GRBs from unstable Poynting dominated outflows

Poynting flux driven outflows from magnetized rotators are a plausible explanation for gamma-ray burst engines. We suggest a new possibility for how such outflows might transfer energy into radiating particles. We argue that the Poynting flux drives non-linearly unstable large amplitude electromagnetic waves (LAEMW) which ``break'' at radii $r_t \sim 10^{14}$ cm where the MHD approximation becomes inapplicable. In the ``foaming'' (relativisticly reconnecting) regions formed during the wave breaks the random electric fields stochastically accelerate particles to ultrarelativistic energies which then radiate in turbulent electromagnetic fields. The typical energy of the emitted photons is a fraction of the fundamental Compton energy $\epsilon \sim f \hbar c/r_e$ with $f \sim 10^{-3}$ plus additional boosting due to the bulk motion of the medium. The emission properties are similar to synchrotron radiation, with a typical cooling time $\sim 10^{-4}$ sec. During the wave break, the plasma is also bulk accelerated in the outward radial direction and at larger radii can produce afterglows due to the interactions with external medium. The near equipartition fields required by afterglow models maybe due to magnetic field regeneration in the outflowing plasma (similarly to the field generation by LAEMW of laser-plasma interactions) and mixing with the upstream plasma.Comment: 15 pages, 1 figur

Practical issues in catalytic and hydrothermal biomass conversion: concentration effects on reaction pathways

Converting biomass to biofuels and chemicals calls for practical and simple processes, since it must compete economically with both burning and anaerobic bacterial digestion. Here we employ concentrated glucose solutions as a biomass model compound, using a pressure-controlled batch reactor setup for hydrothermal and catalytic upgrading. We examine the hydrothermal, acid-catalysed and base-catalysed reactions of concentrated glucose giving gases, tar (biofuels), and char products, and show that working at practical (i.e., high) feed concentrations has a strong effect on the reaction pathways

The Evolution of Research on Sustainable Business Models: Implications for Management Scholars

Business models that lead to reduced consumption of resources and energy and support a Circular Economy can help businesses address the world’s pressing environmental problems. At the same time, they are concepts that have taken decades to garner serious attention in management literature. In this paper we review patterns in scholarship across a wide range of disciplines (sciences, humanities and management) on the Circular Economy and related business models like Extended Producer Responsibility, Product Service Systems, Collaborative Consumption, Sharing Economy, and Voluntary Simplicity. From this review, we discuss how business scholars might learn from these trends, and the implications for future research on business models that will help lower material consumption