Switch on, switch off: stiction in nanoelectromechanical switches

We present a theoretical investigation of stiction in nanoscale electromechanical contact switches. We develop a mathematical model to describe the deflection of a cantilever beam in response to both electrostatic and van der Waals forces. Particular focus is given to the question of whether adhesive van der Waals forces cause the cantilever to remain in the ‘ON’ state even when the electrostatic forces are removed. In contrast to previous studies, our theory accounts for deflections with large slopes (i.e. geometrically nonlinear). We solve the resulting equations numerically to study how a cantilever beam adheres to a rigid electrode: transitions between free, ‘pinned’ and ‘clamped’ states are shown to be discontinuous and to exhibit significant hysteresis. Our findings are compared to previous results from linearized models and the implications for nanoelectromechanical cantilever switch design are discussed

Addressing current challenges in cancer immunotherapy with mathematical and computational modeling

The goal of cancer immunotherapy is to boost a patient's immune response to a tumor. Yet, the design of an effective immunotherapy is complicated by various factors, including a potentially immunosuppressive tumor microenvironment, immune-modulating effects of conventional treatments, and therapy-related toxicities. These complexities can be incorporated into mathematical and computational models of cancer immunotherapy that can then be used to aid in rational therapy design. In this review, we survey modeling approaches under the umbrella of the major challenges facing immunotherapy development, which encompass tumor classification, optimal treatment scheduling, and combination therapy design. Although overlapping, each challenge has presented unique opportunities for modelers to make contributions using analytical and numerical analysis of model outcomes, as well as optimization algorithms. We discuss several examples of models that have grown in complexity as more biological information has become available, showcasing how model development is a dynamic process interlinked with the rapid advances in tumor-immune biology. We conclude the review with recommendations for modelers both with respect to methodology and biological direction that might help keep modelers at the forefront of cancer immunotherapy development.Comment: Accepted for publication in the Journal of the Royal Society Interfac

Simultaneous measurement of multiple parameters of a subwavelength structure based on the weak value formalism

A mathematical extension of the weak value formalism to the simultaneous measurement of multiple parameters is presented in the context of an optical focused vector beam scatterometry experiment. In this example, preselection and postselection are achieved via spatially-varying polarization control, which can be tailored to optimize the sensitivity to parameter variations. Initial experiments for the two-parameter case demonstrate that this method can be used to measure physical parameters with resolutions at least 1000 times smaller than the wavelength of illumination

Capillary deformations of bendable films

We address the partial wetting of liquid drops on ultrathin solid sheets resting on a deformable foundation. Considering the membrane limit of sheets that can relax compression through wrinkling at negligible energetic cost, we revisit the classical theory for the contact of liquid drops on solids. Our calculations and experiments show that the liquid-solid-vapor contact angle is modified from the Young angle, even though the elastic bulk modulus (E) of the sheet is so large that the ratio between the surface tension γ and E is of molecular size. This finding establishes a new type of “soft capillarity” that stems from the bendability of thin elastic bodies rather than from material softness. We also show that the size of the wrinkle pattern that emerges in the sheet is fully predictable, thus resolving a puzzle noticed in several previous attempts to model “drop-on-a-floating-sheet” experiments, and enabling a reliable usage of this setup for the metrology of ultrathin films

Care staff perspectives of the role of music in the care of peopleliving with dementia

The rationale for this study was grounded in the current emphasis on developing non-pharmacological interventions for people living with dementia in the UK. The study investigated the common practice amongst care staff caring for people living with dementia to commission music activities as a recreational pastime. It examined staff perspectives on the value of these activities and the potential to develop the scope of therapeutic benefits that might simultaneously support the well-being of both the cared-for and the care-giver. It investigated personal and professional factors that might underpin inhibitions to staff training to facilitate music activities themselves and to staff exploring music as an education tool to develop creative and reflective practice. The study sought to generate original findings and to contribute to an evidence base to inform future practice. Method triangulation involved a questionnaire survey, telephone and face-to-face interviews, focus group discussions and participant observations. One hundred and ninety two participants took part in the study, comprising 149 care staff and 13 music practitioners who collectively worked in one or more of 27 care settings for older people in east Kent, 27 older people and three informal carers. The results showed that musicians and music practitioners were typically engaged by staff to deliver a fairly similar range of activities, around ten times per year on average. Practical barriers to staff taking part in these activities centred on issues of time-tabling and the challenges of balancing routine care-giving with non-routine activities. Psychological barriers appeared to be influenced by: cultural backgrounds; staff experiences of music education at school; preconceptions about musical skill; personal levels of confidence; social pressures; inter-staff relationships; and the relationships that staff have with visiting musicians. Barriers to formal training for staff to explore music as a catalyst for creative and reflective practice also included low or non-prioritisation of music in relation to their care-giving role and a belief that only musical staff would benefit

Mutation of ornithine transcarbamylase (H136R) in a girl with severe intermittent orotic aciduria but normal enzyme activity

