Intermittent Cooling Reduces Perceived Exertion but Has No Effect on Baseball Hitting or Defense Performance in a Hot Environment.

Hot environments can impair the complex cognitive functions that are crucial to baseball hitting and defense. This study investigated the effects of intermittent forehead and neck cooling on the hitting and reactive agility of baseball players in hot environments. Ten male collegiate baseball players played 7-inning intrasquad games in a hot environment (31.1°C - 33.4°C), completing one cooling and one control trial in a randomized crossover design. In the cooling trial, the participants placed ice-cold towels on their forehead and neck for 3 min during offensive half innings. Hitting and reactive agility tests, a go/no-go task, and the Stroop Color and Word Test were administered before and after each game. The games in the hot environment significantly increased rectal temperatures to the same level in the control (38.15°C ± 0.31°C, p < 0.001) and cooling (38.08°C ± 0.24°C, p < 0.001) trials. Intermittent cooling significantly reduced forehead and tympanic temperatures, perceived exertion, and thermal sensation during the game. Swing power significantly increased after the game, but the exit velocity of batted balls did not significantly differ in both trials. Reactive agility was significantly impaired after the game in the control trial (before: 0.367 ± 0.109 s, after: 0.491 ± 0.212 s, p = 0.008) but displayed a trend of decrease in the cooling trial (before: 0.390 ± 0.183 s, after: 0.518 ± 0.282 s, p = 0.066). The game and cooling intervention had no significant effects on the reaction time or error rate in the go/no-go task and Stroop Color and Word Test. The results showed that intermittent cooling during a baseball game in a hot environment reduces perceived exertion and thermal sensation but has no significant effect on hitting, defense performance, or cognitive function.

Optically tunable/switchable omnidirectionally spherical microlaser based on a dye-doped cholesteric liquid crystal microdroplet with an azo-chiral dopant.

This paper presents an optically wavelength-tunable and intensity-switchable dye-doped cholesteric liquid crystal (DDCLC) spherical microlaser with an azo-chiral dopant. Experimental results present that two functions of optical control - tunability of lasing wavelength and switchability of lasing intensity - can be obtained for this spherical microlaser at low and high intensity regimes of non-polarized UV irradiation, respectively. If the DDCLC microdroplet is subjected to weak UV irradiation, azo-chiral molecules may transform to the bent cis state at a low concentration rate. The effect can slightly decrease the local order of LCs and thus the helical twisting power of the CLC in the microdroplet. As a result, the CLC pitch may become slightly elongated, which will cause the gradual red-shift of both omnidirectional PBG and lasing emission of the DDCLC spherical microdroplet. In contrast, when the microdroplet is subjected to strong UV irradiation, numerous azo-chiral molecules may simultaneously change to bent cis-isomers to seriously disarrange the helical texture of the CLC, which will quickly deform the PBG and deactivate the lasing emission of the microdroplet. Prolonged irradiation of a blue beam after strong UV irradiation may cause the cis azo-chiral molecules quickly convert back rod-like trans-isomers, which may then regenerate the CLC Bragg onion and PBG structures and reactivate the lasing emission of the microdroplet. Optical control of the DDCLC spherical microlaser is realized on a scale of seconds and minutes when UV irradiation is strong and weak, respectively. The 3D DDCLC spherical microlaser is a highly promising controllable 3D micro-light source or microlaser (e.g., all-optical 3D single photon microlaser) for applications of 3D all-optical integrated photonics, laser displays, and biomedical imaging and therapy, and as a 3D UV microdosagemeter or microsensor.