Questions and Answers

Robots are becoming more and more important in war zones, disaster areas, and in every day life, in order to view places people cant access easily or safely. At the moment flying robots can't last for very long because they use so much power, and ground based robots are constrained to fairly flat surfaces.

Various groups have tried to make wall climbing robots based on suction pads, or reusable gecko adhesive, but none of them work on loose surfaces. Researchers from SRI international have invented a really elegant way to make robots climb walls, using the same principle as how you can rub a balloon on your hair and then stick a balloon to a wall.

This works by a process called electro-adhesion, the balloon sticks because when you rub it, you build up a large negative charge. When this is near the wall, the part of the wall close to the balloon will become positive and attract the balloon, this attraction is large enough for friction to hold it up. But on a conducting wall the charge will escape and the balloon will fall off quickly.

Harsh Prahlad and collegues have built a robot on the same principle, it has a series of electrodes insulated form the wall by a thin layer of flexible rubber. The robot charges up these electrodes to several thousand volts which then attract the wall in the same way as the balloon, and because the electrodes are insulated it will work on metal surfaces as well.

The robot will climb walls which are dusty, and can support between 20 and 140g per square cm of clamping area. But the researchers are still working on walls that are wet, as unfortunately the robot sticks to the water rather better than the wall...!

Prostate cancer affects more than 670,000 men worldwide, and researchers have known for a long time that the disease is fuelled by the male sex hormone testosterone.  Men with prostate cancer are often given drugs that block the production or actions for testosterone in the body, and these treatments are often successful to start with, but their cancer eventually develops resistance and starts growing again.

Now scientists at the New York Presbyterian Hospital and the Weill Cornell Medical Centre have made a surprising discovery that could make a big impact on the way that men are treated, if the results hold true.

Led by Dr Mark Rubin, the scientists analysed the activity levels of more than 6,000 genes in 455 prostate cancer samples.  They found that samples from more aggressive cancers appeared to be driven by a receptor for oestrogen, the female sex hormone.  

To get a bit more detailed, around half of all aggressive prostate cancers are driven by a fusion protein, created when two important genes get spliced together.  The researchers found that oestrogen can boost the activity of this fusion protein, fuelling the cancer growth.

But what does this mean for men with prostate cancer? We know that oestrogen plays an important role in fuelling breast cancer, and there are a number of very successful therapies for this disease that target the hormone.  So this discovery raises the possibility that similar drugs could be used to treat men with aggressive prostate cancer.  And, more speculatively, there's the possibility that oestrogen or oestrogen mimics in the environment might be helping to increase the risk of prostate cancer, or fuelling its growth.

US researchers have developed a system which translates brain activity into movements of a prosthetic arm, a discovery which could help patients paralysed by strokes, injuries and other diseases to regain their independence.

Writing in this week's Nature, University of Pittsburgh researcher Andrew Schwartz and his colleagues have successfully trained monkeys to use their thoughts to feed themselves with a robot.  The monkeys were each fitted with a small implantable electrode which was inserted into the main motor area on one side of the brain.The electrodes were able to pick up the electrical chatter of nerve cells signaling to each other about the next movement the animal was going to make. This activity was relayed to a computer which decoded the nerve signals and turned them into movements of a robot arm sitting beside the animal.  With time and training, just by thinking along the right lines, the monkeys were able to use the robot arm to reach out to a variety of locations and to pick up a food item and return it to their mouths with high accuracy.

The trick that the team have used is to develop a way to accurately interpret the neurological signals that encode the direction and speed of planned movements.  Scientists have discovered that individual motor nerve cells become most active when a movement takes place in a certain direction preferred by that cell.  Movements in other directions tend to excite the cell less.  This means that by eavesdropping on the activity of a large number of cells simultaneously it's possible to work out the direction of the planned movement, and this is the information then sent to the robot.

