Science and technology can catch criminals and tackle terrorism. This week, we're exploring two ways to sniff out concealed explosives and a new technique to lift fingerprints from surfaces that have been cleaned or burned. In the news, a new way to halt Huntington's disease and how to identify the influential online. Plus, could gene therapy cheat a DNA test?
In this episode
01:24 - Plastics to Detect Explosives
Plastics to Detect Explosives
with Dr Graham Turnbull, University of St Andrews
Chris - With the advent of global terrorism, it's become apparent that people will go to extreme lengths to conceal bombs. So quickly and accurately detecting trace amounts of explosives could not only save lives, but it could make air travel safer, quicker and a lot more convenient.
Now, researchers at St. Andrews University have invented an explosive-detecting plastic that could be used at airports and even on mine fields. Dr. Graham Turnbull is the inventor. He is with us. Hello, Graham.
Graham - Good evening.
Chris - So tell us, how did this work get started, plastics to pull out explosives? I've heard of plastic explosives, but not the other way around.
Graham - We're using plastics to find explosives. So, in St. Andrews, we're developing a set of materials called organic semi-conductors for a range of different applications in optoelectronics. These materials are a special class of plastic that unusually can conduct electricity, which is an unusual property for a plastic, but also can be stimulated either by illuminating it with light or by passing electricity through it to emit light. So these materials are now being used for a range of applications as plastic light emitting diodes in Samsung mobile phones, plastic solar cells, and plastic lasers. It turns out the same set of materials can also be used as a sensor. And following on from some research by a group at MIT, we started to look and see how we could use our plastic lasers as very sensitive sensors for detecting explosives.
Chris - So what's the technique then that the laser shines on the plastic and it changes the electrical activity of the plastic, but if the explosive is present, you get a different signal or something similar?
Graham - It's something along those lines. Essentially, what our sensors are doing is they're replacing a sniffer dog's nose. So, we operate our plastics by illuminating them with ultraviolet light and then the plastic then re-emits that energy as visible light. Now, if we take a thin film of these light emitting plastic materials and we bring a small number of TNT molecules or molecules similar to TNT into contact with the film, the TNT molecules can interrupt this light emission process. Essentially, it switches off the light. So if there's explosives present in the atmosphere surrounding the plastic film, the light emission is switched or made dimmer. If you blow clean air across the film then the light emission returns. So it's a reversible process that can detect the presence of very, very low concentrations of explosive molecules in the surrounding atmosphere around the film.
Chris - How specific is it? Because you mentioned TNT - trinitrotoluene - the stuff that's in the majority of the 100 million or so land mines that we know are lurking out there somewhere around the world, but other explosives are used too and people are getting cleverer and cleverer in terms of the explosive cocktails they will use. So, is it just TNT or could it work with other chemicals as well?
Graham - Okay, so as you say, TNT is the major component of all military high explosives, but also, when you make TNT, you also fabricate other similar molecules like DNT - dinitrotoluene instead of trinitrotoluene - and various analogues. This technique is able to detect a wide range of these nitro-aromatic molecules. It also has potential to detect some of the other plastic explosive molecules. The process works on a difference in energy states between the light emitting plastic and the explosive molecules, and essentially works by switching off the light emission by electrons hopping from the light emitting plastic onto the explosive molecules. So, it can detect a wide range of different materials. It doesn't intrinsically discriminate between those, but that's one of the next steps that we're trying to look at, to get selectivity.
Chris - What about the problem of selectivity? Because one of the big holdups at airports is that people might have something - their shampoo or something - that triggers this agent and in fact, it's completely innocuous? So, is there a false positivity with this and if so, is that a problem or is it at a level that is going to be tolerable?
Graham - I think with all sensing approaches, there is some danger of false positives. There are things that could be in your luggage that conceivably could trigger these things. Angina sprays contain trinitroglycerine in them in very small quantities, but in general, we believe that it's a workable solution. In a different context which we're interested in, in the area of land mine clearance, which has security implications as well because they're in former war zones, there's a lot of explosives lying around that terrorists in principle could get their hands on. So clearing land mines has a security benefit for the western world.
Chris - How would the technique work though and what would you do? Would you have a box where some of the plastic being illuminated by the UV is in there and is being watched by a camera for example and a gas stream is pulled across your luggage or across the mine field, and that air then interacts with the plastic?
Graham - That's right. So that's the sort of the approach. We take one of our little plastic lasers which are postage stamp-sized lasers and you essentially can draw some of the air across the plastic film, the little polymer laser, and you then monitor the amount of light emission that is being emitted.
Chris - And so, it is very portable. So, the concept of mounting this on some kind of mobile device that could explore a mine field and find hot spots of the gas that could signify an explosive buried underground coming up, that's not beyond the realms of possibility.
