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.     

Small-angle magnetic scattering from a dilute amorphous Fe(Tb) alloy

Low temperature neutron scattering measurements on an amorphous alloy of composition Tb_0.018 Fe_0.982 reveal anomalous small-angle magnetic scattering similar to that observed in the more rare-earth-rich compounds TbFe₂ and HoFe₂. Inferences are drawn from the angular dependence of the scattering concerning cluster size and magnetic structure.     

Neutron depolarization by amorphous magnets in the critical region

The depolarization of neutrons by transmission through amorphous samples of NdFe₂ and HoFe₂ has been measured at temperatures in the neighborhood of their magnetic transitions. The results, when compared to other determinations of the Curie temperature (T_c) suggest that T_c may not be a well-defined quantity in these materials.     

Neutron diffraction study of sputtered and annealed Tb-Fe alloys

Sputtered alloys of composition Tb_x Fe_1?x, with x = 0.118, 0.45 and 0.75 were shown by neutron diffraction to be amorphous. Line-width measurements of an anealed sputtered sample with x = 0.333 indicate microcrystallinity with a particle size of ≈ 100 Å.     

<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.     

Structure simulation of amorphous monatomic and binary systems

A simplified approach to computer simulation of amorphous structures by the dense random packing of hard spheres (DRPHS) has been developed and applied to amorphous Tb and TbFe₂. The computer algorithms devised are rapid and result in uniform, isotropic packing for both the monatomic as well as binary systems; in the latter case, small-atom drift toward the center of the cluster is reduced to the uncertainty in the random number generator. Energy relaxation has been performed using the first term in Keating's expression for the elastic energy; relaxation causes the peaks in the pair correlation functions to broaden, but their relative intensities (peak areas) remain essentially the same. In all cases investigated, the packing fractions are 2% (or less) smaller than those of Finney's ball bearing measurements, and the calculated densities are 13–23% lower than their crystalline counterparts. The pair correlation functions of the monatomic and binary models have been compared with X-ray results on CoP and neutron results on TbFe₂ and found to be in good agreement.