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  • 1
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 40 (1968), S. 1573-1576 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 83 (1984), S. 231-238 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine planktonic diatom Thalassiosira weisflogii was grown in turbidostat culture under both continuous and 12 hL: 12 hD illumination regimes in order to study the kinetics of adaptation to growth-irradiance levels. In both illumination regimes adaptation to a higher growth-irradiance level was accompanied by an increase in cell division rates and a decrease in chlorophyll a cell-1. The rates of adaptation for both processes, derived from first order kinetic analysis, equaled each other in each experiment. The results suggest that during the transition from low-to-high growth-irradiance levels chlorophyll a is diluted by cell division and is not actively degraded. Introduction of a light/dark cycle lowered the rate of adaptation. In transitions from high-to-low growth-irradiance levels there was a sharp drop in growth rates and a slow increase in chlorophyll a cell-1 under both continuous and intermittent illumination. In the 12 hL:12hD cycle there was a circadian rhythm in chlorophyll a cell-1, where cellular chlorophyll contents increased during the light cycle and decreased during the dark cycle. This circadian rhythm was distinctly different from light intensity adaptation. For kinetic analysis of light intensity adaptation in a 12 hL: 12 hD cycle, the circadian periodicity was separated from the light intensity response by subjecting the data to a Kaiser window optimization digital filter. Kinetic parameters for light-intensity adaptation were resolved from the filtered data. The kinetics of lightintensity adaptation of marine phytoplankton are discussed in relation to their spatial variations and time scales of mixing.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 83 (2000), S. 529-542 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. Schöner [Schöner G (1995) Ecol Psychol 7: 291–314] argued that the relative phase dynamics of rhythmic interlimb coordination may be attributed to the timing level in that the stability properties of the relative phase are largely independent of dynamical principles operating at the goal level, such as those related to the maintenance of a particular amplitude or target position. Yet, according to the coupling functions in the coupled oscillator model proposed by Haken et al. [Haken H, Kelso JAS, Bunz H (1985) Biol Cybern 51: 347–356], the effect of frequency on the stability properties of relative phase is either wholly or partially mediated by frequency-induced changes in amplitude, implying that the relative phase dynamics strongly depends on spatial factors. In order to distinguish between these contrasting interpretations of the organizational principles underwriting the phase dynamics of interlimb coordination, an experiment was conducted in which the effects of frequency and amplitude on the stability of relative phase were separated. Six subjects performed both in-phase and anti-phase coordination patterns at seven different frequencies and three different amplitudes. Two measures of pattern stability were used, the standard deviation of relative phase and the exponent of the relaxation process following phasic perturbations of relative phase. According to both measures, pattern stability decreased with increasing frequency, whereas the amplitude manipulation only had a significant effect on the standard deviation of relative phase. This result was interpreted to imply that the organizational principles at the (relative) timing level are affected only moderately by task constraints pertaining to the goal level, and that models of interlimb coordination in which amplitude coupling plays a partial or subordinate role should be preferred above models relying solely on amplitude coupling.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 149 (1987), S. 19-23 
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Photosynthesis ; Light-shade adaptation ; Reserve polymers ; Carbohydrate accumulation ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cyanobacterium Oscillatoria agardhii was subjected to changes in irradiance and to changes in light period. During transient states parameters as growth rate, pigment contents, photosynthetic activities and pool sizes of carbohydrate and proteins were followed. The changes in pigments and photosynthesis were similar for irradiance transitions and transitions in light period length. Carbohydrates served for the supply of carbon and energy during adaptation to low light conditions until a basal level of 125 μg · mg dry wt-1 was reached. After transfer to high light conditions excess carbon fixation led to the storage of carbohydrate reserve polymers up to 600 μg · mg dry wt-1. During adaptation to longer light periods cells showed an overcapacity for carbohydrate accumulation even in the presence of a high carbohydrate content at the start of the light period. A model for the feed back repression of photosynthesis related to carbohydrate accumulation was presented. In all cases protein synthesis was directly maximized under the given conditions. Growth rate defined as specific rate of change in carbon showed the fastest response after a shift in light conditions. It was concluded that adaptation of O. agardhii to changes in light conditions was directed to the optimization of growth. The observation that carbohydrate is used to supply carbon and/or energy during adaptation leads to the conclusion that changes on survival in low light depend on carbohydrate level, the efficiency of its conversion in cell material and the maintenance requirements. Such a survival strategy enables cyanobacteria to cope succesfully with light limiting conditions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 151 (1989), S. 407-410 
    ISSN: 1432-072X
    Keywords: Cyanobacterium ; Geosmin synthesis ; Isoprenoid pathway ; Oscillatoria brevis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cyanobacterium Oscillatoria brevis (Kütz.) Gom., strain NIVA CYA 7, was used to investigate how geosmin production is related to the synthesis of chlorophyll a, phycobiliproteins and β-carotene under nitrogen (NH 4 + ) and light limiting conditions. Chemostat samples were used to inoculate batch cultures that were treated with inhibitors of isoprenoid synthesis, norflurazon and dimethazone, and gabaculine that inhibits tetrapyrrole synthesis. Dimethazone decreased and norflurazon increased geosmin production under light limited conditions, as was expected due to their sites of action in the isoprenoid pathway. This effect was not so pronounced in nitrogen limited cultures due to the additional effect of increasing nitrogen deficiency during the experimental period. Norflurazon was the only inhibitor that uncoupled geosmin production completely from β-carotene formation which indicates a strikt coupling between geosmin and β-carotene biosynthesis. From the observed increase of geosmin production relative to pigment synthesis after norflurazon treatment it was suggested that isoprenoid precursors are directed to geosmin synthesis when the demand for pigment precursors is very low. Within the framework of this study the data strongly support the hypothesis of geosmin formation via the isoprenoid pathway in Oscillatoria brevis as was found for actinomycetes.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5805-5811 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Scaled particle theory is applied to the prediction of the thermodynamic properties of a system of identical hard spheres adsorbed onto another sphere of different diameter. The finite nature of the system requires modification of the usual boundary conditions on the contact correlation function. The calculated activities of the adsorbate are in good agreement with Monte Carlo simulation results and with exact values for systems of few particles.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0003-2697
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0009-3084
    Keywords: epithelial cells ; non-lamellar lipid phase ; resistance ; tight junctions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0009-3084
    Keywords: bilayer-hexagonal phase transition ; calorimetry ; fluorescence spectroscopy ; non-lamellar lipid phase ; tight junctions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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