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  • 1
    Electronic Resource
    Electronic Resource
    Vestibulo-oculomotor testing during the course of a spaceflight mission (1993)
    Springer
    Journal of molecular medicine 71 (1993), S. 740-748 
    Details
    ISSN: 1432-1440
    Keywords: Weightlessness ; Vestibular adaptation ; Caloric testing ; Vestibulo-ocular reflex ; Ocular torsion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The experimental concept and findings from a recent manned orbital spaceflight are presented. In a single-case, longitudinal study, vestibulo-oculomotor function was examined by caloric testing and active head oscillations. The results from preflight, inflight, and postflight measurements of the human vestibulo-ocular reflex, together with those of ongoing terrestrial studies, should enable separation of the canalicular and otolithic contributions to ocular torsion. This analysis enables an accurate evaluation of the adaptation of the otolithic system to the inflight microgravity and, after landing, to the 1- force environment. Video-oculography was employed throughout for the comprehensive measurement of eye and head movements. Caloric testing involved air insufflation at 15° C over 90 s, followed by an observation interval of 2 min. During inflight testing this was continued with a 30-s free-floating interval. Active head oscillations were performed at four discrete frequencies (0.12, 0.32, 0.80, 2.0 Hz) and over a frequency sweep between 0.1 and 2.0 Hz. These head oscillations were performed in yaw, pitch, and roll and for three visual conditions (head-fixed target, space-fixed target, no target). The concomitant stimulation of the semicircular canals and otolithic receptors during these oscillations should yield different oculomotor responses under 1-g and 0-g adaptations. Both the short-form caloric test and the active head movement test were performed on 4 of the 5 available mission days. The results of the caloric tests yield a caloric nystagmus intensity (slow-phase velocity) of approximately 60% of that measured before flight and indicate an adaptation in response over the 10-day period after landing. The preliminary results from the head movement tests about the roll axis indicate an adaptive response in this aspect of the vestibulo-ocular reflex during prolonged microgravity. Some changes in sensomotoric control were also apparent during the inflight and postflight phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00209729
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  • 2
    Electronic Resource
    Electronic Resource
    Estimating microbial biomass N in soils with and without living roots: Limitations of a pre-extraction step (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 314-318 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass N ; Fumigation-extraction ; Pre-extraction ; Rhizosphere ; Roots ; Net-closed soil containers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Special net-closed soil containers were used in a pot experiment with low and high plant densities to give soil samples with and without roots. Soils from the containers were analysed either by the fumigation-extraction method or by a modified procedure starting with a pre-extraction and sieving step to remove plant roots from the samples. In the extracts NO 3 - -N, NH 4 + -N, organic N, and total N were measured. Microbial biomass N was calculated from the differences in total N in fumigated and unfumigated soils. Different plant densities had almost no influence on the values of the N compounds using either method. In soils with roots, significantly more organic N (and total N) was found by the fumigation-extraction method compared to soils without roots while no differences were obtained using pre-extractions and sieving. Though the organic N content in pre-extracts from soils with roots was significantly higher than from soils without roots, the NO 3 - -N and NH 4 + -N content was lower. Significant differences in biomass N in soils with and without roots were found only with the fumigation-extraction method. Biomass N levels calculated using the results after pre-extraction and sieving were about 50% lower than levels detected using fumigation-extraction alone. With the use of special net-closed soil containers, not only were soil samples produced with and without roots, but it was also possible to induce a rhizophere in the soils. A comparison of the two methods using these soils clearly demonstrated that the method used has profound influence on the final biomass N results. While higher “biomass” levels were found by fumigation-extraction in soils with roots, because root N becomes extractable after fumigation, the use of a pre-extraction and a sieving step may underestimate the total biomass N content due to the pre-extraction of microbial N (especially from rhizosphere microorganisms) from the sample. Nevertheless, pre-extraction and sieving followed by fumigation-extraction does seem to be the preferable method for biomass N measurement in comparative studies, because in most cases only minor errors will occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334909
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  • 3
    Electronic Resource
    Electronic Resource
    Significance of soil microorganisms for the mobilization of nonexchangeable ammonium (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 248-251 
    Details
    ISSN: 1432-0789
    Keywords: Key words Nonexchangeable ammonium ; Availability ; Soil microorganisms ; Temperature ; Available carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To estimate the availability of nonexchangeable NH4 +-N for soil microorganisms four incubation experiments were conducted under controlled conditions. The following results were obtained: Incorporating glucose as a source of readily oxidizable organic material favored the release of nonexchangeable NH4 +-N. Mobilization of NH4 + from the interlayers of the clay minerals was decreased by the application of K+, while Ca2+, which is supposed to expand the lattice of the clay minerals, had no influence on the release of NH4 +. Soil temperature had no effect on microbiological mobilization of NH4 +. It is assumed that, generally, the influence of nitrifying bacteria on the mobilization of nonexchangeable NH4 +-N is negligible. However, in soils with abundant amounts of available carbon promoting the activity of heterotrophic soil microorganisms, the release of NH4 + from clay minerals is favored under fallow conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00382520
