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- Fernandez-Prieto, Armando, et al.
(author)
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Glide Symmetry Applied to the Design of Common-Mode Rejection Filters Based on Complementary Split-Ring Resonators
- 2023
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In: IEEE Transactions on Circuits and Systems - II - Express Briefs. - : Institute of Electrical and Electronics Engineers (IEEE). - 1549-7747 .- 1558-3791. ; 70:6, s. 1911-1915
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Journal article (peer-reviewed)abstract
- In this brief, glide symmetry is applied to design common-mode rejection filters based on defected ground structures with bandstop response. To this aim, complementary split-ring resonators are chosen as the basic components for common-mode rejection. To illustrate the advantages of using glide symmetry, three implementations are studied and compared. The results reveal that glide symmetry offers the best performance in terms of common-mode rejection level and fractional bandwidth. Furthermore, glide symmetry barely affects the integrity of the differential mode. A prototype of each of the considered symmetries has been designed, simulated, and tested for practical validation. Good agreement is observed between the simulated and measured results, experimentally demonstrating the advantages of glide symmetry.
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- Householder, John Ethan, et al.
(author)
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One sixth of Amazonian tree diversity is dependent on river floodplains
- 2024
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In: NATURE ECOLOGY & EVOLUTION. - 2397-334X.
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Journal article (peer-reviewed)abstract
- Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.
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- Luize, Bruno Garcia, et al.
(author)
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Geography and ecology shape the phylogenetic composition of Amazonian tree communities
- 2024
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In: JOURNAL OF BIOGEOGRAPHY. - 0305-0270 .- 1365-2699.
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Journal article (peer-reviewed)abstract
- Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and v & aacute;rzea forest types, the phylogenetic composition varies by geographic region, but the igap & oacute; and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R-2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R-2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.
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- Mouris, Boules Atef, et al.
(author)
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Glide Symmetry Applied to Printed Common-Mode Rejection Filters
- 2022
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In: IEEE transactions on microwave theory and techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 70:2, s. 1198-1210
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Journal article (peer-reviewed)abstract
- In this article, we present a novel application of glide symmetry to differential lines with common-mode (CM) rejection filter properties. Two different topologies are investigated. First, glide symmetry is applied to a pair of differential lines where ground-connected mushrooms are employed as a CM rejection structure. The same idea is also used in a pair of differential lines where defective ground structures are introduced to stop the CM propagation. It is demonstrated that the CM rejection bandwidth is drastically increased when glide symmetry is exploited in both topologies when compared with their corresponding structures without glide symmetry. Furthermore, we show that the differential-mode propagation is hardly affected by the use of glide symmetry, ensuring the good integrity of the transmitted information. Experimental demonstration for both mushroom and defected ground structure is provided. Good agreement between simulations and measurements results is observed.
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- Mouris, Boules Atef, et al.
(author)
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Glide Symmetry to Improve the Bandgap Operation of Periodic Microstrip Defected Ground Structures
- 2020
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In: 2020 50th european microwave conference (EuMC). - : IEEE. ; , s. 483-486
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Conference paper (peer-reviewed)abstract
- A novel one-dimensional periodic planar defected ground structure exploiting glide symmetry is proposed here. The planar structure is designed to operate as an electromagnetic bandgap structure that avoids the use of vias. Simulation results show that the glide-symmetric structure offers a wider rejection bandwidth as well as a higher rejection level than the conventional structure (without glide symmetry). Measurement results of the fabricated prototypes are provided to verify the simulation results.
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- Mouris, Boules Atef, et al.
(author)
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On the Increment of the Bandwidth of Mushroom-Type EBG Structures With Glide Symmetry
- 2020
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In: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670.
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Journal article (peer-reviewed)abstract
- Mushroom-type electromagnetic bandgap (EBG) structures are known to operate as high-impedance surfaces at low-frequency bands. They are broadly used in the microwave regime. However, one of the main drawbacks of mushroom-type EBG structures is their narrow bandwidth. In this article, we propose a mushroom-type EBG structure with glide-symmetric edge vias to increase the operational bandwidth. This bandwidth increment is explained by the physical insight provided by an equivalent circuit model of the structure as well as the description of the field behavior. Simulation and measurement results show an improvement of approximately 67% over the case without glide symmetry in the structure. We conclude that applying glide symmetry to the mushroom-type EBG structures can improve their bandwidth without adding additional manufacturing costs.
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- ter Steege, Hans, et al.
(author)
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Mapping density, diversity and species-richness of the Amazon tree flora
- 2023
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In: COMMUNICATIONS BIOLOGY. - 2399-3642. ; 6:1
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Journal article (peer-reviewed)abstract
- Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution. A study mapping the tree species richness in Amazonian forests shows that soil type exerts a strong effect on species richness, probably caused by the areas of these forest types. Cumulative water deficit, tree density and temperature seasonality affect species richness at a regional scale.
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