Articles de revues : « Spectroscopic measurement mappings »

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Wübbeler, Gerd, Manuel Marschall, Eckart Rühl, Bernd Kästner et Clemens Elster. « Compressive nano-FTIR chemical mapping ». Measurement Science and Technology 33, n^o 3 (24 décembre 2021) : 035402. http://dx.doi.org/10.1088/1361-6501/ac407a.

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Abstract Nano-Fourier-transform infrared spectroscopy (nano-FTIR) combines infrared spectroscopy with scanning probe microscopy (SPM) techniques and enables spectroscopic imaging of molecular and electronic properties of matter at nanometer spatial resolution. The spectroscopic imaging can be used to derive chemical mappings, i.e. the spatial distribution of concentrations of the species contained in a given sample. However, due to the sequential scanning principle underlying SPM, recording the complete spectrum over a large spatial area leads to long measurement times. Furthermore, the acquired spectrum often contains additional signals from species and lineshape effects that are not explicitly accounted for. A compressive chemical mapping approach is proposed for undersampled nano-FTIR data that utilizes sparsity of these additional signals in the spectral domain. The approach combines a projection technique with standard compressed sensing, followed by a spatially regularized regression. Using real nano-FTIR measurements superimposed by simulated interferograms representing the chemical mapping of the contained species, it is demonstrated that the proposed procedure performs well even in cases in which the simulated interferograms and the sparse additional signals exhibit a strong spectral overlap.

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He, Pei, Shivashanker Bitla, Doug Bousfield et Carl P. Tripp. « Raman Spectroscopic Analysis of Paper Coatings ». Applied Spectroscopy 56, n^o 9 (septembre 2002) : 1115–21. http://dx.doi.org/10.1366/000370202760295322.

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An overview of the use of Raman spectroscopy for compositional mapping of paper coatings is presented. Raman spectroscopy is able to give the spatial distribution of pigments and binders in coated papers containing kaolin, anatase, and styrene butadiene (SB). Moreover, there are subtle differences in the Raman spectra of two forms of calcite, ground (GCC) and precipitated calcium carbonate (PCC), and these differences can be used to monitor the spatial distribution of coatings containing mixtures of PCC and GCC. Surface compositional mapping is relatively straightforward and is demonstrated with measurements of SB/CaCO3 ratios in mottled regions in printed coatings and the measurement of the same pigment/binder ratio in both thin and thick coated regions. For depth profiling, microtome methods are preferred, whereas the data obtained using confocal-based methods do not work.

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Denney, Kelly D., B. M. Peterson, R. W. Pogge, M. C. Bentz, C. M. Gaskell, T. Minezaki, C. A. Onken, S. G. Sergeev et M. Vestergaard. « Reverberation Mapping Results from MDM Observatory ». Proceedings of the International Astronomical Union 5, S267 (août 2009) : 201. http://dx.doi.org/10.1017/s1743921310006216.

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Reverberation mapping takes advantage of the presence of a time delay or lag, τ, between continuum and emission line flux variations observed through spectroscopic monitoring campaigns to infer the radius of the broad-line region (BLR) and, subsequently, the central black hole mass in type 1 AGNs. We present results from a multi-month reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from around the world. We measure BLR radii and black hole masses for six objects. The primary goal of this campaign was to obtain either new or improved Hβ reverberation lag measurements for several relatively low-luminosity AGNs. Using cross correlation techniques to measure the time delay between the mean optical continuum flux density around 5100 Å and the integrated Hβ flux, we determine the Hβ lags and black hole mass measurements listed in columns 2 and 3 of Table 1, respectively. Column 4 tells if this measurement is new, an improvement meant to replace a previous, less reliable measurement, or simply an additional measurement not used to replace a previous value. The complete results from this study are currently being prepared for publication. A subsequent velocity-resolved analysis of the Hβ response shows that three of the six primary targets demonstrate kinematic signatures (column 5) of infall, outflow, and non-radial virialized motions (see Denney et al. 2009).

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Miller, N. C. « Comprehensive multilayer film analysis with XPS, AES, and EDS ». Proceedings, annual meeting, Electron Microscopy Society of America 50, n^o 2 (août 1992) : 1784–85. http://dx.doi.org/10.1017/s0424820100133552.

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Wavelength and energy dispersive x-ray spectroscopy (WDS and EDS) are routinely utilized to measure qualitatively and quantitatively the composition of microscopic features/phases of thickness 0.5 (μm or greater in solids. Surface spectroscopies, especially x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), are employed to determine surface chemistry and surface composition respectively of microscopic features 0.2-5 nm thick. The combined utilization of AES and EDS (or WDS) permits microanalysis of surface and subsurface features/phases. Two areas of improved analysis through combined utilization of AES and EDS are imaging/elemental mapping and measurement of vertical diffusion profiles. Strengths of XPS in complementing EDS/WDS will also be discussed.High resolution surface elemental or chemical mapping can be carried out with scanning Auger or secondary ion mass spectrometry (SIMS) microanalysis, respectively. In fact, both offer improved spacial resolution over WDS and EDS elemental x-ray dot mapping. Using sample rotation while removing material by ion beam sputter etching, three dimensional mapping can be carried out by either surface analysis technique, permitting microanalysis of buried features even in complex heterostructures.

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Schrader, B., G. Baranović, A. Epding, G. G. Hoffmann, P. J. M. Van Kan, S. Keller, P. Hildebrandt, C. Lehner et J. Sawatzki. « Time-Resolved and Two-Dimensional NIR FT-Raman Spectroscopy ». Applied Spectroscopy 47, n^o 9 (septembre 1993) : 1452–56. http://dx.doi.org/10.1366/0003702934067360.

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The near-infrared Fourier transform (NIR FT) Raman technique permits the measurement of Raman spectra without interference by fluorescence. Absorption by molecules containing X-H bonds in the NIR range requires a 180° scattering geometry. In this way, Raman spectroscopy of samples on surfaces is possible, both the detecting of small spots and the mapping of the sample distribution over larger areas. The spatial resolution extends into the micrometer range. Mapping of the inorganic pigment distribution of an initial letter of a mediaeval manuscript is demonstrated. For time-resolved measurements, the step-scan technique, previously developed for infrared spectroscopy, may be used in NIR FT-Raman spectroscopy as well. It allows the study of photochemical and photophysical processes, the application of modulation techniques, and the investigation of “noisy” samples. Photo-isomerization of the dye merocyanine 540 has been observed with the step-scan technique upon periodic excitation with a flash lamp.

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Kenaz, Ralfy, et Ronen Rapaport. « Mapping spectroscopic micro-ellipsometry with sub-5 microns lateral resolution and simultaneous broadband acquisition at multiple angles ». Review of Scientific Instruments 94, n^o 2 (1 février 2023) : 023908. http://dx.doi.org/10.1063/5.0123249.

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Spectroscopic ellipsometry is a widely used optical technique in both industry and research for determining the optical properties and thickness of thin films. The effective use of spectroscopic ellipsometry on micro-structures is inhibited by technical limitations on the lateral resolution and data acquisition rate. Here, we introduce a spectroscopic micro-ellipsometer (SME), capable of recording spectrally resolved ellipsometric data simultaneously at multiple angles of incidence in a single measurement of a few seconds, with a lateral resolution down to 2 μm in the visible spectral range. The SME can be easily integrated into generic optical microscopes by the addition of a few standard optical components. We demonstrate complex refractive index and thickness measurements by using the SME, which are in excellent agreement with a commercial spectroscopic ellipsometer. The high lateral resolution is displayed by complex refractive index and thickness maps over micron-scale areas. As an application for its accuracy and high lateral resolution, the SME can characterize the optical properties and number of layers of exfoliated transition-metal dichalcogenides and graphene, for structures that are a few microns in size.

