114 research outputs found

    Boundary Conditions for the Diffusion Equation in Radiative Transfer

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    Using the method of images, we examine the three boundary conditions commonly applied to the surface of a semi-infinite turbid medium. We find that the image-charge configurations of the partial-current and extrapolated-boundary conditions have the same dipole and quadrupole moments and that the two corresponding solutions to the diffusion equation are approximately equal. In the application of diffusion theory to frequency-domain photon-migration (FDPM) data, these two approaches yield values for the scattering and absorption coefficients that are equal to within 3%. Moreover, the two boundary conditions can be combined to yield a remarkably simple, accurate, and computationally fast method for extracting values for optical parameters from FDPM data. FDPM data were taken both at the surface and deep inside tissue phantoms, and the difference in data between the two geometries is striking. If one analyzes the surface data without accounting for the boundary, values deduced for the optical coefficients are in error by 50% or more. As expected, when aluminum foil was placed on the surface of a tissue phantom, phase and modulation data were closer to the results for an infinite-medium geometry. Raising the reflectivity of a tissue surface can, in principle, eliminate the effect of the boundary. However, we find that phase and modulation data are highly sensitive to the reflectivity in the range of 80–100%, and a minimum value of 98% is needed to mimic an infinite-medium geometry reliably. We conclude that noninvasive measurements of optically thick tissue require a rigorous treatment of the tissue boundary, and we suggest a unified partial-current-extrapolated boundary approach

    A cognitive framework for the categorisation of auditory objects in urban soundscapes

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    Categorisation is a fundamental cognitive process that plays a central role in everyday behaviour and action. Whereas previous studies have investigated the categorisation of isolated everyday sounds, this paper presents an experiment to investigate the cognitive categorisation of everyday sounds within their original context. A group of eighteen expert and non-expert listeners took part in a free sorting task using 110 sounds identified within ambisonic reproductions of urban soundscapes. The participants were asked to sort the objects into groups of sounds that served a similar purpose in the overall perception of the soundscape. Following this, the participants were asked to provide descriptive labels for the groups they had formed. The results were analysed using hierarchical agglomerative clustering and non-metric multidimensional scaling (MDS) to explore both the structure and dimensionality of the data. The resulting hierarchical clustering of objects show three top level categories relating to transient sounds, continuous sounds, and speech and vocalisations. Sub-categories were identified in each of the top level categories which included harmonic and non-harmonic continuous sounds, clear speech, unintelligible speech, vocalisations, transient sounds that indicate actions, and non-salient transient sounds. The first two dimensions revealed by the MDS analysis relate to temporal extent and intelligibility respectively. Interpretation of the third dimension is less clear, but may be related to harmonic content

    Genetic association analysis of N-methyl-d-aspartate receptor subunit gene GRIN2B and clinical response to clozapine

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    OBJECTIVE: Approximately 30% of patients with schizophrenia fail to respond to antipsychotic therapy and are classified as having treatment-resistant schizophrenia. Clozapine is the most efficacious drug for treatment-resistant schizophrenia and may deliver superior therapeutic effects partly by modulating glutamate neurotransmission. Response to clozapine is highly variable and may depend on genetic factors as indicated by twin studies. We investigated eight polymorphisms in the N-methyl-d-aspartate glutamate receptor subunit gene GRIN2B with response to clozapine. METHODS: GRIN2B variants were genotyped using standard TaqMan procedures in 175 European patients with schizophrenia deemed resistant or intolerant to treatment. Response was assessed using change in Brief Psychiatric Rating Scale scores following six months of clozapine therapy. Categorical and continuous response was assessed using chi-squared test and analysis of covariance, respectively. RESULTS: No associations were observed between the variants and response to clozapine. A-allele carriers of rs1072388 responded marginally better to clozapine therapy than GG-homozygotes; however, the difference was not statistically significant (p = 0.067, uncorrected). CONCLUSIONS: Our findings do not support a role for these GRIN2B variants in altering response to clozapine in our sample. Investigation of additional glutamate variants in clozapine response is warranted. Copyright © 2016 John Wiley & Sons, Ltd

    Improving care for people with dementia: development and initial feasibility study for evaluation of life story work in dementia care

