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PubMed1991

Home environmental consequences of commute travel impedance.

The physical and perceptual dimensions of commuting travel impedance were again found to have stressful consequences in a study of 99 employees of two companies. This quasi-experimental replication study, which focuses here on home environment consequences, investigated the effects of physical impedance and subjective impedance on multivariate measures of residential satisfaction and personal affect in the home. Both sets of residential outcome measures were significantly related to the two impedance dimensions. As predicted, gender was a significant moderator of physical impedance effects. Women commuting on high physical impedance routes were most negatively affected. Previously found subjective impedance effects on negative home mood, regardless of gender, were strongly replicated with several methods and were buttressed by convergent results with objective indices. The theoretical conjecture that subjective impedance mediates the stress effects of physical impedance was supported by the personal affect cluster but only for one variable in the residential satisfaction cluster. Traffic congestion has increased in metropolitan areas nationwide, and commuters, families, and organizations are absorbing associated hidden costs. The results are reviewed in terms of our ecological model, and the moderating effects of gender are discussed in terms of choice and role constraints.

Adult↗

PubMed2003

Occupational, commuting, and leisure-time physical activity in relation to risk for Type 2 diabetes in middle-aged Finnish men and women.

AIM/HYPOTHESIS: Leisure-time physical activity can reduce the risk of Type 2 diabetes, but the potential effect of different types of physical activity is still uncertain. This study is to examine the relationship of occupational, commuting and leisure-time physical activity with the incidence of Type 2 diabetes. METHODS: We prospectively followed 6898 Finnish men and 7392 women of 35 to 64 years of age without a history of stroke, coronary heart disease, or diabetes at baseline. Hazards ratios of incidence of Type 2 diabetes were estimated by levels of occupational, commuting, and leisure-time physical activity. RESULTS: During a mean follow-up of 12 years, there were 373 incident cases of Type 2 diabetes. In both men and women combined, the hazards ratios of diabetes associated with light, moderate and active work were 1.00, 0.70 and 0.74 (p=0.020 for trend) after adjustment for confounding factors (age, study year, sex, systolic blood pressure, smoking, education, the two other types of physical activity and BMI). The multivariate-adjusted hazards ratios of diabetes with none, 1 to 29, and more than 30 min of walking or cycling to and from work were 1.00, 0.96, and 0.64 (p=0.048 for trend). The multivariate-adjusted hazards ratios of diabetes for low, moderate, high levels of leisure-time physical activity were 1.00, 0.67, and 0.61 (p=0.001 for trend); after additional adjustment for BMI, the hazards ratio was no longer significant. CONCLUSIONS/INTERPRETATION: Moderate and high occupational, commuting or leisure-time physical activity independently and significantly reduces risk of Type 2 diabetes among the middle-aged general population.

Adult↗

PubMed1981

Matrix effects in clinical analysis: commutability of control materials between the Ektachem, Beckman and SMA 12/60 glucose and urea methods.

The effects of the protein matrices of selected human and animal based control materials on the Ektachem, Beckman and SMA 12/60 glucose and urea methods have been investigated by means of commutability studies. The commutability of control materials between the Ektachem and SMA 12/60 was greater than that between the Ektachem and Beckman methods and was similar to that reported for conventional methods. No trends were apparent amongst control sera from different species nor with different total protein levels. Some variation in commutability was found with different batches of Ektachem glucose and urea slides. In addition the effect of lyophilisation of fresh human serum on its analytical behaviour with different experimental batches of Ektachem glucose/urea slides was studied and found to be negligible.

Autoanalysis↗

PubMed2006

Exposure to hydrocarbon concentrations while commuting or exercising in Dublin.