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Dobler, Jeremy, T. Scott Zaccheo, Timothy Pernini, Nathan Blume et Michael Braun. « Greenlite™ : a year of carbon dioxide monitoring over paris, france, and recent progress in monitoring methane ». EPJ Web of Conferences 176 (2018) : 05013. http://dx.doi.org/10.1051/epjconf/201817605013.

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GreenLITE™ is a ground-based laser absorption spectroscopy system capable of measuring and mapping CO2 concentrations over areas up to 25 km2. The system was deployed for COP21 as a demonstration and has now completed a year of CO2 measurements over the city of Paris, France. We will discuss lessons learned and relevant data from the year-long deployment. Recently, the system has demonstrated the same measurement capability for CH4, and results from preliminary testing are presented.

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Jafariyazani, Marziye, Daniel Masters, Andreas L. Faisst, Harry I. Teplitz et Olivier Ilbert. « Predicting the Spectroscopic Features of Galaxies by Applying Manifold Learning on Their Broadband Colors : Proof of Concept and Potential Applications for Euclid, Roman, and Rubin LSST ». Astrophysical Journal 967, n^o 1 (1 mai 2024) : 60. http://dx.doi.org/10.3847/1538-4357/ad38b8.

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Abstract Entering the era of large-scale galaxy surveys, which will deliver unprecedented amounts of photometric and spectroscopic data, there is a growing need for more efficient, data-driven, and less model-dependent techniques to analyze the spectral energy distribution of galaxies. In this work, we demonstrate that by taking advantage of manifold learning approaches, we can estimate spectroscopic features of large samples of galaxies from their broadband photometry when spectroscopy is available only for a fraction of the sample. This will be done by applying the self-organizing map algorithm on broadband colors of galaxies and mapping partially available spectroscopic information into the trained maps. In this pilot study, we focus on estimating the 4000 Å break in a magnitude-limited sample of galaxies in the Cosmic Evolution Survey (COSMOS) field. We also examine this method to predict the Hδ A index given our available spectroscopic measurements. We use observed galaxy colors (u,g,r,i,z,Y,J,H), as well as spectroscopic measurements for a fraction of the sample from the LEGA-C and zCOSMOS spectroscopic surveys to estimate this feature for our parent photometric sample. We recover the D4000 feature for galaxies that only have broadband colors with uncertainties about twice the uncertainty of the employed spectroscopic surveys. Using these measurements, we observe a positive correlation between D4000 and the stellar mass of the galaxies in our sample with weaker D4000 features for higher-redshift galaxies at fixed stellar masses. These can be explained by the downsizing scenario for the formation of galaxies and the decrease in their specific star formation rate as well as the aging of their stellar populations over this time period.

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Petronijevic, Emilija, Claudia Skubisz, Luca Seda, Tiziana Cesca, Carlo Scian, Giovanni Mattei, Roberto Li Voti, Concita Sibilia et Alessandro Belardini. « Photo-acoustic spectroscopy with widely tuneable laser enables circular dichroism mapping ». EPJ Web of Conferences 309 (2024) : 09007. http://dx.doi.org/10.1051/epjconf/202430909007.

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Sensitive and reliable characterization of chirality in nanostructures and molecules is of great importance in multidisciplinary research combining physics, chemistry and nanotechnology, with potential applications in pharmaceutical and agrochemical industry. Chirality is connected to circular dichroism (CD) - the absorption difference when the chiral medium is excited with circular polarizations of opposite handedness. Hence, measuring chirality by direct absorption measurements is of great interest in nanophotonics and plasmonics community, where the nanostructured media can enhance chiro-optical effects. Here we present a recently constructed photo-acoustic spectroscopy (PAS) set-up, which offers many degrees of freedom in characterization. We use a laser which is widely tuneable in the near-infrared (680-1080 nm) and visible (340-540 nm) ranges. The laser output is modulated with a mechanical chopper, where its frequency defines the penetration depth of the thermal signal. The input polarization is controlled by a linear polarizer and a quarter-wave plate, and the laser can be focused before impinging on the sample in the tightly closed photo-acoustic cell. The cell is placed on translational and rotational stages, which allows for the spatial mapping and extrinsic chirality measurements. Finally, a sensitive microphone measures the pressure changes in the cell, enabling scattering-free measurement of absorption and CD.

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Zereay, Berhane Nugusse, Sándor Kálvin, György Juhász, Csaba Major, Péter Petrik, Zoltán György Horváth et Miklós Fried. « Optical Calibration of a Multi-Color Ellipsometric Mapping Tool Fabricated Using Cheap Parts ». Photonics 11, n^o 11 (4 novembre 2024) : 1036. http://dx.doi.org/10.3390/photonics11111036.

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We developed and applied a new calibration method to make more accurate measurements with our multi-color ellipsometric mapping tool made from cheap parts. Ellipsometry is an optical technique that measures the relative change in the polarization state of the measurement beam induced by reflection from or transmission through a sample. During conventional ellipsometric measurement, the data collection is relatively slow and measures one spot at a time, so mapping needs a long time compared with our new optical mapping equipment made by an ordinary color LED monitor and a polarization-sensitive camera. The angle of incidence and the incident polarization state is varied point by point, so a special optical calibration method is needed. Three SiO2 samples with different thicknesses were used for the point-by-point determination of the angle of incidence and rho (ρ) corrections. After the calibration, another SiO2 sample was measured and analyzed using the calibrated corrections; further, this sample was independently measured using a conventional spectroscopic ellipsometer. The difference between the two measured thickness maps is less than 1 nm. Our optical mapping tool made from cheap parts is faster and covers wider area samples relative to conventional ellipsometers, and these correction enhancements further demonstrate its performance.

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Yu, Zhefu, Paul Martini, A. Penton, T. M. Davis, U. Malik, C. Lidman, B. E. Tucker et al. « OzDES Reverberation Mapping Programme : the first Mg ii lags from 5 yr of monitoring ». Monthly Notices of the Royal Astronomical Society 507, n^o 3 (5 août 2021) : 3771–88. http://dx.doi.org/10.1093/mnras/stab2244.

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ABSTRACT Reverberation mapping is a robust method to measure the masses of supermassive black holes outside of the local Universe. Measurements of the radius–luminosity (R−L) relation using the Mg ii emission line are critical for determining these masses near the peak of quasar activity at z ≈ 1−2, and for calibrating secondary mass estimators based on Mg ii that can be applied to large samples with only single-epoch spectroscopy. We present the first nine Mg ii lags from our 5-yr Australian Dark Energy Survey reverberation mapping programme, which substantially improves the number and quality of Mg ii lag measurements. As the Mg ii feature is somewhat blended with iron emission, we model and subtract both the continuum and iron contamination from the multiepoch spectra before analysing the Mg ii line. We also develop a new method of quantifying correlated spectroscopic calibration errors based on our numerous, contemporaneous observations of F-stars. The lag measurements for seven of our nine sources are consistent with both the H β and Mg ii R−L relations reported by previous studies. Our simulations verify the lag reliability of our nine measurements, and we estimate that the median false positive rate of the lag measurements is $4{{\ \rm per\ cent}}$.

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Grévin, Benjamin, Olivier Bardagot et Renaud Demadrille. « Implementation of data-cube pump–probe KPFM on organic solar cells ». Beilstein Journal of Nanotechnology 11 (12 février 2020) : 323–37. http://dx.doi.org/10.3762/bjnano.11.24.

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An implementation of pump–probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer.

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Spolenak, R., W. Ludwig, J. Y. Buffiere et J. Michler. « In SituElastic Strain Measurements—Diffraction and Spectroscopy ». MRS Bulletin 35, n^o 5 (mai 2010) : 368–74. http://dx.doi.org/10.1557/mrs2010.569.

