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  • Springer  (16)
  • Blackwell Publishing Ltd  (2)
  • Wiley-Blackwell  (2)
  • Cambridge University Press  (1)
  • Elsevier  (1)
  • 1990-1994  (22)
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  • 1
    Digitale Medien
    Digitale Medien
    A Laboratory and Numerical Investigation of Solute Transport in Discontinuous Fracture Systems (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 28 (1990), S. 0 
    Details
    ISSN: 1745-6584
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Energietechnik , Geologie und Paläontologie
    Notizen: Mixing of fluids at fracture intersections was examined using both a series of plexiglass models and a two-dimensional, finite-element, discrete fracture model. The physical laboratory models included 12 models having two continuous, fully intersecting fractures with different intersection angles and apertures, a single model consisting of a single continuous fracture offsetting a second fracture, and a fracture system model consisting of parallel fractures in two intersecting sets. The plexiglass model results indicated essentially no mixing occurred in the fully intersecting fracture models when the apertures were equal. Mixing was found to be dependent only upon the relative size of the inlet and outlet fractures even with multiple intersections.For transport of a conservative solute in a discontinuous, random, discrete fracture system, the numerical model used the mixing algorithm for fracture intersections, developed from the physical model study. At each four-way intersection, a novel approach was used to uncouple and recouple the nodal points to ensure the proper assignment of concentrations to each fracture element. Using the laboratory-determined mixing algorithm, the numerical model demonstrated that more longitudinal and less lateral dispersion takes place than when complete mixing at fracture intersections is assumed. In addition, more longitudinal transport takes place in discontinuous than in continuous fracture systems. These findings indicate that contaminants migrating through fractured media, where the fracture walls are not in contact, will not be dispersed and diluted to the extent that previous numerical models have predicted; hence, the contaminant will be discharged to the biosphere in much greater concentration than expected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1745-6584.1990.tb02226.x
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  • 2
    Digitale Medien
    Digitale Medien
    Speculations on carbon dioxide starvation, Late Tertiary evolution of stomatal regulation and floristic modernization (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Ambient atmospheric CO2 concentration ([CO2]a) has apparently declined from values above 200μmol mol−1 to values below 200μmol mol−1 within the last several million years. The lower end of this range is marginal for C3 plants. I hypothesize that: (1) declining [CO2]a imposed a physiological strain on plants, and plant taxa evolving under declining [CO2]a tended to develop compensating mechanisms, including increased stomatal efficiency; (2) angiosperms were better able to adjust to declining [CO2]a than were gymnosperms and pteridophytes; and (3) angiosperm adjustment has been uneven. Fast-evolving taxa (e.g. grasses and herbs) have been better able to adapt to CO2 starvation. If these propositions are true, stomatal adjustment mechanisms should show patterned variation, and a single pattern of stomatal regulation cannot be assumed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb00303.x
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  • 3
    Digitale Medien
    Digitale Medien
    Land application of poultry litter and water quality in Oklahoma, U.S.A. (1994)
    Springer
    Nutrient cycling in agroecosystems 40 (1994), S. 165-173 
    Details
    ISSN: 1573-0867
    Schlagwort(e): Animal manure ; eutrophication ; ground water ; nitrogen ; phosphorus ; surface runoff
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract With the rapid growth of the poultry industry in Oklahoma, U.S.A., more litter is applied to farm land. Thus, information is required on the impact of applications on regional soil and water resources. The effect of soil and poultry litter management on nitrogen (N) and phosphorus (P) loss in runoff and subsurface flow from four 16 m2 plots (Ruston fine sandy loam, 6 to 8% slope) was investigated under natural rainfall. Plots under Bermudagrass (Cynodon dactylon) received 11 Mg litter ha−1, which amounts to contributions of approximately 410 kg N and 140 kg P ha−1 yr−1. In spring, litter was broadcast on 3 of the plots; the upper half of one and total area of the other two. One of the total-area broadcast plots was tilled to 6 cm, the other remained as no till. The fourth plot served as a control. Relative to the control, litter application increased mean concentrations of total N and total P in runoff during the 16-week study for no-till (15.4 and 5.8 mg L−1) and tilled treatments (16.7 and 6.1 mg L−1). However, values for the half-area application (5.6 and 2.0 mg L−1) were similar to the control (5.7 and 1.3 mg L−1). Interflow (subsurface lateral flow at 70 cm depth) P was not affected by litter application; however, nitrate-N concentrations increased from 0.6 (control) to 2.9 mg L−1 (no till). In all cases, 〈 2 % litter N and P was lost in runoff and interflow, maintaining acceptable water quality concentrations. Although litter increased grass yield (8518 kg ha−1) compared to the control (3501 kg ha−1), yields were not affected by litter management. An 8-fold increase in the plant available P content of surface soil indicates long-term litter management and application rates will be critical to the environmentally sound use of this nutrient resource.