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  • Chemistry  (39)
  • Polymer and Materials Science  (22)
  • General Chemistry  (13)
  • AIRCRAFT PROPULSION AND POWER
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  • 1995-1999  (22)
  • 1985-1989  (18)
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  • 1
    Digitale Medien
    Digitale Medien
    Commentary: Reflections on “General theory of stationary random sequences with applications to the tacticity of polymers,” by Bernard D. Coleman and Thomas G Fox, J. Polym. Sci. A, 1, 3183 (1963) (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1631-1632 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1996.836
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  • 2
    Digitale Medien
    Digitale Medien
    General theory of stationary random sequences with applications to the tacticity of polymersPaper presented at the 142nd Meeting of the American Chemical Society, Atlantic City, New Jersey, September 1962. (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1635-1649 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: When, in a poly-α-olefin, the probability that a given placement be isotactic depends upon the tacticity of only a finite number of immediate predecessors, the resulting diastereosequence distribution obeys the theory of Markoff chains. When this is not the case, one says that the resulting diastereosequence distribution is non-Markoffian. A special case of a Markoffian distribution is given by a simple Markof chain in which the tacticity of a given placement is assumed to be affected by only the tacticity of the immediately preceding placement. Another special case is, of course, the Bernoulli trial distribution in which the probability that a given placement be isotactic is independent of the tacticity of all other placements. A high resolution NMR spectrum can sometimes yield a quantitative determination of the concentrations of isotactic and syndiotactic placements and the concentrations of the three types of possible adjacent pairs of such placements (i.e., isotactic, syndiotactic, and heterotactic pairs). When this is the case, the spectrum can be used to determine whether or not a given diastereosequence distribution is Bernoullian. However, because the longest diastereosequences whose concentration can be measured by NMR spectroscopy involve only two placements, an NMR spectrum cannot check whether a given non-Bernoullian distribution be simple Markoffian or Markoffian in general. In fact, non-Markoffian distributions are compatible with existing NMR spectra on polymers prepared by anionic polymerizations. In this paper we work within the framework of Kac's theory of stationary statistical processes and point out some general results which are valid for both Markoffian and non-Markoffian processes. The results are applied to NMR spectroscopy and it is pointed out which calculations used to check the self-consistency of NMR data and to obtain the mean length of closed diastereosequences are valid for both Markoffian and non-Markoffian distributions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1996.838
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  • 3
    Digitale Medien
    Digitale Medien
    Determination of reactor biomass by acoustic resonance densitometry (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 28 (1986), S. 1241-1249 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Acoustic resonance densitometry (ARD) is reported as a method suitable not only for precise investigations into changes of specific gravity in bioreactor media but also as a technique able to provide an accurate wide range and direct determination of cellular mass in fermentation processes. It is further shown that this method can replace present optical procedures, minimizing dilution errors and operator involvement and is suitable for development as an on-line biomass monitoring system.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260280816
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  • 4
    Digitale Medien
    Digitale Medien
    Stability studies of immobilized enzyme stir rods (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 24 (1982), S. 1773-1788 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Alcohol dehydrogenase has been covalently attached to the surfaces of nylon stir rods. Several rod types have been evaluated in terms of their mixing efficiency and enzyme loading. Fluorometric monitoring of the rate of conversion of NAD to NADH serves as a measure of the reaction rate under varying conditions. The rate of reaction of the enzyme stir rods has been evaluated in terms of RPM, buffer concentration, NAD reagent concentration, and pH. The rate of reaction is seen to reach a plateau at higher stir rates, indicating a lack of diffusional hindrances. The reaction rate also begins to level off at phosphate buffer concentration of 0.1M to 0.15M. Saturating conditions are reached at an NAD concentration of 2.5mM. The optimum pH is found to be 9.0. The Stability of the covalent bond between the enzyme and the nylon has been assessed by comparing the bond strength to the energies of various disruptive forces to which the enzyme is exposed. Centrifugal, drag, and shear forces are shown to be insufficient to cause rupture of the bond. The stability to the immobilized enzyme preparation has been investigated under varying conditions of immobilization and use. No effect on activity loss was found for rotation rate or for continuous versus intermittent use. It was found that enhanced stability occurred for hydrolytic cleavage of the nylon, using nitric acid, as compared to nonhydrolytic cleavage. Hydrolytic cleavage also led to some degree of adsorption of the enzyme to the surface of the nylon. Thus, the possibility of increased stability to multipoint attachment of the enzyme is discussed. Possible cause of activity loss are discussed, as well as the extension of the enzyme stir rod to use in scale model reactor studies.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260240805
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  • 5
    Digitale Medien
    Digitale Medien
    On-line monitoring of cell mass in mammalian cell cultures by acoustic densitometry (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1379-1384 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Acoustic resonance densitometry (ARD) provides a highly reproducible and stable method for on-line measurement of culture biomass density. The technique provides a direct determination of changes in relative density of culture medium and cell mass. At cell concentrations higher than 106 cells mL-1this method can replace cell counts and provide a continuous measure of total cell mass. In cultures of hybridomas or U937 human lymphoma cells, the ARD value correlates well with cell number except when the average cell size changes during culture. It is argued that cell mass determined by ARD rather than cell number should be used as the basis for measurements of specific biological activity.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260331103
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  • 6
    Digitale Medien
    Digitale Medien
