How are tears like salad dressing? — What is biophysics? #9

6 thoughts on “How are tears like salad dressing? — What is biophysics? #9”

  1. Very interesting!

    But, how do you get 1nm from those?

    3 [s] * (3n) * (c[m])^3 / (6 (c[m])^2) = 1nc[m] = 0.015nm

    1. Thanks! I thought I checked this, but you’re correct — I’m off by a factor of 100! I have updated the post. I’m not sure what this means for the eyes… I suppose the complete oil layer needn’t be replenished between blinks. In any case, thank you for catching this!

  2. Building on MM’s post and my update: I’ve now gotten the full paper from Cho et al, rather than just the abstract, thanks to Interlibrary Loan. Despite stating a volume secretion rate, the authors don’t actually measure volume — they measure the area of the secreted oil and then *assume* a thickness of 67 nm to calculate a volume! This is puzzling, and I’ll think more about it later…

      1. The “67 nm” is not actually measured in this paper, and it’s given without uncertainties. The authors cite another paper; looking at that one: “In normal subjects, the median (range) LLT was 67 (33–100) nm,” so the range is quite large! Returning to the Cho et al. paper, there are aspects of the “3 pL/s” that are puzzling; at this rate and 67 nm thickness, it would take many hours for the film to cover the eyes. I’ve written to the authors for clarification. The saga continues…

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