Why Do I See Stars when I Stand?

17 June 2012

Why does a head injury, or standing up too quickly, make us "see stars"? Are slug pellets painful? How do flies fly in an elevator? We take on your science questions this week, and find out why we should let food ferment, what makes batteries get hot and if the strings in string theory are real. Plus, a new drive to improve science education, new vistas for Voyager 1 and new veins from stem cells.

In this episode

Can slugs and snails feel pain?

I wasn't actually sure about the answer to this to start with, whether things like slugs and snails do actually feel pain. The way that the medicines and the drugs work that you put into slug pellets is they basically just cause them to expire through various toxic ways which are not going to affect humans and other animals and mammals. You're exploiting a chemical problem that the snail has when it eats this stuff compared with us.

Then I looked back at a story I wrote about 5 years ago - "Can prawns feel pain?" Bob Elwood, at Queens University Belfast, published a paper showing that prawns, when he dabbed a vinegar onto their pincers and on their antennae, seem to flinch, and he suggested this was because they felt pain. Then I found that he's actually published a follow up paper and I've looked that up for you. I'm actually quoting from Science Daily, but it says here:

"New research published by Queens University Belfast Academic has shown that crabs don't just suffer pain, but they also remember it too. The study looked at the reactions of hermit crabs to small electric shocks and it was carried out by Professor Bob Elwood at the School of Biological Sciences at Queens University Belfast, and published in Animal Behaviour. Professor Elwood, who has previously carried out a study showing that prawns endure pain, said that his research highlighted the need to investigate how crustaceans used in food industries are treated."

Obviously, this is about crabs and you're asking about slugs and snails, but they are closely related in the grand scheme of things, and therefore, it's reasonable that if we read what happens to a crab, we can sort of extrapolate to a snail. Now he goes on to say, wires were attached to the shells of the hermit crabs to deliver small shocks to the abdomens of some of the crabs in their shells. The crabs that got out of their shells were those that had received shocks, indicating the experiment was unpleasant for them and it shows that central neuronal processing, in other words, they realise it was unpleasant the they decided to vacate their shell. It wasn't just a reflex response. He also says that crabs that have been shocked that had remained in their shell were appeared to remember the experiment of the shock because they quickly move towards a new shell when they were offered one, compared with the shell they were already in. In other words, they prefer certain shells over others and if they're in one that they're already been uncomfortable with and you then shock them, they're much more likely to vacate the premises and go for a new shell. So, this would suggest that simple creatures like prawns and also crabs, and hermit crabs can experience pain. Therefore, I think it's probably not unlikely that if you bring a snail to an untimely end by pouring salt over it or poison it with some slug pellets, it's probably not very pleasant for the slug or the snail.

Can food really "ferment"?

All over the world, cultures will ferment various different food stuffs in order to make them taste a bit more interesting.

So the actual process of fermenting usually involves some kind of living organism like a yeast or a bacterium, and it also involves an anaerobic environment, so no oxygen. I couldn't find very much information about the Viking method of making cod liver oil, but it does seem that they just dumped a load of cod livers into a barrel, left it in some seawater and then just left it outside. Presumably, what would happen is that you would have bacteria that would break down the liver, and because oil isn't quite so easily broken down - and this is a serious problem that the sea actually has - the oil would float to the top, and it won't be broken down as quickly as the other parts of the liver. When it comes to fats and Inuit wrapping up bits of fat in seal skin, what was probably happening there is that you have certain types of bacteria, probably Bacillus bacteria which will break down bits of the fat, make it decompose and make it taste quite different. Interestingly, about a year ago, just after Christmas, Yorkshire Water actually released a load of Bacillus bacteria into the sewers because one of the major problems that we have with Victorian sewers in this country is that people pour a lot of fat down the sink and it builds up into great big lumps, and blocks up the sewers. So what the water company did was they flushed a load of bacteria down there to break it all down.

How efficient are rechargeable batteries?

That will rather depend on what you call an efficient process! Certainly, not all of the energy which you use to charge a battery will come out of the battery in the end. You can feel that by feeling the battery - whilst it is being charged, it is getting warmed. So there must be energy being wasted.

