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P Schuller

Publications and source records attributed to P Schuller.

13 recordsLinked to original sources
PubMed2005

Seasonal variation of the radiocaesium transfer soil-to-Swiss chard (Beta vulgaris var. cicla L.) in allophanic soils from the Lake Region, Chile.

The transfer factor (TF) of radiocaesium from soil-to-Swiss chard (Beta vulgaris var. cicla L.) was studied in two different characteristic allophanic soils (umbric andosol and dystric fluvisol) of the Lake Region, an important agricultural region situated in central-south Chile. To investigate especially the time dependence and the effect of K-fertilisation on the TF, field experiments were conducted. Plots of 7.6 m2 were labelled with 100 kBq 134Cs m(-2) at Santa Rosa Experiment Station close to the city of Valdivia characterised by a temperate climate and high precipitation rates. The variation in time of the radiocaesium TF soil-to-Swiss chard was observed during two consecutive years after soil contamination by sequential harvests and radiocaesium analyses of the plants. The TFs showed no significant ageing effect, but a pronounced seasonal decrease with effective half-lives of about 140 and 160 days for the umbric andosol without and with K-fertilisation, respectively, and of 50 and 60 days for the dystric fluvisol without and with K-fertilisation, respectively. The effect of K-fertilisation on the absolute values of the TF was determined by the ratio between the median TF values obtained for corresponding dates without and with use of K-fertiliser. A ratio of TF(without K)/TF(with K) = 1.8 for the umbric andosol and TF(without K)/TF(with K) = 2.9 for the dystric fluvisol was obtained, indicating a reduction of the TF by applying 90 kg K ha(-1). The maximal values of the TF to chard predicted by the equation characterising the seasonal decrease of the TF at the beginning of the harvest periods are 0.19 for the umbric andosol and 0.11 for the dystric fluvisol, both values for soil treated with common K-fertilisation.

Beta vulgaris↗
PubMed2004

Use of 137Cs measurements to estimate changes in soil erosion rates associated with changes in soil management practices on cultivated land.

Intensification of agricultural production in south-central Chile since the 1970s has caused problems of increased soil erosion and associated soil degradation. These problems have prompted a shift from conventional tillage to no-till management practices. Faced with the need to establish the impact of this shift in soil management on rates of soil loss, the use of caesium-137 (137Cs) measurements has been explored. A novel procedure for using measurements of the 137Cs depth distribution to estimate rates of soil loss at a sampling point under the original conventional tillage and after the shift to no-till management has been developed. This procedure has been successfully applied to a study site at Buenos Aires farm near Carahue in the 9th region of Chile. The results obtained indicate that the shift from conventional tillage to no-till management has caused net rates of soil loss to decrease to about 40% of those existing under conventional tillage. This assessment of the impact of introducing no-till management at the study site must, however, be seen as provisional, since only a limited number of sampling points were used. A simplified procedure aimed at documenting the reduction in erosion rates at additional sampling points, based solely on measurements of the 137Cs inventory of bulk cores and the 137Cs activity in the upper part of the soil has been developed and successfully tested at the study site. Previous application of 137Cs measurements to estimate erosion rates has been limited to estimation of medium-term erosion rates during the period extending from the beginning of fallout receipt to the time of sampling. The procedures described in this paper, which permits estimation of the change in erosion rates associated with a shift in land management practices, must be seen as representing a novel application of 137Cs measurements in soil erosion investigations.

Agriculture↗
PubMed2004

Global fallout (137)Cs accumulation and vertical migration in selected soils from South Patagonia.

