins

Phenol is a toxic compound present in a wide variety of foundry resins. Its quantification is important for the characterization of the resins as well as for the evaluation of free contaminants present in foundry wastes. Two chromatographic methods, liquid chromatography with ultraviolet detection (LC-UV) and gas chromatography with flame ionization detection (GC-FID), for the analysis of free phenol in several foundry resins, after a simple extraction procedure (30 min), were developed. Both chromatographic methods were suitable for the determination of phenol in the studied furanic and phenolic resins, showing good selectivity, accuracy (recovery 99–100%; relative deviations <5%), and precision (coefficients of variation <6%). The used ASTM reference method was only found to be useful in the analysis of phenolic resins, while the LC and GC methods were applicable for all the studied resins. The developed methods reduce the time of analysis from 3.5 hours to about 30 min and can readily be used in routine quality control laboratories