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PubMed2003

Commuter exposure to aromatic VOCs in public transportation modes in Hong Kong.

This study investigated commuter exposure to aromatic volatile organic compounds (VOCs) in different commuting microenvironments. In Hong Kong, more than 90% of the local citizens rely on public transport facilities in their daily commutes. During five winter months in late 2001 and early 2002, in-vehicle monitoring was performed in nine popular public transportation modes: tram, public light bus, air-conditioned bus, non-air-conditioned bus, taxi, ferry and three railway systems (Mass Transit Railway-MTR, Kowloon-Canton Railway-KCR and Light Rail Transit-LRT). These transports were grouped into three categories: railway transport, roadway transport and marine transport. Air samples of benzene, toluene, ethylbenzene and m/p/o-xylene were collected by canisters and analysed by gas chromatography and mass selective detector technique. Results indicated that the in-vehicle VOC exposure levels were greatly influenced by the mode of transport. For benzene, mean concentration ranged from 4.8 to 6.1 microg x m(-3) in roadway transports, 3.0-3.8 microg x m(-3) in railway transports and it was 2.1 microg x m(-3) in ferry. Regardless of the results in MTR and air-conditioned buses, the VOC levels in roadway transport were the highest and was followed by railway transport. The exposure levels in marine transport were the lowest. The TEX concentrations were found to be substantially higher in air-conditioned buses and MTR trains than in other transports, suggesting the existence of additional solvent-related sources in their vehicle interiors. Measurements in non-air-conditioned double deck vehicles indicate that there was slightly higher VOC levels in the lower deck than in the upper deck microenvironment. The average upper to lower deck exposure ratio ranged from 0.79 to 0.87 in trams and 0.78-0.83 in non-air-conditioned buses, depending on the compound of concern. The VOC exposure levels of public transport commuters in Hong Kong are far lower than those in most oversea cities. The experimental concentrations obtained in this study are within the relevant health-protecting limits as stated in the Hong Kong Indoor Air Quality Objective. Influences of recent VOC pollution control measures and local traffic characteristics on in-vehicle level are discussed.

Air Pollution, Indoor↗

PubMed1999

Daily time budgets of long-distance commuting workers in Tokyo megalopolis.

In Tokyo Megalopolis, long-distance commuting between residences in the suburbs and work places in the centre of the city was examined. Using a questionnaire, heads of household in two suburbs were asked about the influences of long commuting hours on their daily time budgets. The results showed that on workdays, the workers who spent longer commuting rose and left home for work earlier, and came back home and retired later; accordingly, both time spent on in-home activities on workdays and hours slept on the day before a workday were shorter. Comparison of time budgets between the subjects who work 5 and 6 days per week revealed more vulnerable influences of long commuting hours in the former than the latter. The expected health consequences of these findings are discussed from a biosocial/human ecological viewpoint.

Adult↗

PubMed2026

CAKR: commutative algebra k-mer representations for genomics.

Despite the availability of various sequence analysis models, comparative genomic analysis remains a challenge in genomics, genetics, and phylogenetics. Commutative algebra, a fundamental tool in algebraic geometry and number theory, has rarely been used in data and biological sciences. In this study, we introduce commutative algebra k-mer representations as a nonlinear algebraic framework for analyzing genomic sequences. This representation bridges commutative algebra, algebraic topology, combinatorics, and machine learning to establish a mathematical framework for comparative genomic analysis. We evaluate its effectiveness on three tasks including genetic variant classification, phylogenetic tree reconstruction, and viral classification, typically requiring alignment-based, alignment-free, and machine-learning approaches, respectively. In this work, we show that commutative algebra k-mer representations outperform five state-of-the-art sequence analysis methods across twelve primary datasets, with two additional supplementary fragment-placement benchmarks, especially in viral classification, and maintain relatively stable predictive accuracy as dataset size increases, underscoring scalability and robustness.

Genomics↗

PubMed1993

Commutability of control materials in cholesterol measurement.

