Although it is a physical/computational chemistry seminar it can be of general interest, as it will be about an unusual formulation of quantum mechanics. We almost always think about quantum mechanics in terms of wave function and waves of probability, but there are other ways of looking at it. Craig Martens will present one of those approaches, in which quantum mechanics is just like classical, with the difference that neighbouring classical trajectories are not independent. They are entangled and push each other in a very specific way, a bit like there were many parallel worlds interacting with each other.
The CHAMPS Project was pleased to host Professor Joel Bowman, the Samuel Candler Dobbs Professor of Theoretical Chemistry at Emory University in Atlanta, Georgia, for a visit during September 3-5, 2019. Professor Bowman presented a seminar entitled “A Machine Learning Approach for Prediction of Rate Constants”, which described a new application of machine learning in chemistry. Actually, the talk had two independent halves, with the first half of the talk devoted to a discussion of the current “state-of-the art” of the roaming mechanism for chemical reactions, which included some discussion of the manifestation of quantum effects in roaming .The CHAMPS PDRAs (as well as the PI) particularly enjoyed a two hour, informal, round table discussion, covering many aspects of contemporary reaction dynamics, as well as a bit of much appreciated career advice.
Figuring premier @ the Wickham Theatre! Posted on September 30, 2018 by David R Glowacki
The last couple weeks have seen some interesting outreach developments! With support from Arts Council England, the EPSRC-funded CHAMPS programme, the Leverhulme Trust, and the Royal Society, David Glowacki and team worked on a project called “Figuring” at the Wickham theatre in the University of Bristol’s Department of Drama, with a talented team drawn across artistic, scientific, and technological practices. On 21 Sept, they worked to premier Figuring to an audience of artists, producers, and technologists. This follows on from a previous prototype showing of Figuring at the Knowle West Media Centre, as part of their Commons Sense programme.
The aim of Figuring is to investigate what can be created when moving, sensing bodies are embedded in simulated virtual worlds, and what arises when somatic and movement based practices are combined with Narupa, a state-of-the-art multi-person VR framework for molecular dynamics simulation, which has been developed within the Intangible Realities Laboratory over the last several years.
Figuring takes its name from its intention to explore ‘string figures’, in both the real world and also in the virtual world. String figures are created through simple movements of folding, looping, twisting, and knotting strings between the hands, fingers and thumbs of one or more people.
During our time at the Wickham theatre, members of the CHAMPS project worked with a group of dancers to facilitate experiments with both physical and virtual strings. For the ‘raw material’ of the virtual strings, the team relied on real-time molecular dynamics simulations of proteins: the molecular strings from which life is woven. Narupa enables audiences to reach out and touch simulated proteins: folding, looping, twisting, and knotting them.
Despite their virtuality, Figuring audiences reported ‘felt’ sensations whilst manipulating virtual simulations of molecular strings. Moving forward, we hope to better understand the origins of such sensations, how they map onto their physical and tangible analogues, and how different sensory and somatic practices might enable us to understand perception across real, virtual and imagined environments.
Figuring represents a collaboration between a diverse team with broad interests, led by David Glowacki and somatic/movement artist Lisa May Thomas. Alex Jones, Dr. Tom Mitchell, and Prof. Joseph Hyde helped to devise algorithms for generating sound from the virtual string dynamics. Computer Scientist Mike O’Connor and Mark Wannacott played a key role in developing the VR interaction capabilities and aesthetic, and Helen Deeks provided key advice on human-computer interaction strategies. Somatic and movement practitioners included Laila Diallo, Ben McEwan, Bryn Thomas, Ania Varez, Will Dickie, Fernanda Munoz-Newsome and Anne-Gaëlle Thiriot. Production is by Emma Hughes, dramaturgy by Tanuja Amarasuriya, and set design by Phillipa Thomas. Photos are by Paul Blakemore and Silvia Cardarelli-Gronau, and film by Adam Laity.
Summer Undergraduate Research Opportunities in the CHAMPS Project
The breadth and scale of research in CHAMPS provides opportunities for researchers from a variety of backgrounds and levels, even for undergraduates. This summer Wenyang Lyu , an undergraduate in the School of Mathematics at the University of Bristol, personified these characteristics of CHAMPS. Supported by a bursary from the London Mathematical Society and the School of Mathematics, Wenyang completed a research project that will be useful for the CHAMPS project, as well as researchers in related areas worldwide.
Periodic orbits are universally acknowledged as a fundamental building block for phase space structure in dynamical systems. For general nonlinear dynamical systems discovering the existence and nature of periodic orbits can only be carried out using computational methods. For this reason it is important to have numerical methods for fining periodic orbits that lead to reproducible results. Wenyang implemented two know numerical methods for finding periodic orbits in Python, and further developed a new numerical method. He has tested these methods on benchmark two degree-of-freedom Hamiltonian systems.
