Model-based analysis of nutrient retention and management for a lowland river

International audienceIn the context of the European Water Framework Directive options for improving the water quality of the lowland river Havel (Germany) were assessed. The lower section of this river is actually a polytrophic river-lake system suffering from high external nutrient loading and exhibiting significant in-river turnover. In order to gain a better understanding of present conditions and to allow integrated scenarios of nutrient management to be evaluated the catchment models SWIM and ArcEGMO-Urban were coupled with a simple, newly developed nutrient TRAnsport Model (TraM). Using the TraM model, the retention of nitrogen and phosphorus in a 55 km reach of the Lower Havel River was quantified and its temporal variation was analyzed. It was examined that about 30% of the external nitrogen input to the Lower Havel is retained within the surveyed river section. A comparison of simulation results generated with and without consideration of phosphorus retention/release revealed that summer TP concentrations are currently increased by 100?200% due to internal loading. Net phosphorus release rates of about 20 mg P m?2 d-1 in late summer were estimated for the Havel lakes. Scenario simulations with lowered external nutrient inputs revealed that persistent phosphorus limitation of primary production cannot be established within the next decade. It was shown that a further reduction in nitrogen concentrations requires emissions to be reduced in all inflows. Though the TraM model needs further extension it proved to be appropriate for conducting integrated catchment and river modeling

Analysis and simulation of nutrient retention and management for a lowland river-lake system

International audienceIn the context of the European Water Framework Directive, we studied the possible impact of reduced emissions on phosphorus and nitrogen concentrations in a lowland river-lake system (Havel River, Germany). As a prerequisite, we quantified the retention of nutrients in the river from mass balances and deduced its seasonal variation. We detected that about 30% of the total nitrogen input is retained within the surveyed river section. In contrast, phosphorus release from sediments was shown to cause a considerable increase in present P concentrations. Average net phosphorus release rates of about 20 mg P m?2 d?1 in late summer were estimated for the Havel Lakes. Based on the observed patterns of N retention and P release we parametrized a newly developed water quality simulation program (TRAM), which allows alternative model approaches of different complexity to be implemented and tested. To account for the future trend of internal P loading, the phosphorus excess in lake sediments was estimated from core samples and included in the model as a state variable. For analyzing scenarios of reduced nutrient emissisions, the water quality simulation program was linked to mesoscale hydrological catchment models for the first time. From scenario simulations we conclude that internal P loading is likely to counteract efforts of emission control for decades. Even by significant reductions in external P loads, a persistent phosphorus limitation of primary production can hardly be established in the analyzed time frame of 13 years. Though in the short run a continued reduction in nitrogen loads appears to be the more promising approach of eutrophication management, we recommend enhanced efforts to diminish both N and P emissions

White matter integrity, fiber count, and other fallacies: The do's and don'ts of diffusion MRI

Diffusion-weighted MRI (DW-MRI) has been increasingly used in imaging neuroscience over the last decade. An early form of this technique, diffusion tensor imaging (DTI) was rapidly implemented by major MRI scanner companies as a scanner selling point. Due to the ease of use of such implementations, and the plausibility of some of their results, DTI was leapt on by imaging neuroscientists who saw it as a powerful and unique new tool for exploring the structural connectivity of human brain. However, DTI is a rather approximate technique, and its results have frequently been given implausible interpretations that have escaped proper critique and have appeared misleadingly in journals of high reputation. In order to encourage the use of improved DW-MRI methods, which have a better chance of characterizing the actual fiber structure of white matter, and to warn against the misuse and misinterpretation of DTI, we review the physics of DW-MRI, indicate currently preferred methodology, and explain the limits of interpretation of its results. We conclude with a list of ‘Do's and Don'ts’ which define good practice in this expanding area of imaging neuroscience

