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Third Quartile (third + quartile)
Selected AbstractsSpatial point-process statistics: concepts and application to the analysis of lead contamination in urban soil,ENVIRONMETRICS, Issue 4 2005Christian Walter Abstract This article explores the use of spatial point-process analysis as an aid to describe topsoil lead distribution in urban environments. The data used were collected in Glebe, an inner suburb of Sydney. The approach focuses on the locations of punctual events defining a point pattern, which can be statistically described through local intensity estimates and between-point distance functions. F -, G - and K -surfaces of a marked spatial point pattern were described and used to estimate nearest distance functions over a sliding band of quantiles belonging to the marking variable. This provided a continuous view of the point pattern properties as a function of the marking variable. Several random fields were simulated by selecting points from random, clustered or regular point processes and diffusing them. Recognition of the underlying point process using variograms derived from dense sampling was difficult because, structurally, the variograms were very similar. Point-event distance functions were useful complimentary tools that, in most cases, enabled clear recognition of the clustered processes. Spatial sampling quantile point pattern analysis was defined and applied to the Glebe data set. The analysis showed that the highest lead concentrations were strongly clustered. The comparison of this data set with the simulation confidence limits of a Poisson process, a short-radius clustered point process and a geostatistical simulation showed a random process for the third quartile of lead concentrations but strong clustering for the data in the upper quartile. Thus the distribution of topsoil lead concentrations over Glebe may have resulted from several contamination processes, mainly from regular or random processes with large diffusion ranges and short-range clustered processes for the hot spots. Point patterns with the same characteristics as the Glebe experimental pattern could be generated by separate additive geostatistical simulation. Spatial sampling quantile point patterns statistics can, in an easy and accurate way, be used complementarily with geostatistical methods. Copyright © 2005 John Wiley & Sons, Ltd. [source] Critical assessment of the applicability of gas chromatography-combustion-isotope ratio mass spectrometry to determine amino sugar dynamics in soilRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Charlotte Decock Amino sugars in soils have been used as markers of microbial necromass and to determine the relative contribution of bacterial and fungal residues to soil organic matter. However, little is known about the dynamics of amino sugars in soil. This is partly because of a lack of adequate techniques to determine ,turnover rates' of amino sugars in soil. We conducted an incubation experiment where 13C-labeled organic substrates of different quality were added to a sandy soil. The objectives were to evaluate the applicability of compound-specific stable isotope analysis via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the determination of 13C amino sugars and to demonstrate amino sugar dynamics in soil. We found total analytical errors between 0.8 and 2.6, for the ,13C-values of the soil amino sugars as a result of the required ,13C-corrections for isotopic alterations due to derivatization, isotopic fractionation and analytical conditions. Furthermore, the ,13C-values of internal standards in samples determined via GC-C-IRMS deviated considerably from the ,13C-values of the pure compounds determined via elemental analyzer IRMS (with a variation of 9 to 10, between the first and third quartile among all samples). This questions the applicability of GC-C-IRMS for soil amino sugar analysis. Liquid chromatography-combustion-IRMS (LC-C-IRMS) might be a promising alternative since derivatization, one of the main sources of error when using GC-C-IRMS, is eliminated from the procedure. The high 13C-enrichment of the substrate allowed for the detection of very high 13C-labels in soil amino sugars after 1 week of incubation, while no significant differences in amino sugar concentrations over time and across treatments were observed. This suggests steady-state conditions upon substrate addition, i.e. amino sugar formation equalled amino sugar decomposition. Furthermore, higher quality substrates seemed to favor the production of fungal-derived amino sugars. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-sensitivity C-reactive protein: A predicative marker in severe asthmaRESPIROLOGY, Issue 5 2008Fen-Hong QIAN Background and objective: Serum levels of high-sensitivity CRP (hs-CRP) are associated with asthma but the relationship between higher levels of hs-CRP and the degree of asthma severity remains unclear. This study investigated whether hs-CRP is associated with asthma severity as well as with other clinical indices of asthma activity (pulmonary function, total serum IgE, and peripheral blood eosinophil counts). Methods: Levels of hs-CRP and clinical indices of asthma were determined among 177 control subjects and 281 asthmatic patients (84 intermittent, 30 mild, 63 moderate and 104 severe). Results: The level of hs-CRP was examined as both a continuous variable and by quartiles (<0.23, 0.23,0.51, 0.51,1.42 and ,1.42 mg/L) in the five groups. Compared with the first quartile of hs-CRP, patients with higher levels were at increased risk of severe asthma independently of other clinical indices (adjusted OR 3.49, 95% CI: 1.51,8.12 for the third quartile; adjusted OR 6.46, 95% CI: 2.85,16.62 for fourth quartile, respectively). Conclusions: These findings suggest that hs-CRP might be a sensitive marker for severe asthma. [source] Serum Copper/Zinc Superoxide Dismutase (Cu/Zn SOD) and Gastric Cancer Risk: a Case-Control StudyCANCER SCIENCE, Issue 10 2002Yingsong Lin We conducted a case-control study to evaluate the association between serum levels of copper/zinc superoxide dismutase (Cu/Zn SOD) and the risk of gastric cancer. Cases were 214 patients who had been diagnosed with gastric cancer and controls were 120 persons who underwent medical checkups. Serum levels of Cu/Zn SOD were determined by enzyme-linked immunosorbent assay (ELISA). Compared with the lowest quartile, the OR (odds ratio) was 4.54 (95% CI (confidence interval), 1.62,12.66) for the third quartile and 15.75 (95% CI, 5.84,42.46) for the highest quartile. With both early and advanced cancers, as well as with the intestinal and diffuse types, a significant increase in risk was observed with increasing levels of serum Cu/Zn SOD. Our case-control study showed that serum levels of Cu/Zn SOD were significantly elevated in gastric cancer patients compared with apparently healthy controls, and higher Cu/Zn SOD levels may be associated with an increased risk of gastric cancer. [source] Cardiovascular Disease Is Associated with Greater Incident Dehydroepiandrosterone Sulfate Decline in the Oldest Old: The Cardiovascular Health Study All Stars StudyJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2010Jason L. Sanders BA OBJECTIVES: To describe cross-sectional and longitudinal associations with dehydroepiandrosterone sulfate (DHEAS) and change in DHEAS with age. DESIGN: Longitudinal cohort study. SETTING: Pittsburgh, Pennsylvania. PARTICIPANTS: Cardiovascular Health Study All Stars study participants assessed in 2005/06 (N=989, mean age 85.2, 63.5% women, 16.5% African American). MEASUREMENTS: Health characteristics were assessed in 2005/06 according to DHEAS level, mean DHEAS and DHEAS change across age categories were tested, and linear and logistic regression was used to identify factors present in 1996/97 associated with continuous and categorical DHEAS change. RESULTS: Mean ± standard deviation DHEAS was 0.555 ± 0.414 ,g/mL in 1996/97 and 0.482 ± 0.449 ,g/mL in 2005/06 for women and 0.845 ± 0.520 ,g/mL in 1996/97 and 0.658 ± 0.516 ,g/mL in 2005/06 for men. In 2005/06, DHEAS was lower in women and subjects with cardiovascular disease (CVD) and chronic pulmonary disease and higher for African Americans and subjects with hypertension and high cholesterol. Mean DHEAS change was greater in men (,0.200 ,g/mL) than in women (,0.078 ,g/mL) (P<.001). Each 1-year increase in age attenuated the effect of male sex by 0.01 ,g/mL (P=.009), abolishing the sex difference in DHEAS change by age 79. Presence of CVD before the study period was associated with greater absolute DHEAS change (,=,0.04 ,g/mL, P=.04) and with the fourth quartile of DHEAS change versus the first to third quartiles (odds ratio=1.46, 95% confidence interval=1.03,2.05). CONCLUSION: DHEAS change continues into very old age, is not homogenous, is affected by sex, and is associated with prevalent CVD. Future studies should investigate factors that might accelerate DHEAS decline. [source] | ||||||||||