Tag Archives: LCN

X-Ray and Laser Imaging using iterative methods by Osman Omar

On my in2scienceUK Placement, I studied ptychography and worked with laser imaging with a PhD student, Stefanos Chalkidis. During my placement, I scanned various different things such as a piece of mica, glass, a sample from a colleague and a wing from a dead fly.

First, we set up the sample by attaching it to a glass substrate using tape and then mounted it to the sample stage which was in a blackout box along with the camera used to capture the image, a diffuser and the laser itself. Next, we received a live feed of the sample on a computer from which we then took various different types of scans, such as ROI scan, which takes images of the sample in a circular pattern within a region of interest, a flat scan which takes images of the background alone without any sample present and a dark scan which takes images with the laser turned off.

Next, we used the data from the scans and by running various different python scripts, we formed reconstructions of our scanned object which we then further analysed. The reconstructions were performed by using two algorithms in succession for which we could choose how many iterations we wanted to run. We used two different amounts, 500 of each algorithm for one reconstruction and 2000 for another, and compared the differences. We also changed the position of the diffuser to see how that would affect our results and what changes we would get.

Here is one set of our results: The insect wing; diffuser at 250mm, original position, closest to laser.

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The left image shows the transmission image of the object, whilst the middle image is the phase change of the object and the right image depicts the phase change of the illumination. We also moved the diffuser to 240mm and here are our results:

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Here are our set of results when analysing the mica:

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I also went to the Diamond Light Source, located in Harwell, which is a synchrotron. Electrons are sped up and accelerated there in a circular pattern to near light speed, from which then X-rays and other lights are emitted. These beams are then directed off into laboratories or beamlines so they can be used for experiments and research such as new medicines or cutting-edge technology. I was given a tour of the building and met scientists who worked with my supervisor in his field of research, which is near-field ptychography.

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Schrödinger’s Equation—¿after that session was I dead or alive or both?

My In2science placement took place between the 21st and the 25th of July at the London Centre for Nanotechnology, UCL. As the week began I was both nervous and excited. I was happy with the placement I’d been given—working alongside PhD students, experts in Physics, both theoretical and experimental. I could not have been placed anywhere better! On the first day, we had a tour of UCL and we were introduced to our Supervisors; Michael, Phil and Tom. They were very helpful and patient with us, myself and the two other students. By the second day we got into some hard-core experimental physics (or so it felt). Scanning-tunnelling microscopy is what we were introduced to by Toby, an experimental physicist who gave us in-depth explanations yet were very easy to understand (see photo below). This was fun, the aim was to scan the surface of graphite and with some luck try to see as close to the atoms as we could get. The tunnelling part comes from quantum physics and psi, the probability amplitude.

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Although we didn’t get to see a perfect picture of the atoms, we got to be very hands on! As the week progressed we got to see various labs and experiments of physicists working with lasers, dust-free microscopes and liquid helium. We got talks on Quantum Physics Really Exists! and the creation (or not) of a quantum computer in the USA.  We also learnt about the differences between Classical Physics and Quantum Physics. But for myself, leaning more towards theoretical physics, the week really got exciting when we began work on differential equations and Schrödinger’s Equation, by which I was feeling very excited yet somewhat intimidated by the complexity I thought such an equation would carry.

Time Independent Equation:

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Time Dependent Equation:

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Using calculus as a starting point we found and solved differential equations for exponential radioactive decay and more, leading to the point of using coding on the computer to create a interactive diagram of the quantum tunnelling process using Schrödinger’s Equation.

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All in all I can say that it was a very productive and fascinating week which not only assured me of my passion for physics but opened my eyes to the wide array of possibilities a career in science could lead to.

By Maria B

Nanotechnology by Daniel C

What goes on at the London Centre for Nanotechnology? Daniel gives us an insight into one project taking place:

Surface Acoustic Waves device, SAWs is an incredibly sensitive machine that measures viscosity. A lab at the London Centre of Nanotechnology uses this device to detect antigens from viruses such as HIV and hepatitis.

However, antigens are tiny and so cannot be detected directly. Researchers here use a layering technique to attach the antigen to the SAWs chip and then a gold nano-particle to the antigen. The nano-particles are relatively large and so change the viscosity on the chip drastically. If no antigens are present then the nano-particles would not be attached to the chip. If no nano-particles are present then it must mean there are no antigens present.

The SAWs device passes waves across the chip. If there are no gold nano-particles attached the waves are unaffected, if there are particles attached they will affect the amplitude of the wave. You can picture it as throwing a stone into a still pond. When the stone hits the surface waves will spread undisturbed across the water, but if there was a duck on the water the waves would change when they reached the duck. Detecting changes like this is how researchers determine the presence of the gold nano-particles.

By Daniel C