Continuous twin screw rheo-extrusion of an AZ91D magnesium alloy

© The Minerals, Metals & Materials Society and ASM International 2012The twin screw rheo-extrusion (TSRE) is designed to take advantage of the nondendritc microstructure and thixotropic characterization of semisolid-metal slurries and produce simple metal profiles directly from melts. The extrusion equipment consists of a rotor-stator high shear slurry maker, a twin screw extruder, and a die assembly. The process is continuous and has a potential for significantly saving energy, manufacturing cost, and enhancing efficiency. The present investigation was carried out to study the process performance for processing rods of an AZ91D magnesium alloy and the microstructure evolution during processing. The semisolid slurry prepared by the process was characterized by uniformly distributed nondendritic granular primary phase particles. AZ91D rods with uniform and fine microstructures and moderate mechanical properties were produced. For the given slurry making parameters, decreasing extrusion temperature was found to improve microstructures and properties. The mechanisms of particle granulation and refinement and the effect of processing parameters on process performance and thermal management are discussed. © 2012 The Minerals, Metals & Materials Society and ASM International.EPSRC (UK) and Rautomead Lt

Performance related characterisation of the mechanical behaviour of asphalt mixtures

Abstract not availableCivil Engineering and Geoscience

The Real Time Predictability of the Size and Value Premium in Japan

This study examines whether the short-term variation in the japanese size and value premium is sufficiently predictable to be exploited by a timing strategy. In the spirit of pesaran and timmermann [j. Finance 50 (1995) 1201], we employ a dynamic modeling approach in which we explicitly allow for permutations among the determinants in order to mitigate typical data-snooping biases. Using a base set of candidate regressors, we perform an in-sample estimation of all economically sensible models. Subsequently, a “best” model is determined according to a selection criterion. However, whereas most studies use in-sample model selection criteria, we introduce an out-of-sample training period to select our models. We then implement our strategy in a second-stage out-of-sample period: the trading period. All stages re-occur on a monthly basis via a rolling window framework. The results confirm sufficient predictability under lower transaction cost levels. Under high transaction costs scenarios it is more difficult to obtain incremental benefits

Lymph node stromal cells constrain immunity via MHC class II self-antigen presentation

Non-hematopoietic lymph node stromal cells shape immunity by inducing MHC-I-dependent deletion of self-reactive CD8(+) T cells and MHC-II-dependent anergy of CD4(+) T cells. In this study, we show that MHC-II expression on lymph node stromal cells is additionally required for homeostatic maintenance of regulatory T cells (Tregs) and maintenance of immune quiescence. In the absence of MHC-II expression in lymph node transplants, i.e. on lymph node stromal cells, CD4(+) as well as CD8(+) T cells became activated, ultimately resulting in transplant rejection. MHC-II self-antigen presentation by lymph node stromal cells allowed the non-proliferative maintenance of antigen-specific Tregs and constrained antigen-specific immunity. Altogether, our results reveal a novel mechanism by which lymph node stromal cells regulate peripheral immunity. DOI: http://dx.doi.org/10.7554/eLife.04433.00