Laminados de CFRP pré-tensionados para o reforço à flexão de vigas de betão armado

No presente trabalho explora-se o desempenho de uma nova estratégia de reforço à flexão com laminados de fibras de carbono aplicados sob determinada pré-tensão e segundo a técnica NSM (“Near Surface Mounted”). Para tal foi necessário encontrar e caracterizar as propriedades de um adesivo de cura rápida que permitisse transferir a pré-tensão do laminado para o betão envolvente no mais curto período de tempo possível. O programa experimental que se apresenta neste trabalho é exploratório, pretendendo evidenciar as vantagens e potencialidades desta técnica. O programa é descrito e os resultados são apresentados e analisados

CFRP group effect and interaction between stirrups and strips on the NSM-shear strengthening of RC beams

Available experimental research shows that the technique based on installing Carbon Fibre Reinforced Polymer (CFRP) strips into slits opened on the cover concrete of the beam’s lateral faces, designated as Near Surface Mounted (NSM), is very effective to increase the shear resistance of reinforced concrete (RC) beams. However, recent research has revealed that, in terms of NSM shear strengthening effectiveness, a detrimental effect can occur between existing steel stirrups and applied strips, as well as amongst the strips when the distance between strips, sf, is lower than a certain limit. In the present work, a test setup was developed and an experimental program was carried out to assess the influence of both sf and interaction between existing steel stirrups and strips on the shear strengthening of RC beams. The experimental program is described and the main results are presented and analyzed.(13-05-04-FDR-00031

Preventing microbial infections with natural phenolic compounds

The struggle between humans and pathogens has taken and is continuing to take countless lives every year. As the misusage of conventional antibiotics increases, the complexity associated with the resistance mechanisms of pathogens has been evolving into gradually more clever mechanisms, diminishing the effectiveness of antibiotics. Hence, there is a growing interest in discovering novel and reliable therapeutics able to struggle with the infection, circumvent the resistance and defend the natural microbiome. In this regard, nature-derived phenolic compounds are gaining considerable attention due to their potential safety and therapeutic effect. Phenolic compounds comprise numerous and widely distributed groups with different biological activities attributed mainly to their structure. Investigations have revealed that phenolic compounds from natural sources exhibit potent antimicrobial activity against various clinically relevant pathogens associated with microbial infection and sensitize multi-drug resistance strains to bactericidal or bacteriostatic antibiotics. This review outlines the current knowledge about the antimicrobial activity of phenolic compounds from various natural sources, with a particular focus on the structure-activity relationship and mechanisms of actions of each class of natural phenolic compounds, including simple phenols, phenolic acids, coumarin, flavonoids, tannins, stilbenes, lignans, quinones, and curcuminoids.The authors acknowledge the financial support by the Portuguese Foundation for Science and Technology (FCT) through the doctoral grant and junior research contract with the reference number PD/BD/150521/2019 (K.E.) and CEECIND/01026/2018 (J.M.S.), respectively

Influence of the chloride attack on the post-cracking behavior of Recycled Steel Fiber Reinforced Concrete

The main purpose of the present work is to study the mechanical behavior and durability performance of recycled steel fiber reinforced concrete (RSFRC) under a chloride environment. To this end, the effect of chloride attack on the load-carrying capacity of pre-cracked RSFRC round panels is investigated by performing round panel tests supported on three points (RPT-3ps), considering the influence of the crack width and the fiber distribution/orientation profile. In addition, the influence of the adopted chloride exposure conditions on the post-cracking constitutive laws of the developed RSFRC is also assessed by performing numerical simulations for the prediction of the long-term performance of RSFRC under these aggressive conditions. The tensile stress–crack width relationship of RSFRC is derived by performing an inverse analysis with the RPT-3ps results. The obtained experimental and numerical results show a negligible effect of the chloride attack on the post-cracking behavior of RSFRC for the chloride exposure conditions and pre-crack width levels adopted in this study.This research was funded by C.F. research grant PD/BD/113638/2015 provided by Fundação para a Ciência e a Tecnologia (FCT) through the Doctoral Program in Eco Construction and Rehabilitation–EcoCoRe, and J.B. through the project ICoSyTec (POCI-01-0145-FEDER-027990) financed by FCT and co-funded by FEDER through Operational Competitiveness and Internationalization Programme (POCI)

An experimental study on the corrosion susceptibility of Recycled Steel Fiber Reinforced Concrete

