Magnetic defects promote ferromagnetism in Zn1-xCoxO

Experimental studies of Zn1-xCoxO as thin films or nanocrystals have found ferromagnetism and Curie temperatures above room temperature and that p- or n-type doping of Zn1-xCoxO can change its magnetic state. Bulk Zn1-xCoxO with a low defect density and x in the range used in experimental thin film studies exhibits ferromagnetism only at very low temperatures. Therefore defects in thin film samples or nanocrystals may play an important role in promoting magnetic interactions between Co ions in Zn1-xCoxO. The electronic structures of Co substituted for Zn in ZnO, Zn and O vacancies, substituted N and interstitial Zn in ZnO were calculated using the B3LYP hybrid density functional in a supercell. The B3LYP functional predicts a band gap of 3.34 eV for bulk ZnO, close to the experimental value of 3.47 eV. Occupied minority spin Co 3d levels are at the top of the valence band and unoccupied levels lie above the conduction band minimum. Majority spin Co 3d levels hybridize strongly with bulk ZnO states. The neutral O vacancy and interstitial Zn are deep and shallow donors, respectively. The Zn vacancy is a deep acceptor and the acceptor level for substituted N is at mid gap. The possibility that p- or n-type dopants promote exchange coupling of Co ions was investigated by computing total energies of magnetic states of ZnO supercells containing two Co ions and an oxygen vacancy, substituted N or interstitial Zn in various charge states. The neutral N defect and the singly-positively charged O vacancy are the only defects which strongly promote ferromagnetic exchange coupling of Co ions at intermediate range.Comment: 9 pages, 11 figure

A Design Methodology for MPEG-21 based Digital Policy Management Systems

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Consumer Perception of Bread Quality

Bread contains a wide range of important nutritional components which provide a positive effect on human health. However, the consumption of bread in Belgium is declining during the last decades. This is due to factors such as changing eating patterns and a increasing choice of substitutes like breakfast cereals and fast foods. The aim of this study is to investigate consumer’s quality perception of bread towards sensory, health and nutrition attributes. Consumer’s quality perception of bread seams to be determined by sensory and health attributes. Three clusters of consumers are identified based on these attributes. In the first cluster, consumers’ quality perception of bread is not dependent on the health attributes it embraces, but to some extent on sensory attributes. For the second cluster, both health and sensory attributes appear to influence quality perception. In the third cluster only sensory attributes appear to be important in determining quality perception, though in a negative direction. The results of this study will possibly help health professionals and policy makers to systematically inform the consumers about the positive effects of bread and its components. Furthermore, firms can use the result to build up a tailor-made marketing strategy.Consumer, Quality perception, Bread, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,

Self-driven lattice-model Monte Carlo simulations of alloy thermodynamic

Monte Carlo (MC) simulations of lattice models are a widely used way to compute thermodynamic properties of substitutional alloys. A limitation to their more widespread use is the difficulty of driving a MC simulation in order to obtain the desired quantities. To address this problem, we have devised a variety of high-level algorithms that serve as an interface between the user and a traditional MC code. The user specifies the goals sought in a high-level form that our algorithms convert into elementary tasks to be performed by a standard MC code. For instance, our algorithms permit the determination of the free energy of an alloy phase over its entire region of stability within a specified accuracy, without requiring any user intervention during the calculations. Our algorithms also enable the direct determination of composition-temperature phase boundaries without requiring the calculation of the whole free energy surface of the alloy system

Control of Mammalian Cell Behaviour Through Mimicry of the Extracellular Matrix Environment

This chapter looks at the control of mammalian cell behaviour through mimicry of the extracellular matrix enviromen