The 'commutability' is the property of a material to show inter-assay changes comparable to those of patients' sera. In order to assess the commutability, the cholesterol concentration was measured in 107 patients' sera and in 24 lyophilized control materials by a direct enzymatic method and by a reference-class procedure. The distance from the regression line of patients' sera results, expressed in SD units (normalized residual), was calculated and used to assess the commutability of each material. Out of 24 materials tested one had a normalized residual outside the +/- 3 interval (-4.4), and was considered as non-commutable. However, the distribution of the normalized residuals from the remaining 23 materials suggested a different behaviour in comparison with patients' sera, in the specific pair of methods. The relevance of this finding to the control of accuracy is discussed.

Animals↗

PubMed2004

Commuting physical activity and risk of colon cancer in Shanghai, China.

Colon cancer incidence rates have been rapidly increasing in Shanghai, China, for reasons still unclear. Low physical activity is a known risk factor for colon cancer. The authors examined the effects of physical activity, particularly commuting physical activity, and its joint effects with body mass index on colon cancer risk in a population-based, case-control study. The study included 931 incident colon cancer patients and 1,552 randomly selected controls in Shanghai between 1990 and 1993. Colon cancer risk was significantly reduced among subjects with high commuting physical activity (odds ratio (OR) = 0.52, 95% confidence interval (CI): 0.27, 0.87 for men; OR = 0.56, 95% CI: 0.21, 0.91 for women), particularly among those who had high commuting physical activity for at least 35 years (OR = 0.34, 95% CI: 0.09, 0.76 for men; OR = 0.31, 95% CI: 0.07, 0.72 for women). Commuting physical activity significantly modified the risk conferred by high body mass index, with the highest risk observed among those at the highest quintile of body mass index and the lowest activity level (OR = 6.43, 95% CI: 1.82, 8.54 for men; OR = 7.42, 95% CI: 2.84, 10.01 for women). Our results suggest that regular and frequent physical activity over a long period of time protects from colon cancer and significantly modifies the body mass index-associated risk.

Adult↗

PubMed2000

Effect of commuter cycling on physical performance of male and female employees.

PURPOSE: The purpose of this study was to determine the effect of commuter cycling on physical performance. Eighty-seven male and 35 female employees volunteered to cycle regularly to their work. METHODS: Sixty-one participants went commuter cycling for 1 yr (cycling group); the others cycled only in the second half year (control group). A maximal exercise test on a cycle ergometer was carried out at the start of the study, after 6 months, and after 1 yr to measure maximal external power (Wmax) and maximal oxygen uptake (VO2max). RESULTS: After the first 6 months of commuter cycling, with a mean single trip distance of 8.5 km and a mean frequency of more than three times a week, a significant increase of 13% was found in the Wmax per kilogram body weight (Wmax x kg(-1)) in both sexes of the cycling group. The improvement in VO2max x kg(-1) was significant for the male participants (6%) but not for the female participants (-2%). At the end of the second half year, the control group also showed a mean gain in Wmax x kg(-1) of 13%. Their VO2max x kg(-1) declined in the first half year, but this was counteracted in the second half year. A dose-response relationship was found between two independent variables and the physical performance; the lower the physical performance at the start of the study and the higher the total amount of kilometers cycled, the higher the gain in Wmax. For subjects with a low initial fitness level, a single trip distance of only 3 km turned out to be enough to improve physical performance. CONCLUSION: Commuter cycling can yield much the same improvement in physical performance as specific training programs.

Adult↗

PubMed2005

Active commuting to and from school and BMI in elementary school children-preliminary data.

