Small Letters, Sorghum and Secrets in Caves

02 February 2009
Presented by Ben Valsler.

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On this week's NewsFlash we find out how fingerprints help you feel fine detail, discover the smallest letters ever written and uncover the genetic secrets of Sorghum's success.  Plus, how a new way to make LED's could slash household bills, the two million year old secrets hidden in a cave in South Africa, and how bees can help to defend fish farms from fungus.

In this episode

Fingerprint

Pointing out how fingerprints help us feel fine details

In a piece of true science detective work, researchers at the Laboratoire de Physique Statistique in Paris have found another reason why we have fingerprints.

FingerprintIt's been known for a while that the distinctive ridges on the pads of our fingers help us to grip things, but now Julien Schiebert and colleagues have shown that fingerprints also help us to feel fine textures and tiny objects, less that 200 micrometers, through vibrations.

Writing in the journal Science, they developed a special mechanical sensor which is fitted with a rubbery cap to act like a fingertip.  Using either smooth caps, or ones ridged to simulate fingerprints, they rubbed their artificial finger across finely textured surfaces.

They found that the cap with a 'fingerprint' was made to vibrate by the contact, at a frequency of around 250Hz, that's 250 vibrations per second.  This coincides with the sensitive range of a type of nerve endings found in the skin, called "Pacinian corpuscles".

Two types of nerve ending are known to be involved in detecting texture, slow reacting nerves are responsible for identifying relatively coarse textures by detecting different pressures at different places on the skin, while fine details are reported by the Pacinian nerve endings.

They have only tested this with a series of straight, parallel ridges, so not exactly the same as the swirly lines of our fingerprints, but their findings suggest that our fingerprints actually fine tune the vibrations, selectively amplifying certain frequencies to ensure our nerves can pick up the fine details.

Using electron wave interference to make the smallest letters in the world

Writing the world’s smallest letters

Keeping with our theme of nanotechnology this week, researchers at Stanford University in the States have managed to write the smallest letters ever - assembled from subatomic particles just 0.3 nanometres in size.  The researchers are particularly pleased with their achievement, because it was Stanford scientists that first created the world's smallest writing in 1985, but lost the record in 1990 to IBM, when they famously arranged xenon atoms to spell out the company's name. Now they have it back.

But how did they do it? The researchers encoded the letters "S" and "U" (standing for Stanford University) by using the interference pattern of electron waves on the surface of a film of copper. The technique actually projects a tiny hologram of the letters, which can only be seen using a very powerful microscope.

Writing about their work in the journal Nature Nanotechnology, the Stanford team's letters are more than four times smaller than the IBM initials, and were created using a scanning tunnelling microscope, which can be used to push atoms around. The scientists used it to put individual molecules of carbon monoxide in a special pattern on a film of copper the size of a fingernail.

Electrons are constantly whizzing around on the copper, because it is a metal. And because electrons can act as waves, as well as the more traditional view that they are particles, the electron waves get shaped by the carbon monoxide, and interfere with each other like ripples in a pond. These interference patterns depend on the position of the carbon monoxide molecules on the copper surface. So eventually they create a consistent pattern that can be read, like a molecular hologram.

It all sounds quite nerdy, but the technique could be very important for the future of computing, as it would enable information to be stored at a very high density in small chips. For example, the researchers could create different holograms on the same chip by using different electron wavelengths, increasing the amount of information that can be stored, and pushing it beyond current boundaries.

A Reed Warbler feeding a Common Cuckoo

Mob rule to scare away cuckoos

Researchers studying Reed warblers have found out that mob rule can avoid being cuckolded by cuckoos.

Reed Warbler Feeding Common CuckooCuckoos live a parasitic lifestyle - laying eggs in the nest of other birds and letting them spend their time and resources bringing up their young.  From an evolutionary perspective, it's a good trick if you can get away with it, but if you're the victim you're wasting your own resources on someone else's DNA.

Writing in Current Biology, Cambridge University researcher Nick Davies reports on how Reed Warblers use mobbing techniques to keep the parasitic cuckoos away from their nests.

