Additional Sampling Sites Research Articles

COVID, Co-Ventilation, and Cross-contamination

Introduction:During the COVID-19 pandemic, consideration was given to co-ventilating multiple patients on a single ventilator. Prior work had shown that this procedure was possible by ventilating four adult-size sheep for twenty-four hours, and other groups had performed this maneuver during dire circumstances. However, no investigation had examined the safety regarding cross-contamination. The purpose of our studies was to investigate if an infection could spread between individuals who were being co-ventilated.Method:Four sterile two-liter anesthesia bags were connected to a sterilized ventilator circuit to simulate the co-ventilated patients’ “lungs.” The circuit utilized Heat and Moisture Exchange filters and bacterial/viral filters, which were strategically inserted to prevent the transmission of infectious droplets. Serratia marcescens was inoculated into “lung” number one. The circuit was then run for 24 hours, after which each “lung” and three additional points in the circuit were cultured to see if S. marcescens had spread. These cultures were examined at 24 and 48 hours to assess for cross-contamination. This entire procedure was performed a total of four times.Results:S. marcescens was not identified in lungs two, three, or four or the three additional sampling sites on the expiratory limb of the tubing at 24 and 48 hours in all four trials.Conclusion:Cross-contamination between co-ventilated patients did not occur within 24 hours utilizing the described ventilator circuit configuration.

A comprehensive evaluation of the use of Lagrangian particle dispersion models for inverse modeling of greenhouse gas emissions

Abstract. Using the example of sulfur hexafluoride (SF6), we investigate the use of Lagrangian particle dispersion models (LPDMs) for inverse modeling of greenhouse gas (GHG) emissions and explore the limitations of this approach. We put the main focus on the impacts of baseline methods and the LPDM backward simulation period on the a posteriori emissions determined by the inversion. We consider baseline methods that are based on a statistical selection of observations at individual measurement sites and a global-distribution-based (GDB) approach, where global mixing ratio fields are coupled to the LPDM back-trajectories at their termination points. We show that purely statistical baseline methods can cause large systematic errors, which lead to inversion results that are sensitive to the LPDM backward simulation period and can generate unrealistic global total a posteriori emissions. The GDB method produces a posteriori emissions that are far less sensitive to the backward simulation period and that show a better agreement with recognized global total emissions. Our results show that longer backward simulation periods, beyond the often used 5 to 10 d, reduce the mean squared error and increase the correlation between a priori modeled and observed mixing ratios. Also, the inversion becomes less sensitive to biases in the a priori emissions and the global mixing ratio fields for longer backward simulation periods. Further, longer periods might help to better constrain emissions in regions poorly covered by the global SF6 monitoring network. We find that the inclusion of existing flask measurements in the inversion helps to further close these gaps and suggest that a few additional and well-placed flask sampling sites would have great value for improving global a posteriori emission fields.

Optimal placement of sampling locations for identification of a two-dimensional space

ABSTRACT In recent years, substantial attention has been given to the optimal placement and planning of sampling or monitoring based on the Value of Information (VoI). The drawback of the VoI approach is its typically high computation cost. The method proposed here can significantly reduce the computation cost of VoI by applying the theory of Gaussian Process Regression. Due to the low computation cost, global optimisation algorithms such as particle swarm optimisation can be used to optimise a set of sampling locations. The proposed method was applied to a soil contamination problem. For comparison purposes, twenty-one subjects (persons) were asked to follow a three-step procedure. In the first step, contamination levels at five fixed sampling locations are given. Based on this information, the contaminated area is estimated by the subject, who is then asked to place five additional sampling sites in order to gather more information. The procedure is repeated three times. The subject is ultimately asked to produce a final estimate of the contaminated area. It was found that the proposed method generally produced better agreement with the true contaminated area than did the participants’ empirical human judgment.

