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  • 1
    Electronic Resource
    Electronic Resource
    Embryonic expression of the engrailed homologue of Rhynchosciara americana (1996)
    Springer
    Development genes and evolution 205 (1996), S. 432-436 
    Details
    ISSN: 1432-041X
    Keywords: engrailed ; Embryonic development ; Gene expression ; Segmentation ; Rhynchosciara americana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The segment polarity gene engrailed is involved in the determination of segment posterior identity in Drosophila. engrailed has been largely used for comparative developmental studies due to its evolutionary conservation from nematodes to humans. By in situ hybridization of an engrailed cDNA probe from Drosophila to polytene chromosomes of fourth instar larvae of Rhynchosciara americana we have shown that engrailed-like sequences must be localized in band 6 of chromosome A in this species. The pattern of engrailed protein expression during R. americana embryo development is diffuse at first evolving into a nuclear striped pattern after quite a length of time. In addition, our results suggest a possible developmentally regulated molecular modification of engrailed protein in R. americana embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377223
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  • 2
    Electronic Resource
    Electronic Resource
    Faraday rotation and the turbulent structure of the Galaxy (1977)
    Springer
    Astrophysics and space science 51 (1977), S. 385-393 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We extend Jokipii and Lerche's analysis of the turbulent structure of our Galaxy by means of a study of the rotation measure of extragalactic sources. Like them we use a simple, statistically homogeneous and isotropic disc model of the Galaxy and assume that the magnetic field has both an average component and a fluctuating one. We assume that the electron density is proportional to some power of the magnetic field (N eαB n with 1≤n≤2). Using the rotation measure data on 242 extragalactic sources given by Vallée and Kronberg we consider both an exponential and a Gaussian two-point correlation function for the (Gaussian) fluctuating component of the magnetic field with a correlation lengthL. We find reasonable agreement between theory and observations for an average magnetic field of about 3 μG, a fluctuating magnetic field component with an amplitude of about 2.6μG, an average electron density of about 0.03 cm−3, a fluctuating density component of about 0.05 cm−3, and a correlation length of about 300 pc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644160
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  • 3
    Electronic Resource
    Electronic Resource
    The diffusion model of cosmic-ray propagation (1979)
    Springer
    Astrophysics and space science 61 (1979), S. 3-17 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We show that the observational data on galactic synchrotron radiation can be explained if there is a break in the electron spectrum at about 2 GeV. We also show that one can explain the occurrence of that break by carefully considering the time evolution of the high-energy electron spectrum in supernova remnants, taking into account synchrotron losses, adiabatic expansion and diffusive losses from the remnant. The model considered is also in agreement with the observed radio spectrum of Cas A and the decay rate of its flux density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645788
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  • 4
    Electronic Resource
    Electronic Resource
    The diffusion model of cosmic-ray propagation (1979)
    Springer
    Astrophysics and space science 61 (1979), S. 19-44 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We set up diffusion equations for the nuclear component of cosmic rays and solve these to find the ratio of light to medium nuclei in the cosmic rays as well as the gamma-ray distribution in our Galaxy. From a comparison of our calculated quantities with observational data we determine the values of various parameters appearing in the model. We find that best agreement between theory and observations is obtained if the cosmic-ray confinement region consists of a narrow disk of total height 160 pc and radius 16 kpc, where the cosmic-ray sources are located, and an extensive halo of height 20 kpc. The diffusion coefficient near the Sun must be between 1026 and 1027 cm2 s−1 while it equals 1028 to 1029 cm2 s−1 in the halo. Finally, we find that the diffusion coefficient in the Galaxy must depend on the gas density as a power law with an index of the order of −1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645789
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  • 5
    Electronic Resource
    Electronic Resource
    The diffusion model of cosmic-ray propagation (1979)
    Springer
    Astrophysics and space science 61 (1979), S. 45-64 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The diffusion equation for the electron component of cosmic rays is solved and the solution obtained is used to evaluate the electron spectrum, its spatial distribution, and the distribution of the galactic synchrotron radiation. We find reasonable agreement between theory and observational data for the same values of the parameters as found in Part II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645790
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  • 6
    Electronic Resource
    Electronic Resource
    Uniform Newtonian models with variable mass (1991)
    Springer
    General relativity and gravitation 23 (1991), S. 455-463 
    Details
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A Newtonian version of the spatially homogeneous and isotropic cosmological models with variable mass is presented. Under the assumption that the mass variation is a strict cosmological effect, its influence on the evolution of the scale function is established for the case of a dust-filled universe. Unlike the usual Newtonian models the present value of the deceleration parameter (q ≏ 1) obtained from the luminosity distance versus redshift relation can be fitted for a time-decreasing mass. It is also shown that the hyperbolic, parabolic or elliptic character of the fluid motion can be modified along the expansion. Likewise, a Friedmann-type equation with a variable “curvature term” indicates that in the frame-work of a full geometric variable mass theory, the same may occur with the open, flat or closed character of the universe spatial section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00756608
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  • 7
    Electronic Resource
    Electronic Resource
    The relation between the relativistic 5D Wesson theory and the Newtonian variable mass theory (1992)
    Springer
    General relativity and gravitation 24 (1992), S. 171-177 
    Details
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The existence of Newtonian analogs to spatially homogeneous and isotropic cosmological models of the relativistic 5D Wesson variable mass theory is investigated. By treating the continuous universe “matter creation process” by the methods of standard hydrodynamics, it is shown that classical analogs are obtained only if the cosmological constant is null and the spatial curvature is positive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00756784
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  • 8
    Electronic Resource
    Electronic Resource
    Dirac's cosmology with varying cosmological constant (1994)
    Springer
    General relativity and gravitation 26 (1994), S. 909-916 
    Details
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The phenomenological approach to investigating the decay of the vacuum energy density is generalized in the spirit of Dirac's large number hypothesis. Different arguments are outlined to justify an universal dependence of the type λ=ΒH 2 (Β is a pure number andH is the Hubble parameter). Such time-varying A does change the predictions of the earlier Dirac's cosmology. The deceleration parameter (q 0=(2−Β)/(1+Β)) and the age parameter (H 0t0=(1+Β)/3) are now compatible with the observations. The model also allows a “power-law” inflationary phase and a rate of matter creation smaller than the one present in the steady state universe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02107147
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  • 9
    Electronic Resource
    Electronic Resource
    Ages of the universe for FRW-type models in wesson's 5D variable mass theory of gravity (1994)
    Springer
    Astrophysics and space science 219 (1994), S. 29-34 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The age of the universe is computed for spatially homogeneous and isotropic cosmological models of the relativistic Wesson's 5D variable mass theory of gravity. It is shown that if the pressure in the mass dimension is negligible, ages old enough to agree with the observations can only be obtained if the cosmological constant is different from zero. In addition, unlike the standard FRW models in Einstein's 4D theory, the age value itself is not affected by the nature of the matter content (matter and radiation dominated models give the same age).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657857
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  • 10
    Electronic Resource
    Electronic Resource
    Non-vacuum cosmological solutions of 5D variable mass theory of gravity (1994)
    Springer
    Astrophysics and space science 215 (1994), S. 53-58 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A class of non-vacuum expanding cosmological solutions of Wesson's 5D theory of gravity with variable rest mass is derived. The models are spatially homogeneous and isotropic and the source of gravitation is a pressureless fluid (dust) plus a cosmological constant term. The general and unified solution is found for the equations and some properties of different limiting cases are studied. Particularly, it is shown that for null cosmological constant the predicted age of the universe is smaller than the ones of the 4D FRW models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627459
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