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  • Elsevier  (223)
  • Wiley-Blackwell  (13)
  • American Meteorological Society
  • Copernicus
  • 2000-2004  (92)
  • 1990-1994  (97)
  • 1975-1979  (57)
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  • 1
    Digitale Medien
    Digitale Medien
    (E,Z) Equilibria, 14. Substituent-Induced Chemical Shifts along the C = N Bond of Schiff Bases (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2033-2040 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 13C NMR, SCS ; Substituent effects ; Imines ; Isomerization, (E,Z) Schiff bases ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sterically congested N-(1,1,3,3-tetraalkyl-2-indanylidene)-amines 8-11, N-(cyclopentylidene)anilines 13-17, and two of their salts are described, together with a short synthesis of 2-imino-1,1,3,3-tetramethylindan (5). Some of these imines show rapid (E,Z) equilibration. Positively and negatively charged nitrogen functions (in 6 and 7) cause opposite 1H- and 13C-NMR chemical shift effects along the C = N bond. Chemical shifts are almost equally affected by the lone electron pair and by the imino N-H bond. Substituent-induced chemical shifts (SCS) have been assigned for all syn and anti positions with respect to methyl, phenyl, and 2,6-dimethylphenyl groups at the imino nitrogen atom. The structurally well-defined, rigid imines recommend themselves as new models for the calibration of theoretical approaches to syn/anti-differentiating SCS.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19921250911
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  • 2
    Digitale Medien
    Digitale Medien
    (E, Z)1-Equilibria, 17 Demonstration of the Nitrogen Inversion Mechanism of Imines in a Schiff Base ModelDedicated to Professor Heinrich Nöth on the occasion of his 65th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 747-754 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diastereotopomerization, (E, Z) ; Imines ; Inversion, nitrogen ; Permethylation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Experimental differentiation between pure C=N double bond rotation and nitrogen inversion in N1-arylimines is possible with a single compound (13b) under the proviso of slow rotation about the N-aryl single bond. Labelling by 1H and 13C nuclei at the diastereotopic faces of the C=N moiety as well as of the N-aryl group is the clue to a successful stereodynamic analysis, as performed by variable-temperature NMR spectroscopy of 13b, a sterically congested and chiral model compound. Interpretation of similar measurements on a second model (13d) is less straightforward. The experimental observation of time-averaged Cs symmetry by NMR coalescences is only compatible with a mechanism of (E/Z) stereomutation either by pure inversion at sp2 nitrogen or by a contribution from C=N rotation together with a synchronized (geared) controtation about the N-aryl single bond. However, the latter combination is concluded to be predominantly inversion-like by comparisons with related imines.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19931260327
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  • 3
    Digitale Medien
    Digitale Medien
    An explicit numerical method for solving transient combined heat conduction and convection problems (1979)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 14 (1979), S. 1141-1163 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper describes an explicit numerical method for solving transient combined heat conduction and convection problems. Applications include the cooling of many types of engineering plant; for example, stator and rotor windings of turbogenerators and high voltage underground cables. The Du Fort-Frankel and the fully implicit finite difference schemes have been used to solve the conduction and convection equations, respectively. It is shown that, with a suitable order of calculation, the overall method becomes explicit. Computational procedures are outlined and stability, accuracy and convergence are considered. Numerical examples are given to illustrate the use of the method and to validate some of the theoretical points. Results have also been obtained using existing numerical methods and have been compared with those from the proposed method. For certain problems, it is shown that the proposed method uses less overall computing time than other methods such as that devised by Crank and Nicolson.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620140804
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  • 4
    Digitale Medien
    Digitale Medien
    Forbidden nodes for curved finite elements (1979)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 14 (1979), S. 1421-1427 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: It is shown here that certain interpolating polynomials of degrees four and five may not always be uniquely defined on triangular-shaped elements which have one curved side. Conditions which indicate non-uniqueness are given, together with some geometrical interpretations concerning the location of the node on the curved side. A numerical example is given to demonstrate that there ar curves for which every point is unsuitable to be chosen as a node.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620140913
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  • 5
    Digitale Medien
    Digitale Medien
    Expression of recombinant protein A from the lac promoter in Escherichia coli JM83 is not subject to catabolite repression when grown under specific conditions of continuous culture (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1050-1058 
    Details
    ISSN: 0006-3592
