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  • 11
    ISSN: 1432-0789
    Schlagwort(e): Phospholipids ; Microbial biomass ; Phosphatase ; Cropping systems ; Long-term experiments Prairie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In agricultural ecosystems that have had consistent cropping histories, standard microbial methods may be used to evaluate past and present practices. Our objective was to evaluate several microbial methods that best indicate cropping histories and soil quality on long-term plots. We selected soil microbial carbon (C), phospholipid analyses, direct counts of total fungal and bacterial biomass, and soil enzymes (phosphatases) to measure direct and indirect microbial activity on the Sanborn Field and Tucker Prairie. The Sanborn Field has been under various cropping and management practices since 1888 and the Tucker Prairie is an uncultivated site. Seven different plots were chosen on the Sanborn Field and random samples were taken in the summit area on the Tucker Prairie, which represented a reference site. Soil microbial biomass C, phospholipids, and enzyme activity were reflective of the cropping and management histories observed on the Sanborn Field. Enzymatic activity was highly correlated to soil organic matter. The direct counts of fungal and bacterial biomass showed that fungal populations dominated these soils, which may be attributed to soil pH. Soil microbial biomass C and enzyme assays seemed to be better potential indicators of cropping histories than the other methods tested in the long-term plots.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 29 (1999), S. 343-347 
    ISSN: 1432-0789
    Schlagwort(e): Key words Aporrectodea trapezoides ; Diplocardia singularis ; Population density ; Ash-free biomass ; Crop rotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract  Agricultural management practices affect earthworm populations. A field experiment was conducted to determine the effect of two rotations and two tillage systems on earthworm population density and biomass in a claypan soil. The rotations were soybean/corn and wheat/corn, and the tillage systems were conventional tillage (chisel plowed and disked) and no-tillage. Earthworm and soil samples were collected in fall 1995, spring 1996, and fall 1996. Aporrectodea trapezoides and Diplocardia singularis were the species identified at the site. A. trapezoides accounted for 92–96% of the total earthworm population density and D. singularis accounted for only 4–8%. In a no-till system, soybean/corn rotation resulted in significantly greater population density of A. trapezoides compared with the wheat/corn rotation. Crop residue quality (low C:N ratio) and quantity were important factors in increasing A. trapezoides population density and biomass. Conventional tillage markedly decreased population density and biomass of both earthworm species. Our results suggest that rotation and tillage significantly affect earthworm population density and biomass.
    Materialart: Digitale Medien
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  • 13
    ISSN: 1438-1435
    Schlagwort(e): Diagnostic radiology ; Observer performance ; Radiology education
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The purpose of this study was to evaluate the etiology of significant false-negative computed tomographic (CT) interpretations by radiology residents on-call. Over a 1-year period, significant on-call false-negative CT interpretations were analyzed to determine whether errors were perceptual (i.e., the resident did not see the finding or findings) or cognitive (i.e., the resident did not recognize the implications or misinterpreted a finding or findings). Significant “misses” were defined as errors that delayed surgical treatment or misdirected management in a potentially life-threatening manner. A total of 12 significant false-negative interpretations occurred over a 1-year period. All head CT misses (extraaxial hemorrhage, pneumocephalus, contusion, subarachnoid hemorrhage due to ruptured aneurysm) were perceptual errors. Misses on thoracic, abdominal, and pelvic CT scans (2 abscesses, abdominal aortic aneurysm rupture, superior vena cava perforation due to catheter placement, ischemic bowel, liver laceration, hypoperfusion syndrome, appendicitis) were mixed (4 cognitive and 4 perceptual errors). Since the diagnostic possibilities of emergency head CT scans are limited, residents missed only subtle, perceptual manifestations and had little difficulty interpreting findings when they were correctly recognized. The gamut of diagnostic possibilities in the thorax, abdomen, and pelvis was more challenging to residents on-call; errors in both perception and interpretation arose with equal frequency, and the significant error rate was higher than that for head CT interpretation. Junior residents, who make most of the significant on-call errors, commonly feel overwhelmed in attempting to assimilate the knowledge required to take call. Prepartion needs to be extensive, yet it should be focused on areas that will engender optimal impact on after-hours performance. When preparing residents to interpret on-call CT studies, perceptual manifestations of neuroradiology should be emphasized, whereas a more comprehensive approach to thoracic, abdominal, and pelvic disorders needs to be stressed.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of the history of biology 29 (1996), S. 309-325 
