Universiteit Leiden

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This Week's Discoveries | 11 April 2017

11 april 2017
Niels Bohrweg 2
2333 CA Leiden
De Sitterzaal

First Lecture

Lyman-alpha photons struggle to escape distant galaxies

Jorryt Matthee (Leiden Observatory) is a Huygens PhD fellow in extragalactic astrophysics. His project focusses on using emission lines to study galaxies in the first 3 billion years of cosmic history and is done in close collaboration with David Sobral.

Already 50 years ago, theory predicted that young galaxies emit up to 7% of their light as Lyman-alpha line emission, rendering their visibility up to extreme distances and look-back times. However, despite these prospects, observers failed to find any distant Lyman-alpha emitter for 30 years, because the fraction of Lyman-alpha photons that escape galaxies is low. With better telescopes, several thousands of Lyman-alpha emitters are now being found, even though their exact escape fraction and the physical processes that determine it remain poorly understood. To overcome this problem, we have undertaken a dedicated experiment, which reveals remarkable insights into the properties of very young galaxies in the distant Universe.

Second Lecture

Colloidal Joints with Designed Motion Range and Tunable Joint Flexibility

Daniela Kraft (LION). The soft condensed matter group of assistant professor Daniela Kraft is interested in the physics and self-organization of soft matter systems. Topics include the rational design of anisotropic and patchy particles for use as model systems and self-assembly, particle-covered emulsions and virus particles.

The miniaturization of machines towards the micro- and nanoscales requires the development of joint-like elements that enable and constrain motion. I will present a facile method to create colloidal joints, that is, anisotropic colloidal particles containing surface mobile DNA linkers that control the motion range of bonded particles. I will show that we can control the flexibility and range of motion that is enabled by a colloidal joint, and demonstrate their potential for programmable bottom-up self-assembly.

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