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Light travel time effects in ilkonova models
No full textThe extremely rapid evolution of kilonovae results in spectra that change on an hourly basis. These spectra are key to understanding the processes occurring within the event, but this rapid evolution is an unfamiliar domain compared to other explosive transient events, such as supernovae. In particular, the most obvious P Cygni feature in the spectra of AT2017gfo – commonly attributed to strontium – possesses an emission component that emerges after, and ultimately outlives, its associated absorption dip. This delay is theorised to arise from reverberation effects, wherein photons emitted earlier in the kilonova’s evolution are scattered before reaching the observer, causing them to be detected at later times. We aim to examine how the finite speed of light – and therefore the light travel time to an observer – contributes to the shape and evolution of spectral features in kilonovae. Using a simple model, and tracking the length of the journey photons undertake to an observer, we are able to test the necessity of accounting for this time delay effect when modelling kilonovae. In periods where the photospheric temperature is rapidly evolving, we show spectra synthesised using a time independent approach are visually distinct from those where these time delay effects are accounted for. Therefore, in rapidly evolving events such as kilonovae, time dependence must be taken into account
Characterizing ‘Atmosphere’: exploring determinants of regular service attendance amongst integrated supervised consumption site clients in Vancouver’s Downtown Eastside
No full textBackgroundResearch has explored barriers and facilitators to supervised consumption sites (SCS) in Canadian settings. Despite this, little is known about what factors drive individuals to initiate and repeatedly attend specific SCS where multiple SCS options are available, such as in Vancouver’s Downtown Eastside (DTES). The aim of this study was to understand the structural, contextual, and operational determinants of regular SCS attendance during Canada's ongoing overdose crisis.MethodsRapid-ethnographic fieldwork was conducted over a six-week period at an integrated SCS in Vancouver’s DTES. This comprised an initial five-week period of non-participant observation (≈200 h) followed by a community consultation regarding the research design and question protocols. Qualitative data were then collected through five focus groups (n = 25) and 20 semi-structured interviews with regular service attendees with data analysed using thematic analysis.ResultsOur findings highlight four important factors related to regular service attendance. The service had a regular clientele who described their attendance as routinized, which they attributed to four distinct factors: (1) the accessible location, (2) the on-site auxiliary health and support services, (3) the diversity of harm reduction provision, and (4) the atmosphere. Exploring the concept of atmosphere in more depth showed that it was characterized by the safety, familiarity, and inclusivity experienced within the service. Together, these factors facilitated a strong sense of belonging among attendees regarding the service and its community of staff and clients.ConclusionWithin the context of an ongoing overdose crisis, our findings highlight SCS service characteristics which facilitate routinized engagement including accessibility, wrap-around support, comprehensive and tailored harm reduction, and an inclusive welcoming atmosphere. These insights can inform policy makers and service providers in scaling and developing effective, client-centred SCSs to reduce harm and promote wellbeing.<br/
The 2025 roadmap to ultrafast dynamics: frontiers of theoretical and computational modeling
No full textThe exploration of ultrafast phenomena is a frontier of condensed matter research, where the interplay of theory, computation, and experiment is unveiling new opportunities for understanding and engineering quantum materials. With the advent of advanced experimental techniques and computational tools, it has become possible to probe and manipulate nonequilibrium processes at unprecedented temporal and spatial resolutions, providing insights into the dynamical behavior of matter under extreme conditions. These capabilities have the potential to revolutionize fields ranging from optoelectronics and quantum information to catalysis and energy storage. This roadmap captures the collective progress and vision of leading researchers, addressing challenges and opportunities across key areas of ultrafast science and condensed matter. Contributions in this roadmap span the development of ab initio methods for time-resolved spectroscopy, the dynamics of driven correlated systems, the engineering of materials in optical cavities, and the adoption of FAIR principles for data sharing and analysis. Together, these efforts highlight the interdisciplinary nature of ultrafast research and its reliance on cutting-edge methodologies, including quantum electrodynamical density-functional theory, correlated electronic structure methods, nonequilibrium Green’s function approaches, quantum and ab initio simulations
Multimodal deep learning model based on ECG and clinical notes for arrhythmia classification
No full textElectrocardiograms (ECGs) are non-invasive tools used to monitor the heart’s electrical activity. It captures the heart’s depolarization and repolarization cycles by measuring the tiny voltage fluctuations on the skin. Analyzing this rhythm requires intensive effort from clinicians. This paper introduce a novel end-to-end multi-modal deep learning model to process 12-lead ECG signals with patient clinical notes to assist cardiologists in classifying eight types of arrhythmia. The ECG signal is processed using a convolutional backbone composed of residual 1D convolutional blocks, a convolutional block attention module, and a bi-directional GRU to capture long-range temporal dependencies. In parallel, 13 clinical features extracted from clinical notes are embedded using an auxiliary multilayer perceptron network. The two modalities are combined through late fusion, followed by a fully connected layer for arrhythmia classification. The model is trained and evaluated on a public dataset. It achieves an accuracy of 92.8% and a macro F1-score of 84.6%, representing +4% increase in accuracy and +9% improvement in macro F1-score compared to processing ECG signals alone. Furthermore, it also outperforms a baseline random forest by a substantial margin. Error analysis shows that the clinical notes help to improve the discriminatory ability of the model for minority and morphologically similar rhythms, particularly Sinus Arrhythmia, Sinus Bradycardia, and Sinus Rhythm. The proposed model demonstrates the clinical potential of fusing waveform morphology with contextual patient data can enable accurate diagnostic tools.<br/
