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A pan-European team of researchers involving the University of Oxford has developed a new technique to provide cellular 'blueprints' that could help scientists interpret the results of X-ray fluorescence (XRF) mapping.

XRF imaging is used for a wide range of elemental analyses and has a number of medicine-based potential applications, including tracking and understanding diseases such as Alzheimer's, and the evaluation of heavy metal poisoning.

One barrier facing this technology has been the lack of cellular blueprints with which to compare the maps arising from XRF imaging. Now, researchers have been able to seal non-biological elements inside carbon nanotubes – tiny tubes 50 thousand times thinner than a human hair – to create 'nanobottles' that can be directed to individual cells to help create these blueprints.

The results of the study are published in the journal Nature Communications.

Dr Chris Serpell, a lecturer in Chemistry at the University of Kent who worked on the project while carrying out a research fellowship in Professor Ben Davis's group at Oxford, said: 'What's amazing about these findings is that the non-biological elements are toxic or gaseous, but they’re securely sealed within the nanobottles by just a single layer of carbon atoms. We're really pleased that this paper can showcase the biological potential of carbon nanotubes.'

Dr Serpell says that by using the contents of these nanobottles – such as barium, lead or gaseous krypton – as 'contrast agents', XRF imaging could become a much more widespread technique, providing insights into behaviours of proteins that use metals, and the role they have in health.

He added: 'Carbon nanotubes were once touted as a panacea to almost every technological problem, but in recent years people have become much more cynical about their utility. These results show that there are unique applications which are only possible using nanotubes – they are now moving towards realistic applications.

'Although it is at a very early stage in the pipeline, this technology can be expected to yield new insights into disease states and the effects of heavy metal poisoning, which can in turn lead to new healthcare technologies. A similar approach could also be used to deliver radioactive elements specifically to tumours for therapy, or to enhance other imaging modes such as MRI.'

Professor Davis, from Oxford's Department of Chemistry, said: 'This work was part of a training network across Europe known as RADDEL that was launched based on an earlier discovery that radioactive iodide could be packed into sealed tubes to be used in living animals.

'This new research has expanded on that finding, creating a spectacular system that encapsulates much more difficult elements and images these in cells using the rarely used technique of XRF. We have been able to use this method to see how the tubes find their way into different compartments in individual cells, controlled largely by how we chemically "decorate" those tubes.

'It's a striking example of something that would be tough to do by any other construct – to take a gas and "bottle" it before steering the bottle to one compartment in a cell so that you can use the gas for imaging.'

The study was a collaboration involving researchers from the universities of Oxford and Kent, Diamond Light Source, and Universitat Autònoma de Barcelona.


Have you ever noticed that liquid stays inside a straw when it’s held horizontally? Or that the same thing doesn't happen when you turn a glass on its side?

A team of researchers including Professor Dirk Aarts from Oxford University's Department of Chemistry has been investigating this phenomenon – one that's 'surprisingly difficult' to explain from a scientific point of view.

Professor Aarts worked with colleagues Carlos Rascón from Universidad Carlos III de Madrid in Spain and Andrew Parry from Imperial College London for the study, which is published in the journal PNAS. Professor Aarts said: 'We considered the following seemingly simple question: why does the liquid spill out when I hold a glass – say, of beer – horizontally, but stays in a straw when I do the same thing?

'This question is actually surprisingly difficult, especially when considering non-circular cross-sections of the capillaries, or tubes.

'For a liquid trapped between two parallel walls, and for a liquid trapped in a circular capillary like a straw, the answer is one that we would intuitively expect: the liquid wants to flow out because of gravity, but is trapped due to the surface tension.'

The 'capillary action' described here is the ability of a liquid to flow in narrow spaces, often in opposition to external forces such as gravity. For example, if you zoom in on the surface of water in a glass, you’ll see that it curves upwards by a couple of millimetres at the wall. This curve is known as the meniscus.

Professor Aarts said: 'The competition between gravity and surface tension leads us to the capillary length, which sets the height to which a meniscus will climb at a wall. Indeed, if the separation between the two walls is less than roughly the capillary length, or if a circular capillary has a diameter less than roughly the capillary length, the liquids will stay put. If not, the liquids will flow out.

'However, if you change the cross-sectional shape of the capillary – for example, making it a triangle – the situation may change completely, and for certain geometries the liquid may spill out at any length scale, well below the capillary length.

'We figured out how to calculate this behaviour for general cross-sectional shapes, although the actual numerical calculations, carried out by Carlos Rascón, took almost seven years to complete. One of the reasons for this was that the spilling out may occur via different pathways, and the crossovers between those pathways were hard to understand.'

The researchers were able to solve the problem by reducing it down to an equivalent two-dimensional problem, which is numerically more accessible. The paper shows how 'emptying diagrams' can be created by calculating the energy of the problem in 2D. As soon as the energy became smaller than zero, no 3D solution for the meniscus exists, and the liquid empties.

Professor Aarts added: 'The surprising result here is that a capillary may empty even at lengths much smaller than the capillary length. This has implications for any technologies where liquids are used or are present on small scales, such as microfluidics, biomedical diagnostics, oil recovery, inkjet printing and so on.'

