Above are crystals in a cave in the Mexican state of Chihuahua. They are huge, note that the person in the picture shows the scale. The crystals are up to 10 m long, have masses of tens of tons, and are made of gypsum, a form of calcium sulphate. It is estimated that they took hundreds of thousands of years to grow. So around about the time our ancestors were wandering around Africa, a tiny nucleus formed, and started to grow. Hundreds of thousands of years later, we have these enormous crystals.
Author Archives: Richard Sear
Computational physicist at the University of Surrey. My research interests are in COVID-19 transmission, especially masks, soft matter & biological physics
Evolution in action
Seeing is believing, so it is good to see evolution in action. The above movie shows a huge petri dish with bacteria starting at both edges where there is no antibiotic. The dish has a gradient of increasing concentration of this antibiotic towards the centre of the plate. Initially they can’t grow in the regions where the antibiotic concentration is high. But they evolve resistance and just march up the gradient of the antibiotic. This takes about two weeks. Impressive.
Mathematics vs Physics degrees & Theoretical vs Computational Physics
I was on the Physics stand for Saturday’s university open day for prospective students and their parents. I got a lot of questions from prospective students who were still deciding whether to do a maths degree, a physics degree, or maths & physics. They were doing maths and physics A levels, but unless they go for a maths & physics joint honours, they will have choose one or the other at university.
Data science gone bad
I am reading, and enjoying, Weapons of Math Destruction by Cathy O’Neil. It is on the problems created for society by the use of algorithms and data. Data analysis is key to science and engineering, and so lies behind new medicines, faster computers etc, but like most powerful tools it is not guaranteed to always lead to good. It can create problems or make existing problems worse if used incompetently and/or in a way that benefits a few while hurting many.
How big is a crystal?
A basic question we can ask about any crystal is: How big is it? Many properties depend on size, so this is often a key question. Often it is not as easy to answer as you might hope. Take a look at the crystalline nanocrystal above. Its total size is about 59,000 atoms, or about 40 atoms across. But it is actually made up of two crystalline domains. To see this, look at the rows of yellow and orange coloured atoms, in most of the particle they are roughly vertical, but at the top right they are tilted a bit below the horizontal. So this is two crystals not one.
Many ways to fall short of perfection
The molecules in a crystal are in a regular arrangement, in which ideally they are all in identical positions, like soldiers in a perfectly ordered parade. And crystals have many useful properties, they are the best conductors of electricity. But crystals are rarely perfect, and these imperfect crystals may have higher resistance to electricity.
Does a restaurant count as research impact?
I am currently pondering this question. UK Universities are assessed by the UK government in many ways. One of which is via the “impact” of our research, defined as being “An effect on, change or benefit to the economy, society, culture, public policy or services, health, the environment or quality of life, beyond academia.”. At the University of Manchester, Andre Geim and Constantin Novosolev won the 2010 Nobel Prize in Physics, for their pioneering research on graphene – a hi-tech material made of incredibly thin chicken-wire-like arrangements of carbon atoms.
Mistakes made in mending a broken heart
I have just come across a striking but slightly scary paper. The paper looked at errors in scientific papers reporting on the use of stem cells to treat heart problems. Our heart is a muscular pump, and its muscle tissue has very little regenerative capacity*, so a heart attack can damage it permanently. The idea here is that by transplanting stem cells into a damaged heart, the stem cells can partially regenerate damaged muscle tissue, and so reverse damage due to the heart attack. The repair can be measured by what is called the ejection fraction (EF), which measures basically the fraction of the blood inside a heart chamber that is pumped out in one heart beat.
When average is not enough: part II
An earlier post showed the data (blue and green symbols) above but not the fits (cyan and re curves). The data are for the number of papers published in two scientific journals, Nature and PLOS One, as a function of the number of citations (+1 so it fits on a log-log scale plot), that the paper received. So for example, the blue circle at the top left edge is at x and y coordinates of 100 = 1 and 13,000, meaning that PLOS One published 13,000 articles that were cited 1-1 = 0 times. The papers were published in 2013 and 2014, and the citations were in 2015. The mean number of citations is the Journal Impact Factor (JIF), so the JIFs of the two journals are the means of the distributions above.
When average is not enough
The modern way to measure the performance of universities, departments and academics, is via metrics, i.e., numbers, as opposed to qualitative opinions of peers in the field. All sorts of numbers are available nowadays, and these numbers are much much faster to work with than getting an expert opinion. They can be used by managers who don’t have the expertise to assess the quality of research, and by academics who don’t have the time. And you need numbers to compile league tables, which are very popular.
Chance & Necessity 