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Advanced pseudocapacitive performances of a Ti3C2Tx-ZnOHF/ZnO nanocomposite for energy storage applications
No full textThe growing demand for efficient and high-performance energy storage systems is driving the exploration of novel materials and composites. Traditional electrode materials often face limitations in terms of energy and power densities. This paper demonstrates novel spray-coated cathode electrode system composed of Ti3C2Tx MXene and zinc hydroxy fluoride/zinc oxide (ZnOHF/ZnO) nanostars (NSs) for energy storage applications in a neutral pH electrolyte. Optimized Ti3C2Tx-NSs electrodes exhibited superior specific capacitance, achieving 236 F g−1 at 5 mV s−1 in cyclic voltammetry (CV) and 139 F g−1 at 5 mV s−1 in galvanostatic charge-discharge (GCD) measurements, which is superior to bare Ti3C2Tx (115 F g−1 at 0.5 A g−1) and bare NSs (108 F g−1 at 0.5 F g−1) electrodes, used as reference. Additionally, an asymmetric Ti3C2Tx||Ti3C2Tx-NSs supercapacitor device achieved a specific capacitance of 147 F g−1 at 0.5 A g−1, an energy density Ed ~ 46 W h kg−1 at a power density Pd ~ 875 W kg−1, and the highest Pd ~ 16650 W kg−1 at Ed ~ 14 W h kg−1. These findings demonstrate that ZnO NSs combined with delaminated Ti3C2Tx MXene, hold a significant promise for efficient energy storage applications, leveraging the synergy between double-layer capacitance and pseudocapacitive effects
An analysis of the continuum hypothesis
No full textThis paper analyzes the Continuum Hypothesis, that the cardinality of a set of real numbers is either finite, countably infinite, or the same as the cardinality of the set of all real numbers. It argues (i) that the real numbers are as similar to the natural numbers as possible in the sense that the relationship between any general method of deciding membership of a set of real numbers and the cardinality of the set should be a natural generalization of the case of the same relationship in the case of a set of natural numbers; and (ii) that CH is a very strong choice principle that is maximally efficient as a principle for deciding whether a real number is in a set of real numbers in the sense that it is uniform in deciding membership for every real number in a countable number of steps. The approach taken is to formulate principles equivalent to or weaker than the Continuum Hypothesis and to use techniques from computer science (infinite binary search), information theory, and set theory to prove theorems that support theses (i) and (ii)
West London Healthy Home and Environment (WellHome) Study: Protocol for a Community-Based Study Investigating Exposures Across the Indoor-Outdoor Air Pollution Continuum in Urban Communities
No full textThe relationship between indoor air quality and public health remains under-researched. WellHome is a transdisciplinary community-based study that will engage with residents to co-design feasible and acceptable research to quantify air pollution exposure in 100 homes in West London and examine its potential to exacerbate asthma symptoms in children. Sampling strategies such as using air quality monitors and passive samplers placed in kitchens, children’s bedrooms, and living rooms, will be developed in collaboration with local ambassadors and participating households to measure multiple physical, chemical, microplastic, and biological contaminants. This will provide a comprehensive understanding of indoor air quality across the city’s socio-economic gradient. Other data collected will include housing types and tenure, ventilation practices, occupant behaviours, time-activity, and airway symptoms. Epidemiological analysis will examine air pollution exposure impacts on children’s respiratory health. The particulate mixture’s relative hazard will be evaluated in toxicity studies based on source profiles and activity patterns of participants, focusing on asthma exacerbation related pathways. The study’s findings will be communicated to participants through co-designed reports and inform evidence-based recommendations for reducing indoor air pollution in London and urban areas worldwide. By raising awareness and providing actionable insights, WellHome seeks to contribute to global efforts to improve the health and well-being of vulnerable communities.</jats:p
Procalcitonin use in febrile children attending European emergency departments: a prospective multicenter study
No full textBackground:
Studies on procalcitonin (PCT) for identifying sepsis were published as early as 1993 and since then, PCT has been the topic of over 8,500 studies. Several studies show PCT to be superior to CRP in differentiating invasive infections such as sepsis from viral infections, especially early in the disease course.
However, its actual use in clinical practice is poorly documented. Our aim was to study the use of PCT in febrile children attending the ED across Europe and compare this to the use of CRP.
Methods:
The MOFICHE/PERFORM study, a prospective multicenter study, took place at 12 European EDs in eight countries and included febrile children < 18 years. In this secondary analysis of nine participating EDs that used PCT, descriptive analyses were performed, describing the use of PCT in all febrile children and for different age groups, foci of fever and fever duration.
Results:
In total, 31,612 pediatric febrile episodes were available for analyses. Blood tests were performed in 15,812 (50.0%, range 9.6–92.6%)) febrile episodes. CRP was included in 98.3% of blood tests (range between hospitals 80–100%), while PCT was included in only 3.9% (range 0.1–86%).
