Extended dynamometry: reference values

Grip strength is used as a measure of capacity in disability and personal injury claims. Although seemingly an objective measure, it is widely recognized that it is fallible to the effects of sub-maximal effort. We have developed an extended test protocol that uses the five positions of a Jamar dynamometer. The protocol mitigates the effect of inconsistency while retaining the ability to detect sub-maximal effort. Dynamometry was undertaken in 242 volunteers (male:female, 124:118) with a median age of 39 years (range 18–89, interquartile range 29–52). Normative values for consistency, curve deviation and variation from the expected curve pattern are provided. None of these measures were significantly affected by laterality, hand dominance, sex or age despite the effects of these variables on grip strength. The study defines the methodology and reference values to allow assessment of both the capacity of a patient and the reliability of the test for use in medicolegal practice. Level of evidence: II

Resistance to Steady Laminar Flow of Pseudoplastic Fluids through Pipes and Valves

The well-known logarithmic friction factor diagram for laminar pipe flow can be extended in the following two respects: For application to non-Newtonian fluids, by incorporating in the plot a modified form of the consistency curve for a given material. Methods are discussed of obtaining these curves, and of transforming them into the required shape. For prediction of flow resistance through valves and fittings, by use of an auxiliary diagram based on results of appropriate tests. The general procedure is outlined, and it is stressed that results cannot be relied on quantitatively, until test data are obtained for wider ranges of sizes and types than hitherto available.

Viscometric Studies of Rubber Solutions

A former communication reported viscometric observations on rubber-toluene solutions in different capillary and rotation viscometers. The consistency curve of solutions from 0.08 to 1.77 per cent concentration starts at the origin as a straight line, inclined at a definite angle until it reaches a certain point a (see Fig. 1). From there it becomes convex toward the stress axis. This convex part extends to an inflection point b where the curve becomes concave up to a point c, where it again becomes a straight line which by extrapolation passes through the origin. The solutions therefore behave as Newtonian liquids between points o and a, and c and ∞. Between point a and c they are non-Newtonian liquids. It was furthermore shown that the “relative” consistency curve, i. e., a curve in which the shearing stress is reduced or the rate of shear increased in proportion to the viscosity of the solvent, is independent of the temperature at which the viscosity measurement is made. From this latter property the conclusion was drawn that the phenomenon of non-Newtonian behavior is a purely mechanical one. It cannot be due, as has been suggested by Staudinger, to a competition between orientation due to laminar flow and rotational diffusion due to Brownian movement because the magnitude of the latter depends on the temperature.