1,405 research outputs found

    A modified Oster-Murray-Harris mechanical model of morphogenesis

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    There are two main modeling paradigms for biological pattern formation in developmental biology: chemical prepattern models and cell aggregation models. This paper focuses on an example of a cell aggregation model, the mechanical model developed by Oster, Murray, and Harris [Development, 78 (1983), pp. 83--125]. We revisit the Oster--Murray--Harris model and find that, due to the infinitesimal displacement assumption made in the original version of this model, there is a restriction on the types of boundary conditions that can be prescribed. We derive a modified form of the model which relaxes the infinitesimal displacement assumption. We analyze the dynamics of this model using linear and multiscale nonlinear analysis and show that it has the same linear behavior as the original Oster--Murray--Harris model. Nonlinear analysis, however, predicts that the modified model will allow for a wider range of parameters where the solution evolves to a bounded steady state. The results from both analyses are verified through numerical simulations of the full nonlinear model in one and two dimensions. The increased range of boundary conditions that are well-posed, as well as a wider range of parameters that yield bounded steady states, renders the modified model more applicable to, and more robust for, comparisons with experiments

    A year in the life of a North Atlantic seabird: behavioural and energetic adjustments during the annual cycle

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    During their annual cycles, animals face a series of energetic challenges as they prioritise different life history events by engaging in temporally and potentially spatially segregated reproductive and non-breeding periods. Investigating behaviour and energy use across these periods is fundamental to understanding how animals survive the changing conditions associated with annual cycles. We estimated year-round activity budgets, energy expenditure, location, colony attendance and foraging behaviour for surviving individuals from a population of common guillemots Uria aalge. Despite the potential constraints of reduced day lengths and sea surface temperatures in winter, guillemots managed their energy expenditure throughout the year. Values were high prior to and during the breeding season, driven by a combination of high thermoregulatory costs, diving activity, colony attendance and associated flight. Guillemots also exhibited partial colony attendance outside the breeding season, likely supported by local resources. Additionally, there was a mismatch in the timing of peaks in dive effort and a peak in nocturnal foraging activity, indicating that guillemots adapted their foraging behaviour to the availability of prey rather than daylight. Our study identifies adaptations in foraging behaviour and flexibility in activity budgets as mechanisms that enable guillemots to manage their energy expenditure and survive the annual cycle

    Investigating rates and risk factors for hepatitis C virus reinfection in people receiving antiviral treatment in England

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    England has committed to the World Health Organization target to eliminate hepatitis C virus (HCV) as a public threat by the year 2030. Given successful treatments for HCV in recent years, it is unclear whether HCV reinfection will impact England's ability to achieve HCV elimination. We aimed to estimate the HCV reinfection rate among a cohort of patients receiving antiviral treatment using available surveillance data. Linkage between a treatment dataset from 2015-2019 and an HCV RNA testing dataset were used to identify people who experienced reinfection using three criteria. A Cox proportional hazards model was used to determine risk factors associated with HCV reinfection among a cohort who received treatment and had follow-up HCV RNA testing. The reinfection rate among those receiving HCV treatment was 7.91 per 100 person-years (PYs, 95% confidence interval (CI) 7.37-8.49) and highest among current injecting drug users (22.55 per 100 PYs, 95%CI 19.98-25.46) and people who had been in prison (20.42 per 100 PYs, 95%CI 17.21-24.24). In the adjusted model, women had a significantly reduced risk of reinfection. Being of younger age, current injecting drug users, and receipt of first treatment in prison were each significantly associated with increased risk of reinfection. Two-fifths of those with reinfection (43%, n=329/767) were linked to treatment after reinfection, and of those starting treatment, three quarters (75%, n=222/296) achieved a sustained virologic response. Guidance for testing groups at risk of reinfection and harm reduction strategies to minimize transmission should be implemented if England is to achieve HCV elimination targets

    ‘It’s like equality now; it’s not as if it’s the old days’: an investigation into gender identity development and football participation of adolescent girls

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    This article explores the influence participating in football has on the development of adolescent girls’ gender identity, an area which currently lacks academic attention. Data were taken from an ethnographic study with a group of adolescent girls and boys and compared to Jeanes’ research. A social constructionist framework was deployed with links to both critical theory and feminist literature. Qualitative and participatory methods were used to fully engage with the complex issue of gender identity. The girls within this study were aware of the normative gender expectations linked to ‘being a female’ but did not find this restrictive. The girls moved between many changing identities and organised their ‘web of selves’ accordingly. The apparent need to measure success by the parameters of male standards created a barrier to girls’ identity development

    Impact of a carbohydrate mouth rinse on corticomotor excitability after mental fatigue in healthy college-aged subjects

