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This paper presents an open platform developed for the teaching of Chemical Processes stressing the synergistic effects of combining in the same platform different tools and also different subjects. The benefit for the students of the approach followed is discussed, namely on what concerns knowledge integration. The results of a questionnaire which has been filled by the students during the last four school years are presented. Access to the platform is continuously monitored and will be reported here. [ABSTRACT FROM AUTHOR]

As a complement to the teaching of university students, the use of web based tools enhances students' autonomy, helps in dealing with different learning rhythms and allows reaching students in different locations. Moreover, the web can also be used to attract youngsters (basic and secondary school students) to science subjects. All these functions have been combined in a single web platform "LABVIRTUAL", based in the Chemical Engineering Department of the University of Coimbra. Even if the Portal was developed for the Teaching of Chemical Processes, a specific section directed to the secondary school students has been created as well, grounded on the basic concepts they acquire at the secondary level. In addition, the portal possesses an area dedicated to the understanding of Chemical Engineering. By guiding the secondary school students to the use of these tools, they are led to understand the connection between Engineering (Chemical Engineering) and the basic phenomena they are studying. Moreover, the proximity factor can contribute to rouse the curiosity of the users to search for more advanced information about Chemical Engineering science and applications. This approach may motivate them to engineering subjects and also to raise their interest in the study of basic science subjects for which they start finding a practical application. [ABSTRACT FROM AUTHOR]

The article examines the effect of a nonionic cosurfactant on the rheology of poly(vinyl chloride) plastisol. Many aspects of the formulations, such as concentration of each component and temperature, affect the rheology of poly(vinyl chloride) plastisols. The study shows that the addition of an ester of sorbitan with a low hydrophilic-lipophilic balance can promote an aggregation effect in the latex that will affect the rheological behavior of the paste. It also shows that the cosurfactant can affect the viscoelastic behavior of the plastisols.

This work presents the production of multimedia tools for distance learning about nanoparticles characterization. The module is fundamentally based on hypermedia contents and can be included in a course delivered in an eor b-learning format. Hypermedia can include several interactive multimedia contents such as interactive video, hypertext, photos, audio, animations or computer graphics, which can be combined among them. In this work the objective was to develop an interactive video to explain the nanoparticles characterization using dynamic light scattering. This option allows the user to choose the better strategy to learn about the measuring technique, since the video is prepared for interaction and offers the access to complementary information using different hypermedia contents. These aspects are particularly important for lifelong learning courses, dedicated to users already in the job market, for whom the access to real laboratories can be more difficult and restricted. [ABSTRACT FROM AUTHOR]

Understanding the inherent toxicity of water-soluble synthetic polyelectrolytes is critical for adequate risk management as well as enhancing product design when biological activity is a key performance index (e.g. for application in biofouling bivalves' control). The toxicity of two cationic acrylamide copolymers with different chain branching degree was evaluated. Standard ecotoxicity tests were conducted with microalgae and daphnids. The susceptibility of Corbicula fluminea, as a biofouling bivalve, was also evaluated. The effect of polyelectrolyte on the test media viscosity and the polymer chain size distributions under the experimental conditions were also examined. The susceptibility of the microalgae to both polymers was similar. As the complexity and size of the test organisms increased, differences in toxicity due to different chain architecture were noticeable. The more branched polymer was significantly less toxic to both daphnids and the bivalves, which could be linked to the distinctive features of its bimodal size chain distribution. This architecture resulted in both more compact globular molecules and the formation of aggregates, which reduce the polymer interaction with the biological surfaces. The results of this study promote the incorporation of environmental considerations in polyelectrolyte development and contribute to the design of improved solutions for controlling biofouling bivalves. [ABSTRACT FROM AUTHOR]