Quantum computing

The exciting new age of quantum computing

Stuart Gillespie | 25 Oct 2016

What does the future hold for computing? Experts at the Networked Quantum Information Technologies Hub (NQIT), based at Oxford University, believe our next great technological leap lies in the development of quantum computing.

Quantum computers could solve problems it takes a conventional computer longer than the lifetime of the universe to solve. This could bring new possibilities, such as advanced drug development, superior military intelligence, greater opportunities for space exploration and enhanced encryption security.

Quantum computers also present real risks, but scientists are already working on new forms of encryption that even a quantum computer couldn't crack. Experience tells us that we should think about the applications and implications of quantum computing long before they become reality as we strive to ensure a safe future in the exciting new age of quantum computing.

A new animation, produced for NQIT by Scriberia, looks at how quantum computing could change our lives.


Five years ago, the Nobel Prize in Physics was awarded to three astronomers for their discovery, in the late 1990s, that the universe is expanding at an accelerating pace.

Their conclusions were based on analysis of Type Ia supernovae – the spectacular thermonuclear explosions of dying stars – picked up by the Hubble space telescope and large ground-based telescopes. It led to the widespread acceptance of the idea that the universe is dominated by a mysterious substance named 'dark energy' that drives this accelerating expansion.

Now, a team of scientists led by Professor Subir Sarkar of Oxford University's Department of Physics has cast doubt on this standard cosmological concept. Making use of a vastly increased data set – a catalogue of 740 Type Ia supernovae, more than ten times the original sample size – the researchers have found that the evidence for acceleration may be flimsier than previously thought, with the data being consistent with a constant rate of expansion.

The study is published in the Nature journal Scientific Reports.

Professor Sarkar, who also holds a position at the Niels Bohr Institute in Copenhagen, said: 'The discovery of the accelerating expansion of the universe won the Nobel Prize, the Gruber Cosmology Prize, and the Breakthrough Prize in Fundamental Physics. It led to the widespread acceptance of the idea that the universe is dominated by "dark energy" that behaves like a cosmological constant – this is now the "standard model" of cosmology.

'However, there now exists a much bigger database of supernovae on which to perform rigorous and detailed statistical analyses. We analysed the latest catalogue of 740 Type Ia supernovae – over ten times bigger than the original samples on which the discovery claim was based – and found that the evidence for accelerated expansion is, at most, what physicists call "3 sigma". This is far short of the 5 sigma standard required to claim a discovery of fundamental significance.

'An analogous example in this context would be the recent suggestion for a new particle weighing 750 GeV based on data from the Large Hadron Collider at CERN. It initially had even higher significance – 3.9 and 3.4 sigma in December last year – and stimulated over 500 theoretical papers. However, it was announced in August that new data shows that the significance has dropped to less than 1 sigma. It was just a statistical fluctuation, and there is no such particle.'

There is other data available that appears to support the idea of an accelerating universe, such as information on the cosmic microwave background – the faint afterglow of the Big Bang – from the Planck satellite. However, Professor Sarkar said: 'All of these tests are indirect, carried out in the framework of an assumed model, and the cosmic microwave background is not directly affected by dark energy. Actually, there is indeed a subtle effect, the late-integrated Sachs-Wolfe effect, but this has not been convincingly detected.

'So it is quite possible that we are being misled and that the apparent manifestation of dark energy is a consequence of analysing the data in an oversimplified theoretical model – one that was in fact constructed in the 1930s, long before there was any real data. A more sophisticated theoretical framework accounting for the observation that the universe is not exactly homogeneous and that its matter content may not behave as an ideal gas – two key assumptions of standard cosmology – may well be able to account for all observations without requiring dark energy. Indeed, vacuum energy is something of which we have absolutely no understanding in fundamental theory.'

Professor Sarkar added: 'Naturally, a lot of work will be necessary to convince the physics community of this, but our work serves to demonstrate that a key pillar of the standard cosmological model is rather shaky. Hopefully this will motivate better analyses of cosmological data, as well as inspiring theorists to investigate more nuanced cosmological models. Significant progress will be made when the European Extremely Large Telescope makes observations with an ultrasensitive "laser comb" to directly measure over a ten to 15-year period whether the expansion rate is indeed accelerating.'

Digital Wildfire project

Our desire to communicate and interact on social media took off long before we considered how this vast and ever-growing mass of information might shape our world, for better or worse.

Scientists involved in the Digital Wildfire project in Oxford's Department of Computer Science are searching for ways to make sense of the huge volume of publicly accessible data that our social media obsession has created. They're exploring the pros and cons of social media, from its positive use as a communications tool to the harmful spread of misinformation and hate speech.

Learn about their work in the latest animation from Oxford Sparks.

Oxford Sparks is a great place to explore and discover science research from the University of Oxford. Oxford Sparks aims to share the University's amazing science, support teachers to enrich their science lessons, and support researchers to get their stories out there. Follow Oxford Sparks on Twitter @OxfordSparks and on Facebook @OxSparks.

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