Abstract:

Ambergris, a rare coprolith produced in the rectum of about one in a hundred the Sperm whales, is also found washed up on beaches worldwide as jetsam.  Its scarcity and physical properties as an incense, fixative and perfume, mean it has been valued since the 9th Century. However, it chemical composition was not established until the 1940s and studies of the jetsam material really only began with Rowland’s studies in 2017. Since then he has studied the composition, worldwide distribution, age (by radiocarbon dating) and natural volatiles, of over 50 pieces. Current studies of the biosynthesis of the major constituent are revealing surprising results and show the involvement of the microbiome. Use of the methods developed to study putative fossil ambergris from the Pleistocene in Italy, are also proving fruitful.

Short bio:

Steve Rowland is Professor of Organic Geochemistry at the University of Plymouth UK, where he has worked for 35 years, with occasional sabbaticals at Stanford University where he was awarded a Blaustein Fellowship and at CSIRO Marine in Hobart, Tasmania. He was a NERDDP postdoctoral Fellow at Curtin in 1983 working with Professor Robert (Bob) Alexander. Steve has published over 230 scientific papers and some of them are even correct! Some of his papers have been cited over 1500 times (e.g. Science 2004) and his latest paper in Environmental Science & Technology, on nanoplastics uptake by scallops, was downloaded over 2000 times within days. His H index is 54, whatever that means! His scientific interests are diverse, ranging from pollution chemistry (oil and plastics in particular), natural product chemistry (notably ambergris), chemical fossils, petroleum geochemistry and even insect chemistry. He will be made redundant by the University on 31st March 2019, when he will be 65, but will continue as a consultant to HM Government (he has signed the Official Secrets Act) and to numerous industrial companies and also as an Editor-in-Chief of the Elsevier journal , Organic Geochemistry, to which he was appointed in 2017.

Abstract:

Many processes in engineering and sciences involve the evolution of interfaces. Among the mathematical models for these types of problems, the phase-field method has emerged as a possible solution. Cahn and Hilliard initially proposed one of the most popular phase-field descriptions to model phenomena associated with spontaneous phase separation of immiscible fluids. This process occurs below a critical temperature, where the phase separation allows for the formation of spatial domains rich in each component. Phase-fields nonetheless lead to complex nonlinear, high-order partial differential equations, whose solution poses mathematical and computational challenges.

We describe two- and three-dimensional simulations of the Allen-Cahn, Cahn-Hilliard, Swift Hohenberg and phase-field crystal equations, which corroborate the theoretical findings, and illustrate the robustness of the method. We also discuss a challenging example, namely the Navier-Stokes Cahn-Hilliard in the context of droplet dynamics. The implementations use PetIGA and PetIGA-MF, which are high-performance isogeometric analysis frameworks, we designed to handle non-linear, time-dependent problems.

Ultimately, this simulation framework will allow us to model thermo-chemo-mechanical processes that are relevant to many geological systems.  Following the work of Cahn and Hilliard, we propose a generalised Cahn-Hilliard system coupled with the law of mass action which reproduces the kinetics of multicomponent systems as a chemical reaction between the species takes place. The understanding of reaction-diffusion systems requires a comprehensive treatment of both the diffusion and reaction parameters that rule the evolution of the interaction. For instance, when considering a diffusion process driven by gradients in the chemical potential, the interfacial energy parameter between the species plays a key role. We will provide a brief description of this thermodynamically consistent model for multiphase chemical reactions that can reproduce dissolution and reprecipitation processes.

Bio:

Dr Calo holds a professional engineering degree in Civil Engineering from the University of Buenos Aires. He received a master‘s in Geomechanics and a doctorate in Civil and Environmental Engineering from Stanford University. In 2009, Dr Calo became a founding Assistant Professor at the King Abdullah University of Science and Technology. In 2012, Prof Calo and Prof Efendiev developed the Center for Numerical Porous Media with the support of the King Abdullah University of Science and Technology (KAUST). In 2013, Dr Calo was promoted to Associate Professor and later in that year he was listed as a Highly Cited Researcher in the List of the Academic Ranking of World Universities by the Shanghai Jiao Tong University and Thomson Reuters. In 2016, he moved to Perth to become the CSIRO Professorial Chair in Computational Geoscience.

