Shadowing Practice: Introduction to focused ion beam scanning electron microscopy (FIB-SEM) - Learn English Speaking with Video
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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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Vocabulario y notas de pronunciación para esta lección
Esta lección de conversación de nivel C2 se basa en el vídeo “Introduction to focused ion beam scanning electron microscopy”. Las palabras que más se repiten: cell, image, Fibsem, imaging, microscopy. Este vídeo tiene 29 frases y 658 palabras para practicar shadowing. La parte hablada dura 4:15. El hablante habla a un ritmo natural de unas 155 palabras por minuto, cercano a una conversación cotidiana. Solo el 67 % de las palabras está entre las 3.000 más comunes del inglés, por lo que el vocabulario es exigente.
Vocabulario clave de este vídeo
Las 15 palabras más avanzadas del vídeo, con su pronunciación y significado:
| Palabra | Pronunciación | Significado |
|---|---|---|
| microscopy sustantivo | /maɪˈkɹɑ.skə.pi/ | microscopia, microscopía |
| resin sustantivo | /ˈɹɛzɪn/ | resina, zopisa |
| electron sustantivo | /ɪˈlɛk.tɹɑn/ | electrón, negatrón |
| embed verbo | /ɪmˈbɛd/ | embutir, empotrar |
| alphanumeric adjetivo | /ˌæl.fə.n(j)uːˈmɛ.ɹɪk/ | alfanumérico |
| nanometre sustantivo | /ˈnænoʊˌmitər/ | nanómetro |
| visualize verbo | /ˈvɪʒuəˌlaɪz/ | visualizar |
| membrane sustantivo | /ˈmɛm.bɹeɪn/ | membrana |
| platinum sustantivo | /ˈplæt.ɪn.əm/ | platino |
| scan verbo | /skæn/ | escrutar |
| automate verbo | /ˈɔ.təˌmeɪt/ | automatizar |
| correlative adjetivo | correlativo | |
| coverslip sustantivo | cubreobjetos | |
| dehydrate verbo | /diːhaɪˈdɹeɪt/ | deshidratar |
| fixation sustantivo | /fɪksˈeɪʃən/ | fijación |
Phrasal verbs que vas a escuchar
| Palabra | Significado |
|---|---|
| move forward verbo | ir adelante, adelantar |
Pronunciación a tener en cuenta
El hablante usa 3 contracciones y formas reducidas, como I'm, you'd. Dilas en su forma corta, tal como las oyes.
- Los sonidos de “sh” y “zh”: visualize /ˈvɪʒuəˌlaɪz/, fixation /fɪksˈeɪʃən/, specialize /ˈspɛʃəˌlaɪz/, extraction /ɪkˈstɹækʃən/, reconstruction /ˌɹiːkənˈstɹʌkʃən/
- Palabras largas — cuida el acento: microscopy /maɪˈkɹɑ.skə.pi/, alphanumeric /ˌæl.fə.n(j)uːˈmɛ.ɹɪk/, nanometre /ˈnænoʊˌmitər/, fluorescently /floʊɹˈɛsəntli/, isotropic /ˌaɪsəˈtɹɑpɪk/
Sonidos difíciles para hispanohablantes:
- s + consonante al inicio — sin añadir una “e” delante: scan /skæn/, specialize /ˈspɛʃəˌlaɪz/, stain /steɪn/, stack /stæk/
- /v/ — no es /b/: los dientes tocan el labio inferior: visualize /ˈvɪʒuəˌlaɪz/, veil /veɪl/, flavor /ˈfleɪvə/
- /z/ — sonora, no /s/: resin /ˈɹɛzɪn/, visualize /ˈvɪʒuəˌlaɪz/, specialize /ˈspɛʃəˌlaɪz/, plasma /ˈplæzmə/, expose /ɪkˈspoʊz/
Cómo practicar con este vídeo
- Escucha el vídeo entero una vez sin hablar y anota las palabras que no conoces.
- Empieza a velocidad 0,75×, haz shadowing frase por frase y vuelve a la velocidad normal cuando te resulte fácil.
- Grábate y compara con el original, prestando atención a palabras como microscopy, resin, electron.
¿Qué es la Técnica de Shadowing?
Shadowing es una técnica de aprendizaje de idiomas respaldada por la ciencia, desarrollada originalmente para la formación de intérpretes profesionales y popularizada por el políglota Dr. Alexander Arguelles. El método es simple pero poderoso: escuchas audio en inglés nativo y lo repites en voz alta de inmediato, como una sombra que sigue al hablante con solo 1-2 segundos de retraso. A diferencia de la escucha pasiva o los ejercicios de gramática, el shadowing obliga a tu cerebro y músculos de la boca a procesar y reproducir simultáneamente patrones de habla reales. Las investigaciones muestran que mejora significativamente la precisión de la pronunciación, la entonación, el ritmo, el habla conectada, la comprensión auditiva y la fluidez al hablar, convirtiéndola en una de las metodologías más efectivas para la preparación del IELTS Speaking y la comunicación en inglés en el mundo real.