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Data Variance (data + variance)

Distribution by Scientific Domains

Earth and Environmental Science	60%
Medical Sciences	40%

Selected Abstracts

Joint full-waveform analysis of off-ground zero-offset ground penetrating radar and electromagnetic induction synthetic data for estimating soil electrical properties

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2010
D. Moghadas
SUMMARY A joint analysis of full-waveform information content in ground penetrating radar (GPR) and electromagnetic induction (EMI) synthetic data was investigated to reconstruct the electrical properties of multilayered media. The GPR and EMI systems operate in zero-offset, off-ground mode and are designed using vector network analyser technology. The inverse problem is formulated in the least-squares sense. We compared four approaches for GPR and EMI data fusion. The two first techniques consisted of defining a single objective function, applying different weighting methods. As a first approach, we weighted the EMI and GPR data using the inverse of the data variance. The ideal point method was also employed as a second weighting scenario. The third approach is the naive Bayesian method and the fourth technique corresponds to GPR,EMI and EMI,GPR sequential inversions. Synthetic GPR and EMI data were generated for the particular case of a two-layered medium. Analysis of the objective function response surfaces from the two first approaches demonstrated the benefit of combining the two sources of information. However, due to the variations of the GPR and EMI model sensitivities with respect to the medium electrical properties, the formulation of an optimal objective function based on the weighting methods is not straightforward. While the Bayesian method relies on assumptions with respect to the statistical distribution of the parameters, it may constitute a relevant alternative for GPR and EMI data fusion. Sequential inversions of different configurations for a two layered medium show that in the case of high conductivity or permittivity for the first layer, the inversion scheme can not fully retrieve the soil hydrogeophysical parameters. But in the case of low permittivity and conductivity for the first layer, GPR,EMI inversion provides proper estimation of values compared to the EMI,GPR inversion. [source]

Genotype x environment interaction in the uptake of Cs and Sr from soils by plants

