Archive for April, 2011

The british press and the issue of mobile phone safety

April 27, 2011
A typical mobile phone user

A typical mobile phone user

Do mobile phones cause brain cancer? This is the question at the heart of concerns around mobile phone safety. This concern continues:

  • despite the fact that there is not a single known case of harm arising from the use of mobile phones* and,
  • despite the fact that incidence of the relevant cancers has not changed significantly over the last two decades during which mobile phone use has risen exponentially and,
  • despite the fact that no one has provided a convincing model of how the phones could even in theory cause harm.

Now there are real issues around mobile phone safety, and we spend an evening discussing them in Protons for Breakfast. These issues should form topics that can addressed rationally by the press. It is possible, and as an example, please read this superb article in New York times (I think you may need to register to read the article, but it is worth it). It is written by Siddhartha Mukherjee, a cancer specialist, and introduces all the complexity of the subject in an intelligent and accessible way. It does not resort to platitudes, but simply reports the situation as it is. Reading it I felt reassured that intelligent journalism was actually possible.

Sadly, I  have yet to read a single rational article about this the British press. I won’t bore you with the all the articles in my database. The stories are uniformly facile – even in apparently august journals such as The Telegraph – and designed explicitly to engender fear, uncertainty, and doubt. These are factors which newspapers believe encourage media consumption.

They stories are simply ‘hacks’ of whatever press release some journalist is required to create a story around. However, the most egregious nonsense moves beyond the pathetic to the truly spectacular, and the prize must be awarded  to The Independent on Sunday for its article Mobile phone radiation wrecks your sleep. This was its front page headline on Sunday 20th January 2008. The story begins routinely enough reporting results of an unrefereed conference article which claims that mobile phone radiation affected the sleep of a cohort of people studied. Scratching around for supporting evidence Geoffrey Lean (again) happens upon the result of a study which he claims supports his thesis:

It also complements other recent research. A massive study, following 1,656 Belgian teenagers for a year, found most of them used their phones after going to bed. It concluded that those who did this once a week were more than three times – and those who used them more often more than five times – as likely to be “very tired”.

Did you catch that? Yes. This is a major UK newspaper reporting on its front page that teenagers who use their mobile phones in bed are likely to report that they are “very tired”. Can you believe that an apparently reputable UK newspaper can publish such risible nonsense? I urge you to laugh – it helps keep back the tears.

* This excludes harm arising from inattention caused by distraction while using the phone which has caused many road deaths and at least one train crash.

NASA Celebrates Earth Day

April 26, 2011
NASA image of the Lena Delta

NASA image of the Lena Delta. Click for larger image.

Satellite imagery has transformed our conception of our planet, and I consider that a blessing. Because of the images we have seen, it is now undeniable that everyone on Earth shares something, even if it is only the atmosphere. Perhaps this single, barely-definable, change of consciousness will in the end prove to be NASA’s greatest achievement.

Anyway. To celebrate Earth day – which I have to confess passed me by – NASA have compiled 70 photographs in a slide show. You can download all the pictures in high resolution and many of them are breathtakingly beautiful. Take a look – it is worth a moment or two of anyone’s time. I chose the picture above because of the abstractness of the pattern, which could have been a micrograph, but in fact shows a river delta. Click to enlarge the picture and just gaze at our planet in wonder.

More illusion confusion

April 26, 2011
Circle Colour Illusion

Circle Colour Illusion designed by Akiyoshi Kitaoka. The image shows 12 sets of concentric circles. The 5 inner circles are all identically coloured, but it does not look like it. Read below to see how you can convince yourself. Click for a larger image.

After writing the article on colour illusions yesterday I was dissatisfied with the poor quality of the images in the Scientific American slideshow. Additionally, some of illusions were so amazing that they were hard to believe at all, and having poorly defined images just confused the issue. So I decided to make some of my own.

I used PowerPoint, which has the advantage that if you download the PowerPoint file you will be able to de-construct the images, and play around and convince yourself that your colour perception really is playing tricks with you! Enjoy 🙂

Blue Circle Illusion

Blue Circle Illusion. The grey circles in this image look 'pink-ish', but in fact they are just grey. Click for larger image.

