Biorheology - Volume 30, issue 3-4

Article Type: Other

DOI: 10.3233/BIR-1993-303-401

Citation: Biorheology, vol. 30, no. 3-4, pp. iii-iii, 1993

Authors: Verdugo, Pedro

Article Type: Editorial

DOI: 10.3233/BIR-1993-303-402

Citation: Biorheology, vol. 30, no. 3-4, pp. v-v, 1993

Authors: Isogai, Yukihide | Verdugo, Pedro

Article Type: Introduction

DOI: 10.3233/BIR-1993-303-403

Citation: Biorheology, vol. 30, no. 3-4, pp. vii-viii, 1993

Authors: Goldsmith, H.L.

Article Type: Research Article

Keywords: Microrheology, deformation, migration, blood corpuscles, interaction forces

DOI: 10.3233/BIR-1993-303-404

Citation: Biorheology, vol. 30, no. 3-4, pp. 165-190, 1993

Authors: Djabourov, Madeleine | Lechaire, Jean-Pierre | Gaill, Françoise

Article Type: Research Article

Abstract: This paper undertakes a parallel analysis of the gelation mechanisms, structure and rheological properties of gelatin and collagen gels. Although the molecular compositions of collagen and gelatin are almost identical, gelation proceeds from distinct mechanisms and leads to different types of molecular assemblies. First are presented the properties of the solutions, based on their structural and rheological characterization; then the mechanisms of gelation in the networks, observed by Transmission Electron Microscopy, of three types of gels: gelatin gels, Type I collagen gels and gels made of cuticle collagen extracted from annelid worms. The rheological investigation of the sol-gel transition of …gelatin is described within the context of the theories of percolation and scaling laws. Different experimental approaches to the kinetics of gelation are presented, combining dynamic light scattering and rheology in respect to gelatin gels. Show more

Keywords: Collagen, gelatin, gels, rheology, electron microscopy

DOI: 10.3233/BIR-1993-303-405

Citation: Biorheology, vol. 30, no. 3-4, pp. 191-205, 1993

Authors: Nakamura, K. | Niki, R.

Article Type: Research Article

Abstract: Rheological studies on the gelation of casein micelles using rennet have been performed in relation to cheese making. The influence of calcium concentration on the time course of storage and loss modulus was investigated using rheological measurements. Observed gelation curves at 30°C were well approximated by first-order reaction kinetics except for the very short time after gelation occurred. The saturated modulus decreased with decreasing calcium ion concentration in the range from 4.5 to 9 mM. The rate constant of gelation, Kg decreased linearly with decreasing calcium ion concentration. A minimum amount of calcium was needed for gelation to occur. …Kg was inversely proportional to the latent time, tL . The value of the product of Kg and tL for the casein micelle gels containing various calcium concentrations was 0.4. Show more

Keywords: Casein micelle, gelation, rennet, viscoelasticity, calcium ion

DOI: 10.3233/BIR-1993-303-406

Citation: Biorheology, vol. 30, no. 3-4, pp. 207-216, 1993

Authors: Ross-Murphy, S.B. | Shatwell, K.P.

Article Type: Research Article

Abstract: Small deformation oscillatory shear measurements have enabled a distinction to be made between so-called “strong” and “weak” gels, in particular those formed from biologically significant polysaccharides. At small enough strains, both systems give essentially the same mechanical spectrum, with G ′ > G ″ , and with both moduli largely independent of frequency. However, the deformation dependence of the two classes of materials is very different. Strong gels are essentially strain independent (linearly viscoelastic) for strains of greater than about 0.25, whereas weak gels show such a response only for strains of …less than about 0.05. At large deformations strong gels will rupture and fail, and will never “heal” without melting and resetting. Conversely, weak gels will recover and can flow without fracture, giving a power law response, with an exponent approaching -1, so-called “yield stress” behavior. The rheological properties of a strong gel, agarose, derived from the Rhodophyceae (marine algae) and a weak gel xanthan, an exocellular slime exuded by bacteria of the genus Xanthomonas , are measured in vitro , and related to in vivo requirements. Show more

Keywords: Agarose, xanthan, viscoelasticity, gel, polysaccharide

DOI: 10.3233/BIR-1993-303-407

Citation: Biorheology, vol. 30, no. 3-4, pp. 217-227, 1993

Authors: Lillie, M.A. | Gosline, J.M.

Article Type: Research Article

Abstract: The viscoelastic behavior of arterial elastin in aqueous solutions of polar solutes has been studied to establish both its range of behavior and the mechanisms by which the behavior is altered by the solutes. We were particularly interested in whether a solute interacted directly with the elastin or whether it acted only indirectly to reduce the activity of water. The behavior of elastin in solutions of glucose, NaCl ammonium sulphate, and in low concentrations of ethylene glycol was similar to that of elastin that had been directly dehydrated or indirectly dehydrated using osmotic agents such as dextran or polyethylene glycol. …This similarity suggests that these solutes interact with elastin only indirectly. Thiocyanate and high concentrations of dimethyl sulfoxide and ethylene glycol appeared to interact directly with the elastin, altering both the swelling and the viscoelastic behavior of the network. Show more

Keywords: Elastin, viscoelasticity, biopolymer, arteries

DOI: 10.3233/BIR-1993-303-408

Citation: Biorheology, vol. 30, no. 3-4, pp. 229-242, 1993

Authors: Nishinari, K. | Hofmann, K.E. | Kohyama, K. | Moritaka, H. | Nishinari, N. | Watase, M.

Article Type: Research Article

Abstract: Viscoelastic parameters for mixtures of gelatin and methy1cellulose were measured as a function of temperature, in order to study the gel-sol transition of the system in which biopolymers forming thermosetting and thermo-melting gels coexist. At higher temperatures than 45°C, the gel network is mainly formed by methylcellulose while at lower temperatures around 5°C, it is mainly formed by gelatin. At higher temperatures than 45°C, gelatin inhibits the gelation of methylcellulose. A small amount of methylcellulose helps gelatin to form a network at lower temperatures. However, excessive amounts of methylcellulose inhibit the growth of network structure. Therefore, this mixture forms a …phase separated gel at higher temperatures while it is not completely phase separated at lower temperatures, probably by some interaction between non-substituted hydroxyl groups in methylcellulose with carboxylic groups in gelatin. Show more

Keywords: Viscoelasticity, gelatin, methylcellulose, gelation

DOI: 10.3233/BIR-1993-303-409

Citation: Biorheology, vol. 30, no. 3-4, pp. 243-252, 1993

Authors: Quemada, D.

Article Type: Research Article

Abstract: For transient shear stress responses at moderate shear rates, predictions of a Non-Linear Maxwell model , in which the viscosity coefficient is assumed to depend on the instantaneous structural state of the material, are compared to measurements on normal blood (McMillan et al ., 1986). This is carried out on a modified viscometer which incorporates a dynamic balance torque monitoring, in order to eliminate apparatus inertia effects. Satisfactory agreement is obtained with model variables closely related to the structure kinetics.

Keywords: Thixotropy, non-linear viscoelasticity, time-dependent models, structure kinetics

DOI: 10.3233/BIR-1993-303-410

Citation: Biorheology, vol. 30, no. 3-4, pp. 253-265, 1993