The work marks a major step forward in the field, which previously offered paralysed patients little more than the ability to move a cursor around a screen.  A system like this could, theoretically, be linked back up to a paralysed person's own muscles, or used to allow an amputee to precisely and naturally control a prosthesis.

This is a really good question and in fact they do. Bees do have segmented legs, consisting of parts called a coax, a trochanter, a femur, a tibia and a tarsus. The jointw between which must be considered to be 'knees'.

There's been some discussion on the Naked Scientists' forum about this and Turnipsock suggests that perhaps the expression "The Bee's Knees" comes from the fact that they store pollen in these hairy baskets on their knees. They have hairs on their knees which are used to collect a big build-up of pollen. So, this could look like something very big and spectacular, hence the expression.

Fortunately the Phoenix mission did land safely last week which was much to the relief of William Boynton.  He's part of that mission.  He designed something called the Thermal and Evolved Gas experiment which is analysing the Martian soil.  He's from the University of Arizona and he's with us again to give us an update. Hello William.

William - Hello there.

Chris - Thank you for joining us again this week on the Naked Scientists. We thought we'd catch up to find out, now we've established Phoenix has landed safely, what it is that you'll now be doing over the next few months to understand more about the surface of Mars.

William - Yes. Well, first of all we're incredibly excited that we've got there. That was really a hairy time when we're not sure everything's going to work but we did eventually get down to the ground and that's good. This last week we've been going through what's called a characterisation phase which is where we're really trying to look around us and take some pictures and map out the landscape so we know what we're working with. It's going to be another three or four days before we get down to actually collecting samples and doing the analyses of them with the various analytical instruments that are brought landward.

Chris - What sorts of experiments will you do?

William - Well, the instrument that I'm responsible for, as you mentioned, which we call a TEGA. It will take some of the soil and ice samples that are dug up by the robotic arm. It puts them into a very tiny oven. We heat the samples up in the oven and there's two things we're looking for. If there are any phase transitions: this is for example if we have ice when we heat it up to 0 Celsius it will melt. It takes more heat to do that and so we are keeping track of the heat required to raise [temperature of] the sample.  That way we can tell how much ice is in the oven. The other thing that we're doing is we're looking at the gases that are given off by the sample as we heat it. We pass the gas on to the evolved gas analyser which has a mass spectrometer analyser in it and tells us what gases are given off. If we see water come off at a certain temperature that can tell us the nature of the mineral that evolved the water.

Chris - What are the big questions that you'll be answering with these experiments?

William - With that particular one we'll be just looking to see how much ice is present, mixed in with the soil. We actually think it's very high ice content once we get beneath the soil. We'll be looking for isotopic ratios. This is, for the same element, two different nuclei that have the different masses. The most important one is for hydrogen. Normally it's mass 1 but there's another form of it called deuterium which is mass 2. The ratio of those two things can tell us something about the history of the water and the temperature at which the ice formed in the past, things like that. We do have one other part of it that we're very hopeful will get some interesting results. We will be looking at organic compounds that might be evolved from the soil as we heat it up to high temperatures.

Dave - What does Mars look like where you've landed?

William - Perhaps surprisingly it looks pretty much as we expected. It's kind of interesting before all of these missions land there's usually some artist's concept of what the lander's going to look like on the surface and things that are passed around to the press and so forth. This time it was actually quite remarkable that the artist's concept agrees pretty much with what we see. We see a very, very flat region with very little topography. We're also on this region called patterned ground or polygonal terrain. What we find is that we land in this area which is filled with these polygons that range in size from a few metres up to really quite large ones. This is due to cracking of the ice. During the very cold winters on Mars the ice will contract and shrink and it leaves cracks. Then in the summertime it expands and the ice expands back to fill the crack. Meanwhile some dirt has fallen back into the crack and after many years of this we end up with this polygons which are formed by these cracks.

Chris - Looking at how you're managing to survive on Earth at the moment, William, I understand that you're living on Mars time. How does that work?