Graham - Not at all. Our plastic lasers are very compact. Within a collaborative project in the UK called Hipix, we've been developing very miniaturised compact versions of these plastic lasers where essentially, we take a high power light emitting diode, we remove the plastic dome lens, and replace it with one of our plastic lasers. And so, the actual source can be the size of an LED. In other work in the Hipix programme, we've also been developing fluorescence based explosive sensors that are based on two silicon chips. So these are all laboratory prototypes, but they show a lot of promise for being able to make very compact sensors.
Chris - And relative to a sniffer dog's nose, where would your plastic sit, more sensitive, less sensitive, or about the same? And what's the absolute numbers in terms of parts per billion or so of explosives that they can pick up?
Graham - Sniffer dog's noses are regarded as the gold standard in sensitivity. I'm not sure I have a quantification for how low they can go in sensitivity. This sort of approach, is the one that gives you the closest to the sniffer dog's nose in sensitivity. In the laboratory, we routinely do tests on new materials with parts per billion quantities of TNT in the air, and the technique can go much lower than that in terms of sensitivity.
Chris - But unlike a sniffer dog, I suppose your plastics won't get tired, don't need to play with a ball periodically to keep it interested!
Graham - That's right. A sniffer dog needs to be playing a game in order to detect explosives and in practice - depending on the environmental conditions the dogs are working in - they may typically work for half an hour at a time. So for long, repetitive searches, or if you want to go into very hazardous areas, there are problems with using dogs in those sorts of conditions and so, a high tech alternative that doesn't get bored is attractive possibility.
10:14 - Seeing through the Subterfuge - Spectroscopy through packaging
Seeing through the Subterfuge - Spectroscopy through packaging
with Professor Pavel Matousek, Cobalt Light Systems
Helen - Some substances, including drugs and explosives, can be concealed by dissolving them in another liquid such as an innocent looking bottle of spirits or packaging them inside an opaque container. This makes it very hard for security or border forces to find them without having to open and potentially compromise the contents. But now, Cobalt Light Systems, a company spun out from research funded by the STFC have developed a device that can see through packaging and tell you exactly what is inside using a technique called Spatially Offset Raman Spectroscopy or SORS. Professor Pavel Matousek developed this technique at the Rutherford Appleton Laboratories near Oxford. He's the Chief Scientific Officer at Cobalt Light Systems and he joins us now. Hi, Pavel. Thanks for joining us.
Pavel - Hi, Helen.
Helen - Well perhaps we'll just start off by saying, what is SORS? What is it and how does it work?
Pavel - So, SORS is basically is a laser spectroscopy technique. It's based around well-established technique called Raman Spectroscopy which provides a high chemical specificity or a high ability to accurately determine the chemical composition of a substance we are probing, but with a twist. That twist, allows us to apply to a much wider range of containers which then, as a consequence, enables us to satisfy requirements of regulatory bodies for use of this technique at aviation security to determine the content of unopened bottles.
Helen - So, what is it? It's a type of laser light, is that right?
Pavel - Indeed, so what we do is to shine a laser light onto the sample, similar to a laser pointer, but slightly higher power. When photons hit the sample, they scatter - most of them elastically, therefore they don't exchange energy with the material. But a tiny, tiny fraction of these photons activate vibration within the molecules we are hitting. And as a consequence, they lose the same amount of energy they use to activate the vibration motion and then as a consequence of that loss of energy, they change colour. And a single molecule can have a number of energies which it can accept. These are discreet and therefore, if you examine the spectrum of the photons which are emitted back at us from the sample, looking at the characteristic lines and different colours and their intensity pattern, we can determine as a fingerprint, what chemical component we are looking at.
So, this is the basis of the Raman Spectroscopy technique. The twist we are using is that we are actually not collecting the signal from the zone which is illuminated by the laser light, which you would do in conventional Raman Spectroscopy, because this would result in you being dazzled by the surface of the sample you are probing, for example, the container wall. We probe several millimetres sideways, where we are seeing much more clearly the substance inside and we are not overwhelmed by the signal coming from the surface. This is a situation similar, for example, to the stars in the sky. In the day, you don't see them because you are dazzled by solar radiation. However, if you wait long enough for the night, you can see stars clearly, or if you have a solar eclipse, you can see them clearly too. In a similar way, we are going sideways and suppressing in effect the dazzling radiation coming from the surface.
Helen - So in a sense, you're being able to see through the container into what's inside it. How can you tell if something is actually dissolved in there, something that you're interested in or that security people are interested in?
Pavel - Well, we basically examine that spectrum, that pattern of lines which we are detecting and that informs us about the content. If we have a mixture, you would see the content of the solvent and solute very clearly. So that's what we are doing and we are comparing those fingerprints against a library which holds prohibited substances which could be explosives. If an explosive is found, we will sound an alarm. A unique feature of this technique is we reach extremely low false alarm rates. So that means if you put a benign bottle into the system, the false alarm rate can be sounded in only half a percent of cases whereas conventional technology would have false alarm rates at least 10 times higher. Therefore, disruption to airport operators is much, much lower. This is an insignificant rate of false alarm if you like.
