Wed 22 May 14:00: Topological defects in spiral spin liquids
Abstract not available
- Speaker: Han Yan, University of Tokyo
- Wednesday 22 May 2024, 14:00-15:00
- Venue: TCM Seminar Room.
- Series: Theory of Condensed Matter; organiser: Gaurav.
Full‐Space Electric Field in Mo‐Decorated Zn2In2S5 Polarization Photocatalyst for Oriented Charge Flow and Efficient Hydrogen Production
Integration of photocatalytic hydrogen (H2) evolution with oxidative organic synthesis presents a highly attractive strategy for the simultaneous production of clean H2 fuel and high-value chemicals. However, the sluggish dynamics of photogenerated charge carriers across the photocatalysts result in low photoconversion efficiency, hindering the wide applications of such a technology. Herein, we overcome this limitation by inducing the full-space electric field via charge polarization engineering on a Mo cluster-decorated Zn2In2S5 (Mo-Zn2In2S5) photocatalyst. Specifically, this full-space electric field arises from a cascade of the bulk electric field (BEF) and local surface electric field (LSEF), triggering the oriented migration of photogenerated electrons from [Zn–S] regions to [In–S] regions and eventually to Mo cluster sites, ensuring efficient separation of bulk and surface charge carriers. Moreover, the surface Mo clusters induce a tip enhancement effect to optimize charge transfer behavior by augmenting electrons and proton concentration around the active sites on the basal plane of Zn2In2S5. Notably, the optimized Mo1.5-Zn2In2S5 catalyst achieves exceptional H2 and benzaldehyde production rates of 34.35 and 45.31 mmol gcat −1 h−1, respectively, outperforming pristine ZnIn2S4 by 3.83- and 4.15-fold. Our findings mark a significant stride in steering charge flow for enhanced photocatalytic performance.
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Revealing the Nature of Binary‐Phase on Structural Stability of Sodium Layered Oxide Cathodes
The emergence of layered sodium transition metal oxides featuring a multiphase structure presents a promising approach for cathode materials in sodium-ion batteries (SIBs), showcasing notably improved energy storage capacity. However, the advancement of cathodes with multiphase structures faces obstacles due to the limited understanding of the integrated structural effects. Herein, we comprehend the integrated structural effects by an in-depth structure-chemistry analysis in the developed layered cathode system NaxCu0.1Co0.1Ni0.25Mn0.4Ti0.15O2 with purposely designed P2/O3 phase integration. Our results affirmed that integrated phase ratio plays a pivotal role in electrochemical/structural stability, particularly at high voltage and with the incorporation of anionic redox. In contrast to previous reports advocating solely for the enhanced electrochemical performance in biphasic structures, we demonstrated an inappropriate composite structure is more destructive than a single-phase design. The in situ X-ray diffraction (XRD) results, coupled with density functional theory (DFT) computations further confirm the biphasic structure with P2:O3 = 4:6 shows suppressed irreversible phase transition at high desodiated states and thus exhibits optimized electrochemical performance. These fundamental discoveries provide clues to the design of high-performance layered oxide cathodes for next-generation SIBs.
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Tunable and Reversible Adhesive of Liquid Metal Ferrofluid Pillars for Magnetically Actuated Non‐Contact Transfer Printing
Transfer printing techniques based on tunable and reversible adhesives enable the heterogeneous integration of materials in desired layouts and are essential for developing both existing and envisioned electronic systems. Here, w e report a novel tunable and reversible adhesive of liquid metal ferrofluid pillars for developing an efficient magnetically actuated non-contact transfer printing. The liquid metal ferrofluid pillars offer the appealing advantages of gentle contact force by minimizing the preload effect and exceptional shape adaptability by maximizing the interfacial contact area due to their inherent fluidity, thus enabling a reliable damage-free pickup. Moreover, the liquid metal ferrofluid pillars harness the rapid stiffness increase and shape change with the magnetic field, generating an instantaneous ejection force to achieve a receiver-independent non-contact printing. Demonstrations of the adhesive of liquid metal ferrofluid pillars in transfer printing of diverse objects with different shapes, materials and dimensions onto various substrates illustrate its great potential in deterministic assembly.
