University of Cambridge

Urban tunnelling projects pose significant risks to the integrity of nearby structures due to ground movements induced by the excavation process. Embedded walls are commonly employed as a protective measure to mitigate these adverse effects. This paper presents a comprehensive numerical investigation into the effects of embedded walls on tunnelling-induced ground displacements, aiming to provide insights and recommendations for optimal embedded wall design. The study assesses the impact of varying embedded wall length and horizontal distance from the tunnel on soil settlement and horizontal displacements. Results demonstrate the complex interplay between embedded wall length, horizontal distance, and ground movement patterns, and the highly non-linear influence of key parameters on embedded wall efficiency (i.e. its ability to reduce settlements). A preliminary design chart is proposed to guide engineers in determining the appropriate horizontal location and depth of embedded walls to effectively reduce tunnelling-induced ground displacements. The findings contribute to a better understanding of embedded wall performance in the context of tunnelling and provide valuable guidance for the practical design and implementation of protective measures in urban areas.

The use of High-temperature superconducting (HTS) flux pumps has emerged as a promising approach for energizing HTS magnets. Compared to conventional power supplies, HTS flux pumps enable the wireless injection of a substantial DC current into a closed HTS magnet, allowing the magnets to operate in a persistent current mode. There are a lot of advantages to energize the HTS magnets in this manner. First of all, it avoids sophisticated power supplies and heavy current leads. Secondly, excessive cryogenic losses caused by thick warm-to-cold current leads can be reduced. Additional benefits include cost-effectiveness, reduced energy consumption, and a compact form factor. The most important parameter to evaluate the performance of the flux pump is its DC output voltage, which determines the charging capability. In this paper, we study both instantaneous and time-averaged DC output voltage for two most popular flux pumps – transformer-rectifier flux pump (TRFP) and high-Tc superconducting dynamo by a finite-element method model. Moreover, their working principles, structures and operation strategies are discussed. This work reveals characteristics and limitations of two flux pumps and is indicative for designing a high performance HTS flux pump for the specific application.

Stacked high-temperature superconducting (HTS) coated conductors (CCs) are preferred for trapped field magnets over HTS bulk due to their improved mechanical strength and shape flexibility. In superconducting machines, the demagnetisation phenomenon in HTS CCs is crucial as it affects the machine's magnetic field loading, affecting power and torque output. The stator slotting effect, common in conventional machines, can also influence TFMs made from HTS CCs in superconducting machines, leading to magnetic flux distortion and additional losses. To gain a comprehensive understanding of these influences, numerical analyses based on the finite element method have been conducted for different variants of a superconducting machine. Findings indicate that in the machine model: (1) a slotted stator yields higher trapped field values compared to a slotless stator, and (2) closed slots prove effectively in eliminating air gap harmonics. A final design with distributed winding and closed slots is recommended for reference in HTS motor development.

The high-temperature superconducting (HTS) Roebel tape is a latest developed concept of high-current and low-loss HTS cables for high-power AC applications. In this work, samples of Roebel tapes with single superconducting layer are manufactured, tested, modelled, and analysed. In the experiments, the critical current degradation and the transport AC losses are measured. In the simulation, with the 3D finite element method (FEM) models based on the T-A formulation, the transport AC losses are calculated and compared with the experimental data, and the current distribution is analysed in detail. This model is then used to simulate long HTS Roebel tapes which could be used in practice and calculate the transport AC losses. The losses are found over 30% lower than that of the normal HTS ReBCO tapes, which verifies the loss-reduction performance of the HTS Roebel tapes. This work provides both experimental and simulation proof of the advantage of the HTS Roebel tape as a high-current and low-loss HTS cable. It could potentially become the key to the compact fusion magnets which require high power density and suppressed losses.