The spatial distribution and vertical migration of global fallout (137)Cs were studied in soils from South Patagonia at the austral region of South America in semi-natural and natural environments located between 50-54 degrees S and 68-74 degrees W. The (137)Cs areal activity density varied from 222 to 858 Bq m(-2), and was found to be significantly positively correlated (p<0.001) with the mean annual precipitation rate. The fraction of the total activity density observed in steppe grass varied from <0.03% to 0.12% (median <0.07%) and is considerably lower than the results obtained at the South Shetland Islands (median 8%) and in other temperate environments in south-central Chile (median 0.2%). The median of the convection velocity v(s) of (137)Cs in the soil in such polar isotundra climate has been determined to be 0.056 cm y(-1). This value is higher than v(s) determined under polar climate (-0.012 cm y(-1)) and is near to the upper limit of v(s)-values determined in temperate environments from Chile (0.019 cm y(-1)). The median value of the diffusion coefficient D(s) (0.048 cm(2) y(-1)) is similar to D(s) observed in an Antarctic region (0.043 cm(2) y(-1)) and lower than D(s) in temperate regions of Chile (1.24 cm(2) y(-1)). About 35 years after the highest depositions, (137)Cs had penetrated to a depth of 6-14 cm in the Patagonian soils and can be expected to remain in the rooting zone of grass for many decades. Nevertheless, because of its low transfer to steppe grass observed at this region, the radioecological sensitivity of this ecosystem with respect to fallout radiocesium seems to be lower than in other polar regions.

Cesium Radioisotopes↗
PubMed2002

Fallout radiocesium in an Antarctic region: deposition history, activity densities and vertical transport in soils.

To improve the knowledge about the (137)Cs spatial distribution and vertical migration in soils of the Southern Hemisphere, the total areal activity density and the vertical transport parameters of this radionuclide were measured in an Antarctic region. For this purpose vegetation and incremental soil samples were collected at 21 representative sites located at 4 islands of the South Shetland Archipelago: King George, Robert, Greenwich and Snow (62-63 degrees S and 58-62 degrees W). The total (137)Cs activity density varied considerably from 118 to 662 Bq m(-2) (median 384 Bq m(-2), reference date 1995), with a high percentage of the total activity retained in the vegetation cover (5-98% in moss, 3-20% in lichen and 4-12% in grass). At most sites, the maximum activity density in soil was observed in the top layer from where it decreased continuously. To evaluate the transport parameters of (137)Cs from the activity-depth profiles, the classical convection-diffusion model was used based on the time-course of the annual deposition density of (137)Cs at the studied region. The values for the diffusion coefficient D(s) (median 0.043 cm(2) year(-1)) and the convection velocity v(s) (median -0.012 cm year(-1)) of radiocesium observed under a polar climate are small compared to the transport parameters determined in temperate zones. The data also indicate that at these sites the convectional transport of (137)Cs is almost negligible compared to the transport by diffusion. The high vulnerability of the Antarctic soils to (137)Cs deposition, as a consequence of its very slow transport due to the extreme climatic conditions at these latitudes, has been confirmed.

Antarctic Regions↗
PubMed2002

Global weapons' fallout 137Cs in soils and transfer to vegetation in south-central Chile.

The contamination and depth distribution of 137Cs in soil due to the fallout from atmospheric weapons' tests were measured at 29 sites in the 9th and 10th administrative regions in Chile located in the 40 degrees latitude in the southern hemisphere. The depth distribution in most of the sites follows no systematic pattern in the upper few centimetres, but below this depth an exponential decline could be deduced. The calculated relaxation depth appears to be a good indicator for estimating the long-term 137Cs distribution in these soil profiles. It ranges from 4.4 +/- 1.9 cm in Palehumults to 8.4 +/- 4.4 and 9.7 +/- 5.1 cm in Hapludands and Psamments, respectively. For these soil types the value for the relaxation depth tends to increase with decreasing clay content and increasing volume of coarse pores. 137Cs activity densities at the selected sites ranged from 450 to 5410 Bq m(-2) and correlate significantly (r = 0.791) with the mean annual rainfall rate of the sampling sites. 137Cs concentration ratios of prairie plants/soil were found to be in the range 0.008-2.3 and could be related to relaxation depths in undisturbed soils.

Cesium Radioisotopes↗
PubMed1998

Long-term decrease of atmospheric test 137Cs in the soil-prairie plant-milk pathway in southern Chile.

