Monitoraggio della corrosione sotto sforzo di acciai trafilati tramite emissione acustica

L’attuale normativa europea (ISO DIS 15630) prescrive di valutare la suscettibilità alla tensocorrosionedegli acciai, utilizzati nelle strutture in c.a.p., in base al tempo di rottura di campioni, mantenuti sottocarico costante, pari ad 80% del carico di rottura, a contatto con soluzioni acide, che si differenziano peril tenore di ioni tiocianato. La soluzione ad elevato tenore di tiocianato d’ammonio (soluzione A) risultainvero troppo aggressiva, non riproducendo le reali condizioni di servizio. La soluzione contenente unbasso tenore di agenti aggressivi (cloruri, solfati e tiocianati), denominata Soluzione B, è piùrappresentativa, ma fornisce viceversa tempi di rottura troppo lunghi. Di conseguenza, una problematicaaperta in campo scientifico è l’individuazione di una soluzione di laboratorio, che garantisca un buoncompromesso tra rappresentatività delle condizioni di servizio e durata delle prove.Nel presente lavoro la suscettibilità alla tensocorrosione di un acciaio trafilato eutettoide di usocommerciale viene valutata utilizzando una soluzione di prova, che è una modifica della soluzione Briportata dalla normativa. Si è visto che la variazione di alcuni parametri di prova (potenziale dipolarizzazione, aerazione della soluzione, presenza di un’interfaccia liquido – aria) determina differentimeccanismi di rottura (corrosione tipo pitting, infragilimento da idrogeno, corrosione sotto sforzo).Monitorando alcune prove tramite un dispositivo di rilevamento di segnali di emissione acustica, si èaltresì verificato che la tipologia di emissione si differenzia in base ai fenomeni corrosivi, che hannoluogo durante le prove

321. Deletion of Mutated GAA Repeats from the Intron 1 of the Frataxin Gene Using the CRISPR System Restores the Protein Expression in a Friedreich Ataxia Model

The CRISPR system is now widely used as a molecular tool to edit the genome. We used this technique in Friedreich Ataxia (FRDA), an inherited autosomal disease known to cause a decrease of the mitochondrial frataxin protein. Genetic analysis revealed a GAA repeat expansion within the intron 1 of the frataxin (FXN) gene. We used cells derived from the YG8sR mouse model where the mouse frataxin gene is knockout but contain a human FXN mutated transgene on one allele. We then deleted the GAA trinucleotide repeat using 2 specific guide RNAs (gRNAs) co-expressed with either S. pyogenes (Sp) or S. aureus (Sa) Cas9. We were able to monitored an increase up to 2-fold of frataxin mRNA and protein levels in clone cells. We also confirmed these results in vivo using DNA electroporation in the Tibialis anterior muscle of the YG8R mice. Ongoing in vivo investigation of a systemically injected AAV-DJ vector expressing the SaCas9 and 2 successful selected gRNAs in the mouse model YG8sR will hopefully provide more details answers on the efficacy of the approach and give us preliminary data to go forward for clinical trial. The deletion of the GAA repeats expansion then might be a highly valuable gene therapy approach for FRDA patients

Hydrogen embrittlement risk of high strength galvanized steel in contact with alkaline media

The critical conditions for hydrogenembrittlement (HE) risk of highstrengthgalvanizedsteel (HSGS) wires and tendons exposed to alkaline concrete pore solutions have been evaluated by means of electrochemical and mechanical testing. There is a relationship between the hydrogenembrittlementrisk in HSGS and the length of hydrogen evolution process in alkalinemedia. The galvanizedsteel suffers anodic dissolution simultaneously to the hydrogen evolution which does not stop until the passivation process is completed. HSGS wires exposed to a very highalkalinemedia have showed HE risk with loss in mechanical properties only if long periods with hydrogen evolution process take place with a simultaneous intensive galvanized coating reduction

Honey, a Gift from Nature to Health and Beauty: A Review

Benefits of honey are contributed by the composition of its elements such as glucose, fructose, glucose oxidase, vitamins and phenolic compounds. For health, honey can be used to treat wounds due to the antibacterial activity conferred by the hydrogen peroxide produced by glucose oxidase in honey. Anti-inflammatory, anti-oxidant, deodorizing and tissue regeneration activities in honey also help in the wound healing process. It can also be an alternative sweetener for diabetic patients to ensure compliance to a healthy diet. Moreover, honey exerts several effects such as lowering low density lipids and increasing high density lipids, thus reducing risk of atherosclerosis. In terms of beauty, honey can be used on skin and hair. It moisturizes skin through its natural humectant properties contributed by high contents of fructose and glucose. Honey treats acne on the skin due to its antibacterial activity, anti-inflammatory action and tissue repair. The hair can benefit from honey in such a way that the hair has abundance, and becomes easier to comb. However, there have not been as many studies regarding the use of honey in skin in comparison to its use for health. Therefore, future studies on honey could research its use, action and benefits in both cosmetics and dermatology

Crack propagation in civil engineering bridge cables: coupled phenomena of fatigue and corrosion

This paper deals with the propagation of a crack initiated by fretting-fatigue in bridge cables. They are submitted to traffic loads and exposed to environmental conditions (rain, wind, marine environment, de-icing salts …). These loads can lead to two main damage causes: fretting-fatigue and corrosion. These both phenomena can be coupled and lead to premature failures of drawn steel wires. In fact, at specific contact points, cracks are often initiated by fretting-fatigue. Fretting-fatigue is due to the cable bending. Near anchorages, the bending deformations are the highest and can generate damage (wire cracks). Cracks may propagate under traffic or wind fatigue load. They are also often submitted to a severe environment. Indeed, even if cables are initially protected, these protections can deteriorate and then cables are subject to corrosion. Experimental results show that wire cracks are often initiated by fretting-fatigue and crack propagation is due to fatigue or fatigue corrosion. In this study wire crack is initiated by fretting-fatigue first and fatigue tests are set up after with several environments in order to evaluate their influence on the crack propagation. The studied corrosive environments are: distilled water, sodium chloride solution and thiocyanate ammonium solutions with different concentrations. Lifetimes of specimens are compared. Metallographic and fractographic observations show the influence of the different solutions on the crack propagation. Indeed, since the microstructure of the steel wires is fully oriented in the longitudinal direction, corrosion changes the crack propagation modes and favours mixed mode propagation or longitudinal propagation

Hydrogen embrittlement of prestressing cables

cited By 38International audienceIn this study, hydrogen embrittlement is simulated in an accelerated way with an ammonium thiocyanate media test. Damage evolution of prestressing strand is monitored with electrochemical measurements and with acoustic emission (AE). Three stages of the damage mechanism are identified with different acoustic activities. For each stage, three pattern parameters coming from AE analyse are highlighted to distinguish each emitting stage. To have a precise description of damage evolution of prestressing cables during the hydrogen embrittlement test, some interrupted tests have been used. For each interruption, metallographic observations enable to characterize degradation mechanisms. Finally, each acoustic stage has been correlated to a degradation mechanism. © 2010 Elsevier Ltd. All rights reserved