The perception of musical phrase structure: A cross-cultural ERP study

Electroencephalography (EEG) was used in a cross-cultural music study investigating phrase boundary perception. Chinese and German musicians performed a cultural categorization task under Chinese and Western music listening conditions. Western music was the major subject for both groups of musicians, while Chinese music was familiar to Chinese subjects only. By manipulating the presence of pauses between two phrases in the biphrasal melodies, EEG correlates for the perception of phrase boundaries were found in both groups under both music listening conditions. Between 450 and 600 ms, the music CPS (closure positive shift), which had been found in earlier studies with a false tone detection task, was replicated for the more global categorization task and for all combinations of subject group and musical style. At short latencies (100 and 450 ms post phrase boundary offset), EEG correlates varied as a function of musical styles and subject group. Both bottom-up (style properties of the music) and top-down (acculturation of the subjects) information interacted during this early processing stage.Electroencephalography (EEG) was used in a cross-cultural music study investigating phrase boundary perception. Chinese and German musicians performed a cultural categorization task under Chinese and Western music listening conditions. Western music was the major subject for both groups of musicians, while Chinese music was familiar to Chinese subjects only. By manipulating the presence of pauses between two phrases in the biphrasal melodies, EEG correlates for the perception of phrase boundaries were found in both groups under both music listening conditions. Between 450 and 600 ms, the music CPS (closure positive shift), which had been found in earlier studies with a false tone detection task, was replicated for the more global categorization task and for all combinations of subject group and musical style. At short latencies (100 and 450 ms post phrase boundary offset), EEG correlates varied as a function of musical styles and subject group. Both bottom-up (style properties of the music) and top-down (acculturation of the subjects) information interacted during this early processing stage. (c) 2006 Elsevier B.V. All rights reserved

Cross-cultural music phrase processing: An fMRI study

The current study used functional magnetic resonance imaging (fMRl) to investigate the neural basis of musical phrase boundary processing during the perception of music from native and non-native cultures. German musicians performed a cultural categorization task while listening to phrased Western (native) and Chinese (non-native) musical excerpts as well as modified versions of these, where the impression of phrasing has been reduced by removing the phrase boundary marking pause (henceforth called "unphrased"). Bilateral planum temporale was found to be associated with an increased difficulty of identifying phrase boundaries in unphrased Western melodies. A network involving frontal and parietal regions showed increased activation for the phrased condition with the orbital part of left inferior frontal gyrus presumably reflecting working memory aspects of the temporal integration between phrases, and the middle frontal gyrus and intraparietal sulcus probably reflecting attention processes. Areas more active in the culturally familiar, native (Western) condition included, in addition to the left planum temporale and right ventro-medial prefrontal cortex, mainly the bilateral motor regions. These latter results are interpreted in light of sensorimotor integration. Regions with increased signal for the unfamiliar, non-native music style (Chinese) included a right lateralized network of angular gyrus and the middle frontal gyrus, possibly reflecting higher demands on attention systems, and the right posterior insula suggesting higher loads on basic auditory processing.The current study used functional magnetic resonance imaging (fMRl) to investigate the neural basis of musical phrase boundary processing during the perception of music from native and non-native cultures. German musicians performed a cultural categorization task while listening to phrased Western (native) and Chinese (non-native) musical excerpts as well as modified versions of these, where the impression of phrasing has been reduced by removing the phrase boundary marking pause (henceforth called "unphrased"). Bilateral planum temporale was found to be associated with an increased difficulty of identifying phrase boundaries in unphrased Western melodies. A network involving frontal and parietal regions showed increased activation for the phrased condition with the orbital part of left inferior frontal gyrus presumably reflecting working memory aspects of the temporal integration between phrases, and the middle frontal gyrus and intraparietal sulcus probably reflecting attention processes. Areas more active in the culturally familiar, native (Western) condition included, in addition to the left planum temporale and right ventro-medial prefrontal cortex, mainly the bilateral motor regions. These latter results are interpreted in light of sensorimotor integration. Regions with increased signal for the unfamiliar, non-native music style (Chinese) included a right lateralized network of angular gyrus and the middle frontal gyrus, possibly reflecting higher demands on attention systems, and the right posterior insula suggesting higher loads on basic auditory processing

