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- Aspegren, H., et al.
(författare)
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The Urban Water System - a Future Swedish Perspective
- 1997
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Ingår i: Water Science and Technology. - 0273-1223. ; 35:9, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- It is argued, that the use of water can no longer be regarded as an almost free commodity. The idea to assess and value the environmental impact of the water use represents a true change of paradigm. The key issue is that any future wastewater treatment system has to be evaluated according to a quantitative criterion. This has to consider: •hygienic aspects: we believe that nobody will accept a lower hygienic standard than today. •environmental impact: the wastewater impact on the environment has steadily increased the need for better treatment. We need to be prepared for changes in the society by having a readiness manifested as continuing dynamic research environment in this area. Too often the knowledge build-up has been re-active instead of pro-active. •economising resources: wastewater treatment looks and probably should look quite different in densely populated urban areas and in rural areas. Considering resource handling one has to consider already invested capital costs, land use, water re-use, organic and nutrient use and re-use, as well as overall use of energy. •user aspects: technical functionality, economy and liability in different aspects require profound consideration. A sustainable wastewater treatment has to adapt to a local environment and the total resource demand has to be calculated, including a direct environmental impact on receiving waters, air and soil as well as energy consumption and nutrient recycling. Thus, there is an apparent need for. •quantitative performance index: the quest for sustainable development has to be based on objective reasons as well as subjective ones. An integrated performance index is part of a necessary decision making model for the design and operation of wastewater treatment systems. In this index, it is evident that a trade-off should be made between the pursued quality of the process outputs (liquid, solids, gas) and the associated efforts (investments, operation) required to achieve this considering the inputs (wastewater). In order to make this trade-off, however, a common framework is needed to quantitatively compare the different objectives. A metric to judge the sustainability of different options will facilitate a fruitful dialogue between e.g. politicians, ecologists, engineers and economists. Only a truly interdisciplinary approach can help to solve the challenges ahead.
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- Bergh, Gösta, et al.
(författare)
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Altered expression of the retinoblastoma tumor-suppressor gene in leukemic cell lines inhibits induction of differentiation but not G1-accumulation
- 1997
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Ingår i: Blood. - 1528-0020. ; 89:8, s. 2938-2950
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Tidskriftsartikel (refereegranskat)abstract
- The retinoblastoma tumor-suppressor gene, RB, has been implicated in tumor suppression, in regulation of the cell cycle, and in mediating cell differentiation. RB is necessary for hematopoiesis in mice, and aberrant RB-expression is associated with the progress and prognosis of leukemia. We have used antisense oligonucleotides, established clones stably expressing an antisense RB construct, and also established clones over expressing the retinoblastoma protein (pRb) to study the role of RB expression in monocytic differentiation induced by all-trans retinoic acid (ATRA) or 1-alpha-25-dihyroxycholecalciferol (Vit D3) in the monoblastic cell line U-937 and erythroid differentiation induced by transforming growth factor beta1 (TGFbeta1) and hemin in the erythroleukemic cell line K562. A reduction in pRb production in antisense RB-transfected U-937 clones was shown. Antisense oligonucleotides as well as expression of the antisense RB construct suppressed differentiation responses to ATRA or Vit D3, as judged by the capability to reduce nitro blue tetrazolium, by the appearance of monocyte-related cell surface antigens and by morphologic criteria. K562 cells showed decreased differentiation response to TGFbeta1, but not to hemin, when incubated with antisense oligonucleotides. U-937 antisense RB-transfected cells were also suppressed in their ability to upregulate levels of hypophosphorylated pRb when induced to differentiate. Although U-937 cells incubated with antisense oligonucleotides and clones expressing the antisense RB construct were hampered in their ability to differentiate on incubation with ATRA or Vit D3, the induced G0/G1-accumulation was similar to differentiating control cells treated with ATRA or Vit D3. Intriguingly, U-937 clones overexpressing RB were also inhibited in their differentiation response to ATRA or Vit D3 but not inhibited in their ability to respond with G0/G1 accumulation when induced with these substances. The results indicate that pRb plays a role in induced differentiation of U-937 cells as well as K562 cells involving mechanisms that, at least partially, are distinct from those inducing G1 accumulation.
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- Diehl, Stefan, et al.
(författare)
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Analytical and numerical description of the settling process in the activated sludge operation
- 1990
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Ingår i: Instrumentation, control, and automation of water and wastewater treatment and transport systems : proceedings of the 5th IAWPRC Workshop held in Yokohama and Kyoto, Japan, 26 July-3 August 1990. - 0080407765 ; , s. 471-478
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Konferensbidrag (refereegranskat)abstract
- The secondary clarifier or settler is crucial for the whole activated sludge operation. Consequently, it is important to obtain a reliable analytical model as well as a useful numerical method, which can be used in the automatic control of the settling process. Discontinuities (shocks) appear physically, and an analytical description as well as a stable numerical algorithm must be able to handle these discontinuities. A model based on the Kynch theory of sedimentation is used, where the settling flux is a function only of the local concentration and is assumed to have one inflexion point. For such non-convex flux functions, the settling process is qualitatively the same, independent of further assumptions on the shapes of the settling functions. Using the theory of nonlinear conservation laws, the main results obtained are: how to calculate transient and asymptotic behavior; how to control the concentration profile of the settler, in particular the depth of the sludge blanket, for a given load; and, a numerical algorithm which automatically preserves shocks and gives the physically correct solution according to the analytical treatment. The algorithm can be applied on any flux function (with more than one inflexion point).
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