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PubMed1999

Color stability and colorant effect on maxillofacial elastomers. Part II: weathering effect on physical properties.

STATEMENT OF PROBLEM: The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement. PURPOSE: This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure. MATERIAL AND METHODS: Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. RESULTS: Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time. CONCLUSION: The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.

Analysis of Variance↗
PubMed2001

Behaviour of chemical elements during weathering of pyroclastic rocks, Hong Kong.

The behaviour of whole-rock major, trace and rare earth elements (REE) during weathering under subtropical conditions is examined along a profile developed over crystal--vitric tuffs with eutaxitic texture. The intensity of weathering within the profile varies erratically, indicating weathering processes operate over different scales. Quartz, K-feldspar, plagioclase and biotite are the main primary minerals, whereas clays, sesquioxides, sericite and chlorite are the alteration products. Kaolinite, halloysite and illite-mica are the dominant clay minerals present in significantly varying proportions. Two competing processes, namely leaching and fixation, are the main regulators of variations in mostly major and some trace element concentrations along the profile. In general, as the intensity of weathering increases, Ca, Na, K, Sr +/- Si decrease, while Fe, Ti, Al and loss of ignition (LOI) increase. Likewise, the intensity of negative Eu-anomaly decreases while the intensity of negative Ce-anomaly and the La/Lu and Sm/Nd ratios increases. In detail, however, the behaviour of chemical elements cannot be solely explained in terms of the degree of weathering. This study makes it clearly evident that the type and abundance of sesquioxides and clay minerals can significantly modify the geochemical signatures of weathering processes.

Aluminum Silicates↗
PubMed2003

Weather and suicide: the present state of knowledge on the association of meteorological factors with suicidal behaviour.

OBJECTIVE: To review the available literature on the association between daily and longer-term weather data and the incidence of attempted and completed suicide. METHOD: A computerized search supplemented by a cross-check of the references sections of the thereby identified papers was performed. RESULTS: A total of 27 studies looking for a relationship between attempted or completed suicide and weather or climate data were found. Most of the papers reported a statistical association of suicidal acts with at least one weather factor. However, the results are not conclusive and in part contradictory. CONCLUSION: Possibly due to the high variance in methodological approaches of the studies it is not possible to identify a specific weather condition associated with a generally higher risk for suicide. Weather and seasonal effects may interact with each other. Environmental effects on brain function and weather-related interactions of people may be involved in the occurrence of suicidal behaviour.

Americas↗
PubMed1980

[Influence of the weather on the course of lumbar syndromes].

Sensation of pain during lumbar syndromes is correlated with weather situations, the definition of which takes into consideration traditional as well as new methods of weather classification. To this end, it was necessary to develop an algesia index for the purpose of defining the subjective pain sensation by classifying it in different groups enabling the application of medico-meteorological statistics. The medical data were correlated with the following meteorological arametes: Weather-phase scheme according to Brezowsky-Ungeheuer; temperature-humidity environment; weather situations for Central Europe; synoptic index cycle; advention of temperature in medium altitudes of the atmosphere; vorticity for cyclogenesis. The following results were obtained: Pain sensation in the lumbar area shows a significant dependence on weather situations. Althoguh singular meteorological parameters are not important, the human body is affected primarily by the sum total of all weather elements.

Back Pain↗
PubMed2005

Are the acute effects of particulate matter on mortality in the National Morbidity, Mortality, and Air Pollution Study the result of inadequate control for weather and season? A sensitivity analysis using flexible distributed lag models.

Time-series studies have linked daily variations in nonaccidental deaths with daily variations in ambient particulate matter air pollution, while controlling for qualitatively larger influences of weather and season. Although time-series analyses typically include nonlinear terms for weather and season, questions remain as to whether models to date have completely controlled for these important predictors. In this paper, the authors use two flexible versions of distributed lag models to control extensively for the confounding effects of weather and season. One version builds on the current approach to controlling for weather, while the other version offers a new approach. The authors conduct a comprehensive sensitivity analysis of the particulate matter-mortality relation by applying these methods to the recently updated National Morbidity, Mortality, and Air Pollution Study database that comprises air pollution, weather, and mortality time series from 1987 to 2000 for 100 US cities. They combine city-specific estimates of the short-term effects of particulate matter on mortality using a Bayesian hierarchical model. They conclude that, within the broad classes of models considered, national average estimates of particulate matter relative risk are consistent with previous estimates from this study and are robust to model specification for weather and seasonal confounding.

