224092 research outputs found
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Nanomechanics with electron beam: detection and control of motion
No full textThe study of nanomechanics using an electron beam has developed into an area of research, with recent works reporting on Brownian and ballistic motion detection, dynamic backaction,visualisation of sub-nm motion and mass sensing. It is important because the electron beam offers a platform for real-time observations of dynamics exhibited by nano- and microscale objects, with sub-nm scale displacement sensitivity and MHz bandwidth, as well as for controlling and characterising mechanical properties. In this study, I report the following yet unexplored aspects:• I have introduced a new technique for detecting and mapping the periodic motion of nano/microscale objects via cathodoluminescence, with nanometric displacement sensitivity and spatial resolution, and MHz bandwidth implemented in a modified scanning electron microscope. Its capability is demonstrated by detecting and mapping driven motion of nanomechanical cantilevers. The technique offers a noise equivalent displacement amplitude spectral density of 1 nm/√Hz.• I have observed the phenomenon of dependence of the frequency of oscillation of a cantilever on the presence of the electron beam. The repulsion between an electron beam and charge accumulated on a nanomechanical cantilever yields a stiffening that increases its resonance frequency, providing a mechanism for controlling resonators and sensing charge. For a cantilever of microscale length and nanoscale cross-section interacting with an electron beam, I observe a resonance shift on the order of 5% per nanocoulomb. The resonance frequency was expressed as a function of induced charge and electron beam parameters such as position, beam current and acceleration voltage. The model was tested experimentally by varying the current of an electron beam and its distance from the edge of grounded and isolated cantilevers.• Driving oscillations of a nanomechanical beam can lead to a bistable response related to the nonlinearity of the mechanical restoring force. I have observed for the first time that the nonlinear response of a nanowire and the regime of bistability can be controlled by the electron beam impinging on the oscillator. A nanowire that is fixed at both ends and driven to the nonlinear regime of bistable resonant oscillation was switched between its bistable states by changing the distance between a 10 kV, 1.3 nA electron beam and the nanowire. The control mechanism has been explained as a consequence of electronbeam-induced heating, leading to thermal expansion that affects stress in the nanowire, which controls its resonance frequency. Therefore, the electron beam can shift thenanowire's bistable resonance relative to a fixed frequency of driven oscillation, enabling it to switch between the bistable states.In summary this thesis reports on new ways for characterizing motion and controlling dynamics of nano- and microscale systems with electron beams
Avelumab with axitinib for untreated advanced renal cell carcinoma (MA review of TA645)
No full textThis report is a critique of the company’s submission (CS) to NICE from Merck on the clinical effectiveness and cost effectiveness of avelumab (Bavencio) in combination with axitinib (Inlyta) for treating adults with untreated advanced renal cell carcinoma (aRCC). It identifies the strengths and weakness of the CS
University of Southampton co-ordinated written evidence submission to: Supporting people with frailty outside of hospitals
Full text linkThe number of older adults living with multiple long-term conditions (MLTC) and frailty in the UK continues to rise. Care for older adults with MLTC and frailty is often divided between routine care in general practice and community health services with most acute care being provided in hospital settings. However, with further investment in community settings, more people could be cared for closer to home. At the University of Southampton, we have a developing portfolio ofresearch investigating best practice in the proactive and urgent community care for older adults living with MLTCs and frailty
Observation of σ–π coupling and mode selection in optically trapped artificial polariton molecules
No full textMicrocavity exciton–polariton condensates under additional transverse confinement constitute a flexible optical platform to study the coupling and hybridization between neighboring nonlinear states of light and matter. Driven farfrom equilibrium, networks of polariton condensates can display spontaneous synchronization, pattern formation,and instabilities depending on the excitation and material parameters. Here, we investigate this coupling mechanismbetween polariton condensates populating the first excited p-state manifold in optical traps and show a rich structure ofpatterns based on excitation parameters. Spontaneous symmetry breaking in the p-orbital manifold upon condensationresults in an ordered arrangement of dipole-shaped condensates between coupled traps reminiscent of σ and π molecular bonding mechanisms but restricted to the plane. A salient advantage is offered by the optical reconfigurability of thelaser excitation patterns, which determine the parameters of the polariton trapping potential and coupling strength withneighboring condensates. Our results underpin the potential role of polariton condensates in exploring the conditionsof spontaneous order in the relative orientation of anisotropic nonlinear states of light and matte
The role of hydration in uncovering the OER activity of amorphous iridium oxide electrocatalysts
No full textUnderstanding the structural properties of iridium oxide electrocatalysts under operational conditions is critical for elucidating the structure–property relationships that enhance the catalytic activity for the oxygen evolution reaction. In this study, in situ X-ray absorption spectroscopy under realistic conditions was employed to investigate the potentiodynamic and time-resolved structural evolution of a commercial iridium oxide, alongside its fully hydrated and crystalline counterparts. Our findings reveal two distinct electrochemical regimes, a low potential plateau associated with a nonconductive Ir3+ state and a linear region where small potential variations induce reversible oxidation state and structural transformations. The structural changes were found to occur reversibly on the commercial material even after prolonged exposure to OER potentials. Notably, the hydrated IrOx exhibits extremely high OER activity, surpassing the commercial material by nearly an order of magnitude, yet it suffers from significant instability. In contrast, the crystalline IrO2 demonstrates poor activity as its catalytic performance appears to be confined to the surface. These findings highlight the critical role of hydration in modulating both activity and stability, offering valuable insights for the rational design of next generation iridium based OER catalysts
Partial learning for MIMO detection
