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  • Chemistry  (28)
  • Cell & Developmental Biology  (6)
  • Computational Chemistry and Molecular Modeling  (4)
  • Field-flow fractionation  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Retention in field-flow fractionation with secondary chemical equilibria (1992)
    Springer
    Chromatographia 34 (1992), S. 325-330 
    Details
    ISSN: 1612-1112
    Keywords: Field-flow fractionation ; Secondary chemical equilibria ; Colloidal systems ; Retention theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application range of field-flow fractionation (FFF) can be extended to low molecular weight solutes, as demonstrated a few years ago by Berthod et al., by taking profit of secondary chemical equilibria (SCE) occurring between the bulk carrier and a retained carrier component. The theory of solute retention in this SCE-FFF method is developed for any value of the solute distribution coefficient and of the retention ratio of the retained carrier component, provided that the Brownian mode of retention applies for this component and that the flow velocity profile is parabolic. This removes some of the limitations of the model previously developed by Berthod and Armstrong and sheds light on the potentialities of the SCE-FFF method for physico-chemical studies about secondary chemical equilibria in colloidal systems. Remaining assumptions in the model are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268363
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  • 2
    Electronic Resource
    Electronic Resource
    Quantum chemical structure-activity relationships on β-carbolines as natural monoamine oxidase inhibitors (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1643-1652 
    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: The electron density and the molecular electrostatic potential of the β-carbolines are studied using ab initio STO-3G wave functions. The analysis was done from the point of view of a previous model built with monoamine oxidase substrates and irreversible inhibitors. The results confirm the usefulness of the model and make it possible to propose new precision to the molecular electrostatic potential patterns needed to have monoamine oxidase inhibitory activity.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230445
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  • 3
    Electronic Resource
    Electronic Resource
    Quantum chemical study of the molecular patterns of MAO inhibitors and substrates (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1627-1641 
    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: Similarities and differences between mitochondrial monoamine oxidase (MAO) substrates and inhibitors (both A and B types) are considered, studying quantitatively two molecular properties: electron density and molecular electrostatic potential (MEP). The following molecules are considered: substrates: PHEA, BZA, tele-N-methyl-histamine, phenylethanolamine, phenylpropylamine, tryptamine, dopamine, phenoxylethylamine, noradrenaline, serotonin, and p-nitro-phenylethanolamine; inhibitors: Deprenil, Clorgyline, and Lilly 51641 (only the moiety involved in the A-B differentiation is considered). The wave functions needed to calculate the analyzed properties are of ab initio quality, and have been calculated in analogous conformations, all near the energetic minima. Electron densities distributions are qualitatively compared by means of a correlation coefficient defined over the whole space. Otherwise, patterns of the possible zones of electrostatic interactions are described by means of the distances and angles between minima, in order to differentiate MAO-A and MAO-B substrates. The results reproduce efficiently the experimental classification and enable us to predict the type of enzymatic action of molecules not yet experimentally classified.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230444
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of stereoregular polygluconamides from D-glucose and D-glucosamine (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 299-305 
    Details
    ISSN: 0887-624X
    Keywords: polygluconamides ; stereoregular polyamides ; stereoregular nylons ; chiral polyamides ; chiral nylons ; aminoaldonic acids ; sugar polyamides ; carbohydrate monomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two stereoregular polygluconamides, one (3) of polypeptide-type and the other (16) being a polycaproamide containing four stereocenters in the main chain of the repeating unit, have been prepared from D-glucosamine and D-glucose, respectively. The new polyamides were characterized by elemental analysis, and IR, 1H- and 13C-NMR spectroscopies. The molecular weights for 3 and 16 were estimated as 25,000 and 67,000, respectively, on the basis of viscosimetric measurements. Both polyamides display high optical activity; they are highly hydrophilic and readily soluble in water as well as in a variety of organic solvents including chloroform. Polyamide 16 is highly crystalline and yields resistant films with spherulitic texture. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330211
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  • 5
    Electronic Resource
    Electronic Resource
    Mathematical model for the optimization of the reaction between 2,3-bis(m-tolyl)quinolizinium bromide and piperidine using a factorial design (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 1-10 
    Details
    ISSN: 0886-9383
    Keywords: Derivatization reaction ; Factorial design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of nucleophiles have been successfully identified and quantified using the Kröhnke reaction with 2,3-diphenyl derivatives of quinolizinium salts. Optimization of the reaction conditions by means of a mathematical model involving analysis of the response surface has led to a better understanding of the factors exerting an influence on the above reaction.The parameters chosen were temperature, reaction time, base concentration, water concentration and nucleophile concentration. The reaction was developed in polar aprotic solvents (acetone, acetonitrile). To facilitate the nucleophilic attack, the presence of an organic base (triethylamine) was necessary, although concentrations in excess of 0·15M did not alter the development of the reaction. Since pharmaceutical solutions are often aqueous, the influence of water on the reaction was studied. Low water volumes have no significant influence on the opening of the quinolizinium ring by the nucleophilic reagent. However, when the water proportion exceeded that of the organic solvent, the fluorescence intensity was lower than expected. Development of the fluorescent reaction product was first detected 5 min after the reaction started. The fluorescence intensity reached its optimum value after 138 min.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060102
