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Tribofilm formation by several zinc dialkyl- and diaryldithiophosphate (ZDDP) solutions in thin film rolling-sliding conditions has been investigated. A primary, a secondary alkyl and a mixed alkyl ZDDP show similar rates of film formation and generate films typically 150 nm thick. Another secondary ZDDP forms a tribofilm much faster and the film is partially lost after extended rubbing. An aryl ZDDP forms a tribofilm much more slowly. The films all have a pad-like structure, characterised by flat pad regions separated by deep valleys. Three different techniques have been used to analyse the thickness and morphology of the tribofilms: spacer layer imaging (SLIM), scanning white light interferometry (SWLI) of the gold-coated film and contact mode atomic force microscopy (AFM). The SLIM method measures considerably thicker films than the other two techniques, probably because of lack of full conformity of a glass disc loaded against the rough tribofilm. No evidence of a highly viscous layer on top of the solid tribofilm is seen. SWLI and contact mode AFM measure similar film thicknesses. The importance of coating the tribofilm with a reflective layer prior to using SWLI is confirmed. As noted in previous work, the formation of a ZDDP tribofilm is accompanied by a marked shift in the Stribeck friction curve towards higher entrainment speed. For a given ZDDP this shift is found to correlate with the measured tribofilm roughness, proving that it results from the influence of this roughness on fluid entrainment in the inlet.

For the successful development and application of lubricants, a full understanding of their complex nanoscale behavior under a wide range of external conditions is required, but this is difficult to obtain experimentally. Nonequilibrium molecular dynamics (NEMD) simulations can be used to yield unique insights into the atomic-scale structure and friction of lubricants and additives; however, the accuracy of the results depend on the chosen force-field. In this study, we demonstrate that the use of an accurate, all-atom force-field is critical in order to; (i) accurately predict important properties of long-chain, linear molecules; and (ii) reproduce experimental friction behavior of multi-component tribological systems. In particular, we focus on n-hexadecane, an important model lubricant with a wide range of industrial applications. Moreover, simulating conditions common in tribological systems, i.e., high temperatures and pressures (HTHP), allows the limits of the selected force-fields to be tested. In the first section, a large number of united-atom and all-atom force-fields are benchmarked in terms of their density and viscosity prediction accuracy of n-hexadecane using equilibrium molecular dynamics (EMD) simulations at ambient and HTHP conditions. Whilst united-atom force-fields accurately reproduce experimental density, the viscosity is significantly under-predicted compared to all-atom force-fields and experiments. Moreover, some all-atom force-fields yield elevated melting points, leading to significant overestimation of both the density and viscosity. In the second section, the most accurate united-atom and all-atom force-field are compared in confined NEMD simulations which probe the structure and friction of stearic acid adsorbed on iron oxide and separated by a thin layer of n-hexadecane. The united-atom force-field provides an accurate representation of the structure of the confined stearic acid film; however, friction coefficients are consistently under-predicted and the friction-coverage and friction-velocity behavior deviates from that observed using all-atom force-fields and experimentally. This has important implications regarding force-field selection for NEMD simulations of systems containing long-chain, linear molecules; specifically, it is recommended that accurate all-atom potentials, such as L-OPLS-AA, are employed.

For the successful development and application of novel lubricant additives, a full understanding of their tribological behaviour at the nanoscale is required, but this can be difficult to obtain experimentally. In this study, nonequilibrium molecular dynamics simulations are used to examine the friction and wear reduction mechanisms of promising carbon nanoparticle friction modifier additives. Specifically, the friction and wear behaviour of carbon nanodiamonds (CNDs) and carbon nano-onions (CNOs) confined between α-iron slabs is probed at a range of coverages, pressures, and sliding velocities. At high coverage and low pressure, the nanoparticles do not indent into the α-iron slabs during sliding, leading to zero wear and a low friction coefficient. At low coverage and high pressure, the nanoparticles indent into, and plough through the slabs during sliding, leading to atomic-scale wear and a much higher friction coefficient. This contribution to the friction coefficient is well predicted by an expression developed for macroscopic indentation by Bowden and Tabor. Even at the highest pressures and lowest coverages simulated, both nanoparticles were able to maintain separation of the opposing slabs and reduce friction by approximately 75 % compared to when no nanoparticle was present, which agrees well with experimental observations. CNO nanoparticles yielded a lower indentation (wear) depth and lower friction coefficients at equal coverage and pressure with respect to CND, making them more attractive friction modifier additives. Potential changes in behaviour on harder and softer surfaces are also discussed, together with the implications that these results have in terms of the application of the studied nanoparticles as lubricants additives.

