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  • 1
    Electronic Resource
    Electronic Resource
    Lateral, normal, and longitudinal spring constants of atomic force microscopy cantilevers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2527-2531 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For a V-shaped atomic force microscopy cantilever beam, the spring constants in the three principal directions are given in terms of the beam geometry and material properties. For the lateral stiffness, a closed-formed expression is presented. Also, the normal and the longitudinal stiffness are obtained from a few simple equations. The results are compared with a finite element study and found to be very accurate. All spring constants depend strongly on the cantilever thickness, which is difficult to measure. In addition, the lateral and longitudinal stiffness are sensitive to the location and the height of the attached pyramid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144646
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  • 2
    Electronic Resource
    Electronic Resource
    The equivalent temperature coefficient of resistance of thin film resistor-conductor structures
    Amsterdam : Elsevier
    Thin Solid Films 90 (1982), S. 385-390 
    Details
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0040-6090(82)90538-7
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  • 3
    Electronic Resource
    Electronic Resource
    Sterol-mediated suppression of HMG-CoA reductase mRNA levels in cultured cells requires protein synthesis
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 161 (1989), S. 267-271 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0006-291X(89)91590-8
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  • 4
    Electronic Resource
    Electronic Resource
    Continuous (R)-mandelic acid production in an enzyme membrane reactor (1989)
    Springer
    Applied microbiology and biotechnology 31 (1989), S. 215-222 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The continuous conversion of phenylglyoxylic acid to (R)-mandelic acid was performed in an enzyme membrane reactor with simultaneous coenzyme regeneration employing mandelate dehydrogenase and formate dehydrogenase. A mathematical model of the coupled enzyme reactions was formulated and applied to determine optimal conditions for (R)-mandelic acid production. The experiments and calculations showed that the optimal operational points depend strongly on enzyme kinetics. The individual kinetic parameters determined were appropriate for the description of (R)-mandelic acid production in the simultaneous two-enzyme process. Space time yields of 700 g/(l·day) were obtained at low enzyme consumption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00258398
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of the oxygen supply on pattern of growth and corrinoid and organic acid production of Propionibacterium shermanii (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 732-736 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Propionibacterium shermanii CDB 10014 is able to grow even at high oxygen transfer rates (24.0 mmol O2 l−1 h−1), in contrast to reports in the specialised literature, where all Propionibacteria are considered oxygen-sensitive microorganisms. Propionic acid is the main product in anaerobiosis. The presence of oxygen in the system leads to an inhibition of propionic acid production while acetic acid formation is enhanced. At high oxygen supply rates no propionic acid is produced and acetic acid is the main product. Lactic acid is also produced in reasonable quantities (2.7 g l−1). The growth rate (μmax) is higher in anaerobiosis (0.19 h−1) than in aerobiosis (0.12–0.15 h−1). The cell yield is higher in aerobiosis (0.18–0.22 g g−1) than in anaerobiosis (0.14 g g−1) suggesting the oxidative metabolism of glucose by Propionibacterium shermanii CDB 10014. No corrinoid production was detected at oxygen transfer rates of more than 13.6 mmol l−1 h−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051239
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of Chironomus plumosus larvae on ammonium flux and denitrification (measured by the acetylene blockage- and the isotope pairing-technique) in eutrophic lake sediment (1997)
    Springer
    Hydrobiologia 346 (1997), S. 157-168 
    Details
    ISSN: 1573-5117
    Keywords: Ammonium ; denitrification ; lake ; sediment ; bioturbation ; Chironomus plumosus ; isotope pairing ; acetylene blockage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oxygen uptake, ammonium flux and denitrification were determined insediment from a eutrophic lake in southern Sweden. Part of the sediment wasbioturbated by incubation in a laboratory mesocosm by incubation containing2000 tube-dwelling larvae of Chironomus plumosus L. m−2.Oxygen consumption was increased 2-fold in the bioturbated compared with thenonbioturbated sediment, some 20% of the increase could be explainedby chironomid respiration. There was a net release of ammonium from thebioturbated sediment to the overlying water. Only 11–45% ofthis could be explained on the basis of larval excretion. With increasingnitrate concentration, denitrification of the nitrate coming from the water(dw) increased to a greater extent in the bioturbated than in thenon-bioturbated sediment, whereas denitrification of the nitrate from thecoupled nitrification-denitrification (dn) was unaffected. The acetyleneblockage technique underestimated denitrification by 63–88%compared with the nitrogen isotope pairing technique. The results indicatethat bioturbation by tube-dwelling chironomid larvae can have a major impacton the nitrogen turnover in lake sediment, mobilising the ammonium to thewater and stimulating denitrification by reducing the diffusive barrierblocking nitrate from reaching anoxic zones in the sediment. Under theaerobic conditions under which the experiments were conducted, thebioturbated eutrophic sediment acted as a more pronounced sink for inorganicnitrogen compared with the non-bioturbated sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002974201570
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  • 7
    Electronic Resource
    Electronic Resource
    Bioavailability and sources of DOC and DON in macrophyte stands of a tropical coastal lake (2000)
    Springer
    Hydrobiologia 436 (2000), S. 241-248 
    Details
    ISSN: 1573-5117
