Representing anisotropic subduction zones with isotropic velocity models: A characterization of the problem and some steps on a possible path forward

Despite the widely known fact that mantle flow in and around subduction zones produces the development of considerable seismic anisotropy, most P-wave tomography efforts still rely on the assumption of isotropy. In this study, we explore the potential effects of erroneous assumption on tomographic images and explore an alternative approach. We conduct a series of synthetic tomography tests based on a geodynamic simulation of subduction and rollback. The simulation results provide a self-consistent distribution of isotropic (thermal) anomalies and seismic anisotropy which we use to calculate synthetic delay times for a number of realistic and hypothetical event distributions. We find that anisotropy-induced artifacts are abundant and significant for teleseismic, local and mixed event distributions. The occurrence of artifacts is not reduced, and indeed can be exacerbated, by increasing richness in ray-path azimuths and incidence angles. The artifacts that we observe are, in all cases, important enough to significantly impact the interpretation of the images. We test an approach based on prescribing the anisotropy field as an a priori constraint and find that even coarse approximations to the true anisotropy field produce useful results. Using approximate anisotropy, fields can result in reduced RMS misfit to the travel time delays and reduced abundance and severity of imaging artifacts. We propose that the use of anisotropy fields derived from geodynamic modeling and constrained by seismic observables may constitute a viable alternative to isotropic tomography that does not require the inversion for anisotropy parameters in each node of the model

Estudio de laboratorio de la susceptibilidad a la corrosión intergranular del cinc y su relación con el contenido de aluminio

A method of test for determining the susceptibility of zinc to the intergranular corrosion was developped, considering that the action of water steam on zinc produces the mentioned type of corrosion. Local and foreing specimens have been studied. In the suscep- tibies specimens, the sign of intergranular corrosion, characterized by visual and micrographic observations, appears after 30 h exposition. Correlation between susceptibility and aluminium content was established: 0,005 $ of aluminium in laminated zinc was the maximum content in order to avoid corrosion.Se ideó un método de ensayo para, determinar la susceptibilidad del cinc a la corrosión intergranular, teniendo en cuenta que el ataque con vapor de agua provoca en el cinc ese tipo corrosión. Se ensayaron probetas de origen nacional y extranjero. En las muestras susceptibles,los signos, de corrosión intergranular — que fueron caracterizados mediante observaciones visuales y micrográficas -r aparecieron después de las 30, horas de exposición. Se estableció una correlación entre esa susceptibilidad y él contenido de aluminio, y se fijó como contenido máximo de aluminio en -cinc laminado el de 0,005 %

Symmetric Periodic Solutions of the Anisotropic Manev Problem

We consider the Manev Potential in an anisotropic space, i.e., such that the force acts differently in each direction. Using a generalization of the Poincare' continuation method we study the existence of periodic solutions for weak anisotropy. In particular we find that the symmetric periodic orbits of the Manev system are perturbed to periodic orbits in the anisotropic problem.Comment: Late

Strength in numbers:combining multi-source remotely sensed data to model plant invasions in coastal dune ecosystems

International audienceA common feature of most theories of invasion ecology is that the extent and intensity of invasions is driven by a combination of drivers, which can be grouped into three main factors propagule pressure (P), abiotic drivers (A) and biotic interactions (B). However, teasing apart the relative contribution of P, A and B on Invasive Alien Species (IAS) distributions is typically hampered by a lack of data. We focused on Mediterranean coastal dunes as a model system to test the ability of a combination of multi-source Remote Sensing (RS) data to characterize the distribution of five IAS. Using generalized linear models, we explored and ranked correlates of P, A and B derived from high-resolution optical imagery and three-dimensional (3D) topographic models obtained from LiDAR, along two coastal systems in Central Italy (Lazio and Molise Regions). Predictors from all three factors contributed significantly to explaining the presence of IAS, but their relative importance varied among the two Regions, supporting previous studies suggesting that invasion is a context-dependent process. The use of RS data allowed us to characterize the distribution of IAS across broad, regional scales and to identify coastal sectors that are most likely to be invaded in the future. © 2019 by the authors

Linear stability of the Lagrangian triangle solutions for quasihomogeneous potentials

In this paper we study the linear stability of the relative equilibria for homogeneous and quasihomogeneous potentials. Firstly, in the case the potential is a homogeneous function of degree $-a$, we find that any relative equilibrium of the $n$-body problem with $a>2$ is spectrally unstable. We also find a similar condition in the quasihomogeneous case. Then we consider the case of three bodies and we study the stability of the equilateral triangle relative equilibria. In the case of homogeneous potentials we recover the classical result obtained by Routh in a simpler way. In the case of quasihomogeneous potentials we find a generalization of Routh inequality and we show that, for certain values of the masses, the stability of the relative equilibria depends on the size of the configuration.Comment: 21 pages 4 figure

