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  • 1
    Electronic Resource
    Electronic Resource
    Co-occurrence patterns of cavity-nesting birds in cottonwood-willow communities (1988)
    Springer
    Oecologia 76 (1988), S. 445-454 
    Details
    ISSN: 1432-1939
    Keywords: Cavity-nesting birds ; Co-occurrence patterns ; Independent autecological responses ; Cottonwood-willow communities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied the covariation of six species of cavity-nesting birds to determine the extent to which species' co-occurrence patterns were attributable to interspecific relations. We tested two null hypotheses: (1) inverse relations did not exist among potential competitors for nest trees or nest cavities, and (2) there were no positive relations among potential commensals for nest cavities. Statistical power analyses, and simple, partial, and multiple partial correlation and regression analyses provided little evidence of species-species or higher-order inverse or positive relations. Most of the variation in co-occurrence patterns was associated with stand characteristics. Collectively, an abundance of nest trees and nest cavities, differences among species in acceptable nest-tree and nest-cavity dimensions, and different periods of peak nesting activity appear to be responsible for the lack of negative relations among potential competitors. Positive relations among potential commensals were weak presumably because (1) secondary cavity nesters (SCNs) frequently used cavities that originated from wind-, lightning-, and/or disease-damaged limbs and were thus not dependent completely on primary cavity nesters for cavities, and (2) the lag time for cavity use by SCNs is often two or more seasons. Interspecific relations were apparently not major determinants of community structure during our investigation; assemblages of cavity nesters appeared instead to be influenced more by independent species-specific habitat responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377041
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of soil water content by X-ray computed tomography and magnetic resonance imaging (1989)
    Springer
    Irrigation science 10 (1989), S. 63-71 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Experiments were conducted to compare the use of X-ray computed tomography (CT) and magnetic resonance imaging (MRI) methods for determining water content in soil. Soil cores of Mexico silt loam packed at bulk densities of 1.2, 1.3, 1.4, and 1.5 Mg/m3 and Crider silty clay packed at bulk densities of 1.3, 1.4, 1.5, and 1.6 Mg/m3 were evaluated using a CT scanner. Results indicate that the X-ray CT explained 98% of the variation in water content over a range from air-dry to saturation. Three attempts were made to obtain MRI scans of soil cores varying in soil water content. Two of these attempts were made with contrasting agents. No images were obtained of the soil cores during all three attempts. It is suggested that the failure to obtain images of soil cores is closely related to the settings of the pulse repetition time and the spin echo time on the MRI unit. The range in settings for these two parameters on the commercial MRI unit used in this study did not allow short increments to be selected and therefore it was not possible to obtain reconstructed images of the soil cores for this experiment. However accessibility to a prototype MRI unit should allow more conclusive work to determine the full capabilities of MRI for determining soil water content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266158
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of bromide ion used as a solute-transport monitor via epithermal neutron activation analysis (1998)
    Springer
    Journal of radioanalytical and nuclear chemistry 235 (1998), S. 249-254 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In soil science (ca. 1970), bromide ion (Br−) in various forms (e.g., KBr, NaBr, SrBr2) was introduced as a non-reactive stable tracer in solute transport studies normally moving freely with the flux of water without substantial chemical or physical interactions with the soil. Typically, Br− is extracted from soil and quantified using either a bromide selective electrode (sensitivity is ≈10μg/ml) or by high-performance liquid chromatography (sensitivity is ≈0.010 μg/ml). Where the sensitivity is adequate, the selective conductivity method, which is simple, affordable and fast, is preferred. More recently (ca. 1990), workers have reported that 20% of Br− tracers, at low groundwater pH, may be adsorbed by iron oxides and kaolinite when present in the alluvial aquifer. We investigated the use of Epithermal Neutron Activation Analysis (ENAA) as a means of measuring Br− directly in soil samples without an extraction. ENAA was chosen because of its high theoretical advantage factor over aluminum (i.e. ≈20), the principal interfering soil constituent, calculated for the79Br(n,γ)80Br reaction compared to27Al(n, γ)28Al. Br− was measured (sensitivity is ≈0.050 μg/g) in one gram soil samples from a 5 s irradiation (φepi=2.5·1012 n·cm-2·s-1) using a BN capsule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02385970
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    Paper (German National Licenses)
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  • 4
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    Abasic Phosphorothioate Oligomers Inhibit HIV-1 Reverse Transcription and Block Virus Transmission across Polarized Ectocervical Organ Cultures [Antiviral Agents] (2014)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2014-11-13
    Description: In the absence of universally available antiretroviral (ARV) drugs or a vaccine against HIV-1, microbicides may offer the most immediate hope for controlling the AIDS pandemic. The most advanced and clinically effective microbicides are based on ARV agents that interfere with the earliest stages of HIV-1 replication. Our objective was to identify and characterize novel ARV-like inhibitors, as well as demonstrate their efficacy at blocking HIV-1 transmission. Abasic phosphorothioate 2' deoxyribose backbone (PDB) oligomers were evaluated in a variety of mechanistic assays and for their ability to inhibit HIV-1 infection and virus transmission through primary human cervical mucosa. Cellular and biochemical assays were used to elucidate the antiviral mechanisms of action of PDB oligomers against both lab-adapted and primary CCR5- and CXCR4-utilizing HIV-1 strains, including a multidrug-resistant isolate. A polarized cervical organ culture was used to test the ability of PDB compounds to block HIV-1 transmission to primary immune cell populations across ectocervical tissue. The antiviral activity and mechanisms of action of PDB-based compounds were dependent on oligomer size, with smaller molecules preventing reverse transcription and larger oligomers blocking viral entry. Importantly, irrespective of molecular size, PDBs potently inhibited virus infection and transmission within genital tissue samples. Furthermore, the PDB inhibitors exhibited excellent toxicity and stability profiles and were found to be safe for vaginal application in vivo . These results, coupled with the previously reported intrinsic anti-inflammatory properties of PDBs, support further investigations in the development of PDB-based topical microbicides for preventing the global spread of HIV-1.
    Print ISSN: 0066-4804
    Electronic ISSN: 1098-6596
    Topics: Biology , Medicine
    Published by The American Society for Microbiology (ASM)
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