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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 8 (1973), S. 299-307 
    ISSN: 1572-9613
    Keywords: Statistical thermodynamics of curved boundary layers ; scaled particle theory ; equation of state ; cycle equation ; fluid-solid phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermodynamics of curved boundary layers, with the assumption that the distance between the surface of a fluid cavity and its surface of tension is a quadratic function of the cavity radius, is applied to the exact thermo-dynamic expression forG, the central function of scaled particle theory. The coefficients in the quadratic representation are determined so as to satisfyall five of the known exact conditions onG valid for cavity radii between one-half and one molecular diameter. The results of the calculation are displayed as the hard-sphere equation of state, the boundary tension associated with the surface of tension, and the distance between the cavity surface and the surface of tension. Although the hard-sphere equation of state obtained by this method using all five conditions onG is more accurate than in the case where only two or three conditions are used, the original scaled particle theory, in whichG itself was represented simply by a quadratic function of inverse powers of cavity radius, still yields the more accurate equation of state. Nevertheless, the present approach limits approximations to the distance between the cavity surface and the surface of tension, a small quantity in itself. The path to a still more improved theory remains well defined, contingent upon the discovery of additional exact conditions, and does not depend, as in the original scaled particle theory, on a form forG arrived at in a somewhat ad hoc manner.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Calcium distribution ; CTC fluorescence ; Najas pollen ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The distribution of membrane-associated calcium was investigated in pollen grains and tubes of the underwater pollinated angiospermNajas marina L. using chlorotetracycline (CTC). Tubes grown in distilled water (pH 6) showed the highest fluorescence in a subapical region that tapered basally into a fluorescent strand centrally located in the tube and extending back towards the pollen grain. The apical cap had low fluorescence as did the cytoplasm surrounding the fluorescent strand, the tube base and the pollen grain. Tubes grown in different pond waters (pH 8) revealed no intracellular CTC fluorescence. Instead there was an external fluorescence forming a distinct layer around the whole tube, frequently enhanced in a subapical region to form an external collar. Modification of the patterns of fluorescence could be induced by manipulation pH of the growth media and content of specific ions. For example tubes grown in distilled water with 10−3 M Mg2+ salts showed a similar CTC fluorescence as those grown in pond water. In contrast, Ca2+ enrichment had no visible influence on the patterns of fluorescence. The pattern of fluorescence displayed by tubes grown in distilled water, could be reproduced in pond water if the pH was artificially reduced to pH 6. Ultrastructurally, there was no detectable difference in the markedly polar distribution of organelles between pollen tubes grown in the various growth media. The secretory vesicles found in the pollen grain prior to germination become distributed throughout the pollen tube but are least concentrated in regions that show highest internal CTC fluorescence. These regions appear to have large amounts of endoplasmic reticulum and include mitochondria. These results are discussed in relation to the significance of calcium gradients for tip growth and limitations in the use of CTC.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1615-6102
    Keywords: Funaria protonema ; Tip growth ; Cellulose fibril formation ; Particle rosettes ; Plasma membrane ; Incorporation kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary ComparingFunaria protonema tip cells of different age and of experimentally modified growth rate (by changing the light-dark-regime, by application of colchicine and of D2O and by plasmolysis) we found that the site and intensity of growth are related closely to the distribution and frequency of particle rosettes in the PF of the plasma membrane. The results confirm previous suggestions that the rosettes are involved in cellulose fibril formation and that they have a rather short life time (about 10–15 minutes,Reiss et al. 1984). The appearance of rosettes seems to depend on the exocytosis of Golgi vesicle containing wall matrix material. Morphometric calculations suggest that each Golgi vesicle may incorporate one rosette into the plasmalemma in caulonema tip cells.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 144 (1988), S. 101-109 
    ISSN: 1615-6102
    Keywords: Lead toxicity ; Lilium ; Microtubules ; Pollen tubes ; Tip growth ; Triethyl lead
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pollen tubes ofLilium longiflorum growingin vitro were treated for 1 h with inorganic lead (Pb) and with triethyl lead (TriEL) and studied by light and electron microscopy. Pb was considerably more toxic in relation to inhibition of pollen tube growth (EC50=6 μM Pb) than was TriEL (EC50=60 μM TriEL). On the other hand, at almost the entire concentration range tested (25-500 μM) TriEL caused aberrant tubes and tube swellings. Pb did not cause tube swellings, even at highly growth-impairing concentrations. Pb (60 μM) predominantly affected the ultrastructure of the growing cell walls without impairing the distribution of the cell organelles in the tube tips. In contrast, 50 and 100 μM TriEL did not visibly influence cell wall ultrastructure but it severely damaged dictyosomes; 100 μM TriEL also disturbed the original order of cell organelles in the tube tips. Cortical microtubules were selectively and completely destructed by TriEL at concentrations (50 μM) where no effect on polar organization of the tube tips occurred but they remained unimpaired by 60 μM Pb, indicating selective and effective interaction of TriEL with these cell organelles.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 185 (1995), S. 113-122 
    ISSN: 1615-6102
    Keywords: Cell wall ; Heavy metals ; Lilium ; Pollen tube ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The influence of different concentrations of the heavy metals cadmium (Cd2+), cobalt (Co2+), copper (Cu2+), iron (Fe2+ and Fe3+), mercury (Hg2+), manganese (Mn2+), and zinc (Zn2+), plus aluminium (Al3+) (a toxic metal in polluted areas), on pollen germination and tube growth ofLilium longiflorum was investigated using light microscopy. Effects could be observed with 3 μM and 100 μM of heavy metal, added as chloride salts to the medium. Cd2+, Cu2+, and Hg2+, showed the greatest toxicity, whereas germination and growth rate was less affected by Mn2+. Affected tubes showed swelling of the tip region. Tubes treated with Cd2+, Co2+, Fe2+, Fe3+, Hg2+, and Mn2+ were also prepared for ultrastructural studies. In all cases, the main effect was abnormal cell wall organization, mostly at the tip, where round, fibrillar aggregates, the shape and size of secretory Golgi vesicles were formed. They built up a loose network which could be up to 10 μm thick compared to untreated tubes where the cell wall was composed of thin layers of long fibrils and about 100 nm thick. Cd2+ was the only metal which produced effects at the intracellular level: organelle distribution within the tip region appeared disorganized. A general mechanism of heavy metal action on pollen tube growth is discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 3 (1971), S. 69-86 
