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  • 1
    Electronic Resource
    Electronic Resource
    A model for the pattern of deposition of microfibrils in the cell wall of Glaucocystis (1978)
    Springer
    Planta 141 (1978), S. 51-58 
    Details
    ISSN: 1432-2048
    Keywords: Cell wall ; Cellulose ; Freeze-etching ; Glaucocystis ; Microfibrils (cellulose) ; Morphogenesis ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freeze-fracturing of Glaucocystis nostochinearum Itzigsohn cells during cell-wall microfibril deposition indicates that unidirectionally polarized microfibril ends are localized in a “zone of synthesis” covering about 30% of the sarface area of the plasma membrane. Within this zone there are about 6 microfibril ends/μm2 cell surface. It is proposed that microfibrils are generated by the passage of their tips over the cell surface and that the pattern of microfibril organization at the poles of the cells, in which microfibrils of alternate layers are interconnected at 3 “rotation centres”, results directly from the pattern of this translation of microfibril tips. In a model of the deposition pattern it is proposed that the zone of synthesis may split into 3 sub-zones as the poles are approached, each sub-zone being responsible for the generation of one rotation centre. It is demonstrated that the microfibrillar component of the entire wall could be generated by the steady translation of the microfibril tips (at which synthesis is presumed to occur) over the cell surface at a rate of 0.25–0.5 μm min-1. Microcinematography indicates that the protoplast rotates during cell-wall deposition, and it is proposed that this rotation may play a role in the generation of the microfibril deposition pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387744
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  • 2
    Electronic Resource
    Electronic Resource
    Further evidence from sectioned material in support of the existence of a linear terminal complex in cellulose synthesis (1987)
    Springer
    Protoplasma 136 (1987), S. 96-103 
    Details
    ISSN: 1615-6102
    Keywords: Boergesenia forbesii ; Microfibrils ; Microtubules ; Plasma membrane ; Sectioned material ; Terminal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transmembrane linear terminal complexes considered to be involved in the synthesis of cellulose microfibrils have been described in the plasma membrane ofBoergesenia forbesii. Evidence for the existence of these structures has been obtained almost exlusively using the freeze etching technique. In the present study an attempt has been made to complete these studies using conventional fixation, staining, and sectioning procedures. In developing cells ofBoergesenia forbesii, strongly stained structures traversing the plasma membrane and averaging 598.9 nm ± 171.3 nm in length, 28.7 nm ± 4.2 nm in width, and 35.2 nm ± 6.6 nm in depth have been demonstrated. These structures are considered to be linear terminal complexes. At their distal (cell wall) surface, they appear to be closely associated with cellulose microfibrils. At the proximal (cytoplasmic) surface, they are associated with microtubules and polysomes. A model of the possible interrelation of the terminal complexes and microtubules leading to the generation of cell wall microfibrils is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276358
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  • 3
    Electronic Resource
    Electronic Resource
    A new putative cellulose-synthesizing complex ofColeochaete scutata (1992)
    Springer
    Protoplasma 168 (1992), S. 51-63 
    Details
    ISSN: 1615-6102
    Keywords: Cellulose microfibril formation ; Chlorophyta ; Coleochaete scutata ; Freeze fracture ; Plasma membrane ; Terminal complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cells of the charophycean alga,Coleochaete scutata active in cell wall formation were freeze fractured in the search for cellulose synthesizing complexes (TCs) since this alga is considered to be among the most advanced and a progenitor to land plant evolution. We have found a new TC which consists of two geometrically distinctive particle complexes complementary to one another in the plasma membrane and occasionally associated with microfibril impressions. In the E-fracture face is found a cluster of 8–50 closely packed particles, each with a diameter of 5–17 nm. Most of these particles are confined within an 80 nm circle. In the P-fracture face is found an 8-fold symmetrical arrangement of 10 nm particles circumferentially arranged around a 28 nm central particle. The TCs ofC. scutata are quite distinctive from the rosette/globule TCs of land plants. The 5.5×3.1 nm microfibril inC. scutata is also distinctive from the 3.5×3.5 nm microfibril typical of land plants. The phylogenetic implications of this unique TC in land plant evolution are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332650
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of 2,6-dichlorobenzonitrile and Tinopal LPW on the structure of the cellulose synthesizing complexes ofVaucheria hamata (1992)
    Springer
    Protoplasma 166 (1992), S. 200-207 
