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  • Springer (CrossRef)  (8)
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  • 1
    Language: English
    In: Ecosystems, 2015, Vol.18(6), pp.1101-1120
    Description: Denitrification is the main process removing nitrate in river drainage basins and buffer input from agricultural land and limits aquatic ecosystem pollution. However, the identification of denitrification hotspots (for example, riparian...
    Keywords: Environmental Sciences ; Biodiversity and Ecology ; Denitrification ; Biogeochemical Hotspot ; Upscaling ; Residence Time Distribution ; Damköhler Ratio ; Diffuse Pollution Control ; Environmental Sciences ; Ecology
    ISSN: 1432-9840
    E-ISSN: 1435-0629
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  • 2
    Language: English
    In: Hydrogeology Journal, 2008, Vol.16(7), pp.1239-1250
    Description: An efficient method to upscale hydraulic conductivity ( K ) from detailed three-dimensional geostatistical models of hydrofacies heterogeneity to a coarser model grid is presented. Geologic heterogeneity of an alluvial fan system was characterized using transition-probability-based geostatistical simulations of hydrofacies distributions. For comparison of different hydrofacies architecture, two alternative models with different hydrofacies structures and geometries and a multi-Gaussian model, all with the same mean and variance in K , were created. Upscaling was performed on five realizations of each of the geostatistical models using the arithmetic and harmonic means of the K -values within vertical grid columns. The effects of upscaling on model domain equivalent K were investigated by means of steady-state flow simulations. A logarithmic increase in model domain equivalent K with increasing upscaling, was found for all fields. The shape of that upscaling function depended on the structure and geometry of the hydrofacies bodies. For different realizations of one geostatistical model, however, the upscaling function was the same. From the upscaling function a factor could be calculated to correct the upscaled K -fields for the local effects of upscaling. Une méthode efficace pour upscale la conductivité hydraulique () à partir de modèles géostatistiques 3D détaillés de l’hétérogénéité d’hydrofaciès vers un maillage de modèle plus grossier est présentée. L’hétérogénéité géologique d’un système de cône alluvial a été caractérisée en utilisant des simulations géostatistiques basées sur une probabilité d’évolution des distributions d’hydrofaciès. Pour comparer plusieurs compositions d’hydrofaciès deux modèles alternatifs avec des structures d’hydrofaciès et des géométries différentes et un modèle Gaussien multiple, tous avec la même moyenne et variance de , ont été créés. L’upscaling a été réalisé sur cinq mises en œuvre de chacun des modèles géostatistiques en utilisant les moyennes arithmétiques et harmoniques des valeurs au sein de colonnes verticales du maillage. Les effets de l’upscaling de l’équivalent dans le domaine du modèle ont été étudiés au moyen de simulations en écoulement permanent. Un accroissement logarithmique de l’équivalent dans le domaine du modèle avec un upscaling croissant, a été trouvé pour tous les domaines. La forme de cette fonction d’upscaling dépendait de la structure et de la géométrie des ensembles d’hydrofaciès. Pour différentes mises en œuvre d’un modèle géostatistique, toutefois, la fonction d’upscaling était la même. A partir de la fonction d’upscaling un facteur peut être calculé pour corriger les domaines de upscaled des effets locaux de l’upscaling. Se presenta un método eficiente para el sobre-escalado de la conductividad hidráulica () a partir de modelos geoestadísticos tridimensionales de heterogeneidades de hidrofacies a modelos con grillas de mayor escala. La heterogeneidad geológica de un abanico aluvial se caracterizó usando probabilidad de transición basada en simulaciones de la distribución de las hidrofacies. Para la comparación de la arquitectura de las distintas hidrofacies, se crearon dos modelos alternativos con diferentes estructuras y geometrías de las hidrofacies y un modelo multi-gaussiano, con la misma media y varianza de . El sobre-escalado se logró con cinco realizaciones de cada modelo geoestadístico usando las medias aritmética y armónica de los valores de en cada columna vertical de la grilla. Los efectos del sobre-escalado se investigaron con simulaciones del flujo en estado estacionario. Se halló que un incremento en el sobre-escalado produce un incremento logarítmico en el dominio del modelo con equivalente. La forma de la función de sobre-escalado depende de la estructura y geometría de los cuerpos de hidrofacies. Sin embargo, para diferentes realizaciones de un dado modelo geoestadístico, la función de sobre-escalado fue la misma. Esa función de sobre-escalado permite calcular un factor que corrige los campos de sobre-escalados por efectos locales del sobre-escalado.