Steel fibers resulting from the industry of tire recycling can be efficiently employed in concrete to improve its mechanical performance, such as post-cracking load bearing and energy absorption capacity. Under chloride attack, an important aspect of Recycled Steel Fiber Reinforced Concrete (RSFRC) durability is its corrosion resistance. However, the insufficient knowledge on this domain contributes for a conservative design philosophy, which can compromise the cost competitiveness of RSFRC and prevent its application in elements where this occurrence, even eventual, is not acceptable. In the present work, an experimental program was performed with the aim of assessing the corrosion susceptibility of RSFRC including the characterization of the micro-mechanical properties and the corrosion resistance of recycled steel fiber (RSF) by means of nano-indentation testing, electrochemical monitoring techniques and scanning electron microscopy (SEM) analysis. The influence of the small rubber debris attached to the RSF surface was also analyzed by using two distinct pre-treatment methods. The adhesive bond behavior between the RSF and the surrounding self-compacting concrete (SCC) matrix was analyzed by performing monotonic RSF pullout tests. Double edge wedge splitting (DEWS) tests were conducted for evaluating the corrosion effects on the post-cracking response of RSFRC.CiviTest Company and the Scientific and Technological Research Assistance Centre (CACTI) of the University of Vigo. The first author would like to thank the FCT for the financial support through the Research Grant PD/BD/113638/2015. The third author acknowledges the grant SFRH/BSAB/114302/2016 provided by FCT. Part of this work is supported by FCT with the reference project UID/EEA/04436/2013, COMPETE 2020 with the code POCI-01- 0145-FEDER-006941. Finally the support of the FCT through the project PTDC/ECM-EST/2635/201

New endoscopic procedure for bladder wall closure: results from the porcine model

Upper urinary tract urothelial carcinomas are usually managed by radical nephroureterectomy (RNU), often followed by intravesical chemotherapy to minimize recurrence. Open surgery is the gold standard procedure for RNU, but it associates with high morbidity, and it has been increasingly replaced by minimally invasive strategies, such as laparoscopy and endoscopy. Although effective, endoscopic ureteral excision leaves the bladder unsutured, increasing the risk of tumor spillage, and precluding the immediate administration of intravesical chemotherapy. Here we describe a new method to close the bladder wall after ureteral excision, using barbed sutures via the endoscopic access. Our results in 8 female pigs demonstrate that this method is effective to close the bladder wall. The procedure was completed in a median time of 24 min, and no adverse events were registered in the follow-up or at the three-week necropsy. This technique improves a previous approach described by our group because the device is more flexible and allows to tie the knots inside the bladder. Barbed sutures have been used in the clinical practice for other types of surgeries, and therefore this method can further be adapted to human patients with no safety concerns. Its use may allow to administer intravesical chemotherapy, which reduces tumor recurrence and improves patient outcomes.The authors acknowledge Ana Goios for support in manuscript writing and technical editing, and for producing original illustrations for Figure 3. Doctoral grant of CUF Jose de Mello Saude

Tailor made degradable ureteral stents from natural origin polysaccharides

A urinary stent is defined as a thin tube, which is inserted in the ureter to prevent or treat the obstruction of urine flow from the kidney. Silicone, latex, polyvinylchloride and polyurethanes are the most widely used materials for the preparation of stents. Nonetheless, severe clinical complications may result from the use of these materials such as fracture, encrustation and infection. In some of the cases, the ureteral stents are temporary and it is often required a second surgery to remove the stent. The main complications with ureteral stents are dislocation, infection, and blockage by encrustation [1]. Recently, a tendency has been noticed favouring less invasive approaches (e.g. pharmacological or catheterization) in treating patients who exhibit symptoms or signs of urinary retention [2]. Currently, nearly 100% of the people who have an urological stent are likely to develop a bacterial infection within 30 days, which increases morbidity threefold [1]. Different types of temporary and permanent stents have been introduced into urological practice to relieve obstructions [3]. Particular attention should be devoted to polymers as they represent a highly versatile class of materials. Despite the fact that silicon continues to be the gold standard material for urological stents, there have been fast developments in manufacturing processes, as well as the introduction of new biodegradable materials in order to overcome the drawbacks of the available products. Polyurethane continues to be the most widely used material for polymeric stents; however it frequently promotes biofilm formation and bacterial adhesion leading to severe infections [2]. The concerns regarding existing stents are the motivation to design new biodegradable urological stent systems based on natural polymers, specifically polysaccharides, which present inherent biocompatibility, anti-bacterial properties and that can be tailor-made into a custom suitable stent for a particular patient

