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  • 1
    Electronic Resource
    Electronic Resource
    On steady force-free dynamos (1977)
    Springer
    Astrophysics and space science 51 (1977), S. 341-348 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown that the amplification of the magnetic energy that results in steady force-free dynamos automatically implies a depletion of the overall mechanical and thermal energies of the fluid in the region. The precise gain and loss of the field and the fluid, respectively, are demonstrated. This offers a natural and direct explanation of the relative coolness of sunspots with respect to their surroundings and also predicts lower velocities over sunspot regions resulting from the smoothing of turbulent fluctuations of velocities by viscous stresses in the magnetic region. The missing energy of the fluid in the region is shown to reside in the increased magnetic energy of the sunspots. It is also suggested that sunspots emerge from the photosphere in a manner analogous to the growth of salt fingers in thermohaline convection. Finally, it is pointed out that the growth and flaring process of solar magnetic fields can also be understood on the basis of the formalism presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644157
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of mass-loss and semiconvection on the evolution of a 15M ⊙ population I star (1978)
    Springer
    Astrophysics and space science 53 (1978), S. 193-216 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Evolutionary sequences are computed from the main sequence to central helium exhaustion for a 15M ⊙ star, with an initial composition ofX=0.70,Y=0.27,Z=0.03. Parallel sequences are computed to investigate the effects of different mass loss rates on the evolution of the star. These rates are chosen to reflect the physical causes of the mass loss, and occur at all phases of evolution. One sequence without, and one with, mass loss are recomputed, allowing for semiconvection and full convection in intermediate mass zones, using the Schwarzschild and Härm criterion for convective neutrality. Low to moderate rates of mass loss in the early evolutionary phases shift the evolution to lower luminosities and effective temperatures, but do not radically alter the form of evolution. However, the resulting evolutionary sequences can be up to 25% undermassive for their luminosity as they enter the red giant branch (RGB). Most sequences evolve through a subsequent stable blue phase (the blue loop), which is shifted to lower luminosities and effective temperatures by the previous mass loss and is also widened. This blue loop is suppressed if approximately 10% of the stellar mass is lost in the RGB. Mass loss delays the evolution of the central region of the star relative to that of the outer region, so that central helium ignition and exhaustion are displaced to later points on the evolutionary tracks. Mass loss also reduces the size of the helium core, although its mass fraction is larger. If semiconvective and intermediate fully convective zones are included, then in a sequence without mass loss these zones greatly alter the chemical profile of the model. The sequence evolves at a higher luminosity, with a stable blue supergiant phase occurring prior to the RGB. Central helium exhaustion occurs during the ascent of the RGB. However, if mass loss is included, the extent of these zones is drastically reduced, and the evolutionary pattern is similar to that without such zones. No blue loop is found. Observations indicate that the blue supergiant region is wider and bluer than predicted by previous evolutionary calculations. The present results show that mass loss widens and reddens this phase. Hence, the inclusion of other factors will be necessary to reconcile theory and observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645914
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  • 3
    Electronic Resource
    Electronic Resource
    On the off-ecliptic distributions of anomalous cosmic rays and their relation to the large-scale geometry of the heliospheric shock (1995)
    Springer
    Space science reviews 72 (1995), S. 435-440 
    Details
    ISSN: 1572-9672
    Keywords: Anomalous Cosmic Rays ; Heliospheric Shock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The scenario explaining the origin of the anomalous component of cosmic rays (ACR) implies a close relation between these high energy particles and the solar wind termination shock representing their main acceleration region. Consequently, one should expect the ACR distributions in the heliosphere to reflect some information about the structure as well as the large-scale geometry of the shock. We study the influence of a non-spherically symmetric heliospheric shock on the off-ecliptic — i.e. high latitude — ACR distributions using a two-dimensional model including their anisotropic diffusion and drift in the heliospheric magnetic field as well as a solar wind flow dependent on the heliographic latitude. The model calculations are used to investigate the probability of a possible polar elongation of the heliospheric shock from observations of the distributions of the ACR at high latitudes during solar minimum conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768817
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  • 4
    Electronic Resource
    Electronic Resource
    On the collisional energy transfer between the constituents of the coronal plasma (1995)
    Springer
    Solar physics 160 (1995), S. 105-120 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It has been suggested that the distribution functions characterizing the constituents of the solar coronal plasma are non-Maxwellian. If so, an accurate treatment of the collisional momentum and energy exchange between the plasma constituents within the framework of hydrodynamic models requires a re-evaluation of the general transfer integrals in multi-component plasmas. We have evaluated these integrals numerically for both Maxwellian and non-Maxwellian distribution functions of the plasma species avoiding the standard approximation for the collision cross sections frequently employed in the literature. Significant differences are shown to exist in the energy exchange rates for different distributions. We also demonstrate the inadequacy of the assumption of thermodynamic equilibrium in the innermost solar wind and reveal the importance of an accurate evaluation of the transfer integrals for the solar coronal plasma based on more realistic velocity distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00679099
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of delignification and alkali treatment on the fine structure of coir fibres (Cocos Nucifera) (1996)
