1,946 research outputs found

    Evolution of Complex Sperm Morphology

    Get PDF
    Sperm form evolves rapidly and dramatically, particularly in taxa with internal fertilization. Post-copulatory sexual selection at the level of individual sperm has been suggested to explain the evolution of two enigmatic sperm phenotypes: sperm heteromorphism, where more than one type of sperm is produced by a male, and sperm conjugation, where multiple sperm join together for motility and transport through the female reproductive tract before dissociation prior to fertilization. I explore the taxonomic distribution of sperm heteromorphism and conjugation, speculate on the potential developmental origins and discuss functional hypotheses for evolutionary maintenance of these remarkable traits. I subsequently focus on the patterns of sperm morphological evolution in diving beetles (Dytiscidae), an excellent model to examine the evolution of sperm heteromorphism and conjugation. I use phylogenetically controlled regression and Bayesian estimation to infer ancestral sperm traits, identify both the rate and directionality of probable evolutionary transitions and test if the evolution of female reproductive tract design might have driven the evolution of complex, multivariate sperm form. I found sperm conjugation to be the ancestral condition in diving beetles, with subsequent diversification into three qualitatively unique forms (i.e., aggregates, pairs and rouleaux), each exhibiting varying degrees of evolutionary loss and convergence. Evolution of sperm head shape was correlated with conjugation, consistent with statistical support for non-random patterns of evolutionary transitions betIen the different forms of conjugation. The results suggest that both sperm length and sperm heteromorphism have independent evolutionary trajectories from conjugation. Results of Bayesian analyses suggest that the evolution of sperm morphology tracks changes in female reproductive structures. Data from both behavioral studies and transmission electron microscopic images of sperm conjugates stored in the female tract support the interpretation that sperm conjugation is an adaptation for maintaining favored positions for fertilization in the female reproductive tract. The results show that although sperm often have complex and varied sperm morphology, diversification of sperm form might also be constrained along particular evolutionary pathways. Moreover, the results highlight the importance of sperm-female interactions as an agent of diversification

    Enhancing graduate employability in product design: a case study exploring approaches taken on a BSc Product Design course

    Get PDF
    Purpose – This paper presents a case study to discuss approaches taken within a traditional undergraduate degree course to embed employability skills, encourage student uptake of sandwich placement and increase graduate prospects. A number of new initiatives are presented, including working with live industrial clients, formally preparing students for placement applications and the introduction of an externally facing student run design consortium. Alongside these new initiatives, details of the existing sandwich year provision are also considered and their effectiveness. Design/methodology/approach – A case study based action research approach presents changes to a specific undergraduate course, measuring the effectiveness over a 4-year period using externally collected national DLHE data and internal student feedback to assess the long-term effects on employability. Findings – The paper considers improvements in the graduate employability over the 4 year period covered, in particular, an increase in the graduate employability from 81%-100% and graduate prospects from 62.5% to 95.2% for sandwich students. Data presented also considers additional student feedback correlating with an increase in their preparedness for employment. Practical implications – The implications of undertaking the changes highlighted within this paper have been relatively straightforward, due to the small incremental nature of the changes and the opportunities available through the agencies within the university, and should be replicable at least in part at other HE institutions. Originality/value – This paper considers the impact of employability initiatives undertaken on a single undergraduate course and how these have affected the employability of graduates over a 4-year period, supported by student feedback both internally and externally through national feedback mechanisms. It is anticipated that this research would be beneficial for informing and guiding the development of employability on other undergraduate programmes

    Police and procedural justice : Perceptions of young people with mental illness

    Get PDF
    Young people with mental illness are significantly more likely to encounter the police than their counterparts who do not identify as having a mental illness. Yet little is known regarding how this cohort perceives the police and whether they believe the police to be a fair, trustworthy, and legitimate service. Research suggests that young people and other vulnerable groups (such as adults with mental illness) value procedural justice policing as a technique for nurturing fair and trustworthy policing, which in turn, increases satisfaction with police interactions and willingness to cooperate with police. This study uses procedural justice as a lens for analysing the perceptions of young people with mental illnesses regarding the police. Drawing upon survey data from a sample of 3147 Australian participants aged between 14 and 25 years old – a third of which identified as having a mental health condition – results demonstrate that young people with a mental illness offered significantly lower perceptions of the police in relation to procedural justice. Young people identifying as not heterosexual or as trans* or gender diverse, and those who report that they are not seen as Australian, also offered significantly lower perceptions of police procedural justice. A theoretical explanation is offered for why these marginalised young groups perceive the police to be procedurally unjust. Tactics for how the police may nurture more trusting and supporting relationships with young people in general are also discussed

    Analysis and evaluation of the environmental impacts of upstream petroleum operations

