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- Comparison of accelerated laboratory curing and maturation under uncontrolled conditions of gravel emulsions using a nonlinear weighted least-squares predictive modelPublication . Rodríguez Pasandín, Ana María; Galán-Diaz, Juan José; Silva, Luís Manuel Sousa da; Orosa Iglesias, Pablo; Pérez Pérez, IgnacioCold-asphalt mixtures (CAMs) are evolved materials whose mechanical strength increases with their maturation. The relationship between CAM field maturation and laboratory-accelerated cure procedures is not well understood. Furthermore, there is controversy on the recommended methodology for laboratory-accelerated cure. So, in this work, the accelerated curing protocol for a CAM-type gravel emulsion was examined, and its uncontrolled maturation and performance were contrasted. For this, the mixture was subjected to either accelerated curing (from 0 to 7 days in a 50 °C oven) or natural curing (from 0 days to 6 months at 20 3 °C in the laboratory and at an unfixed temperature outside the laboratory). We analysed, as functions of time, the moisture, indirect tensile stiffness modulus (ITSM), and moisture damage resistance. A curing protocol of 2 days at 50 °C yielded ITSM values closer to those obtained under uncontrolled conditions. Nevertheless, total maturation of the mixture was achieved after 3.5 days of curing. The nonlinear weighted least-squares method yielded an expression that better predicted the performance of the gravel emulsion for the first six months of life. The model parameters were easily fitted using ITSM measurements derived from samples cured for 2 days in a 50 °C oven.
- Kinetic and equilibrium adsorption parameters estimation based on a heterogeneous intraparticle diffusion modelPublication . Silva, Luís M. S.; Muñoz-Peña, Maria J.; Domínguez-Vargas, Joaquín R.; González, Teresa; Cuerda-Correa, Eduardo M.In this work, a commercial resin with a well-developed internal pore structure was chosen to adsorb four parabens used as probe molecules. The main novelty was to propose and validate a phenomenological transient adsorption model based on conservation law in both phases coupled with Langmuir’s equilibrium law and Fick’s mass transfer rate law inside the pores. With such an aim, a heterogeneous three-parameter intraparticle diffusion model, IPDM, was formulated, and its numerical solution was fitted to time-dependent concentration data by minimizing the sum of squared residuals. Equilibrium constants were also predicted by fitting Langmuir isotherm to equilibrium data. A monolayer capacity of 0.81 mmol/g was calculated for the four parabens regardless of the number of carbons in the ester group. With the optimal parameters values from the IPDM fitting process, a system of ODEs comprising local sensitivity coefficients as dependent variables was solved to compute the parameters’ variance-covariance matrix and infer their ranges for a 95% marginal confidence interval. In order to test the validity of the proposed model, an attempt to crosscheck between the parameters obtained by the estimation of the equilibrium related parameter, κ, and the modified capacity parameter, and the ones obtained by fitting the Langmuir’s isotherm to equilibrium data was carried out. As far as equilibrium related parameters concern, there is a relative agreement inside the limits of the confidence range between the estimated values of the amount adsorbed in equilibrium with initial bulk solution concentration, q0, and Langmuir’s equilibrium constant, K, adjusted to kinetic and equilibrium data, independently. Additionally, the order of magnitude of pore diffusivity obtained in this work is in accordance with the one predicted by Wilke-Chang correlation and is inversely proportional to the van der Waals volume raised to the power 0.53 in close agreement with the literature.
- A factorial design for optimization of the analytical variables on the development of a genoassay for the transgenic soybean detectionPublication . Ramos-Jesus, J.; Barroso, M. Fátima; M. S. Silva, Luís; Pereira, C.; Freire, C.; de-los- Santos-Álvarez, N.; Leite, José Roberto S.A.; Delerue-Matos, CristinaAt the laboratory, analytical method optimizations are performed to achieve the maximum sensitivity and selectivity. Routinely, this procedure is carried out by optimizing one-factor-at-a-time approach until there is no further improvement, where each experimental parameter is optimized separately and independently of the other factors.
