The nonlinear viscoelastic behavior of filled elastomers is examined in detail using a variety of samples including carbon-black filled natural rubbers and fumed silica filled silicone elastomers. New insights into the Payne effect are provided by examining the generic results of sinusoidal dynamic and constant strain rate tests conducted in true simple shear both with and without static strain offsets. The effect of deformation history is explored by probing the low amplitude modulus recovery kinetics resulting from a perturbation by a large strain deformation such as a sinusoidal pulse or the application or removal of a static strain. It is found that a static strain has no effect on either the fully equilibrated dynamic (storage and loss) moduli or the incremental stress-strain curves taken at constant strain rate. The reduction in low amplitude dynamic modulus and subsequent recovery kinetics due to a perturbation is found to be independent of the type of perturbation. Modulus recovery is complete but requires thousands of seconds, and is independent of the static strain. The results suggest that deformation sequence is as critical as strain amplitude in determining the properties, and that currently available theories are inadequate to describe these phenomena. The distinction between fully equilibrated dynamic response and transitory response is critical and must be considered in the formulation of any constitutive equation to be used for design purposes with filled elastomers.

The gas-phase i.r. and liquid-phase Raman spectra of the phosphines CF,-PX, (X = H, F, CI. Br. or I) have been recorded. The observed bands have been assigned on the basis of C, symmetry. However, there is substantial mixing of the internal co-ordinates of vibration, and so simple group-frequency correlations cannot be made for all of the bands. The coupling of vibrations is less severe in the case of CF,PH,.

The hypotheses and findings of this study are as follows(1) Hypothesis 1, that the adjusted mean achievement score of the students taught with the aid of the Spitz Student Response System would be significantly higher than the adjusted mean achievement score of the students taught by the regular lecture-recitation method, was not confirmed at the .05 level.(2) Hypothesis 2, that the adjusted mean anxiety score of the students taught with the aid of the Spitz Student Response System would be significantly lower than the adjusted mean anxiety score of the students taught by the regular lecture-recitation method, was not confirmed at the .05 level.(3) Hypothesis 3> that the adjusted mean positive attitude score of the students taught with the aid of the Spitz Student Response System would be significantly higher than the adjusted mean positive attitude score of the students taught by the regular lecture-recitation method x^as not confirmed at the .05 level. However, the hypothesis was confirmed at the .10 level of significance.(Lf.) Hypothesis I4., that the adjusted mean achievement of the students with a positive attitude toward mathematics would be significantly higher than the adjusted mean achievement of the students with a negative attitude toward mathematics was confirmed at the .025 level of significance.(5) Hypothesis 5> that there would be significant interaction between the level of attitude and the method of instruction as variables affecting achievement in mathematics, was not confirmed at the .05 level. Response System tended to support the system as a useful teaching device and one which improved the attitude of the students toward mathematics.The following conclusions were reached:(1) It aooeared that students learn as well using the Spitz Student Response System as by using more conventional methods.(2) Based upon the subjective evaluation of the Spitz System by the students, one would have to conclude that the use of the System lessened anxiety in class by reinforcing the student's responses without calling attention to the individual student. (!{.) Students who had a positive attitude toward mathematics had a higher achievement level than those which had a negative attitude toward mathematics.

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3)(CO)][B(C6H5)4], 41777-22-4; [Co(Pf-Pf-Pf-Pf)(CO)][B(C6H5)4], 41777-23-5; [Co(Asf-Pf)2(CO)][B(C6H5)4], 41777-24-6; Co2(CO)8,10210-68-1.

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