ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    The functional responses of two benthic algivorous ciliated protozoa with differing feeding strategies (1996)
    Springer
    Microbial ecology 31 (1996), S. 209-224 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Surface-associated algivorous ciliated protozoa are common in the benthos of streams, but little is known about the feeding ecology of these organisms. We compared the functional responses of two algivorous ciliated protozoa, Oxytricha fallax (a filter feeder) and Trithigmostoma cucullulus (an encounter feeder). The ciliates were fed 14C-labeled Navicula cryptocephala in laboratory feeding experiments to determine their potential to consume significant amounts of algal prey. Logistic regression, and plots of the proportion of N. cryptocephala ingested vs. the total number offered, indicated functional responses of a typical rectangular hyperbolic (type II) form for both ciliates. Ingestion rates were estimated from regressions of the number of 14C-labeled N. cryptocephala cells ingested per ciliate vs. time. Maximum feeding rates and half-saturation concentrations were estimated by fitting the observed ingestion rates and experimental algal densities to a function of the Michaelis-Menten enzyme kinetics form using nonlinear regression. For O. fallax, the maximum feeding rate was estimated to be 1.07 N. cryptocephala cells per minute, and the half-saturation concentration was 3.9 × 102 N. cryptocephala per square centimeter. For T. cucullulus the maximum feeding rate was estimated to be 0.2 N. cryptocephala per minute, and the half-saturation concentration was 5.4 × 103 N. cryptocephala per square centimeter. The data were also fitted using only the number of cells ingested at 60 and 120 min, by converting the endpoint consumption to rates. For O. fallax, the estimated maximum feeding rates were 1.3 and 1.0 N. cryptocephala per minute for 60 and 120 min, respectively, and estimated half-saturation concentrations were 5.1 × 102 and 3.5 × 102 N. cryptocephala per square centimeter. For T. cucullulus, estimated maximum feeding rates were 0.6 and 0.4 N. cryptocephala per minute for 60 and 120 min, respectively, and estimated half-saturation concentrations were 1.5 × 104 and 1.1 × 104 N. cryptocephala per square centimeter. These results suggest that kinetic methods for estimating ingestion rates are more accurate than endpoint determinations. Based on field observations of periphyton densities, these ciliates potentially are consuming 4.8% of the total available standing crop of diatom biomass per day and this could represent up to 16% of total available daily primary production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167866
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Organosilicon compounds. XVIII. Silicon-containing dianhydrides (1973)
    s.l. : American Chemical Society
    The @journal of organic chemistry 38 (1973), S. 4271-4274 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00964a013
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Rapid Toxicity Estimation Using Soil Ciliates: Sensitivity and Bioavailability (1997)
    Springer
    Bulletin of environmental contamination and toxicology 58 (1997), S. 387 -393 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001289900346
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Influence of Trophic Status on the Toxic Effects of a Herbicide: A Microcosm Study (1998)
    Springer
    Archives of environmental contamination and toxicology 35 (1998), S. 404-411 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Naturally derived microbial communities were developed in the laboratory under three nutrient regimes by manipulating phosphate and nitrate concentrations. Resulting communities differed in both functional and structural attributes. Low nutrient microcosms (0.05 mg N-NO3 −/L + 0.01 mg P-PO4 −3/L) showed the sharpest differences. Medium (0.5 mg N-NO3 −/L + 0.1 mg P-PO4 −3/L) and high (5.0 mg N-NO3 −/L + 1.0 mg P-PO4 −3/L) nutrient treatments differed in total algal biomass and algal community composition. After a 25-day acclimation period, a single dose of the herbicide diquat (3.5 mg/L) was added to test the response of the microbial communities to herbicide stress. Regardless of nutrient regime, diquat-dosed microcosms had decreased electron transport system activity (ETSA), an almost complete absence of cyanobacteria, and reduced gross photosynthesis (GP), respiration, and pH relative to undosed microcosms. Inorganic nutrients (PO4 −3, NO3 −) were released from the stressed algal communities, probably as a result of their altered metabolism. Alkaline phosphatase activity (APA), total microbial biomass (estimated as protein), algal biomass (estimated as chlorophyll), and relative abundance of green algal taxa proved highly insensitive to herbicide action. Nutrient treatments had a small influence on toxicant effects; the magnitude of the herbicide effects was comparable across nutrient levels. Only the capacity of recovery from the toxic stress was affected by trophic status. At the end of the study period, ETSA had recovered to control values in high nutrient microcosms but not in medium and low ones. Microcosm pH, and to a lesser extent GP, showed recovery under both high and medium nutrient treatments. Trophic status affected the diquat disappearance rate; the herbicide persisted longer in low nutrient microcosms than in high and medium nutrient ones. Differences in recovery capacity may stem from higher nutrient level microcosms reaching less toxic herbicide levels in a shorter period of time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900395
