Ab-Initio Study on the Hard Magnetic Properties of MnBi

We have studied the hard magnetic properties of the low-temperature phase of MnBi with first principle calculations based on the density functional theory. The calculations have been carried out on two distinct unit cell configurations MnBi and BiMn with the element in the unit cell origin named first. Our results show that these configurations are not equivalent and that MnBi describes the system better near T = 0K and the BiMn configuration describes the system better for T > 300K. The magnetic moments of both configurations agree well with experimental measurements considering both spin and orbital contributions. At high temperatures the magneto-crystalline anisotropy energy increases with increasing unit cell volume and reaches a maximum of 2:3MJ=m3 and a c=a ratio of 1:375.Comment: Presented at 20th International Conference on Magnetism (ICM2015) in Barcelona, accepted for publication. 5 pages, 2 figures, 4 table

The export competitiveness of the newly industrialised east Asian economies: How real is the Chinese threat in electronics?

This paper examines the export performance of China in electronics compared to the east Asian NIEs exporting to the USA, the European Union, and Japan between 1988 and 2001 using a dynamic version of shift-share analysis to overcome some of the inherent drawbacks of the widely-used static shift-share methodology. Our findings suggest that China has now emerged as a serious contender in the export market for electronic goods, but this position has not been a dominant one. For electronics as a whole, the principal gainers after 1995 appear to be newcomers China and Malaysia at the expense of the older Tigers, like Singapore and Hong Kong. To some extent this represents a natural process of ‘catch-up’. Moreover, no single NIE has dominated all categories of electronic exports. In the east Asian region, the less developed members of ASEAN would appear to be most at risk in the immediate future since they compete head on with China in lower-end manufacturing and are in danger of being ‘leapfrogged’ in the value-added chain. The more advanced NIEs are in a better position since they have time to increase value-added before China catches up and may benefit more from the opportunities China offers in terms of production and service complementarities

Composing Scalable Nonlinear Algebraic Solvers

Most efficient linear solvers use composable algorithmic components, with the most common model being the combination of a Krylov accelerator and one or more preconditioners. A similar set of concepts may be used for nonlinear algebraic systems, where nonlinear composition of different nonlinear solvers may significantly improve the time to solution. We describe the basic concepts of nonlinear composition and preconditioning and present a number of solvers applicable to nonlinear partial differential equations. We have developed a software framework in order to easily explore the possible combinations of solvers. We show that the performance gains from using composed solvers can be substantial compared with gains from standard Newton-Krylov methods.Comment: 29 pages, 14 figures, 13 table

How to make Dupire's local volatility work with jumps

There are several (mathematical) reasons why Dupire's formula fails in the non-diffusion setting. And yet, in practice, ad-hoc preconditioning of the option data works reasonably well. In this note we attempt to explain why. In particular, we propose a regularization procedure of the option data so that Dupire's local vol diffusion process recreates the correct option prices, even in manifest presence of jumps

Reductive dechlorination of polychlorinated biphenyls is coupled to nitrogen fixation by a legume-rhizobium symbiosis

Chlorinated persistent organic pollutants, including polychlorinated biphenyls (PCBs), represent a particularly serious environmental problem and human health risk worldwide. Leguminous plants and their symbiotic bacteria (rhizobia) are important components of the biogeochemical cycling of nitrogen in both agricultural and natural ecosystems. However, there have been relatively few detailed studies of the remediation of PCB-contaminated soils by legume-rhizobia symbionts. Here we report for the first time evidence of the reductive dechlorination of 2,4,4&#39;-trichlorobiphenyl (PCB 28) by an alfalfa-rhizobium nitrogen fixing symbiont. Alfalfa (Medicago sativa L.) inoculated with wild-type Sinorhizobium meliloti had significantly larger biomass and PCB 28 accumulation than alfalfa inoculated with the nitrogenase negative mutant rhizobium SmY. Dechlorination products of PCB 28, 2,4&#39;-dichlorobiphenyl (PCB 8), and the emission of chloride ion (Cl-) were also found to decrease significantly in the ineffective nodules infected by the mutant strain SmY. We therefore hypothesize that N2-fixation by the legume-rhizobium symbiont is coupled with the reductive dechlorination of PCBs within the nodules. The combination of these two processes is of great importance to the biogeochemical cycling and bioremediation of organochlorine pollutants in terrestrial ecosystems.</p

Self-absorption in the solar transition region

Transient brightenings in the transition region of the Sun have been studied for decades and are usually related to magnetic reconnection. Recently, absorption features due to chromospheric lines have been identified in transition region emission lines raising the question of the thermal stratification during such reconnection events. We analyse data from the Interface Region Imaging Spectrograph (IRIS) in an emerging active region. Here the spectral profiles show clear self-absorption features in the transition region lines of Si\,{\sc{iv}}. While some indications existed that opacity effects might play some role in strong transition region lines, self-absorption has not been observed before. We show why previous instruments could not observe such self-absorption features, and discuss some implications of this observation for the corresponding structure of reconnection events in the atmosphere. Based on this we speculate that a range of phenomena, such as explosive events, blinkers or Ellerman bombs, are just different aspects of the same reconnection event occurring at different heights in the atmosphere.Comment: Accepted for publication in Ap