Rainfall, Cloud Dwelling Bacteria and The Ozone Hole

21 November 2004
Presented by Catherine Hawkins, Chris Smith


In this show, we discuss the weather, climate change, and the hole in the ozone layer. From the University of East London Drs. Tom Hill and Bruce Moffett discuss how they have discovered cloud-living bacteria that could be responsible for triggering rainfall, and Dr. Brian Gardiner, from the British Antarctic Survey (BAS) describes how he and 2 colleagues first discovered the ozone hole in the mid 1980s, why it forms in Antarctica, and how CFCs contribute to ozone-depletion. Also, Rosemary joins us to talk about the benefits of Aloe Vera, and space scientist Dr. Julian Osbourne drops in to tell us about the launch of Swift, a satellite intended to look for gamma-ray bursts (GRBs).

In this episode

Stem Cells Mend a Broken Heart

Scientists at Johns Hopkins in the US announced this week that stem cell therapy can be used effectively to treat heart damage caused by heart attacks (known as myocardial infacts) in pigs, paving the way for using the same technique in humans. The scientists injected each pig with about 200 million mesenchymal stem cells collected from the bone marrow of other adult pigs. The injections, which covered an area of the heart wall about the size of a small coin, were placed directly into a region of heart muscle recently damaged by an infarct, by threading a small catheter into the heart via an artery. A second 'control' group of pigs received placebo injections lacking any stem cells. The pigs were then followed up for 2 months. The pigs that received placebo injections became much worse and they developed congestive heart failure. But those that had received the stem cell injections showed full recovery of heart function and their hearts contained virtually no signs of 'scarring', a cardinal signature of previous heart attacks. In such scars muscle tissue is replaced by stiff fibrous tissue which cannot contract properly, reducing the heart's pumping ability, and the scar itself can also affect the electrical properties of the heart, sometimes triggering rhythm disturbances and cardiac arrest. Pigs provide a useful comparison with humans because their organs and physiology are very similar to our own. These encouraging findings suggest that this technique may work effectively in humans.

- Swift

The Naked Scientists spoke to NEW SATELLITE TO SEEK OUT GAMMA RAY BURSTS (GRBs) - Dr. Julian Osbourne


The Swift mission launched this week. Space scientist Julian Osbourne, from the University of Leicester, joins to explain its purpose.

Chris - What are we hoping to learn from the Swift? And why are Gamma Ray Bursts important?

Julian - The Swift is dedicated to gamma ray bursts. Gamma rays are a very energetic ray of light, about 100 thousand times more energetic than a typical packet of life from a light bulb. Bursts were first seen in 1969 by the Bealer satellite. They found bursts that could be a signature of a nuclear explosion, but were coming from space and not from earth. In1997, the first precise position of the burst was found coming from distant galaxies. Gamma ray bursts are significant because they represent very extreme physics. The energy of a gamma ray burst -which might last between 0.1 and 100 seconds - is equivalent to the energy given off in the same duration by a billion billion suns or 10 million galaxies

Chris - What do gamma ray bursts tell us about our history and our place in the universe?

Julian - We might learn about first generation of stars. We have never seen these stars, but we think the first generation of stars were more massive than our present-day stars. It takes a massive star that collapses in a supernova explosion to make one of these gamma way bursts.

Chris - So why was this satellite called Swift?

Julian - It is named after the fast moving bird. After the Swift detects a gamma ray burst, it immediately and very rapidly re-orientates itself to point that direction. It is predicted to re-point about 3 times a week. All satellites move by a magnetic brake on a reaction wheel - basically, a spinning gyroscope. Swift has 6 of these whereas most spacecrafts only have 4, and the ones on Swift are 2-3 times more massive than those used normally. By suddenly grabbing hold of this spinning thing when it detects a gamma ray burst, the satellite can whiz around very quickly.

