Numerical time-domain modelling of hoof-ground interaction during the stance phase.

BACKGROUND: Hoof-ground interaction impacts on the health and performance characteristics of horses. Due to complex interactions between hoof and ground during the stance phase, previous experimentally dominated studies concentrated on subproblems of the phenomena observed. A multidisciplinary methodology with mathematical modelling, material testing and in vivo experimental measurements seems promising. OBJECTIVES: With the help of a mathematical approach, this contribution aims to explain from a biomechanical point of view the phenomena observed during experimental investigations (hoof acceleration, interacting forces) and aims to contribute to an overall experimental-mathematical multidisciplinary approach. STUDY DESIGN: In silico modelling of hoof-ground interaction (limb, hoof and horizontally unbounded ground). METHODS: Hoof-ground interaction is represented by a time-domain finite element model including the limb, the hoof and the unbounded representation of the ground via the scaled boundary finite element method to capture radiation damping during the stance phase. Motoric forces (driving forces) of the horse during locomotion are included. RESULTS: Numerical model results for acceleration-time relations (hoof) at different trotting velocities are compared with previously published acceleration-time relations and show qualitative agreement. From the model approach, power loss due to different ground properties and ground damping is computed in combination with the maximum limb force during the stance phase. MAIN LIMITATIONS: Intentionally, a simplified model approach for the material and structural representation of the limb, the hoof and the ground in terms of material features and spatial resolution has been used for this study, which might be the basis for a model refinement in terms of contact properties as well as the integration of bone and joint structures. CONCLUSIONS: The comparison to experimentally obtained results demonstrates the applicability of the model, which, in turn, enables an insight into the processes taking place during hoof-ground interaction.

Pastoralists as Optimal Foragers? Reoccupation and Site Selection in the Deserts of Post-Soviet Kazakhstan.

This study explores the drivers of site selection amongst livestock owners under conditions of increasing animal numbers following a low point in the 1990s. Our major goal was to understand whether livestock owners are acting as 'optimal foragers,' targeting areas of highest forage availability as they colonise previously empty areas. The results presented here suggest that they do not. Initially, distance from home settlement was the dominant determinant of site occupancy, with closer sites occupied earlier regardless of other characteristics. Some owners remained on depleted vegetation for longer than would be predicted under conditions of optimal foraging, indicating that distance-related costs constrained resource matching. In the latter period, increases in livestock wealth encouraged the occupation of distant sites exhibiting higher vegetation density and water quality, but some owners still occupied highly depleted sites. Improved transport and water supply infrastructure are needed if pastoralists are to optimise resource use across the landscape.

Evaluation of downscaled, gridded climate data for the conterminous United States.

Weather and climate affect many ecological processes, making spatially continuous yet fine-resolution weather data desirable for ecological research and predictions. Numerous downscaled weather data sets exist, but little attempt has been made to evaluate them systematically. Here we address this shortcoming by focusing on four major questions: (1) How accurate are downscaled, gridded climate data sets in terms of temperature and precipitation estimates? (2) Are there significant regional differences in accuracy among data sets? (3) How accurate are their mean values compared with extremes? (4) Does their accuracy depend on spatial resolution? We compared eight widely used downscaled data sets that provide gridded daily weather data for recent decades across the United States. We found considerable differences among data sets and between downscaled and weather station data. Temperature is represented more accurately than precipitation, and climate averages are more accurate than weather extremes. The data set exhibiting the best agreement with station data varies among ecoregions. Surprisingly, the accuracy of the data sets does not depend on spatial resolution. Although some inherent differences among data sets and weather station data are to be expected, our findings highlight how much different interpolation methods affect downscaled weather data, even for local comparisons with nearby weather stations located inside a grid cell. More broadly, our results highlight the need for careful consideration among different available data sets in terms of which variables they describe best, where they perform best, and their resolution, when selecting a downscaled weather data set for a given ecological application.

Grid-wide subdaily hydrologic alteration under massive wind power penetration in Chile.

