The Experts below are selected from a list of 36198 Experts worldwide ranked by ideXlab platform
Anna De Juan - One of the best experts on this subject based on the ideXlab platform.
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inside front cover combining hyperSpectral imaging and chemometrics to assess and interpret the effects of environmental stressors on zebrafish eye images at tissue level j biophotonics 3 2018
Journal of Biophotonics, 2018Co-Authors: Victor Olmos, Monica Marro, Pablo Lozaalvarez, Demetrio Raldua, Eva Prats, Francesc Padros, Benjamin Pina, Roma Tauler, Anna De JuanAbstract:Raman images were used to study the effect of the contaminant chlorpyriphos-oxon on zebrafish eye samples. Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) was used to obtain the distribution maps and Spectral Signatures of biological components present in the images analyzed. The use of MCRALS Spectral Signatures as starting information for Partial Least Squares-Discriminant Analysis allowed statistical assessment of the effect of the contaminant at a specific tissue level.Further details can be found in the article by Victor Olmos et al. (e201700089).
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combining hyperSpectral imaging and chemometrics to assess and interpret the effects of environmental stressors on zebrafish eye images at tissue level
Journal of Biophotonics, 2018Co-Authors: Victor Olmos, Monica Marro, Pablo Lozaalvarez, Demetrio Raldua, Eva Prats, Francesc Padros, Benjamin Pina, Roma Tauler, Anna De JuanAbstract:Changes on an organism by the exposure to environmental stressors may be characterized by hyperSpectral images (HSI), which preserve the morphology of biological samples, and suitable chemometric tools. The approach proposed allows assessing and interpreting the effect of contaminant exposure on heterogeneous biological samples monitored by HSI at specific tissue levels. In this work, the model example used consists of the study of the effect of the exposure of chlorpyrifos-oxon on zebrafish tissues. To assess this effect, unmixing of the biological sample images followed by tissue-specific classification models based on the unmixed Spectral Signatures is proposed. Unmixing and classification are performed by multivariate curve resolution-alternating least squares (MCR-ALS) and partial least squares-discriminant analysis (PLS-DA), respectively. Crucial aspects of the approach are: (1) the simultaneous MCR-ALS analysis of all images from 1 population to take into account biological variability and provide reliable tissue Spectral Signatures, and (2) the use of resolved Spectral Signatures from control and exposed populations obtained from resampling of pixel subsets analyzed by MCR-ALS multiset analysis as information for the tissue-specific PLS-DA classification models. Classification results diagnose the presence of a significant effect and identify the Spectral regions at a tissue level responsible for the biological change.
R E Denton - One of the best experts on this subject based on the ideXlab platform.
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magnetic Spectral Signatures in the earth s magnetosheath and plasma depletion layer
Journal of Geophysical Research, 1994Co-Authors: B J Anderson, S A Fuselier, Peter S Gary, R E DentonAbstract:Correlations between plasma properties and magnetic fluctuations in the subsolar magnetosheath downstream of a quasi-perpendicular shock have been found and indicate that mirror and ion cyclotronlike fluctuations correlate with the magnetosheath proper and plasma depletion layer, respectively (Anderson and Fuselier, 1993). We explore the entire range of magnetic Spectral Signatures observed from the AMPTE/CCE spacecraft in the magnetosheath downstream of a quasi-perpendicular shock. The magnetic Spectral Signatures typically progress from predominantly compressional fluctuations, δB∥/δB⊥ ≈ 3, with F/Fp <0.2 ( F and Fp are the wave frequency and proton gyrofrequency, respectively) to predominantly transverse fluctuations, δB∥/δB⊥ ≈ 0.3, extending up to Fp. The compressional fluctuations are characterized by anticorrelation between the field magnitude and electron density, ne, and by a small compressibility, Ce ≡ (δne/ne)2(B/δB∥)2 ≈ 0.13, indicative of mirror waves. The Spectral characteristics of the transverse fluctuations are in agreement with predictions of linear Vlasov theory for the H+ and He2+ cyclotron modes. The power spectra and local plasma parameters are found to vary in concert: mirror waves occur for β∥p (β∥p ≡ 2µ0npkT∥p/B2) ≈ 2, Ap ≡ T⊥p/T⊥ - 1 ≈ 0.4, whereas cyclotron waves occur for β∥p ≈ 0.2 and Ap ≈ 2. The transition from mirror to cyclotron modes is predicted by linear theory. The Spectral characteristics overlap for intermediate plasma parameters. The plasma observations are described by Ap = 0.85β∥p−0.48 with a log regression coefficient of −0.74. This inverse Ap - β∥p correlation corresponds closely to the isocontours of maximum ion anisotropy instability growth, γm/Ω = 0.01, for the mirror and cyclotron modes. The agreement of observed properties and predictions of local theory suggests that the Spectral Signatures reflect the local plasma environment and that the anisotropy instabilities regulate Ap. We suggest that the Spectral characteristics may provide a useful basis for ordering observations in the magnetosheath and that the Ap - β ∥p inverse correlation may be used as a beta-dependent upper limit on the proton anisotropy to represent kinetic effects.