Water and carbon dioxide: green solvents for the extraction of collagen/gelatin from marine sponges

"Publication Date (Web): December 23, 2014"Marine sponges are extremely rich in natural products and are considered a promising biological resource. The major objective of this work is to couple a green extraction process with a natural origin raw material to obtain sponge origin collagen/gelatin for biomedical applications. Marine sponge collagen has unique physicochemical properties, but its application is hindered by the lack of availability due to inefficient extraction methodologies. Traditional extraction methods are time consuming as they involve several operating steps and large amounts of solvents. In this work, we propose a new extraction methodology under mild operating conditions in which water is acidified with carbon dioxide (CO2) to promote the extraction of collagen/gelatin from different marine sponge species. An extraction yield of approximately 50% of collagen/gelatin was achieved. The results of Fourier transformed infrared spectroscopy (FTIR), circular dichroism (CD), and differential scanning calorimetry (DSC) spectra suggest a mixture of collagen/gelatin with high purity, and the analysis of the amino acid composition has shown similarities with collagen from other marine sources. Additionally, in vitro cytotoxicity studies did not demonstrate any toxicity effects for three of the extracts.The authors are grateful for financial support of FCT through Grant EXP/QEQ:EPS/0745/2012, SWIMS (Subcritical Water Isolation of compounds from Marine Sponges). The funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement numbers REGPOT-CT2012-316331-POLARIS and KBBE-2010-266033 (project SPECIAL), as well as from ERDF under the project "Novel smart and biomimetic materials for innovative regenerative medicine approaches" RLI-ABMR-NORTE-01-0124-FEDER-000016), cofinanced by North Portugal Regional Operational Programme (ON.2,O Novo Norte), under the National Strategic Reference Framework (NSRF) are also gratefully ackowledged. The authors are also truly thankfull to Prof. Micha flan (Tel Aviv University, Israel), Dr. Ronald Osinga (Porifarma, The Netherlands), Dr. Antonio Sara and Dr. Martina Milanese (Studio Associato GAIA, Italy), and Dr. Joana Xavier (University of Azores) for the kind offer of marine sponges samples

Surface modification of silica-based marine sponge bioceramics induce hydroxyapatite formation

Marine biomaterials are a new emerging area of research with significant applications. Recently, researchers are dedicating considerable attention to marine-sponge biomaterials for various applications. We have focused on the potential of biosilica from Petrosia ficidormis for novel biomedical/industrial applications. A bioceramic structure from this sponge was obtained after calcination at 750ºC for 6 hours in a furnace. The morphological characteristics of the 3D architecture were evaluated by scanning electron microscopy (SEM) and micro-computed tomography revealing a highly porous and interconnected structure. The skeleton of Petrosia ficidormis is a siliceous matrix composed of SiO2, which does not present inherent bioactivity. Induction of bioactivity was attained by subjecting the bioceramics structure to an alkaline treatment (KOH 2M) and acidic treatment (HCl 2M) for 1 and 3 hours. In vitro bioactivity of the bioceramics structure was evaluated in simulated body fluid (SBF), after 7 and 14 days. Observation of the structures by SEM, coupled with spectroscopic elemental analysis (EDS), has shown that the surface morphology presented a calcium-phosphate CaP coating, similar to hydroxyapatite (HA). The determination of the Ca/P ratio, together with the evaluation of the characteristic peaks of HA by infra-red spectroscopy and X-ray diffraction, have proven the existence of HA. In vitro biological performance of the structures was evaluated using an osteoblast cell line andthe acidic treatment has shown to be the most effective treatment. Cells were seeded on the bioceramics structures and their morphology, viability and growth was evaluated by SEM, MTS assay and DNA quantification, respectively, demonstrating that cells are able to grow and colonize the bioceramic structures.Alexandre Barros is grateful for financial support of FCT through Grant EXP/QEQ-EPS/0745/2012, SWIMS - Subcritical Water Isolation of compounds from Marine Sponges. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant REGPOT-CT2012-316331-POLARIS and under Grant no KBBE-2010-266033 (project SPECIAL). Funding from the project "Novel smart and biomimetic materials for innovative regenerative medicine approaches" RL1-ABMR-NORTE-01-0124-FEDER-000016) cofinanced by North Portugal Regional Operational Programme (ON.2 - O Novo Norte), under the National Strategic Reference Framework (NSRF) is also acknowledged