Features

The atomic structure of a zinc-based material has a surprising amount in common with the tentacles of an octopus, Oxford University researchers have found.

When pressure is applied all around them most materials shrink. But materials exhibiting a rare property known as negative linear compressibility (NLC) are different.

'When pressure is applied all around NLC materials, instead of their dimensions getting shorter, they reduce their volume by getting longer,' Andrew Goodwin of Oxford University's Department of Chemistry tells me, 'think of it a bit like one of those collapsible wine racks.'

Andrew and his Oxford colleagues led an international team studying the unusual thermal properties of the material zinc dicyanoaurate. What they did not expect to find was that its honeycomb-like structure gave it uniquely powerful NLC behaviour, far beyond the kind of contraction and expansion exhibited by ordinary engineering materials.

A report of their research is published in Nature Materials.

There's widespread interest in NLC because of how materials with these properties could be used in artificial muscles or new types of sensors.

'It was quite surprising to discover that zinc dicyanoaurate is made up of structures that act rather like sets of supramolecular springs that cause it to behave in this way,' says Andrew. 'What's particularly exciting is that these properties scale up from the atomic scale to that of manmade objects and structures, suggesting all sorts of possible applications.'

Often scientists take inspiration from biological systems, or even try to copy them, but in this case the discovery of atomic structures could make them look afresh at biology.

'It seems that the octopus has found a way of harnessing the same intrinsic properties we've found in zinc dicyanoaurate,' Andrew explains. 'When it wants to contract a particular limb an octopus squirts liquid into the centre of a helical chamber inside the tentacle. This creates the equivalent of negative pressure on the tentacle, causing it to get fatter in cross section and, through the muscle architecture, contract in length.

'These same geometrical motifs found in materials at the atomic scale can also be found around us in the Animal Kingdom.'

The first to benefit from zinc dicyanoaurate's NLC properties could be the construction industry: including an ingredient like it in cement, that 'pushes back' when other components swell due to the presence of water, could help to prevent cracking in structures.

Other likely applications include the optical world where it could be used to create adjustable lenses or sensors that respond to pressure in a different way from those made of conventional materials.

Could it one day be used to make the sort of artificial tentacles sported by Spider-Man's nemesis Doc Ock? That's one application that may have to wait.

A report of the research, entitled 'Giant negative linear compressibility in zinc dicyanoaurate', is published in this week's Nature Materials.

The Oxford authors are: Andrew Goodwin, Andrew Cairns, and Amber Thompson.

At some point – whether it's at the doctors, at the gym, or online – all of us have probably encountered the Body Mass Index.

Body Mass Index (BMI) is derived from a simple mathematical formula, devised by Belgian scientist Adolphe Quetelet in the 1830s, that divides a person's weight in kilograms by their height in metres squared to arrive at an estimate of an individual's body fat.

It's supposed to provide an approximate measure to help judge if someone has a healthy weight – and indicate, for instance, if they are obese. But as Nick Trefethen of Oxford University's Mathematical Institute pointed out in a recent letter to The Economist the basic formula BMI relies on is flawed:

'If all three dimensions of a human being scaled equally as they grew, then a formula of the form weight/height³ would be appropriate. They don't! However, weight/height² is not realistic either,' Nick tells me.

'A better approximation to a complex reality, which is the reform I wish could be adopted, would be weight/height^2.5. Certainly if you plot typical weights of people against their heights, the result comes out closer to height^2.5 than height².'

Sticking with the current formula, he says, leads to confusion and misinformation: 'Because of that height² term, the BMI divides the weight by too large a number for short people and too small a number for tall people. So short people are misled into thinking they are thinner than they are, and tall people are misled into thinking they are fatter than they are.'

Quetelet's formula was invented at time when there were no calculators or computers so it's perhaps little wonder he opted for something so simple. What's stranger, perhaps, is why institutions such as the NHS, the Department of Health, and the National Obesity Observatory continue to use the same flawed formula today.

The reason for its survival may be that all the various agencies have agreed on it and, Nick says, 'nobody wants to rock the boat.'