Phase space structures such as dividing surfaces, normally hyperbolic invariant manifolds, and their stable and unstable manifolds in molecular Hamiltonian have been an integral part of computing quantitative results such as the cumulative reaction probability and rate constants in chemical reactions. Thus, methods that can reveal the geometry of these invariant manifolds in high dimensional phase space (4 or more dimensions) need to be benchmarked by comparing with known results. In these articles, we assessed the capability of one such method called Lagrangian descriptor (LD) for revealing the aforementioned high dimensional phase space structures associated with an index-1 saddle in Hamiltonian systems. The LD based approach is applied to two and three degree-of-freedom quadratic Hamiltonian systems where the high dimensional phase space structures are known, that is as closed-form analytical expressions. This leads to a direct comparison of features in the LD contour maps and the phase space structures’ intersection with an isoenergetic two-dimensional surface, and hence provides a verification of the method. Next, the method of LD is applied to classical two and three degrees of freedom Hamiltonians that model features of dissociation reactions. The result of the LD based approach is compared with an established numerical method for computing unstable periodic orbit and tube manifolds of a two degrees of freedom system, and the results are in good agreement. We have also discussed the results in the context of three degrees of freedom extension of the same model Hamiltonian. References:
Shibabrat Naik, Víctor J. García-Garrido, Stephen Wiggins, Finding NHIM: Identifying high dimensional phase space structures in reaction dynamics using Lagrangian descriptors, Communications in Nonlinear Science and Numerical Simulation, 2019, 79, 104907 https://doi.org/10.1016/j.cnsns.2019.104907
Shibabrat Naik and Stephen Wiggins, Finding normally hyperbolic invariant manifolds in two and three degrees of freedom with Hénon-Heiles-type potential, Phys. Rev. E, 2019, 100 (2), 022204 https://doi.org/10.1103/PhysRevE.100.022204
Chemistry and molecular dynamics of peptides colloquium. School of Chemistry University of Leeds. 11.09.2019 Room: 1.53
15:00-15:45 Enzymatic manipulation of peptides to tackle the next generation therapeutic targets: Facilitating cyclisation of peptides and their membrane permeation
Wael Houssen, Institute of Medical Sciences, University of Aberdeen 15:45-16:00 Coffee break 16:00-16:45 Chemistry research with virtual reality: From speeding up molecular dynamics to reaction network discovery.
Robin Shannon, School of Chemistry University of Bristol and School of chemistry University of Leeds 16:45-17:30 Virtual Reality demonstration. Cyclising peptides with your own hands and more.
Enzymatic manipulation of peptides, to tackle the next generation therapeutic targets: Facilitating cyclisation of peptides and their membrane permeation Dr Wael Houssen Institute of Medical Sciences, University of Aberdeen
Recent advances in our understanding of disease biology have identified a set of challenging targets for drug discovery. One of these is the protein-protein interactions (PPIs) known to be implicated in many critical diseases that are as yet without an effective treatment option e.g. autoimmune disorders and cancer. Although biological drugs can interact with PPIs but they cannot penetrate cellular membranes because of their large size. There is currently a much growing evidence that cyclic and stapled peptides can modulate PPIs and thus hold a great promise in targeting intracellular PPIs for which the transformational potential is greatest. However, the challenges in their production at large scale and their poor cellular permeability have hampered the development of these remarkable compounds. In this talk, I will explain my insights in using synthetic biology, enzyme engineering and computational chemistry to address these challenges.
Chemistry research with virtual reality: From speeding up molecular dynamics to reaction network discovery. Dr Robin Shannon School of Chemistry University of Bristol and School of Chemistry, University of Leeds
With the release of the open source Narupa code (https://gitlab.com/intangiblerealities), it has become possible to interact with dynamical chemistry simulations in virtual reality. You can now submerge yourself into atomistic world where you can push and pull molecules and atoms with your own hands, steering molecular dynamics in a chosen direction. In this talk I will discuss two areas where Narupa is being used to aid or enable research in the general field of rare event simulation. In the first case I show how Narupa can aid the sampling of complex conformation changes, for example in the process of peptide cyclisation or nanotube permeation, in order to obtain quantitative thermodynamic information, and in the second case I will show some initial results where virtual reality and gamification are being used to explore reaction networks. After the talk you will be able to try VR chemistry yourself.
CHAMPS Research Day at the University of Bristol—10 June 2019
CHAMPS held a research day at the University of Bristol on Monday 10th June 2019. The focus of this year’s research day was to give each PDRA an opportunity to discuss the current status of their research and their plans for the future and to obtain feedback from the entire CHAMPS team.