- The Ozone Hole

The Naked Scientists spoke to THE WHOLE STORY - Brian Gardiner

The Ozone Hole
with THE WHOLE STORY - Brian Gardiner

Chris - In 1985, you discovered the hole in the ozone. How did you make that discovery?

Brian - We had been measuring the ozone since 1957, so we had already established the climatology of the ozone - what the ozone does season-by-season, day by day. We got used to what it looked like, so when we saw the pattern changing in the late 1970's, early 1980's, we knew something was happening.

Catherine - What does the ozone layer do on this planet normally?

Brian - It absorbs ultraviolet light (UV) from the sun. UV is dangerous for most living things. It can damage cells, so it can damage skin and crops. We can actually monitor the ozone layer by looking at this UV light. Because the ozone absorbs it, all we have to do is look at the UV coming down from the sun. If there is a lot getting through, there can't be much ozone.

Catherine - What area of the world has problems with its ozone layer?

Brian - Every area of the world has problems. Because we saw it in Antarctic and politicians took some action about it, ozone depletion over most of the world is relatively mild. It's a real problem in the Polar regions and particularly in Antarctica. We got a lucky break. Antarctica is the last place we expected to see the results of man-made pollution when there aren't too many people living there. But if the hole was over more populated areas, we would be in trouble.

Chris - Why is it in Antarctic?

Brian - During long winter months in the Antarctic, you get several months of complete darkness. Because it's dark, the atmosphere radiates infrared radiation into space, and it gets cool -the stratosphere gets below -80C! At that temperature, you get rare clouds forming that you don't get anywhere else. The CFCs -the chemicals from man-made products that started the hole in the ozone -deposit double chlorine particles (Cl2) on these clouds. When the sun comes out in spring, it splits these doublets into separate chlorine molecules, which destroys the ozone

Catherine - Why isn't ozone depletion compensated for by other parts of the ozone layer?

Brian - Darkness in winter causes very cold temperatures. This causes a stratospheric vortex of air, which keeps to itself and excludes other parts of the stratosphere. There isn't a chance to get ozone from elsewhere until the vortex breaks down when the sun comes back. The ozone each year heals in the spring, but it never gets back completely.

Chris - Why isn't there a hole in the North Pole?

Brian - Everything that happens in the South Pole should happen in the North Pole, but the vortex is different. In the South Pole you have one big circular continent with the ocean going around it. In the North Pole, you have the continents and oceans next to each other. Because land and sea heat at different rates, the temperatures are more confused. Instead of getting a circular vortex like in the South Pole, you tend to get different shapes and sizes. You start a hole forming but then it gets blown off to the side.

Chris - Have the measures we introduced such as knocking out CFCs made a difference?

Brian - Yes. We have eliminated tough CFCs, and we are adding more chemicals to the list. The amount of those chemicals in the atmosphere is now turning over. The ozone hole that got worse during the1980s has now bottomed out. But we don't expect to see the ozone getting to where it was before until 2070

- How Cloud-living Bacteria Could Trigger Rainfall

The Naked Scientists spoke to Bruce Moffett and Tom Hill

How Cloud-living Bacteria Could Trigger Rainfall
with Bruce Moffett and Tom Hill

Chris - Are there many bacteria in clouds?

Tom - There are between 1500 and 20 thousand per millilitre of cloud droplet. All samples hold a lot of the bacterial species Pseudomonas. These are known to make ice form at higher temps than would occur normally.

Bruce - A lot of Pseudomonads are plant pathogens and cause ice to form on plant surfaces. The ice crystal formation damages the plant, minerals leach out, and that's how the bacteria obtain nutrients. Bacteria cause the same thing to happen in rain in clouds, leading to ice crystal formation, triggering rain, and at the same time use the cloud as a means of transport. One way to get down from the hostile environment in the clouds - it's very cold, it's very dark, there's a lot of UV light - is to get yourself rained back down. We know from plant studies that Pseudomonas forms ice crystals. The ice crystals attract water. They get larger and larger until the convection currents within the clouds can't hold them out. Rain falls and the bacteria fall back down with it.

