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  • Springer  (116)
  • 1990-1994  (102)
  • 1955-1959  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 260 (1990), S. 337-348 
    ISSN: 1432-0878
    Keywords: Pineal organ ; Organ culture ; Pinealocytes ; Differentiation ; Melatonin ; Radioimmunoassay ; Chick embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of sensory structures in the pineal organ of the chick was examined by means of scanning electron microscopy from embryonic day 10 through day 12 post-hatching. At embryonic day 10, the wall of the tubules within the pineal primordium is composed of cells with unspecialized luminal surface. Differentiation of sensory structures starts at embryonic day 12 when pinealocytes and supporting cells can be distinguished. Pinealocytes are recognized by virtue of an inner segment only rarely endowed with a cilium, whereas supporting cells exhibit numerous short microvilli. Further differentiation of the sensory apparatus is achieved by development of an oval-shaped, biconcave swelling at the tip of the cilium, 1×2 μm in size, and a collar of long microvilli at the base of the inner segment. Membrane specializations of sensory cilia, however, were not detected. Since during embryonic life new tubules and follicles are continuously formed, all stages of differentiation of sensory structures are found in the chick pineal organ during the second half of the incubation period and the first two weeks after hatching. In 200-μm-thick Vibratome sections of chick-embryo pineal organs cultured in medium BM 86 Wissler for periods up to 13 days the cytodifferentiation parallels the development in vivo. Using an organ-culture system the 24-h release of melatonin into the culture medium was measured by means of radioimmunoassay after solid-phase extraction. At embryonic day 10, the 24-h secretion of melatonin was at the lower range of detection of the RIA (5 pg). The rapid increase in 24-h secretion in melatonin until hatching (∼50 μg) is approximated by an exponential curve.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 119 (1994), S. 211-219 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adult Gnathophausia ingens, a bioluminescent deep-sea mysid, were collected off the California coast and brought, protected from the light, to the Marine Laboratory of the University of California, Santa Barbara (UCSB) for single-unit recordings of afferent visual interneurons. These units, which traverse the optic stalk, were classified according to their response to light stimuli varying in intensity, duration and area. The most common were sustaining fibers responding throughout a continuous stimulus. The only other type, “on” fibers, showed a transient response without reference to stimulus movement. Sustaining fibers responded to irradiances as low as, 2.7×103 photons cm-2s-1sr-1, and were characterized by long temporal summations and large receptive fields. These are characteristics of a visual system adapted for maximizing sensitivity. However, the transient response of the “on” fibers also suggests a capability to react to rapidly changing light sources such as bioluminescence, a matter of importance since this mysid requires dietary coelenterazine to sustain its luminescent system.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 34 (1992), S. 471-477 
    ISSN: 1432-1432
    Keywords: Transfer RNA ; Acceptor helix stem ; Primordial code ; Statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The specificity of interaction of amino acids with triplets in the acceptor helix stem of tRNA was investigated by means of a statistical analysis of 1400 tRNA sequences. The imprint of a prototypic genetic code at position 3–5 of the acceptor helix was detected, but only for those major amino acids, glycine, alanine, aspartic acid, and valine, that are formed by spark discharges of simple gases in the laboratory. Although remnants of the code at position 3–5 are typical for tRNAs of archaebacteria, eubacteria, and chloroplasts, eukaryotes do not seem to contain this code, and mitochondria take up an intermediary position. A duplication mechanism for the transposition of the original 3–5 code toward its present position in the anticodon stern of tRNA is proposed. From this viewpoint, the mode of evolution of mRNA and functional ribosomes becomes more understandable.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Integral equations and operator theory 14 (1991), S. 105-119 
    ISSN: 1420-8989
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is shown that certain eigenvalue problems for ordinary differential operators with boundary conditions depending holomorphically on the eigenvalue parameter γ can be linearized by making use of the theory of operator colligations. As examples, first order systems with boundary conditions depending polynomially on γ and Sturm-Liouville problems with γ-holomorphic boundary conditions are considered.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archiv der Mathematik 56 (1991), S. 343-345 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
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  • 6
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    Springer
    Archiv der Mathematik 60 (1993), S. 591-600 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Discrete & computational geometry 9 (1993), S. 427-432 
    ISSN: 1432-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract For alln〉 d there existn points in the Euclidean spaceE d such that not all points are in a hyperplane and all mutual distances are integral. It is proved that the minimum diameter of such integral point sets has an upper bound of 2 c logn log logn .
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  • 8
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    Springer
    Applicable algebra in engineering, communication and computing 4 (1993), S. 103-145 
    ISSN: 1432-0622
    Keywords: Gröbner bases ; Polynomial ideals ; Dual bases ; Interpolation ; 0-dimensional schemes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In this paper we study 0-dimensional polynomial ideals defined by a dual basis, i.e. as the set of polynomials which are in the kernel of a set of linear morphisms from the polynomial ring to the base field. For such ideals, we give polynomial complexity algorithms to compute a Gröbner basis, generalizing the Buchberger-Möller algorithm for computing a basis of an ideal vanishing at a set of points and the FGLM basis conversion algorithm. As an application to Algebraic Geometry, we show how to compute in polynomial time a minimal basis of an ideal of projective points.
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  • 9
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    Electronic Resource
    Springer
    Applicable algebra in engineering, communication and computing 4 (1993), S. 217-230 
    ISSN: 1432-0622
    Keywords: Algebraic variety decomposition ; Gröbner bases ; Systems of nonlinear equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract This paper deals with systems ofm polynomial equations inn unknown, which have only finitely many solutions. A method is presented which decomposes the solution set into finitely many subsets, each of them given by a system of type $$f_1 \left( {x_1 } \right) = 0,f_2 \left( {x_1 ,x_2 } \right) = 0, \ldots ,f_n \left( {x_1 , \ldots ,x_n } \right) = 0$$ . The main tools for the decomposition are from ideal theory and use symbolical manipulations. For the ideal generated by the polynomials which describe the solution set, a lexicographical Gröbner basis is required. A particular element of this basis allows the decomposition of the solution set. By a recursive application of these decomposition techniques the triangular subsystems are finally obtained. The algorithm gives even for non-finite solution sets often also usable decompositions.
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  • 10
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    Springer
    Applied physics 56 (1993), S. 527-546 
    ISSN: 1432-0630
    Keywords: 52.25.Dg ; 79.20.Nc ; 82.65.Yh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The elementary mechanisms are described which determine the plasma and surface processes during the plasma-enhanced chemical vapour deposition of hydrogenated carbon films from methane. Corresponding model calculations are reviewed and critically discussed in comparison to experimental results. A realistic modeling requires the simultaneous and self-consistent treatment of plasma and surface effects. Several experimental data sets on plasma parameters and the growth and the composition of the films have been reproduced successfully. However, a broader experimental data base is needed for more critical tests of the models. The reliability of the modeling, in particular of the surface effects, is still limited due to the poor availability of elementary data.
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