Occurrence and fate of microplastics at two different drinking water treatment plants within a river catchment

Microplastics (MPs) are emerging globally distributed pollutants of aquatic environments, and little is known about their fate at drinking water treatment plants (DWTPs), which provide a barrier preventing MPs from entering water for human consumption. This study investigated MPs ≥ 1 μm in raw and treated water of two DWTPs that both lie on the same river, but the local quality of water and the treatment technology applied differ. In the case of the more complex DWTP, MPs were analysed at 4 additional sampling sites along the treatment chain. The content of MPs varied greatly between the DWTPs. There were 23 ± 2 and 14 ± 1 MPs L−1 in raw and treated water, respectively, at one DWTP, and 1296 ± 35 and 151 ± 4 MPs L−1 at the other. Nevertheless, MPs comprised only a minor proportion (<0.02%) of all detected particles at both DWTPs. With regard to size and shape of MPs, the majority (>70%) were smaller than 10 μm, and only fragments and fibres were found, while fragments clearly prevailed. The most frequently occurring materials were cellulose acetate, polyethylene terephthalate, polyvinyl chloride, polyethylene, and polypropylene. Much higher total removal of MPs was achieved at the DWTP with a higher initial MP load and more complicated treatment (removal of 88% versus 40%); coagulation-flocculation-sedimentation, deep-bed filtration through clay-based material, and granular activated carbon filtration contributed to MP elimination by 62%, 20%, and 6%, respectively. Additionally, results from this more complex DWTP enabled to observe relationships between the removal efficiency and size and shape of MPs, particularly in the case of the filtration steps.

Characterizing bumble bee (Bombus) communities in the United States and assessing a conservation monitoring method.

AimBumble bees (Hymenoptera: Apidae: Bombus) are economically and ecologically important pollinators in agroecosystems and wildland habitats. In the Nearctic region, there are approximately 41 species, of which the IUCN lists twelve species as vulnerable, endangered, or critically endangered. We conducted a standardized faunal survey to inform ongoing conservation efforts including petitions under review for the Endangered Species Act. Furthermore, we test the appropriateness of a methodology for accurately sampling bumble bee communities.LocationThe United States of America, including 31 sites in 15 states.MethodsWe surveyed 15 states in the summer of 2015 to assess community composition and relative species abundance at agricultural and seminatural sites throughout the United States. We collected approximately 100 bees, using aerial nets, from each of 31 sites and identified specimens to species, totaling 3,252 bees. We assessed our survey methodology to understand whether it accurately sampled the potential community of bumble bees at each site for utility in future monitoring efforts.ResultsAverage site species richness was 5.1 ± 2.05, and we detected 30 of the 41 species documented historically within the contiguous United States. Sampling a site beyond 100 bees rarely added additional species detections, whereas adding additional sampling sites within an ecoregion frequently increased the species richness for the ecoregion. Thirteen of the 30 species we detected each accounted for <1% of the total fauna, and two species accounted for 49.02% of all bees captured. Species richness and evenness increased with increasing latitude across communities.Main ConclusionsSpecies diversity and evenness in bumble bees increases in northern latitudes and increasing elevation in the United States; however, a few common species tend to dominate communities while many species occur only in low numbers. The results of this survey effort can inform current conservation evaluations and planning.

Modeling Spatial Patterns of Humus Forms in Montane and Subalpine Forests: Implications of Local Variability for Upscaling

Humus forms are a distinctive morphological indicator of soil organic matter decomposition. The spatial distribution of humus forms depends on environmental factors such as topography, climate and vegetation. In montane and subalpine forests, environmental influences show a high spatial heterogeneity, which is reflected by a high spatial variability of humus forms. This study aims at examining spatial patterns of humus forms and their dependence on the spatial scale in a high mountain forest environment (Val di Sole/Val di Rabbi, Trentino, Italian Alps). On the basis of the distributions of environmental covariates across the study area, we described humus forms at the local scale (six sampling sites), slope scale (60 sampling sites) and landscape scale (30 additional sampling sites). The local variability of humus forms was analyzed with regard to the ground cover type. At the slope and landscape scale, spatial patterns of humus forms were modeled applying random forests and ordinary kriging of the model residuals. The results indicate that the occurrence of the humus form classes Mull, Mullmoder, Moder, Amphi and Eroded Moder generally depends on the topographical position. Local-scale patterns are mostly related to micro-topography (local accumulation and erosion sites) and ground cover, whereas slope-scale patterns are mainly connected with slope exposure and elevation. Patterns at the landscape scale show a rather irregular distribution, as spatial models at this scale do not account for local to slope-scale variations of humus forms. Moreover, models at the slope scale perform distinctly better than at the landscape scale. In conclusion, the results of this study highlight that landscape-scale predictions of humus forms should be accompanied by local- and slope-scale studies in order to enhance the general understanding of humus form patterns.

