This cross-sectional study has shown that athletes, especially those engaged in high-impact sports, have significantly higher total BMD and AMM than controls. These results suggest that the type of sport activity may be an important factor in achieving a high peak bone mass and reducing osteoporosis risk.

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Costas arrays are permutation matrices that provide sequencing schemes for frequency hop in FSK waveforms. Such FSK waveforms can be designed to have nearly ideal ambiguity function properties in both the time and frequency directions: the Costas property permits at most one coincident tone in autocorrelations in both time and frequency. Costas arrays are found by number-theoretic generators and their extensions, and by exhaustive search methods. Two new extensions of numbertheoretic methods are introduced here that find two new Costas arrays. All Costas arrays for orders 24, 25 and 26 are disclosed here, including previously unknown examples.