Helen - So it's not going to set the alarms off when they shouldn't go off, but how sensitive is this as a technique? Will it actually detect small quantities of the stuff that we're interested in?
Pavel - It can certainly determine or detect the quantities which are relevant because trace quantities dissolved in something are not significant. It can detect quantities maybe at a level of half a percent or 0.1 or 1%, but those are concentrations which are relevant for explosives to be viable. And in security settings, this satisfies the requirements of the regulatory body, this instrument passes the so-called ECOCK test which is a European test which is required for this type of technology to be deployed at airports and passes with flying colours.
Helen - And is this sort of technology something that we will see soon and is it quick enough that everyone can be tested, or is it going to be a case of still testing a sample of a number of people who come through security, or it will be a sort of a routine thing that we will all have? Any liquid we have in our bags zapped by your machine and they will tell what's inside all our bags?
Pavel - The speed of the machine is adequate to test every bottle which contains a significant amount of liquid. The test itself takes 5 seconds, so the idea is you have the x-ray machine and if the x-ray machine identifies something suspect in your bag, they would take it out, put it inside the machine and our machine would verify that the content is benign or will sound alarm if there's an explosive found.
Helen - And presumably, again, if terrorists and people who are trying to get these things through come up with some new molecule that isn't in the database then that's going to be a problem. You'll have to keep up with the technology as that advances as well.
Pavel - It's of course up to security authorities to maintain the library databases relevant to this indeed. They would have to update the database as we go along in order to have an effective device or screening device.
Helen - And finally, will this mean that we'll be allowed to take more liquids with us on the plane in the future? So, no longer restricted to - is it 100 mls we're allowed now?
Pavel - Indeed. At the moment, it's 100 ml. The planned anticipation is that this ban, or restriction would be lifted in April 2013 and we are expecting the final verdict on this by European Commission later this summer, we don't know whether this ban is going to be lifted in April whether it's going to be staged one year later.
Helen - We'll wait to find out and I personally hope so because I always end up having to drink all my water before I go to security and that's...
Chris - And then you want a wee all the way through the flight!.
Helen - Exactly! Thanks so much. That was Professor Pavel Matousek from Cobalt Light Systems telling us all about SORS and how it could transform the way we experience going on an aeroplane.
18:08 - Microbes maketh a healthy immune system
Microbes maketh a healthy immune system
Any old bacteria won't do: to be healthy, an animal requires a unique 
consortium of microbes in its intestines, US scientists have revealed.
It's been known for some time that mice raised in a sterile environment, meaning that their intestines remain uncolonised by microorganisms, are paradoxically less healthy than equivalent animals reared in a natural, germ-laden environment.
Some species even depend absolutely upon microbial colonisation in order to develop and reproduce at all. Without the help of the cholera-relative Vibrio fischeri, certain tissues don't develop in squid, for instance, and tsetse flies that fail to team up with the bacterium Wrigglesworthia glossindia lack key vitamins required for fertility.
These and other observations have led to the formulation of the human "hygiene hypothesis", which holds that rising rates of allergy and autoimmune diseases amongst western populations reflect an obsession with sterility and a failure to engage effectively with the microbial world. This, scientists say, hampers the development of the immune system, putting people into a pro-allergic state.
But now, new research presented this week in the journal Cell by Harvard scientist Dennis Kasper and his colleagues suggest that just mere exposure to a microbial milieu isn't sufficient. Instead, what organisms require is colonisaton by a unique collection of highly-specific microorganisms unique to a given species.
The team made the discovery by colonising initially germ-free mice with either normal mouse or human intestinal microbes. A third group of animals were left uncolonised as controls.
Both colonised groups developed similar levels of bacterial loads in their guts, the team found. But when they compared the immune systems of the two, the animals colonised with human flora had fewer white cells known as lymphocytes in their small intestines, they secreted lower levels of defensive antibodies and proteins, and they had fewer immune presenting "dendritic" cells in the gut lining.
And compared with the animals colonised with normal mouse bacteria, those carrying human microbial flora were also highly vulnerable to Salmonella enterica infection. In fact, the human-bug colonised animals were equivalently unhealthy and as vulnerable as the germ-free uncolonised mice.
As Hachung Chung, one of the research team puts it, "Despite the abundant and complex community of bacteria that were in the human flora mice, it seemed like the mouse host did not recognise the bacteria."
The interaction also appears to be highly specific since repeating the experiment even with rat, rather than human, bacteria produced the same result, suggesting that millions of years of co-existence between microbes and hosts has produced animals pre-programmed to depend upon the presence of certain bugs for the immune systems to develop and function normally.
