In the dark depths of solid-state physics labs, a new breed of environmentally concerned scientists is emerging. Their research might seem obscure to those with no background in magnetic domains, hysteresis curves and phase transitions, but the application of their work could have far reaching effects on the way we store our food. Their aim? To change the way our refrigerators remain cold.

Since the late nineteenth century, it has been known that it was possible to change the temperature of a magnetic metal by exposing it to a varying magnetic field at very low temperatures, such as near absolute zero.

By increasing the magnetic field, the metal becomes more disordered and from the laws of thermodynamics it heats up. This heat can then be removed, using a fluid or a gas, so that the metallic material returns to its original temperature. If the applied magnetic field is then decreased, the metal’s temperature drops even lower.

Analogy between magnetic refrigeration and vapor cycle or conventional refrigeration. H = externally applied magnetic field; Q = heat quantity; P = pressure; ΔTad = adiabatic temperature variation – Courtesy of Wikipedia

However, in 1997, Professor Gscheneider, Jr. at the Iowa State University discovered that magnetic cooling was actually possible at room temperatures, leading to a wave of research into the idea of using magnets to provide refrigeration.

“Someone happened to measure what the temperature change was near room temperature and reported the paper and it spread throughout their scientific community…it’s a bit like [the history of] superconductivity” said Dr James Moore, a researcher at Imperial College London who recently published a study in the journal Advanced Materials and is on a quest to produce magnetically-cooled fridges.

Moore’s research focuses on what happens to different metallic materials on a microscopic level when they are magnetised and demagnetised.

“The title of our project is called Solid State Energy Efficient Cooling”, said Moore. “We do materials research into different metallic alloys which show these effects and the whole drive is that the end application would go into a magnetic refrigerator, just like a fridge in your home.”

Magnetic fridges are more efficient, with up to 60% efficiency compared to current refrigeration techniques that rely on gas compression. Another benefit is that they would not contain ozone-depleting gases and would be easier to dispose of at the end of their lifetime.

But, current research relies on expensive metal alloys such as gadolinium, so Moore and his team are desperately trying to find cheaper alternatives. However, they are optimistic that the technology will take off.

“I don’t think you’ll see it in people’s homes straight away, it’ll probably enter more with niche applications and then it will grown from there. But the hope is in the next 4-5 years” advised Moore.

A typical fridge – courtesy of Wikipedia

Refrigerators and air conditioning units are one of the biggest contributors to global energy consumption – in the USA they account for around half of all of the country’s summer energy use. If Moore and his team, in conjunction with their European collaborators, can harness this magnetic power to produce more environmentally friendly fridges then this will have a significant impact on cutting carbon emissions and tackling climate change.

Bendy-buses: the Marmite product of London. Mothers with pushchairs love them; cyclists hate them.

However, despite the aversion many people have towards the bendy-bus (also known as ‘articulated-buses’, ‘accordian-buses’ and ‘jointed buses’ in other countries) they currently make up an essential part of the London transport network.

In 2004, a report by TfL found that more than a third of visitors to the city centre arrive by bus. With bendy-buses capable of carrying 60 passengers more than a double-decker bus and improved disabled access it is obvious to see why they were originally implemented. They also offer several other great advantages: a higher maximum speed, increased stability (thanks to their lower centre of gravity) and a lower roadwheel pressure.

In keeping with the transport theme of my recent blog post, here’s a little look at the engineering behind the bendy-bus.

A typical London bendy-bus – here the 207 which runs between Hayes-By-Pass and White City. Image by Chloé Sharrocks

Their Construction

Previously illegal on British roads until 1980, bendy-buses of around 60 feet are now observed throughout Britain, and especially in London where in 2008 there were over 380 bendy buses in operation.

Fitted with an extra set of wheels compared to a normal bus, some models of articulated buses have a crab-like steering arrangement. In this case, the steering arrangement on the rearmost of the 3 axles turns slightly in opposition to the front steering axle allowing it to negotiate bends more easily.

A heavy pivot pin below the floor level joins the two halves of the bus and a turntable arrangement is constructed inside the vehicle to give a continuous floor, whilst ‘bellows’ seal the interior from the external environment.

