265 research outputs found
Shear Banding in Time-Dependent Flows of Complex Fluids
We explore theoretically the time-dependent rheological response of complex fluids to step stress, shear startup and strain ramp deformations. We study soft glassy materials and entangled polymeric materials above and below the glass transition using the scalar fluidity, soft glassy rheology (SGR), rolie-poly (RP), Giesekus and glassy polymer (GP) models. For each deformation we investigate fluid-universal, deformation specific criteria for the onset of linear instability to shear banding.
In step stress, the shear rate response of the RP and Giesekus models is qualitatively similar to experiment, but only in the RP model does significant transient shear banding arise. Motivated by experiments, we explore `creep' and `fluidisation' in the glass phase of the SGR model. Finally, we show the GP model has similar behaviour in step shear stress as it does in extensional loading; we also explain why strain hardening reduces the magnitude of transient shear banding.
In shear startup, we explore `elastic' and `viscous' contributions to linear instability to shear banding. We use this to explain: the range of shear rates for which time-dependent shear banding arises in the RP model; why no significant time-dependent shear banding arises associated with the stress overshoot in the Giesekus model; the occurrence of age-dependent transient shear banding in the scalar fluidity model; and also why strain hardening again decreases the magnitude of transient shear banding in the GP model.
Finally, we investigate stress relaxation in the RP model after strain ramps with rates that probe the chain stretch relaxation rate. We show that after `slow' ramps (relative to this rate) linear instability to heterogeneity arises for strain amplitudes greater than 1.7, and that `fast' ramps of the same amplitude result in a delayed onset of linear instability, provided convective constraint release is sufficiently inactive
Soft drinks and 'desire to drink' in preschoolers
Interest in soft drink consumption has increased following a dramatic rise in intake over recent years. Research to date has focused primarily on general trends in consumption or on understanding the mechanism by which soft drink consumption may be linked to weight gain. It is clear however that there is considerable individual variability in the extent to which soft drinks are consumed and factors potentially influencing intake have received little attention. This study examines how the Child Eating Behaviour Questionnaire (CEBQ) construct 'Desire to Drink' (DD) relates to drink consumption, preferences and BMI-SDS
Genetic and environmental determinants of children's food preferences
Omnivores have the advantage of a variety of food options but face a challenge in identifying foods that are safe to eat. Not surprisingly, therefore, children show a relative aversion to new foods (neophobia) and a relative preference for familiar, bland, sweet foods. While this may in the past have promoted survival, in the modem food environment it could have an adverse effect on dietary quality. This review examines the evidence for genetic and environmental factors underlying individual differences in children's food preferences and neophobia. Twin studies indicate that neophobia is a strongly heritable characteristic, while specific food preferences show some genetic influence and are also influenced by the family environment. The advantage of the malleability of human food preferences is that dislike of a food can be reduced or even reversed by a combination of modelling and taste exposure. The need for effective guidance for parents who may be seeking to improve the range or nutritional value of foods accepted by their children is highlighted
Perception of the ethical acceptability of live prey feeding to aquatic species kept in captivity.
Previous research into public perceptions of live prey feeding has been focused on terrestrial animals. The reasons for this likely relate to the difficulty humans have in being compassionate to animals who are phylogenetically distantly related. In order to test these assumptions, the general public (two groups; one who had just visited an aquarium; and one group who had just visited a zoo), aquarium professionals in the UK/US and terrestrial zoo animal professionals (UK) were investigated to see how they would differ in their responses when asked about feeding various live aquatic animals to one another. Likert based surveys were used to obtain data face to face and via online social media. Demographics in previous research identified a lower acceptance of live prey feeding by females, however in aquatic animals this was not reflected. Instead, separations in perception were seen to exist between participants dependent on whether they had just visited a zoo or aquarium, or worked with animals
The golden ticket: gaining in-person access to relatives in long-term care homes during the Covid-19 pandemic
Context: Governments made emergency declarations to restrict the presence of family carers in long-term care homes (LTCHs) as part of infection control measures during the pandemic. Within Canada, two visitor statuses were created: ‘essential’ to the health of the resident and ‘non-essential’ or ‘social visitor’, who were subject to additional restrictions. Objective: This study explored family carers’ experiences navigating in-person access to their relatives in LTCH during the pandemic. Methods: Using interpretive description, a sample of 14 family carers (nine daughters, five spouses) living in British Columbia, Canada, participated in in-depth interviews via video call about their experiences between March 2020 and June 2021. Findings: Analyses illustrated variability in carers’ visitor status across families and over time. Two key themes were identified: 1) “Fighting a Losing Battle” describes how reductionist attitudes and policies minimized the role of caregiving and resulted in traumatic disruptions in familial relationships; 2) “Who’s In and Who’s Out” captures inequities in how visitor status policies were applied. Limitations: Restrictions on conducting research during the pandemic resulted in a smaller sample of family carer participants. Implications: Findings highlight the patchwork implementation of visitor policies over the initial 17 months of the pandemic and the precarious space family carers continue to occupy within the LTC sector. Future research should focus on formalising support for family presence during public health emergencies
