Monthly Archives: July 2011

The thermogenesis of a moth

Is a moth warm-blooded or cold-blooded? If you google this, some would tell you it is cold-blooded. They are not completely right. This infrared study shows how a moth warms up before it flies. So at least a moth is warm-blooded when it moves.

Click to view a larger image

The moth (see the close-up photo above--what species is it?) was kept in a jar. The first IR image shows that when it was idle (sleeping?), its body temperature agreed with the ambient temperature. This means that it does not lose heat to the environment--a clever way for saving energy.
However, before making a move, it needs to heat up its flight muscles (near its head where the wings are attached) to above 30 degrees Celsius. In this observation, the warming process took 1-2 minutes for the moth in our experiment, as is shown by the sequence of the IR images. (Note: You may only observe this effect when the moth is energetic. A moth on the verge of death does not have enough energy to warm up.)

Note that we used the automatic color remapping, i.e., the heat map is rescaled based on the lowest and highest temperatures detected in the view. As a result, while the moth warmed up and appeared redder in the IR view, the background--in contrast--became bluer in the IR view. This, however, does not mean that the temperature of the background has decreased. The automatic remapping could create some confusion, but it is necessary in many cases, especially when you don't know what to expect. It maximizes the difference by increasing the contrast and, therefore, allows the observer to pick up small changes.

The last image shows that the temperature was ready and the moth started to move. In this particular experiment, the moth responded slowly because it could have been exhausted as it had struggled quite a bit before it was imaged.


Design your own house with Energy3D

Energy3D is a free, open-source tool we are developing from scratch to empower students to design, make, and test energy-efficient model houses.

Today we had some students design and make their own houses. One student succeeded in designing a model house after her own real house. The first two screenshots show her model under the sun in different months.

Like many architecture design tools, students can "walk" into their own design and imagine "living in the house" virtually. The other two screenshots show two close-ups: one from the outside and the other from the inside. The fifth image is a physical house made of foam board and assembled, based on this design.

If they are satisfied with their designs, students can "print" out their houses, cut out all the pieces, and assemble them.

We feel that computer-aided design tools such as Energy3D would be a big help to students when they are undertaking complicated engineering design challenges such as making a house. 3D reasoning is usually difficult for most students. A What-You-See-Is-What-You-Get (WYSIWYG) CAD tool can help them think through.

You may be wondering why we want to develop this tool. Many students complain that their science and engineering projects in schools are not challenging enough to be interesting. Many teachers do strive to make their student projects more attractive. However, they lack appropriate educational tools to do so. Energy3D is an attempt to provide teachers and students with cutting-edge tools that can teach and learn modern full-cycle engineering processes--from design to manufacturing to test-- through an interesting project about energy-efficient houses. We hope this tool would intrigue, inspire, and prepare students for STEM careers.

PS on 7/28: This is another building designed by the same student, which shows an intersecting roof. These examples show that Energy3D could be used to design quite a variety of architecture. It turns out that roof is the most difficult part to design using tools such as Google's SketchUp. We are trying to simplify that part by figuring out algorithms that would enable easy editing of roofs. Our work focuses on two directions. First, an algorithm is needed to automatically generate a roof of a given type based on the boundary walls the user has laid. Second, the topological transformations between different types of roofs need to be identified so that we can build the user interface for adjusting the roof easily.

An infrared view of bees

A bumble bee.
I have been wanting to see what I can do with IR imaging in my backyard. Folks at the Discovery and Animal Planet channels use IR imaging regularly to show thermal patterns of animals and plants. So I guess I could do something with it. I cannot afford a high-definition IR camera. But I think my low-grade IR camera should be able to catch something. Here is an interesting story about bees.

Bees are warm-blooded insects. In order to fly, bees must heat up their flight muscles to above 30oC. So let's check this using an IR camera.

Indeed, a bee looks warm through the IR camera. To be more specific, the thorax of a bee appears to be warmer than the rest of its body (see the IR image to the right). I observed both a honey bee and a bumble bee. Both types have a warmer thorax, where the flight muscles are located. Exactly why the muscles can operate only at a warm temperature is an interesting question.