Hydropeaking operations can severely degrade ecosystems. As variable renewable sources (e.g. wind power) are integrated into a power grid, fluctuations in the generation-demand balance are expected to increase. In this context, compensating technologies, notably hydropower reservoir plants, could operate in a stronger peaking scheme. This issue calls for an integrated modeling of the entire power system, including not only hydropower reservoirs, but also all other plants. A novel methodology to study the link between the short-term variability of renewable energies and the subdaily hydrologic alteration, due to hydropower reservoir operations is presented. Grid operations under selected wind power portfolios are simulated using a short-term hydro-thermal coordination tool. The resulting turbined flows by relevant reservoir plants are then compared in terms of the Richard-Baker flashiness index to both the baseline and the natural flow regime. Those are then analyzed in order to: i) detect if there is a significant change in the degree of subdaily hydrologic alteration (SDHA) due to a larger wind penetration, and ii) identify which rivers are most affected. The proposed scheme is applied to Chile's Central Interconnect System (SIC) for scenarios up to 15% of wind energy penetration. Results show a major degree of SDHA under the baseline as compared to the natural regime. As wind power increases, so does the SDHA in two important rivers. This suggests a need for further ecological studies in those rivers, along with an analysis of operational constraints to limit the SDHA.

Effect of self-assembled nanofibrous silk/polycaprolactone layer on the osteoconductivity and mechanical properties of biphasic calcium phosphate scaffolds.

We here present the first successful report on combining nanostructured silk and poly(ε-caprolactone) (PCL) with a ceramic scaffold to produce a composite scaffold that is highly porous (porosity ∼85%, pore size ∼500 µm, ∼100% interconnectivity), strong and non-brittle with a surface that resembles extracellular matrix (ECM). The ECM-like surface was developed by self-assembly of nanofibrous structured silk (20-80 nm diameter, similar to native collagen found in ECM) over a thin PCL layer which is coated on biphasic calcium phosphate (BCP) scaffolds. The effects of different concentrations of silk solution on the mechanical and physical properties of the scaffolds were also comprehensively examined. Our results showed that using silk only (irrespective of concentration) for the modification of ceramic scaffolds could drastically reduce the compressive strength of the modified scaffolds in aqueous media, and the modification made a limited contribution to improving scaffold toughness. Using PCL/nanostructured silk the compressive strength and modulus of the modified scaffolds reached 0.42 MPa (compared with 0.07 MPa for BCP) and ∼25 MPa (compared with 5 MPa for BCP), respectively. The failure strain of the modified scaffold increased more than 6% compared with a BCP scaffold (failure strain of less than 1%), indicating a transformation from brittle to elastic behavior. The cytocompatibility of ECM-like composite scaffolds was investigated by studying the attachment, morphology, proliferation and bone-related gene expression of primary human bone-derived cells. Cells cultured on the developed scaffolds for 7 days had significant up-regulation of cell proliferation (∼1.6-fold higher, P<0.001) and osteogenic gene expression levels (collagen type I, osteocalcin and bone sialoprotein) compared with the other groups tested.

Forever young: how to control the elongation, differentiation, and proliferation of cells using nanotechnology.

Within the emerging field of stem cells there is a need for an environment that can regulate cell activity, to slow down differentiation or proliferation, in vitro or in vivo while remaining invisible to the immune system. By creating a nanoenvironment surrounding PC12 cells, Schwann cells, and neural precursor cells (NPCs), we were able to control the proliferation, elongation, differentiation, and maturation in vitro. We extended the method, using self-assembling nanofiber scaffold (SAPNS), to living animals with implants in the brain and spinal cord. Here we show that when cells are placed in a defined system we can delay their proliferation, differentiation, and maturation depending on the density of the cell population, density of the matrix, and the local environment. A combination of SAPNS and young cells can be implanted into the central nervous system (CNS), eliminating the need for immunosuppressants.

Impediments to eye transplantation: ocular viability following optic-nerve transection or enucleation.

Maintenance of ocular viability is one of the major impediments to successful whole-eye transplantation. This review provides a comprehensive understanding of the current literature to help guide future studies in order to overcome this hurdle. A systematic multistage review of published literature was performed. Three specific questions were addressed: (1) Is recovery of visual function following eye transplantation greater in cold-blooded vertebrates when compared with mammals? (2) Is outer retina function following enucleation and reperfusion improved compared with enucleation alone? (3) Following optic-nerve transection, is there a correlation between retinal ganglion cell (RGC) survival and either time after transection or proximity of the transection to the globe? In a majority of the studies performed in the literature, recovery of visual function can occur after whole-eye transplantation in cold-blooded vertebrates. Following enucleation (and reperfusion), outer retinal function is maintained from 4 to 9 h. RGC survival following optic-nerve transection is inversely related to both the time since transection and the proximity of transection to the globe. Lastly, neurotrophins can increase RGC survival following optic-nerve transection. This review of the literature suggests that the use of a donor eye is feasible for whole-eye transplantation.

Using nanotechnology to design potential therapies for CNS regeneration.

