Observation of flow and transport processes in artificial porous media via magnetic resonance imaging in three dimensions     

S. Oswald  W. Kinzelbach  A. Greiner  G. Brix 《Geoderma》1997,80(3-4):417-429

In two series of laboratory experiments solute transport in saturated artificial porous media was observed using magnetic resonance imaging. The objective was to get qualitative and quantitative information on transport in three dimensions including heterogeneity effects and density driven convection phenomena. Characteristic finger growth rates were evaluated and compared to calculation results. The experiments show that magnetic resonance imaging measurements can be used successfully to clarify the role of heterogeneities in transport and to check the results of numerical calculations of density driven flow.  相似文献   

A review of Australia''s extensive grazing livestock industries: size, significance and disease status     

TG MacAULAY  IP McCAUSLAND† 《Australian veterinary journal》1989,66(12):386-392

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Response of Sweet Potato (Ipomoea batatas Lam.) to Shading at Different Growth Stages     

A. Oswald    J. Alkämper  D. J. Midmore 《Journal of Agronomy and Crop Science》1995,175(2):99-107

During 1990 and 1991 growth seasons at two locations in Peru four sweet potato cultivars were tested for their response to a short-term shading. The plants were subjected to artificial shade (42 % light reduction) for 1 month at different growth stages.
A high genetic variability was found in the extent to which tuber and total biomass yield of sweet potato was affected by sub-optimal light conditions. One cultivar was completely tolerant to shade at all growth stages, whereas the others showed a yield decline between 20 % and 55 %. Generally tuber yield was most reduced when shade was imposed at the end of the growth season (fourth and fifth months) and the least at its beginning (first and second months). Yield losses were due to a diminished biomass production and/or an altered assimilate partitioning within the plant. Tuber formation was affected rather than tuber initiation.  相似文献   

Intestinal and hepatic contributions to the pharmacokinetic interaction between gamithromycin and rifampicin after single‐dose and multiple‐dose administration in healthy foals          下载免费PDF全文

S. Berlin  S. Wallstabe  E. Scheuch  S. Oswald  M. Hasan  D. Wegner  M. Grube  M. Venner  A. Ullrich  W. Siegmund 《Equine veterinary journal》2018,50(4):525-531

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Effect of subacute oral doses of nivalenol on immune and metabolic defence systems in mice     

Gouze ME  Laffitte J  Pinton P  Dedieux G  Galinier A  Thouvenot JP  Loiseau N  Oswald IP  Galtier P 《Veterinary research》2007,38(4):635-646

Nivalenol (NIV) is a toxic Fusarium secondary trichothecene metabolite occurring naturally in cereal grains. In order to evaluate the no observed adverse effect level (NOAEL), we tested the effects of a large array of oral doses of this toxin for responses on plasma biochemistry, the immune system and hepatic drug metabolism in mice. C57Bl6 mice received oral doses of toxin (0.014, 0.071, 0.355, 1.774 or 8.87 mg/kg bw) 3 days a week for 4 weeks. Only the highest dose of NIV induced an increase in plasma phosphate, decreases in plasma urea and immunoglobulin M and additional changes like increases in plasma alkaline phosphatase and immunoglobulin G. Interleukin 4 production was increased in cultured murine splenocytes. Regarding liver drug metabolising enzymes, the only glutathione transferase activity accepting 1-chloro-2,4-dinitro-benzene as substrate was transiently increased in mice receiving low doses (0.071 and 0.355 mg/kg bw) of NIV. Regarding the cytochrome P450 monooxygenases, no significant change was observed in ethoxyresorufin O-deethylase activity whereas both methoxyresorufin and pentoxyresorufin O-dealkylase activities were decreased by 38-45% for the highest dose (8.87 mg/kg bw) of NIV. However, when analysed by Western blot analysis, the protein expression of mouse P450 1a, 2b, 2c, 3a and 4a subfamilies was unchanged in animals receiving NIV. In conclusion, the NOAEL of this toxin in our study was 1.774 mg/kg bw, corresponding to an exposure to 5 ppm contaminated food. Indeed hepatotoxicity appears in the only mice treated with a five fold higher oral dose of 8.87 mg/kg bw of NIV. Such exposure levels appear to be by far higher than the maximal natural occurrence measured in European cereals, known to range from 0.34 to 1.86 ppm.  相似文献   

