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The effect of chain extender symmetry, branching and hydrogen bonding capability on the morphology and mechanical properties of thermoplastic polyurethanes
No full textThe chemical architecture of chain extenders within thermoplastic polyurethanes (TPUs) has a marked effect on material properties. To evaluate the structure-property relationships within linear TPUs, three different chain extenders with varying chemical structure (i.e. symmetry, branching and hydrogen bonding capability) were used in the synthesis of three low T g semi-crystalline TPUs with low molecular weight (M n = 18 kDa). These copolymers were compared to a non-chain extended reference. Results showed that the architecture of the chain extender dictated the degree of hard-soft microphase separation and therefore the mechanical properties. A TPU without chain extender (PU-NC) was a brittle hard-soft phase mixed material. Incorporation of the branched asymmetrical chain extender, 1,2-propanediol (PU-PD), also resulted in a phase mixed material which was mechanically weak with low adhesive properties (lap shear max. stress = 1.0 ± 0.1 MPa). The use of the symmetrical linear chain extender 1,4-butanediol (PU-BD) afforded a hard-soft phase separated copolymer where the mechanical and adhesive performance obtained was as expected for such low molecular weight TPUs (E = 72 ± 8 MPa, lap shear max. stress = 2.1 ± 0.4 MPa). The copolymer with a symmetrical bisurea diol chain extender (PU-BU) also exhibited a hard-soft phase separated morphology, but with much higher tensile (E = 210 ± 16 MPa) and adhesive properties (lap shear max. stress = 4.4 ± 0.1 MPa) as a result of strong bidentate urea hydrogen bonding. Incorporating these non-covalent interactions into the chain extender provides a route to superior mechanical performance for TPUs with low molecular weight
Impact of Ageing on the Thermal and Rheological Properties of Conductive Mastics
Get PDFMastic plays a vital role in enhancing both cohesion and adhesion within asphalt mixtures, which are critical determinants of their short-term and long-term performance. This study investigates the influence of ageing on the thermal and rheological characteristics of asphalt mastics incorporating conductive fillers graphene, graphite, and magnetite as partial replacements for conventional limestone filler. Five mastic formulations, prepared using 100/150 penetration grade bitumen, were evaluated under virgin, short-term, and long-term ageing conditions. The inclusion of conductive fillers led to a 20–50% increase in thermal conductivity, with only moderate sensitivity to temperature variations from 5 °C to 40 °C. Although thermal conductivity decreased by up to 17% with ageing, the enhancements attributable to the fillers remained substantial. The conducting mastic also showed enhanced thermal stability and protection against overheating. Rheological analyses demonstrated notable increases in complex modulus (G*) as well as improvements in rutting and fatigue resistance, particularly in formulations containing up to 3% graphene. Importantly, even after long-term ageing, the conductive mastics exhibited stable viscoelastic behaviour and maintained Glover–Rowe (G-R) parameter values below critical cracking thresholds, indicating reduced susceptibility to age related cracking. These results highlight the potential of conductive fillers to enhance the thermal efficiency, mechanical performance and long-term durability of asphalt mastics, offering a viable strategy for improving pavement performance under varying service conditions
Behaviour of 3D Printed Al7075 Square Hollow Sections in Compression
Get PDFHigh strength Aluminium alloys feature low densities, high strength‐to‐stiffness ratio, large ductility range and high fracture toughness, all attractive features for applications in industries such as automotive, aerospace and construction. To date, little attention has been given to the performance of 3D‐printed high strength Aluminium alloys such as Al7075 due to the inherent challenges in the additive manufacturing process. In this context, the present study reports material (tensile) and stub column (compression) tests on additively manufactured (AM) Al7075 square hollow sections (SHS). Both material and SHS samples were manufactured by Direct Metal Laser Sintering (DMLS), a laser powder‐bed fusion (L‐PBF) sub‐technology that uses metal powder as feedstock and a laser to fuse the feedstock layer by layer. Three newly develop set of process parameters that had successfully led to crack free medium sized samples were employed in this study. The effect of post processing treatments on the mechanical properties of printed Al7075 samples is investigated through the application of two heat treatments and a Hot Isostatics Pressing (HIP) treatment. A total of 33 material samples were manufactured and tested in tension, 6 of which in their as built condition and 27 subject to the above post processing treatments. The tensile test results showed that the Al7075 samples manufactured using the new set of parameters used is unable to produce specimens which can then develop their full tensile resistance. Nine square hollow tubes were subsequently manufactured utilising a selected heat treatment and tested in compression. All tubes successfully develop good compression performance and primarily exhibit failure due to local buckling, which led to the formation of a yield‐line‐like pattern of cracks, ultimately resulting in the specimens' failure
Ontological Nuisance in Elite Discourse: Foreign Policy and the Populist Radical Right in Germany
