Advice #21

Don't look over your shoulder too much.

Or if you do, switch shoulders from time to time to avoid straining your neck and back

At last

Since the HMV e-mail telling me that my CD, Best of the Cardigans, is on the way, I have been sick for 3 days out of 7. Maybe there's a link, maybe there isn't, who can say? But it arrived a few minutes ago, and it has certainly cheered me up! Being sick is very stressful as well as being boring. I'm only half-way through listening through CD 1, but it's pretty good! Yay

Self-healing and thermoreversible rubber from supramolecular assembly

That is the title of the Nature article (Nature 451, 977-980 (21 February 2008)) that I wrote about here. At the time I was complaining about the way this BBC article had described the science involved.

So I had a look at the original Nature article, and agree that it is a wonderful and novel substance, so BBC picked up on a good thing. Let me explain it as I understand it. I hope I'm not too far wrong in this, please correct me if I am.

A normal rubber consists of longs chains of atoms, held together by so-called cross-links. The chains like to be coiled up, but if you pull on them, they can uncoil, so the material stretches. If you let go, it will go back, simply because it prefers to be in its coiled-up state*. Since the chains are cross-linked together, it remembers better than other materials how it was before, so it is more elastic than normal materials. Without the cross-links, it would be a plastic, which does not remember its shape as well.

If you cut a rubber, you break some of the bonds. These are covalent bonds, bonds that have strength because they share electrons. Once a covalent bond is broken, one half of the chain takes more electrons than the other, so this half is negatively charged and the other half is positively charged. Positive and negative charges cancel out at the drop of a hat, and they get rid of their charge as quickly as possible. They might grab a gas molecule from the air or react with another part of the rubber, so in a tiny fraction of a second, the loose ends have been tied up and the cut has sealed over. After it has closed up, it's stable and happy, and will not react again. So when you bring the other bit of the rubber back, it will not go back together, even if you do it as quickly as you can posibly imagine.

This rubber is different, because it is made of short molecules, that are all held together by hydrogen bonds. Hydrogen bonds hold the structure together, but they are not quite as strong as covalent bonds. Just like a normal rubber, the end effect is that a network of bonds is created, where segments can stretch and coil up. So this is still a rubber in terms of how it acts normally. The benefit is that a broken hydrogen bond does not leave positive and negative charges. It will tend to attract molecules to tie up the loose ends, but this is not a quick process. This gives you time to put the rubber back together. Slight movement (diffusion) of the chain ends allow the molecules to line up and bonds back together, so that the material heals and the seal is as good as the original rubber if you give it long enough.

There are polymers (materials that come in long chains of atoms) that can re-heal by diffusion already. These chains do not have cross-links, so they are not so rubbery. To heal themselves, the chains just wriggle together until they are knotted together. That works pretty well, entanglements are the way that loads of polymers hold themselves together anyway. But a material like that is able to flow like honey or jelly (two really good foods)**, so it is not a real rubber.

So the material that they have created is unique and special, in being a useful rubber and being able to heal itself. I'm sure there will be lots of places where it can be used, although the authors do not suggest any themselves (they are more interested in the science, as I am too). The same issue of Nature also contained the comment from Justin Mynar and Takuzo Aida “The potential applications are manifold. Tears in clothes that effectively stitch themselves together, long-lasting coatings and paints for houses and cars, and to take one example on the medical front, self-repairing artificial bones and cartilage.” To me, the possibilities seem endless, and given that it is cheap and easy to make, and easy to degrade (so it can be disposed of environmentally), I think we will see a lot of this in the future.

If this article did not make sense, try Physics World. The Times also enjoyed thinking up uses for it.

* it's all about entropy - coiled up structures have a higher disorder so they are preferred, it's a law of physics
**depending on how liquid it is, people talk about creep or viscosity when they talk about a material flowing (under its own weight or otherwise)

Advice #20

Don't get really really drunk like I did yesterday. I haven't done it that bad in a couple of years at least. I have forgotten portions of the evening and everyone who saw me seems to have something to say on the matter. I've had e-mails about it and threats from my housemates to tell me what kind of things I got up to. And this morning in the lab has been horribly unpleasant, I have a pounding headache and a recurring desire to dash to the toilet.

So yeah, just don't

Life goal achieved

Or one of them, anyway. And not a very important one. But I have felt an earthquake. Today, 27th February 2008 (at 1am), an earthquake. Nobody knows what is going on because earthquake websites are crashing. Just imagine what would happen if there was a real crisis, because then websites would have even more problems! I've been chatting about it with Housemate Louisa, but sadly nobody else is awake (unless it woke them up)

It seems to have been felt across the country and been 4.7 on the Richter scale. Just so you know. Hope you felt it too, it's exciting! Centred on Hull, as far as the American Geological Survey knows at this point

Weekend work makes Saturday a sadder day

Why covalent bonds are not welds

According to the BBC article, Self-healing rubber bounces back, "...break a rubber (or most other solids), and the chemical welds - known as covalent bonds - are also broken"

I've never heard from chemical bonds being called welds before, and with good reason! A weld is a join formed by melting two pieces of material together. Having spent a lot of effort creating an atomic structure to make your material strong (by using just the right material and producing it in just the right way), melting it by welding mixes up the atoms, so the layout of atoms is lost and the weld is usually weaker than the rest.

