Wednesday, 18 June 2008

S282: Book2 - Chapter 1 & 2

Well - another weighty tomb awaits us in the shape of Book 2, An Introduction to Galaxies and
(435p). The first book was all about the birth, life loves and death of stars. In this book we take a step back and look at the bigger picture of how galaxies are born, live and die.
If you thought finding out details of stars which are all tiny pin pricks of light was hard, well its much simpler than galaxies. Galaxies are orders of magnitude further away than stars so the amount of light you can capture is typically smaller.

Anyway - we start the book with Chapter 1 looking at the Milky Way - our own galaxy. This allows us to explore what it is made up of (and stars are are pretty minor component!), its shape such as the halo (including the dark matter one) and the bulge, some of the oddities within it such as open cluster and globular clusters.

Then Chapter 2 looks at regular galaxies. There are a lot of different galaxies out there and naturally the first thing the early people did was to lump them together into categories. So we have spirals (with and without bars), ellipticals, lenticular and irregulars. These are classified according to the Hubble scheme (or other variants).
Then there is quite a section on how we work out the distance to these galaxies - which is pretty hard work. Many techniques are not very accurate but give a good appreciation of the order of magnitude.

Friday, 13 June 2008

S320: Book 5 - Evolving infections

Book 5 now and at about 100 pages not too bad either.

It considers some of the theoretical basis of disease. The arms race between pathogen and the host and how they both evolve over time. It also looks at things like the manipulation of the host, particularly by some pathogens that can have a quite large effect on the behaviour of the host. This also considers the patterns of virulence and how the life of the pathogen is affected by the life of the host.
Transmission mechanisms also are looked at in detail, and how effective they are.
Finally in the last chapter it looks at a theoretical model for a host/pathogen infection in a population and how that can be modelled. This is apparently setting us up nicely for the next book on epidemiology.

Monday, 2 June 2008

S282: Chapter 8 and 9

The final two chapters of this tomb relate to the death of stars and what happens to them afterwards.

The death throws can result in stars doing all sorts of things. Some of them eject large rings of material called planetary nebulae. The bigger and brasher stars go out with a bang in a supernova explosion, which as a by product generates most of the common elements with atomic numbers greater than Iron. Supernovae can occur in a couple of ways, mostly its big brash stars blowing up, but occasionally its a white dwarf in a binary system given a second chance to shine.

The death of a star depends largely on how big it is. The smaller stars like our own after going through a red-giant phase tend to start to fizzle out into a white dwarf. In this stage, they are basically out of fuel, and all they can do is sit there and glow with the heat saved from their glory days. They eventually cool down to black dwarfs, but this takes so long to happen, that it probably hasn't had chance yet. However they are rather faint objects so they are difficult to see at the best of times. There is a fairly hard and fast limit (the Chandrasekhar limit) to the size of a white dwarf, and most stars sneak under this limit by blowing off much of their mass in their death throws.

Bigger stars end up as more exotic objects, including neutron stars, quark stars (possibly - the jury is still out on the existence of these) and the more famous black hole.

With that, book 1 is done, and book 2 beckons, but a TMA needs to be finished first!

S320: Book 4 - Diagnosing infection

Well this is a much easier book after the alphabet soup of the Immunology.
It goes into some details of how infections can be diagnosed in practice. This is not the GP having you "Say ahhh" type of diagnosis, but the methods of isolation pathogens.

There are sections on how to culture bacteria, how to breed viruses and so on. What media you can grow them on and how you can tweak this to give you a pure culture. There is also an interesting video on life in the diagnostic lab.

After that, it moves onto the more high tech techniques. These generally involve antibodies, or gels and stuff. So it covers immunofluorescence, Enzyme-linked immunoabsorbent assay (thankfully abbreviated to ELISA) and then things like gel electrophoresis, SDS-PAGE, blotting, and PCR.

The final chapter takes you through the diagnosis of some common diseases, such as cholera, HIV, flu, malaria and flukes.

As I say, positively relaxing after book 3, but I bet the exam questions will be digging around in this material.