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  • 1985-1989  (15)
  • 1975-1979  (10)
  • 1970-1974  (3)
  • 1960-1964  (3)
  • Chemistry  (31)
  • 1
    Electronic Resource
    Electronic Resource
    Deformational dynamics and nmr relaxation of supercoiled DNAs (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1023-1056 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation and internal dynamics of supercoiled pUC 8 DNA (2717 bp) are examined by dynamic light scattering, and the magnitude and uniformity of its torsional rigidity are determined using time-resolved fluorescence polarization anisotropy of intercalated ethidium dye. Neither measurement gives any indication of an appreciably reduced bending or twisting rigidity, or anomalously rapid internal motions. For 31P, in supercoiled pUC 8, we measure T2 = (2.0 ± 0.5) × 10-3 s. This lies within the range of present theoretical estimates obtained using normal rigidities. The proton linewidths observed for pUC 8 and pBR322 (4363 bp) DNAs are within a factor of 2-3 of those similarly estimated assuming ordinary rigidities.According to Bendel, Laub and James [(1982) J. Am. Chem. Soc. 104, 6748-6754], supercoiled pIns36 DNA (7200 bp) exhibits an astonishingly long T2 = 1.17 s for 31P, a slowest rotational relaxation time, τ = 5 × 10-9 s, and an enormously reduced bending rigidity. Serious questions raised by these findings are examined here. The 5 × 10-9 s slowest rotational relaxation time is shown to be physically inadmissible.The nmr relaxation theory developed previously by Allison, Shibata, Wilcoxon, and Schurr [(1982) Biopolymers 21, 729-762], is modified to incorporate new results for deformable filaments, which directly introduce the highly nonexponential tumbling correlation function for reorientation of the local helix axis. Essential requirements for a complete calculation of R2, including estimation of the tumbling correlation function and evaluation of the still unknown DIP/CSA cross-term, are described in detail. Slow coil-deformation modes analogous to the Rouse-Zimm modes of linear DNAs are shown to make an important, if not dominant, contribution to the R2 relaxation rate. Geometrical parameters in the theory are chosen to provide good agreement with literature data for 600-bp linear DNA. Using this theory and an informed guess for the tumbling correlation function, we find that the 31P-nmr relaxation data of Bendel et al., if correct, necessarily impose on their DNA one or more extreme properties, such as enormously reduced bending or twisting rigidities. In contrast, the same theory yields reasonable agreement with the T2 reported here for 31P in supercoiled pUC 8 DNA when its rigidities are assumed to be quite ordinary.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240609
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of the urinary polymer-related material from rats given poly[biguanide-1,5-diylhexamethylene hydrochloride] (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 2591-2605 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die gastrointestinale Absorption von Poly(biguanid-1,5-diylhexamethylen-hydrochlorid) (1) in Ratten beträgt nur 5,6% einer einzigen oralen Dosis, und auch nach Langzeitbehandlung liegen die Konzentrationen im Gewebe höchstens bei 0,3 μg g-1. Durch cinfache chromatographische und spektroskopische Methoden konnte gezeigt werden, daß die im Harn ausgeschiedenen Substanzen in kleinen Mengen aus 1-Oligomeren mit zwer Cyanguanidino-Endgruppen bestehen, sowie aus Spuren von 3,3′-Dicyano-1,1′-hexamethylendiguanidin (8a) und einer Verbindung, die für 1-(6-Aminohexyl)-3-cyanoguanidin (2) gehalten wird, und die bei der Synthese von 1 entsteht. Die Bestandteile von 1 werden demnach in Ratten nicht metabolisiert.
