Publications by authors named "Ovesen N"

Integrated buffer zones (IBZ) are novel mitigation measures designed to decrease the loading of nitrogen (N) transported by subsurface drainage systems from agricultural fields to streams. In IBZ, drainage water flows into a pond with free water surface followed by an inundated, vegetated filterbed. This design provides an environment favorable for denitrification and thus a decrease in nitrate concentration is expected as water flow through the IBZ.

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Drainage systems provide a more or less direct conduit for excess water and nutrients from fields to surface water. High nutrient loads to streams and lakes are known to adversely affect water quality and may potentially cause algae blooms. Therefore, in-field as well as edge-of-field mitigation measures that can assist in reducing the loss of nutrients are needed.

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We validated an existing physically based 3D MIKE SHE groundwater resource model (DK-model) at 175 Danish gauging stations covering different catchment sizes in order to calculate monthly water runoff in the 50% ungauged part of Denmark. Model performance was in most cases good (61% of gauging stations had a Nash-Sutcliffe (NS) coefficient >0.60) but nevertheless showed a large seasonal and georegion specific bias.

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Medulloblastoma is a common paediatric brain tumour, located in the cerebellum and in the IV ventricle, surpassed in frequency only by astrocytomas. 180 children below the age of 15 with a medulloblastoma of the posterior fossa were treated in Denmark in the 25-year period from 1960 to 1984 and followed up until the end of 1996, or until death. During the 25 years they accounted for 20% of all intracranial tumours in children in Denmark.

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A total of 911 Danish children under 15 years of age were treated for an intracranial tumour in the 25-five year period 1960-1984. All cases were followed up to the end of 1994 or to emigration or death if one of these came sooner. The mean annual incidence was 32.

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Twenty-eight patients with spinal tumours (11 malignant and 17 benign) detected in their first two decades of life have been reviewed. Twenty-six of the 28 patients had neurological disturbances, and a significant difference in the duration of debut symptoms in the benign and malignant groups could be demonstrated. X-ray survey was positive in 11 cases in the benign group and in three cases in the malignant group.

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A critical evaluation revealed no distinct clinical complex of symptoms related to the radiological picture of chronic adhesive arachnoiditis in the lower lumbar sac in 72 patients. In all cases the arachnoiditis was diagnosed by myelography with water soluble contrast media and, in 16 cases, verified by operation and microscopy. The assumed cause of arachnoiditis was, in more than half of the cases, the combination of myelography and operation in close relation, and, in ten cases, a previous operation.

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