Mobbing is a risky strategy - it's energy intensive and it exposes you to predators, and may not prevent the cuckoo from getting through.  Worse still, sometimes they mistakenly mob a sparrowhawk, which looks a bit like a cuckoo and actually prays on reed warblers.

Some birds would save their energy, and just reject any eggs that don't look like their own, but the cuckoos have evolved to be able to lay 'mimic' eggs which look similar, establishing an evolutionary arms race between parasite and host.

By placing model cuckoos near the reed warbler's egg-bearing nests, Davies and colleagues could observe how the warblers attempted to defend their nests.  About half the time, the warblers became aggressive and attempted to mob the cuckoos.  In the high risk areas, this made them far less likely to be subject to a cuckoo visit than their more peaceful neighbours.

Significantly, in areas where the Warblers were at much lower risk of being parasitized, they were far less likely to show this mobbing behavior - in fact, in those areas mobbing was likely to attract cuckoos, rather than scare them away

Reed warblers also reserved mobbing behavior only for cuckoos, showing that they adapt their nest defense strategy according to their conditions, not unlike our own military!

Sorghum (Sorghum bicolor) on a field near Fada N'Gourma, Burkina Faso. Shea tree in the background.

Turning up the heat on cereal genome

It's clear that the global climate is changing, and this is having a big impact on food supplies.  For example, if the climate changes in a major crop-growing region, it may not be possible to grow that crop successfully any more. So scientists are investigating whether people living in dry regions - that are only getting drier - can grow alternatives to wheat and other food crops.

Sorghum (Sorghum bicolor) on a field near Fada NOne such alternative is a plant called sorghum. This is a type of grass that originally came from Africa, and it grows well under hot and dry conditions.  Now farmers in warm parts of America, Asia and Europe are growing sorghum for food and animal fodder, as well as for using in biofuels.  Not only that, but it can be burnt to provide energy.

It sounds like an all-round wonder-plant, and in order to uncover the secrets to its versatility and hardiness, researchers in Munich have analysed the whole sorghum genome. This is the first time the genome of a plant of African origin has been sequenced.

Publishing their results in the latest issue of the journal Nature, the scientists say that their results will help us understand more about how plants like sorghum resist drought and high temperatures, and could help with the development of hardier versions of other crops in the future.

And the new data will also enable researchers to compare the genome of sorghum with rice and maize, two important crop plants that have had their genomes sequenced. This will tell us a lot about how crop plants evolve, and the genes that give them their specific properties.

Red, Green, and Blue LEDs

09:35 - New LEDs to Slash household bills

A new way of manufacturing LEDs could see household bills slashed, and even provide clean drinking water wherever it's needed...

New LEDs to Slash household bills
Professor Colin Humphreys, University of Cambridge

Ben - There's a new way to make LEDs and this could slash household lighting bills and help to make clean drinking water accessible to everybody.  Professor Colin Humphreys from the University of Cambridge joins us now on the line. Hi, Colin.

Colin - Hi.

Ben - Tell us a bit about this. We've had LEDs for a long time. They are already turning up in torches, in home lighting. What's the new method that you've got?

Red, Green, and Blue LEDsColin - They've been around for some time. They're not really in home and office lighting and the reason is they're too expensive. All the LEDs you can buy in the shops now are grown on a sapphire substrate and sapphire is quite expensive. What we've done is to develop a method for growing these LEDs on a silicon substrate. In fact we're growing them on a six inch substrate wafer instead of on a two inch sapphire wafer. That's going to be bringing costs down by a factor of ten or so, a really big reduction.

Ben - Wow. These LEDs are very energy efficient, I understand. How will it compare to a normal incandescent light bulb?

Colin - They're very energy efficient and they're really going to help global warming. In fact, they'll help it much more than wind power will. In terms of an incandescent light bulb we're aiming to be twelve times as efficient as a tungsten light bulb and we're aiming to be 3 times as efficient as a low energy light bulb. Already they're more efficient than a low energy light bulb.

