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G I TAYLOR LECTURE - The influence of GI Taylor: granular collapses, viscous gravity currents, explosive eruptions and chemical gardens

The presentation will start will a short summary of the seminal work of G. I. Taylor and his most famous student, G. K. Batchelor. Evaluations of the propagation of muti-sized granular material under a variety of conditions will then be described, as well as being illustrated with desk top experiments.

The lecture will then discuss the all important flow of viscous gravity currents, again illustrated by desk top experiments and actual photos and explanations of the recent eruption of the Soufriere of St. Vincent. A description of the development of chemical gardens will then be described, initially experimented upon by Johan Glauber, said to be the first chemical engineer, and then by Isaac Newton. It is said by some that chemical gardens are the origin of life, at deep-sea smokers, as will be described.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

• Speaker: Professor Herbert Huppert FRS FRSN, Professor of Theoretical Geophysics, Faculty of Mathematics
• Monday 29 January 2024, 18:00-19:00
• Venue: Bristol-Myers Squibb Lecture Theatre, Department of Chemistry.
• Series: Cambridge Philosophical Society; organiser: Beverley Larner.

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The quest for the first stars and first black holes with the James Webb Space Telescope

Finding and understanding the nature of the first stars at cosmic dawn is one of the most important and most ambitious goals for modern astrophysics. The first populations of stars produced the first chemical elements heavier than helium and formed the first, small protogalaxies, which then evolved, across the cosmic epoch, into the large and mature galaxies, such as the Milky Way and those in our local neighbour. Equally important and equally challenging is the search, in the early Universe, of the seeds of the first population of black holes, which later evolved in the supermassive black holes at the centre of galaxies, with masses even exceeding a billion times the mass of the Sun. When matter accretes on such supermassive black holes it can become so luminous to vastly outshine the light emitted by all stars in their host galaxy.

Since its launch, about two years ago, the James Webb Space Telescope has been revolutionizing this area of research. Its sensitivity in detecting infrared light from the remotest parts of the Universe is orders of magnitude higher than any previous observatory, an historical leap in astronomy and, more broadly, in science. I will presents some of the first, extraordinary discoveries from the Webb telescope, which have resulted in several unexpected findings. I will also discuss the new puzzles and areas of investigation that have been opened by Webb’s observations, how these challenge theoretical models, and the prospects of further progress in the coming years.

Check website for latest updates and booking information http://www.cambridgephilosophicalsociety.org

• Speaker: Professor Roberto Maiolino FRS, Professor of Experimental Astrophysics, Kavli Institute for Cosmology
• Monday 26 February 2024, 18:00-19:00
• Venue: Bristol-Myers Squibb Lecture Theatre, Department of Chemistry.
• Series: Cambridge Philosophical Society; organiser: Beverley Larner.

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Reassessing red blood cell invasion in malaria parasites

Malaria parasites rely on cycles of cellular invasion and intracellular growth to proliferate within the blood stream, a process which underpins symptoms of the disease. The cycles of cellular invasion and intracellular growthThe adaptation of P. knowlesi (Pk) to culture in human erythrocytes presents exciting opportunities to study erythrocyte invasion biology. Two major protein families have been studied extensively in P. falciparum (Pf): the erythrocyte binding-like proteins (EBPs/EBAs) and the reticulocyte binding-like proteins (RBLs/RHs). These proteins are hypothesized to have overlapping but critical roles during the invasion process. The zoonotic malaria parasite P. knowlesi, has a smaller repertoire of these proteins, and much larger and polarised invasive stages known as merozoites.

Employing a conditional knockout approach, we’ve demonstrated distinct roles for the two families at different invasion stages, including a specific role for RBL proteins in the initial identification and deformation of target host erythrocytes. Furthermore, we’ve unearthed new features that prompt a significant reassessment of invasion. Notably, we’ve discovered that Pk merozoites can engage in productive gliding motility prior to invasion, and we’ve corrected a longstanding assumption in merozoite topology – the merozoite apex is actually located in the wider end of the cell, contrary to prior beliefs. These findings unveil new aspects of this complex process and introduce fresh tools and techniques to deepen our understanding of invasion across all malaria parasite species. Finally, we will demonstrate how the new genetic tools emerging from studies in basic biology of malaria parasite can be readily adapted to facilitate vaccine, drug and diagnostics targeting a broader range of malaria parasite species.

Please note 16:00 start time for this seminar

• Speaker: Dr Robert Moon - LSHTM
• Wednesday 31 January 2024, 16:00-17:00
• Venue: Seminar Room, Tennis Court Road, Dept of Pathology..
• Series: Parasitology Seminars; organiser: Anna Protasio.