The Vision of Johanna. And Jenny. And you and me

April 25, 2011

The eye on the left appears blue, but in fact it is exactly the same colour as the eye on the right.

Vision and colour are central to our perception of the world. But vision in general, and colour vision in particular, are still in 2011 subtly mysterious. I have been reminded of this several times recently and I just thought I would note three curious things about our vision system which continue to fascinate me.

The first is the variability of colour vision from person to person. At the celebratory drinks after the end of the 14th presentation, Protons for Breakfast graduate and Bob Dylan fan Joanna [pace the title] explained that she had distinctly different colour vision in each eye. The situation was such that at times she simply wasn’t able to say definitely what colour she really thought some things were! My colleague Jenny at NPL has also mentioned this but she seemed less troubled by it. But if I personally know two people with distinctly different colour vision in each eye, then how likely is it that your colour vision is the same as mine? Or that anybody’s colour vision is the same as the ‘standard’ sensitivity curve decided on by the International Commission on Illumination (CIE) in 1931?

  • Test the sensitivity of your colour discrimination here – its tricky!

And then there is the issue of the way we infer colour from context. I took the image at the start of this article from a slide show over at Scientific American. I simply didn’t believe that the two eyes were the same colour. So I downloaded the image, and sure enough in the image on the Scientific American web site, the eyes were slightly different colours. So I edited the image to make them exactly the same – that’s the image at the start of this article – and the illusion is still there. It is very unsettling to realise that our perception of a particular shade as ‘blue’ or ‘grey’ can be quite so context sensitive. In some of the images in the slide show, the author states that the explanation of the illusion is still unknown.

And finally there is the fact that even, after 150 years of careful study, we are still finding out new things about the structure of the eye itself. Scientific American this month reports on some astounding work that has uncovered additional light sensitive cells in the retina of human eye. The work is based on some very simple observations – that blind mice still responded to the daily cycle of light and dark, and still reduced pupil size in a bright light. Following on from this, the author, Ignacio Provencio, and his colleagues, uncovered previously unnoticed cells, comprising around 1% of the normal cone cells which are not part of the normal imaging system. Instead they are linked to the part of the brain which controls our daily cycle – the circadian rhythm – and also controls our pupil size.

So if we understand our visual system so little, how can we be sure that we really understand anything we see? Perhaps, the pattern of tiny pixels on my computer screen do not really indicate that it is now 45 minutes past midnight? Perhaps it is all just an illusion. Somehow, I doubt it. Goodnight.

UPDATED 7:23 a.m. 26th April 2011: Thanks to Nick Day for the comment and the additional links.

RF all around us

April 25, 2011
Infra Red Remote Controlled Helicopter (c) The Register

Infra Red Remote Controlled Helicopter ©The Register

At Protons for Breakfast we talk a lot about the different frequencies of elecromagnetic waves and how they are used in different ways. Over at the computer-tech site The Register, they have published the answers to a competition asking people to specify exactly which frequencies are being used in a variety of devices. The answers are entertainingly written and so probably worth a look, but the summary is below. It shows how we routinely exploit electromagnetic waves with frequencies from   130 kHz to 340 THz – frequencies which differ by a factor of over 2,415,000,000 – more than 2 billion!

  • Toy Helicopter with infra red remote control 340 THz
  • Oil Tank Depth Gauge: 433 MHz
  • Bluetooth Mouse: 2.4 GHz
  • Pet Radio Tag 130 kHz
  • GPS device with a bluetooth link. GPS reception is between 1.1 and 1.5GHz but Bluetooth broadcast is at 2.4GHz
  • Remote control thermostat 433.9 MHz
  • Baby Monitor 50 MHz
  • Car Key with remote locking 418 MHz
  • Oyster Card – read at 13.56 MHz
  • DECT cordless phone 1.9 GHz
  • 3G Femtocell: 2.1 GHz
  • Sky TV dish receiving at 12 GHz
  • Microwave Relay at 5.8 GHz
  • Analogue TV aerial 600 MHz to 800 MHz
  • Satellite Broadband dish receiving at 14 GHz
  • Bluetooth video sender broadcasting at 2.4 GHz
  • Wireless remote controlled light switch 433 MHz or 868 MHz
  • Device for reading household power consumption 868 MHz

Fukushima: What happened?

