A predictive group-contribution framework for the thermodynamic modelling of CO absorption in cyclic amines, alkyl polyamines, alkanolamines and phase-change amines: New data and SAFT- Mie parameters

A significant effort is under way to identify improved solvents for carbon dioxide (CO ) capture by chemisorption. We develop a predictive framework that is applicable to aqueous solvent + CO mixtures containing cyclic amines, alkyl polyamines, and alkanolamines. A number of the mixtures studied exhibit liquid–liquid phase separation, a behaviour that has shown promise in reducing the energetic cost of CO capture. The proposed framework is based on the SAFT- Mie group-contribution (GC) approach, in which chemical reactions are described via physical association models that allow a simpler, implicit, treatment of the chemical speciation characteristic of these mixtures. We use previously optimized group interaction parameters between some amine groups and water (Perdomo et al., 2021), and develop new group interactions for the cNH, cN, NH2, NH, N, cCHNH, and cCHN groups with CO2; a set of second-order group parameters are also developed to account for proximity effects in some alkanolamines. A combination of literature data and new experimental measurements for the absorption of CO2 in aqueous cyclohexylamine systems obtained in our current work, are used to develop and test the proposed models. The SAFT- Mie GC approach is used to predict the thermodynamics of selected mixtures, including ternary phase diagrams and mixing properties relevant in the context of CO2 capture. The current work constitutes a substantial extension of the range of aqueous amine-based solvents that can be modelled and thus offers the most comprehensive thermodynamically consistent platform to date to screen novel candidate solvents for CO2 capture

Is comorbidity in adolescence a predictor for adult low back pain? A prospective study of a young population

BACKGROUND: It has previously been shown that low back pain (LBP) often presents already in the teenage years and that previous LBP predicts future LBP. It is also well documented that there is a large degree of comorbidity associated with LBP, both in adolescents and adults. The objective of this study is to gain a deeper insight into the etiology of low back pain and to possibly develop a tool for early identification of high-risk groups. This is done by investigating whether different types of morbidity in adolescence are associated with LBP in adulthood. METHODS: Almost 10,000 Danish twins born between 1972 and 1982 were surveyed by means of postal questionnaires in 1994 and again in 2002. The questionnaires dealt with various aspects of general health, including the prevalence of LBP, classified according to number of days affected during the previous year (0, 1–7, 8–30, >30). The predictor variables used in this study were LBP, headache, asthma and atopic disease at baseline; the outcome variable was persistent LBP (>30 days during the past year) at follow-up. Associations between morbidity in 1994 and LBP in 2002 were investigated. RESULTS: LBP, headache and asthma in adolescence were positively associated with future LBP. There was no association between atopic disease and future LBP. Individuals with persistent LBP at baseline had an odds ratio of 3.5 (2.8–4.5) for future LBP, while the odds ratio for those with persistent LBP, persistent headache and asthma was 4.5 (2.5–8.1). There was a large degree of clustering of these disorders, but atopic disease was not part of this pattern. CONCLUSION: Young people from 12 to 22 years of age with persistent LBP during the previous year have an odds ratio of 3.5 persistent LBP eight years later. Both headache and asthma are also positively associated with future LBP and there is a large clustering of LBP, headache and asthma in adolescence

Risk factors for sickness absence due to low back pain and prognostic factors for return to work in a cohort of shipyard workers

The purpose of this study was to determine risk factors for the occurrence of sickness absence due to low back pain (LBP) and to evaluate prognostic factors for return to work. A longitudinal study with 1-year follow-up was conducted among 853 shipyard workers. The cohort was drawn around January 2004 among employees in the shipyard industry. Baseline information was obtained by questionnaire on physical and psychosocial work load, need for recovery, perceived general health, musculoskeletal complaints, sickness absence, and health care use during the past year. During the 1-year follow-up for each subject medical certifications were retrieved for information on the frequency and duration of spells of sickness absence and associated diagnoses. Cox regression analyses were conducted on occurrence and on duration of sickness absence with hazard ratios (HR) with 95% confidence interval (95% CI) as measure of association. During the 1-year follow-up period, 14% of the population was on sick leave at least once with LBP while recurrence reached 41%. The main risk factors for sickness absence were previous absence due to a health problem other than LBP (HR 3.07; 95%CI 1.66–5.68) or previous sickness absence due to LBP (HR 6.52; 95%CI 3.16–13.46). Care seeking for LBP and lower educational level also hold significant influences (HR 2.41; 95%CI 1.45–4.01 and HR 2.46; 95%CI 1.19–5.07, respectively). Living with others, night shift and supervising duties were associated with less absenteeism due to LBP. Workers with a history of herniated disc had a significantly decreased rate of returning to work, whereas those who suffered from hand-wrist complaints and LBP returned to work faster. Prior sick leave due to LBP partly captured the effects of work-related physical and psychosocial factors on occurrence of sick leave. Our study showed that individual and job characteristics (living alone, night shift, lower education, sick leave, or care seeking during the last 12 months) influenced the decision to take sick leave due to LBP. An increased awareness of those frequently on sick leave and additional management after return to work may have a beneficial effect on the sickness absence pattern

