Review of rigorous coupled-wave analysis and of homogeneous effective medium approximations for high spatial-frequency surface-relief gratings

A review of the rigorous coupled-wave analysis as applied to the diffraction of electro-magnetic waves by gratings is presented. The analysis is valid for any polarization, angle of incidence, and conical diffraction. Cascaded and/or multiplexed gratings as well as material anisotropy can be incorporated under the same formalism. Small period rectangular groove gratings can also be modeled using approximately equivalent uniaxial homogeneous layers (effective media). The ordinary and extraordinary refractive indices of these layers depend on the gratings filling factor, the refractive indices of the substrate and superstrate, and the ratio of the freespace wavelength to grating period. Comparisons of the homogeneous effective medium approximations with the rigorous coupled-wave analysis are presented. Antireflection designs (single-layer or multilayer) using the effective medium models are presented and compared. These ultra-short period antireflection gratings can also be used to produce soft x-rays. Comparisons of the rigorous coupled-wave analysis with experimental results on soft x-ray generation by gratings are also included

Mixed-species plantations of eucalyptus with nitrogen fixing trees: a review

Mixed-species plantations of Eucalyptus with a nitrogen (N2) fixing species have the potential to increase productivity while maintaining soil fertility, compared to Eucalyptus monocultures. However, it is difficult to predict combinations of species and sites that will lead to these benefits. We review the processes and interactions occurring in mixed plantations, 5 and the influence of species or site attributes, to aid the selection of successful combinations of species and sites. Successful mixtures, where productivity is increased over that of monocultures, have often developed stratified canopies, such that the less shade-tolerant species overtops the more shadetolerant species. Successful mixtures also have significantly higher rates of N and P cycling than 10 Eucalyptus monocultures. It is therefore important to select N2-fixing species with readily decomposable litter and high rates of nutrient cycling, as well as high rates of N2-fixation. While the dynamics of N2-fixation in tree stands are not well understood, it appears as though eucalypts can benefit from fixed N as early as the first or second year following plantation establishment. A meta-analysis of 18 published studies revealed several trials in which mixtures were significantly 15 (

Analysis, design, and applications of subwavelength diffraction gratings

Ph.D.Thomas K. Gaylor

Structural differences in arbuscular mycorrhizal symbioses: more than 100 years after Gallaud where next?

The original publication can be found at www.springerlink.comThis review commemorates and examines the significance of the work of Isobel Gallaud more than 100 years ago that first established the existence of distinct structural classes (Arum-type and Paris-type) within arbuscular mycorrhizal (AM) symbioses. We add new information from recent publications to the previous data last collated 10 years ago to consider whether any patterns have emerged on the basis of different fungal morphology within plant species or families. We discuss: (1) possible control exerted by the fungus over AM morphology; (2) apparent lack of plant phylogenetic relationships between the classes; (3) functions of the interfaces in different structural classes in relation to nutrient transfer in particular; and (4) the occurrence of plants with both of the major classes, and with intermediate AM structures, in different plant habitats. We also give suggestions for future research to help remove uncertainties about the functional and ecological significance of differences in AM morphology. Lastly, we urge retention of the terms Arum- and Paris-type, which are now well recognised by those who study AM symbioses. Electronic supplementary material The online version of this article (doi:10.1007/s00572-007-0130-9) contains supplementary material, which is available to authorized users.S. Dickson, F. A. Smith and S. E. Smit

Position of the reduced mycorrhizal colonisation (Rmc) locus on the tomato genome map

The original publication is available at www.springerlink.comOur research aims to investigate the molecular communication between land plants and arbuscular mycorrhizal (AM) fungi in the establishment of symbiosis. We have identified a mutation in the facultative AM host tomato, which we named rmc. Plants that are homozygous for rmc no longer host most AM fungi. The mutation also affects the interaction of tomato with root knot nematode and Fusarium wilt. However, the function/s encoded by the intact Rmc locus is/are unknown. To clone and sequence the gene or genes that comprise the Rmc locus, we have initiated a positional cloning project. In this paper, we report the construction of mapping populations and use of molecular markers from the published genome map to identify the location of Rmc on tomato chromosome 8. Nucleotide binding site-leucine rich repeat resistance genes, reported to reside in the same region of that chromosome, provided insufficient differences to develop cleaved amplified polymorphic sequence markers. Therefore, we were unable to map these sequences in relation to rmc. Our results potentiate future work to identify the Rmc function and to determine the genetic basis for the multiple plant-microbe interaction functions that the rmc mutation has defined.Nicholas J. Larkan, Sally E. Smith and Susan J. Barke