William - It turns out this lander is powered by solar cells and so it's only in the middle of the day. Actually from about 9am to 5pm local time on Mars that we have enough sunlight to efficiently operate the lander. We're in the high latitudes in summer so there's some sunlight shining on the lander all the time but really not enough to power it. The lander goes to sleep every day about 6pm local time and will wake up about 8 or 9am local time. It turns out Mars' day is about 40 minutes longer than an Earth day and so we can only operate that on this 24 hour and 40 minute cycle.

Chris - So your days are getting 40 minutes longer every day?

William - Yes, our days are getting 400 minutes longer every day because we have to be there when the lander goes to bed and sends down the data for us to look at.

Chris - You have my sympathy. I'm sure your body clock is now totally screwed.

William - It is really messed up. It's like perpetual jet lag of 40 minutes more each day.

Chris - Good luck with that, William!

The first thing to note is that grey hairs are not grey. They're actually white because hair colour is determined by pigment that is made by hair follicle cells. There comes a time in everyone's life where basically the pigment stops being produced. You start producing hairs that have no pigment so they're white. This mixed with your hair colour gives the grey effect. Rather than hairs starting coloured and going white, although that is possible, you tend to get hairs that start off being white.

Another question is, does people's hair really go grey overnight?

Kat: I have looked at it a bit and there seems to be a bit of an argument in it. The only way I can see it's possible is if someone has very short hair. They go grey due to some stress event. Maybe their hair's falling out. It might look like over a very short period of time if you have very short hair that you're going grey overnight.

Chris: I've seen patients who have a hair which they've showed me themselves and say, "This is interesting doc, look at this." It's white at the base and then brown halfway along because it's literally run out of melanin to add to the hair and it's changed colour.

Yes. In theory you could do that. Blood is actually full of protein and it's full of iron, which you need in your diet. Don't forget that black pudding is just congealed blood that you fry. Blood also contains water which you need and there are some salts in there, so you can get protein, salt and iron from drinking blood.

There will be other things that you can't get from blood like water-soluble vitamins which are not present in large amounts. There will also be some fat-soluble vitamins which don't appear in large amounts in blood. You can probably make a reasonable meal out of blood but it wouldn't make up for all of your dietary requirements and so you might want to eat some freeze dried body pellets to supplement your intake. That's no different, really, from eating a microwave meal which is effectively just a dried out bit of body. It may not be human, it's just animal instead.

The process is very likely to be the same as any other hair colour. All you're doing is losing from the hair the ability to add some colour. The colour is accounted for by different forms of melanin: the same hormone, the same chemical in the skin that makes you go brown. You just lose the ability to add that to the hair so you see the natural colour of the hair: the keratin and that's the stuff which is white.

This is a semantics issue. A meteor is a lump of rock on collision course with something - they're whizzing towards them. When they hit the ground they become a meteorite - a congealed lump of rock which has melted on the way through and landed on the ground. So a meteorite is something which has made it to a planet's surface. An asteroid is a huge chunk of debris left in space which is effectively a failed planet that never managed to form.

Chris - What's all this about computers designing new ways to ward of mosquitoes?

Mark - This is fantastic. The chemical compound, DEET is the gold standard in insect repellents. The University of Florida scientists have trained a computer to come up with even better repellents. Basically they took an artificial neural network which is kind of a computer programme that's trained to recognise patterns in huge, complex sets of data. They let it loose on the US Department of Agriculture's database of insect repellents. 60 years' worth of data, 40,000 chemical structures. It slowly learned, with some help from the scientists, how to relate the structure of the compound, the position of atoms to its activity as an insect repellent. Then they gave it 2000 new chemical structures, many of which had never been created, to have a look at. It picked out 11 previously known molecules and 23 completely new and had to be synthesised. When the chemists actually made these molecules and tested them next to DEET they found they were much better in some cases. They were active for 73 days as opposed to 17.5 days.

