Inlet protein aggregation: a new mechanism for lubricating film formation with model synovial fluids.

This paper reports a fundamental study of lubricant film formation with model synovial fluid components (proteins) and bovine serum (BS). The objective was to investigate the role of proteins in the lubrication process. Film thickness was measured by optical interferometry in a ball-on-disc device (mean speed range of 2-60 mm/s). A commercial cobalt-chromium (CoCrMo) metal femoral head was used as the stationary component. The results for BS showed complex time-dependent behaviour, which was not representative of a simple fluid. After a few minutes sliding BS formed a thin adherent film of 10-20 nm, which was attributed to protein absorbance at the surface. This layer was augmented by a hydrodynamic film, which often increased at slow speeds. At the end of the test deposited surface layers of 20-50 nm were measured. Imaging of the contact showed that at slow speeds an apparent 'phase boundary' formed in the inlet just in front of the Hertzian zone. This was associated with the formation of a reservoir of high-viscosity material that periodically moved through the contact forming a much thicker film. The study shows that proteins play an important role in the film-forming process and current lubrication models do not capture these mechanisms

Colloidal suspension simulates linear dynamic pressure profile

Missile nose fairings immersed in colloidal suspension prepared with various specific gravities simulate pressure profiles very similar to those encountered during reentry. Stress and deflection conditions similar to those expected during atmospheric reentry are thus attained in the laboratory

Patients presenting to an acute general hospital with acute mental health needs. A retrospective observational cohort study

Objectives To examine the numbers and patterns of patients presenting to an urban acute general hospital with acute mental health presentations and to further investigate any variation related to the COVID-19 pandemic. Design Retrospective observational cohort study. Setting An urban acute general hospital in London, UK, comprising of five sites and two emergency departments. The hospital provides tertiary level general acute care but is not an acute mental health services provider. There is an inpatient liaison psychiatry service. Participants 358 131 patients attended the emergency departments of our acute general hospital during the study period. Of these, 14 871 patients attended with an acute mental health presentation. A further 14 947 patients attending with a physical illness were also noted to have a concurrent recorded mental health diagnosis. Results Large numbers of patients present to our acute general hospital with mental health illness even though the organisation does not provide mental health services other than inpatient liaison psychiatry. There was some variation in the numbers and patterns of presentations related to the COVID-19 pandemic. Patient numbers reduced to a mean of 9.13 (SD 3.38) patients presenting per day during the first ‘lockdown’ compared with 10.75 (SD 1.96) patients per day in an earlier matched time period (t=3.80, p<0.01). Acute mental health presentations following the third lockdown increased to a mean of 13.84 a day. Conclusions Large numbers of patients present to our acute general hospital with mental health illness. This suggests a need for appropriate resource, staffing and training to address the needs of these patients in a non-mental health provider organisation and subsequent appropriate transfer for timely treatment. The COVID-19 pandemic and the resulting lockdowns have resulted in variation in the numbers and patterns of patients presenting with acute mental health illness but these presentations are not new. Considerable work is still needed to provide integrated care which addresses the physical and mental healthcare needs of patients presenting to acute and general hospitals

Mitochondrial Dna Replacement Versus Nuclear Dna Persistence

In this paper we consider two populations whose generations are not overlapping and whose size is large. The number of males and females in both populations is constant. Any generation is replaced by a new one and any individual has two parents for what concerns nuclear DNA and a single one (the mother) for what concerns mtDNA. Moreover, at any generation some individuals migrate from the first population to the second. In a finite random time $T$, the mtDNA of the second population is completely replaced by the mtDNA of the first. In the same time, the nuclear DNA is not completely replaced and a fraction $F$ of the ancient nuclear DNA persists. We compute both $T$ and $F$. Since this study shows that complete replacement of mtDNA in a population is compatible with the persistence of a large fraction of nuclear DNA, it may have some relevance for the Out of Africa/Multiregional debate in Paleoanthropology

A low friction, biphasic and boundary lubricating hydrogel for cartilage replacement

Partial joint repair is a surgical procedure where an artificial material is used to replace localised chondral damage. These artificial bearing surfaces must articulate against cartilage, but current materials do not replicate both the biphasic and boundary lubrication mechanisms of cartilage. A research challenge therefore exists to provide a material that mimics both boundary and biphasic lubrication mechanisms of cartilage. In this work a polymeric network of a biomimetic boundary lubricant, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), was incorporated into an ultra-tough double network (DN) biphasic (water phase + polymer phase) gel, to form a PMPC triple network (PMPC TN) hydrogel with boundary and biphasic lubrication capability. The presence of this third network of MPC was confirmed using ATR-FTIR. The PMPC TN hydrogel had a yield stress of 26 MPa, which is an order of magnitude higher than the peak stresses found in the native human knee. A preliminary pin on plate tribology study was performed where both the DN and PMPC TN hydrogels experienced a reduction in friction with increasing sliding speed which is consistent with biphasic lubrication. In the physiological sliding speed range, the PMPC TN hydrogel halved the friction compared to the DN hydrogel indicating the boundary lubricating PMPC network was working. A biocompatible, tough, strong and chondral lubrication imitating PMPC TN hydrogel was synthesised in this work. By complementing the biphasic and boundary lubrication mechanisms of cartilage, PMPC TN hydrogel could reduce the reported incidence of chondral damage opposite partial joint repair implants, and therefore increase the clinical efficacy of partial joint repair. Statement of Significance This paper presents the synthesis, characterisation and preliminary tribological testing of a new biomaterial that aims to recreate the primary chondral lubrication mechanisms: boundary and biphasic lubrication. This work has demonstrated that the introduction of an established zwitterionic, biomimetic boundary lubricant can improve the frictional properties of an ultra-tough hydrogel. This new biomaterial, when used as a partial joint replacement bearing material, may help avoid damage to the opposing chondral surface—which has been reported as an issue for other non-biomimetic partial joint replacement materials. Alongside the synthesis of a novel biomaterial focused on complementing the lubrication mechanisms of cartilage, your readership will gain insights into effective mechanical and tribological testing methods and materials characterisation methods for their own biomaterials

