Challenges for time and frequency domain aeroacoustic solvers

The linearized Euler equations (LEE) model acoustic propagation in the presence of rotational mean flows. They can be solved in time [1–3] or in frequency [4–6] domain, with both approaches having advantages and disadvantages. Here, those pros and cons are detailed, both from a modeling and a numerical/computational perspective. Furthermore, a performance comparison and cross-validation between two frequency and time domain state-of-the-art solvers is performed. The frequency domain solutions are obtained with the hybridizable discontinuous Galerkin (HDG) [7–12] and the embedded discontinuous Galerkin (EDG) [13–15] method, while the time domain solver is an explicit discontinuous-Galerkin based solver [1]. The performance comparison and cross-validation is performed on a problem of industrial interest, namely acoustic propagation from a duct exhaust in the presence of realistic mean flow.Peer ReviewedPostprint (published version

Morphometric differentiation in Cornops Aquaticum (Orthoptera: Acrididae): associations with sex, chromosome, and geographic conditions

The water-hyacinth grasshopper Cornops aquaticum (Bruner) (Orthoptera: Acrididae) is native to South America and inhabits lowlands from southern Mexico to central Argentina and Uruguay. This grasshopper feeds and lays eggs on species from the genera Eichhornia and Pontederia. Particularly, Eichhornia crassipes is considered “the world’s worst water weed,” and the release of C. aquaticum was proposed as a form of biological control. Morphometric variation on the chromosomally differentiated populations from the middle and lower Parana´ River and its possible association with geographic, sex, and chromosomal conditions was analyzed. Significant phenotype variation in C. aquaticum population was detected. C. aquaticum presents body-size sexual dimorphism, females being bigger than males. Female-biased sexual size dimorphism for all five analyzed traits was detected. The assessment of variation in sexual size dimorphism for tegmen length showed that this trait scaled allometrically, indicating that males and females did not vary in a similar fashion. The detected allometry was consistent with Rensch’s rule demonstrating greater evolutionary divergence in male size than in female size and suggests that males are more sensitive to environmental condition. The analysis of morphometric variation in the context of chromosome constitution showed that the presence of fusion 1/6 was related to body-size variation. Fusion carriers displayed bigger body size than standard homozygotes. Besides, a positive relationship between tegmen length and the number of fused chromosomes was detected, showing a chromosome dose effect. Because the highest frequency of fusions has been found in the lower Parana´ River, a marginal environment for this species, the results found would support the hypothesis that some supergenes located in the fusions may be favored in the southern populations, thus contributing to the establishment and maintenance of the polymorphism.Fil: Romero, Maria Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Colombo, Pablo Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Remis, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Patterns of Spatial Variation of Assemblages Associated with Intertidal Rocky Shores: A Global Perspective

Assemblages associated with intertidal rocky shores were examined for large scale distribution patterns with specific emphasis on identifying latitudinal trends of species richness and taxonomic distinctiveness. Seventy-two sites distributed around the globe were evaluated following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org). There were no clear patterns of standardized estimators of species richness along latitudinal gradients or among Large Marine Ecosystems (LMEs); however, a strong latitudinal gradient in taxonomic composition (i.e., proportion of different taxonomic groups in a given sample) was observed. Environmental variables related to natural influences were strongly related to the distribution patterns of the assemblages on the LME scale, particularly photoperiod, sea surface temperature (SST) and rainfall. In contrast, no environmental variables directly associated with human influences (with the exception of the inorganic pollution index) were related to assemblage patterns among LMEs. Correlations of the natural assemblages with either latitudinal gradients or environmental variables were equally strong suggesting that neither neutral models nor models based solely on environmental variables sufficiently explain spatial variation of these assemblages at a global scale. Despite the data shortcomings in this study (e.g., unbalanced sample distribution), we show the importance of generating biological global databases for the use in large-scale diversity comparisons of rocky intertidal assemblages to stimulate continued sampling and analyses