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Relationship of alkaline stress and acute copper toxicity in the snailGoniobasis livescens (Menke) (1983)
    Springer
    Bulletin of environmental contamination and toxicology 31 (1983), S. 719-726 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606051
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effects of atrazine on freshwater microbial communities (1988)
    Springer
    Archives of environmental contamination and toxicology 17 (1988), S. 449-457 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract A multispecies toxicity test system using naturally derived microbial communities on polyurethane foam substrates was used to evaluate the toxic effects of the herbicide atrazine. Both structural (e.g., protozoan species number, biomass) and functional (e.g., colonization rate, oxygen production) community responses were measured. Oxygen production and the ability of communities to sequester magnesium and calcium were the most sensitive measures of toxic stress due to atrazine (maximum allowable toxicant concentrations [MATCs]=17.9 μg/L). Dissolved oxygen was 33% lower, and there was 15% less calcium and magnesium in communities at and above 32.0 μg/L atrazine compared to controls. Species richness and estimates of biomass (total protein and chlorophyll a) were less sensitive (MATCs=193) to atrazine. At the highest atrazine concentration (337 μg/L), species numbers were 30% lower than controls, and protein and chlorophyll a content of communities were reduced by 38 and 91%, respectively. Low levels of atrazine (3.2–32.0 μg/L) resulted in a 46% increase in species numbers and a greater concentration of total protein and chlorophyll a (41 and 57%, respectively). Results compared well with other estimates of chronic toxicity for effects of atrazine on aquatic communities. Reported MATCs ranged from 70.7 to 3,400 μg/L. The results from this test emphasize the importance of monitoring both structural and functional measures of community integrity in toxicity testing with multispecies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01055510
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Effects of diquat on freshwater microbial communities (1993)
    Springer
    Archives of environmental contamination and toxicology 25 (1993), S. 95-101 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract A static microcosm system was used to evaluate effects of the herbicide diquat (0.3–30 mg/L) on the structure and function of naturally derived microbial communities on polyurethane foam substrates. Microbial communities were exposed to a single application of diquat and were monitored for 21 days. Effects on community structure included changes in algal cell density at diquat concentrations ⩾0.3 mg/L (after an initial decrease in net productivity), bacterial cell density (1 mg/L diquat), and increased biomass accumulation (10 and 30 mg/L diquat). The species richness of protozoa was reduced at diquat concentrations 〉0.3 mg/L; protozoan species composition was progressively more dissimilar with diquat treatment. Effects on community function included inhibition of net productivity and community respiration (10 and 30 mg/L diquat), and decreased enzyme activities [alkaline phosphatase (1, 10, and 30 mg/L diquat), electron transport system (⩾0.3 mg/L diquat), and β-glucosidase (⩾0.3 mg/L diquat)]. Both photosynthetic and nonphotosynthetic organisms were affected by diquat. Most structural and functional responses were sensitive indicators of stress. Estimated chronic toxicity values ranged from 0.3 mg/L (day 3) to 5.5 mg/L (day 21). Most microbial responses indicated that microbial community structure and function did not recover within the 21-day exposure period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230718
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    A review of development and implementation of an active nonlinear vibration absorber (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 585-620 
    Details
    ISSN: 1432-0681
    Keywords: Key words Active feedback control ; nonlinear absorber ; smart structures ; PZT ; Terfenol-D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary We present an account of an implementation of an active nonlinear vibration absorber that we have developed. The control technique exploits the saturation phenomenon that is known to occur in quadratically-coupled multi-degree-of-freedom systems subjected to primary excitation and possessing a two-to-one internal resonance. The technique is based on introducing an absorber and coupling it with the structure through a sensor and an actuator, where the feedback and control signals are quadratic. First, we consider the case of controlling the vibrations of a single-degree-of-freedom system. We develop the equations governing the response of the closed-loop system and use the method of multiple scales to obtain an approximate solution. We investigate the performance of the control strategy by studying its steady-state and transient characteristics. Additionally, we compare the