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Novel Palladium Hydride Surface Enabling Simultaneous Bacterial Killing and Osteogenic Formation through Proton Capturing and Activation of Antioxidant System in Immune Microenvironments
Achieving bacterial killing and osteogenic formation on an implant surface rarely occurs. In this study, we introduce a novel surface design–a palladium hydride (PdHx) film that enables these two distinct features to coexist. The PdHx lattice captures protons in the extracellular microenvironment of bacteria, disrupting their normal metabolic activities, such as ATP synthesis, nutrient co-transport, and oxidative stress. This disruption leads to significant bacterial death, as evidenced by RNA sequence analysis. Additionally, the unique enzymatic activity and hydrogen-loading properties of PdHx activate the human antioxidant system, resulting in the rapid clearance of reactive oxygen species (ROS). This process reshapes the osteogenic immune microenvironment, promoting accelerated osteogenesis. Our findings reveal that the downregulation of the NOD-like receptor signaling pathway is critical for activating immune cells toward M2 phenotype polarization. This novel surface design provides new strategies for modifying implant coatings to simultaneously prevent bacterial infection, reduce inflammation, and enhance tissue regeneration, making it a noteworthy contribution to the field of advanced materials.
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Dipole Moment Influences the Reversibility and Corrosion of Lithium Metal Anodes
Lithium metal batteries (LMBs) must have both long cycle life and calendar life to be commercially viable. However, “trial and error” methodologies remains prevalent in contemporary research endeavors to identify favorable electrolytes. Here, we propose a guiding principle for the selection of solvents for LMBs, which aims to achieve high coulombic efficiency while minimizing the corrosion. For the first time, our study reveals the dipole moment and orientation of solvent molecules have significant impacts on lithium metal reversibility and corrosion. Solvents with high dipole moments are more likely to adsorb onto lithium metal surfaces, which also influences the solid electrolyte interphase. Using this principle, we demonstrate the use of LiNO3 as the sole salt in NCM811/Li cells can achieve excellent cycling stability. Overall, our work bridges the molecular structure of solvents to the reversibility and corrosion of lithium metal, and these concepts can be extended to other metal-based batteries.
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Directional Formation of Reactive Oxygen Species via a Non‐Redox Catalysis Strategy that Bypasses Electron Transfer Process
A broad range of chemical transformations driven by catalytic processes necessitate the electron transfer between catalyst and substrate. The redox cycle limitation arising from the inequivalent electron donation and acceptance of the involved catalysts, however, generally leads to their deactivation, causing substantial economic losses and environmental risks. Here we provide a “non-redox catalysis” strategy wherein the catalytic units were constructed by atomic Fe and B as dual active sites to create tensile force and electric field, which allowed directional self-decomposition of peroxymonosulfate (PMS) molecules through internal electron transfer to form singlet oxygen, bypassing the need of electron transfer between catalyst and PMS. The proposed catalytic approach with non-redox cycling of catalyst contributed to excellent stability of the active centers, while the generated reactive oxygen species found high efficiency in long-term catalytic pollutant degradation and selective organic oxidation synthesis in aqueous phase. This work offers new avenue for directional substrate conversion, which holds promise to advance the design of alternative catalytic pathways for sustainable energy conversion and valuable chemical production.
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Bioinspired Adaptive Microdrugs Enhance the Chemotherapy of Malignant Glioma: Beyond Their Nanodrugs
Solid nanoparticle-mediated drug delivery systems are usually confined to nanoscale due to the enhanced permeability and retention (EPR) effect. However, they remain a great challenge for malignant glioma chemotherapy because of poor drug delivery efficiency and insufficient tumor penetration resulting from the blood-brain barrier/blood-brain tumor barrier (BBB/BBTB). Inspired by biological microparticles (e.g., cells) with excellent adaptive deformation, we demonstrate that the adaptive microdrugs (even up to 3.0 μm in size) are more efficient than their nanodrugs (less than 200 nm in size) to cross BBB/BBTB and penetrate into tumor tissues, achieving highly efficient chemotherapy of malignant glioma. The distinct delivery of the adaptive microdrugs is mainly attributed to the enhanced interfacial binding and endocytosis via adaptive deformation. As expected, the obtained adaptive microdrugs exhibited enhanced accumulation, deep penetration, and cellular internalization into tumor tissues in comparison with nanodrugs, significantly improving the survival rate of glioblastoma mice. We believe that the bioinspired adaptive microdrugs enable them to efficiently cross physiological barriers and deeply penetrate tumor tissues for drug delivery, providing an avenue for the treatment of solid tumors.
