Transcript March 2008
Gareth Mitchell: You’re listening to the official podcast of Imperial College London. And hello. I’m Gareth Mitchell of the BBC’s Digital Planet and the Science Communication Group here at Imperial. And welcome to the March edition. Today, how being on an airport flightpath could be the path to ill health according to Imperial researchers. More on that in just a moment. Plus, the possibility of sniffing your way to good health.
George Dodd: Working with a pharmaceutical company we’ve invented the world’s first medical perfume that really addresses areas like mild depression, which are very clinically significant. We can access the emotional centres of the brain through the sense of smell without getting other molecules into the body.
GM: The science of smell under analysis this month. And could metamaterials be the next big thing? Well, possibly the next really small thing given that they work on the nanoscale.
John Pendry: These metamaterials have structure on a scale much less than the wavelength of light. They’re going to behave like optical antimatter. They’re going to annihilate a bit of space next to them.
GM: One of our most eminent physicist and his very own material world. That’s coming up as well as our regular roundup of headlines from around the College.
Why aircraft noise can raise blood pressure even while you sleep
GM: Well, to begin, is there a link between aircraft noise and high blood pressure? Well, there is according to research recently published here at Imperial College by Dr Lars Jarup and colleagues in the Department of Epidemiology and Public Health on the St Mary’s Campus, which is where I now am with Dr Jarup. So what have you found in this study? What was it all about?
Lars Jarup: It’s actually two studies that were published, one published before Christmas and the other one last week, which shows that there are both short term or acute effects on blood pressure, if you’re exposed to noise during night, and also long term effects. We looked at around 5,000 people living near six of the major airports in Europe, they had been living there for at least five years, and we found that there was a clear exposure response relationship between exposure to aircraft noise during night and the prevalence of high blood pressure. That is, the higher the night time aircraft noise the higher the risk of having high blood pressure.
GM: But essentially then you’ve been monitoring what’s been going on with these people’s blood pressure as they sleep in their beds on the flightpaths of these airports?
LJ: Yeah, that part of it was one of the studies, which was part of the bigger study, which was on short term effects where we looked at 140 people having lived at various distances, as you said, from the airport. Having then, of course, been exposed to different degrees of noise. We had an ambulant blood pressure monitor during the whole night measuring blood pressure in every 15 minutes. And in parallel, we had a noise recorder as well as an MP3 player so we could playback later on to find out if there was a noise peak on the recorder, we needed to know what the source noise was.
GM: Because that’s what I was going to ask you. You really are clear that you’re studying aircraft noise here? These weren’t lorries rumbling past the house or noise coming up from downstairs or noisy neighbours? These were all aircraft events that you were studying?
JL: Well, that of course was the main focus of the study. But nevertheless what we did find in the short term effects study was that it really didn’t matter what kind of noise it was. We did get an increase in blood pressure after the noise event, as we used to call it. Even if it was an aircraft or it was a lorry or indeed if your partner was snoring. So there were all sorts of noise that could give rise to that blood pressure. However, if when you go back and look at the main study that included the 5,000 people, there it was quite clear that it was aircraft noise and the relationship with the risk of high blood pressure. That of course couldn’t be explained by snoring or anything like that. This was clearly aircraft noise.
GM: And the incredible thing here then was that this is people who were asleep as well so you wouldn’t think they were even consciously aware of the noise?
JL: Yeah, that was a very interesting finding. And I believe this is the first study that has shown this. There have been a few animal experiments where people have looked at reactions in animals, when they are anaesthetised, basically, and they get a kind of sub-conscious reaction in their blood pressure. So we believe that the mechanism here is something very basic in the brain.
GM: And did you gather any data as to how long the blood pressure was raised for after the noise event? I mean, how long did it take for it to subside back down to normal levels?
JL: Well, that’s actually a very good question, which we couldn’t really address since we only had the 15 minute interval to measure the blood pressure. But we are assuming that this is a short term effect obviously. But what we really don’t know is the link between this and the long term effects.
GM: So can we go as far as to say that the headline news from this study is that if you live near an airport there’s very likely to be a link between the aircraft noise and raised blood pressure and therefore health difficulties as a result?
