Peter Frederiksen

Evaluation of a Transcutaneous Oxygen and Carbon Dioxide Monitor in a Neonatal Intensive Care Department

Transcutaneous‐Po2; (tc‐Po2 (tc‐Pco2) at 44oC and transcutaneous‐Pco2) at 38, 42, 43 and 44oC were measured with a currently available monitoring system (TCM222, Radiometer, Copenhagen) in 64 newborn infants with severe respiratory insufficiency during the first five days of life. Tc‐Pco2 at all four temperatures correlated better with arterial blood‐Pco2 (aB‐Pco2)> than tc‐Po2 with aB‐Po2. However, the sensitivity and specificity of tc‐Po2 and tc‐Pco2 were similar with regard to maintaining aB‐Po2, and aB‐Pco2 within specified limits. Tc‐Pco2 increased relatively with increasing electrode temperature by a factor which was similar to the anaerobic temperature coefficient of Po2, in blood. The coefficient of variation of duplicate measurements was 10 % for tc‐Po2 and 5 % for tc‐Pco2. Electrode drift after an average of 3 hours patient monitoring was 2%±6% (1SD) for tc‐Pco2, and ‐3 %±6 % for tc‐Pco2‐ We conclude that tc‐Po2 and tc‐Pco2 are a valuable supplement to arterial blood gas measurements, but the variable correlation with arterial blood gas values and the electrode drifts which may occur, mean that they cannot fully replace arterial sampling.

Electroluminescence of organic thin films based on blends of polystyrene and fluorescent dyes

Blue and red light-emitting diodes were constructed as devices in which a polystyrene/dye blend was sandwiched between a calcium electrode and a transparent indium-tin oxide electrode. As dye molecules, four alkoxy-substituted derivatives of 2,5-dialkoxy-1,4-bis(2-phenylvinyl)benzene (i.e. p-phenylene vinylene oligomers), a derivative of bisanthracene (2,2′,3,3′-tetrachloro-9,9′-dimethoxy-10,10′-bianthracene) and the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminophenylvinyl)-4H-pyran (DCM) were used. The critical field for light emission in devices using 20 wt.% PPV oligomers in polystyrene was found to be of the order of 2 × 108 V m–1. The dependence of the device conductivity on the concentration of dye molecules in the polystyrene film is described by simple percolation theory. The synthesis of 2,2′,3,3′-tetrachloro-9,9′-dimethoxy-10,10′-bianthracene is reported.

THE DANISH SCIENTIFIC EXPEDITION TO PATAGONIA AND TIERRA DEL FUEGO 1978–1979

Madsen, H. B., Nielsen, E. S., odum, S. (eds.): The Danish Scientific Expedition to Patagonia and Tierra del Fuego 1978–1979. Geografisk Tidsskrift 80: 1–28, June 1980. The paper surveys geographical, botanical and zoological projects dealt with during six months of travelling and fieldwork in the Argentinean and Chilean Andes and adjacent lowlands: Soil development in relation to climate. General entomological and botanical studies and collecting work. Entomological collecting especially within certain families of Lepidoptera. Studies on snowbed vegetation an alpine lifeforms. Collecting of seed of Araucaria for provenance trials and of Nothofagus seedlings for forestry experiments on the Faroe Isles. Collecting of Hordeum, Plantago and Solanum for taxonomie studies and experiments.

Sensitivity of DaisyGIS to LAI: Implications for land use based modelling of nitrate leaching

Abstract Geografisk Tidsskrift, Danish Journal of Geography 106(2): 75–85, 2006 Scaling is an important issue when measuring, modelling and understanding coupled socio-environmental terrestrial systems. Scaling may be enhanced through the incorporation of remotely sensed data. This paper assesses the sensitivity of DaisyGIS to changes in the Leaf Area Index (LAI) and discusses the implications for land use based modelling of nitrate leaching using remote sensing based LAI estimates. It is shown how DaisyGIS simulates nitrate leaching quite well over the period 2001 to 2004 except for one plot during a season with winter rape. It was found that the model is sensitive to changes in LAI with increases of up to 262% on nitrate leaching rates when reducing LAI by 15%. At the same time, the nitrate leaching rates at the field level vary considerably due to local changes in the water balance determined by soil profile characteristics. DaisyGIS is already an important tool for aiding decision makers and this study has shown how remote sensing based LAI estimates may be a valuable tool for model parameterisation and potentially for model validation.

Landsat, aerial photography and state factors in soil survey of arid and humid Patagonia, Argentina

Frederiksen, Peter: LANDSAT, aerial photography and state factors in soil survey of arid and humid Patagonia, Argentina. Geografisk Tidsskrift 81: 39–48. Copenhagen, June, 1981 The applicability of LANDSAT, aerial photography, and topographical maps was tested in relation to soil survey of humid and arid Patagonia, Argentina. Fieldwork was carried out as toposequence-studies in five vegetation zones and observations of roadcuts. These data were compared with LANDSAT and aerial photography. Only observations on state factors of soil formation were obtained. These showed as a first rough approximation a consistent relationship between observed state factors as expressed in land systems and stage of soil development.

TURISTSLITAGE I ET KLITLANDSKAB SKALLINGEN 1976

Frederiksen, Peter: Turistslitage i et klitlandskab. Geografisk Tidsskrift 76: 68–77. Kobenhavn, juni 1, 1977. The wear caused by tourists on the peninsula Skallingen, West Jutland, has been investigated by analysing the dune topography and the relative cover of the plant species in selected places and along level lines.

Young dry grassland ecosystems in Denmark: development in soil nutrient pools and root characteristics

Abstract Dry grassland ecosystems are listed habitats in the EU Habitats Directive due to their high biodiversity. Such areas have declined drastically over the last 200 years but set-aside of agricultural areas in recent years has increased the extent of grassland areas with secondary succession. This paper explores the soil nutrient pools of 14 young dry grasslands and compares them to the nutrient pools on heathlands, forested and agricultural land. On two sites, the plant species composition is compared to characteristic species for the EU Habitats Directive in Denmark and the relationship between soil nutrient pools and underground biomass development is investigated. It was found that soil nutrient content was lower as compared to agricultural land but generally higher as compared to forested areas and heathland. The organic matter on the grassland sites after they have been laid fallow is becoming less decomposed and this indicates that an O horizon will eventually develop and hence provide an important nutrient pool as a replacement for the decline in nutrient content in the subsoil. Root density was high in this study and soil nutrient content appeared to be an important parameter determining root development.

The Quest for Highly Conducting LB Films

Alongside our ongoing research in the field of conducting organic materials, we have investigated the possibilities of attaching long-chain fatty acids to various donor molecules, in order to prepare conducting Langmuir-Blodgett (LB) films.

The Measurement of TcPO2 and TcPCO2 in Newborn Infants at 44°C, 42°C and 37°C after Initial Heating to 44°C

Prolonged measurement of the trancutaneous O2 and CO2 tension at an electrode temperature of 44 to 45 C often causes a second degree burn of the underlying skin.

The Third Danish Scientific Expedition to Patagonia and Tierra del Fuego, 1982-83

Frederiksen, Peter: The Third Danish Scientific Expedition to Patagonia and Tierra del Fuego, 1982,83. Geografisk Tidsskrift 84: 1–5. Copenhagen January 1984. Soil and landscape mapping of Tierra del Fuego and Patagonia austral was executed based on LANDSAT false colour composite images, and ground control (augerings and profile studies). A dear relation between 1) the images patterns and land units was established. Further a basis for comparison between northern and southern hemispheric soil development in regions influenced by Pleistocene glaciations was established.