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  • 1
    Electronic Resource
    Electronic Resource
    Conformational analysis of substituted dibenzo-14-crown-4 ethers in solution by 1D and 2D NMR (1993)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 16 (1993), S. 91-95 
    Details
    ISSN: 1573-1111
    Keywords: Dibenzo-14-crown-4 ; NMR ; conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The preferred conformations in solution for substituents onsym-dibenzo-14-crown-4 ethers are shown by NMR to depend on the atom, carbon or oxygen, linking the substituent to the crown ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708765
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Conformational Studies of an Asymmetrical Dibenzo-16-crown-5 Carboxylic Acid (2000)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 36 (2000), S. 287-299 
    Details
    ISSN: 1573-1111
    Keywords: crown ether ; NMR ; complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Asymmetrical cis-5,6-dimethyl-6-oxyacetoxy-(2,3)(9,10)-dibenzo-16-crown-5 was synthesized by a multi-step sequence and its stereochemistry determined by NOE experiments. Introduction of the 6-methyl group markedly reduces the stability constant for complexation of Na+ and K+ by the ionized form of the lariat ether carboxylic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008078220916
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  • 3
    Electronic Resource
    Electronic Resource
    Polymer drying. VII. 1H-NMR studies of evaporation from liquid saturated poly(styrene-co-divinylbenzene) (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1155-1161 
    Details
    ISSN: 0887-624X
    Keywords: adsorption ; desorption ; association ; polystyrene ; NMR ; polymer transitions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composition-studies were carried out in which samples of films composed of poly(styrene-co-divinylbenzene) particles enmeshed by poly(tetrafluoroethylene) fibers were saturated with dichloromethane and then allowed to evaporate at 23°C to virtual dryness as the 1H-NMR signals and residual weight of sorbed liquid were monitored. The correlations, of 1H-NMR line-widths with the corresponding log of the number, αt of residual sorbed molecules per monomer unit show that sharp changes occur as αt passes through αG the composition that exists when all the liquid not sorbed (i.e., not present within the liquid-saturated particles), has been eliminated, and again as αt passes through αg the composition that exists when the particles attain the rigidity characteristic of the glassy state. Correlation of the corresponding T1 relaxation times with log αt show that sharp changes occur when αt becomes equal first to α′s and then to α′g the compositions that exist respectively when, firstly, all the sorbed liquid not immobilized by adsorption to the polymer chains within the particles has been eliminated, and then when the desorption of immobilized liquid from the chains causes the composition to begin to undergo transition from its rubbery state to its glassy state.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300622
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  • 4
    Electronic Resource
    Electronic Resource
    The electret effect in cellulose acetate reverse osmosis membranes (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 92-97 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: The electret potentials developed by reverse osmosis electret membranes help control the undesirable deposition of charged colloidal particles on the membrane surfaces during membrane desalination. These antifouling electret membranes should help prevent the costly flux declines normally associated with deposition of colloidal iron oxides on the reverse osmosis membrane surfaces.Homocharge and heterocharge behavior of cellulose acetate membrane electrets have been studied. Asymmetric reverse osmosis membranes and dense membrane films were studied. The homocharge and heterocharge of cellulose acetate reverse osmosis electret membranes have been explained.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760140203
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  • 5
    Electronic Resource
    Electronic Resource
    Transport properties of polyvinylpyridinium anion-exchange membranes (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 674-676 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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
    Notes: Measurements have been made of the electrical conductivity of water-saturated heterogeneous anion-exchange pyridinium membranes in their carbonate and hydroxyl ionic forms as a function of temperature. The pyridinium membranes were prepared from quaternized poly-4-vinylmethyl-pyridinium resin electrolyte incorporated in a polyvinylidene fluoride matrix; the ratio of the pyridinium electrolyte to polyvinylidene fluoride was 4 to 1 by weight.The ion-exchange capacity and water content of these anion-exchange pyridinium membranes were measured. Corresponding Arrhenius activation energies of ion transport of carbonate and hydroxyl counter-ions have been calculated. Self-diffusion coefficients and the equivalent conductances of these pyridinium membranes in their carbonate and hydroxyl counter-ion forms have also been determined over a wide temperature range and compared to the reported values for present quaternary ammonium anion-exchange membranes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760140915
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  • 6
    Electronic Resource
    Electronic Resource
    CO2/CH4 separation by facilitated transport in amine-polyethylene glycol mixtures (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1135-1145 
