The effect of density (relative densities 0.33 to 0.90) on the impact behavior of microcellular polycarbonate (PC) was investigated. Cell size and foaming gas content were also considered. Flexed-beam Izod impact tests were conducted and the impact strength of these foams appears to be a strong function of both density and cell size. The impact strength was observed to improve over the unproces...

We investigate the high-frequency behavior of the density of vibrational states in three-dimensional elasticity theory with spatially fluctuating elastic moduli. At frequencies well above the mobility edge, instanton solutions yield an exponentially decaying density of states. The instanton solutions describe excitations, which become localized due to the disorder-induced fluctuations, which lo...

We investigate the equilibrium of a fluid in contact with a solid boundary through a density-functional theory. Depending on the conditions, the fluid can be in one phase, gas or liquid, or two phases, while the wall induces an external field acting on the fluid particles. We first examine the case of a liquid film in contact with the wall. We construct bifurcation diagrams for the film thickne...

We present a discussion of a number of conceptual and methodological aspects associated with the theoretical characterization and computat ion of charge densities and momentum distributions in solids. The main ambition has been to stress properties that both exact and approximate quantities must possess. We have also attempted to point out conceptual and computat ional trends which would seem t...

1Department of Physics, University of York, York YO10 5DD, UK 2Scientific Computing Department, STFC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK 3Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK 4Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK 5Department of Physics and Astronomy, University College London, LondonWC1E 6BT...

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It has been suggested that high-density amorphous (HDA) ice is a structurally arrested form of high-density liquid (HDL) water, while low-density amorphous ice is a structurally arrested form of low-density liquid (LDL) water. Recent experiments and simulations have been interpreted to support the possibility of a second distinct high-density structural state, named very high-density amorphous ...

While there are some developments in structure solution and refinement, these represent gradual improvements rather than fundamental leaps in methodology. An exception is the assessment of crystal quality by X-ray diffraction topography using a dedicated solid-state electronic detector; this is an elegant example where the precise physical nature of the crystal has been studied and analyzed. Si...