Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 777-791 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dynamic viscoelastic properties of hyaluronic acid solutions have been measured over the frequency range 0.02-1.67 cps. The effects of varying temperature, hyaluronic acid concentration, pH, and ionic strength on the dynamic shear moduli were studied. The solutions exhibited a sharp transition from viscous to elastic behavior as the strain frequency increased. No entanglement coupling of the hyaluronic acid molecules was evident over the concentration range 2.0-4.0 mg./ml. Solutions at pH 2.5 showed a pronounced elastic behavior relative to both higher and lower pH's. This effect was attributed to a stiffening of the hyaluronic acid molecule at this pH.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new light-scattering experiment which allows a direct determination of the conformation of macromolecules deformed in flow is described. Light-scattering relationships based on the interference function are developed, and results of an experimental study are detailed. The deformed conformation of high molecular weight polyisobutylene was determined in a Couette-type shear field. Decalin was the solvent. Variables investigated were the shear rate (0 to 600 sec-1), the polymer molecular weight (1.0 × 107 to 1.6 × 107), and the polymer concentration (2.0 × 10-4 to 8.0 × 10-4 g/cc). Conformation variables determined were the orientation of the molecule in the shear field and its maximum and minimum extension ratios in the plane defined by the direction of flow and the direction of the shear rate. The deformation of the macromolecule was found to be markedly discrepant when compared to the dynamic macromolecular models which assume complete coil flexibility, and more closely in agreement with the recent theories of Cerf, developed for nonfree-draining coils which exhibit a finite internal viscosity.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 289-294 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The shear dependence of the intrinsic viscosity and the conformation of high molecular weight polyisobutylene in dilute solutions of decahydronaphthalene under shear were determined simultaneously. Experimental variables investigated were the shear rate (0 to 2 × 103 sec-1), the molecular weight (1.0 × 107 to 1.7 × 107) and the polymer concentration (1.8 × 10-4 to 8.4 × 10-4 g/cc). Correlations allowing concentration and shear rate normalization for any one sample are described. Conformational extention ratios along the orientation direction of the deformed molecule to 1.42 and intrinsic viscosity ratios (sheared to zero shear) to 0.5 were observed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 459-488 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The true diffusive permeabilities of commercial, modified commercial, and laboratory cast regenerated cellulose membranes were measured with a batch dialyzer using 15 solutes (sodium chloride, nine radioactively labelled organic solutes, and five low molecular weight proteins) ranging in molecular weight from 58 to 68,000. Additional measurements included membrane thickness, water content, and strength properties, as well as equilibrium solute partition coefficients and solute diffusion coefficients in free solution. All commercial cellophanes were similar in sodium chloride permeability on a unit thickness basis and were significantly less permeable than hydrophilic wet gel membranes. This difference was attributed to the irreversible collapse of membrane structure upon drying. As the solute characteristic size increased, permeability decreased more sharply with commercial cellophane than with wet gel cellulose, the ratio between the two becoming an order of magnitude for large solutes. The ratio between the solute diffusion coefficient in the membrane and in free solution decreased exponentially with increasing solute size. The results suggest further work for higher permeability cellulosic hemodialysis membranes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    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: Der Diffusionstransport des Gelösten durch in Wasser gequollene Membranen wurde an Hand des Modells des freien Volumens (Vf,13) des Polymer/Wasser-Systems untersucht. Die relative Diffusionsfähigkeit (D2,13 in der Membran/D2,1 im Wasser) kann dargestellt werden als das Produkt aus dem Wahrscheinlichkeitsfaktor zum Auffinden von Hohlräumen mit gleichem oder größerem Querschnitt als das Gelöste (Siebmechanismus) und dem Faktor des freien Volumens. Die vorhandenen experimentelle Daten führen zu der Schlußfolgerung, daß der Siebmechanismus in homogenen Cellulosemembranen bis zu der Molekülgröße von Albumin keine beachtliche Rolle spielt. Entscheidend für die Verringerung der Permeabilität für größere Moleküle des Gelösten ist der Faktor mit dem freien Volumen, exp (-Bq2/Vf,13), der den Querschnitt des Gelösten (q2) als negatives Argument in der Exponentialfunktion enthält. In porösen Membranen ist jedoch der Siebmechanismus allein für die Selektivität verantwortlich.
    Notes: The diffusional transport of aqueous solutes through water swollen polymer membranes is examined by the concept of the free volume of the water-polymer systems, Vf,13. The relative diffusivity (D in membrane/D in water) can be expressed by the product of the probability factor of finding holes of equal or larger cross section, q, than the cross section of solute, q2, (sieve mechanism) and the free volume factor. An analysis of experimental data indicates that within the range of solute size investigated (up to albumin) the sieve mechanism is not yet playing a role in homogeneous cellulosic membranes. The main reduction of permeability of larger solutes is caused by the free volume term which is an exponential function of the negative cross section of the solute, q2, exp (-Bq2/Vf,13). In porous membranes, however, the sieve mechanism alone is responsible for the selectivity.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...