Yield Reproducible Results Research Articles

The Mechanical Properties Of Hair I. The Dynamic Sonic Modulus

Sonic velocity measurements allow instantaneous determination of Young's Modulus of Elasticity during stress-strain testing. These studies can be performed on single human hairs and yield reproducible results. A consistent relationship exists between the sonic velocity and the stress-strain curves of hair. Compared to other materials hair is exceptional with a decrease in Young's Modulus persisting until 25% extension. The sonic velocity curve of hair for its initial 20%–25% extension can be reproduced in isolated α-kerat in filaments, and is not observed in other keratins.

Studies on Blood Diastase

Diastase is known to be a normal constituent of human blood, but available information as to its quantity is inconsistent. The variety of measuring units and the multiplicity of methods render it impossible to correlate results and to explain conflicting conclusions. Even one and the same technique yields different results in the hands of different workers. One factor responsible for this situation is the use of soluble starch as substrate in measuring the enzyme action. It is practically impossible to prepare 2 identical batches of soluble starch, and consequently each will give different results with the same quantities of the enzyme, the discrepancies frequently being quite considerable. Moreover, investigators in general fail to consider the intricacies of the kinetics of diastase action and carry out their determinations under conditions where the amount of reaction products determined is not in linear proportion to the amount of enzyme. A study of substrates convinced us that starch pastes prepared from various refined natural starches by boiling at atmospheric pressure furnish adequate substrates. Pastes of 0.5 to 2% concentration, prepared from well washed rice, corn, wheat, potato or arrowroot starches, yield identical amounts of reducing sugars if incubated with identical amounts of enzyme under standardized conditions. It is remarkable that with glycogen the same results are obtained as with starch pastes. In another approach to the quantitative determination of diastase, in the measurement of the rate of cleavage of starch to the point where it no longer gives blue color with iodine, all starch pastes studied yield reproducible results, while every batch of soluble starch differs from the other. Thus the use of starch paste as substrate eliminates one variable in the study of diastatic activity.