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Abstract

Dielectrophoresis (DEP) particle separation has label-free, well-controllable, and low-damage merits. Sidewall microelectrodes made of liquid metal alloy (LMA) inherits the additional advantage of thick electrodes to generate impactful DEP force. However, existing LMA electrode-based devices lack the ability to integrate large-array electrodes in a compact footprint, severely limiting flow rate and thus throughput. Herein, a facile and versatile method is proposed to integrate high-density thick LMA electrodes in microfluidic devices, taking advantage of the passive control ability of capillary burst valves (CBVs). CBVs with carefully designed burst pressures are co-designed in microfluidic channels, allowing self-assembly of LMA electrode array through simple hand-push injection. The arrayed electrode configuration brings the accumulative DEP deflection effect. Specifically, we demonstrate to fabricate 5000 pairs of sidewall electrodes in a compact chip to achieve 10 times higher throughput in DEP deflection. We applied the 5000-electrode-pair device to successfully separate the mixed sample of human peripheral blood mononuclear cells (PBMCs) and A549 cells with the flow rate of 70 µL min−1. It is envisioned that this work can greatly facilitate LMA electrode array fabrication and offer a robust and versatile platform for DEP separation applications.

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Nonparametric conditional factors for unbalanced panels

We introduce a nonparametric estimator for conditional covariance matrices of unbalanced panels. Our approach naturally accommodates a low-dimensional nonlinear factor structure that ensures all structural relations between moments. In high-dimensional large-data applications, we investigate various conditional return expectation and covariance models that depend on asset characteristics. The empirically successful models imply substantial conditional Sharpe ratios, along with respectable ordinal and point predictions. Our approach can easily be extended to accommodate higher-order moments and comes with asymptotic theory that can be used with large unbalanced panels.

• Speaker: Paul Schneider (Swiss Finance Institute)
• Thursday 22 February 2024, 13:00-14:00
• Venue: W4.03.
• Series: Cambridge Finance Workshop Series; organiser: Cerf Admin.

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TBD

TBD

• Speaker: Marta Benozzo, UCL
• Wednesday 21 February 2024, 14:15-15:15
• Venue: CMS MR13.
• Series: Algebraic Geometry Seminar; organiser: Holly Krieger.

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Abstract

Alternating current (AC)-driven quantum-dot light-emitting diodes (QLEDs) are superior to direct current-driven QLEDs because they can be directly integrated into household AC electricity and have high stability. However, achieving high-performance AC-driven QLEDs remains challenging. In this work, a bipolar QLED with coplanar electrodes is realized by horizontally connecting a regular QLED and an inverted QLED in series using an Al bridging layer. The bipolar QLED can be turned on with either a positive or a negative bias voltage, with a high external quantum efficiency (EQE) of 22.9%. By replacing the Al with Ag, the resistances of the electron transport layers are effectively reduced, and thus the bipolar QLED shows an enhanced brightness of 16370 cd/m2 at 15 V. By connecting multiple bipolar QLEDs in series, the resulting light source can be directly driven by a 220 V/50 Hz household power supply without the need for back-end electronics. The bipolar QLED can also be realized by vertically stacking a regular QLED and an inverted QLED with a metallic intermediate connection layer. We demonstrate that the coplanar or vertical bipolar QLEDs could find potential applications in household AC electricity play-and-plug solid-state lighting and single- or double-sided displays.

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Energy Environ. Sci., 2024, Advance Article
DOI: 10.1039/D3EE01659E, PaperYajun Zhao, Shuoxiao Zhang, Yangyang Zhang, Jinrui Liang, Longtao Ren, Hong Jin Fan, Wen Liu, Xiaoming Sun
A novel vacancy-rich, Al-doped MnO2 cathode is proposed for AZIBs, showcasing 3D ion diffusion channels and excellent structural stability. It overcomes the trade-off between electrode kinetics and stability, delivering impressive rate performance and outstanding capacity retention.
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2-torsion rational homology spheres and SL(2,C)-representations

We use instanton gauge theory to prove that if Y is a closed, orientable 3-manifold such that H_1(Y;Z) is nontrivial and 2-torsion, and if Y is neither an r-fold connected sum of RP3s for some r>=1, then there is an irreducible representation of the fundamental group of Y in SL(2,C). This solves a conjecture of Przytycki (Kirby problem 1.92(F)) on torsion in the Kauffman Skein module of reducible 3-manifolds, unless every summand but one is RP3 . This is joint work with Sudipta Ghosh and Steven Sivek.

