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Computer-assisted global analysis for vibro-impact dynamics: a reduced smooth maps approach
No full textWe present a novel approach for studying the global dynamics of a vibro-impact pair, that is, a ball moving in a harmonically forced capsule. Motivated by a specific context of vibro-impact energy harvesting, we develop the method with broader non-smooth systems in mind. The seeming complications of the impacts of the ball with the capsule are exploited as useful non-smooth features in selecting appropriate return maps. This choice yields a computationally efficient framework for constructing return maps on short-time realizations from the state space of possible initial conditions rather than via long-time simulations often used to generate more traditional maps. The different dynamics in sub-regions in the state space yield a small collection of reduced polynomial approximations. Combined into a piecewise composite map, these capture transient and attracting behaviors and reproduce bifurcation sequences of the full system. Further "separable'' reductions of the composite map provide insight into both transient and global dynamics. This composite map is valuable for cobweb analysis, which opens the door to computer-assisted global analysis and is realized via conservative auxiliary maps based on the extreme bounds of the maps in each subregion. We study the global dynamics of energetically favorable states and illustrate the potential of this approach in broader classes of dynamics
Ways of hoping: variegated hope among theatre freelancers during COVID-19
No full textHope has long been articulated as an intrinsic component of creative work, used to alleviate or justify the challenging precarity and narrow pathways to success in this sector. Two key articulations of hope have emerged: a deferred economy model in which present hardship is endured as a down-payment on specific future benefits, however ultimately unlikely; and a more dispersed understanding in which the hoped-for future is unspecified but affectively felt and mobilising in the present. In this article, we draw on qualitative data from an online survey and a policy event timeline developed as part of an 18-month research project with UK theatre freelancers during 2020 and 2021. Our qualitative analysis explores different ways of hoping among this group of creative workers at a time when futures and hopes were severely inhibited. Our findings propose that multiple forms of hope co-existed and intersected with practices of care, time and the self as mechanisms for navigating interrupted lives. The ‘variegated’ model of hope that we propose moves away from totalising theories of hope and helps in the understanding of hope as a force of resilience within cultural work, adding to existing calls to realise its political potential across cultural studies
Understanding the molecular interaction between unconventional T cell antigen receptors and their ligands; paving the way for future immuno-therapy
No full textThe ability of the human immune system to coordinate an effective immune response to stress is a complex and tightly regulated process that brings together many different molecules and mechanisms from multiple interconnecting systems. Understanding these mechanisms and pathways is key in developing novel therapeutic targets to combat the wide and ever-growing array of human diseases. Unconventional T cells and their ligands have recently been established as targets for immunotherapy in diseases such as cancer, primarily due to their major histocompatibility (MHC)-unrestricted nature and strong anti-tumour response. They are often described to bridge the gap between innate and adaptive immunity, due to their ability to display characteristics and phenotypes of both these responses. Despite the growing interest in unconventional immune responses, limited structural data currently represents a bottleneck in understanding them fully, thus hindering the development of successful treatments in the field.My work aims to investigate the hypothesis that CD1 antigen-presenting molecules display substantial conformational plasticity and are thus capable of presenting a wide variety of both stimulatory and inhibitory lipids to diverse TCRs. We utilise structural techniques to investigate the molecular mechanism underpinning CD1 plasticity and unconventional TCR recognition of two CD1 isoforms (CD1d and CD1c) presenting lipid ligands. We also develop an optimised pipeline to generate soluble, refolded gamma delta (γδ) TCRs that can be used to investigate CD1c recognition by the γδ TCR.This work demonstrates that CD1d can alternate its conformation within the vicinity of the lipid binding site, in a lipid cargo-dependent fashion. We display, using X-ray crystallography and molecular dynamics (MD) simulations, that CD1d can ‘relax’ and ‘constrict’ its lipid binding groove providing potential mechanisms for its ability to accommodate a range of lipid sizes and properties, a feature previously demonstrated in other CD1 isoforms. Furthermore, we use X-ray crystallography to produce structural data of a novel macaque CD1d structure, to explore the conservation of CD1d lipid-binding groove flexibility across species. We also demonstrate successful optimisation of a refolding and purification pipeline to produce soluble, stable CD1c-reactive γδ TCRs. Further to this, we utilise an in-house generated bead display system to confirm the CD1c-reactivity of the refolded γδ TCR. Our findings suggest CD1d shares the same conformational adaptability of other CD1 isoforms such as CD1b and CD1c, providing a potential molecular mechanism to explain CD1d’s ability to bind ligands that exceed the standard groove size. We also show that we can refold stable, CD1c-reactive γδ TCRs that can be used to explore the molecular mechanisms underlying the recognition of CD1c lipid complexes by the γδ TCR. These results can be used to build on a greater understanding of how CD1 antigen-presenting molecules can modulate their conformation to perform different functions, and they pave the way for further studies to unravel CD1 recognition by TCRs
