Bainite Interviews

I have a new job in my research group now, I get to interview people when they publish a paper, and the interview will go online with the paper on the group website. I think this was partially my idea when podcasting first became hot, but I’m not sure I imagined my supervisor would be using me to do the interviews. Anyway I hope people like it.

Interviews

1. Cracking of Bainite paper by Chatterjee and Bhadeshia. Interview with Sourabh Chatterjee.
2. Stabilisation of austenite by Chatterjee, Wang, Yang and Bhadeshia. Interview with Sourabh Chatterjee.
3. Roughness of Bainite paper by Kang and Bhadeshia. Interview with Harry Bhadeshia.

How do trees raise water?

Capillarity can raise liquid against gravity, I was interested to know how much this can account for the movement of water in trees, is capillarity alone enough to lift water up a tree trunk?

For water in a tube there is an equation like this;

h = 2T cos (theta) / pgr
where; T = 0.0728 J/m^2 at 20 degrees C, the contact angle theta = 20 degrees, density of water, p = 1000 kg/m^3, and the local acceleration due to gravity can usually be taken to be 9.8 m/s^2.


So the height is given by;

h = 1.4x10^{-5) / r


So tubes of the following diameters can lift water to the following heights.

Diameter (mm)	Height (m)
1	0.014
0.1	0.14
0.01	1.4
0.001	14
0.0001	140

If we assume perfect contact these heights become only slightly larger. (cos(theta)=1)
1 micrometre diameter tube can lift water 14.85 m, it’s necessary to have a tube 0.1 micrometres or 100 nanometers to lift water a height of 148 meters by capillary action alone, if the above equations are valid. Looking around on the internet gave a size of xylem in a tree to be around 20-30 micrometres (0.02 – 0.03 mm) in size, which if true enough to lift water around half a meter. It would be interesting to see if this value is correct.

If you are interested to find more there is a 2004 nature article on the limits of tree height here.