The Effect Of Height And Post-Landing Movement Task On Landing Performance

The purpose of this research was to evaluate selected biomechanical aspects of drop jumps and stable landings performed from increasing heights. The related literature indicates that landings performed in an experimental setting have been to a large degree isolated landing tasks, with subjects landing and remaining in a stable position. It was the intent of this research to address the interactive demands of the complete jumping/landing task. Seven subjects performed three stable landings (L) and three drop jumps (DJ) from each of four initial drop heights (15, 30, 45 and 60cm). All landings were performed with both feet contacting a force platform (500 Hz). Right knee sagittal plane angular displacement was recorded at 500 Hz via an electrogoniometer. Vertical GRF variables used to evaluate landing included maximum impact force (Fmax) normalized to subject body mass, and the time at which the amount of vertical impulse (Timp-land) necessary to account for the downward momentum of the body was achieved. To derive Timp-land, the total body vertical momentum at contact was estimated using contact velocity (calculated from initial drop height) and subject mass. Integration of the GRF curve was perforrned to establish the time relative to contact at which impulse sufficient to reduce landing momentum to zero was achieved. Timpland was therefore indicative of the time period over which the landing phase could be considered complete. In addition, maximum flexion angle at the knee (Kmax) was used in the analysis. Group mean values summarized across heights were as follows for the Land D movement tasks, respectively: Fmax: 52.0 and 41.8N /kg; Timp-land 0.118 and 0.126 sec; Kmax: 71.3 and 80.1 deg. Pearson product correrations were performed for each subject, relating initial drop height (Ht) to each of the three independent variables describing landing. Six of seven subjects (86%) exhibited strong positive correlations (r > .7071; explained variance> 50%) between Ht and Kmax and Ht and Timp-land . indicating an impact force increase and concomitant increase in time over which greater landing momentums were accounted for, observable for landing with and without the peformance of a subsequent jump. The Ht, Kmax relationship was strong and positive for the L conditions (71 % with r > .7071), but only one of seven subjects exhibited a significant Ht, Kmax relationship for the DJ performances. These results suggest that increased knee flexion is a common component of a strategy to absorb landing momentum over longer periods as height increases for stable landings. This does not, however, appear to allow for complete accommodation of Fmax across the full range of heights. The absence of a strong relationship between Ht and Kmax with DJ performance is suggestive of a change in kinematic strategy with the addition of the post-landing movement task

Evaluation of a Maximum A-Posteriori Slope Estimator for a Hartmann Wavefront Sensor

Current methods for estimating the wavefront slope at the aperture of a telescope using a Hartmann wavefront sensor are based upon a centroid shift estimator. The centroid shift estimator determines the displacement, or shift, of the centroid off the optical axis using a moment calculation of the intensity distributions recorded in each subaperture. This centroid shift is proportional to the average slope of the wavefront in each subaperture. A maximum a-posteriori (MAP) slope estimator takes advantage of a-priori knowledge of the wavefront slope statistics and total irradiance falling on the subaperture detector arrays when determining the shift estimate. In order to derive a closed form solution for the MAP estimator, several assumptions were made: infinite resolution on the detector arrays, no read noise in the detection process, and no intensity spillover into adjacent subapertures. By implementing the Hartmann wavefront sensor and MAP estimator in simulation, the performance of the MAP estimator was evaluated using realizable wavefront sensor parameters. While the MAP estimator mean square error (MSE) performance decreased relative to the centroid estimator MSE performance as a result of spillover, finite detector resolution, and read noise, the MAP estimator MSE performance was found to be upper bounded by the centroid estimator MSE in all cases

Relationship between Youth and Parent Perceptions of Family Environment and Social Anxiety

This study concurrently examined the relationship between adolescents’ perceptions of their parents’ child-rearing styles and family environment and their reports of social anxiety. Adolescents reporting higher levels of social anxiety perceived their parents as being more socially isolating, overly concerned about others’ opinions, ashamed of their shyness and poor performance, and less socially active than did youth reporting lower levels of social anxiety. Parent perceptions of child-rearing styles and family environment, however, did not differ between parents of socially anxious and nonsocially anxious adolescents. Results are comparable to studies using adult retrospective reports and are discussed with regard to the role of the family environment in the development of social anxiety

Refining adverse drug reaction signals by incorporating interaction variables identified using emergent pattern mining

Purpose: To develop a framework for identifying and incorporating candidate confounding interaction terms into a regularised cox regression analysis to refine adverse drug reaction signals obtained via longitudinal observational data. Methods: We considered six drug families that are commonly associated with myocardial infarction in observational healthcare data, but where the causal relationship ground truth is known (adverse drug reaction or not). We applied emergent pattern mining to find itemsets of drugs and medical events that are associated with the development of myocardial infarction. These are the candidate confounding interaction terms. We then implemented a cohort study design using regularised cox regression that incorporated and accounted for the candidate confounding interaction terms. Results: The methodology was able to account for signals generated due to confounding and a cox regression with elastic net regularisation correctly ranking the drug families known to be true adverse drug reactions above those that are not. This was not the case without the inclusion of the candidate confounding interaction terms, where confounding leads to a non-adverse drug reaction being ranked highest. Conclusions: The methodology is efficient, can identify high-order confounding interactions and does not require expert input to specify outcome specific confounders, so it can be applied for any outcome of interest to quickly refine its signals. The proposed method shows excellent potential to overcome some forms of confounding and therefore reduce the false positive rate for signal analysis using longitudinal data