In Ireland, several studies have monitored the air pollution due to traffic in both urban and rural environments. However, few studies have attempted to quantify the relative exposure to traffic derived HC pollutants between different modes of commuter transport. In this study, the difference in pollution exposure between bus and cycling commuters on a route in Dublin was compared by sampling for five vehicle related hydrocarbons: benzene, 1,3-butadiene, acetylene, ethane and ethylene. Samples were collected during both morning and afternoon rush hour periods using a fixed speed pump to gain representative concentrations across the whole journey. Journey times were also measured, as were typical breathing rates in order to calculate the overall dose of pollutant inhaled on the journey. Results clearly picked up significantly higher pollutant concentrations in the bus compared to cycling and also revealed elevated concentrations on the congested side of the road compared to the side moving against the traffic. However, when respiration rates and travel times were taken into account to reveal the mass of pollutants inhaled over the course of a journey, the pattern was reversed, showing slightly enhanced levels of hydrocarbons for the cyclist compared to the bus passenger. In addition, the concentrations of these compounds (excluding ethane), were ascertained at playing pitches in the vicinity of a heavily trafficked suburban motorway and in Dublin city centre. Although the concentrations were relatively low at all sites, when breathing rates were taken into consideration, the average inhaled weights of pollutants were, on occasion, higher than those average values observed for both bus and bicycle commuters.

Bicycling↗

PubMed2005

Active commuting to school among NSW primary school children: implications for public health.

Regular active commuting by walking/cycling can help maintain an active lifestyle. The frequency, duration and correlates of school active commuting were examined for primary school children in NSW, Australia. Walking/cycling-only and in combination with bus/car were of short duration (median 7 or 4 min, respectively) and their frequency dropped within a short distance (>0.75 km) from school. Apart from distance, child's age, school affiliation and perceived safety, regular walking/cycling (10 trips, 22%) was associated with parents' travel mode to work and with father taking the child to school. Frequent walking/cycling (5 trips, 37%) was associated with child's level of independence and the perceived benefits of active commuting. Behaviour change in this setting requires multi-level strategies.

Bicycling↗

PubMed1999

Bus commuters' coping strategies and anxiety from terrorism: an example of the Israeli experience.

This study examined the use of three coping strategies: (1) emotion-focused coping (calming-distraction); (2) problem-focused coping (checking-behavior); and (3) denial (reduced perceived vulnerability), and their relationship to anxiety from terrorism among 50 Israeli bus commuters. Their mean age was 31 years (60% females). Commuting frequency was negatively correlated, and problem-focused coping was positively correlated with anxiety from terrorism. Ratios of problem-focused coping/denial and of problem-focused/emotion-focused coping were each positively correlated with anxiety from terrorism. Coping ratios accounted for 15% of the variance in anxiety from terrorism, after considering commuting frequency. Combining minimal problem-focused preventative acts with distraction and reduced perceived vulnerability may be beneficial.

Adaptation, Psychological↗

PubMed2005

Characterizing the range of children's air pollutant exposure during school bus commutes.

Real-time and integrated measurements of gaseous and particulate pollutants were conducted inside five conventional diesel school buses, a diesel bus with a particulate trap, and a bus powered by compressed natural gas (CNG) to determine the range of children's exposures during school bus commutes and conditions leading to high exposures. Measurements were made during 24 morning and afternoon commutes on two Los Angeles Unified School District bus routes from South to West Los Angeles, with seven additional runs on a rural/suburban route, and three runs to test the effect of window position. For these commutes, the mean concentrations of diesel vehicle-related pollutants ranged from 0.9 to 19 microg/m(3) for black carbon, 23 to 400 ng/m(3) for particle-bound polycyclic aromatic hydrocarbon (PB-PAH), and 64 to 220 microg/m(3) for NO(2). Concentrations of benzene and formaldehyde ranged from 0.1 to 11 microg/m(3) and 0.3 to 5 microg/m(3), respectively. The highest real-time concentrations of black carbon, PB-PAH and NO(2) inside the buses were 52 microg/m(3), 2000 ng/m(3), and 370 microg/m(3), respectively. These pollutants were significantly higher inside conventional diesel buses compared to the CNG bus, although formaldehyde concentrations were higher inside the CNG bus. Mean black carbon, PB-PAH, benzene and formaldehyde concentrations were higher when the windows were closed, compared with partially open, in part, due to intrusion of the bus's own exhaust into the bus cabin, as demonstrated through the use of a tracer gas added to each bus's exhaust. These same pollutants tended to be higher on urban routes compared to the rural/suburban route, and substantially higher inside the bus cabins compared to ambient measurements. Mean concentrations of pollutants with substantial secondary formation, such as PM(2.5), showed smaller differences between open and closed window conditions and between bus routes. Type of bus, traffic congestion levels, and encounters with other diesel vehicles contributed to high exposure variability between runs.