This paper proposes a new power electronic packaging for discrete dies, namely Standard Cell which consists of a step-etched active metal brazed (AMB) substrate and a flexible printed circuit board (flex-PCB). The standard cell exhibits high thermal conductivity, complete electrical insulation, and low stray inductance, thereby enhancing the performance of SiC MOSFET devices. The standard cell has a stray power loop inductance of less than $\rm{1}~nH$ and a gate loop inductance of less than $\rm{1.5}~nH$ . The standard cell has a flat body with surface-mounting electrical connections on one side and direct thermal connections on the other. The use of flex-PCB die interconnection enables maximum utilization of source pads while providing a flexible gate-source connection and the converter PCB. This paper presents the design concept of the standard cell and experimentally validates its effectiveness in a converter system.

Despite decades of molecular research, phylogenetic relationships in Palearctic vipers (genus Vipera) still essentially rely on a few loci, such as mitochondrial barcoding genes. Here we examined the diversity and evolution of Vipera with ddRAD-seq data from 33 representative species and subspecies. Phylogenomic analyses of ∼ 1.1 Mb recovered nine major clades corresponding to known species/species complexes which are generally consistent with the mitochondrial phylogeny, albeit with a few deep discrepancies that highlight past hybridization events. The most spectacular case is the Italian-endemic V. walser, which is grouped with the alpine genetic diversity of V. berus in the nuclear tree despite carrying a divergent mitogenome related to the Caucasian V. kaznakovi complex. Clustering analyses of SNPs suggest potential admixture between diverged Iberian taxa (V. aspis zinnikeri and V. seoanei), and confirm that the Anatolian V. pontica corresponds to occasional hybrids between V. (ammodytes) meridionalis and V. kaznakovi. Finally, all analyzed lineages of the V. berus complex (including V. walser and V. barani) form vast areas of admixture and may be delimited as subspecies. Our study sets grounds for future taxonomic and phylogeographic surveys on Palearctic vipers, a group of prime interest for toxinological, ecological, biogeographic and conservation research.

This paper considers the control of AC-AC interlinking converters (ILCs) in a multi-grid network. We overview the control schemes in the literature and propose a passivity framework for the stabilization of multi-grid networks, considering both AC grid-following and AC grid-forming behavior for the ILC connections. We then analyze a range of AC/AC interlinking converter control methods derived from the literature and propose suitable controllers for this purpose including both AC grid-forming and grid-following behavior. The controller we propose is partially grid-forming; in particular, it is based on a combination of a grid-following and a grid-forming converter to improve the stability properties of the network. Simulation results and theoretical analysis confirm that the proposed ILC control designs are appropriate for the multi-grid network.

The statement of Theorem 1 in [1] should have read as follows.

Coefficients of thermal expansion (CTE) of various materials in packaging structure layers vary largely, causing significant thermomechanical stress in power electronic packages during operation. For wirebond-less SiC modules, the stress is even larger due to the structure's rigidity and the high Young's Modulus of SiC crystals. This paper takes a FPCB/die/AMB packaging stack as an example to prove the feasibility of floating die structure enabled by liquid metal (LM) fluidic connection. The CTE mismatch among the die, PCB and AMB substrate is decoupled by the LM layer without compromise of thermal and electrical conduction. Finite element analysis demonstrates a 56 reduction in von Mises stress of the device and more than 99 shear stress reduction at the FPCB-AMB interface, compared with a conventional rigid solder connection. Testing results show that LM-based packaging has similar thermal and electrical conduction and higher breakdown voltage when compared with the soldered counterpart. Accelerated thermal cycling aging tests validate the stability of the insulation ring for LM-based packaging, especially under high-temperature conditions. The feasibility of using LM fluidic interconnections for a floating die structure of SiC packaging is validated.