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Tue 11 Jun 11:00: The MUonE Experiment: Understanding Muon g−2 Puzzle via Muon- electron Scattering
Abstract not available
- Speaker: Ce Zhang (University of Liverpool)
- Tuesday 11 June 2024, 11:00-12:00
- Venue: Ryle Seminar Room (930), Cavendish Laboratory, Department of Physics.
- Series: Cavendish HEP Seminars; organiser: Dr Steve Dennis.
Mechanical strengthening of perovskite-substrate heterointerface for highly stable solar cells
DOI: 10.1039/D4EE00244J, PaperXuesong Leng, Yichu Zheng, Jingjing He, Benben Shen, Haonan Wang, Qing Li, Xinyi Liu, Miaoyu Lin, Yifeng Shi, Zhanpeng Wei, Yu Peng, Huagui Yang, Qiang Niu, Shuang Yang, Yu Hou
Perovskite solar cells (PSCs) have shown power conversion efficiencies (PCEs) of over 26% that rival the crystalline silicon cells, but their projected application was largely postponed by the device instability,...
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Wed 22 May 14:00: Communication over many-user channels via Approximate Message Passing
This talk considers communication over the Gaussian multiple-access channel in the regime where the number of users scales linearly with the codelength. I will begin by discussing near-optimal coding schemes for small user payloads, and explain why these cannot be adapted efficiently to larger payloads. I will then describe a coded CDMA scheme for larger payloads, where each user’s information is encoded via a linear code before being transmitted using a signature sequence. With an efficient Approximate Message Passing (AMP) decoder that can be tailored to the structure of the linear code, I show that coded CDMA schemes can achieve state-of-the-art performance for payloads up to hundreds of bits, with exact asymptotic performance guarantees. I will also explain how the proposed schemes can be adapted to incorporate random user activity.
This is joint work with Pablo Pascual Cobo, Kuan Hsieh and Ramji Venkataramanan.
- Speaker: Xiaoqi (Shirley) Liu, University of Cambridge
- Wednesday 22 May 2024, 14:00-15:00
- Venue: MR5, CMS Pavilion A.
- Series: Information Theory Seminar; organiser: Prof. Ramji Venkataramanan.
Mismatched Supramolecular Interactions Facilitate the Reprocessing of Super‐Strong and Ultra‐Tough Thermoset Elastomers
Thermoset elastomers have been extensively applied in many fields because of their excellent mechanical strengths and durable characteristics, such as an excellent chemical resistance. However, in the context of environmental issues, the non-recyclability of thermosets has become a major barrier to the further development of these materials. Here, we report a well-tailored strategy to solve this problem by introducing mismatched supramolecular interactions (MMSIs) into a covalently cross-linked poly(urethane-urea) network with dynamic acylsemicarbazide moieties. The MMSIs significantly strengthen and toughen the thermoset elastomer by effectively dissipating energy and resisting external stress. In addition, the elastomer recycling efficiency is improved 2.7-fold due to the superior reversibility of the MMSIs. The optimized thermoset elastomer, i.e., SPUUN-IE, features outstanding characteristics, including an ultra-high tensile strength (110.8 MPa), an unprecedented tensile toughness (1245.2 MJ m–3), as well as remarkable resistance to chemical media, creep, and damage. Most importantly, SPUUN-IE exhibits an extraordinary multi-recyclability, and the 4th recycling efficiency remains close to 100%. This scalable method promotes the development of thermosets with both high performance and excellent recyclability, thereby providing valuable guidance for addressing the issue of non-recyclability from a molecular design standpoint.
