Physical Acoustics

Contains research objectives and reports on three research projects.U.S. Navy (Office of Naval Research) under Contract Nonr-1841(42

Physical Acoustics

Contains reports on six research projects.National Science Foundation (Grant G-9330)United States Navy, Office of Naval Research (Contract Nonr-1841(42)

Physical Acoustics

Contains reports on four research projects.U. S. Navy (Office of Naval Research) under Contract Nonr-1841(42

Dynamic effective anisotropy: Asymptotics, simulations, and microwave experiments with dielectric fibers

International audienceWe investigate dynamic effective anisotropy in photonic crystals (PCs) through a combination of an effective medium theory, which is a high-frequency homogenization (HFH) method explicitly developed to operate for short waves, as well as through numerical simulations and microwave experiments. The HFH yields accurate predictions of the effective anisotropic properties of periodic structures when the wavelength is of comparable order to the pitch of the array; specifically, we investigate a square array of pitch 2 cm consisting of dielectric rods of radius 0.5 cm and refractive index n=6√ within an air matrix. This behaves as an effective medium, with strong artificial anisotropy, at a frequency corresponding to a flat band emerging from a Dirac-like point in transverse magnetic (TM) polarization. At this frequency, highly directive emission is predicted for an electric source placed inside this PC, and this artificial anisotropy can be shown to coincide with a change of character of the underlying effective equation from isotropic to unidirective, with coefficients of markedly different magnitudes appearing in the effective equation tensor. In transverse electric (TE) polarization, we note a second radical change of character of the underlying effective equation, this time from elliptic to hyperbolic, near a frequency at which a saddle point occurs in the corresponding dispersion curves. Delicate microwave experiments are performed in both polarizations for such a PC consisting of 80 rods, and we demonstrate that a directive emission in the form of a + (respectively, an X) is indeed seen experimentally at the predicted frequency 9.5 GHz in TM polarization (respectively, 5.9 GHz in TE polarization). These are clearly dynamic effects since in the quasistatic regime the PC just behaves as an isotropic medium

Physical Acoustics

Contains research objectives and reports on five research projects.U. S. Navy (Office of Naval Research under Contract Nonr- 1841(42)National Aeronautics and Space Administratio

Physical Acoustics

Contains reports on eight research projects.Office of Naval Research (Contract Nonr-1841(42)United States Air Force, Air Force Cambridge Research Center, Air Research and Development Command (Contract AF19(604)-2051

Physical Acoustics

Contains reports on two research projects.U. S. Navy. Office of Naval Research (Contract Nonr-1841(42)

The source ambiguity problem: Distinguishing the effects of grammar and processing on acceptability judgments

Judgments of linguistic unacceptability may theoretically arise from either grammatical deviance or significant processing difficulty. Acceptability data are thus naturally ambiguous in theories that explicitly distinguish formal and functional constraints. Here, we consider this source ambiguity problem in the context of Superiority effects: the dispreference for ordering a wh-phrase in front of a syntactically “superior” wh-phrase in multiple wh-questions, e.g., What did who buy? More specifically, we consider the acceptability contrast between such examples and so-called D-linked examples, e.g., Which toys did which parents buy? Evidence from acceptability and self-paced reading experiments demonstrates that (i) judgments and processing times for Superiority violations vary in parallel, as determined by the kind of wh-phrases they contain, (ii) judgments increase with exposure, while processing times decrease, (iii) reading times are highly predictive of acceptability judgments for the same items, and (iv) the effects of the complexity of the wh-phrases combine in both acceptability judgments and reading times. This evidence supports the conclusion that D-linking effects are likely reducible to independently motivated cognitive mechanisms whose effects emerge in a wide range of sentence contexts. This in turn suggests that Superiority effects, in general, may owe their character to differential processing difficulty

Forest disturbance increases functional diversity but decreases phylogenetic diversity of an arboreal tropical ant community

