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Viewing upcoming talks containing the keyword: 19
Physics and Astronomy Colloquia
Speaker: Prof Jane Greaves (Cardiff University )
A very small number of planet-forming discs around young stars host hydrogenated nano-diamonds. These nano-particles were discovered in meteorites on Earth in the 1930s, and their infrared signatures were first found in space environments in 1980. The origins of the particles are obscure, even in the solar system, and most astronomers have been happily oblivious of the whole topic. I will discuss an unexpected outcome of our observations made to track grain growth in these proto-planetary discs, where the only three systems known to host nano-diamonds also showed anomalous microwave emission. This serendipitous result has led to a well-evidenced carrier-particle for this AME (after twenty years of debate), using the well characterised environments of circumstellar discs.
On: April 12, 2019 From: 10h00 To: 11h00View talk
Speaker: Paul Lusby (Edinburgh)
Abstract: Bio -inspired catalysis is central to the themes of supramolecular chemistry. Substrate pre - organization has dominated this form of catalysis, however, initial acceleration followed by severe product inhibition has been a re -occurring pattern. This is a par ticular problem for synthetically more useful and interesting annulation reactions (A+B→C) thus highlighting the limitation of this catalytic strategy. Here, we will present a novel catalytic approach using the host -guest chemistry of simple Pd2L4 assemb lies.1 We show that the avoidance of entropic mechanisms alleviates the product inhibition problem synonymous with capsule -mediated Diels -Alder (DA) reactions.2 Instead, reactivity is underpinned by the polarizing metallo -organic framework, which electroni cally activates the substrate. This approach reveals remarkably efficient DA catalysis, combining excellent activity with efficient turnover.2 In the final part of the talk we will show how encapsulation chemistry can be more generally applied to catalysis using new modes of reactivity. References 1 August, D. P.; Nichol, G. S.; Lusby, P. J. Angew. Chem. Int. Ed. 2016 , 55 , 15022. 2 Marti -Centelles, V.; Lawrence, A. L.; Lusby, P. J. J. Am. Chem. Soc. 2018 , 140 , 2862. Download PDF
On: April 17, 2019 From: 15h30 To: 16h30View talk
Cond Mat Seminars
A Scanning Single-Electron Transistor Array Microscope Probes the Hall Potential Profile in the Fractional Quantum Hall Effect
Speaker: Andreas Gauß (Max Planck Institute for Solid State Research Stuttgart)
The Hall potential distribution and thus the current distribution in integer quantum Hall samples have been measured since 1999  by an electrostatic potential probing scanning force microscope, limited to temperatures above 1.4 K. The results contradict the widely used edge-state picture and have given a new microscopic picture of the QHE . Similar measurements on the fractional quantum Hall effect require much lower temperature and a strongly enhanced sensitivity. Thus we have built a scanning SET microscope using a 1D array of eight single-electron transistors (SET), acting as local electrometers . The instrument is working below 40 mK electron temperature and up to applied magnetic fields of 18 T.We present Hall potential distribution measurements in the integer quantum Hall regime. The data confirms our previous results  obtained at 1.4 K. Further we present novel results for the Hall potential profiles and therefore the current distribution in the ν=2/3 fractional quantum Hall state. P. Weitz, E. Ahlswede, J. Weis, K. v. Klitzing, and K. Eberl, Physica E 6, 1 (2000). J. Weis, K. von Klitzing, Phil. Trans. of the Royal Society A 369, 3954 (2011) J. Weber, J. Weis, M. Hauser, and K. v. Klitzing, Nanotechnology 19, 37 (2008).
On: April 17, 2019 From: 13h00 To: 14h00View talk
Physics and Astronomy Colloquia
Speaker: Marc W. Buie (Southwest Research Institute, Boulder, Colorado)
Following the successful flyby of Pluto in 2015, New Horizons continued out into the Kuiper Belt to pursue its mission of explorations of the outer reaches of the solar system. The next chapter in this exploration is being written through the encounter with (486958) 2014MU69, nicknamed "Ultima Thule" that occurred on 2019 Jan 1. This phase of the mission was very challenging but worth all of that effort as we see the new data continuing to be received from the spacecraft. This chapter that New Horizons is now writing would not have been possible without broad support from the community and formidible ground-based and space-based telescopes we have at our disposal. However, there is a special synergy between New Horizons, the Hubble Space Telescope, and ESA's Gaia Mission and the people behind these missions.
My presentation will provide a glimpse into the work that began in 2004 and culminating in the first ever flyby of a cold-classical Kuiper Belt object. I will present a summary of what it took to get there as well as an update on the current scientific results from the mission.
On: April 19, 2019 From: 10h00 To: 11h00View talk
Speaker: Graham Smith (University of St Andrews)
In this talk I will describe our recent work on mm-wave antennas to create specialised optical output beams from single mode waveguide. I will show how combinations of HE1n modes, Gaussian beams (LG0n modes), and Airy beams can all be accurately synthesized using mode transformation techniques over wide bandwidths and how they can be used in a wide variety of metrology, instrumentation, radar and radiometric applications. In particular I will show how it is possible to continuously refocus a Gaussian beam without using mirrors or lenses, as an alternative to conventional quasi-optical techniques.
On: April 23, 2019 From: 13h00 To: 14h00View talk
RSC Award Lectures
Speaker: Artem Bakulin (Imperial College London)
Ultrafast photocurrent spectroscopy of molecular electronic devices Artem A. Bakulin Department of Chemistry, Imperial College London London SW7 2AZ, UK email@example.com
I will present an old but well -forgotten advanced time -resolved spectroscopic technique based on the ultrafast optical control of molecular excited states followed by photocurrent detection. The method is very useful to study electronic dynamics in molecular semiconducting materials and organic optoelectronic devices , like plastic solar cells, under working conditions. 1 Using th is method , we were able to identify and track in time the precursor and charge trapping states in a variety of material systems, including polymer -fullerene blends, polyme r-oxide hybrids, colloidal quantum dots and perovskites. We show that a careful management of charge and energy dynamics in the excited st ate can substantially suppress the loss pathways and improve the device performance.
1 Bakulin A.A., Silva C., Ve lla E., Ultrafast Spectroscopy with Photocurrent Detection: Watching Excitonic Optoelectronic Systems at Work, J. Phys. Chem. Lett. 7, 250 (2016) Download PDF
On: April 24, 2019 From: 14h00 To: 15h00View talk