A manufacturing technique to increase the bonding between bone cement and metal prostheses has been assessed in the laboratory by "push-out" tests, and the effects of contamination of the cement and of the prosthesis with blood and intramedullary contents have been studied. The technique, known as pre-coating, increases bond strength; this increase is preserved after contamination of the cement which does, however, cause some lowering of interface shear strength. The implications for clinical practice are discussed.
Interactions mediated by layers of -casein and para--casein have been calculated and compared using the self consistent field (SCF) approach, at pH and electrolyte concentrations found in milk. Our results show the interaction potentials at close separation distances to be repulsive for -casein, while they are attractive for para--casein. We have also studied -casein chains stripped of their sugar moieties and highlighted the important role that the carbohydrate side chains play in the provision of steric forces. The point of transition from a repulsive to an attractive interaction is found to be rather sensitive to the degree of coverage of the surface by the protein chains. At =0.0025 chains per unit monomer area, the value is just over 40%, whereas at =0.0032 this increases to 87%. At the coverage values higher than those we estimate for the surface of casein micelles, no transition is detected and the interactions remain repulsive even when all of -casein has been converted to para--casein, as already shown by Mellema, Leermakers, & de Kruif (1999). At lower surface coverage values, the interaction potential curves for otherwise uncharged surfaces, covered with para--casein, posses an energy barrier. We have demonstrated that the origin of this energy barrier is electrostatic, with para--casein contributing a net positive charge to the surface.We have also explored the importance of the asymmetry in the distribution of charge between the para--casein and the glycomacropeptide sides of the protein. The glycomacropeptide is net negative while para--casein side is net positive at neutral pH. Our results suggest that on a negatively charged surface, such as the surface of casein micelles, this uneven distribution of charge is just as important in determining the conformation of -casein chains as is the difference in the hydrophobic and hydrophilic nature of the two sides of this protein.
TRI-n-BUTYL phosphate in an inert paraffinic d~lu~nt i~ of interest for the solvent processing of p1le-irrad1ated nuclear fuels 1 •"• If the specific activity of the process solution should be very high, radiation damage to the solvent will have a significant effect on plant efficiency, since it leads to the simultaneous production of din -butyl phosphate and mono-n-The suggestion of Cathers• that a radiation-induced hydrolysis is responsible for the breakdown of tri-nbutyl phosphate is not supported by these findings. The actual mechanism of radiolysis may involve both 'radical' and 'ultimate-molecule ' processes, arising from a 'direct' effect caused by energy absorbed by the ester itself.
We used a high frequency response, ultra-thin transducer to measure forefoot pressures at predetermined sites on the sole of the foot in 10 normal subjects.We demonstrated impact pressure peaks, which have not previously been identified, and which were separate from the roll-off peak. We report preliminary results on the effect of various forms of footwear and insoles on sub-pedal pressure during walking.
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