If you look at the efficiency of charging standard, nickel cadmium or nickel metal hydride battery, the efficiency is about 60 to 70%, so you're wasting 30 or 40% of the energy you're putting into the battery itself, and you're probably also wasting some more energy in the charger because that's not going to be 100% efficient either. So, you might be talking about half the energy you're using actually ending up in that battery.

That doesn't sound very good, but if you're going to use something with a battery, you need some power and you need to get it from somewhere. If you compare that to using a throw-away battery, that's going to be - I would've thought - only a few percent efficient. Only 1 or 2% efficient because you've got to get materials to make a battery, you've got to refine them, you've got to put them all into a case. And so, [60% efficiency] doesn't sound very good, but it's far, far better than the alternatives.

Is there an evolutionary reason for being repelled by cockroaches?

Diana - This seems to be an almost entirely cultural thing. There was a study done last year by a group at the Karolinska Institute in Sweden, they looked at toddlers and small children, and introduced them to various creepy crawlies and snakes, or showed them images of them and found that actually, they weren't scared of them. There was no flinch effect and there was no expression of fear. But what they did find was that the children learned to fear things much faster than they learned to understand things that weren't things that they should be afraid of. So, when they showed an image of say, a snake or a cockroach and played someone's voice which had a warning tone in it, the children learn much faster that they should be afraid of this. And so, this is probably what's happening when people learn to be afraid of spiders - it's probably a parent around going, "Oh, there's a spider!" And that's how they pick it up.

Chris - I remember watching a documentary on the television, featuring a psychologist in America. He was demonstrating what you've just discussed by giving children bed pans to drink out of. They were quite happy to pour apple juice, which obviously looks a bit like urine, into the bed pan and drink it, until they knew it was a bed pan! But the interesting thing was when he put a cockroach in the bed pan with the liquid, they then wouldn't drink it because they said it had a bug in it.

Diana - That's interesting. How old were they?

Chris - Well he said there was a threshold age and once they got to a certain age, they then started to recognise that this isn't quite as seemly as it should be. They say no they won't drink that because it's got wee in it and things like that. This aversion to bodily fluids kicks in from about age 4 or so. Whereas before that very young kids are happy to play in their own poo!

Why do bits of my kids grow at different rates?

Diana - Genetics is probably a major determinant. Certainly, I was disappointed when I didn't grow quite as tall as my sister who has a different father who's obviously taller. There's also a nutritional element to it. If you've got lots of protein and good vitamins, and all that stuff in your diet then you're going to grow a bit taller. Disease actually can affect how tall you end up as an adult, especially if you have some major disease during your childhood. So, one of the things that we find in archaeology is that when people started farming and living in very built up environments next to each other, they got more diseases, and their heights actually reduced whereas the hunter gatherers wandering around a few thousand years before were quite a bit taller and healthier. There is gender as well; girls generally don't tend to get as tall as men.

Chris - So there's a combination of availability of food and the interaction of your environment with your genes, but also, genes control your body at the level of individual tissues developing a different rate. Your body puts itself together in the right order so that you're growing at the right rate to support the right size frame. So, your liver and heart don't turn into an adult liver and heart, for instance, in a very young baby, everything grows at the right rate and that at the end of the day is going to be programmed by genes too.

Diana - And there's also the question of when your bones fuse because that's one of the things that the archaeologists look at. The collar bone is actually the very last bone to fuse and that's when you're 25. And presumably, you should've finished growing, but actually, your bones haven't finished growing technically until then.

Why do some batteries get hot?

Dave - Charging batteries isn't 100% efficient and similarly, discharging batteries isn't 100% efficient. The way electronic engineers like to think about it is that the battery has a resistance, so if you draw a current from that battery then you're pushing that current through a certain resistance and so, it will heat up. If you short out a battery, basically taking a wire from under the battery and connecting it to the other end of the battery then there's no resistance anywhere else - there's nowhere else the energy to go so all that energy will get dumped into the internal resistance of the battery and it will get very, very warm. One thing which could've caused it is that your remote control somehow shorted itself out. That could've been in the remote control itself, but if you changed a battery and it worked fine, then probably not - but it could also be inside the battery. Something could have even gone wrong with bits of metal touching inside the battery.