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    Background: Improving dementia care quality is an urgent priority nationally and internationally. Life story work (LSW) is an intervention that aims to improve individual outcomes and care for people with dementia and their carers. LSW gathers information and artefacts about the person, their history and interests, and produces a tangible output: the ‘life story’. Objective: To establish whether or not full evaluation of LSW was feasible. Design: Mixed-methods feasibility study. Methods: In-depth interviews and focus groups explored experiences of LSW and best practice with people with dementia, family members and dementia care staff. A systematic review explored best practice and theories of change for LSW. These stages helped to identify the outcomes and resources to explore in the feasibility study. A representative sample survey of health and social care dementia care providers in England established LSW practice in different settings. A survey of a self-selected sample of family members of people with dementia explored how LSW is experienced. Two small outcome studies (stepped-wedge study in six care homes and pre-test post-test study in inpatient specialist dementia care wards) explored the feasibility of full evaluation of LSW in these settings. Settings: Survey: generalist and specialist care homes; NHS dementia care settings; and community dementia services. Feasibility study: care homes and NHS inpatient dementia care wards. Participants: NHS and social care services, people with dementia, family carers, care home staff and NHS staff. Interventions: LSW. Main outcome measures: Spread of LSW and good practice, quality of life (QoL) for the person with dementia and carers, relationships between people with dementia and family carers, staff attitudes about dementia, staff burnout, resource use and costs. Review methods: Narrative review and synthesis, following Centre for Review and Dissemination guidelines. Results: Good practice in LSW is identifiable, as are theories of change about how it might affect given outcomes. Indicators of best practice were produced. LSW is spreading but practice and use vary between care settings and are not always in line with identified good practice. Two different models of LSW are evident; these are likely to be appropriate at different stages of the dementia journey. The feasibility study showed some positive changes in staff attitudes towards dementia and, for some people with dementia, improvements in QoL. These may be attributable to LSW but these potential benefits require full evaluation. The feasibility work established the likely costs of LSW and highlighted the challenges of future evaluation in care homes and inpatient dementia care settings. Limitations: There was insufficient evidence in the literature to allow estimation of outcome size. We did not carry out planned Markov chain modelling to inform decisions about carrying out future evaluation because of the dearth of outcome data in the literature; low levels of data return for people with dementia in the hospital settings; lack of detected effect for most people with dementia; and questions about implementation in the research settings. Conclusions: LSW is used across different health and social care settings in England, but in different ways, not all of which reflect ‘good practice’. This large, complex study identified a wide range of challenges for future research, but also the possibility that LSW may help to improve care staff attitudes towards dementia and QoL for some people with dementia. Future work: Full evaluation of LSW as an intervention to improve staff attitudes and care is feasible with researchers based in or very close to care settings to ensure high-quality data collection. Funding: The National Institute for Health Research Health Services and Delivery Research programme. Keywords

    Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

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    IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

    Words Matter: The Impact of “Catchy” vs Conventional Course Titles on Student Interest

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    Anecdotal evidence suggests that post-secondary institutions in Canada and beyond are experimenting with the practice of substituting conventional, discipline-centred course titles with more creatively phrased, learner-centred titles. However, we could find no scholarly research to affirm, challenge or guide this practice. This study represents a preliminary foray into that research. We surveyed 368 business undergraduate and graduate students at a mid-sized Canadian university to address, and explore the implications of, this question: "Does a catchy course title elicit more student interest than its conventional counterpart?" Our findings provide some, but not unqualified, support for the practice of using catchy course titles as a way of attracting student interest. We found the most significant influence on student preference toward conventional or catchy course titles to be year of registration (first year and fourth year students showed the most interest in catchy course titles; graduate students and those registered in second and third year showed a preference for conventional course titles). Implications regarding marketing and pedagogy are discussed, as is the need for further research. Des preuves non scientifiques sembleraient suggĂ©rer que les Ă©tablissements d’enseignement supĂ©rieur du Canada et au-delĂ  sont en train d’essayer de substituer les titres de cours conventionnels centrĂ©s sur la discipline par des titres centrĂ©s sur l’apprenant et formulĂ©s de façon plus crĂ©atrice. Toutefois, nous n’avons trouvĂ© aucune recherche savante qui pourrait affirmer, mettre au dĂ©fi ou guider cette pratique. Cette Ă©tude reprĂ©sente une expĂ©rience prĂ©liminaire dans cette recherche. Nous avons fait un sondage auprĂšs de 368 Ă©tudiants de premier cycle et de cycles supĂ©rieurs en administration des affaires dans une universitĂ© canadienne de taille moyenne afin d’explorer les implications de la question suivante : « Est-ce qu’un titre de cours accrocheur attire davantage l’intĂ©rĂȘt des Ă©tudiants qu’un titre plus conventionnel? » Nos rĂ©sultats prĂ©sentent un certain soutien non qualifiĂ© Ă  cette pratique qui consiste Ă  utiliser des titres de cours accrocheurs dans le but d’attirer l’intĂ©rĂȘt des Ă©tudiants. Nous avons trouvĂ© que l’influence la plus significative sur la prĂ©fĂ©rence des Ă©tudiants entre les titres conventionnels et les titres accrocheurs Ă©tait l’annĂ©e d’inscription (les Ă©tudiants de premiĂšre et de quatriĂšme annĂ©e Ă©taient davantage attirĂ©s par les titres de cours accrocheurs; les Ă©tudiants des cycles supĂ©rieurs et ceux inscrits en deuxiĂšme et troisiĂšme annĂ©e semblaient prĂ©fĂ©rer les titres de cours conventionnels). Les implications en matiĂšre de marketing et de pĂ©dagogie sont discutĂ©es, ainsi que la nĂ©cessitĂ© de faire des recherches plus avancĂ©es sur la question
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