Aged↗
PubMed1996

Synoptic weather modeling and estimates of the exposure-response relationship between daily mortality and particulate air pollution.

This study estimated the association between particulate air pollution and daily mortality in Utah Valley using the synoptic climatological approach to control for potential weather effects. This approach was compared with alternative weather modeling approaches. Although seasonality explained a significant amount of variability in mortality, other weather variables explained only a very small amount of additional variability in mortality. The synoptic climatological approach performed as well or slightly better than alternative approaches to controlling for weather. However, the estimated effect of particulate pollution on mortality was mostly unchanged or slightly larger when synoptic categories were used to control for weather. Furthermore, the shape of the estimated dose-response relationship was similar when alternative approaches to controlling for weather were used. The associations between particulate pollution and daily mortality were not significantly different from a linear exposure-response relationship that extends throughout the full observed range of pollution.

Air Pollution↗
PubMed2006

Weathering and toxicity of marine sediments contaminated with oils and polycyclic aromatic hydrocarbons.

Many sediments are contaminated with mixtures of oil residues and polycyclic aromatic hydrocarbons (PAHs), but little is known about the toxicity of such mixtures to sediment-dwelling organisms and the change in toxicity on weathering. In the present study, we investigated the effects of a seminatural, two-year weathering period on PAH/oil chemistry and toxicity in a marine sediment that had been spiked with three different oils (a gas oil, a lubricating oil, and a crude oil; all tested at five concentrations). Toxicity of bioavailable, pore water-accommodated oil/PAH fractions was quantified using a bacterial (Vibrio fischeri) assay and the in vitro chemical-activated luciferase expression assay (DR-CALUX; using conditions to detect PAHs). Results of chemical analyses pointed to (microbial) degradation of all three oils: Sediment oxygen demand during weathering increased with increasing oil concentration, total oil concentrations decreased to between 17 and 29% of initial levels, and resolved n-alkanes were depleted in weathered oil fractions. Furthermore, a shift in the relative importance of different boiling-point fraction ranges of the oils was observed on weathering. Generally, the lowest fraction range (C10-C16) disappeared, whereas the relative proportion of the highest (C28-C40) fraction range increased considerably. Remarkably, for the gas oil, this fraction shift was dependent on the oil concentration in sediment. Similarly, degradation of PAHs was strongly affected by the sedimentary oil content, indicating that the presence of oil stimulated PAH degradation. This phenomenon applied to both low- and high-molecular-weight PAHs, although the first group (3- and 4-ring PAHs) was degraded most. Results from the V. fischeri and DR-CALUX assay showed that in most cases, pore-water toxicity decreased on weathering. Combining the assay responses with chemical data indicated that the observed toxicity probably was not caused by the analyzed PAHs but, rather, by specific oil constituents instead.

Aliivibrio fischeri↗
PubMed2002

Influence of weather conditions on rheumatic pain.

OBJECTIVE: To evaluate the influence of the weather in Cordoba City, Argentina, on pain in patients with rheumatic pain; to correlate different climate variables with the patients' impression of weather sensitivity; and to assess correlations between pain and climate conditions on 5 days preceding and following painful episode. METHODS: Self-reported questionnaires to assess the presence and features of spontaneous daily pain during one year (1998) were completed by 151 outpatients with osteoarthritis (OA) (n = 52), rheumatoid arthritis (RA) (n = 82), and fibromyalgia (FM) (n = 17) and 32 healthy subjects. Data were correlated with daily temperature, atmospheric pressure, and relative humidity obtained during the same period. Only p values < 0.001 were considered significant. RESULTS: Low temperature, high atmospheric pressure, and high humidity were significantly correlated with pain in RA (r = -0.30, r = 0.34, r = 0.23, respectively; p < 0.001); in OA, pain correlated with low temperature and high humidity (r = -0.23, r = 0.24; p < 0.001); in FM, with low temperature and high atmospheric pressure (r = -0.255, r = 0.22; p < 0.001) and no correlation was found in controls. Patients self-described as being weather sensitive correlated only with high humidity (r = 0.45; p < 0.001). There was no better correlation with climate variables, except for humidity, 5 days before or after the day of the painful episode. CONCLUSION: These results support the belief that weather influences rheumatic pain, albeit in different ways depending on the subjacent pathology and subjective weather sensitivity. This influence may not depend on weather conditions of the previous or following days, indicating that climate would not be a pain predictor and vice versa.