BACKGROUND: United States National Health Objectives include increasing the proportion of trips made by walking to and from school for children who live within 1.6 km to 50%. The purpose of this objective is to increase the level of physical activity among children. However, the impact of walking, bicycling or skating (active commuting) to and from school on the prevalence of overweight is unknown. METHODS: Body mass index (BMI) was measured for 320 children (age 10.2+/-0.7 years) in September. Over 5 months, an active commuting index (SI) and daily physical activity were estimated via questionnaire. In April, BMI and body fat were measured. RESULTS: A significant positive association was found between April BMI and SI adjusting for September BMI (partial r=0.03, P<0.05). Positive associations were found between SI and physical activity before school (r=0.17, P<0.05) and daily moderate intensity physical activity (r=0.13, P<0.05). There were no significant association between SI and BF (P>0.05). CONCLUSIONS: This preliminary data suggests that active commuting does not appear to provide sufficient amounts of physical activity to attenuate BMI; however, it may contribute to the attainment of physical activity recommendations. Future research is needed to objectively measure the impact of active commuting on the prevalence of overweight.

Adipose Tissue↗

PubMed2005

Leisure time, occupational, and commuting physical activity and the risk of stroke.

BACKGROUND AND PURPOSE: The role of physical activity, especially that of occupational and commuting physical activity, in the prediction of stroke risk is not properly established. We assessed the relationship of different types of physical activity with total and type-specific stroke risk. METHODS: We prospectively followed 47 721 Finnish subjects 25 to 64 years of age without a history of coronary heart disease, stroke, or cancer at baseline. Hazard ratios (HRs) for incident stroke were estimated for different levels of leisure time, occupational, and commuting physical activity. RESULTS: During a mean follow-up of 19.0 years, 2863 incident stroke events were ascertained. The multivariate-adjusted (age, sex, area, study year, body mass index, systolic blood pressure, cholesterol, education, smoking, alcohol consumption, diabetes, and other 2 types of physical activity) HRs associated with low, moderate, and high leisure time physical activity were 1.00, 0.86, and 0.74 (Ptrend<0.001) for total stroke, 1.00, 0.87, and 0.46 (Ptrend=0.011) for subarachnoid hemorrhage, 1.00, 0.77, and 0.63 (Ptrend=0.024) for intracerebral hemorrhage, and 1.00, 0.87, and 0.80 (Ptrend=0.001) for ischemic stroke, respectively. The multivariate-adjusted HRs associated with none, 1 to 29, and > or =30 minutes of active commuting were 1.00, 0.92, and 0.89 (Ptrend=0.043) for total stroke, and 1.00, 0.93, and 0.86 (Ptrend=0.028) for ischemic stroke, respectively. Occupational activity had a modest association with ischemic stroke in the multivariate analysis (Ptrend=0.046). CONCLUSIONS: A high level of leisure time physical activity reduces the risk of all subtypes of stroke. Daily active commuting also reduces the risk of ischemic stroke.

Adult↗

PubMed2006

Toward standardization of cardiac troponin I measurements part II: assessing commutability of candidate reference materials and harmonization of cardiac troponin I assays.

BACKGROUND: Cardiac tropoin I (cTnI) measurements show an approximately 20- to 40-fold difference between assays, and better standardization and harmonization are needed. Toward this goal, the AACC cTnI Standardization Committee collaborated with the National Institute of Standards and Technology (NIST) in an earlier study to select 2 candidate reference materials (cRMs). METHODS: Two troponin cRMs, a troponin C-troponin I-troponin T (CIT) complex from human heart tissue and a CIT complex from recombinant technology, were supplied to NIST for assessment of composition and purity, and cTnI value assignment. These cRMs and 6 cTnI-positive human serum pools were shipped to manufacturers of 15 cTnI assays. Commutability of the materials was examined by determining the numerical relationship for the cRM preparations between each manufacturer-specified field method and each of the other 14 field methods. These relationships were then compared with the corresponding numerical relationships for the human serum pools. Harmonization of methods was accomplished by determining regression parameters relative to the analytical system yielding values closest to the median for each serum pool. These regression parameters were used to recalculate pool values to harmonize the assays. Interassay CVs before and after harmonization were determined. RESULTS: Characterization of the CIT and CI cRMs showed that these materials were of specified composition. The proportion of cTnI methods that demonstrated commutability for the CIT cRM was 45%; for the CI cRM, 39% of methods demonstrated commutability. Interassay cTnI variability for the field methods ranged from 82% to 97%, median 88%. After harmonization, variability of the serum pools for the cTnI methods was decreased to between 9.0% and 23%, median 15.5%. CONCLUSIONS: The proportion of methods demonstrating commutability was too low for use as a common calibrator for the cTnI field methods. However a simple strategy using serum pools can improve harmonization of field cTnI methods by more than 5-fold. The CIT cRM was selected by the AACC cTnI standardization committee, and a new lot has been classified as the cTnI certified reference material Standard Reference Material 2921 by NIST.