    Keywords: DOC ; DON ; microbial utilization ; tropical lake ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dissolved organic carbon (DOC) and nitrogen (DON) derived from aquatic and terrestrial vascular plants provide a major energy and nutrient source for freshwater and coastal marine biota. The bioavailability of this material may to a large extent depend on plant species. In this study, we have compared the bioavailability of DOC and DON sampled in two distinct stands of Typha domingensisand Eleocharis mutatain a coastal tropical lake and in the adjacent ocean in the state of Rio de Janeiro, Brazil. Bioavailability of organic matter was assessed by regrowth bioassays using natural bacterial inocula. Nutrients were added to achieve carbon or nitrogen limitation. At all sampling sites, DON comprised over 95% of the total bioavailable nitrogen, suggesting its dominant role as a nitrogen source. The bioavailability of lacustrine DON (22% in the Typhastand and 34% in the Eleocharisstand) exceeded the bioavailability of DOC (8 and 10%, respectively) and exhibited a larger difference between the stands. 3H-leucine incorporation studies showed that lake bacterioplankton had a well balanced supply of C, N and P. Therefore, an accumulation of labile DON due to an excess nitrogen supply is not probable. We propose that a substantial part of the lake DON was newly formed within the macrophyte stands, while DOC was predominantly of terrestrial origin and more diagenetically changed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026537905947
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  • 8
    Electronic Resource
    Electronic Resource
    Impact of cyprinid reduction on the benthic macroinvertebrate community and implications for increased nitrogen retention (1999)
    Springer
    Hydrobiologia 404 (1999), S. 99-112 
    Details
    ISSN: 1573-5117
    Keywords: benthic macroinvertebrates ; fish reduction ; biomanipulation ; bioturbation ; nutrient retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The benthic macroinvertebrate community in a severely eutrophicated South Swedish lake, Lake Ringsjön, was found to re-establish after the lake was subjected to a substantial reduction of cyprinids (mainly bream and roach). Being totally dominated by chironomids and oligochaetes during the 1980s, the lake became repopulated by groups like Amphipoda, Ephemeroptera, Coleoptera and Mollusca after the fish reduction in 1988–1992. These groups appeared in numbers similar to that found in 1969, before the lake entered its worst stage of eutrophication. The re-establishment of the invertebrates mainly occurred in the littoral parts of the lake. The profundal community was still dominated by chironomids and oligochaetes after the fish reduction. The increase in numbers of benthic macroinvertebrates in the littoral zone of the lake was likely an effect of lowered predation pressure from fish. The potential role of an increased macroinvertebrate abundance due to fish removal and its effects on recirculation of nutrients over the sediment–water interface is discussed. It was observed that average total nitrogen retention in Lake Ringsjön before and after the reduction was 59±5% and 82±15%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003772529654
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  • 9
    Electronic Resource
    Electronic Resource
    Impact of cyprinid reduction on the benthic macroinvertebrate community and implications for increased nitrogen retention (1999)
    Springer
    Hydrobiologia 404 (1999), S. 99-112 
    Details
    ISSN: 1573-5117
    Keywords: benthic macroinvertebrates ; fish reduction ; biomanipulation ; bioturbation ; nutrient retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The benthic macroinvertebrate community in a severely eutrophicated South Swedish lake, Lake Ringsjön, was found to re-establish after the lake was subjected to a substantial reduction of cyprinids (mainly bream and roach). Being totally dominated by chironomids and oligochaetes during the 1980s, the lake became repopulated by groups like Amphipoda, Ephemeroptera, Coleoptera and Mollusca after the fish reduction in 1988–1992. These groups appeared in numbers similar to that found in 1969, before the lake entered its worst stage of eutrophication. The re-establishment of the invertebrates mainly occurred in the littoral parts of the lake. The profundal community was still dominated by chironomids and oligochaetes after the fish reduction. The increase in numbers of benthic macroinvertebrates in the littoral zone of the lake was likely an effect of lowered predation pressure from fish. The potential role of an increased macroinvertebrate abundance due to fish removal and its effects on recirculation of nutrients over the sediment–water interface is discussed. It was observed that average total nitrogen retention in Lake Ringsjön before and after the reduction was 59±5% and 82±15%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003772529654
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  • 10
    Electronic Resource
    Electronic Resource
    The radii inversion problem associated with the Hg capillary pressure experiment (1994)
    Springer
    Transport in porous media 14 (1994), S. 33-72 
    Details
    ISSN: 1573-1634
    Keywords: Inversion ; radii frequency ranges ; geometrically modelled pore space ; continuous radii distribution ; structural hysteresis ; contact angle hysteresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Today's practice of interpreting Hg capillary pressure curves — a widespread method in porosimetry — is generally unsatisfactory. This has already been demonstrated by Fatt. First, the saturation branch of such a curve is interpreted using the concept of a pore space model in which essential features of a network structure are disregarded. Second, the data provided by the desaturation branch are not used. Distributions of radii of capillaries within porous materials derived by this technique are usually incorrect in that the frequencies of occurrence of the greater radii turn out too small, those of the smaller radii too large. We present a more reliable approach which constrains radii frequency ranges for the Hg saturated pore space and for both the part of the pore space that desaturates and the part that traps mercury when Hg pressure is released. The pore space may be of an arbitrary geometrical structure, the radii distribution may be continuous. Also, the Hg desaturation may enable one to distinguish experimentally between structural and contact angle hysteresis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617027
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