On the interactions of sound waves and vortices

The effects of vortices on the propagation of acoustic waves are numerous, from simple convection effects to instabilities in the acoustic phenomena, including absorption,reflection and refraction effects. This work focusses on the effects of mean flowvorticity on the acoustic propagation. First, a theoretical background is presentedin chapters 2-5. This part contains: (i) the fluid dynamics and thermodynamicsrelations; (ii) theories of sound generation by turbulent flows; and (iii) operators takenfrom scientific literature to take into account the vorticity effects on acoustics. Later,a family of scalar operators based on total enthalpy terms are derived to handle meanvorticity effects of arbitrary flows in acoustics (chapter 6). Furthermore, analyticalsolutions of Pridmore-Brown’s equation are featured considering exponential boundarylayers whose profile depend on the acoustic parameters of the problem (chapter 7).Finally, an extension of Pridmore-Brown’s equation is formulated for predicting theacoustic propagation over a locally-reacting liner in presence of a boundary layer oflinear velocity profile superimposed to a constant cross flow (chapter 8).Doctorat en Sciences de l'ingénieurinfo:eu-repo/semantics/nonPublishe

On the interactions of sound waves and vortices

The effects of vortices on the propagation of acoustic waves are numerous, from simple convection effects to instabilities in the acoustic phenomena, including absorption,reflection and refraction effects. This work focusses on the effects of mean flowvorticity on the acoustic propagation. First, a theoretical background is presentedin chapters 2-5. This part contains: (i) the fluid dynamics and thermodynamicsrelations; (ii) theories of sound generation by turbulent flows; and (iii) operators takenfrom scientific literature to take into account the vorticity effects on acoustics. Later,a family of scalar operators based on total enthalpy terms are derived to handle meanvorticity effects of arbitrary flows in acoustics (chapter 6). Furthermore, analyticalsolutions of Pridmore-Brown’s equation are featured considering exponential boundarylayers whose profile depend on the acoustic parameters of the problem (chapter 7).Finally, an extension of Pridmore-Brown’s equation is formulated for predicting theacoustic propagation over a locally-reacting liner in presence of a boundary layer oflinear velocity profile superimposed to a constant cross flow (chapter 8).Doctorat en Sciences de l'ingénieurinfo:eu-repo/semantics/nonPublishe

Solution of Pierce’s equation for Tam & Auriault's mixing noise model

International audienceThe adjoint method introduced by Tam & Auriault (1998) enables to properly taking into account the acoustic propagation effects when jet noise is modelled from the statistics of a turbulent flow. This technique is recast in a systematic way valid for arbitrary propagation media, linear operators and sound sources. An acoustic analogy based on Pierce's wave equation for the acoustic potential (1990) is proposed in this study. Tam & Auriault's mixing noise model (1999) is reformulated for this operator. This approach presents three main advantages; no instability wave can occur since the acoustic energy conservation is enforced, then for being self-adjoint the adjoint solution to the propagation problem may straightforwardly be computed by flow reversal, finally Pierce's wave equation is a simple and computationally efficient equation that several existing solvers are able to solve. Work performed with Actran TM software is presented illustrating the ability of a commercial tool to solve this equation and to compute adjoint Green's function required in statistical jet noise modelling. The nighty-degree acoustic spectrum of a Mj=0.9 round jet is computed with Green's functions properly tailored to the jet mean flow

GABAA Receptor Subunit Composition Drives Its Sensitivity to the Insecticide Fipronil

International audienceFipronil (FPN) is a worldwide-used neurotoxic insecticide, targeting, and blocking GABA A receptors (GABA A Rs). Beyond its efficiency on insect GABA A Rs, FPN causes neurotoxic effects in humans and mammals. Here, we investigated the mode of action of FPN on mammalian α6-containing GABA A Rs to understand its inhibitory effects on GABA-induced currents, as a function of the synaptic or extrasynaptic localization of GABA A Rs. We characterized the effects of FPN by electrophysiology using Xenopus oocytes which were microtransplanted with cerebellum membranes or injected with α6β3, α6β3γ2S (synaptic), and α6β3δ (extrasynaptic) cDNAs. At micromolar concentrations, FPN dose-dependently inhibited cerebellar GABA currents. FPN acts as a non-competitive antagonist on ternary receptors. Surprisingly, the inhibition of GABA-induced currents was partial for extra-synaptic (α6β3δ) and binary (α6β3) receptors, while synaptic α6β3γ2S receptors were fully blocked, indicating that the complementary γ or δ subunit participates in FPN-GABA A R interaction. FPN unexpectedly behaved as a positive modulator on β3 homopentamers. These data show that FPN action is driven by the subunit composition of GABA A Rs—highlighting the role of the complementary subunit—and thus their localization within a physiological synapse. We built a docking model of FPN on GABA A Rs, which reveals two putative binding sites. This is consistent with a double binding mode of FPN on GABA A Rs, possibly one being of high affinity and the other of low affinity. Physiologically, the γ/δ subunit incorporation drives its inhibitory level and has important significance for its toxicity on the mammalian nervous system, especially in acute exposure