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  • 6
    Electronic Resource
    Electronic Resource
    Polymer analysis by fractionation with on-line light scattering detectors (1982)
    Springer
    Chromatographia 15 (1982), S. 426-432 
    Details
    ISSN: 1612-1112
    Keywords: Polymer analysis ; Molecular weight distribution ; Steric exclusion chromatography ; Field-flow fractionation ; Light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The classical method for the determination of the molecular weight distribution (MWD) curve of a polymer requires fractionation according to the molecular weight and prior calibration of the separator. It is shown that the use of a dual detection system which includes a molecular mass sensitive detector eliminates the need for prior calibration. The principles of operation of a low-angle light scattering photometer, working as such a detector, are presented, as well as the basic equations for determination of the MWD curve from the elution curve and of the average molecular weights. Then the performances of the light scattering photometer are discussed with special emphasis on the various sources of errors and unaccuracies in these determinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02261602
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of approximate and exact description of isoviscous flow velocity profile formed in rectangular cross-section channel for field-flow fractionation (1992)
    Springer
    Chromatographia 33 (1992), S. 284-286 
    Details
    ISSN: 1612-1112
    Keywords: Field-flow fractionation ; Three-dimensional flow velocity profile ; Rectangular cross-section channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The shape of the velocity profile established in a carrier liquid flowing in a duct of rectangular cross-section under conditions of isoviscous flow is well known and can be calculated by using an approximate or the exact solution of Navier-Stokes equation. The series evaluated when applying the exact solution were found to converge very rapidly. Consequently, computing can be substantially shortened without loss of accuracy by summing only the first three terms of the series. A fair agreement between the approximate solution of Takahashi and Gill and the exact solution was obtained for all practically applicable aspect ratios of the separation channels used in field-flow fractionation. This conclusion is of interest when calculating various separation parameters in three-dimensional channels for field-flow fractionation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276196
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  • 8
    Electronic Resource
    Electronic Resource
    Chiroptical properties, structure, and absolute configuration of heterosubstituted 2(5H)-furanones (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 537-544 
    Details
    ISSN: 0899-0042
    Keywords: Circular dichroism ; helicity rule ; X-ray structure determination ; ultraviolet spectra ; n - π* and π - π* bands ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiroptical properties of a series of 3 and/or 4-heterosubstituted 2(5H)-furanones were investigated with respect to correlation with absolute configuration. The n - π* and π - π* Cotton effects have been assigned on the basis of comparison with the UV spectra in solvents of varying polarity. It is demonstrated that the n - π* transition in 4-amino substituted 2(5H)-furanones appears at shorter wavelength with respect to the π - π* transition. With the exception of 4-pyrrolidino and 4-benzylamino substituted 2(5H)-furanones, other heterosubstituted 2(5H)-furanones follow the butenolide configurational rule (Gawronski et al. J. Org. Chem. 61:1513-1515, 1996). Absolute configuration of 2(5H)-furanone derivatives can also be assigned according to the sign of the Cotton effect (of unknown origin) at 200-230 nm. The structure of four representative sulfur and nitrogen substituted 2(5H)-furanones has been analyzed by X-ray diffraction. The results indicate planarity of the furanone ring and extended conjugation in 4-amino substituted 2(5H)-furanones. Chirality 9:537-544, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxidation der Pb-Ca-Legierungen in flüssigem Zustand (1978)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 29 (1978), S. 815-820 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Oxidation of PbCa alloys in the liquid stateThe effect of various temperatures, the composition of the alloy and the corroding atmosphere is studied with a thermobalance during the oxidation of molten PbCa alloys. The rate controlling step of the oxidation depends on the test conditions. The results obtained at 700°C are in agreement with data found in literature and according to which the oxidation increases with the Ca content; in this range calcium is subject to preferential oxidation. At 600°C and temperatures below that the addition of calcium does not only not increase oxidation but may give rise to a decrease.
    Notes: Mit einer Thermowaage wird die Wirkung verschiedener Temperaturen, der Zusammensetzung der Legierung und der Zusammensetzung der angreifenden Atmosphäre bei der Oxidation geschmolzener Pb-Ca-Legierungen untersucht. Der geschwindigkeitsbestimmende Schritt der Oxidation hängt von den Versuchsbedingungen ab. Bei 700°C bestätigen die bei der vorliegenden Untersuchung erhaltenen Ergebnisse die Literaturangaben, wonach die Oxidation bei zunehmendem Ca-Gehalt ansteigt; dabei wird das Calcium vorzugsweise oxidiert. Dagegen wird bei 600°C und darunter die Oxidation durch Zusatz von Calcium nicht nur nicht verstärkt, sondern sogar verringert.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19780291206
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  • 10
    Electronic Resource
    Electronic Resource
    A computer model of the fixed bed catalytic reactor: The adiabatic and quasi-adiabatic cases (1963)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 9 (1963), S. 129-133 
    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 digital computer model of the adiabatic-fixed bed catalytic reactor is developed which includes axial dispersion of heat and mass, interparticle heat and mass transport, and intraparticle diffusion of reacting species. The influence of these transport processes upon conversion and yield is discussed. The model is readily extended to nonisothermal, nonadiabatic cases in the absence of radial gradients.The technique of computer solution avoids the inherent instability problem associated with explicit techniques as applied to flux boundary condition problems which involve flow, diffusion, and reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690090128
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