    Keywords: Upscaling ; Hydraulic properties ; Heterogeneity ; Geostatistics ; Numerical modeling
    ISSN: 1431-2174
    E-ISSN: 1435-0157
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  • 3
    Language: English
    In: Environmental Earth Sciences, 2017, Vol.76(1), pp.1-25
    Description: This article provides an overview about the Bode River catchment that was selected as the hydrological observatory and main region for hydro-ecological research within the TERrestrial ENvironmental Observatories Harz/Central German Lowland Observatory. It first provides information about the general characteristics of the catchment including climate, geology, soils, land use, water quality and aquatic ecology, followed by the description of the interdisciplinary research framework and the monitoring concept with the main components of the multi-scale and multi-temporal monitoring infrastructure. It also shows examples of interdisciplinary research projects aiming to advance the understanding of complex hydrological processes under natural and anthropogenic forcings and their interactions in a catchment context. The overview is complemented with research work conducted at a number of intensive research sites, each focusing on a particular functional zone or specific components and processes of the hydro-ecological system.
    Keywords: Monitoring ; Catchment ; Water quality ; Observatory ; Water fluxes
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 4
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.317-333
    Description: Sustainable water quality management requires a profound understanding of water fluxes (precipitation, run-off, recharge, etc.) and solute turnover such as retention, reaction, transformation, etc. at the catchment or landscape scale. The Water and Earth System Science competence cluster (WESS, http://www.wess.info/ ) aims at a holistic analysis of the water cycle coupled to reactive solute transport, including soil–plant–atmosphere and groundwater–surface water interactions. To facilitate exploring the impact of land-use and climate changes on water cycling and water quality, special emphasis is placed on feedbacks between the atmosphere, the land surface, and the subsurface. A major challenge lies in bridging the scales in monitoring and modeling of surface/subsurface versus atmospheric processes. The field work follows the approach of contrasting catchments, i.e. neighboring watersheds with different land use or similar watersheds with different climate. This paper introduces the featured catchments and explains methodologies of WESS by selected examples.
    Keywords: Water and solute fluxes ; Water quality ; Catchments ; Land-surface atmosphere exchange ; Processes and feedbacks ; Modeling ; Monitoring
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 5
    Language: English
    In: Strahlentherapie und Onkologie, 2016, Vol.192(2), pp.75-82
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s00066-015-0900-9 Byline: Jochen Fleckenstein (1), Katharina Kremp (1), Stephanie Kremp (1), Jan Palm (1), Christian Rube (1) Keywords: Non-small cell lung carcinoma; Intensity-modulated radiation therapy; Conformal radiotherapy; Positron emission tomography; Organs at risk; Nichtkleinzelliges Bronchialkarzinom; Intensitatsmodulierte Strahlentherapie; Konformale Radiotherapie; Positronenemissionstomographie; Risikoorgane Abstract: Aim The potential of intensity-modulated radiation therapy (IMRT) as opposed to three-dimensional conformal radiotherapy (3D-CRT) is analyzed for two different concepts of fluorodeoxyglucose positron emission tomography (FDG PET)-based target volume delineation in locally advanced non-small cell lung cancer (LA-NSCLC): involved-field radiotherapy (IF-RT) vs. elective nodal irradiation (ENI). Methods Treatment planning was performed for 41 patients with LA-NSCLC, using four different planning approaches (3D-CRT-IF, 3D-CRT-ENI, IMRT-IF, IMRT-ENI). ENI included a boost irradiation after 50 Gy. For each plan, maximum dose escalation was calculated based on prespecified normal tissue constraints. The maximum prescription dose (PD), tumor control probability (TCP), conformal indices (CI), and normal tissue complication probabilities (NTCP) were analyzed. Results IMRT resulted in statistically significant higher prescription doses for both target volume concepts as compared with 3D-CRT (ENI: 68.4 vs. 60.9 Gy, p〈0.001 IF: 74.3 vs. 70.1 Gy, p〈0.03). With IMRT-IF, a PD of at least 66 Gy was achieved for 95% of all plans. For IF as compared with ENI, there was a considerable theoretical increase in TCP (IMRT: 27.3 vs. 17.7%, p〈0.00001 3D-CRT: 20.2 vs. 9.9%, p〈0.00001). The esophageal NTCP showed a particularly good sparing with IMRT vs. 3D-CRT (ENI: 12.3 vs. 30.9% p〈0.0001 IF: 15.9 vs. 24.1% p〈0.001). Conclusion The IMRT technique and IF target volume delineation allow a significant dose escalation and an