Oxostephanine, Thalmiculine, and Thaliphyline—Three Isoquinoleine Alkaloids That Inhibit L-Type Voltage-Gated Ca2+ Channels

International audienceThe isoquinoline alkaloids (IAs) represent a large and diverse subfamily of phytochemicals in terms of structures and pharmacological activities, including ion channel inhibition. Several IAs, such as liriodenine (an oxoaporphine) and curine (a bisbenzylisoquinoline (BBIQ), inhibit the L-type voltage-gated Ca2+ channels (LTCC). In this study, we aimed to search for new blockers of LTCC, which are therapeutic targets in neurological and cardiovascular diseases. We set up a screening assay using the rat pituitary GH3b6 cell line, which expresses two LTCC isoforms, CaV1.2 and CaV1.3. Both LTCC subtypes can be indirectly activated by KCl concentration elevation or directly by the dihydropyridine (DHP), BAY K8644, leading to an increase in the intracellular Ca2+ concentration ([Ca2+]i). These Ca2+ responses were completely blocked by the selective LTCC DHP inhibitor, nifedipine. Thereby, 16 selected IAs were tested for their ability to inhibit KCl and BAY K8644-induced Ca2+ responses. We then identified three new potent LTCC blockers, namely, oxostephanine, thaliphyline, and thalmiculine. They inhibited LTCC with IC50 values in the micromolar range through interaction to a binding site different to that of dihydropyridines. The two subfamilies of IAs, oxoaporphine with oxostephanine, and BBIQs with both thalyphilline and thalmiculine, constitute interesting pharmacophores for the development of future therapeutic leads for neurological and cardiovascular diseases

Partial Agonist Activity of Neonicotinoids on Rat Nicotinic Receptors: Consequences over Epinephrine Secretion and In Vivo Blood Pressure

International audienceNeonicotinoid insecticides are nicotine-derived molecules which exert acute neurotoxic effects over the insect central nervous system by activating nicotinic acetylcholine receptors (nAChRs). However, these receptors are also present in the mammalian central and peripheral nervous system, where the effects of neonicotinoids are faintly known. In mammals, cholinergic synapses are crucial for the control of vascular tone, blood pressure and skeletal muscle contraction. We therefore hypothesized that neonicotinoids could affect cholinergic networks in mammals and sought to highlight functional consequences of acute intoxication in rats with sub-lethal concentrations of the highly used acetamiprid (ACE) and clothianidin (CLO). In this view, we characterized their electrophysiological effects on rat α3β4 nAChRs, knowing that it is predominantly expressed in ganglia of the vegetative nervous system and the adrenal medulla, which initiates catecholamine secretion. Both molecules exhibited a weak agonist effect on α3β4 receptors. Accordingly, their influence on epinephrine secretion from rat adrenal glands was also weak at 100 μM, but it was stronger at 500 μM. Challenging ACE or CLO together with nicotine (NIC) ended up with paradoxical effects on secretion. In addition, we measured the rat arterial blood pressure (ABP) in vivo by arterial catheterization. As expected, NIC induced a significant increase in ABP. ACE and CLO did not affect the ABP in the same conditions. However, simultaneous exposure of rats to both NIC and ACE/CLO promoted an increase of ABP and induced a biphasic response. Modeling the interaction of ACE or CLO on α3β4 nAChR is consistent with a binding site located in the agonist pocket of the receptor. We present a transversal experimental approach of mammal intoxication with neonicotinoids at different scales, including in vitro, ex vivo, in vivo and in silico. It paves the way of the acute and chronic toxicity for this class of insecticides on mammalian organisms