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Dioxide Levels (dioxide + level)

Distribution by Scientific Domains
Life Sciences40%
Medical Sciences20%

Kinds of Dioxide Levels

  • carbon dioxide level
    		•

    Selected Abstracts

    Breathing patterns, oxygen and carbon dioxide levels during infancy

    ACTA PAEDIATRICA, Issue 11 2000
    A Greenough
    First page of article [source]

    Influence of atmospheric carbon dioxide enrichment on induced response and growth compensation after herbivore damage in Lotus corniculatus

    ECOLOGICAL ENTOMOLOGY, Issue 3 2002
    Alain Bazin
    Abstract 1. Plant growth and chemical defence compounds in four Lotus corniculatus genotypes exposed to factorial combinations of ambient and elevated carbon dioxide, and herbivory by caterpillars of Polyommatus icarus were measured to test the predictions of the carbon/nutrient balance hypothesis. 2. Shoot and root biomass, allocation to shoots versus roots, and carbon-based defence compounds were greater under elevated carbon dioxide. Pupal weight of P. icarus was greater and development time shorter under elevated carbon dioxide. 3. Herbivory decreased shoot growth relative to root growth and production of nitrogen-based defence (cyanide). Young leaves contained more defence compounds than old leaves, and this response depended on carbon dioxide and herbivory treatments (significant interactions). 4. Genotype-specific responses of plants to carbon dioxide and herbivory were found for the production of cyanide. Furthermore, maternal butterfly-specific responses of caterpillars to carbon dioxide were found for development time. This suggests the existence of genetic variation for important defence and life-history traits in plants and herbivores in response to rising carbon dioxide levels. [source]

    A missing values imputation method for time series data: an efficient method to investigate the health effects of sulphur dioxide levels

    ENVIRONMETRICS, Issue 2 2010
    Swarna Weerasinghe
    Abstract Environmental data contains lengthy records of sequential missing values. Practical problem arose in the analysis of adverse health effects of sulphur dioxide (SO2) levels and asthma hospital admissions for Sydney, Nova Scotia, Canada. Reliable missing values imputation techniques are required to obtain valid estimates of the associations with sparse health outcomes such as asthma hospital admissions. In this paper, a new method that incorporates prediction errors to impute missing values is described using mean daily average sulphur dioxide levels following a stationary time series with a random error. Existing imputation methods failed to incorporate the prediction errors. An optimal method is developed by extending a between forecast method to include prediction errors. Validity and efficacy are demonstrated comparing the performances with the values that do not include prediction errors. The performances of the optimal method are demonstrated by increased validity and accuracy of the , coefficient of the Poisson regression model for the association with asthma hospital admissions. Visual inspection of the imputed values of sulphur dioxide levels with prediction errors demonstrated that the variation is better captured. The method is computationally simple and can be incorporated into the existing statistical software. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    The evolution of water transport in plants: an integrated approach

    GEOBIOLOGY, Issue 2 2010
    J. PITTERMANN
    This review examines the evolution of the plant vascular system from its beginnings in the green algae to modern arborescent plants, highlighting the recent advances in developmental, organismal, geochemical and climatological research that have contributed to our understanding of the evolution of xylem. Hydraulic trade-offs in vascular structure,function are discussed in the context of canopy support and drought and freeze,thaw stress resistance. This qualitative and quantitative neontological approach to palaeobotany may be useful for interpreting the water-transport efficiencies and hydraulic limits in fossil plants. Large variations in atmospheric carbon dioxide levels are recorded in leaf stomatal densities, and may have had profound impacts on the water conservation strategies of ancient plants. A hypothesis that links vascular function with stomatal density is presented and examined in the context of the evolution of wood and/or vessels. A discussion of the broader impacts of plant transport on hydrology and climate concludes this review. [source]

    [CO2]- and density-dependent competition between grassland species

    GLOBAL CHANGE BIOLOGY, Issue 11 2006
    MARK Van KLEUNEN
    Abstract The predicted ongoing increase of atmospheric carbon dioxide levels is considered to be one of the main threats to biodiversity due to potential changes in biotic interactions. We tested whether effects of intra- and interspecific planting density of the calcareous grassland perennials Bromus erectus and Carex flacca change in response to elevated [CO2] (600 ppm) by using factorial combinations of seven densities (0, 1, 2, 4, 8, 16, 24 tillers per 8 × 8 cm2 cell) of both species in plots with and without CO2 enrichment. Although aboveground biomass of C. flacca was increased by 54% under elevated [CO2], the combined aboveground biomass of the whole stand was not significantly increased. C. flacca tended to produce more tillers under elevated [CO2] while B. erectus produced less tillers. The positive effect of [CO2] on the number of tillers of C. flacca was strongest at high intraspecific densities. On the other hand, the negative effect of [CO2] on the number of tillers of B. erectus was not present at intermediate intraspecific planting densities. Seed production of C. flacca was more than doubled under elevated [CO2], while seed production of B. erectus was not affected. Moreover, the mass per seed of C. flacca was increased by elevated [CO2] at intermediate interspecific planting densities while the mass per seed of B. erectus was decreased by elevated [CO2] at high interspecific planting densities. Our results show that the responses of C. flacca and B. erectus to elevated [CO2] depend in a complex way on initial planting densities of both species. In other words, competition between these two model species is both [CO2]- and density dependent. On average, however, the effects of [CO2] on the individual species indicate that the composition of calcareous grasslands is likely to change under elevated [CO2] in favor of C. flacca. [source]

