Fixed-point elimination in the intuitionistic propositional calculus

It is a consequence of existing literature that least and greatest fixed-points of monotone polynomials on Heyting algebras-that is, the algebraic models of the Intuitionistic Propositional Calculus-always exist, even when these algebras are not complete as lattices. The reason is that these extremal fixed-points are definable by formulas of the IPC. Consequently, the $\mu$-calculus based on intuitionistic logic is trivial, every $\mu$-formula being equivalent to a fixed-point free formula. We give in this paper an axiomatization of least and greatest fixed-points of formulas, and an algorithm to compute a fixed-point free formula equivalent to a given $\mu$-formula. The axiomatization of the greatest fixed-point is simple. The axiomatization of the least fixed-point is more complex, in particular every monotone formula converges to its least fixed-point by Kleene's iteration in a finite number of steps, but there is no uniform upper bound on the number of iterations. We extract, out of the algorithm, upper bounds for such n, depending on the size of the formula. For some formulas, we show that these upper bounds are polynomial and optimal

The prevalence of common mental disorders among hospital physicians and their association with self-reported work ability: a cross-sectional study

Background: We studied the prevalence of common mental disorders among Dutch hospital physicians and investigated whether the presence of a mental disorder was associated with insufficient self-reported work ability. Methods: A questionnaire was sent to all (n = 958) hospital physicians of one academic medical center, using validated scales to assess burnout, work-related fatigue, stress, posttraumatic stress disorder (PTSD), anxiety and depression. Furthermore, respondents were asked to rate their current work ability against the work ability in their own best period (adapted version of the first WAI item). The prevalence of each common mental disorder was calculated. In addition, odds ratios of reporting insufficient work ability for subjects with high complaint scores compared to physicians with low complaint scores were calculated for each mental disorder. Results: The response rate was 51%, and 423 questionnaires were eligible for analysis. The mental disorder prevalence rates were as follows: work-related fatigue 42%, depression 29%, anxiety 24%, posttraumatic stress complaints 15%, stress complaints 15% and burnout 6%. The mean score for self-reported work ability was 8.1 (range 0-10), and 4% of respondents rated their own work ability as insufficient. Physicians with high mental health complaints were 3.5- for fatigue, 5.6- for PTSD, 7.1- for anxiety, 9.5- for burnout, 10.8- for depression and 13.6- fold for stress more likely to report their work ability as insufficient. Conclusions: The prevalence of common mental disorders among hospital physicians varied from 6% for burnout to 42% for work-related fatigue. Those physicians with high complaints had significantly 4- to 14 times increased odds of reporting their own work ability as insufficient. This work suggests that to ensure future workers health and patients safety occupational health services should plan appropriate intervention strategie

Physical job demands and related health complaints among surgeons

Surgeons' poor physical health and high physical job demands might threaten good quality of care. We aimed to compare the prevalence of physical complaints of surgeons, their physical work ability and the physical job demands of surgeons with that of other hospital physicians. All medical doctors (n = 958) of one academic medical center were invited to complete the online questionnaire to assess the physical work ability and the prevalence of regional musculoskeletal complaints. A purposive sample of 44 surgeons and 82 other hospital physicians were systematically observed during work to quantify the physical job demands for an average working day. More surgeons found their work to be physically strenuous (41 vs. 13 %, p < .000) and more were bothered by working in uncomfortable or exhausting postures (73 vs. 27 %, p < .001). Both groups reported that most of their physical complaints were in the neck (39 and 32 %) and arm regions (36 and 27 %). The majority of surgeons (86 %) and other hospital physicians (79 %) experienced difficulties coping with their job demands because of their physical state once a month or less. Compared with other hospital physicians, surgeons stand longer (4 vs. 3 h, p = .004) and perform fine repetitive movements longer (80 vs. 3 min, p < .001) during an average working day. Exposure to several physical job demands that are perceived as uncomfortable and exhausting and the presence of physical health complaints reduce surgeons' work functionin

Feasibility and acceptability of a workers' health surveillance program for hospital physicians

A Workers' Health Surveillance (WHS) program is an occupational health strategy used to detect and address the health of individual workers to improve their ability to work. This study aims to investigate the feasibility and acceptability of a new job-specific WHS for hospital physicians. All hospital physicians of the general surgery, radiotherapy and obstetrics and gynecology departments from 1 academic hospital were invited to participate in the WHS by the in-company occupational health service. An occupational physician and a medical assistant were trained to use the protocol. Feasibility was operationalized as the received and delivered dose, observed success factors and potential obstacles. Acceptability was assessed by asking whether the WHS was desirable and feasible for future use and by estimating the effects on health and work ability. Written questions and semi-structured interviews were conducted with the participating physicians, 5 department managers and the 2 occupational health professionals involved in the study. One-third of the hospital physicians (34%) participated in every part of the WHS. The delivered dose was 77/84 (92%). Almost all hospital physicians who received recommendations expected to adhere to this advice. The study participants appreciated the organization of the WHS. This WHS was positively graded (8 out of 10 max) in terms of acceptability. Positive effects of the WHS on health, work functioning and long-term work ability were perceived by 2/3 of the physicians. The new job-specific WHS for hospital physicians showed good feasibility and acceptability among participating hospital physicians, occupational health professionals and medical manager

On-site observations of physical work demands of train conductors and service electricians in the Netherlands

The objective of the present study was to assess the exposure to physical work demands of train conductors and service electricians at a railway company in the Netherlands. On-site observations were performed using the Task Recording and Analysis on Computer observation system to identify the mean duration and frequency of tasks, activities and body postures. In total, 36 train conductors and 41 service electricians were observed for a net working day of 7 h. Results showed that train conductors and service electricians climbed a flight of stairs on average 249 and 258 times, respectively, and that service electricians worked above shoulder height for 65 min on average. In both jobs, guidelines were exceeded, e.g. duration of standing, the number of times climbing a flight of stairs, kneeling and squatting or working in awkward postures, which are risk factors for developing musculoskeletal complaints. Suggestions are made concerning how to reduce these risk factors. STATEMENT OF RELEVANCE: Understanding physical work demands is essential for recognising risk factors for musculoskeletal disorders. Since train conductors and service electricians in the Netherlands reported work-related complaints, on-site observations were performed to determine the duration and frequency of physical work demands. Risk factors were identified in both professions, providing insights concerning preventative measure