Chris - That's good. So it sounds like, if nothing else is to blame, probably the battery has developed an internal short and shorted itself out, and it's dissipating all the energy into itself, making itself get hot.

Dave - Yeah, certainly in a remote control because the remote control draws so little current, that there shouldn't be enough power being dissipated anywhere else.

15:14 - Homegrown portal vein replacement

The first replacement tissue-engineered vein grown from a patient's own stem cells has been successfully transplanted into a 10-year-old Swedish girl.

Homegrown portal vein replacement

The first replacement tissue-engineered vein grown from a patient's own stem cells has been successfully transplanted into a 10-year-old Swedish Portal Vein, Liver and Mesenteric Anatomygirl.

Writing in the Lancet, University of Gothenburg researcher Michael Olausson and his colleagues were seeking a treatment for the girl who was suffering from a syndrome caused by an obstruction to her portal vein, the main vessel that carries blood from the intestines to the liver.

When this occurs, the blood finds alternative routes around the obstruction, dangerously dilating other blood vessels that are then prone to rupture and haemorrhage.

One approach is to transplant vascular tissues from other parts of the body including the neck's jugular vein, the saphenous veins in the leg or even the veins around the umbilicus (belly button), to bypass the blockage. But this sort of surgery is truamatic, risky not always possible and also far from ideal in a child.

Instead the team built a new blood vessel segment for their patient. Their approach was to obtain a piece of iliac (top of the leg) vein tissue from a dead 30-year-old donor. This was treated with detergents to remove all of the donor cells, leaving behind just a scaffolding of sterile connective tissue.

Stem cells were harvested from the girl's bone marrow and applied to the decelluarised vein tissue, which they slowly re-populated with muscle over a period of about a month.

Throughout this time the replacement vessel was maintained in a nutrient solution in a specialised culture flask. Endothelial cells (which coat the inner surface of blood vessels and were collected alongside the stem cells) were also added and re-lined the re-built vessel, which was then implanted into the patient, restoring normal blood flow.

Subsequently the graft developed a "kink" and required lengthening with a further section of vein prepared in the same way, but the patient's condition was otherwise dramatically improved and there was no need to resort to other major vein grafting surgeries and their associated risks.

According to the team, "The new stem-cell derived graft resulted not only in good blood flow rates and normal laboratory test values but also in strikingly improved quality of life for the patient."

How does a fly fly in an elevator?

Dave - You have to think about the forces on a fly. It's got two big forces on it. There is gravity pulling it down and then there's aerodynamic forces pulling it up. If you effectively let the lift start dropping then effectively, gravity is reduced because the lift is accelerating downwards so there's less force upwards on the floor on everybody, and essentially, the lift is moving down around the fly. Now, to start with, the fly has got quite a lot of inertia and it's just going to sit there, essentially staying still when the lift is going to move around it. But a fly has got all sorts of complicated algorithms going on in its head to try and keep it where it wants to be. And I would've thought what goes on is that the fly notices it is higher than it wants to be so it stops flapping its wings as hard, so it will tend to drop down within the lift. And so, it stays where it wants to be essentially just because it flies to where it wants to be.

Chris - So if the fly weren't compensating, which is your answer, it probably would go visibly upwards or downwards according to which direction the lift is moving in?

Dave - Yes, and probably, if the lift suddenly jolted downwards, then the fly would stay still and the lift would move around it and then certainly move upwards.

What causes us to "see stars"?

