Entanglement and Sources of Magnetic Anisotropy in Radical Pair-Based Avian Magnetoreceptors

One of the principal models of magnetic sensing in migratory birds rests on the quantum spin-dynamics of transient radical pairs created photochemically in ocular cryptochrome proteins. We consider here the role of electron spin entanglement and coherence in determining the sensitivity of a radical pair-based geomagnetic compass and the origins of the directional response. It emerges that the anisotropy of radical pairs formed from spin-polarized molecular triplets could form the basis of a more sensitive compass sensor than one founded on the conventional hyperfine-anisotropy model. This property offers new and more flexible opportunities for the design of biologically inspired magnetic compass sensors

Asymmetric recombination and electron spin relaxation in the semiclassical theory of radical pair reactions

We describe how the semiclassical theory of radical pair recombination reactions recently introduced by two of us [D. E. Manolopoulos and P. J. Hore, J. Chem. Phys. 139, 124106 (2013)] can be generalised to allow for different singlet and triplet recombination rates. This is a non-trivial generalisation because when the recombination rates are different the recombination process is dynamically coupled to the coherent electron spin dynamics of the radical pair. Furthermore, because the recombination operator is a two-electron operator, it is no longer sufficient simply to consider the two electrons as classical vectors: one has to consider the complete set of 16 two-electron spin operators as independent classical variables. The resulting semiclassical theory is first validated by comparison with exact quantum mechanical results for a model radical pair containing 12 nuclear spins. It is then used to shed light on the spin dynamics of a carotenoid-porphyrin-fullerene (CPF) triad containing considerably more nuclear spins which has recently been used to establish a 'proof of principle' for the operation of a chemical compass [K. Maeda et al., Nature 453, 387 (2008)]. We find in particular that the intriguing biphasic behaviour that has been observed in the effect of an Earth-strength magnetic field on the time-dependent survival probability of the photo-excited C+PF- radical pair arises from a delicate balance between its asymmetric recombination and the relaxation of the electron spin in the carotenoid radical

Digital Construction and BIM Research in Ireland 2016-2020

As the construction industry opens up post pandemic, new and significant challenges will demand considerable expertise, not least in financial viability, solving the housing crisis and facing the very significant climate change pressures to make the industry less wasteful and less carbon intensive. This presents an excellent opportunity to further inculcate aspects of lean construction, particularly BIM into many aspects of construction not traditionally associated with digital construction, provided the necessary expertise is available and known to exist. Following a well-received recent conference paper summarising BIM-related research published by academics in Ireland’s higher education institutions in 2020, this paper will review and identify noteworthy publications in digital technologies, including BIM, by academics of this island’s third level institutions in the last five years. Areas of expertise of individuals will be identified to act as a useful directory for both industry and fellow researchers as well as providing a valuable national resource to identify research gaps which need funding if the ambitions of the national plan for the digitisation of the industry are to be realised. Using an already proven methodology, a survey of the 16 academic institutions in Ireland will be conducted through identified representatives in each institution, seeking all conference and journal papers published in the 2016-2020 period. The assembled database will be categorised, sorted and analysed to identify academic individuals in the workforce with extant research strengths in the various themes to establish the available expertise and areas for growth in the next five years

BIM Research in Irish Academic Institutions 2015-19

The use of BIM in the Irish construction industry has become pervasive in the last decade and it is an essential element in improving productivity in the market. The developments in BIM education and training in supporting the increase in Ireland’s BIM maturity has been well documented in recent years, principally through the proceedings of the BIM Gatherings and the BIM in Ireland 2017 and 2019 reviews. Similarly, the public and private sectors have been surveyed to establish their readiness for digital transformation on their BIM journey. However, BIM research undertaken by Irish academics, while individually strong, has not been strategic at national level nor has it yet met all the needs of industry. This paper will review the learned publications of all research-active academics on this island in the various aspects of the field of BIM-related research in the last 5 years. It will categorise and analyse their achievements, acting as a national reference source for all parties in this industry. It will also suggest areas where further research opportunities exist in support of the continuing fast-paced evolution of this digital technology in the construction industry, nationally and internationally

Bandit algorithms in recommender systems

Peer reviewe

The Irish Construction Industry’s State of Readiness for a BIM mandate in 2020

It was recently announced that a BIM mandate for the Irish public sector is not imminent, suggesting that the sector is not yet ready for what such a mandate implies. Following on from a forward-looking BIM Roadmap for Ireland in 2017 and the publication by the authors of a detailed BIM in Ireland study in 2017 and 2019, what is the actual state of readiness for a more general BIM mandate in Ireland? This paper will review recent publications, seminars and industry initiatives on this topic of interest supported by an online survey to assess the current state of readiness for a BIM mandate in Ireland. An assessment will be made of what deficits, if any, need to be addressed before the introduction of a BIM mandate would be a practical proposition. Reflections on the success of other similar-sized economies will be referred to in identifying the priorities for Ireland in its preparation for a full BIM mandate, in addition to the relative importance of BIM given the ongoing impact of the CoVID-19 global pandemic on Ireland’s economy

Time evolution of spin state of radical ion pair in microwave field: An analytical solution

The paper reports an exact solution for the problem of spin evolution of radical ion pair in static magnetic and resonant microwave field taking into account Zeeman and hyperfine interactions and spin relaxation. The values of parameters that provide one of the four possible types of solution are analysed. It is demonstrated that in the absence of spin relaxation, besides the zero field invariant an invariant at large amplitudes of the resonant microwave field can be found. The two invariants open the possibility for simple calculation of microwave pulses to control quantum state of the radical pair. The effect of relaxation on the invariants is analysed and it is shown that changes in the high field invariant are induced by phase relaxation.Comment: 18 pages, 7 figure

Electron spin relaxation can enhance the performance of a cryptochrome-based magnetic compass sensor

The radical pair model of the avian magnetoreceptor relies on long‐lived electron spin coherence. Dephasing, resulting from interactions of the spins with their fluctuating environment, is generally assumed to degrade the sensitivity of this compass to the direction of the Earth's magnetic field. Here we argue that certain spin relaxation mechanisms can enhance its performance. We focus on the flavin‐tryptophan radical pair in cryptochrome, currently the only candidate magnetoreceptor molecule. Correlation functions for fluctuations in the distance between the two radicals in Arabidopsis thaliana cryptochrome 1 were obtained from molecular dynamics simulations and used to calculate the spin relaxation caused by modulation of the exchange and dipolar interactions. We find that intermediate spin relaxation rates afford substantial enhancements in the sensitivity of the reaction yields to an Earth‐strength magnetic field. Supported by calculations using toy radical pair models, we argue that these enhancements could be consistent with the molecular dynamics and magnetic interactions in avian cryptochromes

Fluorescence-detected magnetic field effects on radical pair reactions from femtolitre volumes

We show that the effects of applied magnetic fields on radical pair reactions can be sensitively measured from sample volumes as low as ~100 femtolitres using total internal reflection fluorescence microscopy. Development of a fluorescence-based microscope method is likely to be a key step in further miniaturisation that will allow detection of magnetic field effects on single molecules