Uncertainty in predicting the spatial pattern of soil water temporal stability at the hillslope scale

Soil water temporal stability is subject to spatial variation, which influences the prediction of mean soil water status on a hillslope. However, estimation of the spatial pattern of soil water temporal stability and quantification of the uncertainties associated with the predictions are often ignored. In this study, volumetric soil water contents at 10 and 30cm depths on tea garden and forest hillslopes were monitored across 17 dates from January 2013 to April 2014. Soil moisture maps on these 17 dates were interpolated using ordinary kriging and then the spatial distribution of the relative difference of soil moisture was assessed. Based on these maps, standard deviations of relative difference (SDRD) of soil moisture were calculated to represent the spatial variation of soil water temporal stability. Uncertainties in predicted patterns of SDRD due to the limited number of sampling days used for calculating SDRD (U1) and for spatial interpolation of soil moisture by ordinary kriging (U2) were investigated using bootstrap and sequential Gaussian simulation techniques respectively. Results showed that soil water content on the forest hillslope generally exhibited stronger spatial variability than that on the tea garden hillslope. The SDRD substantially varied in space at the hillslope scale. Temporal stabilities of soil water content at 30cm depth were significantly (P&lt;0.05) stronger than those at 10cm soil depth, regardless of the land use type. However, differences in soil water temporal stabilities on these two land use hillslopes were not significant. In addition, U2 was generally more important than U1 on both hillslopes. This suggests that additional sampling sites and more robust interpolation methods rather than additional sampling days should be developed to reduce SDRD prediction uncertainty on the study hillslopes.

Mitochondrial DNA sequence divergence and diversity of Glossina fuscipes fuscipes in the Lake Victoria basin of Uganda: implications for control.

BackgroundGlossina fuscipes fuscipes is the main vector of African Trypanosomiasis affecting both humans and livestock in Uganda. The human disease (sleeping sickness) manifests itself in two forms: acute and chronic. The Lake Victoria basin in Uganda has the acute form and a history of tsetse re-emergence despite concerted efforts to control tsetse. The government of Uganda has targeted the basin for tsetse eradication. To provide empirical data for this initiative, we screened tsetse flies from the basin for genetic variation at the mitochondrial DNA cytochrome oxidase II (mtDNA COII) gene with the goal of investigating genetic diversity and gene flow among tsetse, tsetse demographic history; and compare these results with results from a previous study based on microsatellite loci data in the same area.MethodsWe collected 429 Gff tsetse fly samples from 14 localities in the entire Ugandan portion of the Lake Victoria coast, covering 40,000 km2. We performed genetic analyses on them and added data collected for 56 Gff individuals from 4 additional sampling sites in the basin. The 529pb partial mitochondrial DNA cytochrome oxidase II (mtDNA COII) sequences totaling 485 were analysed for genetic differentiation, structuring and demographic history. The results were compared with findings from a previous study based on microsatellite loci data from the basin.ResultsThe differences within sampling sites explained a significant proportion of the genetic variation. We found three very closely related mtDNA population clusters, which co-occurred in multiple sites. Although ΦST (0 – 0.592; P < 0.05) and Bayesian analyses suggest some level of weak genetic differentiation, there is no correlation between genetic divergence and geographic distance (r = 0.109, P = 0.185), and demographic tests provide evidence of locality-based demographic history.ConclusionThe mtDNA data analysed here complement inferences made in a previous study based on microsatellite data. Given the differences in mutation rates, mtDNA afforded a look further back in time than microsatellites and revealed that Gff populations were more connected in the past. Microsatellite data revealed more genetic structuring than mtDNA. The differences in connectedness and structuring over time could be related to vector control efforts. Tsetse re-emergence after control interventions may be due to re-invasions from outside the treated areas, which emphasizes the need for an integrated area-wide tsetse eradication strategy for sustainable removal of the tsetse and trypanosomiasis problem from this area.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-0984-1) contains supplementary material, which is available to authorized users.