Adulthood dietary and lifestyle patterns and risk of breast cancer: Global Cancer Update Programme (CUP Global) systematic literature review
No full textBackgroundAn increasing number of studies in recent years investigate various dietary and lifestyle patterns and associated breast cancer (BC) risk.ObjectivesThis study aimed to comprehensively synthesize and grade the evidence on dietary and lifestyle patterns and BC risk.MethodsDatabases were systematically searched up to 31 March, 2022, for evidence from randomised controlled trials and prospective cohort studies on adherence to a dietary pattern alone or in combination with lifestyle behaviors and incidence of or mortality from primary BC in adult females. Findings in all, premenopausal, and postmenopausal females were descriptively synthesized instead of meta-analyzed due to patterns heterogeneity. An independent Global Cancer Update Programme Expert Panel graded the strength of the evidence.ResultsA total of 84 publications were included. Results for patterns reflecting both a healthy diet and lifestyle were more consistent than for patterns that included diet only. There was strong-probable evidence that a priori World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) and American Cancer Society (ACS) dietary and lifestyle scores may reduce BC risk in all and postmenopausal females, whereas in premenopausal females, less evidence was found contributing to limited-suggestive grade. There was also a limited-suggestive evidence that adherence to the Healthy Lifestyle Index and other diet and lifestyle scores may reduce BC risk in postmenopausal females; a posteriori Western/Meat/Alcohol dietary patterns may increase BC risk in postmenopausal females; and Prudent/Vegetarian/Mediterranean dietary patterns may reduce BC risk in all females. For the remaining patterns, evidence was graded as limited-no conclusions.ConclusionsAdvice to adopt combined aspects of a healthy diet and lifestyle according to WCRF/AICR and ACS scores, encouraging a healthy weight, physical activity, alcohol and smoking avoidance, and a healthy diet rich in fruits, vegetables, (whole)grains and cereals and discouraging red and processed meat, can be proposed to females to lower BC risk.<p/
Nanocellulose-based Battery Electrodes
No full textModern wearable electronic devices are limited by the development of power sources that are mechanically flexible and safe at the same time. The development of flexible Li-ion batteries has been demonstrated; however, the remaining challenges include the re-design of all battery components in order to make each one flexible. Graphite electrodes are the most widely used anodes in Li-ion batteries, but their conventional structure suffers from rigidity and brittleness. Here, nanocellulose which is a natural biopolymer, is integrated with graphite and is used as component for the fabrication of inherently flexible electrodes, that also address battery sustainability concerns.In this work, flexible nanocellulose/graphite electrodes are manufactured, and their mechanical and electrochemical performance characteristics are examined via SEM, AFM, CV and EIS in Li-ion environment. The electrode can undergo a deformation of a 180o bending angle, trading-off 1/3 of conductivity. It is also shown that nanocellulose not only works as a flexible additive, but it can also promote ion mass transport, enabling ion access from the electrolyte, even to the bulk of the graphite electrode with reduced diffusion limitations. Parameters like nanocellulose content and nanoarchitecture are also correlated with fluctuations in ion mass transport. Molecular interactions between Li-ions and nanocellulose are examined by solid state NMR.Wearable devices where safety is of crucial importance would potentially benefit more by the implementation of beyond Li-ion technologies, like aluminum-graphite batteries which are inherently safe. In this case, nanocellulose/graphite electrodes are also tested in the Al-ion battery chemistry and are proven to improve mass transport properties by 17%. This demonstrates the versatility of nanocellulose in different battery chemistries.This work offers a perspective on the material-driven design of flexible nanocellulose/graphite electrodes, by investigating the contribution of nanocellulose to charge storage mechanisms and mechanical resilience, aligning with modern energy storage requisites. The use of nanocellulose/graphite electrodes in both Li-ion and Al-ion systems paves the way towards the diversification of the battery market
Advanced methodology for 103Rh NMR spectroscopy
No full textDespite the ubiquitous presence of rhodium complexes in catalysis, and the favourable 100% natural abundance of the spin-1/2 103Rh nucleus, 103Rh NMR parameters in the literature are notably sparse. This apparent dissonance is in part a consequence of the very low gyromagnetic ratio of 103Rh and hence its dismal NMR sensitivity. In this thesis, we aim to improve the accessibility of 103Rh NMR by developing advanced methodologies, which build upon existing techniques to improve 103Rh NMR sensitivity whilst simultaneously mitigating experimental hurdles associated with the practice. Furthermore, we will broaden the scope of 103Rh NMR by developing methodology to access and study the nascent singlet state in a 103Rh spin pair. To mitigate the poor sensitivity of the 103Rh nucleus, we demonstrate 1H enhanced 103Rh NMR methodology for the rapid acquisition of 103Rh NMR spectra and parameters; including 103Rh relaxation time constants over a range of magnetic fields. Moreover, a scheme is described for suppressing ringing artifacts, a common hurdle in the direct observation of low gyromagnetic ratio nuclei. We employ selective 18O labelling to break the magnetic equivalence of a 103Rh spin pair and facilitate the estimation of the 103Rh-103Rh J-coupling; as well as provide access to the 103Rh singlet state. We present the first measurement of an 18O induced 103Rh secondary isotope shift and report the first instance of singlet order generated in a 103Rh spin pair. The field dependence of both the relaxation of 103Rh longitudinal and singlet spin order is measured via field cycling experiments. We evaluate the rhodium formate paddlewheel complex as a vehicle for sustaining long lived 103Rh singlet order. Through the development of polarisation transfer techniques, we stand to greatly improve the accessibility, sensitivity and scope of the NMR technique for 103Rh nuclei in complexes that exhibit prerequisite heteronuclear scalar couplings
