Comparative analysis of canine and human melanomas

This paper presents epidemiological and clinical data from 2350 cases of melanocytic tumours from dogs sampled in France. In addition, we present the histological and genetic characterization of subsets of melanoma cases (n=153 and n=100, respectively), with a comparative aspect to human melanomas. Dog melanomas occur at the same anatomical sites than human melanomas, but with different frequency and severity. We demonstrate that the specificities of dog melanomas make them good models to understand the non-UV pathways of human melanomas. Interestingly, somatic mutations in oral canine melanomas were detected in the NRAS and PTEN genes, precisely at the same hotspots as human mutations. In contrast, mutations in the BRAF gene were not detected. This paper highlights the similarities and differences of dog and human melanoma types and the strong potential of dog melanomas to decipher the non-UV light pathways in different melanoma types, especially mucosal and acral types.Cet article présente les données épidémiologiques et cliniques de 2350 cas de tumeurs mélanocytaires canines collectées en France. Nous avons réalisé la caractérisation histologique (n = 153) et génétique (n = 100) d'un sous-groupe de mélanomes dont les résultats ont été comparés aux données des mélanomes humains. Les mélanomes apparaissent aux mêmes sites anatomiques chez le chien et l'Homme, mais avec des fréquences et des sévérités différentes. Nous montrons les prédispositions raciales des mélanomes canins et l'intérêt de ce modèle pour rechercher les gènes prédisposant difficiles à identifier chez l'Homme. Des mutations somatiques dans les gènes NRAS et PTEN ont été détectées dans les mélanomes buccaux canins, précisément aux mêmes points chauds (hotspots) que les mutations de ces gènes chez l'homme. Au contraire, aucune mutation dans le gène BRAF n'a été retrouvée dans les échantillons canins analysés. Ce travail met en lumière les homologies et différences entre les types de mélanomes humains et canins et démontre la force du modèle canin pour analyser les voies de signalisation non UV-dépendantes des mélanomes humains, particulièrement dans les types muqueux et acraux

Further experimental study of the role of wavelets in the hiss bandfor triggering chorus emmissions

The results of detailed spectral analyses and direction finding for ELF data containing simultaneous hiss and chorus have been reported on the basis of the data observed onboard GEOS1 satellite in the outer magnetosphere at a high geomagnetic latitude (Λ～_25°). A combination of the present results with those from our previous equatorial studies, has yielded the following findings : (1) Each chorus element has a tendency to be originated from the hiss band and is asymptotic to the hiss band. (2) The intensity and occurrence of chorus are closely correlated with the intensity of the underlying hiss. (3) The hiss band exhibits some structures or wavelets (i. e. monochromatic wave components with significant duration), and we notice the existence of the causative wavelet at the foot of each chorus element. (4) There is a tendency that the intensity of wavelet increases with decreasing its duration. Furthermore, when we expect triggering chorus from a wavelet near the upper edge of the hiss band, the duration of the wavelet increases with decreasing its intenisty. (5) Very similar φ (azimuthal angle) values are noticed for both the hiss and chorus, suggesting that both phenomena come from the same source region. These observational facts might lead us to conclude that a wavelet existing near the upper edge of the hiss band is able to generate a chorus emission through coherent wave-particle interaction in the outer magnetosphere as in the case of active VLF wave injection experiments

On the use of the wave distribution function concept to determine the directions of arrivals of radar echoes

International audienceConditions of application of the Storey and Lefeuvre (Geophys. J. R. Astron. Soc. 56 (1979) 255–270; Geophys. J. R. Astron. Soc. 62 (1980) 173–194) wave distribution function concept (WDF) to the determination of the directions of arrival of the NETLANDER Ground Penetrating Radar echoes are examined. The hypotheses used to make a WDF analysis from wave field components measured in a space plasma are recalled. An example of application is given. Following Lagoutte (1981 Rapport de DEA, Université d'Orléans) the WDF concept is extended to the case of an isotropic and non-ionized medium. The application to the analysis of the radar echoes within the Mars subsurface is discussed. The main point is to have a thickness of the dry layer between the surface and the first reflector much larger than the wavelengths

