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At least 397 records · Page 22Linked to original sources
PubMed1998

Validation of an enzyme calibrator--an IFCC guideline. International Federation of Clinical Chemistry.

OBJECTIVES: The objective of this guideline is to improve standardization in clinical enzymology in order to improve intermethod comparability of patients' results. DESIGN AND METHODS: The reference system, combination of the reference method and the reference material, is used to produce a reference value for a given catalytic activity. Sets of methods are formed of methods exhibiting the same analytical specificity. Materials intended to be used as enzyme calibrators are experimentally checked for their commutability. RESULTS: The transfer of accuracy from the reference value to patients' results is dependent on methods (analytical specificity) and on materials (experimentally assessed commutability). The feasibility of this approach was demonstrated with materials of high level for several enzymes and for each of them for several routine methods. CONCLUSION: Expected advantages of this approach in clinical enzymology are presented.

Calibration↗
PubMed1999

Personal exposures to airborne metals in London taxi drivers and office workers in 1995 and 1996.

In 1995, a petroleum marketer introduced a diesel fuel additive in the UK containing Mn as MMT (methylcyclopentadienyl manganese tricarbonyl). A small study of personal exposures to airborne Mn in London was conducted before and after introduction of the additive to identify any major impact of the additive on exposures. In 1995, personal exposures to Mn were measured in two groups, taxi drivers and office workers (10 subjects per group) for two consecutive 7-day periods. A similar study was carried out in 1996 to determine if exposures had changed. Samples were also analyzed for Ca, Al, Mg and Pb. In 1996, exposures to aerosol mass as total suspended particulates (TSP) and PM2.5 were measured in addition to the metals. Manganese exposures in this cohort did not increase as a result of introduction of the additive. However, a significant source of Mn exposure was discovered during the conduct of these tests. The mean exposure to Mn was higher among the office workers in both years than that of the taxi drivers. This was due to the fact that approximately half of the office workers commuted via the underground railway system where airborne dust and metal concentrations are significantly elevated over those in the general environment. Similar results have been noted in other cities having underground rail systems. Exposure to Mn, Pb, Ca, and Mg were not significantly different between the 2 years. Taxi drivers had higher exposures than office workers to Mg and Pb in both years. Commuting via the underground also had a significant impact on exposures to TSP, PM2.5, Al, and Ca, but had little effect on exposures to Mg. The aerosol in the underground was particularly enriched in Mn, approximately 10-fold, when compared to the aerosol in the general environment. There are several possible sources for this Mn, including mechanical wear of the steel wheels on the steel rais, vaporization of metal from sparking of the third rail, or brake wear.

Air Pollutants, Occupational↗
PubMed2001

Computer-assisted health impact assessment for intersectoral health policy.

Intersectoral health policy implies negotiations with politicians outside the health sector. Health politicians have a stronger position if they can quantify health impact. In this Dutch case-study we used a computer simulation approach to answer the following questions: Which anti-tobacco intervention has the largest health gain? Will a commuter cycling policy result in any substantial health gain? What is the relative health gain of promoting higher consumption of vegetables and fruit? We concluded that substantial health gain can be achieved if cigarette packet price were to increase by 2 Dutch guilders. A commitment of all general practitioners to implement a smoking cessation intervention will result in a similar health gain. Stimulating commuter cycling could be a promising example of intersectoral health policy. Interventions to promote higher vegetable and fruit consumption will result in a relatively small health gain. Pros and cons of simulation models to support intersectoral health policy are discussed.

Adult↗
PubMed1997

Survey and assessment of the actual state of routine measurement of glycohaemoglobin/GHb by commercial methods: warning to the users and the providers.

As the clinical availability of glycohaemoglobin/GHb measurement increases, so does the need for comparable and accurate values among different laboratories and different methods. At least there should be comparability, i.e., commutability or feasibility of providing comparable results from different assays in different laboratories. A clinical joint study on insulin therapy, a survey of the actual inter-laboratory differences in GHb measurement among 41 institutions and an assessment of 11 assay methods for the determination of GHb were performed using commercial calibrators and fresh blood samples. Data on the actual state of inter-laboratory and inter-assay differences of observed values were useful for comparing results among facilities. The recommendation of the Japan Diabetes Society to measure only the stable GHb component and to correct the GHb percentage by two-point calibration with assigned values, was effective but not sufficient. Even after correction, 8 out of 11 methods still remained of little practical use because of their large relative errors. Inter-method differences among 11 available assay methods were great even after correction and depended on not only the methods but the samples used for the determination. The performance of some methods or instruments used are only poor at distinguishing the stable glycated haemoglobin itself. Some alternative measurement system with comparability, commutability and precision should be established. An urgent and worldwide problem to remove inter-laboratory differences in the measurement of GHb needs to be solved. Users in clinical practice must recognize these problems, and, before supply, the providers should check their method and keep records that are readily traceable.