A supervised adverse drug reaction signalling framework imitating Bradford Hill’s causality considerations

Big longitudinal observational medical data potentially hold a wealth of information and have been recognised as potential sources for gaining new drug safety knowledge. Unfortunately there are many complexities and underlying issues when analysing longitudinal observational data. Due to these complexities, existing methods for large-scale detection of negative side effects using observational data all tend to have issues distinguishing between association and causality. New methods that can better discriminate causal and non-causal relationships need to be developed to fully utilise the data. In this paper we propose using a set of causality considerations developed by the epidemiologist Bradford Hill as a basis for engineering features that enable the application of supervised learning for the problem of detecting negative side effects. The Bradford Hill considerations look at various perspectives of a drug and outcome relationship to determine whether it shows causal traits. We taught a classifier to find patterns within these perspectives and it learned to discriminate between association and causality. The novelty of this research is the combination of supervised learning and Bradford Hill’s causality considerations to automate the Bradford Hill’s causality assessment. We evaluated the framework on a drug safety gold standard known as the observational medical outcomes partnership’s non-specified association reference set. The methodology obtained excellent discrimination ability with area under the curves ranging between 0.792 and 0.940 (existing method optimal: 0.73) and a mean average precision of 0.640 (existing method optimal: 0.141). The proposed features can be calculated efficiently and be readily updated, making the framework suitable for big observational data

Midwest vision for sustainable fuel production

This article charts the progress of CenUSA Bioenergy, a USDA-NIFA-AFRI coordinated agricultural project focused on the North Central region of the US. CenUSA’s vision is to develop a regional system for producing fuels and other products from perennial grass crops grown on marginally productive land or land that is otherwise unsuitable for annual cropping. This article focuses on contributions CenUSA has made to nine primary systems needed to make this vision a reality: feedstock improvement; feedstock production on marginal land; feedstock logistics; modeling system performance; feedstock conversion into biofuels and other products; marketing; health and safety; education, and outreach. The final section, Future Perspectives, sets forth a roadmap of additional research, technology development and education required to realize commercialization

Knee movement patterns of injured and uninjured adolescent basketball players when landing from a jump: A case-control study

BACKGROUND: A common knee injury mechanism sustained during basketball is landing badly from a jump. Landing is a complex task and requires good coordination, dynamic muscle control and flexibility. For adolescents whose coordination and motor control has not fully matured, landing badly from a jump can present a significant risk for injury. There is currently limited biomechanical information regarding the lower limb kinetics of adolescents when jumping, specifically regarding jump kinematics comparing injured with uninjured adolescents. This study reports on an investigation of biomechanical differences in landing patterns of uninjured and injured adolescent basketball players. METHODS: A matched case-control study design was employed. Twenty-two basketball players aged 14–16 years participated in the study: eleven previously knee-injured and eleven uninjured players matched with cases for age, gender, weight, height and years of play, and playing for the same club. Six high-speed, three-dimensional Vicon 370 cameras (120 Hz), Vicon biomechanical software and SAS Version 8 software were employed to analyse landing patterns when subjects performed a "jump shot". Linear correlations determined functional relationships between the biomechanical performance of lower limb joints, and paired t-tests determined differences between the normalised peak biomechanical parameters. RESULTS: The average peak vertical ground reaction forces between the cases and controls were similar. The average peak ground reaction forces between the cases and controls were moderately correlated (r = -0.47). The control (uninjured) players had significantly greater hip and knee flexion angles and significantly greater eccentric activity on landing than the uninjured cases (p < 0.01). CONCLUSION: The findings of the study indicate that players with a history of knee injuries had biomechanically compromised landing techniques when compared with uninjured players matched for gender, age and club. Descriptions (norms) of expected levels of knee control, proprioceptive acuity and eccentric strength relative to landing from a jump, at different ages and physical developmental stages, would assist clinicians and coaches to identify players with inappropriate knee performance comparable to their age or developmental stage

Moving from a continuum to a community: reconceptualising the provision of support

The notion of the continuum is applied to special education in diverse contexts across many nations. This paper explores its conceptual underpinnings, drawing upon a systematic search of the literature to review recurring ideas associated with the notion and to explicate both its uses and short-comings. Through a thematic analysis of the literature the research team derived twenty-nine continua, situated within six broad groupings (space, students, staffing, support, strategies and systems). This provides a clear structure for reconsidering the issues which the notion of the continuum is supposed to describe and enables a reconceptualisation of how the delivery of services is represented. We present the initial underpinnings for a community of provision, in which settings and services work together to provide learning and support for all children and young people in their locality

Genetic association analyses implicate aberrant regulation of innate and adaptive immunity genes in the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a genetically complex autoimmune disease characterized by loss of immune tolerance to nuclear and cell surface antigens. Previous genome-wide association studies (GWAS) had modest sample sizes, reducing their scope and reliability. Our study comprised 7,219 cases and 15,991 controls of European ancestry, constituting a new GWAS, a meta-analysis with a published GWAS and a replication study. We have mapped 43 susceptibility loci, including ten new associations. Assisted by dense genome coverage, imputation provided evidence for missense variants underpinning associations in eight genes. Other likely causal genes were established by examining associated alleles for cis-acting eQTL effects in a range of ex vivo immune cells. We found an over-representation (n = 16) of transcription factors among SLE susceptibility genes. This finding supports the view that aberrantly regulated gene expression networks in multiple cell types in both the innate and adaptive immune response contribute to the risk of developing SLE