    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: In this work, the separation of carbon dioxide from methane by reactive liquid membranes consisting of the secondary amines, diethanolamine, and diisopropanolamine in polyethylene glycol with an average molecular weight of 400 was studied. A mathematical model was developed to describe the transport process. This model employs the zwitterion mechanism for the CO2 amine reaction kinetics. Membrane flux experiments utilizing a flat plate device were carried out to verify the model predictions. It was found that large permeabilities and separations were achieved for low CO2 feed concentrations. The results also show that DEA based solutions give better separation than DIPA based solutions.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390706
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  • 7
    Electronic Resource
    Electronic Resource
    Two-dimensional modeling of electroremediation (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1685-1696 
    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 and numerical code for the simulation of contaminant removal from soils by electric fields are applied in two dimensions. The model describes the coupled transport of mass and charge, and the chemical speciation of a multicomponent system subjected to an electric field. Transport mechanisms included are electroosmosis, pressure-driven convection, electromigration, and diffusion. The model can also describe complexation, dissolution and precipitation reactions, surface complexation and sorption processes, and electrochemical reactions. Chemical and sorption equilibria are assumed. Transport equations used are based on quantities conserved throughout chemical reactions so that only the time scales of transport processes need to be resolved. The model is used to simulate the removal of phenol from kaolin clay for which experiments are presented. The successful explanation of the experimental observations confirms the theoretical bases of the model.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420620
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  • 8
    Electronic Resource
    Electronic Resource
    Predicting drying in coatings that react and gel: Drying regime maps (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 55-67 
    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: The competition between drying and reactions in a liquid coating containing precursors to a random network polymer can give rise to a variety of drying phenomena. Solidification, or gelation, of the polymer may occur before, after, or during the removal of solvents from the coating. Rates of drying and reaction are probed by solving the equations of mass transfer by diffusion along with chemical reaction in one dimension. Solutions to this system of equations are obtained by Galerkin's method with finite-element basis functions and entail large-scale computation. Skinning, or solidification at the surface of the coating while the bulk is still liquid, occurs in thick coatings when the diffusional resistance to drying is significant, that is, at high mass-transfer coefficients. Homogeneous solidification occurs in thin coatings at low mass-transfer coefficients. Drying regime maps represent these solidification phenomena as regions in parameter space.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420107
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  • 9
    Electronic Resource
    Electronic Resource
    A model for drying of viscoelastic polymer coatings (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2415-2425 
    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: Drying of polymeric coatings often occurs under conditions where the relaxation time of polymer molecules is significant with respect to the processing time scales. The nonequilibrium thermodynamic theory of Durning and Tabor (1986) is applied to model 1-D drying of viscoelastic solutions with concentration-dependent physical properties. Transport of solvent to the surface of the coating occurs by viscoelastic diffusion down the gradient of a diffusion potential with a relaxing, nonequilibrium contribution. Galerkin's method with finite-element basis functions and a differential/algebraic equation system solver enable efficient solution of this stiff nonlinear model. Predictions show that elasticity enhances diffusion within the coating. At high Deborah numbers, however, a fall in the surface activity slows the rate of desorption. The coating thickness after a specified time under fixed total driving force is the smallest at intermediate Deborah numbers, showing that a small amount of viscoelasticity actually aids in drying. This can be interpreted as a skinning effect.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420903
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  • 10
    Electronic Resource
    Electronic Resource
    Reaction equilibrium of real fluid mixtures (1971)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 167-170 
    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 theoretical approach to equilibrium calculations for homogeneous real fluid mixtures is presented. The overall approach is developed for, although not theoretically restricted to, a corresponding states equation of state, z(Tr, pr). The method is applied to the gaseous ammonia synthesis data of Larson and Dodge. Excellent agreement was attained with the data. Quite significant improvement was observed over the ideal gas and ideal solutions approximations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690170133
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