Demonstration of Selective Single-Barium Ion Detection with Dry Diazacrown Ether Naphthalimide Turn-on Chemosensors.

Single-molecule fluorescence imaging (SMFI) of gas-phase ions has been proposed for "barium tagging," a burgeoning area of research in particle physics to detect individual barium daughter ions. This has potential to significantly enhance the sensitivity of searches for neutrinoless double-beta decay (0νßß) that is obscured by background radiation events. The chemistry required to make such sensitive detection of Ba2+ by SMFI in dry Xe gas at solid interfaces has implications for solid-phase detection methods but has not been demonstrated. Here, we synthesized simple, robust, and effective Ba2+-selective chemosensors capable of function within ultrapure high-pressure 136Xe gas. Turn-on fluorescent naphthalimide-(di)azacrown ether chemosensors were Ba2+-selective and achieved SMFI in a polyacrylamide matrix. Fluorescence and NMR experiments supported a photoinduced electron transfer mechanism for turn-on sensing. Ba2+ selectivity was achieved with computational calculations correctly predicting the fluorescence responses of sensors to barium, mercury, and potassium ions. With these molecules, dry-phase single-Ba2+ ion imaging with turn-on fluorescence was realized using an oil-free microscopy technique for the first time-a significant advance toward single-Ba2+ ion detection within large volumes of 136Xe, plausibly enabling a background-independent technique to search for the hypothetical process of 0νßß.

The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles.

The purpose of this study was to measure the relative contributions of 4 hip and thigh muscles while performing squats at 3 depths. Ten experienced lifters performed randomized trials of squats at partial, parallel, and full depths, using 100-125% of body weight as resistance. Electromyographic (EMG) surface electrodes were placed on the vastus medialis (VMO), the vastus lateralis, (VL), the biceps femoris (BF), and the gluteus maximus (GM). EMG data were quantified by integration and expressed as a percentage of the total electrical activity of the 4 muscles. Analysis of variance (ANOVA) and Tukey post hoc tests indicated a significant difference (p < 0.001*, p = 0.056**) in the relative contribution of the GM during the concentric phases among the partial- (16.9%*), parallel- (28.0%**), and full-depth (35.4%*) squats. There were no significant differences between the relative contributions of the BF, the VMO, and the VL at different squatting depths during this phase. The results suggest that the GM, rather than the BF, the VMO, or the VL, becomes more active in concentric contraction as squat depth increases.