JL: I think that that’s fair. I mean obviously as I’m sure you know as well that one study doesn’t make the whole truth, if you like. So there will be other studies to come. And I believe there are already a few studies that have shown similar effects. So I think it is fair to say that there is a link between noise, particularly aircraft noise during night time, and the risk of having high blood pressure. And of course, as we all know, hypertension, high blood pressure, is a risk factor for other severe diseases like myocardial infarction or stroke so it is of course an important link there.
GM: And as for the 140 volunteers that you studied in these trials with the noise recordings and the blood pressure recordings as they slept, how sure are you that what you were looking at were real health effects here? I mean were these people generally older people? Were they smokers? Were they people who were at risk of high blood pressure events anyway?
JL: Well, that again was a good question. But we tried to eliminate people with previous diseases. The age range here in the study, and that goes for the whole study, was between 45 and 70. As always in these type of studies you try to have various ranges there. So we have various ranges of age and also ranges of exposure and so on to get the best possible analysis done.
GM: And it seems to me almost unprecedented that we have this data about the link between air cr aft noise and blood pressure. I’m just surprised that you’re the first people to have studied this.
JL: That’s true. I think we were quite surprised as well, when we started in the group to discuss this five or six years ago. But that’s the case. There was very little done around the airports. What had been done before I think most is focusing on psychological/psychiatric effects. There was a study, again, coordinated by colleagues here in London, that looked at children’s cognition and so on under the Heathrow flightpath. But very little on cardiovascular effects. There had been quite a few studies on road traffic noise and cardiovascular effects but nothing really on aircraft noise before.
GM: And I suppose a lot of the focus on health effects from transport have been more pollution related rather than noise pollution related?
JL: That’s absolutely right. And it’s obvious of course that if you look at air pollution from road traffic, which has been studied extensively, it’s fair to say I think that at the same time you will be exposed to noise. In fact many of the air pollution studies have used as a proxy for exposure the distance/road. And it doesn’t take much to realise that distance/road is an equally good proxy for noise exposure. This is I think now started to be realised. And that’s one of the next lines of research that’s going on, to try to disentangle these effects. To look for combinations of effects from air pollution and noise.
GM: And I know there have been previous studies looking at people, for instance, in sleep labs where obviously you have laboratory conditions but they don’t tell you what’s going on in real life. I wonder if this is slightly unprecedented because you’ve had to go to all the effort of putting noise meters in people’s homes, measuring their blood pressure whilst they’re in situ in bed. This is actually quite hard fieldwork to do isn’t it?
JL: It is very labour intensive and that’s why we only included 140 people. It took quite a long time to do that, as you say. It is labour intensive. And that’s possibly also one reason why it hasn’t been done before.
GM: I have a feeling the answer to the next question is, look I’m a doctor, I’m not going to get into the policy side of things. But I still have to ask you. Are the health effects here so serious do you think that something really should be done about aircraft noise?
JL: I think that the answer to that is that this is one or a couple of studies that we’re now talking about and of course you can’t build policy on just a couple of studies. Obviously if we believe that night time aircraft noise is a real problem, which I think this study shows, the obvious from a health point of view would be to try to eliminate this somehow. Either making the aircraft quieter, if that’s possible. Or of course have night time flight bans, which are in place in several airports in Europe already.
GM: Dr Lars Jarup there with his research on the health effects of aircraft noise, which unsurprisingly made quite a few headlines around the world. But now let’s have some headlines from around the Imperial campus.
Headlines from around the College
GM: When is evolution a slow gradual process and when does it progress in giant leaps? Imperial research in a species of African butterfly has given insights into understanding how the latter form of evolution might work. The Mocha Swallowtail butterfly, which is harmless, has evolved patterns on its wings that resemble those of its poisonous cousins thereby warding off predators. With the obvious ever present dangers from hungry predators it would seem that the Mocha Swallowtail had no choice but to evolve this cunning adaptation very quickly. And now researchers from Imperial’s Department of Life Sciences, along with colleagues just down the road at the Natural History Museum, using molecular tabs and DNA sequencing have nailed down the area on the butterfly’s genome that brings its defence mechanism about. This unique insight into the butterfly’s genes could reveal whether or not the Mocha Swallowtail’s mockery really did come about by a sudden evolutionary leap and that in turn could yield some brand new thinking about the genetics of evolution in the fast lane.
