Laser pulses could allow more accurate tumor detection in the near future

If you play a guitar string, you will hear a note, whose tone will depend on the string diameter and on the string tension. This sound is not just made of a pure (“single”) vibration, which would sound rather ugly and boring, but rather to the overlap of several acoustic frequencies playing simultaneously, which makes the note “round” and pleasant. More than that: it makes the note unique. You will be able, in fact, to tell it’s a guitar and not a piano, or even which kind of guitar. The very same concept applies to the voice of people: you can easily distinguish two persons pronouncing the same sentence at the phone because they have a different tone. The ensemble of the vibrating frequencies that form the sound and the voice is called the timbre. In physics, we call it spectrum, and it not only applies to sound but also to light, indicating its various frequency components, i.e. its colors!

This is a typical vibrational spectrum of a cell. The various peaks correspond to the notes of the various molecules present and can be used for the precise characterization of the cell content and cell state. Credit: adapted from J. R. Thomas, Annu. Rev. Biophys. Biomol. Struct. 28, 1 (1999), http://dx.doi.org/10.1146/annurev.biophys.28.1.1.

This is a typical vibrational spectrum of a cell. The various peaks correspond to the notes of the various molecules present and can be used for the precise characterization of the cell content and cell state. Credit: adapted from J. R. Thomas, Annu. Rev. Biophys. Biomol. Struct. 28, 1 (1999), http://dx.doi.org/10.1146/annurev.biophys.28.1.1.

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