3 research outputs found
Short review: Potential impact of delamination cracks on fracture toughness of structural materials
The current energy policy envisages extended lifetime for the current nuclear power plants (GEN II NPP). This policy imposes a large research effort to understand the ageing of power plant components. In this goal, it is necessary to improve knowledge about safety, reliability and components’ integrity for more than forty years of operation. In Central and Eastern Europe, the majority of NPPs are VVER types, where some of the components are produced from austenitic steel 08Ch18N10T. Irradiated 08Ch18N10T may exhibit brittle behavior, namely delamination cracks are found in some cases on the fracture surface of irradiated 08Ch18N10T with elongated ?-ferrite. Delamination cracks have also been observed on the fracture surface of high-strength steels or aluminum-lithium alloys. This article presents a state-of-the art review to provide a detailed analysis of the influence of delamination cracks on the toughness of metal alloys. In general, the delamination cracks are present in metal alloys having a high texture and microstructure anisotropy. Three types of delamination cracks have been observed and are classified as crack arrester delamination, crack divider delamination and crack splitting delamination. The microscopy characterization, 3D fracture theories and computational studies explaining possible causes and effects of delamination cracks on the mechanical properties of metal alloys are presented
Ocular surface injuries in autoimmune dry eye. The severity of microscopical disturbances goes parallel with the severity of symptoms of dryness
Autoimmune dry eye (Sjögren’s syndrome,
SS) is a chronic systemic disease characterized by
salivary and lacrimal gland inflammation and tissue
damage leading to keratoconjunctivitis sicca and
xerostomia. In this review attention has been devoted to
the cause of the development of oxidative injuries of the
ocular surface of patients suffering from SS. It was
shown that lacrimal glands and diseased conjunctival
epithelium reveal increased expression of proinflammatory
cytokines which are released into the tear
fluid. A high amount of pro-inflammatory cytokines
highly induce the elevated expression and activity of
enzymatic systems that generate reactive oxygen and
nitrogen species. An abundant amount of these toxic
products leads to a decrease in antioxidants and to the
formation of cytotoxic related oxidants, such as
peroxynitrite. All these factors, together with reactive
oxygen species from polymorphonuclear leukocytes,
contribute to the development of oxidative injuries at the
ocular surface. From the clinical point of view it is
important that the level of severity of the above
described microscopical disturbances found in
conjunctival epithelial cells goes parallel with the level
of severity of dry eye symptoms