April 19, 2011

It’s been 6 weeks since the Fukushima nuclear accident, and news reports of the incident vary from the facile

to the mundanely exagerated

However, I have yet to read a clear web account of what has actually happened! The Wikipedia timeline somehow confuses rather than elucidates. A couple of weeks back I was lucky enough to receive a PowerPoint presentation by Mattias Braun from Areva. Using this and other sources I have attempted to summarise what actually happened.

The Fukushima Daiichi Site #1 consisted of 4 boiling water reactors:

  • Unit 1 – GE Mark I BWR (439 MW), Operating since 1971
  • Units 2-4 – GE Mark I BWR (760 MW), Operating since 1974
Unit 4 was shut down at the time of the accident and a pool in the building was used to store spent fuel rods – of which more later. A key feature worthy of note is that  these units were more than 35 years old, and nearly at the end of their operating life.
The reactor structure was similar for each reactor. The inner pressure vessel was contained within a ‘pear-shaped’ dry containment vessel, surrounded by a torus-shaped so-called ‘wet well’. So, yes, everything was already ‘pear-shaped’ even before the accident 😉
The structure of each reactor was similar

The structure of each reactor was similar

The structure of each reactor.

The structure of each reactor. Click to enlarge.

11th March 2011: 14:46 The Earthquake struck causing an immediate ‘scram’ and all three operating reactors shut down safely. As I have described previously, this reduced the heat generated in the core from a breathtaking 1500 MW to something close to 100 MW – still a great deal of heat. Diesel generators started to provide power to circulate water to keep the cores cool. At this point the plant was stable and the operators were perhaps feeling relieved that things had gone at least roughly according to plan.

11th March 2011: 15:41 Now the tsunami arrives. With a height of 14 metres, it overtopped the defences designed for a 7 metre tsunami. The entire plant was disconnected from mains electricity, and the diesel generators and their fuel supplies were destroyed. The cooling system continued to cool the core powered by batteries and the operators began to cope with what had happened.

Reactor#1 At 16:36 – barely two hours after shutdown – the batteries failed. The  operators now had only one core-cooling option. This was to relieve the excess pressure in the reactor vessel by discharging steam into the ‘wet well’ where it can condense as long as the temperature is below 100 °C. This reduces the temperature and pressure in the  reactor vessel and provides some cooling, but inevitably lowers the level of water in the reactor vessel, eventually exposing the core material.

Cooling the reactor core by discharging steam to the wet well lowers the water level in the core.

Cooling the reactor core by discharging steam to the wet well lowers the water level in the core. Click to enlarge.

The liquid water in the core is now a boiling mass, and the foam provides some cooling to all the core, so even at 50% exposure of the core material, the core is safe. However further loss of coolant is critical:

  • When the water level falls to 33%, the temperature of the central part of the core exceeds 900 °C, and the zirconium cladding that surrounds each fuel element swells and breaks releasing volatile fission products into the cooling water.
  • When the water level falls to 25%, the temperature of the central part of the core exceeds 1200 °C, and the zirconium cladding begins to burn in the steam creating zirconium oxide, and hydrogen gas. In unit 1 it is believed that more than 300 kg of hydrogen gas was created.
  • The core is believed to have been exposed for 27 hours and the temperature is believed to have eventually risen to an astonishing 2700 °C, at which point the uranium and zirconium would form a molten blob in the centre of the core.
The progressive exposure of the core

The progressive exposure of the core is the price paid for reducing pressure and temperature in the reactor. In Reactor 1 temperatures eventually exceeded 2700 C causing a partial meltdown. The reaction of the zirconium with water released hydrogen gas into the steam.

At this point the containment is successfully containing
  • steam,
  • hydrogen gas caused by the dissociation of water in reaction with the zirconium.
  • volatile elements from the core – most notably the fission products, Caesium and Iodine
However the pressure is now over 8 atmospheres in a containment with a design pressure of 4 bar. Operators decide to release the gas and so lower the pressure. They understand that this will (a) release relatively short-lived isotopes into the atmosphere and (b) will probably result in an explosion as the hydrogen mixes with air. However, they really have no options left. And the core remains contained with very little release of the very long-lived radioactive elements in the core.
The inevitable progression towards an explosion in the superstructure of the reactor.

