Modelling inorganic nitrogen in runoff: Seasonal dynamics at four European catchments as simulated by the MAGIC model.

Nitrogen (N) deposition is globally considered as a major threat to ecosystem functioning with important consequences for biodiversity, carbon sequestration and N retention. Lowered N retention as manifested by elevated concentrations of inorganic N in surface waters indicates ecosystem N saturation. Nitrate (NO3) concentrations in runoff from semi-natural catchments typically show an annual cycle, with low concentrations during the summer and high concentrations during the winter. Process-oriented catchment-scale biogeochemical models provide tools for simulation and testing changes in surface water and soil chemistry in response to changes in sulphur (S) and N deposition and climate. Here we examine the ability of MAGIC to simulate the observed monthly as well as the long-term trends over 10-35 years of inorganic N concentrations in streamwaters from four monitored headwater catchments in Europe: Certovo Lake in the Czech Republic, Afon Gwy at Plynlimon, UK, Storgama, Norway and G2 NITREX at Gårdsjön, Sweden. The balance between N inputs (mineralization+deposition) and microbial immobilization and plant uptake defined the seasonal pattern of NO3 leaching. N mineralization and N uptake were assumed to be governed by temperature, described by Q10 functions. Seasonality in NO3 concentration and fluxes were satisfactorily reproduced at three sites (R2 of predicted vs. modelled concentrations varied between 0.32 and 0.47 and for fluxes between 0.36 and 0.88). The model was less successful in reproducing the observed NO3 concentrations and fluxes at the experimental N addition site G2 NITREX (R2=0.01 and R2=0.19, respectively). In contrast to the three monitored sites, Gårdsjön is in a state of change from a N-limited to N-rich ecosystem due to 20 years of experimental N addition. At Gårdsjön the measured NO3 seasonal pattern did not follow typical annual cycle for reasons which are not well understood, and thus not simulated by the model. CAPSULE: The MAGIC model is able to simulate NO3 leaching on a monthly as well as an annual basis, and thus to reproduce the seasonal and short-term variations in N dynamics.

Modelling soil nitrogen: the MAGIC model with nitrogen retention linked to carbon turnover using decomposer dynamics.

We present a new formulation of the acidification model MAGIC that uses decomposer dynamics to link nitrogen (N) cycling to carbon (C) turnover in soils. The new model is evaluated by application to 15-30 years of water chemistry data at three coniferous-forested sites in the Czech Republic where deposition of sulphur (S) and N have decreased by >80% and 40%, respectively. Sulphate concentrations in waters have declined commensurately with S deposition, but nitrate concentrations have shown much larger decreases relative to N deposition. This behaviour is inconsistent with most conceptual models of N saturation, and with earlier versions of MAGIC which assume N retention to be a first-order function of N deposition and/or controlled by the soil C/N ratio. In comparison with earlier versions, the new formulation more correctly simulates observed short-term changes in nitrate leaching, as well as long-term retention of N in soils. The model suggests that, despite recent deposition reductions and recovery, progressive N saturation will lead to increased future nitrate leaching, ecosystem eutrophication and re-acidification.

Increased nitrogen in runoff and soil following 13 years of experimentally increased nitrogen deposition to a coniferous-forested catchment at Gårdsjön, Sweden.

Beginning in 1991, we have added nitrogen (N) to the 0.5-ha, N-poor, coniferous-forested catchment G2 NITREX at Gårdsjön, Sweden, to investigate the consequences of chronic elevated N deposition. We have added 40 kg N ha-1 yr-1 in fortnightly doses of NH4NO3 to the ambient 15 kg N ha-1 yr-1 by means of a sprinkling system. NO3 concentrations in runoff increased during 13 years from<1 to 70 microeq L-1, and in 2004 comprised about 10% of N input. Inhibition of NO3 immobilisation due to increased availability of NH4 might explain the increased leaching of NO3. C and N pools in the forest floor increased but C/N ratio has not changed. The increase in NO3 leaching thus occurred independently of change in C/N ratio. The results from Gårdsjön demonstrate that increased leaching of inorganic N and decrease in C/N ratio respond to increased N deposition at greatly different time scales.

Linked models to assess the impacts of climate change on nitrogen in a Norwegian river basin and FJORD system.