Both of [these situations] are basically artificial phenomena in a sense that in one case - the standing up too quickly - this is an entoptic phenomenon, which means "something going on inside the eyeball". The retina, as you'll know as an ophthalmologist, has one of the highest metabolic rates of any tissue in the body. The brain and central nervous system tissue burn off about 20% of the energy that you consume in any given moment in time and yet they contribute only a small fraction [about 2%] of body mass. So the retina is very metabolically hungry. And if you stand up too quickly you can have what's called a "postural drop" in blood pressure. Blood comes up from your legs into your heart to get pumped around the body. When you stand up, and before your heart compensates, the return of blood drops slightly which causes the perfusion pressure to drop briefly. That causes a momentary reduction in perfusion of your retina. That slightly reduces the supply of oxygen and sugar to the retina from the blood, which causes the retina to start to fire off abnormal signals, which we experience as "sparkly" light signals; the brain is fooled into thinking you're seeing light when it's not there.

Now, conversely, when you bash your head, what's probably going on there is that because the brain is bobbing around inside your head in a fluid - the cerebrospinal fluid - and has a very soft, blancmange-like consistency, if you have a sudden interruption of movement to your head - so you hit your head very hard against the wall or pavement for instance - the brain cannons into the inside surface of your skull; it then can rebound and hit the back of your skull as well. And if you irritate the part of the brain that decodes what you're seeing - the visual cortex which is right at the back of your head - then it's possible that, in the same way that irritating the nerve cells in the retina by not having enough blood flow makes them fire abnormal signals which you see as stars, you can also affect the brain cells in the visual system similarly. So I think, probably, this is responsible for triggering the experience of "seeing stars" when we suffer a head injury.

It's an excellent question and thank you very much for asking it!

Could I see neutrino interactions in a deep mine?

Neutrinos are very interesting particles. They almost don't interact with the rest of the universe at all. In fact, the neutrinos which come from the Sun, billions and billions of them are created in nuclear reactions in the Sun, they can travel the equivalent of 10 times the distance between the Earth and the Sun through water before they hit anything to make any kind of interaction at all. And not all of those interactions will actually produce a light which you'll be able to see. So, just working on the number of interactions, that sounds incredibly unlikely, but there's also about 65 billion neutrinos going through every square centimetre of everything in the world all the time every second.

You can work out the relative ratios, how often they interact in a cubic centimetre (for this purpose, let's assume your eyes are very roughly about a cubic centimetre). In that liquid in your eye, it's probably going to take about 200 seconds for a neutrino to interact with some of that liquid.

The number of those that produce enough light for your eye to see is probably going to be a relatively low proportion, so you're probably talking thousands of seconds; every few hours maybe a neutrino hits your eye and produces some light, but actually, would you be able to see that? I think that's almost entirely unlikely because it's going to produce a tiny amount of light, and the sensors in your back of your eye getting triggered by thermal radiation. Probably radiation from radioactive elements inside your eye and in the atmosphere around you is going to be far, far greater effect than neutrinos.

I think camera sensors will be even less likely [to record a neutrino interaction] because your eyes are filled with water which will interact with neutrinos whereas a camera sensor, in front of it is just air, therefore there're fewer particles from the neutrinos to interact with. You need to have that interaction with a very thin layer of a camera sensor, so probably slightly more likely with your eye.

26:30 - Improving Education

Is science education up to scratch? Universities have complained that the A-Level curriculum doesn't prepare students for a degree, so exam boards are taking a stand to improve...

Improving Education
with Colin Black, OCR

Chris -   It's exam time and across the country tens of thousands of young people are sitting public exams that will determine their future, including whether they go on to University.

But, Michael Gove, the Secretary of State for Education, wrote recently to the examinations regulator saying:

"I am increasingly concerned that current A levels - though they have much to commend them - fall short of commanding the level of confidence we would want to see. Leading university academics tell me that A levels do not prepare students well enough for the demands of an undergraduate degree, and I am troubled by reports from learned bodies such as the Institute of Physics..."

As a result, the government want the exam boards, who develop A level exams, to fundamentally change the way they operate.

Joining us to explain what this might mean is Colin Black from the Cambridge-based exam board OCR, who set about 25% of the papers sat by learners in England.  Colin, welcome to the Naked Scientists.

Colin -   Thanks, Chris.

Chris -   First of all, what does the government actually want you to do differently?