And when a butterfly flaps its decoy wings in one place at Imperial, elsewhere across the campus, in the Department of Earth Science and Engineering, researchers come up with some new thinking about predicting earthquakes. Under certain circumstances the way that tectonic plates shift in practice differs from what’s predicted in theory. And that’s a bit of a problem if you’re trying to accurately forecast the location and severity of quakes. So the team took a closer look at what happens in the Earth’s mantle, a layer of hot churning rock beneath the crust. Older more dense plates sink down into the mantle differently to how younger less dense plates do. And by using mathematical models that account for these variations and then matching them to real life observations, scientists have refined their predictions of how the plates shift in the mantle. And that, they reckon, could help them determine earthquake risks in regions where none previously have been recorded.
And that mantle piece wraps up our headline section for this month. Remember that you can stay right up to date with the big science stories from Imperial before the rest of the media gets hold of them, and probably before I even do, by hitting the press office website. And that’s at imperial.ac.uk/news
The science of smell
GM: Well, in a moment the weird world of metamaterials but ahead of that a roam around the realm of aroma and the Imperial chemical biology professor who’s working on technology for analysing various odours. An electronic nose would have all kinds of applications in science and medicine but as our reporter, Vivien Lee, has been finding out there’s still a place for creatures with highly evolved senses of smell. In this sideways glance, or should I say sniff, into the science of smell. Vivien, who recently graduated from our Science Communication MSc, has visited Imperial’s Institute of Biomedical Engineering and explored the worlds where high tech sensors meet the sweetest scents from a traditional style perfumer. Her quest begins in windswept rural Scotland.
Vivien Lee: I’m at AromaSciences, also called the Perfume Studio, in a village called Mellon Charles about two hours drive west-northwest of Inverness in Scotland. I’ve come all the way here to speak to someone who’s both a scientist and a perfumist.
George Dodd: Hello, this is George Dodd the only working perfumer in Scotland. When it comes to the sense of smell I guess everything to do with smell, making perfumes and teaching people about perfumes and doing research on the sense of smell, has really been one of the major passions of my life. One of the big surprises of the human genome project was to discover that five per cent of our DNA is actually devoted to smelling. You take so much in the way of smell for granted. The joy of the first warm spring day. The smell of cut grass. A lot of the emotional pleasure, the emotional colour, of our surroundings actually comes through smell. We’ve lost the art of smelling particularly in areas like medicine.
Tony Cass: I’m Tony Cass. I’m deputy director of the Institute of Biomedical Engineerin g and professor in chemical biology at Imperial College. I’m an analytical chemist by training and I got interested in odour as an analytical target developing sensors that could measure different types of odours. Certain diseases are associated with certain patterns of volatile molecule. So, for example, if you have liver disease you’ll generate certain organic molecules which have a distinctive odour. And tradition a l ly docto rs would smell your breath as part of the diagnostic process. That’s a very inexact science so if you could more objectively measure volatiles in, say, exhaled breath, that could be used then as a diagnosis for a particular disease. And the advantage of that is that you wouldn’t need to do things like take blood samples or have any kind of invasive probe. You just ask someone to breath into a box and measure the volatiles in their breath.
GD: We’re as sensitive to pheromones as most animals are. To put this in perspective, if you train your sense of smell as a human you’re as good as most animals we know. Amazingly, we can go a long way to being a sniffer dog. Dogs know where smells are. Most smells aren’t in the air. Most instant smells are around surfaces so they sniff surfaces.
VL: I’m at Brockwell Park in Brixton, London with another smell expert, Ellie. Today Ellie is going to use her expert knowledge to show me some of the hidden smells that exist all around us but which we normally take for granted. So Ellie is sensing the place now to try and find some smell for us. Oh, I think Ellie has located something on the ground. I’m going to have a smell of what she’s found and then try and describe the smell back to you. Quite strong scent of grass. I’m just going to sniff another bit next to it where she didn’t smell and see what the difference is. Okay, there is a difference. The background that Ellie just smelt has got a very strong grassy smell to it but the other part next to it didn’t smell as strong. Ellie, shall we look for somewhere else?