It highlights, perhaps, how uncritical many of us are of the mathematics behind widely-used measures. There are probably many more flawed formulas out there but as Nick comments 'it would be hard to compete with this one in impact in a world approaching a billion obese people!'

So what's the alternative and what difference would changing the formula make to the medical measure of BMI?

Nick proposes a new formula [more detail here] where BMI = 1.3*weight(kg)/height(m)^2.5 = 5734*weight(lb)/height(in)^2.5

'Suppose we changed that exponent from 2.0 to 2.5 and adjusted the constant so that an average-height person did not change in BMI. Suddenly millions of people of height around 5' would gain a point in their readings, and millions of people of height around 6' would lose a point,' Nick explains. 

'In our overweight world, such changes would distress some short people and please some tall people, but the number they'd be using would be closer to the truth and good information must surely be good for health in the long run.'

Intriguingly, it's likely that Quetelet would have approved of using the 2.5 exponent. Alain Goriely, also of Oxford University's Mathematical Institute, says that Quetelet himself was well aware of the wrong choice of scaling.

In 1842 Quetelet wrote in 'A Treatise on Man and the Development of his Faculties':

'If man increased equally in all dimensions, his weight at different ages would be as the cube of his height. Now, this is not what we really observe. The increase of weight is slower, except during the first year after birth; then the proportion we have just pointed out is pretty regularly observed.

'But after this period, and until near the age of puberty, weight increases nearly as the square of the height. The development of weight again becomes very rapid at puberty, and almost stops after the twenty-fifth year. In general, we do not err much when we assume that during development the squares of the weight at different ages are as the fifth powers of the height; which naturally leads to this conclusion, in supporting the specific gravity constant, that the transverse growth of man is less than the vertical.'

Alain comments: 'So according to Quetelet the scaling is 3 for babies (babies are spheres), 2 for kids (kids grow more like celery sticks, as we know), then 5/2=2.5 for grownups (beefing up so to speak). It seems Quetelet never cared about obesity (not a big issue in the 1840's).'

Nick Trefethen is Professor of Numerical Analysis at the University of Oxford.

Alain Goriely is Professor of Mathematical Modelling at the University of Oxford.

Research groups are moving into the new £11m annexe of the Botnar Research Centre at Oxford University. The annexe essentially doubles the size of the centre located on the site of the Nuffield Orthopaedic Centre in Headington.

Last year the centre celebrated its 10th anniversary. It's a celebration that is certainly justified, as that decade has seen an extraordinary growth and flowering of research in the centre, which focuses on musculoskeletal diseases such as arthritis and osteoporosis.

This is not always a high-profile area of research and the scientists involved certainly feel it loses out on funding to other areas more in vogue, like cancer or heart disease. Yet there is great clinical need here with a large burden of disease, pain and disability affecting the quality of life of many people, particularly with an ageing population.

The potential for developing improved treatments that will make a difference to the lives of large numbers of people with arthritis and osteoporosis is certainly there. Researchers in the Botnar centre develop and test not only existing technologies such as joint replacements but also novel tissue engineering implants which aim to treat early disease, maintain mobility, and keep many of us pain free for much longer in our lives.

Yet despite the field of orthopaedics in general facing some difficulties, it is an area of research that has actively grown at Oxford University.

'Generally speaking, this area of research has suffered in the last 10 years,' says Professor Andy Carr, head of the University's NDORMS department, Director of the Botnar Research Centre and a practising orthopaedic surgeon. 'It's remarkable that we've been able to grow in the way we have.'

The Botnar Research Centre currently houses the vast majority of the research going on in the Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, or NDORMS. Until the centre came along 10 years ago and provided new impetus and opportunities, the department was one of the smaller parts of Oxford medicine with perhaps 20 researchers, Professor Carr explains. There will be around 220 University researchers working in the Botnar, once the new annexe of the building is fully occupied.

'I think there are three reasons for this expansion,' says Professor Carr. 'There is a huge need for advances in this area with an ageing population no longer dying from heart disease or cancer as they perhaps did, but now experiencing more arthritis and disability in later life. There was the brave step of the University, which decided to invest in this area when others were pulling out. And there has been the extraordinary philanthropy of first Lord Nuffield, secondly the Nuffield Orthopaedic Centre appeal and Botnar family, and thirdly the Kennedy Trust.'