In contrast, a covalent bond is simply a force holding atoms together (arising because the electrons are happier if the atoms are together). If you have two atoms held together by a covalent bond, the bond has a particular strength - The quality of a weld varies depending on how much of the material you melt and how the material reacts to being heated up (and cooled down again) REALLY fast. But a covalent bond has a particular strength irrespective of how you make it.

So covalent bonds are not a weak link, not caused by melting and not variable in quality. A weld is just not a good analogy. If they don't want to call it a chemical bond, call it a chemical link or just a force binding the molecular chains, surely people understand that just as well as "weld". After all, what fraction of brits have tried welding for themselves? Well, on the bright side, they didn't call it a glue!

The material they have made sounds pretty amazing, I really want to look up the paper and read it properly, because a hydrogen-bonded rubber, diffusing quickly back into itself to regain its strength is a pretty cool invention

Engineering challenges of our time

It's been well-publicised in the last day or two, but here are the top 14 challenges facing engineers at the present according to the National Academy of Engineering:

• Make solar energy affordable


• Provide energy from fusion


• Develop carbon sequestration


• Manage the nitrogen cycle


• Provide access to clean water


• Reverse engineer the brain


• Prevent nuclear terror


• Secure cyberspace


• Enhance virtual reality


• Improve urban infrastructure


• Advance health informatics


• Engineer better medicines


• Advance personalised learning


• Explore natural frontiers

It really got me thinking, what were the challenges 50 years ago, or a hundred years ago, or a thousand years ago? What will they be in a hundred years? Well, even fifty years ago, almost none of these would be on the list. Of course, explore natural frontiers would still be there along with prevent nuclear war (not so much "terror" back then, people did not understand the meaning of the word terror: they were simply aware of a danger in a dignified and undoubtably British way)

Fifty years ago there were no mobile phones or personal computers, few people used aircraft or owned televisions, especially colour ones. The cassette tape, now worthless, was not yet in mass production. Smallpox still existed and the MMR vaccine had not even been invented. As I write, more and more things come into my head, some technical, some not. The world has changed hugely in the last fifty years; in terms of technology as much as by any other measure. And that's within many people's lifetimes, it's no wonder old people can get a bit bewildered by new-fangled things.

In fifty years' time, the world is likely to change a whole lot more. In my opinion, the main danger is the damage we do to the world as the other 5 billion people catch up with the West in terms of living standards. So for me, the top four are the most important (although transport infrastructure could be included).

I have known for a long time that we cannot tackle environmental issues (esp climate change) without widespread support from the genera public, but it was put to me in an interesting way a few days ago. Technology has increased steadily for the past few thousand years, and at no time during that has it caused us to treat the world better. As an example, commercial flights have got more and more efficient, meaning that less fuel is needed to travel the same distance. This should be a positive environmental effect. In fact, companies designing aircraft engines such as Rolls Royce are using this to promote their business. However, while the changes do increase efficiency, they simply allow flights to become cheaper because aircraft use less fuel. So in fact we fly more often and cause more damage to the environment in this way than we did before. There is little evidence that scientific development can actually save the environment on its own.

Of course, saying that scientific advances do not always help does not mean they cannot. And if they are combined with a general public who are determined to make the world better, then why not (the ozone layer problem is on the way to being fixed, for example)? Surely development of printable organic solar cells or even nuclear fusion can only help the situation. I am aware more than ever though, that engineering and science can give people the option of improving their lives but they have to do it themselves. Looking back at the list: if the problem of water supply is solved, that doesn't stop farmers polluting it with fertiliser; if personalised learning is improved, it gives more choice to people about whether they learn at all or not; and if nuclear terror is alleviated, another problem will arise unless we sort out the social and political reasons for terrorism. Dealing with the great challenges of engineering are nothing without tackling equally difficult challenges in society as a whole.

This blog is a year old

I've become quite attached to blogging over the last year. I enjoy thinking about what to write and what might be interesting to someone who's not me, often to people who don't even know me. It has to be varied and not just descend into a pathetic diary, while being personal and interesting, and without being pretentious - basically I hate stereotypes so most of this is trying not to drop into one. Oh, and it has to make sense - I'm not very good at that, so I have to concentrate!

When I started, I said I'd write short posts, so I apologise if they have been long in places. They were meant to be pointless too, but sometimes it's nice to write things with meaning.

