Swollen region

Investigations have been made to explore the potential of case II kinetics in the design of constant rate delivery systems [44-47], The idea is that if the preloaded drug molecules have a high diffusivity in the swollen region and the... 

We seek to determine an effective fixed-charge density which influences ion uptake and transport. This may be different from an analytical determination of total carboxyl content because some groups may not be in swollen regions of the polymer and so may not... 

Chromosome puff. A swollen region of a giant chromosome the swelling reflects a high degree of transcription activity. 

A further finding from the observations presented here is that no significant difference appears between the effects of the different phenols in the swollen region. At the transition, however, the repulsion towards the PNIPA network increases with the OH-substitution. 

Fig. 2 Left . Simulated monomer density profile (distribution of intrastar density around the center of mass) for a melt of stars of varying arm number f (from left star to right open square . 2 (linear chain), 4, 8, 16, 24, 36, 48, 64) [41]. The low intrastar density at low functionalities indicates penetrability by other stars (to satisfy incompressibility condition), whereas at high functionality the star core is formed with constant density. Inset . Cartoon illustration of a multiarm star with the three areas in different colors melt-like inner black core, theta-like intermediate blue unswollen and excluded-volume outer red swollen region. Right . The predicted Daoud-Cotton [28] monomer density distribution. The horizontal dashed line indicates the average solution concentration...

While the ingress of liquids in elastomers is diffusion controlled and thus Case I, because the polymer chains are well above the glass transition temperature Tg, liquid transport into glassy polymers is more complex [112, 135]. The swelling behavior below Tg is characterized by a sharp boundary between the remaining polymer core and the swollen region which proceeds with constant velocity. This behavior is also called relaxation controlled because the diffusion is much faster than the segmental relaxation of the polymer. 

This low additive concentration Casi < sparks off the gel collapse due to the suddently decreasing polymer-solution affinity. The interface between the outer collapsed and the irmer swollen regions (shrinking front) proceeds from the outside towards the inside of the gel within the time Qlayer thickness at small times t t is proportional to The concentration c i increases with the time according to Eq. (6). 

Stanton, A.W. et al.. Differences in lymph drainage between swollen and non-swollen regions in arms with breast-cancer-related lymphoedema, C/i . (Bond.), 101 (2), 131-140,2001. 

Onset of bubonic plague is usually 2 to 6 days after a person is exposed. Initial manifestations include fever, headache, and general illness, followed by the development of painful, swollen regional lymph nodes. Occasionally, buboes cannot be detected for a day or so after the onset of other symptoms. The disease progresses rapidly and the bacteria can invade the bloodstream, producing severe illness, called plague septicemia. 

The film comprises two parts a compact region and a region swollen to varying degrees by the two phases. This can affect both spontaneous curvature and surface pressure, hence also 7. The compact region constitutes a hard sphere and the swollen region a hydrodynamic volume. 

The crossover temperature where the theta region changes into the high-temperature swollen region is decided by the condition t / 6>. This gives r 1 /n for the boundary... 

A direct correlation exists between the redox state and the PPy film volume. Although, not surprisingly, this correlation confirms that the ion diffusion drives the actuation process. The film thickness was measured by profilometry across the phase boundary. A clear height step was observed at the boundary between the oxidized and reduced phases. The thickness of polymer was constant in the reduced (swollen) region behind the boundary, showing that the polymer was fiiUy reduced in this entire region. Thus, reduction of the polymer requires the diffusing ions to reach the next reduction site on the polymer. 

As shown in Fig. 15, v is die propagation rate of the interface between the rubbery state and glassy state assuming that they are clearly separated, (r) is the thickness of the swollen region at time t, and A is the diffusion coefficient of the drug in die swollen region. 

Figure 7.1.11 illustrates that both equations ([7.1.5] and [7.1.6]) apply only to the steady state diEfusion but they do not describe sorption which is the initial stage of difiu-sioa DiEfusion in unswollen and swollen regions are characteristic for two different stages, namely sorption and permeation, with the last characterized by a steady state diEfu-... 

A solvent diffusion is defined anomalous whenever the exponent of t in Equation 11.16 is greater than 1/2, and in the case where the exponent is unity, it is considered a case II diffusion. For that latter case, a sharp concentration front separates the equilibrium swollen region from the glassy inner core and advances at a constant velocity where the flux is controlled by the stress gradient [33]. 

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