http://talks.cam.ac.uk/show/rss/5408

The coldest, ice laden, and most seasonal seas on the Earth hold an abundance of life that is the most bizarre and extreme in its biology of life anywhere. Life in the seas around Antarctica is unexpectedly diverse and abundant.  It houses true giant species and animals that cannot live elsewhere because their biology is so tuned to the constant low temperature and extreme seasonality.  They are also amongst the most threatened by change and are in some of the fastest areas of change on the planet.  This presentation will discuss the limitations faced by the animals living in Antarctic seas, how they cope and thrive in the conditions and just how unusual and bizarre some of their biology is.

• Speaker: Professor Lloyd Peck
• Tuesday 25 November 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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In studies of modern landscapes, biogeomorphology describes the two-way interaction between biotic and dynamic abiotic landscape elements. As organisms interact with landforms and Earth surface processes, they can modify attributes such as sediment stability, fluid dynamics and roughness, all of which can moderate erosion, deposition and stasis, and thus register signals in the landforms and sedimentary deposits of an environment. The recognition of such signatures in the deep time geological record has potential significance for understanding the role of life in planetary surface process because ancient strata enable access to timescales in excess of the finite historicity of instrumental records afforded in the study of modern biogeomorphology. Further, the ancient record encapsulates a wide range of spatio-temporal scales, which enable ancient life-sediment interactions to be interrogated on a micro- to global scale and over durations from the instantaneous to evolutionary timescales. Accessing all of these means a better understanding of how effect cascades can cause the small scale to impact the large scale and thus set boundary conditions for further effects. Using a series of case studies we demonstrate how an understanding of deep time biogeomorphology can be accessed from the sedimentary geological record at outcrop. In doing so we seek to demonstrate the fundamental role that life and evolution have has in constructing the siliciclastic record and underline that many sedimentary phenomena are essentially physical processes that are mediated through biological processes. Given that populations which evolve on timescales congruent to that of landscape change can have their evolution affected by the change, we emphasise how further investigation in the vein has the potential to shift perceptions of the history of Earth as a living planet through means of coeval interrogation of sedimentary and fossil records

• Speaker: Professor Neil Davies
• Tuesday 18 November 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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Living organisms are the most complex objects we know of in the universe, with many different molecules, chemical reactions and processes arranged in precise patterns that give rise to cells, tissues, organs and individuals. We can measure many of these molecules, from DNA through RNA to proteins at scale, and we can often place these molecules, cells and tissue structures into 3 dimensiona space, sometimes in living systems with changes over time. The result is an increasingly detailed observation on life, from genome onwards. However, analysing these multi-modal datasets is challenging for a variety of reasons. Over the last decade Machine Learning, Deep Learning and AI - all part of a continuum of high parameter statistical models has been making great strides in predicting and sometimes providing insight into this work.

• Speaker: Professor Ewan Birney
• Tuesday 11 November 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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Low-frequency radio observations present a unique opportunity to fill a critical gap in our understanding of the early universe, bridging the cosmic microwave background (CMB) last scattering surface with the era of high-redshift galaxies observed by the JWST and ALMA . In this talk, I will discuss the latest theoretical developments, existing observational constraints, and prospects for future observations. The formation of the first stars and the subsequent population of X-ray binaries drove a fundamental transition in the state of the universe that the radio telescopes can probe. Due to the lack of direct observations, the properties of these sources remain highly uncertain. The cosmological 21-cm signal produced by neutral hydrogen gas contains unique information about the first generations of UV and X-ray sources, as well as their impact on the surrounding environment. Observations of the 21-cm signal with the Square Kilometre Array (SKA) and its precursors will open a new observational window, allowing us to significantly improve our understanding of these objects and the evolution of the universe.

• Speaker: Professor Anastasia Fialkov
• Tuesday 04 November 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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The direct amidation of C–H bonds is a highly desirable reaction owing to the widespread utility of amidated products in total synthesis, medicinal chemistry, and materials science. In this context, we have developed a new mechanistic platform that employs custom-designed transition metal-based catalyst systems in combination with dioxazolones as robust and practical amino sources. This strategy enables the generation of metal-nitrenoid intermediates, ultimately achieving C–H amidation via either inner or outer-sphere C–H activation of insertion pathways. Building on this foundation, we recently introduced transition metal-based catalyst systems for asymmetric C−H amidation, providing an efficient route to synthesize chiral lactams and functional amino compounds from readily available commodity chemicals.