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00750462
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  • 4
    Digitale Medien
    Digitale Medien
    A review of the molecular structure of tetanus toxin (1991)
    Springer
    Molecular and cellular biochemistry 107 (1991), S. 33-44 
    Details
    ISSN: 1573-4919
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Summary A discontinuous preparative polyacrylamide gel electrophoresis system has been developed and used to purify both the nicked and unnicked forms of tetanus toxin. The system was also used to prepare purified H and L chain peptides from the nicked toxin. The results show that the endogenous protease(s), which convert unnicked toxin to the nicked form, produce multiple species of nicked toxin, and heterogeneity in the H and L chains. The major amino termini of the toxins and their peptide components are: extract toxin, proline; filtrate toxin, proline, serine and asparagine; L chain, proline; and H chain, serine and asparagine. The L chain is located in the amino terminal position of the toxin molecule and the H chain the carboxy terminal end. A model is proposed to explain these results. Using the analytical ultracentrifuge, we have determined the molecular weights of extract and filtrate toxins to be 140 000 ± 5 000 and 128 000 ± 3 000, respectively. Using S DS-polyacrylamide gel electrophoresis we estimate the molecular weights of the H and L chains to be 87 000 and 48 000 daltons, respectively. Circular dichroic spectra of the toxins and their peptide components indicate that: the major tryptophanyl band in the toxin is contributed almost entirely by the H chain, the microenvironments of all the aromatics and disulfides in the two toxins appear to have small if any differences, the two toxins show little difference in their ordered secondary structure, and the two peptides when separated from one another still retain 80% of the helical structure that is present in the intact toxin but show a considerable loss of β-structure. The crystalline form of the nicked toxin has a hexagonal symmetry with two dimensional reciprocal lattice constants of 1/150 Å−1 and 1/150 Å−1. The crystals appear to belong to the two dimensional plane group P6 suggesting that each unit cell contains 6 or a multiple of 6 toxin molecules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00214820
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    A simple method for ultrastructural enzyme cytochemistry on small volumes and numbers of isolated cells (1991)
    Springer
    Journal of molecular histology 23 (1991), S. 10-12 
    Details
    ISSN: 1573-6865
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A simple technique is described for ultrastructural enzyme cytochemistry using small volumes and numbers of single cells. Small aliquots (1–5 μl) of single cells suspended in a glutaraldehyde fixative are incubated on poly-L-lysine-coated glass coverslips. Cells in contact with the coated coverslip become immobilized to that support. All changes of solutions are accomplished without repeated centrifugation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01886502
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  • 6
    Digitale Medien
    Digitale Medien
    Scaleup of Oral Extended-Release Dosage Forms (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1800-1805 
    Details
    ISSN: 1573-904X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018946819849
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  • 7
    Digitale Medien
    Digitale Medien
    Symptoms of mineral nutrient deficiencies and the nutrient concentration ranges in seedlings of Eucalyptus maculata Hook. (1993)
    Springer
    Plant and soil 155-156 (1993), S. 255-261 
    Details
    ISSN: 1573-5036
    Schlagwort(e): concentration ranges ; deficiency symptoms ; macronutrients ; micronutrients ; spotted iron gum (Eucalyptus maculata Hook.)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract With the establishment of plantation eucalypts around the world there is an increasing need for reference data which can be used to diagnose the nutrient status of eucalypt seedlings. Therefore, deletion glasshouse nutrient trials were set up in sand and solution culture to obtain deficiencies of N, P, K, Mg, Ca, S, Fe, Zn, Cu and Mn in the spotted iron gum (Eucalyptus maculata). Nutrient concentration ranges were obtained for leaves at defined growth stages for (a) healthy plants, (b) plants where yield was just depressed or where symptoms first appeared, and (c) plants with severe symptoms. The defined symptoms and nutrient concentration ranges should be useful in identifying single nutrient deficiencies in nursury grown seedlings or young plants with juvenile foliage in the field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00025032