Calibration↗

PubMed1998

Normalizing intermethod free triiodothyronine patient results: need for commutable materials.

The aim of this work was to check the suitability of control materials to normalize intermethod results for the measurement of free triiodothyronine in patient sera. In the main experiment, 108 patient sera and 11 commercially available control materials were assayed by a pair of methods. In a confirmatory experiment, two of the control materials and 142 patient sera were assayed with an alternative pair of methods. In the main experiment, the intermethod variability of 6/11 control materials differed significantly from that of patient sera (i. e. control materials were non-commutable). Recalculation of patient results using control materials as calibrators lowered the intermethod difference only if commutable materials were used. The confirmatory experiment demonstrated that the pattern of commutability changed if a different pair of methods was used. We conclude that in the case of free triiodothyronine the commutability of control materials should be tested if they are to be used to normalize patient results obtained by different methods.

Humans↗

PubMed2001

Active commuting to school: an overlooked source of childrens' physical activity?

The assessment and promotion of childrens' healthful physical activity is important: (i) to combat the international obesity epidemic that extends to childhood; and (ii) to establish an early habit of lifestyle physical activity that can be sustained into adolescence and adulthood. The primary focus of both assessment and promotion efforts has been on in-school physical education classes and, to a lesser extent, out-of-school structured exercise, sport and play. A potential source of continuous moderate activity, active commuting to school by means of walking or by bicycle, has been largely ignored in surveys of physical activity. Suggestive evidence of steep declines in the amount of childrens' destination walking can be gleaned from national transportation surveys. At the same time, there has been a dramatic increase in the reported use of motorised vehicles, including the use for chauffeuring children. There is very little evidence to support or refute active commuting to school as an important source of childrens' physical activity; however, this is largely because it has been overlooked in the stampede to assess time in more vigorous activities. The promotion of active commuting to school must be considered in the context of parents' real and perceived concerns for their children's personal and pedestrian safety. We certainly do not have a full understanding at this time of all the factors related to decisions about transportation mode, whether by child, parent, community, or school. Such information is necessary if successful and sustainable interventions can be implemented, important transport policy decisions can be made, and community and school designs can be modified. Practice rarely waits for research, however, and there are numerous examples of innovative programming, policies and environmental designs occurring internationally that can serve as natural experiments for enterprising researchers willing to push the envelope of our understanding of active commuting and childrens' physical activity. Since we know so little, there is much to learn.

Adolescent↗

PubMed1991

The nature of calibrators in immunoassays: are they commutable with test samples? Must they be?

Immunoassay systems require calibration protocols that are normally more sophisticated than many analytical techniques in routine clinical use. Calibrators used in such assays may differ significantly from the analyte in clinical specimens. Differences in the properties of calibrators, or reference materials, from those of clinical specimens may include: species origin of the calibrator for an analyte; integrity of the molecular species; matrix of the calibration solution; addition of preservative agents. Owing to the large number of potential differences in the properties of calibrators and those of serum specimens that may affect immunoassay results, the concept of commutability that we originated and first applied to enzyme activity measurements can readily be applied to immunoassay determinations. We specifically examined the properties of calibration materials in nine commercial immunoassay tests for human thyrotropin. Significant non-commutability of materials was demonstrated. The measured results obtained with authentic patient sera differed by a factor of approximately two fold between the techniques exhibiting the lowest and greatest numeric results. Considerably larger intermethod biases were found for calibration materials. Multivariate analysis revealed that the patient sera formed a highly focussed pattern. The calibration materials for one instrument system also focussed in this group. Other calibrators formed three foci indicating similar patterns of commutability within each of the three groups. Clustering was independent of the amount of thyrotropin in the patient specimens, but appeared to be concentration-dependent for at least some of the calibrators. Thus the availability of a common calibration material appears feasible, but not presently available in many commercial products. A processed human serum, a candidate material for use in our proficiency testing program, was projected in the same cluster as authentic patient sera indicating that this material has intermethod properties identical to patient sera (i.e. fully commutable).

