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  • 1
    Electronic Resource
    Electronic Resource
    Generalized-molecular-orbital theory: Simple multiconfiguration self-consistent-field method (1978)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 613-621 
    Details
    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: Even after completing a multiconfiguration self-consistent-field (MCSCF) calculation, one must often include additional configuration interaction (CI) to obtain quantitative or semiquantitative results. There is some question of whether the prior MCSCF calculation is worthwhile, if additional CI is needed later. We have developed a new MCSCF computational method, which, because of our assumptions about the nature of the configurations, yields one Fock-like operator for all the “filled” orbitals (high occupation numbers) and a second Fock-like operator for all the “virtual” orbitals (low occupation numbers). Since there are only two matrices to build, our method is considerably faster than other MCSCF approaches. Because of these similarities to standard molecular-orbital (MO) calculations, we have termed our approach generalized-molecular-orbital (GMO) theory. However, the “virtual” orbitals, unlike those of standard MO theory, are optimized to correlate the “filled” ones and can he used in a subsequent CI calculation. Results are presented for the correlation energy of H2O, the spectroscopic constants of N2, the singlet-triplet energy separations in CH2, and the nature of the chromium-chromium quadruple bond. Although these results are at a very low level of CI, the GMO approach appears to correct for the gross deficiencies of the single-determinant SCF procedure.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560140508
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  • 2
    Electronic Resource
    Electronic Resource
    Geometry optimization of organometallic complexes: A study of basis sets (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 503-512 
    Details
    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: Total geometry optimizations are reported for Cr(CO)6, HMn(CO)5, Fe(CO)5, Ni(CO)4, Cr(C6H6)2, Fe(C5H5)2, Ni(C4H4)2, Cr(NO)4, (C5H5)Mn(CO)3, and (C6H6)Cr(CO)3. A variety of basis sets were examined, and, based on the results, a relatively compact and accurate basis set is proposed. The differences between the calculated and experimental metal-carbonyl, metal-benzene, and metal-nitrosyl bond distances average 0.03, 0.08, and 0.07 Å, respectively. Calculated metal-cyclopentadienyl bond lengths were found to be an average of 0.15 Å longer than experimental bond lengths. Addition of electron correlation at the perfect pairing GVB level reduced the average difference in the metal-cyclopentadienyl bond length to 0.08 Å.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320749
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  • 3
    Electronic Resource
    Electronic Resource
    The flammability of polyacrylonitrile and its copolymers III. Effect of flame retardants (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 18 (1994), S. 231-241 
    Details
    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: This paper extends previously reported work 1,2 and describes the influence that a range of selected flame retardants have on the burning behaviour and pyrolyses of homo-and copolymers of acrylonitrile. Various inorganic and organic phosphorus and nitrogen- or sulphur-containing, halogen-containing (in the absence and presence of halogen or antimony (III) oxide) and nitrogen-containing flame retardants and red phosphorus were studied using LOI, TGA, DSC and residual char measuring techniques. Flame retardancy relates directly to char-forming tendency for all retardants and their ability to reduce the dominance of flammable volatiles formed during the first stage of acrylic polymer pyrolysis. Ammonium phosphates are particularly effective flame retardants for the selected copolymers. Possible mechanisms of retardant activity are discussed, including the char-forming tendency of antimony-bromine combiniations.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fam.810180406
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  • 4
    Electronic Resource
    Electronic Resource
    Basis sets for geometry optimizations of second-row transition metal inorganic and organometallic complexes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 923-933 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Modest-sized basis sets for the second-row transition metal atoms are developed for use in geometry optimization calculations. Our method is patterned after previous work on basis sets for first-row transition metal atoms. The basis sets are constructed from the minimal basis sets of Huzinaga and are augmented with a set of diffuse p and d functions. The exponents of these diffuse functions are chosen to minimize both the difference between the calculated and experimental equilibrium geometries and the total molecular energies for several second-row transition metal inorganic and organon etallic complexes. Slightly smaller basis sets, based on the same Huzinaga minimal sets but augmented with a set of diffuse s and p functions rather than diffuse p and d functions, are also presented. The performance of these basis sets is tested on a wide variety of second-row transition metal inorganic and organometallic complexes and is compared to pseudopotential basis sets incorporating effective core potentials.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120804
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  • 5
    Electronic Resource
    Electronic Resource