In developing our C-H amination reactions, we also thoroughly investigated the involvement of key nitrenoid intermediates using both experimental and computational mechanistic studies. In fact, we designed a chromophoric octahedral rhodium complex featuring a bidentate dioxazolone ligand, in which photoinduced metal-to-ligand charge transfer initiates catalytic C–H amidation. X-Ray photocrystallographic analysis of Rh-dioxazolone complexes enabled structural characterization of Rh-acylnitrenoid intermediate for the first time and provided definitive evidence that the singlet nitrenoid species is primarily responsible for acylamino transfer process. Furthermore, in crystallo monitoring of the reaction between a nucleophile and the in situ generated Rh-acylnitrenoid established a crystallographically traceable system, capturing the key mechanistic snapshots of nitrenoid transfer.

• Speaker: Professor Sukbok Chang
• Tuesday 28 October 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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I will introduce the general problem of first principles force fields: creating surrogate models for quantum mechanics that yield the energy of a configuration of atoms in 3D space, as we would find them in materials or molecules. Over the last decade significant advances were made in the attainable accuracy, and today we can model materials and molecules with a per-atom energy accuracy of up to 1 part in 10,000 with a speedup of over a million or more compared to the explicit quantum mechanical calculation, enabling accurate molecular dynamics simulations on large length and time scales. The most surprising aspect of the best models is its extreme generalisation: fitted only on small periodic crystals, it shows stable trajectories on arbitrary chemical systems, from water to nanoparticles and proteins. The precise relationship between the architectural elements and the extreme generalisation is still a mystery. The locality of the graph neural network structure is key to its success, as well as high body order and message passing. The force fields get significantly better with more data, yet model size and complexity can remain largely the same. Current challenges include integrating explicit long range electrostatics and combining large datasets for materials and organic molecules where the appropriate levels of electronic structure theory are incompatible.

• Speaker: Professor Gabor Csanyi
• Tuesday 21 October 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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Polar disconnections are intuitive and underlie much of retrosynthetic logic. Undergraduates exposed to multistep synthesis are often taught to assemble organic molecules through the combination of positively and negatively charged synthons because, after all, opposites attract. Indeed, the most employed two-electron C–C bond forming reactions today are those either based upon classical cross-coupling reactions (e.g., Suzuki, Negishi, Heck) or polar additions (aldol, Michael, Grignard). These reactions are the mainstay of modern synthesis and have revolutionized the way molecules are constructed due to their robust and predictable nature. In contrast, radical chemistry is sparsely covered beyond the basic principles of radical chain processes (i.e., radical halogenation). The historical perception of radicals as somewhat uncontrollable species does not help the situation. As a result, synthetic chemists are not prone to make radical-based strategic bond disconnections during first-pass retrosynthetic analyses. In this talk recent studies from our lab will be discussed to illustrate the strategic advantages that can result when unconventional radical disconnections are incorporated into synthetic design plans.

• Speaker: Professor Phil S. Baran
• Thursday 09 October 2025, 18:00-19:30
• Venue: Pfizer Lecture Theatre, Department of Chemistry, Lensfield Road.
• Series: SciSoc – Cambridge University Scientific Society; organiser: ajaf3.

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Autism is a neurodevelopmental condition that occurs in around 2% of people, and can be associated with differences in social interaction, communication and interests. Autism is connected with genetic changes that are present from conception, but is often not identified until children are in school. Prospective longitudinal studies that follow infants from near birth to childhood can reveal the earliest developmental changes that precede the later emergence of autistic traits. Here, I describe a series of studies examining some of the earliest changes in infants with later autism and their interrelation over both short and long timescales. Within prospective studies, we see differences in sensory reactivity across touch, audition and visual domains, and changes in sleep that precede an autism diagnosis. Sensory differences are related to sleep differences, and both may relate to emerging trajectories of fearfulness and later anxiety, indicating they may be important targets for supportive interventions. Further, changes in sleep may be linked to alterations in daytime brain states that have been associated with longer-term cognitive development. Taken together, examining changes in early sensory development and sleep may provide important insights into the early development of children with neurodevelopmental conditions. I discuss how these approaches can help us think about neurodevelopment from the perspective of neurodiversity.

