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Theory, design, realization and measurements of an X-band isoflux circularly polarized antenna for LEO satellite platforms are presented. The antenna is based on a metasurface composed by a dense texture of sub-wavelength metal patches on a grounded dielectric slab, excited by a surface wave generated by a coplanar feeder. The antenna is extremely flat (1.57 mm) and light (less than 1Kg) and represents a competitive solution for space-to-ground data link applications.Index Terms-Leaky wave antennas, surface impedance, holographic antennas.

Summary• Soil-borne pathogens are a key component of the belowground community because of the significance of their ecological and socio-economic impacts. However, very little is known about the complexity of their distribution patterns in natural systems. Here, we explored the patterns, causes and ecological consequences of spatial variability in pathogen abundance in Mediterranean forests affected by oak decline.• We used spatially explicit neighborhood models to predict the abundance of soil-borne pathogen species (Phytophthora cinnamomi, Pythium spiculum and Pythium spp.) as a function of local abiotic conditions (soil texture) and the characteristics of the tree and shrub neighborhoods (species composition, size and health status). The implications of pathogen abundance for tree seedling performance were explored by conducting a sowing experiment in the same locations in which pathogen abundance was quantified.• Pathogen abundance in the forest soil was not randomly distributed, but exhibited spatially predictable patterns influenced by both abiotic and, particularly, biotic factors (tree and shrub species). Pathogen abundance reduced seedling emergence and survival, but not in all sites or tree species.• Our findings suggest that heterogeneous spatial patterns of pathogen abundance at fine spatial scale can be important for the dynamics and restoration of declining Mediterranean forests.

Summary Abies pinsapo, a fir endemic to a small area in southernmost Spain, is frequently attacked in natural stands by Heterobasidion root rot. To identify the Heterobasidion species causing the disease, pure cultures of the fungus were isolated from symptomatic trees in five localities in Sierra de las Nieves Natural Park and identified by pairing tests. In addition, genets of the fungus were identified in two pure stands of A. pinsapo. All the Heterobasidion specimens collected belonged to the species Heterobasidion abietinum. The largest genet found was 57 m long, and had colonized 10 trees. The large size of the main genets implied that H. abietinum had spread via root contacts from old infections generated before the establishment of the Sierra de las Nieves National Park in 1989. Exceptionally dry summers in the last 20 years may have weakened A. pinsapo and favoured spread of the disease.

We present a synthesis of the sparse matrix/adaptive integral method (SM/AIM) and the multiresolution (MR) approach for the analysis of electrically large finite arrays, with planar or 3-D radiating elements; the two methods were separately introduced previously. The use of the MR has the effect of a preconditioner and speeds up the convergence rate of the SM/AIM of almost two orders of magnitude, with a total reduction of the numerical complexity with respect to the standard MoM of almost three orders of magnitude.