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  • 1
    Digitale Medien
    Digitale Medien
    ‘Sub-Grains’ and Etch Figures in Lead (1958)
    [s.l.] : Nature Publishing Group
    Nature 181 (1958), S. 180-181 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Specimens of unalloyed lead which were given the same etching treatment were found to show this structure over their entire surfaces even in cast material, and modifications in straining and annealing procedure did not produce changes in sub-grain dimensions. Repeatedly re-etching the same area of ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/181180b0
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  • 2
    Digitale Medien
    Digitale Medien
    Antiviral optically pure dioxolane purine nucleosides analogues
    Amsterdam : Elsevier
    Bioorganic & Medicinal Chemistry Letters 3 (1993), S. 1543-1546 
    Details
    ISSN: 0960-894X
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0960-894X(00)80014-1
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  • 3
    Digitale Medien
    Digitale Medien
    Optimal conditions for primary production in a polymictic tropical lake (Lake Xolotlán, Nicaragua) (1998)
    Springer
    Hydrobiologia 382 (1998), S. 1-16 
    Details
    ISSN: 1573-5117
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract From 1987 to 1993 we assessed the variation of phytoplankton biomass, underwater irradiance and primary production in Lake Xolotlán (L. Managua, Nicaragua). Chlorophyll- a averaged 65 mg m-3 and maximum and minimum concentrations were 120 and 30 mg m-3, respectively. The variability over depths and weeks was low (CV 〈 20%). There were strong correlations between particulate carbon and chlorophyll- a (the ratio ≈ 100: 1) and between particulate carbon and particulate nitrogen and phosphorus (the ratio ≈ 100: 11: 1). Gross primary production averaged 6.8 g C m-2 d- 1 and was stable over the years (CV ≈ 10%). Algal cell growth was approximately 4–5 g C m-2 d- 1. Productivity was limited only by the availability of underwater light and the depth of the photic zone was mainly regulated by the chlorophyll- a concentration. Therefore, areal photic zone chlorophyll- a was the only factor directly correlated to the integral photosynthetic activity but, contrary to theoretical models, the production did not increase in proportion to chlorophyll- a. Data from African lakes show a similar pattern.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003271614344
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  • 4
    Digitale Medien
    Digitale Medien
    Phytoplankton community composition in Lake Xolotlán (Managua) (1991)
    Springer
    Aquatic ecology 25 (1991), S. 121-124 
    Details
    ISSN: 1573-5125
    Schlagwort(e): community composition ; phytoplankton ; tropical lake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Results of two years of research on phytoplankton species composition in Lake Xolotlán (Managua) are presented. A summary of the planktonic algae from other Nicaraguan lakes is also included. One hundred and twenty phytoplankton taxa were identified. A list of species and comments about relevant properties of the most frequent taxa are given. The qualitative composition of Lake Xolotlán phytoplankton is compared with that of other tropical waterbodies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02291242
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  • 5
    Digitale Medien
    Digitale Medien
    Phytoplankton biomass in Lake Xolotlán (Managua): Its seasonal and horizontal distribution (1991)
    Springer
    Aquatic ecology 25 (1991), S. 125-131 
    Details
    ISSN: 1573-5125
    Schlagwort(e): biomass ; phytoplankton ; seasonal distribution ; tropical lake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Seasonal changes in the pytoplankton community was studied in Lake Xolotlán (Managua). Cyanophyta were found to be dominant throughout the year. Phytoplankton biomass was estimated by volume (wet weight) and by chlorophyll-a at two localities. Seasonal biomass fluctuations were monthly measured for two years. The lowest annual phytoplankton biomass was observed at the end of the rainy season (October-November), and the highest during the dry period (January–February). Short-term studies (3–14 days) on daily biomass changes were also performed. Significant variations in total biomass over short time spans were detected at both localities. Horizontal distribution of phytoplankton was also determined during 30 months. It proved that the lake was quite homogeneous. The results also revealed a great homogeneity with regard to species composition throughout the year. Biomass was permanently high (15.75±5.89 mg.l−1 wet weight, annual average) in front of Managua city where anthropogenic influence is more immediate, whereas the north central region has a comparatively lower biomass (9.07±2.4 mg.l−). Lake Xolotlán may be considered as hypertrophic, taking into account its high chlorophyll-a concentration (79 μg.l−1 as annual average for 1987–1988).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02291243
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  • 6
    Digitale Medien
    Digitale Medien
    Underwater light penetration, phytoplankton biomass and photosynthetic activity in Lake Xolotlán (Managua) (1991)
    Springer
    Aquatic ecology 25 (1991), S. 137-144 
    Details
    ISSN: 1573-5125
    Schlagwort(e): light penetration ; phytoplankton biomass ; primary productivity ; photosynthesis ; tropical lake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We measured underwater light penetration, phytoplankton biomass and photosynthetic activity during three years (1987–1990) in Lake Xolotlán (L. Managua), Nicaragua. Phytoplankton biomass governed the light climate of the photic zone, but as biomass also was composed of a varying proportion of dead algae, light availability for the potential biomass of actively photosynthesizing algae (170 mg Chl-a.m−2) was reduced. The concentration of chlorophyll-a within the photic zone was thus lower and ranged between 58 and 141 mg Chl-a.m−2. Still, photosynthetic activity was high (2,162 mg 02.m-2.h−1) due to an extremely high specific rate of photosynthesis; light was the only factor that limited growth. As also other conditions in Lake Xolotlán, beside light limitation, met with the requirements of the models that have been used to analyse production and photosynthetic characteristics in tropical lakes there was a striking agreement between observed and predicted values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02291245
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  • 7
    Digitale Medien
    Digitale Medien
    Natural diet of herbivorous zooplankton in Lake Xolotlán (Managua) (1991)
    Springer
    Aquatic ecology 25 (1991), S. 163-167 
    Details
    ISSN: 1573-5125
    Schlagwort(e): zooplankton ; food ; trophic relations ; gut contents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The natural diet of herbivorous zooplankton was analyzed for a better understanding of the trophic relationships in Lake Xolotlán (Managua). Gut content of the most common zooplankton species (Arctodiaptomus dorsalis, Moina micrura andDiaphanosoma fluviatile) were analyzed. The quality and the relative abundance of ingested algae was studied. The most consumed algae during the dry season (February) wereCyclotella, Oocystis andLyngbya, and during the rainy season (November)Cyclotella, Oocystis andChroococcus. The kind of food ingested byA. dorsalis andM. micrura was similar in both periods. There was no similarity with the diet ofD. fluviatile. During the dry season, when algal biomass in the lake was high,A. dorsalis andM. micrura ingested a higher proportion of diatoms. During the rainy season, when food was scarce, the diet was more diverse and bluegreen algae (Chroococcus) were ingested in a larger proportion.Diaphanosoma fluviatile ingested predominantly tiny particles (bacteria and detritus) and algal food consisted mainly of green algae (Oocystis) and probably (not studied) nanoplanktonic algae. The results were consistent with those obtained in other lakes, indicating the importance of diatoms and green algae for zooplankton nutrition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02291249
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