• Speaker: Emily Jones, Professor, Centre for Brain and Cognitive Development, School of Psychological Sciences, Birkbeck, University of London
• Wednesday 01 October 2025, 11:30-12:30
• Venue: https://us02web.zoom.us/j/81286610099?pwd=HsKTIo1MzZ7eEOJUaVYrEBbCvSSW1g.1.
• Series: ARClub Talks; organiser: Simon Braschi.

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Majorana zero modes (MZMs)—spinless, charge-neutral, zero-energy excitations—arise at the boundaries of one-dimensional p-wave superconductors and are promising building blocks for fault-tolerant quantum computing. Candidate platforms include topological insulators, spin–orbit-coupled semiconducting nanowires, iron-based superconductors, and fractional quantum Hall systems. Here we pursue a bottom-up route: semiconductor quantum dots with strong spin–orbit coupling, coupled via superconductors to realize the unit cell of the Kitaev chain [1,2]. Using InSb nanowires clad with epitaxial aluminum half-shells, we engineer fine-tuned paired MZMs within minimal chains, enabling controlled studies of their hybridization, fermion parity, and robustness to disorder and gating [3]. I will present an experimental framework for assembling and characterizing basic Kitaev-chain components in this hybrid platform, followed by systematic “chain-scaling” results that track the evolution from a single unit cell to extended chains [4]. I will conclude with outlook protocols for reading out quantum information in this architecture.

[1] Wang, G., Dvir, T., Mazur, G. P., Liu, C. X., van Loo, N., Ten Haaf, S. L., ... & Kouwenhoven, L. P. (2022). Singlet and triplet Cooper pair splitting in hybrid superconducting nanowires. Nature, 612(7940), 448-453. [2] Dvir, T., Wang, G., van Loo, N., Liu, C. X., Mazur, G. P., Bordin, A., ... & Kouwenhoven, L. P. (2023). Realization of a minimal Kitaev chain in coupled quantum dots. Nature, 614(7948), 445-450. [3] Leijnse, M. and Flensberg, K., 2012. Parity qubits and poor man’s Majorana bound states in double quantum dots. PRB , 86(13), p.134528. [4] Bordin, A., Liu, C. X., Dvir, T., Zatelli, F., Ten Haaf, S. L., van Driel, D., ... & Mazur, G. P. (2025). Enhanced Majorana stability in a three-site Kitaev chain. Nature Nanotechnology, 1-6.

• Speaker: Prof. Greg Mazur
• Thursday 02 October 2025, 14:00-15:30
• Venue: Seminar Room 3, RDC.
• Series: Theory of Condensed Matter; organiser: Bo Peng.

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Abstract Stay Tuned

Bio

Dr. David Moffat is the AI Data Science Lead at Plymouth Marine Laboratory. With a strong foundation in computer science and extensive experience in applying AI and data science techniques across diverse datasets, David is currently focused on advancing environmental and marine science research. His work involves leveraging both modern and traditional AI methodologies to enhance our understanding of the natural world.

David’s expertise lies in applied AI, particularly in interdisciplinary research, such as signal processing and time series data analysis. He holds a BSc in Artificial Intelligence and Computer Science from the University of Edinburgh and an MSc. in Signal Processing and PhD. in Computer Science from Queen Mary University of London. Following his academic journey, he has held roles as a postdoctoral researcher, university lecturer, and now leads innovative AI-driven initiatives at Plymouth Marine Laboratory. David has authored 17 peer-reviewed articles, 13 peer-reviewed conference papers, and four book chapters. He has also delivered AI and Earth Observation training courses to over 500 participants. In addition to his academic accomplishments, he has a background in technical support, project management, and research leadership.

• Speaker: David Moffat, AI Data Science Lead at Plymouth Marine Laboratory
• Friday 21 November 2025, 13:00-14:00
• Venue: Room GS15 at the William Gates Building and on Zoom: https://cl-cam-ac-uk.zoom.us/j/4361570789?pwd=Nkl2T3ZLaTZwRm05bzRTOUUxY3Q4QT09&from=addon .
• Series: Energy and Environment Group, Department of CST; organiser: lyr24.

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This free event is open only to members of the University of Cambridge (and affiliated institutes). Please be aware that we are unable to offer consultations outside clinic hours.

If you would like to participate, please sign up as we will not be able to offer a consultation otherwise. Please sign up through the following link: https://forms.gle/w9xuaQ9TTATqaT6CA. Sign-up is possible from Oct 2 midday (12pm) until Oct 6 midday or until we reach full capacity, whichever is earlier. If you successfully signed up, we will confirm your appointment by Oct 8 midday.

