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A collection of all the seminars going on at the Department, either on the downtown site, or out at the Bullard Laboratories
URL: http://talks.cam.ac.uk/show/index/15125
Updated: 37 min 11 sec ago

Wed 15 May 16:00: The Turkana Rift Arrays Investigating Lithospheric Structure (TRAILS) Experiment

Mon, 19/02/2024 - 11:55
The Turkana Rift Arrays Investigating Lithospheric Structure (TRAILS) Experiment

The Turkana Depression is a broad ( 500km-wide), topographically-subdued ( 0.5km), region between the elevated Ethiopian ( 1.5km) and East African Plateaus ( 2.5km). The Depression is unique in East Africa for being host to a NW-SE-trending failed Mesozoic (Anza) rift system through which the near-orthogonal, N-S-trending East African Rift subsequently developed. Whether the Depression’s low-lying nature is a result of a significantly thinned crust instigated by its multiple rifting phases, or instead due to a lack of dynamic mantle support is debated. Also poorly understood is the extent to which Cenozoic rifting and magmatism have developed across the Depression during the linkage of other comparatively narrow East African Rift zones to the north and south. Utilising data from the 2019-2021 Turkana Rift Arrays Investigating Lithospheric Structure project and surrounding networks, receiver function analysis and its joint inversion with surface-waves2, are used to probe Moho architecture and the lithosphere-asthenosphere system. Receiver function results1 reveal a thinned crust (20-25km) throughout the Depression: 10-20km thinner than the Ethiopian Plateau and Tanzania Craton. The Depression’s low elevations are thus likely an isostatic response from a thinned crust and not a lack of mantle dynamic support. High associated crustal stretching factors (β

1. Ogden, C. et al., (2023), Earth Planet. Sci. Lett., 609, 118,088, doi:10.1016/j.epsl.2023.118088. 2. Kounoudis, R. et al., (2023), Earth Planet. Sci. Lett., doi:10.1016/j.epsl.2023.118386. 3. Boyce, A., et al., (2023), Geochem. Geophys. Geosyst., 24 (8), e2022GC010,775, doi:10.1029/2022GC010775.

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Mon 19 Feb 21:00: Disasters by design In collaboration with the Stokes Society - Room Change, Unconventional Time

Wed, 14/02/2024 - 09:05
Disasters by design

Globally, two thirds of deaths arising from natural hazards in recent decades were caused by geological hazards. But how and why do natural hazards turn into disasters? In this talk I will explore this question through the lens of one particularly troublesome hazard: earthquakes. We will focus on general issues but make specific references to the 2023 Turkiye earthquake disaster. The death toll for a given earthquake magnitude will depend not only on geographic location, but also the social vulnerability of communities and the quality of the building stock. But these are dynamic features of evolving societies, which means earthquake risk varies in time and space. This talk will compare and contrast global trends in earthquake fatalities and aim to extract common themes that exacerbate the impact of natural hazards, and consider where and why these turn into disasters.

In collaboration with the Stokes Society - Room Change, Unconventional Time

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Wed 14 Feb 16:00: Cancelled: postponed to May 1st, 2024

Wed, 14/02/2024 - 00:36
Cancelled: postponed to May 1st, 2024

Due to health issues of the speaker, we regrettably have to cancel this seminar. It is rescheduled for May 1st, 2024.

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Tue 12 Mar 17:00: Film Screening: Pure Clean Water

Tue, 13/02/2024 - 09:45
Film Screening: Pure Clean Water

On Tuesday 12th March, at 5 pm, the Department will host a screening the feature documentary “Pure Clean Water”, which addresses the Chalk stream crisis in Cambridge. We will be joined by Tony Eva, who wrote and produced the film. You can watch a short trailer at https://purecleanwater.film/

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Tue 12 Mar 12:00: Microbial responses to warming and their impact on carbon stocks

Tue, 13/02/2024 - 09:05
Microbial responses to warming and their impact on carbon stocks