"This raises serious questions regarding our current overuse of antibiotics, as well as ultra-hygienic environments that many of us live in," says Dennis Kasper. "If the bacteria within us is specific to us and necessary for normal immune system function, then it's important to know if we are in fact losing these vital bacteria. If that is the case, then this is yet further evidence that the loss of the good bacteria is partly to blame for the increased rates of autoimmunity that we are now seeing."
22:37 - Pitcher plants use raindrops to catch ants
Pitcher plants use raindrops to catch ants
Scientists have discovered a new way that carnivorous plants catch their prey, using the power of raindrops to flip insects into their trap.
Tropical pitcher plants have evolved specially adapted leaves that form a deep bowl, partially filled with digestive fluids, and with a little lid projecting over the top to stop the plant from getting filled up with rainwater. The plants produce nectar to attract insects and set various traps to catch them - the inner wall of many pitchers is covered in platelet-shaped wax crystals that become extremely slippery when wet.
The pitcher plant, Nepenthes gracilis, is unusual because they also produce crystals on the underside of their lids - and researchers wondered whether the lid itself is involved in helping to trap prey. After all, for an insect to cling upside down, right over the trap, is a very precarious position to be in.
Watching these plants in northern Borneo, Ulrike Bauer of the University of Cambridge and her team, saw ants happily walking upside down on the pitcher plant lids and not falling in. Then, during a rain shower, they happened to spot a ladybird crawling beneath the pitcher lid to take shelter only to be flicked by a raindrop into the trap.
To test whether lids really are helping to trap prey when it's raining, the team took some pitcher plants and ants into the lab and doused them in showers of artificial rain.
They found that around 40% of all the ants visiting the pitcher were caught when it rained. And when the rain was switched off, no ants fell into the traps showing that the lids aren't becoming more slippery with increased humidity after it rains.
Performing the same tests on pitcher lids cut off and mounted with a paper clip gave a very similar result. When it's raining, ants find it much harder to hang on.
Back in the field, adding a smear of anti-slip silicon to the underside of pitcher lids made them much less efficient at catching prey in the rain.
The paper appears in the journal PloS ONE and is accompanied by video clips of the ants having a tough time getting to grips with the pitcher plants in the rain.
So it seems that Nepenthes gracilis has evolved to be a lid specialist - they make more nectar in their lids than other pitcher plants, and the team also found the crystals on their lids have a different microscopic structure than other plants, letting ants hang on in dry conditions, but the vibration of raindrops is enough to catapult them into the digestive juices. It's thought that the ants that escape when its dry act as scouts returning to their colony and bringing back lots more ants. And living in very rainy places, chances are that when the ants return, they could find that the heavens have opened and the pitcher plant is a much more dangerous place to be.
25:43 - Identifying the Influential
Identifying the Influential
with Prof. Sinan Aral, New York University
Chris - Are you a leader or are you a follower? An intriguing new study shows how you can identify influential people from their activities on Facebook. Sinan Aral is at the New York University Stern School of Business. He's with us now. Hello, Sinan.
Sinan - Hi.
Chris - So first of all, what were you trying to prove with this study?
Sinan - Well, in essence, finding influencers or as you said influential people
is sort of all the rage today. Companies like Klout are trying to measure influence scores for people on social networks like Facebook and Twitter, but beyond marketers, managers and policy makers are more generally interested in how behaviours spread through society. In this paper, we present a general method for measuring influence susceptibility in networks and the main contribution of the method is that it avoids known biases in current methods such as homophily bias. Homophily means that we tend to make friends with people like ourselves. For example, if two friends adopt a product or a behaviour one right after the other, current methods have a hard time distinguishing whether it's because of pure influence; one friend influencing the other, or if friends simply have similar preferences and thus, behaves similarly.
Chris - And obviously, the world doesn't work like that because an influential person isn't just influencing their friends. They have the ability to influence a range of different demographics.
Sinan - Exactly, so what we did was we applied this general method to measure influence and susceptibility in the adoption of a commercial product on Facebook among 1.3 million users and we were able to recover influence and susceptibility scores that aren't subject to these known biases like homophily bias.
Chris - Okay, so can you talk us through what you actually did? How did you recruit the people and then what actually happened to discover this?
Sinan - We worked with a company that developed a commercial movie application where you can rate movies and buy movie tickets, and read about directors and actors. And as people adopted this application, we randomly assigned them to send messages to their friends in a random manner. So, every time you did something on the application like rate a movie or talk about a celebrity or something like that, it would randomly select a subset of your Facebook friends to send a message to. And this randomization removed the selection bias of people selecting friends with similar preferences or selecting people who they knew would be specifically susceptible to influence. And with this randomization, we were able to measure, for example, how your characteristics or your traits, your age, your gender, your relationship status on Facebook or anything that we could observe about you on Facebook, was correlated with your likelihood of responding positively and adopting this application upon receiving this influence mediating message. And because the messages were randomised, we could make causal inferences about whether this message was causing you to adopt or not.
