Viewing upcoming talks in: Physics and Astronomy Colloquia
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Physics and Astronomy ColloquiaEPR of heme proteins in mesoporous matrices – a successful match between spectroscopy, protein research, and hybrid material and biosensor development
Speaker: Prof. Sabine Van Doorslaer (Antwerp University)
The incorporation of proteins in mesoporous materials provides a promising tool to create new hybrid materials for biosensing or biocatalysis applications. The confinement of the proteins in these materials may stabilize the protein structure and even improve protein activity, but finding the optimal incorporation conditions and best protein-matrix matches is not trivial. This requires not only an in-depth understanding of the biochemical working of the used proteins under diverse chemical conditions and knowledge of the characteristics of the mesoporous host, it also calls for a variety of characterization tools that can probe the individual components as well as the hybrid materials. Although simple optical absorption techniques can be used to follow the adsorption and incorporation of the proteins, the faith of the proteins inside the synthetic host needs to be addressed by different techniques. Using the example of the incorporation of heme proteins, more specifically globins and peroxidases, in mesoporous titania and silica, it will be shown that EPR can provide unique information that cannot be obtained by other characterization methods. Moreover, EPR can play a role in monitoring and understand radical-formation reactions during the working of the final electrochemical biosensor. This requires developments of improved in-situ EPR hydrodynamic electrochemical cells, allowing fast and easy replacement of parts and adjustments to electrodes.
On: November 15, 2019 From: 10h00 To: 11h00
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Physics and Astronomy ColloquiaWhat we learned from the first interstellar comets, ‘Oumuamua and Borisov, and what we can do with the next ones
Speaker: Dr Colin Snodgrass (University of Edinburgh)
In 2017 a strange object was discovered by near-Earth asteroid surveys, with the appearance of a small asteroid, but an orbit that showed it to have come from another star. I will describe what we learned about this object, called ‘Oumuamua, and what we are now learning about the second interstellar object, comet Borisov, which was discovered in September this year and is currently being observed as it approaches the Sun. In addition to what we can measure with telescopes, I will also describe a newly approved ESA space mission that may one day investigate an interstellar object up close: Comet Interceptor.
On: November 22, 2019 From: 10h00 To: 11h00
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Physics and Astronomy ColloquiaCosmic Dust in Planetary Atmospheres
Speaker: Prof John Plane ()
C osmic D ust in Planetary A tmosphere s J. M. C. Plane School of Chemistry, University of Leeds, United Kingdom
Cosmic dust particles are produced in the solar system from the sublimation of comets as they orbit close to the sun, a nd also from asteroidal collisions between Mars and Jupiter. Recent advances in interplanetary dust modelling provide much improved estimates of the fluxes of cosmic dust particles into planetary (and lunar) atmospheres throughout the solar system. Combini ng the dust particle size and velocity distributions with new chemical ablation models enables the injection rates of individual elements to be predicted as a function of location and time. Th is information is essential for understanding a variety of atmos pheric impacts, including : the formation of layers of metal atoms and ions; meteoric smoke particles and ice cloud nucleation; perturbations to atmospheric gas -phase chemistry; the injection of bio -available phosphorous and organics; and the effects of the surface deposition of m icrometeorites and cosmic spherules. In this seminar I will describe the results of a large study designed to determine the input rate of cosmic dust to the terrestrial atmosphere, using a self -consistent treatment of cosmic dust from the outer solar system to the Earth’s surface. An astronomical model which tracks the evolution of dust from various sources into the inner solar system was combined with a chemical ablation model to determine the rate of injection of metallic vapours into the atmosphere. Constraining these coupled models with observations of IR emission from the Zodiacal Cloud, lidar measurements of the vertical fluxes of Na and Fe in the terrestrial mesosphere , and the rate of accretion of cosmic spherules at the South Pole, indicates that about 30 tonnes of dust enters the Earth’s atmosphere each day. Having fitted the astronomical model to the terrestrial input, the same model can be used to predict the dust inputs into the atmospheres of Venus and Mars. A separate outer solar system model has also been used to determine the dust input into Titan’s atmosphere. The Chemical Ablation Model (CABMOD) , which is central to quantifying planetary i mpacts, has recently been tested using a novel experimental system developed at Leeds: a Meteor Ablation Simulator, which measures the evaporation of metals from meteoritic particles that are flash heated to over 2800 K with a time -resolved temperature pr ofile simulating atmospheric entry. Examples of the impacts of meteoric ablation will then be described. For Earth: mesospheric metal layers; noctilucent cloud nucleation; freezing of polar stratospheric clouds ; and deposition of bio - available Fe and P . Fo r Venus : oxidation of CO and removal of O 2 on meteoric smoke particles in the hot troposphere. For Mars: production of an Mg + layer which has recently been observed by the MAVEN spacecraft. And f or Titan: the production of benzene in the troposphere by the cyclo - trimerization of acetylene on dust particles. Download PDFOn: November 29, 2019 From: 10h00 To: 11h00
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