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Archive for the 'UCL Science Picture of the Week' Category

Picture of the week: X-ray speckles

By Oli Usher, on 21 July 2014

Intensity landscape of x-ray speckles. Photo credit: I. Zanette (TUM).

Intensity landscape of x-ray speckles.

Counterintuitively, scrambling X-rays can help scientists make better X-ray images.

New research from an international collaboration including Pierre Thibault (UCL Physics & Astronomy) uses the random speckles of scrambled X-rays to produce improved images of objects when X-rays are passed through them.

The location and brightness of the speckles encodes information about the object being studied, allowing a detailed image to be reconstructed.

Today’s Picture of the Week shows the intensity (shown as the height and colour) and position of X-ray speckles detected in an experiment that was carried out as part of this research.

Photo credit: I. Zanette (TUM). This photo may be freely reproduced for the purposes of news reporting of this research, but it is not released under a Creative Commons licence.

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Picture of the week: skulls, subs, and selective laser sintering

By Kate Oliver, on 14 July 2014

We hear a lot about 3D printing as the future of manufacture, but it’s also finding many applications in research.

Today’s picture of the week shows three of the uses researchers at UCL Engineering are finding for additive manufacture.

Examples of research objects created using 3D printing at UCL Engineering

Examples of research objects created using 3D printing at UCL Engineering

On the left, a model submarine printed by a student in Naval Architecture lets them see their designs in 3D. In the middle, UCL computer scientists experiment with the exciting new problem of creating virtual models that can be printed out with movable, posable parts; and on the right, a section of 3D printed skull, recreated from scans by researchers at UCL Medical Physics based within UCLH, enables surgeons to plan their operations.

Old school meets new tech: a chimp skull from UCL's zoological teaching collections next to a high-tech 3D print from UCL Medical Physics.

Just for fun: old school meets new tech: a chimp skull from UCL’s Bioanthropology Collections next to a high-tech 3D print of a modern human from UCL Medical Physics. Will 3D printed skulls be the future of anatomy teaching?

All of these models were printed using a method called Selective Laser Sintering (SLS). This is a kind of 3D printing that uses lasers to melt bits of a polymer powder together in the shape of a cross-section through the object you want to print. Then, a layer of power is added on top, and another layer melted. If it is resting on powder, that powder will just brush off when the plastic model is removed: if it is resting on a previously melted bit, it will stick to it.

This is a more expensive way to 3D print than the hobby-level 3D printers which are more commonly seen, which basically squeeze out layers of plastic like toothpaste, stacking them up into shapes . However, it allows the printing of more complicated shapes, with overhangs and interpenetrating parts – so it’s really handy for detailed research uses. UCL has a number of 3D printers, some free for all our staff and students to use in our open access Makespace.

Picture of the week: Release valve

By Oli Usher, on 7 July 2014

Semiconductors are the basis of almost all the electronics we are used to today. Transistors are tiny switches (often microscopic) which govern how electricity flows through a device, thanks to their variable electrical conductivity. Putting many transistors in sequence means the flow of electrons through the circuit can begin to follow logical rules and make calculations – the basis of all computing. Even small devices like smartphones can today contain over a billion transistors squeezed onto the tiny chips inside them.

But electronics existed before semiconductors. The transistor was invented in the late 1940s, and only became widely used in the mid 1950s, a decade after the invention of electronic computers.

Early electronic devices, including the first computers such as Colossus and ENIAC, relied instead on thermionic valves.

Mullard electronic valve

A small electronic valve manufactured by Mullard. (This is the same Mullard that endowed UCL’s Mullard Space Science Laboratory). Photo: O. Usher (UCL MAPS)

Dating back to the early 20th century, valves can carry out the same functions as semiconductors do today, acting as switches and diodes. But the principles they work on are totally different – instead of exploiting the quantum properties of semiconductors, valves use brute force: glowing hot filaments that flood the valve with electrons.

This means they are extremely energy-inefficient – the ENIAC computer, with just under 18,000 valves (compare this to over a billion transistors in an iPhone) drew 150 kilowatts of power. A typical oven uses around 2 kW, a modern laptop computer uses less than 0.1 kW.

This high power consumption also means that valves look a lot like another device with a glowing filament, appalling energy efficiency and vast production of waste heat: the filament light bulb. (Like old-style light bulbs, valves also regularly burn out and need to be replaced.)

A selection of thermionic valves found in UCL Chemistry

A selection of larger thermionic valves found in UCL Chemistry. Photo: O. Usher (UCL MAPS)

Valves were widely used for electronic applications in university labs until their relatively sudden obsolescence in the 1950s left unused stocks in store rooms. They still occasionally turn up when cupboards are cleared out – including a large haul of several crates of mint-condition valves recently found in UCL’s Department of Chemistry, pictured here. These are of little use for research today, but they are of great historical interest, not least for restoring and repairing old electronic devices.