GD: Sometimes get down on your knees and explore the world like a dog. And if you do that you’ll find there’s an amazing amount of smell information we’re not accessing because culturally we choose not to. In all kinds of societies, West Africa, the wild jungles there, the hunters can track game using their sense of smell. They will kneel down and sniff, sniff, sniff.
VL: So we can follow a dog around? That gives a new meaning to the term guide dogs. We’re crossing a big field and some parts where the grass is shorter. She’s pulling me along running really quickly. Ellie’s ears are flopping in the air. I see lots of rubbish ahead of us. Oh, there’s been a takeaway here and all the rubbish is just scattered over the place. Tinfoil and cardboard covers, which Ellie is sniffing so I’m going to have a go now and get down on my hands and knees again. Well, my sense is obviously very rubbish because I can still smell the grass. The grass is much stronger than anything else. Has there been a bit of food there? I can see it but not quite smell it. So what I’m going to do now is I’m going to take out my little spray bottle of water that I prepared earlier. I’m going to spray the spot and see if I can get more scent out of it. I can certainly smell something and it smells something like barbeque sauce. The water bottle has definitely brought out the smell. Now Ellie is licking the cover. What or where do you think is the future for the science of smell?
TC: In terms of the diagnostics applications you can build the sensors to measure volatiles. So the question is how much will it take to build up a database of different diseases, different smells, different precision of diagnosis? And the real utility will come once we have a volatiles database that we can link directly to particular diseases.
GD: Working with a pharmaceutical company we’ve invented the world’s first medical perfume that really addresses areas like mild depression, which are very clinically significant. The majority of people taking antidepressant drugs don’t need foreign molecules floating around their bloodstream causing side effects. We can access the emotional centres of the brain through the sense of smell without getting other molecules into the body. Using molecular engineering we can invent a smelly molecule that’s actually engineered out side effects. We now actually have something that’s been through a clinical trial and is addressing very important psychological needs of people for a huge world market.
VL: Ellie is a black five month old Labrador. So, Ellie, thanks for taking time out to show me around. I learnt a lot today and done those things that I wouldn’t otherwise have had the opportunity to do and show me what your world smells like.
GM: That report from Vivien Lee on the science of smell.
Metamaterials and the perfect lens
GM: Well, finally in this podcast, from the olfactory to refractory and specifically materials with strange refractory properties. That’s the research interest and has been for many years for John Pendry, who I think it’s fair to say is one of the longest serving and most distinguished scientists we have here on campus at Imperial. John, people may have heard of these rather exotic materials already but for those of us who haven’t what do you mean by a material specifically with a negative refractive index?
John Pendry: Well, refractive index of course describes how a material bends light as it enters that material. And normally it bends light the way you’d see a pencil going into water. It has it bending at what we call a positive angle. But if the pencil seemed to bend back on itself, as though it were about to snap, then that’s what we mean by a negative refractive index. And put like that it doesn’t seem so startling. But recently we’ve discovered that there are hidden links of the refractive index to other sorts of science.
GM: And I suppose that’s where the really exciting aspect comes in, especially because there are no natural materials that have this strange negative refractive index.
JP: That’s right. For sometime we’ve been working on an extraordinary type of new material called the metamaterial. It has the property that the way it refracts is determined only partly by the chemical composition. Really more due to the way it’s microstructured. So these metamaterials have structure on a scale much less than the wavelength of light. So the light doesn’t see the individual bits of the structure but the way that structure is composed dictates the way that the light responds to it. But to come back to this business of why a negative refractive index is interesting and different. It relates to a strange relationship that Einstein found many years ago in his general theory of Relativity. As you probably know, he predicted that gravity bends space, it distorts it, and that’s why stars bend light. They appear to have a refractive index so it’s really space that’s bent around them. And so if we come back to ordinary refractive indices, then if you make them negative then that’s equivalent, as far as the light is concerned, to having negative space. And I think you’d agree with me that that’s a little bit extraordinary. And that’s why we’re so excited about it.
