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  • 1
    Electronic Resource
    Electronic Resource
    Nuclear cytoplasmic domains, microtubules and organelles in microsporocytes of the slipper orchid Cypripedium californicum A. Gray dividing by simultaneous cytokinesis (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 145-152 
    Details
    ISSN: 1432-2145
    Keywords: Cytokinesis ; Microtubules ; Microsporogenesis ; Orchids ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microsporocytes of the slipper orchidCypripedium californicum A. Gray divide simultaneously after second meiosis. The organization and apportionment of the cytoplasm throughout meiosis are functions of nuclear-based radial microtubule systems (RMSs) that define domains of cytoplasm - a single sporocyte domain before meiosis, dyad domains within the undivided cytoplasm after first meiosis, and four spore domains after second meiosis. Organelles migrate to the interface of dyad domains in the undivided cytoplasm after first meiotic division, and second meiotic division takes place simultaneously on both sides of the equatorial organelle band. Microtubules emanating from the telophase II nuclei interact to form columnar arrrays that interconnect all four nuclei, non-sister as well as sister. Cell plates are initiated in these columns of microtubules and expand centrifugally along the interface of opposing RMSs, coalescing in the center of the sporocyte and joining with the original sporocyte wall at the periphery to form the tetrad of microspores. Organelles are distributed into the spore domains in conjunction with RMSs. These data, demonstrating that cytokinesis in microsporogenesis can occur in the absence of both components of the typical cytokinetic apparatus (the preprophase band of microtubules which predicts the division site and the phragmoplast which controls cell-plate deposition), suggest that plant nuclei have an inherent ability to establish a domain of cytoplasm via radial microtubule systems and to regulate wall deposition independently of the more complex cytokinetic apparatus of vegetative cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221394
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  • 2
    Electronic Resource
    Electronic Resource
    Minispindles and cytoplasmic domains in microsporogenesis of orchids (1989)
    Springer
    Protoplasma 148 (1989), S. 26-32 
    Details
    ISSN: 1615-6102
    Keywords: Cytokinesis ; Cytoplasmic domains ; Meiosis ; Microtubules ; Minispindles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes in the microtubular cytoskeleton during meiosis and cytokinesis in hybrid moth orchids were studied by indirect immunofluorescence. Lagging chromosomes not incorporated into telophase nuclei after first meiotic division behave as small extra nuclei. Events in the microtubular cycle associated with these micronuclei are similar to and synchronous with those of the principal nuclei. During second meiotic division the micronuclei trigger formation of minispindles which are variously oriented with respect to the two principal spindles. After meiosis, radial systems of microtubules measure cytoplasmic domains around each nucleus in the coenocyte. Cleavage planes are established in regions where opposing radial arrays interact and the cytoplasm cleaved around micronuclei is proportionately smaller than that around the four principal nuclei. These observations clearly demonstrate that nuclei in plant cells are of fundamental importance in microtubule organization and provide strong evidence in support of our recently advanced hypothesis that division planes in simultaneous cytokinesis following meiosis are determined by establishment of cytoplasmic domains via radial systems of nuclear-based microtubules rather than by division sites established before nuclear division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403988
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  • 3
    Electronic Resource
    Electronic Resource
    Pollen development in orchids (1991)
    Springer
    Protoplasma 165 (1991), S. 155-166 
    Details
    ISSN: 1615-6102
    Keywords: Cytokinesis ; F-actin ; Microsporogenesis ; Microtubules ; Orchids ; Phragmoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytokinesis in microsporocytes of moth orchids is unusual in that it occurs simultaneously after meiosis, the cytoplasm does not infurrow in the division planes, and cell plates are deposited in association with centrifugal expansion of phragmoplasts. Microtubules radiating from the nuclear envelopes appear to be of fundamental importance in establishment of division planes. Primary interzonal spindles develop between sister nuclei and interaction of radial microtubules triggers development of secondary interzonal spindles between non-sister nuclei. From three to six or more phragmoplasts, depending upon the arrangement of nuclei in the coenocyte, develop from these postmeiotic arrays. The phragmoplasts consist of co-aligned microtubules and F-actin organized into bundles that are broad proximal to the mid-plane and taper distally. Ultrastructure of the phragmoplast/cell plate reveals that abundant ER is associated with vesicle aggregation and coalescence. Cell plates are deposited in association with phragmoplasts as they expand centrifugally to join the parental wall and/or fuse with one another in the interior of the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322286
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  • 4
    Electronic Resource
    Electronic Resource
    Division polarity, development and configuration of microtubule arrays in bryophyte meiosis (1987)
    Springer
    Protoplasma 138 (1987), S. 1-10 
    Details
    ISSN: 1615-6102
    Keywords: Meiosis ; Microtubules ; Cytokinesis ; Immunofluorescence ; Bryophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary First and second division spindles and the three cell plates of moss meiosis are oriented in accordance with polarity established during meiotic prophase. Plastids are located at the second division poles and cytoplasmic infurrowing marks the planes along which the cytoplasm will cleave into four spores. Anaphase I spindles that terminate in two focal points of microtubules straddling opposite cleavage furrows reflect the unusual tetrahedral origin of the functionally bipolar spindle. The organelles (except for the plastids which remain in the four cytoplasmic lobes) are polarized in the first division equatorial region at the time of phragmoplast microtubule assembly and remain in a distinct band after microtubule disassembly. Prophasic spindles appear to be directly transformed into metaphase II spindles in the predetermined axes between mutually perpendicular pairs of plastids. Cell plates form by vesicle coalescence in the equatorial regions of the two sets of second division phragmoplasts at approximately the same time as a cell plate belatedly forms in the organelle band. The cytoplasmic markers (plastid migration, cytoplasmic lobing and infurrowing) that predict poles and cleavage planes in free cells lacking a preprophase band strongly strengthens the concept that division sites are capable of preserving preprogrammed signals that can be triggered later in the process of cell division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281179