Air Pollution, Indoor↗

PubMedDate not supplied

Relation between commuting, leisure time physical activity and serum lipids in a Chinese urban population.

PRIMARY OBJECTIVE: To analyse the association between both commuting and leisure time physical activity and serum lipids in a Chinese population. POPULATION: A total of 1786 males and 1922 females aged 20-49 years. METHODS: A cross-sectional survey was carried out in 1989 in urban area of the city of Tianjin, China. Commuting and leisure time physical activity, total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol and triglycerides were determined. RESULTS: Daily walking or cycling to and from work was inversely associated with serum total cholesterol, low-density lipoprotein cholesterol and triglyceride concentrations among men and positively associated with high-density lipoprotein cholesterol concentrations among women as compared to travelling to and from work by bus. CONCLUSIONS: The present study showed a significant association between serum lipids and commuting physical activity, but no relation with leisure time sports.

Adult↗

PubMed2003

Mortality risk in a birth cohort of commuter air carrier and air taxi pilots.

Commuter and air taxi pilots have higher work-related death rates than most other occupational groups. In this longitudinal study, the authors examined the mortality in a cohort of 3263 commuter and air taxi pilots. With adjustment for age, proportional hazards modeling revealed that termination or downgrading of medical certificates during the 11-year follow-up was associated with a significantly increased risk of overall mortality (relative risk, 2.32; 95% confidence interval [CI] = 1.43-3.77). Relative to the general population with similar demographic characteristics, commuter air carrier and air taxi pilots had significantly lower overall mortality (standard mortality ratio [SMR], 0.36; 95% CI = 0.32-0.41) and mortality from cardiovascular diseases (SMR, 0.18, 95% CI = 0.15-0.22), but considerably higher mortality from aviation crashes (SMR, 128.88; 95% CI = 6.35-2624.36). The results indicate that the current medical certification system is effective in maintaining a healthy pilot workforce.

Accident Proneness↗

PubMed2005

Non-Hamiltonian commutators in quantum mechanics.

The symplectic structure of quantum commutators is first unveiled and then exploited to describe generalized non-Hamiltonian brackets in quantum mechanics. It is easily recognized that quantum-classical systems are described by a particular realization of such a bracket. In light of previous work, this paper explains a unified approach to classical and quantum-classical non-Hamiltonian dynamics. In order to illustrate the use of non-Hamiltonian commutators, it is shown how to define thermodynamic constraints in quantum-classical systems. In particular, quantum-classical Nosé-Hoover equations of motion and the associated stationary density matrix are derived. The non-Hamiltonian commutators for both Nosé-Hoover chains and Nosé-Andersen (constant-pressure, constant-temperature) dynamics are also given. Perspectives of the formalism are discussed.

Journal Article↗

PubMed2006

Synchronization in dynamical networks: evolution along commutative graphs.

Starting from an initial wiring of connections, we show that the synchronizability of a network can be significantly improved by evolving the graph along a time dependent connectivity matrix. We consider the case of connectivity matrices that commute at all times, and compare several approaches to engineer the corresponding commutative graphs. In particular, we show that synchronization in a dynamical network can be achieved even in the case in which each individual commutative graphs does not give rise to synchronized behavior.

Journal Article↗

PubMed2004

Occupational, commuting, and leisure-time physical activity in relation to total and cardiovascular mortality among Finnish subjects with type 2 diabetes.