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AbstractUnderstanding the mechanical properties of materials is crucial for their reliable application as bulk materials as well as in a miniaturized form. The deformation of materials is usually non-uniform and, hence, needs to be characterized on a local level. The following article focuses on thein-Situdetermination of mechanical stresses in crystalline materials during deformation. This can be achieved by both diffraction as well as spectroscopical methods, where the elastic strain is the parameter measured, which is subsequently converted into stresses by the application of Hooke's law. Asin Situmeasurements require rapid data acquisition in conjunction with reasonable penetration depths, we will focus on x-rays. However, the different techniques described can be applied to any other diffraction probe as well. The description of diffraction techniques, which span the range from averaging techniques to 2D and 3D strain mapping, is complemented by a section on Raman spectroscopy as an alternative method for stress determination for non-metallic materials. Local stresses also can be correlated to local defect densities.

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Breysse, Patrick C., et Rachael M. Alexandroff. « Observing AGN feedback with CO intensity mapping ». Monthly Notices of the Royal Astronomical Society 490, n^o 1 (13 septembre 2019) : 260–73. http://dx.doi.org/10.1093/mnras/stz2534.

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ABSTRACT Current models of galaxy formation require star formation in high-mass galaxies to be limited by poorly understood mechanisms of quasar feedback. Feedback processes can be studied by examining the molecular gas content of AGN hosts through the CO rotational ladder, but the complexity of these observations means that current data are limited to only extremely CO-bright objects. Upcoming CO intensity mapping experiments offer an opportunity for a less biased probe of quasar feedback. By correlating intensity maps with spectroscopic AGN surveys, we can obtain a measurement of the mean CO luminosity of a large population of quasars simultaneously. We show that experiments like COMAP, CCAT-prime, and CONCERTO have enough sensitivity to detect this cross-correlation if existing AGN observations are representative of the whole population, and to place interesting upper limits if they are not. Future surveys will be able to increase the precision of these measurements by orders of magnitude, allowing detailed studies of quasar properties across a wide range of cosmic history.

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Minasny, Budiman, Alex B. McBratney, Leo Pichon, Wei Sun et Michael G. Short. « Evaluating near infrared spectroscopy for field prediction of soil properties ». Soil Research 47, n^o 7 (2009) : 664. http://dx.doi.org/10.1071/sr09005.

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This paper demonstrates the application of near infrared diffuse reflectance spectroscopy (NIR-DRS) measurements as part of digital soil mapping. We also investigate whether calibration functions developed from a spectral library can be used for rapid characterisation of soil properties in the field. Soil samples were collected along 24 toposequences in the Pokolbin irrigation district, ~7 km2 of predominantly agricultural land in the Hunter Valley, NSW, Australia. Soil samples at 2 depths: 0–0.10 and 0.40–0.50 m were collected. The soil samples were scanned using NIR under 3 different conditions: field condition, dried unground, and dried ground. A separate spectral library containing soil laboratory measurements was used to develop functions to predict 3 main soil properties from NIR spectra (total C content, clay content, and sum of exchangeable cations). The absorbance spectra were found to be different for the 3 soil conditions. The field spectra appear to have higher absorbance, followed by dried unground samples and then dried ground samples. Although most spectral signatures or peaks were similar for the 3 soil conditions, field samples appear to have higher absorbance, particularly at 1400 nm and 1900 nm. The convex hull of the first 2 principal components of the soil spectra is an easy tool to evaluate the similarity of spectra from a calibration set to an observation. For field prediction, samples need to be calibrated using field samples. Finally, this study shows that NIR-DRS measurement is a useful part of digital soil mapping.

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Gower, J. F. R. « Mapping ocean dynamic structure using optical spectroscopic measurements from space ». Advances in Space Research 5, n^o 6 (janvier 1985) : 237–46. http://dx.doi.org/10.1016/0273-1177(85)90327-8.

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Usher, Emery T., et Scott A. Showalter. « Mapping invisible epitopes by NMR spectroscopy ». Journal of Biological Chemistry 295, n^o 51 (18 décembre 2020) : 17411–12. http://dx.doi.org/10.1074/jbc.h120.016607.

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Defining discontinuous antigenic epitopes remains a substantial challenge, as exemplified by the case of lipid transfer polyproteins, which are common pollen allergens. Hydrogen/deuterium exchange monitored by NMR can be used to map epitopes onto folded protein surfaces, but only if the complex rapidly dissociates. Modifying the standard NMR-exchange measurement to detect substoichiometric complexes overcomes this time scale limitation and provides new insights into recognition of lipid transfer polyprotein by antibodies. In the future, this new and exciting development should see broad application to a range of tight macromolecular interactions.

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Asner, Gregory P., Nicholas R. Vaughn, Christopher Balzotti, Philip G. Brodrick et Joseph Heckler. « High-Resolution Reef Bathymetry and Coral Habitat Complexity from Airborne Imaging Spectroscopy ». Remote Sensing 12, n^o 2 (17 janvier 2020) : 310. http://dx.doi.org/10.3390/rs12020310.

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Coral reef ecosystems are rapidly changing, and a persistent problem with monitoring changes in reef habitat complexity rests in the spatial resolution and repeatability of measurement techniques. We developed a new approach for high spatial resolution (<1 m) mapping of nearshore bathymetry and three-dimensional habitat complexity (rugosity) using airborne high-fidelity imaging spectroscopy. Using this new method, we mapped coral reef habitat throughout two bays to a maximum depth of 25 m and compared the results to the laser-based SHOALS bathymetry standard. We also compared the results derived from imaging spectroscopy to a more conventional 4-band multispectral dataset. The spectroscopic approach yielded consistent results on repeat flights, despite variability in viewing and solar geometries and sea state conditions. We found that the spectroscopy-based results were comparable to those derived from SHOALS, and they were a major improvement over the multispectral approach. Yet, spectroscopy provided much finer spatial information than that which is available with SHOALS, which is valuable for analyzing changes in benthic composition at the scale of individual coral colonies. Monitoring temporal changes in reef 3D complexity at high spatial resolution will provide an improved means to assess the impacts of climate change and coastal processes that affect reef complexity.

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Cho, Sanghoon, Si Won Song, Hyung Min Kim et Hoeil Chung. « Spatially offset Raman scattering line-mapping as a potential tool for particle size analysis ». Analyst 146, n^o 11 (2021) : 3666–72. http://dx.doi.org/10.1039/d1an00246e.

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Robaschik, Peter, Pablo F. Siles, Daniel Bülz, Peter Richter, Manuel Monecke, Michael Fronk, Svetlana Klyatskaya et al. « Optical properties and electrical transport of thin films of terbium(III) bis(phthalocyanine) on cobalt ». Beilstein Journal of Nanotechnology 5 (11 novembre 2014) : 2070–78. http://dx.doi.org/10.3762/bjnano.5.215.

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The optical and electrical properties of terbium(III) bis(phthalocyanine) (TbPc2) films on cobalt substrates were studied using variable angle spectroscopic ellipsometry (VASE) and current sensing atomic force microscopy (cs-AFM). Thin films of TbPc2 with a thickness between 18 nm and 87 nm were prepared by organic molecular beam deposition onto a cobalt layer grown by electron beam evaporation. The molecular orientation of the molecules on the metallic film was estimated from the analysis of the spectroscopic ellipsometry data. A detailed analysis of the AFM topography shows that the TbPc2 films consist of islands which increase in size with the thickness of the organic film. Furthermore, the cs-AFM technique allows local variations of the organic film topography to be correlated with electrical transport properties. Local current mapping as well as local I–V spectroscopy shows that despite the granular structure of the films, the electrical transport is uniform through the organic films on the microscale. The AFM-based electrical measurements allow the local charge carrier mobility of the TbPc2 thin films to be quantified with nanoscale resolution.

