DETERMINING THE GROUND REACTION FORCE EXPERIENCED IN BEACH RUNNING

INTRODUCTION: Running on a beach is a popular fitness activity, as well as a critical component in the professional sport of ironman. In this event, ironmen athletes run over terrain ranging from wet compacted sand to dry uncompacted sand, as their distance from the ocean surf line increases. The dynamic loading response of sand surfaces at the extremes of this range has been investigated recently by Barrett et al. using a force plate, and variables such as the peak impact force and the surface stiffness were calculated. In this study we demonstrate how the time response of the ground reaction force (GRF) experienced in beach running can be predicted from the measured plate reaction force, for either wet or dry sand surfaces. METHODS: The ground reaction force experienced in beach running can be measured directly using an accelerometer attached to the runner’s lower extremity. However it is often more convenient to sample the reaction force from a sandcovered force plate in a controlled environment. This idea motivated us to consider the resulting problem of determining the GRF indirectly using the measured plate force. In the measurement process, the instrument response of the force plate, which can be described in the linear regime by a transfer function, is convoluted with the GRF in the time domain. Thus in order to reconstruct the GRF we need to apply the reverse process: a deconvolution of the measured plate force using a known transfer function. The deconvolution is performed in the frequency domain. The transfer function corresponding to the force plate has to be determined a priori by „calibrating“ direct GRF measurements with plate force measurements. RESULTS: The reconstruction of the GRF allows us to estimate any physical quantity we are interested in, such as the time of delay between the moment of impact and the trigger of the plate force reaction, or the peak GRF. We have also determined that the frequency characteristics of the force plate transfer function depend on the impact mass, the impact energy and the effective depth of the sand, and have investigated the changes apparent in this parameter space. CONCLUSIONS: The transfer function approach presented in this study reconstructs the time response of the GRF experienced in beach running conditions, using plate force measurements. Thus, with the exception of calibration measurements, we can eliminate the need to attach an accelerometer to the runner when taking GRF measurements. REFERENCES: Barrett, R.S., Neal, R.J., Roberts, L.J. (1998). The Dynamic Loading Response of Surfaces Encountered in Beach Running. Journal of Science and Medicine in Sport 1, 3-13, 1998

Computing the first eigenpair of the p-Laplacian via inverse iteration of sublinear supersolutions

We introduce an iterative method for computing the first eigenpair $(\lambda_{p},e_{p})$ for the $p$-Laplacian operator with homogeneous Dirichlet data as the limit of $(\mu_{q,}u_{q})$ as $q\rightarrow p^{-}$, where $u_{q}$ is the positive solution of the sublinear Lane-Emden equation $-\Delta_{p}u_{q}=\mu_{q}u_{q}^{q-1}$ with same boundary data. The method is shown to work for any smooth, bounded domain. Solutions to the Lane-Emden problem are obtained through inverse iteration of a super-solution which is derived from the solution to the torsional creep problem. Convergence of $u_{q}$ to $e_{p}$ is in the $C^{1}$-norm and the rate of convergence of $\mu_{q}$ to $\lambda_{p}$ is at least $O(p-q)$. Numerical evidence is presented.Comment: Section 5 was rewritten. Jed Brown was added as autho

Biomass Production of Herbaceous Energy Crops in the United States: Field Trial Results and Yield Potential Maps from the Multiyear Regional Feedstock Partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small‐scale and short‐term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long‐term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field‐scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm‐scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM‐ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country

Insights into the Genetic Architecture of Early Stage Age-Related Macular Degeneration: A Genome-Wide Association Study Meta-Analysis

10.1371/journal.pone.0053830PLoS ONE81

Common genetic variation and susceptibility to partial epilepsies: a genome-wide association study

Partial epilepsies have a substantial heritability. However, the actual genetic causes are largely unknown. In contrast to many other common diseases for which genetic association-studies have successfully revealed common variants associated with disease risk, the role of common variation in partial epilepsies has not yet been explored in a well-powered study. We undertook a genome-wide association-study to identify common variants which influence risk for epilepsy shared amongst partial epilepsy syndromes, in 3445 patients and 6935 controls of European ancestry. We did not identify any genome-wide significant association. A few single nucleotide polymorphisms may warrant further investigation. We exclude common genetic variants with effect sizes above a modest 1.3 odds ratio for a single variant as contributors to genetic susceptibility shared across the partial epilepsies. We show that, at best, common genetic variation can only have a modest role in predisposition to the partial epilepsies when considered across syndromes in Europeans. The genetic architecture of the partial epilepsies is likely to be very complex, reflecting genotypic and phenotypic heterogeneity. Larger meta-analyses are required to identify variants of smaller effect sizes (odds ratio <1.3) or syndrome-specific variants. Further, our results suggest research efforts should also be directed towards identifying the multiple rare variants likely to account for at least part of the heritability of the partial epilepsies. Data emerging from genome-wide association-studies will be valuable during the next serious challenge of interpreting all the genetic variation emerging from whole-genome sequencing studies

Large-scale sequencing identifies multiple genes and rare variants associated with Crohn’s disease susceptibility

peer reviewe

The measurement and assessment of lumbar stress during bedmaking

The hospitality industry is a growth area that plays an important role in our tourist-dependent economy. However, working conditions disadvantage some staff. Hotel linenmaids, responsible for early morning room cleaning, tend to comprise poorly paid ethnic females from low socioeconomic groups that perform difficult manual work under demanding time contraints. The bedmaking task has been identified by many of these workers as a major factor contributing toward the causation of musculoskeletal injury, particularly to the low-back region. This is not surprising given the magnitude of the loads encountered in bedmaking and the extreme postures necessitated by the location and nature of these loads. Furthermore, it was feared that the trend toward the introduction of larger, heavier beds which are lower to the floor may have exacerbated this risk. The purpose of this study was to assess the level of lumbar stress associated with standard bed size and bed height combinations in order to determine guidelines for safer work practices in the hospitality industry

SQUIRT: The Prototypical Mobile Robot for Autonomous Graduate Students

This paper describes an exercise in building a complete robot aimed at being as small as possible but using off-the-shelf components exclusively. The result is an autonomous mobile robot slightly larger than one cubic inch which incorporates sensing, actuation, onboard computation, and onboard power supplies. Nicknamed Squirt, this robot acts as a 'bug', hiding in dark corners and venturing out in the direction of last heard noises, only moving after the noises are long gone