From sandbox to "sandbox"

During that time, the neighborhood was a combination of dirt, sand, and asphalt. Big trees were still common, and kids could run around freely. Nowadays, asphalt roads have replaced the dirt roads, skyscrapers and housing complexes were erected in the large empty ground, and big trees have been cut down. The kids now sit safely inside their parents' cars, and once they go out, the parks offer an uninterrupted experience of artificial grass.

A novel Tick Carousel Assay for testing efficacy of repellents on Amblyomma americanum L.

Ticks are important vectors of human and veterinary diseases. A primary way ticks gain access to human hosts is by engaging to clothing. Repellents or acaricides sprayed onto fabric are used to deter ticks’ access to human hosts. However, there are a limited amount of standardized laboratory assays that can determine the potency and efficacy of repellents. We present a novel fabric-engagement assay referred to as the ‘Tick Carousel Assay’. This assay utilizes fabric brushing past ticks located on an artificial grass patch and measures tick engagements to fabric over time. After screening a variety of tick species, we used the lone star tick (Amblyomma americanum) to test the efficacy of four commonly used active ingredients in repellents: DEET, Picaridin, IR3535, and Oil of Lemon Eucalyptus. Repellency was tested immediately, after three hours, and six hours post application to fabric. Our data show that each repellent we tested significantly reduced the number of tick engagements to fabric for at least 6 hours. We did not find significant differences in repellent efficacy between the four active ingredients tested directly and three hours after application. After six hours, Oil of Lemon Eucalyptus repelled ticks more than the other active ingredients. We show that our Tick Carousel Assay provides an affordable, repeatable, and standardized way to compare and test repellent efficacy on treated fabrics. Our results confirm that commonly used repellents applied to fabric are an effective way to reduce tick engagement.

Influence of Vegetation Coverage on Hydraulic Characteristics of Overland Flow

Soil erosion is a major problem in the Loess Plateau (China); however, it can be alleviated through vegetation restoration. In this study, the overland flow on a slope during soil erosion was experimentally simulated using artificial grass as vegetation cover. Nine degrees of vegetation coverage and seven flow rates were tested in combinations along a 12° slope gradient. As the coverage degree increased, the water depth of the overland flow increased, but the flow velocity decreased. The resistance coefficient increased with increasing degree of coverage, especially after a certain point. The resistance coefficient and the Reynolds number had an inverse relationship. When the Reynolds number was relatively small, the resistance coefficient decreased faster; however, when it exceeded 600, the resistance coefficient decreased at a slower rate. A critical degree of vegetation cover was observed in the relationship between the resistance coefficient and submergence degree. When the degree of coverage was greater than 66.42%, the resistance coefficient first decreased and then increased with a higher submergence degree. Finally, the formula for the resistance coefficient under vegetation coverage was derived. This formula has a relatively high accuracy and can serve as a reference for predicting soil erosion.

Influence of the population spatial structure on seed rain distribution of an invasive plant under harsh environment

Distribution of seeds of an invasive species is important for the spread of the invasion and for any directed eradication action. This distribution is driven by seed rain. We studied the influence of tussocks on the spatial pattern of seed rain and resulting population spatial pattern of an invasive Antarctic Poa annua L. population. Our hypothesis was that the tussocks trap wind-dispersed seeds. We set 40 artificial grass seed traps simulating tussocks and 40 soil seed traps (control) in the area occupied by the population. The traps were exposed for a total of 3 years and exchanged periodically. We assessed the seed bank in soil extracted for installation of our control traps. Seed number was determined by the germination method. We did not find any significant difference between the types of traps regarding the number of trapped seeds and the number of traps containing seeds, however trapping events were greater for artificial grass traps. The average size of the seed rain was 13.5 seeds m−2 year−1 and the size of the soil seed bank was 216 seeds m−2. We estimated that accumulation of the soil seed bank required around 16 years. Artificial grass discs may be more efficient than bare soil in accumulating seeds, therefore grass tussocks may influence the spatial population structure not only through local seed deposition, but also by intercepting seeds dispersed by wind. Our research further supports, that directed soil removal from underneath the tussocks is the most efficient eradication method of P. annua in Antarctica.

Effects of Running Surface Stiffness on Three-Segment Foot Kinematics Responses with Different Shod Conditions

Objective. The aim of this study was to investigate the effects of surface stiffness on multisegment foot kinematics and temporal parameters during running. Methods. Eighteen male subjects ran on three different surfaces (i.e., concrete, artificial grass, and rubber) in both heeled running shoes (HS) and minimal running shoes (MS). Both these shoes had dissimilar sole profiles. The heeled shoes had a higher sole at the heel, a thick base, and arch support, whereas the minimal shoes had a flat base sole. Indeed, the studied biomechanical parameters responded differently in the different footwear during running. Subjects ran in recreational mode speed while 3D foot kinematics (i.e., joint rotation and peak medial longitudinal arch (MLA) angle) were determined using a motion capture system (Qualysis, Gothenburg, Sweden). Information on stance time and plantar fascia strain (PFS) was also collected. Results. Running on different surface stiffness was found to significantly affect the peak MLA angles and stance times for both HS and MS conditions. However, the results showed that the joint rotation angles were not sensitive to surface stiffness. Also, PFS showed no relationship with surface stiffness, as the results were varied as the surface stiffness was changed. Conclusion. The surface stiffness significantly contributed towards the effects of peak MLA angle and stance time. These findings may enhance the understanding of biomechanical responses on various running surfaces stiffness in different shoe conditions.

Lower extremity stiffness in habitual forefoot strikers during running on different overground surfaces

Purpose: Sports surface is one of the known external factors affecting running performance and injury. To date, we have found no study that examined the lower extremity stiffness in habitual forefoot strikers running on different overground surfaces. Therefore, the objective of this study was to investigate lower extremity stiffness and relevant kinematic adjustments in habitual forefoot strikers while running on different surfaces. Methods: Thirty-one male habitual forefoot strikers were recruited in this study. Runners were instructed to run at a speed of 3.3 m/s (±5%) on three surfaces, named synthetic rubber, concrete, and artificial grass. Results: No significant differences were found in leg stiffness, vertical stiffness, and joint stiffness in the sagittal plane during running on the three surfaces (p > 0.05). Running on artificial grass exerted a greater displacement in knee joint angle than running on synthetic rubber (p = 0.002, 95% CI = 1.52–7.35 degrees) and concrete (p = 0.006, 95% CI = 1.04–7.25 degrees). In the sagittal plane, peak knee moment was lower on concrete than on artificial grass (p = 0.003, 95% CI = 0.11–0.58 Nm/kg), whereas peak ankle moment was lower on synthetic rubber than on concrete (p < 0.001, 95% CI = 0.03–0.07 Nm/kg) and on artificial grass (p < 0.001, 95% CI = 0.02–0.06 Nm/kg). Among the three surfaces, the maximal ground reaction forces on concrete were the lowest (p < 0.05). Conclusions: This study indicated that running surfaces cannot influence lower extremity stiffness in habitual forefoot strikers at current running speed. Kinematic adjustments of knee and ankle, as well as ground reaction forces, may contribute to maintaining similar lower extremity stiffness.