Application of Bicoherence Analysis in Study of Wave Interactions in Space Plasma

International audienceA spectral analysis at the second order (power spectrum) loses the phase information among the different Fourier components. To retain this information, the bispectrum (third order) and/or the bicoherence (normalized bispectrum) are calculated. Application to simulated data, shows the dependence of the bispectrum to amplitudes of involved waves and of the bicoherence to signal-to-noise ratio. Bicoherence technique is applied in the analysis of harmonics produced by an electronic receiver, as well as in the investigation of phase coherence between a ground-transmitter signal, a natural ELF emission near the proton gyrofrequency, and the sidebands around the carrier. Strong arguments are provided that the sidebands are generated by a parametric interaction between the transmitter signal and the ELF emission

On the Estimation of Wave Energy Distribution of Magnetospheric VLF Waves at the Ionospheric Base with Ground-Based Multiple Electromagnetic Field Components

International audienceAn inversion method is proposed to estimate the wave energy distribution of magnetospheric VLF radio waves (VLF/ELF emissions and whistlers) at the ionospheric base by using the simultaneously observed two horizontal magnetic and a vertical electric field components. The simulation experiments are extensively carried out to examine the effectiveness of the method. Two models for the wave source (a single source and two simultaneous sources) have been used, in which the observed signal is simulated to be composed of a number of elementary plane waves whose arriving directions are distributed around a specific direction in the case of a single source (two specific directions for the case of two simultaneous sources) and whose polarizations are distributed around right-handed circular. The distributions how the wave energy density is distributed at the ionospheric base have been obtained as an inversion problem in which the entropy of the wave distribution function is made maximum for the spectral matrix composed of the auto- and cross-power spectra of the three field components. It is then found that the present new method is very promising especially for the situation when a few wave sources (ducts) are present or when the ionospheric exit region is widely spread for which the previous direction finding systems are ineffective. Finally, the present method is applied to the actual data of whistlers observed at a low latitude, and it is found that the method is very effective in locating the wave source distribution, being in good agreement with the results by the previous direction finding methods. Further useful information on the mechanism of magnetospheric duct propagation and the ionospheric transmission is obtainable from the present method

On the use of tricoherent analysis to detect non-linear wave-wave interactions

International audienceZur Beschreibung nichtlinearer Effekte in dispersiven Medien kann man den Ansatz der Drei- und Vier-Wellen-Wechselwirkungen verwenden. Man benötigt eine Analyse der Spektren höherer Ordnung, um sich gegenseitig beeinflussende Wellen in Zufallssignalen zu identifizieren. Das Bikohärenzspektrum, d.h. das normierte Kumulantenspektrum dritter Ordnung, ist in zahlreichen Untersuchungen zur Analyse von Drei-Wellen-Wechselwirkungen in numerischen, labormäβigen und natürlichen Experimenten verwendet worden. Hier entwickeln wir das Trikohärenzspektrum zur Detektion von Vier-Wellen-Wechselwirkungen. Wir berechnen statistische Eigenschaften des Trispektrums und von Trikohärenzschätzungen sowie das Vertrauensintervall der letzteren. Wir legen Ergebnisse numerischer Schätzungen der Trikohärenz zu synthetischen Signalen vor.For the description of non-linear effects in dispersive media, the approach of three- and four-wave interactions may be used. Higher-order spectral analysis is required for identifying interacting waves in random signals. The bicoherence spectrum, which is the normalized cumulant spectrum of the third order, has been applied to numerous studies for analysing three-wave interactions in numerical, laboratory and natural experiments. Here, we develop the Incoherence spectrum to detect four-wave interactions, calculate statistical properties of the trispectrum and tricoherence estimators as well as the confidence interval for the latter, and present results of numerical estimations of the tricoherence using synthetic signals.Afin de décrire les effets non-linéaires dans un milieu dissipatif, il est possible d'utiliser l'approche par interaction de trois ou quatre ondes. L'analyse spectrale d'ordre supérieur est nécessaire pour identifier les ondes en interaction dans les signaux stochastiques. Le spectre de bicohérence, qui est le spectre cumulant normalisé du troisième ordre, a été utilisé dans de nombreuses études pour analyser l'interaction de trois ondes dans des expériences numériques, de laboratoire ou naturelles. Ici, nous développons le spectre de tricohérence pour détecter les interactions de quatre ondes, calculons les propriétés statistiques du trispectre et des estimateurs de tricohérence, de même que l'intervalle de confiance pour ce dernier, et présentons le résultat d'estimations numériques de la tricohérence utilisant des signaux synthétiques