The inevitable progression towards an explosion in the superstructure of the reactor. Click for a larger version.

In reactor 1 the pressure release occurred at 4:00 on 12th March and the hydrogen explosion followed shortly thereafter. The superstructure of the reactor building was blown apart, but there was no damage to critical containment systems. Eventually the entire system was cooled by flooding with seawater.
Eventually - and currently - the entire containment was flooded with sea water coolant.

Eventually - and currently - the entire containment was flooded with sea water coolant.

Reactor#2 The story for reactor 2 is similar to that for reactor 1, but the battery system operated until 13th March at 2:44. Thereafter the progression to an explosion was inevitable. However in this case the core was only left exposed for around 7 hours so the temperature probably ‘only’ reached 2500 °C, not quite enough to cause melting of the uranium-zirconium mixture. However, in this case, the hydrogen explosion at least partly took place within the containment vessel, fracturing part of the ‘wet well’

In Reactor 2 a hydrogen explosion damaged the containment.

In Reactor 2 a hydrogen explosion damaged the containment. The reasons for this are not clear, and the consequences are not clear either.

Reactor#3 The story for reactor 3 is similar to that for reactor 1, but the battery system operated until a pump failure at 14th March at 13:25. Thereafter the progression to an explosion was similar to reactor 1. However in this case the core was only left exposed for around 7 hours so the temperature probably ‘only’ reached 1800 °C.

Reactor#4 was closed down, and the storage pool was used to store spent fuel. Without additional cooling,  the water began to evaporate and eventually the used fuel rods were completely exposed allowing volatile fission products to reach the atmosphere – possibly a more serious event than the reactor accidents.

The drying out of the spent storage pool above Reactor 4.

The drying out of the spent storage pool above Reactor 4. This led to direct exposure of volatile fission products to the atmosphere - possibly more serious than the reactor accidents.

What I did on my holidays

April 17, 2011
Wind Turbines on Rhyl Flats: Is this really an eyesore?

Wind Turbines on Rhyl Flats: Is this really an eyesore? Click on the picture to see a more detailed view.

Wind Turbines on Rhyl Flats: Close up using a 520 mm focal length lens

Wind Turbines on Rhyl Flats: Close up using a 520 mm focal length lens

Just back from a much needed break in North Wales during which I made no phone calls and did not switch on my computer once :-). However, I was unable to switch off my interest in UK energy policy, and I found much to stimulate my thinking.

Wind: One of my most surprising observations was the lack of wind turbines in this famously windy part of the UK. We saw only one on-shore wind farm [Mawla (Moel Maelogen)] and one off-shore farm Rhyl Flats.The 25 turbine, off-shore farm was only just visible on the horizon – the photograph above was taken through a 520 mm focal length lens – but even constructing this farm and its planned extension had caused heated local objections. For example:

Janet Haworth from Llandudno: Llandudno and Rhos-on-Sea have formed an action group…. Save Our Scenery S.O.S. to save the heritage bay… from a wanton act of vandalism to place up to 260 wind turbines in the bay. It will fence off our horizon with a wall of steel…

Lucia Pritchard. aged 12, from Llandudno. I think it will be horrible to put these monsters in our town, it is so beatiful now but for how long will it be like this if they put the wind turbines there? I love on Saturdays going to the beach with my friends and sit down and look at a lovely view and it must stay like that! People think it will make tourists come more, well I doubt that very much.

Hearing these views – and there were many more like them – makes me weary. People living in an economically deprived but beautiful part of the UK are unwilling to put up with even a hint of a windmill on their horizon.

Gas: Adjacent to the Rhyl Sands Wind Farm – at least as viewed from Llandudno Bay, is the The Douglas Complex is a 54-metre high system of three linked oil /gas platforms. I was amazed to see this as I did not realise we produced any fossil energy so close to shore.

Douglas Gas Platforms viewed from Llandudno

Douglas Gas Platforms viewed from Llandudno

Pumped Storage: North Wales is home to one of the most awesome energy projects in the world – the Dinorwig pumped storage facility. The engineering involved is breathtaking – basically a generator/pump connecting two lakes separated by a 600 metre vertical drop. The main manifold connecting the two reservoirs is shown below and gives some idea of the scale of the engineering. The plant is now 40 years old and the turbines, generators and transformers are contained entirely within vast chambers mined out of a mountain. They call it Electric Mountain and local people seemed proud of the facility, but strangely the visitor centre contained only one booklet, and no models or souvenirs. It is worth the tour – but do book in advance.