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  • 8
    Digitale Medien
    Digitale Medien
    Inheritance of resistance to Russian wheat aphid in barley (1992)
    Springer
    Euphytica 62 (1992), S. 213-217 
    Details
    ISSN: 1573-5060
    Schlagwort(e): Russian wheat aphid ; Diuraphis noxia ; barley ; resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The inheritance of resistance to Russian wheat aphid Diuraphis noxia (Mordvilko), in two resistant barleys, Hordeum vulgare L., ASE/2CM//B76BB and ‘Gloria/Come’, was studied in the field and in the greenhouse. The resistant genotypes were crossed with susceptible genotypes ‘Esperanza’ and ‘Shyri’. Resistance reactions of F1, BC1, and F2 plants, and individual F2 plant derived F3 families indicated that resistance in each genotype was controlled by the same single dominant gene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00041755
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  • 9
    Digitale Medien
    Digitale Medien
    Influence of calcium carbonate on the dissolution of Sechura phosphate rock in soils (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 91-99 
    Details
    ISSN: 1573-0867
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Different amounts of CaCO3 (5.3 to 20% w/w) (180-75µm) were mixed with Sechura phosphate rock (SPR) (180-75µm) and incubated with Davidstow and Withnell soils. These soils differ in their proton supply and Ca-buffering capacity. The Ca-buffering capacity of Davidstow soil was also changed by adding different amounts of cation-exchange resin (CER). The consumption of protons and the release of Ca during the preferential dissolution of CaCO3 decreased the dissolution of the SPR (measured by P release). However, the negative effect of CaCO3 on SPR dissolution at near equilibrium (60 d) depended on both the proton supply and Ca-sink size of the soil. The Davidstow soil had an adequate proton supply (43.6 mmol H kg−1 pH unit−1) but a small Ca sink (32.0 mmol kg−1), and the dissolution of SPR at 60 d decreased linearly from 27.5 to 19.5% with increasing CaCO3 content. The Withnell soil had an adequate Ca sink (75.5 mmol kg−1) but a small proton supply (21.4 mmol H kg−1 pH unit−1), and the amount of P dissolved at 60 d also decreased (from 49 to 35%) with increasing CaCO3 content. Adding CER to the Davidstow soil increased the Ca-sink size from 32.0 to 39.0 mmol kg−1 and almost prevented the decrease in SPR dissolution with increasing CaCO3 content. This suggests that, in soils with an adequate proton supply and Ca-sink size, CaCO3 present as an accessory mineral in PR materials has a negligible effect on the dissolution of the PR.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01054398
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  • 10
    Digitale Medien
    Digitale Medien
    DNA methylation of the fragile X locus in somatic and germ cells during fetal development: Relevance to the fragile X syndrome and X inactivation (1993)
    Springer
    Somatic cell and molecular genetics 19 (1993), S. 393-404 
    Details
    ISSN: 1572-9931
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract To obtain insights into mechanisms responsible for methylation of CpG islands on the inactive X chromosome of normal females, we examined methylation of the fragile X (FraX) locus in a variety of tissues from normal fetuses and adults, and from males with the FraX syndrome. We identified 20 CCGG sites (MspI-HpaII sites M1–M20) within a 12-kb BglII fragment that includes the CpG island. Sites M3–M18, within the 1.2-kb CpG island are unmethylated on the active X in normal males and females at all ages and in all tissues studied. In contrast, these sites are at least partially methylated on the inactive X chromosome in a variety of tissues from normal females by six weeks from conception. The exceptional tissues are chorionic villi and gonads, which are significantly undermethylated. In addition, fetal germ cells are unmethylated at site M3, which is methylated on the inactive X in other tissues; thus, the methylation imprint of the inactive X has been erased. Methylation of the locus on the fragile X chromosome is similar to that of the normal inactive X but is more extensive and less heterogeneous. This suggests that the expansion of the island and the greater number of CpGs that result from amplification of the CGG repeat enhance the methylatibility of the island. Additional studies show that the chromatin of the CpG island is nuclease hypersensitive on the active X but insensitive on both inactive and FraX.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01232750
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