The effect of lubricant supply and frequency upon the behaviour of EHD films subjected to vibrations

Machine elements such as rolling element bearings or gears often experience vibrations due to for example geometrical inaccuracies, shock loading, rotating unbalanced masses, and others. These machine elements rely on a very thin lubricant film to protect the metallic surfaces from direct contact and eventual damage. Rapid variation of load in elastohydrodynamic contacts it is influenced by the so-called squeeze film effect, however, when both entrainment and squeeze are present, the conditions of film formation are more complex. It is expected that the lubricant film thickness is influenced by the amplitude and frequency of the vibrations. At the same time, as it is known that the film thickness is established in the inlet of the contact, it is equally important to evaluate what is the role played by the supply of lubricant to the contact under oscillatory conditions. To date there are not many studies on the effect of the oscillatory motion parameters upon the behaviour of the lubricant film. In this study the focus is on the effect of the frequency of vibrations and the supply of lubricant upon the film thickness

Parental decision making about safer sleep practices: A qualitative study of the perspectives of families with additional health and social care needs

\ua9 2024 Barrett et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Introduction Despite a decline in Sudden Unexpected Death in Infancy in the UK since 2004, inequalities have widened with higher rates among families from deprived backgrounds and those known to child protection services. Almost all cases involve parents who had engaged in unsafe sleeping practices despite awareness of safer sleeping advice. Objective To understand the perspectives surrounding safer sleep of families supported by statutory child protection agencies, and use behavior change theory to inform how approaches to providing safer sleep advice to these families may be modified. Participants and setting We interviewed 14 mothers, 2 fathers and one grandmother, who had recent contact with child protection services in northeast England. Methods In-depth, semi-structured interviews, with purposive sampling. The COM-B model (Capability, Opportunity, and Motivation) structured our analysis. Results Parents described how anxiety, sleep deprivation, settling infants, illness, and a desire to bond with infants influence their decision making about sleep. Parents valued credible, trusted sources and understanding how safer sleep practices protect infants. Responses to questions about \u27out of routine\u27 situations suggested social pressures surrounding routines and \u27good parenting\u27 may preclude parents from acknowledging risks and planning for these situations. Conclusion Open conversations tailored to the needs of families, focused upon understanding why and when parent(s) do or do not follow safer sleep guidance seem a promising way of promoting safer sleep practices. Safer sleep discussions with these families are likely to be best delivered as part of wider infant care by professionals who have an established and continuing trusting relationship with parents. While advice and information should be provided by any professional in contact with the family with the necessary expertise, sensitive conversations around sleeping practices, particularly co-sleeping, may be more easily facilitated by professionals where the statutory responsibility for safeguarding is less apparent

A Behaviour Change Analysis of Safer Sleep Interventions for Infants at Risk of Sudden and Unexpected Death

\ua9 2024 The Authors. Child Abuse Review published by Association of Child Protection Professionals and John Wiley &amp; Sons Ltd.Rates of sudden unexpected death in infancy have been found to occur disproportionately amongst families living in the most deprived neighbourhoods. This suggests that standard safer sleep messaging may not be effective for this population and that research is required to identify ways of working that are better associated with behavioural change in parents with children at increased risk of SUDI. In this study, we aimed to explore the behavioural change components and mechanisms of action of safer sleep interventions for families with children at increased risk of SUDI. We conducted an analysis of the literature on safer sleep interventions using the COM-B model, Theoretical Domains Framework and Behavioural Change Technique Taxonomy. All interventions targeted parents\u27 capability; 15 interventions targeted parents\u27 opportunity; and six interventions targeted parents\u27 motivation to engage in safer sleep practices. Nineteen behavioural change techniques were identified. The focus of practitioners may need to shift from solely the delivery of safer sleep information towards working with parents to understand their capability, opportunity and, in particular, motivation to engage in safer sleep practices, identified as being a key driver of behaviour in this population

Flow-driven transition and associated velocity profiles in a nematic liquid-crystal cell

S. A. Jewell, S. L. Cornford, F. Yang, P. S. Cann, and J. R. Sambles, Physical Review E, Vol. 80, article 041706 (2009) "Copyright © 2009 by the American Physical Society."The alignment properties and distribution of flow speed during Poiseuille flow through a microchannel of a nematic liquid crystal in a cell with homeotropic surface alignment has been measured using a combination of conoscopy, fluorescence confocal polarizing microscopy, and time-lapse imaging. Two topologically distinct director profiles, with associated fluid velocity fields, are found to exist with the preferred state dictated by the volumetric flow rate of the liquid crystal. The results show excellent agreement with model data produced using the Ericksen-Leslie nematodynamics theory