Colin -   The major change the government is looking for is for us to work - when we're developing the A-levels - actually with people who work at universities.  So rather than developing them with our experts and third party experts that we would talk with, and also the various professional organisations, they've asked us to open the door, and actually start speaking to people in higher education.

Chris -   What do you think has provoked Michael Gove to say and I'll quote again, "A-levels fall short of commanding the level of confidence we want to see," and university academics are telling us that A-levels do not prepare students well enough for the demands of their undergraduate degrees.

Chemistry lesson at a German Gymnasium, Bonn, 1988Colin -   Well, I don't think that statement has really come as a surprise to us.  Ourselves and also our parent organisation, Cambridge assessment, have been undertaking some research over the last 18 months or so.  We've been talking to people from HE, we've been talking with professional organisations, and there's a general sense that there's a gap between the A-level student, as they enter higher education, and some of the skills are required.  It isn't necessarily about the full content of the subject areas.  It may be a bit more about being able to explain things in more depth and things around experimentations, not just of taking the facts as is, and the ability for critical thinking, those sorts of areas.  And that's what we've been getting back from higher education.  So, it comes as no surprise that Michael Gove has taken all this onboard and come out with the statements that he has recently.

Chris -   Is this a problem confined just to science or is this more comprehensive than that because I can see it being more of a problem for science because science is moving a lot more rapidly at the say, history is?

Colin -   Yeah, you could see difficulties in a syllabus which lasts 5 years, keeping up with some of the new changes and the various knowledge that comes in to the body of science.  But to be honest with you, I think some of this is around the way that the A-levels have been assessed. So therefore, you could apply some of these problems across the whole of the A-level syllabus.

Chris -   So, what are boards like yours - OCR - doing about it?  How are you responding to this call to action and what are you going to try and do?

Colin -   Well, as I previously mentioned, we've already setup some really strong links with higher education; OCR, of course, is part of the University of Cambridge.  So what we'll be looking to do is, across all the subject areas, we'll be setting up forums, we'll be setting up discussion groups to see exactly what we want coming out of A-levels.  From there, we will setup development panels which we will use, and which will include university lecturers, which we'll use about to start developing not just the content, but also the way that we might look to assess going forwards.

Chris -   So, the whole emphasis being on more, giving people the big picture of their subject rather than looking at it in bite-size chunks because I think a major criticism that's often raised to me by students I talk with is that they're taught in bite-size chunks.  You learn this module of the subject and you learn it really very well, and you work very hard and you get a good mark in it, but then you forget that move on to the next module and at no time does anyone really expect you to link up all of those different little bits of intensive learning to see this big picture that's so important in science.

Colin -   Yeah, I think you're right there actually.  The way things are going now are moving away from modularisation which is the bite-size chunk way of learning, and to what's called linearisation at GCSE, I think that'll be exactly the same A-level.  And as you say, it's about linking all these things together rather than being an expert over a short period of time, just on one specific area.

Chris -   Now, when you and I first met Colin - and we declare an interest here because you approached me a couple of years ago and asked me to come and speak at an inset day that you were running for teachers - now I sat down at the lunch time recess with a lot of teachers and I asked them what they felt the biggest impediments to teaching hard science subjects was.  They were saying to me that actually, for the most part, the last time for many of them that they were in a university environment learning like an academic at a university may have been in some cases 20 years ago.  And they're trying to turn kids into the right sorts of people who will flourish in that environment, but they felt ill-equipped because it was so long since they've been in it.  I think that's probably a reasonable thing isn't it?  So the whole idea of trying to bring educators at high level closer to school educators together, I think that's probably really, really fundamental to actually making this get better.

Colin -   Yes.  One of the things we can specifically do, we can start sort of doing now rather than waiting for this sort of A-level development, is the professional development activities that we've been looking to be able to do for the last couple of years, but we're looking to expand on.  And that's actually bringing a lot of new concepts within science and trying to explain that, and going into much more depth with that, and put more events on for teachers because as you say, with the full time teaching that they happen to do, sometimes it's difficult for them to keep up with the sort of current knowledge and all these various changes and lots of them going on.