• Speaker: Speaker to be confirmed
• Wednesday 08 October 2025, 16:30-18:00
• Venue: MR5.
• Series: Cambridge Statistics Clinic; organiser: tm681.

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Active solids consume energy to allow for actuation and shape change not possible in equilibrium. We discover anomalies in the continuum description of non-reciprocal active solids, a ubiquitous class of active materials. In the first half of the talk, I will describe our work on “more is less” [1]: We find that as microscopic activity increases, macroscale active response can vanish below an active percolation transition. In the second half, I will talk about the formation and coarsening of dynamical patterns when active solids undergo instabilities [2]. Our results unveil surprising facets of active matter, offering new principles for engineering materials far from equilibrium.

[1] More is less in unpercolated active solids. Jack Binysh, Guido Baardink, Jonas Veenstra, Corentin Coulais, Anton Souslov. arXiv:2504.18362

[2] Wave coarsening drives time crystallization in active solids. Jonas Veenstra, Jack Binysh, Vito Seinen, Rutger Naber, Damien Robledo-Poisson, Andres Hunt, Wim van Saarloos, Anton Souslov, Corentin Coulais. arXiv:2508.20052

• Speaker: Dr Anton Souslov, Dept. of Physics, University of Cambridge
• Friday 07 November 2025, 14:00-15:00
• Venue: Oatley 1 Meeting Room, Department of Engineering.
• Series: Engineering - Mechanics and Materials Seminar Series; organiser: div-c.

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Hydrogen embrittlement in metals and alloys, which occurs following hydrogen adsorption, is a well-documented failure mechanism where hydrogen diffusion leads to material degradation through various processes, such as hydride formation. Conventional microscopy struggles to detect hydrogen due to its low electron density and minimal electron/X-ray cross-section, making direct imaging challenging. In contrast, neutral atom microscopy offers a novel approach to surface imaging. Specifically, hydrogen has a high scattering cross-section for the extremely low-energy helium atom beams used in the scanning helium atom microscope (SHeM). This large cross-section enables highly sensitive, non-destructive imaging of hydrogen-passivated surfaces for the first time. This paper presents the initial SHeM imaging of hydrogen-passivated silicon (H/Si(111)) surfaces, revealing distinct contrast between passivated and non-passivated regions across millimetre-scale lateral dimensions. The resulting images highlight surface defects and wetting-induced structures within the hydrogen passivation layers. Helium atom scattering experiments confirm that passivated areas exhibit ordered surface diffraction aligned with the Si(111) lattice structure, whereas non-passivated regions show no significant diffraction signal. Additionally, thermal desorption spectroscopy (TDS) studies identify desorption peaks corresponding to mono-, di-, and tri-hydride formation, aligning with observed variations in scattered helium intensity. These findings underscore the potential of SHeM as a powerful tool for probing the initiation and evolution of hydrogen adsorption and desorption on surfaces.

• Speaker: Paul Dastoor, Department of Physics, University of Newcastle, New South Wales, Australia
• Thursday 06 November 2025, 15:00-16:00
• Venue: Seminar Room West, Room A0.015, Ray Dolby Centre, Cavendish Laboratory.
• Series: Physics and Chemistry of Solids Group; organiser: Stephen Walley.

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Abstract TBC

• Speaker: Dr. Lily Whitler (Kavli Institute for Cosmology)
• Tuesday 18 November 2025, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Abstract TBC

• Speaker: Daniel Robins (Cavendish Astrophysics)
• Tuesday 02 December 2025, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Abstract TBC

• Speaker: Dr. John Cumner (Cavendish Astrophysics)
• Tuesday 11 November 2025, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Coinduction, the mathematical dual of induction, is a fundamental proof principle in computer science, essential for reasoning about infinite structures, concurrent systems, and compiler correctness. While full coinductive data support in proof assistants typically requires foundational support and careful considerations, such as syntactic guardedness checking, focusing on the simpler case of coinductive predicates can recover many important use cases. This is sufficient for defining concepts like bisimulations and other coinductive relations crucial for program verification.