Study of nitrogen pollution in Croatia by moss biomonitoring and Kjeldahl method

During the summer and autumn of 2006 moss samples were collected from 98 sampling sites evenly distributed all over the territory of Croatia. Moss sampling was repeated in 2010 when additional sampling sites were added and a total of 121 samples were collected. Kjeldahl method was used to determine the nitrogen content in the samples. Descriptive statistics and distribution maps were prepared. Data obtained from these two surveys were compared, and additional comparison was done with data obtained from similar studies in neighbouring countries and Finland as a clean area. The median value of N content in the samples collected in 2006 is 1.60% and varies from 0.79% to 3.16%. The content of N in samples collected in 2010 ranges between 0.71% and 2.93% with the median value of 1.49%. High contents of N (2.32% − 3.17%) were found in the regions of Slavonia, Podravina, Posavina and cities Zagreb and Sisak as a result of agricultural activities, industry and traffic.

Anuran amphibians' diversity in a northwestern area of the Brazilian Pantanal

In the Pantanal, the largest continuous floodplain in the world, the diversity and distribution of anuran amphibians vary in and across distinct subregions and distinct habitats occurring along inundation gradients. Permanent and natural aquatic habitats are relatively scarce in the Pantanal, and occurrence of temporary aquatic habitats varies seasonally, depending on rains. We here present results of evaluations of anuran's species richness and abundance in a seasonally flooded area in the northwestern section of the Pantanal (Fazenda Baía de Pedra, Cáceres municipality, state of Mato Grosso, Brazil), comparing values obtained in 10 plots systematically distributed over 5 km² with those obtained in additional aquatic plots in the study area. Data were obtained in five field trips, from February 2008 to March 2009. In addition to the plots, 36 water bodies (20 permanent and 16 temporary) were also sampled for the presence of anurans. In total, 3,983 individuals from 34 anuran species distributed in five families were recorded: Hylidae (14 species), Leptodactylidae (8), Leiuperidae (6), Microhylidae (4), and Bufonidae (2). Local richness represents 77.3% of the anuran diversity already recorded for the Brazilian Pantanal. The number of species recorded exclusively in systematically distributed terrestrial plots and in water bodies was 28 and 32, respectively. Sampling methods used at Fazenda Baía da Pedra were efficient in determining anuran richness, abundance, composition and distribution. Evaluations of anuran richness and abundance by using permanent sampling plots in the Pantanal may benefit from additional sampling sites, particularly permanent and temporary water bodies.

Antibiotic Resistance Characteristics of Environmental Bacteria from an Oxytetracycline Production Wastewater Treatment Plant and the Receiving River

We characterized the bacterial populations in surface water receiving effluent from an oxytetracycline (OTC) production plant. Additional sampling sites included the receiving river water 5 km upstream and 20 km downstream from the discharge point. High levels of OTC were found in the wastewater (WW), and the antibiotic was still detectable in river water downstream (RWD), with undetectable levels in river water upstream (RWU). A total of 341 bacterial strains were isolated using nonselective media, with the majority being identified as Gammaproteobacteria. The MICs were determined for 10 antibiotics representing seven different classes of antibiotics, and the corresponding values were significantly higher for the WW and RWD isolates than for the RWU isolates. Almost all bacteria (97%) from the WW and RWD samples demonstrated multidrug-resistant (MDR) phenotypes, while in RWU samples, these were less frequent (28%). The WW and RWD isolates were analyzed for the presence of 23 tetracycline (tet) resistance genes. The majority of isolates (94.2% and 95.4% in WW and RWD, respectively) harbored the corresponding genes, with tet(A) being the most common (67.0%), followed by tet(W), tet(C), tet(J), tet(L), tet(D), tet(Y), and tet(K) (in the range between 21.0% and 40.6%). Class I integrons were detected in the majority of WW and RWD isolates (97.4% and 86.2%, respectively) but were not associated with the tet genes. We hypothesize that the strong selective pressure imposed by a high concentration of OTC contributes to the wide dissemination of tetracycline resistance genes and other antibiotic resistance genes, possibly through mobile genetic elements.