    Details
    ISSN: 1615-6102
    Keywords: Cellulose formation ; 2,6-Dichlorobenzonitrile ; Freeze etching ; Plasma membrane ; Cellulose synthesizing enzyme complex ; Tinopal LPW ; Vaucheria hamata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of 2,6-dichlorobenzonitrile (DCB, a known inhibitor of cellulose synthesis) and Tinopal LPW (TPL, an agent which disrupts glucan crystallization) on the structure of cellulose synthesizing complexes (terminal complexes, TCs) in the xanthophycean algaVaucheria hamata were investigated. DCB (10 μM) inhibits nascent fibril formation from the TC subunit (based on the absence of impressions) although it does not alter the overall shape of the rectangular TC during the short treatment of 20 min. With a prolonged treatment (60 min), the arrangement of TC subunits becomes disordered, and particles generally exhibited as doublets of subunits are released from each other. DCB also interferes with the formation of the overall shape of the TC although it does not disturb the conversion into TC rows of the subunits (the zymogenic precursor of the TC) packed in the globules. A 15 min treatment with TPL (1 mM) destroys the TC integrity by reducing the subunits into small fragments or particulate aggregates. The particulate rows of the TC are interrupted at many points, and fragments and particulate aggregates are dispersed by prolonged treatment (45 min) with TPL. Unlike DCB, TPL inhibits the conversion of globule subunits into TC rows. New insights on the structural characteristics necessary for cellulose microfibril assembly and possible mechanisms for the biogenesis of theVaucheria TC come from these data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322782
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    A finite element method for analysis of fluid flow, heat transfer and free interfaces in Czochralski crystal growth (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 453-492 
    Details
    ISSN: 0271-2091
    Keywords: Czochralski crystal growth ; Finite element method ; Free boundary problem ; Incompressible fluid flow ; Heat transfer ; 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 finite element algorithm is presented for simultaneous calculation of the steady state, axisymmetric flows and the crystal, melt/crystal and melt/ambient interface shapes in the Czochralski technique for crystal growth from the melt. The analysis is based on mixed Lagrangian finite element approximations to the velocity, temperature and pressure fields and isoparametric approximations to the interface shape. Galerkin's method is used to reduce the problem to a non-linear algebraic set, which is solved by Newton's method. Sample solutions are reported for the thermophysical properties appropriate for silicon, a low-Prandtl-number semiconductor, and for GGG, a high-Prandtl-number oxide material. The algorithm is capable of computing solutions for both materials at realistic values of the Grashof number, and the calculations are convergent with mesh refinement. Flow transitions and interface shapes are calculated as a function of increasing flow intensity and compared for the two material systems. The flow pattern near the melt/gas/crystal tri-junction has the asymptotic form predicted by an inertialess analysis assuming the meniscus and solidification interfaces are fixed.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650090406
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  • 7
    Electronic Resource
    Electronic Resource
    Solution of free-boundary problems using finite-element/Newton methods and locally refined grids: Application to analysis of solidification microstructure (1993)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 16 (1993), S. 827-843 
    Details
    ISSN: 0271-2091
    Keywords: Local mesh refinement ; Free boundary ; Finite element method ; Co-ordinate mapping ; 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 method is presented for the solution of free-boundary problems using Lagrangian finite element approximations defined on locally refined grids. The formulation allows for direct transition from coarse to fine grids without introducing non-conforming basis functions. The calculation of elemental stiffness matrices and residual vectors are unaffected by changes in the refinement level, which are accounted for in the loading of elemental data to the global stiffness matrix and residual vector. This technique for local mesh refinement is combined with recently developed mapping methods and Newton's method to form an efficient algorithm for the solution of free-boundary problems, as demonstrated here by sample calculations of cellular interfacial microstructure during directional solidification of a binary alloy.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650160906
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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
    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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  • 10
    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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