Objectives The impact of incident investigations in improving patient safety may be linked to the quality of risk controls recommended in investigation reports. We aimed to identify the range and apparent strength of risk controls generated from investigations into serious incidents, map them against contributory factors identified in investigation reports, and characterize the nature of the risk controls proposed. Methods We undertook a content analysis of 126 action plans of serious incident investigation reports from a multisite and multispeciality UK hospital over a 3-year period to identify the risk controls proposed. We coded each risk control against the contributory factor it aimed to address. Using a hierarchy of risk controls model, we assessed the strength of proposed risk controls. We used thematic analysis to characterize the nature of proposed risk controls. Results A substantial proportion (15%) of factors identified in investigation reports as contributing to serious incidents were not addressed by identifiable risk controls. Of the 822 proposed risk controls in action plans, most (74%) were assessed as weak, typically focusing on individualized interventions—even when the problems were organizational or systemic in character. The following 6 broad approaches to risk controls could be identified: improving individual or team performance; defining, standardizing, or reinforcing expected practice; improving the working environment; improving communication; process improvements; and disciplinary actions. Conclusions The identified shortfalls in the quality of risk controls following serious incident investigations—including a 15% mismatch between contributory factors and aligned risk controls and 74% of proposed risk controls centering on weaker interventions—represent significant gaps in translating incident investigations into meaningful systemic improvements. Advancing the quality of risk controls after serious incident investigations will require involvement of human factors specialists in their design, a theory-of-change approach, evaluation, and curation and sharing of learning, all supported by a common framework.

Individuals who belong to a sexual minority are at greater risk of adverse health and social outcomes. These effects are observed during adolescence when many mental health problems, such as depression, first emerge. Here, we used a network analytic approach to better understand the role that sexual minority status plays in the association between depression, interpersonal difficulties and substance use in a large sample of mid-adolescents. In doing so, we used data from 8017 fourteen year olds from the UK’s Millennium Cohort Study, of which 490 self-identified as belonging to a sexual minority. We found that sexual minority status was highly central in the network and connected to multiple adverse outcomes, sometimes directly and sometimes indirectly. The largest single association was between sexual minority status and depression, and this link mediated multiple negative associations with being in a sexual minority. The shortest path to drinking, poor social support and closeness with parents and victimization occurred via depression. The shortest path to smoking and drug use occurred via conduct problems. We also identified three distinct profiles of adverse outcomes among those belonging to a sexual minority, highlighting the heterogeneous nature of this group.

Despite the growing interest in using multimodal data to analyse students' actions in Computers‐Supported Collaborative Learning (CSCL) settings, studying teacher's orchestration load in such settings remains overlooked. The notion of classroom orchestration, and orchestration load, offer a lens to study the implications of increasingly complex technology‐supported learning environments on teacher performance. A combination of multimodal data may aid in understanding teachers' orchestration actions and, as a result, gain insights regarding the orchestration load teachers perceive in scripted CSCL situations. Studying teacher orchestration load in CSCL helps understand the workload teachers experience while facilitating student collaboration and assists in informing design decisions for teacher supporting tools. In this paper, we collect and analyse data from different modalities (i.e. electrodermal activity, observation notes, log data, dashboard screen recordings and responses to self‐reported questionnaires) to study teachers' orchestration load in scripted CSCL. A tool called X was used to deploy CSCL activities and a teacher‐facing dashboard was used to facilitate teachers in managing collaboration in real time. The findings of the study show the potential of multimodal data analysis in investigating and estimating the orchestration load experienced by teachers in scripted CSCL activities. Study findings further demonstrate factors emerging from multimodal data such as task type, activity duration, and number of students influenced teachers' orchestration load.

Biologically engineered nanomaterials give rise to unique and intriguing properties, which are not available in nature. The full‐realization of such has been hindered by the lack of robust and straightforward techniques to produce the required architectures. Here a new bottomup bionano‐engineering route is developed to construct nanomaterials using a guided assembly of collagen building blocks, establishing a lithographic process for three‐dimensional collagen‐based hierarchical micronano‐architectures. By introducing optimized hybrid electro‐hydrodynamic micronano‐lithography exploiting collagen molecules as biological building blocks to self‐assemble into a complex variety of structures, quasi‐ordered mimics of metamaterials‐like are constructed. The tailor‐designed engineered apparatus generates the underlying substrates with vertical orientation of collagen at controlled speeds. Templating these hierarchical structures into inorganic materials allows the replication of their network into periodic metal micronano‐assemblies. These generate substrates with interesting optical properties, suggesting that size‐and‐orientation dependent nanofilaments with varying degree of lateral order yield distinctly coloured structures with characteristic optical spectra correlated with observed colours, which varying diameters and interspacing, are attributable to coherent scattering by different periodicity of each fibrous micronano‐structure. The artificial mimics display similar optical characteristics to the natural butterfly wing's structure, known to exhibit extraordinary electromagnetic properties, driving future applications in cloaking, super‐lenses, photovoltaics and photodetectors.