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Visualizing Dynamic Single Atom Catalysis
Many industrial chemical processes, including for producing fuels, foods, pharmaceuticals, chemicals and environmental controls, employ heterogeneous solid state catalysts at elevated temperatures in gas or liquid environments. Dynamic reactions at the atomic level play a critical role in catalyst stability and functionality. In-situ visualization and analysis of atomic-scale processes in real time under controlled reaction environments can provide important insights into practical frameworks to improve catalytic processes and materials. This review focuses on innovative real time in-situ EM methods, including recent progress in analytical in-situ environmental (scanning) transmission EM (ESTEM and ETEM) with single atom resolution for visualizing dynamic single atom catalysis under controlled flowing gas reaction environments. ESTEM studies of single atom dynamics of reactions, and of sintering deactivation, contribute to a better-informed understanding of the yield and stability of catalyst operations. Advances in in-situ technologies, including gas and liquid sample holders, nano-tomography and higher voltages, as well as challenges and opportunities in tracking reacting atoms, are highlighted. The findings show that the understanding and application of fundamental processes in catalysis can be improved, with valuable economic, environmental, and societal benefits.
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Sailing towards sustainability: offshore wind's green hydrogen potential for decarbonization in coastal USA
DOI: 10.1039/D4EE01460J, Analysis Open Access   This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Rishi Kaashyap Balaji, Fengqi You
In the pursuit of achieving net-zero emissions to combat climate change, green hydrogen is expected to be an important decarbonization vector for hard-to-abate sectors. Scaling up green hydrogen production necessitates...
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Thu 23 May 17:00: Little theories for big formal proofs
The growing practice of using proof assistant software to create and mechanically check formal proofs of challenging mathematical results relies crucially on the prior formalisation of their elementary prerequisites. These include both common undergraduate material and mundane, essentially trivial facts about symbol manipulation. The feasibility of bigger proofs depends, sometimes critically, on how one has chosen to formalise these « little theories ». This talk will explore some instances of such dependencies, drawn from my experience in formalising the proofs of the Four Colour and Odd Order theorems.
- Speaker: Georges Gonthier
- Thursday 23 May 2024, 17:00-18:00
- Venue: Live-streamed at MR14 Centre for Mathematical Sciences.
- Series: Formalisation of mathematics with interactive theorem provers ; organiser: Jonas Bayer.
Thu 23 May 17:00: Cambridge RNA Club - May session IN PERSON
Dr. Joanna Krupka (Wellcome-MRC Cambridge Stem Cell Institute, University of Cambridge) In search of lost proteome: characterising bioactive small ORFs and microproteins in lymphoma and immunity
Dr. Jeremy Sanford (UC Santa Cruz, USA ) CURE-ing aberrant pre-mRNA splicing
- Speaker: Dr. Joanna Krupka (Wellcome-MRC Cambridge Stem Cell Institute, University of Cambridge) and Dr. Jeremy Sanford (UC Santa Cruz, USA)
- Thursday 23 May 2024, 17:00-18:00
- Venue: Gurdon Institute Tea Room - RNA Club.
- Series: Cambridge RNA Club; organiser: .
Mon 24 Jun 10:00: Causal inference during motion perception, and its neural basis
Short abstract: In this talk I’ll present our work on explaining motion perception as hierarchical causal inference. I’ll describe the intuitions behind the theory and show new psychophysics data task that quantitatively tests our theory. I’ll also describe our work in progress on using neural responses to test our theory, as well as Bayesian models of behavior in general.
Long abstract: If motion is always defined relative to a reference frame, what is the brain’s reference frame for the perception of a moving object? A century of psychophysical studies has provided us with seemingly conflicting evidence about motion perception in a variety of reference frames: from egocentric, to world-centric, to reference frames defined by other moving objects. We present a hierarchical Bayesian model which describes how observed retinal velocities give rise to perceived velocities. The hierarchically recurring generative model motif represents each perceived object’s motion in its natural reference frame which reflects the causal structure of the world. The degeneracy of object motion and reference frame motion is broken by a spike and slab prior reflecting the fact that most objects are exactly stationary in their natural reference frame. Data from three new psychophysical experiments quantitatively confirm key predictions of our model. Finally, I will present a stepwise method for generating neural predictions from our, and other, Bayesian models of the brain, and for comparing them against each other using neural data. Interestingly, a neural circuit implementing a generalized version of divisive normalization can generate the center-surround tuning curves predicted by causal inference.