The time dependency of nuclear test 137Cs in soil, prairie plants, and milk was observed on pastures of seven dairy farms in the 10th Region, Chile, from 1982 to 1997, without any appreciable deposition of radioactive fallout after 1983. Whereas the 137Cs concentration in the soil decreased at a rate close to that of the radionuclide's physical decay during the whole observation period, the rate of decrease of the 137Cs concentration in the prairie plants and in the milk, having been very rapid between 1982-1990, became slower between 1991-1997. The effective half-lives of the concentration in plants were found to be 5.6 y and 12 y during the first and second observation periods, respectively. Similar half-lives of 5.5 y and 13 y were found for the concentration decline in milk during each period. These data clearly demonstrate a reduction in the long-term decrease of the 137Cs plant uptake, and consequently in the decrease of the 137Cs concentration in milk, resulting from a decline of 137Cs availability for prairie plants in the Hapludand soils over the whole 15-y observation period.

Animals↗
PubMed1994

The effects of spiramycin and/or scaling on advanced periodontitis in humans.

It has long been questioned whether antibiotics, used as a supplement to traditional therapy, provide any lasting benefit in the treatment of chronic periodontitis. This study was designed to evaluate Spiramycin as an adjunct to scaling and root planing in the treatment of advanced chronic periodontitis. In total, 193 patients with advanced periodontitis were recruited in seven centres using selection criteria previously described. After undergoing thorough scaling and root planing, all patients randomly received either Spiramycin, 1,500,000 international units, twice per day (IU, bid) for 14 days (96 patients), or a visually-identical placebo capsule (97 patients). The clinical parameters measured were plaque index, crevicular fluid level, probing depths, bleeding on probing and attachment level changes. Data was recorded at baseline, two-, eight-, 12- and 24-weeks visits. A total of 189 patients completed the study (96 placebo, 93 Spiramycin). Statistically significant differences in probing depth, favoring Spiramycin, were seen at two weeks (p < 0.0125), eight weeks (p < 0.0020), 12 weeks (p < 0.0032) and 24 weeks (p < 0.0075). Spiramycin also produced a significant improvement in attachment level at 12 weeks (p < 0.0146). All other clinical parameters showed no difference between drug and placebo. This study shows that Spiramycin, as an adjunct to thorough scaling and root planing, provides a statistically significant improvement in probing depths for up to 24 weeks when compared with scaling and root planing alone. Both longer studies and microbiologic evaluations are necessary to determine whether a more lasting benefit is possible.

Adult↗
PubMed1993

137Cs concentration in soil, prairie plants, and milk from sites in southern Chile.

Soil, prairie plants, and milk samples were collected at 39 dairy farms in the 9th and 10th Region in Southern Chile (38 degrees 44'-41 degrees 08' S) between 1982 and 1990. 137Cs concentrations found in soil, plant, and milk samples ranged from 3.8-17.1 Bq kg-1 for soil, from < 0.3-20 Bq kg-1 dry mass for plants, and from 0.10-0.71 Bq kg-1 for milk. Cesium concentration levels resulting from soil sample measurements exhibit a close similarity with corresponding values found in soils from Central Europe before 1986. The concentration ratio prairie plants:soil ranged from 0.05-0.62, 0.52-5.0, and < 0.02-0.40 corresponding to Dystrandepts, Placandepts, and Palehumults soil groups, respectively. At seven selected dairy farms in the vicinity of Valdivia city (10th Region), soil, prairie plant, and milk samples were taken yearly during the grazing period between 1982 and 1990. Results obtained from soil samples taken after April 1986 show no significant increase of the 137Cs concentration. Concentrations in plants and milk for 137Cs decreased during the observation time. 134Cs (as an indicator of Chernobyl fallout) was not found in soil, plant, or milk samples during 1986-1990.

Animals↗
PubMed1993

Biospheric 129I concentrations in the pre-nuclear and nuclear age.

