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Viewing upcoming talks containing the keyword: 19
Physics and Astronomy Colloquia
Speaker: Prof Richard Ellis (European Southern Observatory, University Colled London and Carnegie Centenary Professor, University of Edinburgh)
In conjunction with Carnegie Trust for the Universities of Scotland, we are pleased to host:
The first billion years after the Big Bang can be regarded as the final observational frontier in assembling a coherent picture of cosmic history. During this period early stars and galaxies formed and the Universe became bathed in ultraviolet light for the first time. Sometime during this era the hydrogen inbetween galaxies transformed from a neutral gas to one that was ionised into its protons and electrons. How and when did this `cosmic reionisation’ occur and were early star-forming galaxies the primary agents? Deep exposures with the Hubble Space Telescope have provided the primary evidence that star-forming galaxies were present during the relevant period. Detailed spectroscopy of these galaxies is now required to address these important questions. I will review the rapid progress being made in this area with current facilities, and the prospects with upcoming ones, including the James Webb Space Telescope and extremely large ground-based telescopes now under construction.
On: May 20, 2016 From: 17h15 To: 18h30View talk
Speaker: Marie-Paule Pileni (University Pierre and Marie Curie, Paris)
The influence of the crystalline structure of nanocrystals called nanocrystallinity on their chemical and physical properties is presented. The nanocrystals with low size distribution self assemble in 3D superlattices called supracrystals. Heterogeneous and homogeneous growth processes of supracrystals take place inducing marked changes in their physical properties. Note that a hierarchy in supracrystal growth processes, nanocrystalinity segregation, growth of quasi supracrystals and supracr ystals characterized by vicinal surfaces are pointed out.
Supracrystal intrinsic properties of either one or two components are demonstrated. Analogy between atoms ordered in a nanocrystal and nanocrystals ordered in a supracrystal is presented. Solubiliz ation of hydrophobic supracrystal in aqueous solution is obtained with Co and Au supracrystals with appearance of tunable plasmonic metamaterials. Download PDF
On: May 25, 2016 From: 15h30 To: 16h30View talk
Speaker: Prof Dan Nocera (Harvard)
The artificial leaf accomplishes a solar fuels process that captures the elements of photosynthesis – the splitting of water to hydrogen and oxygen using light, from neutral water, at atmospheric pressure and room temperature. These conditions are met owing to the development of water splitting catalysts of the elements of Mn, Co and Ni that are self-healing; the design principles for self-healing catalysis will be presented. The self-healing catalysts are coated on a silicon wafer in a buried junction configuration, which enables light harvesting and charge separation to be coupled to catalysis under simple conditions. We have advanced the design of the artificial leaf by utilizing the hydrogen from the artificial leaf and combining it with carbon dioxide to make liquid fuels. Using the tools of synthetic biology, a bio-engineered bacterium has been developed to convert carbon dioxide, along with the hydrogen produced from the artificial leaf, into biomass and fusel alcohols. This hybrid microbial | artificial leaf system scrubs 180 grams of CO2 from air, equivalent to 230,000 liters of air per 1 kWh of electricity. Coupling this hybrid device to existing photovoltaic systems leads to unprecedented solar-to-biomass (10.7%) and solar-to-liquid fuels (6.2%) yields, which greatly exceeding natural photosynthetic systems.
On: May 30, 2016 From: 16h00 To: 17h00View talk
Stand-alone and hybrid structural characterization of proteins using EPR spectroscopy on spin labels (EaStCHEM/BSRC joint colloquium)
Speaker: Gunnar Jeschke (ETHZ)
Proteins and their complexes are not always accessible to established approaches for determination of atomistic structures, and even if they are, a single structure with atomistic resolution may not be representative of the whole conformational space that is required for their function. Alternative information on this conformational space can be obtained by electron paramagnetic resonance (EPR spectroscopy), usually after spin labels have been introduced via site-directed mutations. Since paramagnetic centres are rare in proteins and in their native environment, no assignment or resolution problems arise even in large proteins or complexes and in physiologically relevant environments. If two labels are introduced, the distance distribution between them rather than only a mean distance can be measured, so that direct information on conformational distributions is obtained, which is hard to come by with other approaches.
These potential advantages come at a price. Site-directed mutations and spin labelling are elaborate. Thus, EPR restraints on structure are usually sparse and need to be combined in hybrid approaches with information from other techniques. The labels themselves are flexible side groups with their own conformational distribution, a property that limits precision of the restraints and requires extension of existing approaches for modelling structure.
