Simultaneous measurements of ozone outside and inside cabins of two B-747 airliners and a Gates Learjet business jet

The average amount of ozone measured in the cabins of two B-747 airliners varied from 40 percent to 80 percent of the atmospheric concentrations without special ozone destruction systems. A charcoal filter in the cabin air inlet system of one B-747 reduced the ozone to about 5 percent of the atmospheric concentration. A Learjet 23 was also instrumented with monitors to measure simultaneously the atmospheric and ozone concentrations. Results indicate that a significant portion of the atmospheric ozone is not destroyed in the pressurization system and remains in the aircraft cabin of the Learjet. For the two cabin configurations tested, the ozone retentions were 63 and 41 percent of the atmospheric ozone concentrations. Ozone concentrations measured in the cabin near the conditioned-air outlets were reduced only slightly from atmospheric ozone concentrations. It is concluded that a constant difference between ozone concentrations inside and outside the cabin does not exist

A descriptive study of force production and muscle recruitment ratios in healthy shoulders: a quantitative cross sectional study

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, for the degree of Master of Science in Physiotherapy. Johannesburg 2018.Background The scapula’s stabilising muscles position the glenoid dynamically as well as statically so that efficient glenohumeral articulation can occur. Due to a lack of bony support both the static and the dynamic stability of the scapulothoracic joint is dependent on the scapula’s stabilising musculature. The strength of the individual muscles is important, but the ideal force ratios within the different force-couples are more important. Scapular stability ensures optimal placement of the glenoid of the scapula, which in turn ensures joint congruency at the glenohumeral joint. Normal subacromial and subcoracoid spacing is dependent on the ideal functioning of the scapulothoracic musculature. This leads to full and pain free kinematics at the scapulothoracic and the glenohumeral joints. No baseline values, to the researcher’s knowledge, exist in literature of the scapula’s stabiliser force couple ratios. Objectives The first objective was the determination of normative values for the ratios within the force couples of the scapular stabilising muscles in healthy shoulders. The force couple ratios between the upper trapezius versus the lower trapezius, the middle trapezius versus the serratus anterior upper fibres, the serratus anterior lower fibres versus the rhomboids, the serratus anterior lower fibres versus the lower trapezius and the lower trapezius versus the rhomboids, were investigated. The force couple ratios between the sexes was determined, as well as between the non-dominant versus the dominant sides, comparing the sexes. The second objective was the investigation of the electromyographical (EMG) muscle activity of the lower force couple (the serratus anterior lower fibres and the lower trapezius) in the two movement planes, namely flexion in the sagittal plane and abduction in the frontal plane. The third objective was the determination of the correlation between the EMG muscle activity ratio of serratus anterior lower fibres and of lower trapezius in the sagittal and frontal planes, using kinematic analysis. Method This was a cross sectional quantitative study design. There were 58 participants (29 females and 29 males) with healthy shoulders recruited for this study. A convenience sample of 42 participants, who fulfilled the required criteria, was recruited from the general public. The remaining 16 participants were recruited from the student body of the Physiotherapy Department of the University of the Witwatersrand. Measurements were collected of the force couples of the scapulae of both the shoulders of the participants. Force measurements were collected of the serratus anterior upper fibres, the upper trapezius, the middle trapezius, the serratus anterior lower fibres, the rhomboids and the lower trapezius. EMG activity was recorded of the serratus anterior lower fibres and the lower trapezius. This study utilised largely descriptive analysis. A paired-t test analysis was used for the comparison between the non-dominant and the dominant side and for the comparison between female and male participants. The means, standard deviations and ranges were calculated for all force measurements. Kinematic data collected was of the serratus anterior lower fibres and the lower trapezius in flexion in the sagittal plane and in abduction in the frontal plane. A repeated analysis of variance (ANOVA) with a Bonferroni post- hoc test was run for the variance of the serratus anterior lower fibres and lower trapezius. A Spearman test was run to determine the consistency of serratus anterior lower fibres versus lower trapezius in flexion and in abduction. In the familiarisation session all participants completed the informed consent form, were weighed, measured and kinematic inertial measurements were collected. A priori sample size calculation was calculated using G*Power (version 3.1.9.2). Statistical significance was set at p< 0.05, with the confidence level at 95% (alpha <0.05). It was determined that the sample size required with an alpha of 0.05, a power level of 0.95 and using a two-tailed design would be n=58. Results Statistically significant differences were found to exist within the combined (females and males) groups in some of the mean force couple ratios. The mean force couple ratio for upper trapezius versus lower trapezius was found to be higher in the non-dominant and the dominant sides in the females, compared to that of the males. The ratio between the middle trapezius versus serratus anterior upper fibres in the non-dominant and the dominant sides of the females was lower compared to that of the males. The other major finding was the increased EMG activity of serratus anterior lower fibres versus lower trapezius in abduction in the frontal plane, at 70%, 80% and 90%. Correlating the EMG muscle activity ratios of the lower fibres of serratus anterior and the lower fibres of trapezius in sagittal flexion and in frontal abduction: a significant negative relationship concluded from the start to 10% of abduction, and no relationship existed for the rest of the movement cycle of both flexion and abduction. Conclusion The most significant finding was that different force couple ratios exist within some of the force couples of the scapula between sexes. The main results obtained with the EMG and kinematic analysis were that the lower fibres of serratus anterior were consistently more active in abduction in the frontal plane, compared to flexion in the sagittal plane. The EMG ratio correlation between the lower fibres of serratus anterior and the lower fibres of trapezius was consistent at the start and at 10% of abduction.LG201