    Climate change: the science and the policy

    JOURNAL OF APPLIED ECOLOGY, Issue 5 2005
    DAVID KING
    Summary Globally we face serious challenges from the effects of climate change. The causal link between global warming and increased greenhouse gas emissions is well established. Carbon dioxide levels are at a higher level than at any time in the past 750 000 years at least, and it is too late to stop further warming and consequent impacts on UK and global societies. Here I summarize the latest scientific evidence for anthropogenic global warming and outline strategies for adapting to its impacts and mitigating the effects in the longer term. [source]

    Acute changes in carbon dioxide levels alter the electroencephalogram without affecting cognitive function

    PSYCHOPHYSIOLOGY, Issue 4 2000
    Elisabeth Bloch-Salisbury
    The partial pressure of carbon dioxide in the arterial blood (PaCO2) is usually tightly regulated, yet it varies among healthy people at rest (range ,32,44 mmHg) as well as within an individual during many natural life situations. The present study examined whether modest changes in end-tidal PCO2 (PetCO2; a noninvasive measure of PaCO2) affect electroencephalographic (EEG) activity, cognitive function, and vigilance. Nine adults were ventilated mechanically using a mouthpiece; respiratory rate and breath size were held constant while PetCO2 was set to levels that produced minimal discomfort. Despite discrete changes in EEG, neither acute PetCO2 increases (mean = 47 mmHg) nor decreases (mean = 30 mmHg) from resting levels (mean = 38 mmHg) affected performance on cognitive tasks, latency or amplitude of the N1, P2, or P3 event-related potential, or alertness. Modest changes in PetCO2 may cause significant alterations in the EEG without disturbing cognitive function. [source]

    PERIOPERATIVE HIGH-DOSE OXYGEN THERAPY IN VASCULAR SURGERY

    ANZ JOURNAL OF SURGERY, Issue 6 2007
    Phillip J. Puckridge
    Background: Patients undergoing infrainguinal bypass surgery have reduced baseline tissue oxygen tension and high rates of wound infections. The hypoxaemia worsens during surgery, potentially reducing the ability to combat bacterial lodgement. We investigated whether high-dose perioperative oxygen administration to patients undergoing infrainguinal arterial surgery results in increased tissue oxygenation. Methods: Ten consecutive patients undergoing infrainguinal arterial surgery had transcutaneous partial pressure of oxygen (TcpO2) measured preoperatively, intraoperatively after arterial clamps applied, postoperatively and at discharge. Measurements were taken with inspired oxygen concentration (FiO2) of 30% then 80%. Arterial blood gases were measured at the same times. Results: Tissue oxygenation showed no difference intraoperatively while arterial clamps were in place, but significantly higher tissue oxygenation was seen with use of high-dose oxygen (FiO2 80%) postoperatively (P < 0.05). Carbon dioxide levels in tissue increased while arterial clamps were in place (P < 0.01) and pH fell intraoperatively and following reperfusion (P < 0.05). Conclusion: The administration of high-dose oxygen to vascular surgical patients undergoing lower-limb arterial surgery results in increased tissue oxygen concentrations when perfusion is not reduced by the presence of arterial clamps. These results suggest the administration of high-dose oxygen intraoperatively may be beneficial in reducing wound infections, but further research is required. [source]

    Tropical rainforest canopies and climate change

    AUSTRAL ECOLOGY, Issue 1 2007
    NIGEL E. STORK
    Abstract There is less certainty about the impact of climate change on tropical rainforests than on temperate forests because of the comparative lack of background data and because few large scale experiments have been, and are being, carried out in tropical rainforests. Many of the factors critical to the future of tropical rainforests concern canopies, the key processes that take place there, and the roles and interactions of canopy biodiversity. In particular there are almost no data on how forest canopies and processes are changing with increased carbon dioxide levels. The implications of elevated carbon dioxide, climatic stress and related changes in water-use efficiency, nutrient availability and other such changes are discussed particularly with references to Australia's tropical rainforests. [source]