PCT was most often performed in children below 3 months (12.0% versus 3.6% in older children, p < 0.001). PCT was used slightly more often in children with fever less than 24 h in comparison to children with a duration of fever ≥ 24 h (4.9% versus 3.4%, p < 0.001). Regarding clinical alarming signs, PCT was used most often in children with meningeal signs (7.0%) or a non-blanching rash (10.9%).
Conclusion:
Actual PCT use in febrile children at European EDs is limited and varies largely between hospitals. Possible explanations include lack of guidelines, limited availability, higher costs and lack of readiness to adapt new clinical strategies
Investigation of microstructure and mechanical properties of welds in wide stiffened panels from an innovative multi-container extrusion technology
No full textThe emerging multi-container extrusion, known for its notable advantage of low extrusion force requirements, offers an opportunity to produce profiles with wider cross-sections. However, the presence of intrinsic welding defects and their impact on the profile quality have not been properly studied, which limits its wider industrial application. This study aims to characterise the weld microstructures and mechanical properties of profiles produced through multi-container extrusion by conducting a series of consecutive extrusion tests under varying temperatures and speeds, followed by post-extrusion microstructural analysis and tensile tests. The findings reveal that longitudinal weld (L-weld), formed by bonding adjacent billets, becomes indistinguishable and exhibits a uniform microstructure similar to the matrix material. In addition, a pair of transverse welds (T-welds) are formed by bonding the current billet to the previous one during the consecutive extrusion process, with their gap narrowing along the extrusion direction. Microscopically, T-welds are distinct, with their width increasing with the number of consecutive extrusions, due to their differing microstructure compared to the matrix material. Macroscopically, T-welds demonstrate much lower welding quality compared with L-weld, as evidenced by all tensile specimens with welds fracturing at the T-weld without displaying the necking seen in specimens without welds. Furthermore, in specimens without welds, representing the matrix material area of the extruded profile, yield strength (YS) and ultimate tensile strength (UTS) are more sensitive to extrusion speed, while elongation is more affected by extrusion temperature
The scalable growth of high-performance nanostructured heterojunction photoanodes for applications in tandem photoelectrochemical-photovoltaic solar water splitting devices
No full textDue to their complementary absorption characteristics and band energy structure, the BiVO4-coated WO3 heterojunction architecture is commonly employed as a metal oxide photoanode for the water oxidation half-reaction. The energy level ordering results in a staggered heterojunction that can effectively separate photoexcited electrons into the WO3 layer towards the current collector and photoexcited holes into the BiVO4 layer towards the interface with the electrolyte. Chemical vapour deposition (CVD) is an upscalable technique for fabricating large-area thin films of a wide range of semiconductors with nanoscale control. The fluorine-doped tin oxide (FTO)-coated transparent conductive glass substrates used herein are mass-produced by the glass industry with atmospheric pressure CVD and so the entire photoelectrode could be produced in one production process on float glass panels. This work is a detailed study of the use of atmospheric pressure CVD to fully-fabricate high-performance BiVO4-coated WO3 nanostructures (500–2000 nm in length with 25–100 nm thick BiVO4 coatings) for photoelectrochemical (PEC) water splitting. Incident photon-to-current efficiency measurements were used to calculate optimal solar predicted photocurrents of 1.92 and 2.61 mA cm−2 (2.3% and 3.2% solar-to-hydrogen efficiency if coupled to a hypothetical photovoltaic providing 1.23 V) for WO3/BiVO4 heterojunction samples under front and back-illumination, respectively. The heterojunction showed more than additive improvements over the parent materials, with bare WO3 and BiVO4 samples showing 0.68 and 0.27 mA cm−2 and 0.50 and 0.87 mA cm−2 under front and back-illumination, respectively. Simulations of the current–voltage characteristics of tandem crystalline silicon photovoltaic modules coupled to the PEC devices were consistent with the solar predicted photocurrents. These promising results for BiVO4-coated WO3 nanoneedles fully-deposited by atmospheric pressure CVD enables future research into photoanodes amenable to large-area scale-up
Impact of magnetic ion substitution on the crystal structure of multiferroic Aurivillius phases
No full textThe five-layered (m = 5) Bi6Ti2.99Fe1.46Mn0.55O18 Aurivillius material is a rare example of a single-phase room temperature ferroelectric–ferrimagnetic multiferroic that shows promise for energy-efficient memory devices. Its ferrimagnetism is thought to derive from the natural partitioning of magnetic ions to the central perovskite layer, engendered by chemically driven lattice strains, together with ferromagnetic coupling via super-exchange mechanisms. Motivated by the expectation of an enhancement in magnetization with increased magnetic ion content, this study examines systematic B-site substitutions with the aim of increasing (from the current level of 40%) the proportion of magnetic ions within the structure. The solubility limits of magnetic cations in this structure and their influence on the superlattice layering are investigated. The studies of Aurivillius phase films on c-sapphire with composition Bi6TixFeyMnzO18 (B6TFMO; x = 2.3–3.2, y = 1.2–2.0, z = 0.3–0.9) demonstrated that above ∼46% of B-site magnetic cations, the m = 5 structure first rearranges into a mixed-phase material based on m = 5 and six-layered (m = 6) structures and eventually evolves into an m = 6 phase with 54% magnetic cations at the B-site. It is demonstrated that higher-layered Aurivillius homologs can be synthesized using aliovalent substitution, without requiring epitaxial growth or kinetically constrained methods. It is postulated that increasing the number of perovskite layers by forming the m = 6 structure facilitates the accommodation of additional magnetic cations at a lower average manganese oxidation state (+3.3) compared with an equivalent m = 5 stoichiometry (+4.0). While the minor out-of-plane ferroelectric response decreases as expected with increasing structural reorganization toward the m = 6 phase, the predominant in-plane piezoresponse remains unaffected by increased magnetic cation substitution. This work implies possibilities for enhanced magnetic properties in room temperature multiferroic materials, initiating the development of technologically viable ultralow-power multiferroic memory devices
