Science Centre Showoff

Professor Rod Jones is a Professor of Atmospheric Physics in the Chemistry Department at Cambridge University. He explained explained how he's developed a pollution detector which fits in your pocket to Chris Smith and an audience at the Cambridge Science Centre...

Rod - Well, I do lots of different things, all the way from looking at the ozone layer, through to looking at climate change. But tonight, what I've brought along is one of the very small sensors that we make so that we can actually look at air pollution and try to understand how air pollution itself works and then we try and build slightly more sophisticated gizmos which allow us to monitor what a person walking the streets might be exposed to.

So, inside this box which the people can see here, those on radio, it's about 20cmx8cmx2cm it's got one nice green button which is the GO button and inside it, there is a mobile phone. I'm going to hand it out in a minute and what this does, it's also got a navigation system inside so that we can know where it is. We have three different gases being measured, somebody can put this in their pocket. We know where they are, we know what they're exposed to.

Chris - How do you know where they are?

Rod - Well, because we've got what's called a GPS aerial inside it, which is what you need in your car satnav to help you navigate. And so, inside here, there's a mobile phone. We have a satnav effectively, and we have some chemical sensors. So, we can actually monitor every second or so, what a person is being exposed to, and then we can relate that back to what we know is causing pollution in the town. We can also relate it back to somebody getting more asthmatic or wheezy as they go through a more polluted area. So, we're trying to conduct experiments which are linking those two.

Chris - Why is this better than what we have already?

Rod - It's better because you'd have a real problem in putting conventional instruments into your pocket. They weigh about 60kg and they're about the size of this table.

Chris - So, how have you managed to make it so small?

Rod - Well, we've taken sensors which are traditionally used in alarm systems and we've just made them better, and about a thousand times more sensitive. We can now make them about a thousand times smaller, which is what you can see here, what the audience can see here. Because we can make them really small, we can now make them much more portable and we can just give them to people to carry around.

Chris - What can you detect with it?

Rod - Well, these little chappies can just detect gases like carbon monoxide and nitrogen oxides. We've got other ones which can do other gases as well, but nitrogen oxide is particularly well-known or thought to be associated with health impacts. So, that's one gas that we can go for.

Chris - Let's take some questions. Get your hands up in the air if you'd like to ask anything. Let's start down here at the front. Who are you sir?

Mujal - I'm Mujal. I live in Cambridge. I just wanted to ask, what is air pollution and how do you measure it?

Rod - Well, air pollution that we're worried about is probably nitrogen oxides which come from cars. It's probably particles that come from cars and buses particularly. A lot of it is linked to transport, but those are the principal gases that you'd expect us to link to air pollution and those are the ones which are monitored by the national networks.

Chris - Who's next? What's your name sir?

Elliott - Elliott. How long does it take to make one?

Rod - Gosh! Well, to design and build one from first principles, it takes a few years. But once you know how to do it, it probably takes a few minutes.

Chris - So, there's hope for you yet, Elliott. You can do it with Lego perhaps. Yes, madam.

Ailish - Hi, my name is Ailish. I live here in Cambridge. I was just wondering you mentioned putting the device in your pocket. How accurate a test would that be compared to breathing in harmful chemicals?

Rod - That's a very good question. Of course, if you put it in your inside pocket, not very accurate. So, what we're actually doing and I've not brought them along this evening is make much smaller versions of these which effectively, you can put on your lapel much closer to where you breathe in. So, we're trying to get closer and as we build these things smaller and smaller, we can put them in much more sensible places.

Chris -  Can I just ask a quick question, Rod? What happens if you put it in your trouser pocket and you've had beans?

Rod - Well, we don't measure methane.

Chris - But isn't that quite an important greenhouse gas?

Rod - It is an important greenhouse gas and in fact, I don't know whether you're trying to lead me into another area, but we've got other sensors just like this which are designed to measure greenhouse gases so that we can for example work out how much CO2 Cambridge is emitting. Not methane yet, but we could go that far, but I'll keep that for another story I think.

Chris - What's your name?

Laura - Laura.

Chris - Hello, Laura.

Laura - Once we've created pollution, can we get rid of it?