BACKGROUND: Some previous studies have assessed the association between leisure-time physical activity and mortality among patients with diabetes, but the potential effect of occupational and commuting physical activity remains uncertain. METHODS AND RESULTS: We prospectively followed up 3316 Finnish participants 25 to 74 years of age with type 2 diabetes. The association of different types of physical activity with mortality was examined with Cox proportional-hazard models. During a mean follow-up of 18.4 years, 1410 deaths were recorded, 903 of which were due to cardiovascular disease (CVD). The multivariate-adjusted (age, sex, study year, body mass index, systolic blood pressure, cholesterol, smoking, and the 2 other types of physical activity) hazard ratios associated with light, moderate, and active work were 1.00, 0.86, and 0.60 (P(trend)<0.001) for total mortality and 1.00, 0.91, and 0.60 (P(trend)<0.001) for CVD mortality, respectively. The multivariate-adjusted hazard ratios associated with low, moderate, and high leisure-time physical activity were 1.00, 0.82, and 0.71 (P(trend)<0.001) for total mortality and 1.00, 0.83, and 0.67 (P(trend)=0.005) for CVD mortality, respectively. Active commuting had significant inverse associations with total and CVD mortality, but these relations were no longer significant after additional adjustment for occupational and leisure-time physical activity. CONCLUSIONS: Moderate or high levels of physical activity reduce total and CVD mortality among patients with type 2 diabetes. Not only leisure-time physical activity but also occupational and commuting physical activities are important components of a healthy lifestyle among patients with diabetes.

Cardiovascular Diseases↗

PubMed2005

Prevalence of active commuting at urban and suburban elementary schools in Columbia, SC.

We directly observed the prevalence of walking and bicycling (active commuting) to 8 randomly selected urban and suburban elementary schools. When school was used as the unit of analysis, only 5.0% of the students actively commuted to or from school across all observed trips. Active commuting was not affected (P >/=; 18) by school urbanization level, school socioeconomic status, time of day, day of week, weather conditions, or temperature. These results indicate a need for school- and community-based interventions.

Bicycling↗

PubMed1993

Commutability of reference materials in clinical chemistry.

The term commutability applied to reference materials denotes the ability of the material to show interassay changes comparable to those observed in the measurement of the same analyte in human serum. In this study commutability was studied by first establishing the relationship between the results obtained on patient serum samples with two independent methods for a given analyte. Then, the calibration or control material was assayed with the same pair of methods, and its interassay bias was statistically compared with that shown by patient sera. The results obtained in 27 experiments showed that the frequencies of noncommutability in the measurement of some nonenzymic organic components, enzymes, and inorganic ions were, respectively, 25/83, 44/99, and 32/61. The impact of noncommutability of the materials on the results of external quality assessment schemes (EQAS), matrix interferences, and the behavior of particular components are considered. The conclusion drawn is that each material should be tested for commutability before it is used as a reference material.

Calibration↗

PubMed1999

[Tuberculosis microepidemic in a commuter bus].

A tuberculosis microepidemic in a commuter bus was reported. Index patient was a 22-year-old woman who was an employee of an electronic company. An abnormal shadow was found on her chest roentgenogram during an annual medical check-up in June, 1996. As her sputum smear was Gaffky 6, she was admitted to our hospital for medication. Extraordinary examinations including PPD skin test and chest X-ray were carried out on 49 employees of the company in October, 1996. As the result of these examinations, the distribution of maximum diameters of erythema in PPD skin test showed bimodal distribution, and tuberculosis was discovered in two patients by Chest X-ray examination. Moreover, preventive administration of Isonicotinic acid hydrazide (INH) was indicated for 3 employees based on very strong skin reaction to PPD. These five employees were working separately from the index patient and had little contact with the patient in the work places, but using a same commuter bus. Therefore, we strongly suspect that they were infected from the index patient not in the work place but in the commuter bus. The air-conditioning of the bus used a closed recirculation system, hence insufficient ventilation in the bus contributed to the spread of tuberculosis infection.

Adult↗

PubMed2002

Commutability assessment of potential reference materials using a multicenter split-patient-sample between-field-methods (twin-study) design: study within the framework of the Dutch project "Calibration 2000".

