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- Brussaard, Lijbert, et al.
(author)
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Biodiversity and ecosystem functioning in soil
- 1997
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In: Ambio: a Journal of Human Environment. - 0044-7447. ; 26:8, s. 563-570
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Journal article (peer-reviewed)abstract
- We review the current knowledge on biodiversity in soils, its role in ecosystem processes, its importance for human purposes, and its resilience against stress and disturbance. The number of existing species is vastly higher than the number described, even in the macroscopically visible taxa, and biogeographical syntheses are largely lacking. A major effort in taxonomy and the training of a new generation of systematists is imperative. This effort has to be focussed on the groups of soil organisms that, to the best of our knowledge, play key roles in ecosystem functioning. To identify such groups, spheres of influence (SOI) of soil biota - such as the root biota, the shredders of organic matter and the soil bioturbators - are recognized that presumably control ecosystem processes, for example, through interactions with plants. Within those SOI, functional groups of soil organisms are recognized. Research questions of the highest urgency are the assignment of species to functional groups and determining the redundancy of species within functional groups. These priorities follow from the need to address the extent of any loss of functioning in soils, associated with intensive agriculture, forest disturbance, pollution of the environment, and global environmental change. The soil biota considered at present to be most at risk are species-poor functional groups among macrofaunal shredders of organic matter, bioturbators of soil, specialized bacteria like nitrifiers and nitrogen fixers, and fungiforming mycorrhizas. An experimental approach in addressing these research priorities is needed, using longterm and large-scale field experiments and modern methods of geostatistics and geographic information systems.
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| 15. |
- Folmer, BM, et al.
(author)
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The physicochemical behavior of phytosterol ethoxylates
- 1999
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In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 213, s. 112-120
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Journal article (peer-reviewed)abstract
- In this work the physicochemical behavior of a series of phytosterol ethoxylates in water is presented. The influence of the length of the polyoxyethylene chain is studied. The surfactant solutions have been examined by means of birifringent microscopy, surface tension, self diffusion 1H-NMR, dynamic and static light scattering, and rheology. The surfactants with a hydrophilic chain of 10 oxyethylene units or more gave a micellar region. The CMC values were generally very low and a reverse relationship between the CMC value and the polyoxyethylene chain length was obtained. The time required to reach equilibrium surface tension was very long, more then 150 minutes. For the hydrophobic surfactants large lamellar regions appeared while for the more hydrophilic surfactants cubic and hexagonal structures were present which remained stable up to temperatures of 100°C. In the micellar region prolate aggregates were formed which showed 'ghostlike' behavior, consisting of crossliked micelles with very fast relaxation times.
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| 16. |
- Folmer, BM, et al.
(author)
-
The physicochemical behavior of phytosterol ethoxylates
- 1999
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In: JOURNAL OF COLLOID AND INTERFACE SCIENCE. - : ACADEMIC PRESS INC. - 0021-9797. ; 213:1, s. 112-120
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Journal article (other academic/artistic)abstract
- In this work the physicochemical behavior of a series of phytosterol ethoxylates in water is presented. The influence of the length of the polyoxyethylene chain is studied. The surfactant solutions have been examined by means of birefringent microscopy, s
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| 17. |
- Hagell, Peter, et al.
(author)
-
Sequential bilateral transplantation in Parkinson's disease: effects of the second graft
- 1999
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In: Brain. - : Oxford University Press (OUP). - 1460-2156. ; 122:6, s. 1121-1132
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Journal article (peer-reviewed)abstract
- Five parkinsonian patients who had received implants of human embryonic mesencephalic tissue unilaterally in the striatum 10-56 months earlier were grafted with tissue from four to eight donors into the putamen (four patients) or the putamen plus the caudate nucleus (one patient) on the other side, and were followed for 18-24 months. After 12-18 months, PET showed a mean 85% increase in 6-L-[18F]fluorodopa uptake in the putamen with the second graft, whereas there was no significant further change in the previously transplanted putamen. Two patients exhibited marked additional improvements after their second graft: 'on-off' fluctuations virtually disappeared, movement speed increased, and L-dopa could be withdrawn in one patient and reduced by 70% in the other. The improvement in one patient was moderate. Two patients with atypical features, who responded poorly to the first graft, worsened following the second transplantation. These findings indicate that sequential transplantation in patients does not compromise the survival and function of either the first or the second graft. Moreover, putamen grafts that restore fluorodopa uptake to normal levels can give improvements of major therapeutic value.
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