Wiederherstellung der Fliessfaehigkeit des umweltgeschaedigten Parkgrabens Sanssouci durch die Anwendung einer innovativen und landschaftsschonenden Schlammsedimentation mittels Carbo-Oxygen-Injektion (Brandenburg) Abschlussbericht

SIGLEAvailable from TIB Hannover: F04B1660 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Bundesstiftung Umwelt, Osnabrueck (Germany)DEGerman

Counting in everyday life: Discrimination and enumeration

Enumerating the number of items in a set accurately and quickly is a basic mathematical skill. This ability is especially crucial in the more real-life situations, where relevant items have to be discriminated from irrelevant distracters. Although much work has been done on the brain mechanisms and neural correlates of the enumeration and/or discrimination process, no agreement has been reached yet. We used event-related potentials (ERPs) to show the time course of brain activity elicited by a task that involved both enumeration and discrimination at the same time. We found that even though the two processes run to some extent in parallel, discrimination seems to take place mainly in an earlier time window (from 100 ms after the stimulus onset) than enumeration (beyond 200 ms after the stimulus onset). Moreover, electrophysiological evidence based on the N2 and P3 components make it reasonable to argue for the existence of a dichotomy between subitizing (for sets of less than four items) and counting (for sets of four and more items). Source estimation suggests that subitizing and counting, though being distinct brain processes, do recruit similar brain areas.Enumerating the number of items in a set accurately and quickly is a basic mathematical skill. This ability is especially crucial in the more real-life situations, where relevant items have to be discriminated from irrelevant distracters. Although much work has been done on the brain mechanisms and neural correlates of the enumeration and/or discrimination process, no agreement has been reached yet. We used event-related potentials (ERPs) to show the time course of brain activity elicited by a task that involved both enumeration and discrimination at the same time. We found that even though the two processes run to some extent in parallel, discrimination seems to take place mainly in an earlier time window (from 100 ms after the stimulus onset) than enumeration (beyond 200 ms after the stimulus onset). Moreover, electrophysiological evidence based on the N2 and P3 components make it reasonable to argue for the existence of a dichotomy between subitizing (for sets of less than four items) and counting (for sets of four and more items). Source estimation suggests that subitizing and counting, though being distinct brain processes, do recruit similar brain areas. (c) 2005 Elsevier Ltd. All rights reserved

Anatomical and functional parcellation of the human lateral premotor cortex

The lateral premotor cortex of the macaque monkey is an anatomically multifaceted area, which serves multiple sensorimotor and cognitive functions. While evidence for the functional organization of human premotor cortex accumulates, much less is known about the underlying anatomical properties of this brain region. Based on the findings in macaques, we hypothesized the existence of at least two major fields, corresponding to the ventral and the dorsal lateral premotor cortex, the border between which is still a matter of debate in the human brain. Since a further subdivision running orthogonally in the rostro-caudal direction has been suggested and often reconfirmed in macaques, we set out to find whether our data would also support four distinct fields on the lateral convexity. We used diffusion tractography and functional Magnetic Resonance Imaging (fMRI) to investigate whether the supposed homologue area in humans can be segregated on the basis of anatomical connectivity and functional activation in a set of cognitive and motor tasks. Tractographic data suggested a distinction between ventral and dorsal premotor cortex, as well as inferior and superior sub-parcellation of both. Functional MRI data corroborated these four areas, showing that anatomical parcellation based on the tractography predicts the distribution of functional activation and vice versa. Functional data from movement of different body parts, prediction of rhythmic, object-based or spatial sequences, and observation of different types of movement of an actor were largely consistent with the interpretation of -based parcellation of four sub-regions in the human precentral gyrus (PCG). However, they also showed that functional activations were not sharply restricted to these fields. In line with evidence from macaque research, we therefore suggest that even under optimal signal-to-noise ratio, the contributions of the sub-regions of the PCG are differently weighted for different functional requirements rather than exclusively engaged in only the one or the other function or task. In sum, results may encourage the application of combined diffusion tractography and fMRI in vivo in order to shed light on the correspondence of brain function and anatomy