STUDIES OF ADHESION OF METAL PARTICLES TO SILICA PARTICLES BASED ON ZETA POTENTIAL MEASUREMENTS

The zeta-potentials of silica, copper, platinum and gold particles have been measured as a function of pH. The isoelectric points were found to be at pH 3.0, 5.8, 3.0 and 3.5, respectively. In the pH range 3.0 to 5.8 copper and silica particles are oppositely charged and accordingly the coating of silica with copper particles could be demonstrated. In the case of gold and platinum the sign of the charge is such that direct adhesion to silica particles cannot be expected and this was also demonstrated in the case of platinum.     

Corrosion fatigue on 2024T3 and 6056T4 aluminum alloys

Fatigue corrosion phenomenon is a form of degradation that is because of the combined occurrence of a mechanical cyclical stress and a corrosive environment. Fatigue corrosion can be an issue in commercial and military aircraft, and has the potential to affect the structural integrity and the useful life of an aerostructure. Although the distinct consequences of both fatigue and corrosion have been extensively documented for aluminum alloys, their synergistic action is not completely understood and continues to be an area of considerable scientific and industrial interest. In this paper, a novel approach is proposed and applied for monitoring the electrochemical behavior of different types of aluminum alloy samples while they are subjected to fatigue loading. Cyclic load experiments were conducted on bare 2024T3 and 6056T4 aluminum alloy samples in the presence of an aggressive aerated solution of 3.5% NaCl over a range of frequencies. The R‐ratio was 0. Two different aluminum alloys have been tested in both high‐ and low‐cycle fatigue. In the former case, the maximum stress experienced by the specimen is lower than the material yield strength, which means that the average expected number of cycles to failure is high; in the latter case, the maximum stress experienced by the specimen during the test is higher than the material yield strength, which means that the average expected number of cycles to failure is low. The open circuit potential(OCP) was monitored versus time during the tests described above. The observed OCP variations are interpreted as the occurrence of corrosion during crack initiation and propagation at the air formed oxide/solution interface film. As expected, there is a more pronounced influence of corrosion at lower fatigue frequencies. Crack propagation allows bulk material to be progressively more exposed to the aggressive environment, which stimulates accelerated crack propagation, resulting in a lower fatigue resistance. Copyright © 2010 John Wiley & Sons, Ltd.     

<Emphasis Type="Italic">N</Emphasis>-arachidonoyl glycine,an abundant endogenous lipid,potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor

Background  

Microglia provide continuous immune surveillance of the CNS and upon activation rapidly change phenotype to express receptors that respond to chemoattractants during CNS damage or infection. These activated microglia undergo directed migration towards affected tissue. Importantly, the molecular species of chemoattractant encountered determines if microglia respond with pro- or anti-inflammatory behaviour, yet the signaling molecules that trigger migration remain poorly understood. The endogenous cannabinoid system regulates microglial migration via CB₂ receptors and an as yet unidentified GPCR termed the 'abnormal cannabidiol' (Abn-CBD) receptor. Abn-CBD is a synthetic isomer of the phytocannabinoid cannabidiol (CBD) and is inactive at CB₁ or CB₂ receptors, but functions as a selective agonist at this G_i/o-coupled GPCR. N-arachidonoyl glycine (NAGly) is an endogenous metabolite of the endocannabinoid anandamide and acts as an efficacious agonist at GPR18. Here, we investigate the relationship between NAGly, Abn-CBD, the unidentified 'Abn-CBD' receptor, GPR18, and BV-2 microglial migration.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.