Category: Past colloquia

Our next colloquium will be held on 26th October. Our next talk is by another new professor in our department, Simo Huotari.

Simo is a Professor in Experimental Materials Physics here in Helsinki.  He has made an international  career in the use of synchrotron light for materials research, having most notably worked 7 years at ESRF – The European Light Source. In his talk, titled Let there be light: X-rays for life sciences, mathematics, cultural heritage, energy, health, and environment, he will tell us about his research. Here is what he has to say about his research and the colloquium talk:

Solutions to many of the crucial challenges facing humanity, such as developing alternative sources of energy, improving health, mitigating environmental and climate problems and developing new green economies, depend on the detailed understanding of the constitution of matter and on the molecular and electronic control of processes that determine the function of materials and biological systems.

X-rays offer a light for insights in both basic and applied research, covering virtually all fields of science from physics, chemistry, and biology, to energy, medicine, cultural heritage, environmental sciences, medical physics and engineering.

The brighter the light, the better the vision. The large-scale light sources such as synchrotrons and  x-ray free electron lasers (XFEL) have seen an exponential growth of brilliance that magnificiently outruns even Moore’s law. They are giant microscopes, which enable research on materials  in the tiniest detail, helping make invisible information strikingly visible.

For example, the world’s most powerful x-ray laser is now in operation in Hamburg. The 3.4-km long European XFEL produces light in <100-fs short pulses and its light drills a hole in a 5-cm thick piece of steel in a matter of seconds. The extremely powerful  laser strips the target’s atoms from electrons, resulting in Coulomb explosion and forming hot dense plasma, giving access to the  studies of transient behavior of matter in extreme conditions such as in warm dense matter found in cores of giant planets. As an ultrafast probe, XFEL gives access to fs-scale dynamics in materials and has great potential for imaging of single molecules.

On a local and less destructive level,  the X-ray Laboratory at the University of Helsinki works together with all four campuses of the University, many national facilities and organisations such  as VTT, Finnish Environment Institute (Suomen Ympäristökeskus, SYKE),  National Resources Institute Finland (Luonnovarakeskus, LUKE), and  Natural History Museum (Luonnontieteellinen museo, LUOMUS).

The X-ray Laboratory is an integral part of the Helsinki Institute of Life Science through the Helsinki In-vivo Animal Imaging Platform.

In this colloquium, an overlook to novel aspects of this exponentially growing field is given and the entirely new possibilities given by new emerging light sources are discussed.

After the 30 minute talk, there will be a cocktail reception. Welcome!

Update 8.11.2018: Simo’s slides are available to download here.

Our first colloquium of the new academic year will be held on 7th September. The speaker is Samuli Siltanen, Professor of Industrial Mathematics here in Helsinki. He is an expert in inverse problems, particularly as applied to medical imaging

We think that his work will be of great interest to physicists too – as it has connections with physics in a variety of ways, ranging from the imaging technologies on which it relies through to the mathematical techniques employed in his work. His talk, titled Three-dimensional X-ray vision by sparse tomography, will introduce us to his latest research.

Here is the abstract:

Traditional X-ray tomography is used routinely in hospital CAT-scans and in industrial non-destructive testing. There the idea is to collect a large number of X-ray projection images from all around the object, interpret the data as line integrals over a non-negative X-ray attenuation coefficient function, and reconstruct the inner structure of the target. Typically, the reconstruction algorithm of choice is some variant of Filtered Back-Projection (FBP). However, in many practical applications there are radiation dose restrictions or geometric obstacles preventing the collection of a comprehensive dataset. In such cases the FBP algorithm does not perform optimally. In recent years there has been tremendous progress in the development of robust reconstruction algorithms for sparse-data tomography. One of the successful approaches is variational regularization with a sparsity constraint; this approach is closely related to compressed sensing. The new algorithms open up novel imaging possibilities in the fields of dental imaging, welding inspection, adaptive optics in telescopes and environmental monitoring. Changing the physics does not necessarily change the mathematics of reconstruction, so the methods apply as well to electron tomography, neutron tomography and more.

After the 30 minute talk, there will be a cocktail reception. Welcome!

Update 10.9.2018: Samuli’s slides are available to download here.

Our final colloquium for the spring semester will be held on 18th May. Our speaker will be Mark Hindmarsh, professor of theoretical physics at the University of Sussex, and visiting professor at Helsinki. His work is principally concerned with the exciting topic of gravitational waves produced in the early universe, and so the title of his talk is Higgs Fizz in the Big Bang. Exceptionally, his talk will be in E204.

Here is his abstract:

About 10 picoseconds after the beginning of the Universe, the Higgs field turned on. In extensions of the Standard Model of particle physics, this could have been a first order phase transition, with bubbles of the Higgs phase expanding and colliding at relativistic speeds.  I will discuss how the Higgs “fizz” generates gravitational radiation, prospects for observing the radiation at the future space-based gravitational wave detector LISA, and outline how LISA complements the LHC as a probe of physics beyond the Standard Model.

After the 30 minute talk, there will be a cocktail reception. Welcome!

Update 21.5.2018: Mark’s slides are available to download here.

Our fourth colloquium again features a new professor giving a first talk to their peers in Kumpula. On 13th April Ilpo Vattulainen will speak about his work and how it connects physics to the life sciences, in a talk titled A physicist’s random walk in the life sciences.

Here is his abstract:

We have five primitive needs: food, warmth, security, pleasure, and health. In this colloquium, we will discuss how physical sciences can reveal secrets related to health. Quite surprisingly it appears that we know quite little about biological structures and phenomena that maintain our health, yet we often take them for granted. Our skin protects us from forbidden substances, however its structure is still a genuine mystery. The surface of our eyes protects us from the dry eye syndrome, but we do not understand how. The beating of our heart keeps us alive, yet we do not fully understand how the signaling in our cells controls the beat. Given how fascinating it is to examine these challenges, it is a true privilege to be a physicist: the toolbox of physics provides the means to reveal the principles and mechanisms that nature uses to maintain life and foster our health.

After the 30 minute talk, there will be a cocktail reception. Welcome!

Update 25.4.2018: You can watch a video of Ilpo’s talk here:

On Wednesday 28th of March we will hold a special event to celebrate the life, work and influence of Stephen Hawking. Coffee will be served from 16.00, then we will have a series of talks by experts from across the university: Kari Enqvist, Esko Keski-Vakkuri, Paavo Pylkkänen and Pentti Tienari, chaired by Director of the Helsinki Institute of Physics Katri Huitu. The talks will start at 16.30 in D101, Physicum, and the programme is expected to finish at 18.00. The talks will be accessible to a general audience. Welcome!

During this event (in particular during the coffee 16.00-16.30 and after the discussion 18.00-18.30) we will have a “memorial booth” in the Physicum lobby. We invite everyone to come and pay their respect to Hawking through a Hawking-related story: how his work has inspired you to pursue a career in Physics, or any other short anecdote about Hawking and his legacy. The stories will be filmed and collected into a “Hawking memorial video” from the Department of Physics in collaboration with The Science Basement.

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