Sunday, February 8, 2009

Monarch Butterfly Egg

Some science images are easy, and some are very complex. This is a scanning electron microscope image of a Monarch Butterfly egg case is a very difficult picture. Just the sample preparation of this image took over a week. For years I have collected butterfly eggs, usually for my young kids. We will have a bottle with several eggs that hatch into microscopic worms that feed on milkweed leaves. In this case my kids and I went for several hikes in the finger lakes region of New York. After a few hours of looking on every milkweed plant we saw, we were able to find three eggs. The eggs were placed in a dilute solution of alcohol and the alcohol solution was slowly increased in strength until it was at 100% - a week later. The egg is then placed in a high pressure solution of carbon dioxide gas to remove all the water. This process is called critical point drying. The egg was then coated with a conductive layer of gold in a sputter coater. At this point the egg is ready for the scanning electron microscope (SEM). Since the microscope only collects a black and white image, the image needs to be colorized using Photo shop. The coloration process itself can be very complex. For this egg image I used two different images – one image contained the red part of the image, while the send image contained the blue data.

Popping a balloon

This is one of my favorite images and like most science images it has a story behind it. This image was taken during an assignment for a British science magazine. The magazine requested a young girl popping a balloon and needed to show the human reflex of closing your eyes near a loud noise. I used my then 7 year old daughter for the shoot. After it was over my assistant Roger was playing around with over-inflating a balloon until it burst. This does take a good set of lungs. After a few test shots we were able to get this shot. Balloons do not always burst like this, but this one in particular turned out nice. The balloon had a teaspoon of water placed inside of it. The water is in the gas phase when the balloon is inflated, but when the balloon pops, there is a sudden drop in pressure that creates a cloud. The resulting cloud lasts less than 1/1,000th of a second. The action was captured by a high speed flash that had a duration of 1/20,000th of a second. Many interesting science photos are taken by messing around in the high speed photo

A drip of water.

This is a relatively simple image of a drop of water. The images from a simple drop are dependent on the speed of the drop in this case the height it falls from, the viscosity or the fluid, and the depth of water the droplet falls into. The time the image is taken after the collision with the surface will also greatly influence the image. If the high speed flash it triggered too soon, the droplet is still in mid-air. Too late, and the collision is over. The set up involves placing a pipette about two feet above a shallow pan of water, as the drip falls though an infrared light beam, a microprocessor starts counting time. After a specified time a high speed flash is triggered. This image represents a slice of time of 1/20,000th of a second. This is often called freezing time, this image looks like frozen water.
The simple collision of a drip of water and a surface is actually quite complicated. The physics of this situation influences everything from an ink jet printer to an industrial water cutting jet. The fluid dynamics has fascinated many scientists over the years, but Dr. A.M. Worthington was so taken by the process that he wrote two books on the topic in 1908. These books were compiled from his earlier lectures and greatly influenced the use of high speed photography. In the coming weeks I will write more about high speed photography.

Sunday, February 1, 2009

Love is in the Water

Reproduction is one of the driving biological forces and often commands readers attention. This photo shoot was done under difficult conditions. Toads are one of the first amphibians to mate in our northern climates and often beat out other species by a month. Here in New York these toads will only mate for two days in the ice cold waters in the early days of April. The mating starts at dusk and is most active if there has been rain. So there you have all the conditions that make up an enjoyable photo shoot – 40 degree weather, light rain, dark, and I am wearing a wet suit and in water knee deep. On this photo shoot I also had an assistant holding a remote flash as I used the underwater camera. The goal was to get a solitary male with a huge inflated air sack as the male calls to the females. The males call in the females, as well a jockey for prime territory. The females will answer with a deeper sound, and I am sure there are frequencies involved below the human hearing range. The males will often mount another male, but with out the correct sounds will quickly identify that something is wrong and go back to calling. Once the male finds a female and is accepted he will hold on until the female lays the eggs and external fertilization takes place. After three nights the mating was over and I still did not get the shot I was seeking – I will return this spring.

This image shows the male firmly positioned, awaiting the egg laying . The male is on top while the female is on the bottom. The female is larger than the male due to she has to carry a large percentage of her mass in eggs. On a rainy night in the summer you can collect toads hopping on the roads. If you take the weight of each of the toads you find and make a bar graph of number of frogs vs their weight - you will see the data points are bunched together. Such a graph will show the average weight a toad gains each year – thus you can determine the age of a toad that you find. The oldest toad I have found was six years old, although I suspect there are older ones. The especially large toads I run across I call toadzilla.