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  • Author: Adam Stępień x
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The Kinematics of Trunk and Upper Extremities in One-Handed and Two-Handed Backhand Stroke

The aim of this study was to present kinematics of trunk and upper extremities in tennis players who perform one-handed and two-handed backhand strokes. The study aimed to address the question of whether one of those techniques has some important advantage over the other. If so, what makes it superior?

The study included 10 tennis coaches with average coaching experience of 9 years. The coaches were asked to hit 15 one-handed and two-handed backhands. The tests were carried out in a laboratory. A sponge ball was used in order to protect the measurement equipment. Video motion analysis was carried out using BTS SMART system; images were recorded with 6 cameras with a rate of 120 frames per second. The analysis of both backhand strokes focused on the second phase of the stroke (acceleration).

The use of an eight-element model of human body for description of upper body motion in both techniques revealed kinematic differences in how both backhands are performed. The two-handed backhand was performed in closed kinetic chain with 8 degrees of freedom, whereas the one-handed backhand involved an open kinetic chain with 7 degrees of freedom. Higher rigidity of upper extremities which are connected with trunk in the two-handed backhand, contributes to an elevated trunk effect in this stroke. This is confirmed by higher component velocities for racket handle, which result from trunk rotation in the two-handed backhand and a negative separation angle in the two-handed backhand at the moment of contact of the racket with the ball.

The study does not provide a clear-cut answer to the question of advantages of one technique over the other; however, it reveals dissimilar patterns of driving the racket in both techniques, which suggests the need for extending the analysis of techniques of both backhands with additional kinematics of tennis racket in consideration of measurements of ball velocities.

Abstract

The study was conducted in the Polish (Roztoczanski National Park) and Ukrainian (Rava-Rus’ka Landscape Reserve and Yavorivskyi National Park) parts of the Roztocze region. In each of these locations three research areas were established in Scots pine (Pinus sylvestris L.) stands under similar ecological conditions. The purpose of this study was to carry out a survey of possible scenarios for pine stand dynamics in the Polish and Ukrainian parts of Roztocze using the FORKOME model. A control scenario was compared with four other climate change scenarios (warm dry and warm humid; cold dry and cold humid) for a period of covering the next 100 years. Using the control scenario, the FORKOME model predicted that for the next 100 years pine stands will dominate in terms of biomass and number of trees. The warm-dry and warm-humid climate scenarios resulted in slightly reduced biomass of pine stands. However pine would still maintain its dominance, although with a noticeable increase in beech and fir biomass. Nevertheless, in term of the number of trees during the second half of the simulation, it is beech and fir that dominate stand 1 in Roztoczanski National Park. Under the climate cooling scenario (cold dry and cold humid), the biomass of pine and spruce would increase during the next 100 years. Pine trees that would dominate in terms of their numbers, although the number of spruce individuals also tends to increase. The results presented in the paper indicate that the FORKOME model is very useful when investigating different climate changes scenarios in the Roztocze region.

Abstract

The fungi of the genus Fusarium cause Fusarium head blight (FHB), a devastating disease that reduces grain yield and quality. They also produce mycotoxins which may pose a serious threat to human and animal health. This study investigated the effects of NPK fertilisation, foliar application of Cu, Zn, and Mn, applied separately and in combination, and of the Nano-Gro® organic growth stimulator on the occurrence of FHB in cultivar Dańkowskie Diament rye based on the mycological analysis of kernels and on the concentrations of Fusarium mycotoxins in grain. The severity of FHB caused by seven species of the genus Fusarium was influenced by weather conditions in the analysed growing seasons. The applied fertilisation and the Nano-Gro® organic growth stimulator exerted varied effects on FHB development and the biosynthesis of Fusarium mycotoxins (deoxynivalenol, nivalenol, zearalenone and fumonisins) in grain. The greatest reduction in deoxynivalenol and nivalenol concentrations was noted in 2013, and the levels of moniliformin were lower in treated samples than in absolute control (untreated) samples in both years of the study. The severity of FHB positively correlated with the concentrations of zearalenone, deoxynivalenol, nivalenol, and moniliformin in the grain samples. Greater accumulation of ergosterol was noted in the rye grain harvested in 2013 than in 2012, and fertiliser treatment led to higher ergosterol concentrations than did control treatment.

Abstract

This paper presents the perspectives of FORKOME model use regarding the simulation of fre and its impact on forest stands. The calculation of probability of forest fres and predicting its effect on forest stands are analysed as well. The model is supposed to examine the impact of fres on pine stands, which ultimately leads to a decline in the viability of those trees. As a result of fre activity there were determined the following categories of trees - undamaged, slightly damaged, heavily damaged and destroyed. Moreover, by conducting simulations on forests with Scots pine (Pinus sylvestris L.), there were demonstrated the possibilities of FORKOME model practical application. Simulation shows the possibility of the model to predict the fre damage in a particular year and the perspective of a stand development, taking into account climate change and its influence on the frequency of fres. Prospects and directions of further developments of the model concerning simulation of fre in forest stands were discussed as well.