Kinetics of Release

Limit of Low SDS Concentration and Low Internal Droplet Volume Fraction 

The regime governed by coalescence was examined in more detail. The process of film rupture is initiated by the spontaneous formation of a small hole. The nucleation frequency. A, of a hole that reaches a critical size, above which it becomes unstable and grows, determines the lifetime of the films with respect to coalescence. A mean field description [19] predicts that A varies with temperature T according to an Arrhenius law  

The adsorption isotherm was modeled in order to deduce a numerical value for A. Following the model of Frumkin and Fowler reported in [21], is given by the following set of equations  

Assuming that the internal droplets experience a hard-sphere-like repulsion when surfactant layers come in contact, an estimation of the van der Waals interactions can be obtained from the average length of the surfactant tails (1 3 nm) [20]. The coalescence frequency is therefore the unique free pa- 

Limit of High SDS Concentration or High Internal Droplet Volume Fraction 

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Two distinct phases can be distinguished in the kinetic of release of reducing groups in order to study the regultion and synthesis of PG by the SCPP strain. Thus, we decided to estimate the effect of glucose on the PG activity at the start of the culture and define the cause of the stabilization phase in the release of the reducing groups... 

Figure 3 Comparison of the kinetics of release of reducing groups by various yeast strains grown on Pg glc medium...

A further development of this system has been the preparation of drug delivery systems whereby the releasing area exposed has been reduced by an impermeable partial coating. As a result, the kinetics of release was zero order [9,10]. 

Gas-liquid chromatography used for the determination of C-terminal amino acids and C-terminal amino acid sequences in nanomolar amounts of proteins was described in 1976 by Davy and Morris. Based on carboxypeptidase A digestion of the protein, the partially digested protein was removed and the amino acids released after known time intervals were analyzed by quantitative gas-liquid chromatography. Sequences deduced from the kinetics of release of specific amino acids are compared with the known C-terminal sequences of well-characterized proteins. Thus the amino acid sequences were determined. 

S. S. Ozturk, B. 0. Palsson, B. Donohoe, and J. B. Dressman. Kinetics of release from enteric-coated tablets. Pharm. Res. 5 550-565, 1988. 

Polyphosphazenes are a relatively new class of biodegradable polymers. Their hydrolytic stability or instability is determined not by changes in the backbone structure but by changes in the side groups attached to an unconventional macromolecular backbone. Synthetic flexibility and versatile adaptability of polyphosphazenes make them unique for drug delivery applications. For example, Veronese et al.18 prepared polyphos-phazene microspheres with phenylalanine ethyl ester as a phosphorous substituent and loaded it with succinylsulphathiazole or naproxen. The kinetics of release from these matrices were very convenient in yielding local concentrations of the two drugs that are useful per se or when mixed with hydroxyapatite for better bone formation. Polyphosphazene matrices are also considered as potential vehicles for the delivery of proteins and vaccines.19... 

The kinetics of release from a monolithic solution system have been derived for a number of geometries by Crank [20], For a slab geometry, the release kinetics can be expressed by either of two series, both given here for completeness... 

Figure 1 shows the kinetics of release of radioiodinated protein from antibody-complement-treated tumor cells. Guinea pig serum caused the maximum enhanced release compared to untreated cells of I-labeled protein from anti-Forssman antibody-sensitized cells within 10 min of incubation there was no enhanced release of I-labeled protein compared to controls from anti-line-10 antibody-sensitized cells treated with GPC (Fig. lA). Similarly, HuC caused maximal enhanced release of cell surface protein from cells sensitized with either antibody within 10 min (Fig. IE). No enhanced release of membrane protein was observed from cells treated with antibody alone or complement alone (Fig. 1). The values in Fig. 1 represent 23-40% of the total cell-bound activity associated with [ I]ISA.

Ruckmani K, Muneera MS, Vijaya R. Eudragit matrices for sustained release of ketorolac tromethamine formulation and kinetics of release. Boll Chim Form 2000 139 205-208. 

Kinetics of release of pre-adsorbed Zn on addition of diethylene triamine pentaacetic acid was also studied. 

STUDY OF THE KINETICS OF RELEASE OF BIOCIDES FROM SWOLLEN GELS OF 2-HYDROXYETHYLMETHACRYLATE/N-VINYL-... 

Recently [16] we have shown that water diffusion in the PHB films with 100 pm thick was completed in several tens of minutes, whereupon the films absorbed the limiting equilibrium concentration of water (ca. 1 wt %). Structural relaxation in PHB under humid conditions is finished in longer period of time (nearly 1000 minutes). We have investigated kinetics of release for several tens of days, therefore, to a first approximation, a water transport phenomenon in PHB is not essential. However, long-term kinetics of drug release from PHB films has an intricate form and demands special analysis for both diffusion modeling and drug delivery application. 

Understanding of fate and transport of hydrophobic contaminants in the soil environment and the thermodynamics and kinetics of release. 

C. A. Differences in the synthesis and kinetics of release of interleukin-1 alpha, interleukin-1 beta and tumor necrosis factor from human mononuclear ceils. ur.J. Immunol. 19,1531-1536 (1989). 

Preliminary results are shown in Figs. 36-38 [56]. As with 4-homosulfanilamide, the pH of the drug was found to have a significant effect on kinetics of release. Thus, naltrexone pamoate is acidic by virtue of its unreacted phenolic hydrogens and as shown in Fig. 36, release rate is relatively fast. On the other hand, naltrexone is basic and release rate as shown in Fig. 37 is slower. As shown in Fig.38, when a 50/50 mixture of the two forms is used, good linear release kinetics have been achieved. 

As pointed out by these workers [147], the rates of release of ATP or other biological substrates are generally deduced indirectly and are frequently inferred solely from the decay rate of aci-nitro anion intermediates (44), which absorb in the near-UV. Such analyses can sometimes be complicated by non singleexponential kinetics that may be the result of overlapping bands from other byproducts of photolysis. As nicely demonstrated [147], structurally more informative TRIR experiments can not only monitor directly the kinetics of release of the biological compound of interest but also provide valuable information concerning the identities and chemical fates of byproducts. 

Table 10-6. Arrhenius Parameters of Kinetics of Releasing of Different Functional Groups and Their Decomposition Products from Coal During Its Pyrolysis...

In drug delivery, injectable systems can be administered systemically or topically, producing dosage forms that can have an extended circulation (dispersed systems) or provide a localized reservoir of an active ingredient (depot systems). Different combinations of route of administration and physical nature of the formulation can be used to spatially (biodistribution) and temporally (kinetics of release) control the concentration of the active principle and thus its bioavailability. For example, the characteristics of the administration (e.g. subcutaneous or intravenous) and the size of the carrier (e.g. capable or not of... 

Marszalek, P.E., Farrell, B., Verdugo, P., Fernandez, J.M., 1997. Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin. Biophys. J. 73, 1169—1183. 

Pectin-hydrox5rpropyl methyl cellulose has been used as compression coating material (35). This envelope was foimd to be a promising drug delivery system for those drugs to be delivered to the colon. The kinetics of release of 5-aminosalicylic acid is shown in Figure 8.3. 

The purpose of this chapter was studying of influence finely divided schungite on structure, mechanical characteristics and kinetics of release of a medicinal drag furacilinum from films poly hydroxyl butyrate. 

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