Post-death Transmission of Ebola: Challenges for Inference and Opportunities for Control

Multiple epidemiological models have been proposed to predict the spread of Ebola in West Africa. These models include consideration of counter-measures meant to slow and, eventually, stop the spread of the disease. Here, we examine one component of Ebola dynamics that is of growing concern -- the transmission of Ebola from the dead to the living. We do so by applying the toolkit of mathematical epidemiology to analyze the consequences of post-death transmission. We show that underlying disease parameters cannot be inferred with confidence from early-stage incidence data (that is, they are not identifiable) because different parameter combinations can produce virtually the same epidemic trajectory. Despite this identifiability problem, we find robustly that inferences that dont account for post-death transmission tend to underestimate the basic reproductive number -- thus, given the observed rate of epidemic growth, larger amounts of post-death transmission imply larger reproductive numbers. From a control perspective, we explain how improvements in reducing post-death transmission of Ebola may reduce the overall epidemic spread and scope substantially. Increased attention to the proportion of post-death transmission has the potential to aid both in projecting the course of the epidemic and in evaluating a portfolio of control strategies.

Achromatic late-time variability in thermonuclear X-ray bursts - an accretion disk disrupted by a nova-like shell?

An unusual Eddington-limited thermonuclear X-ray burst was detected from the accreting neutron star in 2S 0918-549 with the Rossi X-ray Timing Explorer. The burst commenced with a brief (40 ms) precursor and maintained near-Eddington fluxes during the initial 77 s. These characteristics are indicative of a nova-like expulsion of a shell from the neutron star surface. Starting 122 s into the burst, the burst shows strong (87 +/- 1% peak-to-peak amplitude) achromatic fluctuations for 60 s. We speculate that the fluctuations are due to Thompson scattering by fully-ionized inhomogeneities in a resettling accretion disk that was disrupted by the effects of super-Eddington fluxes. An expanding shell may be the necessary prerequisite for the fluctuations.

Magnetic Properties of Ni-Fe Nanowire Arrays: Effect of Template Material and Deposition Conditions

The objective of this work is to study the magnetic properties of arrays of Ni-Fe nanowires electrodeposited in different template materials such as porous silicon, polycarbonate and alumina. Magnetic properties were studied as a function of template material, applied magnetic field (parallel and perpendicular) during deposition, wire length, as well as magnetic field orientation during measurement. The results show that application of magnetic field during deposition strongly influences the c-axis preferred orientation growth of Ni-Fe nanowires. The samples with magnetic field perpendicular to template plane during deposition exhibits strong perpendicular anisotropy with greatly enhanced coercivity and squareness ratio, particularly in Ni-Fe nanowires deposited in polycarbonate templates. In case of polycarbonate template, as magnetic field during deposition increases, both coercivity and squareness ratio also increase. The wire length dependence was also measured for polycarbonate templates. As wire length increases, coercivity and squareness ratio decrease, but saturation field increases. Such magnetic behavior (dependence on template material, magnetic field, wire length) can be qualitatively explained by preferential growth phenomena, dipolar interactio