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magnetic Spectral Signatures in the earth s magnetosheath and plasma depletion layer
Journal of Geophysical Research, 1994Co-Authors: B J Anderson, S A Fuselier, Peter S Gary, R E DentonAbstract:Correlations between plasma properties and magnetic fluctuations in the sub-solar magnetosheath downstream of a quasi-perpendicular shock have been found and indicate that mirror and ion cyclotronlike fluctuations correlate with the magnetosheath proper and plasma depletion layer, respectively (Anderson and Fueselier, 1993). We explore the entire range of magnetic Spectral Signatures observed from the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE)spacecraft in the magnetosheath downstream of a quasi-perpendicular shock. The magnetic Spectral Signatures typically progress from predominantly compressional fluctuations,delta B(sub parallel)/delta B perpendicular to approximately 3, with F/F (sub p) less than 0.2 (F and F (sub p) are the wave frequency and proton gyrofrequency, respectively) to predominantly transverse fluctuations, delta B(sub parallel)/delta B perpendicular to approximately 0.3, extending up to F(sub p). The compressional fluctuations are characterized by anticorrelation between the field magnitude and electron density, n(sub e), and by a small compressibility, C(sub e) identically equal to (delta n(sub e)/n(sub e)) (exp 2) (B/delta B(sub parallel)) (exp 2) approximately 0.13, indicative of mirror waves. The Spectral characteristics of the transverse fluctuations are in agreement with predictions of linear Vlasov theory for the H(+) and He(2+) cyclotron modes. The power spectra and local plasma parameters are found to vary in concert: mirror waves occur for beta(s ub parallel p) (beta (sub parallel p) identically = 2 mu(sub zero) n(sub p) kT (sub parallel p) / B(exp 2) approximately = 2, A(sub p) indentically = T(sub perpendicular to p)/T(sub parallel p) - 1 approximately = 0.4, whereas cyclotron waves occur for beta (sub parallel p) approximately = 0.2 and A(sub p) approximately = 2. The transition from mirror to cyclotron modes is predicted by linear theory. The Spectral characteristics overlap for intermediate plasma parameters. The plasma observations are described by A(sub p) = 0.85 beta(sub parallel P) (exp - 0.48) with a log regression coefficient of -0.74. This inverse A(sub p) - beta(sub parallel p) correlation corresponds closely to the isocontours of maximum ion anisotropy instability growth, gamma (sub m)/omega(sub p) = 0.01, for the mirror and cyclotron modes. The agreement of observed properties and predictions of local theory suggests that the Spectral Signatures reflect the local plasma environment and that the anisotropy instabilities regulate A(sub p). We suggest that the Spectral characteristics may provide a useful basis for ordering observations in the magnetosheath and that the A(sub p) - beta(sub parallel p) inverse correlation may be used as a beta-dependent upper limit on the proton anisotropy to represent kinetic effects.
B M Poggianti - One of the best experts on this subject based on the ideXlab platform.
