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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 389-396 
    ISSN: 0006-3592
    Keywords: length-projected area ; length-number scaling ; Zoogloea ramigera ; Saccharomyces cerevisae ; fractal geometry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fractal nature microbial aggregates is a function of the type of microorganism and mixing conditions used to develop aggregates. We determined fractal dimensions from length-projected area (D2) and length-number scaling (D3) relationships. Aggregates of Zoogloea ramigera developed in rotating test tubes were both surface and mass fractals, with fractal dimensions of D2 = 1.69 ± 0.11 and D3= 1.79 ± 0.28 (±standard deviation), respectively. When we grew this bacteria in a bench-top fermentor, aggregates maintained their surface fractal characteristics (D2 = 1.78 ± 0.11) but lost their mass fractal characteristics (D3 = 2.99 ± 0.36). Yeast aggregates (Saccharomyces cerevisae) grown in rotating tests tubes had higher average fractal dimensions than bacterial aggregates grown under physically identical conditions, and were also considered fractal (D2 = 1.92 ± 0.08 and D3 = 2.66 ± 0.34). Aggregates porosity can be expressed in term of a fractal dimensions, but average porosities are higher than expected. The porosities of yeast aggregates (0.9250-0.9966) were similar to porosities of bacterial aggregates (0.9250-0.9966) cultured under the same physical conditions, although bacterial aggregates developed in the reactor had higher average porosities (0.9857-0.9980). These results suggest that that scaling relationships based on fractal geometry may be more useful than equations derived from Euclidean geometry for quantifying the effects of different fluid mechanical environments on aggregates morphology and characteristics such as density, porosity, and projected surface area.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 213-235 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small nickel atom clusters exhibit an energetic preference for localized, open 3d-shells. This tendency is attributed to weak 3d-3d overlap and is analyzed in terms of the competition between resonance integrals and screening terms. Analogous competition between resonance and screening leads to (spatially) symmetry-broken charge-localized SCF solutions for 3d ion-hole states in nickel atom clusters. Charge-localized symmetry broken wavefunctions are also employed as initial and final diabatic (nonstationary) states in the electron transfer processes associated with transition metal complexes of the type MX6n +, where M = Fe, Ru; X = H2O; NH3, n = 2, 3. Resonance integrals coupling the initial (reactants) and final (products) states have been calculated for several geometrical structures and electronic states of interest. An important contributor to the screening effects which promote charge localization in these systems is the charge-dependence of metal-ligand bond lengths. The decrease in oxidation-state dependence of metal-ligand bond length in the series Fe2+/3+ (H2O)6 → Ru2+/3+ (H2O)6 → Ru2+/3+ (NH3)6 is analyzed in terms of ligand-to-metal charge transfer (LMCT), and the trend is attributed to diminished participation of the metal atom in the redox process. The electronic rearrangement upon reduction is dominated by the eg (σ) manifold, even though the reducing electron is added to the t2g (π) manifold.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We start by pointing out relationships between production of information, global simulation, and supercomputing, thus placing our research activities in today's society context. Then we detail the evolution in hardware and software for 1CAP, our experimental supercomputer, which we claim to be especially well suited for supercomputing in science and engineering. A preliminary discussion of 1CAP/3090 (our latest experimental effort) is included. Many examples from different disciplines are provided to verify our assertions. We “prove” our point by presenting an example of global supercomputing. Starting with 3 nuclei and 10 electrons, building up to a single water molecule, then to a few hundred, we learn, for example, about Raman, infrared, and neutron scattering; we then move up to a few hundred thousand molecules to analyze particle flow and obstructions; finally we experiment, but only preliminarily, with a few million particles to learn more on nonequilibrium dynamics as in the Rayleigh-Benard systems. In this way, quantum mechanics is overlapped with statistical mechanics and expanded into microdynamics. The entire paper is finally reanalyzed from a different perspective, presenting rather systematically, even if most briefly, our ideas on “modern” computational chemistry, where quantum mechanics is as much needed as fluid dynamics and graphics. In this section the main computational techniques are analyzed in terms of computer programs and their associated flow diagrams to solve the basic equations using parallel supercomputers.
    Additional Material: 33 Ill.
