104 research outputs found
Generality of shear thickening in suspensions
Suspensions are of wide interest and form the basis for many smart fluids.
For most suspensions, the viscosity decreases with increasing shear rate, i.e.
they shear thin. Few are reported to do the opposite, i.e. shear thicken,
despite the longstanding expectation that shear thickening is a generic type of
suspension behavior. Here we resolve this apparent contradiction. We
demonstrate that shear thickening can be masked by a yield stress and can be
recovered when the yield stress is decreased below a threshold. We show the
generality of this argument and quantify the threshold in rheology experiments
where we control yield stresses arising from a variety of sources, such as
attractions from particle surface interactions, induced dipoles from applied
electric and magnetic fields, as well as confinement of hard particles at high
packing fractions. These findings open up possibilities for the design of smart
suspensions that combine shear thickening with electro- or magnetorheological
response.Comment: 11 pages, 9 figures, accepted for publication in Nature Material
Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases
The production of peroxide and superoxide is an inevitable consequence of
aerobic metabolism, and while these particular "reactive oxygen species" (ROSs)
can exhibit a number of biological effects, they are not of themselves
excessively reactive and thus they are not especially damaging at physiological
concentrations. However, their reactions with poorly liganded iron species can
lead to the catalytic production of the very reactive and dangerous hydroxyl
radical, which is exceptionally damaging, and a major cause of chronic
inflammation. We review the considerable and wide-ranging evidence for the
involvement of this combination of (su)peroxide and poorly liganded iron in a
large number of physiological and indeed pathological processes and
inflammatory disorders, especially those involving the progressive degradation
of cellular and organismal performance. These diseases share a great many
similarities and thus might be considered to have a common cause (i.e.
iron-catalysed free radical and especially hydroxyl radical generation). The
studies reviewed include those focused on a series of cardiovascular, metabolic
and neurological diseases, where iron can be found at the sites of plaques and
lesions, as well as studies showing the significance of iron to aging and
longevity. The effective chelation of iron by natural or synthetic ligands is
thus of major physiological (and potentially therapeutic) importance. As
systems properties, we need to recognise that physiological observables have
multiple molecular causes, and studying them in isolation leads to inconsistent
patterns of apparent causality when it is the simultaneous combination of
multiple factors that is responsible. This explains, for instance, the
decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference
THE EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON PATTERNING OF A FERROELECTRIC POLYMER P(VDF-TrFE) VIA DIP-PEN NANOLITHOGRAPHY
Creating Nanoscale Patterns of Dendrimers on Silicon Surfaces with Dip-Pen Nanolithography
Australian schools as deliberative spaces: Framing the goal of active and informed citizenship
Australian schools as deliberative spaces: framing the goal of active and informed citizenship
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