Role of N-acetylcysteine in the management of COPD

The importance of the underlying local and systemic oxidative stress and inflammation in chronic obstructive pulmonary disease (COPD) has long been established. In view of the lack of therapy that might inhibit the progress of the disease, there is an urgent need for a successful therapeutic approach that, through affecting the pathological processes, will influence the subsequent issues in COPD management such as lung function, airway clearance, dyspnoea, exacerbation, and quality of life. N-acetylcysteine (NAC) is a mucolytic and antioxidant drug that may also influence several inflammatory pathways. It provides the sulfhydryl groups and acts both as a precursor of reduced glutathione and as a direct reactive oxygen species (ROS) scavenger, hence regulating the redox status in the cells. The changed redox status may, in turn, influence the inflammation-controlling pathways. Moreover, as a mucolytic drug, it may, by means of decreasing viscosity of the sputum, clean the bronchi leading to a decrease in dyspnoea and improved lung function. Nevertheless, as successful as it is in the in vitro studies and in vivo studies with high dosage, its actions at the dosages used in COPD management are debatable. It seems to influence exacerbation rate and limit the number of hospitalization days, however, with little or no influence on the lung function parameters. Despite these considerations and in view of the present lack of effective therapies to inhibit disease progression in COPD, NAC and its derivatives with their multiple molecular modes of action remain promising medication once doses and route of administration are optimized

Behaviour of slag cement concrete under restraint conditions

Some constructions built with slag cement concrete exhibit cracking at early age due to restrained shrinkage. To determine the slag effect on cracking, this study focuses on the autogenous deformation evolution of concretes characterized by different percentages of slag (0 and 42% of the binder mass) under free and restraint conditions by means of the TSTM device (Temperature Stress Testing Machine). Despite the fast kinetics of its autogenous deformation, the cracking appears later for the slag cement concrete than for the Portland cement concrete. This behaviour is related to the swelling of its cementitious matrix at early age and its large capacity for relaxing the stresses. © 2011 Lavoisier, Paris.SCOPUS: ar.jSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Cementitious materials with mineral additions: impact on the self-healing kinetics and the products formation

International audienceGround granulated blast-furnace slags (GGBFS), as a hydraulic binder, are widely used for many years in engineering concretes. The French standards allow substituting 50% of Portland cement by GGBFS. This approach leads to a decrease in the CO2 emissions produced during clinkerisation process. Portland cement substitution by GGBFS can also improve the workability, decreases the hydration heat and increases the long-term compressive strength. GGBFS can also significantly improve the resistance to sulfate attack. Concrete structures made with GGBFS cement can be cracked at early age due to restrained shrinkage. This cracking can reduce mechanical and transport properties, leading to an increased risk of aggressive agents’ penetration. Self-healing of cracks, already observed on building sites, could partially overcome these durability issues.To understand the effect of GGBFS on self-healing kinetics and the type of self-healing products, five hydraulic binders were studied: two Portland cement (French and Canadian), two GGBFS (French and Canadian) mixed with Portland cement (named GGBFS formulation hereafter) and a French blended cement (62% of slag) named CEMIII/A. Each material was characterized by XRF, XRD, PZD test, fineness Blaine test and TGA. At 7 and 28 days, French and Canadian mortar specimens were cracked respectively to obtain three crack sizes: 50, 100 and 150 µm. The cracked specimens were then stored at 23 °C and 100% R.H for up to 6 months. The evolution of self-healing is followed by X-ray tomography or air-flow measurements. SEM with EDS were performed on the sawed samples to identify and analyze self-healing products.Results show that two main products are formed: (1) calcite by the carbonation of portlandite in the matrix, and (2) supplementary reaction products (mainly C-S-H with various C/S ratios), formed by the reaction of anhydrous particles. Both GGBFS formulations show a good self-healing potential but the kinetics of the phenomenon are slightly different. Mortar made with French GGBFS presents the best self-healing potential compared to the four others formulations. Mortar with Canadian GGBFS presents a similar behavior as Canadian Portland cement. These results can be explained by the material characteristics but also by their hydration kinetics. A hydration model is currently developed in order to investigate more deeply these observations

Cementitious materials with mineral additions: impact on the self-healing kinetics and the products formation

