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  • Immunocytochemistry  (1)
  • Key words. Defocusing instabilities, homoclinic orbits, coupling instabilities, integrable pdes, birefringent fibers  (1)
  • numerical simulation  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of nonlinear science 10 (2000), S. 291-331 
    ISSN: 1432-1467
    Schlagwort(e): Key words. Defocusing instabilities, homoclinic orbits, coupling instabilities, integrable pdes, birefringent fibers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: nonfocusing instabilities that exist independently of the well-known modulational instability of the focusing NLS equation. The focusing versus defocusing behavior of scalar NLS fields is a well-known model for the corresponding behavior of pulse transmission in optical fibers in the anomalous (focusing) versus normal (defocusing) dispersion regime [19], [20]. For fibers with birefringence (induced by an asymmetry in the cross section), the scalar NLS fields for two orthogonal polarization modes couple nonlinearly [26]. Experiments by Rothenberg [32], [33] have demonstrated a new type of modulational instability in a birefringent normal dispersion fiber, and he proposes this cross-phase coupling instability as a mechanism for the generation of ultrafast, terahertz optical oscillations. In this paper the nonfocusing plane wave instability in an integrable coupled nonlinear Schrödinger (CNLS) partial differential equation system is contrasted with the focusing instability from two perspectives: traditional linearized stability analysis and integrable methods based on periodic inverse spectral theory. The latter approach is a crucial first step toward a nonlinear , nonlocal understanding of this new optical instability analogous to that developed for the focusing modulational instability of the sine-Gordon equations by Ercolani, Forest, and McLaughlin [13], [14], [15], [17] and the scalar NLS equation by Tracy, Chen, and Lee [36], [37], Forest and Lee [18], and McLaughlin, Li, and Overman [23], [24].
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of nonlinear science 3 (1993), S. 393-426 
    ISSN: 1432-1467
    Schlagwort(e): nearly integrable PDE ; nonlinear modes ; modulation equations ; numerical simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: Summary The purpose of this paper is the derivation of reduced, finite-dimensional dynamical systems that govern the near-integrable modulations ofN-phase, spatially periodic, integrable wavetrains. The small parameter in this perturbation theory is the size of the nonintegrable perturbation in the equation, rather than the amplitude of the solution, which is arbitrary. Therefore, these reduced equations locally approximate strongly nonlinear behavior of the nearly integrable PDE. The derivation we present relies heavily on the integrability of the underlying PDE and applies, in general, to anyN-phase periodic wavetrain. For specific applications, however, a numerical pretest is applied to fix the truncation orderN. We present one example of the reduction philosophy with the damped, driven sine-Gordon system and summarize our present progress toward application of the modulation equations to this numerical study.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 235 (1984), S. 159-169 
    ISSN: 1432-0878
    Schlagwort(e): Anterior pituitary ; Gonadotropic cells ; Immunocytochemistry ; Testosterone binding ; Cryo-ultramicrotomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Several attempts have been made to localize steroids by means of immunocytological techniques. However, these methods were found inadequate for detecting steroids bound to their receptors. To localize endogenous testosterone (T) in its target cells at the ultrastructural level, an immunocytological technique was performed on ultrathin sections obtained by cryo-ultramicrotomy. T was detected in the pituitary glands obtained from intact male or female rats and castrated rats, but not in castrated + adrenalectomized rats. Animals were also injected either with testosterone, with other steroids (estradiol, progesterone, corticosterone) or with an androgen antagonist (cyproterone acetate). In addition, some ultrathin sections were preincubated either with phosphate buffers of various pH, corticosterone, cyproterone acetate solution, or with T solution. The content of T in the pituitary before and after fixation was measured by radioimmunoassay; it decreased after fixation. T immunoreactivity was localized in the gonadotropic cells only, both in the male and female rats. At the subcellular level, the immunoreactivity was detected in the cytoplasmic matrix and in the nucleus. Immunoreactive T disappeared 1) in rats after castration+adrenalectomy; by means of radioimmunoassay no T was measured in these pituitary glands; 2) in rats injected with 25 (μg/rat of cyproterone acetate; 3) after preincubation of pituitary sections on a drop of cyproterone acetate (1 × 10-6 M). The immunocytological reaction was not modified when the rats were injected with estradiol, progesterone or corticosterone (1 mg/rat), or after preincubation of the sections with corticosterone (1 × 10-3 M), or a buffer solution at pH 7.6. Lower or higher pH values led to a strong decrease in the immunoreactivity. After injection of T (15 μg/rat) the immunocytological reaction was more abundant in the nucleus and less in the cytoplasm. The immunoreactivity was again observed when the sections were preincubated with cyproterone acetate solution and then with T solution. These data suggest that T can be detected by means of immunocytochemistry. It is probably bound to a specific binding site.
    Materialart: Digitale Medien
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