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Viewing upcoming talks containing the keyword: 19
Physics and Astronomy Colloquia
Speaker: Inga Kamp (University of Groningen)
The disks around young stars, protoplanetary disks, are thought to be the birthplaces of planetary systems such as our own.
Spitzer, Herschel and ground-based observations showed in several cases the existence of water in such disks around young stars and JWST will dig even deeper from 2018 on. On the other hand, Solar System exploration and observations of comets allow us to study specific processes in much more detail compared to protoplanetary disk research.
The combination of evidence from protoplanetary disks and our own Solar System is inspiring the discussion of how much water vapour and ice is present at early times to form gas giant planets, water worlds, but also at later times to deliver the Earth oceans and eventually lead to the emergence of life. I will discuss our current understanding of the chemistry in proptoplanetary disks, the water vapour and ice reservoirs and potential mixing processes and relate this to evidence collected within our own Solar System.
On: September 30, 2016 From: 10h00 To: 11h00View talk
Physics and Astronomy Colloquia
Speaker: Judith Driscoll (University of Cambridge)
Since the discovery of high temperature superconductivity in perovskite oxides in 1986, the unearthing of a huge range of physical phenomena in transition metal oxides (TMOs) has been nothing short of remarkable, e.g. new magnetics, ferroelectrics, multiferroics, semiconductors, transparent conductors, calorics, plasmonics, catalysts, ionic conductors. Nearly 150,000 papers were published on the topic â€˜oxide+thin filmâ€™ in the last 10 years, not far from the number published on graphene in this same period. However, there are few applications of complex oxide thin films today. The underlying reason is the lack of understanding of the materials, in terms of their defective nature and in terms of how to engineer them to be perfect and strained optimally. As stated in a recent perspective publication by the EU commission about emerging applications, â€œwe have passed from the perception that materials are in the drawer to the realisation that materials are the bottleneckâ€.
Addressing the oxide thin film bottleneck is long overdue. This talk will discuss new insight into oxide thin films. Then solutions to the problem from the author will be presented, with examples given of unprecedented functional property enhancements in systems such as ferroelectrics, ferromagnetics and ionics. Examples will also be given of the authorâ€™s work in the area of oxide superconductors which has enabled applications to take off.
On: October 28, 2016 From: 10h00 To: 11h00View talk
Speaker: Jeff Long (University of California, Berkeley)
Owing to their high surface areas, tunable pore dimensions, and adjustable surface functionality, metal-organic frameworks (MOFs) can offer advantages for a variety of gas storage and gas separation applications.Â In an effort to help curb greenhouse gas emissions from power plants, we are developing new MOFs for use as solid adsorbents in post- and pre-combustion CO2 capture, and for the separation of O2 from air, as required for oxy-fuel combustion.1Â In particular, MOFs with open metal cation sites or diamine-functionalized surfaces are demonstrated to provide high selectivities and working capacities for the adsorption of CO2 over N2 under dry flue gas conditions.2Â Multicomponent adsorption measurements further show compounds of the latter type to be effective in the presence of water,3 while calorimetry and temperature swing cycling data reveal a low regeneration energy compared to aqueous amine solutions.4Â MOFs with open metal sites, such as Mg2(dobdc) (dobdc4â€“ = 2,5-dioxido-1,4- benzenedicarboxylate), are highly effective in the removal of CO2 under conditions relevant to H2 production, including in the presence of CH4 impurities.5Â Redox-active Fe2+ sites in the isostructural compound Fe2(dobdc) allow the selective adsorption of O2 over N2 via an electron transfer mechanism.6Â The same material is demonstrated to be effective at 45 Â°C for the fractionation of mixtures of C1 and C2 hydrocarbons, and for the high-purity separation of ethylene/ethane and propylene/propane mixtures.7Â Finally, it will be shown that certain structural features possible within MOFs, but not in zeolites, can enable the fractionation of hexane isomers according to the degree of branching or octane number.8
1.Â Â Â Â Â Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Chem. Rev. 2012, 112, 724.
2.Â Â Â Â Â McDonald, T. M.; Lee, W. R.; Mason, J. A.; Wiers, B. M.; Hong, C. S.; Long, J. R. J. Am. Chem. Soc. 2012, 134, 7056.
3.Â Â Â Â Â Mason, J. A.; McDonald, T. M.; Bae, T.-H.; Bachman, J. E.; Sumida, K.; Dutton, J. J.; Kaye, S. S.; Long, J. R. J. Am. Chem. Soc. 2015, 137, 4787.
4.Â Â Â Â Â McDonald, T. M.; Mason, J. A.; Kong, X.; Bloch, E. D.; Gygi, D.; Dani, A.; CrocellÃ , V.; Giordano, F.; Odoh, S.; Drisdell, W.; Vlaisavljevich, B.; Dzubak, A. L.; Poloni, R.; Schnell, S. K.; Planas, N.; Kyuho, L.; Pascal, T.; Prendergast, D.; Neaton, J. B.; Smit, B.; Kortright, J. B.; Gagliardi, L.; Bordiga, S.; Reimer, J. A.; Long, J. R. Nature 2015, 519, 303.
5.Â Â Â Â Â Herm, Z. R.; Swisher, J. A.; Smit, B.; Krishna, R.; Long, J. R. J. Am. Chem. Soc. 2011, 133, 5664.
6.Â Â Â Â Â Bloch, E. D.; Murray, L. J.; Queen, W. L.; Maximoff, S. N.; Chavan, S.; Bigi, J. P.; Krishna, R.; Peterson, V. K.; Grandjean, F.; Long, G. J.; Smit, B.; Bordiga, S.; Brown, C. M.; Long, J. R. J. Am. Chem. Soc. 2011, 133, 14814.