- Minerals and fatty acids profile of Northwest Portuguese coast shrimpsPublication . Maia, Maria Luz; Almeida, Agostinho; Soares, Cristina; Silva, Luís M. S.; Delerue-Matos, Cristina; Calhau, Conceição; Domingues, ValentinaTwo shrimp species were sampled in different seasons and locations on Portuguese coast. Their fatty acid content and 28 essential, probably essential and potentially toxic/non-essential elements were quantified. A 100 g serving of shrimp muscle from the Portuguese coast provides 78 % of the recommended daily intake. Both species presented low ω-6/ω-3 ratio, 0.15 for P. serratus and 0.23 for P. varians, respectively. The quality indices presented also good values for shrimp samples, hypocholesterolemic/hypercholesterolemic ratio (HH) was 2.60 for P. serratus and 2.55 for P.varians. The index of thrombogenicity (IT) were 0.24 and 0.25 for P. serratus and P. varians, respectively and index of atherogenicity (IA) was 0.41 and 0.43 for P. serratus and P. varians, respectively. The Mg, Na, K, Ca, I, Cr, Cu and Se in shrimp samples analyzed can provide more than 5 % of the Recommended Dietary Allowance (RDA)/ Adequate Intake (AI). The best nutritional Ca/Mg ratio was found in P. serratus (1.7). Portuguese shrimp has proven to be a good dietary source of EPA, DHA and some essential elements, also Target Hazard Quotient (THQ) and risk-benefit evaluation shown that there is no significant danger associated with the consumption of Portuguese shrimp
- Evaluation of the Resilient Modulus of Hot-Mix Asphalt Made with Recycled Concrete Aggregates from Construction and Demolition WastePublication . Galan, Juan J.; Silva, Luís M. S.; Pasandín, Ana R.; Pérez, IgnacioThis paper reports the influence of the percentage of recycled aggregate (RCA) fromconstruction and demolition waste (C&DW) together with the percentage of binder (L), curing time(t) and temperature (T) of the samples on the stiffness of a hot asphalt mixture. The study was carriedout using the response surface methodology (RSM). The resilient modulus was chosen to estimate thestiffness of the mixture. The percentages of RCA studied were 0% (control), 5%, 10%, 20% and 30%,whilst 3.5%, 4% and 4.5% were those chosen for the binder content. Before compacting the samples,they were left into the oven to cure. Curing time, or pretreatment time, were set at 0 (control), 2 and4 h. The samples were subjected to temperatures of 0, 10 and 20◦C. The natural aggregate is of thehornfels type. All the specimens studied showed high stiffness at low temperatures. According tothis research, temperature proved to be the most influential factor on the decrease in the resilientmodulus and, conversely, the percentage of recycled aggregate is not a significant factor in the rangeof values studied.
- Life cycle analysis of a particleboard based on cardoon and starch/chitosanPublication . Mata, Teresa Margarida; Freitas, Clara; Silva, Gabriela Ventura; Monteiro, Sandra; Martins, Jorge Manuel; Carvalho, Luísa Hora de; Silva, Luís Manuel; Martins, Antonio AreosaThis work analyzes the life cycle environmental impacts of producing a particleboard based on cardoon fibers and a starch/chitosan adhesive from a “cradle-to-gate” perspective, considering the following life cycle steps: raw material production, adhesive preparation (component mixing and heating), cardoon fiber preparation (crushing and sieving), adhesive and fiber mixing, hot-pressing and final processing. The functional unit is a particleboard with the dimensions of 220 × 220 × 16 mm3. For the life cycle inventory, experimental data obtained from the production of particleboard on a pilot scale were used. The Aspen Plus V9 software was used to simulate the heating process in the manufacture of the biological adhesive and obtain the data associated with this stage. Portuguese or European conditions were considered for the background processes, using data from the EcoInvent V3.5 LCI database. The environmental impacts were quantified using the RECIPE methodology. To complement the study, the VOCs present in the panel were analyzed using the “active headspace” technique. The results show that for most of the environmental impact categories, energy consumption is dominant, followed by starch and chitosan production. Using fully renewable electricity produced in photovoltaic panels, instead of the Portuguese electricity mix, significantly reduces the impacts in most of the environmental impact categories, for example, the carbon footprint is reduced by 34%. Future studies will analyze how the environmental impacts can be further reduced, and how process scale-up may influence them.
- Optimization of the Ion Source-Mass Spectrometry Parameters in Non-Steroidal Anti-Inflammatory and Analgesic Pharmaceuticals Analysis by a Design of Experiments ApproachPublication . Paíga, Paula; Silva, Luís M. S.; Delerue-Matos, CristinaThe flow rates of drying and nebulizing gas, heat block and desolvation line temperatures and interface voltage are potential electrospray ionization parameters as they may enhance sensitivity of the mass spectrometer. The conditions that give higher sensitivity of 13 pharmaceuticals were explored. First, Plackett-Burman design was implemented to screen significant factors, and it was concluded that interface voltage and nebulizing gas flow were the only factors that influence the intensity signal for all pharmaceuticals. This fractionated factorial design was projected to set a full 2(2) factorial design with center points. The lack-of-fit test proved to be significant. Then, a central composite face-centered design was conducted. Finally, a stepwise multiple linear regression and subsequently an optimization problem solving were carried out. Two main drug clusters were found concerning the signal intensities of all runs of the augmented factorial design. p-Aminophenol, salicylic acid, and nimesulide constitute one cluster as a result of showing much higher sensitivity than the remaining drugs. The other cluster is more homogeneous with some sub-clusters comprising one pharmaceutical and its respective metabolite. It was observed that instrumental signal increased when both significant factors increased with maximum signal occurring when both codified factors are set at level +1. It was also found that, for most of the pharmaceuticals, interface voltage influences the intensity of the instrument more than the nebulizing gas flowrate. The only exceptions refer to nimesulide where the relative importance of the factors is reversed and still salicylic acid where both factors equally influence the instrumental signal. Graphical Abstract ᅟ.