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Stringy KLT Relations on AdS
Full text linkWe study the building blocks of open and closed string amplitudes on AdS. These are given by two infinite towers of world-sheet integrals generalising the Euler and complex beta functions respectively. We show that the open and closed building blocks are related by an AdS version of the KLT relations, whose Kernel can be computed exactly. We furthermore show that the building blocks for open string amplitudes are given by Aomoto-Gelfand hypergeometric functions, and give their closed-form expression up to weight four
Exploring normative models of the visual and auditory systems
Full text linkThe brain’s sensory systems transform the incoming stimuli which impinge on the periphery into useful representations that can guide an organism’s behaviour. Indeed, understanding the complex neural computations which underpin these transformations across sensory pathways remains an enduring goal of systems neuroscience. Normative modelling provides one approach to tackling this complexity, by describing neural systems from an optimization perspective. In this way, a normative approach can answer to what extentthe diverse structural and functional properties of the sensory brain might emerge by optimizing for a few more fundamental principles of neural function. This normative approach forms the core of this thesis, which I explore across the visual and auditory systems.To that end, in the first two results chapters, I investigate how optimizing recurrent artificial neural networks for predictive information – termed temporal prediction – can capture both the structural and functional properties of the mammalian visual system. Specifically, in chapter two, I describe how a shallow recurrent model trained for temporal prediction can recapitulate the functional connectivity motifs of mouse primary visual cortex (V1). In chapter three, I extend this V1 model into a hierarchical recurrent model of the dorsal visual pathway. There, I demonstrate how feedback connectivity in the network captures many of the known functional properties of higher-order feedback to V1. Finally, in chapter four, I move from the visual system to the auditory system where I take a broader view across the wider landscape of normative models. In this chapter, I investigate which properties determine how well normative models can predict neural activity and how this relates to the models’ learned representations. In particular, I show that networks which learn more general representations are better able to model auditory neural activity.Overall, this thesis demonstrates the utility of normative networksas models of the brain and shows how the complexity sensory systems might emerge by optimizing for much simpler principles such as temporal prediction
Enhancing the experience of film with a wearable tactile/haptic suit
Full text linkThis study investigated whether synchronized, full-body pressure feedback from a wearable suit (the “bubble suit”) could enhance audience engagement during film viewing. While vibrotactile haptics have been explored in gaming and Virtual Reality (VR), pressure-based haptics remain unexplored in cinematic contexts. A within-subjects experiment was conducted with 42 participants who viewed two short film clips, one with synchronized pressure feedback delivered via an inflatable wearable suit, and one without. The custom-designed inflatable suit provided pressure across the torso, back, and limbs, controlled by an Arduino system synchronized with on-screen events. After each viewing, participants completed questionnaires measuring immersion, narrative engagement, attention, and realism. Notably, participants’ willingness to pay for the experience more than doubled. The haptic feedback also altered character empathy, shifting viewers’ emotional focus from the protagonists to side character experiencing the haptic-related event. However, the effects varied between participants, influenced by factors such as the suit’s fit and individual sensory interpretation. In conclusion, wearable pressure feedback can significantly enhance the perceived cinematic experience, offering a powerful tool for increasing audience engagement and the perceived value of entertainment. While the findings inform future designs for haptic-enhanced media, key implementation challenges remain, including technical limitations, ergonomic design, and managing individual perceptual differences
Simulating radio emission from flickering AGN jets: travelling shocks and hotspot brightening