High-latitude ionospheric electrostatic turbulence studied by means of the wavelet transform

International audienceThe wavelet transform, after performing a time-scale decomposition by means of wavelet coefficients, displays the energy of a signal simultaneously in time and frequency. According to the uncertainty principle, at each frequency an optimal compromise between time resolution and frequency resolution is provided. The Morlet (complex-valued) wavelet is applied to the study of high-latitude electrostatic turbulence recorded onboard the AUREOL-3 satellite. The transforms of electron density and of one electric field component (approximately perpendicular to the Earth's magnetic field) are presented. The modulus of wavelet coefficients show vertical structures that are due to intensifications of the signal at a high frequency occurring at the same lime as at a low frequency. At each frequency, the duration of a turbulent event is of the order of a few periods, which implies that electrostatic turbulence is highly inhomogeneous. We can compare the two signals by calculating the ratio of the modulus of their wavelet transform and the phase difference. This comparison illustrates the differences between the frequency-time behaviours of the two fields, which are probably related to the nonlinear regime of turbulence

Excitation of Sidebands Due to Nonlinear Coupling Between a VLF Transmitter Signal and a Natural ELF Emission

International audienceSymmetric sidebands are observed in the ionosphere by the AUREOL 3 satellite when it passes at a height of 1200 km above the VLF transmitter at the Komsomolsk‐on‐Amur Alpha station (50°5 N, 135° E, frequency 11.90 and 12.65 kHz). The sidebands are about 500 Hz off the carrier frequency of Alpha pulses. They are approximately 20 dB lower than the transmitter signal, and they appear only when ELF natural emission above the local proton gyrofrequency is observed. The data are presented and analyzed. The nonlinear coupling of the VLF transmitter signal to natural ELF emission is invoked to explain the symmetric sidebands. It is shown that the nonlinear current excited by the beats of VLF and ELF waves is strong enough to explain the sideband amplitude

An experimental study of the role of hiss in the generation of chorus in the outer magnetosphere, as based on spectral analyses and direction finding measurements onboard GEOS 1

The satellite and ground VLF data have indicated that chorus is often accompanied by a background hiss, and the purpose of this paper is to investigate the association between hiss and chorus and to present detailed experimental findings on the cause and effect relationship between hiss and chorus. The present study is based on detailed spectral analyses and direction finding measurements for VLF emission events with the simultaneous occurrence of hiss and chorus observed by GEOS-1 satellite in the outer magnetosphere. Two different events are analyzed : one is the equatorial (geomag. lat.=6.8°-8.5°) event, and the other the off-equatorial (24.2°-23.6°) event. The following important experimental findings have emerged from the present study : (1) Each chorus element originates from the hiss band and is asymptotic to the hiss band. (2) The intensity and occurrence of chorus emissions are closely correlated with the intensity of the underlying hiss band, such that when the intensity of the hiss band exceeds a threshold value of some mγ/√, the excitation of chorus emission is enhanced. (3) Some parts of hiss band exhibit some structures or wavelets (i.e. monochromatic wave components with duration of more than 100ms), although hiss has been considered to be incoherent and turbulent. Furthermore, on some occasions, we can notice an existence of wavelets at the foot of chorus elements. (4) The direction finding results have newly indicated similar values for the azimuthal direction φ for both phenomena, suggesting that both hiss and chorus come from the same source region. These experimental facts suggest that a wavelet existing in the hiss band may generate a chorus emission through coherent wave-particle interaction in the outer magnetosphere as in the case of active VLF wave injection experiments