Evaluating the impact of inequality constraints and parameter uncertainty on optimal portfolio choice

© 2015 Taylor & Francis. We present new analytical results for the impact of portfolio weight constraints on an investor’s optimal portfolio when parameter uncertainty is taken into account. While it is well known that parameter uncertainty and imposing weight constraints results in reduced certainty equivalent returns, in the general case, there are no analytical results. In a special case, commonly used in the funds management literature, we derive analytical expression for the certainty equivalent loss that does not depend on the risk aversion parameter. We illustrate our theoretical results using hedge fund data, from the perspective of a fund-of-fund manager. Our contribution is to formalize the framework to investigate this problem, as well as providing tractable analytical solutions that can be implemented using either simulated or asset manager returns

The ecology of seamounts: structure, function, and human impacts.

In this review of seamount ecology, we address a number of key scientific issues concerning the structure and function of benthic communities, human impacts, and seamount management and conservation. We consider whether community composition and diversity differ between seamounts and continental slopes, how important dispersal capabilities are in seamount connectivity, what environmental factors drive species composition and diversity, whether seamounts are centers of enhanced biological productivity, and whether they have unique trophic architecture. We discuss how vulnerable seamount communities are to fishing and mining, and how we can balance exploitation of resources and conservation of habitat. Despite considerable advances in recent years, there remain many questions about seamount ecosystems that need closer integration of molecular, oceanographic, and ecological research

Neogene history of fluvial to shallow marine successions in the Kendari Basin, SE Sulawesi, Indonesia

Collision between Australia and SE Asia began in Sulawesi, the world's eleventh-largest island, in the Early Miocene and subsequently Neogene sediments were deposited largely in coastal to shelf environments throughout the island. These sediments have been assigned to the Celebes Molasse, previously considered as a single post-orogenic unit deposited unconformably on pre-Neogene sedimentary, metamorphic and ophiolitic rocks. The most complete and extensive sequences of Neogene sediments are in the Kendari Basin, situated at the southern end of the SE Arm of Sulawesi, where an outcrop-based sedimentological study was undertaken to interpret depositional environments, palaeogeography and stratigraphy. The oldest Neogene sediments are shallow marine carbonates and deltaic siliciclastics of the Bungku Formation. They are unconformably overlain by the Upper Miocene Pandua Formation which consists of sediments deposited in a variety of environments including braided river channels, fluvio-tidal channels, tidal flats, mouth bar complex and shoreface deposits. A Mio-Pliocene subaerial unconformity separates the marginal marine serpentinite-rich sediments of the Pandua Formation from the overlying fluviatile quartz-rich Langkowala Formation. The sediments of the lower part of the Langkowala Formation include conglomeratic channel fill, while the sediments of the upper part are transgressive deposits decreasing in maximum grain-size, marked by a reduction in channel/overbank ratio and increasing tidal influence. The transgressive Pliocene Eemoiko Formation is characterised by transgressive lags or onlap shell beds and deposits of a landwards-backstepping carbonate platform. The improved understanding of the Kendari Basin will aid the interpretation of the sedimentation history of frontier basins surrounding SE Sulawesi, many of which have not yet been drilled

Heat and fluid flow in a scraped-surface heat exchanger containing a fluid with temperature-dependent viscosity

Scraped-surface heat exchangers (SSHEs) are extensively used in a wide variety of industrial settings where the continuous processing of fluids and fluid-like materials is involved. The steady non-isothermal flow of a Newtonian fluid with temperature-dependent viscosity in a narrow-gap SSHE when a constant temperature difference is imposed across the gap between the rotor and the stator is investigated. The mathematical model is formulated and the exact analytical solutions for the heat and fluid flow of a fluid with a general dependence of viscosity on temperature for a general blade shape are obtained. These solutions are then presented for the specific case of an exponential dependence of viscosity on temperature. Asymptotic methods are employed to investigate the behaviour of the solutions in several special limiting geometries and in the limits of weak and strong thermoviscosity. In particular, in the limit of strong thermoviscosity (i.e., strong heating or cooling and/or strong dependence of viscosity on temperature) the transverse and axial velocities become uniform in the bulk of the flow with boundary layers forming either just below the blade and just below the stationary upper wall or just above the blade and just above the moving lower wall. Results are presented for the most realistic case of a linear blade which illustrate the effect of varying the thermoviscosity of the fluid and the geometry of the SSHE on the flow

Enterobacter cloacae Outbreak and Emergence of Quinolone Resistance Gene in Dutch Hospital

Plasmid-mediated qnrA1 is an emerging resistance trait

Higher resources decrease fluctuating selection during host-parasite coevolution

This is the final version of the article. Available from the publisher via the DOI in this record.We still know very little about how the environment influences coevolutionary dynamics. Here, we investigated both theoretically and empirically how nutrient availability affects the relative extent of escalation of resistance and infectivity (arms race dynamic; ARD) and fluctuating selection (fluctuating selection dynamic; FSD) in experimentally coevolving populations of bacteria and viruses. By comparing interactions between clones of bacteria and viruses both within- and between-time points, we show that increasing nutrient availability resulted in coevolution shifting from FSD, with fluctuations in average infectivity and resistance ranges over time, to ARD. Our model shows that range fluctuations with lower nutrient availability can be explained both by elevated costs of resistance (a direct effect of nutrient availability), and reduced benefits of resistance when population sizes of hosts and parasites are lower (an indirect effect). Nutrient availability can therefore predictably and generally affect qualitative coevolutionary dynamics by both direct and indirect (mediated through ecological feedbacks) effects on costs of resistance.This work was funded by NERC (UK). ABu was supported by the Royal Society and ABe by a the Leverhulme Trust Early Career Fellowship