Full text linkWe investigate the impact of flickering variability in jet power on the luminosity and morphology of radio galaxies. We use a Lagrangian particle method together with relativistic hydrodynamics simulations using the pluto code to track the evolution of electron spectra through particle acceleration at shocks and cooling processes. We introduce an adapted version of this method which improves tracking of adiabatic cooling in regimes where low density jet material mixes with high density from the ambient medium in the lobes. We find that rapid increases in jet power can lead to large increases in hotspot luminosity due to the interaction of a travelling shock structure with the pre-existing shock structure at the jet head. We show that in some cases it may be possible to identify a bright region of emission corresponding to a shock travelling along the jet axis. We find that the time-averaged radiative efficiency of variable jets is similar to their steady counterparts, but find significant departures from this on an instantaneous basis. We suggest that, together with environmental effects and differences in the average powers of jets, variable jet powers may have a significant impact on how we understand the diversity of radio jets seen in observations and have significant implications for interpretations of jet powers, energy budgets, and luminosity-linear size diagrams
Lineage-linked biofilm formation and widespread multidrug resistance among indian Acinetobacter baumannii clinical isolates
Full text linkAIMS: This study aimed to investigate the diversity and determinants of biofilm formation among clinical Acinetobacter baumannii Indian isolates and assess their relationship with antimicrobial resistance profiles, biofilm-associated genes, and genetic lineages revealed through whole-genome analysis.METHODS AND RESULTS: 230 A. baumannii clinical isolates across India (2015-2022) were tested for antibiotic susceptibility using the VITEK 2 system. Biofilm formation was quantified via the Tissue Culture Plate method. Whole genome sequencing (Illumina MiSeq) and bioinformatic analysis were performed to identify biofilm-associated genes, antimicrobial resistance genes and sequence types. Statistical associations were assessed using Kruskal-Wallis, Spearman's, and Fisher's tests. 85.22% of isolates were multidrug-resistant (MDR), and 100% exhibited biofilm formation, with 52.17% strong, 39.57% moderate, and 8.26% weak biofilm producers. Genes including ompA, bfmR, pgaA, pgaB, and pgaD were universally present. No significant association was observed between biofilm formation and antibiotic resistance (P = 0.55), specimen type (P = 0.54), or the presence of specific biofilm-related genes (P > 0.05). 21 sequence types (STs) were identified, with ST2 being the most prevalent (51.73%). Strong biofilm formation was more common in ST164, ST1, and ST575. CONCLUSIONS: This study demonstrates a high prevalence of MDR and strong biofilm-forming A. baumannii isolates in India. Biofilm formation appeared independent of resistance or gene carriage but showed lineage-linked variation across sequence types
Unravelling co-mutational patterns with prognostic implications in NPM1 mutated adult acute myeloid leukemia – a HARMONY study
Full text linkNPM1-mutated (NPM1-mut) acute myeloid leukemia (AML) is generally associated with a more favorable outcome, although the presence of additional gene mutations can influence patient prognosis. We analyzed intensively-treated adult NPM1-mut AML patients included in the HARMONY Alliance database. A newly developed risk classification, which included combinations of co-mutations in FLT3-ITD, DNMT3A, IDH1/IDH2, and TET2 genes, was applied to a training cohort of NPM1-mut AML patients included in clinical trials (n = 1001), an internal validation cohort more representative of real-world settings (n = 762), and an external validation cohort enrolled in UK-NCRI trials (n = 585). The HARMONY classification considered 51.8% of the NPM1-mut AML training cohort patients as favorable, 24.8% as intermediate, and 23.4% as adverse risk, with median overall survival (OS) of 14.4, 2.2, and 0.9 years, respectively; p < 0.001), thereby reclassifying 42.7% of NPM1-mut patients into a different European LeukemiaNet (ELN) 2022 risk category. These results were confirmed both in an internal and external validation cohort. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first complete remission (CR1) showed the highest benefit in the NPM1-mut adverse-risk subgroup. The HARMONY classification provides the basis for a refined genetic risk stratification for adult NPM1-mut AML with potential clinical impact on allo-HSCT decision-making
Sociotechnical challenge modeling: a design method for responsible AI in healthcare and social welfare
Full text linkWe present Sociotechnical Challenge Modeling (STCM), a workshopbased design method to help healthcare and social welfare practitioners identify and address sociotechnical challenges in machine learning (ML) deployments. We evaluated STCM in a field experiment with two UK organizations, involving 26 practitioners including managers, data scientists, and frontline care professionals. The evaluation found that STCM cultivated a sociotechnical perspective by revealing interdependencies between ML tools and organizational practices. The physical cards stimulated exchange and experimentation, while the workshop fostered collaboration across disciplines. However, participants found predefined countermeasures too prescriptive, which prompted revisions to support more open-ended ideation. Our contributions are a novel design method for anticipating and mitigating sociotechnical challenges of ML in care settings, and an empirical evaluation of its perceived value and limitations. To support adoption and further research, all STCM materials, including editable card templates and worksheets, are available at: https://bit.ly/4plXk