I’ve been collaborating with professor Craig Butts and his PhD student Will Gerard on trying to predict scalar coupling constants from molecular structures using machine learning. So far, the chemistry machine learning community has mostly focused on the prediction of molecular or atomic properties, so there’s no precedence on how to predict atom-pair properties like scalar coupling constants. While we’ve had some initial success modelling one bond couplings between carbon and hydrogen by extending the methods used for atomic properties, I felt like we should be able to improve on this.
Last year I went to the International Workshop on Machine Learning for Materials Science conference in Helsinki. As mentioned in a previous blog post, Dr. Christopher Sutton gave a great talk there on his experience with competition-based research on Kaggle and I figured that a similar competition could yield a wide range of distinct and well performing algorithms for predicting scalar coupling constants.
Because of this, my last few months have been busy with preparing a data set suitable for the competition format as well as sorting out the funding. Luckily, I was able to secure the funding via my grant (CHAMPS).
Kaggle waives their usual fees for a few competitions a year if the competition is hosted by an academic institution for research purposes and luckily they decided that they would do so as well for my proposed competition. At this point it should be noted that all communication with the Kaggle team as been very painless and that the team has been extremely helpful. They even decided to add a large pot of their own money to the prize pool!
The competition launched less than a week ago and there’s already been hundreds of submissions. The community has proved very helpful in gathering the related theory and information, answering questions and providing helpful code snippets or full solutions. The leaderboard continues to show improvements daily and I’m very excited to see what results from this.
Check out the competition by clicking the link here
A 1-day workshop, entitled “Recent Developments and Possible Extensions to the World of the Exact Factorization and Bohmian Dynamics” was held at the University of Bristol on Monday 22 April 2019. The workshop comprised a forum of eight 40-minute seminars with four breaks for discussion with world experts in the two related subjects of Bohmian Dynamics (BD) and Exact Factorization. This 1-day scientific encounter was intended to engage the CHAMPS team’s postdocs in these two topics, disseminate the recent work in these two areas performed by members of the CHAMPS team to the visiting world experts and inform all of the participants of the latest advances in these topics in the chemistry community.
To define the topics, Bohmian trajectories are meant to represent classical particle paths corresponding to quantum solutions when the quantum coupling constant h-bar has been set equal to zero in the 1927 Born-Oppenheimer (BO) approximation. J von Neumann’s 1931 approach (described in his textbook) is now called the “Exact Factorization” (EXF). The EXF approach generalised the formulation of the quantum-classical problem which has recently seen an active revival and development in numerical simulations of molecular chemistry.
Sophya Garashchuk discussed finite-dimensional representations of Bohmian trajectories and numerical difficulties in the implementation of Bohmian dynamics.
Salvador Miret-Artes discussed stochastic Bohmian particle trajectories as a possible representation of solutions of the Schrödinger-Langevin equation. In one of the discussion sessions which followed this lecture, the idea of stochasticity as a means of quantifying uncertainty in numerical simulations of the dynamics of molecular chemistry was a prominent topic.
Werner Koch discussed Bohmian trajectories whose space and time parameters and complex. This intriguing concept led to considerable discussion.
Cesare Tronci discussed a new mathematical formulation of EXF in terms of density matrices. In this new formulation, an analogue of the Bohmian trajectories arises as the Lagrangian paths of quantum complex-fluid parcels. The talk was based on a paper co-authored with a CHAMPS co-PI (Holm), which is to appear in Acta Mathematica Applicandae.
Eberhard Gross surveyed the modern development of the EXF approach and many of its successful applications in computational simulations of molecular chemistry processes during the past few years.
Ivano Tavernelli surveyed a series of standard applications of Bohmian trajectories in the BO framework, obtained upon setting the quantum coupling constant h-bar equal to zero.
Basile Curchod surveyed recent applications of the more modern EXF which involved the effects of h-bar at linear order. He also discussed many successful applications of EXF in computational simulations of molecular chemistry and explained the strategy of design of modern computational algorithms for these applications. Also
Mike Robb discussed recent applications of the BO approximation to computational simulations of atto-second processes in quantum molecular chemistry.
The many computational results displayed during the workshop raised the question of quantifying the uncertainty in these solutions. The discussions of these questions among the participants raised issues about how to model the combination of theoretical and computational errors in the quantum-classical interaction problem at the foundations of molecular chemistry which has an intrinsic uncertainty. We hope that the workshop will stimulate our efforts in improving the understanding of mathematical features of Bohmian Dynamics and Exact Factorization and creating new computational simulation techniques for use in chemistry.
Abstracts and slides for the lectures can be found here soon…