Pratique du Shadowing: Introduction to focused ion beam scanning electron microscopy (FIB-SEM) - Apprendre l'anglais à l'oral avec la vidéo

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29 phrases
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Hi, I'm Kedar Narayan, a group leader at the Center for Molecular Microscopy, or CMM, at the National Cancer Institute and Frederick National Laboratory for Cancer Research.
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Imaging three-dimensional objects in 2D can be limiting, yielding an incomplete or even a misleading picture.
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And so, at the CMM, we apply cutting-edge electron microscopy, or EM, technologies to image biological samples at the highest possible resolutions.
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My group specializes in the imaging of cells and tissues, that is, larger volumes, in 3D and at nanoscale resolutions.
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In this short video, I'm going to give you a flavor of an imaging technique that we employ in our lab, Focused Ion Beam Scanning Electron Microscopy, or FibSem.
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FibSem, as you will see, is a powerful 3D-EM imaging approach, and in this specific example, we highlight a correlative light microscopy and FibSem, or CLEM-FibSem workflow.
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CLEM-FibSem combines the advantages of light and electron microscopy to generate image reconstructions of targeted features of interest in 3D at resolutions of tens of nanometers.
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So here you have a group of cells of which a subset is fluorescently labeled.
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These cells are grown on a gridded cover slip, a glass substrate on which an alphanumeric code has been etched.
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You can now image these cells either live or after fixation using fluorescence microscopy and also record their x-y coordinates using the gridded pattern.
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Once this step is completed, the cells can be fixed, stained, dehydrated, and resin-embedded in situ.
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When the gridded coverslip is removed, the alphanumeric pattern is transferred to the resin surface in relief, with the cells embedded just beneath that surface.
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In other words, you now know exactly where to find your cells of interest.
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At this point, the cell sample is transferred to the FibSem instrument.
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This Martian looking surface is a close up of the resin where you expect to find your targeted cell.
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The resin embedded cell is protected by a patterned platinum and carbon pad deposited by the focused ion beam or fib, which appears as a rapidly moving blue beam in this movie.
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Remarkably, the same focused ion beam that deposits the platinum and carbon pad can now be used to mill a trench in front of the targeted cell.
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The tightly controlled fib inches towards the cell, ablating away the resin, and eventually reveals the cell itself in cross-section.
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The scanning electron imaging beam, shown here as a yellow band, now rasters over the polished resin surface, and a detector records a high-resolution backscatter electron signal.
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This process is repeated over and over.
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As the fib moves forward and mills away a few more nanometers of the resin, the SEM images the newly exposed section of the cell to generate the next image, and so on and so on.
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Typically, we generate SEM images at 3 to 5 nanometer pixel size in the imaging plane, and 3 to 15 nanometer fib step size, meaning that this automated loop is often repeated several thousand times to generate a highly information-rich ultra-structural image stack covering entire mammalian cells.
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These images are then registered using the notch marks in the pad and converted to an isotropic image volume that allows you to visualize architectural features throughout the bulk of the cell sample.
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The final step is segmentation.
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Here we show the extraction and rendering of the plasma membrane of the cell.
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Fibsem imaging reveals that the membrane extensions in the cell that looked like spaghetti in 2D cross-section are actually veils when visualized in three dimensions.
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FibSem imaging can be applied to a wide variety of systems to confirm observations, generate hypotheses, and most fun of all, make unexpected discoveries in cell biology.
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If you'd like to know more, you can contact me, Kedhar Narayan, at the Center for Molecular Microscopy at the National Cancer Institute and Frederick National Laboratory for Cancer Research.
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You can also visit cmm.nci.nih.gov.

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Vocabulaire et conseils d’expression pour cette leçon

Cette leçon d’expression orale de niveau C2 s’appuie sur la vidéo « Introduction to focused ion beam scanning electron microscopy ». Les mots qui reviennent le plus souvent : cell, image, Fibsem, imaging, microscopy. Cette vidéo contient 29 phrases et 658 mots à répéter en shadowing. La partie parlée dure 4:15. Le locuteur parle à un rythme naturel d’environ 155 mots par minute, proche d’une conversation courante. Seuls 67 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc exigeant.

Vocabulaire clé de cette vidéo

Les 15 mots les plus avancés de la vidéo, avec leur prononciation et leur sens :

MotPrononciationSens
microscopy nom/maɪˈkɹɑ.skə.pi/microscopie
resin nom/ˈɹɛzɪn/résine
electron nom/ɪˈlɛk.tɹɑn/électron
embed verbe/ɪmˈbɛd/insérer, encastrer
alphanumeric adjectif/ˌæl.fə.n(j)uːˈmɛ.ɹɪk/alphanumérique
nanometre nom/ˈnænoʊˌmitər/nanomètre
visualize verbe/ˈvɪʒuəˌlaɪz/visualiser
membrane nom/ˈmɛm.bɹeɪn/membrane
platinum nom/ˈplæt.ɪn.əm/platine
scan verbe/skæn/scanner, fouiller
automate verbe/ˈɔ.təˌmeɪt/automatiser
correlative adjectifcorrélatif
dehydrate verbe/diːhaɪˈdɹeɪt/déshydrater
fixation nom/fɪksˈeɪʃən/fixation
fluorescence nom/flʊˈɹɛsəns/fluorescence

Prononciation à surveiller

Le locuteur utilise 3 contractions et formes réduites, comme I'm, you'd. Prononcez-les sous leur forme courte, telles que vous les entendez.

  • Les sons « sh » et « zh »: visualize /ˈvɪʒuəˌlaɪz/, fixation /fɪksˈeɪʃən/, specialize /ˈspɛʃəˌlaɪz/, extraction /ɪkˈstɹækʃən/, reconstruction /ˌɹiːkənˈstɹʌkʃən/
  • Mots longs — placez bien l’accent: microscopy /maɪˈkɹɑ.skə.pi/, alphanumeric /ˌæl.fə.n(j)uːˈmɛ.ɹɪk/, nanometre /ˈnænoʊˌmitər/, fluorescently /floʊɹˈɛsəntli/, isotropic /ˌaɪsəˈtɹɑpɪk/

Les sons difficiles pour les francophones :

  • /h/ — il se souffle, il n’est pas muet: dehydrate /diːhaɪˈdɹeɪt/, hypothesis /haɪˈpɒθɪsɪs/
  • /tʃ/ et /dʒ/ — à ne pas adoucir en « ch » et « j »: trench /ˈtɹɛnt͡ʃ/, notch /nɑtʃ/, architectural /ˌɑɹkɪˈtɛkt͡ʃəɹəl/
  • /r/ anglais — langue recourbée, sans frotter la gorge: microscopy /maɪˈkɹɑ.skə.pi/, resin /ˈɹɛzɪn/, electron /ɪˈlɛk.tɹɑn/, alphanumeric /ˌæl.fə.n(j)uːˈmɛ.ɹɪk/, nanometre /ˈnænoʊˌmitər/

Comment s’entraîner avec cette vidéo

  1. Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
  2. Commencez à la vitesse 0,75×, répétez phrase par phrase, puis revenez à la vitesse normale quand cela devient facile.
  3. Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme microscopy, resin, electron.

Qu'est-ce que la technique du Shadowing ?

Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.

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