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.

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The Salmon of Doubt*

Salmon for sale in a Parisian fish marketI 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.

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The Tin Man Lecture

Tin WoodmanIn 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.

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Has modern medicine run out of luck?

This week I have mostly been doing 11 contact hours of teaching plus prep for that, and a little reading of James Le Fanu’s interesting if a bit depressing book The Rise and Fall of Modern MedicineThe 11 contact hours included six on Friday in which rather ridiculously I introduced the beautiful symmetry of the cowpea mosaic virus to two entirely different audiences on the same day — one at 11:00 am and the other at 2:00 pm. I was doing my best at 2pm but it was a long week, so I had probably had a bit more enthusiasm in the morning.

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Six chances to win, yet sadly I still miss out

GFP Superresolution Christoph CremerOver the last two days, six physicists have won Nobel Prizes, but just like last year, and the year before, etc, I missed out. Ah well, it could have been worse, at least actual biologists won the Nobel in Physiology or Medicine. Yesterday, three physicists changed the light bulb, forever, and were awarded the Nobel Prize in Physics. Today, three physicists saw smaller things than they should have been able to, and picked up the Nobel Prize in Chemistry. They won it for developing techniques for imaging with light, objects that are smaller than the wavelength of the light. The effect is illustrated in the figure up top of this post, on the left is a living cell imaged using a conventional microscopy — details are blurred by the size of light photons we are using to image the cell. On the right is the cell imaged using one of the techniques that got the prize. There you can see individual spots in the image, these spots are the locations of individual protein molecules .

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No choice but to be beautiful

CowpeaMosaicVirus3D The beautiful structure to the left is a reconstruction of the protein shell of the cowpea mosaic virus. This is a virus that infects the cowpea, a type of bean cultivated in warmer climes than the UK*. Viruses are the simplest form of life. They simply consist of a protein shell that contains and protects their genetic material, which is inside this shell. This virus’s coat is made of 120 molecules, of just two different types of protein – shown in green and yellow here. Inside are two molecules of RNA that cary the virus’s genes, plus a couple more proteins.

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Ola Brazil! Hello Switzerland!

One of the nice things about WordPress is that it shows the countries people are in when they read this blog. The result for about 7 months of this blog is below. Somewhat to my surprise, Brazil is in 4th place. Hello nice people from Brazil! At the other end of the spectrum, in 7 months only a single post has been viewed from Tunisia. Hope I haven’t offended my one Tunisian reader.

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Giants in Chihuahua

Silicon single crystalWe take crystals for granted, maybe because they are so common. The Earth’s crust is crystalline, as are our cutlery, and even our bones and teeth are partly crystalline. But crystals are remarkable things. Although most crystalline materials are made of many tiny crystals mushed together (our bones are like this), sometimes huge single crystals can grow. There are crystals in the Naica mine in the Chihuahua state* of Mexico that are over 10 cubic metres in volume. This corresponds to maybe 1030 atoms. And in a single crystal, all atoms are on the same crystal lattice, all 1030 of them here. So the relative positions of pairs of atoms in one corner of the crystal are the same as in the opposite corner over 10 metres or more than 10 billion layers of atoms away. That’s a lot of layers, and presumably they grew one at a time. These big crystals may have started growing before the first civilisations arose in what is now Egypt and Iraq, thousands of years ago. The growth of large perfect crystals can be a slow business.

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Frogs and snails, And puppy-dogs’ tails

Raw cane sugar Demerara

According to the nursery rhyme* I was told when I was a child, boys are made from “Frogs and snails, And puppy dog’s tails” while girls are made from “Sugar and spice, And everything nice”. I am rewriting my biological physics lectures to talk a little bit about what we are really made of. This does include sugars, but is mainly water, protein, fats and related molecules, and mineral. We are roughly half water, with the remainder 20% protein, and 10% each of lipids and the mineral in our bones. Lipids are the molecules that make up the membranes in our cells as well as what we call fat. There are smaller amounts of lots of other stuff, like sugars, DNA, etc.

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