Over Christmas, as is traditional, I have been eating and drinking a lot. The drinks include beer, wine, dessert wine, liqueurs, etc, but no ouzo, pastis or sambuca. Ouzo, pastis and sambuca all have the distinctive flavour of aniseeed. While Googling something for a paper I am drafting I came across the explanation for why these drinks become cloudy when you add water. Ouzo for example is quite strong, about 40%, and so it is often diluted with water, but as soon as the water is added, the ouzo goes from clear to cloudy.
Titan, the one place in the Solar System where the Titanic could have cruised with impunity
Pretty much everywhere on Earth where there is liquid water there is life. The biochemistry that powers our cells only runs in liquid water. In the Universe liquids are rare, like Little Red Riding Hood liquids are very particular, requiring conditions that are neither too hot nor too cold. Much of the Universe is near 0 K (-273 C), which is way too cold, or inside in stars at thousands of degrees, which is way too hot. Saturn’s moon Titan is at a refreshing – 180 C, which is too cold for liquid water, but methane is liquid at this temperature. The image to the left is of the surface of Titan and the dark regions are huge lakes of liquid methane and ethane.
Taller by degrees
The plot to the left shows the distribution of heights of American women, ages 20 to 29, according to the 2007/2008 census. Data here. I couldn’t find data on UK heights, but it should be similar. Data for the heights of men are similar but shifted up a bit. The circles are the data and the line is fit of a Gaussian function to this data. The most probable heights are around 165 to 170 cm (5 ft 4 in to 5 ft 6 in). The width (standard deviation) of the Gaussian fit is 7 cm.
Shapeshifting to survive
All organisms, from us to bacteria, need to adapt to survive. As I start to write this post, I have just had lunch and so I guess my blood sugar is probably peaking nicely. Some of this sugar will need to stored for later consumption, and doing this will involve flipping switches in my biochemistry to go from my pre-lunch state of burning food reserves to storing excess calories from my lunch.
In a dog-eat-dog competitive world, I lose to a Siamese cat
In a post on Surrey’s blog I boasted that I was twice as good as a hamster, according to one common metric for measuring the achievements of an academic scientist. However, I am sadly not superior to all furry mammals, a cat beats me, by that same metric. I average out at about 28 citations per paper I have published. F.D.C Willard*, who was a cat, averages out at 34.
Blondes and the KITLG gene
This Friday I am teaching an introductory lecture on genetic switches, so I had a look around on the web for topical examples. My favourite is recent work by Guenther, Kingsley and others in Stanford on work on the genetics of blond hair. Of course we know what blond hair must be determined by our genes, blond parents tend to have blond children. But we are still working out what are the genes involved. Amongst our twenty-odd thousand genes is KITLG, which like a a lot of our genes is involved in a lot of different things, including how our bodies make blood, and whether we have blond hair.
Almost enough to make me take up smoking
In the biological physics course I am teaching, I talked a lot about the fact that on lengths greater than around a tenth of millimetre, diffusion of molecules is too slow to supply the needs of living organisms. To get round this they had to evolve pumps, propellers and cargo transport infrastructures. The time to diffuse a distances increases as the square of the distance travelled and so diffusion is slow on all lengths large enough to be visible to the human eye.
Where does a flock of starlings end and the sky begin?
This shows a flock, also called a murmuration, of starlings at sunset. The hundreds or thousands of starlings are moving almost as if they are a single body, and mostly there is a pretty clear edge to the flock. It is pretty obvious where the flock ends and the rest of the sky begins. As the flock is a three-dimensional object, this should mean that the flock has a well defined surface, which separates the volume of sky occupied by the starling flock, from the surrounding sky where there are no starlings.
The Salmon of Doubt*
I don’t think I am particularly good at reading social situations, but I get by. But I would guess that I am better at reading social situations than a dead salmon. A few years ago, Bennett and coworkers used the latest hi-tech method to study brain activity, functional magnetic resonance imaging (fMRI), to study the brain of dead salmon. While they were using the brain imaging technique on the brain of the deceased salmon, they showed it pictures of groups of people in different social situations.
The Tin Man Lecture
In The Wizard of Oz, the Tin Man is seeking a heart. Lacking a heart is taken to mean that you cannot love. This is poor science of course, our emotions are felt by our brain, and our heart is a pump. Without a heart, our blood would not be pumped around our body, our tissues would be starved of oxygen and food, and we would rapidly die.
In Friday’s lecture on biological physics I covered why we and all animals bigger than roughly a few millimetres need hearts, why we need pumps to pump fluid round our bodies. The reason is some simple physics: We need pumps as without the flow pumps produce, molecules such as oxygen would only diffuse around our bodies. I am about 1.85 m tall. Diffusion is agonisingly slow over distances like that. Oxygen takes decades to diffuse over a metre. This is far far too slow to support life. Hence the need for a pump.
Chance & Necessity 