The nanodelivery of therapeutics into the brain will require a step-change in thinking; overcoming the blood brain barrier is one of the major challenges to any neural therapy. The promise of nanotechnology is that the selective delivery of therapeutics can be delivered through to the brain without causing secondary damage. There are several formidable barriers that must be overcome in order to achieve axonal regeneration after injury in the CNS. The development of new biological materials, in particular biologically compatible scaffolds that can serve as permissive substrates for cell growth, differentiation and biological function is a key area for advancing medical technology. This review focuses on four areas: First, the barriers of delivering therapies to the central nervous system and how nanotechnology can potentially solve them; second, current research in neuro nanomedicine featuring brain repair, brain imaging, nanomachines, protein misfolding diseases, nanosurgery, implanted devices and nanotechnologies for crossing the blood brain barrier; third, health and safety issues and fourth, the future of neuro nanomedicine as it relates to the pharmaceutical industry.

Behavioral testing and preliminary analysis of the hamster visual system.

The dependence of visual orienting ability in hamsters on the axonal projections from retina to midbrain tectum provides experimenters with a good model for assessing the functional regeneration of this central nervous system axonal pathway. For reliable testing of this behavior, male animals at least 10-12 weeks old are prepared by regular pretesting, with all procedures carried out during the less active portion of the daily activity cycle. Using a sunflower seed attached to a small black ball held at the end of a stiff wire, and avoiding whisker contact, turning movements toward visual stimuli are video recorded from above. Because at the eye level, the nasal-most 30 degrees of the visual field can be seen by both the eyes, this part of the field is avoided in assessments of a single side. Daily sessions consist of ten presentations per side. Measures are frequency of responding and detailed turning trajectories. Complete assessment of the functional return of behavior in this testing paradigm takes 3-6 months to complete.

The effect of timing of initial bath on newborn's temperature.

OBJECTIVE: To determine the effect of the early timing of an initial bath on newborn temperature. DESIGN: Random assignment to group, comparative study. SETTING: Newborn nursery of a 20-bed obstetric unit in a regional hospital in the Midwest. PATIENTS: 80 healthy, full-term newborns. INTERVENTIONS: 40 neonates were bathed at 1 hour of age and 40 were bathed at 2 hours of age. MAIN OUTCOME MEASURES: Axillary temperatures were measured before the admission bath and at 10, 20, and 60 minutes after the bath with disposable thermometers; the maximum drop in temperature also was determined. RESULTS: No significant differences were noted in axillary temperatures between the two groups before the bath or at 10, 20, or 60 minutes after the bath. The groups did not differ significantly by gender, birth weight, length of bath in minutes, room temperature during bath, Apgar score at 5 minutes, or gestational age. CONCLUSION: Healthy full-term newborns with an axillary temperature > or = 36.8 degrees C (98.2 degrees F) can be bathed after 1 hour of age when appropriate care is taken to support thermal stability.

Pulmonary infiltrates in an elderly man.

An 80-year-old man presented with subjective fever, chronic cough occasionally producing scant yellow sputum, retrosternal pleuritic pain, and dyspnea on walking one block. Since symptom onset three months earlier, he had lost 20 pounds; he had had two loose stools a day, fatigue, malaise, and anorexia but not hemoptysis, nausea, vomiting, hematemesis, hematochezia, or melena. He denied paroxysmal nocturnal dyspnea or orthopnea. As far as could be ascertained, he not recently been exposed to tuberculosis or any other infectious disease. He had previously been seen at another clinic and had completed a 10-day trial of erythromycin (500 mg p.o. q12 h) without apparent change in symptoms.

The history and evolution of athletic training education in the United States.

OBJECTIVE: To present a chronologic review of the history and evolution of athletic training education in the United States as related to the professional growth of athletic training and the National Athletic Trainers' Association. BACKGROUND: Commonly accepted characteristics of a profession are an identifiable body of knowledge, the emergence of practitioners as professional authorities, and community recognition. These characteristics establish the criteria by which the professional growth, or professionalization, of athletic training can be judged. With guidance from the National Athletic Trainers' Association, the development of athletic training education programs and credentialing of athletic trainers during the past 50 years have contributed to the professionalization of athletic training. DESCRIPTION: We present a chronology of the contributions of the National Athletic Trainers' Association to the development of athletic training education in the United States. The activities of various committees, task forces, and Association members are reviewed and traced through the past 5 decades. Early curriculum models and the development of education programs in colleges and universities are discussed. ADVANTAGES: The historical review of athletic training education in this article will enhance the reader's understanding of the relationships among education, credentialing of practitioners, and professionalism in athletic training.