International audienceGround granulated blast-furnace slags (GGBFS), as a hydraulic binder, are widely used for many years in engineering concretes. The French standards allow substituting 50% of Portland cement by GGBFS. This approach leads to a decrease in the CO2 emissions produced during clinkerisation process. Portland cement substitution by GGBFS can also improve the workability, decreases the hydration heat and increases the long-term compressive strength. GGBFS can also significantly improve the resistance to sulfate attack. Concrete structures made with GGBFS cement can be cracked at early age due to restrained shrinkage. This cracking can reduce mechanical and transport properties, leading to an increased risk of aggressive agents’ penetration. Self-healing of cracks, already observed on building sites, could partially overcome these durability issues.To understand the effect of GGBFS on self-healing kinetics and the type of self-healing products, five hydraulic binders were studied: two Portland cement (French and Canadian), two GGBFS (French and Canadian) mixed with Portland cement (named GGBFS formulation hereafter) and a French blended cement (62% of slag) named CEMIII/A. Each material was characterized by XRF, XRD, PZD test, fineness Blaine test and TGA. At 7 and 28 days, French and Canadian mortar specimens were cracked respectively to obtain three crack sizes: 50, 100 and 150 µm. The cracked specimens were then stored at 23 °C and 100% R.H for up to 6 months. The evolution of self-healing is followed by X-ray tomography or air-flow measurements. SEM with EDS were performed on the sawed samples to identify and analyze self-healing products.Results show that two main products are formed: (1) calcite by the carbonation of portlandite in the matrix, and (2) supplementary reaction products (mainly C-S-H with various C/S ratios), formed by the reaction of anhydrous particles. Both GGBFS formulations show a good self-healing potential but the kinetics of the phenomenon are slightly different. Mortar made with French GGBFS presents the best self-healing potential compared to the four others formulations. Mortar with Canadian GGBFS presents a similar behavior as Canadian Portland cement. These results can be explained by the material characteristics but also by their hydration kinetics. A hydration model is currently developed in order to investigate more deeply these observations

DECIMAL - Phenomenological description of the corrosion and its impact on the durability of encapsulated magnesium wastes in hydraulic binders

International audienc

Extraction Efficiency of N-13 (t1/2 = 9.96 Min) Atoms From a Graphite Target - Comparison Between Off-line and Online Obtained Results

An off-line release study N-13 (T1/2 = 9.96 min) produced by a proton induced reaction on a graphite target (POCO-graphite EDM3, density = 1.84 g/cm3, grain size approximately 3-mu-m) has been performed. The activation energy for the diffusion process is determined to be 6.15(16)x10(5) J/Mol. With this acitivation energy, extraction efficiences for N-13 are obtained at different temperatures and are compared to on-line measured extraction efficiencies

How to monitor the modulus of elasticity of concrete, automatically since the earliest age ?

Monitoring the evolution of an early age set of parameters on concrete is necessary to predict the early age behaviour of structures. The difficulty lies in the fact that this monitoring must be automatic because the concrete hardening process takes place over a long period after the casting. This paper presents a new methodology and an apparatus, specifically designed at IFSTTAR, to monitor the hardening process of a concrete. Mainly, the Young's modulus can be monitored in compression. Measurements start soon after having cast the concrete and the sample temperature is completely controlled so that the concrete maturity is well mastered. The performances of this apparatus, obtained on an ordinary concrete, are compared to more classical measurements using an extensometer mounted on the sample just after the setting time and to ultrasonic measurements. In these cases, the temperatures were not controlled and results have to be expressed in equivalent time. A comparison with another method developed and used at ULB by using the same concrete, in the frame of a joined cooperation between our two laboratories is achieved. This test set up is based on the so called Temperature Stress Testing Machine (TSTM). This device has been specifically designed with a control of the concrete maturity by the use of a dummy specimen only submitted to free deformations (thermal, shrinkage). The TSTM allows compressive and tensile testing starting just after the setting time. In addition, concrete properties, such as compressive and tensile strength, have been characterized at early age. These values have been used for the design of the loading histories applied in the automatic tests. The heat released by the cement hydration has also been measured in order to express the results on a maturity scale. © 2013 RILEM.SCOPUS: ar.jinfo:eu-repo/semantics/publishe