Related manuscripts: Shivkumar, S., DeAngelis, G. C., & Haefner, R. M. (2023). Hierarchical motion perception as causal inference. https://doi.org/10.1101/2023.11.18.567582 Lengyel, G., Shivkumar, S., & Haefner, R. M. (2023). A General Method for Testing Bayesian Models using Neural Data. UniReps: The First Workshop on Unifying Representations in Neural Models. https://openreview.net/forum?id=oWJP0NhcY7
- Speaker: Ralf Haefner, Department for Brain & Cognitive Sciences, University of Rochester
- Monday 24 June 2024, 10:00-11:00
- Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
- Series: Computational Neuroscience; organiser: Samuel Eckmann.
Fri 31 May 16:00: QFT constraints as Bayesian priors for Standard-Model tests
In this talk I will discuss how Standard-Model constraints, for instance due to analyticity and unitarity, can be used to complement theory computations of hadronic observables. Such constraints can play a decisive role in the analysis of lattice-QCD results of exclusive as well as inclusive semileptonic B-meson decays. In the former case, the use of Bayesian inference allows for formulating a model- and truncation independent parameterisation of hadronic form factors. In the latter case, QFT constraints allow for tackling the computation of the inclusive decay rate for the first time.
- Speaker: Andreas Juttner (Southampton U./CERN)
- Friday 31 May 2024, 16:00-17:00
- Venue: MR19 (Potter Room, Pavilion B), CMS.
- Series: HEP phenomenology joint Cavendish-DAMTP seminar; organiser: Nico Gubernari.
Fri 24 May 10:00: Circuit for memory-based action selection
Animal behavior is shaped both by evolution and by individual experience. In many species parallel brain pathways encode innate and learnt valences of stimuli. Furthermore, within the learning centers, opposite valences may be associated with the same cues, in parallel. How these opposing valences are integrated into an overall predicted value and used to drive a single coherent action is not well understood. In insects, the Mushroom Body Output Neurons (MBONs) and the Lateral Horn Neurons (LHNs) are thought to provide the learnt and innate drives, respectively. However, their patterns of convergence and the mechanisms by which their outputs are used to select actions are not well understood. Our recently published connectome of the entire Drosophila larval brain has revealed a complex, multi-layered network of neurons downstream of MBO Ns and LHNs and upstream of descending neurons that implements action selection. To discover the basic operational principles of this action-selection network, we have performed an optogenetic activation screen for neurons that promote distinct actions, and we have characterised the responses of these neurons to stimuli of distinct innate and learnt valances. Together, these studies reveal the circuit mechanisms allowing integration of opposing drives from parallel olfactory pathways.
- Speaker: Marta Zlatic, Department of Zoology, University of Cambridge
- Friday 24 May 2024, 10:00-11:00
- Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
- Series: Computational Neuroscience; organiser: Samuel Eckmann.
Ultrafast Laser Processing of 2D Materials: Novel Routes to Advanced Devices
This paper explores the cutting-edge use of ultrafast laser technology to precisely modify 2D materials. It presents a leap from theory to real-world applications, demonstrating how ultrafast lasers can tailor material properties for advanced devices. This method offers nanometer precision without heat-related issues, revolutionizing novel electronic, photonic, and sensing devices design, making it a key tool for future innovations.
Abstract
Ultrafast laser processing has emerged as a versatile technique for modifying materials and introducing novel functionalities. Over the past decade, this method has demonstrated remarkable advantages in the manipulation of 2D layered materials, including synthesis, structuring, functionalization, and local patterning. Unlike continuous-wave and long-pulsed optical methods, ultrafast lasers offer a solution for thermal heating issues. Nonlinear interactions between ultrafast laser pulses and the atomic lattice of 2D materials substantially influence their chemical and physical properties. This paper highlights the transformative role of ultrafast laser pulses in maskless green technology, enabling subtractive, and additive processes that unveil ways for advanced devices. Utilizing the synergetic effect between the energy states within the atomic layers and ultrafast laser irradiation, it is feasible to achieve unprecedented resolutions down to several nanometers. Recent advancements are discussed in functionalization, doping, atomic reconstruction, phase transformation, and 2D and 3D micro- and nanopatterning. A forward-looking perspective on a wide array of applications of 2D materials, along with device fabrication featuring novel physical and chemical properties through direct ultrafast laser writing, is also provided.