    ISSN: 1572-9613
    Keywords: Protein ; helix-coil transition ; thermoelastic properties ; statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effect of stress on the helix-coil transition in a protein or polypeptide is investigated using the methods of statistical mechanics. A case is treated in which the helical sections are regarded as flexible chains withvery long, freely “orienting” segments and another in which they are considered to be rigid rods. Thermoelastic relations are derived; and it turns out that, depending upon conditions, stress can induce the helix-coil transition in one or another direction or do nothing at all. The most probable situations either involve stress applied to a molecule initially helical, in which case the helix is stabilized, or stress applied to the coil form, in which case transformation to the helical form is induced. The helical form exhibits a very low modulus of elasticity (which we also compute), and it is speculated that preservation of, or transition to, the helical form under stress aids in the protection of living tissue from disruption when subjected to large applied strain. Real tissues involve highly organized or quasirandom networks of protein chains. The results of this analysis suggest that, insofar as the mechanical properties of the networks are concerned, the chains can be treated as quasiharmonic strings whose configurations (weighted by potential energy) can be enumerated in order to include entropy effects in the calculation of the network modulus.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 3 (1971), S. 191-210 
    ISSN: 1572-9613
    Keywords: Information theory ; coding ; statistical mechanics ; ensembles ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This is the first of several papers dealing with the application of statistical thermodynamic methodology to the solution of coding and communication theory problems. Emphasis is placed on the various “ensemble techniques” of statistical mechanics, the words or “samples” of a message taking the place of molecules in the prototype physical system. Analogs of temperature, internal energy, pressure, chemical potential, volume, entropy, etc., are developed. The isomorphism with thermodynamics is complete and these quantities transform (for example, by partial differentiation) in exactly the same way as the prototype physical quantities. The methods are nicely applicable to coding cases involving sources with memory, in which case, correlation can be discussed in terms of analog “coupling energies” between signals or words so that the store of “many-body-problem” techniques can be used. In addition, the manipulative freedom stemming from the possibility of choosing from a multiplicity of ensembles constrained by “intensive” parameters proves a distinct advantage. A concrete example dealing with the choice of a compact code for a nonextended source with memory is presented. The compact code is derived, and some discussion is given concerning the breadth of its power spectrum. In a following paper, its autocorrelation function within the framework of “pulse code modulation” is derived and transformed by Wiener theory so that the power spectrum is directly exhibited (along with the spectra for several other cases).
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 3 (1971), S. 261-289 
    ISSN: 1572-9613
    Keywords: Pulse code modulation ; transmission time ; bandwidth ; statistical mechanics ; power spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Employing the “statistical thermodynamic formalism” developed in an earlier paper, it is possible to determine “compact” sets of transmission times for the words of PCM (pulse code modulation) messages. In particular, we deal with pulses of zero or unit heights. These compact signals, which lead to shorter message times and eliminate redundancy even when successive words are correlated (Markov source), may, however, require additional bandwidth. We examine two simple cases where autocorrelation functions, and therefore power spectra, can be evaluated. In one case, that of the Markov source, it proves possible to accomplishboth shorter transmission time and narrower bandwidth (half-width of the power spectrum), showing that optimization of transmission times can be very worthwhile. Techniques for deriving autocorrelation functions are discussed at length.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 7 (1973), S. 143-159 
    ISSN: 1572-9613
    Keywords: Statistical thermodynamics of curved boundary layers ; scaledparticle theory ; equation of state ; cycle equation ; fluid-solid phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermodynamics of curved boundary layers is combined with scaled particle theory to determine the rigid-sphere equation of state. In particular, the boundary analog of the Gibbs-Tolman-Koenig-Buff equation is solved for a rigid-sphere fluid, using the approximation that the distance between the surface of a cavity and its surface of tension is a function of the density only (the first-order approximation). This, in conjunction with several exact conditions onG, the central function of scaled particle theory, leads to an approximate rigid-sphere fluid equation of state and a qualitatively correct rigid-sphere solid equation of state. The fluid isotherm compares favorably with previous results (2.9 % error in the fourth virial coefficient), but due to the inaccuracy of the solid isotherm, no phase transition is obtained. The theory described here is to be contrasted with previous approaches in that a less arbitrary functional form forG is assumed, and the surface of tension and cavity surface are not assumed to be coincident. The “cycle equation” of Reiss and Tully-Smith is rederived by a simpler route and shown to be correct to all orders of cavity curvature, rather than only first order as was originally thought. A new exact condition, obtained from the compressibility equation of state, is used as a boundary condition for the “cycle equation” to determine the location of the equimolecular surface. This molecular calculation compares favorably (discrepancy of 〈2 %) with a thermodynamic calculation based on the boundary analog of the Gibbs adsorption equation and indicates the accuracy and consistency of the first-order approximation.
    Type of Medium: Electronic Resource
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