No full textReliable and efficient multiple-input multiple-output (MIMO) detection remains a central challenge in modern wireless receivers. Optimal maximum-likelihood (Max-L) detection delivers the best performance. However, its exponential complexity is prohibitive, while linear schemes such as zero-forcing (ZF) and minimum mean square error (MMSE) are computationally attractive yet they suffer from poor performance. Fully learned detectors improve robustness but introduce substantial parameter counts and computational complexity. Building on prior work on partial learning (PL), this thesis contributes a unified detection framework based on PL that addresses these trade-offs by applying learning only where it yields the most benefits: a subset of the weakest symbol streams, with the remaining streams detected using low-complexity linear detection. The first part of the thesis designs a soft-output PL demapper implemented with a small fully connected neural network (FCNN) for quasi-static channels and embeds it into an iterative detection. The inner MIMO detector produces log-likelihood ratios (LLRs) that are exchanged with an outer convolutional decoder. EXIT charts and decoding trajectories are used to analyze convergence. Across representative 2×2 and 4×4 quadrature phase-shift keying (QPSK) systems, the iterative PL (Iter-PL) technique closes most of the gap to iterative Max-L and full-learning detectors while operating at a fraction of their complexity. Operation counts are reported and related to the number of learning-assisted streams d, demonstrating explicit performance versus complexity trade-off. The second part extends Iter-PL to time-varying channels, while also considering channel state information (CSI) error. The same FCNN-based soft demapper is trained using CSI errors. Results show that Iter-PL retains its iterative gains under 5% CSI error and remains markedly superior to purely linear detection. An adaptive PL strategy is further introduced to select d based on the average received signal-to-noise ratio (SNR), thereby achieving a near-constant target bit error rate (BER) with reduced average complexity. The final part addresses scalability in dynamic multi-user uplinks. A graph neural network (GNN)–based PL detector is proposed, where an approximate message passing (AMP) frontend supplies soft symbols and variance estimates to the GNN. The GNN then detects only the d weakest users, while ZF detects the remaining users. By operating on user graphs, the model generalizes across changing activity masks without requiring retraining and maintains a low parameter count. Simulations over multiple activity patterns consistently confirm low BER and favorable performance–complexity trade-offs. Overall, the thesis demonstrates that PL enables near-optimal soft detection, accompanied by clear and quantifiable reductions in complexity, and that GNN-based partial learning offers the same benefits in multi-user scenarios. The proposed technique offers a practical approach to scalable, low-latency MIMO detection, making it suitable for evolving wireless systems
Language in migrant discourse
No full textDiscourse studies, in general, have captured how migrants position themselves, make sense of their migratory experiences, navigate social relations, and identify what matters to them in the diaspora. Language plays a crucial role in the migration experience, acting either as a tool to facilitate social participation in new networks or as a barrier that hinders interaction with other social groups. These discourses are context-dependent and continually shaped by evolving circumstances
Gradient information and regularization for gene expression programming to develop data-driven physics closure models
No full textLearning accurate numerical constants when developing algebraic models is a known challenge for evolutionary algorithms, such as Gene Expression Programming (GEP). This paper introduces the concept of adaptive symbols to the GEP framework by Weatheritt and Sandberg (J Comput Phys 325:22–37, 2016a) to develop advanced physics closure models. Adaptive symbols utilize gradient information to learn locally optimal numerical constants during model training, for which we investigate two types of nonlinear optimization algorithms. The second contribution of this work is implementing two regularization techniques to incentivize the development of implementable and interpretable closure models. We apply L2 regularization to ensure small magnitude numerical constants and devise a novel complexity metric that supports the development of low complexity models via custom symbol complexities and multi-objective optimization. This extended framework is employed to four use cases, namely rediscovering Sutherland’s viscosity law, developing laminar flame speed combustion models and training two types of fluid dynamics turbulence models. The model prediction accuracy and the convergence speed of training are improved significantly across all of the more and less complex use cases, respectively. The two regularization methods are essential for developing implementable closure models and we demonstrate that the developed turbulence models substantially improve simulations over state-of-the-art models.</p
Exploring the intersection of cancer, domestic homicide, and domestic abuse-related suicides using domestic homicide reviews
No full textPurpose: research about the overlap between cancer and domestic abuse (DA) is limited. We analyzed Domestic Homicide Review (DHR) reports from England and Wales where the victim or perpetrator had a cancer diagnosis to investigate the nature of DA in a cancer context, and cancer care and other healthcare professionals’ (HCPs) responses to DA.Methods: we adopted the READ approach to document analysis: Readying materials (including manually searching reports for the term ‘cancer’); Extracting data; Analyzing data; and Distilling findings (using thematic analysis). We framed results using the social-ecological model of violence.Results: we retrieved 24 DHR reports, which covered 27 domestic homicides/DA-related suicides. Victims had cancer diagnoses in 15/27 cases, perpetrators in 8/27, and both in 1/27. Three cases involved two homicides. Victims were mostly older (median 67). Most (19/24) domestic homicides/DA-related suicides occurred within 3 years of diagnosis, yet cancer HCPs rarely made explicit contributions to the DHR process. Our qualitative themes explain how: (1) cancer and DA affected each other; (2) professionals missed opportunities to identify and respond to DA (including because cancer masked DA indicators, turning down care and support offers were underrecognized indicators, and care was fragmented and non-holistic with insufficient information-exchange); and (3) cancer diagnoses were under-considered and misunderstood in the DHR process.Conclusions: since cancer masked DA indicators, professionals working with affected people and families should have a low threshold for concern. More explicit contributions to DHRs by cancer HCPs may improve understanding of this intersection and improve future practic
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