Frequency and Interrelations of Risk Factors for Chronic Low Back Pain in a Primary Care Setting

INTRODUCTION: Many risk factors have been identified for chronic low back pain (cLBP), but only one study evaluated their interrelations. We aimed to investigate the frequency of cLBP risk factors and their interrelations in patients consulting their general practitioners (GPs) for cLBP. METHODS: A cross-sectional, descriptive, national survey was performed. 3000 GPs randomly selected were asked to include at least one patient consulting for cLBP. Demographic, clinical characteristics and the presence of cLBP risk factors were recorded. The frequency of each cLBP risk factor was calculated and multiple correspondence analysis (MCA) was performed to study their interrelations. RESULTS: A total of 2068 GPs (68.9%) included at least 1 patient, for 4522 questionnaires analyzed. In the whole sample of patients, the 2 risk factors most commonly observed were history of recurrent LBP (72.1%) and initial limitation of activities of daily living (66.4%). For working patients, common professional risk factors were beliefs, that LBP was due to maintaining a specific posture at work (79.0%) and frequent heavy lifting at work (65.5%). On MCA, we identified 3 risk-factor dimensions (axes) for working and nonworking patients. The main dimension for working patients involved professional risk factors and among these factors, patients' job satisfaction and job recognition largely contribute to this dimension. DISCUSSION: Our results shed in light for the first time the interrelation and the respective contribution of several previously identified cLBP risk factors. They suggest that risk factors representing a "work-related" dimension are the most important cLBP risk factors in the working population

The clinical course of low back pain: a meta-analysis comparing outcomes in randomised clinical trials (RCTs) and observational studies.

BACKGROUND: Evidence suggests that the course of low back pain (LBP) symptoms in randomised clinical trials (RCTs) follows a pattern of large improvement regardless of the type of treatment. A similar pattern was independently observed in observational studies. However, there is an assumption that the clinical course of symptoms is particularly influenced in RCTs by mere participation in the trials. To test this assumption, the aim of our study was to compare the course of LBP in RCTs and observational studies. METHODS: Source of studies CENTRAL database for RCTs and MEDLINE, CINAHL, EMBASE and hand search of systematic reviews for cohort studies. Studies include individuals aged 18 or over, and concern non-specific LBP. Trials had to concern primary care treatments. Data were extracted on pain intensity. Meta-regression analysis was used to compare the pooled within-group change in pain in RCTs with that in cohort studies calculated as the standardised mean change (SMC). RESULTS: 70 RCTs and 19 cohort studies were included, out of 1134 and 653 identified respectively. LBP symptoms followed a similar course in RCTs and cohort studies: a rapid improvement in the first 6 weeks followed by a smaller further improvement until 52 weeks. There was no statistically significant difference in pooled SMC between RCTs and cohort studies at any time point:- 6 weeks: RCTs: SMC 1.0 (95% CI 0.9 to 1.0) and cohorts 1.2 (0.7to 1.7); 13 weeks: RCTs 1.2 (1.1 to 1.3) and cohorts 1.0 (0.8 to 1.3); 27 weeks: RCTs 1.1 (1.0 to 1.2) and cohorts 1.2 (0.8 to 1.7); 52 weeks: RCTs 0.9 (0.8 to 1.0) and cohorts 1.1 (0.8 to 1.6). CONCLUSIONS: The clinical course of LBP symptoms followed a pattern that was similar in RCTs and cohort observational studies. In addition to a shared 'natural history', enrolment of LBP patients in clinical studies is likely to provoke responses that reflect the nonspecific effects of seeking and receiving care, independent of the study design

Age related changes in ocular motor testing in healthy subjects

The aim of the present study was the investigation of age influenced changes in ocular motility testing in healthy subjects. Two hundred and fifty subjects between 18 and 70 years old were enrolled in a prospective study. Study population was divided in 5 groups of 50 subjects each (group A: 18-30 years old, group B: 31-40 years old, group C: 41-50 years old, group D: 51-60 years old and group E: 61-70 years old). Ocular motility was recorded by video-oculography and age related normative data were obtained with respect to: a) gain and slow phase velocity of smooth pursuit tracking, b) latency, velocity and accuracy of saccade eye movements and c) gain and slow phase velocity of optokinetic eye movements. The influence of age on all parameters was examined by one-way ANOVA. A statistically significant difference was found in all parameters analyzed for smooth pursuit test, saccade eye movements and optokinetic eye movements in between groups. In conclusion, aging influences the majority of the parameters in ocular motility testing, carried out by means of video-oculography. Elderly healthy subjects showed a deterioration of performance in all parameters of the eye tracking tested. Age must be taken into account during interpretation of the eye tracking tests, especially in patients with central nervous system lesions