Travelling waves in hyperbolic chemotaxis equations

Mathematical models of bacterial populations are often written as systems of partial differential equations for the densities of bacteria and concentrations of extracellular (signal) chemicals. This approach has been employed since the seminal work of Keller and Segel in the 1970s [Keller and Segel, J. Theor. Biol., 1971]. The system has been shown to permit travelling wave solutions which correspond to travelling band formation in bacterial colonies, yet only under specific criteria, such as a singularity in the chemotactic sensitivity function as the signal approaches zero. Such a singularity generates infinite macroscopic velocities which are biologically unrealistic. In this paper, we formulate a model that takes into consideration relevant details of the intracellular processes while avoiding the singularity in the chemotactic sensitivity. We prove the global existence of solutions and then show the existence of travelling wave solutions both numerically and analytically

China: A Tiger only in the East or a World Player in High Quality Fresh Produce Exports?

This paper examines patterns of recent change in Chinas international export trade in high quality fresh-vegetables between 2002 and 2005 since its WTO membership and some of the underlying determinants that will determine its future export opportunities. Concepts of product quality are first reviewed and the key characteristics of Chinas international trade in fresh produce are outlined based on a detailed analysis from the UN Comtrade international trade data at the 2, 4 digit and finally 6 digit levels. High quality fresh and chilled vegetables are identified through their average unit export values. In 2005, China was the 4th largest exporter of vegetables in the world with a 9.8 percent share of world trade, and almost a 6 percent share in fresh and chilled vegetables. The competitiveness of China in world trade in high value fresh produce is assessed through a trade-shares accounting and decomposition approach which enables both structural and performance effects on Chinas exports to be isolated, and the contributions its major trading partners have made to changes its share of world trade. Chinas aggregate market share rose by over 1.5 percentage points over the period, and there is evidence of an emerging orientation in its trade shares from E Asia to SE Asia, and to further progress in the Russian Federation and US markets. Chinas underlying comparative advantage in such labour-intensive products is reflected in the positive performance effect on the increase in its market share.China, vegetables, international trade., International Relations/Trade,

Material modelling and springback analysis for multi-stage rotary draw bending of thin-walled tube using homogeneous anisotropic hardening model

The aim of this paper is to compare several hardening models and to show their relevance for the prediction of springback and deformation of an asymmetric aluminium alloy tube in multi-stage rotary draw bending process. A three-dimensional finite-element model of the process is developed using the ABAQUS code. For material modelling, the newly developed homogeneous anisotropic hardening model is adopted to capture the Bauschinger effect and transient hardening behaviour of the aluminium alloy tube subjected to non-proportional loading. The material parameters of the hardening model are obtained from uniaxial tension and forward-reverse shear test results of tube specimens. This work shows that this approach reproduces the transient Bauschinger behaviour of the material reasonably well. However, a curve-crossing phenomenon observed for this material cannot be captured by the homogeneous anisotropic hardening model. For comparison purpose, the isotropic and combined isotropic-kinematic hardening models are also adopted for the analysis of the same problem. The predictions of springback and cross-section deformation based on these models are discussed. (C) 2014 The Authors. Published by Elsevier Ltd.open1134Nsciescopu

Neutrino masses and mixings

We propose a novel theoretical understanding of neutrino masses and mixings, which is attributed to the intrinsic vector-like feature of the regularized Standard Model at short distances. We try to explain the smallness of Dirac neutrino masses and the decoupling of the right-handed neutrino as a free particle. Neutrino masses and mixing angles are completely related to each other in the Schwinger-Dyson equations for their self-energy functions. The solutions to these equations and a possible pattern of masses and mixings are discussed.Comment: LaTex 11 page

Learning distance to subspace for the nearest subspace methods in high-dimensional data classification

The nearest subspace methods (NSM) are a category of classification methods widely applied to classify high-dimensional data. In this paper, we propose to improve the classification performance of NSM through learning tailored distance metrics from samples to class subspaces. The learned distance metric is termed as ‘learned distance to subspace’ (LD2S). Using LD2S in the classification rule of NSM can make the samples closer to their correct class subspaces while farther away from their wrong class subspaces. In this way, the classification task becomes easier and the classification performance of NSM can be improved. The superior classification performance of using LD2S for NSM is demonstrated on three real-world high-dimensional spectral datasets