Ben - Is that for the same brightness as well?

Colin - That's for the same brightness, absolutely. We want to make them better quality and better bright light than the low energy bright light ones, which as you know are not very popular. They're a popular cause for divorce in the country now, I'm told, low energy light bulbs!

Ben - Hopefully your gallium nitride LED light won't be a cause for divorce but I've also heard these could be used to make clean drinking water. I understand what you can do with these is make ultraviolet light.

Colin - That's right so the light emission from the gallium nitride - we actually add some indium to it to get visible light emission. If you add aluminium you can get deep ultraviolet. Deep ultraviolet has certain wavelengths, it's about 270nm. It destroys the nucleic acid in both DNA and RNA and it stops viruses and bacteria from reproducing so it effectively kills them. If we can make LEDs that emit this deep UV we can kill all known viruses, all known bacteria and you could put a ring of these LEDs on the inside of a water pipe coming into a home in the third world. Water riddled with bacteria and viruses, you can make it harmless. Also it could be useful for our country as well, particularly for third world people.

Ben - And we could use them in hospitals as well to ensure things are sterile without having to go through the chemical cleansing that we do now. As they are so efficient does this mean we can set this up with a solar panel and make this water purification very portable?

Colin - Absolutely. That's absolutely right. These are very efficient. They'll run of 4 volts, which is ideal for a solar panel, you have a solar panel and a battery connected as well if you like and then have these connected to that. You have these for lighting in the developing world but also for water purification in the developing world.

Ben - These sound fantastic but what's different about gallium nitride that allows us to make this seemingly wider range of frequencies? If we can make UV that we couldn't before. Why is gallium nitride so special?

Colin - Gallium nitride's called a wideband gap semiconductor. Before it came along the only light emission which you get from semiconductors was in the infrared and in the red and rather weakly in the green and the yellow. Silicon doesn't emit light anyway. Gallium arsenide emits light and indium phosphate but they're narrow band gap materials. If it's a much wider band gap material, gallium nitride itself emits near ultraviolet and then there's another material called indium nitride which emits in the infrared. If you mix those two together you can get any energy you want from the near-infrared going right through the visible spectrum to near-ultraviolet. If you add some aluminium to it you can go really into deep ultraviolet. This is a new material system. It's man-made. It can cover this range of the electro-magnetic spectrum that we've never had before form a solid state semiconductor.

Ben - This sounds quite incredible. When should we expect to see these on the market?

Colin - For the home and office lighting -scientists always predict thing will happen before they're going to happen! I think within the next five years, certainly. Maybe two or three years. The UV problem is more difficult to solve. We've already got the right wavelength being emitted but the intensity at the moment is too low. We've got to push up that intensity. I think realistically that may be 5-10 years. I really believe it's going to happen.

Ben - Clearly getting clean and drinkable water to everyone in the world is going to be a challenge and I suspect unfortunately it will still be a challenge in those 5-10 years. Good luck, I hope we get them to market as soon as possible!

Various LEDs

Skull of Homo Habilis

15:13 - New Evidence from Old Caves

New evidence from an old cave could cast light on how our ancestors lived 2 million years ago, as Meera Senthilingam found out when she spoke to spoke to Kelvin Kemm …

New Evidence from Old Caves
Kelvin Kemm, South Africa

Kelvin -   There's a cave system called the Wonderwerk Cave System, and it is in rocks that are 2 billion years old, some of the oldest rocks on Earth.  The cave itself has been dated at 2 million years old, which is more than twice as old as the oldest other cave in Spain which has been dated to about 800 thousand years ago, where it was known that people intentionally lived in caves.  So what this means now is it has been found that human beings were intentionally living in this cave some 2 million year ago, which is quite amazing.  It's very big, by the way, it's 2,500 square meters, quite sizeable - if you look at pictures of it, you can drive a double decker bus into parts of the cave.