The rapid decomposition of carbon in organic soil layers in association with climate warming has drawn a large amount of attention in years; however, the ecological and biogeochemical feedbacks surrounding this process are still relatively unknown. In the Arctic, net gains in plant biomass are compensating for net carbon losses and “greening” previously barren landscapes. This presentation will describe new insights into these interactions through the discussion of a series of greenhouse experiments paired with field observations from a collection of sites throughout the high Arctic archipelago of Svalbard. Our results highlight the vital role that microorganisms play in the greening of the Arctic, the increased turnover of newly-accessible carbon in a warming climate and how these changes compare to other ecosystems that are undergoing rapid warming.

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Thu 15 Feb 11:30: Modelling the Response of Ice to Subglacial Flooding

Fri, 09/02/2024 - 15:55
Modelling the Response of Ice to Subglacial Flooding

Abstract not available

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Thu 22 Feb 11:30: High-performance Computing to Support Wind Energy Research

Fri, 09/02/2024 - 15:55
High-performance Computing to Support Wind Energy Research

High-performance computing (HPC) has emerged as a crucial tool for advancing wind energy research and development. The ever-increasing demand for clean and renewable energy sources, coupled with the inherent complexities of wind energy systems, requires the use of HPC to address the various challenges in this field. This talk will highlight the significance, applications, and potential benefits of HPC for wind energy research.

I will briefly introduce the open-source framework Xcompact3d, dedicated to the study of turbulent flows on HPC systems. Based on high-order finite-difference schemes on a Cartesian mesh, it combines accuracy, efficiency, versatility and scalability. Xcompact3d can be used as a wind farm simulator for simulating and analysing wind energy scenarios in a virtual environment. I will present a collection of results ranging from the study of the stability of wind turbine tip vortices, the entrainment process in large-scale wind farms, some layout optimisations with complex terrains, and some power maximisation studies using wake steering.

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Thu 29 Feb 11:30: TBC

Fri, 09/02/2024 - 15:55
TBC

Abstract not available

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Thu 07 Mar 11:30: Novel processing and 3D correlative imaging of electrodes for batteries

Fri, 09/02/2024 - 15:55
Novel processing and 3D correlative imaging of electrodes for batteries

Rechargeable batteries can contribute to powering electric transportation and storing electrical energy generated from intermittent renewable sources. There are increasing demands for improving the rate capability and energy density of current Li ion batteries (LIBs) and solid-state Li metal batteries (SSLMBs), along with other types of batteries. Two novel processing technologies have been developed to optimise the battery electrode microstructure and improve ion diffusion kinetics: (i) directional ice templating (DIT) for fabricating thick (900 µm) cathodes with vertical pore arrays and porosity gradient for LIBs [1]; and (ii) directional freezing and polymerisation (DFP) for fabricating cathodes with vertical arrays of solid polymer electrolyte (SPE) directly incorporated in the cathode microstructure during processing for SSLM Bs [2]. Both techniques reduced tortuosity τ of ion diffusion pathways through electrode thickness to 1.5 from ~3.3 for commercial electrodes.

We then show a new correlative imaging technique of combining X-ray Compton scattering imaging (XCS-I) and computed tomography (XCT) that allows 3D pixel-by-pixel mapping of Li chemical stoichiometry variations in a LiNi0.8Mn0.1Co0.1O2 electrode within a coin cell battery (Fig. 1) [3,4]. Using this technique, we show how the anisotropic electrode microstructure improved Li+ ion diffusivity, homogenised Li+ ion concentration, and improved energy storage performance.

Abstract attached

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Thu 14 Mar 11:30: New understanding of liquid thermodynamics, viscosity and its lower bounds

Fri, 09/02/2024 - 15:55
New understanding of liquid thermodynamics, viscosity and its lower bounds

Theories of gases and solids are well developed and date back 100-150 years ago. In contrast, understanding most basic thermodynamic properties (eg energy and heat capacity) of the third state of matter – the liquid state – turned out to be a long-standing problem in physics [1]. Landau&Lifshitz textbook states that no general formulas can be derived for liquid thermodynamic functions because the interactions are both strong and system-specific. Phrased aptly by Pitaevskii, liquids have no small parameter.