Ornithine transcarbamylase deficiency shows X-linked inheritance with partial dominant expression in carrier females. We studied a girl with intermittent severe orotic aciduria and mild hyperammonaemia despite apparently normal enzyme activity in the liver. Sequence analysis of all 10 exons of the ornithine transcarbamylase gene revealed a novel a → G exchange (A502G) in exon 5 which changes His-136 to arginine in the ornithine transcarbamylase protein. Km values for carbamyl phosphate and ornithine determined in the patient's liver were comparable to those of wild-type enzyme but, unlike the wild-type enzyme, the mutant enzyme was unstable upon freezing and thawing. Electron microscopy revealed several giant mitochondria with paracrystalline inclusions. The results are compatible with the assumption that the mutant enzyme cannot form a functional complex with carbamyl phosphate synthetase and the ornithine carrier, resulting in decreased availability of substrates and diminished enzyme activity in viv

Measuring Markers of Liver Function Using a Micropatterned Paper Device Designed for Blood from a Fingerstick

This paper describes a paper-based microfluidic device that measures two enzymatic markers of liver function (alkaline phosphatase, ALP, and aspartate aminotransferase, AST) and total serum protein. A device consists of four components: (i) a top plastic sheet, (ii) a filter membrane, (iii) a patterned paper chip containing the reagents necessary for analysis, and (iv) a bottom plastic sheet. The device performs both the sample preparation (separating blood plasma from erythrocytes) and the assays; it also enables both qualitative and quantitative analysis of data. The data obtained from the paper-microfluidic devices show standard deviations in calibration runs and “spiked” standards that are acceptable for routine clinical use. This device illustrates a type of test useable for a range of assays in resource-poor settings.Chemistry and Chemical Biolog

Older gay men and active ageing: unpacking narratives

This chapter illuminates the experiences of gay men living in Malta who are a marginalised community within the ageing population. There is a growing area of empirical evidence that highlights the unique perspectives of lesbian, gay, bisexual, and transgender (LGBT) older people. As a result of historical, social and cultural contexts the ageing LGBT community have, until relatively recently, tended to be wholly invisible in gerontological and geriatric research (Giunta & Rowan, 2015; Harley & Teaster, 2016). The research evidence demonstrates that the intersection of multiple identities in LGBT ageing are combined with risk factors which include significant health disparities, heightened exposure to discrimination and victimisation and the fear of and potential challenges in accessing culturally responsive environments (Higgins et al., 2011; Hafford-Letchfield et al., 2018). Despite these adversities, LGBT older people have shown remarkable resilience and strengths which can be harnessed when engaging in discourses of active ageing (Hash & Rogers, 2013; Vella, 2013). Substantial achievements in legislative and human rights within many states in Europe and the increasing visibility of LGBT older people have certainly softened attitudes and promoted their recognition. However, the life stories, relationships and culture of older LGBT people can often be overlooked by those with responsibilities for promoting wellbeing in later life and providing direct support. The use of narrative and biographical approaches to inquiry within research with LGBT older people can provide a useful tool for engaging with these experiences, and for meaning-making to try to understand in greater depth the complexities and cultural experiences of growing old, so that strategies can be developed at all different levels and for different communities (Ray et al., 2008). Within gerontology, for example, narratives are used as direct agents for achieving social change by drawing on humanistic and critical studies of ageing. The study reported herein drew on a biographical narrative approach to explore the experiences of five older gay men living in Malta aged 45-60 years old and in particular how they negotiated their sexual identity and exercised agency in their relationships with others. This approach is particularly relevant because it can be woven into public policy, as it responds to issues of ageing faced at a societal level (Clark, 2011). Research into lived experience of individuals facilitates our understanding of both the inner and the outer worlds of “historically-evolving persons-in-historically-evolving situations” (Wengraf, 2001 : 1). A narrative approach to researching with older gay men can provide a structure for exploring the stories and sub-stories in relation to Maltese and broader policy discourse and for identifying a better foundation for practice. This chapter reviews the broader literature for clarification of who LGBT older people are and how their sexual and gender minority status influences social relationships from an interdisciplinary perspective. It captures some key demographic and epidemiological factors contributing to LGBT ageing experiences including those specific to the Maltese context. This public picture enables us to move to the private realm of ageing in the gay community as seen through the five individuals who participated in this study. The chapter concludes by proposing a number of recommendations for policies, principles and practices which have the potential to engender a more inclusive approach to active ageing in Malta

Anomalous density dependence of static friction in sand

We measured experimentally the static friction force $F_s$ on the surface of a glass rod immersed in dry sand. We observed that $F_s$ is extremely sensitive to the closeness of packing of grains. A linear increase of the grain-density yields to an exponentially increasing friction force. We also report on a novel periodicity of $F_s$ during gradual pulling out of the rod. Our observations demonstrate the central role of grain bridges and arches in the macroscopic properties of granular packings.Comment: plain tex, 6 pages, to appear in Phys.Rev.