A quick flip through my students' problem sets tells me more about them than just their ability to do quantum mechanics. My greener students make good use of the reverse side of the mountain of pages their colleagues print out every day. The paper drafts and announcements on the back side often catch my eye and offer a window into a student world I don't often get to see. Of course, recycling sheets for writing is hardly a new phenomenon. Palimpsests are parchment or vellum pages that have been erased by various methods and reused. The earlier, generally chemical, methods of erasure left faint traces of the original writing on the sheets. As methods improved, and relied more on mechanical means, such as sanding with pumice, the erasure became more complete.
In my quantum chemistry class we talked about fluorescence today. A common example of fluorescence is the odd luminescence of white t-shirts under a black light. The black light is a source of UV light, which excites some of the molecules in the detergent residue (yep - that bright white shirt is not quite as clean as you think!). The molecules then re-emit light at a slightly lower energy, which happens to be in the visible, and that we perceive as an eerie glow. The glow is present even in daylight, but the amount of visible radiation emitted through fluorscence is so much smaller than what is in incident sunlight that it swamps out the effect. But it does make your whites look subtly brighter, which is why detergent companies include "brighteners" in their formulations.
So what do white shirts have to do with palimpsests? X-rays are just another form of light (albeit very high energy light) and can cause fluorescence, too. Iron in the ink is the source of the fluorescence. Researchers at Stanford have recently uncovered not only an Archimedes manuscript hidden underneath a 13th century Byzantine prayer book, but also a text by Hyperides, a contemporary of Aristotle. The discovery of this text extends the known works of Hyperides by 20%!
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Field of Science
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The Hayflick Limit: why humans can't live forever1 month ago in Genomics, Medicine, and Pseudoscience
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Course Corrections4 months ago in Angry by Choice
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The Site is Dead, Long Live the Site2 years ago in Catalogue of Organisms
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The Site is Dead, Long Live the Site2 years ago in Variety of Life
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Does mathematics carry human biases?3 years ago in PLEKTIX
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A New Placodont from the Late Triassic of China5 years ago in Chinleana
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Posted: July 22, 2018 at 03:03PM6 years ago in Field Notes
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Bryophyte Herbarium Survey6 years ago in Moss Plants and More
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Harnessing innate immunity to cure HIV8 years ago in Rule of 6ix
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WE MOVED!8 years ago in Games with Words
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post doc job opportunity on ribosome biochemistry!9 years ago in Protein Evolution and Other Musings
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Growing the kidney: re-blogged from Science Bitez9 years ago in The View from a Microbiologist
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Blogging Microbes- Communicating Microbiology to Netizens10 years ago in Memoirs of a Defective Brain
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The Lure of the Obscure? Guest Post by Frank Stahl12 years ago in Sex, Genes & Evolution
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Lab Rat Moving House13 years ago in Life of a Lab Rat
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Goodbye FoS, thanks for all the laughs13 years ago in Disease Prone
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Slideshow of NASA's Stardust-NExT Mission Comet Tempel 1 Flyby13 years ago in The Large Picture Blog
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in The Biology Files
The Who, What, When, Where and Why of Chemistry
Chemistry is not a world unto itself. It is woven firmly into the fabric of the rest of the world, and various fields, from literature to archeology, thread their way through the chemist's text.
A Request to Readers
In March I'm giving a talk at the American Chemical Society National Meeting in Chicago. To prepare for the talk, I'd like to know more about my audience beyond what I can get from technorati and StatCounter. If you're a regular reader, can you tell me what is interesting about this blog? Do you learn anything from it?
Thanks!
Thanks!
Half-awake, half-life
I had a moderate allergic reaction to peanuts last night. I took diphenhydramine (Benadryl) and the hives had subsided by this morning. Lecturing on perturbation theory was more challenging. I felt like I was walking in a fog. Which got me to wondering, just what was the half-life of Benadryl? Benadryl has a relatively long half-life, between 8 and 10 hours. A typical 50 mg dose leads to a peak blood level of around 80 nanograms/ml. Most people feel drowsy at blood levels around 30 nanograms/ml. Assuming first order kinetics apply to the breakdown/elimination of Benadryl, a 30 nanogram/ml is not unlikely 10 to 15 hours later. Which would certainly explain my fogged state this morning! But not so foggy as to be unable to work the kinetics....
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