902 research outputs found

    Segmenting color image of plants with a spatio-colorimetric approach

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    An unsupervised vectorial segmentation method using both spatial and color information is presented. To overcome the problem of memory space, this method is based on a multidimensional compact histogram and an original compact spatial neighborhood probability matrix (SNPM). The multidimensional compact histogram allows a drastic reduction of memory space without any data loss. Leaning upon the compact histogram, a SNPM has been computed. It contains all non-negative probabilities of spatial connectivity between pixel colors. In an unsupervised histogram analysis classification process, two phases are classically distinguished: (i) a learning process during which histogram modes are identified and (ii) a second step called the decision step in which a full partition of the colorimetric space is carried out according the previously defined classes. During the second step of a standard colorimetric approach, a colorimetric distance like Euclidean or Mahalanobis is used. We insert here a spatio-colorimetric distance defined as a weighed mixture between a colorimetric distance and the spatial distance calculated from the SNPM. The vectorial classification method is based on previously presented principles, achieving a hierarchical analysis of the color histogram by means of a 3D-connected components labeling. Results are applied to color images of plants to separate plantlets and loam

    Electrical Surface Breakdown: Secondary Electron Emission and Electron Spectroscopy of Insulators

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    These results question the usual scheme of flashover. They lead to a different interpretation based on classical concepts in solid state physics which can be verified at every step. An ionizing cascade in the bands, rather than a cascade of electron multiplication on the insulating surface, could explain the flashover, the conditioning and the deconditioning of high voltage generators through the building of a surface charge. As in the usual model the positive charge is responsible for the flashover, in this new model the building of this charge is the basis of the conditioning. The ionizing cascade in the bands is initiated by a tunnel injection into the insulator from the soldering metal-insulator junction or by electronic excitation. This interpretation is supported by the analysis of charging phenomena in insulators, the study of localization sites of carriers and by the neutralization mechanisms, charge diffusion or defect annealling. These studies are achieved by scanning electron microscopy and electron spectroscopy

    Invited Paper. The Hermeneutic Wager: Building Community in Pediatric Neuro-Oncology

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    During the Covid-19 pandemic, Hovey was contacted by the lead of a pan-Canadian working group on pediatric brain tumours (PBTWG). While all stakeholders (researchers, clinicians, regulators, patient advocates, ethicists, and industry experts) were highly motivated to address barriers through innovative strategies in collaboration, clinical research, regulation, and business models, advancement has been challenging on multiple levels. Hovey and his team were tasked to facilitate and successfully engage this diverse divisive group of stakeholders to achieve their goals. Inspired by Richard Kearney’s anatheistic wager, the hermeneutic wager acts simultaneously as a team building and research approach, as it serves to gain insight into the perspectives of members of a purposeful community. Through its five conversations, namely imagination, humility, commitment, discernment, and hospitality, the hermeneutic wager elicits responses from the participants that are based on meaningful participation in a relational approach of community co-creation. We individually interviewed the PBTWG facilitators (5). With informed consent, our research team also recorded all 5 of the PBTWG work group meetings (20 participants from 6 stakeholder groups) and break-out room meetings and took notes which consist of rich and extensive narrative data. This data was analyzed alongside the individual PBTWG interviews. The audio and visual data collected via a secure Zoom platform was then transcribed verbatim and analyzed interpretively according to the applied philosophical hermeneutic tradition. Findings centered around six points: “The Work of Stories,” “Changing Landscapes: Community / Communication not Consensus,” “Let the Words Lead You,” â€œThose Words Matter,” â€œMetaphors as a Bridge to Understanding,” and “A Road Map to be Inspired By.” Through these findings, we contend that the hermeneutic wager is an invitation for conversation that builds a path to the generation of new and creative understandings that transcend previous ways of knowing. The efficacy of the hermeneutic wager resides in its ability to help build a community of people who work together through and across difference to arrive at a shared understanding and collective outcome. &nbsp

    Intensity of Valence Auger Transitions (L23VV) of Al and Si in Metal, Oxide and Nitride

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    L23VV Auger transition has been studied in Si, SiO2, Al, AlN, Al2O3 by electron spectroscopy excited either by electron beam or X Rays. A strong difference is observed in intensity between pure solid and oxide or nitride under electron bombardment. Auger intensity is very sensitive to changes in the backscattering coefficient or inelastic mean free path. However transient local trapping of electrons seems to be responsible for the large change observed