Effect of fly ash, basalt fibre and attapulgite nanoclay on the fresh properties, rheology and shrinkage behaviour of printable concrete
No full textThe application of 3D concrete printing (3DCP) has attracted significant attention in the construction sector for its potential to revolutionize building processes. Unlike traditional methods, 3D printing eliminates the need for formwork, but it requires concrete mixtures with specific rheological properties to enable smooth extrusion and shape retention after printing. This study delves into the formulation of a unique blend of Portland Cement with fly ash, basalt fibre, and attapulgite nanoclay (nC) specifically tailored for 3D printing applications. This study provides new insights into the early-stage hydration kinetics and microstructural intricacies of these mixtures using techniques like X-ray diffraction and thermogravimetric analysis. This research investigates the influence of nanoclay on key properties such as initial rheological properties, structural build-up rate, setting time, the printing speed of 3D printable concrete and shrinkage properties. Microstructural analyses like XRD and TGA were conducted on a ternary system of fly ash, cement, and nanoclay, to interpret the mechanisms underlying early strength development. Standardized field-friendly testing methodologies have been adapted to suit printable concrete for 3D printing, and a framework has been introduced to gauge the rate of structural build-up using tests like cone penetration and scissometer tests. Within the scope of this study, a new cyclic unconfined uniaxial compressive testing (UUCT) process has been introduced as a tool for ascertaining the printing speed in 3DCP applications. The effects of nanoclay and basalt fibre on shrinkage properties of printed specimens, from initial plastic shrinkage to drying shrinkage over a span of 90 days, have been examined, an aspect not discussed in existing literature. The research findings highlight that incorporating up to 6 kg/m3 of nanoclay and about 2.1 kg/m3 of basalt fibre to the mix, the structural build-up rate is enhanced, permitting faster concrete printing, and reducing shrinkage post printing process.<br/
Interacting drivers of Holocene climate change in southwestern Africa: the influence of insolation, rainbelt dynamics and upwelling
No full textUnderstanding regional-scale patterns of long-term climate variability is essential for identifying the drivers of past environmental change. In southern Africa, the continent is often divided into three rainfall zones—summer, winter, and aseasonal—but this framework fails to capture the finer dynamics of transitional areas where tropical, subtropical, and temperate systems converge. This study examines Holocene climate variability along the western margin of the southern African monsoon region using a new 7300-year nitrogen isotope record from rock hyrax middens at Omanyne-4 in northern Namibia. Unlike other Namib Desert records that indicate progressive aridification through the Holocene, the Omanyne-4 sequence shows a long-term trend toward increasing humidity, consistent with insolation-driven enhancement of tropical and Indian Ocean moisture advection. Comparisons with records from northern Namibia, Botswana, and western Zambia reveal a coherent pattern of mid-to late Holocene humidification across the northwestern interior, in contrast to coastal aridification. Periods of both in-phase and antiphase variability with other regional records highlight the role of the Angola–Benguela Front and associated upwelling dynamics in modulating Namibian hydroclimate. These results delineate distinct Holocene climate response regions in northern Namibia and Botswana and demonstrate the non-linear nature of regional responses to insolation forcing and underscore the importance of coastal–inland atmospheric interactions in shaping long-term hydroclimate variability in southwestern Africa.</p
Can instrumental effects obscure the true photospheric wave spectrum?
No full textOptical aberrations and instrument resolution can affect the observed morphological properties of features in the solar atmosphere. However, little work has been done to study the effects of spatial resolution on the dynamical processes occurring in the Sun’s atmosphere. In this work, owing to the availability of high-resolution observations of a magnetic pore captured with the Interferometric BIdimensional Spectrometer mounted at the Dunn Solar Telescope, we studied the impact of the diffraction limit and the sampling of an instrument on line-of-sight Doppler velocity oscillations. We reported a noticeable shift in the dominant frequency band from 5 to 3 mHz, as both the angular and detector resolutions of the instruments were degraded. We argue that the observed behavior is a result of the increased contamination of straylight from neighboring quiet Sun regions, masking the true behavior of umbral oscillations. These results suggest that the wave energy contributions reported in the literature and based on low-resolution instrumentation may be fundamentally underestimated. As we move into the era of high-resolution instrumentation such as DKIST and MUSE, this paper will offer a critical baseline for interpreting new observations, especially in terms of distinguishing true dynamic behaviors from artifacts introduced by instrument-related limitations
From policy to practice: Green Human Resource implementation and stakeholder collaboration for effective environmental sustainability within university settings. A comparative case study at Queen's University Belfast, United Kingdom, and King Abdulaziz University, Jeddah, Saudi Arabia
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