Chris - What about the other way around because that's looking at people how they respond to receiving the message? What about in terms of the people who actually send the message? Are you inferring whether they're influential or not based on what the response of the recipients is?
Sinan - Exactly, so we estimated a statistical model that estimated both influence and susceptibility simultaneously while these random messages were being sent to people from their friends.
Chris - So, spill the beans then. What makes someone highly influential? Is it just that they're very well connected or is there something special? Is there some special recipe that means that if they say something on Facebook, everyone's going to be talking about it?
Sinan - We found that it's not just how many people you're connected to and lots of people have been focused on that in the past, how many followers you have, but more importantly, it's whether you persuade your followers to change their behaviour. What we found was that in the context of this particular movie application when we applied this method, that men were more influential than women, that women influence men more than they influence other women, that older people are more influential and less susceptible to influence than younger people. Married people are the least susceptible to influence and influence and susceptibility trade off. Meaning, people who are more influential tend not to be susceptible and people who are susceptible tend not to be influential.
Chris - Isn't this just what we see in politics though? If you take a look at the Houses of Parliament here in the UK or you look at Congress in America, do you not already see this playing out we're just basically proving what we already know?
Sinan - Not exactly. So, it's not clear whether or not influential people should be more susceptible or whether older people should be more influential than younger people, and my intuition is, that as we begin to apply this method across different behaviours and products, that we're going to see different types of influence emerging in different contexts. In a different context, it could be that women are more influential than men or that younger people are more influential than older people - the opposite of what we find here, and the value of this paper is it provides a method to measure this in any context. I'm really excited to see what we might find for other types of products or behaviours.
Chris - If we could just look at the question of the men and the women, do you think the fact that it was movies might have led you to conclude that men were more influential than women in this context? Do you think if you've done something on a subject that women are regarded as more authority figures in, you'd have seen the flip side of the argument?
Sinan - It very well could be true, absolutely. So, you could imagine other contexts in which women might be more potentially influential than men, but this, in every context is an empirical question and the benefit of this measure is that we can now talk more scientifically, more rigorously about influence and susceptibility in a causal way.
Chris - And do you see this being applied to job interviews any time soon in a sense that you come from your job interview and someone decides they want management material or they want someone who'll be well-trained and toe the line and it subjects you to this sort of analysis and you can put people into those sorts of categories?
Sinan - Yes, I think that it could certainly be applied to those types of situations, but I actually think it's much broader and it's interesting for other types of question as well. For instance, it's not only about targeted advertising or jobs. We're also now working on applying these same methods and the same science to promote HIV testing in Africa by trying to understand how we can use peer to peer influence to spread positive behaviours in society - diet, exercise, political awareness and like I said, HIV testing in South Africa.
33:15 - Blocking degenerative brain disease
Blocking degenerative brain disease
Huntington's Disease, a fatal inherited degenerative brain condition, can be controlled in animals using DNA technology, suggesting it might be reversible in humans too.
Huntington's, which affects about 1 person in ten thousand, is a genetically-transmitted disease of the nervous system that leads to behavioural changes and abnormal movements. These symptoms usually begin after the age of 40.
The nervous systems of sufferers show loss of grey matter, with the brain shrinking by up to a third of its volume once the disease has run its course.
The cause of this degeneration appears to be the accumulation inside nerve cells of a substance called polyglutamine. This occurs because, in carriers of the condition, the gene linked to Huntington's - called huntingtin - contains a repeating sequence of three genetic letters - CAG - that has been abnormally duplicated, making it much longer than it should be.
Repeated CAG signatures like this tell a cell to link glutamine molecules together; unfortunately these glutamine chains are then not easily disposed of, so they inexorably accumulate within the cell with ultimately toxic effect.
But now a paper in the journal Neuron has shown that the application of a technology that won a recent Nobel prize - RNA interference - to the problem can potentially arrest the disease.
University of California San Diego scientist Don Cleveland and his colleagues have been working with mice endowed with a copy of the abnormal human Huntington's gene.
These animals manifest a similar degenerative disease to human sufferers, developing abnormal movements and behavioural deficits from a young age.
The UCSD team constructed and infused into the cerebrospinal fluid around the brains of these animals an RNA sequence that is the genetic mirror image of part of the Huntington's gene. When taken up by cells, these short pieces of genetic material pair up with the products of their matching gene, in this case the huntingtin gene, and cause the genetic message to be shut off so the gene is not expressed.
When administered to the test animals over a two week period, the therapeutic genetic sequences produced a 75% reduction in the levels of expression of the abnormal gene and an improvement in symptoms and disease progression that was still measurable months later.