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Ekanayake, Ruwini S. K., Christopher T. Chantler, Daniel Sier, Martin J. Schalken, Alexis J. Illig, Martin D. de Jonge, Bernt Johannessen, Peter Kappen et Chanh Q. Tran. « High-accuracy mass attenuation coefficients and X-ray absorption spectroscopy of zinc – the first X-ray Extended Range Technique-like experiment in Australia ». Journal of Synchrotron Radiation 28, n^o 5 (19 juillet 2021) : 1476–91. http://dx.doi.org/10.1107/s1600577521005993.

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The first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron, Australia, is presented. In this experiment X-ray mass attenuation coefficients are measured across an energy range including the zinc K-absorption edge and X-ray absorption fine structure (XAFS). These high-accuracy measurements are recorded at 496 energies from 8.51 keV to 11.59 keV. The XERT protocol dictates that systematic errors due to dark current nonlinearities, correction for blank measurements, full-foil mapping to characterize the absolute value of attenuation, scattering, harmonics and roughness are measured over an extended range of experimental parameter space. This results in data for better analysis, culminating in measurement of mass attenuation coefficients across the zinc K-edge to 0.023–0.036% accuracy. Dark current corrections are energy- and structure-dependent and the magnitude of correction reached 57% for thicker samples but was still large and significant for thin samples. Blank measurements scaled thin foil attenuation coefficients by 60–500%; and up to 90% even for thicker foils. Full-foil mapping and characterization corrected discrepancies between foils of up to 20%, rendering the possibility of absolute measurements of attenuation. Fluorescence scattering was also a major correction. Harmonics, roughness and bandwidth were explored. The energy was calibrated using standard reference foils. These results represent the most extensive and accurate measurements of zinc which enable investigations of discrepancies between current theory and experiments. This work was almost fully automated from this first experiment at the Australian Synchrotron, greatly increasing the possibility for large-scale studies using XERT.

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Ivanović, Nikola V. « The Study of Ar I and Ne I Spectral Line Shapes in the Cathode Sheath Region of an Abnormal Glow Discharge ». Atoms 7, n^o 1 (9 janvier 2019) : 9. http://dx.doi.org/10.3390/atoms7010009.

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The cathode sheath (CS) region is the most important part of abnormal glow discharge (GD), where various processes relevant for the operation and application occur. The most important parameter of the CS is the distribution of electric field strength E which is of crucial importance for charged particles acceleration, their trajectories, kinetic energies, and collisions with other particles and cathode sputtering. All these processes are relevant for the operation of GD as well as for numerous applications in the field of spectroscopic analysis, plasma etching, thin film deposition, and depth profiling of cathode material. Thus, the importance of non-perturbing technique for E distribution measurement in the CS region was recognized long time ago. Within this article, a simple technique based on standard optical emission spectroscopy (OES) and typical laboratory equipment has been used for E mapping in the CS region of an abnormal glow discharge.

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Abellan, Patricia, Patrick Z. El-Khoury et Quentin M. Ramasse. « Mapping VIS-terahertz (≤17 THz) surface plasmons sustained on native and chemically functionalized percolated gold thin films using EELS ». Microscopy 67, suppl_1 (9 novembre 2017) : i30—i39. http://dx.doi.org/10.1093/jmicro/dfx092.

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Abstract Heterogeneous assemblies of molecules (Rhodamine B) adsorbed onto a nano-corrugated metallic surface (a percolated Au network) are investigated using electron energy loss spectroscopy in the scanning transmission electron microscope (STEM-EELS). Our first measurements target the native metallic substrate, which consists of a commercial Au thin film atop an ultrathin carbon membrane. The Au film displays a percolated morphology with nanostructures of estimated thickness ≤10 nm approximately. We observe a rich plasmonic response from the metallic substrate; one which varies nanometrically and spans the VIS-terahertz region. Multiple localized plasmons are detected at individual nanometric integrated areas, while an analysis of their spatial distribution reveals that for each integrated energy range (50 meV integration window) resonances are simultaneously supported at different locations within the film. We record subsequent EEL spectrum images of the hybrid molecular–metallic construct after deposition of Rhodamine B molecules onto the substrate, where plasmons, molecular vibrations and electronic excitations might all be simultaneously detected. A comparison of average signals for both systems is performed and spectral variations within the three spectral regions where molecular signatures may be observed are discussed. Our measurements and their analysis, if applied to the same location before and after molecular deposition, may be used to rationalize optical microscopic and spectroscopic measurements that take advantage of the interplay between molecules and plasmons.

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Kim, Hee-Jin, Yongliang Liu et Linghe Zeng. « Fourier Transform Infrared (FT-IR) Spectroscopy and Simple Algorithm Analysis for Rapid and Non-Destructive Assessment of Cotton Fiber Maturity and Crystallinity for Plant Mapping ». Sensors 24, n^o 9 (30 avril 2024) : 2888. http://dx.doi.org/10.3390/s24092888.

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Information on boll distribution within a cotton plant is critical to evaluate the adaptation and response of cotton plants to environmental and biotic stress in cotton production. Cotton researchers have applied available conventional fiber measurements, such as the high volume instrument (HVI) and advanced fiber information system (AFIS), to map the location and the timing of boll development and distribution within plants and further to determine within-plant variability of cotton fiber properties. Both HVI and AFIS require numerous cotton bolls combined for the measurement. As an alternative approach, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy was proposed to measure fiber maturity (MIR) and crystallinity (CIIR) of a sample as little as 0.5 mg lint. Extending fiber maturity and crystallinity measurement into a single boll for node-by-node mapping, FT-IR method might be advantageous due to less sampling amount compared with HVI and AFIS methods. Results showed that FT-IR technique enabled the evaluation of fiber MIR and CIIR at a boll level, which resulted in average MIR and CIIR values highly correlated with HVI micronaire (MIC) and AFIS maturity ratio (M). Hence, FT-IR technique possesses a good potential for a rapid and non-destructive node-by-node mapping of cotton boll maturity and crystallinity distribution.

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Chen, Andrew, Arjun Virk, Zachery Harris, Azin Abazari, Robert Honkanen et M. Hassan Arbab. « Non-contact terahertz spectroscopic measurement of the intraocular pressure through corneal hydration mapping ». Biomedical Optics Express 12, n^o 6 (17 mai 2021) : 3438. http://dx.doi.org/10.1364/boe.423741.

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Hlabathe, Michael S., David A. Starkey, Keith Horne, Encarni Romero-Colmenero, Steven M. Crawford, Stefano Valenti, Hartmut Winkler et al. « Robotic reverberation mapping of the broad-line radio galaxy 3C 120 ». Monthly Notices of the Royal Astronomical Society 497, n^o 3 (25 juillet 2020) : 2910–29. http://dx.doi.org/10.1093/mnras/staa2171.

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ABSTRACT We carried out photometric and spectroscopic observations of the well-studied broad-line radio galaxy 3C 120 with the Las Cumbres Observatory (LCO) global robotic telescope network from 2016 December to 2018 April as part of the LCO AGN Key Project on Reverberation Mapping of Accretion Flows. Here, we present both spectroscopic and photometric reverberation mapping results. We used the interpolated cross-correlation function to perform multiple-line lag measurements in 3C 120. We find the H γ, He ii λ4686, H β, and He i λ5876 lags of $\tau _{\text{cen}} = 18.8_{-1.0}^{+1.3}$, $2.7_{-0.8}^{+0.7}$, $21.2_{-1.0}^{+1.6}$, and $16.9_{-1.1}^{+0.9}$ d, respectively, relative to the V-band continuum. Using the measured lag and rms velocity width of the H β emission line, we determine the mass of the black hole for 3C 120 to be $M=(6.3^{+0.5}_{-0.3})\times 10^7\, (f/5.5)$ M⊙. Our black hole mass measurement is consistent with similar previous studies on 3C 120, but with small uncertainties. In addition, velocity-resolved lags in 3C 120 show a symmetric pattern across the H β line, 25 d at line centre decreasing to 17 d in the line wings at ±4000 km s−1. We also investigate the inter-band continuum lags in 3C 120 and find that they are generally consistent with τ ∝ λ4/3 as predicted from a geometrically thin, optically thick accretion disc. From the continuum lags, we measure the best-fitting value τ0 = 3.5 ± 0.2 d at $\lambda _{\rm 0} = 5477\, \mathring{\rm A}$. It implies a disc size a factor of 1.6 times larger than prediction from the standard disc model with L/LEdd = 0.4. This is consistent with previous studies in which larger than expected disc sizes were measured.

