Loss angle 510 Subject

Experimentally DMTA is carried out on a small specimen of polymer held in a temperature-controlled chamber. The specimen is subjected to a sinusoidal mechanical loading (stress), which induces a corresponding extension (strain) in the material. The technique of DMTA essentially uses these measurements to evaluate a property known as the complex dynamic modulus, , which is resolved into two component parts, the storage modulus, E and the loss modulus, E . Mathematically these moduli are out of phase by an angle 5, the ratio of these moduli being defined as tan 5, Le. 

Watanabe and Ohnishi [39] have proposed another model for the polymer consumption rate (in place of Eq. 2) and have also integrated their model to obtain the time dependence of the oxide thickness. Time dependent oxide thickness measurement in the transient regime is the clearest way to test the kinetic assumptions in these models however, neither model has been subjected to experimental verification in the transient regime. Equation 9 may be used to obtain time dependent oxide thickness estimates from the time dependence of the total thickness loss, but such results have not been published. Hartney et al. [42] have recently used variable angle XPS spectroscopy to determine the time dependence of the oxide thickness for two organosilicon polymers and several etching conditions. They did not present kinetic model fits to their results, nor did they compare their results to time dependent thickness estimates from the material balance (Eq. 9). More research on the transient regime is needed to determine the validity of Eq. 10 or the comparable result for the kinetic model presented by Watanabe and Ohnishi [39]. 

Figure 7.27 Schematic illustration of Surface Plasmon Resonance (SPR). Incident light is normally subject to total internal reflection in the prism block except for losses due to evanescent wave penetration of the hydrogel layer at the resonant angle. Changes in resonant angle due to receptor-ligand interactions are the basis for the real time observation of molecular recognition and association/dissociation events.

The second study question was whether the clinically available transtibial procedure for anatomic DB reconstruction can really obtain significantly better knee stability in comparison with the conventional SB reconstruction procedure. The anterior translation laxity in response to a 90-N anterior drawer force was significantly less after the anatomic DB reconstmction than after the SB reconstruction from 0 to 75° of knee flexion. Previous biomechanical studies have shown that the PL bundle of the intact ACL carries one-half to two-thirds of the total force in the ACL near full extension of the knee, when the knee is subjected to an anterior tibial load [8, 26, 27]. As the conventional SB reconstmction reproduces only the AM bundle, loss of the function of the natural PL bundle is considered to result in the insufficient function in the conventional SB reconstmction in the range between 0 and 75° of knee flexion. On the other hand, Yamamoto et al. [22] and Yasuda et al. [28] reported that the reconstmcted PL bundle cannot restrain anterior tibial translation at flexion angles of the knee. This fact explains the similarity concerning the knee laxity between the two reconstmctions namely, only the reconstmcted AM bundle stabilizes the knee near flexion position in response to anterior tibial load. 

Pig. 1. (a) When a sample is subjected to a sinusoidal oscillating stress, it responds in a similar strain wave, provided the material stays within its elastic limits. When the material responds to the applied wave perfectly elastically, an in-phase, storage, or elastic response is seen (b), while a viscous response gives an out-of-phase, loss, or viscous response (c). Viscoelastic materials fall in between these two extremes as shown in (d). For the real sample in (d), the phase angle S and the amplitude at peak k are the values used for the calculation of modulus, viscosity, damping, and other properties. 

---