July 24, 2008 at 8:21 am | | science and the public

In a recent “Policy Forum” article in Science, a business professor from Duke argued that we should start reporting gallons per mile instead of MPG. The reason is that fuel used is a linear function of GPM, but an inverse function of MPG. Since humans think best in linear relationships, GPM is the most straight-forward measure to report fuel efficiency.

The real problem with MPG is that the same change in the MPG correspond to a huge change in fuel used at the low MPG end, and almost no change if a car already has a high MPG rating. Going from 20-25 MPG saves more gas that going from 35-50 MPG; going from 12-14 MPG saves more than either. This isn’t intuitive, and you really need to calculate the savings per mile in order to make a rational decision.

The take-away message is that we can’t do calculations like (1/a – 1/b) in our heads.


July 17, 2008 at 2:38 pm | | grad life, great finds

The undergrads in my lab introduced me to a new phenomena called “rickrolling.”  Follow the link to the wikipedia explanation – weird stuff.  Source

the south is strange

July 9, 2008 at 8:44 am | | great finds

…Evidenced by this currency I received as change in Columbia, SC:

I was forced to spend it when I ran out of cash. Unfortunately, I handed it to a Black cashier in Chicago; I hope she didn’t notice.

I actually really like the South: I spent a few years in Chapel Hill, NC, and enjoyed it. Racism and anti-intellectualism is sickening, though.


July 3, 2008 at 12:52 pm | | everyday science, great finds, science@home, tutorial

I’m on vacation with my financier fiancée for a week in South Carolina: a few days at our friends’ wedding, a few days at Hilton Head, and a few days with my soon-to-be in-laws. The weather has been beautiful: heat and humidity reminding of my UNC days. The shark that swam past me gave me the creeps, but otherwise Hilton Head was perfect.

One strange event: a friend got a sunburn and a strange rash. The dermatologist asked if she had been making Mojitos or drinking Coronas. Huh? Diagnosis: Phytophotodermatitis. This is really cool: limes (and various other plants) contain furocoumarins (particularly psoralen, structure below), coumarin-type chromophores that absorb strongly in the UV.

Psoralens act as photosensitizers: absorbing UV light and releasing reactive triplets or radicals. With fluorescence quantum yields only around 1-2%, psoralens transition to the triplet state (via El-Sayed’s rule, I expect, from the Jablonski diagram below) and phosphoresce strongly. Chromophores stuck in their triplet state can return to the singlet ground state by coupling with triplet O2, producing a highly reactive singlet O2 species. This may be one mechanism of the photosensitizing properties of psoralens. Alternatively, a psoralen molecule in its triplet state can react directly with DNA or other biomolecules with electron-donating capability. Various other photosensitizing reactions are discussed in an interesting review (Kitamura, N.; Kohtani, S.; Nakagaki, R. J. Photochem. Photobiol. C 2005, 6, 168-185).

So, basically, my friend was spraying tan accelerator on her skin, then sitting in the sun for hours! That equals strangely shaped splotches of sunburn. In fact, psoralens have been used in photochemotherapy (also called PUVA) for certain skin ailments, such as eczema and psoriasis. So be careful squeezing limes on the beach, or picking parsnips or playing with celery in the sun.

Check out some doctory stories in this article: Weber, I. C.; Davis, C. P.; Greeson, D. M. J. Emer. Med. 1999, 17, 235-237.

Powered by WordPress, Theme Based on "Pool" by Borja Fernandez
Entries and comments feeds. Valid XHTML and CSS.