Rod - Gosh! That's another very good question. Well, it gradually decays in the atmosphere. Even when it rains, we get rid of a lot of pollution, but some pollution takes quite a few months to get rid of. So, there's a natural process of getting rid of it, but if you're emitting it locally then you can easily get very high concentrations even though you're losing it gradually. It's like filling a bath.

Chris - What's the amount of time that carbon dioxide, once it comes out of the exhaust pipe of a car or whatever for instance stays in the atmosphere once we've released it? How long is it around for causing a greenhouse effect?

Rod - Well, of course, carbon dioxide isn't a pollutant - an air quality pollutant - in the way that we were talking about a couple of minutes ago. But once it comes out of your tail pipe, it's probably in the atmosphere for 100 or 200 years.

Chris - So, anything we emit now, we've potentially got to deal with for 100 or 200 years. We got to live with their consequences for that long.

Rod - Yes, I think that's absolutely right.

Carlo - Good evening. My name is Carlo and I would like to know when we walk in the street, are children more exposed to pollution than adults are because maybe adults are taller or does it make no difference?

Rod - We're looking at that and the effect doesn't seem that great. Of course, if you park your buggy at the exhaust of a bus, you're in trouble. But actually, what's really important quite often is which side of the street you walk on. And so, one of the things we're leading towards doing is developing a phone app to tell you which side of the street you want to walk on if you want to take a low pollution route. So, that's good question.

Chris - That could mean that everyone takes that route and then they walk really slowly because they're all stuck behind the slowest person in the world who is inevitably going to be on that same pavement. Then you get more exposure because you got to breath the air for longer.

Rod - Well, that's probably true so maybe we should...

Chris -  You have to factor that into the app. One more question here.

Errol -  Hi, Errol. How many data points do you actually need to get a good map of a town? So, how many people carrying it for how long to give you a really good sort of map of pollution across say, a city centre?

Rod - We've been trying for years to get that number and we haven't got there yet. Every time we can make a measurement with more sensors, we see more detail. So, we're trying to unpick that problem at the moment.

Virologist Margaret Stanley explained her work developing the HPV vaccine, aimed at lowering the rates of cervical cancers to Chris Smith and an audience at the Cambridge Science Centre..

Margaret - Well, I work on viruses called papillomaviruses. They're incredibly interesting because they only live in the epithelium that covers your body like the skin and the interior of your mouth and the interior of the reproductive tract, and your back passage. Most of the time, these viruses do no harm. In fact, if you ever see - an effective one it's likely to be a wart. But they're a huge family and like all families, they have black sheep.

The black sheep of this big family cause cancer. The cancers they cause, the big one is cancer of the cervix in women. Now, that is a huge problem in the world. It's the second commonest cancer in women worldwide. In Sub-Saharan Africa, it's the commonest cancer in women. So, we're talking about a really serious disease. Now, it's not just the cervix. In men and women, it causes cancer of the anus which is the back passage. It causes cancer of the tonsil and it also causes cancer in women in the vagina and vulva. So, we're talking about something really important. In fact, 5% of all cancers are caused by these viruses to one in particular...

Chris - How does it cause cancer in those places?

Margaret - Well, that's a very interesting question. First of all, the virus doesn't intend to cause cancer. Cancer for a virus is a dead end because viruses exist to make more viruses and that means they have to reproduce. Now, when viruses cause cancer, they are no longer able to reproduce in the cell, so it's a bad news for the virus.

It's because these viruses, particularly this 116, carries two genes which are really important for the virus to reproduce. But if those genes are expressed in the wrong place in the epithelium because epithelium we're talking about looks like a brick wall. Normally, these two genes in the virus are made in the upper parts of the bricks. But in the cancers, they're made right in the bottom and that's absolutely the wrong place because that's where the cells are dividing. These genes distort the way cells divide and that's...

Chris - So, the virus puts those genes into the cells and makes the cells grow more than they should.

Margaret - Grow more than they should and not only that. It stops them distributing their DNA and their chromosomes properly. So, they end up with abnormal numbers of chromosomes and they end up able to accumulate more and more errors. That's how cancers develop.

Chris - So, how did you turn the virus into a vaccine that could prevent those diseases? How did you do that?