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Jamal, S., V. Le Brun, O. Le Fèvre, D. Vibert, A. Schmitt, C. Surace, Y. Copin, B. Garilli, M. Moresco et L. Pozzetti. « Automated reliability assessment for spectroscopic redshift measurements ». Astronomy & ; Astrophysics 611 (mars 2018) : A53. http://dx.doi.org/10.1051/0004-6361/201731305.

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Context. Future large-scale surveys, such as the ESA Euclid mission, will produce a large set of galaxy redshifts (≥106) that will require fully automated data-processing pipelines to analyze the data, extract crucial information and ensure that all requirements are met. A fundamental element in these pipelines is to associate to each galaxy redshift measurement a quality, or reliability, estimate.Aim. In this work, we introduce a new approach to automate the spectroscopic redshift reliability assessment based on machine learning (ML) and characteristics of the redshift probability density function.Methods. We propose to rephrase the spectroscopic redshift estimation into a Bayesian framework, in order to incorporate all sources of information and uncertainties related to the redshift estimation process and produce a redshift posterior probability density function (PDF). To automate the assessment of a reliability flag, we exploit key features in the redshift posterior PDF and machine learning algorithms.Results. As a working example, public data from the VIMOS VLT Deep Survey is exploited to present and test this new methodology. We first tried to reproduce the existing reliability flags using supervised classification in order to describe different types of redshift PDFs, but due to the subjective definition of these flags (classification accuracy ~58%), we soon opted for a new homogeneous partitioning of the data into distinct clusters via unsupervised classification. After assessing the accuracy of the new clusters via resubstitution and test predictions (classification accuracy ~98%), we projected unlabeled data from preliminary mock simulations for the Euclid space mission into this mapping to predict their redshift reliability labels.Conclusions. Through the development of a methodology in which a system can build its own experience to assess the quality of a parameter, we are able to set a preliminary basis of an automated reliability assessment for spectroscopic redshift measurements. This newly-defined method is very promising for next-generation large spectroscopic surveys from the ground and in space, such as Euclid and WFIRST.

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Sun, Xiaoli. « Review of Photodetectors for Space Lidars ». Sensors 24, n^o 20 (14 octobre 2024) : 6620. http://dx.doi.org/10.3390/s24206620.

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Photodetectors play a critical role in space lidars designed for scientific investigations from orbit around planetary bodies. The detectors must be highly sensitive due to the long range of measurements and tight constraints on the size, weight, and power of the instrument. The detectors must also be space radiation tolerant over multi-year mission lifetimes with no significant performance degradation. Early space lidars used diode-pumped Nd:YAG lasers with a single beam for range and atmospheric backscattering measurements at 1064 nm or its frequency harmonics. The photodetectors used were single-element photomultiplier tubes and infrared performance-enhanced silicon avalanche photodiodes. Space lidars have advanced to multiple beams for surface topographic mapping and active infrared spectroscopic measurements of atmospheric species and surface composition, which demand increased performance and new capabilities for lidar detectors. Higher sensitivity detectors are required so that multi-beam and multi-wavelength measurements can be performed without increasing the laser and instrument power. Pixelated photodetectors are needed so that a single detector assembly can be used for simultaneous multi-channel measurements. Photon-counting photodetectors are needed for active spectroscopy measurements from short-wave infrared to mid-wave infrared. HgCdTe avalanche photodiode arrays have emerged recently as a promising technology to fill these needs. This paper gives a review of the photodetectors used in past and present lidars and the development and outlook of HgCdTe APD arrays for future space lidars.

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Jatana, Gurneesh, Lyle Kocher, Suk-Min Moon, Sriram Popuri, Kevin Augustin, Feng Tao, Yifeng Wu et al. « Mapping of exhaust gas recirculation and combustion-residual backflow in the intake ports of a heavy-duty diesel engine using a multiplexed multi-species absorption spectroscopy sensor ». International Journal of Engine Research 19, n^o 5 (31 juillet 2017) : 542–52. http://dx.doi.org/10.1177/1468087417720588.

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The combustion-residual backflow into the intake ports of a commercial diesel engine (Cummins ISX series) was spatiotemporally mapped using a multiplexed multi-species absorption spectroscopy sensor system; the resulting cycle- and cylinder-resolved measurements are applicable for assessing cylinder charge uniformity, control strategies, and computational fluid dynamics tools. On-engine measurements were made using four compact (3/8 in Outside Diameter) stainless steel probes which enabled simultaneous multi-point measurements, required minimal engine hardware modification, and featured a novel tip design for measurement of gas flows parallel to the probe axis. Three sensor probes were used to perform simultaneous backflow measurements in intake runners corresponding to three of the six engine cylinders, and a fourth probe was installed in the intake manifold plenum for tracking dynamics introduced by an external exhaust gas recirculation mixer. Near-crank-angle resolved measurements (5 kHz, that is, 1.2 crank angle resolution at 1000 RPM) were performed during steady-state engine operation at various levels of external exhaust gas recirculation to measure the gas properties and penetration distance of the backflow into the intake runners on a cylinder- and cycle-basis. Validation of computational fluid dynamics model results is also presented to demonstrate the utility of such measurements in advancing engine research.

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Gomez, A. L., et E. P. Rosen. « Fast response cavity enhanced ozone monitor ». Atmospheric Measurement Techniques 6, n^o 2 (27 février 2013) : 487–94. http://dx.doi.org/10.5194/amt-6-487-2013.

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Abstract. Ozone is an important atmospheric gas due to its role in air quality and radiative forcing. A new method for sensitive, rapid monitoring of ambient ozone has been developed using a compact platform and relatively inexpensive components. Based on incoherent broadband cavity enhanced absorption spectroscopy (IBB-CEAS), the device utilizes an optical cavity of just 14.5 cm and 99.3% reflective mirrors. Performance of the instrument has been validated against direct absorption measurements in a single-pass measurement cell. Currently, the IBB-CEAS ozone instrument can achieve ∼1 ppb sensitivities at 0.1 s integration time with a dynamic range over four orders of magnitude, accessing relevant ozone concentrations in both the stratosphere and troposphere. This new device offers improved sensitivity and time response for mapping ozone aboard airborne platforms.

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Gomez, A. L., et E. P. Rosen. « Fast response cavity enhanced ozone monitor ». Atmospheric Measurement Techniques Discussions 5, n^o 5 (26 septembre 2012) : 7223–41. http://dx.doi.org/10.5194/amtd-5-7223-2012.

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Abstract. Ozone is an important atmospheric gas due to its role in air quality and radiative forcing. A new method for sensitive, rapid monitoring of ambient ozone has been developed using a compact platform and relatively inexpensive components. Based on Incoherent Broadband Cavity Enhanced Absorption Spectroscopy (IBB-CEAS), the device utilizes an optical cavity of just 14.5 cm and moderately high reflectivity mirrors (R = 99.3%). Performance of the instrument has been validated against direct absorption measurements in a single-pass measurement cell. Currently, the IBB-CEAS ozone instrument can achieve 1 ppb sensitivities at 0.1 s integration time with a dynamic range over four orders of magnitude, accessing relevant ozone concentrations in both the stratosphere and troposphere. This new device offers improved sensitivity and time response for mapping ozone aboard airborne platforms.