ATHEENA: Automated Toolflow for Hardware Early-Exit Network Acceleration
No full textThe continued need for improvements in accuracy, throughput, and efficiency of Deep Neural Networks has resulted in a multitude of static parameter reduction methods, like quantisation and pruning, which leverage the custom architectures possible on FPGAs. However, the potential of these solutions is already well exploited, reaching the limits of what can be achieved by reducing the number or size of the parameters while still maintaining accuracy. We propose a shift of focus to input-dependent computation to improve efficiency and reduce the average compute required for inference. Early-Exit (EE) networks have become an increasingly popular way to implement dynamic parameter reduction by varying network depth, essentially customising the computation level according to the difficulty of an input at run-time.
We create Automated Toolflow for Hardware Early-Exit Network Acceleration (ATHEENA), an automated, open-source CNN-to-FPGA toolflow which utilises the probability of samples exiting early from EE networks to optimally allocate the limited resources of an FPGA to different sections of the network. This ultimately results in improved throughput. The toolflow uses the data-flow model of the existing fpgaConvNet tool, extended to support Early-Exit networks, as well as Design Space Exploration (DSE) to optimise the generated streaming architecture hardware with the goal of increasing throughput/reducing area while maintaining accuracy. To this end, we incorporate abstracted hardware models, based on Queueing Theory, to aid the DSE with a more accurate analysis of performance and resource requirements. This improves the robustness of the accelerator.
Experimental results on three different networks demonstrate a throughput increase of 2.00 to 3.12 times compared to an optimised baseline network implementation with no early exits. Additionally, the toolflow can achieve a throughput matching the same baseline with as low as 48% of the resources the baseline requires
Novel deep learning approaches for imaging, localisation and data post-processing in single molecule localisation microscopy
No full textThis thesis contributes to the field of Single Molecule Localisation Microscopy (SMLM) through three interconnected projects. Firstly, a novel method for 3D localisation is developed utilizing intrinsic optical aberrations, eliminating the need for specialized optical components while providing fast and computationally efficient z-localisation. We demonstrate the method is capable of reconstructing nuclear pores complexes with a performance comparable to alternative methodologies, but at a greatly reduced computational cost. Building on this, an improved autofocus system is developed which leverages the aforementioned 3D localisation tool, potentially surpassing existing solutions in accuracy and reliability. Lastly, the thesis explores an unsupervised clustering algorithm using Graph Neural Networks (GNN) for SMLM data clustering. Existing algorithms are shown to outperform the GNN in speed and ease of tuning within the targeted domain, and the work concludes by suggesting future research directions to adapt the GNN if a more complex domain could be found, thereby contributing to the ongoing advancement of SMLM techniques and their applications in biological imaging.Open Acces
Cortico-striatal contributions to behaviour
No full textHumans are capable of performing a wide range of movements. Some of these movements require extensive training to master, while others come as naturally as breathing. Understanding how movement is generated in the brain requires exploring the contributions of different brain areas across this spectrum of movements.
Recent work in the neural control of movement shows that neural activity is typically constrained to a lower-dimensional space known as the neural manifold. This perspective has provided significant insights into movement generation, yet much remains to be understood. In this thesis, we leverage this framework to uncover the contributions of the sensorimotor cortex and the striatum to behaviour generation.
This thesis is divided into two main projects:
- What factors shape the neural manifold?
- How do sensorimotor regions contribute to generating complex 'naturalistic' behaviour?
In the first project, we investigate the factors that shape the neural manifold. By combining neural population recordings from the motor cortex of monkeys, humans, and mice, as well as the mouse striatum, we demonstrate that neural manifolds are intrinsically nonlinear. The degree of nonlinearity is region-specific and increases with task complexity.
In the second project, we explore how the sensorimotor cortex and striatum contribute to movement during spontaneous and randomly perturbed running. Our findings show that these areas are engaged during both periods of running, but striatal neurons contain the most information about kinematics, particularly when the animal is being perturbed. This supports a growing body of research suggesting the striatum’s involvement in movement specification.
Overall, our work offers new perspectives on neural manifolds and emphasises the need to explore more complex 'naturalistic' tasks to truly understand how behaviour is generated.Open Acces