increase in TCP. IMRT results in an improved sparing of OARs as compared with 3D-CRT at equivalent dose levels. Abstract (German): Zielsetzung Das Potenzial der intensitatsmodulierten Strahlentherapie (IMRT) soll im Rahmen der FDG-PET basierten Bestrahlungsplanung des lokal fortgeschrittenen nichtkleinzelligen Bronchialkarzinoms (LA-NSCLC) fur 2 Zielvolumenansatze (Involved-Field-Bestrahlung, IF) sowie elektive Nodalbestrahlung (ENI) gepruft und mit der 3-D-konformalen Strahlentherapie (3-D-CRT) als Referenz verglichen werden. Material und Methoden Die Bestrahlungsplanung erfolgte an CT-Datensatzen von 41 Patienten mit LA-NSCLC in 4 Ansatzen (3-D-CRT-IF, 3-D-CRT-ENI, IMRT-IF, IMRT-ENI) jeweils mit 2 Gy Einzeldosis. ENI beinhaltete einen zusatzlichen Boost nach 50 Gy. Fur jeden Plan wurde die maximal mogliche Dosiseskalation nach vordefinierten Grenzwerten fur Normalgewebe vorgenommen. Es wurden die maximal erreichbare Dosis, die Tumorkontrollwahrscheinlichkeit (TCP), der Konformitatsindex (CI) und Normalgewebsrisiken nach dem NTCP-Modell ("normal tissue complication probabilities") analysiert. Ergebnisse Die IMRT-Plane resultierten in statistisch signifikant hoheren Gesamtdosen fur beide Zielvolumenkonzepte im Vergleich zur 3-D-CRT (ENI: 68,4 Gy vs. 60,9 Gy p〈0,001 IF: 74,3 vs. 70,1 Gy p〈0,03). Mittels IMRT-IF wurde eine Gesamtdosis von 66 Gy fur 95% der Plane erreicht. Der rechnerische TCP-Anstieg mittels IF im Vergleich zu ENI war erheblich (IMRT: 27,3 vs. 17,7% p〈0,00001 3-D-CRT: 20,2 vs. 9,9% p〈0,00001). NTCP-Werte fur den Osophagus waren mit der IMRT im Vergleich zur 3-D-CRT signifikant niedriger (ENI: 12,3 vs. 30,9% p〈0,0001 IF: 15,9 vs. 24,1% p〈0,001). Schlussfolgerung Mittels IMRT und IF lasst sich beim LA-NSCLC eine signifikante Dosiseskalation und ein Anstieg der TCP erreichen. Die IMRT ermoglicht au[sz]erdem eine signifikant geringere Normalgewebsbelastung im Vergleich zur 3-D-CRT bei aquivalenten Gesamtdosen. Author Affiliation: (1) Department of Radiotherapy and Radiation Oncology, Saarland University Medical School, 66421, Homburg/Saar, Germany Article History: Registration Date: 10/09/2015 Received Date: 24/04/2015 Accepted Date: 09/09/2015 Online Date: 05/10/2015
    Keywords: Non-small cell lung carcinoma ; Intensity-modulated radiation therapy ; Conformal radiotherapy ; Positron emission tomography ; Organs at risk
    ISSN: 0179-7158
    E-ISSN: 1439-099X
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  • 6
    Language: English
    In: European Journal of Nuclear Medicine and Molecular Imaging, 2011, Vol.38(5), pp.856-864
    Description: Assessment of the metabolically active tumour tissue by FDG PET is evolving for use in the diagnosis of non-small-cell lung cancer (NSCLC), in the planning of radiotherapy, and in follow-up and response evaluation. For exact evaluation accurate registration of PET and CT data is required. The registration process is usually based on rigid algorithms; however, nonrigid algorithms are increasingly being used. The influence of the registration method on FDG PET-based standardized uptake value (SUVmax) and metabolic tumour volume (MTV) definition has not yet been evaluated. the authors compared intra- and interindividual differences in SUV and MTV between rigid- and nonrigid-registered PET and CT acquired during different breathing manoeuvres. The study group comprised 28 radiotherapy candidates with histologically proven NSCLC who underwent FDG PET acquisition and three CT acquisitions (expiration - EXP, inspiration - INS, mid-breath-hold - MID). All scans were registered with both a rigid (R) and a nonrigid (NR) procedure resulting in six fused datasets: R-INS, R-EXP, R-MID, NR-INS, NR-EXP and NR-MID. For the delineation of MTVs a contrast-oriented contouring algorithm developed in-house was used. To accelerate the delineation a semiautomatic software prototype was utilized. Tumour mean SUVmax did not differ for R and NR registration (R 17.5 +/- 7, NR 17.4 +/- 7; p = 0.2). The mean MTV was higher by 3 +/- 12 ml (p = 0.02) in the NR group than in the R group, as was the mean tumour diameter (by 0.1 +/- 0.2 cm; p 〈0.01). With respect to the three different breathing manoeuvres, there were no differences in MTV in the R group (p 〉 0.7). In intraindividual comparison there were no significant differences in MTVs concerning the registration pairs R-EXP (68 +/- 88 ml) vs. NR-EXP (69 +/- 85 ml) und R-MID (68 +/- 86 ml) vs. NR-MID (69 +/- 83 ml) (both p 〉 0.4). However, the MTVs were larger after NR registration during inspiration (R-INS 68 +/- 82 vs. NR-INS 78 +/- 93 ml; p = 0.02). The use of nonrigid algorithms may lead to a change in MTV, whose extent is influenced by the breathing manoeuvre on CT. Nonrigid registration methods cannot be recommended for the definition of MTV if the CT scan is performed during inspiration. The choice of registration algorithm has no significant impact on SUVmax.