Variational Bayesian learning for 3D localization of extended targets in mmWave MIMO OFDM ISAC system
No full textVariational Bayesian learning (VBL)-aided extended target localization is conceived for orthogonal frequency division multiplexing (OFDM) based-mmWave MIMO systems using the OFDM integrated sensing and communication (ISAC) waveform. The proposed framework also considers the intercarrier interference (ICI) effects encountered in mobile scenarios and the clutter present in the environment. The proposed algorithm is based on a hybrid mmWave MIMO architecture, where the number of radio frequency (RF) chains is significantly lower than the number of antennas. A range, Doppler and angular (RDA)-domain representation of the target in three-dimensional (3D) space is conceived for accurate target parameter estimation. The proposed algorithm exploits the four-dimensional (4D) sparsity arising in the RDA domain of the scattering scene and employs the powerful VBL framework for the estimation of target parameters, such as elevation angle, azimuth angle, range and velocity. To handle a practical scenario where the actual target parameters typically deviate from their finite-resolution grid, a super-resolution-based improved off-grid VBL is developed for recursively updating the parameter grid, thereby progressively improving the estimates. We also determine the Cramér-Rao bound (CRB) and Bayesian CRB for the estimation of the target parameters in order to bound the estimation performance. Our simulation results validate the superior performance of the proposed approach in comparison to the existing algorithms
Reduced loss and bend sensitivity in hermetically-sealed hollow-core fiber gas cells using gas-induced differential refractive index
No full textHollow-core optical fiber (HCF) gas cells are an attractive option for many applications including metrology and non-linear optics due to the enhanced gas-light interaction length in a compact and lightweight format. Here, we report the first demonstration and characterization of a selectively pressurized, hermetically sealed hollow-core fiber-based gas cell, where the core is filled with a higher gas pressure than the cladding to enhance the optical performance. This differential gas pressure creates a gas-induced differential refractive index (GDRI) that is shown to enable significant modification of the HCF’s optical performance. Measurements on fabricated gas cells indicate a significant broadband reduction in attenuation of up to ∼10 dB (at 1100 nm) for a 24 m fiber length and an estimated pressure difference of ∼6 bar between the gas in the core and cladding regions. Additionally, using the fabricated gas cells, we show experimentally for the first time that GDRI can reduce macrobend loss in HCFs. Finally, long term (one year) measurements indicate no degradation in the gas cell performance due to gas permeation or gas exchange between the core and cladding regions, demonstrating the viability of using this gas cell format to implement a GDRI within a HCF to improve optical performance over an extended time period in an all-fiber format.</p
Empowering communities through citizen science in seaweed management
No full textBrown seaweed blooms (i.e. overgrowth of native seaweed) and invasions (i.e. introduction, establishment and dispersal of non-native seaweed with associated impacts) have affected 29% of the Earth's coast. For example, the proliferation of invasive pelagic sargassum across the tropical Atlantic poses significant environmental challenges and socio-economic problems to coastal communities. This study investigates the role of citizen science in enhancing local responses to nuisance seaweed. By integrating communities in Ghana, Mexico and Jamaica affected by invasive sargassum spp., and the UK affected by blooming ulva spp., the research uses four innovative approaches: (1) establishing permanent volunteer monitoring stations, (2) providing training on coastal monitoring, (3) co-creating educational content for schools and (4) forming an international network for experience sharing. The monitoring stations – Ghana (n = 7), Mexico (n = 7), Jamaica (n = 2) and the UK (n = 1) – enable communities to collect data by photographing their coastlines. These images provide valuable insights into seaweed seasonality and its localised impacts. Community engagement is deepened through tailored educational programs for students aged 11-18, fostering an understanding of seaweed dynamics and adaptive measures. The establishment of the Seaweed School and Community Network amplifies these efforts by connecting seaweed-affected regions, facilitating knowledge exchange and collaborative problem-solving. Our findings suggest that citizen science offers an intervention point to work with communities to help them learn about the problem and share knowledge of how to handle these challenges. It generates important data and more informed citizens can engage more effectively in co-developing locally-appropriate seaweed policy through this process. Given that other seaweed species are blooming/invading in coastal regions across the planet, the lessons being generated from community monitoring of sargassum and ulva have the potential to drive improved adaptations to nuisance algae globally
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