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1

Comparison of Static Balance and the Role of Vision in Elite Athletes

100%

Hammami R., Behm D. G., Chtara M., Othman A. B., Chaouachi A.

Journal of Human Kinetics

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2014

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vol. 41

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issue 1

33-41

EN

When prescribing balance exercises to athletes in different sports, it may be important to recognize performance variations. Indeed, how athletes from different sports perform on balance tests is not well understood. The goal of the present study was to compare static balance and the role of vision among elite sprinters, jumpers and rugby players. The modified clinical test of sensory interaction on balance (mCTSIB) was used to assess the velocity of the center-of-pressure (CoP) on a force platform during a 30 s bipedal quiet standing posture in 4 conditions: firm surface with opened and closed eyes, foam surface with opened and closed eyes. Three-factor ANOVA indicated a significant main effect for groups (F=21.69, df=2, p<0.001, η2 = 0.34). Significant main effect of vision (F=43.20, df=1, p<0.001, η2 = 0.34) and surface (F=193.41, df=1, p<0.001, η2 = 0.70) as well as an interaction between vision (eyes open, eyes closed) and surface (firm and foam) (F=21.79, df=1, p=0.001) were reported in all groups. The subsequent Bonferroni-Dunn post hoc test indicated that rugby players displayed better static balance than sprinters and jumpers (p=0.001). The comparison of sprinters and jumpers did not reveal significant differences (p>0.05). The nature of the sport practiced and the absence of visual control are linked to modify static balance in elite athletes. Coaches and strength and conditioning professionals are recommended to use a variety of exercises to improve balance, including both exercises with opened and closed eyes on progressively challenging surfaces in order to make decisions about tasks and sensory availability during assessment and training.

2

Match Characteristics and Rally Pace of Male Tennis Matches in Three Grand Slam Tournaments

88%

Carboch J., Siman J., Sklenarik M., Blau M.

Physical Activity Review

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2019

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issue 7

49-56

EN

A tennis player has a very limited time to hit an incoming ball; however, the ball delivery time is affected by playing on different surfaces. Consequently, the playing surface can affect also other match characteristics as players can reach more incoming balls or can move on the court with different intensity (cover more distance). Aim of Study: The aim is to analyze the rally pace characteristics and the frequency of rally shots in men's matches in the Australian Open, French Open and Wimbledon in 2017. Material and Methods: We analyzed 24 male matches in the Australian Open, French Open and Wimbledon in 2017. Analysis of variance including post-hoc tests and Cohen d were used to compare the point duration, number of rally shots, time between the points, rally pace and work to rest ratio among these tournaments. Results: The rally pace (mean ball flight time between the opponents) was the fastest in the Australian Open (1.22 s) and was significantly faster (p=0.003) compared to the French Open (1.35 s). The rally pace in the Wimbledon reached 1.27 s and Cohen d showed large effect between the rally pace in the Wimbledon and French Open or moderate effect between the Australian Open and Wimbledon. There were other differences among the tournaments, but the lowest number of rally shots (4.07), point duration (5.30 s) and time between points (18.82 s) was reached in the Wimbledon. More than 50 % of all points were finished within the first four shots (most in the Wimbledon - 66%). Conclusion: These findings show and endorse the impact of surface differences on the game performance in professional tennis and can be used to shape specific training sessions on different surfaces.

3

Effects of Vacancy-Defected, Dopant and the Adsorption of Water upon Mn_{2}O_{3} and Mn_{3}O_{4} (001) Surfaces: A First-Principles Study

88%

Mansouri M.

Acta Physica Polonica A

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2018

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vol. 133

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issue 5

1178-1185

EN

In this study, a first-principles study using the spin-polarized density functional theory approach within corrected functional was carried out to investigate the electronic features of manganese oxide surfaces under three situations of (a) cation vacancy, (b) intercalation of multi- and univalent ions, and (c) adsorption of a water molecule upon the surface as catalytic performance. The possibility of obtaining the significant absolute magnetic momentum phases from native defects in orthorhombic structures of Mn_{2}O_{3} and Mn_{3}O_{4} (001) surface is explored, whereas Mn vacancy provides a transition from the insulating phase into a metal-like nature and modifies the electronic transport. Moreover, bandgap engineering via impurity intercalation has been explored. Ca^{+2} and Al^{+3} intercalations have manifested substantial attributes and explain the experimental results as efficient conducting system and catalytic activity. Furthermore, the adsorption of one water molecule and the most stable configuration, adsorption energies and electronic properties were thoroughly discussed. Accordingly, it was explored that H_{2}O: Mn_{2}O_{3} and Mn_{3}O_{4} exhibit suitable parameters as efficient catalytic synthesis.

4

The Role of CeO₂-Doping of γ-Al₂O₃ on its Structural and Superficial Area

88%

Aribi K., Ghelamallah M., Bellifa A., Bousehaba F.

Acta Physica Polonica A

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2017

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vol. 132

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issue 3

445-447

EN

A series of samples, noted Al_xCe_{1-x} has been prepared by hydrolysis, from γ-Al₂O₃ and CeO₂. These samples were calcined under air at 450, 900 and 1200°C, and then characterized by specific surface area, X-ray diffraction and thermoreduction programmed under H₂. Obtained results show that after calcination at 450 and 900°C, the cerium decreases the surface of alumina. Results of X-ray diffraction and thermoreduction programmed under H₂ experiments showed that the samples are constituted of: γ-Al₂O₃ and CeO₂. The global consumption of hydrogen increase with rate of CeO₂ added. At 1200°C, the sintering of the samples is very important and γ-Al₂O₃ is transformed into the α-phase. The decrease in specific surface area is more accentuated for Al₁Ce₀ sample, since sintering occurs due to the growth in crystallite size. Thermoreduction programmed under H₂ experiments show that reduction of CeO₂ much more accentuated for ceria samples or its decrease can reflect some alterations of the nature of interactions between Al₂O₃ and CeO₂.

5

Effect of adsorbed Sn on Ge diffusivity on Si(111) surface

63%

Dolbak A., Olshanetsky B.

Open Physics

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2008

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vol. 6

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issue 3

634-637

EN

The effect of adsorbed Sn as a surfactant on Ge diffusion on a Si(111) surface has been studied by Low Energy Electron Diffraction and Auger Electron Spectroscopy. The experimental dependence of Ge diffusion coefficients on the Si(111) surface versus temperature in the presence of adsorbed Sn atoms has been measured in the range from 300 to 650°C. It has been shown that at a Sn coverage of about 1 monolayer the mobility of Ge atoms increases by several orders of magnitude.

6

THE INVESTIGATION OF PROPERTIES OF HIGH-SPEED STEEL AFTER LASER SURFACE TREATMENT

63%

Bonek M.

Archives of Metallurgy and Materials

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2018

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vol. 63

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issue 1

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