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Unger, Miriam, Harumi Sato, Yukihiro Ozaki, Dieter Fischer et Heinz W. Siesler. « Temperature-Dependent Fourier Transform Infrared Spectroscopy and Raman Mapping Spectroscopy of Phase-Separation in a Poly(3-hydroxybutyrate)–Poly(l-Lactic Acid) Blend ». Applied Spectroscopy 67, n^o 2 (février 2013) : 141–48. http://dx.doi.org/10.1366/12-06712.

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Variable-temperature Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopic mapping measurements were applied to study the phase separation of a poly(3-hydroxybutyrate) (PHB)–poly(l-lactic acid) (PLA) (50:50 wt.%) polymer-blend film as a function of temperature between 25 and 175 °C. Because of the better band separation compared with the fundamental absorptions, the first overtones of the v(C=O) bands of PHB and PLA were used to evaluate the temperature-dependent FT-IR images as PLA–PHB and PHB–PLA band-ratio contour plots, respectively. From the visualization of the band-ratio FT-IR images, it could be derived that even beyond the melting point of PLA (145 °C), the lateral position and the geometry of the PHB-rich and PLA-rich phases were retained up to 165 °C. Furthermore, the FT-IR images derived during and after the melting of PHB (174 °C) provided an interesting insight into the homogenization process of the polymer melt. By exploiting its higher lateral resolution, valuable additional information became available from the Raman mapping measurements. Based on the Raman data, the scenario of phase-separated PHB-rich and PLA-rich domains of about 50 iμ size, based on the FT-IR imaging measurements, had to be revised. Instead, the originally interpreted PHB-rich and PLA-rich domains are actually clusters of much smaller grains. Additionally, the Raman images measured in the same temperature interval revealed that the clusters of small PHB-rich grain structures aggregated as a function of temperature increase. These investigations prove that FT-IR and Raman imaging in combination with variable-temperature measurements can provide new (and so far unavailable) insights into structural phenomena of phase-separated polymer blends.

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Alexander, Jessica A., Frank J. Scheltens, Lawrence F. Drummy, Michael F. Durstock, James B. Gilchrist, Sandrine Heutz et David W. McComb. « Measurement of optical properties in organic photovoltaic materials using monochromated electron energy-loss spectroscopy ». Journal of Materials Chemistry A 4, n^o 35 (2016) : 13636–45. http://dx.doi.org/10.1039/c6ta06201f.

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Merrell, Katie A., Eugene Vasiliev, Misty C. Bentz, Monica Valluri et Christopher A. Onken. « The Mass of the Black Hole in NGC 5273 from Stellar Dynamical Modeling ». Astrophysical Journal 949, n^o 1 (1 mai 2023) : 13. http://dx.doi.org/10.3847/1538-4357/acc4bc.

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Abstract We present a new constraint on the mass of the black hole in the active S0 galaxy NGC 5273. Due to the proximity of the galaxy at 16.6 ± 2.1 Mpc, we were able to resolve and extract the bulk motions of stars near the central black hole using adaptive-optics-assisted observations with the Gemini Near-infrared Integral Field Spectrograph, as well as constrain the large-scale kinematics using archival Spectroscopic Areal Unit for Research and Optical Nebulae spectroscopy. High-resolution Hubble Space Telescope imaging allowed us to generate a surface-brightness decomposition, determine approximate mass-to-light ratios for the bulge and disk, and obtain an estimate for the disk inclination. We constructed an extensive library of dynamical models using the Schwarzschild orbit-superposition code FORSTAND, exploring a range of disk and bulge shapes, halo masses, etc. We determined a black hole mass of M • = [0.5–2] × 107 M ⊙, where the low side of the range is in agreement with the reverberation mapping measurement of M • = [4.7 ± 1.6] × 106 M ⊙. NGC 5273 is one of the few nearby galaxies that hosts a broad-lined active galactic nucleus, allowing a crucial comparison of black hole masses derived from independent mass-measurement techniques.

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Jones, Tucker. « Spatially resolved spectroscopy of lensed galaxies in the Frontier Fields ». Proceedings of the International Astronomical Union 11, A29B (août 2015) : 772–75. http://dx.doi.org/10.1017/s1743921316006773.

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AbstractThe Grism Lens-Amplified Survey from Space (GLASS) has obtained slitless near-infrared spectroscopy of 10 galaxy clusters selected for their strong lensing properties, including all six Hubble Frontier Fields. Slitless grism spectra are ideal for mapping emission lines such as [O ii], [O iii], and Hα at z=1–3. The combination of strong gravitational lensing and Hubble's diffraction limit provides excellent sensitivity with spatial resolution as fine as 100 pc for highly magnified sources, and ~500 pc for less magnified sources near the edge of the field of view. The GLASS survey represents the largest spectroscopic sample with such high resolution at z > 1. GLASS and Hubble Frontier Field data provide the distribution of stellar mass, star formation, gas-phase metallicity, and other aspects of the physical structure of high redshift galaxies, reaching stellar masses as low as ~107 M⊙ at z=2. I discuss precise measurements of these physical properties and implications for galaxy evolution.

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Eitelwein, Mateus Tonini, Tiago Rodrigues Tavares, José Paulo Molin, Rodrigo Gonçalves Trevisan, Rafael Vieira de Sousa et José Alexandre Melo Demattê. « Predictive Performance of Mobile Vis–NIR Spectroscopy for Mapping Key Fertility Attributes in Tropical Soils through Local Models Using PLS and ANN ». Automation 3, n^o 1 (3 février 2022) : 116–31. http://dx.doi.org/10.3390/automation3010006.

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Mapping soil fertility attributes at fine spatial resolution is crucial for site-specific management in precision agriculture. This paper evaluated the performance of mobile measurements using visible and near-infrared spectroscopy (vis–NIR) to predict and map key fertility attributes in tropical soils through local data modeling with partial least squares regression (PLS) and artificial neural network (ANN). Models were calibrated and tested in a calibration area (18-ha) with high spatial variability of soil attributes and then extrapolated in the entire field (138-ha). The models calibrated with ANN obtained superior performance for all attributes. Although ANN models obtained satisfactory predictions in the calibration area (ratio of performance to interquartile range (RPIQ) ≥ 1.7) for clay, organic matter (OM), cation exchange capacity (CEC), base saturation (V), and exchangeable (ex-) Ca, it was not repeated for some of them when extrapolated into the entire field. In conclusion, robust mappings (RPIQ = 2.49) were obtained for clay and OM, indicating that these attributes can be successfully mapped on tropical soils using mobile vis–NIR spectroscopy and local calibrations using ANN. This study highlights the need to implement an independent test to assess reliability and extrapolability of previously calibrated models, even when extrapolating the models to neighboring areas.

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Zhu, Wenliang, et Giuseppe Pezzotti. « Spatially Resolved Stress Analysis in Al2O3/3Y-TZP Multilayered Composite Using Confocal Fluorescence Spectroscopy ». Applied Spectroscopy 59, n^o 8 (août 2005) : 1042–48. http://dx.doi.org/10.1366/0003702054615250.

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Fluorescence piezo-spectroscopy (PS) was applied to evaluate the residual stress fields stored in a multilayered Al2O3/3Y-TZP (3 mol % Y2O3-stabilized ZrO2) composite using the chromophoric fluorescence spectra of Al2O3. The PS results were compared with a theoretical stress distribution in the laminate, calculated according to a repeating unit cell model. However, in practical fluorescence spectroscopy, each measurement point corresponded to a finite volume of material, within which the scattered light experienced fluorescence wavelengths characteristic of the local (weight-average) stress fields. Because of the finite volume of material probed in PS measurements, a comparison between the experimental and calculated values requires that the calculated stresses be convoluted according to the depth-response function of the probe. A pinhole aperture incorporated in the Raman microprobe was used to control the collection probe depth and to modulate the portion of the whole fluorescence emission reaching the detector. According to calibrations of the probe depth and probe response function, probe-convoluted stresses were obtained and a spatially resolved mapping of residual stresses could be obtained.