The money to build the Botnar Research Centre in 2002, and then the equally large annexe last year, was achieved through an appeal at the Nuffield Orthopaedic Centre (NOC), now part of the Oxford University Hospitals NHS Trust, with the Botnar family being a substantial benefactor.

2012 was also the 75th anniversary of an academic department in this area at Oxford, with Lord Nuffield endowing a chair in orthopaedic surgery in 1937. There is an unlikely link between these benefactions too, Professor Carr notes. Lord Nuffield was a car manufacturer, who founded Morris Motors in Oxford, and the Botnars founded Datsun UK, importing Datsun (now Nissan) cars into the UK for the first time.

The Botnar centre is a real partnership between the NOC and the University, not just in the way funds have been raised but also in practice.

The point of it was to bring the University's bone, joint and arthritis research together in a purpose-built building on the hospital site – it's just across the car park from the main NOC building. It allows truly multidisciplinary science right where patients are, offering a partnership between University research and teaching and the work that goes on in NHS clinical practice.

NOC patients are asked whether they want to participate in research projects as a matter of course – it's part of the culture in both institutions. For example, Professor Carr says, 'over 90% of people undergoing operations at the NOC consent to donating tissue samples that are then stored and made available to researchers. We couldn’t do the research we do without it. It's a remarkable resource.'

This 'biobank' of stored tissue samples and associated data allows researchers to investigate the biological pathways underlying disease.

'But the real advantage of having aspects of a University department embedded in a hospital,' Professor Carr says, 'is that when we make a discovery, we can ask patients if they would be willing to participate in a clinical trial to discover whether there is clinical benefit for patients.'

Given the participation rates, it's clear that most patients see aiding research as a positive thing to being involved in. But Professor Carr believes there are direct benefits for them too: 'There is good evidence that if you're being treated in a research-intensive hospital that you are generally seen to do better.' He explains that there may be a range of reasons for this: it may be that the hospital culture is one of high standards, or it attracts staff that are engaged in their work, or that patients might be the first to benefit from novel treatments with improved results.

The department's achievements suggest this approach is working. Successes include the development and introduction of novel joint replacements that are now used in operations worldwide. The Oxford Knee and Oxford Shoulder are particular types of artificial joints that were invented here and are used in patients with severe or advanced arthritis.

NDORMS also played a big role in introducing patient-focussed measures of how successful orthopaedic surgery has been. After all the difference these treatments make to a patient's daily life is the most important outcome, rather than only recording how quickly a joint replacement fails. Given that 5% people over 65 have a joint replacement, this is of value for huge numbers of people.

Oxford scores are now used worldwide for assessing joint operations. Professor Carr says: '130,000 people a year are monitored in the UK alone using our scores, and they have transformed our understanding. Many other countries also use the Oxford Scores. Rather than just waiting for joint to fail, we ask the patient whether the pain has gone away, whether they are able to drive a car, go up stairs, live independently. These are the things that are really important to people later in life. We can also pick up issues or problems with new designs of joint implants much earlier than might otherwise be the case.'

As well as clinical research moving into the new annexe to the Botnar Research Centre, this year will also see the move of the Kennedy Institute of Rheumatology from their existing base in London to a new building across the road from the NOC in the University's Old Road Campus. This follows the institute's decision to move and join Oxford University in August 2011.

The Kennedy Insitute has great expertise in arthritis and inflammatory disease, most notably when researchers there discovered novel biological therapies for rheumatoid arthritis. These antibody therapies have transformed management of the condition. The future for NDORMS will see three streams of work all linked together, says Professor Carr:

The Kennedy Institute will concentrate on the basic discovery science in the biological pathways underlying disease, science that is directly relevant for developing new treatments.

The Botnar centre will continue to see more growth in its research based on access to tissue and blood donated by patients, and will also house those running and managing large trials to test the efficacy of new treatments.

