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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 247 (1997), S. 61-72 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: UV stabilization of polymer systems containing brominated flame retardants has proven to be a difficult technical challenge. Generation of acidic products during processing or exposure can cause a catastrophic deactivation of the Hindered Amine Light Stabilizer (HALS). An understanding of the mechanism for bromine generation from aliphatic and aromatic based flame retardants has lead to formulation approaches based on flame retardant structure. In formulations containing aromatic brominated flame retardants, combinations of UV absorbèrs and a new class of siloxane HALS provide the highest level of UV stabilization to date. Alternatively, bicomponent fiber spinning technology can also provide outstanding UV resistance at significantly lower levels of stabilizers than that used in the monocomponent formulation approach.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-2940
    Keywords: Alkali metals ; ate compounds ; Dihydrotriazine ; Potassium ; N ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of dihydro-s-triazinidopotassium complexes have been synthesised and structurally characterised by X-ray diffraction. Two of them, the sesqui-pyridine solvate 2 and the mono-THF solvate 3, can be classified in formal terms as “potassium potassates” in conforming to the structural pattern established previously for the sesqui-THF solvate 1, the first reported ate of this type. Formally complex [(R2K)-] anions are linked to K+ cations in polymeric, zig-zag chain arrangements. Solvate 3 also possesses a unique RK coordination as a direct result of having fewer solvent ligands. DMSO analogue 4 deviates from this uniformity in adopting a centrosymmetric, dimeric (OK)2 ring structure featuring both terminal and bridging DMSO ligands. The dihydro-s-triazinidosodium tris(THF) solvate 5 is found to be a monomer. For comparative purposes, the metal-free, parent triazine molecule 6 has also been subjected to an X-ray crystallographic study: it displays a 1,2-dihydro ring setup as opposed to the 1,4-dihydro alternative existing in the metallo examples. Triazine 6 is also found to form a N-H…Br bridge in the dimeric structure of the lithium bromide bis (THF) solvate 7, a suspected hydrolysis product from the reaction of dihydro-s-triazinidolithium 8 and magnesium bromide bis(ether) adduct.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1293-1300 
    ISSN: 0009-2940
    Keywords: Calculations, ab initio ; Aluminium compounds ; Heterometallic compounds ; Lithium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the simple alane adduct [Me3Al · HN(CH2Ph)2] (2) with the lithium amide [(PhCH2)2NLi] leads to the formation of the mixed adduct [Me3Al · (PhCH2)2NLi · HN(CH2Ph)2] (1). The crystal structures of 1 and 2 are reported. Exhibiting a four-membered, mixed-metal, mixedanion ring-core, the structure of 1 is unusual in containing a monomeric lithium dibenzylamide fragment. Such fragments generally convert to aza-allyl derivatives, so its existence here can be attributed to the stabilising effect of the attached Me3Al ligand. Crystalline 2 adopts the classical, distorted-tetrahedral arrangement of simple monomeric alane adducts. Ab initio MO calculations on model systems show that mixed adduct formation from Me3Al and Me2NLi is exothermic, while further reaction to give Me2AlNMe2 and MeLi (i.e., complete transmetallation) is endothermic.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0887-3585
    Keywords: crystallization ; folate ; multifunctional ; twinning ; dehydrogenase ; cyclohydrolase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Methylenetetrahydrofolate([H4] folate) dehydrogenase (D) and methenyl[H4] folate cyclohydrolase (C) coexist as a bifunctional enzyme (DC) or as the amino-terminal domain of a trifunctional enzyme (DCS) where the third activity is 10-formyl[H4]lfolate synthetase (S). Two crystal forms of the DC domain of the human cytosolic DCS enzyme have been grown from polyethyleneglycol solution. The monoclinic P21 crystals diffract to 2.8 Å with a = 72.5 Å, b = 68.5 Å, c = 125.2 Å, and β = 91.8° but were found to be twinned. The orthorhombic P212121 crystals diffract to 2.5 Å with a = 67.7 Å, b = 135.9 Å, c = 61.6 Å, and contain two molecules per asymmetric unit. Proteins 26:479-480 © 1996 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 986-996 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Efficient algorithms were developed for estimating model parameters from measured data, even in the presence of gross errors. In addition to point estimates of parameters, however, assessments of uncertainty are needed. Linear approximations provide standard errors, but they can be misleading when applied to models that are substantially nonlinear. To overcome this difficulty, profiling methods were developed for the case in which the regressor variables are error free. These methods provide accurate nonlinear confidence regions, but become expensive for a large number of parameters. These profiling methods are modified to error-in-variable-measurement models with many incidental parameters. Laplace's method is used to integrate out the incidental parameters associated with the measurement errors, and then profiling methods are applied to obtain approximate confidence contours for the parameters. This approach is computationally efficient, requires few function evaluations, and can be applied to large-scale problems. It is useful when certain measurement errors (such as input variables) are relatively small, but not so small that they can be ignored.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1200-1200 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0935-9648