Margaret - Well, what you have to do is prevent infection with the virus. We can't act on the cancer, but what you can do is prevent women and men being infected by this virus by giving them a strong immune response. And so, what you do, this is what's been so interesting is we make shells of the virus particle. A virus looks like an egg.  It's got a shell and what you do when you make the vaccine is, you make the shell, but you don't have the interior, you don't have the DNA. This shell, to the body's immune system, is exactly like the real virus and it makes antibodies to the proteins in the virus shell.

The big technical advance was being able to make these shells we call them virus-like particles. They're incredibly effective. They generate really strong defence responses and we know that these vaccines work. We know they work because the vaccines are now being laid out in certainly the industrialised world. In Australia in particular where they've been vaccinating since 2007, we can already see the decline in infection with the virus and we can see the decline in the pre-cancers caused by these viruses. So, it's a triumph.

Chris - Let's take some questions. First one over here...

Julian - My name is Julian.

Chris - Hello, Julian.

Julian - You were talking about vaccination and we have a policy in this country to offer vaccination to teenage girls for human papillomavirus. Do you think we should extend that to teenage boys as well?

Margaret - Yes. You're talking to the converted. The policy of giving it to girls was developed because at the time when all these policies were being generated, focusing on cervical cancer was the focus. But now, in the time that's elapsed, we've got a lot more information. So, we know how much male cancer there is. Basically, if you leave 50% of your population unprotected, then you've always got a great big pool of susceptibles. So, it's a much more sensible policy to immunize everybody. Then you don't have to worry how long the protection's going to last because everybody's protected.

Chris - Yes, madam.

Joti - My name is Joti and I'm from Cambridgeshire. Is there any selective population who is more susceptible to the viruses?

Margaret - No, that's another thing. If you went out and took a million women, we know that probably 800,000 of them would get infected, just because that's the way that virus transmits. But we don't know why some people are susceptible and can't get rid of it. It's not to do with ethnicity. It's not to do with behaviour. ..

Jodi - Haplotype?

Margaret - Haplotype, no. We do not have a handle on what the immunogenetics are, what is it about an individual and their ability to defend themselves against this virus.

Chris - Why is it Margaret that you catch it, but then you don't get the cancer for years?

Margaret - Because you get rid of it. Most of it, you get rid of. But also, you're looking in those people who develop the cancers, you're looking at chance events. You're looking at the probability of a molecular accident. Now, you can do the statistics - how often do mutations occur? So these are chance events and that's why it takes time.

Chris - Yes, sir.

Alex - Hi. My name is Alex. I'm from Cambridge. I have two very quick questions for you. The first is, you said we're all exposed to these viruses and yet, we need a vaccine to make an immune response so why is that? And secondly, you also said that we couldn't make a vaccine against the cancer. Why can't we make a vaccine against the cancer since the cancer would also have these viral particles in it?

Margaret - First question, I forgot it.

Chris - If we can make an immune response to the vaccine, why can't you just use your own immune response to boot virus out?

Margaret - Okay. This is a virus that only lives in the skin. Because of that, it is not very well exposed to the immune system. Now, you have to get into the circulation to the lymph nodes to generate a good immune response. And so, actually, in natural infections, you don't make a good immune response to this virus. Even though it's a pretty lousy immune response, still most people actually manage to get rid of it. The real issue for whether you're going to get cancer or not is whether you're one of those individuals who cannot clear this virus, cannot get their immune system to really deal with it. And I don't know who these people are, which is why you immunise everybody to give them a strong immune response because when you are immunised, you put your vaccine into the muscle. So, you go way beyond the skin and that way, you get straight into the lymph nodes to where the body really generates its defences.

Chris - Just very briefly Margaret, the second question which is, we can vaccinate against the virus. Why can't we just vaccinate against the cancer?

Margaret - Because cancers as they develop have evasion strategies which evade the immune response, which deregulate the immune response. So, it's a bit like turning a huge tanker around, trying to generate an immune response against the cancer that's going to be effective because that cancer has spent 15, 20 years, avoiding the immune response in the host.

Chris - It's become quite well practised We've got time probably just for one more question, young lady just down here.

