104,403 research outputs found
Distribution anisotropy: the influence of magnetic interactions on the anisotropy of magnetic remanence
The anisotropy of magnetic remanence (AMR) is often used as a tool for examining magnetic anisotropy of rocks. However, the influence of magnetostatic interactions on AMR has not been previously rigorously addressed either theoretically or experimentally, though it is widely thought to be highly significant. Using a three-dimensional micromagnetic algorithm, we have conducted a systematic numerical study of the role of magnetostatic interactions on AMR. We have considered both lineation and foliation, by modelling assemblages of ideal single domain grains and magnetically non-uniform magnetite-like cubic grains. We show that magnetostatic interactions strongly affect the measured AMR signal. It is found that depending on the orientation of the single-grain anisotropy and grain spacing it is possible for the AMR signal from a chain or grid of grains to be either oblate or prolate. For non-uniform grains, the degree of anisotropy generally increases with increasing interactions. In the modelling of AMR anisotropy, saturation isothermal remanence was chosen for numerical tractability. The influence of interactions on other types of more commonly measured AMR, are considered in light of the results in this paper. © The Geological Society of London 2004.Accepted versio
Liquid-cooled liner for helmets
Liner acts as coolant tubing, manifold, and supporting structures. Fabric of waffle-design is made of several integrated channels (or capillaries) through which coolant liquid can flow. Thin and light-weight liner can be incorporated into any type of helmet or head gear
Hamiltonians of Spherically Symmetric, Scale-Free Galaxies in Action-Angle Coordinates
We present a simple formula for the Hamiltonian in terms of the actions for
spherically symmetric, scale-free potentials. The Hamiltonian is a power-law or
logarithmic function of a linear combination of the actions. Our expression
reduces to the well-known results for the familiar cases of the harmonic
oscillator and the Kepler potential. For other power-laws, as well as for the
singular isothermal sphere, it is exact for the radial and circular orbits, and
very accurate for general orbits. Numerical tests show that the errors are
always small, with mean errors across a grid of actions always less than 1 %
and maximum errors less than 2.5 %. Simple first-order corrections can reduce
mean errors to less than 0.6 % and maximum errors to less than 1 %. We use our
new result to show that :[1] the misalignment angle between debris in a stream
and a progenitor is always very nearly zero in spherical scale-free potentials,
demonstrating that streams can be sometimes well approximated by orbits, [2]
the effects of an adiabatic change in the stellar density profile in the inner
regions of a galaxy weaken any existing 1/r density cusp, which is reduced to
. More generally, we derive the full range of adiabatic cusp
transformations and show how to relate the starting cusp index to the final
cusp index. It follows that adiabatic transformations can never erase a dark
matter cusp.Comment: 6 pages, MNRAS, in pres
Glycosylphosphatidylinositols: More than just an anchor?
There is increasing interest in the role of glycosylphosphatidylinositol (GPI) anchors that attach some proteins to cell membranes. Far from being biologically inert, GPIs influence the targeting, intracellular trafficking and function of the attached protein. Our recent paper demonstrated the role of sialic acid on the GPI of the cellular prion protein (PrPC). The “prion diseases” arise following the conversion of PrPC to a disease-associated isoform called PrPSc or “prion”. Our paper showed that desialylated PrPC inhibited PrPSc formation. Aggregated PrPSc creates a signaling platform in the cell membrane incorporating and activating cytoplasmic phospholipase A2 (cPLA2), an enzyme that regulates PrPC trafficking and hence PrPSc formation. The presence of desialylated PrPC caused the dissociation of cPLA2 from PrP-containing platforms, reduced the activation of cPLA2 and inhibited PrPSc production. We concluded that sialic acid contained within the GPI attached to PrPC modifies local membrane microenvironments that are important in PrP-mediated cell signaling and PrPSc formation
Dynamic Modulus and Damping of Boron, Silicon Carbide, and Alumina Fibers
The dynamic modulus and damping capacity for boron, silicon carbide, and silicon carbide coated boron fibers were measured from-190 to 800 C. The single fiber vibration test also allowed measurement of transverse thermal conductivity for the silicon carbide fibers. Temperature dependent damping capacity data for alumina fibers were calculated from axial damping results for alumina-aluminum composites. The dynamics fiber data indicate essentially elastic behavior for both the silicon carbide and alumina fibers. In contrast, the boron based fibers are strongly anelastic, displaying frequency dependent moduli and very high microstructural damping. Ths single fiber damping results were compared with composite damping data in order to investigate the practical and basic effects of employing the four fiber types as reinforcement for aluminum and titanium matrices
Phase transition from hadronic matter to quark matter
We study the phase transition from nuclear matter to quark matter within the
SU(3) quark mean field model and NJL model. The SU(3) quark mean field model is
used to give the equation of state for nuclear matter, while the equation of
state for color superconducting quark matter is calculated within the NJL
model. It is found that at low temperature, the phase transition from nuclear
to color superconducting quark matter will take place when the density is of
order 2.5 - 5. At zero density, the quark phase will appear
when the temperature is larger than about 148 MeV. The phase transition from
nuclear matter to quark matter is always first order, whereas the transition
between color superconducting quark matter and normal quark matter is second
order.Comment: 18 pages, 11 figure
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