Chris - How do the bacteria get back in the clouds again?

Bruce - They can be blown up by wind currents. If air is heated it will rise. Because bacteria are so small, they don't fall out quickly. So once they get up there, they will be carried along for quite some time

Chris - When you did your field work, how do you know the bacteria weren't blowing off the grass or plants? That they weren't ground-dwelling bacteria that were contaminants?

Tom - Some of them could have come off the ground, but whatever is on the ground will be up in the air a few kilometres away anyway. We got as close to the ocean as we could and we had westerly winds, so we minimised the effects of the ground. But we are going to have to go up in the air. We have a design for what we call a Cyclomic Air Catcher - a vacuum cleaner that spins small particles into a collector. We have a design but we are after someone to build it. We can then go up in aeroplanes or alternatively in balloons.

Aloe Vera

- A History of Aloe Vera

What's the history of aloe vera?

A History of Aloe Vera
with Rosemary


Human use of Aloe Vera goes back thousands of years and it was named by the Arabs. But how do we actually make preparations from it ?

Rosemary - The plant is like a cactus and the inner gel is used for the products. The leaf is sliced and you scoop out the gel from inside. That can be used to make all sorts of products. You can put it on your skin and you can drink it as a detox. . It's absolutely wonderful for the skin. It has anti-bacterial effects -it just cleans the system out. We get lots of referrals from vets for dogs with skin problems, problems with their immune system and arthritis. It's also used to treat burns in many tropical places.

Chris - What do we know about the history of aloe vera?

Rosemary - It goes back thousands of years -it's written in the history books. Alexander the Great used it, Cleopatra used it for skin cleaning and toning up.

- Why do bubbles stick together in soapy water ?

Why do bubbles stick together in soapy water?

Why do bubbles stick together in soapy water ?

Bubbles are made of an oily substance from. Oily substances like other oily substances just like water likes water. Oil and water don't like mixing, so bubbles stick together and exclude water. The chemistry is similar to how people like to mix with groups of friends, but they don't like to mix with strangers. Soap has an oily bit it sticks into grease and grime. It also has an acid bit on the other end that likes water. Because you have these two parts on one bit of soap, you manage to drag the grease into the water and make these 2 things that don't like to mix, mix together - which is how soap works.

- How can we tell what noises the dinosaurs make ?

How can we tell what noises the dinosaurs make?

How can we tell what noises the dinosaurs make ?

The reason you hear those sounds on TV is to make it more interesting. We know dinosaurs probably made noises because they had very good sense of hearing. If you look at dinosaur fossil skulls, you can trace their ear canals and work out where their ears would have been and the kinds of sound they would have responded to. If they could hear sounds, they could probably make sounds. In the late 90's scientists put a fossil through a CT scanner to look at the bone structure. The headpiece was a series of intricately connected tubes a bit like organ pipes. They analysed the structure of these canals and airways, and used a computer to model what would happen if air were blown past. They found that the dinosaur could probably have produced low pitched rumbling noises that could have carried a long way. So what we use for dinosaur sounds on TV is what can be inferred from studying the shape of their fossilised remains, with a bit of artistic license thrown in.

- Can aspartame, the food sweetner, cause or worsen epilepsy ?

Can aspartame, the food sweetner, cause or worsen epilepsy?

Can aspartame, the food sweetner, cause or worsen epilepsy ?

Aspartame is made when the amino acids phenylalanine and alanine are glued together and a methanol group is added on the side. Aspartame stimulates sweetness receptors on the tongue. But when you eat it, it breaks down releasing the 2 amino acids - alanine and phenylalanine, and the methanol. Methanol is poisonous to the brain, so people are concerned that it might make nervous problems worse. To test this, they looked at epileptics. Half were given a harmless placebo and half were given aspartame. There was no increase in the number of seizures amongst the people given aspartame so it probably doesn't cause, or exacerbate epilepsy. It might pickle your brain though, if you ate it in large enough quantities.


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