Aged↗
PubMed2004

[The specific features of circadian blood pressure variations in patients with hypertensive disease in different types of weather].

The specific features of circadian blood pressure (BP) variations were studied in 162 patients aged 20 to 60 years who had hypertensive disease (HD) in the warm period of a year in different types of weather. In accordance with the type of weather in which daily BP monitoring (DBPM) was performed, the examinees were divided into 2 groups: 1) those examined in droughty (anticyclonic) weather; 2) those examined in moist (cyclonic) weather, The groups were matched by the number (81) of patients, age, gender, duration of the disease, and office BP values. The mean BP during a day, daylight and night hours, the maximum and minimum BP during wake and sleep was significantly high in moist weather. Examining the magnitude of a nocturnal BP decrease indicated that in Group 1, its adequate decrease (the dipper daily curve) was recorded in 72.3% of the patients; inadequate BP decrease (the non-dipper daily curve) was in 24.2%; paradoxical nocturnal hypertension (night peaker) was seen in 1.8%. In Group 2, adequate and inadequate nocturnal BP decreases were observed in 44.4 and 41.3%, respectively; paradoxical nocturnal hypertension was in 7.7%. Statistical processing confirmed the validity of the findings. Moist (cyclonic) weather was ascertained to be marked by the changes in adequate circadian BP variations: a significant mean daily, maximum, and minimum systolic BP (SBP) and diastolic BP (DBP), as well as by the inadequate nocturnal lowering of SBP and DBP, which determines a poor prognosis and may serve as a basis for preventing HD complications in this period of a year.

Adult↗
PubMed1985

Weather and arthritis symptoms.

In a one month prospective, double blind study of 70 patients (35 with rheumatoid arthritis [RA], 35 with osteoarthritis [OA]), severity of rheumatic symptoms was compared to changes in daily weather conditions using a visual analogue scale. The majority of patients (62%) believed that various aspects of weather aggravated their symptoms. There was no difference in age, sex, diagnosis or perceived symptom severity between weather sensitive and weather insensitive patients. No significant correlation was found between symptoms of any patient group or individual and any of 13 combinations of weather features. These results suggest that contrary to the belief of the majority of patients with RA or OA external weather conditions do not significantly influence the day-to-day symptoms of arthritis.

Adult↗
PubMed2005

Groundwater quality under the influence of spent mushroom substrate weathering.

Nitrate and other solutes resulting from field-weathering of spent mushroom substrate (SMS) percolate into underlying soils and may migrate to groundwater. A field trial was conducted to investigate the potential influences of SMS weathering on groundwater quality. Spent mushroom substrate was deposited at 90 and 150 cm pile depths over a Typic Hapludult and weathered for 2 years. Eight casing wells were installed around the SMS piles to monitor the quality changes of groundwater with a high seasonal water table of 760 cm below the surface. Although leachate solutes had moved more than 200 cm deep in soil from the surface, no significant changes of groundwater quality caused by SMS weathering were observed even one year after removal of the SMS piles (3 years total). The groundwater had pH, electrical conductivity (EC) and dissolved organic carbon (DOC) of 4.3-5.7, 0.2-0.3 dS m(-1) and 0.7-2.2 mg L(-1), respectively. The major inorganic ions were Mg(2+), Ca(2+), Na(+), Cl(-), SO(4)(2-) and NO(3)(-), with a concentration range of 2.5-68.3 mg L(-1). The results suggest that SMS leachate solutes migrated fairly slow in deep subsurface soils of the experimental field. Considering that leachate solutes may move several meters in soil through preferential flow channels, weathering of SMS in fields with a high seasonal groundwater table >or=5 m below the ground is recommended. Conservatively, SMS weathering should be conducted on compact surfaces and leachate be collected and reused as liquid fertilizers.

Agaricales↗
PubMed2006

Root-associated bacteria contribute to mineral weathering and to mineral nutrition in trees: a budgeting analysis.