Humans↗

PubMed2001

Commutability of calibration and control materials for serum lipase.

BACKGROUND: To effectively assess and correct for intermethod variability, calibration and control materials (CCMs) must show the same intermethod behavior as patient sera, i.e., they must be commutable. We describe the commutability of selected CCMs for lipase assays, the impact of noncommutability of CCMs in normalizing patient results, and characteristics of reagents that affect assay specificity and commutability. METHODS: Lipase was measured in 98 patient sera and in 29 commercial CCMs, with 2 commercial methods using different substrates and with 4 experimental methods using 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6'-methylresorufin) ester as substrate and colipase as cofactor, but differing in the stabilizing proteins used and in the size of the substrate micelles. RESULTS: The noncommutability rate, i.e., the frequency of aberrant intermethod behavior of CCMs in comparison with patient sera, was 27% for liquid CCMs and 47% for lyophilized CCMs. The normalized residuals, measuring the degree of noncommutability, were -2.3 to 2.4 for CCMs with "normal" lipase activity, and -3.5 to 21.7 for CCMs with higher lipase activity. Recalculation of patient results with CCMs as calibrators decreased or increased the original bias according to whether the CCMs were commutable. CONCLUSIONS: For the lipase methods in this study, the frequency of noncommutability of CCMs is affected by assay-specific characteristics, including size of substrate micelles and the presence or absence of added proteins.

Calibration↗

PubMed2025

CAKL: Commutative algebra k-mer learning of genomics.

Despite the availability of various sequence analysis models, comparative genomic analysis remains a challenge in genomics, genetics, and phylogenetics. Commutative algebra, a fundamental tool in algebraic geometry and number theory, has rarely been used in data and biological sciences. In this study, we introduce commutative algebra k-mer learning (CAKL) as the first-ever nonlinear algebraic framework for analyzing genomic sequences. CAKL bridges between commutative algebra, algebraic topology, combinatorics, and machine learning to establish a new mathematical paradigm for comparative genomic analysis. We evaluate its effectiveness on three tasks-genetic variant identification, phylogenetic tree analysis, and viral genome classification-typically requiring alignment-based, alignment-free, and machine-learning approaches, respectively. Across eleven datasets, CAKL outperforms five state-of-the-art sequence analysis methods, particularly in viral classification, and maintains stable predictive accuracy as dataset size increases, underscoring its scalability and robustness. This work ushers in a new era in commutative algebraic data analysis and learning.

Journal Article↗

PubMed1994

Prior crash and violation records of pilots in commuter and air taxi crashes: a case-control study.

With a case-control design, this study examined the relationships of crash/incident history, violation history, pilot age, flight experience, and recent flight time with the likelihood of being involved in commuter aircraft and air taxi crashes. Cases (n = 725) were pilots who had been involved in commuter aircraft or air taxi crashes during 1983-88, identified from the National Transportation Safety Board aviation crash data base. From the Federal Aviation Administration (FAA) airmen information system, 1,555 pilots were randomly selected as controls. Controls were frequently-matched with cases on medical class and calendar year. Different data bases within the FAA's airmen information system were linked to ascertain information about crash/incident and violation records in the previous 3 years, age, total flight time, and flight time in the prior 6 months. Multivariate logistic regression models were fitted to estimate odds ratios and evaluate dose-response effects, non-linear relationships, and interactions. Cases had significantly higher prevalence rates of prior crash/incident and violation records. The estimated odds ratio of being involved in a commuter aircraft or an air taxi crash was 1.7 (95% confidence interval [CI], 1.3-2.4) for crash/incident history, and 1.6 (95% CI, 1.1-2.2) for violation history. A "dose-response effect" was found with both crash/incident history and violation history, with higher odds ratios for pilots with crashes versus incidents or with more serious violations. Total flight time showed a diminishing protective effect. Either very small or very large recent flight time increased the risk of being involved in a commuter aircraft or an air taxi crash.