Tests on a rhesus monkey also suggest that the approach could be delivered to humans using a spinal cannula like that employed to deliver epidural pain relief during labour.
Concluding their paper, the researchers point out that "transient suppression of huntingtin can be sufficient to ameliorate disease for an extended period of time... this finding opens up the provocative possibility that transient suppression of huntingtin can lead to a prolonged effect in patients."
35:49 - Transmitting H5N1 and A 50 Gigapixel Camera!
Transmitting H5N1 and A 50 Gigapixel Camera!
with Ron Fouchier, Erasmus Medical Centre; David Brady, Duke University; Steve Nowicki, Duke University; Bob MacCallum, Imperial College London
Transmitting H5N1
The H5N1 bid flu virus could evolve into a form that is transmissible in humans according to research published in the journal
Science.
In this controversial project, Ron Fouchier from the Erasmus medical centre in the Netherlands infected ferrets with versions of the virus that were genetically modified to increase their affinity to mammalian cells and monitored how the virus continued to mutate upon infection.
The team found that just five mutations in total were enough for an airborne and transmissible strain of the virus to develop.
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A 50,000 Megapixel Camera
A 50,000 megapixel camera has been created by scientists at Duke University in the US.
Using improved optical elements, electronics and processors, the camera uses an array of 98 microcameras within a spherical lens each capturing visual information from a specific point. Computer processors then stitch the information together to create images covering a 120 degree field of view with 5 times greater resolution than the human eye.
David Brady led the work published in
Nature.
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Songs through the Noise
The calls learned by songbirds vary in response to noise in their environment.
Publishing in the journal
Biology Letters, Steve Nowicki from Duke University investigated how noise from nature and humans affects the calls learned by baby songbirds by raising 9 male swamp-sparrow nestlings in a sound-proof room and exposing them to recordings of song types sung by adult males of their species.
The songs played were either clear...
Click this button to hear the clear birdsong
Or degraded...
Click this button to hear the degraded birdsong
The team found that when the birds matured and began to sing, only the clear recordings had been learned.
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Selecting your Music
And finally, the process of natural selection has been used to compose and refine pieces of music enjoyed by the masses.
The website Darwin tunes, which has been online since 2009, invited online users to listen to a range of short audio loops and rate them, with the highest ranking then combined to produce the next generation of sounds for rating again, resulting in over 2500 generations in their paper in the journal
PNAS.
One of the more popular loops was...
Click this button to hear the popular song
Each successive generation created more recognisable and rhythmical versions of the tunes enabling the sounds to evolve from noise to music.
Bob MacCallum from Imperial College London led the work published in the journal PNAS.
If you'd like to add to the next generations of music, which has now reached nearly 4200, visit
darwintunes.org.
40:54 - Medical Diagnostics in a Star Trek Sick Bay - Planet Earth Online
Medical Diagnostics in a Star Trek Sick Bay - Planet Earth Online
with Tim Coats, Professor of Emergency Medicine; Paul Monks, Professor of atmospheric chemistry, University of Leicester…
Technology designed to monitor environmental pollution has been adopted by scientists to detect disease. The project, by researchers at the University of Leicester, is known as the Diagnostics Development Unit and has been likened to a 'Star Trek' style sick-bay. At the moment, the equipment is under test at the Leicester Royal Infirmary.
Planet Earth Podcast presenter, Richard Hollingham, went along to the hospital's busy Emergency Department, where he met Tim Coats - Professor 
of Emergency Medicine at the Hospital - and Paul Monks - Professor of Atmospheric Chemistry at the University of Leicester...
Paul - We've taken instrumentation that we use in the laboratory and outside in the environment for actually smelling the air, sniffing the chemicals in the air and we're now using it in the hospital environment to smell peoples breath.
Richard - So what is the set up here? It looks like there is computer monitors there - a camera stand, a tripod there. Now, this I recognise. This a mass spectrometer so you can analyse individual chemicals, a series of long metal tubes with complicated piping and the like.
Paul - Yes, what you've got in front of you is what we call a proton transfer reaction timer flight mass spectrometer but it's a way actually of measuring and weighing molecules very, very quickly. So we can take the molecules coming out of your breath and weigh them and actually look at the composition in terms of the chemical composition of your breath and what we hope to be able to do with that is actually smell disease.
Richard - Now, Tim, we're in a room full of this equipment, but on the other side of this are the bays where there are patients coming in as we speak being attended to in the emergency department.
Tim Coates - That's correct and we've got a series of ports through the wall there both electronic and physical so that the patient the other side of the wall can be monitored using the equipment in this room. Now that means that the doctors and nurses in the emergency department can continue treating the patient while the monitoring is going on. So even the sickest patients can be in there and we can be monitoring them.