    ISSN: 1573-0387
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geschichte
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 15
    ISSN: 1435-1463
    Schlagwort(e): Autoradiography ; substance P ; ontogenesis ; sudden infant death syndrome ; SIDS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The precise distribution of substance P (SP) binding sites in the human brainstem was investigated in normal cases (3 fetuses and 24 newborns) and in 9 cases of Sudden Infant Death Syndrome (SIDS) by in vitro quantitative autoradiography. We discussed the widely but uneven distribution of SP binding sites as regards to the role of SP in brainstem cardio-respiratory ontogenic control and its possible involvement in SIDS.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 24 (1997), S. 347-352 
    ISSN: 1432-0789
    Schlagwort(e): Key words Phosphate-solubilizing bacteria ; Hydroxyapatite ; Enterobacter agglomerans ; Organic acids ; Phosphate-solubilizing genes ; Rhizosphere ; Wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Phosphate-solubilizing bacteria (PSB) possessing the ability to solubilize insoluble inorganic phosphate were isolated from the rhizosphere soil of wheat. A laboratory study was conducted to investigate the solubilization of phosphate by a known PSB, Enterobacter agglomerans, and by a genetically manipulated bacterium, Escherichia coli. A second laboratory study investigated the release of P from E. agglomerans compared with known acids. For the first laboratory study, a cosmid (pHC79) library of phosphate-solubilizing gene(s) from E. agglomerans chromosome DNA was constructed in E. coli JM109. The clone JM109 (pKKY) showing phosphate solubilization properties was screened on standard medium containing hydroxyapatite (HY). The P concentration significantly increased at 5 and 10 days for JM109 (pKKY) compared with JM109 (pHC79), the control. Although the P concentration increased, there was no significant change in their pHs. Furthermore, an increase in colony-forming units (CFUs) was seen at 5 and 10 days for JM109 (pKKY) but not for JM109 (pHC79). Artificial acidification of the culture medium with HCl, citric acid, oxalic acid, and lactic acid was achieved by shaking for 48h. Acidification with these selected acids solubilized more HY than E. agglomerans growing for 42h at similar pHs. However, a high P concentration was measured in culture medium with E. agglomerans growing for 84h despite similar pHs. Our results suggest that acid production may play an important role in HY solubilization, but is not the sole reason for the increase in P concentration in culture medium.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 26 (1997), S. 79-87 
    ISSN: 1432-0789
    Schlagwort(e): Key words Organic acids ; Phosphate-solubilizing ; bacteria ; Vesicular-arbuscular mycorrhizae ; Glomus etunicatum ; Enterobacter agglomerans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The interaction of vesicular-arbuscular mycorrhizae (VAM) and phosphate-solubilizing bacteria (PSB) on plant growth, soil microbial activities, and the production of organic acids was studied in non-sterile soil containing hydroxyapatite and glucose. Glomus etunicatum (VAM), a fungus, and Enterobacter agglomerans, a bacterium able to solubilize insoluble phosphate, were used as inocula. Three treatments and a control were used: inoculation with E. agglomerans (treatment E), inoculation with G. etunicatum (treatment G), inoculation with E. agglomerans+G. etunicatum (treatment E+G) and the control (C). Inoculation with E, G, or E+G had increased plant growth by days 35, 55, and 75 compared with the control. Microbial biomass carbon (C) and alkaline phosphatase activity in the rhizosphere generally increased with time. Alkaline phosphatase activity was higher in treatments G and E+G compared with the control at 35 and 55 days. The highest acid phosphatase activity was observed in treatment E at 35 days; however, this markedly decreased with time. A significantly higher soluble phosphorus (P) concentration was observed in treatments E and E+G on day 55 compared with C. However, there was no significant difference in soluble P concentration in the rhizosphere between treatments with time. The P concentration was greatest in all treatments on day 55. The highest oxalic acid concentration was observed in the rhizosphere of the non-sterile soil in E+G on day 35. Total N and P uptake in plants from treatments E and G were higher compared with the control. However, the highest N and P uptake was observed in treatment E+G. This study suggests a synergistic interaction between E. agglomerans and G. etunicatum.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 21 (1996), S. 271-276 
