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OQuPy : a Python package to efficiently simulate non-Markovian open quantum systems with process tensors
Get PDFFunding: G.E.F. acknowledges the support from EPSRC (Grant No. EP/L015110/1) and from ERC under Grant Agreement No. 101053159 (RAVE). J.B. acknowledges the support from the Laidlaw Foundation (Leadership and Research Program scholarship). E.P.B. acknowledges the support from the Irish Research Council (Grant No. GOIPG/2019/1871). D.G. acknowledges the support from the QuantERA II Program that has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 101017733 (“QuSiED”). P.R.E. acknowledges the support from Science Foundation Ireland (Grant No. 21-FFP-10142). E.D.C.L. acknowledges the support from EPSRC (Grant No. EP/T517938/1). R.d.W. acknowledges the support from EPSRC (Grant No. EP/W524505/1). B.W.L. and J.K. acknowledge the support from EPSRC (Grant No. EP/T014032/1).Non-Markovian dynamics arising from the strong coupling of a system to a structured environment is essential in many applications of quantum mechanics and emerging technologies. Deriving an accurate description of general quantum dynamics including memory effects is however a demanding task, prohibitive to standard analytical or direct numerical approaches. We present a major release of our open source software package, OQuPy (Open Quantum System in Python), which provides several recently developed numerical methods that address this challenging task. It utilizes the process tensor approach to open quantum systems in which a single map, the process tensor, captures all possible effects of an environment on the system. The representation of the process tensor in a tensor network form allows an exact yet highly efficient description of non-Markovian open quantum systems (NM-OQS). The OQuPy package provides methods to (1) compute the dynamics and multi-time correlations of quantum systems coupled to single and multiple environments, (2) optimize control protocols for NM-OQS, (3) simulate interacting chains of NM-OQS, and (4) compute the mean-field dynamics of an ensemble of NM-OQS coupled to a common central system. Our aim is to provide an easily accessible and extensible tool for researchers of open quantum systems in fields such as quantum chemistry, quantum sensing, and quantum information.Peer reviewe
Defining the mode of action of cisplatin combined with NUC-1031, a phosphoramidate modification of gemcitabine
Get PDFFunding: DP and GMZ were funded by Nucana plc (XIUN20-18695) (https://www.nucana.com).The combination of gemcitabine with platinum agents is a widely used chemotherapy regimen for a number of tumour types. Gemcitabine plus cisplatin remains the current therapeutic choice for biliary tract cancer. Gemcitabine is associated with multiple cellular drug resistance mechanisms and other limitations and has thereforelined in use. NUC-1031 (Acelarin) is a phosphorylated form of gemcitabine, protected by the addition of a phosphoramidate moiety, developed to circumvent the key limitations and generate high levels of the cytotoxic metabolite, dFdCTP. The rationale for combination of gemcitabine and cisplatin is determined by in vitro cytotoxicity. This, however, does not offer an explanation of how these drugs lead to cell death. In this study we investigate the mechanism of action for NUC-1031 combined with cisplatin as a rationale for treatment. NUC-1031 is metabolised to dFdCTP, detectable up to 72 h post-treatment and incorporated into DNA, to stall the cell cycle and cause DNA damage in biliary tract and ovarian cancer cell lines. In combination with cisplatin, DNA damage was increased and occurred earlier compared to monotherapy. The damage associated with NUC-1031 may be potentiated by a second mechanism, via binding the RRM1 subunit of ribonucleotide reductase and perturbing the nucleotide pools; however, this may be mitigated by increased RRM1 expression. The implication of this was investigated in case studies from a Phase I clinical trial to observe whether baseline RRM1 expression in tumour tissue at time of diagnosis correlates with patient survival.Peer reviewe
Origin of the intermediate-temperature magnetic specific heat capacity in the spin-liquid candidate Ca10Cr7O28
Get PDFFunding: JAC acknowledges support from UKRI via EPSRC grant EP/T518062/1. CAH acknowledges support from UKRI via EPSRC grant EP/R031924/1.We present several approximate calculations of the specific heat capacity of the model for Ca10Cr7O28 proposed by Balz et al. [Phys. Rev. B 95, 174414 (2017)], using methods including exact diagonalization, thermal pure quantum states, and high-temperature expansions. In none of these cases are we able to reproduce the magnitude of the zero-field specific heat capacity shown in the intermediate-temperature (∼5–15K) experimental data. We discuss possible reasons for the discrepancy, and what it might tell us about the magnetic Hamiltonian for Ca10Cr7O28.Peer reviewe
Cleaning up the legacy : reassessing intergenerational justice in the context of nuclear decommissioning operations in the UK
Get PDFThere are over 150 nuclear power reactors in a state of shut down worldwide. Only 19 in three countries have, however, completed the decommissioning process. Decommissioning of a nuclear power plant is a complex and expensive operation, which takes decades to complete. The management of waste after the completion is another ongoing issue, and there is no authorised facility established yet to store the accumulating waste, which will remain toxic for thousands of years. Due to our collective lack of experience in decommissioning, it is difficult to estimate the work needed in both technical and financial terms. Lessons are still to be learned and unprecedented efforts are needed to minimise the environmental and financial burden imposed upon future generations.