Calibration↗
PubMed2006

Calculating multidimensional discrete variable representations from cubature formulas.

Finding multidimensional nondirect product discrete variable representations (DVRs) of Hamiltonian operators is one of the long standing challenges in computational quantum mechanics. The concept of a "DVR set" was introduced as a general framework for treating this problem by R. G. Littlejohn, M. Cargo, T. Carrington, Jr., K. A. Mitchell, and B. Poirier (J. Chem. Phys. 2002, 116, 8691). We present a general solution of the problem of calculating multidimensional DVR sets whose points are those of a known cubature formula. As an illustration, we calculate several new nondirect product cubature DVRs on the plane and on the sphere with up to 110 points. We also discuss simple and potentially very useful finite basis representations (FBRs), based on general (nonproduct) cubatures. Connections are drawn to a novel view on cubature presented by I. Degani, J. Schiff, and D. J. Tannor (Num. Math. 2005, 101, 479), in which commuting extensions of coordinate matrices play a central role. Our construction of DVR sets answers a problem left unresolved in the latter paper, namely, the problem of interpreting as function spaces the vector spaces on which commuting extensions act.

Journal Article↗
PubMed2005

Maternal working conditions and child well-being in welfare-leaving families.

In the wake of welfare reform, thousands of low-income single mothers have transitioned into the labor market. In this article, the authors examine how the work conditions of mothers leaving welfare for employment are associated with the emotional well-being of 372 children ages 5 to 15 years. The authors examine the cumulative incidence, over a 5-year period, of maternal non-family-friendly work conditions, including long work hours, erratic work schedules, nonday shifts, and lengthy commute times, in association with children's internalizing and externalizing behavior problems and levels of positive behavior. The authors found that mothers' lengthy commute times are associated with higher levels of internalizing problem behaviors and lower levels of positive behaviors.

Adolescent↗
PubMed2003

Physical activity and inactivity in Chinese school-aged youth: the China Health and Nutrition Survey.

OBJECTIVE: To describe physical activity (PA) and inactivity levels and patterns in Chinese school children (aged 6-18 y). DESIGN: PA and inactivity were assessed in a youth cohort enrolled in the China Health and Nutrition Survey (CHNS) in 1997. SUBJECTS: A total of 1423 males (11.5+/-3.2 y) and 1252 females (11.5+/-3.3 y). MEASUREMENTS: PA and inactivity were assessed by self-reported usual activity (questionnaire). Children under 10 y were assisted by parents. RESULTS: Approximately 84% of Chinese youth actively commute to school for a median of 100-150 min/week. A total of 72% engage in in-school moderate/vigorous (MOD/VIG) PA for a median of 90-110 min/week. Relatively few children ( approximately 8%) participate in any MOD/VIG PA outside of school. A total of 72% engage in study-related activities outside of school for a median of 420 min/week. Only 8% of Chinese school children, regardless of gender, watch television > or =2 h/day; less than 1% watch > or =4 h/day. Chores related to housework are not a part of life for Chinese school children; fewer than 20% performed these tasks. CONCLUSION: Chinese youth are unique compared to those in other developing countries because they do not perform household chores. Instead, they are under pressure to achieve scholastically. Participation in MOD/VIG PA outside of school is almost nonexistent. Current television watching habits are relatively low compared to developed countries and walking/biking is a common form of commuting. The descriptive analysis herein represents the foundation upon which future longitudinal studies of PA in this population will be based.

Adolescent↗
PubMed2005

Physical activity is inversely related to waist circumference in 12-y-old French adolescents.