    ISSN: 1432-0789
    Schlagwort(e): 15N transformations ; Crop residues ; Soil texture ; Soil aggregation ; Microbial pool ; Microbial biomass
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In a greenhouse pot study, we examined the availability of N to grain sorghum from organic and inorganic N sources. The treatments were15N-labeled clover residues, wheat residues, and fertilizer placed on a sandy clay loam and loamy sand soil surface for an 8-week period. Soil aggregates formed under each soil texture were measured after 8 weeks for each treatment. Significantly greater 15N was taken up and recovered by grain sorghum in sandy clay loam pots compared with loamy sand pots. Greater 15N recovery was consistently observed with the inorganic source than the organic sources regardless of soil texture or time. Microbial biomass C and N were significantly greater for sandy clay loam soil compared with the loamy sand. Microbial biomass 15N was also significantly greater in the sandy clay loam treatment compared to the loamy sand. The fertilizer treatment initially had the greatest pool of microbial biomass 15N but decreased with time. The crop residue treatments generally had less microbial biomass 15N with time. The crop residues and soil texture had a significant effect on the water-stable aggregates formed after 8 weeks of treatments. Significantly greater water-stable aggregates were formed in the sandy clay loam than the loamy sand. Approximately 20% greater water-stable aggregates were formed under the crop residue treatments compared to the fertilizer only treatment. Soil texture seemed to be one of the most important factors affecting the availability of N from organic or inorganic N sources in these soils.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Journal of radioanalytical and nuclear chemistry 193 (1995), S. 113-117 
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract A new method for the determination of Tc-99 in different environmental samples has been developed. The sample is carefully ashed in a muffle furnace and then fused with Na2CO3 and K2CO3. The first step is an enrichment and purification of TcO 4 − on an anion exchange resin. The Tc is desorbed as a cationic thiourea complex, which is held on a cation exchange resin. The complex is destroyed by oxidation to TcO 4 − with (NH4)2S2O8 in sulfuric acid. From this solution TcO 4 − is extracted into TBP/toluene and the organic phase is mixed with a scintillation cocktail and counted in an anticoincidence shielded LSC. Tc-99m is used as a chemical yield tracer. The decontamination factors for all important fission and activation products and naturally occurring radionuclides are in the range between 〉 105 and 〉 108. The detection limit is about 5 mBq per sample at a counting time of 1000 minutes. The maximum sample amount of plants is 500 g dry weight and therefore the lowest detection limit achievable is 10 mBq/kg. Ashing and dissolution of the samples takes 24 h and 4 analyses are performed by one technician in 8 hours. The chemical yield ranges from 50 to 80%.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 831-833 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: It is now possible to do molecular weight distribution of polymeric material almost as fast as you can put them in solution. μSYRAGEL® has opened a new era in the determination of molecular weight distribution of polymers. With operational efficiencies of 800 plates/min., one can obtain a molecular weight distribution in 15 mins. Combining three of the newest advances in liquid chromatography - solvent delivery, septumless injection, and μSYRAGEL - now makes it possible to use molecular weight distribution as a quality control tool in polymerization and fabrication. The reproducibility of the molecular weight distribution is now good enough that overlays can be done from the raw data. The chromatograms can be used right off the recorder. The reproducibility of the weight average and number average molecular weight is 2-3 percent.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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