Why Ni3_3Al is an itinerant ferromagnet but Ni3_3Ga is not

Ni$_3$Al and Ni$_3$Ga are closely related materials on opposite sides of a ferromagnetic quantum critical point. The Stoner factor of Ni is virtually the same in both compounds and the density of states is larger in Ni$_3$Ga. So, according to the Stoner theory, it should be more magnetic, and, in LDA calculations, it is. However, experimentally, it is a paramagnet, while Ni$_3$Al is an itinerant ferromagnet. We show that the critical spin fluctuations are stronger than in Ni$_3$Ga, due to a weaker q-dependence of the susceptibility, and this effect is strong enough to reverse the trend. The approach combines LDA calculations with the Landau theory and the fluctuation-dissipation theorem using the same momentum cut-off for both materials. The calculations provide evidence for strong, beyond LDA, spin fluctuations associated with the critical point in both materials, but stronger in Ni$_3$Ga than in Ni$_3$Al.Comment: replaced (incorrect version submitted

The role of pericytes in brain disorders: from the periphery to the brain

It is becoming increasingly apparent that disorders of the brain microvasculature contribute to many neurological disorders. In recent years it has become clear that a major player in these events is the capillary pericyte which, in the brain, is now known to control the blood-brain barrier, regulate blood flow, influence immune cell entry and be crucial for angiogenesis. In this review we consider the under-explored possibility that peripheral diseases which affect the microvasculature, such as hypertension, kidney disease and diabetes, produce central nervous system (CNS) dysfunction by mechanisms affecting capillary pericytes within the CNS. We highlight how cellular messengers produced peripherally can act via signalling pathways within CNS pericytes to reshape blood vessels, restrict blood flow or compromise blood-brain barrier function, thus causing neuronal dysfunction. Increased understanding of how renin-angiotensin, Rho-kinase and PDGFRβ signalling affect CNS pericytes may suggest novel therapeutic approaches to reducing the CNS effects of peripheral disorders

Effect of surfactants on electroosmotic flow and trapping behavior in a polymeric insulator-based dielectrophoretic (idep) device

We have previously reported on the use of insulator-based dielectrophoresis (iDEP) for the separation and concentration of biological particles in water. We have found that the applied DC field required to trap these particles depends on particle size, shape, and the zeta potential of the material utilized to form the device. In order to improve device performance, and decrease the power required for optimal performance, it is necessary to adjust one (or several) of these parameters. Surfactants are known to adsorb onto polymeric surfaces in a dynamic fashion, and have been utilized extensively to modify device performance in such related fields as capillary electrophoresis and micellar electrokinetic chromatography. We present here the effect of the anionic surfactant, sodium dodecyl sulfate, on the applied field strengths required to achieve effective isolation and trapping of polystyrene beads