New Frontiers in the Therapeutic Application of Boron and Gadolinium

Prof Lou Rendina

School of Chemistry, The University of Sydney, Sydney NSW 2006
lou.rendina@sydney.edu.au
http://sydney.edu.au/science/chemistry/~lmrgroup/

Boron and gadolinium are two elements which are central to our research program. Their respective chemistry is not only fascinating but each element offers its own distinct challenges and unique characteristics which to date have been heavily under- utilised in medicine. In this seminar I will present some of our key results in the recent development of new gadolinium agents for application in cutting-edge binary therapies known as photon activation therapy (PAT) and neutron capture therapy (NCT), both of which have the potential to treat intractable malignant cancers such as those of the brain. I will also present recent work on the use of polyhedral boron clusters, particularly the carboranes, as unique structural frameworks in medicinal chemistry.

Prof Pieter T. Visscher

Center for Integrative Geosciences, University of Connecticut, Storrs, CT
Department of Marine Sciences, University of Connecticut, Groton, CT

Microbial mats are organosedimentary biofilms that greatly impacted the geochemical and physicochemical conditions on Earth through geological time. These laminated ecosystems are formed by various geomicrobiological processes, including biomass production, binding and trapping of sediments, and mineral precipitation. Lithified mats, or microbialites date back over 3 billion years in the rock record.

The interpretation of fossil microbial mats in the rock record and, consecutively, assessment of their potential role in the alteration of Earth’s geochemical environment through time is hampered by the poor preservation of these organic-rich structures. The preservation potential, however, can be enhanced through microbially-mediated lithification. The three key components of microbially- mediated mineral precipitation are: 1) the “alkalinity” engine (i.e., microbial community metabolism and environmental conditions impacting the calcium (or magnesium) carbonate saturation index); 2) the complex organic matrix comprised of exopolymeric substances (EPS); and 3) the coordination of community physiologies and sensing of environmental conditions (e.g., pH, oxygen concentration) through chemical communication, or quorum sensing. These combined geochemical-microbial activities provide conditions that allow specific microbialites to form, both on a macroscale (i.e., morphology) as well as on a microscale (i.e., shape and composition of minerals)

While mineral shape and composition may be a function of the EPS properties and therefore has the potential to reflect a specific signature of the microbial community, it is unresolved how, for example, continuous laminae vs. clotted fabrics form. The cyanobacterial community, situated near the surface according to the ambient light conditions, provides the organic carbon for heterotrophs. All these respiring organisms (including “strict” anaerobes, such as sulfate-reducing bacteria and methanogens) display their maximum metabolic activity along a surface horizon that may lithify. Some ideas emerge how chemical communication may play a role in this, and how microbial signaling compounds may be used to detect specific environmental conditions and may allow synchronizing of intra- and interspecies metabolic activities. These recent observations and ideas are, however, merely a first step in the understanding of microbialite formation, and their potential to weather the diagenetic processes so that some of the biological signatures are preserved.

Biography

Pieter Visscher is director of the Center for Integrative Geosciences and Professor of Organic Geochemistry in the Department of Marine Sciences at the University of Connecticut, USA. He is a Fulbright Scholar, obtained a MS Cum Laude and a PhD from the University of Groningen, The Netherlands, was post-doc in Marine and Atmospheric Chemistry at the University of Miami, and research associate at the US Geological Survey in Menlo Park, CA. He joined UConn in 1994, has written 100 peer-reviewed publications and obtained over $15M in extramural grant support throughout his career. He is director of the Geomicrobiology Laboratory where he combines organic and inorganic geochemistry with microbiology to address environment and geologic questions. Visscher is founding member of NASA’s Astrobiology Institute and member of the Australian Centre for Astrobiology.

