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  • 1
    Electronic Resource
    Electronic Resource
    The shape of the sunspot cycle (1994)
    Springer
    Solar physics 151 (1994), S. 177-190 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The temporal behavior of a sunspot cycle, as described by the International sunspot numbers, can be represented by a simple function with four parameters: starting time, amplitude, rise time, and asymmetry. Of these, the parameter that governs the asymmetry between the rise to maximum and the fall to minimum is found to vary little from cycle to cycle and can be fixed at a single value for all cycles. A close relationship is found between rise time and amplitude which allows for a representation of each cycle by a function containing only two parameters: the starting time and the amplitude. These parameters are determined for the previous 22 sunspot cycles and examined for any predictable behavior. A weak correlation is found between the amplitude of a cycle and the length of the previous cycle. This allows for an estimate of the amplitude accurate to within about 30% right at the start of the cycle. As the cycle progresses, the amplitude can be better determined to within 20% at 30 months and to within 10% at 42 months into the cycle, thereby providing a good prediction both for the timing and size of sunspot maximum and for the behavior of the remaining 7–12 years of the cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654090
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of purified myosin light chain kinase on myosin light chain phosphorylation and catecholamine secretion in digitonin-permeabilized chromaffin cells (1987)
    Springer
    Bioscience reports 7 (1987), S. 323-332 
    Details
    ISSN: 1573-4935
    Keywords: myosin ; light chain ; phosphorylation ; catecholamine ; chromaffin cell ; protein kinase ; exocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Many non-muscle cells including chromaffin cells contain actin and myosin. The 20,000 dalton light chain subunits of myosin can be phosphorylated by a Ca2+/calmodulin-dependent enzyme, myosin light chain kinase. In tissues other than striated muscle, light chain phosphorylation is required for actin-induced myosin ATPase activity. The possibility that actin and myosin are involved in catecholamine secretion was investigated by determining whether increased phosphorylation in the presence of [γ-32P]ATP of myosin light chain by myosin light chain kinase enhances secretion from digitonin-treated chromaffin cells. In the absence of exogenous myosin light chain kinase, 1 μM Ca2+ caused a 30–40% enhancement of the phosphorylation of a 20 kDa protein. This protein was identified on 2-dimensional gels as myosin light chain by its comigration with purified myosin light chain. Purified myosin light chain kinase (400 μg/ml) in the presence of calmodulin (10 μM) caused little or no enhancement of myosin light chain phosphorylation in the absence of Ca2+ in digitonin-treated cells. In the presence of 1 μM Ca2+, myosin light chain kinase (400 μg/ml) caused an approximately two-fold increase in myosin light chain phosphorylation in digitonin-treated cells in 5 min. The phosphorylation required permeabilization of the cells by digitonin and occurred within the cells rather than in the medium. Myosin light chain kinase-induced phosphorylation of myosin light chain was maximal at 1 μM. Ca2+. Under identical conditions to those of the phosphorylation experiments, secretion was unaltered by myosin light chain kinase. The experiments indicate that the phosphorylation of myosin light chain by myosin light chain kinase is not a limiting factor in secretion in digitonin-treated chromaffin cells and suggest that the activation of myosin is not directly involved in secretion from the cells. The experiments also demonstrate the feasibility of investigation of effects of exogenously added proteins on secretion in digitonin-treated cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01121454
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  • 3
    Electronic Resource
    Electronic Resource
    Caldesmon content of mammalian smooth muscles (1992)
    Springer
    Journal of muscle research and cell motility 13 (1992), S. 81-89 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the present study we have used a quantitative immunoblotting method to measure the caldesmon content of a variety of smooth muscles with distinctly different contractile phenotypes. Two tonic vascular smooth muscles and several phasic smooth muscles were examined. The caldesmon, actin and myosin contents of each muscle type were measured. Smooth muscle from large arteries (i.e. bovine aorta and porcine carotid artery) had the lowest caldesmon content and phasic muscles (e.g. rat uterus and guinea pig taenia coli) had the highest. The molar ratio of monomeric caldesmon to monomeric actin was 1∶205 for the aorta and carotid arteryversus 1∶22–28 for the taenia coli and uterus. The molar ratio of caldesmon to monomeric myosin heavy chain was 1∶9 for the aorta and carotidversus 1∶2 for the uterus and taenia coli. The caldesmon contents of canine trachealis and rabbit ileum were intermediate between these extremes. Evidence was found for the presence of both tissue- and species-specific caldesmon isoforms. The relatively high caldesmon content in rat uterus and guinea pig taenia coli suggests the possibility that the contractile phenotype associated with phasic smooth muscles may be dependent on the presence of caldesmon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01738431
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of a calcium dependent protease on the ultrastructure and contractile mechanics of skinned uterine smooth muscle (1985)
    Springer
    Journal of muscle research and cell motility 6 (1985), S. 347-363 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In situ substrates for a vascular smooth muscle calcium-dependent protease (CDP) were investigated using a chemically skinned uterine smooth muscle preparation. Treatment of skinned smooth muscles with CDP had no effect on the total content of actin and myosin. Electron microscopical observations demonstrated that membrane plaques, cytoplasmic dense bodies, and intermediate filaments were all degraded by CDP. In addition, CDP reduced both isometric force and isotonic shortening velocity of contracted muscles in a concentration and time-dependent manner. Treatment of contracting muscles with CDP resulted in a condensation of myofilaments away from the plasma membrane concurrent with the loss of contractility. The condensation of myofilaments was ATP-dependent and could be inhibited by removal of ATP prior to proteolysis. The effects of proteolysis on smooth muscle ultrastructure and contractility support previously proposed models which assign a role to cytoskeletal elements in coordinating the molecular interaction of actomyosin to produce muscle contraction. The loss of cytoskeletal structures following protease treatment suggests that one of the functions of CDP in smooth muscle may be the disassembly of the cell cytoskeleton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713174
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  • 5
    Electronic Resource
    Electronic Resource
    Correspondence (1992)
    Springer
    Journal of muscle research and cell motility 13 (1992), S. 584-585 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01738001