Dynamically downscaled data from two Atmosphere-Ocean General Circulation Models (AOGCMs), ECHAM4 from the Max-Planck Institute (MPI), Germany and HadAm3H from the Hadley Centre (HAD), UK, driven with two scenarios of greenhouse gas emissions (IS92a and A2, respectively) were used to make climate change projections. These projections were then used to drive four effect models linked to assess the effects on hydrology, and nitrogen (N) concentrations and fluxes, in the Bjerkreim river basin (685-km(2)) and its coastal fjord, southwestern Norway. The four effect models were the hydrological model HBV, the water quality models MAGIC, INCA-N and the NIVA FJORD model. The downscaled climate scenarios project a general temperature increase in the study region of approximately 1 degrees C by 2030-2049 (MPI IS92a) and approximately 3 degrees C by 2071-2100 (HAD A2). Both scenarios imply increased winter precipitation, whereas the projections of summer and autumn precipitation are quite different, with the MPI scenario projecting a slight increase and the HAD scenario a significant decrease. As a response to increased winter temperature, the HBV model simulates a dramatic reduction of snow accumulation in the upper parts of the catchment, which in turn lead to higher runoff during winter and lower runoff during snowmelt in the spring. With the HAD scenario, runoff in summer and early autumn is substantially reduced as a result of reduced precipitation, increased temperatures and thereby increased evapotranspiration. The water quality models, MAGIC and INCA-N project no major changes in nitrate (NO(3)(-)) concentrations and fluxes within the MPI scenario, but a significant increase in concentrations and a 40-50% increase in fluxes in the HAD scenario. As a consequence, the acidification of the river could increase, thus offsetting ongoing recovery from acidification due to reductions in acid deposition. Additionally, the increased N loading may stimulate growth of N-limited benthic algae and macrophytes along the river channels and lead to undesirable eutrophication effects in the estuarine area. Simulations made by the FJORD model and the HAD scenario indicate that primary production in the estuary might increase up to 15-20%, based on the climate-induced changes in river flow and nitrate concentrations alone.

Modelling the effect of climate change on recovery of acidified freshwaters: relative sensitivity of individual processes in the MAGIC model.

The MAGIC model was used to evaluate the relative sensitivity of several possible climate-induced effects on the recovery of soil and surface water from acidification. A common protocol was used at 14 intensively studied sites in Europe and eastern North America. The results show that several of the factors are of only minor importance (increase in pCO(2) in soil air and runoff, for example), several are important at only a few sites (seasalts at near-coastal sites, for example) and several are important at nearly all sites (increased concentrations of organic acids in soil solution and runoff, for example). In addition changes in forest growth and decomposition of soil organic matter are important at forested sites and sites at risk of nitrogen saturation. The trials suggest that in future modelling of recovery from acidification should take into account possible concurrent climate changes and focus specially on the climate-induced changes in organic acids and nitrogen retention.

Newer molecular approaches to detect known viruses and previously unrecognized viruses in cell substrates.

The theme of this brief presentation is that there are tremendous advances not only in PCR-based detection but in other novel ways of detecting viruses and other agents. Much of the research is now being driven by the bio-defence agenda. Somehow those with manufacturing and regulatory responsibilities have to keep abreast of these developments and incorporate them as they become available into defining the safety of cell substrates. I am concerned that these techniques are and may remain academic research tools without validation or standardization, and that individual academic laboratories will not develop the capacity and special skills necessary to satisfy regulatory requirements, but that there is a tremendous research incentive in this area that needs to be linked with the development of safe prophylactic and therapeutic biologicals. With that, I will finish what I would consider as a report rather than an original talk.

A radiation-shielding device for craniofacial implant placement.

The use of radiation shields in the head and neck cancer patient receiving adjuvant radiation therapy is a treatment alternative for protecting anticipated prosthetic implant sites. Shields can be fabricated easily as part of an interdisciplinary treatment protocol. In this article, the methods used to fabricate an extraoral radiation shield are described, and a patient treatment that illustrates possible uses of the shield for both extraoral and intraoral sites is presented.

Prosthodontic management of periodontally compromised patient.

The fabrication and placement of a conventional immediate denture following extraction of periodontally compromised, non-restorable remaining teeth is a method that is frequently used to help restore form and function in an esthetically pleasing manner. This technique demands knowledge in applied basic sciences and prosthodontic principles. Accurate diagnosis and scrupulous treatment planning help the dentist address the patient's needs.

Modification of a Super-Sep bottle for paint-on application of a separating medium used in flasking dentures.

Modifying a Super-Sep bottle by adding a brush to the lid for paint-on use allows for the precise application of the separating medium used when flasking dentures. Super-Sep offers many advantages over other commonly used separating mediums: It is virtually dimensionless, allowing for better accuracy; it dries quickly and functions best on moist stone; and it can be poured against immediately. The latter fact means less time is needed before the subsequent layers of stone can be applied when denture flasking.

Effect of evaporation and mixing technique on die spacer thickness: a preliminary study.