Tropical rainforest trees host a diverse arthropod fauna that can be characterised by their functional diversity (FD) and phylogenetic diversity (PD). Human disturbance degrades tropical forests, often coinciding with species invasion and altered assembly that leads to a decrease in FD and PD. Tree canopies are thought to be particularly vulnerable, but rarely investigated. Here, we studied the effects of forest disturbance on an ecologically important invertebrate group, the ants, in a lowland rainforest in New Guinea. We compared an early successional disturbed plot (secondary forest) to an old‐growth plot (primary forest) by exhaustively sampling their ant communities in a total of 852 trees. We expected that for each tree community (1) disturbance would decrease FD and PD in tree‐dwelling ants, mediated through species invasion. (2) Disturbance would decrease ant trait variation due to a more homogeneous environment. (3) The main drivers behind these changes would be different contributions of true tree‐nesting species and visiting species. We calculated FD and PD based on a species‐level phylogeny and 10 ecomorphological traits. Furthermore, we assessed by data exclusion the influence of species, which were not nesting in individual trees (visitors) or only nesting species (nesters), and of non‐native species on FD and PD. Primary forests had higher ant species richness and PD than secondary forest. However, we consistently found increased FD in secondary forest. This pattern was robust even if we decoupled functional and phylogenetic signals, or if non‐native ant species were excluded from the data. Visitors did not contribute strongly to FD, but they increased PD and their community weighted trait means often varied from nesters. Moreover, all community‐weighted trait means changed after forest disturbance. Our finding of contradictory FD and PD patterns highlights the importance of integrative measures of diversity. Our results indicate that the tree community trait diversity is not negatively affected, but possibly even enhanced by disturbance. Therefore, the functional diversity of arboreal ants is relatively robust when compared between old‐growth and young trees. However, further study with higher plot‐replication is necessary to solidify and generalise our findings

Forest disturbance increases functional diversity but decreases phylogenetic diversity of an arboreal tropical ant community

DATA AVAILABILITY STATEMENT : All data and R scripts underlying this work are publicly available in the Zenodo Digital Repository: https://doi.org/10.5281/zenodo.10624632 (Hoenle et al., 2024).SUPPLEMENTARY MATERIAL : TEXT S1: Molecular methods for obtaining sequences of ant species and assembly of the phylogenetic tree. TABLE S1: List of the 127 species with gathered molecular information. TABLE S2: Ant traits used in this study. TABLE S3: Characteristics of arboreal ant communities sampled in 0.4 ha of primary and 0.4 ha of secondary lowland rainforest in Papua New Guinea, and of their taxonomic, functional (FD) and phylogenetic (PD) diversity, with non-native species excluded from the dataset. TABLE S4: Blomberg's K of all traits used in this study. FIGURE S1: Correlations between all traits used in this study. FIGURE S2: Arboreal ant functional diversity (A), phylogenetic diversity (B), the correlation between functional and phylogenetic diversity (C), the decoupled functional (D) and phylogenetic diversity (E) and the species richness (F) on tree scale after excluding all non-native species. FIGURE S3: The SES Rao Q of ten individual traits, calculated from three different community matrices (all, visitors and nesters).Tropical rainforest trees host a diverse arthropod fauna that can be characterised by their functional diversity (FD) and phylogenetic diversity (PD). Human disturbance degrades tropical forests, often coinciding with species invasion and altered assembly that leads to a decrease in FD and PD. Tree canopies are thought to be particularly vulnerable, but rarely investigated. Here, we studied the effects of forest disturbance on an ecologically important invertebrate group, the ants, in a lowland rainforest in New Guinea. We compared an early successional disturbed plot (secondary forest) to an old-growth plot (primary forest) by exhaustively sampling their ant communities in a total of 852 trees. We expected that for each tree community (1) disturbance would decrease FD and PD in tree-dwelling ants, mediated through species invasion. (2) Disturbance would decrease ant trait variation due to a more homogeneous environment. (3) The main drivers behind these changes would be different contributions of true tree-nesting species and visiting species. We calculated FD and PD based on a species-level phylogeny and 10 ecomorphological traits. Furthermore, we assessed by data exclusion the influence of species, which were not nesting in individual trees (visitors) or only nesting species (nesters), and of non-native species on FD and PD. Primary forests had higher ant species richness and PD than secondary forest. However, we consistently found increased FD in secondary forest. This pattern was robust even if we decoupled functional and phylogenetic signals, or if non-native ant species were excluded from the data. Visitors did not contribute strongly to FD, but they increased PD and their community weighted trait means often varied from nesters. Moreover, all community-weighted trait means changed after forest disturbance. Our finding of contradictory FD and PD patterns highlights the importance of integrative measures of diversity. Our results indicate that the tree community trait diversity is not negatively affected, but possibly even enhanced by disturbance. Therefore, the functional diversity of arboreal ants is relatively robust when compared between old-growth and young trees. However, further study with higher plot-replication is necessary to solidify and generalise our findings.Grant Agency of University of South Bohemia and Czech Science Foundation. Open access publishing facilitated by Biologicke centrum Akademie ved Ceske republiky, as part of the Wiley - CzechELib agreement.http://www.wileyonlinelibrary.com/journal/janehj2024Zoology and EntomologySDG-15:Life on lan