The influence of precipitated calcium carbonate (PCC) characteristics on the flocculation process and flocs structure was investigated in the presence of a linear, high molecular weight, cationic polyacrylamide of high charge density. For that, a commercial PCC sample was used, either as supplied (original PCC) or after a washing process (treated PCC). The PCC samples were characterised, and the flocculation process, for different flocculant concentrations, was monitored using the light diffraction scattering technique (LDS). Flocs structure was evaluated by determining the mass fractal dimension of the flocs. It was found that the particle size of the original PCC was larger than that of the PCC submitted to the cleaning process. As a consequence, the optimum flocculant dosage was lower for the original PCC than for the treated PCC. Despite the kinetics of flocculation being independent of the differences in the PCC samples, the flocs compactness at the end of flocculation was higher in the case of the original PCC, resulting in more resistant flocs to shearing. The results showed that the PCC characteristics affect mainly the optimum flocculant dosage, the flocs structure and, thus, the flocs resistance and their reflocculation capability. [ABSTRACT FROM AUTHOR]

Wood from invasive tree species Acacia dealbata and Ailanthus altissima was used to produce high value-added nanocellulose. Firstly, bleached pulps were produced from the wood of these tree species after kraft cooking. Afterwards, the resultant pulps were pre-treated by TEMPO-mediated oxidation (Acacia dealbata) or enzymatic hydrolysis (Ailanthus altissima) followed by high-pressure homogenization. Hydrogels were obtained and characterized for their main physical and chemical properties, including rheology measurements. After freeze-drying, the surface properties of the materials were evaluated by inverse gas chromatography. Results showed that nano/micro fibrils could be obtained from the wood of these invasive species. Rheometry studies showed that Acacia-TEMPO cellulose nanofibrils form strong gels with high yield stress point and viscosities (reaching ca. 100,000 Pa·s). Additionally, the surfaces of the obtained nanocelluloses showed a dispersive component of the surface energy near 40 mJ/m 2 and a prevalence of the Lewis acidic character over the basic one, as typical for cellulose-based materials. Finally, films with good mechanical and optical properties could be obtained from the cellulose hydrogels. Acacia-TEMPO film (produced by filtration/hot pressing) showed a tensile strength of 79 MPa, Young's modulus of 7.9 GPa, and a transparency of 88%. The water vapor barrier, however, was modest (permeability of 4.9 × 10 -6 g/(Pa·day·m))., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The present work intends to study the variations in the rheological properties and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils (CNF) aqueous suspensions, as a function of changes in concentration and systematic changes in the pH, by addition of acids with different anions. It was found that CNF suspensions form strong gels at mass fractions higher than 0.35 % and the gel point is ca. 0.18 %. On the other hand, aggregation is enhanced at acidic pH conditions due to lower charge repulsion among fibrils, leading to an increase of the suspension viscosity. However, distinct rheological behaviours were presented by CNF suspensions as different acids were applied. It was found that phosphate ions resulted in significant aggregation leading to formation of particles of large size and very strong gels, at pH 2.3; distinctly, the presence of acetate ions resulted in lower aggregation, lower particle size and weaker gels, at the same pH value., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Aiming at contributing new insights into the effects of nanomaterials (NMs) in the terrestrial ecosystem, this study evaluated the impacts of organic nano-vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide (SDS/DDAB) on the emergence and growth of plant seeds, and on the avoidance and reproduction of soil invertebrates. For this purpose several ecotoxicological assays were performed with different test species (terrestrial plants: Zea mays, Avena sativa, Brassica oleracea and Lycopersicon esculentum; soil invertebrates: Eisenia andrei and Folsomia candida). A wide range of SDS/DDAB concentrations were tested, following standard protocols, and using the standard OECD soil as a test substrate (5% of organic matter). The aqueous suspensions of SDS/DDAB, used to spike the soils, were characterised by light scattering techniques for hydrodynamic size of the vesicles, aggregation index, polydispersity index, zeta potential and surface charge. The SDS/DDAB concentrations in the test soil were analysed by HPLC-UV at the end of the assays. Invertebrate species were revealed to be sensitive to nano-SDS/DDAB upon immediate exposure to freshly spiked soils. However, the degradation of SDS/DDAB nano-vesicles in the soil with time prevented the occurrence of significant reproduction effects on soil invertebrates. Plants were not particularly sensitive to SDS/DDAB, except B. oleracea (at concentrations above 375 mg kg(-1)dw). The results gathered in this study allowed a preliminary determination of a risk limit to nano-SDS/DDAB. The low toxicity of SDS/DDAB nano-vesicles could be explained by its high and fast degradation in the soil. The soil microbial community could have an important role in the fate of this NM, thus it is of remarkable importance to improve this risk limit by taking into account specific data addressing this community., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The rapid development of nanoparticles (NP) for industrial applications and large-volume manufacturing, with its subsequent release into the environment, raised the need to understand and characterize the potential effects of NP to biota. Accordingly, this work aimed to assess sublethal effects of five NP to the white-rot fungi species Trametes versicolor, Lentinus sajor caju, Pleurotus ostreatus, and Phanerochaete chrysosporium. Each species was exposed to serial dilutions of the following NP: organic-vesicles of SDS/DDAB and of Mo/NaO; gold-NP, quantum dot CdSe/ZnS, and Fe/Co. Fungi growth rate was monitored every day, and at the end of assay the mycelium from each replicate was collected to evaluate possible changes in its chemical composition. For all NP-suspensions the following parameters were characterized: hydrodynamic diameter, surface charge, aggregation index, zeta potential, and conductivity. All tested NP tended to aggregate when suspended in aqueous media. The obtained results showed that gold-NP, CdSe/ZnS, Mo/NaO, and SDS/DDAB significantly inhibited the growth of fungi with effects on the mycelium chemical composition. Among the tested NP, gold-NP and CdSe/ZnS were the ones exerting a higher effect on the four fungi. Finally to our knowledge, this is the first study reporting that different types of NP induce changes in the chemical composition of fungi mycelium., (Copyright © 2013 Elsevier B.V. All rights reserved.)