Recent theoretical results open a new way to understand liquid thermodynamics on the basis of collective excitations (phonons) as is done in the solid state theory. Differently from solids, the number of phonons is variable in liquids and decreases with temperature [1,2]. This effect is quantified in a phonon theory of liquid thermodynamics and explains the universal decrease of liquid constant-volume specific heat with temperature. One implication of this theory is that liquids can now be consistently understood on par with solids and are no longer “Cinderella of Physics” as believed until recently. I will also explain how this picture extends above the critical point where the Frenkel line separates two physically distinct states on the supercritical phase diagram [3].

I will subsequently describe how this picture leads to the theory of minimal quantum viscosity in terms of fundamental physical constants including the Planck constant [4]. This answers the long-standing question discussed by Purcell and Weisskopf of why viscosity never drops below a certain value [5]. This also means that water and life and well attuned to the degree of quantumness of the physical world [5]. This, in turn, implies, that we can better understand fundamental physical constants from biological and life processes [6].

1. K Trachenko, Theory of liquids: from excitation to thermodynamics (Cambridge University Press, 2023); K Trachenko and V Brazhkin, Reports on Progress in Physics 2016 2. M Baggioli, M Vasin, V Brazhkin and K Trachenko, Physics Reports 2020 3. C Cockrell, V Brazhkin and K Trachenko, Physics Reports 2021 4. K Trachenko and V Brazhkin, Minimal quantum viscosity from fundamental physical constants, Science Advances 2020; K Trachenko, Properties of condensed matter from fundamental physical constants, Advances in Physics (2023) 5. K Trachenko and V Brazhkin, Physics Today 74, 12, 66 (2021) 6. K Trachenko, Constraints on fundamental constants from bio-friendly viscosity and diffusion, Science Advances 2023

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Wed 06 Mar 17:30: 50,000 years of turnover and extinction in high-latitude megafauna communities Building doors are card operated, so latecomers may not be able to access the venue.

Thu, 08/02/2024 - 13:48
50,000 years of turnover and extinction in high-latitude megafauna communities

Abstract not available

Building doors are card operated, so latecomers may not be able to access the venue.

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Wed 21 Feb 17:30: Microplastics from geologists' perspective Building doors are card operated, so latecomers may not be able to access the venue.

Thu, 08/02/2024 - 13:44
Microplastics from geologists' perspective

Abstract not available

Building doors are card operated, so latecomers may not be able to access the venue.

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Thu 14 Mar 11:30: New understanding of liquid thermodynamics, viscosity and its lower bounds

Thu, 08/02/2024 - 09:16
New understanding of liquid thermodynamics, viscosity and its lower bounds

Theories of gases and solids are well developed and date back 100-150 years ago. In contrast, understanding most basic thermodynamic properties (eg energy and heat capacity) of the third state of matter – the liquid state – turned out to be a long-standing problem in physics [1]. Landau&Lifshitz textbook states that no general formulas can be derived for liquid thermodynamic functions because the interactions are both strong and system-specific. Phrased aptly by Pitaevskii, liquids have no small parameter.

Recent theoretical results open a new way to understand liquid thermodynamics on the basis of collective excitations (phonons) as is done in the solid state theory. Differently from solids, the number of phonons is variable in liquids and decreases with temperature [1,2]. This effect is quantified in a phonon theory of liquid thermodynamics and explains the universal decrease of liquid constant-volume specific heat with temperature. One implication of this theory is that liquids can now be consistently understood on par with solids and are no longer “Cinderella of Physics” as believed until recently. I will also explain how this picture extends above the critical point where the Frenkel line separates two physically distinct states on the supercritical phase diagram [3].