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Kunze, Karsten. « Crystal orientation measurements using SEM–EBSD under unconventional conditions ». Powder Diffraction 30, n^o 2 (12 mai 2015) : 104–8. http://dx.doi.org/10.1017/s0885715615000263.

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Electron backscatter diffraction (EBSD) is a micro-analytical technique typically attached to a scanning electron microscope (SEM). The vast majority of EBSD measurements is applied to planar and polished surfaces of polycrystalline bulk specimen. In this paper, we present examples of using EBSD and energy-dispersive X-ray spectroscopy (EDX) to analyze specimens that are not flat, not planar, or not bulk – but pillars, needles, and rods. The benefits of low vacuum SEM operation to reduced drift problems are displayed. It is further demonstrated that small and thin specimens enhance the attainable spatial resolution for orientation mapping (by EBSD or transmission Kikuchi diffraction) as well as for element mapping (by EDX).

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Makin, Fadiyah, Dalal Alzahrani, Firoz Alam, Floriana Tuna et David J. Lewis. « Testing the Efficacy of the Synthesis of Iron Antimony Sulfide Powders from Single Source Precursors ». Inorganics 9, n^o 8 (2 août 2021) : 61. http://dx.doi.org/10.3390/inorganics9080061.

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The antimony-iron sulfide system in general does not produce alloys below 540 °C from traditional solid-state methods. However, single source precursors have been known to produce unexpected products that arise from kinetically trapped polymorphs. In this paper, we test the efficacy of this approach toward the Fe-Sb-S system. Antimony and iron diethyldithiocarbamate complexes of the form Sb[S2CN(Et2)]3 (1) and Fe[S2CN(Et2)]3 (2) were synthesised, characterised, and used as single-source precursors for the preparation of Sb2S3, FexSy, and mixed iron antimony sulfide Sb2(1−x)Fe2xS3 (0 ≥ x ≥ 1) powders using the solvent-less thermolysis method at different temperatures ranging from 300 to 475 °C. The effect of different mole fractions of the iron precursor was evaluated on morphology, shape, and optical and magnetic properties of Sb2(1−x)Fe2xS3 (0 ≥ x ≥ 1). The obtained powders were characterized by X-ray diffraction (XRD), Raman spectroscopy scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, magnetometer measurement, and UV/vis/NIR spectroscopy. The results demonstrated that the crystalline structure, morphology, and elemental composition of the samples changed with the mole fraction of the precursor. There was significant phase separation between Sb and Fe sulfides noted from EDX spectroscopic mapping, yet an optoelectronic study monitoring the direct band gap energy of antimony sulfide shows that the band gap energy increases as a function of Fe content, which suggests limited alloying is possible from the single source route.

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Obitayo, Waris, Sida Luo, Zhiwei Xiao, Tao Liu et Jingjiao Guan. « Gel electrophoresis and Raman mapping for determining the length distribution of SWCNTs ». RSC Adv. 4, n^o 70 (2014) : 37070–78. http://dx.doi.org/10.1039/c4ra05885b.

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Ala-Myllymäki, Juho, Tommi Paakkonen, Antti Joukainen, Heikki Kröger, Petri Lehenkari, Juha Töyräs et Isaac O. Afara. « Near-Infrared Spectroscopy for Mapping of Human Meniscus Biochemical Constituents ». Annals of Biomedical Engineering 49, n^o 1 (27 juillet 2020) : 469–76. http://dx.doi.org/10.1007/s10439-020-02578-x.

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AbstractDegenerative changes in meniscus are diagnosed during surgery by means of mechanical testing and visual evaluation. This method is qualitative and highly subjective, providing very little information on the internal state of the meniscus. Thus, there is need for novel quantitative methods that can support decision-making during arthroscopic surgery. In this study, we investigate the potential of near-infrared spectroscopy (NIRS) for mapping the biochemical constituents of human meniscus, including water, uronic acid, and hydroxyproline contents. Partial least squares regression models were developed using data from 115 measurement locations of menisci samples extracted from 7 cadavers and 11 surgery patient donors. Model performance was evaluated using an independent test set consisting of 55 measurement locations within a meniscus sample obtained from a separate cadaver. The correlation coefficient of calibration (ρtraining), test set (ρtest), and root-mean-squared error of test set (RMSEP) were as follows: water (ρtraining = 0.61, ρtest = 0.39, and RMSEP = 2.27 percentage points), uronic acid (ρtraining = 0.68, ρtest = 0.69, and RMSEP = 6.09 basis points), and hydroxyproline (ρtraining = 0.84, ρtest = 0.58, and error = 0.54 percentage points). In conclusion, the results suggest that NIRS could enable rapid arthroscopic mapping of changes in meniscus biochemical constituents, thus providing means for quantitative assessment of meniscus degeneration.

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Pittenger, Bede, et Andrea Slade. « Performing Quantitative Nanomechanical AFM Measurements on Live Cells ». Microscopy Today 21, n^o 6 (novembre 2013) : 12–17. http://dx.doi.org/10.1017/s1551929513001077.

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Atomic force microscopy (AFM) has been recognized since the mid-eighties as an excellent technique to image a wide range of samples in their near-natural environment. Although the primary function of AFM is to generate three-dimensional (3D) profiles of the scanned surface, much more information can be delivered via this technique. In 1993, TappingMode was developed, which prevents tip and sample damage due to friction and shear forces and allows qualitative mechanical property mapping through phase imaging. About the same time, force spectroscopy and force volume (FV) were developed to study tip-sample forces at a point or over an area, respectively. To date, force spectroscopy and FV are the most commonly used AFM modes for measuring nanometer-scale mechanical forces in a quantitative manner. Unfortunately, force spectroscopy and FV suffer from slow acquisition speed and a lack of automated tools; these operating characteristics limit their use because of the hundreds or thousands of curves that are required for good statistics.

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Du, Jiaren, et Dirk Poelman. « Facile Synthesis of Mn4+-Activated Double Perovskite Germanate Phosphors with Near-Infrared Persistent Luminescence ». Nanomaterials 9, n^o 12 (11 décembre 2019) : 1759. http://dx.doi.org/10.3390/nano9121759.

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Tetravalent manganese doped phosphors are emerging as a new class of efficient near-infrared emitters for applications in a variety of areas, such as bioimaging and night-vision surveillance. Novel double perovskite-type La2MgGeO6:Mn4+ phosphors were successfully prepared using a microwave-assisted energy-saving solid state method. This simple technique involving the use of a microwave susceptor allows for a reduction of the preparation time compared to a conventional solid state reaction. The samples were investigated using powder X-ray diffraction, scanning electron microscopy, as well as energy-dispersive X-ray spectroscopy mapping, photoluminescence excitation/emission spectroscopy, persistent luminescence decay and temperature-dependent photoluminescence analysis. Substitution between isovalent Mn4+ and Ge4+ can be achieved without additional charge compensators in this germanate-based phosphor, which provides strong emission in the near-infrared spectral region, assigned to the characteristic transitions of tetravalent manganese ions. Additionally, the double perovskite-type germanate phosphor exhibits excellent luminescence thermal stability. Moreover, the spectroscopic properties, excitation wavelength-dependent and temperature-dependent persistent luminescence were studied. A series of thermoluminescence measurements were presented trying to give clear information on the charging process, afterglow behavior and the nature of the traps responsible for the persistent luminescence. The present investigation expands the range of available promising near-infrared emitting persistent phosphors for medical imaging.

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N’Dohi, Atse Julien Eric, Camille Sonneville, Soufiane Saidi, Thi Huong Ngo, Philippe De Mierry, Eric Frayssinet, Yvon Cordier et al. « Micro-Raman Spectroscopy Study of Vertical GaN Schottky Diode ». Crystals 13, n^o 5 (22 avril 2023) : 713. http://dx.doi.org/10.3390/cryst13050713.

