52 research outputs found

    PrélÚvement racinaire et foliaire de Césium (134Cs) dans trois variétés de tabac.

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    Le prĂ©lĂšvement racinaire de CĂ©sium (134Cs) et sa distribution subsĂ©quente dans les pousses, fleurs et feuilles, de mĂȘme que son dĂ©pĂŽt direct sur ces parties de la plante, ont Ă©tĂ© Ă©tudiĂ©s expĂ©rimentalement par culture en pot en utilisant trois variĂ©tĂ©s de tabac (McNair, Kaba Koulac et Katerinis) trĂšs cultivĂ©es en GrĂšce. La migration verticale du 134Cs dans le sol et la teneur en cet Ă©lĂ©ment de la fumĂ©e produite par la combustion de feuilles radio-polluĂ©es ont Ă©galement Ă©tĂ© Ă©tudiĂ©es. Une diffĂ©rence variĂ©tale significative a Ă©tĂ© observĂ©e dans le prĂ©lĂšvement racinaire de 134Cs, tant dans le Facteur de Transfert (TF) calculĂ© que dans la distribution du 134Cs dans les diffĂ©rentes parties de la plante. Une diffĂ©rence variĂ©tĂ©-dĂ©pendante de la teneur en 134Cs a aussi Ă©tĂ© mesurĂ©e pour la fixation foliaire (dĂ©pĂŽt direct). On a observĂ© que, par rapport aux autres parties (tiges, feuilles supĂ©rieures et fleurs), les feuilles du bas de la plante absorbaient ou interceptaient la plus grande quantitĂ© de 134Cs. Durant les deux mois de culture du tabac, le 134Cs rĂ©sultant d'un dĂ©pĂŽt humide se retrouvait dans les cinq centimĂštres supĂ©rieurs du sol mais aucune migration de radionuclĂ©ide n'a Ă©tĂ© dĂ©tectĂ©e dans les dĂ©pĂŽts Ă  sec. Enfin la teneur en 134Cs de la fumĂ©e Ă©tait infĂ©rieure Ă  1 % de la quantitĂ© totale dans les cendres des feuilles.The root uptake of Caesium (134Cs) and its subsequent distribution into the shoots, flowers and leaves, as well as the direct deposition of 134Cs on these parts of the plant, were studied in pot experiments, using three tobacco plant varieties (McNair, Kaba Koulac and Katerinis) that are widely cultivated in Greece. The vertical migration of 134Cs into the soil and the quantity of this element contained in the smoke of burning radio-polluted leaves were also studied. For the root uptake of 134Cs, a significant varietal difference was observed, both in calculated Transfer Factor (TF) and in distribution of 134Cs in the different plant parts. A variety dependent difference in 134Cs content was also measured for foliar uptake (direct deposition). It was observed that the main quantity of 134Cs was absorbed or intercepted by the lower leaves of the plants, compared to the quantity absorbed or intercepted by the other plant parts (stems, upper leaves and flowers). During the two-month period of tobacco cultivation, the wet-deposed 134Cs was contained in the upper five centimeters of soil, while no radionuclide migration was detected in dry deposition. Finally, the amount of 134Cs detected in the smoke was measured to be less than 1% of the total amount in the ashes of the leaves

    An Extended Nonlinear Hicks Model of the Cycle for a Semi-Open Economy: Application to the USA (1960-2008)

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    This paper presents both an extended nonlinear Hicks model of the cycle for a semi-open economy and a method for deriving estimators based on Nonlinear Least Squares as a Numerical Optimization Problem. Hicks thought that fluctuations in investment, caused by nonlinear changes in autonomous investment and the acceleration principle governing induced investment, led to an adjustment process taking place throughout many periods. An empirical application for the US economy (1960-2008), demonstrates the validity of the model and its almost ideal fit to real world data

    Early Nonlinear Modelling in Economic Analysis: The Hicks Model for Greece Revisited

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    The present paper discusses the transition from linear modelling to the first nonlinear models in economic analysis. In this vein, an important contribution was J. Hicks’s A Contribution to the Theory of the Trade Cycle where he developed his own endogenous model of the cycle. Hicks thought that fluctuations in investment,– caused by nonlinear changes in autonomous investment and the acceleration principle governing induced investment – led to an adjustment process taking place throughout many periods. In this paper we introduce some modifications regarding the econometric estimation of Hicks’s nonlinear model and an empirical application for Greece (1960-2007) takes place demonstrating the almost ideal fit of the model

    Estimating a modified nonlinear Hicks model: Evidence from the US economy (1960-2008)

