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  • 1
    Electronic Resource
    Electronic Resource
    Computer simulation studies of anisotropic systems. XXVII. The direct pair correlation function of the Gay–Berne discotic nematic and estimates of its elastic constants (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 7483-7492 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulations have been performed for a discotic liquid crystal composed of Gay–Berne particles. On the basis of these simulations for the nematic phase, a subset of the spherical harmonic expansion coefficients of the direct pair correlation function (DPCF) were determined from the pair distribution function (PDF) by solving the Ornstein–Zernike (OZ) equation. This was achieved by generalizing the Wiener–Hopf factorization scheme for the numerical solution of the OZ equation. Only the expansion coefficients gl1,l2,l(r) (lα≤4) of the PDF in the laboratory frame were used when solving the OZ equation; this means that the DPCF so obtained is equivalent to that for a nematic in which the director is randomly distributed. From the DPCF, the scaled Oseen–Zöcher–Frank elastic constants K11*, K22*, and K33*, as well as the surface constant K13*, have been calculated from the subset of expansion coefficients. Generally, we find that K33*〈K11*〈K22*, in agreement with what is expected and found for discotic nematics. These results are quantitatively but not qualitatively different from those calculated with the help of analytical approximations for the the same spherical harmonic expansion coefficients of the direct pair correlation function. For example, the values of the bulk elastic constants determined via the OZ equation are about three times larger than the bulk elasticity obtained with the low density approximation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474988
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of surface anchoring and viscosity upon the switching behavior of twisted nematic cells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6046-6052 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical calculations are presented on the dynamics of twisted chiral nematic cells. We are emphasizing the influence of surface effects on the optical switching behavior. Apart from the anchoring strength we have taken into account viscous effects at the surface by constructing a surface dissipation function. The dynamical light transmission curve has been determined for different strengths of the surface anchoring and various viscosity parameters by computer simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355220
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  • 3
    Electronic Resource
    Electronic Resource
    Switching of surface-stabilized ferroelectric liquid crystal cells by motion of defects (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1381-1387 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical calculations are presented on both equilibrium states and switching processes of surface-stabilized ferroelectric liquid crystal cells. Defect mediated switching by Bloch walls and by disclination lines is studied in particular. Our examinations are based on an idealized bookshelf configuration of the molecules with fixed tilt angle of the director. Numerical solutions for the scalar fields both of the director twist angle and the electric potential have been determined in two spatial dimensions, assuming the fields to be constant along the third dimension. In the bulk we employ the full Frank–Oseen energy (i.e., no one-constant approximation) with electric terms added represented by a uniaxial dielectric tensor and the spontaneous polarization. On the surface the director is anchored by a Rapini–Papoular potential with medium anchoring strength. The calculations were performed in high precision with a multigrid method on an adaptive grid. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362937
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of viscoelastic coefficients from the optical transmission of a planar liquid crystal cell with low-frequency modulated voltage (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6053-6057 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The viscoelastic response of the nematic director field to low-frequency modulations of the driving voltage was studied by means of optical transmission measurements. An external ac voltage above the critical field Uc was weakly amplitude modulated with frequencies in the range of 1 to 100 Hz. The viscosity coefficients α1, γ1, γ2, and ηb influence the time dependence of the director field. They were determined by fitting the phase and amplitude of theoretically calculated optical transmission curves to measured data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355221
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  • 5
    Electronic Resource
    Electronic Resource
    Gene flow between African- and European-derived honey bee populations in Argentina (1991)
    [s.l.] : Nature Publishing Group
    Nature 349 (1991), S. 782-784 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] For several decades the northward expansion of African-derived (Africanized) honey bee populations has been tracked with behavioural, morphological and biochemical studies8"13. In general, behavioural studies have shown that certain characters of the African race, especially those with adaptive ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/349782a0
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  • 6
    Electronic Resource
    Electronic Resource
    Water droplets in a spherically confined nematic solvent: A numerical investigation (1999)
    Springer
    The European physical journal 10 (1999), S. 515-523 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets, but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a defect between them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050881
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  • 7
    Electronic Resource
    Electronic Resource
    DNA Evidence of the Origin of Varroa jacobsoni Oudemans in the Americas (1997)
    Springer
    Biochemical genetics 35 (1997), S. 327-335 
    Details
    ISSN: 1573-4927
    Keywords: Varroa jacobsoni ; honey bees ; randomly amplified polymorphic DNA ; genetic variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Randomly amplified polymorphic DNA (RAPD) was used to examine possible origin of Varroa jacobsoni Oudemans in the Americas. Among 64 primers screened, 2 primers provided variation which was informative for this study. All V. jacobsoni collected from the United States had the same banding pattern to that of mites collected from Russia, Morocco, Germany, Italy, Spain, and Portugal (Russian pattern). This banding pattern was different from the pattern found for mites collected from Japan, Brazil, and Puerto Rico (Japanese pattern). The Japanese pattern lacked a 766-bp band found in the Russian pattern (OPE-07). With primer OPP-03, the Russian pattern had a distinct band at 442 bp not found in the Japanese pattern. Two bands located at 675 and 412 bp were specific to the Japanese pattern. These results suggest that the V. jacobsoni of the United States is probably predominantly Russian in origin (via Europe), while the V. jacobsoni of Brazil and Puerto Rico are probably predominantly Japanese in origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021821821728
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  • 8
    Electronic Resource
    Electronic Resource
    Treating exceptionally non-linear temperature fields (1988)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 25 (1988), S. 571-580 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: By some examples it is shown how to treat non-everyday heat transfer problems which are characterized by temperature dependent heat sources and heat radiation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620250218
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  • 9
    Electronic Resource
    Electronic Resource
    Experiences in non-linear analysis of temperature fields with finite elements (1987)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 24 (1987), S. 59-73 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper describes practical experiences in dealing with non-linearities in temperature field calculations. First the use of the load vector for representing the heat radiation on the outer surfaces is reported. However, if there are also additional non-linearities in the conductance matrix, then it may happen that because of possible counteractions of the non-linearities no convergence is achieved, at least with the direct iteration. Therefore it is more appropriate to put the radiation terms into the conductance matrix where the other non-linearities, such as temperature dependent thermal conductivity and natural convection also appear. It is shown how the Newton-Raphson iteration can be applied in an easy way. In the case of temperature dependent heat sources the load vector also needs to be considered. The appropriate special measures are described.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620240105
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  • 10
    Electronic Resource
    Electronic Resource
    Plotting of contours in a natural way (1987)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 24 (1987), S. 1757-1769 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple and straightforward scheme for plotting contours is introduced. For any function the appropriate contours are traced on the paths of constant function values disclosing the information contained in the shape functions. The exactness of the contours matches that of the finite element analysis. Extreme value considerations must be carried out to decide whether contours appear in an element at all. Three co-ordinate systems are dealt with: the local, the global and the screen co-ordinate system, and the necessary mutual transformations. A short section deals with the treatment of contour discontinuities across element borders which frequently occur with stresses and heat fluxes. Finally, some examples are shown.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620240911
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