With more than 200 reactors expected to end their lives in the next two decades, conscientious commitment is required not only from today’s society, but also from future generations, to contain the radioactive material safely. While the responsibilities and burdens imposed upon future generations are unknown, decommissioning is a “clean-up job” that does not produce any material product or monetary profit. Non-financial motivational factors are needed, and ethical concerns, or notions of justice, could be instrumental.
This study identifies the motivational factors needed to pursue nuclear decommissioning in a fair and sustainable manner. Grounded in a constructivist paradigm, a qualitative approach was employed. Following a review of relevant literature on the history of nuclear industry, as well as conceptualisation and application of justice in the modern society, 24 semi-structured interviews were conducted to understand what nuclear decommissioning operations mean to stakeholders. In the context of a comparative case-study, two prominent decommissioning sites in the UK, namely, Dounreay and Bradwell, were selected as places of research. The respondents include policy makers and site workers, as well as academics and activists.
In addition to general understanding that the financial aspect of nuclear decommissioning is the key issue to be tackled, empirical findings indicate the importance of non-financial, intergenerational justice considerations to pursue decommissioning in a fair and sustainable manner. However, the notion of justice is vulnerable to manipulation to benefit interested parties that wield more power than others and existing justice framework must be contested. Based on insights gained from the research, policy and practice implications are suggested, in hope that they may expand the existing understanding of decommissioning operations and help to reinforce the commitment and drive for generations to come
External validation of the QCovid 2 and 3 risk prediction algorithms for risk of COVID-19 hospitalisation and mortality in adults : national cohort study in Scotland
Get PDFFunding: National Institute for Health Research (NIHR) following a commission by the Chief Medical Officer for England. EAVE II is funded by the Medical Research Council (MC_PC_19075) with the support of BREATHE: the Health Data Research Hub for Respiratory Health (MC_PC_19004), which is funded through the UK Research and Innovation Industrial Strategy Challenge Fund and delivered through Health Data Research UK. Additional support has been provided through Public Health Scotland and the Community Health and Social Care Directorate of the Scottish Government.Objective The QCovid 2 and 3 algorithms are risk prediction tools developed during the second wave of the COVID-19 pandemic that can be used to predict the risk of COVID-19 hospitalisation and mortality, taking vaccination status into account. In this study, we assess their performance in Scotland. Methods We used the Early Pandemic Evaluation and Enhanced Surveillance of COVID-19 national data platform consisting of individual-level data for the population of Scotland (5.4 million residents). Primary care data were linked to reverse-transcription PCR virology testing, hospitalisation and mortality data. We assessed the discrimination and calibration of the QCovid 2 and 3 algorithms in predicting COVID-19 hospitalisations and deaths between 8 December 2020 and 15 June 2021. Results Our validation dataset comprised 465 058 individuals, aged 19–100. We found the following performance metrics (95% CIs) for QCovid 2 and 3: Harrell’s C 0.84 (0.82 to 0.86) for hospitalisation, and 0.92 (0.90 to 0.94) for death, observed-expected ratio of 0.24 for hospitalisation and 0.26 for death (ie, both the number of hospitalisations and the number of deaths were overestimated), and a Brier score of 0.0009 (0.00084 to 0.00096) for hospitalisation and 0.00036 (0.00032 to 0.0004) for death. Conclusions We found good discrimination of the QCovid 2 and 3 algorithms in Scotland, although performance was worse in higher age groups. Both the number of hospitalisations and the number of deaths were overestimated.Peer reviewe
Properties of magnetohydrodynamic normal modes in the Earth’s magnetosphere
