Effect of vegetation growth in drainage canals on water management

In 2002 a new regulation was adopted in the Netherlands to protect flora and fauna. As a consequence mowing of drainage canals will be restricted during the growing season leading to vegetated canals that may hamper the discharge of water. In the summer of 2006 a field experiment has been executed in combination with a model study to investigate the effects of vegetation growth in the Fliert, a drainage canal located in the central part of the Netherlands. The field experiments showed extensive vegetation growth in absence of mowing. For the model study SOBEK Rural was used to evaluate different rainfall and vegetation (mowing) scenarios. From the model study it could be concluded that vegetation growth in combination with high rainfall can lead to water management problems. This means that if mowing is not allowed alternative measures are necessary. Unfortunately, model results could not be validated due to a relative dry summer

Hydraulic Resistance of Vegetation in River Flow Applications

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732If vegetated regions become part of a river’s flow field, the hydraulic resistance of vegetation affects the overall conveyance. Several descriptions exist to describe this type of flow; among them are empirical relations and relations that are process-based. In the current work three expressions are considered that have equal input parameters, similar levels of complexity but different theoretical backgrounds. The performance of the three methods is evaluated by comparison with flow measurements (collected from literature), and limits are given for their practical use

Hydrodynamic modelling with unstructured grid using D-Flow-FM: case study Afferden-Deest

Accurate predictions of water levels play an important role in the management of flood safety. Nowadays, it has become common practice to use multi-dimensional numerical hydrodynamic models for such purposes. Currently, two model types are the standard tools in the Netherlands, namely WAQUA/TRIWAQ (Rijkswaterstaat, 2012) and Delft3D (Deltares, 2014). WAQUA and Delft3D are both based on a structured curvilinear grid, which can follow large-scale topographical changes and uses similar grid resolution throughout the entire computational domain. Drawbacks of the structured curvilinear grid approach are that elevation jumps in the river's topography may lead to unrealistic staircase representations in the model, and the inner bends of meandering rivers gridlines may become focussed to unnecessarily small grid cells (Kernkamp et al., 2011). To improve on these issues, Deltares is developing the unstructured-grid-based hydrodynamic model Flexible Mesh (also referred to as “D-Flow-FM”). The unstructured grid approach enables the user to use a spatially variable grid resolution. By combining curvilinear grid cells with triangular grid cells, the modeller can increase grid resolution on the locations where, because of local topographical variations, it is most desired. In this study, modelling results of Flexible Mesh and WAQUA are presented for a selected river reach near Afferden-Deest and benefits of local grid refinements in Flexible Mesh are demonstrated

HIV-1 pathogenicity and virion production are dependent on the metabolic phenotype of activated CD4+ T cells

BACKGROUND:HIV-1, like all viruses, is entirely dependent on the host cell for providing the metabolic resources for completion of the viral replication cycle and the production of virions. It is well established that HIV-1 replicates efficiently in activated CD4+ T cells, whereas resting CD4+ T cells are refractory to infection with HIV-1. A hallmark of T cell activation is the upregulation of glycolysis to meet the biosynthetic and bioenergetic needs of cell proliferation and the execution of effector functions by the secretion of cytokines. To date, it has remained unknown if HIV-1 requires the high glycolytic activity of activated T cells to support its replication.RESULTS:We report that in primary CD4+ T cells, the flux through the glycolytic pathway is increased upon infection with HIV-1. This increase in glycolytic activity does not occur in T cell lines when infected with HIV-1. By providing cells with galactose instead of glucose, the former being a poor substrate for glycolysis, we monitored the effect of preventing glycolysis in CD4+ T cells on virus replication cycle and cell fate. We observed that HIV-1 infected primary CD4+ T cells cultured in galactose have a survival advantage over those cultured in glucose and this coincides with reduced caspase 3 activation and apoptosis in cultures with galactose. T cell lines do not recapitulate this difference in cell death. Finally, we demonstrate that virion production is dependent on glycolysis as cultures containing galactose yield reduced amounts of HIV-1 virions compared with cultures containing glucose.CONCLUSIONS:The replication of HIV-1 in primary CD4+ T cells causes an increase in glycolytic flux of the cell. Glycolysis is particularly required for virion production and additionally increases the sensitivity of the infected cell to virus-induced cell death

Анализ составляющих теплового баланса системы "прокатный стан - прокатываемая полоса" и пути снижения энергозатрат в процессе сортовой прокатки

Выполнен анализ составляющих теплового баланса системы «прокатный стан – прокатываемая полоса». Рассмотрены основные направления решения температурной задачи сортовой прокатки. Предложен ряд мероприятий, позволяющих снизить расход энергоресурсов на прокатку и уменьшить расходную часть теплового баланса системы «прокатный стан – прокатываемая полоса»

Modeling hydraulic resistance of floodplain vegetation

In this thesis, methods are investigated that describe the impact of vegetation on a flow field, and their potential for application in river-reach hydraulic computational models. This field of research is of great importance to river flood studies, as vegetation-covered foodplains commonly become part of the river flow section during high-discharge conditions. In this respect, the obstruction\ud of vegetation to flow needs to be taken into account if trying to predict overall flow behavior. To describe the impact of vegetation on a river-reach scale, ob-\ud structing vegetation should be incorporated in terms of easily measurable input parameters and require only minimal additional computational effort. In the current work, such a method is proposed

Forming a constant density medium close to long gamma-ray bursts

The progenitor stars of long Gamma-Ray Bursts (GRBs) are thought to be Wolf-Rayet stars, which generate a massive and energetic wind. Nevertheless, about 25 percent of all GRB afterglows light curves indicate a constant density medium close to the exploding star. We explore various ways to produce this, by creating situations where the wind termination shock arrives very close to the star, as the shocked wind material has a nearly constant density. Typically, the distance between a Wolf-Rayet star and the wind termination shock is too large to allow afterglow formation in the shocked wind material. Here, we investigate possible causes allowing for a smaller distance: A high density or a high pressure in the surrounding interstellar medium (ISM), a weak Wolf-Rayet star wind, the presence of a binary companion, and fast motion of the Wolf-Rayet star relative to the ISM. We find that all four scenarios are possible in a limited parameter space, but that none of them is by itself likely to explain the large fraction of constant density afterglows. A low GRB progenitor metallicity, and a high GRB energy make the occurrence of a GRB afterglow in a constant density medium more likely. This may be consistent with constant densities beingpreferentially found for energetic, high redshift GRBs.Comment: 13 pages, 13 figures, new version: as accepted by Astronomy & Astrophysic