Synthesis challenges in complex evidence: A critical analysis of systematic reviews of face mask efficacy
Full text linkThe evaluation of the role of face masks in preventing respiratory infections is a paradigm case in synthesising complex evidence (i.e. extensive, diverse, technically specialised, and with multilevel chains of causality). Primary studies have assessed different mask types, diseases, populations, and settings using different research designs. Numerous review teams have attempted to synthesise this literature, in which observational (case–control, cohort, cross-sectional) and ecological studies predominate. Their findings and conclusions vary widely. This article critically examines how 66 systematic reviews dealt with mask efficacy studies. Risk-of-bias tools produced unreliable assessments when—as was often the case—review teams lacked methodological expertise or topic-specific understanding. This was especially true when datasets were large and heterogeneous, with multiple biases playing out in different ways and requiring nuanced adjustments. In such circumstances, tools were sometimes used crudely and reductively rather than to support close reading of primary studies and guide expert judgments. Various moves by reviewers—excluding observational evidence altogether, assessing risk but not direction of biases, omitting distinguishing details of primary studies, and producing meta-analyses that combined studies of different designs or included studies at critical risk of bias—served to obscure important aspects of heterogeneity, resulting in bland and unhelpful summary statements. We draw on philosophy to question the formulaic use of generic risk-of-bias tools, especially when the primary evidence demands expert understanding and tailoring of study quality questions to the topic. We call for more rigorous training and oversight of reviewers of complex evidence and for new review methods designed specifically for such evidence
Intrabandgap States Engineering in Functionalized Nanodiamond to Generate Solvated Electrons for Photocatalysis Under Solar Illumination
Full text linkDiamond, a wide‐bandgap material with unique electronic properties, has shown great promise as a photoreduction catalyst due to its ability to produce highly reductive solvated electrons. However, this requires deep UV illumination, which hampers its sustainable application for real‐world photocatalytic processes. Here, it is reported that the tailored introduction of suitable intra‐bandgap states in diamond can be achieved by functionalizing nanoscale detonation diamond with a ruthenium‐based photosensitizer. The nature of the electronic interaction between the diamond, its surface and the surface‐bound moieties is elucidated through X‐ray absorption, transient optical absorption, and ultraviolet photoemission spectroscopies both in vacuum and water. The electron emission upon irradiation with visible light is enabled by the surface‐induced bangdap engineering. Solar‐light‐driven reduction of CO2 to formate is performed as a proof‐of‐concept reaction. The potential for photoexcited electron transfer (PET) mediated photosensitization in reductive diamond catalysis opens the way for the application of surface‐engineered diamond as a sustainable photo(electro)catalyst
Metal transport by magmatic volatile phases in crustal systems
Full text linkMagmatic volatile phases (MVPs) are multicomponent fluids that are a transport medium for metals being transferred from deep magmatic sources to sites of ore formation. However, the melt-to-fluid exchange of metals remains elusive because existing empirical simulations primarily address metal transport through the fate of one chemical element. We use a comprehensive thermochemical model to simulate the fractional crystallization of a silicate melt that degasses a multicomponent MVP. We show that the major and trace element abundances in MVPs formed from non-enriched magmatic systems are indistinguishable from MVPs found as fluid inclusions in mineralized and non-mineralized systems. We therefore conclude that ore formation is the consequence of repetitive intrusion-fractionation-degassing cycles common to crustal systems without pre-enriched sources, as opposed to scenarios wherein a particular or complex chemical system is required. Instead, the driving force of ore formation is a long-lived system fueled by an H2O- and Cl-bearing melt. Variations in metal signatures of fluids therefore reflect the pressure-temperature path of melt ascent and the changes in major element composition of the melt