Cosmogenic nuclides and Dating (by sarah)

Wednesday before last I had another really interesting lecture - at first I thought I was going mad as it seemed to me that I had remembered fission track stuff incorrectly from my undergraduate but no it is a similar related technic and when i asked about it Peter Vermeesh said said I was trying to jump straight to the more advance applications of the subject.

I have to confess I was eeek maths, difficult panic and when he stopped for the break and asked if anyone had any questions we all said no and then me and two others dashed out to get a cup of 'tea' which actually involved bitting knuckles and looking at each other in dispair and asking if the other two had understood - we all shook our heads and started stressing.

But....

the lecture had followed us out and had a)over heard us and b) had realised he'd lost the class - he'd said it happens to him as well - infact it had happened to him at the Tuesday Seminar the night before!

We said we thought we got the concept but it was the equations that were scaring us - then he said there was only one little bit of maths - we looked at him increduosly. But I then had a cool disgussion with him about fission tracks.

I can not wikipedia link either of these two concepts/techniques as the pages do not exist yet - ok gosmogenic nuclids are like highly charged particals from like cosmic rays - hmmm.... ok I'll just delve into the notes I made and hope that they make scense!

There are two types of cosmic rays - GCR (Galatic Cosmic Rays) which are highly energetic and come from super novas, the others are solar rays.

The GCR are 38% something I've written as +P which will either be protons or positrons (but I normally write these as +e) or a cation of P(but I feel this option unlickely if anyone knows let me know!), they are also 3% electrons. Now apparently the amount of energy in these +P is alot - they travel at near the speed of light and form black wholes in our upper atmosphere all the time - I think I want to see more evidence for that particular claim personally!

These cosmic rays are deflected by the earths magnetic field and due to how the feild forms there is more protection/sheilding at the equators that there is at the poles - at the poles the low energy solar cosmic rays can sneak in giving us the aurora.

Even with the high energy particles there is a defernce in how many of the rays/particles can crash into the ground giving us somehting to count - this gives us geomagnetic latitudes with the effects.

Just help make things more complicated there are secondary particles produced when a +P enters our atmosphere ie it hits/collids with oxygen, nitrogen molecules and the atom they hit sort of explodes into a host of secondary particles - this is called spillation (sigh there is no wikipedia article on this either 🙁 )

So from these collisions in the atmosphere we now have nuetrons,protons, alpha particles and many more - these are secondary cosmic rays and you get a somic ray cascade - sort of the priamid selling of the sub-atomic particle world.

There is a big increase in the number of nuetrons as they are the most abundent secondary particle. Of cource the secopndary particles hit other molecules and atoms in the atmosphere and so the cascade propogates through the atmosphere but the energy of the origonal cosmic ray is being spread out and there is a corrasponding - and basically exponential decrease in the energy,

This means that not many of the cosmogenic nuclids actually hit the ground - those that hit the ground are called in-situ and until recently (the 80's) these could not be measured!

Anyway new elements are made in this way - now 99% of those will be useless for dating rocks as there will be so much of that element around on the earth you can not detect the new from old! This means we need the rarer elements and then there is all complexiaty with the expected amounts of that element in a sample and the actual amount then there is weather they are radio active etc...

Then there is the fact that the cosmic rays only penitrate the very surface rocks - this is actually cool as it gives you burial and erosion rates.

We ploted a graph which looks at the rates of burial and exposure - when done on a log scale it is known as the Banana Plot! (no wikipedia again :'( ) this is becuase it looks like a banana!

Anyway I got very excited about the applications of this and asked about the nuclear disastor/test factor and think I might have agreed to look for a cesium spike in one of my milk teeth - though I did get a bit too excited and started on about brizil nuts affecting the results - not sure what I was going on about there!

Still I also asked about extraterrestrial material and therefore made the class late leaving yet again! But this was sooooo interesting - becuase in space there is no or little shielding the rate of rays hitting the surface is higher and you can therefore get a 'burial' age for say a meteorite which has landed on the earth due to the atmophere stopping most of the cosmic rays! - now this is info I can use!

Oh and I got told off for trying to solve an equation - I didn't initially know what I was doing with the ploting of the graph - as always I thought he was asking for somehting much harder than what he actually wanted - I am awear that this is a really really bad explanation of this subject but I'm still sorting it out in my own head :/

Deep Stuff (by sarah)

Last Wednesday I went to the first of the departmental research seminars it was by Lars Strixrude and was on an area I basically knew nothing about. It was called Minerals to Mantles: The Planetary Mosaic.

There was alot of stuff in this I didn't understand but it did manage to answer some of the more pressing questions I had come out of the Solar Physics lecture with - namely about what was actually being detected/repressented with all the Tomography stuff and so it was I feel a good job I went.

As far as I could tell he was extrapolating say mineral physics to the mantle as a whole and using a similar principle to those you use in transmitted light microscopy in that the direction of the mineral and type affects the way the waves are propogated. This means you would be able to tell alot about say the actual structure of the mantle and the internal workings of the earth - I sort of felt a vagueness that eutectic and peritectic stuff should make an appearance but as I can't really remember what that was all about the reality is probably very far away from my comprehension :/

I felt intreged by the topic and thought I understood what was going on at the time but now I come to write it up its all gone 🙁

But it really reminded me of second year ingneos petrology (at least I think thats what he was teaching) with Stephan Matthai - sometimes I wish my brain worked properlly :/

I had the vague feeling that this fitted into my general thing of wanting to treat things as systems rather than confined subjects but am not really sure - hmmm - not the best blog ever and probably completely round my neck :/

Trains, Boats and Swimming (by sarah)

After the World of Beatrix Potter we went for a train ride on a narrow gauge railway - this was uphill and downdale and as the fog was coming in on root to the train station I got a bit nervous - it turned out that this was an historical trip for Lionel who has memories of his fathers car breaking down and all sorts along those roads.