Get PDFThis article calls for a research agenda which looks at narrative challenge and disruption from within, that is, within political elites. Merging ontological security studies (OSS) with insights from narrative studies, we introduce the idea of political elites as being split between disruptors and defenders of identity narratives. This is different from conventional accounts of OSS which usually and often implicitly attribute the role of ontological repairers to political elites. We argue that members of the elite sometimes intervene in political debates through disruptive language which challenges established identity narratives and pushes the boundaries of acceptable foreign policy discourse. We conceptualize this type of disruption as ontological nuisance: a predictably recurring disturbance to biographical narratives from within the narrating elite. The article illustrates ontological nuisance empirically by systematically analyzing how populist radical right parties (PRRPs) engage with elite narratives about foreign policy and identity. By foregrounding contestation in the discourse among political elites, we show how interventions by PRRPs can call into question the relative elite consensus across the political spectrum. Specifically, we show how articulations by the German radical right party Alternative für Deutschland (AfD) tap into fundamental pillars of the ongoing foreign policy discourse about the national “Self” (internal dimension), relations with “significant Others” (intersubjective dimension), and the nature of the international order (systemic dimension). In this way, opposition parties can shape the nature of the debate about biographical narratives without ever being in government
Linear stability of nanofluid boundary-layer flow over a flat plate
Get PDFThe linear stability of nanofluid boundary-layer flow over a flat plate is investigated using a two-phase formulation that incorporates the Brinkman (1952 J. Chem. Phys., vol. 20, pp. 571–581) model for viscosity along with Brownian motion (BM) and thermophoresis (TP), building upon the earlier work of Buongiorno (2006 J. Heat Transfer, vol. 128, pp. 240–250). Solutions to the steady boundary-layer equations reveal a thin nanoparticle concentration layer near the plate surface, with a characteristic thickness of O(Re−1/2Sc−1/3), for a Reynolds number Re and Schmidt number Sc. When BM and TP are neglected, the governing equations reduce to the standard Blasius formulation for a single-phase fluid, and the nanoparticle concentration layer disappears, resulting in a uniform concentration across the boundary layer. Neutral stability curves and critical conditions for the onset of the Tollmien–Schlichting (TS) wave are computed for a range of nanoparticle materials and volume concentrations. Results indicate that while the effects of BM and TP are negligible, the impact of nanoparticle density is significant. Denser nanoparticles, such as silver and copper, destabilise the TS wave, whereas lighter nanoparticles, like aluminium and silicon, establish a small stabilising effect. Additionally, the viscosity model plays a crucial role, with alternative formulations leading to different stability behaviour. Finally, a high Reynolds number asymptotic analysis is undertaken for the lower branch of the neutral stability curve
Investigating the Barriers Faced by Biomedical Science Undergraduates in Completing a Placement Year
Get PDFIntroduction: Research shows completing a placement year is associated with improved academic and employment outcomes. For Biomedical science courses, pathology placements allow completion of the Institute of Biomedical Science (IBMS) registration training portfolio and obtaining Health and Care Professions Council (HCPC) registration post-graduation. This study sought to identify the barriers biomedical science students across the West Midlands region of England face when completing a placement year, to identify strategies which promote inclusivity to overcome these barriers. Materials and Methods: Level 5 and Level 6 students from Aston, Coventry, Keele and Wolverhampton universities were invited to complete a questionnaire which included a mixture of Likert scale and free-text responses. A range of questions assessed student perceptions on the importance of placement opportunities, as well as identifying factors which were important when pursuing a placement year. Likert scale data was analysed quantitatively, and a Mann Whitney U or Kruskal Wallis test were used to infer significance, whereas free text responses were analysed using thematic analysis. Results: A total of 107 students completed the questionnaire. Students who declared a disability were less likely to undertake an unpaid placement compared to their peers (p = 0.013). Of those students who declared caring responsibilities, 33.3% chose not to apply for a placement year compared to 18.2% of those who did not have caring responsibilities (p = 0.020). Participants reported that funding was important when deciding whether to pursue a placement (88.8%). Thematic analysis revealed several recurring themes deterring student placement applications, including financial support and placement availability within their geographical area. Students valued the importance of professional recognition following the placement and the development of technical and transferable skills. Discussion: Many of the barriers are fuelled by financial constraints which deter students from applying to placement positions. Despite the need to increase the Biomedical Scientist workforce, the strategies to increase training opportunities are not well established. Equity in placement funding from centralised sources is key to ensuring Biomedical Scientists can excel in their professional careers. Through availability of funding, marginalised populations will have the same opportunities as their peers therefore producing more employable graduates to meet pathology workforce demands
German Technology, Caribbean Rum: Georg Stade and the Industrialization of Rum Production in Barbados, 1892-1898
