Removing instabilities in the hierarchical equations of motion: exact and approximate projection approaches

The hierarchical equations of motion (HEOM) provide a numerically exact approach for computing the reduced dynamics of a quantum system linearly coupled to a bath. We have found that HEOM contains temperature-dependent instabilities that grow exponentially in time. In the case of continuous-bath models, these instabilities may be delayed to later times by increasing the hierarchy dimension; however, for systems coupled to discrete, non-dispersive modes, increasing the hierarchy dimension does little to alleviate the problem. We show that these instabilities can also be removed completely at a potentially much lower cost via projection onto the space of stable eigenmodes; furthermore, we find that for discrete-bath models at zero temperature, the remaining projected dynamics computed with few hierarchy levels are essentially identical to the exact dynamics that otherwise might require an intractably large number of hierarchy levels for convergence. Recognizing that computation of the eigenmodes might be prohibitive, e.g. for large or strongly-coupled models, we present a Prony filtration algorithm that may be useful as an alternative for accomplishing this projection when diagonalization is too costly. We present results demonstrating the efficacy of HEOM projected via diagonalization and Prony filtration. We also discuss issues associated with the nonnormality of HEOM.Comment: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 150, 184109 (2019) and may be found at https://doi.org/10.1063/1.509261

Overcoming cross-cultural group work tensions: mixed student perspectives on the role of social relationships

As universities worldwide rapidly internationalise, higher education classrooms have become unique spaces for collaboration between students from different countries. One common way to encourage collaboration between diverse peers is through group work. However, previous research has highlighted that cross-cultural group work can be challenging and has hinted at potential social tensions. To understand this notion better, we have used robust quantitative tools in this study to select 20 participants from a larger classroom of 860 students to take part in an in-depth qualitative interview about cross-cultural group work experiences. Participant views on social tensions in cross-cultural group work were elicited using a unique mediating artefact method to encourage reflection and in-depth discussion. In our analysis of emergent interview themes, we compared student perspectives on the role of social relationships in group work by their academic performance level. Our findings indicated that all students interviewed desired the opportunity to form social relationships with their group work members, but their motivations for doing so varied widely by academic performance level

Overcoming positivity violations for density matrices in surface hopping

Fewest-switches surface hopping (FSSH) has emerged as one of the leading methods for modeling the quantum dynamics of molecular systems. While its original formulation was limited to adiabatic populations, the growing interest in the application of FSSH to coherent phenomena prompts the question how one should construct a complete density matrix based on FSSH trajectories. A straightforward solution is to define adiabatic coherences based on wavefunction coefficients. In this Paper, we demonstrate that inconsistencies introduced in the density matrix through such treatment may lead to a violation of positivity. We furthermore show that a recently proposed coherent generalization of FSSH results in density matrices that satisfy positivity, while yielding an improved accuracy throughout much (but not all) of parameter space

A Cost-Effectiveness Analysis of Abemaciclib in Combination with Adjuvant Endocrine Therapy for HR+, HER2–, Node-Positive, High-Risk Early Breast Cancer

IntroductionThe monarchE trial demonstrated that the addition of 2 years of abemaciclib to adjuvant endocrine therapy (ET) significantly reduced the risk of disease recurrence in patients with hormone receptor positive (HR+), and human epidermal growth factor receptor 2–negative (HER2–), node-positive early breast cancer (EBC) at high risk of disease recurrence. Abemaciclib meets a critical unmet need for more effective adjuvant therapy for this patient population. This study evaluates the cost-effectiveness (CE) of abemaciclib plus ET compared to ET alone.MethodsA five-state cohort transition model, which presents a United Kingdom (UK) perspective, is parameterized using data from the monarchE trial and literature. Cost-effectiveness results are presented in terms of cost/quality-adjusted life year (QALY) over a lifetime time horizon. Various assumptions were tested through sensitivity and scenario analyses and uncertainty was assessed through probabilistic analysis.ResultsPatients receiving abemaciclib plus ET were predicted to experience higher QALYs (11.16 compared to 10.42) at an increased cost (£87,541 compared to £48,625), leading to an incremental cost-effectiveness ratio (ICER) of £52,317 per QALY gain compared to ET alone. The increased costs associated with the addition of abemaciclib were partially offset by a reduction in distant disease recurrence and associated costs. The scenario and sensitivity analyses supported robust base case results.ConclusionDespite the ICER exceeding usual willingness-to-pay (WTP) levels in the UK, a consequence of using list prices, the CE model utilizing the latest data cut from the monarchE trial, demonstrated that the upfront cost of abemaciclib reduces the risk of a terminal breast cancer prognosis and its associated cost and quality of life impact. The addition of 2 years of abemaciclib provides an option for the treatment of HR+, HER2–, node-positive, high-risk EBC

Factors contributing to posttraumatic growth and its buffering effect in adult chidren of cancer patients undergoing treatment

This study examined relationships among demographic, clinical, and psychosocial variables in adult children of cancer patients. Two hundred and fourteen participants completed measures of posttraumatic growth (PTG), distress, posttraumatic stress disorder (PTSD) symptoms, social support, and family functioning. Significant gender differences in all PTG dimensions were found, as well as associations among PTG, gender, parental dependency, distress, PTSD, and family functioning. Social support was not a mediator in the relationship between gender and PTG. Gender, education, disease duration, dependency, distress, and family flexibility predicted PTG. Finally, PTG had amoderating effect in the relationship between distress and PTSD/social support. These results may guide psychosocial interventions in this population.Fundação para a Ciência e Tecnologia (FCT