Diversity in Secondary Metabolites Including Mycotoxins from Strains of <i>Aspergillus </i>Section <i>Nigri </i>Isolated from Raw Cashew Nuts from Benin, West Africa

<p>In a previous study, raw cashew kernels were assayed for the fungal contamination focusin on strains belonging to the genus Aspergillus and on aflatoxins producers. These sample showed high contamination with Aspergillus section Nigri species and absence o aflatoxins. To investigate the diversity of secondary metabolites, including mycotoxins, th species of A. section Nigri may produce and thus threaten to contaminate the raw cashe kernels, 150 strains were isolated from cashew samples and assayed for their productio of secondary metabolites using liquid chromatography high resolution mass spectrometr (LC-HRMS). Seven species of black Aspergilli were isolated based on morphological an chemical identification: A.Tubingensis (44%), A. niger (32%), A. brasiliensis (10%), A. carbonariu (8.7%), A. luchuensis (2.7%), A. aculeatus (2%) and A. aculeatinus (0.7%). Fro these, 45 metabolites and their isomers were identified. Aurasperone and pyranonigrin A produced by all species excluding A. aculeatus and A. aculeatinus, were most prevalen and were encountered in 146 (97.3%) and 145 (95.7%) isolates, respectively. Three mycotoxin groups were detected: fumonisins (B2 and B4) (2.7%) ochratoxin A (13.3%), an secalonic acids (2%), indicating that these mycotoxins could occur in raw cashew nuts Thirty strains of black Aspergilli were randomly sampled for verification of species identit based on sequences of β-Tubulin and calmodulin genes. Among them, 27 isolates wer positive to the primers used and 11 were identified as A. niger, 7 as A.Tubingensis, 6 as A carbonarius, 2 as A. luchuensis and 1 as A. welwitschiae confirming the species names a based on morphology and chemical features. These strains clustered in 5 clades in A. sectio Nigri. Chemical profile clustering also showed also 5 groups confirming the speciespecific metabolites production.</p

Diagnostic accuracy of optical coherence tomography for diagnosing glaucoma: secondary analyses of the GATE study

Background/Aims: To assess the diagnostic performance of retinal nerve fibre layer (RNFL) data of optical coherence tomography (OCT) for detecting glaucoma. Methods: Secondary analyses of a prospective, multicentre diagnostic study (Glaucoma Automated Tests Evaluation (GATE)) referred to hospital eye services in the UK were conducted. We included data from 899 of 966 participants referred to hospital eye services with suspected glaucoma or ocular hypertension. We used both eyes’ data and logistic regression-based receiver operator characteristics analysis to build a set of models to measure the sensitivity and specificity of the average and inferior quadrant RNFL thickness data of OCT. The reference standard was expert clinician examination including automated perimetry. The main outcome measures were sensitivity at 0.95 specificity and specificity at 0.95 sensitivity and the corresponding RNFL thickness thresholds. We explored the possibility of accuracy improvement by adding measures of within-eye and between-eye variation, scan quality, intraocular pressure (IOP) and age. Results: Glaucoma was diagnosed in at least one eye in 17% of participants. Areas under the curve were between 0.83 and 0.88. When specificity was fixed at 0.95, the sensitivity was between 0.38 and 0.55, and the highest values were reached with models including the inferior quadrant rather than the average RNFL thickness. Fixing specificity at 0.95, the sensitivity was between 0.36 and 0.58. The addition of age, refractive error, IOP or within-subject variation did not improve the accuracy. Conclusion: RNFL thickness data of OCT can be used as a diagnostic test, but accuracy estimates remain moderate even in exploratory multivariable modelling of aiming to improve accuracy

Measurement of pesticide residues from chemical control of the invasive Spodoptera frugiperda (Lepidoptera: Noctuidae) in a maize experimental field in Mokwa, Nigeria

Open Access JournalThe management of the fall armyworm Spodoptera frugiperda in maize field necessitates the use a big quantities of insecticides and sometimes the use of multiple types and formulations of chemicals. The use of insecticides in crops is associated with environmental risks and health hazards to both producers and consumers. This study was designed to evaluate the residue of 11 insecticides that were used to control high population of the fall armyworm in maize field in Mokwa, Nigeria. Maize and soil samples were collected from an experimental field to investigate the residue level using high performance liquid chromatography (HPLC, Agilent Technologies, Santa Clara, CA, USA) analysis techniques. Results revealed the presence of five insecticide compounds (Cypermethrin, Deltamethrin, Lambda-Cyhalothrin, Permethrin, and Chorpyrifos) in soil samples with possible adverse effects on soil born organisms and other non-targeted species. In contrast, no residue was found in maize stems and seeds. From these results, we conclude that the treated maize remains safe for consumption and the producers may not get any serious risk of contamination from the chemical control of the fall armywor