Grace - Hi. My name is Grace and I just wondered why some people get cancer and others don't.

Margaret - If I knew that question, I'd be on the plane to Stockholm for the Nobel Prize. Some people are susceptible to these virus infections. Cancer is not one disease. It's a word that describes many diseases which occur in particular sites. So, I'm talking about cancer in the cervix and I know what causes that cancer which is a virus. But if I was talking about cancer in the breast, I don't know what causes cancer in the breast. I don't know why some women get it and others don't. Each cancer has its own profile, has its own risks, and these are different to a cancer in a different site. So, I can't answer your question properly.

Material Scientist, Caroline Goddard, explained to Chris Smith and an audience at the Cambridge Science Centre, how new alloys are made and how you select metals for different tasks...

Caroline - I work on developing alloys which is when you mix a couple of metals together, a bit like baking, you mix things together, heat it up, see what happens. So, the reason we do this is because essentially, when it's in its pure state, metal isn't that good. You need to add something else to it that's got some good properties that you also like to it to make it much better. For example, steel is made up of iron and carbon. The carbon is what makes it strong and more brittle.

Chris - So, what is the difference between iron and steel? If I looked down a microscope, they're both iron, right? But it's just the trace element carbon that's there. Why does it make a difference?

Caroline - So, the carbon sits in the spaces between the iron atoms which stops the atoms from moving around which makes it much, much stronger.

Chris - Why is it then that a piece of iron, if I just put it out on the street will go rusty, but stainless steel doesn't?

Caroline - Stainless steel includes another element which is really, really environmentally resistant, which is chromium because chromium reacts with the oxygen and creates this layer of oxide on the surface which prevents it from corroding. So, if you put some chromium into your steel then you'll get this layer on the surface which prevents it from rusting.

Chris - Tell us about the jet engines because I'm dying to know what you do with those. How does one work? Just a simple starter for 10 points.

Caroline - So, a jet engine works by, air goes in through the front and is compressed as it moves through the engine. It's compressed really, really small and then at that point, it gets really hot. You inject some fuel into it and ignite it, and the air expands very quickly, and goes out back of the jet engine which creates some thrust. This expulsion of air creates enough power to turn the turbines in the engine which turns a huge fan at the front which you've probably all seen when you fly off in your holidays which sucks in a huge more amount of air which flings it back, which makes the plane go forwards.

Chris - Brilliant! Suck, squeeze, bang, blow! I think that's what Rolls Royce say how an engine works. So, what are you doing to make these things better? They work pretty well, I've just taken a very long flight, and I think there were Rolls Royce engines on the plane because you can tell because they paint those little spirals on the nose cones and they also go clockwise. Interesting fact I learned about Rolls Royce aero - you can tell a Rolls Royce engine because they go clockwise. All the other engines go the other way. But why are these not good enough? What can we do to make them better?

Caroline - To make an engine go fast, it has to be very efficient at burning fuel and to make it more efficient, you need to make it go at higher temperatures. So, in order to do that, you need to develop a material that can reach higher temperatures.

Chris - So, how hot is it inside the jet engine then?

Caroline - It depends on where in the jet engine. At the front, it's relatively low, perhaps 300 degrees, something like that. When you get to the combustor and the turbine at the back of the engine, you're reaching 800, or even higher degrees. So, it's very, very hot. So, what happens is, the engineers design an engine that can tolerate all of these temperatures and they come to the material scientists and said, "We need a material that can reach this temperature."

Chris - "So, this is what we want to do. Go and make the material that can do it." And no material like that exists yet.

Caroline - Exactly, so then they get lots of PhD students like myself to go around and make lots of materials that will reach this temperature and then the engineers will come back to us and say that they want it to go even higher. So, we have to go back to the drawing board again.

Chris - So, there's the challenge - how do we actually make materials better? Over to you. What would you like to know? Yes, sir. What's your name?

Errol - Hi, it's Errol again. It can't be trial and error. You must start with some base materials with some obviously, standard sort of functionality. How do you decide which ones to put together to come up with the problem you're trying to solve?