Prof. Bart Kahr

Department of Chemistry, New York University, NY

Hückel theory is an approximate molecular orbital theory for planar, conjugated hydrocarbons whereas optical activity is typically associated with molecular chirality, a geometrical property of three-dimensional structures. Hückel theory and optical activity are subjects that at first blush brook no intersection. Why the conjunction “and” in the title? Some achiral compounds can indeed be optically active, but these have been traditionally excluded from considerations of optical activity because the spatial average of the optical activity of such compounds is zero. Thus, nothing can be measured in solution. On the other hand, these are perfectly appropriate targets for measurement on crystals. Optical rotations and rotatory strengths are here calculated for planar, conjugated hydrocarbons with the aim of determining to what extent the sum-over-π→π* rotatory strengths are sufficient to account for non-resonant optical activity, as well as to what extent qualitative molecular orbital theory can be used to interpret chiroptical structure-property relations. It is shown that by restricting our analyses to planar π-systems, an intuitive understanding of the vexing property of optical activity is forthcoming for the following reasons: Wave functions under the Hückel approximations are simply determined and graphically computed to yield transition dipole and quadrupole moments; the forms of the gyration tensors are given by symmetry with simple representation surfaces whose orientations are completely (C_2v) or partly (C_s) determined by symmetry; transition electric dipole and magnetic dipole moments have fixed, orthogonal dispositions relative to one another, and the most optically active directions are found at their bisectors. Throughout, the emphasis is on reckoning long wavelength optical rotation using simple models that are part of organic chemistry pedagogy. Attempts to measure the optical activity of oriented, isolated achiral molecules is also discussed.

Glycobiology: The Development of Chemical Tools to Study Carbohydrates

Assoc/Prof Keith Stubbs

School of Chemistry and Biochemistry, The University of Western Australia

Glycobiology is the study of the structures and roles of carbohydrates in biology. Carbohydrates are present in every living system and traditionally, have been known for their role in structural integrity and as energy sources. Recently, however, carbohydrates have been shown to be involved in a variety of fundamental biological processes such as protein folding and trafficking, as well as cellular signaling and regulation. As a result glycoconjugates continue to be uncovered as important factors in health and disease.

As we gain greater understanding into the roles that carbohydrates play at the cellular level, chemists need to develop carbohydrate-based tools to investigate the specific roles that a single mono- or polysaccharide plays in the dynamics of the cell. This seminar will describe examples from my laboratory of the development of chemical-based tools to study specific carbohydrate-processing enzymes and how they can be used in the field of glycoscience.

Some constraints on the redox budget of subduction zones

Dr Katy A. Evans

Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.

A number of lines of evidence suggest that the sub-arc mantle is 1-2 log units more oxidised than mantle elsewhere, though this conclusion is controversial, and the processes that may contribute to sub-arc mantle oxidation are poorly understood.

A simple analytical model was used to constrain the evolution of sub-arc mantle oxidation state as a function of redox-budget fluxes into, and out of, subduction zones. The model shows that plausible Archean and Proterozoic redox budget fluxes would not have created oxidised sub-arc mantle. Phanerozoic redox budget fluxes, on the other hand, which are dominated by the sulfate component, could increase sub-arc fO2 by up to three log10 units. The paucity of Cu and Au deposits associated with oxidised magmas in the Precambrian may be explained as a consequence of a lack of subducted oxidised material, rather than simply as a consequence of preservation potential. The redox budget of arc lavas is related to arc characteristics; samples from seven arcs show a significant correlation (P < 0.0005) between redox budget, subduction zone convergence rate, and subduction zone age.

Sulfate may be present in altered ocean crust in significant quantities, and even the most conservative model calculations suggest that sulfate is likely to dominate Phanerozoic subduction zone redox budget inputs. However, little is known of the relative stability or solubility of sulfur-bearing phases under subduction conditions, so large uncertainties are associated with absolute fluxes.

Sulfur isotopes provide one way to investigate sulfur sources, and the processes that affect sulfur during subduction. In-situ sulfur isotope measurements of pyrite associated with high pressure mineral parageneses in high pressure mafic rocks from the Eastern Alps and from New Caledonia were performed. The New Caledonia samples contain pyrite with δ34S in excess of 5‰, while samples from Pfulwe pass in the Eastern Alps contain pyrite with δ34S up to 15‰. These elevated δ34S values suggest that sulfur ultimately derived from seawater is preserved in these rocks to depths greater than 60km.