In this talk I will explain how information on label accessibility by oxygen and water and on label-to-label distance distribution can be obtained. Modelling of the conformational distribution of the spin label and its accuracy limits will be shortly discussed. Based on this, I will explain how a label at a structurally unresolved site can be located by an approach similar to the global position system,1 how conformational ensembles can be generated from distance distribution restraints,2 and how relative orientation and translation of structurally resolved domains can be determined.3 Hybrid approaches will be illustrated using NMR and EPR on a protein-RNA complex,4 x-ray crystallography, SAXS, and EPR on the FnIII-3,4 domains of integrin a6b4,5 and x-ray crystallography, NMR, and EPR on the active form of the pro-apoptotic protein Bax.1
1S. Bleicken, G. Jeschke, C. Stegmüller, R. Salvador-Gallego, A.J. García-Sáez, E. Bordignon, Mol. Cell 2014, 56, 496-505. Structural Model of Active Bax at the Membrane
2G. Jeschke, Proteins, 2016, in press, DOI: 10.1002/prot.25000 Ensemble models of proteins and protein domains based on distance distribution restraints
3 D. Hilger, Ye. Polyhach, E. Padan, H. Jung, G. Jeschke, Biophys. J., 2007, 93, 3675-3683. High-resolution structure of a Na+/H+ antiporter dimer obtained by pulsed EPR distance measurements
4 O. Duss, E. Michel, M. Yulikov, M. Schubert, G. Jeschke, F. H.-T. Allain, Nature, 2014, 509, 588-592. Structural basis of the non-coding RNA RsmZ acting as protein sponge
5N. Alonso-García, I. García-Rubio, J. A. Manso, R. M. Buey, H. Urien, A. Sonnenberg, G. Jeschke, J. M. de Pereda, Acta Cryst. D, 2015 71, 969-985. Combination of X-ray crystallography, SAXS and DEER to obtain the structure of the FnIII-3,4 domains of integrin a6b4
On: June 1, 2016 From: 15h30 To: 16h30View talk
Physics and Astronomy Colloquia
Speaker: Professor J.C. SÃ©amus Davis (School of Physics and Astronomy, University of St Andrews)
Everything around us, everything each of us has ever experienced, and virtually everything underpinning our technological society and economy is governed by quantum mechanics. Yet this most fundamental physical theory of nature often feels as if it is a set of somewhat eerie and counterintuitive ideas of no direct relevance to our lives. Why is this? One reason is that we cannot perceive the strangeness (and astonishing beauty) of the quantum mechanical phenomena all around us by using our own senses.
In this lecture I will describe the recent development of techniques that allow us to image electronic quantum phenomena directly at the atomic scale. As examples, we will visually explore the previously unseen and very beautiful forms of quantum matter making up electronic liquid crystals and high temperature superconductors and find that they are closely related. I will discuss the implications for fundamental physics research and also for advanced materials and new technologies, arising from quantum matter visualization.
On: June 8, 2016 From: 18h00 To: 19h00View talk
Cond Mat Seminars
Speaker: Hannah Price (Trento Univ)
Synthetic dimensions have recently emerged as a powerful way to implement artificial gauge fields and create topological energy bands for neutral particles. In this approach, discrete internal degrees of freedom are externally coupled and reinterpreted as lattice sites along an additional synthetic dimension, where an artificial magnetic field can be imprinted via the applied coupling. In the first half of my talk, I will present our new generic proposal for how to realise a synthetic dimension in ultracold atoms that relies only on a harmonic potential and a time-dependent modulation . This simple scheme is able to overcome many limitations of previous implementations, extending these ideas to a much wider range of experimental set-ups and providing an intriguing route towards quantum Hall physics and strongly-correlated states. In the second half of my talk, I will focus on how synthetic dimensions may allow us to probe higher-dimensional topological physics for the first time. In particular, I will motivate the 4D quantum Hall effect through a semiclassical analysis and discuss how this physics could be explored in the center-of-mass drift of an ultracold atomic cloud [2,3]. H. M. Price, T. Ozawa and N. Goldman, in preparation. H. M. Price, O. Zilberberg, T. Ozawa, I. Carusotto, N. Goldman, Phys. Rev. Lett. 115, 195303 (2015). H. M. Price, O. Zilberberg, T. Ozawa, I. Carusotto and N. Goldman, arXiv:1602.01696.
On: June 13, 2016 From: 10h00 To: 11h00View talk