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optical Spectral Signatures of dusty starburst galaxies
The Astrophysical Journal, 2000Co-Authors: B M PoggiantiAbstract:We analyze the optical Spectral properties of the complete sample of Very Luminous Infrared Galaxies presented by Wu et al., and we find a high fraction (~50%) of spectra showing both a strong Hδ line in absorption and relatively modest [O II] emission [e(a) spectra]. The e(a) signature has been proposed as an efficient method to identify dusty starburst galaxies, and we study the star formation activity and the nature of these galaxies, as well as the effects of dust on their observed properties. We examine their emission-line characteristics, in particular their [O II]/Hα ratio, and we find this to be greatly affected by reddening. A search for AGN Spectral Signatures reveals that the e(a) galaxies are typically H II/LINER galaxies. We compare the star formation rates derived from the FIR luminosities with the estimates based on the Hα line and find that the values obtained from the optical emission lines are a factor of 10-70 (Hα) and 20-140 ([O II]) lower than the FIR estimates (50-300 M☉ yr-1). We then study the morphological properties of the e(a) galaxies, looking for a near companion or signs of a merger/interaction. In order to explore the evolution of the e(a) population, we present an overview of the available observations of e(a) galaxies in different environments both at low and high redshift. Finally, we discuss the role of dust in determining the e(a) Spectral properties and we propose a scenario of selective obscuration in which the extinction decreases with the stellar age.
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optical Spectral Signatures of dusty starburst galaxies
arXiv: Astrophysics, 1999Co-Authors: B M PoggiantiAbstract:We analyse the optical Spectral properties of the complete sample of Very Luminous Infrared Galaxies presented by Wu et al. (1998a,b) and we find a high fraction (~50 %) of spectra showing both a strong H_delta line in absorption and relatively modest [OII] emission (e(a) spectra). The e(a) signature has been proposed as an efficient method to identify dusty starburst galaxies and we study the star formation activity and the nature of these galaxies, as well as the effects of dust on their observed properties. We examine their emission line characteristics, in particular their [OII]/H_alpha ratio, and we find this to be greatly affected by reddening. A search for AGN Spectral Signatures reveals that the e(a)'s are typically HII/LINER galaxies. We compare the star formation rates derived from the FIR luminosities with the estimates based on the H_alpha line and find that the values obtained from the optical emission lines are a factor of 10-70 (H_alpha) and 20-140 ([OII]) lower than the FIR estimates (50-300 M_sun yr^-1). We then study the morphological properties of the e(a) galaxies, looking for a near companion or signs of a merger/interaction. In order to explore the evolution of the e(a) population, we present an overview of the available observations of e(a)'s in different environments both at low and high redshift. Finally, we discuss the role of dust in determining the e(a) Spectral properties and we propose a scenario of selective obscuration in which the extinction decreases with the stellar age.
Victor Olmos - One of the best experts on this subject based on the ideXlab platform.
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inside front cover combining hyperSpectral imaging and chemometrics to assess and interpret the effects of environmental stressors on zebrafish eye images at tissue level j biophotonics 3 2018
Journal of Biophotonics, 2018Co-Authors: Victor Olmos, Monica Marro, Pablo Lozaalvarez, Demetrio Raldua, Eva Prats, Francesc Padros, Benjamin Pina, Roma Tauler, Anna De JuanAbstract:Raman images were used to study the effect of the contaminant chlorpyriphos-oxon on zebrafish eye samples. Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) was used to obtain the distribution maps and Spectral Signatures of biological components present in the images analyzed. The use of MCRALS Spectral Signatures as starting information for Partial Least Squares-Discriminant Analysis allowed statistical assessment of the effect of the contaminant at a specific tissue level.Further details can be found in the article by Victor Olmos et al. (e201700089).