Kinetic heterogeneity of Na-D-glucose cotransport in teleost gastrointestinal tract.

D-[3H]glucose transport properties of brush-border membrane vesicles (BBMV) of upper intestine and pyloric ceca of the Pacific copper rockfish (Sebastes caurinus) were characterized and compared. Vesicles from both organs exhibited Na-dependent, phloridzin-sensitive, carrier-mediated transport systems. Kinetic constants for D-[3H]glucose influx across vesicle membranes were as follows: upper intestine, apparent affinity of glucose (Kt) = 0.14 +/- 0.02 mM, maximal glucose influx (JM) = 1,649 +/- 57 pmol.mg protein-1.10 s-1; pyloric ceca, Kt = 0.58 +/- 0.12 mM, JM = 2,439 +/- 178 pmol.mg protein-1.10 s-1. A hyperbolic relationship, following Michaelis-Menten kinetics, occurred between D-glucose influx and external Na concentration for pyloric ceca, while a sigmoidal function, following Hill cooperativity kinetics (n = 1.71 +/- 0.31), was disclosed between the variables for the intestine. External phloridzin, D-glucose, methyl alpha-D-glucopyranoside, and D-galactose were the most potent inhibitors of D-[3H]glucose influx in each organ. Other compounds were generally more inhibitory in vesicles from the pyloric cecum than those of the intestine except for D-mannose which was considerably more potent in the intestine. Results suggest that there may be proximal-to-distal hexose- and Na-binding gradients in the teleost gut for optimizing sugar absorption during passage of food through the gastrointestinal tract.

Invertebrate gut diverticula are nutrient absorptive organs.

Physiological mechanisms of gastrointestinal absorption and secretion of organic and inorganic solutes among invertebrates remain severely underinvestigated. In this review we briefly discuss some of the physical and biological forces affecting solute transfer across epithelial cells and membranes of vertebrate and invertebrate guts. Next, we present some features of the described processes for sugar and amino acid transport in the tubular portion of gastrointestinal tracts of three major invertebrate groups: echinoderms, molluscs, and arthropods. A detailed discussion follows of recent nutrient transport studies using purified epithelial brush-border membrane vesicles of two invertebrate gut diverticula, the crustacean hepatopancreas and the starfish pyloric cecum. Lastly, transepithelial nutrient and ion transport studies of crustacean hepatopancreatic epithelial cell monolayers, grown in primary culture and mounted in flux chambers, are used to demonstrate the nature of absorption and secretion of solutes by this organ and to show the general applicability of these methods to structurally complex invertebrate organs.

Proline transport by brush-border membrane vesicles of lobster antennal glands.

Purified brush-border membrane vesicles (BBMV) of lobster antennal gland labyrinth and bladder were separately formed by a magnesium precipitation technique. L-[3H]proline uptake was stimulated by a transmembrane NaCl gradient [outside (o) greater than inside (i)] to a greater extent in BBMV from labyrinth than those from the bladder. Detailed study of the labyrinth proline-transport processes revealed a specific dependence on NaCl, with negligible stimulatory effects by NaSCN, Na-gluconate, or KCl. A transmembrane proton gradient (o greater than i) was without stimulatory effect on proline transport. A transmembrane potential difference alone, in the presence of equilibrated NaCl and L-[3H]proline, led to net influx of the labeled amino acid, suggesting that the uptake process was electrogenic and capable of bringing about the net transfer of positive charge to the vesicle interior. Although a transmembrane Na gradient alone, in the presence of equilibrated Cl and L-[3H]proline, was able to bring about the net influx of the amino acid, a transmembrane Cl gradient alone under Na- and L-[3H]proline-equilibrated conditions was not, suggesting that only the Na gradient could energize the carrier process through cotransport, while the anion served an essential activating role. Proline influx by these vesicles occurred by the combination of at least one saturable Michaelis-Menten carrier system (apparent Kt = 0.37 mM; apparent JM = 1.19 nmol.mg protein-1.10 s-1) and apparent diffusion (P = 0.33 nmol.mg protein-1.10 s-1.mM-1). Static head analysis of the transport process suggested a cotransport stoichiometry of 2 Na:1 proline with essential activation by Cl ion.

Recognition and management of alcohol withdrawal syndrome.

Since alcoholism is not only widespread but often cryptic, the index of suspicion for the withdrawal syndrome in an unfamiliar patient should be high, particularly since failure to diagnose it is common and can eventuate fatally. Yet the signs and symptoms are consistent. A staged approach to the diagnosis is outlined and principles are given for the use of sedation and other therapeutic measures.