&lt;i&gt;Mycobacterium avium&lt;/i&gt; Complex Organisms Predominantly Colonize in the Bathtub Inlets of Patients’ Bathrooms

Medical treatment of pulmonary Mycobacterium avium complex (MAC) disease does not always provide curative effects and is frequently hampered by recurrence. This suggests the presence of a reservoir for MAC in the environment surrounding patients. We previously reported the recovery of MAC isolates from the residential bathrooms of outpatients. In the present study, to ascertain the colonizing sites and the possibility of an MAC reservoir in the bathrooms of patients, we tested the recovery and the genetic diversity of MAC isolates from 6 sites of specimens, including 2 additional sampling sites, inside the showerhead and the bathtub inlet, in the residential bathrooms of patients with pulmonary MAC disease. MAC isolates were recovered from 15 out of the 29 bathrooms (52%), including specimens from 14 bathtub inlets and 3 showerheads. Nearly half of these bathrooms (7/15) contained MAC strains that were identical or similar to their respective clinical isolates Additionally, in 5 out of 15 bathrooms, polyclonal colonization was revealed by pulsed-field gel electrophoresis. The results imply that colonization of MAC organisms in the bathrooms of MAC patients occurs predominantly in the bathtub inlets, and there is thus a risk of infection and/or reinfection for patients via use of the bathtub and other sites in the bathroom.

Mitochondrial phylogeography of baboons (Papiospp.) – Indication for introgressive hybridization?

BackgroundBaboons of the genus Papio are distributed over wide ranges of Africa and even colonized parts of the Arabian Peninsula. Traditionally, five phenotypically distinct species are recognized, but recent molecular studies were not able to resolve their phylogenetic relationships. Moreover, these studies revealed para- and polyphyletic (hereafter paraphyletic) mitochondrial clades for baboons from eastern Africa, and it was hypothesized that introgressive hybridization might have contributed substantially to their evolutionary history. To further elucidate the phylogenetic relationships among baboons, we extended earlier studies by analysing the complete mitochondrial cytochrome b gene and the 'Brown region' from 67 specimens collected at 53 sites, which represent all species and which cover most of the baboons' range.ResultsBased on phylogenetic tree reconstructions seven well supported major haplogroups were detected, which reflect geographic populations and discordance between mitochondrial phylogeny and baboon morphology. Our divergence age estimates indicate an initial separation into southern and northern baboon clades 2.09 (1.54–2.71) million years ago (mya). We found deep divergences between haplogroups within several species (~2 mya, northern and southern yellow baboons, western and eastern olive baboons and northern and southern chacma baboons), but also recent divergence ages among species (< 0.7 mya, yellow, olive and hamadryas baboons in eastern Africa).ConclusionOur study confirms earlier findings for eastern Africa, but shows that baboon species from other parts of the continent are also mitochondrially paraphyletic. The phylogenetic patterns suggest a complex evolutionary history with multiple phases of isolation and reconnection of populations. Most likely all these biogeographic events were triggered by multiple cycles of expansion and retreat of savannah biomes during Pleistocene glacial and inter-glacial periods. During contact phases of populations reticulate events (i.e. introgressive hybridization) were highly likely, similar to ongoing hybridization, which is observed between East African baboon populations. Defining the extent of the introgressive hybridization will require further molecular studies that incorporate additional sampling sites and nuclear loci.