The Folding Bellows

The concertina portion of a bendy-bus can be made from a hypalon-coated synthetic fabric or polyurethane. They are often furnished with additional properties such as UV resistance and low and high temperature insulation, to optimise fire resistance. The fabric is rubber-coated to protect the bellows from salt, grit, petrol, oil and stones. A key feature of the design is that despite being flexible they must also allow for a high-degree of road clearance.

The bellows can be produced using a vulcanisation process in which layers of elastomer-coated fabric are bonded together under intense heat and pressure which causes polymer molecules to link together with strong atomic bonds. Aluminium binding is also used within the bellows to help reinforce their shape. This prevents distortion from automatic vehicle-washers and damage from everyday wear and tear.

The Future of the Bendy-Bus?

In 2008, Mercedes-Benz were awarded the DEKRA Environmental Award for their new design of a hybrid bendy-bus.

Image of the new hybrid bendy-bus courtesy of the Mercedes-Benz website

Although the new Citaro bus has a diesel engine this does not power the vehicle itself, only acting as a generator, producing power which is stored in lithium-ion batteries stored on the roof of the bus. The batteries however, are not only charged by the diesel generator, but also when the bus brakes. This process, known as recuperation, means that each time the bus brakes when in traffic or nearing a bus-stop, energy is stored for use when the vehicle subsequently pulls-away and accelerates. This means that when in use, the bus produces virtually no emissions as well as little noise.

Despite Mercedes-Benz’s hard work, it would appear that the bendy-buses might not have a future if Boris Johnson is successful in phasing them out.

So do you agree with Boris’s opinion that they are “jack-knifing, traffic-blocking, self-combusting, cyclist-crushing bendy buses” or can you see them as a useful addition to a busy transport network?

Many cyclists have an aversion to the bendy-bus amid fears that the driver may not always see them on their nearside, especially when over-taking and subsequently pulling-in. Image by Chloé Sharrocks

A district line train to Upminster arriving at Tower Hill Station. Image courtesy of Wikipedia

Arriving at an Underground station and seeing the words “severe delays” (usually as a result of a signal failure somewhere on the circle line) most commuters can’t help but feel let down by the world’s first underground railway.

The tube’s apparent inefficiency makes it sometimes hard to remember and appreciate that it relies on a large amount of science – a discipline usually regarded as efficient and logical.

So in an attempt to remind all you frustrated commuters out there that the tube is perhaps sometimes not as bad as you may think, here are two detailed science facts about the London Underground:

Engineering Excellence

No-one can argue that the London Underground tunnels are a remarkable engineering feat. With several of the current tube lines as much as 20 metres underground, eg. the Piccadilly, Central and Bakerloo Lines, the engineering dangers were also very apparant. Thankfully the necessary equipment had recently been developed when construction on the tube tunnels began.

In 1818, Sir Marc Isambard Brunel developed the original tunnelling shield. Effectively a support structure for maintaining the tunnel while it was being excavated, the shield allowed engineers and miners to work without the risk of the tunnel collapsing. It was used when the soil was unstable and helped maintain the structure whilst the tunnel was being lined with a support structure of concrete, cast iron or steel.

This design was then enhanced by Peter W. Barlow for his construction of the Tower Subway under the River Thames in 1870, which enabled miners to dig behind a watertight screen without damaging any properties above ground. Further developments occurred when Barlow joined with James Henry Greathead, enabling them to use their tunnelling experience to construct of the City & South London Railway (now part of the Northern Line) in 1884. This developement of the tunnelling shield has since enabled approximately 250 miles of track to be laid under London and its surrounding areas, serving 270 stations, with a daily weekday ridership of 3.4million passengers.

With the first London underground trains running on steam (the first electric trains were not used until 1890), other considerations were important in the construction of the tunnels. Ventilation shafts were built at various points along the routes to allow the engines to expel the steam and bring fresh air into the tunnels. One such vent is at Leinster Gardens where a concrete façade was constructed to resemble a genuine house frontage – in keeping with the visual aesthetics of the well-to-do street.

