736 research outputs found

    Growth and dislocation studies of β-HMX

    Get PDF
    Background: The defect structure of organic materials is important as it plays a major role in their crystal growth properties. It also can play a subcritical role in “hot-spot” detonation processes of energetics and one such energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX). Results: The as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic of mechanical deformation by dislocation slip. Conclusions: Crystals of β-HMX grown from acetone show good morphological agreement with that predicted by modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution. Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays. On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits are associated with pure screw dislocations with b = [010]

    Combination therapy with reovirus and anti-PD-1 blockade controls tumor growth through innate and adaptive immune responses.

    Get PDF
    Oncolytic reovirus can be delivered both systemically and intratumorally, in both pre-clinical models and in early phase clinical trials. Reovirus has direct oncolytic activity against a variety of tumor types and anti-tumor activity is directly associated with immune activation by virus replication in tumors. Immune mechanisms of therapy include both innate immune activation against virally infected tumor cells, and the generation of adaptive anti-tumor immune responses as a result of in vivo priming against tumor-associated antigens. We tested the combination of local oncolytic reovirus therapy with systemic immune checkpoint inhibition. We show that treatment of subcutaneous B16 melanomas with a combination of intravenous (i.v.) anti-PD-1 antibody and intratumoral (i.t.) reovirus significantly enhanced survival of mice compared to i.t. reovirus (p<0.01) or anti-PD-1 therapy alone. In vitro immune analysis demonstrated that checkpoint inhibition improved the ability of NK cells to kill reovirus-infected tumor cells, reduced Treg activity, and increased the adaptive CD8(+) T cell dependent anti-tumor T cell response. PD-1 blockade also enhanced the anti-viral immune response but through effector mechanisms which overlapped with, but also differed from those affecting the antitumor response. Therefore, combination with checkpoint inhibition represents a readily translatable next step in the clinical development of reovirus

    Reflections of physiotherapy students in the United Arab Emirates during their clinical placements: A qualitative study

    Get PDF
    BACKGROUND: Although Western models of education are being used to establish health professional programs in non-Western countries, little is known about how students in these countries perceive their learning experiences. The purpose of this qualitative study was to describe the reflections of physiotherapy students from a Middle East culture during their clinical placements and to compare them to reflections of physiotherapy students from a Western culture. METHODS: Subjects were six senior students (3 females, 3 males, mean age 22.6 years) and 15 junior, female students (mean age 20.1 years) in the baccalaureate physiotherapy program at a university in the United Arab Emirates (UAE). They wrote weekly entries in a journal while in their clinical placements. They described an event, their reaction to it, and how it might affect their future behavior. Two evaluators independently read and coded the content of all the journals, and then worked together to categorize the data and develop themes. A third evaluator, an UAE national, independently read the journals to validate the content analysis. A feedback session with students was used to further validate the data interpretation. The themes were compared to those derived from a similar study of Canadian physiotherapy students. RESULTS: The content of the students' reflections were grouped into 4 themes: professional behavior, awareness of learning, self-development and shift to a patient orientation, and identification and analysis of ethical issues. Although the events were different, students from the UAE considered many of the same issues reflected on by Canadian students. CONCLUSION: Physiotherapy students from a Middle East culture consider many of the same issues as students from a Western culture when asked to reflect on their clinical experience. They reflect on their personal growth, on how they learn in a clinical setting, and on the ethical and professional behaviors of themselves and others

    Doing research in peoples’ homes: fieldwork, ethics and safety – on the practical challenges of researching and representing life on the margins

    Get PDF
    Drawing on the author’s experiences and reflections of researching vulnerable people for a housing research project, this article explores the ethical dilemmas, and the health and safety challenges, of conducting in-depth, qualitative interviews with ‘vulnerable’ research participants in their own homes. Vulnerability, in a housing research context, takes account of: living in poverty; insecure housing/employment situations; poor health and/or mental ill health; alcohol and /or drug dependency, etc. Diary notes are used to illustrate the challenging situations that can unfold when working alone in the field in disadvantaged areas, with vulnerable people, which can present physical and emotional risk. Concern with risk and the potential impact on individuals is two-fold: that on the participant; and that on the researcher. Through reflexivity and revisiting of experiences in the field, this paper explains the difficulties and negotiations, and it provides some suggestions for better research practice

    Appointing Women to Boards: Is There a Cultural Bias?

