A group G is a PT -group if, for subgroups H and K with H permutable in K and K permutable in G, it is always the case that H is permutable in G. It is shown that a finite group is a soluble PT -group if and only if each subgroup of a Sylow subgroup is permutable in the Sylow normalizer.
Abstract. Rip currents pose a major global beach hazard; estimates of annual rip-current-related deaths in the United States alone range from 35 to 100 per year. Despite increased social research into beach-goer experience, little is known about levels of rip current knowledge within the general population. This study describes the results of an online survey to determine the extent of rip current knowledge across the United States, with the aim of improving and enhancing existing beach safety education material. Results suggest that the US-based "Break the Grip of the Rip!" ® campaign has been successful in educating the public about rip current safety directly or indirectly, with the majority of respondents able to provide an accurate description of how to escape a rip current. However, the success of the campaign is limited by discrepancies between personal observations at the beach and rip forecasts that are broadcasted for a large area and time. It was the infrequent beach user that identified the largest discrepancies between the forecast and their observations. Since infrequent beach users also do not seek out lifeguards or take the same precautions as frequent beach users, it is argued that they are also at greatest risk of being caught in a dangerous situation. Results of this study suggest a need for the national campaign to provide greater focus on locally specific and verified rip forecasts and signage in coordination with lifeguards, but not at the expense of the successful national awareness program.
Abstract. Rip currents are the greatest
hazard to swimmers on surf beaches, but due to a lack of consistent incident
reporting in many countries, it is often difficult to quantify the number of
rip-current-related rescues and
drowning deaths occurring along surf beaches. This study examines this
problem using rescue data reported to the United States Lifesaving
Association (USLA) by surf beach rescuers from 1997 through 2016. These data
were checked, corrected, and culled so that only data from surf beach rescue
agencies that reported the primary cause of rescue were included. Results
show that rip currents are the primary cause of 81.9 % of rescues on surf
beaches, with regional variation from 75.3 % (East Coast) to 84.7 %
(West Coast). These values are significantly higher than those previously
reported in the scientific literature (e.g., 36.5 %, 53.7 %). Using
this value as a proxy when examining overall surf beach drowning fatalities,
it is suggested that more than 100 fatal drownings per year occur due to rip
currents in the United States. However, it is clear that the United States
data would benefit by an increase in the number of lifeguard agencies which
report surf-related rescues by primary cause.
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