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  • 1
    ISSN: 1432-0568
    Keywords: Kidney ; Mesonephric tubule ; Ontogenesis ; Amphibia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The morphological changes produced in the mesonephric tubule during ontogenesis, not previously reported in amphibians, are described in Rana ridibunda tadpoles using light and electron microscopic methods. The rudimentary nephron units do not develop synchronously along the subperitoneal nephrogenic ridged cord. The first signs of morphogenesis are the presence of round euchromatinic nuclei and mitotic figures. The subsequent developmental stages are characterized by detachment of the rudimentary nephrons from the nephrogenic cord. Renal corpuscle formation is characterized by glomerular expansion, differentiation of large fenestrated capillaries and the presence of a discrete mesangium and a small capsular space. Interstitial capillaries next to the renal corpuscle rudiments appear to induce invagination and differentiation of the capsular epithelium. Developing podocytes were cuboidal undifferentiated epithelial cells with scarce primary processes and with an extensive part of the cell surface lying flat on the glomerular basement membrane. These features reflect low or no glomerular filtration during nephron development. The ciliated neck segment and peritoneal funnels show similar structural features. The latter were not physically connected with the nephrons, but opened into renal blood vessels. Involutive peritoneal funnels were observed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine sponge Dysidea fragilis from El Mar Menor, a hypersaline coastal lagoon (Murcia, Spain), contains the furanosesquiterpenoid ent-furodysinin as the major secondary metabolite. D. fragilis emits a defensive white fluid when it is disturbed. Electron micrographs of this fluid revealed intact vesiculated cells together with other amorphous material. Dissociated cells are more rounded in shape but maintain the same ultrastructural features as cells observed in ultra-thin sections of the whole sponge. The defensive secretion is composed mainly of sponge cells with abundant light vesicles. Sometimes these light vesicles appear to open into the intercellular space; this correlates with surface blebs on these cells observed under scanning electron microscopy. The intracellular location of ent-furodysinin was confirmed by Erlich staining. In laboratory assays, we examined the role of ent-furodysinin as a feeding deterrent to generalist fish predators. It was isolated from D. fragilis and incorporated into a carrageenan-based artificial diet. The addition of ent-furodysinin to the artificial diet reduced feeding by the fish Thalassoma pavo. Similarly, fish did not feed on artificial diet above which defensive secretion of D. fragilis had been ejected with a small syringe.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0003-2670
    Keywords: Fish ; Foods ; Hydride generation ; Lead ; Vegetable ; Water ; Wine
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 677-680 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper deals with the influence of axial microgravity on the stability limits of axisymmetric, cylindrical liquid columns held by capillary forces between two circular, concentric, solid disks. A fair number of experiments have been performed and both the maximum and the minimum volume of liquid that a capillary liquid bridge can withstand have been obtained as a function of the geometry of the liquid bridge and of the value of the axial microgravity acting on it. Experimental results are compared with published theoretical predictions made by other investigators and discrepancies between those results criticized.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2332-2336 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper deals with the dynamics of isothermal, axisymmetric, cylindrical liquid columns held by capillary forces between two circular, concentric, solid disks; in particular, it deals with the dynamic response of the bridge to an excitation consisting of a small change in the value of the microgravity level. The problem has been solved by using a linearized one-dimensional Cosserat model, which includes viscosity effects, and with the axial velocity considered as constant in each section of the liquid bridge. The analysis has been performed by using the Laplace transform, and the time variation of both the axial velocity field and the liquid bridge interface have been obtained.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 2724-2727 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of an isothermal liquid mass of constant properties (density and surface tension) held by capillary forces between two solid disks placed a distance L apart (the so-called liquid bridge model) is considered. For a weightless liquid bridge that is a right circular cylinder, the well-known Rayleigh stability limit holds, and the liquid column becomes unstable when its length is larger than its circumference. Many perturbations from this ideal configuration have been studied in the past, but the supporting disk shape has always been assumed circular. In this Brief Communication the influence of noncircular supports on stability limits of almost cylindrical liquid bridges is analyzed through an asymptotic analysis. Closed form expressions for the stability limits are presented. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 3181-3185 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability limits of nonaxisymmetric liquid bridges between equal in diameter, coaxial disks have been determined experimentally. Experiments have been performed by working with very small size liquid bridges. The experimental setup allows any orientation of the liquid bridge axis with respect to the local gravity vector acceleration. By appropriately orienting the liquid bridge axis, the influence on the stability limits of both the lateral and the axial component of the acceleration acting on the liquid bridge has been investigated. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1110-1130 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the dynamics of axisymmetric liquid columns held by capillary forces between two circular, concentric, solid disks is considered. The problem has been solved by using a one-dimensional model known in the literature as the Cosserat model, which includes viscosity effects, where the axial velocity is considered constant in each section of the liquid bridge. The dynamic response of the bridge to an excitation consisting of a small-amplitude vibration of the supporting disks has been solved by linearizing the Cosserat model. It has been assumed that such excitation is harmonic so that the analysis has been performed in the frequency domain. The particular case of a cylindrical liquid bridge has been analytically studied and the transfer function has been calculated in the cases of oscillation of both disks (either in phase or in counterphase) or only of one of them. The resolution of the general formulation for a noncylindrical liquid bridge has been numerically made by using an implicit finite difference method. In this case, the influence of the volume of the liquid column and of the residual gravity level on the first resonance has been studied, and the results compared, for the inviscid case, with other potential models, both one and three dimensional. To demonstrate the usefulness of this theoretical model in predicting the vibrational behavior of axisymmetric viscous liquid bridges, some experiments have been performed by using the neutral buoyancy technique (also known as the Plateau technique) to simulate reduced gravity conditions, with good agreement between the results of the model and experiments.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Crystal Growth 67 (1984), S. 141-143 
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Crystal Growth 73 (1985), S. 599-608 
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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