At about the same time, I started reading blogs, so in recognition of this, here are some that I sometimes look at when I'm wasting time:
http://conspiracyfactory.blogspot.com/
http://www.thepropheticyears.com/wordpress/
http://www.bristlingbadger.blogspot.com/
http://soundofmusique.blogspot.com/
http://mccabism.blogspot.com/

Advice #19

Don't put your hand in the fire, you pillock! it'll really sting you know

She likes her hair to be real orange; she uses tangerines

The event has been on the horizon for a while. When the house went girly and the henna came out. The girls told me that they wanted me to join in, and having never tried dyeing my hair before, I gave in quickly and joined the party.

To do that, I had to go into Lush. I was horrified. I have always walked past Lush, blinked a little at the tackily applied bright colours, coughed briefly at the stench exuded from the dimly lit shop, and walked straight on. Out of all the shops in town, this is the one that appeals least. It advertises various crumbly blocks of "stuff", containing something "essential" for your well-being. But this is apparently THE PLACE to get henna, because it is good at having organic things that are healthy and ethical, and henna is healthy and organic and presumably ethical too (as I have learned). I felt every muscle in my body tense as I came up to the shop, resisted the urge to go on to HMV instead, and set foot inside. The shop assistant who looked least scary (he had a beard and may not have washed in the last couple of hours, shock horror) kindly tried to make eye contact as he wrapped some of their trademark crumbly blocks, but I resisted, knowing that it would take a moment to gain the confidence to speak and the breath not to cough. Indeed, my first breath was stuttering and shallow, but I didn't cough and possibly also didn't even grimace too much. I tried in vain to get my bearings, but every small surface was covered in crumbly blocks of different colours and sizes that smelled too badly to get too close and read the label. Having seen my way around though, I went to the shop assistant, the one with the beard, and asked him about it. He was actually very friendly, to my joy. He didn't mind that I had no comprehension of anything, and explained what you do, how much I needed and which type to use (yes, they come in different colours). He guessed that I was connected to Jo, who had come in the day before and warned him that a houseful of people would all descend on him for henna imminently. As I left, I reflected that it had not been so scary after all, and that if the man was there next time, I could probably brave the stench and crumbly blocks to go in again.

I arrived back in the evening to find the first henna-ing already underway. Maria had henna'ed her hair last december in a ginger colour that all the boys seemed to love, and was keen to have it re-done. I should guess that the attention from the boys didn't enter into the decision, but it certainly made the rest of the girls think... Jo couldn't have anything too extreme (what would Chris say?!), but the others launched into it with much abandon! Go them! So we took it in turns to take the hotseat and have the henna applied.


Henna is like poo. Of course, it starts off as a smelly, crumbly block, but it is heated with a bit of water until it gets properly pooey and warm, and even more smelly. Then someone spreads it into your hair, making sure it's all covered while trying to miss the floor, your skin and your clothes, all of which stain. Next it is covered in cling film, and you just wait for the colour to seep into your hair, while the smell attacks and attacks your nostrils unrelentingly. It was JUST TYPICAL that my hair was darkest and so took the longest, and I left it 4 1/2 hrs before washing it off.

Of course, the girls were drinking wine and listening to the Madonna cover of American Pie, just to make the evening more like a girly sleepover. Then Jo decided it would be a good moment to paint my nails. She cornered me while I read my book, and reminded me that I had agreed to it at some unspecified point in the past, in return for occasional football related conversation. And, while the conversations in the house about football have been very occasional indeed, I went along with it, probably caving in more easily than I should have. About 2 nails in, I realised my mistake, but there was no going back. I take full responsibility for it, I can't really blame Jo except for her timing, I could have refused at any moment.

But I was traumatised. I went into the shower to wash off the vile stuff, and all the poo-stuff ran down my face suffocating me most horribly. I looked down at my hands and gasped as I noticed my nails, breathing in some henna-water, leaving me spluttering. And did the henna do anything to my *black* hair? Did it hell! Why no, no, it didn't! Yes, I'll admit that in daylight you can stand at the right angle and looked carefully at the way it glistens brownishly, but did it change colour? No, of course not! In lectures the next day I had comment after comment about my nails and how silly they looked, but not one about my hair. Pah!

The others look great of course. Maria looks stunningly ginger as before, Louisa looks similarly wonderful with the same colour, Louise has gone a very sexy dark brown colour that glistens nicely and is a bit more understated, and Jo has highlights of ginger that make her hair more interesting somehow, while leaving her hair effectively her normal blond (who'd really change their hair from her pretty blond anyway?)

So of course they want to do it again. Now, in my book, trying everything once, from bungee jumping to sushi, is important, so I do not regret any of this for a second, but I am not doing it again. I'll watch if they'd like male company, or leave the house otherwise

My Grandma introduced

This is Grandma. She has travelled all over the world, but likes nothing better than sitting at home with a piece of cake and a cup of tea and telling stories of her life or of the books she has been reading. She doesn't often leave her flat these days, she's just content where she is and prefers to stay in her comfort zone. She's amazing, so full of knowledge and just a lovely sweet old lady.

Now imagine her with a megaphone!