    Schlagwort(e): catabolite repression ; protein A ; membrane proteins ; continuous culture ; protein expression ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Although widely used in experimental and industrial situations, genetically engineered plasmids containing the lac promoter from Escherichia coli are subject to catabolite repression when grown in glucose-containing media. Several methods of overcoming this problem have been investigated by studying the expression of the protein A gene from Staphylococcus aureus under the control of the Escherichia coli lac promoter. When glycerol is used as a sole carbon source, the plasmid is unstable and is rapidly lost from the culture. When the bacteria are grown in chemostats under glucose limitation, the plasmid is maintained, even at high dilution rates, and the expression of protein A is similar to that observed when glycerol was used. The balance between metabolic load and protein A expression seems to be maintained by reducing the gene dose to a tolerable level. Depending on the metabolic conditions prevailing in the culture, this is achieved, either by reducing the copy number of the plasmid or in extreme cases by removing the plasmid altogether.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260380914
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  • 6
    Digitale Medien
    Digitale Medien
    The load-bearing capability of short-fiber thermoplastics composites - A new practical system of evaluation (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 173-180 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The load-bearing capabilities of short-fiber reinforced thermoplastics composites can be evaluated, in principle, by the methods known to be satisfactory for unreinforced thermoplastics, but in practice the cost of a comprehensive evaluation of a composite would be prohibitive because of the anisotropy of the properties and its variation from point to point. For the same reasons the properties measured on a specimen cut from a molding may have little relevance to its overall performance. This paper describes recent experiments that could lead to a radical change in testing strategy. Instead of the classical method in which standard specimens cut from moldings are assumed to provide the various stiffness coefficients needed for anisotropic stress analysis, simple moldings such as discs or plaques are tested directly. The sacrifice of precision in the measurements and the loss of rigor in the definition of the measured quantities is more than compensated for by a gain in the general utility of the data and the substantial reduction in the cost of evaluations. The mechanical properties of shortfiber thermoplastics composites are particularly sensitive to mold geometry and the new methods of testing enable the effects to be assessed readily, whereas the information generated by the classical method is virtually indecipherable in that context. Examples are given in the paper.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760190303
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  • 7
    Digitale Medien
    Digitale Medien
    Localized flow birefringence of polyethylene oxide solutions in a four roll mill (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1111-1119 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: We report flow birefringence observations of polyethylene oxide solutions in a four roll mill where the flow field in the central region of the mill approximates well to that of pure shearing flow. When flow birefringence is observed it is seen to be highly localized within a region close to the “outgoing” asymptotic plane of flow. The phenomenon can be explained in terms of the flow birefringence corresponding to high extension of some polymer chains where the localization is caused by the chains requiring sufficient time in the flow field to become extended. This explanation has important consequences in all “persistently extensional flows” and can explain the origin of previously published results of localized flow birefringence observed for polyethylene solutions in axial compression and axial extensional flows.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1976.180140613
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  • 8
    Digitale Medien
    Digitale Medien
    Paving: A new approach to automated quadrilateral mesh generation (1991)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 32 (1991), S. 811-847 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper presents a new mesh generation technique, paving, which meshes arbitrary 2-D geometries with an all-quadrilateral mesh. Paving allows varying element size distributions on the boundary as well as the interior of a region. The generated mesh is well formed (i.e. nearly square elements, elements perpendicular to boundaries, etc.) and geometrically pleasing (i.e. mesh contours tend to follow geometric contours of the boundary). In this paper we describe the theory behind this algorithmic/heuristic technique, evaluate the performance of the approach and present examples of automatically generated meshes.
    Zusätzliches Material: 42 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620320410
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  • 9
    Digitale Medien
    Digitale Medien
    Mass spectra of trimethylsilyl derivatives of naturally occurring flavonoid aglycones and chalcones (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 157-160 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Electron impact mass spectra of the trimethylsilyl derivatives of a series of flavonoid aglycones and chalcones are reported. The spectra show prominent ions arising from fragmentation of the trimethylsilyl (TMS) groups. Inter-actions between adjacent TMS groups, and between TMS groups in the 3- or 5-position (6′-position for the chalcones) and the C-ring carbonyl, yield structurally significant ions. Few fragments associated with the retro-Diels-Alder cleavage of the C-ring characteristic of the underivatized compounds, are observed. The TMS derivatives thus provide complementary information for the identification of flavonoid aglycones and chalcones in biological systems.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210260310
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  • 10
    Digitale Medien
    Digitale Medien
    A fast x-ray counting system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 58-60 
    Details
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: An unusually fast x-ray detector and pulse processing counting system has been devised and tested. The overall dead time of the system was determined experimentally to be 42 ns.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/xrs.1300220113
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