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  • 4
    Electronic Resource
    Electronic Resource
    N2 fixation and growth of legumes as affected by sulphur fertilization (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 449-453 
    Details
    ISSN: 1432-0789
    Keywords: Key words Sulphur ; Legumes ; N2 fixation ; Rhizobia ; Nitrogenase ; Nodulation ; Acetylene reduction assay ; 15N dilution technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of three sulphur application rates in combination with two nitrogen application rates on N2 fixation and growth of different legumes was investigated. N was applied as N-labelled 15NH4 15NO3. The 15N isotope dilution technique was used to estimate N2 fixation. At both N increments dry matter yield was highest with high S supply. Independently of the N supply, the high S application rate resulted in a significantly higher N accumulation, which was mainly caused by a higher N2 fixation rate. With the grain legumes the weight of nodules was increased by the high S application rate. The higher number of nodules per pot with optimum S supply was the result of a better root growth. Rates of acetylene reduction correlated significantly with S supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335921
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanisms of fixation and release of ammonium in paddy soils after flooding II. Effect of transformation of nitrogen forms on ammonium fixation (2000)
    Springer
    Biology and fertility of soils 31 (2000), S. 517-521 
    Details
    ISSN: 1432-0789
    Keywords: Key words Ammonium fixation ; Rice paddy soil ; Nitrogen transformation ; Aseptic incubation ; Wetland rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  An incubation experiment under aseptic and septic conditions using 15N-labelled NH4 +-N and NO3 –-N, was carried out to study the effect of N transformations after flooding on NH4 + fixation in a paddy soil from China. After flooding ammonification was favoured, providing NH4 + for fixation by clay minerals. NH4 + fixation was more pronounced under low redox potential (Eh) conditions. Close correlations existed between exchangeable NH4 +, Eh, and non-exchangeable NH4 +. Therefore, two major conditions for NH4 + fixation induced by flooding in paddy soil were found, namely flooding promoted net production of NH4 + due to the deamination of organic N and, in addition, decreased the Eh of the soil. A lower Eh was caused by reduction and dissolution of Fe oxide coating on the clay minerals' surfaces, eliminating the obstacles for NH4 + diffusing into or out of the interlayers of clay minerals. A higher concentration of exchangeable NH4 + from deamination of organic N would drive NH4 + diffusing from the soil solution into the interlayers of clay minerals. 15N-labelled NO3 – incorporated into the flooded soil was not reduced to NH3. The addition of NO3 – retarded the decrease in the soil Eh and, therefore, NH4 + fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000202
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of organic manure on organic phosphorus fractions in two paddy soils (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 64-68 
    Details
    ISSN: 1432-0789
    Keywords: Paddy soils ; Anaerobic conditions ; Organic P fractions ; Organic manure ; Cellulose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We investigated the transformation of the organic P fractions from organic manure in two paddy soils (Ultisol, Entisol) and the influence of organic manure or cellulose on organic P under anaerobic conditions. The results obtained from the P fractionation experiment indicated that during the incubation labile and moderately labile organic P fractions increased in the Ultisol and decreased in the Entisol, which might be related to the difference in the organic matter content of both soils. Immediately after the application of organic manure, a large part of labile and moderately labile organic P supplied with the manure was transformed into moderately resistant organic P, possibly Ca- or Mg-inositol P were transformed into Fe-inositol P. During anaerobic incubation, the labile forms of organic P in the soils treated with organic manure were increased along with the incubation period in the first 4 weeks. The change in the moderately labile fraction was dramatic. It increased sharply in the first 2 weeks, then decreased, which was more pronounced in the soils treated with pig faeces. The moderately resistant fraction decreased during the whole incubation period. This indicated that under anaerobic conditions, the moderately resistant fraction can be transformed into labile and moderately labile organic P fractions, perhaps as Fe3+-inositol P is reduced to Fe+2-inositol P. Cellulose as an organic substrate had an increasing effect on organic P, especially when it was combined with inorganic P. Therefore, it is suggested that the application of inorganic P fertilizer combined with organic manure may be an effective way of protecting inorganic P against intensive sorption in soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418674
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of pretreatment of soil samples on N mineralization in incubation experiments (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 135-139 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen ; Mineralization ; Soil pretreatment ; Incubation experiment ; Freezing/thawing ; Long term field experiment ; Farmyard manure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the effects of pretreating soil samples (field-fresh, drying at 40° and 105°C, freezing/thawing) on N mineralization in an incubation experiment and on the dynamics of the organic N fraction extracted by K2SO4 solution. The soil samples were collected from plots in a long-term field experiment with the application of mineral fertilizer and farmyard manure. Compared with the field-fresh soil samples, freezing/thawing resulted in higher NO 3 − -N contents while the NH 4 + -N and the organic N content were increased by drying at 105°C. During the incubation period N mineralization was highest after the samples were dried at 105°C and a little lower in those dried at 40°C. After freezing/thawing the order of magnitude of N mineralization remained the same. The difference in organic N between the beginning and the end of the incubation experiment and the mineral N content at the end of the experiment were correlated significantly. Despite this correlation, however, the change in the organic N content underestimated the N mineralization rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336263
