Assistant Professor of Chemistry
Mailing Address:
Department of Chemistry and Mathematics
10501 FGCU Blvd South
Fort Myers, FL 33967
Office: Whitaker 210
Email: kdaviesBLARG@fgcu.edu (remove THIS part from address - my spam filter...)
Phone: 239-590-1459 Fax: 239-590-7200
Jump to: Key Research Interests - Chemical Imaging
Key Research Interests - Landmine Degredation
Teaching
Analyzing plastics taken from
a landmine while in Cambodia
- Photoacoustic Imaging Agents and Chemical Reporters
Peeking into our body is like looking into a fogbank - light is scattered around, making it difficult to see fine features inside. In addition, most tissue looks pretty similar to most imaging technologies, making it difficult to identify things like tumors, blood vessels, etc., depenging on the technique being used. - Photoacoustic imaging can overcome many of these issues, but is a 'new' technology, and needs a toolkit of molecules to allow us to see specific internal features, and make chemical measurements without 'poking' the body.
- The photoacoustic effect, "Photo-" part:
If you leave a containter with a dark lid on a picnic table, the lid bulges out - because the lid turned the light into heat, and the contents expanded when they got hotter. A dark lid absorbs more light - if we make it a color that doesn't absorb, we 'turn off' the effect. - ...the "-acoustic" part:
In the lab, we use very short (picosecond) pulses of light; instead of slowly bubbling the lid like in the previous example, it happens suddenly, like in a firecracker - the sudden heat-expansion makes a pressure wave (i.e. a sound). If we have a bunch of microphones spaced out in a line, we can tell where the sound came from based on how long it took the sound to get to the microphone. - We are identifying molecules that will be useful for this aparoach - they have these general requirements:
- High molar absorptivity (i.e. they must be 'darkly stained'
- They should be non-fluorescent, or not very fluorescent (and energy given off as light is NOT given as heat, and gives weaker signals)
- They should not break down when hit with light (best case, we've burned out our signal; worst case, we made a new compound that causes damage of its own!)
- The heat-deposition processes should happen much faster than the resolution of the microphone, or the molecule may appear deeper in the skin than it actually is.
- These molecules should also allow us to rapidly make measurements in any other 'foggy-looking' sample (e.g. river water), allowing rapid measurements in these samples without filtering, etc.
- Landmine Components, and how the Environment Breaks Them Down
- Our report can be read at: http://maic.jmu.edu/aging/aging_intro.html
- Very briefly, landmines are commonly made from some combination of plastics and metals (occasionally, even wood casings.) Different components interact with their enviornments at different rates, leading to the eventual breakdown of the landmine. From our perspective, this breakdown is desirable: mines developed since the 1970's are largely low-metal mines that are challenging to detect, and require labor-intensive (and dangerous) manual clearance methods. Moneies for these activities are in short supply vs. the number of emplaces mines that need to be cleared. If we can better understand how landmines interact with their environments (rubbers embrittled by wildfires, calcium in groundwater leaving hard-water deposits between springs and firing pins, rusting, etc.) we can better allocate clearance efforts by focusing on the 'more live' fields (though of course, a 40% live field with heavy traffic will be a higher priority than even a 100%live field in the middle of nowhere!)
- Our team has been successful in identifying the materials in these mines (they don't exactly come with detailed parts lists w/ suppliers!), and highlighting some interesting and unexpected results of these interactions. For example, it is commonly assumed that an agin mine become less dangerous with time - but we have found that for a time, mines often are more dangerous; e.g. the spring holding up the pressue plate has rusted and weakened, requiring less pressure to trigger the mine, and making it more likely that stepping near the mine might be enough to detonate it!
A new and pristine PMN-2, the same mine seen aged to the right.
- Aging dramatically changes the appearance of mines; however, most Mine Risk Education efforts have pictures of the new-and-pristine mine. Our landmine photos taken during this research should also act as a valuable resource for teaching civilians what the mine looks like NOW.
Minefield, right next to a foot road, and 20 meters from the landmine training facility where we disassembled the mines.
Spring-loaded strikers; these have their springs compressed, until the pressure plate is pushed diwn. Then, the striker can spring forward and hit the detonator. On the left are examples that remain in good shape; moving rightward, the springs have rusted through or become 'glued' to the striker my mineral deposits.
Wildfires have burned off the rubber cover on this mine. This allowed roots to grow beneath the pressure plate. Dirt also was deposited by the groundwater into the triggering system, 'gumming' it up. Though the detonator and explosive charge were still live, this mine was inactivated by degredation over time.
Top-view of the interior of the mine shown above. The striker and spring were in the up/down chamber, and the detonator/spring assembly were in the left-right chamber. The striker had expanded into the pressure plate trigger (center) so much that it had to be hammered out - and could not have fired the mine. Also note that the explosive (yellow, waxy compound) is in good condition.