document: A convenient and widely reported technique for detection of the GP involves measurements of the complex shear modulus, G∗, over a range of frequencies, ω, in oscillatory shear. At the GP the elastic and viscous components of the complex modulus, G′ and G″, respectively scale in oscillatory frequency, ω, as G′(ω)∼G″(ω)∼ωα where α is termed the stress relaxation exponent [15]. Thus, the GP may be identified as the instant where the G′ and G″ scale in frequency according to identical power laws [15], behaviour corresponding to attainment of a frequency independent phase angle, δ(=atan(G″/G′)). GP measurements may involve ‘frequency sweeps’ with repeated consecutive application of a set of small amplitude oscillatory shear, SAOS, waveforms [15,16], or by Fourier Transform Mechanical Spectroscopy, FTMS, in which G∗(ω) is found by simultaneous application of several harmonic frequencies in a composite waveform and its subsequent Fourier analysis [17,18]. Frequency sweeps are limited to relatively slow gelation processes due to sample mutation and interpolation errors [9,19,20]. FTMS may overcome these limitations, but is unsuitable for markedly strain sensitive materials, such as fibrin gels, due to the strain amplitude of the composite waveform exceeding the linear viscoelastic range (LVR) [9].
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extractive_keyphrases: application of several harmonic frequencies composite waveform detection of the gp fibrin gels fourier analysis fourier transform mechanical spectroscopy frequency sweeps ftms gelation processes gp measurements markedly strain sensitive materials measurements of the complex shear modulus saos small amplitude oscillatory shear waveforms