    Notes: Gastro-intestinal absorption in rats of poly[biguanide-1,5-diylhexamethylene hydrochloride] (1) amounts to only 5,6% of a single oral dose, and after chronic administration, tissue concentrations do not exceed 0,3 μg g-1. It has been shown by simple chromatographic and spectroscopic methods that urinary polymer-related material consists of small amounts of 1-oligomers, with two cyanoguanidino end groups, as well as the trace constituents, 3,3′-dicyano-1,1′-hexamethylenediguanidine (8a) and a compound which is considered to be 1-(6-aminohexyl)-3-cyanoguanidine (2) that is formed during the synthesis of 1. Hence, the constituents of 1 are unmetabolized in rats.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770902
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  • 3
    Electronic Resource
    Electronic Resource
    Packed column supercritical fluid chromatography/mass spectrometry using a thermospray source in the filament-on mode (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 105-109 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combined packed column supercritical fluid chromatography/mass spectrometry has been effected using a thermospray ion source in the filament-on mode. If organic modifiers are used with carbon dioxide as the supercritical mobile phase, chemical ionization mass spectra are obtained. With carbon dioxide electron impact type mass spectra are obtained. The potential of the system is illustrated with studies of mixtures of carbamate and organochlorine pesticides and a crude ergot fermentation extract.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150208
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  • 4
    Electronic Resource
    Electronic Resource
    Continuous flow fast atom bombardment liquid chromatography/mass spectrometry: Studies involving conventional bore liquid chromatography with simultaneous ultraviolet detection (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 179-182 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A conventional bore liquid chromatograph has been interfaced to quadrupole and magnetic sector mass spectrometers configured for fast atom bombardment ionization via a continuous flow FAB probe. It is shown that post-column addition of FAB matrix and in-line ultraviolet detection facilities do not significantly compromise chromatographic integrity and that high quality mass spectra are obtainable from such FAB LC/MS studies.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150310
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  • 5
    Electronic Resource
    Electronic Resource
    Detection of residues of chloramphenicol in crude extracts of fish and milk by tandem mass spectrometry (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 5-11 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collision-induced dissociation mass spectrum, observed with a hybrid tandem instrument, of the ammonia chemical ionization protonated molecular ion of chloramphenicol was used for the detection of residues of the drug in biological samples. The extracted oil from fish was subjected to a rapid clean-up on a pre-packed silica gel cartridge prior to non-chromatographic tandem mass spectral analysis. Fat extracted from milk was analysed directly by on-line combined high-performance liquid chromatography/tandem mass spectrometry with rapid elution of chloramphenicol. Identification was on the basis of agreement of the daughter ion spectra obtained from sample extracts with that of the chloramphenicol standard. Detection was unambiguous at 0.5 mg kg-1. The sensitivity advantage normally expected with multiple reaction monitoring was not achieved owing to the effect of neutral noise phenomena.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180103
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  • 6
    Electronic Resource
    Electronic Resource
    Anionic syntheses of terminally functionalized ethylene oligomers (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 4205-4226 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic procedures for preparation of terminally functionalized linear ethylene oligomers are described. The preferred synthetic method is anionic oligomerization of ethylene with n-butyllithium-tetramethylethylenediamine and electrophilic substitution of the living oligomer so-formed. Conditions and procedures for subsequent chemistry to elaborate the end groups of these oligomers are described. These procedures afford strictly linear ethylene oligomers which contain a wide variety of end groups and which range in molecular weight from 1000 to 4500 (Mn). The product oligomers were characterized spectroscopically as toluene-d8 solutions at 110°C using multinuclear NMR, FT-IR, fluorescence, and UV-visible spectroscopies as appropriate. Alternative stepwise approaches to such oligomers are also discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271226
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  • 7
    Electronic Resource
    Electronic Resource
    Mathematical modeling and optimization of the dehydrogenation of ethylbenzene to form styrene (1976)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 22 (1976), S. 1097-1105 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model is developed for a styrene pilot plant reactor. The steady state version of this model was used to optimize the location of a steam injection port part way along the catalytic bed. Significant improvement in reactor performance was predicted by splitting the steam feed between the reactor inlet and the injection port. Performance was measured in terms of market value of products minus a utility cost for the steam. Studies were also carried out via computer simulation to determine optimal operating conditions. An important result was the relationship of optimal steam-to-ethylbenzene feed ratio to the kinetic parameters which describe the main dehydrogenation reaction. A pilot plant was constructed and operated in order to investigate experimentally the predictions of the mathematical model. Instrumentation was designed and installed so that an on-line digital computer could acquire process measurements directly and establish operating conditions. The experimental program confirmed the improved performance by operation of the reactor with a steam injection port and the existence of an optimum of the steam-to-ethylbenzene feed ratio as indicated by simulation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690220621
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  • 8
    Electronic Resource
    Electronic Resource
    Letters to the editor (1978)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 1143-1144 
    Details
    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
    URL: http://dx.doi.org/10.1002/aic.690240639
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  • 9
    Electronic Resource
    Electronic Resource
    A critical evaluation of the semiimplicit Runge-Kutta methods for stiff systems (1979)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 25 (1979), S. 730-732 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690250424
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  • 10
    Electronic Resource
    Electronic Resource
    Local stability of tubular reactors (1972)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 18 (1972), S. 393-401 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liapunov analysis techniques employing a general quadratic functional are used to derive stability conditions for tubular reactor systems. The adiabatic tubular reactor without axial dispersion is shown to be locally stable, which excludes the possibility of multiple steady states, and the reactor with axial dispersion is proven locally stable if a condition involving only system parameters and steady state values is satisfied. Peclet numbers for heat and mass transfer are not specified equal for the latter proof.Results of simulation studies are used to confirm the validity of the derived stability condition, and it is shown that the parametric region of multiplicity is quite well defined. For the nonlinear equations, single steady state cases appear to possess nonuniform stability.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690180223
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