Caroline - So, choosing your base metal gives most of the properties. So, if you use iron then most of your properties are very steel-like. If you use titanium, you'll have a very lightweight material, that's strong for its weight. So, you choose a base metal based on that. High temperatures, in the turbines, we use nickel as our base. And then you put chromium in to make it environmentally resistant and then put some other elements in that will make it stronger or make it better at resisting vibrations. But the proportions, it's not guess work.

Chris - So, it's guess work, yeah.

Caroline - We do have informed guess work.

Chris - It's called trial and error. Thank you, great question. We've got another question here. What's your name?

Olivia - My name is Olivia. I'm just wondering, can you separate an alloy?

Caroline - Can you separate an alloy?

Chris - So, you mean Olivia, can you get the other things that have been added, mixed in? Can you get them out again?

Olivia - Yes.

Caroline - I don't know. I don't think you can.

Chris - Because when I was going to South Africa and I met this bloke, this is the kind of thing you meet in an airplane. I met this guy as we flew into the airport in South Africa and he said, just looking out the window, "Ah! They've got another airplane for me." I said, "What do you mean?" And, he said, "Well, they line up all the airplanes over there because I recycle airplanes." And they line it all up on the runway and then he'd sort of literally takes them to pieces. He said, "We can't re-use the aluminium in the shell of the airplane because it's got stuff added to it. You can't turn that into another airplane because no one will guarantee the composition of the alloy and if you mix that up with other metals, you don't know that it's got a purity that you can rely on. And so, it may have characteristics that you can't predict. With something like an airplane, it's a bit too dangerous. So, I think it's really tricky, but Dave, what do you think?

Dave - Basically, to separate something you need to have properties which are different. So, if you have an alloy with something with quite a low melting point or a very high melting point, or very high boiling point, you can heat it up until the low boiling point one boils off and you'd get slowly a more and more concentrated solution of one of them and other one kind of boils off. But if you've got two metals which are very, very similar, it gets very, very nasty. I don't know if you've heard of the rare Earth metals, things like neodymium. They're actually not very rare. The problem is, that when you find them, they're mixed all up together and splitting them apart is incredibly difficult. You can do it, but it's very, very difficult and messy chemistry.

Ginny - Could you do it if you actually went down to the molecular level because I remember there was that video that was made recently where people were actually moving individual molecules around. They made a little video of a guy playing with a ball. So, if you went down to the molecular level, could you just tweak out the carbons?

Chris - So Caroline, how many atoms are there?

Caroline - I guess in theory, you could do that, but it would take a very long time.

Chris - There's a question at the back.

Jamie - Hi. I'm Jamie from Cambridge. I was wondering if you could explain how turbine blades operate at temperatures above their melting point. Is that correct?

Chris - Maybe we should just explain the context to the question, how do these turbine blades operate above their melting point because the reality is in these engines, the stream of gas going by is hotter than the metal melts at, isn't it?

Caroline - Yes.

Chris - So, you think I've got an engine running here which has got stuff going on inside it, hotter than the engine components actually melt at. Sounds a bit worrying, but the engines stay up there. How do they deal with that?

Caroline - So, it's a combination of two things. The first is, we coat the blades in a ceramic which has a much higher melting temperature and it conducts heat through it very slowly, so it doesn't reach the metal. And the second reason which sort of - they work together is that we blow cooling air through the blades themselves which works with the coatings to stop that.

Chris - There's one more question here. What's your name?

Freya - Hi. My name is Freya. I have two questions. I was wondering how many parts would be in a common jet engine and my second question is, how many metals would be in a common jet engine?

Chris - Pretty simple there Caroline. So, how many bits to an engine? How many different metals?

Caroline - Bit's - a lot.

Chris - Is that an SI unit then?

Caroline - Yes. So, with the jet engine, you've got the disks and the blades and the shaft which do the main amount of work. But then you've also got the casings and they all have to have sensors on them. So, there's lots of electronics all over them, so there's lots and lots of parts. For different metals, well, in a jet engine, you'll have steels, titanium and nickel based alloys. They are the main three, but within those alloys, you'll have a lot of other elements. In some cases, up to 13 different elements that you've thrown in there.

Chris - Thirteen in one alloy? And do you know exactly what composition of all those different elements there is?

Caroline - Yeah.

Chris - It's amazing. No wonder it's so expensive.