The invasive round goby Apollonia melanostoma (Actinopterygii: Gobiidae) - a new intermediate host of the trematode Neochasmus umbellus (Trematoda: Cryptogonimidae) in Lake Erie, Ohio, USA

The invasive round goby Apollonia melanostoma (Actinopterygii: Gobiidae) - a new intermediate host of the trematode Neochasmus umbellus (Trematoda: Cryptogonimidae) in Lake Erie, Ohio, USA

Geostatistical approaches and optimal additional sampling schemes for spatial patterns and future sampling of bird diversity

ABSTRACTAim To evaluate geostatistical approaches, namely kriging, co‐kriging and geostatistical simulation, and to develop an optimal sampling design for mapping the spatial patterns of bird diversity, estimating their spatial autocorrelations and selecting additional samples of bird diversity in a 2450 km2 basin.Location Taiwan.Methods Kriging, co‐kriging and simulated annealing are applied to estimate and simulate the spatial patterns of bird diversity. In addition, kriging and co‐kriging with a genetic algorithm are used to optimally select further samples to improve the kriging and co‐kriging estimations. The association between bird diversity and elevation, and bird diversity and land cover, is analysed with estimated and simulated maps.Results The Simpson index correlates spatially with the normalized difference vegetation index (NDVI) within the micro‐scale and the macro‐scale in the study basin, but the Shannon diversity index only correlates spatially with NDVI within the micro‐scale. Co‐kriging and simulated annealing simulation accurately simulate the statistical and spatial patterns of bird diversity. The mean estimated diversity and the simulated diversity increase with elevation and decrease with increasing urbanization. The proposed optimal sampling approach selects 43 additional sampling sites with a high spatial estimation variance in bird diversity.Main conclusions Small‐scale variations dominate the total spatial variation of the observed diversity due to a lack of spatial information and insufficient sampling. However, simulations of bird diversity consistently capture the sampling statistics and spatial patterns of the observed bird diversity. The data thus accumulated can be used to understand the spatial patterns of bird diversity associated with different types of land cover and elevation, and to optimize sample selection. Co‐kriging combined with a genetic algorithm yields additional optimal sampling sites, which can be used to augment existing sampling points in future studies of bird diversity.

Apportionment of Ambient Primary and Secondary Pollutants during a 2001 Summer Study in Pittsburgh Using U.S. Environmental Protection Agency UNMIX

Apportionment of primary and secondary pollutants during the summer 2001 Pittsburgh Air Quality Study (PAQS) is reported. Several sites were included in PAQS, with the main site (the supersite) adjacent to the Carnegie Mellon University campus in Schenley Park. One of the additional sampling sites was located at the National Energy Technology Laboratory, located ∼18 km southeast of downtown Pittsburgh. Fine particulate matter (PM2.5) mass, gas-phase volatile organic material (VOM), particulate semivolatile and nonvolatile organic material (NVOM), and ammonium sulfate were apportioned at the two sites into their primary and secondary contributions using the U.S. Environmental Protection Agency UNMIX 2.3 multivariate receptor modeling and analysis software. A portion of each of these species was identified as originating from gasoline and diesel primary mobile sources. Some of the organic material was formed from local secondary transformation processes, whereas the great majority of the secondary sulfate was associated with regional transformation contributions. The results indicated that the diurnal patterns of secondary gas-phase VOM and particulate semivolatile and NVOM were not correlated with secondary ammonium sulfate contributions but were associated with separate formation pathways. These findings are consistent with the bulk of the secondary ammonium sulfate in the Pittsburgh area being the result of contributions from distant transport and, thus, decoupled from local activity involving organic pollutants in the metropolitan area.