Human‐induced environmental change has caused widespread loss of species that support important functions for ecosystems and society. For example, vertebrate scavengers contribute to the functional health of ecosystems and provide services to agricultural landscapes by removing carcasses and associated pests. Widespread extirpation of native Australian mammals since the arrival of Europeans in Australia has removed many scavenging species from landscapes, while scavenging mammals such as European red foxes (Vulpes vulpes) have been introduced. In much of Australia, squamate reptiles are the largest native terrestrial scavengers remaining, where large native mammals are extinct and conservation management is being undertaken to remove invasive mammals. The contribution of reptiles to scavenging functions is not well understood. In this study, we investigated the ecosystem functions provided by large reptiles as scavengers to better understand how populations can be managed to support ecosystem services. We investigated the ecosystem services provided by vertebrate scavengers in Australian coastal mallee ecosystems, focusing on the heath goanna (Varanus rosenbergi), the only extant native terrestrial scavenger in the region. We carried out exclosure experiments, isolating the scavenging activity of different taxonomic groups to quantify the contribution of different taxa to scavenging services, specifically the removal of rat carcasses, and its impact on the occurrence of agriculturally damaging blowflies. We compared areas with different native and invasive scavenger communities to investigate the impact of invasive species removal and native species abundance on scavenging services. Our results indicated that vertebrate scavenging significantly contributes to carcass removal and limitation of necrophagous fly breeding in carcasses and that levels of removal are higher in areas associated with high densities of heath goannas and low densities of invasive mammals. Therefore, augmentation of heath goanna populations represents a promising management strategy to restore and maximize scavenging ecosystem services.

Recently, lanthanide‐based 0D metal halides have attracted considerable attention for their applications in X‐ray imaging, light‐emitting diodes (LEDs), sensors, and photodetectors. Herein, lead‐free 0D gadolinium‐alloyed cesium cerium chloride (Gd³⁺‐alloyed Cs3CeCl6) nanocrystals (NCs) are introduced as promising materials for optoelectronic application owing to their unique optical properties. The incorporation of Gd³⁺ in Cs3CeCl6 (CCC) NCs is proposed to increase the photoluminescence quantum yield (PLQY) from 57% to 96%, along with significantly enhanced phase and chemical stability. The structural analysis is performed by density functional theory (DFT) to confirm the effect of Gd³⁺ in Cs3Ce1‐xGdxCl6 (CCGC) alloy system. Moreover, the CCGC NCs are applied as the active layer in UVPDs with different Gd³⁺ concentration. The excellent device performance is shown at 20% of Gd³⁺ in CCGC NCs with high detectivity (7.938 × 10¹¹ Jones) and responsivity (0.195 A W⁻¹) at ‐0.1 V at 310 nm. This study paves the way for the development of lanthanide‐based metal halide NCs for next‐generation UVPDs and other optoelectronic applications.