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  • 5
    Electronic Resource
    Electronic Resource
    Residual correction applied to a sequence of block tridiagonal matrices (1979)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 14 (1979), S. 1079-1084 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The decomposition of a block tridiagonal matrix into the product of block lowe and upper matrices is described. The cost of solving a block tridiagonal system of equations is given and compared to profile gaussian elimination. The desirability of a less expensive method is coupled to physical intuition about a common problem of solving a slowly varying sequence of such systems to motivate an iterative method based on residual correction. The method is described and convergence criteria are derived. An expression of the cost is developed and is shown to compare favourably with decomposition in many cases. Problems and advantages in computer implementation of the method are discussed and results of tests of a particular implementation on a well-known problem are given.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620140711
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of boundary and finite element methods for moving-boundary problems governed by a potential (1985)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 21 (1985), S. 1295-1314 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Three formulations of the boundary element method (BEM) and one of the Galerkin finite element method (FEM) are compared according to accuracy and efficiency for the spatial discretization of two-dimensional, moving-boundary problems based on Laplace's equation. The same Euler-predictor, trapezoid-corrector scheme for time integration is used for all four methods. The model problems are on either a bounded or a semi-infinite strip and are formulated so that closed-form solutions are known. Infinite elements are used with both the BEM and FEM techniques for the unbounded domain. For problems with the bounded region, the BEM using the free-space Green's function and piecewise quadratic interpolating functions (QBEM) is more accurate and efficient than the BEM with linear interpolation. However, the FEM with biquadratic basis functions is more efficient for a given accuracy requirement than the QBEM, except when very high accuracy is demanded. For the unbounded domain, the preferred method is the BEM based on a Green's function that satisfies the lateral symmetry conditions and which leads to discretization of the potential only along the moving surface. This last formulation is the only one that reliably satisfies the far-field boundary condition.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620210710
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  • 7
    Electronic Resource
    Electronic Resource
    LU decomposition of matrices with augmented dense constraints (1987)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 24 (1987), S. 1451-1459 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Sparse matrices composed of a central band and augmented dense rows and columns are becoming prevalent in the numerical solution of a large class of boundary and initial-value problems. A Fortran Subroutine ARROW is presented for the LU decomposition and solution of linear equation systems with such a structure. The computational speed of the program is compared in MFLOPS (millions of floating point operations per second) to the LINPACK benchmark for the solution of a dense linear system and is found to be of comparable speed on both supercomputers and minicomputers. Use of the Basic Linear Algebra Subroutines (BLAS) available on most machines significantly enhances the speed of ARROW.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620240804
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  • 8
    Electronic Resource
    Electronic Resource
    Finite element/Newton method for the analysis of Czochralski crystal growth with diffuse-grey radiative heat transfer (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 30 (1990), S. 133-154 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A quasi-steady-state, integrated system model describing high temperature heat transfer, solidification and the action of capillarity in the Czochralski crystal growth process is solved by a finite element/Newton method. The numerical analysis couples the calculation of the temperature field in all phases and the determination of the melt/crystal and melt/gas interfaces and the crystal radius free boundaries. The analysis includes conductive heat transfer in the melt, crystal, crucible, pedestal, heater and the surrounding insulation and diffuse-grey radiation, which couples the heat transfer between surfaces, the crystal radius and the melt/gas free boundary through the view factors. Finite element approximations are used to reduce the entire problem to a coupled set of non-linear algebraic equations. These are solved simultaneously by Newton's method with the Jacobian matrix computed by a combination of closed form expressions and finite difference approximations. Quadratic convergence of the Newton iteration is demonstrated along with a factor of four increase in computational efficiency over a successive iteration procedure that decouples the calculation of radiation from the rest of the heat transfer model.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620300109
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  • 9
    Electronic Resource
    Electronic Resource
    Computer economy and accuracy of the method of lines applied to laminar flame problems (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 5 (1989), S. 181-190 
    Details
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1630050306
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  • 10
    Electronic Resource
    Electronic Resource
    Boundary-conforming mapping applied to computations of highly deformed solidification interfaces (1992)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 14 (1992), S. 981-1003 
    Details
    ISSN: 0271-2091
    Keywords: Co-ordinate mapping ; Finite element method ; Free-boundary ; Solidification ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new boundary-conforming mapping is developed for the calculation of highly deformed cellular solidification interfaces in a model of directional solidification of a binary alloy. The mapping is derived through a variational fomulation that is designed so that the grid penetrates the grooves between cells along the interface without causing a loss of ellipticity of the mapping equations. A finite element/Newton method is presented for simultaneous solution of the free boundary problem described by the solutal model of directional solidification and the mapping equations. Results are compared to previous calculations and demonstrate the importance of accurate representation of the interface shape for understanding the solution structure.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650140807
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