UV Florescence

 iNat has a great project dedicated to UV florescence.  

Fluorescence generally means you’re absorbing one wavelength and emitting another. most UV flashlights emit light that is mostly invisible to humans, except for maybe a little that folks would describe as purple or pale blue.

So if you shine a UV light on something and see other colors emerge, you’ve almost certainly got fluorescence. but if you see the same purple or pale blue that your flashlight emits, then it’s possible that’s just reflection.

From left to right: visible light, UVIVF, and UV reflected light.  From: https://www.wildflower.org/magazine/native-plants/a-different-light

This article with beautiful UV and visible light photos helped me understand the difference between UV reflective and UV-induced fluorescence (UVIVF) images. However, I think many people, including the author of that article, are still confused about the biological meaning of UVIVF. For example, the False Gromwell writeup implies that insects can see UVIVF to help find flowers that are otherwise inconspicuous.

But UVIVF is never normally visible…except maybe as an added glow. The best example is laundry detergent that makes whites brighter. By adding a UVIVF chemical to the detergent, clothes actually slightly glow in any UV light, making them appear brighter.  

Meme by apermar.  Veritaseum explains more on Youtube.

Photographs of UVIVF in darkness show the extra brightness we see in sunlight, but usually don’t notice.  However, UVIVF may be biologically important to some animals, such as scorpions, frogs, and flying squirrels.  Taboada et al. (2017) documented biofluorescence in response to UV light can contribute between 18 and 29% of the total light emitted from some species of tree frogs under natural, dimly lit conditions.  

Flying squirrels fluorescence is hypothesized to aid in camouflage against a backdrop of lichens emitting similar fluorescent spectra, or potentially in Batesian mimicry of co-occurring predatory owls with similar biofluorescent profiles.

Biofluorescence could be a useful tool to document amphibians where the small, cryptically colored, and/or nocturnally active species can be hard to locate among leaf litter or dense vegetation. 

The study of UV florescence is relatively new, with new discoveries being made every year.  For example, 2017 was the first documentation (published paper) of an amphibian with natural fluorescence. A 2020 paper then found fluorescence widespread among amphibians.  iNat users had documented fluorescent amphibian from frogs starting in 2018 and salamanders in 2021.

A photo I took with a 390-405 nm (just barely UV) blacklight.  Most UV photographers use a 365nm (UV-A) flashlight, sometimes with extra filters to block all of the blue and violet light. 

More discussion of florescence can be found on the iNat forum.  

Taboada, Carlos; Brunetti, Andrés E.; Pedron, Federico N.; Neto, Fausto Carnevale; Estrin, Darío A.; Bari, Sara E.; Chemes, Lucía B.; Lopes, Norberto Peporine; Lagorio, María G.; Faivovich, Julián (2017-03-13). "Naturally occurring fluorescence in frogs". Proceedings of the National Academy of Sciences. 114 (14)

Lamb, J.Y.; M.P. Davis (2020). "Salamanders and other amphibians are aglow with biofluorescence". Scientific Reports. 10 (1): 2821.

Dendritic Stream Branching in the Piedmont and Triassic Basic

Who can spot Chapel Hill??

February Blocking Pattern

This computer model (GFS) of near-surface temperature (actually, just above the boundary layer) and atmospheric pressure shows an interesting pattern of high and low pressure areas.  A high pressure region over the Azores is predicted to hold steady for the next several weeks, in effect blocking the normal flow of the jet stream and Eastward-migrating low pressure regions.  These lows are forced to travel (clockwise) all the way around the high pressure region.  The consequence appears to be a trough in the jet stream over Eastern  North America, leading to large incursions of Arctic air, and very, very cold temperatures (see graph).

Idaho Fires at night

For more night satellite imagery.

3D Protein Structures!

http://www.rcsb.org/pdb/home/home.do

Environmental Degradation in Haiti

Google maps has high-quality satellite imagery of Haiti, and reading remote-sensing images is a big part of my job as an ecologist so I decided to take a brief fly-over to see what it looks like. What immediately called out to me was the widespread and obvious degradation of the rivers and streams; the images of Haiti are consistent with a highly disturbed landscape. Most unconfined rivers in Haiti appear braided, meandering over large areas of bare ground.

These rivers are rapidly aggrading (depositing sediment), most likely due to excess sediment from erosion in the uplands. Of course, natural disturbances such as hurricanes, forest fires, and perhaps even earthquakes, could cause similar river channel adjustments. Braided channels may be a natural response to naturally high-erosional areas. Here is such a stream in Southern California:

If Haiti had a Californian/Mediterranean climate instead of a Carribean climate, these levels of disturbance could be explained naturally. Instead, these high-disturbance, silt-choked rivers and streams are likely better explained by human overuse and consequent environmental degradation: "Haiti...was largely self-sufficient in grain 40 years ago. In the years since, though, it has lost nearly all its forests and much of its topsoil, forcing the country to import more than half of its grain." Brown, Lester R. "Could food shortages bring down civilization?" Scientific American. May 2009. p. 50




Closeup view of wide, unvegetated floodplain in Haiti:

Of course, Haiti is not the only place with altered erosion visible from space. In fact, the images above are becoming the norm across much of the world. Even richer countries have impacted rivers, but some, such as Costa Rica, also have many rivers that are allowed to remain in their unimpacted, natural state. This is what tropical rivers should look like when they have a natural disturbance regime:

More Science Books

Nutrition and Physical Degeneration by Dr. Weston Price

Cells Gels and Engines of Life by Gerald H Pollack

7 Clues to the Origins of Life

Structure of Evolutionary Theory by SJ Gould

Maxwell's Demon: entropy, information, computing / compiled by Harvey S. Leff and Andrew F. Rex

An Album of Fluid Motion by Milton Van Dyke

Atlas of Optical Phenomena