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combining hyperSpectral imaging and chemometrics to assess and interpret the effects of environmental stressors on zebrafish eye images at tissue level
Journal of Biophotonics, 2018Co-Authors: Victor Olmos, Monica Marro, Pablo Lozaalvarez, Demetrio Raldua, Eva Prats, Francesc Padros, Benjamin Pina, Roma Tauler, Anna De JuanAbstract:Changes on an organism by the exposure to environmental stressors may be characterized by hyperSpectral images (HSI), which preserve the morphology of biological samples, and suitable chemometric tools. The approach proposed allows assessing and interpreting the effect of contaminant exposure on heterogeneous biological samples monitored by HSI at specific tissue levels. In this work, the model example used consists of the study of the effect of the exposure of chlorpyrifos-oxon on zebrafish tissues. To assess this effect, unmixing of the biological sample images followed by tissue-specific classification models based on the unmixed Spectral Signatures is proposed. Unmixing and classification are performed by multivariate curve resolution-alternating least squares (MCR-ALS) and partial least squares-discriminant analysis (PLS-DA), respectively. Crucial aspects of the approach are: (1) the simultaneous MCR-ALS analysis of all images from 1 population to take into account biological variability and provide reliable tissue Spectral Signatures, and (2) the use of resolved Spectral Signatures from control and exposed populations obtained from resampling of pixel subsets analyzed by MCR-ALS multiset analysis as information for the tissue-specific PLS-DA classification models. Classification results diagnose the presence of a significant effect and identify the Spectral regions at a tissue level responsible for the biological change.
Audrey Lesaignoux - One of the best experts on this subject based on the ideXlab platform.
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estimation of soil moisture content from the Spectral reflectance of bare soils in the 0 4 2 5 µm domain
Sensors, 2015Co-Authors: Sophie Fabre, Xavier Briottet, Audrey LesaignouxAbstract:Abstract: This work aims to compare the performance of new methods to estimate the Soil Moisture Content (SMC) of bare soils from their Spectral Signatures in the reflective domain (0.4–2.5 µm) in comparison with widely used Spectral indices like Normalized Soil Moisture Index (NSMI) and Water Index SOIL (WISOIL). Indeed, these reference Spectral indices use wavelengths located in the water vapour absorption bands and their performance are thus very sensitive to the quality of the atmospheric compensation. To reduce these limitations, two new Spectral indices are proposed which wavelengths are defined using the determination matrix tool by taking into account the atmospheric transmission: Normalized Index of Nswir domain for Smc estimatiOn from Linear correlation (NINSOL) and Normalized Index of Nswir domain for Smc estimatiOn from Non linear correlation (NINSON). These Spectral indices are completed by two new methods based on the global shape of the soil Spectral Signatures. These methods are the Inverse Soil semi-Empirical Reflectance model (ISER), using the inversion of an existing empirical soil model simulating the soil Spectral reflectance according to soil moisture content for a given soil class, and the convex envelope model, linking the area between the envelope and the Spectral signature to the SMC. All these methods are compared using a reference database built with 32 soil samples and composed of 190 Spectral Signatures with five or six soil moisture contents. Half of the database is used for the calibration stage and the remaining to evaluate the performance of the SMC estimation methods. The results show that the four new methods lead to similar or better performance than the one obtained by the reference indices. The RMSE is ranging from 3.8% to 6.2% and the coefficient of
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influence of soil moisture content on Spectral reflectance of bare soils in the 0 4 14 μm domain
Journal of remote sensing, 2013Co-Authors: Audrey Lesaignoux, Sophie Fabre, Xavier BriottetAbstract:A new semi-empirical soil model simulating the Spectral Signatures of bare soils in the optical domain 0.4–14 μm according to surface moisture content variation is presented and applied to several databases. The model specification is based on laboratory Spectral reflectance measurements of many bare soils at different moisture contents. The measurement analysis leads to the definition of groups of bare soil samples according to their Spectral behaviours. These laboratory measurements are made also to characterize the impact of soil moisture on Spectral Signatures reflectance levels increasing with moisture content and to give information on absorption peaks related to soil mineral components hydroxyl, carbonate, and quartz. The procedure of modelling the Spectral Signatures of bare soil groups according to moisture content is discussed. The model is applied to a laboratory reflectance database and to the data available in the literature. The Spectral reflectances, estimated with a semi-empirical model, compare favourably with reflectance observations.