    Keywords: Non-small cell lung carcinoma (NSCLC) ; Spiral computed tomography ; Positron emission tomography ; Image registration ; Image analysis ; Computer-assisted
    ISSN: 1619-7070
    E-ISSN: 1619-7089
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  • 7
    Language: English
    In: European Journal of Nuclear Medicine and Molecular Imaging, 2013, Vol.40(8), pp.1233-1244
    Description: Purpose: The objective of the study was to validate an adaptive, contrast-oriented thresholding algorithm (COA) for tumour delineation in 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for non-small cell lung cancer (NSCLC) in comparison with pathological findings. The impact of tumour localization, tumour size and uptake heterogeneity on PET delineation results was also investigated. Methods: PET tumour delineation by COA was compared with both CT delineation and pathological findings in 15 patients to investigate its validity. Correlations between anatomical volume, metabolic volume and the pathology reference as well as between the corresponding maximal diameters were determined. Differences between PET delineations and pathological results were investigated with respect to tumour localization and uptake heterogeneity. Results: The delineated volumes and maximal diameters measured on PET and CT images significantly correlated with the pathology reference (both r 〉 0.95, p 〈 0.0001). Both PET and CT contours resulted in overestimation of the pathological volume (PET 32.5 ± 26.5 %, CT 46.6 ± 27.4 %). CT volumes were larger than those delineated on PET images (CT 60.6 ± 86.3 ml, PET 48.3 ± 61.7 ml). Maximal tumour diameters were similar for PET and CT (51.4 ± 19.8 mm for CT versus 53.4 ± 19.1 mm for PET), slightly overestimating the pathological reference (mean difference CT 4.3 ± 3.2 mm, PET 6.2 ± 5.1 mm). PET volumes of lung tumours located in the lower lobe were significantly different from those determined from pathology (p = 0.037), whereas no significant differences were observed for tumours located in the upper lobe (p = 0.066). Only minor correlation was found between pathological tumour size and PET heterogeneity (r = −0.24). Conclusion: PET tumour delineation by COA showed a good correlation with pathological findings. Tumour localization had an influence on PET delineation results. The impact of tracer uptake heterogeneity on PET delineation should be considered carefully and individually in each patient. Altogether, PET tumour delineation by COA for NSCLC patients is feasible and reliable with the potential for routine clinical application.
    Keywords: Volume delineation ; F-FDG ; PET ; Lung cancer ; Radiotherapy ; Pathology
    ISSN: 1619-7070
    E-ISSN: 1619-7089
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  • 8
    Language: English
    In: Journal of Plant Diseases and Protection, 1 June 2008, Vol.115(3), pp.139-143
    Keywords: Biological sciences -- Biology -- Botany -- Barley ; Biological sciences -- Biology -- Mycology -- Barley ; Biological sciences -- Biology -- Microbiology -- Barley ; Biological sciences -- Agriculture -- Agricultural sciences -- Barley ; Biological sciences -- Wildlife studies -- Wildlife management -- Barley ; Biological sciences -- Biology -- Cytology -- Barley ; Health sciences -- Medical conditions -- Infections -- Barley ; Applied sciences -- Food science -- Foodstuffs -- Barley ; Health sciences -- Medical conditions -- Physical trauma -- Barley ; Biological sciences -- Biology -- Evolutionary studies -- Barley
    ISSN: 18613829
    E-ISSN: 18613837
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