This study aimed to evaluate sublethal effects of a short-term exposure (96 h) to titanium silicate nanoparticles (TiSiO(4)-NP) on Pelophylax perezi tadpoles. Tadpoles were exposed to five concentrations of TiSiO(4)-NP (8.2, 10.2, 12.8, 16 and 20 mg/L) plus a control. Effect criteria were: mortality, cholinesterases, glutathione S-transferases, lactate dehydrogenase, and catalase activities, and alanine and lactate contents. Light scattering was used for physical characterization of TiSiO(4)-NP suspensions, revealing a high aggregation state of the NP, consistent with low z-potential values (<30 mV). Mortality among TiSiO(4)-NP treatments was <11%. Significant differences relatively to the control were observed at the biochemical level (for CAT and LDH) and in lactate and alanine contents, which may end-up in increased oxidative stress. Overall, some of the monitored endpoints suggest metabolic alterations in TiSiO(4)-NP exposed tadpoles, highlighting the potential of TiSiO(4)-NP long-term effects on these organisms., (Copyright © 2012 Elsevier B.V. All rights reserved.)

This study aimed to evaluate the toxicity and genotoxicity of soils, and corresponding elutriates, contaminated with aqueous suspensions of two organic (vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide and of monoolein and sodium oleate) and five inorganic nanoparticles (NPs) (TiO(2), TiSiO(4), CdSe/ZnS quantum dots, Fe/Co magnetic fluid and gold nanorods) to Vibrio fischeri and Salmonella typhimurium (TA98 and TA100 strains). Soil samples were tested 2h and 30 days after contamination. Suspensions of NPs were characterized by Dynamic Light Scattering. Soils were highly toxic to V. fischeri, especially after 2h. After 30 days toxicity was maintained only for soils spiked with suspensions of more stable NPs (zeta potential>30 mV or <-30 mV). Elutriates were particularly toxic after 2h, except for soil spiked with Fe/Co magnetic fluid, suggesting that ageing may have contributed for degrading the organic shell of these NPs, increasing the mobility of core elements and the toxicity of elutriates. TA98 was the most sensitive strain to the mutagenic potential of soil elutriates. Only elutriates from soils spiked with gold nanorods, quantum dots (QDs) and TiSiO(4) induced mutations in both strains of S. typhimurium, suggesting more diversified mechanisms of genotoxicity., (Copyright © 2011 Elsevier B.V. All rights reserved.)