Front eroding

Figure 7 Schematic illustration of a self-polishing antifouling paint with soluble CU2O particles exposed to seawater (no insoluble pigments present for simplicity). Notice the pigment-leached layer and the two moving fronts (eroding polymer front, zE, and dissolving pigment front, zP). After Kiil et al. (2002c).

Fig. 8. Diagrammatic representation of a swelling polymeric system in contact with a penetrant indicating the initial position of the tablet surface a, the dissolution medium/swollen polymer front (eroding front) S, and the rubbery-glassy front (swelling front) R. The coordinate 0 is the center of the tablet and x is the distance coordinate [78]...

Computer simulation of eroding matrices (Fig. 8.36) can give an accurate representation of the process and can predict the position of the erosion front and the weight of the matrix. 

Since the concentration is constant as long as the injection plateau has not been eroded, the retention time of the front of the first component (a shock with... 

The condition for the validity of the equations derived in this subsection is that iR,2 (Eq. 8.19) needs to be shorter than tr,i, so the front shock of the second component elutes before the injection plateau ends. Otherwise, the plateau vanishes, the front shocks are eroded, and their velocities are no longer constant. Then, the problem becomes the elution of a narrow rectangular injection pulse see next section. 

The release kinetics are characterized by an initial lag-phase, a zero release phase and a depletion phase. During the lag-phase water intrudes into the polymer matrix and activates the latent catalyst. During the zero-order release phase, an equilibrium between water intrusion and polymer erosion is established and an eroding front, (V2), that penetrates the device is established. Because thin disks were used, device geometry remains essentially constant and zero order release uncomplicated by a decrease in total surface area is observed. The depletion phase characterizes a decrease in device and depletion of the incorporated acidic excipient. 

Because drug release in a surface-eroding polymer occurs as a consequence of an eroding front that moves through the device, rate of drug release depends... 

In some conditions, the normalized gel layer thickness (=(S — R)/a) may reach a constant value because the synchronization of the swelling and eroding fronts generates pseudo-order release of a solute incorporated in the polymeric matrix. Experimental results concern mixes made of the drug diclofenac sodium and the excipient poly(vinyl alcohol), HPMC type 2208 or NaCMC (Fig. 9). 

The synchronization of the two fronts is rapidly achieved with PVAL and soon produces a zero-order release. In the system containing HPMC, the synchronization is still not reached when, at approximately 300 min, the swelling front stops. Nevertheless, from that moment, drug release is constant because the system behaves as a conventional erodible system. 

In times like these, just remember to be grateful about what s right in front of you, what s li t, and what s true. Nothing is worth losing your grotmding for. All the excitement and self-importance may shake you for a moment, but don t let it erode the precious soil where you re planted. 

An overthrust is a thrust fault that has a dip of 10° or less, and its net slip measures several kilometres. Overthrusts may be folded or even overturned. As a consequence, when they are subsequently eroded, remnants of the overthrust rocks may be left as outliers surrounded by rocks that lay beneath the thrust. These remnant areas are termed klippe, and the area that separates them from the parent overthrust is referred to as a fenster or a window. The area that occurs in front of the overthrust is called the foreland. 

In fact, the expansion front Is eroded by bubbles In cavitation zone. This Is the basis of the theory of Dubesset and Lavergne. The Introduction In calculation... 

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