21,104 research outputs found

    Investigation of blown boundary layers with an improved wall jet system

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    The behavior of two dimensional incompressible turbulent wall jets submerged in a boundary layer when they are used to prevent boundary layer separation on plane surfaces is investigated. The experimental set-up and instrumentation are described. Experimental results of zero pressure gradient flow and adverse pressure gradient flow are presented. Conclusions are given and discussed

    Investigation of blown boundary layers with an improved wall jet system

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    Measurements were made in a two dimensional incompressible wall jet submerged under a thick upstream boundary layer with a zero pressure gradient and an adverse pressure gradient. The measurements included mean velocity and Reynolds stresses profiles, skin friction, and turbulence spectra. The measurements were confined to practical ratios (less than 2) of the jet velocity to the free stream velocity. The wall jet used in the experiments had an asymmetric velocity profile with a relatively higher concentration of momentum away from the wall. An asymmetric jet velocity profile has distinct advantages over a uniform jet velocity profile, especially in the control of separation. Predictions were made using Irwin's (1974) method for blown boundary layers. The predictions clearly show the difference in flow development between an asymmetric jet velocity profile and a uniform jet velocity profile

    A simple model for the kinetics of packaging of DNA in to a capsid against an external force

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    We propose a simple model for the kinetics of packaging of viral DNA in to a capsid against an external force trying to prevent it. The model leads to a Butler-Volmer type dependence of the rate of packaging on the pulling force F

    Experimental study of two separating turbulent boundary layers

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    A detailed study of two strong adverse pressure gradient flows, one with a free-stream velocity of 35 m/sec, at throat (producing a Re sub theta of 27000 at detachment) and another with free-stream velocity of 22 m/sec, at throat (producing a Re sub theta of 19000 at detachment) is presented. In these examples flows separate slowly and reattach very rapidly over a very short distance in a streamwise direction. In the backflow region, there appears to be a semi-logarithmically flat region in the streamwise fluctuating velocity component, u', which spreads over a definite range of y/delta. In power spectra, the flow variables phi sub upsilon upsilon (kappa sub 1 delta)/ -uv bar sub max vs. kappa sub 1 delta forms a unique set of scaling parameters for adverse pressure gradient flows. Experimental results show good agreement with previous studies

    Major Colonic Problems in Human Homotransplant Recipients

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    Historical Arctic Logbooks Provide Insights into Past Diets and Climatic Responses of Cod

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    Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s. Causes for the population increase last century, and understanding of whether such large numbers will be maintained in the future, are unclear. To explore this, we digitised and interrogated historical cod catch and diet datasets from the Barents Sea. Seventeen years of catch data and 12 years of prey data spanning 1930–1959 cover unexplored spatial and temporal ranges, and importantly capture the end of a previous warm period, when temperatures were similar to those currently being experienced. This study aimed to evaluate cod catch per unit effort and prey frequency in relation to spatial, temporal and environmental variables. There was substantial spatio-temporal heterogeneity in catches through the time series. The highest catches were generally in the 1930s and 1940s, although at some localities more cod were recorded late in the 1950s. Generalized Additive Models showed that environmental, spatial and temporal variables are all valuable descriptors of cod catches, with the highest occurring from 15–45°E longitude and 73–77°N latitude, at bottom temperatures between 2 and 4°C and at depths between 150 and 250 m. Cod diets were highly variable during the study period, with frequent changes in the relative frequencies of different prey species, particularly Mallotus villosus (capelin). Environmental variables were particularly good at describing the importance of capelin and Clupea harengus (herring) in the diet. These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability. When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond

    Well-being and College Success of Undergraduate Students

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    Background:  In order to build a culture of well-being among students in post-secondary academic communities, an assessment of current well-being and related factors is necessary. Common barriers to optimal well-being may include stress, anxiety, and depression in college students. Low levels of well-being have been associated with higher levels of impaired academic performance. Aim: Explore the relationship between academic success and time spent performing well-being activities. Methods:  Seligman’s Well-Being Theory was used to guide this study. The relationship between well-being and academic success of undergraduate students at a large Midwestern university (N = 5008) was evaluated using data from a 278 item 2018 Student Experience at a Research University (SERU) survey. Measures of academic success included late assignments, going to class unprepared, and skipping class. Measures of well-being included time spent in: physical exercise, spiritual practice, community service, and club participation; time with family and friends were also included. Results: Pearson Chi-Square analysis revealed a total of five significant relationships between well-being activities and late assignments, being unprepared for class, and skipping class at α=.05. Conclusions:  Further research is needed to understand the relationship between well-being and academic success to guide development of strategies to support well-being in university students

    TikTok, Tomatoes, and Teenagers: Using New Social Media Apps to Connect Extension Education with Younger Audiences

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    Social media usage has precipitated changes in Cooperative Extension’s delivery of programs to amplify involvement with selected audiences and it is important that we craft relevant content for a variety of audiences. Current research tells us that social media and related content can enrich education and can create broader audiences for programming. Resources like blogs, podcasts, and geofilters have shown to be received positively by a wide range of audiences and have created greater rates of engagement. Yet, one platform that has received limited attention is TikTok, perhaps due to TikTok’s mixed reviews in educational systems. With current trends showing that 48% of 18-29 year olds are using the app, we believe that TikTok has great potential for connecting audiences with research-based information and engaging previously unreached communities

    Acceptance and commitment therapy delivered in a dyad after a severe traumatic brain injury: a feasibility study

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    Objective: There is a high prevalence of complex psychological distress after a traumatic brain injury but limited evidence of effective interventions. We examined the feasibility of Acceptance and Commitment Therapy after a severe traumatic brain injury using the criteria, investigating a therapeutic effect, and reviewing the acceptability of measures, treatment protocol, and delivery method (in a dyad of two clients and a therapist). Method: Two male outpatients with severe traumatic brain injury and associated psychological distress jointly engaged in a seven session treatment program based on Acceptance and Commitment Therapy principles. Pre- and post-treatment measures of mood, psychological flexibility, and participation were taken in addition to weekly measures. Results: The intervention showed a therapeutic effect with one participant, and appeared to be acceptable for both participants with regard to program content, measures, and delivery mode by in a dyad. One participant showed both significant clinical and reliable change across several outcome measures including measures of mood and psychological flexibility. The second participant did not show a reduction in psychological inflexibility, but did show a significant drop in negative affect. Significant changes pre- to post-treatment for measures of participation were not indicated. Qualitatively, both participants engaged in committed action set in accordance with their values. Conclusions: This study suggests that Acceptance and Commitment Therapy may be feasible to be delivered in a dyad with individuals who have a severe traumatic brain injury. A further test of its potential efficacy in a phase II clinical trial is recommended
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