performance of the quadratic absorber with that of a linear absorber. Then, we present theoretical and experimental results that demonstrate the versatility of the technique. We design an electronic circuit to emulate the absorber and use a variety of sensors and actuators to implement the active control strategy. First, we use a motor and a potentiometer to control the vibration of a rigid beam. We develop a plant model that includes Coulomb friction and demonstrate that the closed-loop system exhibits the saturation phenomenon. Second, we extend the strategy to multi-degree-of-freedom systems. We use PZT ceramics and strain gages to suppress vibrations of flexible steel beams when subjected to single- and simultaneous two-mode excitations. Third, we employ Terfenol-D, a nonlinear actuator, and accelerometers to control the vibrations of flexible beams. In all instances, the technique is successful in reducing the response amplitude of the structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050245
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    A comparison of the responses of two microcosm designs to a toxic input of copper (1994)
    Springer
    Hydrobiologia 281 (1994), S. 101-114 
    Details
    ISSN: 1573-5117
    Keywords: microcosms ; copper ; ecotoxicology ; community structure ; community function ; variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two microcosm designs were compared for their sensitivity to toxic concentrations of copper. One design simulated a littoral zone, including macrophytes, sediment, and associated organisms. The other design used a periphyton community collected on polyurethane foam artificial substrata. Microcosms were dosed with copper sulfate (0–300 µg Cu 1−1, nominal concentrations) and monitored for changes in several structural and process variables. Coefficients of variation of responses measured from the littoral microcosms were greater than from responses measured from the artificial-substrata microcosms. Effects were detected more frequently at lower concentrations of copper in the artificial-substrata microcosms than in the littoral microcosms. Lowest observable effect concentrations (LOECs) for measures of community structure ranged from 20.2–42.8 µg Cu 1−1 in the artificial-substrata microcosms and from 24.0–98.5 µg Cu 1−1 in the littoral microcosms. LOECs for measures of community process ranged from 42.8–310.3 µg 1−1 in the artificial substrata microcosms. Significant differences from controls for community process were detected only at 304.7 µg Cu 1−1 in the littoral microcosms. While there were differences between the two microcosm designs in the concentrations of copper that resulted in adverse effects, response trends were similar. Often, dose-response relationships between variables and copper concentrations were not log-linear, but showed stimulations at intermediate concentrations of copper (10–100 µg 1−1, nominal concentrations). The choice of microcosm design should be dependent on the particular research question, as the designs differ in complexity and in the ease of construction and maintenance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006439
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Evaluating soluble toxicants in contaminated soils (1988)
    Springer
    Water, air & soil pollution 37 (1988), S. 293-307 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Complex mixtures of water soluble materials from contaminated soils can move into groundwater and surface water by leaching, percolation, and runoff. We evaluated the potential toxicity of leachable materials from seven soils. Five soil samples were obtained at designated toxic or hazardous waste sites, and two additional soils samples were obtained from a coal storage area and from an agricultural field. Acidified tap water (pH 4.5) was used to extract toxic materials from elution columns filled with soil samples. Extracts were used as complex mixtures to conduct acute toxicity tests using Daphnia and chronic effects tests using aquatic microcosms. Three classes of effects were observed. Three soil leachates showed acute and chronic toxicity at less than 3% leachate. Two of these soils were contaminated by materials used in wood preserving, and the third soil was contaminated with heavy metals and acid. Two soils showed moderate acute toxicity but no chronic toxicity in microcosm tests. One of these soils was contaminated with low levels of chromium while the other soil was from a coal storage area. The remaining two soil samples showed no toxicity in either acute or chronic toxicity tests. One of these soils was from a reference agricultural field while the other soil was contaminated with solvents. The failure to detect toxicity in the solvent contaminated sample was attributed to the hydrophobicity of the toxicity materials. Results of these toxic screenings are in the same range as leachate toxicities estimated using other methods, although other methods use extraction materials that may interfere with some biological tests. Toxicological evaluations of materials from suspected contaminated soil are recommended for prioritizing clean up efforts at waste sites and for determining if toxic materials and contaminated soils have been effectively removed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192942
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...