Dekatrons (counting tubes), widely used in early computers including the Harwell Dekatron Computer, which is now at the National Museum of Computing.

Dekatrons (counting tubes) were widely used in early computers including the Harwell Dekatron Computer, which is now at the National Museum of Computing.

For this reason, the valves have been donated to the National Museum of Computing at Bletchley Park.

Picture of the week: Cleaning up in the cleanroom

By Oli Usher, on 30 June 2014

Inside LCN's cleanroom. Photo: O. Usher (UCL MAPS)

Inside LCN’s cleanroom. Photo: O. Usher (UCL MAPS)

Many scientific processes need spotlessly clean labs. In the life sciences, samples can be contaminated by bacteria or moulds; in chemistry, samples may become impure. In the London Centre for Nanotechnology, where scientists and engineers develop and study microscopic devices, dust is one of the major enemies – and it must be excluded before the researchers can do their work.

The LCN’s cleanroom is a large, sealed facility in which much of this type of research takes place. Users of the facility have to wear special protective suits to prevent dirt and dust from their clothes from contaminating the lab, while any equipment brought into the room needs to be carefully cleaned.

This spotlessly clean environment means that highly precise work can be carried out. One example is photolithography, where the tiny electronic circuits on chips are etched using ultraviolet light. (The room is lit in orange, which is far away from ultraviolet in the electromagnetic spectrum, to avoid damaging this process.) The clean environment helps ensure that the correct patterns are imprinted on the silicon surfaces.

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Picture of the week: What’s the chance?

By Oli Usher, on 23 June 2014

Montage of two dreidels and a die. Photo: O. Usher (UCL MAPS)

Montage of two dreidels and a die. Photo: O. Usher (UCL MAPS)

What are the chances of a fair dice landing on each of its faces? One in six of course. But unfair dice are another matter entirely: nobody has ever come up with a complete mathematical explanation of their probabilities.

Two UCL PhD students from UCL Department of Physics & Astronomy, George Pender and Martin Uhrin have taken a step closer to this, coming up with a theory that can explain the behaviour of biased two-dimensional (four sided) dice, and similar objects such as dreidels (a type of spinning top).

This picture shows a fair spinning dreidel (top left), a biased one (top right) and a fair die.

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Picture of the week: Message to Mercury

By Oli Usher, on 16 June 2014

Artist's impression of Mariner 10. Credit: NASA/RPIF/UCL Earth Sciences (public domain)

Artist’s impression of Mariner 10. Credit: NASA/RPIF/UCL Earth Sciences (public domain)

Of all the planets of the inner Solar System, Mercury is the least-visited. No mission has ever landed on its surface, only two missions have studied it from space, and only one of those has reached orbit.

Travelling to Mercury is difficult as the proximity to the Sun makes for unstable orbits and fast orbital speeds.

The first spacecraft to visit Mercury was Mariner 10, pictured here in an artist’s impression from UCL’s planetary science archives. UCL is the only UK institution to host a NASA Regional Planetary Image Facility.

Mariner 10 made three fly-bys of Mercury in 1974 and 1975, mapping a little under half of the planet’s surface.

The complex path to Mercury, involving multiple fly-bys, was designed by scientist Bepi Colombo, whose name is honoured by a forthcoming mission planned by the European Space Agency and the Japan Aerospace Exploration Agency. The BepiColombo mission, expected to launch in 2016, will feature two orbiters, and will fly past the planet several times before reaching orbit in 2024.

UCL’s Prof Alan Smith is chair of the UK Space Agency’s BepiColombo management board.

Image credit: NASA/RPIF/UCL Earth Sciences

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Picture of the week: What’s the charge?

By Oli Usher, on 9 June 2014

Tool used to demonstrate electric charges. Credit: O. Usher (UCL MAPS). Acknowledgement: Jim Grozier

Tool used to demonstrate electric charges. Credit: O. Usher (UCL MAPS). Acknowledgement: Jim Grozier

When metal objects are given an electric charge, the charge is not evenly spread through it. It collects on the surface, and in particular on parts of the surface which are curved.

This object from the collections of the Department of Physics & Astronomy is a historic teaching device that would have been used to demonstrate this phenomenon in times past.

Sitting atop an insulating stand, the device would be charged up and retain the charge long enough for a lecturer to carry out a demonstration. Using a small square of metal on an insulating handle, attached to an electroscope, the demonstrator would be able to show that the charge was concentrated on the sharply curved area on the right hand side in this photo.

Photo credit: O. Usher (UCL MAPS). Acknowledgement: Jim Grozier

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Picture of the week archive

By Oli Usher, on 2 June 2014

From now on UCL science pictures of the week will be published on this blog.

For older entries, see the picture of the week section of the Faculty of Mathematical & Physical Sciences website.