The transition to low-carbon energy systems requires efficient hydrogen production methods that minimise CO2 emissions. This study presents a techno-economic assessment of hydrogen production via methane pyrolysis, utilising a novel liquid metal bubble column reactor (LMBCR) designed for CO2-free hydrogen and solid carbon outputs. Operating at 20 bar and 1100 °C, the reactor employs a molten nickel-bismuth alloy as both catalyst and heat transfer medium, alongside a sodium bromide layer to enhance carbon purity and facilitate separation. Four operational scenarios were modelled, comparing various heating and recycling configurations to optimise hydrogen yield and process economics. Results indicate that the levelised cost of hydrogen (LCOH) is highly sensitive to methane and electricity prices, CO2 taxation, and the value of carbon by-products. Two reactor configurations demonstrate competitive LCOHs of 1.29$/kgH2 and 1.53 $ /kgH2, highlighting methane pyrolysis as a viable low-carbon alternative to steam methane reforming (SMR) with carbon capture and storage (CCS). This analysis underscores the potential of methane pyrolysis for scalable, economically viable hydrogen production under specificmarket conditions.

Background Currently there is insufficient evidence to inform the co-design of an exercise intervention as part of a multimodal intervention for renal cachexia. Co-design is an effective approach in collaborating with service users, carers and healthcare professionals to identify acceptable methods of improving delivery of care. The aim of this study was to use a co-design process to adapt an exercise intervention for patients with or at risk of renal cachexia as part of a cRCT for a multimodal intervention (NCT07107087) Methods The objectives were as follows: (1) To co-design a strategy to promote optimal recruitment and adherence to an exercise intervention for those with or at risk of renal cachexia receiving HD, (2) To produce a conceptual model in relation to the implementation of an exercise intervention for this group. Using Bird and colleagues generative co-design framework for healthcare innovation, we adopted three stages of pre-design, co-design, and post-design. Accordingly, three workshops were conducted to correspond to each stage and the operational decisions recorded in seven steps to report the iterative design of the exercise intervention. The co-design workshops took place in November 2023 ( n  = 10), June 2024 ( n  = 11) and February 2025 ( n  = 6). Public co-design partners from Northern Ireland and England representing Kidney Care UK, Northern Ireland Kidney Patients Association and Northern Ireland Kidney Research Fund, participated in the workshops. Results Contexts, intervention factors, mechanisms and outcomes which influence the uptake of, and adherence to, an exercise intervention within this patient population were identified. These included: the exercise intervention with an individualised and flexible approach; ensuring the exercise programme is manageable for patients receiving HD (session duration, timing and fistula awareness); ensuring the content of the exercise booklets is relatable and achievable (using household items rather than traditional exercise equipment and accrediting everyday activities as part of exercise log); providing support during the intervention (weekly telephone calls and progress tracking); and invitation to patients receiving HD considered most promising to encourage recruitment, sustain involvement and maximise impact from trusted healthcare professionals. Conclusion Using the generative co-design framework for healthcare innovation, a conceptual model has been produced to promote optimal recruitment and adherence to an exercise intervention as part of a multimodal intervention for renal cachexia management in practice. This has informed component design, the wider implementation plan and evaluation design of a multimodal intervention for renal cachexia. Plain English summary People living with kidney failure who receive haemodialysis (HD) can develop renal cachexia, a serious condition that causes muscle loss, weakness and poor quality of life. Exercise could help, but we do not yet know the best way to design and deliver an exercise programme that patients will find acceptable and manageable. Working with patients, carers and healthcare staff through co-design can help make sure any programme meets their needs. What we did We used a co-design approach to shape an exercise programme that will form part of a wider treatment package for people who have, or are at risk of, renal cachexia. Our goals were to: Work with patients, carers and subject experts to design the best ways to invite people to join the programme and to help them stick with it. Develop a clear model showing how an exercise programme for this group could be put into practice. We followed a three-stage co-design framework (pre-design, co-design and post-design). Three workshops were held in 2023, 2024 and 2025 with public partners from Northern Ireland and England, including representatives from Kidney Care UK, the Northern Ireland Kidney Patients Association and the Northern Ireland Kidney Research Fund. We recorded decisions at each stage to guide the ongoing design of the programme. What we found Participants identified what helps, or makes it harder, for people receiving HD to take part in and continue with an exercise programme. Key points included: The programme must be personalised and flexible. Exercise sessions need to be manageable for people receiving HD, considering session length, timing and fistula (dialysis access site) safety. Exercise materials should feel achievable, using everyday items and recognising daily activities as exercise. Ongoing support, such as weekly phone calls and tracking progress, can encourage people to stay involved. Invitations to join the programme should come from trusted healthcare staff, which may improve recruitment and continued participation. What this means By using a co-design approach, we developed a clear model to support recruitment and adherence to an exercise programme for renal cachexia. The results directly shaped how the programme will be built, delivered and evaluated as part of a wider multimodal treatment approach.