Get PDFFunding: MDH was supported by NASA 80NSSC19K0127, 80NSSC19K0907, 80NSSC21K1683, 80NSSC21K1677, 80NSSC23K0903, and NSF AGS-2307204. KT was supported by NASA 80NSSC19K0259 and 80NSSC21K0453. MOA was supported by a UKRI (STFC / EPSRC) Stephen Hawking Fellowship EP/T01735X/1. The research of A.W. was funded in part by Science and Technology Facilities Council (STFC) grant ST/W001195/1 (UK). T.E. was funded in part by a Leverhulme Early Career Fellowship ECF-2019-155 (UK). AA and XZ were supported by NASA 80NSSC21K0729 and 80NSSC23K0108. We acknowledge support from ISSI Bern through ISSI International Team projects 483 “The Identification And Classification Of 3D Alfven Resonances” and 546 “Magnetohydrodynamic Surface Waves at Earth’s Magnetosphere (and Beyond).” We acknowledge NASA contract NAS5-02099.The Earth's magnetosphere supports a variety of Magnetohydrodynamic (MHD) normal modes with Ultra Low Frequencies (ULF) including standing Alfvén waves and cavity/waveguide modes. Their amplitudes and frequencies depend in part on the properties of the magnetosphere (size of cavity, wave speed distribution). In this work, we use ∼13 years of Time History of Events and Macroscale Interactions during Substorms satellite magnetic field observations, combined with linearized MHD numerical simulations, to examine the properties of MHD normal modes in the region L > 5 and for frequencies 5 depend on both the magnetopause location and the location of peaks in the radial Alfvén speed profile. Finally, we discuss how these results might be used to better model radiation belt electron dynamics related to ULF waves.Peer reviewe
Recent advances in metalloproteomics
Get PDFFunding: This work was funded by the BBSRC (Biological and Biotechnological Sciences Research Council), Grant No BB/V014684/1. We also thank FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo), Grant Nos. 2014/50867-3, 2018/25207-0 and 2020/08543-7, and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnologico), Grant No 303231/2020-3. JPCC thanks the Royal Society of Chemistry for an Enablement grant (E22-1637945680). The APC was funded by MDPI. .Interactions between proteins and metal ions and their complexes are important in many areas of the life sciences, including physiology, medicine and toxicology. Despite the involvement of essential elements in all major processes necessary for sustaining life, metalloproteomes remain ill-defined. This is not only owed to the complexity of metalloproteomes, but also the non-covalent character of the complexes that most essential metals form, which complicates analysis. Similar issues may also be encountered for some toxic metals. The review discusses recently developed approaches and current challenges for the study of interactions involving entire (sub-)proteomes with such labile metal ions. In the second part transition metals from the 4th and 5th period are examined, most of which are xenobiotic, and also tend to form more inert complexes. A large research area in this respect concerns metallodrug-protein interactions. Particular attention is paid to separation approaches, as these need to be adapted to the reactivity of the metal under consideration.Peer reviewe
Peripheral halogen atoms in multi-resonant thermally activated delayed fluorescence emitters : the role of heavy atom on intermolecular interactions and spin orbit coupling
Get PDFThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement Nos 812872 and 101073045 (TADFlife and TADFsolutions). J.W. thanks the China Scholarship Council (202006250026).Multi-resonant thermally activated delayed fluorescence materials (MR-TADF) can show narrow-band emission with high photoluminescence quantum efficiency, desirable for applications in organic light emitting diodes (OLEDS). However, they frequently suffer from slow reverse intersystem crossing (RISC) compared to established donor-acceptor TADF emitters, leading to severe device efficiency roll-off at high exciton densities. Introducing heavy atom effects (HAE) by core-substitution has been previously shown to enhance spin orbit coupling and thus RISC in MR-TADF emitters, frequently with oxygen atoms replaced by isoelectronic sulfur or selenium. Here, we explore an alternate HAE strategy using peripheral halogenation of the MR-TADF DiKTa core, comparing tBr-DiKTa and dBr-tBu-DiKTa with non-halogenated Mes3-DiKTa. The two brominated emitters demonstrate improved kRISC because of the HAE, while the rate appears