No full textIn 1892, the German born and British naturalized engineer Georg Stade set up a modern rum factory in Barbados. Machinery, capital and technical staff came from Germany. The enterprise quickly established itself as the largest distillery on the island, pushing smaller competitors out of the market. It occupies this position up until today. The case study of technology transfer has so far not been researched, not least because some core primary sources are not publicly accessible. It is integrated into broader research on transnational entanglements between Germany, Britain and – for the first time – Barbados, questioning notions of the inherently ‘British’ nature of the Empire. Based on a broad empirical basis, the article argues that detailed case histories of mobile engineers and technology transfers can do much to explain the mechanics of nineteenth century globalization but are currently underrepresented in pertinent research. This is particularly relevant for Imperial Germany with its emerging technology and export sectors
Hydrogen/deuterium exchange mass spectrometry analysis of ribosome-nascent chain complexes to study protein biogenesis at the peptide level
No full textNascent proteins begin to fold during their synthesis, while still attached to the ribosome. The dynamic nature of ribosome–nascent chain complexes (RNCs) poses a challenge for conventional structural biology approaches, limiting our understanding of dynamic cotranslational events. Hydrogen–deuterium exchange mass spectrometry (HDX-MS) is a powerful label-free technique for studying the conformational equilibria and refolding of full-length proteins with peptide resolution. However, the large size of the ribosome and the need for stable, highly homogeneous samples have hindered the application of HDX-MS to RNCs. Here we present a strategy for analysing conformational dynamics and interactors of Escherichia coli RNCs using HDX-MS. High-quality RNCs are obtained through the gentle lysis of high-density cultures expressing uniformly stalled ribosomes, followed by ultracentrifugation and tag-based affinity purification. Peptide-resolution information on protein conformational dynamics is obtained by pulse deuterium labeling, quenching with an RNA-compatible low pH buffer and offline digestion with pepsin. Extensive data analysis with use of specific internal controls allows for the confident assignment of mass spectra to specific peptides, ensuring good coverage of the nascent chain and ribosomal proteins. This method provides a valuable complement to existing structural techniques such as cryo-electron microscopy and nuclear magnetic resonance, and enables detailed characterization of large, partially structured nascent chains and their interactions with the ribosomal proteins and molecular chaperones. The protocol takes 1–3 months, from sample preparation and data acquisition to data analysis, and requires standard expertise in cloning and protein purification and intermediate expertise in HDX-MS
Home Mealtimes in Kenya and Zambia: Recognising culturally grounded practices that foster healthy eating behaviours
Get PDFGlobally, mealtimes provide key insights into cultural and social values and practices. We examine mealtime environments and eating practices in two different African settings using quantitative observational and questionnaire data. Participating families (N = 80) were recruited from two rural locations in Zambia and Kenya. Results following descriptive analysis showed that meals are typically taken as a family in a sociable context, providing opportunities to nurture children’s positive behaviours. In both communities, mothers (71.25%) were most likely to be present and typically prepared meals and provided the food. We observed a few distractions being used during mealtimes, and children finished their food with little to no conflict. Plate sharing varied across the two sites and was more common in Zambia, where we also observed more traditional practices such as eating with hands (as opposed to cutlery) and sitting on mats on the ground (as opposed to seated on chairs or sofas). Overall, our findings suggest more similarities in the cultural and social values across the two African contexts despite slight differences in mealtime practices. In particular, positive mealtime behaviours (little food refusal, lack of conflict) were common across all contexts, regardless of the extent to which traditional practices (such as plate-sharing and sitting on the floor) were used. Findings align with Family Systems theory, which states that the family is understood best by conceptualizing it as a complex, dynamic, and changing collection of parts, subsystems, and family members
Empathy-Inspired Voice Companion Design for Older Adults
No full textThe rapid growth of the global ageing population highlights the urgent need for effective strategies to address key challenges, such as loneliness—a common issue with serious health consequences. Interventions that provide companionship by promoting emotional support, social connection, and active engagement have been shown to reduce loneliness, improve quality of life, and decrease health risks linked to social isolation. However, consistent access to human companionship is often limited by practical constraints, creating a need for sustainable alternative. In this context, recent advances in AI-driven voice assistants (VAs) have gained attention for their potential to support the well-being of older adults. Studies suggest that, over time, older adults may perceive VAs as companions, helping to ease feelings of loneliness and isolation. Despite this potential, current VAs are limited in their ability to function as true digital voice companions (VCs), mainly due to a lack of emotional depth and empathetic interaction. Research emphasises that a high level of expressed empathy is essential for older adults to perceive a VA as a genuine social companion. Yet, most existing systems lack sufficient empathy modelling, limiting their ability to build emotional connections. This paper contributes to ongoing efforts to enhance empathy in AI-based VCs. It offers a detailed review of key concepts, such as companionship, empathy, and the current state of empathetic VA technologies. Building on this analysis, the paper proposes a novel VC system design that integrates advanced empathy modelling to improve the emotional and social experiences of older adults through AI-enabled conversations
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