Background Kidney cachexia is a debilitating and under-recognised complication of advanced chronic kidney disease (CKD), characterised by unintentional weight loss, muscle wasting, inflammation, and reduced functional capacity. Its profound impact on morbidity, quality of life, and healthcare utilisation underscores the need for targeted, implementable interventions. The multicomponent implementation strategy for a multi-modal, integrated, exercise, anti-inflammatory, and dietary advice (MMIEAD) intervention seeks to address this gap. Guided by the practical, robust implementation, and sustainability model (PRISM), which incorporates reach, effectiveness, adoption, implementation, and maintenance (RE-AIM) outcomes, this study aims to ensure strong intervention–context alignment to support future scalability. Methods The MMIEAD model will be evaluated by determining patient eligibility and recruitment rates, identifying intervention retention and adherence, assessing key statistical and methodological considerations to inform optimal study design and data collection burden, conducting a qualitative process evaluation to examine intervention acceptability and practicality, and determining the feasibility of undertaking a definitive economic evaluation. Design This mixed-methods study consists of three phases. Phase 1 will deliver and evaluate a 12-week multimodal intervention using a feasibility cluster randomised controlled trial (cRCT) design. Phase 2 will undertake a qualitative process evaluation with healthcare practitioners (HCPs) and patients. Phase 3 will assess the feasibility of conducting a full economic evaluation. Participants Patients will be eligible if they have haemodialysis-dependent CKD stage 5 for more than 3 months, have experienced unintentional weight loss of at least 5% in the previous 12 months, or have a body mass index <20 kg/m 2 , and are aged over 18 years. HCPs will be eligible if they are members of the multidisciplinary healthcare team for more than 3 months and have had exposure to the study. Setting and randomisation The study will be conducted across four outpatient haemodialysis units in the UK. Two sites have been randomly allocated to the intervention group and two to the control group. Sample For phases 1 and 3, a total of 40 patient participants will be recruited (10 per intervention site and 10 per control site). For phase 2, qualitative data will be collected through interviews with approximately 15 patients and interviews or focus groups with 15 HCPs across all sites. Recruitment commenced on 08.09.25 following ethical approval (REC reference: 25/NI/0069). Discussion Using multi-method analyses informed by PRISM/RE-AIM dimensions, we will generate evidence on the feasibility, acceptability, and contextual fit of the MMIEAD intervention to prepare for a definitive UK-wide multi-site cRCT. Trial registration Trial registration number NCT07107087 (30 July 2025). https://clinicaltrials.gov/study/NCT07107087

Experiments over the last 50 years have suggested a tentative correlation between the surface (shear) viscosity and the stability of a foam or emulsion. We examine this link theoretically using small-amplitude capillary waves in the presence of a surfactant solution of dilute concentration, where the associated Marangoni and surface viscosity effects are modelled via the Boussinesq–Scriven formulation. The resulting integro-differential initial value problem is solved analytically, and surface viscosity is found to contribute an overall damping effect to the amplitude of the capillary wave with varying degree depending on the length scale of the system. Numerically, we find that the critical damping wavelength increases for increasing surface concentration but the rate of increase remains different for both the surface viscosity and the Marangoni effect.