Accidents, Aviation↗

PubMed1993

Crashes of commuter aircraft and air taxis. What determines pilot survival?

Pilots have been recognized as an occupational group having very high work-related death rates. Commuter aircraft and air taxis are far more likely to be involved in fatal crashes than are larger airplanes. To examine the factors related to pilot survival in commuter aircraft and air taxi crashes, we analyzed National Transportation Safety Board data for the years 1983 to 1988. Case fatality rates were calculated for the pilots-in-command and odds ratios were estimated from a multivariate logistic regression model for variables related to pilots, aircraft, and circumstances. During the 6-year period, 536 people were killed and 744 injured in 888 commuter aircraft and air taxi crashes. The pilot case fatality rate was 20%. The most important determinants of pilot fatality were postcrash fire (odds ratio [OR] 8.2), off-airport location (OR 8.1), bad weather (OR 4.3), and nonuse of shoulder restraints (OR 3.7); all were significant at P < .01. Crash survival could be enhanced by more crashworthy fuel systems, aircraft seats, and use of restraint systems in commuter aircraft and air taxis. The value of shoulder restraints for pilots in these aircraft is confirmed and their use should be vigorously promoted.

Accidents, Aviation↗

PubMed1993

Human factors in crashes of commuter airplanes.

Pilots and frequent travelers on commuter aircraft are exposed to higher risks of death or injury than those on major air carriers. To provide a better understanding of the circumstances of crashes of scheduled commuter airplanes, National Transportation Safety Board data were analyzed for all cases of death, serious injury, or major damage involving commuter airplanes during 1983-88, when 172 people were killed and 207 injured in 118 events. Three-fourths of cases involved inadequate pilot performance, notably poor handling of emergencies and improper instrument flying procedures. Pilot errors occurred disproportionately in bad weather, which played a role in 30% of crashes. Aircraft malfunctions were involved in 42% of crashes. Certain airplanes were overinvolved in gear-up landings or in crashes due to fuel mismanagement. Greater priority should be given to applying known preventive measures to the problem of commuter crashes.

Accidents, Aviation↗

PubMed1995

Crash and violation experience of pilots involved in prior commuter and air taxi crashes: a historical cohort study.

BACKGROUND: Commuter flights and air taxis represent a major category of aviation losses in terms of both human life and economic resources. Previous studies have examined human factors involved in these crashes. A retrospective study revealed that pilots' prior crash and violation records are associated with an increased risk of being involved in a commuter aircraft or an air taxi crash. HYPOTHESIS: Pilots who are involved in crashes are at increased risk of involvement in future crashes and violations. METHODS: Pilots who had been involved in and survived commuter aircraft or air taxi crashes during 1983-88 (crash group, n = 580) and a random sample of pilots who were flying for these commercial operations (control group, n = 1555) were followed up for 3 yr. The crash/incident and violation experience during the 3 yr of follow-up was compared between the two groups at univariate level and at multivariate level. RESULTS: During the 3 yr of follow-up, the incidence rate of crashes/incidents was significantly higher for the crash group than for the control group (12.4% vs. 7.2%, p < 0.01). The crash group also was more likely to have a violation record than the control group during the 3 yr of follow-up (8.6% vs. 3.7%, p < 0.01). These differences were not changed by adjusting for pilot age, total flight time and medical class. CONCLUSIONS: Pilots who were involved in commuter aircraft or air taxi crashes have significantly higher subsequent crash and violation rates than their counterparts. In order to develop effective prevention strategies, environmental and psychosocial factors that predispose pilots to increased risk of involvement in aviation crashes and violations should be examined.

Accident Proneness↗