    Get PDF
    Sustainability is increasingly considered an essential business function, but in Libya, petroleum companies are slow to address operational issues that could reduce environmental concerns. This study aims to evaluate the environmental impacts of upstream petroleum operations. The methods adopted in the study are a literature review, an environmental impact assessment (EIA) study and qualitative analyses from, fieldwork trials and 56 semi-structured interviews. The results of the study show that the main environmental impacts are aquatic, terrestrial or atmospheric, with the most significant pollutants linked to the latter category, mainly from engine exhausts, turbine emissions, gas flaring and venting. Major environmental degradations are identified in Libyan upstream operations and a number of recommendations formulated minimising their effect. Particular importance is placed on establishing strict sustainability policies and regulations, and the implementation of an environmental management system

    Development of a patient-reported palliative care-specific health classification system: the POS-E

    Get PDF
    BackgroundGeneric preference-based measures are commonly used to estimate quality-adjusted life-years (QALYs) to inform resource-allocation decisions. However, concerns have been raised that generic measures may be inappropriate in palliative care.ObjectiveOur objective was to derive a health-state classification system that is amenable to valuation from the ten-item Palliative Care Outcome Scale (POS), a widely used patient-reported outcome measure in palliative care.MethodsThe dimensional structure of the original POS was assessed using factor analysis. Item performance was assessed, using Rasch analysis and psychometric criteria, to enable the selection of items that represent the dimensions covered by the POS. Data from six studies of patients receiving palliative care were combined (N = 1011) and randomly split into two halves for development and validation. Analysis was undertaken on the development data, and results were validated by repeating the analysis with the validation dataset.ResultsFollowing Rasch and factor analyses, a classification system of seven items was derived. Each item had two to three levels. Rasch threshold map helped identify a set of 14 plausible health states that can be used for the valuation of the instrument to derive a preference-based index.ConclusionCombining factor analysis and Rasch analysis with psychometric criteria provides a valid method of constructing a classification system for a palliative care-specific preference-based measure. The next stage is to obtain preference weights so the measure can be used in economic evaluations in palliative care

    The influence of the starvation-predation trade-off on the relationship between ambient temperature and body size among endotherms

    Get PDF
    Aim: The tendency for animals at higher latitudes to be larger (Bergmann's rule) is generally explained by recourse to latitudinal effects on ambient temperature and the food supply, but these receive only mixed support and do not explain observations of the inverse to Bergmann's rule. Our aim was to better understand how ecological variables might influence body size and thereby explain this mixed support. Location: World-wide. Methods: Previous explanations do not allow for the selective pressure exerted by the trade-off between predation and starvation, which we incorporate in a model of optimal body size and energy storage of a generalized homeotherm. In contrast to existing arguments, we concentrate on survival over winter when the food supply is poor and can be interrupted for short periods. Results: We use our model to assess the logical validity of the heat conservation hypothesis and show that it must allow for the roles of both food availability and predation risk. We find that whether the effect of temperature on body size is positive or negative depends on temperature range, predator density, and the likelihood of long interruptions to foraging. Furthermore, changing day length explains differing effects of altitude and latitude on body size, leading to opposite predictions for nocturnal and diurnal endotherms. Food availability and ambient temperature can have counteracting selective pressures on body mass, and can lead to a non-monotonic relationship between latitude and size, as observed in several studies. Main conclusions: Our work provides a theoretical framework for understanding the relationships between the costs and benefits of large body size and eco-geographical patterns among endotherms world-wide

    Symptoms and quality of life in late stage Parkinson syndromes: a longitudinal community study of predictive factors

    Get PDF
    BACKGROUND Palliative care is increasingly offered earlier in the cancer trajectory but rarely in Idiopathic Parkinson's Disease(IPD), Progressive Supranuclear Palsy(PSP) or Multiple System Atrophy(MSA). There is little longitudinal data of people with late stage disease to understand levels of need. We aimed to determine how symptoms and quality of life of these patients change over time; and what demographic and clinical factors predicted changes. METHODS We recruited 82 patients into a longitudinal study, consenting patients with a diagnosis of IPD, MSA or PSP, stages 3-5 Hoehn and Yahr(H&Y). At baseline and then on up to 3 occasions over one year, we collected self-reported demographic, clinical, symptom, palliative and quality of life data, using Parkinson's specific and generic validated scales, including the Palliative care Outcome Scale (POS). We tested for predictors using multivariable analysis, adjusting for confounders. FINDINGS Over two thirds of patients had severe disability, over one third being wheelchair-bound/bedridden. Symptoms were highly prevalent in all conditions - mean (SD) of 10.6(4.0) symptoms. More than 50% of the MSA and PSP patients died over the year. Over the year, half of the patients showed either an upward (worsening, 24/60) or fluctuant (8/60) trajectory for POS and symptoms. The strongest predictors of higher levels of symptoms at the end of follow-up were initial scores on POS (AOR 1.30; 95%CI:1.05-1.60) and being male (AOR 5.18; 95% CI 1.17 to 22.92), both were more predictive than initial H&Y scores. INTERPRETATION The findings point to profound and complex mix of non-motor and motor symptoms in patients with late stage IPD, MSA and PSP. Symptoms are not resolved and half of the patients deteriorate. Palliative problems are predictive of future symptoms, suggesting that an early palliative assessment might help screen for those in need of earlier intervention
    corecore