Background Depression and anxiety are commonly experienced by people with chronic kidney disease (CKD). This study aimed to evaluate person- and service-level factors associated with depression and anxiety symptoms. We sought to also understand utilisation of mental health treatments and preferences for future psychological support. Methods An online survey recruited participants from six UK kidney services with varying levels of psychosocial provision. The survey was also advertised on social media. Participants completed screening questionnaires for depression and anxiety, alongside questions about mental health history, self-efficacy, treatment and support. The study included adults (18 years or older) living with CKD (stages 3b and above) or those receiving any form of Kidney Replacement Therapy (KRT), including individuals with a functioning kidney transplant. Eligible participants had to complete study measures and be proficient in reading and writing in either English or Welsh, as the survey was administered in these languages. This survey was developed with our Patient and Public Involvement group and was administered from January 2023 until 31st January, 2024 using Qualtrics and RedCap. Results Four hundred fifty-eight people completed the survey. Moderate-severe symptoms of depression and anxiety were 37.7% and 26.5%, respectively. Over 50% reported a history of diagnosed depression. In addition to depression, sleep problems and fatigue were identified as future support needs, with over a third indicating a preference for in-centre provision. In case-mix adjusted analysis, there was no variability in depression and anxiety symptoms across centres. Centre location and size were unrelated to symptoms. Age, female gender, current mental health treatments, self-efficacy and perceptions regarding opportunity for support, were associated with symptoms of depression and anxiety. In sub-analysis, there was a negative association between psychosocial staffing levels and depression symptoms. Conclusion Patient-related factors and behavioural characteristics were related to variation of these symptoms. There was little evidence of symptom variability across centres, although in a small sub-analysis, psychosocial provision showed a weak negative correlation with depression symptoms. Our findings highlight preferences of future needs which could be helpful for designing future research and service provision. Graphical abstract

IntroductionContrast induced acute kidney injury (CI-AKI), defined as a delta rise in creatinine of >26.5 umol/L or a 50% relative rise within 48 hours following iodinated contrast, is associated with considerable mortality risk. Our previous study of 301 patients undergoing contrast coronary angiography/percutaneous coronary intervention (PCI) highlighted a CI-AKI rate of 9.3% at index procedure. Few studies have looked at long term prognosis, adverse events and mortality following CI-AKI. Our objective is to assess the 5 year mortality rate following contrast coronary angiography and to evaluate independent risk factors and presence of index CI-AKI on 5 year mortality.MethodsA prospective cohort study in a single cardiology centre in the UK was carried out from 2011–2013, the results of which have been previously published.1 In total 2,519 patients were screened, 321 (12.7%) of which had CKD, in total 301 (93.7%) patients were recruited. Written consent was obtained from all patients. Patient demographics, CI-AKI risk factors, CKD stage and contrast dose at initial contrast angiography were recorded. A Mehran risk score was calculated for each patient. Samples for plasma NGAL, serum L-FABP, serum KIM-1, serum IL-18 and serum creatinine were previously collected pre and post contrast angiography and statistically analysed to assess prediction of CI-AKI as previously described.1 At 5 years following index contrast procedure we analysed for MACE and mortality by accessing up to date electronic medical records. Patient consent was granted to access medical notes. Statistical analysis was performed to assess the predicative ability of CI-AKI risk factors and Mehran risk score on 5 year mortality risk.ResultsAt 5 years follow up data was available for 292 (97%) of the original 301 patients. Type 2 diabetes, contrast volume, Mehran risk score, lower glomerular filtration rate (GFR) and use of intravenous fluids at index procedure were independently associated with five year mortality, p <0.05, table 1. A Mehran score ≥10 had an AUC of 0.67, p <0.001, sensitivity 65%, specificity 67%, PPV 41%, NPV 85%, RR 2.7 and OR 3.9 for five year mortality.Abstract 62 Table 1Baseline characteristics of patients with 5 year mortality DemographicAt 5 year follow up 76 (26.0%) of the total cohort of patient had died. Out of the 28 patients who developed CI-AKI at index contrast procedure 17 (60.7%) of the 28 patients had died at 5 years versus 58 (22.0%) of the 264 non CI-AKI patients (p<0.001), table 2, figure 1. At 5 year follow up MACE occurred in 20 (71.4%) of the 28 CI-AKI patients versus 78 (29.5%) of the 264 non CI-AKI patients.Abstract 62 Figure 1Percentage of 5 year mortality and MACE in CI-AKI vs non CI-AKI patientsAbstract 62 Table 2Comparison of 5 year mortality and MACE in baseline CI-AKI vs non CI-AKIBold - statistically significant (p<0.05)ConclusionThis study highlights that index CI-AKI is an independent risk factor for 5 year mortality and MACE. Several risk factors act independently as surrogate markers of CI-AKI prior to administration of iodinated contrast, many of which are incorporated in the Mehran CI-AKI risk score. Furthermore, these are associated with adverse incidents and mortality at five years following index contrast procedure. A combination approach of these findings, including novel biomarkers as previously demonstrated, will help to reduce risk and early identify CI-AKI to facilitate timely therapeutic intervention.ReferenceConnolly M, Kinnin M, McEneaney D, Menown I, Kurth M, Lamont J, et al. Prediction of contrast induced acute kidney injury using novel biomarkers following contrast coronary angiography. Quarterly Journal of Medicine - An International Journal of Medicine 2018:103–110.Conflict of Interestn/a