The main inlet manifold - shown during construction. © First Hydro

The main inlet manifold - shown during construction. © First Hydro

They use cheap night-time electricity to pump water uphill, lowering the lower lake level by 14 m and increasing the smaller upper lake level by 37 m. And then come peak time, they release the water – responding within seconds to peaks and troughs in demand. It can supply up to 1.2 GW at 12 seconds notice, and sustain 1.7 GW for up to 5 hours. In principle, engineering like this is essential to cope with future supply fluctuations associated with variable renewable electricity sources – particularly wind. But this device is used simply to exploit a change in the price of electricity during the day. And since it is only 75% efficient – this is not actually a power station at all, but a net consumer of quite a bit of power.

Nuclear:  We were close, but sadly my children refused to allow me to visit Wylfa nuclear power station 😦 which unobtrusively generates 40% of the electricity requirements of Wales and so essentially bankrolls the Dinorwig operation. Oh Well. There is always next year.

On my holidays, I learned that people in North Wales were just the same as people everywhere else in the UK. They want electricity to be there when they want it, and they want it to be cheap. They care less about abstract ills such as carbon emissions or global warming, than they do about their immediate environment. So if a single blade of a wind turbine disturbs their view of the hills or the sea, they feel oppressed. But if energy generation is invisible or unobtrusive (nuclear, coal, gas or pumped storage) then like the rest of the UK, they care only about the price. People were more concerned with preserving the past and the present, than in creating a sustainable future.

And just in case any of you are worried for my mental health – we did actually spend most of the time walking, looking at sheep, visiting monuments and  encountering a waterfall or two.

Aber falls

Aber falls

Be careful what you put on your chips…

April 9, 2011
Image etched onto a UTMC 5962R9657101VXC chip

Image etched onto a UTMC 5962R9657101VXC chip

A curious article at Wired.com about microscopic ‘doodles’ left by integrated circuit designers put me in mind of a day back in 1986 when an idle doodle on an integrated circuit led to the theft of my wallet. 😦

I was 26, and had just finished my PhD on the electronic properties of potassium metal. I decided to break out into a new research area and chose to build a micro-calorimeter, a device consisting of a sample holder, a heater and a thermometer. The idea was to supply a known amount of heat energy to a sample of some material under investigation and then to measure the resulting temperature rise. Its a very simple measurement and a very powerful way of working out what is happening inside a material. But it is a difficult measurement to make, especially at temperatures close to absolute zero. The innovation of this technique was to make the heater, thermometer and sample holder out of a single integrated circuit chip.

Because this was a non-standard device, I had to design everything myself at a fancy design centre on the top floor of the engineering department of UCL. Afterwards they gave me a plan of my 3 mm x 3 mm chip blown up to 1 metre x 1 metre! I was really amazed by this and I placed it on the wall of my office. I had been told that I had to put an identifier on each chip and so I put MIKE001. I thought it was really cool to have my name in writing 10 microns tall. It was very own chip-doodle.

And on that day back in 1986 in Bristol University, someone walked into my office and took my wallet. As he left, a colleague thought he looked suspicious and asked what he was doing? He replied – “I have just been to see MIKE”. No one one calls me Mike, and I conclude now that he must have seen this name written on the poster. My colleague assumed that he knew me, and let him go. Moments later he discovered I was not in my office, but it was too late.

So be careful what you put onto your chips, you never know where or when someone may look.

SOS Chips

Silicon on Sapphire Chips still on their wafer. When cut up each individual chip could be used in a microcalorimeter.

A Compact Fluorescent warms up

April 8, 2011
Cold Compact Fluorescent Light Bulb

Removing a compact fluorescent light bulb from my freezer.