Spatial and temporal distribution of blackflies (Diptera: Simuliidae) in the Itatiaia National Park, Brazil

The distribution of the blackfly larval taxocenoses of different altitudes in the Itatiaia National Park (located in the southeast of Rio de Janeiro state, Brazil 44 degrees 34' - 44 degrees 42' W, 22 degrees 16' - 22 degrees 28' S) was investigated on four campaigns, one in each season of 2003. On each campaign 60 samples were collected, using 30 x 30 cm wooden quadrats, distributed at four sites: Taquaral, Véu da Noiva, Três Picos and Brejo da Lapa. The winter and spring campaigns included two additional sampling sites: Alsene and Agulhas Negras. A total of 3578 larvae and 292 pupae were sampled, representative of six species: Simulium clavibranchium Lutz, S. subnigrum Lutz, S. rappae Py-Daniel, S. incrustatum Lutz, S. stellatum Gil-Azevedo, Figueiró & Maia-Herzog and Lutzsimulium pernigrum Lutz 1910. The highest larvae abundance and diversity were reported at the intermediate altitude site, Brejo da Lapa. Principal Components Analysis (PCA) revealed that L. pernigrum, S. stellatum and S. incrustatum were associated with the smaller breeding sites, the first two species being associated with sunny sites, while S. incrustatum occurred in sites with little sunlight.

Ulcerative colitis with low-grade dysplasia

37-year-old woman with a 17-year history of ulerative colitis that extends up to the mid-descendng colon undergoes routine surveillance colonosopy. Her disease is quiescent at the time of the rocedure (and has been for 5 years) and no lesions r masses are identified. Thirty-six biopsies are aken from 10-cm intervals up to the cecum. Histoogical exam reveals findings consistent with idioathic inflammatory bowel disease in the rectum, igmoid colon, and descending colon. Three biopies from her sigmoid colon are reported as lowrade dysplasia. The biopsies are sent to a local niversity pathologist with a special interest in GI athology, and she suggests that the biopsies are ndeterminate for dysplasia. The patient returns for repeat dysplasia surveillance endoscopy 3 months ater and 8 extra biopsies are obtained from the igmoid and descending colon. Four biopsies from er sigmoid colon are identified as containing lowrade dysplasia, and there is agreement between the pathologists.

How geostatistics can help you

Abstract. Geostatistics is basically a technology for estimating the local values of properties that vary in space from sample data. Research and development in the last 15 years has shown it to be eminently suited for soil and ripe for application in soil survey and land management. The basic technique, ordinary kriging, provides unbiased estimates with minimum and known variance. Data for related variables can be incorporated to improve estimates using cokriging. By more elaborate analysis using disjunctive kriging the probabilities of deficiency and excess can be estimated to aid decision.The variogram is crucial in all geostatistics; it must be estimated reliably from sufficient data at a sensible scale and modelled properly. Once obtained it can be used not only in the estimation itself but also to choose additional sampling sites, improve a monitoring network or design an optimal sampling scheme for a survey. It may also be used to control a multivariate classification so that the resulting classes are not too fragmented spatially to manage.

Sulfate in precipitation as observed by the European atmospheric chemistry network

The temporal variation in sulfur concentration/deposition involves long term fluctuations which show striking similarities within certain areas but are different between areas in different positions relative to major sulfur emission areas in Europe. As an example, the deposition has been constant or decreasing during the last ten years in most of the area covered by the network, indicating that an increasing amount of the sulfur emitted in Europe is transported and deposited elsewhere, possibly in an eastward direction. The seasonal variation in deposition resembles that for amount of precipitation and shows a maximum during the summer or autumn for most areas. The concentration shows a maximum in the spring and a minimum in the autumn at most stations. The concentration field has a maximum approximately over Belgium and Holland with decreasing concentrations towards SW to NE (over W) but with comparatively high levels extending up over Finland. (Areas to the east and south are not covered by the network.) The deposition field was, based on a brief discussion of the relation between concentration and amount of precipitation, obtained as the product of these latter fields. High deposition rates are found in the south of Norway and in the middle of Britain in addition to the areas with high concentration. Sulfur and hydrogen ion are the dominating ions in precipitation followed by ammonium and nitrate except in coastal areas and in places where the soil is bare. Sources of errors in the data base are discussed and the results from a large number of additional sampling sites around and between the regular network sampling sites are most helpful in this regard. These latter measurements also permit an estimate of the uncertainty in areal concentration averages which are due to local and mesoscale variability. Finally, past and future importance of continuous measurements (as in the EACN) is discussed briefly.