BACKGROUND: The Dutch project "Calibration 2000" aims at harmonization of laboratory results via calibration by development of commutable, matrix-based, secondary reference materials. An alternative approach to the NCCLS EP14 protocol for studying commutability of reference materials is presented, the "twin-study design", which in essence is a multicenter, split-patient-sample, between-field-methods protocol. METHODS: The study consisted of the simultaneous analysis of fresh patient sera and potential reference materials (PRMs) for HDL-cholesterol (HDL-C) by 86 laboratories forming 43 laboratory couples. Six subgroups of method combinations were formed. The patient sera were selected and interchanged by each laboratory couple. The PRMs consisted of three types: C37, prepared according to the NCCLS C37 protocol; Fro, frozen selectively pooled human serum; and Lyo, which was the same serum pool as Fro but lyophilized in the presence of sucrose. All PRMs were provided in three HDL-C concentrations. The regression line residuals for the PRMs were normalized by expressing them as multiples of the state-of-the-art within laboratory SD (SD(SA)). In addition, the extra contribution of each PRM to the total measurement uncertainty, CV(Netto), was calculated. RESULTS: Averaged over the three PRM concentrations, 1.6% of the C37 residuals were outside the 3 SD(SA) limit. For the Fro and Lyo PRMs, these values were 2.4% and 11.1%. CV(Netto) values for C37, Fro, and Lyo were 2.9%, 4.3%, and 5.3%, respectively. CONCLUSIONS: The present twin-study design, as a practical alternative to the NCCLS EP14 protocol, is a viable way of studying commutability characteristics of PRMs. The study suggests that the C37 PRMs are the best candidates for a future reference material.

Algorithms↗

PubMed1987

Problem size and mentally retarded children's judgment of commutativity.

The effects of problem size on judgments of commutativity by 51 moderately and mildly mentally retarded students were investigated. The task required subjects to judge whether commuted addition problems (e.g., 5 + 2 and 2 + 5) and noncommuted problems (e.g., 5 + 3 and 5 + 0) would have the same or different sum. Small problems had addends of five or less; large problems had at least one addend greater than five. The subjects' responses to the commutativity task were highly consistent across the two problem sizes. Results indicated that many retarded students who are given computational practice recognize the general principle that addend order does not affect the sum.

Adolescent↗

PubMed1996

The epidemiology of aircraft fire in commuter and air taxi crashes.

BACKGROUND: Aircraft fire is recognized as an important risk factor for occupant fatality in aviation crashes, but its epidemiology has not been adequately studied. OBJECTIVE: This study examines factors related to the occurrence of aircraft fire, ignition sources, and factors influencing rescue and firefighting in commuter and air taxi crashes. METHODS: Commuter and air taxi crashes in 1983-88 that involved aircraft fire were analyzed using National Transportation Safety Board (NTSB) data, including NTSB supplemental forms on fire and on rescue and firefighting. RESULTS: Aircraft fire was recorded in 17% of the 888 commuter and air taxi crashes. Factors associated with increased likelihood of fire in these crashes were non-airport location (adjusted relative risk 2.7, 95% confidence interval 1.8-4.1), twin-engine aircraft (RR 2.5, 95% Cl 1.6-3.9), and nighttime (RR 1.7, 95% Cl 1.1-2.5). Fire was more common in Beech 18's than other twin-engine airplanes. The majority (59%) of fires occurred during impact sequence, and an additional 17% occurred after the aircraft came to rest. The engine was identified as the ignition source in 59% of the crashes, followed by hot surface (18%), short circuit (9%), and sparks (9%). Fire sensing and extinguishing systems were installed in only 19% of the aircraft. Rescue and firefighting efforts were hampered most commonly by terrain (48%), weather (47%), and darkness (38%). CONCLUSIONS: Typically induced by impact and started at the engine, aircraft fire is most likely when a crash occurs at night, in a non-airport location, and in instrument meteorological conditions. These high-risk circumstances also often thwart rescue and firefighting efforts.

Accidents, Aviation↗