The principal nutrient source for forest trees derives from the weathering of soil minerals which results from water circulation and from plant and microbial activity. The main objectives of this work were to quantify the respective effects of plant- and root-associated bacteria on mineral weathering and their consequences on tree seedling growth and nutrition. That is why we carried out two column experiments with a quartz-biotite substrate. The columns were planted with or without pine seedlings and inoculated or not with three ectomycorrhizosphere bacterial strains to quantify biotite weathering and pine growth and to determine how bacteria improve pine growth. We showed that the pine roots significantly increased biotite weathering by a factor of 1.3 for magnesium and 1.7 for potassium. We also demonstrated that the inoculation of Burkholderia glathei PML1(12) significantly increased biotite weathering by a factor of 1.4 for magnesium and 1.5 for potassium in comparison with the pine alone. In addition, we observed a significant positive effect of B. glathei PMB1(7) and PML1(12) on pine growth and on root morphology (number of lateral roots and root hairs). We demonstrated that PML1(12) improved pine growth when the seedlings were supplied with a nutrient solution which did not contain the nutrients present in the biotite. No improvement of pine growth was observed when the seedlings were supplied with all the nutrients necessary for pine growth. We therefore propose that the growth-promoting effect of B. glathei PML1(12) mainly resulted from the improved plant nutrition via increased mineral weathering.

Burkholderia↗
PubMed2003

Reductive dechlorination of weathered Aroclor 1260 during anaerobic biotreatment of Arctic soils.

We investigated the microbial reductive dechlorination of both weathered (aged) and nonweathered (freshly added) Aroclor 1260 in aerobic soil from Resolution Island, Nunavut, Canada. Initial polychlorinated biphenyl (PCB) concentrations were 106 and 100 ppm, respectively. The aerobic soil samples were inoculated with anaerobic sediment, incubated at 30 degrees C until methanogenic, inoculated with a dechlorinating enrichment culture, and incubated a further 8 weeks. The average number of chlorine substituents per biphenyl molecule was biologically reduced from 6.6 to 5.1 and from 6.2 to 4.5 for weathered and nonweathered Aroclor 1260, respectively. Removal of hexa- and heptachlorobiphenyls (CBs), the major homolog groups present, was significantly greater for nonweathered than for weathered Aroclor 1260. Formation of dechlorination products, primarily 2,2',4,4'- and 2,2',4,6'-tetraCBs, was also significantly greater for nonweathered than for weathered Aroclor 1260. We additionally compared the dechlorination at 21 degrees C of weathered Aroclor 1260 in soils from Resolution Island and Saglek, Labrador, Canada. The average number of chlorine substituents per biphenyl molecule was biologically reduced from 6.7 to 5.1 and from 6.5 to 4.6, respectively. This study demonstrated the potential for bioremediation of aerobic soil contaminated with Aroclor 1260 and showed that weathering may limit such treatment to an extent variable among different soils.

Arctic Regions↗
PubMed2006

Relationship between objective measures of physical activity and weather: a longitudinal study.

BACKGROUND: The weather may be a barrier to physical activity but objective assessment of this hypothesis is lacking. Therefore we evaluated the effect of temperature, rain or snow, and wind speed on the daily physical activity of adults. METHODS: This report contains data from 25 males (BMI (mean +/- SD): 28.7 +/- 3.83 kg/m2) and 177 females (BMI: 29.2 +/- 5.92 kg/m2) enrolled in an intervention to increase physical activity. Steps/day of the participants was measured by pedometer. Weather data were obtained from Environment Canada. A total of 8,125 observations were included in a mixed linear model analysis. RESULTS: Significant weather related variables (at the 5% level) impacting steps/day included: seasonal effects related to the interaction between weekday and month; mean temperature, total rainfall, interactions between gender, BMI and total snow, interactions between maximum wind speed and BMI, and the amount of snow on the ground. The estimated magnitudes for the various effects were modest, ranging from approximately 1% to approximately 20%. Thus for an average individual taking approximately 10,000 steps/day, weather-dependent changes in physical activity could reach 2,000 steps/day. CONCLUSION: We conclude that weather had modest effects on physical activity of participants in an intervention to increase their activity. It should be stressed that these effects may be different for less or more motivated people. With this in mind, we suggest that the effect of weather on physical activity in the general population needs to be objectively assessed to better understand the barrier it poses, especially as it relates to outdoor recreation or work activities.

