Over the summer I am thinking a bit about how proteins and other stuff move around inside our cells, and those of other living organisms. I am trying to do this quantitatively, and so I need numbers for various aspects of living cells and of organisms. So I was delighted to find that there is an entire searchable website just for numbers related to living organisms, called, sensibly enough, BioNumbers, plus a related book: Cell Biology by the Numbers, by Ron Milo and Rob Phillips. Both websites are a mine of useful information. For example, one entry is the total length of fibres of the protein collagen in our bodies. The total length is about 100 billion kilometres, or to put in another way, in each of our bodies there is enough collagen to go from the Earth to the Sun 10,000 times.
Last year, Chrétien et al. published a paper in PLOS Biology on mitochondria. Two mitochondria are shown above, they are structures inside our cells where a key part of our energy metabolism take place. I don’t want to be harsh, but the central claim of their work is clearly wrong. This claim is that the mitochondria inside cells are at a temperature of around 50 C, more than 10 C higher than the rest of the cell which is about 37 C. This really cannot be right, the mitochondria inside your body are at the same 37 C that the rest of you is, and with a little physics it is easy to see why.
In an earlier blog post, I noted that by one metric for the impact of my published work I lose out to F.D.C. Willard, who was a cat. In a similar vein, above I have plotted the number of citations to my most highly cited paper of the last few years, Dynamic Stratification in Drying Films of Colloidal Mixtures by Fortini et al., together with the number of citations of a 1970 paper by Laemmli. In Laemmli’s paper, he pioneered a technique called SDS PAGE. Note that the column with our paper appears blank, this is because on the scale of the plot, the bar for our paper is less than one pixel high. At the bottom I have replotted this bar graph on a logscale, where you can see the number of citations of our work. Continue reading
We have all added salt or sugar to water and seen it dissolve. Both salt and sugar dissolve rapidly, but exactly how fast do they dissolve? This is one of those seemingly innocent questions, that is a lot harder to answer than you might expect, or hope. For something highly soluble like salt we expect the sodium and chloride ions at the surface of the dissolving salt crystal, to very rapidly move into solution in the surrounding water. But if the water is stationary, not stirred, then near the surface of the salt crystal, we quickly reach the point where the water is saturated with salt, and no more can dissolve, until the sodium and chloride ions move away.
There is a pretty big push at the University of Surrey to record lectures, so students can view them at another time. I think recording lectures is popular among many students, and I plan to do it for one of my courses next year. But another question is: Does it help students learn more? A recent study by Edwards and Clinton suggests that it does not.
The Department of Education and the Institute for Fiscal Studies have a report out on graduate earnings. The plot for average graduate earnings for women, 5 years after graduation is above (it is Figure 9 of the report, the plot for men is similar). Graduate earnings vary widely by course and by institution — the two are strongly correlated of course, the degrees the London School of Economics (LSE) offers are very different from those offered by the Royal College of Music (shown as ‘RC Music’ above).
Rheology is essentially the study of how things flow, and in practice it is mainly the study of things that have complex flow behaviour, things that are between solid and liquids. A classic example is toothpaste. In the tube it is more or less a solid, but a firm squeeze turns it into a liquid that flows out onto your toothbrush.
I am at a conference in Sorrento, Italy. My hotel room is described as having a ‘hill view’, and as you can see from this picture taken from my hotel room, the description is accurate. That is a genuine Italian hill. In Sorrento, I will be talking about my work on paint drying, but I have a bit of time before the conference sessions start. So, I am also working on a course I am teaching next month for the EU network on RAtionalising Membrane Protein crystallisation (RAMP).
Few things are more boring and take less thought than putting a load of washing in the washing machine, but there is a lot of physics and chemistry going on inside washing machines. The basic idea is remove stains and dirt particles from your clothes, and to then carry them away down the drain. To do this washing powders and pods contain surfactants (soaps) to help detach stains and dirt from clothes, but then these molecules and particles must be removed from the clothes, and washed away.