In order to detect characteristic regional differences or temporal changes of 129I concentrations in the biosphere, thyroids from humans, grazing livestock, and herbivorous wildlife species (reindeer and roedeer) were collected in various areas of the world which are not affected by reprocessing plants. For reasons of comparison, all samples were analyzed for their 129I:127I atom ratios. Human and bovine thyroids taken from the 10th region in Southern Chile (39 degrees-41 degrees South) indicated values of the 129I:127I atom ratio between 1.1 x 10(-9) and 2.0 x 10(-9) and between 1.2 x 10(-10) and 9 x 10(-9), respectively. They showed no significant increase in the concentration of biospheric 129I in comparison with that established in the pre-nuclear age. Atom ratios found in human thyroids collected in Lower Saxony (Federal Republic of Germany), which is a region not directly affected by reprocessing plants, exhibited 129I:127I values between 8 x 10(-9) and 6 x 10(-8) from February 1988 to September 1990. Thyroid glands of reindeer and roedeer as well as heather, moss, and lichen were taken from the Vilhelmina, Heby, and Gävle communes in Sweden and analyzed for 129I and 127I. All three communes were found to be seriously contaminated by fallout from the Chernobyl accident. Highest 129I:127I atom ratios between 3.5 x 10(-7) and 1 x 10(-6) were found in the Gävle commune (approximately 150 km northwest of Stockholm) where the highest 137Cs ground deposition (70-80 kBq m-2) was measured. Two soil samples taken from Krasnaya Gora and Mirny locations in Russia (approximately 200 km northeast of Chernobyl) exhibited ratios of about 1 x 10(-6). These locations showed a 137Cs ground deposition of 370 and 1,300 kBq m-2, respectively.

Animals↗
PubMed1984

The influence of soil parameters on 137Cs+-uptake by plants from long-term fallout on forest clearings and grassland.

An attempt was made to show if and to what extent the 137Cs transfer from soil to plants (grass) in forest clearings and grassland is related closely enough to different soil parameters to make it worthwhile to develop mathematical models for the prediction of transfer coefficients for certain plants and sites based solely on soil parameters. For this reason 62 soil samples from 0- to 5-cm in depth as well as from 5- to 10-cm in depth were measured for worldwide 137Cs fallout and analyzed for exchangeable potassium content, total potassium content, clay fraction, potential exchange capacity, pH value and carbon content. For both ecosystems, large variations of the transfer coefficients were observed: between 0.01 and 0.1 for grassland and 0.05 and 6 for forest clearings . Correlations, such as has been found between soil parameters, specific activities of the plants and transfer coefficients can in principle be integrated into different calculations for the estimation of radiation burden.

Cesium Radioisotopes↗
PubMedDate not supplied

[Outcome of patients after obliteration of esophageal varices by endoscopic sclerosis. Results of a prospective study].

The purpose of this prospective was study to investigate the course of patients after obliteration of bleeding esophageal varices by endoscopic sclerotherapy and to outline prognostic factors. Sixty-seven patients (45 men, 22 women, mean age: 53.3 +/- 14 years) were followed for a mean of 14 +/- 8 months median = 15 months-range: 1-33 months) from the time of obliteration. Etiology of portal hypertension was portal vein thrombosis in 3 patients and cirrhosis in 64, 44 of whom (65 p. 100) were due to alcoholism (Child-Pugh's class: A: 8 p. 100, B: 42 p. 100, C: 50 p. 100). Recurrence of varices was observed in 23 patients within 1.4 to 25 months (median: 6.6 months). The recurrence rate increased in a linear fashion with time. Reobliteration was achieved in one to three sessions of sclerotherapy. More than one bleeding episodes was observed more often, before sclerotherapy (p less than 0.05) and esophageal stenosis was seen less often during treatment (p less than 0.05) than in patients without recurrence. Variceal bleeding occurred in 14 patients (21 p. 100) within 0.1 to 23 months (median = 5.6), 6 of whom (43 p. 100) died. In the subgroup of alcoholic cirrhosis, absence of withdrawal was associated with a higher risk of rebleeding (p = 0.04). Fifteen patients (22 p. 100) died within 1 to 26 months (median = 12.3). They had a higher mean age (p less than 0.01) and a lower blood fibrinogen (p less than 0.05) than survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Esophageal Stenosis↗