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  • 6
    Electronic Resource
    Electronic Resource
    Spherical harmonic analysis of steady photospheric flows (1987)
    Springer
    Solar physics 108 (1987), S. 1-20 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Steady photospheric flows can be represented by a spectrum of spherical harmonic modes. A technique is described in which full disc doppler velocity measurements are analysed using the spherical harmonic functions to determine the characteristics of this spectrum and the nature of these flows. Synthetic data is constructed for testing this technique. This data contains limb shift, rotation, differential rotation, meridional circulation, supergranules, giant cells and various levels of noise. The data is analysed in several steps. First, the limb shift is calculated by finding the average velocity in concentric rings about disc center. A polynomial representation of the limb shift is then removed from the data. Secondly, the rotation profile is calculated by finding an average slope in the velocity across the disc at each latitude position. This rotation profile is fit with Legendre polynomials and removed from the data. The third step is to find the meridional circulation by calculating the spherical harmonic transform for the axisymmetric poloidal modes and correcting for the effects of the limb shift analysis. The final step is to calculate the full spectrum of spherical harmonic components for the convective flows. Supergranules are separated from giant cells by spectral filtering for high (l 〉32) and low (l 〈32) wavenumbers, respectively. Some information about the spectrum is lost because only one hemisphere is seen, only the line-of-sight velocity is measured and the measurements contain noise. The lack of information about the motions on the backside of the Sun produces a broad smearing of the spectrum into nearby modes. The lack of information about the transverse velocity component produces a mixing between modes whose longitudinal wavenumbers differ by two and between the poloidal and toroidal components with the same wavenumber. In spite of this mode mixing much can be learned from this analysis. Solar rotation and differential rotation can be accurately measured and monitored for secular changes. Meridional circulations with small amplitudes can be measured and monitored and giant cells can be separated from supergranules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152073
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  • 7
    Electronic Resource
    Electronic Resource
    Simulating photospheric Doppler velocity fields (1988)
    Springer
    Solar physics 117 (1988), S. 329-341 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method is described for constructing artificial data that realistically simulate photospheric velocity fields. The velocity fields include rotation, differential rotation, meridional circulation, giant cell convection, supergranulation, convective limb shift, p-mode oscillations, and observer motion. Data constructed by this method can be used for testing algorithms designed to extract and analyze these velocity fields in real Doppler velocity data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147251
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  • 8
    Electronic Resource
    Electronic Resource
    Nonlinear simulations of solar rotation effects in supergranules (1982)
    Springer
    Solar physics 77 (1982), S. 341-356 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Nonlinear calculations for the three-dimensional and time dependent convective flow in a plane parallel layer of fluid are carried out with parameter values appropriate for supergranules on the Sun. A rotation vector is used which is tilted from the vertical to represent various latitudes. For the incompressible fluid used in this model the solar rotation produces turning motions sufficient to completely twist a fluid column in about one day. It is suggested that this effect will be greatly enhanced in a compressible fluid. The tilted rotation vector produces anisotropies and systematic Reynolds stresses which drive mean flows. The resulting flows produce a rotation rate which increases inward and a meridional circulation with poleward flow along the outer surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156116
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  • 9
    Electronic Resource
    Electronic Resource
    Spherical harmonic analysis of steady photospheric flows, II (1992)
    Springer
    Solar physics 137 (1992), S. 15-32 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The use of the spherical harmonic functions to analyse the nearly steady flows in the solar photosphere is extended to situations in which B 0, the latitude at disk center, is nonzero and spurious velocities are present. The procedures for extracting the rotation profile and meridional circulation are altered to account for the seasonal tilt of the Sun's rotation axis toward and away from the observer. A more robust and accurate method for separating the limb shift and meridional circulation signals is described. The analysis procedures include the ability to mask out areas containing spurious velocities (velocity-like signals that do not represent true flow velocities in the photosphere). The procedures are shown to work well in extracting the various flow components from realistic artificial data with a broad, continuous spectrum for the supergranulation. The presence of this supergranulation signal introduces errors of a few m s -1 in the measurements of the rotation profile, meridional circulation, and limb shift from a single Doppler image. While averaging the results of 24 hourly measurements has little effect in reducing these errors, an average of 27 daily measurements reduces the errors to well under 1 m s -1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146573
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  • 10
    Electronic Resource
    Electronic Resource
    Temporal filters for isolating steady photospheric flows (1988)
    Springer
    Solar physics 117 (1988), S. 1-12 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A variety of temporal filters are tested on artificial data with 60 and 75 s sampling intervals to determine their accuracy in separating the nearly-steady photospheric flows from the p-mode oscillations in Doppler velocity data. Longer temporal averages are better at reducing the residual signal due to p-modes but they introduce additional errors from the rotation of the supergranule pattern across the solar disk. Unweighted filters (boxcar averages) leave residual r.m.s. errors of about 6 m s−1 from the p-modes after 60 min of averaging. Weighted filters, with nearly Gaussian shapes, leave similar residual errors after only 20 min of averaging and introduce smaller errors from the rotation of the supergranule pattern. The best filters found are weighted filters that use data separated by 150 or 120 s so that the p-modes are sampled at opposite phases. These filters achieve an optimum error level after about 20 min, with the r.m.s. errors due to the p-mode oscillations and the rotation of the supergranules both at a level of only 1.5 m s−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148567
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