I will subsequently describe how this picture leads to the theory of minimal quantum viscosity in terms of fundamental physical constants including the Planck constant [4]. This answers the long-standing question discussed by Purcell and Weisskopf of why viscosity never drops below a certain value [5]. This also means that water and life and well attuned to the degree of quantumness of the physical world [5]. This, in turn, implies, that we can better understand fundamental physical constants from biological and life processes [6].

1. K Trachenko, Theory of liquids: from excitation to thermodynamics (Cambridge University Press, 2023); K Trachenko and V Brazhkin, Reports on Progress in Physics 2016 2. M Baggioli, M Vasin, V Brazhkin and K Trachenko, Physics Reports 2020 3. C Cockrell, V Brazhkin and K Trachenko, Physics Reports 2021 4. K Trachenko and V Brazhkin, Minimal quantum viscosity from fundamental physical constants, Science Advances 2020; K Trachenko, Properties of condensed matter from fundamental physical constants, Advances in Physics (2023) 5. K Trachenko and V Brazhkin, Physics Today 74, 12, 66 (2021) 6. K Trachenko, Constraints on fundamental constants from bio-friendly viscosity and diffusion, Science Advances 2023

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Mon 12 Feb 18:00: Understanding the circumstances surrounding Late Pleistocene Megafaunal Extinctions in Australia

Wed, 07/02/2024 - 18:10
Understanding the circumstances surrounding Late Pleistocene Megafaunal Extinctions in Australia

The timing, drivers, and ecological consequences of Late Pleistocene megafaunal extinctions remain subjects of global debate, constrained by limited data spanning this period. This study employs a novel combination of proxy-based palaeoecological and a functional palaeoecological approach to identify the most precise timing of megafaunal extinction in Australia to date, as well as the likely occurrences surrounding extinction and the floristic response to extinction. This talk will explore the topic and results within the context of the global debate.

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Wed 07 Feb 17:30: The West Antarctic Ice Sheet and sea level in the last interglacial Building doors are card operated, so latecomers may not be able to access the venue.

Tue, 06/02/2024 - 10:25
The West Antarctic Ice Sheet and sea level in the last interglacial

There is intense interest in the future stability of the West Antarctic Ice Sheet (WAIS). Models range widely in their predictions and in the physics they include. We can constrain possible outcomes by observing what happened to ice sheets at previous times when the polar regions were warmer than present. The last interglacial (LIG) is a particularly important time because both Greenland and Antarctic temperature were higher than present and so was sea level.

Within the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) project, in 2019 we retrieved a 651 metre ice core to the bed of Skytrain Ice Rise. This ice rise is adjacent to the Ronne Ice Shelf and the WAIS , and therefore sensitive to their extent. The ice core has been processed and analysed continuously for a range of analytes, and we can show that ice from the LIG is present.

I will start by describing the project, fieldwork and analyses. Eventually, I will show what happened to the ice around Skytrain Ice Rise in the LIG , and discuss how this fits with other evidence about LIG sea level.

Building doors are card operated, so latecomers may not be able to access the venue.

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Thu 07 Mar 11:30: Novel processing and 3D correlative imaging of electrodes for batteries

Tue, 06/02/2024 - 10:22
Novel processing and 3D correlative imaging of electrodes for batteries

Rechargeable batteries can contribute to powering electric transportation and storing electrical energy generated from intermittent renewable sources. There are increasing demands for improving the rate capability and energy density of current Li ion batteries (LIBs) and solid-state Li metal batteries (SSLMBs), along with other types of batteries. Two novel processing technologies have been developed to optimise the battery electrode microstructure and improve ion diffusion kinetics: (i) directional ice templating (DIT) for fabricating thick (900 µm) cathodes with vertical pore arrays and porosity gradient for LIBs [1]; and (ii) directional freezing and polymerisation (DFP) for fabricating cathodes with vertical arrays of solid polymer electrolyte (SPE) directly incorporated in the cathode microstructure during processing for SSLM Bs [2]. Both techniques reduced tortuosity τ of ion diffusion pathways through electrode thickness to 1.5 from ~3.3 for commercial electrodes.

