Organ Transplants without Rejection

Four out of five patients participating in a recent kidney transplant trial in America have been able to stop using immune-suppressing drugs.

The patients, aged 22-46 years old, had all developed kidney failure for different reasons.  Prior to receiving the donor organ each of the patients received a course of drugs to partially destroy their bone marrow and the T lymphocytes, white blood cells that recognise and reject foreign tissue.  After this "conditioning" regimen was complete the patients underwent a combined transplant during which they received the new donor kidney and were also injected with their donor's bone marrow cells.

The results have been striking.  Between nine and fourteen months after each transplant all but one of the patients have been able to stop taking any immunosuppressive drugs, and their kidneys remain healthy without any signs of rejection up to 5 years later.  The scientists think that the transplantation of the donor bone marrow triggers the recipient's body to develop "tolerance" to the foreign organ, possibly by re-educating the recipient's white blood cells into ignoring what was previously viewed as hostile.

According to senior study author David Sachs from the Massachusetts General Hospital Transplantation Biology Research Center in Boston, "we are very encouraged by our initial success in inducing tolerance.  While we need to study this approach in a larger group of patients before it is ready for broad clinical use, this is the first time that tolerance to a series of mismatched transplants has been intentionally and successfully induced."

The findings will almost certainly come as welcome news to the thousands of patients who face a twice-weekly trek to their nearest hospital for dialysis whilst they wait for a suitable donor organ to be found.

27th Jan 2008

Cell phones to Detect Nuclear Terrorism

One of the biggest nightmares of the police and security services is a dirty bomb, this is where a terrorist blows up a conventional bomb surrounded with radioactive material. This is not a real nuclear bomb, but could make a small area radioactive for a long time, and create a huge amount of panic. The real headache is that without special equipment is is very hard to tell if something is radioactive so you could walk down a street with a bag full of nuclear waste without being noticed.

Researchers at Purdue university and a consulting scientists called Andrew Longman have come up with a possible solution by taking advantage of mobile phones. The idea is to put a small cheap solid state radiation detector in as many mobile phones as possible. Many mobile phones especially in the US have positioning devices built into them, so if a phone detects more than a certain level of radiation it can automatically call into a base station and report the radiation level and its position.

Andrew has developed software that will put together hundreds of these reports and only give a warning if several phones detect radiation which is in the same place or moving at a sensible speed and could be from the same source.

The whole system would be dependent on getting mobile phone manufacturers to put detectors into enough phones that you can build up a useful network of detectors, not picking up legitimately radioactive things such a people undergoing a course of nuclear medicine, and persuading people they want to carry a phone that is reporting back to the government all the time.

27th Jan 2008

Pregnancy-Caffeine Combo Bad Idea

Researchers have shown that caffeine exposure is linked to an increase risk of miscarriage.

De-Kun Li, from Californian health insurer Kaiser-Permanente, followed 1063 women during the first twenty weeks of their pregnancies or until they had a miscarriage. Amongst the details collected, the participants were asked about their caffeine consumption.  The data is published in the American Journal of Obstetrics and Gynecology and shows that women drinking more than 200 milligrams of caffeine per day - the equivalent to just over one cup of coffee - had a two-fold rise in their miscarriage risk.

But it wasn't just coffee that was to blame - all caffeinated beverages including fizzy drinks, tea and even hot chocolate had the same effect.  According to Li, caffeine might be triggering vaso-constriction - blood vessel narrowing - in the placenta, cutting blood flow and the delivery of oxygen and collection of waste products from the developing foetus.  Alternatively, he says, caffeine may be directly toxic to a foetus.  Either way he suggests that women avoid caffeine altogether during pregnancy. "It's not a big sacrifice," he says.

27th Jan 2008

Grass could be the fuel of the future

Transport systems have been powered by grass for hundreds of years in the form of horses, but it looks like it will be a fuel of the future as well. Farmers in Nebraska and the Dakotas have been taking part in a study on Switchgrass a perennial native American plant, that often grows as a weed.

