Editorial for Special Issue “Advances in Experimental and Computational Rheology”

Rheology, defined as the science of deformation and flow of matter, is a multidisciplinary scientific field, covering both fundamental and applied approaches [...

Editorial for Special Issue “Advances in Experimental and Computational Rheology, Volume II”

Rheology, defined as the science of the deformation and flow of matter, is a multidisciplinary scientific field, covering both fundamental and applied approaches [...

Experimental study and modeling of rheological and mechanical properties of NHL grouts

The support from the strategic project Pest-C/CTM/LA0025/2011This paper aims to model the effect of grout composition on properties of two natural hydraulic lime (NHL) grouts based on the correlation between grout rheometer results and simple flow tests. First, the effects of water:binder ratio and superplasticizer dosage on its rheological properties and flowability were analyzed. Dosage of superplasticizer and water:binder ratio were varied from 0.6 to 1.2% (by mass of binder) and 0.45-0.55, respectively. A good correlation between classical flow tests and the rheological properties was obtained. Then, statistical models were formulated in order to estimating the grout parameters, such as plastic viscosity and yield stress just by performing simple flow tests. The models coefficients were calculated using multiple regression analysis. The statistical modeling results indicated that the properties of the grouts studied are linearly related to water:binder ratio, superplasticizer dosage, and specific surface area of natural hydraulic limes. Finally, the accuracy of the models was experimentally confirmed using random grout compositions. The predicted-to-measured ratio ranged from 0.97 to 1.08, indicating a good agreement between the confirmation results and the expected results from the statistical models.authorsversionpublishe

Effects of polypropylene fibers and measurement methods on the yield stress of grouts for the consolidation of heritage masonry walls

FeDeR funds through the COMPeTe 2020 Programme under the project number POCI-01-0145-FeDeR-007688.The injection of grouts is a consolidation technique suitable for overcoming the structural deterioration of old stone masonry walls. Grouting operations involve introducing a suspension (grout) into a masonry core with the aim of improving the load capacity of the wall, as well as reducing its brittle mechanisms. The yield stress of injection grouts will affect the injection pressure and their flow inside the masonry. However, the determination of some rheological properties such as yield stress in hydraulic grout is challenging, due to the combined effects of hydration reactions and interactions between the particles present in the suspension. In this study, the determination of the yield stress of natural hydraulic lime-based grouts with polypropylene fibers was carried out. The changes in yield stress with time, fibers content and hydration were evaluated by two measurement methods using a rotational rheometer. Additionally, the static and dynamic yield stress as well as the critical shear-strain rate were determined, which provided useful information on the grout design in order to achieve successful grouting operations.publishersversionpublishe

DOE Production Optimization and Drug Delivery

Funding Information: This work is funded by National Funds through the FCT-Fundação para a Ciência e a Tecnologia, I.P., under the scope of the projects UID/50025/2020-2023 and LA/0037/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication-i3N. H.C. acknowledges FCT for the PhD grant with reference SFRH/BD/144986/2019 and P.S. acknowledges the individual contract CEECIND.03189.2020. Publisher Copyright: © 2023 by the authors.Gellan gum is a biocompatible and easily accessible polysaccharide with excellent properties to produce microparticles as drug delivery systems. However, the production methods often fail in reproducibility, compromising the translational potential of such systems. In this work, the production of gellan gum-based microparticles was optimized using the coaxial air flow method, and an inexpensive and reproducible production method. A design of experiments was used to identify the main parameters that affect microparticle production and optimization, focusing on diameter and dispersibility. Airflow was the most significant factor for both parameters. Pump flow affected the diameter, while the gellan gum/alginate ratio affected dispersibility. Microparticles were revealed to be sensitive to pH with swelling, degradation, and encapsulation efficiency affected by pH. Using methylene blue as a model drug, higher encapsulation, and swelling indexes were obtained at pH 7.4, while a more pronounced release occurred at pH 6.5. Within PBs solutions, the microparticles endured up to two months. The microparticle release profiles were studied using well-known models, showing a Fickian-type release, but with no alteration by pH. The developed microparticles showed promising results as drug-delivery vehicles sensitive to pH.publishersversionpublishe

Injectable composite systems based on microparticles in hydrogels for bioactive cargo controlled delivery

Funding Information: Funding: This work is funded by FEDER funds through the COMPETE 2020 Program and National Funds through FCT—Portuguese Foundation for Science and Technology under the project POCI— 01-0145-FEDER-007688 (Reference UID/CTM/50025) and PTDC/CTMCTM/30623/2017 (DREaMM). H.C. also acknowledges FCT for the PhD grant with reference SFRH/BD/144986/2019. P.S. also acknowledges the individual contract CEECIND.03189.2020. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Engineering drug delivery systems (DDS) aim to release bioactive cargo to a specific site within the human body safely and efficiently. Hydrogels have been used as delivery matrices in different studies due to their biocompatibility, biodegradability, and versatility in biomedical purposes. Microparticles have also been used as drug delivery systems for similar reasons. The combination of microparticles and hydrogels in a composite system has been the topic of many research works. These composite systems can be injected in loco as DDS. The hydrogel will serve as a barrier to protect the particles and retard the release of any bioactive cargo within the particles. Additionally, these systems allow different release profiles, where different loads can be released sequentially, thus allowing a synergistic treatment. The reported advantages from several studies of these systems can be of great use in biomedicine for the development of more effective DDS. This review will focus on in situ injectable microparticles in hydrogel composite DDS for biomedical purposes, where a compilation of different studies will be analysed and reported herein.publishersversionpublishe

