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Digitale Medien

Regional reference sites: a method for assessing stream potentials (1986)

Hughes, Robert M. ; Larsen, David P. ; Omernik, James M.

Springer

Environmental management 10 (1986), S. 629-635

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ISSN: 1432-1009

Schlagwort(e): Aquatic ecosystems ; Aquatic ecoregions ; Control sites ; Stream classification ; Land classification ; Water body standards

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract Field assessments of impacted streams require a control or at least an unbiased estimate of attainable conditions. Control sites, such as upstream/downstream or wilderness sites, have proven inadequate for assessing attainable ecological conditions where the control streams differ naturally from the impacted streams to a considerable degree or where different disturbances exist than those being studied. Relatively undisturbed reference sites with watersheds in areas having the same land-surface form, soil, potential natural vegetation, and land use as are predominant in large, relatively homogeneous regions are suggested as alternative control sites. These areas are considered typical of the region and therefore the sites also are considered typical of the region because their watersheds exhibit all the terrestrial variables that make that region a region. The logical basis for developing regional reference sites lies in the ability to group watersheds and common stream types into regions by integrating available maps of terrestrial variables that influence streams. Relatively undisturbed reference sites can be selected from typical areas of the regions and from transition zones where one or two of the terrestrial variables are not the predominant one(s) of the region. These reference sites are useful for estimating attainable conditions, for evaluating temporal and spatial changes in ecological integrity, for classifying attainable uses of streams, and for setting biological and environmental criteria.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01866767

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Digitale Medien

Effects of iron-limitation ofEscherichia coli on growth, the respiratory chains and gallium uptake (1986)

Hubbard, Julia A. M. ; Lewandowska, Krystyna B. ; Hughes, Martin N. ; [weitere]

Springer

Archives of microbiology 146 (1986), S. 80-86

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ISSN: 1432-072X

Schlagwort(e): Iron-limitation ; Escherichia coli ; Respiratory chains ; Cytochromes ; Gallium ; Metal uptake

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The effects of iron limitation on growth, the composition and function of the respiratory chains, and gallium uptake inEscherichia coli have been studied. Decreasing the iron concentration in a defined medium using Chelex resin gave lower growth yields in both continuous culture and prolonged batch culture. In the former, ironlimited (entering [Fe]≤2.0 μM) cells exhibited diminished respiration rates, respiration-driven proton translocation quotients, and levels of non-haem iron and cytochromes. The cellular concentration of haemoproteinb-590 (a cytochromea 1-like hydroperoxidase) decreased 20-fold on iron limitation, whilst a CO-binding pigment with an absorption maximum in the dithionite-treated form near 500 nm appeared. Gallium(III) (9 μM) added to iron-limited, but not iron-sufficient, cultures diminished growth yields further; cells grown with low entering concentrations of iron took up less gallium than iron-sufficient cells. These results are attributed to the interference by gallium(III) with siderophore-mediated metal uptake. Gallium also stimulated iron uptake and was itself accumulated by iron-sufficient cells, suggesting that gallium(III) also affects the iron transport system(s) of low affinity.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00690163

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Optical image quality and the cone mosaic (1986)

A. W. Snyder ; T. R. Bossomaier ; A. Hughes

American Association for the Advancement of Science (AAAS)

In: Science. 231(4737): 499-501.

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Publikationsdatum: 1986-01-31

Beschreibung: Contrary to the orthodox view that optical image quality should "match" the photoreceptor grain, anatomical data from the eyes of various animals suggest that the image quality is significantly superior to the potential resolution of the cone mosaic in most retinal regions. A new theory is presented to explain the existence of this relation and to better appreciate eye design. It predicts that photoreceptors are potentially visible through the natural optics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Snyder, A W -- Bossomaier, T R -- Hughes, A -- New York, N.Y. -- Science. 1986 Jan 31;231(4737):499-501.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3941914" target="_blank"〉PubMed〈/a〉

Schlagwort(e): Animals ; Cats ; Humans ; Models, Neurological ; Photoreceptor Cells/*anatomy & histology ; Rats ; Snakes ; Species Specificity ; *Vision, Ocular ; *Visual Perception

Print ISSN: 0036-8075

Digitale ISSN: 1095-9203

Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik

Publiziert von American Association for the Advancement of Science (AAAS)

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