			Home About us Contact

Variation Range (variation + range)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Stable water isotope simulation in different reservoirs of Manaus, Brazil, by Community Land Model incorporating stable isotopic effect

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2009
Xin-Ping Zhang
Abstract The daily and monthly variations of stable water isotopes in different reservoirs at Manaus, Brazil, are simulated and inter-compared in an equilibrium year, using the Community Land Model (CLM) involving the stable isotopic effects as a diagnostic tool for an in-depth understanding of the hydrometeorological processes. On the daily scale, the ,18O in precipitation, vapour and surface runoff have clear seasonality, with marked negative correlations with the corresponding water amount. However, the ,18O in surface dew displays marked positive correlation with dew amount. On the diurnal time scale, the ,18O in precipitation displays an unclear diurnal variation and an unmarked correlation with the precipitation amount. However, the ,18O in vapour keeps consistency with specific humidity. On the monthly time scale, the ,18O in precipitation and surface runoff displays distinct bimodal seasonality, with two maxima in January and in July, and two minima in April and in October; Vapor displays a similar bimodal pattern, two maxima appear in January and August, and two minima in April and November. The amount effect simulated on the monthly time scale has consistency with the actual survey result at the Manaus station, from 1965 to 1990, set up by International Atomic Energy Agency (IAEA)/World Meteorological Organization (WMO). In addition, the slope (7.49) and the intercept (6.25) of the simulated meteoric water line (MWL) are all smaller than those of the actual mean MWL. However, compared with the annual MWL, the simulated MWL lies within the variation range of actual MWLs. Copyright © 2008 Royal Meteorological Society [source]

Determination of total homocysteine in dried blood spots using high performance liquid chromatography for homocystinuria newborn screening

PEDIATRICS INTERNATIONAL, Issue 1 2004
Andi Dwi Bahagia Febriani
AbstractBackground: The most widely used method for newborn screening for homocystinuria (HCU) is a semiquantitative bacterial inhibition assay for measuring methionine concentration in dried blood spots (DBS). Because this method has resulted in a number of missed cases due to many factors, we developed a high performance liquid chromatography (HPLC) method with fluorescence detection to measure total homocysteine (tHcy) in DBS which might be useful for newborn screening for HCU. Methods: One disk of DBS 3 mm in diameter was sonicated in 10 min. The extract was reduced with dithioerythritol and was derivatized with 4-aminosulfonyl-7fluoro-2,1,3-benzoxadiazole before injection into HPLC. Results: This method showed good linearity (r = 0.996), precision (coefficient of variation range 2.7,5%), and excellent correlation coefficient between DBS and serum tHcy, both in control (r = 0.932) and patient samples (r = 0.952). By this method, the mean tHcy concentration in DBS of preterm newborns, full-term newborns, and adults was 1.4 ± 1.0, 2.5 ± 1.6, and 4.9 ± 1.5 µmol/L, respectively. The mean tHcy DBS concentration in two cases of cystathionine-,-synthase deficiency and one case of 5,10-methylentetrahydrofolate reductase deficiency was 22.7 ± 2.88, 29.3 ± 1.90, and 41.3 µmol/L, respectively. Conclusions: The present method, which is rapid, user friendly and reliable, seems applicable to newborn screening of HCU in place of methionine measurement. [source]

Robust H, control for uncertain discrete-time systems with probabilistic state delays,

ASIAN JOURNAL OF CONTROL, Issue 5 2009
Engang Tian
Abstract In this paper, we propose a novel design problem of robust H, control for discrete-time systems with probabilistic time delay, where both the variation range of the delay and the probability distribution of the delay taking values in an interval are available. Based on the information on the probability distribution of the delay taking values in an interval, a new modeling method is put forward, with which the probabilistic effects of the delay are reflected into a parameter matrix of certain transformed system. Based on such a new model, criteria for the H, control design are derived by using a combination of the convexity of the matrix equations, the Lyapunov functional method and the linear matrix inequality technique. It is shown via numerical examples that our developed method in the paper can lead to less conservative results than those obtained by existing methods and, furthermore, if the probability distribution of the delay occurrence is available, the allowable upper bound of the delay may be larger than those derived for the case when only the variation range of the delay can be known. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

Variations of Microbial Communities and the Contents and Isotopic Compositions of Total Organic Carbon and Total Nitrogen in Soil Samples during Their Preservation

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2009
Qianye TAO
Abstract: Semi-sealed preservation of soil samples at different moisture of 4% and 23%, respectively, was simulated to observe the variations of soil microbial communities and determine the contents and isotopic compositions of the total organic carbon and total nitrogen on the 7th and 30th day, respectively. The results show that during preservation, the quantity of microbial communities tended to increase first and then decrease, with a wider variation range at higher moisture (23%). At the moisture content of 23%, the microbial communities became more active on the 7th day, but less after 30 days, and their activity was stable with little fluctuation at the moisture content of 4%. However, there were no significant changes in the contents and isotopic compositions of the total organic carbon and total nitrogen. During preservation, the responses of soil microbes to the environment are more sensitive to changes in the total nitrogen and organic carbon contents. It is thus suggested that the variations of microbial communities have not exerted remarkable impacts on the isotope compositions of the total nitrogen and total organic carbon. [source]