State laws governing school physical education in relation to attendance and physical activity among students in the USA: A systematic review and meta-analysis

Background:This study systematically synthesized and quantified the relationship linking state laws governing school physical education(PE)to PE attendance and physical activity(PA)in class and throughout the day and week among students in the USA.Methods:A keyword search was performed in PubMed,Web of Science,Cumulative Index to Nursing and Allied Health Literature(CINAHL),Academic Search Complete,and EconLit.Meta-analyses were performed to estimate the effects of state PE laws.Results:A total of 17 studies were included in the review,and five contributed to the meta-analyses.A total of 8 studies used nationally representative school-or student-level data,three focused on multiple states,and the remaining six examined the PE laws of a single state.The presence and strength of state PE laws were positively associated with PE attendance and the frequency and duration of PA during PE classes and throughout the school day.Compared to those residing in states with weak or no PE laws,students in states with strong PE laws had an additional 0.2 days(95%confidence interval(95%CI):0.10.4)of PE attendance per week and spent an additional 33.9 min(95%CI:22.745.0)participating PE classes per week.State PE laws affected girls’PA more than boys’.Different aspects of state PE laws tended to affect students’PE attendance differently.Disparities in the implementation of state PE laws existed across schools.Conclusion:Future studies should adopt objective measures on PE and PA participation and examine the roles schools and districts play in mediating the effect of state PE laws on students’PE attendance and PA.

Protonated acetone ion chemical ionization time-of-flight mass spectrometry for real-time measurement of atmospheric ammonia

Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultraviolet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.%high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A signal normalization processing method was designed,and with this new method,the quantitative relative standard deviation(RSD)of the instrument was decreased from 17.5%to9.1%,and the coefficient of determination was increased from 0.8340 to 0.9856.The humidity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signalto-noise ratio S/N=3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.