Crack propagation monitoring using an image deformation approach

An image deformation method is herein proposed to monitor the crack propagation in structures. The proposed approach is based on a computational algorithm that uses displacements measured by photogrammetry or image correlation to generate a virtual image of the surface, from an initial input to any given stage of analysis. This virtual image is then compared with the real image of the specimen to identify any discontinuities that appeared or evolved during the monitored period. The procedure was experimentally validated in the characterisation of crack propagation in concrete specimens. When compared with other image processing techniques, for instance based on edge detectors, the image deformation approach showed insensitiveness to any discontinuity previously existing on the surface, such as cracks, stains, voids or shadows, and did not require any specific surface treatments or lighting conditions. With this approach the global crack maps could be extracted from the surface of the structure and extremely small changes occurring within a given time interval could be characterised, such as the movement associated with the opening of cracks. It is highlighted that the proposed procedure is general and therefore applicable to detect and characterise surface discontinuities in different materials and test set-ups.FEDER FCOMP‐01‐0124‐FEDER‐020275, FCT PTDC/ECM/119214/2010, ARC DE150101703, FCT SFRH/BPD/102790/201

Influence of concrete strength and steel fibre geometry on the fibre/matrix interface

The main objective of the research described in this paper was to evaluate how the concrete compressive strength and the geometry of the steel fibres influence the behaviour of the fibre/matrix interface. With this aim, three different concrete matrices were designed with 20, 60 and 100 MPa, and two types of steel fibres were adopted (Dramix® 3D and Dramix® 5D). Specific pull-out specimens were produced and three sets of axial tensile tests were defined with different fibres (3D fibres, and 3D and 5D fibres with trimmed ends). A numerical model was calibrated and used to expand the scope of results obtained from the experimental tests. It can be concluded that the concrete compressive strength strongly influences the fibre/matrix strength. In the set with untrimmed 3D fibres, higher strengths are reached due to the hook shaped endings, for all concrete strengths, varying between 64% and 72% of the total load. For fibres with straight endings, increasing both diameter and length increases lead to higher adhesion and friction strengths.FCT PTDC/ECM/119214/2010, FCT SFRH/BD/84355/2012, FCT SFRH/BD/85922/2012 and FCT SFRH/BPD/102790/2014, ARC DE15010170

Portuguese propolis disturbs glycolytic metabolism of human colorectal cancer in vitro

Propolis is a resin collected by bees from plant buds and exudates, which is further processed through the activity of bee enzymes. Propolis has been shown to possess many biological and pharmacological properties, such as antimicrobial, antioxidant, immunostimulant and antitumor activities. Due to this bioactivity profile, this resin can become an alternative, economic and safe source of natural bioactive compounds.Antitumor action has been reported in vitro and in vivo for propolis extracts or its isolated compounds; however, Portuguese propolis has been little explored. The aim of this work was to evaluate the in vitro antitumor activity of Portuguese propolis on the human colon carcinoma cell line HCT-15, assessing the effect of different fractions (hexane, chloroform and ethanol residual) of a propolis ethanol extract on cell viability, proliferation, metabolism and death. METHODS: Propolis from Angra do Heroísmo (Azores) was extracted with ethanol and sequentially fractionated in solvents with increasing polarity, n-hexane and chloroform. To assess cell viability, cell proliferation and cell death, Sulforhodamine B, BrDU incorporation assay and Anexin V/Propidium iodide were used, respectively. Glycolytic metabolism was estimated using specific kits. RESULTS: All propolis samples exhibited a cytotoxic effect against tumor cells, in a dose- and time-dependent way. Chloroform fraction, the most enriched in phenolic compounds, appears to be the most active, both in terms of inhibition of viability and cell death. Data also show that this cytotoxicity involves disturbance in tumor cell glycolytic metabolism, seen by a decrease in glucose consumption and lactate production. CONCLUSION: Our results show that Portuguese propolis from Angra do Heroísmo (Azores) can be a potential therapeutic agent against human colorectal cancer.We thank the Portuguese Science and Technology Foundation (FCT) for VMG fellowship (ref. SFRH/BI/33503/2008). The authors thank Mr. Antonio Marques from Frutercoop - Azores, who kindly collected and provided the propolis sample for the study