BACKGROUND AND OBJECTIVE: Waist circumference (W) has been shown to be a good predictor of cardiovascular risk. The aim of this study was to investigate whether physical activity (PA) is related to W in adolescents as previously shown in adults. DESIGN AND SUBJECTS: Cross-sectional population-based survey of 2,714 12-y-old adolescents from the eastern part of France. MEASUREMENTS: Body mass index (BMI) and W were measured. Structured PA, active commuting to and from school and sedentary activities (SED), for example television viewing, computer/video games and reading and different potential confounders (dietary habits, parental overweight, family annual income tax and educational level) were assessed by a questionnaire. RESULTS: The adolescents had a mean BMI of 19.0+/-3.4 kg/m2, and 20.2% of them were overweight, with no gender difference. Boys had a greater W than girls (67.6+/-9.1 vs 65.7+/-8.9 cm, P<0.0001). In all, 42% of the girls and 25% of the boys did not practice any structured PA outside school and less than 40% of the adolescents commuted actively to school more than 20 min/day. About one-third of the adolescents devoted more than 2 h/day to SED. In univariate analyses, BMI was negatively associated with structured PA but significantly only for girls (P<0.01) and positively associated with SED for both genders (P<0.0001 for girls, P<0.01 for boys). W was negatively associated with structured PA and positively associated with SED both in girls (P<0.0001 and P=0.03, respectively) and boys (P<0.01 and P=0.08, respectively). Multiple general linear models show that SED is associated with BMI, independently of structured PA, in both genders. On the other hand, structured PA was inversely associated with W, independently of SED. The inverse relation between structured PA and W persisted after additional adjustment on BMI, with a greater effect of PA for the adolescents with higher BMI. CONCLUSIONS: In 12-y-old adolescents, structured PA is inversely associated with W, an indicator of total adiposity but also more specifically of abdominal fat. This suggests that PA may have a beneficial effect on youth metabolic and cardiovascular risks, in particular in the presence of overweight..

Abdomen↗
PubMed2003

Physical activity in Filipino youth: the Cebu Longitudinal Health and Nutrition Survey.

OBJECTIVE: To describe physical activity (PA) and inactivity levels of Filipino youth aged 14-16 y. DESIGN: PA type and patterns were assessed in an adolescent cohort enrolled in the Cebu Longitudinal Health and Nutrition Survey. SUBJECTS: A total of 1053 males (aged 15.6+/-0.5 y; body mass index (BMI)=18.6+/-2.6 kg/m(2)) and 990 females (aged 14.6+/-0.5 y; BMI=18.8+/-2.4 kg/m(2)). MEASUREMENTS: PA was assessed by (1) self-reported usual PA (questionnaire); (2) 24-h objective monitoring (Caltrac accelerometer); and (3) 24 h recalls of PA during the objectively monitored time frame. RESULTS: As measured by Caltrac, males expended 378.0+/-164.5 kcal and females 271.0+/-105.4 kcal. The measurement approaches employed agreed in expected ways, given the limitations of each. Together the approaches used indicated that the primary sources of PA for this population are chores and active commuting. In all, 40% of the sample walked to school, less than 1% rode a bicycle, 22% rode in/on motorized transport, and 37% used some combination of walking and motorized transport. Further, gender differences exist for type, frequency, and duration of physical activities performed by Filipino youth. Specifically, females report engaging in few leisure-time physical activities and more household chores. In total, 48% of Filipino youth report watching > or =2 h/day of television; relatively few youth (7%) report watching >4 h/day at this time. An 18% of males report no vigorous activities compared to 87% of females. CONCLUSION: Clear gender differences in PA patterns and levels exist in Filipino adolescents. Nonsport/exercise type activities (eg chores and active commuting) currently provide a large proportion of daily activity for both males and females, however. It is anticipated that as modernization and technological advancement continue in this developing country, these primary sources of PA will decrease.

Activities of Daily Living↗
PubMed2006

Microflow injection system based on a multicommutation technique for nitrite determination in wastewaters.

In this work a microflow structure, suitable for micro-FIA (micro flow injection analysis), will be described, evaluated and applied to real samples. Microchannels, the detector flow cell and input/output ports have been micromachined in silicon and sealed with anodically bonded Pyrex glass. The channels are defined by etching approximately 200 microm depth in silicon using a dry reactive ion etching (RIE) process. Optical windows integrated in the chip structure allow simple absorbance/transmission measurements to be made. The optical measurements were made using an LED as emitter (lambda=525 nm) and a photodiode as a detector. A Visual-Basic program has been developed to control an automatic burette, three-way solenoid valves and the data acquisition system. The micro-FIA for nitrite determination using the Griess-Ilosvay reaction has been implemented for the on-line monitoring of wastewater treatment plants (WWTPs). The multicommutation concept has been applied in order to enhance the mixing process inside the microsystem. Tandem streams of reagent and sample were generated and evaluated at different commutation frequencies. Two optimal frequencies, 400/200 ms and 150/450 ms, were found to be the most suitable ones. The first commutation ratio gave rise to wide linear working range (0-250 ppm), in spite of a high detection limit (0.35 ppm) and a low sensitivity (0.0041+/-0.0004 AU ppm-1). With the second ratio, the working linear range was smaller (0-50 ppm) but the detection limit (0.17 ppm) and the sensitivity (0.0091+/-0.0003 AU ppm-1) improved remarkably. Finally, real samples with a high nitrite concentration (0-1500 ppm) coming from a study of kinetic inhibition in the nitrification process at a WWTP has been analysed with the proposed micro-FIA system. The obtained results have allowed the corroboration of the model of inhibition by the nitrite ion with great exactitude.