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2004
Alexei Melnitchouck
Abstract The soil-plant transfer factors for Cs and Sr were analyzed in relationship to soil properties, crops, and varieties of crops. Two crops and two varieties of each crop: lettuce (Lactuca sativa L.), cv. Salad Bowl Green and cv. Lobjoits Green Cos, and radish (Raphanus sativus L.), cv. French Breakfast 3 and cv. Scarlet Globe, were grown on five different soils amended with Cs and Sr to give concentrations of 1 mg kg,1 and 50,mg,kg,1 of each element. Soil-plant transfer coefficients ranged between 0.12,19.10 (Cs) and 1.48,146.10 (Sr) for lettuce and 0.09,13.24 (Cs) and 2.99,93.00 (Sr) for radish. Uptake of Cs and Sr by plants depended on both plant and soil properties. There were significant (P , 0.05) differences between soil-plant transfer factors for each plant type at the two soil concentrations. At each soil concentration about 60,% of the variance in the uptake of the Cs and Sr was due to soil properties. For a given concentration of Cs or Sr in soil, the most important factor effecting soil-plant transfer of these elements was the soil properties rather than the crops or varieties of crops. Therefore, for the varieties considered here, soil-plant transfer of Cs and Sr would be best regulated through the management of soil properties. At each concentration of Cs and Sr, the main soil properties effecting the uptake of Cs and Sr by lettuce and radish were the concentrations of K and Ca, pH and CEC. Together with the concentrations of contaminants in soils, they explained about 80,% of total data variance, and were the best predictors for soil-plant transfer. The different varieties of lettuce and radish gave different responses in soil-plant transfer of Cs and Sr in different soil conditions, i.e. genotype x environment interaction caused about 30,% of the variability in the uptake of Cs and Sr by plants. This means that a plant variety with a low soil-plant transfer of Cs and Sr in one soil could have an increased soil-plant transfer factor in other soils. The broad implications of this work are that in contaminated agricultural lands still used for plant growing, contaminant-excluding crop varieties may not be a reliable method for decreasing contaminant transfer to foodstuffs. Modification of soil properties would be a more reliable technique. This is particularly relevant to agricultural soils in the former USSR still affected by fallout from the Chernobyl disaster. Wechselwirkungen Genotyp x Umwelt im Hinblick auf die Aufnahme von Cs und Sr aus Böden durch Pflanzen Die Transferfaktoren von Cs und Sr vom Boden zur Pflanze wurden in Zusammenhang mit den Bodeneigenschaften, der Fruchtart und der Sorte untersucht. Zwei Fruchtarten mit je zwei Sorten: Salat (Lactua sativa L.) cv. Salad Bowl Green und cv. Lobjoits Green Cos, und Rettich (Raphanus sativus L.) cv. French Breakfast 3 und cv. Scarlet Globe, wurden in fünf verschiedenen Böden, die mit Cs und Sr in Konzentrationen von je 1 mg kg,1 und 50 mg kg,1 angereichert wurden, untersucht. Die Boden-Pflanze-Transferkoeffizienten variierten für Salat von 0,12,19,10 (Cs) und 1,48,146,1 (Sr) und für Rettich von 0,09,13,24 (Cs) und 2,99,93,00 (Sr). Die Aufnahme von Cs und Sr durch Pflanzen hängt sowohl von der Pflanze als auch von den Bodeneigenschaften ab. Es gab signifikante (P , 0,05) Unterschiede zwischen den Boden-Pflanze-Transferfaktoren für jede Pflanzensorte bei beiden Konzentrationen im Boden. Bei jeder Konzentration im Boden wurde die Varianz für die Aufnahme von Cs und Sr zu ca. 60,% von den Bodeneigenschaften bestimmt. Für jede vorgegebene Konzentration von Cs oder Sr im Boden wurde der Boden-Pflanze-Transfer mehr durch die Bodeneigenschaften beeinflusst als durch die Fruchtart oder Sorte. Daher ist der Transfer von Cs und Sr für die hier untersuchten Sorten am besten über eine Beeinflussung der Bodeneigenschaften steuerbar. Die Aufnahme in Rettich und Salat wurde für alle untersuchten Cs- und Sr-Konzentrationen am stärksten durch die K- und Ca-Konzentrationen, den pH-Wert und die KAK der jeweiligen Böden beeinflusst. Die Konzentrationen der Schadstoffe in Böden und die beschriebenen Bodeneigenschaften erklärten ca. 80,% die Gesamtdatenvarianz und sind die besten Voranzeiger für den Boden-Pflanze-Transfer. Die verschiedenen Salat- und Rettichsorten reagierten im Transport von Cs und Sr vom Boden zur Pflanze unterschiedlich auf die verschiedenen Bodeneigenschaften. So erklärte z.,B. die Wechselwirkung Genotyp x Umweltbedingungen ca. 30,% der Variabilität der Pflanzenaufnahme von Cs und Sr. Das bedeutet, dass eine Sorte, die auf einem Boden einen geringen Boden-Pflanze-Transfer von Cs und Sr aufweist, auf einem anderen Boden einen höheren Boden-Pflanze-Transfer aufweisen kann. Die wichtigste Erkenntnis dieser Untersuchung besteht darin, dass die Veränderung der Bodeneigenschaften im Vergleich zum Einsatz von Sorten mit einer geringen Cs- und Sr-Akkumulationsrate auf kontaminierten landwirtschaftlichen Standorten eine aussichtsreichere Methode sein könnte, um die Aufnahme von Cs und Sr in Nahrungsmittel zu minimieren. Diese Aussage ist besonders für landwirtschaftliche Flächen in der früheren UdSSR relevant, die durch die Katastrophe von Chernobyl kontaminiert wurden. [source]

The German version of the chronic urticaria quality-of-life questionnaire: factor analysis, validation, and initial clinical findings

ALLERGY, Issue 6 2009
ynek
Background:, Chronic urticaria (CU) is a common skin disorder that causes a substantial burden on patients' quality-of-life (QoL). The aim of this work was to generate and validate a German version of the Chronic Urticaria Quality of Life Questionnaire (CU-Q2oL) and to provide reference assessments of QoL. Methods:, The Italian CU-Q2oL was translated into German and administered to 157 CU patients. They also completed two well-established general dermatology QoL questionnaires, the Dermatology Life Quality Index (DLQI) and Skindex-29. Factor analysis was used to identify scales of the German CU-Q2oL. Correlation to the DLQI and Skindex-29 was used for validation. Multiple linear regression was used to determine which patient characteristics were associated with which dimensions of QoL. Results:, The factor analysis identified six scales of the German CU-Q2oL: functioning, sleep, itching/embarrassment, mental status, swelling/eating, and limits looks, which accounted for 70% of the data variance. Five of these six scales showed good internal consistency, and another five demonstrated convergent validity. On a percentile scale, they had these median CU-Q2oL scores: 29 functioning, 44 sleep, 50 itching/embarrassment, 50 mental status, 31 swelling/eating, 31 limits looks. Disease severity significantly predicted scores on all scales. Age predicted functioning, sleep, itching/embarrassment, and swelling/eating. Sex predicted itching/embarrassment and limits looks. Conclusion:, This study yielded a robust validation of the German version of the CU-Q2oL. It confirmed previous studies that CU has a clinically meaningful burden on QoL, especially for sleep and mental health, and that women are more severely affected by pruritus. The German CU-Q2oL should be widely adopted in clinical research on the treatment of CU. [source]