Bees are known to form societies that depend on successful division of work. Researchers have been using high-definition IR imaging to study bee behavior. With the assistance of IR imaging, German researchers led by Prof. Dr. Jürgen Tautz at Würzburg University found a new type of role known as the heater bees. The heater bees are responsible for maintaining the temperature in the hive where young bees (pupae) grow in sealed wax cells. The bees purposely leave some empty cells among those pupa cells so that the heater bees can crawl into them to warm up the pupae. By varying the temperature of each pupa they can determine what kind of bee it will become. As a result, the heater bees are vital in determining what job a young bee will perform once it matures. In the IR video, heater bees' thoraxes also appeared to be warmer, agreeing with what I observed using my IR camera for a worker bee.

Another article published in Optics Express discussed using IR imaging to evaluate beehive population. The idea is based on the assumption that the more bees in a hive, the warmer it would be. An unhealthy colony that has lost population would appear colder in the IR view, as the number of heater bees might have died down because of the lack of worker bees and hence the food they bring back. And if there are not enough heater bees, the pupae would not grow up normally, worsening the situation.

If you don't want to disturb bees and get stung by them, the non-touch, non-invasive IR imaging is probably the best way to go. :-)

PS on 8/3/2011:

Other flying insects like flies, dragonflies, cicadas, and wasps have a similar thermogram (i.e., warm thorax while active). See these two additional images. Or see this blog post about a moth.

I didn't observe warming in ants. They probably don't produce heat. Or they could be just too small to emit any appreciable IR radiation.

Theo Jansen’s mechanism

Go to the simulation


Water permeation across paper and colors under the sun

Yesterday I reported evidence of tiny water permeation across a piece of paper on top of a cup of water. In order to double-check my theory, I placed a piece of transparency film on top of another cup of water and left the two cups overnight. When I came back this morning, I removed the paper and the film from the two cups and viewed the IR image of the two cups of water. To the right is the image I saw.

The cup of water that had paper atop was cooler (the dark circle on the right) than the cup of water that had transparency film atop (the light gray circle on the left). This means evaporation was stopped by the film but not the paper. The only explanation of this effect is that water can permeate through the paper but not the film.

Last October, I blogged about visualizing different colors' ability to absorb light. In that experiment, I used a table lamp as the light source. Later, I realized a flaw in that experiment because a table lamp is, after all, a point source. For the color bars to have equal illumination, we need a light source that is far far way. The sun is such a light source. So I brought the color plate outside and put it under the sun. You can now have a better idea of which color is more capable of absorbing heat. No doubt black won. To my surprise, purple and yellow have approximately the same light absorptivity. So do blue and green. Red, on the other hand, absorbed about the same amount of light as light gray. The background is white. It absorbed the least amount of light energy and appeared to be bluest in the IR image. Amazingly, paper doesn't conduct heat well, otherwise the color bars in the IR image would not have been so well separated.

Seeing permeation of water molecules

I have blogged about some intriguing IR images when a piece of paper is placed on top of a cup of water. The part of paper above the water warms up (Figure 1) because of the release of latent heat of condensation of water vapor to its underside. If you want to reproduce this effect, note that the shallow the cup, the more pronounced the effect (I used a lid and turned it over to use as a shallow cup). In these IR images, I chose the gray coloring mode. So white represents the hottest and black the coldest.
The warming stops after a minute because the condensate layer reaches the maximal thickness due to the dynamic equilibrium of condensation and evaporation. So we see there is no difference of temperature across the paper any more (see Figure 2). (Well, except for the ring area that touches the edge of the cup, in which it gets the temperature of the cup.)

If we leave the paper for a couple more minutes, the part of paper actually becomes cooler (Figure 3). So what is going on?

My theory is that water molecules have percolated through the paper, which is porous (having a lot of small holes), to the other side and evaporate from there. So we are seeing the evaporative cooling effect from the above side of the paper. Figure 4 presents evidence that supports this theory. If we shift the paper a little bit, we will see three zones with three different temperatures. The coolest zone shows the effect of evaporative cooling from both sides. The overlap zone shows the effect of evaporative cooling from only the above side. And the warmest zone shows the effect of condensation heating from the underside. (Is this pattern beautiful?!)

Figure 5 shows the comparison between direct evaporation (the dark area on the left) and permeation-then-evaporation (the less dark area on the right). The result indicates that the paper did impede evaporation, even though its micro pores allow water to percolate through.

This follow-up study shows that even a humble experiment like placing a piece of paper atop water has many surprises that reveal the richness of science, which all become transparent under an IR camera. I will blog more surprises derived from this experiment later.

Why Aren’t There Probes in More Classrooms?