    Get PDF
    Companies that are serious about corporate governance and business ethics are turning their attention to gender diversity at the most senior levels of business (Institute of Business Ethics, Business Ethics Briefing 21:1, 2011). Board gender diversity has been the subject of several studies carried out by international organizations such as Catalyst (Increasing gender diversity on boards: Current index of formal approaches, 2012), the World Economic Forum (Hausmann et al., The global gender gap report, 2010), and the European Board Diversity Analysis (Is it getting easier to find women on European boards? 2010). They all lead to reports confirming the overall relatively low proportion of women on boards and the slow pace at which more women are being appointed. Furthermore, the proportion of women on corporate boards varies much across countries. Based on institutional theory, this study hypothesizes and tests whether this variation can be attributed to differences in cultural settings across countries. Our analysis of the representation of women on boards for 32 countries during 2010 reveals that two cultural characteristics are indeed associated with the observed differences. We use the cultural dimensions proposed by Hofstede (Culture’s consequences: International differences in work-related values, 1980) to measure this construct. Results show that countries which have the greatest tolerance for inequalities in the distribution of power and those that tend to value the role of men generally exhibit lower representations of women on boards

    A Theoretical Model of Ultrasonic Examination of Smooth Flat Cracks

    Get PDF
    As the Introductory Paper to this Conference explains,1 the CEGB and other high technology organisations are very interested in quantitative NDE for the guidance it gives in the design of inspections and for the support it offers in Safety Submissions to the Regulatory Authorities. An important part of this work is the theoretical modelling and prediction of defect detectability and signal behaviour. This present paper complements the Introductory Paper by describing the technical content of a model we have developed at the CEGB NDT Applications Centre

    Novice Learner Experiences in Software Development: A Study of Freshman Undergraduates

    Get PDF
    This paper presents a study that is part of a larger research project aimed at addressing the gap in the provision of educational software development processes for freshman, novice undergraduate learners, to improve proficiency levels. With the aim of understanding how such learners problem solve in software development in the absence of a formal process, this case study examines the experiences and depth of learning acquired by a sample set of novice undergraduates. A novel adaption of the Kirkpatrick framework known as AKM-SOLO is used to frame the evaluation. The study finds that without the scaffolding of an appropriate structured development process tailored to novices, students are in danger of failing to engage with the problem solving skills necessary for software development, particularly the skill of designing solutions prior to coding. It also finds that this lack of engagement directly impacts their affective state on the course and continues to negatively impact their proficiency and affective state in the second year of their studies leading to just under half of students surveyed being unsure if they wish to pursue a career in software development when they graduate

    West Nile Virus Experimental Evolution in vivo and the Trade-off Hypothesis

    Get PDF
    In nature, arthropod-borne viruses (arboviruses) perpetuate through alternating replication in vertebrate and invertebrate hosts. The trade-off hypothesis proposes that these viruses maintain adequate replicative fitness in two disparate hosts in exchange for superior fitness in one host. Releasing the virus from the constraints of a two-host cycle should thus facilitate adaptation to a single host. This theory has been addressed in a variety of systems, but remains poorly understood. We sought to determine the fitness implications of alternating host replication for West Nile virus (WNV) using an in vivo model system. Previously, WNV was serially or alternately passed 20 times in vivo in chicks or mosquitoes and resulting viruses were characterized genetically. In this study, these test viruses were competed in vivo in fitness assays against an unpassed marked reference virus. Fitness was assayed in chicks and in two important WNV vectors, Culex pipiens and Culex quinquefasciatus. Chick-specialized virus displayed clear fitness gains in chicks and in Cx. pipiens but not in Cx. quinquefasciatus. Cx. pipiens-specialized virus experienced reduced fitness in chicks and little change in either mosquito species. These data suggest that when fitness is measured in birds the trade-off hypothesis is supported; but in mosquitoes it is not. Overall, these results suggest that WNV evolution is driven by alternate cycles of genetic expansion in mosquitoes, where purifying selection is weak and genetic diversity generated, and restriction in birds, where purifying selection is strong
    corecore