Chris -   And one of those things is something that you've actually asked us to help you with.  You're running an event in London, you're trying it with physics first, but I presume you're going to try and expand this to other science subjects, so we're trying with physics first.  This is to bring a whole bunch of top tier scientists together in one day and whole load of teachers, and give the teachers the opportunity to hear what is cutting edge in the science world according to those academics and then interact with them.  And then that will hopefully mean they take that message back to the classroom and they can - I suppose - make their lessons more relevant to what those academics' expectations will be.

Colin -   Absolutely.  We've pooled together a number of experts in their fields.  We've looked at various subject areas within the A-level, so we've linked all this together to the A-level specification and we pulled in people who are able to talk around cosmology and particle physics, and then we're talking about their specific areas of expertise throughout the day.  There'll be opportunities for the A-level teachers, those delivering their qualifications, to interact both with themselves, but also with higher education experts.  And as you say, it's about reinvigorating some of the passion some of the teachers had when they first went off to do their first degrees or whatever engaged them with science in the first place, physics in this particular instance, and trying to get that into them, trying to get that spark that they can then deliver back to the students.

Chris -   And if people want to come to this, where is it on and when?  How do they go about finding out more?

Colin -   Okay.  It's running on Thursday, the 28th of June so it's in a couple of weeks' time.  We're running it at the Royal College of Pathologists in London.  The best thing for people to do, if they're interested in attending, is to go on to our website. 
www.ocreventbooker.org.uk.  If they go on there, they'll be able to see all the details and book online.

What exactly is string theory?

Dave - String theory is essentially trying to explain why we have all the fundamental particles we have. So, protons and neutrons are made up of even smaller particles called quarks, and you get electrons and higher energy, more exotic particles - things like muons, and all sorts of different particles. They can combine in different ways and they all have different masses.

People who are much better at maths than I am have spent a long time trying to find mathematical constructs, so ways of putting maths together to produce objects which look like the particles that we see and have similar properties which we can call mass. One of the ways they've done this is with some maths which look a bit like strings. You can have oscillations on a string. If you wobble the string slowly, you get one wobble in it as it wobbles left and right. If you wobble it faster, you can get it to start making a snaking wobble. As you make it faster and faster, these different vibrations could be associated with different particles.

The actual strings themselves are probably just maths. We have no evidence to say there are actual little bits of cotton wobbling very, very rapidly. So all we know is that there is some maths which gives rise to things which look a bit like the particles we have. I'm not even sure that there's any actual evidence to say that string theory is better than any other particular theory. They haven't actually got that far, but that's what the guys in CERN are trying to do.

36:25 - Voyager is leaving the system

Voyager 1, launched in the 70s, appears to be leaving the solar system

Voyager is leaving the system

Voyager 1 was the first spacecraft to visit Jupiter and Saturn, it was launched in 1977, visited Jupiter in 1979 and Saturn in 1980, when its main mission was over. But 34 years on it is still doing science.  Whilst Voyager 1's instruments may be outdated, and its radioactive power system is starting to run down, it is the furthest man made object from the earth, it is now 17.8 billion km from the sun over 120 times further than the earth is, and at least 3 times further than Pluto. So by being where no other spacecraft has been before it can still do new science.

VoyagerAt the moment it is passing through the edge of the Heliosphere where the sun's magnetic field is starting to be overwhelmed by the galactic magnetic field. This solar magnetic field deflects very high energy cosmic ray particles created when stars explode forming supernovae, so there should be fewer cosmic ray particles inside the Heliosphere than outside it.

In the three years up to January Voyager 1 saw a 25% increase in the galactic cosmic rays, which indicates that it is getting close to the boundary, but during may the cosmic rays increased by 9% in a month and 5% in a week, which in a 30 year mission is a very rapid change. It has also been seeing a drop in particles coming from the sun, though the final piece of data they need to be sure that it has left the sun, is if the direction of the magnetic field changes, but they need more data and time to analyse it to be sure.

The Voyager spacecraft are thought to have enough fuel and electrical power to last until 2025, so we may soon be finding what deep space is like.