    Basis sets for transition metals: Optimized outer p functions (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 1359-1370 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Although the (n + 1)p orbital is unoccupied in transition-metal ground-state configurations which are all ndx(n + 1)sy, these (n + 1)p functions play a crucial role in the structure of transition metal complexes. As we show here, the usual solution, adding one or more diffuse functions, can be insufficient to create an orbital of the correct energy. The major problem appears to be due to the incorrect placement of the (n + 1)p orbital's node. Even splitting the most diffuse component of the np orbital and adding a second diffuse function does not completely solve this problem. Although one can usually solve this deficiency by further uncontracting of the np function, here we offer a set of properly optimized (n + 1)p functions that offer a more compact and satisfactory solution to the proper placements of the node. We show an example of the common deficiencies seen in typical basis sets, including standard basis sets in GAUSSIAN94, and show that the new optimized (n + 1)p function performs well compared to a fully uncontracted basis set. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Environmental consequences of using flame-retardant textiles - a simple life cycle analytical model (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 21 (1997), S. 229-234 
    Details
    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: This paper extends earlier work which explored the possibility of undertaking a life cycle analysis of flame-retardant cotton and polyester textiles and consequently enabled semi-quantitative estimations of their relative environmental impacts to be made. This model is extended to undertake full environmental audits of a range of flame-retardant textiles and requires full consideration of each stage from fibre/raw material production to eventual disposal. The need for comprehensive data at all stages, however, demonstrates that comparisons between competing products are neither simple nor, at present, possible. Thus an environmental rank value is given to each stage in the manufacturing process and product life of each flame retardant fibre and derived textile. Summation of rank values enables an overall environmental index to be defined which may be used to compare the environmental impact of each generic type of currently available flame retardant, single fibre-containing textile. The results show that each of the eleven generic fibres analysed yield environmental index values within a range 32-51% where 100% denotes the worst environmental position possible. This relatively low range of values suggests that current production and processes which attempt to maximize economic viability also tend to reduce environmental impact. © 1997 John Wiley & Sons Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Flammability of polyacrylonitrile and its copolymers II. Thermal behaviour and mechanism of degradation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 303-314 
    Details
    ISSN: 0959-8103
    Keywords: polyacrylonitrile ; flammability ; pyrolysis ; degradation ; thermal analysis ; mechanism ; copolymer ; 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: Homopolymeric polyacrylonitrile and fibre-forming copolymers containing either vinyl acetate or methyl acrylate comonomer have been studied by thermal analysis (DSC, TGA and DTG) at various heating rates (10-100 K min-1) and under air and nitrogen. Three well-defined pyrolysis stages have been observed which occur over the temperature ranges 250-350°C, 350-550°C and above 550°C. Each stage involves a competition between volatilisation and cyclisation or char-forming reactions which depends on heating rate and the presence or absence of oxygen.The well-established dominance of cyclisation in the 250-350°C temperature range obtained during carbon fibre production from acrylic precursors occurs only at low heating rates. At high heating rates, volatilisation dominates and this explains why acrylic polymers have high flammabilities when heating rapidly.The full pyrolysis mechanism has been semi-quantitatively analysed and the role that comonomers play discussed. This has enabled a fuller understanding of the potential burning behaviour of these polymers to be developed.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210330310
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  • 8
    Electronic Resource
    Electronic Resource
    Genetic studies on mechanisms of protein localization in escherichia coli K-12 (1980)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 147-163 
    Details
    ISSN: 0091-7419
    Keywords: gene fusions ; λ receptor ; major outer membrane proteins ; signal sequence mutations ; ribosome ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the last few years, several laboratories have demonstrated that many proteins (both from eukaryotic and prokaryotic organisms) that are destined to be localized in noncytoplasmic locations initially are synthesized as a precursor with a 15-30 amino acid extension at the NH2-terminal end of the molecule. This extra peptide has been termed the signal sequence, and it has been proposed that this signal plays a role in the localization of the extracytoplasmic protein. We are studying the process by which proteins are exported to the envelope region of Escherichia coli. Our work deals primarily with the outer membrane proteins, λ receptor, the product of the lamB gene, and the major outer membrane (porin) proteins 1a and 1b, products of the ompF and ompC genes.Using techniques of gene fusion, we have demonstrated that information specifying the cellular location of the λ receptor is contained within the lamB gene. Furthermore, we have shown that this information is capable of directing even a normally cytoplasmic protein, β-galactosidase, to the outer membrane. Some of this information is contained within the signal sequence. Mutations that alter this sequence prevent export of the λ receptor protein. Again using techniques of gene fusion, we have shown that the signal sequence alone is not sufficient to cause export of β-galactosidase from the cytoplasm. Other information within the lamB gene is required.Selection procedures have been developed to isolate mutations that exhibit a general alteration in the export process. Genetic analysis of these mutations has provided evidence for the involvement of the ribosome in the process of protein localization.The structural genes for the porin proteins, 1a and 1b, are regulated at the transcriptional level by the ompB locus. This has permitted us to extend our studies on outer membrane protein localization to protein 1. With this genetic system, it should be possible to determine if E coli employs more than a single mechanism for the export of proteins to the outer membrane.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400130203
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