That's something in the past that's been really difficult to do. For example, a patient with a chest infection coming in - we know that different bacteria produce different molecules, we can sniff those molecules using the mass spec and perhaps tell which bacteria is in a patient's chest. Now that might help us give them the right antibiotic for their infection. We don't know that we can do that but that's the sort of potential we're looking at.
Richard - What do patients do? What do you attach to them?
Tim Coates - So they have a mouthpiece that they breathe in and out to get the breath sample. They also have a series of stickers that we put on the body - we have a series of cardiovascular monitors. So we're really looking at their heart with the cardiovascular monitors, their lungs with the breath analysis and then we're also doing some imaging - you mentioned the camera and tripod - that's a high perceptual imager which has been translated across from space science. We're doing a battery of different tests on our patients.
Richard - What we really needed was a volunteer, so I agreed to try it out. The test involved breathing into a mouthpiece in time to a regular beep.
Paul - What you can see on the screen now, as you are doing this, is actually the CO2 which is what we use as a marker in order to do that and then on the top is the volume of air that you are putting out into our instrument. And we can see on the mass spectrometer screen behind us the chemical data coming up from the measurements that we're making.
Richard - I must say I was pretty rubbish at breathing in time with the beep - that was quite difficult.
Paul - Actually, your breathing was quite regular but your volume was a bit all over the place.
Richard - Oh okay, yes. So now we move over to the mass spectrometer which is this shiny collection of tubes and here's the screen with my breath analysed.
Paul - Yes. We're actually looking at the chemicals in your breath and we've looked at it in real time and what we've got up on the screen here are peaks like acetone, which is a diabetic marker, also ethanol just to check that you haven't had a drink this afternoon before you came to join us.
Richard - So is it okay?
Paul - Yes, you will live.
Richard - And for a hospital environment this is a fairly fearsome bit of equipment. I imagine it is also very expensive. You really need to miniaturise this don't you?
Paul - The idea, at the end of the day, is actually to miniaturise these things and maybe even produce handheld diagnostics, something like the size of a glasses case that you would be able to breathe into. Maybe even one day your mobile phone.
45:37 - Fingerprinting the Unfingerprintable
Fingerprinting the Unfingerprintable
with Dr Geraint Williams, Swansea University
Chris - Fingerprints have been used to catch criminals since at least 1858 and since then, they've been the key to solving countless crimes. But some surfaces are hard to lift fingerprints from especially if that surface has been cleaned or chemically altered in the interim. Now, researchers at Swansea University have developed a new technique to fingerprint some things that were previously unfingerprintable. Dr. Geraint Williams helped to develop the system and he's with us. Hello, Geraint.
Geraint - Good evening, Chris.
Chris - So first of all, what actually, chemically speaking, is a fingerprint?
Geraint - Well, I guess if you wanted to define what a fingerprint is, it would be the deposit that's left behind when the fingerprint ridges or the fingertip friction ridges make contact with the surface. But compositionally speaking, there's a whole chemical cocktail in a fingerprint deposit. There are two parts to a fingerprint. There's the eccrine part which is basically secretions produced by the eccrine glands in your fingertips - and that is basically sweat. But sweat is pretty complex on its own; principally water but it contains things like chloride salts of various metals, sodium, magnesium chloride for example, things like urea, lactic acid, amino acids, et cetera. But there's also a second component to a fingerprint. These are sebaceous deposits which are produced by sebaceous glands, not in your fingertips paradoxically, but other parts of the human body, for example, in your face. So a person might touch their foreheads or the side of their nose and pick up these sebaceous deposits which are basically a whole cocktail of long chain fatty acids and fats by themselves. So the fingerprint is made up of a real chemical cocktail which is difficult to actually characterise.
Chris - So normally, if you dusted for prints, you'd be dusting, applying a chemical that would stick to those residues and that's how you'd visualise it, but why then would some surfaces not be fingerprintable?
Geraint - I guess if a fingerprint has changed or if it's simply just made up of an eccrine deposit. So, lots of the developers that are used to give you a high visual contrast between a fingerprint pattern and the surface in which it's deposited rely on the interaction of a developer with that sort of organic part, the fatty part, of the fingerprint. So if it's missing, lots of these developers simply won't work.
Chris - So how does your approach differ?
Geraint - Our approach differs from most schematic techniques in that it relies on measuring the interaction that the fingerprint itself makes with the surface on which it's deposited.
Chris - So talk us actually about your method. What does it involve?
Geraint - It's an instrumental method. The instrument we use is called a scanning Kelvin probe and it relies on scanning a very fine probe over their surface of interest. So, we're mechanically scanning the probe over the surface, the probe doesn't actually touch the surface. And what it does is measure a quantity called the Volta potential difference between the probe and the area of the sample directly underneath the probe, and that is an indicator of the chemical nature of that surface. So, if for example, a fingerprint deposit is on that part of the surface, then we'll have a considerably different Volta potential difference to a part which isn't in contact with the fingerprint deposit. Usually our technique is good for metallic or conducting surfaces and basically metals, and the chloride salts in the fingerprints actually de-passivate, cause a small amount of corrosion to occur, underneath the fingerprint deposit and it's that small amount of corrosion that we actually pickup with our scanning Kelvin probe.