Head and Neck Cancer: The Importance of Oxygen ,

THE LARYNGOSCOPE, Issue 5 2000
David J. Terris MD
Abstract Objectives To use recently introduced polarographic technology to characterize the distribution of oxygenation in solid tumors, explore the differences between severe hypoxia and true necrosis, and evaluate the ability to predict treatment outcomes based on tumor oxygenation. Study Design Prospective, nonrandomized trial of patients with advanced head and neck cancer, conducted at an academic institution. Methods A total of 63 patients underwent polarographic oxygen measurements of their tumors. Experiment 1 was designed to determine whether a gradient of oxygenation exists within tumors by examining several series of measurements in each tumor. Experiment 2 was an analysis of the difference in data variance incurred when comparing oxygen measurements using oxygen electrodes of two different sizes. Experiment 3 compared the proportion of tumor necrosis to the proportion of very low (,2.5 mm Hg) polarographic oxygen measurements. Experiment 4 was designed to explore the correlation between oxygenation and treatment outcomes after nonsurgical management. Results No gradient of oxygenation was found within cervical lymph node metastases from head and neck squamous cell carcinomas (P > .9). Tumor measurements achieved with larger (17 ,m) electrodes displayed smaller variances than those obtained with smaller (12 ,m) electrodes, although this difference failed to reach statistical significance (P = .60). There was no correlation between tumor necrosis and the proportion of very low (,2.5 mm Hg) oxygen measurements. There was a nonsignificant trend toward poorer locoregional control and overall survival in hypoxic tumors. Conclusions Hypoxia exists within cervical lymph node metastases from head and neck squamous carcinomas, but the hypoxic regions are distributed essentially randomly. As expected, measurements of oxygen achieved with larger electrodes results in lowered variance, but with no change in overall tumor mean oxygen levels. Polarographic oxygen measurements are independent of tumor necrosis. Finally, oxygenation as an independent variable is incapable of predicting prognosis, probably reflecting the multifactorial nature of the biological behavior of head and neck cancers. [source]

SEISMIC FACIES ANALYSIS BASED ON 3D MULTI-ATTRIBUTE VOLUME CLASSIFICATION, DARIYAN FORMATION, SE PERSIAN GULF

JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2006
P. Farzadi
Interpretation of recently acquired 3D seismic data from the adjacent Sirri C and D oilfields in the SE Persian Gulf indicates that a 3D interpretation of seismic facies is crucial to resolve the internal stratal geometries of the Aptian Dariyan Formation. This carbonate formation passes southward into the Shu'aiba Formation, a prolific reservoir rock of similar facies in the UAE. Lack of exposures and limited cored intervals have forced reliance on the seismic data for evidence of the depositional environment and the internal architecture of potential reservoir rocks. The progradational nature of the Dariyan Formation and the occurrence of carbonate build-ups within it make this stratal geometry complex. The complex internal heterogeneity of the build-ups and presence of seismic noise make mapping of the build-ups in 3D space using conventional seismic interpretation tools difficult, despite the availability of high-quality 3D seismic data covering the area. The high quality seismic and limited well data from this field is one of the few datasets of this kind presented in the literature. A procedure for the hierarchical multi-attribute analysis of seismic facies using Paradigm's Seis Facies software is used in this study to provide a 3D interpretation of the stratal patterns. Principal component analysis reduces the noise and redundant data by representing the main data variances as a few vector components in a transformed coordinate system. Cluster analysis is performed using those components which have the greatest contribution to the maximum spread of the data variability. Six seismic attribute volumes are used in this study and the result is a single 3D classified volume. Important new information obtained from within the Dariyan Formation gives new insights into its stratigraphic distribution and internal variability. This method of processing seismic data is a step towards exploring for subtle stratigraphic traps in the study area, and may help to identify exploration targets. [source]