Collaborative Writing as Bio‐Digital Quilting: A Relational, Feminist Practice Towards “Academia Otherwise”
In this article, we explore how quilted poetry as methodology, through the practice of collaborative writing, can help us to attune to and think with what is un/seen, un/heard, and un/spoken in our bio‐digital ways of working, as a way of resisting normative, exploitative practices in the neoliberal academia. We are a group of academics with different journeys and localities, connected by a common interest in the effects of boundaries, the dynamics of power, and the desire to do things differently. Drawing on our daily mundane encounters with/in both virtual and physical spaces of academia, including Teams meetings, Outlook emails, Google documents, and Miro board collaborations, we write quilted poetry with fragments of precarious matter: silences, messages, rhythms, feelings, and materialities. We attend to the entanglement of our bodies and their enmeshment in technology and share how bringing relational, feminist theories and the bio‐digital together has helped us to both materialise new patterns of relations and enact a more ethical approach to working in academia
Common genetic architecture underlying young children's food fussiness and liking for vegetables and fruit
Background: Food fussiness (FF) is common in early childhood and is often associated with the rejection of nutrient-dense foods such as vegetables and fruit. FF and liking for vegetables and fruit are likely all heritable phenotypes; the genetic influence underlying FF may explain the observed genetic influence on liking for vegetables and fruit. Twin analyses make it possible to get a broad-based estimate of the extent of the shared genetic influence that underlies these traits. Objective: We quantified the extent of the shared genetic influence that underlies FF and liking for vegetables and fruit in early childhood with the use of a twin design. Design: Data were from the Gemini cohort, which is a populationbased sample of twins born in England and Wales in 2007. Parents of 3-y-old twins (n = 1330 pairs) completed questionnaire measures of their children's food preferences (liking for vegetables and fruit) and the FF scale from the Children's Eating Behavior Questionnaire. Multivariate quantitative genetic modeling was used to estimate common genetic influences that underlie FF and liking for vegetables and fruit. Results: Genetic correlations were significant and moderate to large in size between FF and liking for both vegetables (20.65) and fruit (20.43), which indicated that a substantial proportion of the genes that influence FF also influence liking. Common genes that underlie FF and liking for vegetables and fruit largely explained the observed phenotypic correlations between them (68-70%). Conclusions: FF and liking for fruit and vegetables in young children share a large proportion of common genetic factors. The genetic influence on FF may determine why fussy children typically reject fruit and vegetables
Alterations in PTEN and PIK3CA in colorectal cancers in the EPIC Norfolk study: associations with clinicopathological and dietary factors.
BACKGROUND: The PTEN tumour suppressor gene and PIK3CA proto-oncogene encode proteins which contribute to regulation and propagation of signal transduction through the PI3K/AKT signalling pathway. This study investigates the prevalence of loss of PTEN expression and mutations in both PTEN and PIK3CA in colorectal cancers (CRC) and their associations with tumour clinicopathological features, lifestyle factors and dietary consumptions. METHODS: 186 adenocarcinomas and 16 adenomas from the EPIC Norfolk study were tested for PTEN and PIK3CA mutations by DNA sequencing and PTEN expression changes by immunohistochemistry. Dietary and lifestyle data were collected prospectively using seven day food diaries and lifestyle questionnaires. RESULTS: Mutations in exons 7 and 8 of PTEN were observed in 2.2% of CRC and PTEN loss of expression was identified in 34.9% CRC. Negative PTEN expression was associated with lower blood low-density lipoprotein concentrations (p = 0.05). PIK3CA mutations were observed in 7% of cancers and were more frequent in CRCs in females (p = 0.04). Analysis of dietary intakes demonstrated no link between PTEN expression status and any specific dietary factor. PTEN expression negative, proximal CRC were of more advanced Dukes' stage (p = 0.02) and poor differentiation (p < 0.01). Testing of the prevalence of PIK3CA mutations and loss of PTEN expression demonstrated that these two events were independent (p = 0.55). CONCLUSION: These data demonstrated the frequent occurrence (34.9%) of PTEN loss of expression in colorectal cancers, for which gene mutations do not appear to be the main cause. Furthermore, dietary factors are not associated with loss of PTEN expression. PTEN expression negative CRC were not homogenous, as proximal cancers were associated with a more advanced Dukes' stage and poor differentiation, whereas distal cancers were associated with earlier Dukes' stage.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
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