Autoanalysis↗
PubMed2026

Reconstructing the early spatial spread of pandemic respiratory viruses in the United States.

Understanding the geographic spread of emerging respiratory viruses is critical for pandemic preparedness, yet the early spatiotemporal dynamics of the 2009 H1N1 pandemic influenza and severe acute respiratory syndrome coronavirus 2 in the United States remain unclear. While mobility and genomic data have revealed important aspects of pandemic spatial spread, several key questions remain: Did the two pandemics follow similar spatial transmission routes? How rapidly did they spread across the United States? What role did stochastic processes play in early spatial transmission? To address these questions, we integrated high-resolution disease data with a robust, data-efficient inference framework combining air travel, commuting flows, and pathogen superspreading potentials to reconstruct their spatial spread across US metropolitan areas. The two pandemics exhibited distinct transmission pathways across locations; however, both pandemics established local circulation in most metropolitan areas within weeks, driven by several shared transmission hubs. Early spatial spread was more strongly associated with air travel than with commuting, though stochastic dynamics introduced substantial uncertainty in transmission routes, creating challenges for timely detection and control. Simulations indicate that broad wastewater surveillance coverage beyond top transmission hubs coupled with effective infection control may slow initial spatial expansion. Our findings highlight the rapid, stochastic spread of pandemic respiratory pathogens and the difficulties of early outbreak containment.

Humans↗
PubMed1980

Internal supersymmetry and unification.

We construct a family of finite-dimensional representations of the superalgebra sl(n/m) that depend on an integer parameter for m > 1 and on a complex parameter, b, for m = 1. We describe some models of elementary particles for sl(2/1), sl(3/1), and sl(5/1). This involves the choice of the parameter b and the choice of the operators I(3) (the third component of the weak left-handed isospin) and U (the weak hypercharge). These must commute, and are related to the electric charge by the usual formula Q = I(3) + (1/2)U. In particular, taking I(3) to be in its standard form in su(2) subset sl(5) subset sl(5/1) and requiring that U commute with color su(3) subset sl(5) subset sl(5/1) leaves three free parameters, two for the choice of U and one for the choice of b. We show that there are just two possible choices of these parameters yielding exactly all 32 quark and lepton charges: the Georgi-Glashow U in su(5), corresponding to U(1,-(2/3)) and arbitrary b and U(0,(1/3)) negated set membership su(5), with b = 2. We provide a general construction of representations of sl(n/1) consisting exactly of sequences of generations of quarks and leptons.

Journal Article↗
PubMed1984

A natural representation of the Fischer-Griess Monster with the modular function J as character.

We announce the construction of an irreducible graded module V for an "affine" commutative nonassociative algebra [unk]. This algebra is an "affinization" of a slight variant [unk] of the commutative nonassociative algebra B defined by Griess in his construction of the Monster sporadic group F(1). The character of V is given by the modular function J(q) = q(-1) + 0 + 196884q +.... We obtain a natural action of the Monster on V compatible with the action of [unk], thus conceptually explaining a major part of the numerical observations known as Monstrous Moonshine. Our construction starts from ideas in the theory of the basic representations of affine Lie algebras and develops further the calculus of vertex operators. In particular, the homogeneous and principal representations of the simplest affine Lie algebra A(1) ((l)) and the relation between them play an important role in our construction. As a corollary we deduce Griess's results, obtained previously by direct calculation, about the algebra structure of B and the action of F(1) on it. In this work, the Monster, a finite group, is defined and studied by means of a canonical infinite-dimensional representation.

Journal Article↗
PubMed1984

Post-classification version of Jordan's theorem on finite linear groups.

Using classification of finite simple groups, I show that a finite subgroup G of GL(n)(C), where C = the complex numbers, contains a commutative normal subgroup M of index at most (n + 1)!n(alogn+b). Moreover, if G is primitive and does not contain normal subgroups that are direct products of large alternating groups, then the factor (n + 1)! can be dropped. I further show that similar statements hold also in characteristics p >/= 2, if one takes M to be an extension of a group of Lie type of characteristic p by a solvable group that has a normal p-subgroup with commutative p'-quotient. These results improve the celebrated theorems of Jordan and of Brauer and Feit.