External Human–Machine Interfaces: The Effect of Display Location on Crossing Intentions and Eye Movements

In the future, automated cars may feature external human&ndash machine interfaces (eHMIs) to communicate relevant information to other road users. However, it is currently unknown where on the car the eHMI should be placed. In this study, 61 participants each viewed 36 animations of cars with eHMIs on either the roof, windscreen, grill, above the wheels, or a projection on the road. The eHMI showed &lsquo Waiting&rsquo combined with a walking symbol 1.2 s before the car started to slow down, or &lsquo Driving&rsquo while the car continued driving. Participants had to press and hold the spacebar when they felt it safe to cross. Results showed that, averaged over the period when the car approached and slowed down, the roof, windscreen, and grill eHMIs yielded the best performance (i.e., the highest spacebar press time). The projection and wheels eHMIs scored relatively poorly, yet still better than no eHMI. The wheels eHMI received a relatively high percentage of spacebar presses when the car appeared from a corner, a situation in which the roof, windscreen, and grill eHMIs were out of view. Eye-tracking analyses showed that the projection yielded dispersed eye movements, as participants scanned back and forth between the projection and the car. It is concluded that eHMIs should be presented on multiple sides of the car. A projection on the road is visually effortful for pedestrians, as it causes them to divide their attention between the projection and the car itself. Document type: Articl

Intentional intoxication with monkshood plant leading to atrioventricular dissociation and ventricular ectopy in a 17-year-old female: a case report

Background: Monkshood, a toxic plant containing a potent cardio- and neurotoxin called aconitine, can lead to a range of symptoms, including nausea, vomiting, dizziness, seizures, and cardiac arrhythmias. Mortality associated with this intoxication are due to ventricular tachyarrhythmias which are difficult to treat and often refractory in nature. Case presentation: We present a case of a 17-year-old female patient who presented to the emergency department after intentionally ingesting a monkshood plant and developed atrioventricular dissociation and frequent ventricular ectopy. The patient was successfully treated with activated charcoal, supportive care, and cardiac monitoring. Conclusion: This case highlights the importance of early recognition of aconitine poisoning and the need for prompt supportive care, cardiac rhythm monitoring, and preemptive antiarrhythmic treatment planning

Genotyping a second growth coast redwood forest : a high throughput methodology

The idea that excitonic (electronic) coherences are of fundamental importance to natural photosynthesis gained popularity when slowly dephasing quantum beats (QBs) were observed in the two-dimensional electronic spectra of the Fenna–Matthews–Olson (FMO) complex at 77 K. These were assigned to superpositions of excitonic states, a controversial interpretation, as the strong chromophore–environment interactions in the complex suggest fast dephasing. Although it has been pointed out that vibrational motion produces similar spectral signatures, a concrete assignment of these oscillatory signals to distinct physical processes is still lacking. Here we revisit the coherence dynamics of the FMO complex using polarization-controlled two-dimensional electronic spectroscopy, supported by theoretical modelling. We show that the long-lived QBs are exclusively vibrational in origin, whereas the dephasing of the electronic coherences is completed within 240 fs even at 77 K. We further find that specific vibrational coherences are produced via vibronically coupled excited states. The presence of such states suggests that vibronic coupling is relevant for photosynthetic energy transfer

Transmembrane protein 97 is a potential synaptic amyloid beta receptor in human Alzheimer’s disease

Synapse loss correlates with cognitive decline in Alzheimer’s disease, and soluble oligomeric amyloid beta (Aβ) is implicated in synaptic dysfunction and loss. An important knowledge gap is the lack of understanding of how Aβ leads to synapse degeneration. In particular, there has been difficulty in determining whether there is a synaptic receptor that binds Aβ and mediates toxicity. While many candidates have been observed in model systems, their relevance to human AD brain remains unknown. This is in part due to methodological limitations preventing visualization of Aβ binding at individual synapses. To overcome this limitation, we combined two high resolution microscopy techniques: array tomography and Förster resonance energy transfer (FRET) to image over 1 million individual synaptic terminals in temporal cortex from AD (n = 11) and control cases (n = 9). Within presynapses and post-synaptic densities, oligomeric Aβ generates a FRET signal with transmembrane protein 97. Further, Aβ generates a FRET signal with cellular prion protein, and post-synaptic density 95 within post synapses. Transmembrane protein 97 is also present in a higher proportion of post synapses in Alzheimer’s brain compared to controls. We inhibited Aβ/transmembrane protein 97 interaction in a mouse model of amyloidopathy by treating with the allosteric modulator CT1812. CT1812 drug concentration correlated negatively with synaptic FRET signal between transmembrane protein 97 and Aβ. In human-induced pluripotent stem cell derived neurons, transmembrane protein 97 is present in synapses and colocalizes with Aβ when neurons are challenged with human Alzheimer’s brain homogenate. Transcriptional changes are induced by Aβ including changes in genes involved in neurodegeneration and neuroinflammation. CT1812 treatment of these neurons caused changes in gene sets involved in synaptic function. These data support a role for transmembrane protein 97 in the synaptic binding of Aβ in human Alzheimer’s disease brain where it may mediate synaptotoxicity