We then show a new correlative imaging technique of combining X-ray Compton scattering imaging (XCS-I) and computed tomography (XCT) that allows 3D pixel-by-pixel mapping of Li chemical stoichiometry variations in a LiNi0.8Mn0.1Co0.1O2 electrode within a coin cell battery (Fig. 1) [3,4]. Using this technique, we show how the anisotropic electrode microstructure improved Li+ ion diffusivity, homogenised Li+ ion concentration, and improved energy storage performance.

Abstract attached

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Wed 07 Feb 16:00: Repeated rupture of persistent fault zone asperities: structure and variability of large earthquakes at the Kermadec subduction zone

Mon, 05/02/2024 - 17:19
Repeated rupture of persistent fault zone asperities: structure and variability of large earthquakes at the Kermadec subduction zone

Repeated slip on the same section of fault with earthquakes of similar size and mechanism, are so-called ‘characteristic earthquakes’. Such fault patches may be created by the existence of persistent asperities (isolated high strength regions) on the fault interface. However, many aspects of this apparent repeating behaviour are unclear – including i) how variable large events on the same fault segment are, ii) whether the same asperities are truly re-rupturing each time and iii) what factors limit slip to a particular region.

Rare occurrences of a complete earthquake cycle within the time of modern instrumentation are at rapidly slipping faults, particularly old oceanic subduction zones, such as Tonga-Kermadec. Here, the same portion of the plate interface has ruptured in M8+ earthquakes in 1917, 1976 and 2021. In this talk, I’ll present detailed observations of these earthquakes and show that although the same asperities likely re-ruptured in 1976 and 2021, the detailed slip distribution is different. Additionally, all earthquakes occur in an isolated area of the megathrust, which is bounded by changes in the lithospheric structure of the overriding plate. This high-seismicity region is coincident with an isolated forearc sedimentary basin, possibly formed by basal erosion related to seismogenesis, suggesting that seismic slip has persisted in this isolated area for several million years. I conclude that stress heterogeneity within this bounded seismogenic zone is long-lived and has produced a rich spectrum of earthquake ruptures.

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Thu 08 Feb 11:30: Catalysing Net Zero and Energy Transition Strategies through Thermodynamic Principles

Mon, 05/02/2024 - 11:56
Catalysing Net Zero and Energy Transition Strategies through Thermodynamic Principles

Efficient repurposing of existing oil and gas infrastructure for Carbon Capture, Utilisation, and Storage (CCUS) and hydrogen applications necessitates careful consideration of challenges, including potential inaccuracies in flow measurement and heightened risks of corrosion and rock dissolution leading to gas leakage. These challenges are largely rooted in the inherent thermodynamic properties of CCUS and hydrogen systems. Hence, a foundational requirement is a comprehensive understanding of the theoretical and thermodynamic principles governing the entire CCUS process and hydrogen economy. Addressing these challenges requires the development of a robust model capable of accurately predicting properties in H2 and CO2 -rich streams. Precise determination of critical parameters, including density, speed of sound, and phase boundaries, is essential for accurate flow measurement. This approach seeks to establish safer CO2 and hydrogen transportation and storage processes by proactively avoiding conditions contributing to corrosion and reservoir rock dissolution challenges. An informed and thorough grasp of thermodynamic aspects, coupled with the creation of an appropriate prediction model, will play a critical role in ensuring the success and sustainability of CCUS and hydrogen implementations.

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Wed 15 May 17:30: Title to be confirmed

Mon, 05/02/2024 - 10:30
Title to be confirmed

Abstract not available

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Fri 09 Feb 16:00: Seismicity distribution and fault plane solutions from the 2021 Fagradalsfjall dyke intrusion, Reykjanes Peninsula

Mon, 05/02/2024 - 10:09
Seismicity distribution and fault plane solutions from the 2021 Fagradalsfjall dyke intrusion, Reykjanes Peninsula

Abstract not available

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