This talk presents our design and implementation of coinductive predicates in Lean 4. Our approach leverages lattice theory and the impredicativity of Lean’s propositional universe to encode coinductive predicates and their proof principles directly within Lean’s existing type theory, no kernel extensions required. Our implementation supports mutual coinduction, including mixed coinductive and inductive definitions. The talk will also touch on supporting syntax similar to the one for usual inductive types and compiling such definitions to monotone maps.

Joint work with Joachim Breitner (Lean FRO , Germany).

Bio: Wojciech Różowski is a Research Software Engineer at Lean FRO , where he works on the development of the Lean theorem prover. His research interests include automated reasoning, formal semantics, and program verification. He obtained his PhD at University College London under the supervision of Alexandra Silva, as a member of the Programming Principles, Logic and Verification Group.

• Speaker: Wojciech Różowski, Lean FRO
• Thursday 02 October 2025, 11:30-12:30
• Venue: Computer Laboratory, William Gates Building, Lecture Theatre 2.
• Series: ack55's list; organiser: ack55.

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This study investigates the internal representations used in machine learning potentials or deep learning models, focusing on the high-dimensional feature vectors, also known as descriptors, that encode atomic structures. These descriptors form an inner space that appears to possess an intrinsic structure, which we aim to exploit for the characterization of complex energy landscapes. This structured space provides a powerful framework for studying the interactions and transformations within networks of crystal defects, which give rise to a remarkably diverse range of defect morphologies [1]. Rather than spending effort on developing yet another machine learning potential, an already mature and widely explored topic, we will instead concentrate on inspecting and exploiting the descriptor space itself. By analyzing this descriptor space, we can: (i) identify and statistically characterize complex defect networks [1,2]; (ii) combine these insights with accelerated Molecular Dynamics methods, such as the Bayesian Adaptive Biasing Force approach [3], to efficiently sample intricate defect energy landscapes; (iii) construct surrogate models that bypass traditional methodologies to predict demanding properties, such as vibrational entropies, with significantly reduced computational effort [4]; and (iv) demonstrate that descriptors can encode an agnostic entropy, thereby establishing a link between Gibbs and Shannon entropy and enabling a natural generalization of anharmonic free energies across a wide range of relevant physical systems [5]. For the broad class of generalized linear models we show free energies can be cast as the Legendre transform of a high-dimensional descriptor entropy, accurately estimated via score matching. This last concept provides the first example in the literature where the free energy itself can be backpropagated. We present a model agnostic estimator which returns meV/atom accurate, end-to-end differentiable free energies over a diverse, multi-element range of parameters. [1] A. M. Goryaeva et al. Nature Commun. 14, 3003 (2023); A. M. Goryaeva et al. Nature Commun. 11, 4691 (2020); P. Lafourcade et al. Comp. Mater. Sci. 230, 112534 (2025) [2] M.-C. Marinica, A. M. Goryaeva, T. D. Swinburne et al, MiLaDy – Machine Learning Dynamics, CEA Saclay, 2015-2025: https://ai-atoms.github.io/milady/ ; [3] A. Zhong et al, Phys. Rev. Mater. 7, 023802 (2023); A. Zhong et al. PRX Energy 4, 013008 (2025); C. Lapointe et al. Phys. Rev. Mater. 9, 093801 (2025) ; A. Allera et al Nature Commun. 16, 8367 (2025). [4] C. Lapointe, et al, Phys. Rev. Mater. 6, 113803 (2022). [5] T. D. Swinburne et al arXiv:2502.18191 (2025).

• Speaker: Dr Mihai-Cosmin Marinica, Université Paris-Saclay, CEA
• Wednesday 22 October 2025, 14:30-15:30
• Venue: Unilever Lecture Theatre, Yusuf Hamied Department of Chemistry.
• Series: Theory - Chemistry Research Interest Group; organiser: Lisa Masters.

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Abstract not available

Hosts – Alex Cagan, Elena Scarpa and Ben Steventon

• Speaker: Professor Richard White from Ludwig Institute for Cancer Research, University of Oxford
• Thursday 14 May 2026, 14:00-15:00
• Venue: Biffen Lecture theatre tbc and Zoom.
• Series: Genetics Seminar ; organiser: Caroline Newnham.

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Abstract not available

• Speaker: Speaker to be confirmed
• Tuesday 21 October 2025, 15:00-16:00
• Venue: BAS Seminar Room 1.
• Series: British Antarctic Survey - Polar Oceans seminar series; organiser: Katherine Turner.

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