We were later than we intended as Jean had thrown up earlier in the day etc... so Al and Lionel had to drive to the terminous whilst me Simon, Lynne and Jean rode in the open air carrages.

The landscape was cool but I become frustrated with the phone camera and doubt anything came out well - there just was not the right kind of lightlevel. Still we saw a buetiful black sow which reminded me of the pigs in Pigling Bland and then we saw a stolk or crain in the mudflates 🙂 There where also sheep and cows but too my suprise they where actually quiet different to what we have here. The sheep where fluffy black and white 🙂

Everytime the train whistle went Jean pretended to be scared and need a cuddle which was sweet - there was no door to the cart we were in so she was sitting firmly in the corner with Lionels waistcoat over her to keep her warm. We had a little argument about standing up and another about sticking her hands outside the cart but over all it was great with her serving me pretend tea from a pretend flask - I sort of wished it hadnt been pretend :/

We then had the most fantastic meal in a place called... Cockermouth... (yes that is actually the name :/) the resturant was called Junipers and was fantastic 🙂 And the staff were really nice.

The next morning I was dropped off ouchy early to get my ouchy priced train down to London from Pentrith. Poor Lynne had to go to a Dr as it turned out the cough she'd had all weekend had resulted in ulcers in her throat 🙁 Whilst she was sorting that out Al took Jean to the swimming pool which apparently was sweet even if Jean didn't swim - she jjust walked around in the water but enjoyed herself lots 🙂

They then spent the afternoon on a steamer - Jeany also got to watch Wallace and Gromet so I think she had a fantastic holiday - she told me all about the boat yesturday morning as we got her ready for pre-school 🙂

Fun in computer games (by alaric)

I've noticed a pattern in computer games which I find fun. Not all games I find fun; they can be fun in different ways. I'm just saying I've noticed a particular element which subtly contributes towards the funness.

Namely, having to make a tradeoff between two or more competing requirements.

Let's have an example - Desktop Tower Defence. It's a tower defence game, which means that you use your resources to build a set of defences that waves of attackers then flow into.

Firstly, clever placement of defences has a much greater effect than simply how much you spend on them. So the game requires some measure of thought, rather than repetitive accumulation of resources followed by spending them.

But the crux of the matter is that there are different kinds of attackers, which have different weaknesses. A defence set up in the way that would be the strongest against land-based attackers - a long winding zig-zag with turrets along it - would be weak against flying attackers, since they just fly over your layout in a straight line rather than being constrained to the paths. Against them, you want a solid block of turrets in a cross, under the two orthogonal lines they fly along. So you need to establish some tradeoff between the two challenges. Not to mention that there are turrets which only attack air targets, but have a high damage per cost ratio, and turrets which only attack ground targets, and turrets that attack both but have a worse damage per cost ratio. And turrets with long ranges, or high fire rates, or that do a lot of damage per shot, or damage neighbouring targets due to a splash effect, and so on.

Sometimes you can have a tradeoff that's too simple - it's amenable to mathematical analysis to find an optimal result. That's no good. It has to be too complex to work out on paper, but not too complex to grasp. The middle ground between the two is the area where experimentation is rewarding.

I probably ought to read A Theory of Fun for Game Design...

Beatrix Potter (by sarah)

Saturday night we got out Miss Potter a film about who the Beatrix Potter books got published and about her life. This was actually really interesting - especially for me as I feel that some of the children's stories I have written are the modern day equivolent of Peter Rabbit and the rest. Well my characters are called Ester Rabbit and Christina Cluckelsworth and so on. But mine live in the now as did her creations - the characters need to be contempory and in contempory language.

Anyway I digress - Jean has the entire works and we tend to read them alot - we are also near Gloucester which obviously makes a big thing out of the Tailor of Gloucesterwith Beatrix Potter mice everywhere etc...

What I had not realised was that she had taken an active role in trying to preserve the country side and mantain the farms - I feel she was a very far sighted women in many respects - I now a an itch to know more especially as Sunday we went to the World of Beatrix Potter - Jean is still running around with her rabbit ears on she liked the place so much!

Unfortunatly she did throw up on route so Lynne kindly bought her some cloths to wear - this included a Peter Rabbit T-shirt which we have had to crow bar Jean out off for a wash! The exhibition was good but I dont think I'd have gone if I hadnt of had a three year old 🙂

Al did notice a few quiet big disgrepencies between the infor at the exhibition and the film - we have not yet investigated to find out which one is correct. I was intreged to find that Beatrix Potter had really wanted to be of a science/art bent and had applied to do botanical art - I think if I'd been born into her society with the same sort of family rank I'd have been very similar to be honest.

The funniest thing I managed was to announce that I thought the film Beatrix was like Bridget Jones - to which I got a chorus of 'well it is the same actress' - I have not seen the Bridget Jones films I was just running from an extract I had read (but I probably saw trailers somewhere along the line so can not claim complete innocence) - sigh - this always happens to me :/

I took alot of pictures of this so hopefully they will becoming soon 🙂