Publications by authors named "Andrew J Higgins"

Bleomycin is a chemotherapy agent that, when administered systemically, can cause severe pulmonary toxicity. Bleosome is a novel formulation of bleomycin encapsulated in ultra-deformable (UD) liposomes that may be applicable as a topical chemotherapy for diseases such as non-melanoma skin cancer. To date, the ability of Bleosome to effectively penetrate through the skin has not been evaluated.

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The morphology of flame fronts propagating in reactive systems composed of randomly positioned, pointlike sources is studied. The solution of the temperature field and the initiation of new sources is implemented using the superposition of the Green's function for the diffusion equation, eliminating the need to use finite-difference approximations. The heat released from triggered sources diffuses outward from each source, activating new sources and enabling a mechanism of flame propagation.

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An analog to the equations of compressible flow that is based on the inviscid Burgers equation is utilized to investigate the effect of spatial discreteness of energy release on the propagation of a detonation wave. While the traditional Chapman-Jouguet (CJ) treatment of a detonation wave assumes that the energy release of the medium is homogeneous through space, the system examined here consists of sources represented by δ functions embedded in an otherwise inert medium. The sources are triggered by the passage of the leading shock wave following a delay that is either of fixed period or randomly generated.

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The effect of spatially randomizing a system of pointlike sources on the propagation of reaction-diffusion fronts is investigated in multidimensions. The dynamics of the reactive front are modeled by superimposing the solutions for diffusion from a single point source. A nondimensional parameter is introduced to quantify the discreteness of the system, based on the characteristic reaction time of sources compared to the diffusion time between sources.

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Shock wave propagation in multiphase media is typically dominated by the relative compressibility of the two components of the mixture. The difference in the compressibility of the components results in a shock-induced variation in the effective volume fraction of the suspension tending toward the random-close-packing limit for the system, and a disordered solid can take form within the suspension. The present study uses a Hugoniot-based model to demonstrate this variation in the volume fraction of the solid phase as well as a simple hard-sphere model to investigate the formation of disordered structures within uniaxially compressed model suspensions.

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The exact solution for a reaction-diffusion front propagating in a heterogeneous system of discrete, point-like sources is obtained without resorting to a representation of the sources by a spatially continuous function. When the reaction time is smaller than the characteristic diffusion time between neighboring sources, the front speed predicted by this discrete source model differs from the continuum theory based on the spatial averaging of the heterogeneities. Furthermore, when the sources are regularly distributed in space, discreteness introduces a limit and propagation beyond this limit is only possible in a system with randomly distributed sources via local fluctuations of the concentration.

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