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    This paper presents a modified nonlinear Hicks model of the cycle and a method for deriving estimators based on Nonlinear Least Squares and other relevant criteria. Hicks thought that fluctuations in investment, caused by nonlinear changes in autonomous investment and the acceleration principle governing induced investment, led to an adjustment process taking place throughout many periods. An empirical application for the US economy (1960-2008) demonstrates the almost ideal performance of the modified model and the proposed method

    Estimating a modified nonlinear Hicks model: Evidence from the US economy (1960-2008)

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    This paper presents a modified nonlinear Hicks model of the cycle and a method for deriving estimators based on Nonlinear Least Squares and other relevant criteria. Hicks thought that fluctuations in investment, caused by nonlinear changes in autonomous investment and the acceleration principle governing induced investment, led to an adjustment process taking place throughout many periods. An empirical application for the US economy (1960-2008) demonstrates the almost ideal performance of the modified model and the proposed method

    Endoscopic internal drainage for the management of leak, fistula, and collection after sleeve gastrectomy: our experience in 617 consecutive patients

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    Background: Endoscopy plays a pivotal role in the management of adverse events (AE) following bariatric surgery. Leaks, fistulae, and post-operative collection after sleeve gastrectomy (SG) may occur in up to 10% of cases. Objectives: To evaluate the efficacy and safety of endoscopic internal drainage (EID) for the management of leak, fistula, and collection following SG. Setting: Retrospective, observational, single center study on patients referred from several bariatric surgery departments to an endoscopic referral center. Methods: EID was used as first-line treatment for the management of leaks, fistulae, and collections. Leaks and fistulae were treated with double pigtail stent (DPS) deployment in order to guarantee internal drainage and second intention cavity obliteration. Collections were treated with endoscropic ultrasound (EUS)–guided deployment of DPS or lumen apposing metal stents. Results: A total of 617 patients (83.3% female; mean age, 43.1 yr) were enrolled in the study for leak (n = 300, 48.6%), fistula (n = 285, 46.2%), and collection (n = 32, 5.2%). Median follow-up was 19.5 months. Overall clinical success was 84.7% whereas 15.3% of cases required revisional surgery after EID failure. Clinical success according to type of AE was 89.5%, 78.5%, and 90% for leak, fistula, and collection, respectively. A total of 10 of 547 (1.8%) presented a recurrence during follow-up. A total of 28 (4.5%) AE related to the endoscopic treatment occurred. At univariate logistic regression predictors of failure were: fistula (OR 2.012), combined endoscopic approach (OR 2.319), need for emergency surgery (OR 1.755), and previous endoscopic treatment (OR 4.818). Conclusion: Early EID for the management of leak, fistula, and post-operative collection after SG seems a safe and effective first-line approach with good long-term results

    Biodiversity and structure of spider communities along a metal pollution gradient

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    The objective of the study was to determine whether long-term metal pollution affects communities of epigeal spiders (Aranea), studied at three taxonomic levels: species, genera, and families. Biodiversity was defined by three indices: the Hierarchical Richness Index (HRI), Margalef index (DM) and Pielou evenness index (J). In different ways the indices describe taxa richness and the distribution of individuals among taxa. The dominance pattern of the communities was described with four measures: number of dominant species at a site, percentage of dominant species at a site, average dominant species abundance at a site, and the share of the most numerous species (Alopecosa cuneata) at a site. Spiders were collected along a metal pollution gradient in southern Poland, extending ca. 33 km from zinc and lead smelter to an uncontaminated area. The zinc concentration in soil was used as the pollution index.The study revealed a significant effect of metal pollution on spider biodiversity as described by HRI for species (p = 0.039), genera (p = 0.0041) and families (p = 0.0147), and by DM for genera (p = 0.0259) and families (p = 0.0028). HRI correlated negatively with pollution level, while DM correlated positively. This means that although broadly described HRI diversity decreased with increasing pollution level, species richness increased with increasing contamination. Mesophilic meadows were generally richer. Pielou (J) did not show any significant correlations. There were a few evidences for the intermediate disturbance hypothesis: certain indices reached their highest values at moderate pollution levels rather than at the cleanest or most polluted sites

    An extended nonlinear Hicks model of the cycle for a semi-open economy: Application to the USA (1960-2008)

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    This paper presents both an extended nonlinear Hicks model of the cycle for a semi-open economy and a method for deriving estimators based on Nonlinear Least Squares as a Numerical Optimization Problem. Hicks thought that fluctuations in investment, caused by nonlinear changes in autonomous investment and the acceleration principle governing induced investment, led to an adjustment process taking place throughout many periods. An empirical application for the US economy (1960-2008), demonstrates the validity of the model and its almost ideal fit to real world data
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