They have been studying how much energy it takes to grow the grass, including fuel to power the tractors, and the energy required to make the fertilizer used to speed its growth and to produce the seeds.

Once the grass is established they have found that it produces 5-11 tonnes of grass per hectare depending on the weather which translates into ethanol with at least 5 ½ times the energy that was put in, which compares very favourably to other methods of making biofuels based on fermenting foodstuffs such as maize which only produce 1 ¼ times the energy that is put in.

The major unknown in this calculation is the large scale conversion of cellulose, which makes up most of the energy in grass, into ethanol which conventional yeast fermentation can't do. Conventional methods of doing this involve using large amounts of enzymes to break down the cellulose into sugars which yeasts can then break down.

And in another related story this week a company called Coskata in America has developed a new strategy and they claim to be able to produce ethanol at about $1 a gallon or about 12p a litre. This relies of heating up the vegetable material without oxygen to form a mixture of carbon monoxide and and hydrogen known as syngas. This gas is then fed through a tank full of bacteria which convert the syngas into ethanol.

So with any luck a form of biofuel which is actually useful at combatting global warming may be around the corner.

27th Jan 2008

The Blackest Black

One big thing that’s been in the news in the last weeks or so is a story about the blackest black that’s ever been seen.  Using carbon nanotubes Professor Pulickel Ajayan from Rensselaer Polytechnic has developed a material that he says absorbs over 99.9% of all the light that falls on it.  That’s 30 times darker than our current benchmark, or what we call black. 

Chris - Hello Pulickel, thank you for joining us.

Pulickel - Thank you.

Chris - So why have you done this?  What is this stuff?

Pulickel - Well, an ideal black material absorbs light at all wavelengths and all angles, basically.  There were some speculations published by Spanish and English scientists who said if you take these tiny carbon cylinders and organise them into an array you can get very high absorbancy and very low integral refraction.  Of course to get a very black substance you also need to minimise the reflectants on the surface and you can do that by creating a surface softness.

Chris - So how does your technique actually work?  If I was to zoom in with a very powerful microscope on the surface that you’ve created that is very back, what would I see?

Pulickel - Right, you will see nano scale cylinders of these carbon materials.  A nanometre is about a billionth of a metre so you have several of these structures that are just randomly placed on the surface.  That’s what actually decreases the surface reflectance.

Chris - So you have these tiny tubes.  I mean, looking at the scale of them that would make them 400 or 500 times thinner than a human hair wouldn’t it?

Pulickel - It would be more than that, about 3 orders of magnitude smaller than..[a human hair]

Chris - So you have these peppered all over a surface?  How do you make them..

Pulickel - There is a periodicity of these structures in the bulk of the material.  In the surface you have a random array so it satisfies both criteria: that you have a very highly absorbent material and also it reflects very little on the surface.

Chris - So how does it actually work to mean that so little light comes back off?

Pulickel - It’s basically almost like the light enters this material and it gets trapped because of this periodicity.  That’s why you have a very low index of refraction.

Chris - How would you see this being used?  It’s one thing to get into the Guinness Book of Records for the World’s blackest substance but how is this actually useful?

Pulickel - It was done mostly from an academic curiosity but something that absorbs a lot of light would be useful as a solar collector.  Again, in order to make this into an appropriate device you would have to worry about some other losses from material as a result of light.  Certainly it’ll be a very strong absorber.  It could also be useful in areas where you want a very black background so that you can have a high definition of the areas which are light and black.

 Chris - So you could use it to trap sunlight which would make solar cells more efficient.  What about other things?  Does it work outside the visible spectrum of light?  Of course, there’s much more to light than just what we can see: things like radio waves, microwaves and at the other end of the scale x-rays and gamma waves.

Pulickel - Absolutely, that’s our hope.  We have not done these things yet but we are in the process of doing the high end IR and other wavelengths.  That’ll be much more interesting from various points of view.

Chris - Thank you very much, Pulickel.  Good to have you on the show.

January 2008

Inverted Bucket

Have a bucket full of water upside down over your head, and stay dry!

What you need

What to Do

What may Happen

With any luck you should have stayed entirely dry.