Can you spot which of these houses is a façade? Image courtesy of Wikipedia

Some further great photos of the structure can be seen here.

Air Pollution

An “urban myth”: https://en.wikipedia.org/wiki/London_Underground_air_pollution exists that suggests that 20minutes on the Tube is equivalent to smoking one cigarette and has even been previously quoted by the BBC and the London Evening Standard.

The myth originated from work done by Dr Ben Croxford, a researcher at University College London who at the request of a journalist carried out an estimate of the weight of particulate matter inhaled when smoking a cigarette. Croxford subsequently calculated that a person would have to spend 20minutes in the most polluted part of the London Underground to breathe in the same amount of matter.

However, the calculation only made a comparison of the weight of matter breathed in and Croxford’s research never intended to suggest that breathing in Underground dust was as harmful as smoking cigarettes. The subsequent interpretations of this data by the media is a classic example of how lying can be easily achieved with statistics and how scientists must be careful that their data does not mean the lay-reader draws an incorrect conclusion.

Dust in the tube tunnels is primarily iron (from the wheel-rail interface), quartz silica (from the train’s brakes), passengers’ clothing fibres and cells from human skin and hair.

These particulates are much less harmful than those found in traffic exhaust which have been found to aggravate asthma. . With concerns about asthma growing worldwide, particularly following the campaigning on Asthma Day 2009 last week, it’s reassuring to know that although the air you’re breathing in when squashed into a packed-tube might smell of body-odour, it’s unlikely to cause you too much harm.

Sitting on the London Underground the other day I saw people flinch when one of the passengers sneezed – looking at the front page of a copy of The London Paper lying on a seat it’s not hard to see why. The media’s rather sensationalist reporting that swine flu could cause up to 94,000 deaths in London alone, is enough to make even the toughest of Londoners that little bit more cautionary on the tube.

However, London has previously faced seemingly disastrous epidemics and natural killers and still come out fighting. So to provide a backdrop to the media sensationalism of “farmageddon” here is a look back at some of London’s previous killers:

Killer Fog

Over 50 years ago London experienced its deadliest environmental episode when the killer fog of 1952 descended on London. Estimates suggest that over 12,000 people were killed in just four days.

A mass of stagnant air enclosed London, trapping the coal smoke from millions of residential fires. When this smoke combined with the natural fog, the air turned colder causing more coal fires to be burnt leading to an ever increasing production of smog.

On 9th December the wind arrived unexpectedly and swept away the killer fog as quickly as it had arrived.

Cholera Epidemic

Occurred during the summer of 1854 in the Soho district of London resulting in more than 600 deaths.

Scanning Electron Microscope image of Vibrio cholerae, courtesy of Wikipedia

The outbreak was initially hard to explain. Dr John Snow was sceptical of the dominant miasma theory, which implicated a noxious form of ‘bad air’. He eventually identified the Broad Street water pump as the source of the outbreak.

The Broad Street water pump, courtesy of the Londonist

Later it was discovered that the public well was situated only 3 feet from an old cesspit that had begun to leak faecal bacteria. It had been contaminated with another source of cholera contracted by an ill baby, whose diapers had been subsequently washed into this cesspit.

Snow’s observational study is often hailed as starting the science of epidemiology.

The Great Plague of London

Still one of the largest ever London killers, the Great Plague, in 1665-1666, killed an estimated 100,000 people – equivalent to 20% of the population. However, this epidemic was still on a smaller scale that the earlier “Black Death” pandemic which is estimated to have caused between 75 million deaths worldwide in the 14th Century.

The infections were caused by the bacterium Yersinia pestis which was transmitted through a flea vector.

Other Notable Epidemics

1485 & 1528: Sweating sickness epidemic

1647 – 1893: Smallpox epidemics. During the years 1837 – 1840, 6400 deaths were recorded in London

1647 – 1837: Measles epidemics in London

Throughout history, there have also been several whooping cough and influenza epidemic in London and the rest of the UK.

Perhaps the media should put the current swine flu pandemic in context by considering that their estimates are only equivalent to about 1% of the current population and London has survived far worse epidemics in the past.