    Springer
    Journal of materials science 31 (1996), S. 721-726 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The present communication reports the effect of a softening treatment carried out with 18% NaOH on the fine structure and structure-property relations in coir fibres. The effect of successive removal of lignin and hemicelluloses on the fine structure has also been studied. Unlike other cellulosic fibres, alkali treatment failed to produce any increase in fibre elongation in coir. However, the spiral structure was found to be considerably modified by swelling. X-ray and infrared spectral measurements revealed that a part of the noncellulosic components does occupy the intracellular space and plays a significant role on fine structural changes produced during the alkali treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367891
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  • 6
    Electronic Resource
    Electronic Resource
    The post-main sequence evolution of a star of 20M ⊙ to core helium exhaustion (1974)
    Springer
    Astrophysics and space science 30 (1974), S. 57-70 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An evolutionary model of a Population I star of 20M ⊙ and of compsitionX=0.70;Y=0.28, beyond the main sequence and up to core helium exhaustion is reported. Calculations were carried out to determine the effect of semi-convection using a method of mixing considered physically more appropriate than previous methods. Both the density as wel as the temperature stability criteria were employed in parallel calculations and reasons are advanced to prefer the temperature criterion. The results of the model calculations reported here underline the importance of the proper choice of the stability criterion and an appropriate mixing-scheme. In addition it is demonstrated that the loop phenomenon seen in the helium burning evolution of less massive stars is either absent or very unpronounced at 20M ⊙.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645753
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  • 7
    Electronic Resource
    Electronic Resource
    A new method for achieving cellulose IV → cellulose III lattice transformations (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 18 (1980), S. 603-606 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.130180904
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  • 8
    Electronic Resource
    Electronic Resource
    Fine structural changes in native and mercerized fibrous cellulose brought about by ethylenediamine and methyl alcohol (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 3089-3099 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: X-Ray diffraction (XRD) studies were made on native as well as mercerized ramie and cotton fibers after swelling them in ethylenediamine (EDA) solutions and washing out the swelling agent using methyl alcohol (MeOH). These treatments are shown to convert the cellulose I and II lattices into cellulose IIII and IIIII type lattices, respectively. Treatment of the IIII and IIIII samples in boiling water or hydrochloric acid results in reconversions of their crystal lattices into the respective parent types. Alkali treatment causes a III → II type conversion. Studies using alkali-swollen fibers as well as fibers of different lateral order as starting materials indicate the importance of the structural organization in the cellulosic materials in the production of the cellulose III lattices. Possible mechanisms involved in the lattice transformations in cellulose brought about by the EDA and MeOH treatments are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1978.070221105
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  • 9
    Electronic Resource
    Electronic Resource
    Further studies on cellulose III polymorphs. Transformations to cellulose IV lattices and subsequent reactions (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 709-730 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Production of cellulose IV polymorphs, their characterization using X-ray diffraction and infrared spectroscopy, as well as the effect of chemical treatments on these polymorphs have been investigated. Cellulose IIII and IIIII polymorphs, produced from celluloses I and II using EDA - MeOH treatments, were of particular interest as starting materials in the study. Celluloses IVI and IVII gave identical equatorial X-ray patterns in the absence of other crystal lattices in the samples. Crystallinity as well as conformation were indicated to influence production and further reactions of the samples. The latter included boiling in water, acid hydrolysis, and treatments with EDA - water, EDA - MeOH, and NaOH solutions. Cellulose IVI → I, IVI → I → II, and cellulose IVII → II lattice conversions were demonstrated to occur with EDA - water treatments, thereby providing a new technique for observing these transformations. Conformational differences were apparent among celluloses I, II, IIII, and IIIII, each produced using different experimental procedures.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070270233
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  • 10
    Electronic Resource
    Electronic Resource
    Studies on swelling of cotton fibers in alkali metal hydroxides. II. Influence of morphology and fine structure on tensile behavior (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 1739-1752 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cotton fibers varying widely in gravimetric fineness but having nearly same percentage mature fibers have been subjected to swelling in 4.5N LiOH, NaOH, and KOH at room temperature and 0°C. The resultant changes in fine structure are analyzed by X-ray diffraction and infrared absorption methods while variations in surface morphology are followed by scanning electron microscopy. Extent of swelling measured by changes in gravimetric fineness follows the order LiOH ≥ NaOH ≥ KOH, the exact gradation being dependent on the variety. Analysis of tensile data shows that whereas moderate swelling leads to an increase in tenacity at 3.2 mm gauge length, excessive swelling leads to a decrease of the same, the extent of decrease being a function of swelling. KOH treatment produced uniform swelling and gave better retention of T0 and T3 for all varieties. Tensile behavior after slack swelling in the various reagents could be interpreted on the basis of fine structural variations produced by them. However, the differential response of cottons to a swelling agent is explained by postulating variations in the packing of structural elements along the radii.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370701
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