7.Â Â Â Â Â Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Science 2012, 335, 1606.
8.Â Â Â Â Â Herm, Z. R.; Wiers, B. M.; Mason, J. A.; van Baten, J. M.; Hudson, M. R.; Zajdel, P.; Brown, C. M.; Masciocchi, N.; Krishna, R.; Long, J. R. Science 2013, 340, 960.
On: November 15, 2016 From: 13h30 To: 14h30View talk
Physics and Astronomy Colloquia
Speaker: Ilya Kuprov (University of Southhampton)
Pseudocontact shift (PCS) is an additional chemical shift caused by the presence of a rapidly relaxing paramagnetic centre near the nucleus. PCS is well understood theoretically and is widely employed as a source of structural restraints in metalloproteins, where commonly occurring Ca2+, Mg2+, Mn2+ and Zn2+ binding sites can often coordinate a lanthanide ion instead. A paramagnetic centre may also be introduced artificially by attaching a lanthanide ligand tag to the protein surface.
The subject has a long-standing problem â€“ lanthanide-containing protein tags have significant conformational mobility. Even DOTA-M8, which uses a sterically overcrowded â€“ and therefore rigid â€“ metal cage, still has a flexible linker. The conformational mobility of lanthanide tags is visible in the distance distributions measured by double electron resonance, and in molecular dynamics simulations. In this situation the commonly used point paramagnetic centre approximation for PCS is not expected to be valid, but quantum chemical calculations are prohibitively expensive.
In this talk I will describe a new method for extracting probability densities of lanthanide tags from PCS data. The method relies on Tikhonov-regularised 3D reconstruction and opens a new window into biomolecular structure and dynamics because it explores a very different range of conditions from those accessible to double electron resonance work on paramagnetic tags: a room-temperature solution rather than a glass at cryogenic temperatures. The method is illustrated using four different Tm3+ DOTA-M8 tagged mutants of human carbonic anhydrase II; the results are in excellent agreement with rotamer library and DEER data.
The wealth of high-quality pseudocontact shift data accumulated by the biological magnetic resonance community over the last 30 years, and so far only processed using point models, could now become a major source of useful information in conformational dynamics research.
On: November 25, 2016 From: 10h00 To: 11h00View talk
Cond Mat Seminars
Speaker: S. Thomson / S. Edkins (St Andrews)
Disordered Quantum Systems: From Ultracold Atoms to Dimerised Magnets and Back AgainNothing in life is perfect and whatâ€™s true in life is true for quantum materials. Disorder and impurities are present in every substance, no matter how much we try to avoid them, but sometimes these imperfections can lead to useful quantum mechanical effects.In this talk, Iâ€™ll summarise the main parts of my PhD research, telling the story of an unusual disordered phase of matter where insulating and superfluid regions coexist within a single sample. This phase is known as the Bose glass and is most conveniently realised in ultracold atomic gases. Iâ€™ll show how some of my work revealed this phase to be more exotic than previously thought, and how by chance some of my later research on insulating antiferromagnets turned out to rely crucially on a controversial claim made in my earlier work on ultracold atoms. Iâ€™ll then show how weâ€™ve recently proposed a new way for quantum gas microscopes to test these predictions, and outline where we go from here.
Detection of a Cooper-Pair Density Wave in Bi2Sr2CaCu2O8 using Scanned Josephson TunnellingThe quantum condensate of Cooper-pairs forming a superconductor was originally conceived to be translationally invariant. In theory, however, pairs can exist with finite momentum Q resulting in a new state with spatially modulating Cooper-pair density. This is the famous FFLO state [1,2] which has never been directly observed in any superconductor. Research has recently refocused on FFLO type physics because the cuprate pseudogap phase is hypothesised to contain a closely related â€˜pair density waveâ€™ state.
I will report on the use of scanned Josephson tunnelling microscopy (SJTM) to image Cooper-pair tunnelling from a d-wave superconducting STM tip at millikelvin temperatures to the Cooper-pair condensate of Bi2Sr2CaCu2O8. The resulting images of the Cooper-pair condensate show clear pair density modulations oriented along the Cu-O bond directionsÂ .
I will discuss the implications of this discovery for the microscopic theory of the cuprate pseudogap phase as well as the extension of SJTM to other emergent intertwined phases and quantum devices.
 P. Fulde and R.A. Ferrell, Phys. Rev. 135: A550 (1964). A.I. Larkin, Yu.N. Ovchinnikov, Sov. Phys. JETP 20, 762 (1965). M. HamidianÂ & S. D .EdkinsÂ et al. Nature 532, 343 (2016).
On: November 29, 2016 From: 15h00 To: 16h00View talk
Speaker: Eleanor Campbell (Edinburgh)
Free -Flying Fullerenes The properties of gas phase fullerenes were studied extensively during the 1990s -2000s and showed the incredible resilience of this unusual molecule. Astronomical observations in the last few years combined with laboratory studies have now proved that neutral and charged fullerenes are present in surprisingly large amounts in space. Their u nusual properties make them particularly resistant to the harsh environment allowing them to survive radiation conditions that would destroy most complex organic molecules. This is reviving an interest in the fundamental properties of these molecules and h ow they may contribute to the chemistry of interstellar space. I will review the current status and describe experiments being carried out in Edinburgh and St Andrews to probe exotic excited electronic states of fullerene species that may play an importan t role under the conditions of space, as well as discussing the types of experiments now needed to provide input for astrochemical models. Download PDF
On: January 18, 2017 From: 15h30 To: 16h30View talk