Acheulean handaxesThe depth of the sediment that's in the cave is some six metres, they've dug down through the six meters and found nine layers that go right back as far as 2 million years.  At the 2 million years ago level, tools have been found and an indication of the intentional use of fire and suchlike.  Now what's interesting is that the humidity in the area is so low that the amount of water precipitation inside this cave is one millimetre per year - in other words there's nothing in there.  So this is why it's been so dry for so long.  It's also clearly the case that the tools were left there and not washed there.  The cave is, in fact, about 140 metres deep, but it's horizontal into the rocks, therefore there's been no water flow over the years so these materials couldn't have been washed down to the bottom.

Meera -   Now what tools have the actually found down there?

Kelvin -   Well, there's primitive hand axes and there's also some ornamental stones as well that have got some shaped lines on them - so there's 'artwork' so to speak on some of these very old stones that have been found down there. 

Meera -   Which of our ancestors is thought to have lived there?

Kelvin -   It appears to be Homo habilis.  There were numbers of different types of pre-humans that were living at the time and of course the Homo sapiens, which is us, the one that won out at the end of the day.

Meera -   What else has managed to have been learned from the findings in this cave?

Skull of Homo HabilisKelvin -   Something that is very interesting is that hand axes were found in the cave that were dated to 270 thousand years ago, which is when they were last being made there.  However, they continued to be made in East Africa up to 130 thousand years ago and in Europe 40 thousand years ago.  Meantime, in South Africa the technology had moved on to what we call convergent points, this is like a more modern arrowhead, with two sides or cuts to make a point.  So what it now indicates is that the technology of the making of tools originated here in South Africa and moved from here up to Europe, and then was defined to a great degree in Europe.  Previously, it was thought that the technology was developed there and then moved back down to Africa and elsewhere, but that appears not to be the case now.

Honeycomb

18:21 - Bees Defend Fish Farms from Fungi

Plants make it, bees collect it, and now Propolis could be protecting farmed fish from fungi. Meera spoke to Kelvin Kemm...

Bees Defend Fish Farms from Fungi
Kelvin Kemm

Meera - It seems that bees could be helping out the fish farming industry.

Kelvin -   Absolutely, there's been the most interesting development here, by a couple of scientists, Paul Collet and Ernst Thompson, who both, in fact have an interest in bee keeping but are both trained in Aquaculture.  What they've found is a black sticky substance that bees put around the entrance to their hives, it's called Propolis - pro from the Greek 'in front' and polis from the Greek word for 'city'.  So 'in front of the city', it's a protection at the gate.  It's a black sticky stuff and the bees actually collect it from plants.  When plants get damaged, by insects or wounded in some way the plants get like scabs.  These little scabs defend the plant against bacteria or other pathogens that could harm the plant.  Now the bees have found this out, and the bees collect this stuff and roll it up into little balls and carry it back to the hive.  This stuff has got anti-fungal and anti-yeast and anti-bacterial properties, so they build an entrance protection at the hive and also if there's any cracks or holes in the hive, they bees seal them up with this Propolis.

Meera -   Why is this useful to the fish industry?  What are the problems with farming fish?

Kelvin -   The fish farming business is big money all over the world.  However, the fish are very vulnerable when they're in the form of eggs and larvae and of course if you lose a number it can affect your profitability substantially.  They've traditionally used certain anti-fungals that have been artificially manufactured in factories, but a lot of laws and standards around the world have been passed to ban the use of some of these traditional anti-fungals.

Now these two fellows have found out that this Propolis from the bee hives can be converted into chemicals that can be used in the aquaculture business and seem to be producing results just as good, if not better, than the traditional medicines that have been used in the aquaculture business.

They've actually manufactured a product now which is on sale, it's called Speelmanskop Biobalsam.  Now interestingly, Propolis itself has already been used in products as diverse as toothpaste, lip balm and chewing gum, so it's been indicated as very safe for human consumption - there's no problem using it in the water and for fish. 

It's working, so they look as if they're on to a good thing.  Maybe it will spread all over the world and become a really amazing product.

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