Chris - What happens when someone comes along and cleans the surface? Of course, if a corrosion event has occurred, that won't be wiped off then.
Geraint - No, exactly. For example, if a criminal has been trying to cover his tracks by wiping off the fingerprints with a cloth, there is sufficient interaction of the chloride salts in fingerprints with the oxide film covering the metal for that chloride to be retained in that particular region, and it won't be wiped off physically.
Chris - What sorts of things are you using this for or could this be used for where present techniques just wouldn't cut it?
Geraint - The major items of interest to us are things like spent cartridge cases.
Chris - From guns for example.
Geraint - Yes, from serious gun crimes and those pieces of evidence. So if for example there's a shooting and somebody has left some shell cases at the scene of the crime, typically, it's almost impossible to lift any fingerprint detail from those pieces of evidence, providing maybe that the criminal has actually put his fingerprints on them to start with before they're actually fired. And that's because obviously, when you fire a bullet, the casings are subjected to fairly high temperatures in the firing mechanism. There's also some contamination from blowback propellant for example. There's also friction from the ejection mechanism. All these phenomena can try to make it extremely difficult to actually give any kind of fingerprint visualisation on that type of surface. But with the Kelvin probe, because most of the organic part of the fingerprint will be lost for example at the high temperatures to which the casing will be exposed, the Kelvin probe gives you a fighting chance because there's always a good chance that the chloride-rich deposits will still be there because they won't be volatilised at those kind of temperatures.
Chris - Terrific, Geraint. That's Geraint Williams from the Department of Engineering at Swansea University.
Can bees sniff out explosives?
Graham - As well as dogs, you can use other animals to find explosives and bees are one of those. Bees use several different cues to find food including the smell of sources of food, so you can train them to associate the source of food with the smell of TNT. Then, if you grab hold of a trained bee and pass TNT vapour across it, it sticks its tongue out. So this is an interesting new way of using animals in order to detect TNT and there's a UK company called Insentinel that are developing this biotechnology.
See also: "Humble Honey Bee Helping National Security" by Anna Khot.
Why don't terrorists combine chemicals in flight?
Pavel - Well, the existing restrictions are meant to deal with such situations because 100ml is not to make a viable bomb and obviously, any precursors for explosives will be detected by the instrumentation I was describing. So, it's not just that explosives are detected, but also explosive precursors. So the list against which we are comparing the data is very comprehensive.
Can you remove fingerprints with sandpaper?
Geraint - Yes, I would guess you could. If you were ablate enough of that surface then you'll remove any kind of interaction. The other advice, of course, is to wear gloves when loading your shells. Chris - So basically, if you did actually scrape hard, you could erode the surface and then you wouldn't stand any chance of getting a fingerprint from that. Geraint - That is correct, yes.
53:58 - Could gene therapy be used to cheat a DNA test?
Could gene therapy be used to cheat a DNA test?
We posed this question to Dr. Paul Debenham Director of Innovation and Development at LGC and Professor Hardev Pandha from the University of Surrey...
Paul - The possibility proposed is of some sort of sci-fi mouthwash which is able to transfer false DNA profile sequences into your mouth cells. To achieve an efficient DNA transfer, one would need to piggyback the DNA profiling sequences into a human virus to achieve infection of the mouth cells. It doesn't sound the sort of treatment many people would volunteer for. This treatment will not destroy the existing person's DNA in their mouth cells, so one would expect to see evidence of a multiple DNA profile and immediately suspect something strange afoot. Current profiling methods can indicate the presence of more than one source of the DNA when the minor component is of the order of a few percent of the major component. There are many technical caveats to that ratio, but that's a ballpark figure that people can work with. If such a mouthwash technique ever became possible, then I could imagine that the sampling procedure deployed would just change to swabbing from a skin surface, plucking out hair roots, or the use of blood, just a pin prick would suffice. Hannah - So, even if any or few percent of your own DNA was left in your cheek, DNA fingerprinting is so sensitive that it would still pick up the real you. But what about grafting tissue containing someone else's DNA onto your inner cheek? We ask Surrey University Oncologist, Professor Hardeev Pandha. Hardeev - If you do that, the take up of the cells is incredibly inefficient. It wouldn't last very long and would most likely be sloughed off or rejected that would be from a different genetic background. So, it's a nice idea but I think this is one that won't be a problem for the police forensics folks. Hannah - So, rather than trying to change your own DNA, we think that a better way to outwit the justice system would be to deluge the crime scene with other people's DNA. For instance, by emptying the contents of a vacuum cleaner bag into the area.
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