Interaction between water-soluble polymers and anionic surfactants has been studied by surface tension and conductivity measurements. Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) were used as surfactant while polyacrylamide (PAA), commercial grade partially hydrolyzed polyacrylamide (PHPA), and xanthan gum were used as water-soluble polymers for the present study. The behavior of surfactant-polymer interaction was found to be dependent on both surfactant and polymer concentrations. After the critical aggregation concentration (CAC), interaction between the water-soluble polymer and surfactants was started and above the polymer saturation point (PSP) polymer was saturated by surfactant with no further change of surface tension and conductivity of the solution. It has also been found that alkali (NaOH) and salts (Na 2 CO 3 , NaCl) have significant influence on the polymer-surfactant interaction.
BackgroundDaytime sleepiness is highly prevalent across the globe. The Epworth sleepiness scale (ESS) is the most widely used tool for screening daytime sleepiness. The psychometric properties of the ESS have not been comprehensively examined in African populations.Material and methodsA cross-sectional design with simple random sampling was used in the present study. The study recruited 600 students from Mizan-Tepi University, Ethiopia, of which 329 (age = 18–28 years and body mass index = 21.19 ± 3.17 kg/m2) completed the study. ESS, a semi-structured socio-demographics questionnaire and a clinical interview to diagnose insomnia according to the International Classification of Sleep Disorders were employed.ResultsAll except one item of the ESS showed a floor effect, while only one item score showed ceiling effect. However, no ceiling/floor effect was observed in the ESS total score. The Cronbach’s alpha (0.75) and composite reliability (0.75), indicated good internal consistency, while a moderate item-total score correlation (r = 0.55–0.67) implied favorable internal homogeneity. The known-group validity was established by significantly higher scores for all the ESS item scores and the ESS total scores among those with symptoms of insomnia than among non-symptomatic students. Fit indices along with the consideration of inter-factor correlation coefficient, measures of item retention favored the unidimensional structure of the ESS.ConclusionThe ESS has excellent psychometric validity for screening daytime sleepiness in Ethiopian university students.Electronic supplementary materialThe online version of this article (10.1186/s12955-019-1098-9) contains supplementary material, which is available to authorized users.
The aim of this study is to assess whether the effect of gender on the excessive daytime sleepiness (EDS) is influenced by two confounders (age and hours of sleep per night). A cross-sectional study was conducted at King Abdulaziz Medical City-Riyadh (KAMC-R). A total of 2095 respondents answered a questionnaire that included questions regarding gender, age, hours of sleep per night, and daytime sleepiness using the Epworth Sleepiness Scale (ESS). The prevalence of EDS was 20.5% (females 22.2%, males 19.5%, p-value=0.136). The EDS did not differ between genders, age groups, or hours of sleep per night (<6 vs. ⩾6h). However, stratified statistical analysis shows that the prevalence of EDS did differ according to gender (25.3% in females, 19.0% in males, p-value=0.036) in respondents with shorter hours of sleep per night. EDS was strongly related to female gender and young age (ages⩽29years) in respondents with short hours of sleep. This study reveals that one out of five of the general Saudi population has EDS. The effect of gender on EDS appeared to be influenced by hours of sleep per night. High EDS strongly related to female gender with short hours of sleep.
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