Soil properties influencing the denitrification potential of Flemish agricultural soils   总被引：3，自引：0，他引：3  

D'Haene  Karoline  Moreels  Edwin  De Neve  Stefaan  Chaves Daguilar  Barbara  Boeckx  Pascal  Hofman  Georges  Van Cleemput  Oswald 《Biology and Fertility of Soils》2003,38(6):358-366

The denitrification potential of the soil horizons between 0- and 90-cm depth of 20 agricultural fields, representative of the most frequent combinations of agricultural crops and soil textures in Flanders (Belgium), and the factors affecting the denitrification potential were studied in the laboratory under controlled conditions. The denitrification potential in the presence of an added soluble C and N source was measured at 15°C after saturation of air-dried soil samples with water. The denitrification potential of the lower horizons was generally negligible compared to the upper horizons. The lower denitrification potential of the deeper horizons could partially be explained by their limited C availability. The denitrification potential of the upper horizons strongly depended on texture. Based on this parameter the soils could be divided into three groups: soils with a high clay content (>30% clay) were characterised by a high denitrification potential (>8.33 µg N g^-1 dry soil day^-1); soils with medium texture had a medium denitrification potential, between 0.41 and 7.25 µg N g^-1 dry soil day^-1; and soils with a high sand content (>80% sand) had a low denitrification potential (<2.58 µg N g^-1 dry soil day^-1). In most cases, extending the saturation period during pre-incubation increased the denitrification potential. Comparison of the denitrification potential of the upper horizons with and without addition of a soluble C source showed that the denitrification potential of the upper horizons of these soils was limited by their percentage of endogenous C. The measured denitrification potentials indicate that denitrification losses in soils high in clay content can be important when NO₃ ^- concentrations are high.  相似文献   

Use of principal component analysis to assess factors controlling net N mineralization in deciduous and coniferous forest soils   总被引：3，自引：0，他引：3  

Hilde Vervaet  Bernard Massart  Pascal Boeckx  Oswald Van Cleemput  Georges Hofman 《Biology and Fertility of Soils》2002,36(2):93-101

Net N mineralization was studied in three different forest sites (Belgium): a mixed deciduous forest with oak (Quercus robur L. and Quercus rubra L.) and birch (Betula pendula Roth) as dominant species, a deciduous stand of silver birch (Betula pendula) and a coniferous stand of Corsican pine (Pinus nigra ssp. Laricio). The organic (F + H) layer and mineral soil at different depths (0-10, 10-20 and 20-30 cm) were sampled at three locations in the mixed deciduous forest (GE, GF1, GF2), at one location in the silver birch stand (SB) and one in the Corsican pine stand (CP). All samples were incubated over 10 weeks under controlled temperature and moisture conditions. The net N mineralization rates in the organic and upper mineral layer (0-10 cm) were found to be significantly different from the other layers and accounted for 66-95% of the total mineralization over the first 30 cm. Net N mineralization rates in the organic layer ranged from 4.2 to 27.3 mg N m^-2 day^-1. Net N mineralization and nitrification rates were positively correlated. For the mineral soil, net N mineralization rates decreased with depth and the upper 10 cm showed significantly higher rates, ranging from 8.9 to 33.5 mg N m^-2 day^-1. The rates of the 10-20 cm and 20-30 cm sublayers were similar, ranging from 1.2 to 7.4 mg N m^-2 day^-1. The net N mineralization rates for the total mineral layer (0-30 cm) ranged from 17.4 mg N m^-2 day^-1 (SB) to 36.1 mg N m^-2 day^-1 (CP). Both from PCA and multiple regression analysis, we could conclude that net N mineralization rates were closely related to the initial mineral N content (N_initial). Furthermore, significant correlations were observed between the net N mineralization rate, the total carbon (TC) and NH₄⁺-N content for the mineral layers and between net N mineralization rate, total nitrogen (TN), hemicellulose content and C/N for the organic layers.  相似文献   

Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons     

Toncian T  Borghesi M  Fuchs J  d'Humières E  Antici P  Audebert P  Brambrink E  Cecchetti CA  Pipahl A  Romagnani L  Willi O 《Science (New York, N.Y.)》2006,312(5772):410-413

We present a technique for simultaneous focusing and energy selection of high-current, mega-electron volt proton beams with the use of radial, transient electric fields (10(7) to 10(10) volts per meter) triggered on the inner walls of a hollow microcylinder by an intense subpicosecond laser pulse. Because of the transient nature of the focusing fields, the proposed method allows selection of a desired range out of the spectrum of the polyenergetic proton beam. This technique addresses current drawbacks of laser-accelerated proton beams, such as their broad spectrum and divergence at the source.  相似文献   

Influence of DCD and DMPP on soil N dynamics after incorporation of vegetable crop residues   总被引：5，自引：0，他引：5  

Barbara Chaves  Andrews Opoku  Stefaan De Neve  Pascal Boeckx  Oswald Van Cleemput  Georges Hofman 《Biology and Fertility of Soils》2006,43(1):62-68

We have investigated the effect of two nitrification inhibitors, 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD), on the accumulation of and after incorporation of cauliflower residues in incubation experiments. Cauliflower leaves were incubated with soil and DCD or DMPP at two application rates [8.93 and 17.9 mg active component (ac) kg⁻¹ for DCD; 0.89 and 1.79 mg ac kg⁻¹ for DMPP]. Both doses of DCD and DMPP increased on average by 18.9 and 26.0 mg N kg⁻¹ for DCD1 (during 30 days) and DCD2 (during 45 days), respectively, and on average by 14.4 mg N kg⁻¹ for DMPP1 and DMPP2 during a period of at least 95 days. In DCD-treated soils, data followed an S-shaped curve, indicating that nitrification restarted during the experiment: inhibition was on average 24% during 35 days for DCD1 and on average 45% during 49 days for DCD2. Thereafter, amount in DCD-treated soils exceeded that of the cauliflower-only treatment by 31% for DCD1 and 78% for DCD2, probably due to a nitrogen release from DCD itself and a priming effect induced by DCD. In DMPP-treated soils, data followed a linear pattern since nitrification was inhibited during the complete incubation (95 days): inhibition was on average 56 and 64% for DMPP1 and DMPP2, respectively. DMPP did not affect the N mineralization of the crop residues. Under favourable conditions, DCD is able to inhibit the nitrification from crop residues for 50 days and DMPP for at least 95 days. Hence, especially DMPP shows a potential to reduce leaching after incorporation of crop residues.  相似文献   

Escherichia coli induces DNA double-strand breaks in eukaryotic cells     

Nougayrède JP  Homburg S  Taieb F  Boury M  Brzuszkiewicz E  Gottschalk G  Buchrieser C  Hacker J  Dobrindt U  Oswald E 《Science (New York, N.Y.)》2006,313(5788):848-851

Transient infection of eukaryotic cells with commensal and extraintestinal pathogenic Escherichia coli of phylogenetic group B2 blocks mitosis and induces megalocytosis. This trait is linked to a widely spread genomic island that encodes giant modular nonribosomal peptide and polyketide synthases. Contact with E. coli expressing this gene cluster causes DNA double-strand breaks and activation of the DNA damage checkpoint pathway, leading to cell cycle arrest and eventually to cell death. Discovery of hybrid peptide-polyketide genotoxins in E. coli will change our view on pathogenesis and commensalism and open new biotechnological applications.  相似文献