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In this work, the physical and the electrical properties of vertical GaN Schottky diodes were investigated. Cathodo-luminescence (CL), micro-Raman spectroscopy, SIMS, and current-voltage (I-V) measurements were performed to better understand the effects of physical parameters, for example structural defects and doping level inhomogeneity, on the diode electrical performances. Evidence of dislocations in the diode epilayer was spotted thanks to the CL measurements. Then, using 2D mappings of the E2h and A1 (LO) Raman modes, dislocations and other peculiar structural defects were observed. The I-V measurements of the diodes revealed a significant increase in the leakage current with applied reverse bias up to 200 V. The combination of physical and electrical characterization methods indicated that the electrical leakage in the reverse biased diodes seems more correlated with short range non-uniformities of the effective doping than with strain fluctuation induced by dislocations.

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Radosavljević, Jasna Simonović, Aleksandra Lj Mitrović, Ksenija Radotić, László Zimányi, Győző Garab et Gábor Steinbach. « Differential Polarization Imaging of Plant Cells. Mapping the Anisotropy of Cell Walls and Chloroplasts ». International Journal of Molecular Sciences 22, n^o 14 (17 juillet 2021) : 7661. http://dx.doi.org/10.3390/ijms22147661.

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Modern light microscopy imaging techniques have substantially advanced our knowledge about the ultrastructure of plant cells and their organelles. Laser-scanning microscopy and digital light microscopy imaging techniques, in general—in addition to their high sensitivity, fast data acquisition, and great versatility of 2D–4D image analyses—also opened the technical possibilities to combine microscopy imaging with spectroscopic measurements. In this review, we focus our attention on differential polarization (DP) imaging techniques and on their applications on plant cell walls and chloroplasts, and show how these techniques provided unique and quantitative information on the anisotropic molecular organization of plant cell constituents: (i) We briefly describe how laser-scanning microscopes (LSMs) and the enhanced-resolution Re-scan Confocal Microscope (RCM of Confocal.nl Ltd. Amsterdam, Netherlands) can be equipped with DP attachments—making them capable of measuring different polarization spectroscopy parameters, parallel with the ‘conventional’ intensity imaging. (ii) We show examples of different faces of the strong anisotropic molecular organization of chloroplast thylakoid membranes. (iii) We illustrate the use of DP imaging of cell walls from a variety of wood samples and demonstrate the use of quantitative analysis. (iv) Finally, we outline the perspectives of further technical developments of micro-spectropolarimetry imaging and its use in plant cell studies.

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Ren, Dan, Jet Ing Ngie Yeo, Tian-Yin Liu et Xiaolin Wang. « Time-dependent FTIR microscopy for mechanism investigations and kinetic measurements in interfacial polymerisation : a microporous polymer film study ». Polymer Chemistry 10, n^o 22 (2019) : 2769–73. http://dx.doi.org/10.1039/c9py00257j.

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Vuillermet, Enora, Kuan Ting Wu, Anael Sedilot, Regis Deturche, Nicolas Bercu, Elise Usureau, Jérémie Beal et Mihai Lazar. « Coupled Non-Destructive Methods, Kelvin Force Probe Microscopy and µ-Raman to Characterize Doping in 4H-SiC Power Devices ». Solid State Phenomena 358 (21 août 2024) : 13–21. http://dx.doi.org/10.4028/p-suilp5.

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Investigation of the doped areas in 4H-SiC power devices has been done by non-destructive characterization methods. It consists of local surface potential measurements by Kelvin Probe Force Microscopy (KPFM) coupled with scanning electron microscopy (SEM) and µ-Raman spectroscopy. Near-field mappings of the devices’ surface have been realized, allowing us to discern the differently doped areas.

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Alangari, Mashari, Busra Demir, Caglanaz Akin Gultakti, Ersin Emre Oren et Joshua Hihath. « Mapping DNA Conformations Using Single-Molecule Conductance Measurements ». Biomolecules 13, n^o 1 (8 janvier 2023) : 129. http://dx.doi.org/10.3390/biom13010129.

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DNA is an attractive material for a range of applications in nanoscience and nanotechnology, and it has recently been demonstrated that the electronic properties of DNA are uniquely sensitive to its sequence and structure, opening new opportunities for the development of electronic DNA biosensors. In this report, we examine the origin of multiple conductance peaks that can occur during single-molecule break-junction (SMBJ)-based conductance measurements on DNA. We demonstrate that these peaks originate from the presence of multiple DNA conformations within the solutions, in particular, double-stranded B-form DNA (dsDNA) and G-quadruplex structures. Using a combination of circular dichroism (CD) spectroscopy, computational approaches, sequence and environmental controls, and single-molecule conductance measurements, we disentangle the conductance information and demonstrate that specific conductance values come from specific conformations of the DNA and that the occurrence of these peaks can be controlled by controlling the local environment. In addition, we demonstrate that conductance measurements are uniquely sensitive to identifying these conformations in solutions and that multiple configurations can be detected in solutions over an extremely large concentration range, opening new possibilities for examining low-probability DNA conformations in solutions.

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Kaiser, M. E., L. D. Bradley, J. B. Hutchings, S. B. Kraemer, D. M. Crenshaw, J. Ruiz, D. Weistrop, C. Nelson et T. R. Gull. « Kinematic Mapping of the Narrow Line Region of NGC4151 ». Symposium - International Astronomical Union 194 (1999) : 79–81. http://dx.doi.org/10.1017/s0074180900161777.

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We present HSTSpace Telescope Imaging Spectrograph (STIS) slitless spectroscopy of the NGC4151 narrow line region (NLR) as a probe of the kinematic stucture of the extended emission-line gas emanating from the nucleus. Using slitless spectroscopy at two roll angles (with a spatial resolution of 0.051 ″/pixel and a point source spectral resolution of 0.55 Å) augmented with narrow band images, we have mapped the velocity field of the NLR as defined by ˜60 discrete cloud structures in [OIII]. Flux measurements of [OII], Hβ, [OIII], [OI], and [SII] were made for individual cloud structures wherever possible.

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Cucchetti, E., N. Clerc, E. Pointecouteau, P. Peille et F. Pajot. « Towards mapping turbulence in the intra-cluster medium ». Astronomy & ; Astrophysics 629 (septembre 2019) : A144. http://dx.doi.org/10.1051/0004-6361/201935677.

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X-ray observations of the hot gas filling the intra-cluster medium (ICM) provide a wealth of information on the dynamics of clusters of galaxies. The global equilibrium of the ICM is believed to be ensured by non-thermal and thermal pressure support sources, among which gas movements and the dissipation of energy through turbulent motions. Accurate mapping of turbulence using X-ray emission lines is challenging due to the lack of spatially resolved spectroscopy. Only future instruments such as the X-ray Integral Field Unit (X-IFU) on Athena will have the spatial and spectral resolution to quantitatively investigate the ICM turbulence over a broad range of spatial scales. Powerful diagnostics for these studies are line shift and the line broadening maps, and the second-order structure function. When estimating these quantities, instruments will be limited by uncertainties of their measurements, and by the sampling variance (also known as cosmic variance) of the observation. Here, we extend the formalism started in our companion Paper I to include the effect of statistical uncertainties of measurements in the estimation of these line diagnostics, in particular for structure functions. We demonstrate that statistics contribute to the total variance through different terms, which depend on the geometry of the detector, the spatial binning and the nature of the turbulent field. These terms are particularly important when probing the small scales of the turbulence. An application of these equations is performed for the X-IFU, using synthetic turbulent velocity maps of a Coma-like cluster. Results are in excellent agreement with the formulas both for the structure function estimation (≤3%) and its variance (≤10%). The expressions derived here and in Paper I are generic, and ensure an estimation of the total errors in any X-ray measurement of turbulent structure functions. They also open the way for optimisations in the upcoming instrumentation and in observational strategies.

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