39:01 - Empathy through Music, Cracking Materials and Mammoth Extinctions

How music can make children more empathetic, the electrical charge of cracked materials, the slow extinction of the wooly mammoth and the benefits of spitting seeds in Israel...

Empathy through Music, Cracking Materials and Mammoth Extinctions
with Tal-Chen Rabinowitch, University of Cambridge; Troy Shinbrot, Rutgers University; Glen MacDonald, UCLA; Denise Dearing, University of Utah.

Empathy to our Ears

Playing music in groups increases empathy levels in young children, according to work published in the journal Psychology of Music.

Working with 52 children aged 8 to 11 and exposing them to a range of weekly activities including musical games  or word activities, Tal-Chen Rabinowitch from the University of Cambridge found that children in the musical groups showed significantly increased levels of empathy when tested for compassion and responses to facial expressions.

It's thought that  musical activities enabled the children to experience shared intentions with their peers...

Tal-Chen -   Empathy is good for everyone; for children, for adults.  Empathy has been seen to be a precursor for pro-social behaviour.  So when we empathise, when we understand an other's emotional state, we tend to want to help them.  We are looking to and we want to look at also children in the autistic spectrum for example, in which empathy might be able to help them in their social interactions.  Right now, I think we're concentrating on the regular population.

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Thin sectionA Cracking way to predict Material Failure

Electrical signals could be used to monitor cracks in industrial materials and predict their impending failure or breakage, according to work published in the journal PNAS.

Troy Shinbrot from Rutgers University in the US used powders such as flour and pharmaceutical drugs to model the composition and movement of materials such as ceramics and concrete, which are made by compressing powders together, and found that spikes in voltage occurred as crack-like defects occurred.

Troy -   Ceramics are used in everything from catalytic converters to artificial teeth.  It may be the case that these kinds of products could also exhibit precursors.  So, one might be able to measure voltages and detect whether or not a failure is imminent in these kinds of systems.

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A Not-So Mammoth Extinctionmammoth

The woolly mammoth had a slow decline to extinction due to a range of factors including changes in climate, habitat and living alongside humans.

Using radiocarbon dating on samples of tusks, bones and tissue from the mammoths, Glen MacDonald from the University of California at Los Angeles found that whilst the animals were abundant 30-45,000 years ago, they migrated and changed distribution due to warming climates, human civilisations and the growth of forests in the region of Beringia, which is now Alaska and Eastern Siberia, with their final extinction about 4000 years ago.

Glen -   Despite the fact that they were abundant, despite the fact that they had a widespread geography, despite the fact that they could take advantage of a wide range of climates from the northern coastal regions, into the central parts of Siberia, they still at the end of the day went extinct about 4000 years ago.  Lots of things we count on for species persistence - rapid ability to recover, large population size, geographically widespread, and we've seen with the mammoth, wasn't good enough.

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Spitting Seeds

And finally, the Taily weed plant produces toxic compounds in its seeds to aids its spread across the Negev desert in Israel.

Denise Dearing from the University of Utah monitored the interactions of the plant with predators such as the spiny mouse in both wild and captive environments and found when the mice consumed the plants fruit, they spat out rather than ate the seeds inside.

Enzymes within the seeds activate toxic compounds when the seed is chewed, encouraging predators to spit them out and aid the seed's dispersal instead.

Denise -   So, there's this long standing battle between plants that don't want to have their tissues eaten, but they will need to have their seeds dispersed, and this is just a new twist in that battle where this seed predator has now been turned into a seed disperser at the whim of the plant toxins.  So, it seems on first glance that the mouse has overcome the senses of the plant, but in this game, the plant is actually winning because it's getting the mouse to do its spitting by dispersing its seeds to suitable locations for germination.

43:37 - Putting a Value on Biodiversity

A major seven year study has been launched in the UK to investigate the link between biodiversity and the services nature provides - such as food, clean air, water and flood protection....

Putting a Value on Biodiversity
with Dave Raffaelli, University of York

A major seven-year study has been launched in the UK to investigate the link between biodiversity and the services nature provides;  Such as food, clean air, water and flood protection.