• Speaker: Raphael Zentner (Durham)
• Wednesday 31 January 2024, 16:00-17:00
• Venue: MR13.
• Series: Differential Geometry and Topology Seminar; organiser: Oscar Randal-Williams.

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Abstract

Spin-polarized bands in pristine and proximity-induced magnetic materials are promising building blocks for future devices. Conceptually new memory, logic, and neuromorphic devices have been conceived based on atomically thin magnetic materials and the manipulation of their spin-polarized bands via electrical and optical methods. A critical remaining issue is the direct probe and the optimized use of the magnetic coupling effect in van der Waals heterostructures, which requires further delicate design of atomically thin magnetic materials and devices. Here, we report a spin-selective memtransistor with magnetized single-layered graphene on a reactive antiferromagnetic material, CrI3. The spin-dependent hybridization between graphene and CrI3 atomic layers enables the spin-selective bandgap opening in the single-layered graphene and the electric field control of magnetization in a specific CrI3 layer. The microscopic working principle is clarified by our first-principles calculations and theoretical analysis of our transport data. We achieved reliable memtransistor operations (i.e., memory and logic device-combined operations) as well as a spin-selective probe of Landau levels in the magnetized graphene by using the subtle manipulation of the magnetic proximity effect via electrical means.

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TBC

Abstract not available

Please note 16:00 start time for this seminar

• Speaker: Dr Robert Moon - LSHTM
• Wednesday 31 January 2024, 16:00-17:00
• Venue: Seminar Room, Tennis Court Road, Dept of Pathology..
• Series: Parasitology Seminars; organiser: Anna Protasio.

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Programming for the Planet: the challenges of repeatable and reproducible computing for enviromental sciences

Abstract:

As we race to deal with the climate crisis facing the planet, ecologists are increasingly turning to computational analysis, both in the domains of academic research, and in other domains like assessing carbon impact of field projects for carbon offsets. But as if this wasn’t enough, both the expression of computation and the management of the vast amounts of data involved prevent significant hurdles in ensuring that we can generate results that are repeatable, transparent and timely. In the EEG group we are looking at how computer science needs to step in to support ecologists achieve this goal, and this talk will outline the specific challenges we’ve observed working closely with members of the Cambridge Conservation Initiative and avenues we’re taking to solve these problems.

Bio:

Michael is a research associate in the Computer Lab, part of the EEG , working at the intersection of computer science and ecology: how can computing best support those trying to save the planet. Previously he’s worked in many different domains, all linked by an aim to use technology to solve problems people face: at Bromium he lead the Mac product team working on virtualisation based security software, he worked at Ndiyo, an attempt to make thin client computing a solution to equitable internet access in the developing world, and he’s worked in gaming and education in the earlier days of geolocation in mobile. Outside of computing, he builds guitars that mix traditional woodwork with the cutting edge of 3D printing and generative design.

• Speaker: Michael Dales, University of Camridge
• Friday 19 January 2024, 13:00-14:00
• Venue: FW11, William Gates Building. Zoom link: 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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A dual-acceptor strategy in all-polymer photovoltaic blends pushes the efficiency up to 18.81%, with decent changes in maximal power point (MPP) tracked and thermal stress applied stability tests, where a new phenomenon in that donor aggregation is modulated by the acceptor component is focused on and carefully analyzed. The experience of ternary blend design from here is also expected to be instructive for other organic photovoltaics systems.

Abstract

Using two structurally similar polymer acceptors in constructing high-efficiency ternary all-polymer solar cells is a widely acknowledged strategy; however, the focus thus far has not been on how polymer acceptor(s) would tune the aggregation of polymer donors, and furthermore film morphology and device performance (efficiency and stability). Herein, it is reported that matching of the celebrity acceptor PY-IT and the donor PBQx-TCl results in enhanced H-aggregation in PBQx-TCl, which can be finely tuned by controlling the amount of the second acceptor PY-IV. Consequently, the efficiency-optimized PY-IV weight ratio (0.2/1.2) leads to a state-of-the-art power conversion efficiency of 18.81%, wherein light-illuminated operational stability is also enhanced along with well-protected thermal stability. Such enhancements in the efficiency and operational and thermal stabilities of solar cells can be attributed to morphology optimization and the desired glass transition temperature of the target active layer based on comprehensive characterization. In addition to being a high-power conversion efficiency case for all-polymer solar cells, these enhancements are also a successful attempt for using combined acceptors to tune donor aggregation toward optimal morphology, which provides a theoretical basis for the construction of other types of organic photovoltaics beyond all-polymer solar cells.

