A large number of life-events perceived as having a negative impact on quality of life may indicate chronic stress, and the results of our study indicate that stress may reduce the chances of a successful outcome following IVF, possibly through psychobiological mechanisms affecting medical end-points such as oocyte retrieval outcome.

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Coupled nitrification-denitrification rates in the rhizosphere of 4 different aquatic macrophytes, Zostera manna, Lobelia dortmanna, Littorella uniflora and Potamogeton pectinatus, were measured by means of both an indirect and a direct l s~ technique. Using the indirect technique we estimated the fraction of 02, excreted by plant roots in the rhizosphere, that was used by coupled nitrification-denitrification. Incubations were carried out in ' ' NH,' amended oxic slurries. This fraction was multiplied with values for root 0, excretion reported in the literature. The indirect technique allowed us to quantify both the oxidation of NH4+ to NO3 . and the reduction of NO3-to NH,+ compared to denitrification. Using the direct technique we estimated coupled nitrification-denitrification from the amount of I5Nz labeled gas that accumulated in intact sediment-plant systems. The 2 techniques recorded similar trends. In these cores '"F&+ was added homogeneously to the rhizosphcrr by peifusion. Denitrification activity in the rhizosphere of 2, and P. pectinatus was low (1.5 to 5 1.1rnol N m-' h-') compared to the activity measured in L. dortmanna and L. uniflora vegetated sediments (24 and 30 pm01 N m-2 h-'). The variability in denitrification activity was due to differences in the ability of the plants to oxidize the rhizosphere, and difference in the character of sediment O2 and N O , consumption. This study attempts to clarify how rooted aquatic vegetation affects the sediment nitrogen cycle via oxygen excretion from the roots. Rhizosphere associated nitrogen transformations (coupled nitrification-denitrification) are central to the understanding of nutrient cycling in shallow aquatic ecosystems

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Exposure to visible light (400-700 nm wavelengths) is an unnatural stress factor to preimplantation embryos cultured in vitro. This study investigated the spectral composition and intensity of light during IVF procedures, and calculated radiation doses reaching the embryo during handling and manipulation. The study shows that normal IVF procedure may result in stressing radiation doses, unless filters are applied. This is at present not sufficiently recognised. No Danish IVF clinics use filters to protect embryos against visible light. 95% of the radiation was from microscopes. Ambient light, in contrast, was not a significant contributor to light stress and the use of dark laboratories is not justified.

GAC or electrodes). A comparison of functional gene categories between the two Methanosarcina showed differences regarding energy metabolism, which could explain dissimilarities concerning electromethanogenesis at fixed potentials. We suggest that these dissimilarities are minimized in the presence of an electrogenic DIET partner (e.g., Geobacter), which can modulate its surface redox potentials by adjusting the expression of electroactive surface proteins.

Purpose: The purpose of the present study was to evaluate statistical prediction models and simple allocation criteria, based on predictors for pregnancy, as tools to identify a good prognosis group in a possible eSET setting.Methods: A pregnancy prediction model based on logistic regression models was generated by analysis of 1675 DET treatment cycles. The model was evaluated and compared to simple eSET allocation criteria.Results: Embryo quality, patient age, and basal FSH were identified as significant predictors (at 5% significance level) of pregnancy. Although comparable to previously generated models, the predictive ability of the present model was relatively poor and practically similar to simple allocation criteria based on age and embryo quality.Conclusions: Existing prediction models, or simple allocation criteria, are limited in identifying good prognosis patients. Future studies of the applicability of improved pregnancy prediction models will need very comprehensive and detailed patient and embryo information.