3,353 research outputs found

    Full transmission through perfect-conductor subwavelength hole arrays

    Full text link
    Light transmission through 2D subwavelength hole arrays in perfect-conductor films is shown to be complete (100%) at some resonant wavelengths even for arbitrarily narrow holes. Conversely, the reflection on a 2D planar array of non-absorbing scatterers is shown to be complete at some wavelengths regardless how weak the scatterers are. These results are proven analytically and corroborated by rigorous numerical solution of Maxwell's equations. This work supports the central role played by dynamical diffraction during light transmission through subwavelength hole arrays and it provides a systematics to analyze more complex geometries and many of the features observed in connection with transmission through hole arrays.Comment: 5 pages, 4 figure

    Southern expansion of the brown alga Colpomenia peregrina Sauvageau (Scytosiphonales) in the Northwest Atlantic Ocean

    Get PDF
    Blackler first recorded Colpomenia peregrina in the Northwest Atlantic based on collections from Nova Scotia, Canada. Five decades later we found large quantities of C. peregrina in Maine, USA, even though it was absent during earlier floristic studies in this region. Thus, C. peregrina has undergone a rapid southern expansion along the Northwest Atlantic coast. While the causes of such an expansion are unknown, it could have a major effect on both shellfish cultivation and native seaweeds within New England because of competitive interactions and increased drag

    A qualitative study exploring the impact of the COVID-19 pandemic on People Who Inject Drugs (PWID) and drug service provision in the UK: PWID and service provider perspectives

    Get PDF
    Background: People Who Inject Drugs (PWID) are subject to distinct socio-structural inequalities that can expose them to high risks of COVID –19 transmission and related health and social complications. In response to COVID –19 mitigation strategies, these vulnerabilities are being experienced in the context of adapted drug treatment service provision, including reduced in–person support and increased regulatory flexibility in opioid substitution therapy (OST) guidelines. This study aimed to explore the longer–term impact of the pandemic on the health and wellbeing of PWID, including provider and client experiences of treatment changes. / Methods: Interviews were conducted with 19 PWID and 17 drug treatment providers between May – September 2021, recruited from third –sector drug services in the UK. Data were analysed using reflexive thematic analysis. / Results: Most participants expressed ongoing fears of COVID –19 transmission, although socio-structural inequalities limited the contexts in which physical distancing could be practised. In addition, virus mitigation strategies altered the risk environment for PWID, resulting in ongoing physical (e.g. drug use patterns and characteristics), economic (e.g. sex work engagement and income generation) and social (e.g. stigmatization and marginalization) harms. Finally, whilst clients reported favourable experiences from service adaptations prompted by COVID –19, there was continued scepticism and caution among providers toward sustaining any treatment changes beyond the pandemic period. / Conclusions: Whilst our findings emphasize the importance of accessible support measures attending to the immediate priorities of PWID during this period, there is a need for additional supports to ensure socio–structural vulnerabilities that disproportionality affect PWID are not exacerbated by the pandemic. In addition, treatment adaptations initiated in response to the pandemic require further attention to ensure they are acceptable to both clients and providers

    Are older people putting themselves at risk when using their walking frames?

    Get PDF
    Background Walking aids are issued to older adults to prevent falls, however, paradoxically their use has been identified as a risk factor for falling. To prevent falls, walking aids must be used in a stable manner, but it remains unknown to what extent associated clinical guidance is adhered to at home, and whether following guidance facilitates a stable walking pattern. It was the aim of this study to investigate adherence to guidance on walking frame use, and to quantify user stability whilst using walking frames. Additionally, we explored the views of users and healthcare professionals on walking aid use, and regarding the instrumented walking frames (‘Smart Walkers’) utilized in this study. Methods This observational study used Smart Walkers and pressure-sensing insoles to investigate usage patterns of 17 older people in their home environment; corresponding video captured contextual information. Additionally, stability when following, or not, clinical guidance was quantified for a subset of users during walking in an Activities of Daily Living Flat and in a gait laboratory. Two focus groups (users, healthcare professionals) shared their experiences with walking aids and provided feedback on the Smart Walkers. Results Incorrect use was observed for 16% of single support periods and for 29% of dual support periods, and was associated with environmental constraints and a specific frame design feature. Incorrect use was associated with reduced stability. Participants and healthcare professionals perceived the Smart Walker technology positively. Conclusions Clinical guidance cannot easily be adhered to and self-selected strategies reduce stability, hence are placing the user at risk. Current guidance needs to be improved to address environmental constraints whilst facilitating stable walking. The research is highly relevant considering the rising number of walking aid users, their increased falls-risk, and the costs of falls. Trial Registration Not applicable

    All-Optical Switching with Transverse Optical Patterns

    Full text link
    We demonstrate an all-optical switch that operates at ultra-low-light levels and exhibits several features necessary for use in optical switching networks. An input switching beam, wavelength λ\lambda, with an energy density of 10−210^{-2} photons per optical cross section [σ=λ2/(2π)\sigma=\lambda^2/(2\pi)] changes the orientation of a two-spot pattern generated via parametric instability in warm rubidium vapor. The instability is induced with less than 1 mW of total pump power and generates several μ\muWs of output light. The switch is cascadable: the device output is capable of driving multiple inputs, and exhibits transistor-like signal-level restoration with both saturated and intermediate response regimes. Additionally, the system requires an input power proportional to the inverse of the response time, which suggests thermal dissipation does not necessarily limit the practicality of optical logic devices

    Impact of the COVID-19 pandemic on the mental health and wellbeing of parents with young children: a qualitative interview study

