Release pattern

Nutrient release patterns vary with the amount of coating appHed and the substrate used. Coating weights vary from 10 to 20%. Typically, commercial products are blends of different coating weights. Coated substrates kiclude, but are not limited to, urea, potassium sulfate, and ammonium nitrate-based N—P—K fertilizers. 

The concept of hyperconjugation arose from the discovery of apparently anomalous electron-release patterns for alkyl groups. By the field effect alone, the order of electron release for simple alkyl groups connected to an unsaturated system is fert-butyl > isopropyl > ethyl > methyl, and this order is observed in many phenomena. Thus, the dipole moments in the gas phase of PhCHa, PhC2Hs, PhCH(CHa)2, and PhC(CHa)a are, respectively, 0.37, 0.58, 0.65 and 0.700. ... 

The influence of polymer composition and molecular weight on the estrus-suppressing activity of the microspheres in female rats was determined. A triphasic release pattern was observed. An initial rapid release over the first few days was attributed to diffusion from superficial areas of the microspheres. A second phase of lower release levels then occurs and continues until the onset of the third, major phase of release. This phase is facilitated by the onset of erosion of the polymer matrix. 

United States Patent 4,767,628 assigned to Imperial Chemical Industries describes a similar lactide/glycolide delivery system for LHRH polypeptide (122,123). A multiphase release pattern is again postulated. The first phase occurs by diffusion of drug through aqueous polypeptide domains linked to the exterior surface of the matrix. 

The second phase occurs when the polymer undergoes significant biodegradation. Broad molecular weight compositions were proposed as one method of reducing the triphasic nature of these release patterns. ... 

The polymer may behave as a weak acid ion exchange resin. Branched copolymers have also been proposed as an approach to achieving "smoother" release patterns for polypeptide systems (40). 

The release behavior depends on both the choice of polymer and on the formulation procedure. The best results were obtained with injection-molded samples. For prototypical drugs like p-nitroaniline, the drug release pattern followed closely that of the polymer degradation over a period of 9 months for PCPP. The correlation between release and degradation was still maintained in the more hydrophilic PCPP-SA, 20 80, where both processes were completed in 2 weeks. Compression molding can also be used for these polymers, but the correlation between drug release and polymer degradation is not as... 

Reproducibility of the production process in terms of, e.g., size distribution, encapsulation efficiency, and release pattern Absence of unwanted side products (e.g., residues of organic solvents in the bilayer)... 

In this brief overview some considerations with respect to the biological system vis-a-vis polymeric drug delivery have been qualitatively presented. Delivery systems can be designed to either overcome a barrier or take advantage of a property associated with a route of administration. Once introduced into a biological system, a delivery system s operation must be consistent with the operation of the biological system to achieve the desired goal based on temporal release pattern. 

A coating may be applied to a tablet to modify the release pattern of the active ingredient from it. There... 

To investigate heparin release in response to an electric current, the swollen heparin-polymer matrix was attached to a woven platinum cathode in a continuously stirred PBS solution (pH 7.4), and an electric current of 20 mA was applied. When the electric current was on, the polymer surface facing the cathode dissolved, thereby releasing heparin. The amount of heparin released was assayed by the Azure II method at pH 11 to prevent complexation of the two dissolved polymers. The release pattern of heparin showed a complete on-off profile in response to the applied electric field, as shown in Figure 23 [50],... 

In choosing a model, the user can optimize fate assessment efforts by delineating first, the source release patterns and second, the dominant dynamical processes. Taking the intramedia processes first, one can address model criteria by considering the ratio of characteristic times. The advection time is the principal length scale of the domain L divided by the average flow speed u i.e. 

A schematic drawing of the potential pathways of PS in industry (primary producers, secondary producers, applications) and release patterns are presented in Fig. 12. 

A laser probe study of Apollo 17 basalts [4] illustrates the use of the laser dating to interpret temperature release patterns. The laser 39Ar-40Ar method has been used to study three Apollo 17 basalts 70215, a basalt with a normal well-behaved 39Ar-40Ar release pattern 70017, a basalt with a disturbed 39Ar-40Ar release... 

Rasmussen, L.E.L. (2001) Source and cyclic release pattern of Z-7-dodecenyl acetate, the preovulatory pheromone of the female Asian elephant. Chem. Senses 26, 611-623. 

Release results with this method are shown in Figure 11. The BioDis method enables the release pattern to be interpreted in terms of release at sites of inflammation. In Crohn s disease, the inflammation often starts at the ileocecal junction and spreads from there in the proximal and/or distal direction and may affect the entire GI tract in severe cases, whereas in colitis the inflammation is restricted to the large bowel. The release patterns in Figure 11 can be used in combination with a knowledge of the sites of inflammation in a given patient to choose the most suitable dosage form available on the market for that patient (Klein, 18). 

Mn(III) r Mn(IV) transition, 33 226-227 Mn-K edge spectra, 33 228-229 Oj-evolving complex, 33 221 proton release pattern, 33 235 rebinding, 33 223 spin echo studies, 33 233-234 S state model, 33 221 temperature dependence of EPR signals, 33 231-232... 

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