Chris - Could they be applied to the skin safely without risk to health?

Mark - Certainly the quickest way to try these things is to try them on your skin. Indeed, the fearless chemists did try these out with little swabs, patches with this chemical absorbed - stuck onto their skin. This is obviously a little way from being a new insect repellent going on the market. They have identified the best seven compounds which are now under further study.

Chris - It's very exciting because mosquitoes are responsible for spreading so many diseases. Incidentally on of those chemists who tested it is just having his other arm removed as we speak. There's another interesting thing here about bubbles that can last for donkey's years.

Mark - A year at least. Gas bubbles are an essential part of everything from ice cream, foams, paint. The size of the bubbles really affects their properties. The trouble is that bubbles less than a micrometre in size, just a millionth of a metre, are really hard to make. The trouble is smaller bubbles tend to aggregate and merge into bigger ones. Now a group of scientists at Unilever, the people who make everything from paint to ice cream to washing powder, teamed up with people from Harvard University. They found a way to make microbubbles that last longer than a year. Basically they've used a really clever mix of surfactants. They're often used in detergents to keep oil, grease and water apart. These are molecules that look kind of like little tadpoles. They have a water-loving head and a fat-loving tail. These tadpole molecules all line up in a big sphere and actually encapsulate and stabilise these microbubbles.

Chris - So it would mean better paints, better ice cream?

Mark - Exactly. If you think about it beer is a good example. If you think about the difference in taste between Guinness and the lager a lot of it is to do with the feel of it on your tongue. You have really big fat bubbles in lager and tiny little microbubbles in Guinness so all these things are very important for the chemists that make, like I said, everything from ice cream to paint.

Chris - Thank you, Mark. Lastly, superconductors. This is really big business. We've heard about data centres consuming enormous amounts of energy and being very bad for the environment but superconductors are a way of potentially alleviating that problem if we can find a way to make them work.

Mark - It's one of the challenges which is, I think, up there alongside developing fusion power. Superconductors carry electricity with no resistance at all. There are already many small-scale uses for them. If you could use them on a very large scale replacing cables on a power grid you could transform the way we use energy. Resistance takes up about 10% of power that's pumped into the American grid, for example. The trouble is superconductivity only switches on at very low temperatures. About 20 years ago scientists found some copper-based compounds which are our best candidates for high temperature superconductors. They start doing that at -135 degrees.

Chris - But it's still -135 degrees.

Mark - It's still pretty chilly. The trouble is progress stalled at that stage and no one knows how they work and for a decade no one's been able to improve much on that temperature. In the last three months about half a dozen different groups in China and Japan have made really rapid progress with a completely different set of compounds. Instead of copper and oxygen atoms in these compounds they have iron and arsenic. There's a smattering of other elements which they've been tweaking: lanthanum, samarium. Exotic things. Already in three months they've seen a 30 degree improvement in these compounds which in the field is quite a significant improvement. That superconducting temperature, that threshold temperature is still at -218 so it's a long way from being practical but they key thing is it's revitalised a field where physicists had been banging their head against the wall for ten years, making very little progress. Crucially these are the best alternative candidates you can actually compare to. No one really knows how these materials really work. If you've got one set of copper-based compounds you can now compare them to these new iron compounds and try and work out how they're functioning.

Well, actually you could sit on an electricity wire and not get electrocuted as long as you didn't touch anything else. The birds aren't doing anything special. The reason they're able to sit there is because they're not earthing or producing a route for the electricity to get from the wire down to the ground. If you were to hang on to the wire and touch the pylon that's holding the wire then you'd have a problem. The wires are at a very high voltage, the pylon's at a very low voltage and you provide a very convenient circuit down to earth for the electricity. The birds that are sitting on the wire there's no difference in potential between one leg and the other. Both legs are sitting on the wire so there's no reason for the electricity to want to flow through them.