    Physical Basis for Spectrometer Calibration

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    Progress in quantitative surface analysis is hampered by the lack of experimental procedure including spectrometer calibration, sample preparation, and general experimental setting-up. Two methods for spectrometer alignment are compared: the linearization method and the elastic peak test. Experimental spectra are presented, which can be considered as stringent reference data to check the instrument response and the analyser transmission at low energies

    Influence of Ion Implantation and Gas Exposure on the Charge in Silicon Oxide Created by Electronic Excitation

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    Low energy electron bombardment of amorphous SiO2 induces point defects such as oxygen vacancy by electronic excitation. The defects build a macroscopic negative charge by trapping of electrons on the localized levels in the band gap; this phenomenon was previously described as the mirror effect. In the present paper, we investigate, by mirror effect, the behavior of the charge after an argon, nitrogen and oxygen implantation at 1 and 4 keV, and after exposure to the same gases at various low pressures. We observe a difference of behavior between Ar (or N2) and O2, The results reinforce the outstanding role of oxygen in the defect production in SiO2 by electronic excitation

    Study by Scanning Electron Microscopy and Electron Spectroscopy of the Cascade of Electron Multiplication in an Insulator Submitted to an Electric Field

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    An original method for revealing the dielectric heterogeneities on an insulating surface has been developed on creation of an electron multiplication cascade inside the insulator placed in an electric field. The steps of the physical process are: (i) excitation of electrons into the conduction band, (ii) electric field acceleration of the conduction electrons, (iii) ionization of the valence levels, (iv) creation of many more new defects in the vicinity of dielectric heterogeneities, (v) charge localization on defects and appearance of a local residual potential. The potential map is observable by scanning electron microscopy after propagation of the ionizing cascade, but only during the first scan which smoothes the surface potential. By electron spectroscopy the energy of the secondary negative particles emitted during the cascade can be analysed

    Oxidation of Aluminum Studied by Ion Scattering Spectroscopy (I.S.S) in a Scanning Auger Microscope

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    The set up of an ion gun, producing a focused beam in the analysis chamber of a Scanning Auger Microscope permits ion scattering experiments: surface studies performed by electron spectroscopies can then be enlarged by Ion Scattering Spectroscopy (I.S.S.) to get additional information. I.S.S. appears to be very sensitive to the cleanliness of the surface: comparison between Electron Energy Loss Spectroscopy (E.E.L.S.) and I.S.S. studies on clean samples show that I.S.S. can still detect oxygen even when it is not detectable by E.E.L.S. Preliminary results on oxidation of Al (111) and Al (100) give oxidation curves in good agreement with those obtained by Auger Electron Spectroscopy (A.E.S.) and X Ray Photoemission Spectroscopy (X.P.S.)

    fMRI visualization of transient activations in the rat olfactory bulb using short odor stimulations

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    International audienceOdor-evoked activity in the olfactory bulb displays both spatial and temporal organization. The difficulty when assessing spatio-temporal dynamics of olfactory representation is to find a method that reconciles the appropriate resolution for both dimensions. Imaging methods based on optical recordings can reach high temporal and spatial resolution but are limited to the observation of the accessible dorsal surface. Functional magnetic resonance imaging (fMRI) may be useful to overcome this limitation as it allows recording from the whole brain. In this study, we combined ultra fast imaging sequence and short stimulus duration to improve temporal resolution of odor-evoked BOLD responses. Short odor stimulations evoked high amplitude BOLD responses and patterns of activation were similar to those obtained in previous studies using longer stimulations. Moreover, short odor exposures prevented habituation processes. Analysis of the BOLD signal time course in the different areas of activation revealed that odorant response maps are not static entities but rather are temporally dynamic as reported by recent studies using optical imaging. These data demonstrated that fMRI is a non-invasive method which could represent a powerful tool to study not only the spatial dimension of odor representation but also the temporal dimension of information processing

    Measurements of hydrogen cyanide (HCN) and acetylene (C2H2) from the Infrared Atmospheric Sounding Interferometer (IASI)

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    Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q branch near 720 cm−1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO2 line mixing, we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S, 55° E) and Jungfraujoch (46° N, 8° E) in 2009–2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). A first order comparison with local ground-based Fourier transform InfraRed (FTIR) measurements has been carried out allowing tests of seasonal consistency which is reasonably captured, except for HCN at Jungfraujoch. The IASI data shows a greater tendency to high C2H2 values. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values
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