Journal Article↗
PubMed2001

Beating the heat: development and evaluation of a Canadian hot weather health-response plan.

An increasing number of cities subject to hazardous summer weather in the United States and Canada have begun to develop and implement hot weather response plans to prevent heat-related illnesses and deaths. In this study we focus on heat-mortality relationships in Toronto, Ontario, between 1980 and 1996 and evaluate the potential effectiveness of the city's interim hot weather-health response plan. Using two heat stress indexes--humidex and apparent temperature--we identified excess mortality associated with hot and humid weather and then estimated excess deaths for hot and cool summers. Mortality rates for all ages and for > 64 years age groups rose with increasing humidex and apparent temperature, with no significant increase for the population < 65 years. Excess mortality occurred as low as the 30-35 degrees C humidex range, which is below the 40 degrees C humidex used to issue a heat warning under Toronto's interim hot weather response plan. During a hot summer (such as 1988 or 1995), 32 excess deaths would be expected, whereas 34 fewer deaths than baseline levels would be expected during a cool summer like 1982 or 1992. Days with high humidex levels occur infrequently in Toronto, and thus exposure is limited under current climatic conditions. In the event of a warming climate, more days with dangerously high humidex levels are likely to occur, and summer deaths are expected to increase. Toronto's hot weather health-response plan is an important early step for adaptation to climate change.

Adult↗
PubMed2005

Spatial variability of characteristics and origins of urban wet weather pollution in combined sewers.

An experimental on-site observatory of urban pollutant loads in combined sewers was created in the centre of Paris to quantify and characterise the dry and wet weather flow in relation to spatial scale. Eight rainfall events were studied from April 2003 to May 2004. Samples were analysed for suspended solids, organic matter, nitrogen and heavy metals. Results confirm the extent of wet weather pollution. They have shown the relative homogeneity of SS and organic matter characteristics from one urban catchment area to another. Two groups of heavy metals were identified. The first one concerns Cu, which has a higher concentration in wet weather flow (WWF) than in dry weather flow (DWF), and runoff. The second includes Cd, Pb and Zn, where higher concentrations were measured in urban runoff than in WWF and DWF. A first evaluation of contribution of wastewater, urban runoff and sewer deposit erosion sources to wet weather pollution was established and has highlighted the contribution of wastewater and sewer deposits to this pollution. However, it has shown that sewer deposit erosion remains an important source of wet weather pollution at different spatial scales.

Cities↗
PubMed1991

Aircrew decision-making behavior in hazardous weather avoidance.

In-flight encounters with hazardous weather represent one of the most significant safety issues in civil aviation operations. Aircrew judgment is often cited as the probable cause of incidents and accidents involving weather, although lack of information is also a factor. The present study examines how information, presented at different times and in different forms, affects the awareness and decision-making behavior of aircrews in a flight simulation study of a recent microburst/windshear incident. In order to examine the influence of enhanced information transfer on aircrew behavior, intracrew communications and approach-to-land decisions were evaluated with conventional ATC communications and with automated cockpit alerting and display of weather information. Results of the study revealed that aircrews provided only with conventional ATC transmissions of weather information had difficulty discriminating conditions conducive to microburst events from less hazardous windshear events. Improved situation awareness for microburst events was found when ground-based convective weather information was provided in real time to aircrews. Avoidance decision-making was found to be less efficient with conventional ATC alert transmissions when compared to the performance of crews provided with a visual display of microburst events. The importance of information transfer on aircrew situation awareness and decision-making in hazardous weather avoidance is discussed.

Adult↗
PubMed1976

[The effects of the weather on hemophilic hemarthrosis (author's transl)].

Hemophilic hemarthroses occur more frequently in spring and autumn. In the present study, possible weather situations are investigated which are characterized by a particular action on the increasing of hemorrhagic tendency. In 574 hemarthroses in 45 patients, the regional weather events were set in relation to the hemarthroses by means of a computer program. The following weather constellations significantly increase the tendency to bleed: Regional west weather conditions combined with longer lasting ascending procedures. The weather dynamics are dominated by the warm face of weak frontal zones with formation of a warm front. The biotropic weather elements demonstrated are also shown to be biotropic in other disease processes.

Germany, West↗