During the 14th presentation of Protons for Breakfast, someone asked me why compact fluorescent (CF) light bulbs are so dim when they are first switched on. I explained that I thought it was due to the temperature dependence of the vapour pressure of the mercury within the lamp. This evening I got a chance do an experiment with my 4-in-1 multi purpose measuring device, and removed a CF bulb from my freezer where I had stored it for a couple of days at a temperature of around -12 °C. I then plugged it into a light fitting as quickly as possible, and measured the light output as a function of time using my 4-in-1 multi purpose measuring device.

Measuring the light intensity of a compact fluorescent light bulb

Measuring the light intensity of a compact fluorescent light bulb

The variation of intensity is dramatic. The lamp became  over 34 times brighter during the first 30 minutes. After 90 minutes the bulb reached a temperature of 85 °C and was more than 40 times brighter than it had been initially.

Graph of the brightness of a compact fluorescent light bulb versus time.

Graph of the brightness of a compact fluorescent light bulb (lumens per square metre)versus time in minutes.

This result looks pleasing, but is actually quite confusing when looked at in detail. The problem is that the vapour pressure of mercury increases by a factor of roughly 1000 as one warms up from -12 °C to 85 °C. So at first sight one might expect that, since there are 1000 times more atoms of mercury, there ought to be 1000 times as much light. However, I suspect that three other factors are relevant:

  • Firstly the increase in the density of mercury atoms affects the electrical resistance of the plasma, and in particular the energy with electrons collide with mercury atoms.
  • Secondly, as the density of mercury atoms increases, the some parts of the plasma begin to absorb light (probably UV light) emitted by other parts of the plasma.
  • Finally, the efficiency of the phosphor coating on the tube almost certainly increases with increasing temperature.

So I suspect that some combination of these three factors results in the curve seen above. Wikipedia covers this issue here – but it looks even more complicated than I thought!

Contrails: one more thing!

April 8, 2011

 

Condensation Trails - Contrails for short.

Condensation Trails - Contrails for short. It's not just the water that matters.

My colleague Richard Gilham was unable to control himself when he read my earlier article about contrails. In fact he literally exploded! He wrote to tell me about the critical role of nucleation in cloud formation.

In order to form a cloud – or as Richard calls it: an aerosol – at some point, the water molecules have to form droplets. The first stage of droplet formation is when  just a few molecules cluster together – a process called nucleation. Richard is fascinated by how water vapour makes the transition from being a vapour to being a collection of droplets or crystals because – despite the fact that it happens every day and is critical to understanding climate and weather – it is still not completely understood. Richard wanted to tell me something really important about this process but before he could tell me the important thing he needed to tell me some jargon.

First of all he wanted to tell me about the two types of aerosols:

  • A primary aerosol is when the material comprising the particles enters the air as particles e.g. dust.
  • A secondary aerosol forms out of gaseous material already in the air

So dust particles form a primary aerosol, and clouds are secondary aerosols. In order to form a secondary aerosol – a cloud to you and me – the air must be supersaturated. This is when  there are enough water molecules to form liquid droplets or solid crystals, but the droplets or crystals  haven’t formed yet. There are two ways they can begin to form:

  • Homogeneous nucleation is when the clusters of water molecules form spontaneously. This is really unlikely unless there is a very very high concentration of water molecules.
  • Heterogeneous nucleation is when the water molecules cluster around a seed particle (part of a primary aerosol) which forms a  ‘meeting place’ for water molecules. Water molecules stick to the surface of the particle and then stick to each other and clump together to make a droplet or a crystal. This is much easier and quicker than homogeneous nucleation, but it needs a seed particle.

So, eventually Richard got around to what he wanted to say: which is that contrails don’t form because of the additional water alone. Frequently they rely on particles that come out of the back of the engines. These are Richard’s favourite type of particles – nano particles.

Richard then told me that the temperature and pressure inside the combustion chamber of the jet is chosen to be hot enough to ensure almost complete combustion of the fuel (and so extract every joule of energy from the fuel). But running the engine too hot is bad for the engine and also causes reactions between the oxygen and nitrogen in the air creating various oxides of nitrogen (NOx). So there are always some nano-particles of partially-burned fuel which provide the necessary nucleation points for water droplets/crystals in the contrail.

And I thought that was what he had wanted to me. But at every end, it turned out that what he really wanted to tell me about was the OPAL project: which features a climate and weather survey including a contrail survey to which people could contribute.


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