    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
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 643-646 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Electogenerated chemiluminescence ; Ru(bpy)32+ ; Tripropylamine ; Proline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A post- column chemiluminescent technique for thedetection of compounds that are poor chromoshores using electorogenerated chemiluminescence following separation by capillartgy electrophoresis is described. The luminrescent signal is generated followintg the reaction of anlyres (e.g. amines) with Ru(bpy)33+, which isx electrochemically generated post-columan from Ru(bpy)32+. Tripropylamine and proline are used as two model compounds to demostrate the feasibility of the method. Detection limits for the prototype system were in the micromolar rage, suggesting that this technnique offers an alternative to indirect detection of compounds that are poor chromophores with an added selectivity advangage. The system includes the use of a conductive joint to isolate the separation field from the potential necessary to drive the elctrogenerated chemiluminescent reactiion. Addition of the chemiluminescent reagent Ru(bpy)32+ post-column did not decrease the efficiency of the separation. The design and favrication of the novel cell is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0947-6539
    Keywords: exchange coupling ; ferromagnetic properties ; ligand design ; magnetic properties ; multimetallic complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approach is suggested for using ligands to control exchange coupling in multinuclear ions. The idea arose from structural, EPR, and magnetic studies of [PPh4]3 (Scheme 1). Ferromagnetic coupling has been found between the CoII and each CoIII in 3 with J = -22 ± 5 cm-1 (JS1 · S2). It is suggested that dominant antiferromagnetic superexchange is absent because of the strong σ-donor capacity of the tetradentate ligand [k4-PAC*]4- (Fig. 1). The ligand interacts at CoIII primarily with a single d orbital; it is thus best able to participate in superexchange. The interaction makes the unique d orbital strongly σ-antibonding and empty for each d6, S = 1, CoIII ion in 3, that is, unavailable for antiferromagnetic coupling, but available for ferromagnetic pathways by a Goodenough-Kanamori mechanism. By corollary, when any [k4-PAC*]4--type ligand with any magnetic ion Ma in the tetradentate site binds any magnetic ion Mb in the bidentate site, ferromagnetic coupling should be favored provided Ma is not a d9 ion.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 273-285 
    ISSN: 0020-7608
    Keywords: Lanczos propagation ; laser-molecule interaction ; Chebyshev propagation ; time-dependent Schrödinger equation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two Lanczos subspace propagation techniques are discussed in this work and compared with the Chebyshev method applied to the original Hamiltonian matrix. Both procedures involve the use of a reduced propagator in the Lanczos subspace to calculate the solution to the time-dependent Schrödinger equation but differ in the way the propagator is evaluated. The LSC (Lanczos subspace Chebyshev) expresses the propagator in terms of Chebyshev polynomials that are functions of the tridiagonal Hamiltonian matrix in the Lanczos space. In contrast, the LSV (Lanczos subspace variational) is implemented by solving the eigenproblem in the Lanczos subspace and then performing a variational expansion of the propagator in the M-dimensional eigenvector space. Although the LSV is the same as the reduced propagator scheme proposed by Park and Light, in the present study the LSV is implemented as a one-step long-time propagator. As a numerical example, the interaction of a molecule with a strong laser pulse is investigated. The Hamiltonian is explicitly time dependent in this case, and thus the stationary formalism is employed in this work to solve the time-dependent Schrödinger equation. Application of either the LSC or LSV yields a wave function in the M-dimensional Lanczos subspace. Nonetheless, the transition amplitudes computed from this wave function are in excellent agreement with those calculated by direct application of the Chebyshev method in the original space used to define the Hamiltonian matrix.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 273-285, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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