    Get PDF
    Background: Parents have faced unique challenges during the coronavirus disease 2019 (COVID-19) pandemic, including mobility constraints, isolation measures, working from home, and the closure of schools and childcare facilities. There is presently a lack of in-depth qualitative research exploring how these changes have affected parents’ mental health and wellbeing. Methods: Semi-structured qualitative interviews with 29 parents of young children. Interviews were analysed using reflexive thematic analysis. Results: We identified five superordinate themes affecting participant mental health and wellbeing: (1) navigation of multiple responsibilities and change inside the home; (2) disruption to home life; (3) changes to usual support networks; (4) changes in personal relationships; and (5) use of coping strategies. Participants described stress and exhaustion from navigating multiple pressures and conflicting responsibilities with home, schooling, and work, without their usual support networks and in the context of disrupted routines. Family roles and relationships were sometimes tested, however, many parents identified coping strategies that protected their wellbeing including access to outdoor space, spending time away from family, and avoiding conflict and pandemic-related media coverage. Conclusions: Employers must be cognisant of the challenges that the pandemic has placed on parents, particularly women and lone parents. Flexible working arrangements and support might therefore relieve stress and increase productivity. Coping strategies identified by parents in this study could be harnessed and encouraged by employers and policymakers to promote positive wellbeing during times of stress throughout the pandemic and beyond

    Lower-Body Strength Relationships with Sprint, Jump, and Sport-Specific Skill Performance in High School Girls Softball Players

    Get PDF
    International Journal of Exercise Science 17(4): 86-98, 2024. Softball athletes require multiple fitness traits (e.g., strength, speed, power) and sport-specific skills (e.g., hitting, throwing) for success. Lower-body strength could underpin these qualities; this has received little analysis among high school female athletes. This research investigated correlations between absolute and relative lower-body strength with age, linear speed, lower-body power, and throwing and hitting velocity in high school girls softball athletes. Archival data collected from 34 high school girls softball players (age=14.91±1.00 years; height=1.66±0.07 m; body mass=63.21±9.59 kg) from a private strength and conditioning facility was analyzed. The data included: age, height, and body mass; 0-9.14 and 0-18.29 m sprint interval times; standing broad jump (SBJ) distance (lower-body power); batted ball exit (i.e., hitting) and throwing velocity; and absolute and relative three-repetition maximum (3RM) front squat and hexagonal bar deadlift (HBD). Pearson’s correlations (p\u3c0.05) derived relationships between absolute and relative strength with the fitness and sport-specific tests. The results indicated significant relationships between the 3RM HBD with age (r=0.389) and hitting velocity (r=0.418). The 3RM front squat related to the SBJ (r=0.422) and hitting velocity (r=0.457). Relative 3RM HBD correlated with the 0-18.29 m sprint interval (r=–0.349). These results suggested that a strength and conditioning program that improves the lower-body strength of high school girls softball players could contribute to faster sprinting speed, further horizontal jumps, and greater hitting velocity. The results from this study highlights the value of strength enhancement in high school girls softball athletes and provides support for strength and conditioning program provision for these individuals

    Voting and the Cardinal Aggregation of Judgments

    Get PDF
    The paper elaborates the idea that voting is an instance of the aggregation of judgments, this being a more general concept than the aggregation of preferences. To aggregate judgments one must first measure them. I show that such aggregation has been unproblematic whenever it has been based on an independent and unrestricted scale. The scales analyzed in voting theory are either context dependent or subject to unreasonable restrictions. This is the real source of the diverse 'paradoxes of voting' that would better be termed 'voting pathologies'. The theory leads me to advocate what I term evaluative voting. It can also be called utilitarian voting as it is based on having voters express their cardinal preferences. The alternative that maximizes the sum wins. This proposal operationalizes, in an election context, the abstract cardinal theories of collective choice due to Fleming and Harsanyi. On pragmatic grounds, I argue for a three valued scale for general elections

    Development and validation of the ACE tool: Assessing medical trainees' competency in evidence based medicine

    Get PDF
    BACKGROUND: While a variety of instruments have been developed to assess knowledge and skills in evidence based medicine (EBM), few assess all aspects of EBM - including knowledge, skills attitudes and behaviour - or have been psychometrically evaluated. The aim of this study was to develop and validate an instrument that evaluates medical trainees’ competency in EBM across knowledge, skills and attitude. METHODS: The ‘Assessing Competency in EBM’ (ACE) tool was developed by the authors, with content and face validity assessed by expert opinion. A cross-sectional sample of 342 medical trainees representing ‘novice’, ‘intermediate’ and ‘advanced’ EBM trainees were recruited to complete the ACE tool. Construct validity, item difficulty, internal reliability and item discrimination were analysed. RESULTS: We recruited 98 EBM-novice, 108 EBM-intermediate and 136 EBM-advanced participants. A statistically significant difference in the total ACE score was observed and corresponded to the level of training: on a 0-15-point test, the mean ACE scores were 8.6 for EBM-novice; 9.5 for EBM-intermediate; and 10.4 for EBM-advanced (p < 0.0001). Individual item discrimination was excellent (Item Discrimination Index ranging from 0.37 to 0.84), with internal reliability consistent across all but three items (Item Total Correlations were all positive ranging from 0.14 to 0.20). CONCLUSION: The 15-item ACE tool is a reliable and valid instrument to assess medical trainees’ competency in EBM. The ACE tool provides a novel assessment that measures user performance across the four main steps of EBM. To provide a complete suite of instruments to assess EBM competency across various patient scenarios, future refinement of the ACE instrument should include further scenarios across harm, diagnosis and prognosis
    • …
    corecore