The intestinal barrier plays a crucial role in homeostasis, both by facilitating absorption of nutrients and fluids, and providing a tight shield to prevent the invasion by either pathogen or commensal microorganisms. Intestinal barrier malfunction is associated with systemic inflammation, oxidative stress, and decreased insulin sensitivity, which may lead to the dysregulation of other tissues. Therefore, a deeper understanding of physiological aspects related to an enhanced barrier function is of significant scientific and clinical relevance. The naked mole-rat has many unusual biological features, including attenuated colonic neuron sensitivity to acid and bradykinin, and resistance to chemical-induced intestinal damage. However, insight into their intestinal barrier physiology is scarce. Here, we observed notable macroscopic and microscopic differences in intestinal tissue structure between naked mole-rats and mice. Moreover, naked mole-rats showed increased number of larger goblet cells and elevated mucus content. In measuring gut permeability, naked mole-rats showed reduced permeability compared to mice, measured as transepithelial electrical resistance, especially in ileum. Furthermore, intestinal ion secretion induced by serotonin, bradykinin, histamine, and capsaicin was significantly reduced in naked mole-rats compared to mice, despite the expression of receptors for all these agonists. In addition, naked mole-rats exhibited reduced pro-secretory responses to the non-selective adenylate cyclase activator forskolin. Collectively, these findings indicate that naked mole-rats possess a robust and hard-to-penetrate gastrointestinal barrier, that is resistant to environmental and endogenous irritants. Naked mole-rats may therefore provide valuable insights into the physiology of the intestinal barrier and set the stage for the development of innovative and effective therapies.

Today, volcanic sulfur emissions into the atmosphere are measured spectroscopically from the ground, air and space. For eruptions prior to the satellite era, two main sulfur proxies are used, the rock and ice core records, as illustrated by Peccia et al. (2023, https://doi.org/10.1029/2023gl103334). The first approach is based on calculations of the sulfur content of the magma, while the second uses traces of sulfur deposited in ice. Both approaches have their limitations. For glaciochemistry, the volcano responsible for a sulfur anomaly is often unknown and the atmospheric pathway by which the sulfur reached the ice uncertain. The petrologic method relies, too, on uncertain estimates of eruption size and a number of geochemical assumptions that are hard to verify. A deeper knowledge of processes occurring both within magma bodies prior to eruption, and within volcanic plumes in the atmosphere is needed to further our understanding of the impacts of volcanism on climate.

This paper explores how linguistic data annotation can be made (semi-)automatic by means of machine learning. More specifically, we focus on the use of “contextualized word embeddings” (i.e. vectorized representations of the meaning of word tokens based on the sentential context in which they appear) extracted by large language models (LLMs). In three example case studies, we assess how the contextualized embeddings generated by LLMs can be combined with different machine learning approaches to serve as a flexible, adaptable semi-automated data annotation tool for corpus linguists. Subsequently, to evaluate which approach is most reliable across the different case studies, we use a Bayesian framework for model comparison, which estimates the probability that the performance of a given classification approach is stronger than that of an alternative approach. Our results indicate that combining contextualized word embeddings with metric fine-tuning yield highly accurate automatic annotations.

Surgical innovation in ophthalmology is impeded by the physiological limits of human motion, and robotic assistance may facilitate an expansion of the surgical repertoire. We conducted a systematic review to identify ophthalmic procedures in which robotic systems have been trialled, evaluate their performance, and explore future directions for research and development of robotic techniques. The Cochrane Library, Embase, MEDLINE, Scopus, and Web of Science were searched. Screening adhered to five criteria: (1) English language; (2) primary research article; (3) human patients; (4) ophthalmological surgery; and (5) robot-assisted surgery. Quality assessment was conducted with Joanna Briggs Institute Tools for Critical Appraisal. The study protocol was registered prospectively (PROSPERO ID CRD42023449793). Twelve studies were included. In comparative studies, there was no difference in the occurrence of ocular harms in robot-assisted procedures and conventional surgery. However, robotic assistance did not demonstrate consistent benefits over manual surgery in terms of effectiveness or practicality, likely reflecting the learning curve associated with these systems. Single studies indicated the potential of robotic assistance to improve the consistency of subretinal drug infusion and efficiency of instrument manipulation in vitreoretinal surgery. Proof-of-concept studies have demonstrated the potential of robotic assistance to facilitate procedures otherwise infeasible or impractical, and may broaden access to surgery. However, robot-assisted surgery has not yet demonstrated any significant benefits over standard surgical practice. Improving the speed and reducing perioperative requirements of robot-assisted surgery are particular priorities for research and innovation to improve the practicality of these novel techniques. This systematic review summarizes the potential and limitations of robotic systems for assisting eye surgery and outlines what is required for these systems to benefit patients and surgeons.