Investigation on the influence of particle preheating temperature on bonding of cold-sprayed nickel coatings

Spherical nickel (Ni) particles were deposited onto aluminium (Al) substrates in order to investigate the deformation and bonding mechanisms of particles as a function of their temperature. The particles were preheated to 473 K, 673 K and 873 K prior to be sprayed onto the substrates. The microstructure and microhardness of the coatings were evaluated. Results show that the microhardness of the coatings deposited using preheated particles decreased due to the elimination of work hardening after coating deposition. The relationship between the adhesion strength of coatings and the preheated temperature of particles was also discussed. The result shows that a stronger adhesion strength can be obtained using preheated particles. However, the adhesion strength decreased when the preheated temperature of particles was too high. Ni-Al diffusion layer generated during annealing process was also used to explain the effect of particle preheating temperature on the bonding mechanism of coatings. (C) 2016 Elsevier B.V. All rights reserved

Reactive oxygen species and cerebrovascular diseases

In the normal physiologic state, reactive oxygen species (ROS) generation is intentional and important for the functioning of cerebral and systemic circulations. Furthermore, emerging evidence indicates that cerebral arteries generate higher levels of ROS than arteries outside of the brain in the normal physiologic state. As such, it has been proposed that ROS may play a more prominent role in the physiologic regulation of cerebral arteries. There are numerous potential enzymatic sources of ROS in the cerebral vasculature; however, increasing evidence indicates that the family of NADPH oxidases is a major source. Aberrant redox signaling or oxidative stress in the cerebral circulation, usually as a result of excessive production of ROS and reactive nitrogen species (RNS), is a common feature in diverse models of cardiovascular risk factors (e.g., hypertension, hypercholesterolemia) and cerebrovascular disease. Furthermore, oxidative stress is now believed to be an underlying cause of cerebrovascular dysfunction and damage associated with these disease states. In this chapter, we summarize the effects and potential roles of ROS/RNS in modulating cerebral artery function in the normal physiologic state, with a particular focus on their roles in modulating cerebrovascular tone. Furthermore, we will highlight current evidence for the involvement of ROS/RNS in cerebrovascular dysfunction associated with cardiovascular risk factors, stroke, and Alzheimer's disease