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  • 4
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0192-253X
    Keywords: Vertebrates ; homeodomain ; engrailed ; evolutionary conservation ; gene regulation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have isolated and characterized genomic DNA clones for the human and chicken homologues of the mouse En-1 and En-2 genes and determined the genomic structure and predicted protein sequences of both En genes in all three species. Comparison of these vertebrate En sequences with the Xenopus En-2 (Hemmati-Brivanlou et al., 1991) and invertebrate engrailed- like genes showed that the two previously identified highly conserved regions within the En protein [reviewed in Joyner and Hanks, 1991] can be divided into five distinct subregions, designated EH1 to EH5. Sequences 5′ and 3′ to the predicted coding regions of the vertebrate En genes were also analyzed in an attempt to identify cis-acting DNA sequences important for the regulation of En gene expression. Considerable sequence similarity was found between the mouse and human homologues both within the putative 5′ and 3′ untranslated as well as 5′ flanking regions. Between the mouse and Xenopus En-2 genes, shorter stretches of sequence similarity were found within the 3′ untranslated region. The 5′ untranslated regions of the mouse, chicken and Xenopus En-2 genes, however, showed no similarly conserved stretches. In a preliminary analysis of the expression pattern of the human En genes, En-2 protein and RNA were detected in the embryonic and adult cerebellum respectively and not in other tissues tested. These patterns are analogous to those seen in other vertebrates. Taken together these results further strengthen the suggestion that En gene function and regulation has been conserved throughout vertebrate evolution and along with the five highly conserved regions within the En protein, raise an interesting question about the presence of conserved genetic pathways. © 1992 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 10 (1986), S. 137-140 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The limiting oxygen indices of flame-retardant treated wools have been determined at environmental temperatures up to 380°C. As the ambient temperature increases, the LOI decreases significantly until, within the temperature range of 308°C and 325°C, it reaches a minimum value, Above 325°C, the LOI of the carbonaceous residue increases rapidly with temperature. The minimum value reached for a number of retardant treated wools was below that for untreated wool. Broadly similar behaviour is exhibited by flame-retardant cotton, modacrylic and Nomex°, although with the latter there is no increase in oxygen index at the upper end of the temperature range studied.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 1837-1845 
    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: Multiaxially oriented ultrahigh molecular weight polyethylene films were prepared recently under curvilinear flow conditions generated by the combined effects of compression and rotation. The films were prepared by melt flow crystallization in an optical apparatus specially designed for rheo-optical observations. Morphological studies indicate that the films were fibrillar with the fibrils oriented along the circular flow lines. The fibrils were lamellar, and their lamellar thickness (150-450 Å) and spacing (400-2000 Å) depended on the processing conditions. The film exhibited strong birefringence (1.4 × 10-2) and had a Young modulus of 15-25 GPa along the flow lines and 3-5 GPa in the transverse direction.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 2009-2014 
    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: The structure of the aromatic copolyester of poly(ethylene terephthalate) and 80 mol % of p-acetoxybenzoic acid was investigated by optical and electron microscopy, wide angle X-ray, and thermal analysis. The results of optical (LM) and electron microscopy (TEM and STEM) suggest the existence of ordered domains which appear as large lamellar thickness (∼200 Å) as has been described earlier for single crystals of the pure hompolymer of p-hydroxybenzoic acid (PHBA). However, the characteristic reversible endotherm at 330-360°C for PHBA could not be obtained. In isolated cases, the lamellar blocks retained their general dimensions up to 535°C whereas the surrounding matrix had degraded severely. An irreversible endotherm was observed at 303°C which suggested the presence of a higher degree of order than expected for a random copolymer. The irreversible nature of the endotherm is consistent with a transition from a semicrystalline structure to a liquid crystalline state. X-ray analysis with as received samples and thermally treated specimen provided additional support for more ordered regions.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 821-830 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the course of melt-flow crystallization studies with ultrahigh-molecular-weight polyethylene (UHMWPE), we observed that the melt of UHMWPE is highly anisotropic above its equilibrium melting point and has a tendency to fibrillate. An examination of the melt anisotropy of UHMWPE by optical, Thermal, and x-ray analysis indicates that the melt anisotropy persists at 345°C, i.e., the temperature at which the polymer degrades under nitrogen, and appears similar to a smectic liquid-crystalline phase.
    Additional Material: 8 Ill.
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  • 10
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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