Cereal Chem. 79(2):301-307Understanding the relationship between basic and applied rheological parameters and the contribution of wheat flour protein content and composition in defining these parameters requires information on the roles of individual flour protein components. The high molecular weight glutenin subunit (HMW-GS) proteins are major contributors to dough strength and stability. This study focused on eight homozygous wheat lines derived from the bread wheat cvs. Olympic and Gabo with systematic deletions at each of three HMW-GS encoding gene loci, Glu-A1, Glu-B1, and Glu-D1. Flour protein levels were adjusted to a constant 9% by adding starch. Functionality of the flours was characterized by small-scale methods (2-g mixograph, microextension tester). End-use quality was evaluated by 2-g microbaking and 10-g noodle-making procedures. In this sample set, the Glu-D1 HMW-GS (5+10) made a significantly larger contribution to dough properties than HMW-GS coded by Glu-B1 (17+18), while subunit 1 coded by Glu-A1 made the smallest contribution to functionality. These differences remained after removing variations in glutenin-to-gliadin ratio. Correlations showed that both basic rheological characteristics and protein size distributions of these flours were good predictors of several applied rheological and end-use quality tests.
Monodisperse polystyrene lattices, at high electrolyte concentrations and with an adsorbed layer of nonionic surface active agent, produced weakly flocculated dispersions which sedimented rapidly to give a final sediment concentration of -30% by volume. Three lattices were used with particle sizes in the range 1-2/lm. The surface active agent used was C 12 E 6 • Optical microscopy of dilute systems showed that dense flocs were formed which were easily disrupted by small shear stresses. Shear wave propagation experiments were used to give the volume fraction dependence of the wave rigidity modulus, G, of these systems at high frequency. The high frequency limit to the shear modulus, G( (0), was calculated from the particle pair potential and the particle pair distribution function determined by using one of the current perturbation theories. The interparticle pair potential was calculated from a combination of van der Waals' attraction, and both steric and electrostatic repulsion. Good agreement was obtained between the value of G( 00 ) obtained from this statistical mechanical analysis and the experimental value of G over the full range of volume fraction studied.
Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing.
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