    Chiral recognition in liquid chromatography utilising chargeable cyclodextrins for resolution of doxazosin enantiomers (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 184-190 
    Details
    ISSN: 0899-0042
    Schlagwort(e): rac-doxazosin ; doxazosin ; liquid chromatography ; chiral ; carboxymethyl-β-cyclodextrin ; optimisation ; central composite design ; mobile phase additive ; experimental design ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chromatographic resolution of rac-doxazosin using reversed-phase high performance liquid chromatography (HPLC) with the chargeable chiral mobile phase additive, carboxymethyl-β-cyclodextrin (CM-β-CD), is described. The effects of different modifiers (acetonitrile, methanol and tetrahydrofuran), pH, temperature, and cyclodextrin concentration were investigated to (a) assess the key chromatographic parameters for subsequent chemometric optimisation, and (b) explore the enantioselective mechanism. Assuming a 1:1 complex between each doxazosin enantiomer and CM-β-CD, studies of the relationship between the capacity factors (k′) and functions of CM-β-CD concentration indicate that the mechanisms for retention and chiral selectivity are comparable with those proposed earlier by Sybilska et al.1 Stability constants (KG) calculated for rac-doxazosin complexed with CM-β-CD (647 ± 55 and 594 ± 45 M-1 for each enantiomer respectively) are significantly larger than those calculated for the barbiturates complexed with β-CD (ca. 101-108 M-1).1 Investigations on pH indicate an ionic or ion-pair interaction between the anionic CM-β-CD and the cationic doxazosin enantiomers.A central composite design was used to optimise the key chromatographic parameters: pH, methanol (v/v) and CM/β-CD concentration. The Kaiser peak separation index, Pi, was used for the response function. The predicted response for this chiral separation has been compared with that observed experimentally and samples of the four-dimensional response surface have been assessed for their value in showing robustness. Chirality 9:184-190, 1997. © 1997 Wiley-Liss, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Method development in liquid chromatography with a charged cyclodextrin additive for chiral resolution of rac-amlodipine utilising a central composite design (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 466-476 
    Details
    ISSN: 0899-0042
    Schlagwort(e): rac-amlodipine ; amlodipine ; liquid chromatography ; chiral ; charged cyclodextrin ; optimisation ; central composite design ; mobile phase additive ; experimental design ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A negatively charged derivative of β-cyclodextrin, sulphobutyl ether-β-cyclodextrin (SBE-β-CD), was examined as a chiral mobile phase additive in reversed-phase high-performance liquid chromatography for the enantiomeric resolution of the calcium channel blocker rac-amlodipine. Theoretical and practical aspects are discussed for setting up a central composite design applicable to any analytical method. These include the correct location of factor points for maintaining orthogonality within the design and the augmentation of centrepoint experiments to allow a larger factor space by increasing the distance of axial star points. Optimised separation was achieved using a reverse-phase column with eluent comprising: acetonitrile (ACN) - potassium dihydrogen phosphate (pH 3.93) containing 2.66 mM SBE-bgr;-CD (26.5:73.5% v/v) at a flow rate of 1.0 ml/min. This yielded a Kaiser peak separation index, Pi = 0.96, at tR2 = 52 min with satisfactory reproducibility, relative standard deviation values: tR1, 0.39%; tR2, 0.47% (n = 5). These experimental results were in excellent agreement with those predicted by the SAS software package for a chromatographic response function model. Multiple regression analysis in four dimensions, with three response models based on Rs, Pi, and a function of Pi, produced response surfaces which revealed zones of optimum robustness and illustrated the interactions involved between the key chromatographic factors. Putative proposals for a mechanism involving the interaction of each of the positively charged enantiomers with the negatively charged cyclodextrin are also discussed. These examine the possibility of ion-pairing and inclusion phenomena to account for the excellent resolution observed. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Analysis of gases containing inorganic and organic compounds using a combination of a thick-film capillary column and a packed adsorption column (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 112-118 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography, GC ; Fused silica capillary columns ; Packed absorption columns ; Thick liquid phase films ; Natural, refinery, and reactor gas analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A gas chromatographic system consisting of one multiport valve, two (hot-wire and flame-ionization) detectors and two analytical columns (one thick-film capillary and one packed adsorption column) is used for the analysis of gas samples containing a number of inorganic compounds (hydrogen, argon, oxygen, nitrogen, carbon monoxide, and carbon dioxide) and organic compounds. Examples include samples containing hydrocarbons up to n-nonane and benzene and toluene. The system also permits the analysis of more complicated samples containing, for example, alcohols, in addition to hydrocarbons.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240080302
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  • 9
    Digitale Medien
    Digitale Medien
    Central composite design for the rapid optimisation of ruggedness and chiral separation of amlodipine in capillary electrophoresis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 226-234 
    Details
    ISSN: 0899-0042
    Schlagwort(e): central composite design ; liquid chromatography ; capillary electrophoresis ; amlodipine ; cyclodextrin ; ruggedness ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Systematic optimisation with central composite design offers an efficient route for rapid optimisation of resolution with multiple interacting parameters in chiral CE. This is illustrated by separations of amlodipine with α-CD as chiral selector in the running buffer, for which the predicted performance of central composite design is assessed. The utility of response surface methodology for locating optimum ruggedness in CE is also described. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530070408
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  • 10
    Digitale Medien
    Digitale Medien
    Selective Catalytic Oxidation of Alcohols by a Ruthenium-Copper Bifunctional System Using Molecular Oxygen (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1673-1675 
    Details
    ISSN: 1434-1948
    Schlagwort(e): Ruthenium ; Copper ; Oxidations ; Catalysis ; Alcohols ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The oxidation of allylic and benzylic alcohols to aldehydes can be carried out at room temperature with molecular oxygen, in the presence of the bifunctional ruthenium-copper system (nPr4N)(RuO4)-CuCl acting as the catalyst.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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