GM: And I suppose the same wonder that was ascribed to Einstein’s revelations in the early Twentieth Century about the way that gravity could deflect light in these incredible ways, you know, that can apply also to the wonder associated wi th these negative refractive index materials that you’re talking about?
JP: Yes, it certainly caused a lot of astonishment and a certain amount of abuse as well from people who didn’t believe in it in the first instance. One of the more remarkable things you can do with negative refractive materials is that if you really believe that they are a bit of negative space then they’re going to behave like optical antimatter. They’re going to annihilate a bit a space next to them. In a way it’s just a fancy way of saying that they can focus light. Because if you have a distance which is positive and then a distance which you see also as positive but really the light sees as negative because it has this funny n egative refractive index, then those two materials together, when you add them together, it looks as though there’s nothing there. That of course means that you’ve brought the object right to the image plane. And this is one way of thinking about a lens which Veselago, the man who proposed negative refraction, suggested some time ago. But it also gives another insight into that lens, which Veselago didn’t see but I predicted about five or ten years ago, which is that the lens can be made to be perfect. That is to say it doesn’t suffer from the restriction of resolution of wavelength which normal lenses do. So the ‘perfect lens’ is the consequence of negative refraction and the very unusual way in which it focuses by simply annihilating the space between two objects.
GM: So what kind of applications would you see for this notion of the ‘perfect lens’?
JP: The ability or inability of light with ordinary lenses to focus better than the wavelength is a huge barrier. Light has to operate on this scale of a wavelength, which for visible light is about half a micron. And we often use light these days in conjunction with electrons, so we talk about optical electronics. Now, the electron works on a length scale of 30 nanometres which is the finest line in a computer chip these days. That’s a thousand times smaller than the light operates on. So it’s a conversation between a mouse and an elephant. And it stops us from doing all sorts of things. For example, the first CDs to store music, about an hour’s worth of music, 600 megabytes of data. And now we have the Blu-Ray of course which 60 gigabytes of data and you can get a high resolution picture from that. And the difference is simply that you’re using a shorter wavelength. CDs work with infrared light, longwave length. Blu-rays, blue light, shorter wavelength. But there’s a limit to how short you can make the wavelength. But of course if you made it really short the radiation would be uncontrollable. X-rays are very difficult to focus and it would cost a lot to make a CD that worked with x-rays. So if you could short circuit that problem and find a way of focusing light to lessen the wavelength you would be able to do something like make DVDs with much higher density. But beyond that you would be able to have a much more flexible interface between light and electrons. So we would start to do all sorts of exciting things with optical chips if we could concentrate light into a much, much smaller volume than we can at the moment.
GM: And I see that throughout that sentence you were using the word ‘if’. So how conditional is this? I mean basically do we have the technology now to make these devices or is that still someway off?
JP: There’s been an enormous amount of progress in nanotechnology. And indeed we have several initiatives on that nanotechnology in this College. But it’s work in progress. What we can do very easily these days is to make two dimensional structures. So you take a surface, typically of silicone, you pattern it, you can make all sorts of wonderful structures on it. But to control light you’ve got to do more than that. Light is essentially a three dimensional object and what you have to do is to make a three dimensional structure. You can sort of do that by stacking up a lot of 2D bits but that’s a clumsy way of doing it. And nanotechnology in three dimensions is much more difficult. People try to get small objects to recognise one another and form into some specific structure. People have even used DNA stuck to little gold nanoparticles to try and make them recognise one another. And to some extent that works but we’ve a ways to go yet. But we’ll get there I think.
GM: Professor Sir John Pendry. And that’s about it for this month but do come back again in April. This podcast is available on the first working day of each month. But before I go I think I should mention that this music is called Lila and it comes from Ozgur Buldum. Check out his website at ozgurbuldum.com. Lots of fine music up there. Well, I’m Gareth Mitchell. The producer this month was me actually which means I’d better tell myself to wrap it up and point out that this podcast is a collaboration of the Imperial Press Office and the Science Communication Group. Thanks very much for listening to this edition. Hope you enjoyed it. But until next time, it’s goodbye for now.