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Background: Rowing is a sport that places significant stress on the lower back, often leading to low back pain (LBP) injuries among athletes. Laboratory studies have shown that rowing with an oar blade under an angle is more efficient compared to a traditional blade. The effect of blade angle on the lower back is unknown. Therefore, the aim of this study is to investigate the effect of different oar blade angles on the muscle activation of the lower back muscles during on-water rowing. Methods: Seven collegiate (five males, two females) athletes row 500 m on water twice, once with a traditional (0-degrees blade) and once with an oar blade under a 5-degrees angle. Surface electromyography of the longissimus muscle of the erector spinae was measured bilaterally at the thoracic and lumbar level with a sample frequency of 2,000 Hz. In total 1,443 strokes were analyzed. Statistical Parametric Mapping was used to investigate the differences in muscle activity between the 0-degrees and 5-degrees oar blade. Results: No significant differences in muscle activity were found between the 0- and 5-degrees oar blade. Conclusion: Rowing with an oar blade under 5-degrees did not alter the muscle activity during on-water rowing. This indicates that rowing with an oar blade under 5-degrees may not increase the muscle activation. These results are important as it seems that a change in oar blade angle does not increase the injury risk, longitudinal studies should investigate the effect of oar blade angles on LBP injuries.
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Background: Rowing is a sport that places significant stress on the lower back, often leading to low back pain (LBP) injuries among athletes. Laboratory studies have shown that rowing with an oar blade under an angle is more efficient compared to a traditional blade. The effect of blade angle on the lower back is unknown. Therefore, the aim of this study is to investigate the effect of different oar blade angles on the muscle activation of the lower back muscles during on-water rowing. Methods: Seven collegiate (five males, two females) athletes row 500 m on water twice, once with a traditional (0-degrees blade) and once with an oar blade under a 5-degrees angle. Surface electromyography of the longissimus muscle of the erector spinae was measured bilaterally at the thoracic and lumbar level with a sample frequency of 2,000 Hz. In total 1,443 strokes were analyzed. Statistical Parametric Mapping was used to investigate the differences in muscle activity between the 0-degrees and 5-degrees oar blade. Results: No significant differences in muscle activity were found between the 0- and 5-degrees oar blade. Conclusion: Rowing with an oar blade under 5-degrees did not alter the muscle activity during on-water rowing. This indicates that rowing with an oar blade under 5-degrees may not increase the muscle activation. These results are important as it seems that a change in oar blade angle does not increase the injury risk, longitudinal studies should investigate the effect of oar blade angles on LBP injuries.
In conventional solar cell semiconductor materials (predominantlySi)photons with energy higher than the band gap initially generate hot electrons and holes, which subsequently cool down to the band edge by phonon emission. Due to the latter process,the energy of the charge carriers in excess of the band gap is lost as heat and does not contribute to the conversion of solar to electrical power. If the excess energy is more than the band gap itcan in principle be utilized through a process known as carrier multiplication (CM) in which a single absorbed photon generates two (or more) pairs of electrons and holes. Thus, through CM the photon energy abovetwice the band gap enhancesthe photocurrentofa solar cell. In this review, we discuss recent progress in CM research in terms of fundamental understanding, emergenceof new materials for efficient CM, and CM based solar cell applications. Based on our current understanding, the CM threshold can get close to the minimal value of twice the band gap in materials where a photon induces an asymmetric electronic transition from a deeper valence band or to a higher conduction band. In addition,the material must have a low exciton binding energy and high charge carrier mobility, so that photoexcitation leads directly to the formation of free charges that can readily be extracted at external electrodes of a photovoltaic device. Percolative networks of coupled PbSe quantum dots, Sn/Pb based halide perovskites,and transition metal dichalcogenides such as MoTe2fulfill these requirements to a large extent. These findings pointtowards promising prospects for further development of new materials for highly efficient photovoltaics.
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In conventional solar cell semiconductor materials (predominantlySi)photons with energy higher than the band gap initially generate hot electrons and holes, which subsequently cool down to the band edge by phonon emission. Due to the latter process,the energy of the charge carriers in excess of the band gap is lost as heat and does not contribute to the conversion of solar to electrical power. If the excess energy is more than the band gap itcan in principle be utilized through a process known as carrier multiplication (CM) in which a single absorbed photon generates two (or more) pairs of electrons and holes. Thus, through CM the photon energy abovetwice the band gap enhancesthe photocurrentofa solar cell. In this review, we discuss recent progress in CM research in terms of fundamental understanding, emergenceof new materials for efficient CM, and CM based solar cell applications. Based on our current understanding, the CM threshold can get close to the minimal value of twice the band gap in materials where a photon induces an asymmetric electronic transition from a deeper valence band or to a higher conduction band. In addition,the material must have a low exciton binding energy and high charge carrier mobility, so that photoexcitation leads directly to the formation of free charges that can readily be extracted at external electrodes of a photovoltaic device. Percolative networks of coupled PbSe quantum dots, Sn/Pb based halide perovskites,and transition metal dichalcogenides such as MoTe2fulfill these requirements to a large extent. These findings pointtowards promising prospects for further development of new materials for highly efficient photovoltaics.