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  • 8
    Electronic Resource
    Electronic Resource
    Estimating microbial biomass N in soils with and without living roots: Limitations of a pre-extraction step (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 314-318 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass N ; Fumigation-extraction ; Pre-extraction ; Rhizosphere ; Roots ; Net-closed soil containers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Special net-closed soil containers were used in a pot experiment with low and high plant densities to give soil samples with and without roots. Soils from the containers were analysed either by the fumigation-extraction method or by a modified procedure starting with a pre-extraction and sieving step to remove plant roots from the samples. In the extracts NO-N, NH-N, organic N, and total N were measured. Microbial biomass N was calculated from the differences in total N in fumigated and unfumigated soils. Different plant densities had almost no influence on the values of the N compounds using either method. In soils with roots, significantly more organic N (and total N) was found by the fumigation-extraction method compared to soils without roots while no differences were obtained using pre-extractions and sieving. Though the organic N content in pre-extracts from soils with roots was significantly higher than from soils without roots, the NO-N and NH-N content was lower. Significant differences in biomass N in soils with and without roots were found only with the fumigation-extraction method. Biomass N levels calculated using the results after pre-extraction and sieving were about 50% lower than levels detected using fumigation-extraction alone. With the use of special net-closed soil containers, not only were soil samples produced with and without roots, but it was also possible to induce a rhizophere in the soils. A comparison of the two methods using these soils clearly demonstrated that the method used has profound influence on the final biomass N results. While higher ”biomass“ levels were found by fumigation-extraction in soils with roots, because root N becomes extractable after fumigation, the use of a pre-extraction and a sieving step may underestimate the total biomass N content due to the pre-extraction of microbial N (especially from rhizosphere microorganisms) from the sample. Nevertheless, pre-extraction and sieving followed by fumigation-extraction does seem to be the preferable method for biomass N measurement in comparative studies, because in most cases only minor errors will occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334909
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  • 9
    Electronic Resource
    Electronic Resource
    Significance of soil microorganisms for the mobilization of nonexchangeable ammonium (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 248-251 
    Details
    ISSN: 1432-0789
    Keywords: Nonexchangeable ammonium ; Availability ; Soil microorganisms ; Temperature ; Available carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To estimate the availability of nonexchangeable NH inf4 sup+ −N for soil microorganisms four incubation experiments were conducted under controlled conditions. The following results were obtained: Incorporating glucose as a source of readily oxidizable organic material favored the release of nonexchangeable NH inf4 sup+ −N. Mobilization of NH inf4 sup+ from the interlayers of the clay minerals was decreased by the application of K++, while Ca2+, which is supposed to expand the lattice of the clay minerals, had no influence on the release of NH inf4 sup+ . Soil temperature had no effect on microbiological mobilization of NH inf4 sup+ . It is assumed that, generally, the influence of nitrifying bacteria on the mobilization of nonexchangeable NH inf4 sup+ −N is negligible. However, in soils with abundant amounts of available carbon promoting the activity of heterotrophic soil microorganisms, the release of NH inf4 sup+ from clay minerals is favored under fallow conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00382520
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  • 10
    Electronic Resource
    Electronic Resource
    European vestibular experiments on the Spacelab-1 mission: 3. Caloric nystagmus in microgravity (1986)
    Springer
    Experimental brain research 64 (1986), S. 255-263 
    Details
    ISSN: 1432-1106
    Keywords: Caloric stimulation ; Microgravity ; Nystagmus ; Bárány ; Spacelab 1 ; Orbital flight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Response to caloric stimulation was examined in two subjects in the weightless environment of orbital flight. Using air insufflation, a binaural temperature stimulus profile was performed twice on each subject during flight. In all but one test, which was carried out on the first mission day, a caloric nystagmus was registered. This zero-g nystagmus was similar to ground-based pre and postflight responses with regard to its intensity, its temporal correlation with the stimulus profile (nystagmus was always directed towards the warmer ear) and the subjective sensations reported by the tested subjects. These findings demonstrate that mechanisms other than thermoconvection are involved in the elicitation of the caloric nystagmus response. At each stage of the temperature stimulus profile, linear acceleratory stimulation was presented in the form of oscillations in the X-axis. Some differences were found between one-g and zero-g conditions in the resultant modification of the nystagmus response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237741
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