Planet Earth Podcast presenter Richard Hollingham went to meet the leader of the project, Dave Raffaelli from the University of York, at Blacktoft Sands nature reserve on the banks of the River Humber in South Yorkshire.

The reserve is home to a herd of wild Konik ponies as well as a multitude of bird species. Looking out from a bird hide across the marshes, Dave explained about the benefits of biodiversity...

Dave - If you look out at the area we're looking at at the moment you can see it's dominated mostly by reeds.  These have many, many functions in the natural environment that people don't really appreciate. Traditionally they were used for thatching, for making roofs and so on, but they have many other really interesting functions. So, they provide a kind of soft engineering for storm surges and for wave action and so on which means that we don't have to build solid seawalls, so they take the energy out of the waves. They also filter water before it goes from agricultural land into the rivers and strip out all the nitrates and so on. So they have a purification function, they have a storm defense function as well as providing lots of biodiversity for us as well.

Richard -   And these sorts of functions they're termed ecosystem services and that's what your project is investigating and looking at - a rather ugly word but I suppose it describes what it does.

Konik, displaying dorsal line & other physical featuresDave -   Yes, I think the best way to think about them is that nature provides lots of benefits for us and this is one of several habitats we're looking at in the United Kingdom, so we're looking at coastal marshes like these, we're looking at upland rivers, we're looking at lowland farms and we're looking at urban areas as well down south in England and we hope to extend that to many other kinds of habitats.  Each of these habitats has lots of biodiversity which provides those kinds of benefits for us.  Food production from agricultural land, in an area like this there's lots of recreation provided for us as well as climate regulation in forests and so on and what we're trying to do is find out how much of that biodiversity you really need to sustain those benefits in a changing world.

Richard -   So are you trying to quantify this and put numbers on this and say "we need this many reeds to stop the flooding here" or "we need this diversity of plants and insects..."

Dave -   That's right and unless we quantify those then they won't be valued properly in decision making. Many of these so called benefits from the landscape, these ecosystem services, they don't actually have monetary value attached to them because we can't trade them. But, actually, if we didn't have them then we would have problems with flooding, we would have problems associated with climate change, carbon sequestration and so on.  We're trying to put numbers of those so that when we need to make decisions about the way we manage our landscapes in the UK we can do that on a properly informed basis.

Richard -   And so when we peer out through this slit across the water in front of us; it's almost like a pond, it's so still today, there's no wind at all.  Then there's the reeds and then there's a butterfly just flitting past, there's a pony in the distance and then the river and then into a haze of the hill and trees. You put numbers and say, right we need that and that will mean we get this amount of benefit from that?

Dave -   That right. So the kind of trade-offs that people like the Environment Agency, for instance, have to make on a daily basis but we all do in society is what should we do about whether we want to build sea defences to stop flooding or river defences to stop flooding? One of the decisions that we might want to make is not to invest huge amounts of money into those sea defences but maybe to purchase adjacent agricultural land, which also has monetary value, in order to let that land accommodate the flood rather than trying to stop it and then pushing the water further downstream. So that's why we're trying to put the numbers on these benefits so that people can have a common currency, if you like.  It doesn't have to be money it can be anything, but a common currency to provide a rational basis for actually making those kinds of decisions.

Richard -   I'm just watching that pony over there swishing its tail, swishing the flies away, grazing on the marsh, grazing on some sort of grass or sedge or something over there.  How do you put a number on the benefit of that grazing, or benefit or otherwise of that?

Dave -   Well that's what the project is really all about. What we want to know is, and that's a very good example for this konik pony, is how many konik ponies do you need to change the vegetation in such a way and keep it in a particular condition but it's the best possible condition to stop flooding?  Although it all looks like reed here there is many, many species and the essential question is how many species of these reeds and sedges do you actually need in order to provide that benefit of flood regulation or water purification for us and of course the konik pony is one of the moderators of that biodiversity because by feeding selectively they can increase the diversity or decrease it, so that's a very good example of why biodiversity is important in these questions.

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