IntroductionChronic Kidney Disease (CKD) is a risk factor for contrast induced nephropathy (CIN), defined as an increase in serum creatinine of >25% from baseline or a delta rise of >26.5 µmol/L within 48 h. Early diagnosis of CIN requires validated novel biomarkers.MethodsA prospective observation study of 301 consecutive CKD patients undergoing elective invasive coronary angiography was performed. Low-osmolar contrast was standard. Demographics and Mehran risk score were recorded. Samples for plasma neutrophil gelatinase-associated lipocalin (NGAL), serum liver fatty acid-binding protein (L-FABP), serum kidney injury marker 1 (KIM-1), serum interleukin 18 (IL-18) and serum creatinine were taken at 0, 1, 2, 4, 6 and 48 h post contrast. Urinary NGAL and urinary cystatin C (CysC) were collected at 0, 6 and 48 h. Incidence of major adverse clinical events (MACE); acute myocardial infarction, heart failure hospitalisation, stroke and death were recorded at 1 year.ResultsCIN occurred in 28 (9.3%) patients and were independently associated with older age, diabetes, higher Mehran score, larger contrast volume and anaemia (p < 0.05). Logistic regression analysis showed diabetes, CKD stage and GFR to be most predictive of CIN. The predictive power of plasma NGAL was greatest at 6 h with median levels of 1,337 ng/ml in CIN patients compared with 931 ng/ml in non-CIN patients (p = 0.002, AUC 0.71, sensitivity 75.0%, specificity 96.1%, OR 2.86), see figure 1 and table 1. L-FABP performed best at 4 h with median levels of 10.7 ng/ml in CIN patients compared with 6.2 ng/ml in non-CIN patients, p = 0.001, AUC 0.69, sensitivity 42.3%, specificity 90.2%, OR 6.75, Figure 1 and Table 1. Median urinary NGAL was higher only after 48 h, 487 ng/ml in CIN patients versus 155 ng/ml in non-CIN patients, p = 0.008, AUC 0.63. CysC, IL-18 and KIM-1 were not predictive at any time-point (p > 0.05). A Mehran score ≥10 performed prior to procedure achieved an AUC of 0.65, p = 0.006. MACE occurred in 7 (25.0%) CIN patients but only 17 (6.2%) non-CIN patients (p < 0.001). CIN cases also had considerably higher mortality (10.7% compared to 3.3%, p = 0.037). Exploratory analysis showed that the combination of Mehran score >10, 6 hr NGAL and 4 hr L-FABP improved specificity to 96.7%. Figure 2 highlights a proposed pathway of how biomarkers could be used to identify CIN early and facilitate timely therapeutic intervention to reduce morbidity and mortality.Abstract 208 Figure 1Median plasma NGAL (ng/ml) and serum L-FABP (ng/ml) in AKI and non-AKIAbstract 208 Figure 2Proposed patient pathwaysAbstract 208 Table 1Summary of NGAL (ng/ml) and L-FABP (ng/ml) in AKI and non-AKI patientsSensit: sensitivity; specif: specificity; PPV: positive predictive value; NPV: negative predictive value; RR: relative risk; OR: odds ratioConclusions/implicationsMehran risk score, 6 h plasma NGAL and 4 h serum L-FABP performed best at early CIN prediction. CIN patients were four times more likely to develop MACE and had a trebling of mortality risk at 1 year. The implications of our results, translated to the design of safer elective coronary intervention services able to more efficiently manage the increasing volume of contrast studies, should be a key health priority for cardiac and renal services.