Energy Environ. Sci., 2024, Advance Article
DOI: 10.1039/D3EE90072J, Correction Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Jaehyeong Bae, Tae Gwang Yun, Bong Lim Suh, Jihan Kim, Il-Doo Kim
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Energy Environ. Sci., 2024, Advance Article
DOI: 10.1039/D4EE90005G, Correction Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Liang Zhao, Zheng Lv, Yue Shi, Shuanglong Zhou, Yan Liu, Jiani Han, Qi Zhang, Jianping Lai, Lei Wang
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Modelling the Response of Ice to Subglacial Flooding

Abstract not available

• Speaker: Sophie Tobin, University of Cambridge
• Thursday 15 February 2024, 11:30-12:30
• Venue: Open Plan Area, Institute for Energy and Environmental Flows, Madingley Rise CB3 0EZ.
• Series: Institute for Energy and Environmental Flows (IEEF); organiser: Catherine Pearson.

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Competition for phospholipids drives astrocyte morphogenesis in the CNS

Astrocytes play crucial roles in regulating neural circuit function by forming a dense network of synapse-associated membrane specializations, but signaling pathways regulating astrocyte morphogenesis remain poorly defined. We found the Drosophila lipid-binding G protein-coupled receptor (GPCR) Tre1 is required for astrocytes to establish their intricate morphology in vivo. The lipid phosphate phosphatases Wunen/Wunen2 also regulate astrocyte morphology and, via Tre1, mediate astrocyte-astrocyte competition for growth-promoting lipids. Loss of s1pr1, the functional analog of Tre1 in zebrafish, disrupts astrocyte process elaboration, and live imaging and pharmacology demonstrate that S1pr1 balances proper astrocyte process extension/retraction dynamics during growth. Loss of Tre1 in flies or S1pr1 in zebrafish results in defects in simple assays of motor behavior. Tre1 and S1pr1 are thus potent evolutionarily conserved regulators of the elaboration of astrocyte morphological complexity and, ultimately, astrocyte control of behavior.

Host - Cahir O'Kane

• Speaker: Professor Marc Freeman from The Vollum Institute, Oregon Health & Science University, USA
• Thursday 15 February 2024, 15:00-16:00
• Venue: Zoom meeting.
• Series: Genetics Seminar ; organiser: Caroline Newnham.

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Short term forecasting of Acute Respiratory Infections and their impact on NHS hospital pressures for situational awareness over Winter.

Mitigations put in place during the SARS -Cov-2 pandemic supressed the transmission of seasonal respiratory viruses. There was an anticipated resurgence of non-COVID-19 seasonal respiratory diseases in Winter 2022-23 which were much harder to predict following extremely low pandemic baselines. These diseases caused an additive burden on healthcare systems, in the context of ongoing COVID -19 waves. We developed modelling methods to short term forecast a range of acute respiratory infections (COVID-19, Influenza, RSV ) at a range of geographies and metrics meaningful to healthcare managers. These forecasts used a range of Generalised Additive Models, time series techniques, leading indicators, and ensemble methods to improve assessments of trends.

• Speaker: Jonathon Mellor (UKHSA)
• Wednesday 24 January 2024, 14:00-15:00
• Venue: Zoom.
• Series: Worms and Bugs; organiser: Dr Ciara Dangerfield.

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Abstract

The development of X-ray scintillators with ultrahigh light yields and ultrafast response times is a long sought-after goal. In this work, we theoretically predict and experimentally demonstrate a fundamental mechanism that pushes the frontiers of ultrafast X-ray scintillator performance: the use of nanoscale-confined surface plasmon polariton modes to tailor the scintillator response time via the Purcell effect. By incorporating nanoplasmonic materials in scintillator devices, this work predicts over 10-fold enhancement in decay rate and 38% reduction in time resolution even with only a simple planar design. we experimentally demonstrate the nanoplasmonic Purcell effect using perovskite scintillators, enhancing the light yield by over 120% to 88 ±$\pm$ 11 ph/keV, and the decay rate by over 60% to 2.0 ±$\pm$ 0.2 ns for the average decay time, and 0.7 ±$\pm$ 0.1 ns for the ultrafast decay component, in good agreement with the predictions of our theoretical framework. we perform proof-of-concept X-ray imaging experiments using nanoplasmonic scintillators, demonstrating 182% enhancement in the modulation transfer function at 4 line pairs per millimeter spatial frequency. This work highlights the enormous potential of nanoplasmonics in optimizing ultrafast scintillator devices for applications including time-of-flight X-ray imaging and photon-counting computed tomography.

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