to improve by an additional order of magnitude in mCP host, because of intermolecular (guest-host) interaction. Despite the beneficial hetero-intermolecular interactions, strong homo-intermolecular interactions result in enhanced non-radiative pathways and lower photoluminescence quantum yields. OLEDs of dBr-tBu-DiKTa hence showed comparable EQEmax with Mes3-DiKTa (21%) and improved efficiency roll-off until 500 cd m-2, although with accelerated roll-off beyond a critical current density. Together with comparisons in less strongly doped devices, these results show that the HAE provided by peripheral halogens improves the device performance up to 500 cd m-2, but also support detrimental intermolecular interactions that dominate at higher device currents.Peer reviewe
Identifying Alfvén wave modes in the solar corona
Get PDFFunding: EE received funding from the University of St Andrews Global Fellowship Scheme. IDM received funding from the Research Council of Norway through its Centres of Excellence scheme, project number 262622.Context. Oscillations are observed to be pervasive throughout the solar corona, however, positively identifying different wave modes remains challenging. Improving this identification would provide a powerful tool for investigating coronal wave heating and improving seismological inversions. Aims. To establish whether theoretical methods used to identify MHD wave modes in numerical simulations can be employed on observational datasets. Methods. We apply wave identifiers based on fundamental wave characteristics such as compressibility and direction of propagation to a fully 3D numerical simulation of a transversly oscillating coronal loop. The same wave identifiers are applied to the line-of-sight integrated synthetic emission derived from the numerical simulation data to investigate whether this method could feasibly be useful for observational studies. Results. We established that, for particular line(s)-of-sight and assumptions about the magnetic field, we can correctly identify properties of the Alfvén mode in synthetic observations of a transversely oscillating loop. Under suitable conditions, we find strong agreement between the simulation and synthetic emission results. Conclusions. For the first time, we have provided a proof-of-concept that this theoretically-derived classification of MHD wave modes, can be applied to observational data.Peer reviewe
EcoFed : efficient communication for DNN partitioning-based federated learning
Get PDFFunding: This work was sponsored by Rakuten Mobile, Japan.Efficiently running federated learning (FL) on resource-constrained devices is challenging since they are required to train computationally intensive deep neural networks (DNN) independently. DNN partitioning-based FL (DPFL) has been proposed as one mechanism to accelerate training where the layers of a DNN (or computation) are offloaded from the device to the server. However, this creates significant communication overheads since the intermediate activation and gradient need to be transferred between the device and the server during training. While current research reduces the communication introduced by DNN partitioning using local loss-based methods, we demonstrate that these methods are ineffective in improving the overall efficiency (communication overhead and training speed) of a DPFL system. This is because they suffer from accuracy degradation and ignore the communication costs incurred when transferring the activation from the device to the server. This article proposes Eco Fed-a communication efficient framework for DPFL systems. Eco Fed-a eliminates the transmission of the gradient by developing pre-trained initialization of the DNN model on the device for the first time. This reduces the accuracy degradation seen in local loss-based methods. In addition, EcoFed proposes a novel replay buffer mechanism and implements a quantization-based compression technique to reduce the transmission of the activation. It is experimentally demonstrated that EcoFed can reduce the communication cost by up to 133× and accelerate training by up to 21× when compared to classic FL. Compared to vanilla DPFL, EcoFed achieves a 16× communication reduction and 2.86× training time speed-up. EcoFed is available from https://github.com/blessonvar/EcoFed .Peer reviewe
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