And the NOC will house clinical trial units where patients can receive new treatments.

'We've created a critical mass,' believes Professor Carr. 'It is a complete package of research that is transforming this area of science. There’s nothing like it elsewhere in the UK or Europe. There’s great potential for the future.'

So what would count as success for Professor Carr's department in the next 10 years? 'I would like for a number of genuinely new therapies to reach the point of getting into the clinic,' he says, 'that we are geared up to discover amazing things, to train the best new researchers and create new therapies that work.'

Are you watching BBC Stargazing Live? You should be, especially as it features OxSciBlog regular Chris Lintott giving you the chance to (virtually) explore Mars in the citizen science project Planet Four.

Tonight's episode will also see Oxford physicist Jo Dunkley talking about the Big Bang and how scientists are making the earliest picture of the universe using the Planck satellite.

But wait, how can you join in the astronomical fun?

Glad you asked: after last year's phenomenal success Stargazing Oxford is back this Saturday, 12 January: it's a free public event, running 2pm-10pm at Oxford University's Department of Physics with space-related activities for all ages.

Will kids get to make things with 'Astrocrafts'? Check. Will you get the chance to observe the Sun (safely) through solar telescopes and (after dark) use a range of telescopes to observe the stars and get hints and tips on DIY astronomy? Check. Will there be astronomers to answer questions like ''Why do stars explode?'' and ''Is there life on other planets?'', as well as talks on the latest discoveries, workshops, star trails, an inflatable planetarium, and much more besides? Check.

If all that sounds appealing there's no need to book just drop in to the Denys Wilkinson Building, Keble Road, OX1 3RH, on Saturday between 2pm-10pm, (although at peak times there may be short queues and a bit of waiting involved).

We're also tweeting more info and astronomy tips all this week so follow #stargazingoxford or revisit this post on Friday when we'll update it with a list of (hopefully) useful links.

UPDATE: Some useful links and astrotips:

• Read a guide to the planets you can see in the night's sky.
• For advice on getting started check out either the Chipping Norton Amateur Astronomy Group or the Abingdon Astronomical Society.
• Discover when the International Space Station is overhead with ISS Tracker or watch a preview of the planetary movies on show at Stargazing Oxford.
• Improve your chances of seeing the 'Northern Lights' with AuroraWatch UK.

Have you been on virtual safari yet?

If you haven't then you should visit Snapshot Serengeti, a new citizen science project asking online volunteers to identify animals in millions of photos taken by camera traps across Serengeti National Park.

The project is a collaboration between biologists at the University of Minnesota and the Zooniverse project, led by Oxford University and Adler Planetarium.

As Oxford University's Chris Lintott explained to BBC Nature humans are far better than computers at identifying species from images and by getting people to study millions of photos scientists hope to get a better understanding of what the animals are getting up to when they're not looking.

The project launched on 12 December and the response has been phenomenal.

'For days after launch volunteers were classifying more than 10 images a second - 50 a second at peak times,' Rob Simpson of Oxford University and the Zooniverse tells me. 'These people have come from the Zooniverse community and from Facebook - it's been amazing to watch the reaction spread around the globe.'

Snapshot Serengeti is now at 3.7 million classifications and counting with over 70,000 people visiting and 21,000 people registering with the site. You can see just some of the amazing animal photos people have found already here. The team are currently working hard to add more images to the site and are already moving on to season 4 and 5 [more about the seasons here].

But that isn't all that's going on with the Zooniverse just now:

The Andromeda Project, which is searching for clusters and galaxies in images, is homing in on its target of over 1,000,000 classifications (now 950,000 and counting). This means that each image has been searched by 80 people, giving scientists excellent data on what's out there.

There'll be more from The Andromeda Project in 2013 with the Hubble Space Telescope currently taking more images to add to the site.

Then there's the Milky Way Project: Clouds that has only launched today and uses data from ESA's Herschel telescope to find dark clouds in images of our galaxy. You'll get the idea from this Milky Way Blog post.

So whether you love animals, galaxies, or cloud-spotting, the Zooniverse really does have something for everyone.