Journal Article↗
PubMed1990

Bialgebra cohomology, deformations, and quantum groups.

We introduce cohomology and deformation theories for a bialgebra A (over a commutative unital ring k) such that the second cohomology group is the space of infinitesimal deformations. Our theory gives a natural identification between the underlying k-modules of the original and the deformed bialgebra. Certain explicit deformation formulas are given for the construction of quantum groups--i.e., Hopf algebras that are neither commutative nor cocommutative (whether or not they arise from quantum Yang-Baxter operators). These formulas yield, in particular, all GLq(n) and SLq(n) as deformations of GL(n) and SL(n). Using a Hodge decomposition of the underlying cochain complex, we compute our cohomology for GL(n). With this, we show that every deformation of GL(n) is equivalent to one in which the comultiplication is unchanged, not merely on elements of degree one but on all elements (settling in the strongest way a decade-old conjecture) and in which the quantum determinant, as an element of the underlying k-module, is identical with the usual one.

Journal Article↗
PubMed2002

Comparison of dietary and non-dietary risk factors in overweight and normal-weight Chinese adults.

The aim of the present study was to compare the differences in dietary and non-dietary factors contributing to normal weight and overweight among urban Chinese adults. Two cross-sectional population surveys were carried out in Tianjin, one of the largest cities in China. A total of 2631 subjects aged 25-64 years were selected by random stratified cluster sampling; 398 men and 490 women were overweight, and 886 men and 857 women were of normal weight. The diet was assessed by food weighing plus consecutive individual 3 d food records. Health-related behaviours and anthropometry were assessed. The overweight group had significantly higher mean daily intakes of energy and carbohydrate than the normal-weight group. Overweight men also had significantly higher mean daily intakes of protein and fat than normal-weight men. Age, daily intakes of energy and carbohydrate, and marital status were positively associated with overweight, while occupational and commuting physical activity, as well as smoking, were inversely associated with overweight among both genders. Daily intakes of protein, fat and alcohol were positively related to the incidence of being overweight among men. People with 7-12 years education were more likely to be overweight compared with those with less than 6 years of education. High intakes of energy and carbohydrate among both genders, as well as high intakes of protein and fat among men, and lower levels of occupational and commuting physical activity, being a non-smoker, and partly higher socio-economic status were related to a greater incidence of being overweight in this population.

Adult↗
PubMedDate not supplied

Exposure to methyl tertiary-butyl ether from oxygenated gasoline in Stamford, Connecticut.

In 1993, state health officials in Connecticut invited the Centers for Disease Control and Prevention (CDC) to assist in an investigation of exposure to methyl tertiary-butyl ether in oxygenated gasoline in Stamford, Connecticut. Venous blood samples were collected from 14 commuters and from 30 other persons who worked in the vicinity of traffic or automobiles, and the samples were analyzed for methyl tertiary-butyl ether, tertiary-butyl alcohol, benzene, m-/p-xylene, o-xylene, and toluene. The highest levels of methyl tertiary-butyl ether in blood were measured among gasoline service station attendants (median = 15 micrograms/l, range = 7.6-28.9 micrograms/l). Blood levels of methyl tertiary-butyl ether were highly variable among persons who worked in car-repair shops (median = 1.73 micrograms/l, range = 0.17-36.7 micrograms/l) and were generally lowest among commuters (median = 0.11 micrograms/l, range = < 0.05-2.60 micrograms/l). Blood levels of methyl tertiary-butyl ether were correlated strongly with personal-breathing-zone samples of methyl tertiary-butyl ether and blood levels of other volatile organic compounds. This exposure information should prove useful to a future risk analysis of this high-volume chemical.

Air Pollutants↗
PubMed2005

Optimal fleetwide emissions reductions for passenger ferries: an application of a mixed-integer nonlinear programming model for the New York-New Jersey Harbor.

Emissions from passenger ferries operating in urban harbors may contribute significantly to emissions inventories and commuter exposure to air pollution. In particular, ferries are problematic because of high emissions of oxides of nitrogen (NOx) and particulate matter (PM) from primarily unregulated diesel engines. This paper explores technical solutions to reduce pollution from passenger ferries operating in the New York-New Jersey Harbor. The paper discusses and demonstrates a mixed-integer, non-linear programming model used to identify optimal control strategies for meeting NOx and PM reduction targets for 45 privately owned commuter ferries in the harbor. Results from the model can be used by policy-makers to craft programs aimed at achieving least-cost reduction targets.

Air Pollutants↗