STATEMENT OF PROBLEM: Casting relief is required for proper seating of castings to allow for luting agent thickness. The application of die spacer to the die is the most common method of obtaining casting relief. Die spacer film thicknesses that are outside the ideal range of 25 to 40 microm can cause clinical problems. Thickness can be affected by the separation of die spacer constituents, which may not be reconstituted by mixing, in the bottle and by the evaporation of volatile components while the bottle is open. PURPOSE: The purpose of this study was to determine the effects of component evaporation and die spacer mixing technique on applied die spacer thickness. MATERIAL AND METHODS: Bottles of Gold Tru-fit die spacer were left open for 0, 1, 4, 8, and 24 hours at 22 degrees C. Spacer solutions were shaken either by hand per the manufacturer's directions or on a dental vibrator for 1 minute. One even brush stroke of spacer was applied to clean glass slides. Three die spacer films were made for each combination of time and mixing technique. Eighteen thickness measurements per sample at various sites were recorded with profilometer tracings. Statistical differences were determined with a 2-way ANOVA. RESULTS: Handshaking provided greater die spacer thickness, which increased with the time that the bottle was open. Vibration provided lower thickness with no statistical increase with time. CONCLUSION: Insufficient agitation caused lower film thickness. Excessive evaporation caused higher film thickness.

Surface water acidification in the South Pennines I. Current status and spatial variability.

The South Pennines, an area of acid-sensitive geology at the centre of a major industrial region, have undergone perhaps the most severe historic exposure to sulphur and nitrogen deposition in the UK. This study addresses a lack of existing research on the region by presenting the findings of a survey of 62 surface waters sampled during a 1-week period in April 1998. Results indicate that acidification in the region is acute; 27 of the sampled surface waters had a negative acid neutralising capacity (ANC) and 28 had a pH below 5.0. Minimum recorded pH values were below 4.0. Non-marine sulphate levels were extremely high (median 222 microeq/1), and widespread high nitrate concentrations (median 41 microeq/1) suggest that soils in the region as a whole may be at an advanced stage of nitrogen saturation. A consistent relationship was identified between site acidity and the balance between the major weathering-derived cations, calcium and magnesium, and sulphate. This could in turn be linked to catchment soil type and land use, with the most acidic conditions occurring in peat-dominated catchments, where weathering is minimal and the influence of atmospheric deposition most pronounced. Percentage of peat in each catchment was the single best predictor of surface water acidity. Nitrate concentrations, although not a dominant control on acidity, varied significantly according to land use. Elevated concentrations were observed in catchments containing forestry, due to enhanced deposition inputs, and in catchments containing improved land, linked to fertiliser use. Ammonium concentrations, although low at most catchments, were a significant component of the inorganic nitrogen total in a number of surface waters draining waterlogged peat catchments.

Clinical decision making in patients with congestive heart failure: the role of thoracic electrical bioimpedance.

Optimizing appropriate pharmacologic therapy in patients with congestive heart failure has been difficult due to a lack of easily obtainable hemodynamic information to guide the approach to the patient. Recently, thoracic electrical bioimpedance has allowed reliable outpatient determination of these hemodynamic variables, potentially allowing tailored adjustment of therapy in patients with cardiac dysfunction. Case studies are presented in which bioimpedance data were important contributing factors in optimizing patient management. Utilization of this new technology to individualize patient therapy should lead to improved outcomes and more efficient use of health care resources. (c)2000 by CHF, Inc.

Multidisciplinary treatment for an implant retained auricular prosthesis rehabilitation.

Retention of a facial prosthesis is the most important factor in creating a useful prosthesis for the patient. This paper presents a detailed case study of an auricular defect that was rehabilitated using two types of prosthetic retention: adhesive and osseointegration. We present the patient selection criteria, the surgical considerations prior to implant placement, retention component selection, prosthetic fabrication techniques and patient management after prosthetic delivery. The osseointegrated prosthesis made a large improvement in the patient's quality of life.

Fabrication and use of a surgical template for placing implants to retain an auricular prosthesis.

A procedure is described for the fabrication of a 3-dimensional surgical template to guide the placement of implants to retain an auricular prosthesis. This procedure requires a diagnostic wax pattern that is checked while on the patient to ensure it is positioned correctly and is also the correct size. The wax pattern is processed into a clear, methyl methacrylate resin, 3-dimensional surgical template. The most effective type of surgical template for planning implant placement is a 3-dimensional acrylic template that closely resembles the final prosthesis. This template will direct the implant placement where the retentive elements are most easily concealed, under the thickest areas of the prosthesis, which are the antihelix and antitragus. This location allows the best esthetic and functional results. An additional advantage of this technique is that it allows the retrieval of the diagnostic wax pattern of the auricle so that it can be used to fabricate the definitive prosthesis.

A technique to create appropriate abutment tooth contours for removable partial dentures.

A technique is presented for using light-cured composite resin to create desirable contours on abutment teeth for the retention and support of removable partial dentures. The desired tooth shape is created on a diagnostic cast, captured in a clear temporary splint material, and formed in resin on the abutment teeth with the splint acting as a matrix.