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    Mental Fatigue (MF) has been associated with reduced physical performance but the mechanisms underlying this result are unclear. A reduction in excitability of the corticomotor system is a way mental fatigue could negatively impact physical performance. Carbohydrate (CHO) mouth rinse (MR) has been shown to increase corticomotor excitability. The purpose of this study was to determine if CHO MR impacts corticomotor excitability after MF. Fifteen subjects (nine females, six males; age = 23 ± 1 years; height = 171 ± 2 cm; body mass = 69 ± 3 kg; BMI = 23.8 ± 0.7) completed two sessions under different MR conditions (Placebo (PLAC), 6.4% glucose (CHO)) separated by at least 48 h and applied in a double-blinded randomized fashion. Motor-evoked potential (MEP) of the left first dorsal interosseous (FDI) was determined by transcranial magnetic stimulation (TMS) before and after MF. Perceived MF was recorded before and after the MF task using a 100 mm visual analog scale (VAS). MF was greater following PLAC (+30.4 ± 4.0 mm) than CHO (+19.4 ± 3.9 mm) ( = 0.005). MEP was reduced more following PLAC (-16.6 ± 4.4%) than CHO (-3.7 ± 4.7%) ( < 0.001). CHO MR was successful at attenuating the reduction in corticomotor excitability after MF. Carbohydrate mouth rinse may be a valuable tool at combating the negative consequences of mental fatigue

    Cochrane Qualitative and Implementation Methods Group guidance paper 6:Methods for question formulation, searching, and protocol development for qualitative evidence synthesis

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    This paper updates previous Cochrane guidance on question formulation, searching, and protocol development, reflecting recent developments in methods for conducting qualitative evidence syntheses to inform Cochrane intervention reviews. Examples are used to illustrate how decisions about boundaries for a review are formed via an iterative process of constructing lines of inquiry and mapping the available information to ascertain whether evidence exists to answer questions related to effectiveness, implementation, feasibility, appropriateness, economic evidence, and equity. The process of question formulation allows reviewers to situate the topic in relation to how it informs and explains effectiveness, using the criterion of meaningfulness, appropriateness, feasibility, and implementation. Questions related to complex questions and interventions can be structured by drawing on an increasingly wide range of question frameworks. Logic models and theoretical frameworks are useful tools for conceptually mapping the literature to illustrate the complexity of the phenomenon of interest. Furthermore, protocol development may require iterative question formulation and searching. Consequently, the final protocol may function as a guide rather than a prescriptive route map, particularly in qualitative reviews that ask more exploratory and open-ended questions

    Accessing elite nurses for research: reflections on the theoretical and practical issues of telephone interviewing

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    Elite groups are interesting as they frequently are powerful (in terms of position, knowledge and influence) and enjoy considerable authority. It is important, therefore, to involve them in research concerned with understanding social contexts and processes. This is particularly pertinent in healthcare, where considerable strategic development and change are features of everyday practice that may be guided or perceived as being guided, by elites. This paper evolved from a study investigating the availability and role of nurses whose remit involved leading nursing research and development within acute NHS Trusts in two health regions in Southern England. The study design included telephone interviews with Directors of Nursing Services during which time the researchers engaged in a reflective analysis of their experiences of conducting research with an `elite' group. Important issues identified were the role of gatekeepers, engagement with elites and the use of the telephone interview method in this context. The paper examines these issues and makes a case for involving executive nurses in further research. The paper also offers strategies to help researchers design and implement telephone interview studies successfully to maximise access to the views and experiences of `hard to reach groups', such as elites, while minimising the associated disruption

    Modelling and mapping how common guillemots balance their energy budgets over a full annual cycle

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    The ability of individual animals to balance their energy budgets throughout the annual cycle is important for their survival, reproduction and population dynamics. However, the annual cycles of many wild, mobile animals are difficult to observe and our understanding of how individuals balance their energy budgets throughout the year therefore remains poor. We developed a hierarchical Bayesian state-space model to investigate how key components of animal energy budgets (namely individual energy gain and storage) varied in space and time. Our model used biologger-derived estimates of time-activity budgets, locations and energy expenditure to infer year-round time series of energy income and reserves. The model accounted for seasonality in environmental drivers such as sea surface temperature and daylength, allowing us to identify times and locations of high energy gain. Our study system was a population of common guillemots Uria aalge breeding at a western North Sea colony. These seabirds manage their energy budgets by adjusting their behaviour and accumulating fat reserves. However, typically during severe weather conditions, birds can experience an energy deficit over a sustained period, leading to starvation and large-scale mortality events. We show that guillemot energy gain varied in both time and space. Estimates of guillemot body mass varied throughout the annual cycle and birds periodically experienced losses in mass. Mass losses were likely to have either been adaptive, or due to energetic bottlenecks, the latter leading to increased susceptibility to mortality. Guillemots tended to be lighter towards the edge of their spatial distribution. We describe a framework that combines biologging data, time-activity budget analysis and Bayesian state-space modelling to identify times and locations of high energetic reward or potential energetic bottlenecks in a wild animal population. Our approach can be extended to address ecological and conservation-driven questions that were previously unanswerable due to logistical complexities in collecting data on wild, mobile animals across full annual cycles
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