Os Huni Kuin entre o regime do seringal e o regime tutelar

Desde fins do século XIX as populações indígenas do Acre foram tratadas como empecilho na extração da borracha, ou “ouro negro” como ficou conhecida. Os exploradores visando expulsar para longe os indígenas de seus próprios territórios e tornar estas terras colocações de seringais, organizavam expedições punitivas chamadas correrias, que consistia na matança de indígenas, com a captura de mulheres e crianças. As populações que sobreviveram a este morticínio permaneceram nos seringais como trabalhadores de um sistema que não apenas explorava a sua mão de obra, como também censurava toda forma de expressão cultural. Assim os indígenas atravessaram dois regimes o seringal, e o regime de tutela das políticas indigenistas, inicialmente como Serviço de Proteção ao Índio (SPI) e depois como Fundação Nacional do Índio (Funai). Na perspectiva do pensamento decolonial este trabalho procura evidenciar a agência indígena na superação da tutela no seringal e nas negociações políticas com a Funai que os Huni Kuin utilizaram para conquistar seu território. As fontes utilizadas são arquivos do Serviço Nacional de Informação (SNI) que pertencem ao projeto Memórias Reveladas

Optimization of Hydrogel Composition based on Rheological Behavior

Funding Information: This work was financed by national funds from FCT-Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication–i3N. H.C. acknowledges FCT for the PhD grant with reference SFRH/BD/144986/2019 and P.S. acknowledges the individual contract CEECIND. 03189.2020. Publisher Copyright: © 2022 by the authors.Due to the high complexity of some treatments, there is a need to develop drug-delivery systems that can release multiple drugs/bioactive agents at different stages of treatment. In this study, a thermoresponsive injectable dual-release system was developed with gellan gum/alginate microparticles (GG:Alg) within a thermoresponsive Pluronic hydrogel composed of a mixture of Pluronic F127 and F68. The increase in F68 ratio and decrease in F127 lead to higher transition temperatures. The addition of the GG:Alg microparticles decreased the transition temperatures with a linear tendency. In Pluronic aqueous solutions (20 wt.%), the F127:F68 ratios of 16:4 and 17:3 (wt.%:wt.%) and the addition of microparticles (up to 15 wt.%) maintained the sol–gel transition temperatures within a suitable range (between 25 °C and 37 °C). Microparticles did not hinder the injectability of the system in the sol phase. Methylene blue was used as a model drug to evaluate the release mechanisms from microparticles, hydrogel, and composite system. The hydrogel delayed the release of methylene blue from the microparticles. The hydrogel loaded with methylene blue released at a faster rate than the microparticles within the hydrogel, thus demonstrating a dual-release profile.publishersversionpublishe

Contribution to the design of hydraulic lime-based grouts for masonry consolidation

Grout is a concentrated suspension that can be employed for the homogenisation and consolidation of systems presenting pores, voids and cracks, such as inner core of old stone masonries. A grout should be well conceived, taking into account the optimisation of its performance; this means that simple binder and water formulations prove to be inadequate. Hence, the effect of different admixtures and pozzolans, which are traditionally used in concrete, on the fresh and hardened properties of hydraulic lime grouts, were investigated. Hydraulic lime binder plays a role of great importance in the rehabilitation of historic structures, due to its compatibility with pre-existing materials, like mortars. However, hardly any information is presently known regarding the effect of these materials on the behaviour of hydraulic lime grouts. The improvement of their properties through the use of these products is still an open field. Hence, and as a first step, the prediction of grout properties in a laboratory setting were made. The results summarised in this paper are part of a large research project and precede the fine tuning of grout composition according to the characteristics of the masonry to which such a grout is to be injected

Polyurea dendrimer for efficient cytosolic siRNA delivery

PEst-OE/SAU/UI0009/2013 SFRH/BD/62957/2009The design of small interfering RNA (siRNA) delivery materials showing efficacy in vivo is at the forefront of nanotherapeutics research. Polyurea (PURE-type) dendrimers are 'smart' biocompatible 3D polymers that unveil a dynamic and elegant back-folding mechanism involving hydrogen bonding between primary amines at the surface and tertiary amines and ureas at the core. Similarly, to a biological proton pump, they are able to automatically and reversibly transform their conformation in response to pH stimulus. Here, we show that PURE-G4 is a useful gene silencing platform showing no cellular toxicity. As a proof of concept we investigated the PURE-G4-siRNA dendriplex, which was shown to be an attractive platform with high transfection efficacy. The simplicity associated with the complexation of siRNA with polyurea dendrimers makes them a powerful tool for efficient cytosolic siRNA delivery.authorsversionpublishe