Bulk developments

Coated photographic layers are immersed in developer solutions and rely on the diffusion of active components into and out of the layer. Since chemical development occurs at local sites within the layer, agitation helps to remove oxidized developing agent into the effectively infinite sink of the bulk developer solution, and to replace it with the reduced form. In addition agitation removes development byproducts which can influence the course and rate of development. 

To account for surface inhibition effects, an assumption is made that the development rate near the surface of the resist exponentially approaches the bulk development rate, giving a rate as a function of depth r(z) as ... 

From the above definitions, a discussion of the specifics of each stage is now possible, also based on the depiction of the bulk drug process development cycle on the know-how vs. applied effort plane introduced in Fig. 6. During these stage-specific discussions, the three bulk development tasks will serve as the basis and along the lines of Fig. 5. 

Yet, scale-up is inevitable, even in the relatively low throughput environment of bulk drugs. Skillful use of the pilot plant environment, by which the preparative task and the process development scale-up coincide in time and place, is essential to a vigorous bulk development program lest the activity oscillate between the extremes of unskilled scale-up and fear of scale-up. Indeed, lack of sufficient scale-up skills is a major disadvantage in bulk drug process development. 

The difficulty of the dosage form task cannot be underestimated. Its need for making judgments with partial data actually exceeds that of the bulk development task, as the crucial feedback on the bioavailability and stability of its developmental materials cannot be obtained rapidly, not unlike the feedback that the bulk development team needs as to the suitability of the its bulk drug for the dosage form purposes. Figure 15 is an attempt to depict the scope of dosage form development. 

Chiu FC, Ung MH (2007) Thermal properties rmd phase morphology of melt-mixed poly (trimethylene terephthalate)/polycarbonate blends-mixing time effect. Polym Test 26 338-350 Chuah HH (2004) Effect of process variables on bulk development of air-textured poly (trimethylene terephthalate) bulk continuous filament. J Appl Polym Sci 92 1011-1017 Chuah HH, Lin VD, Soni U (2001) PTT molecular weight and Mark-Houwink equation. Polymer 42 7137-7139... 

Bulk development n. Any of various relaxation treatments to produce maximum bulk in textured or latent crimp yarns or in fabrics made there from. The essential conditions are heat, lubrication, movement, and the absence of tension. Bulk development may be accomplished during wet processing or may be a separate operation such as hot-air tumbling, steam-injection tumbling, or dry cleaning. 

Thin film dissolution behavior has been the subject of stuity for many applications. In the case of positive photoresists, a number of techniques have been used to characterize the kinetics of dissolution (1-12). The earliest such e q>eriments were performed by exposing the resist to a solvent for a fixed time and then measuring the thidmess of the remaining film (2). From repeated measurements of this type, a bulk development rate could be determined. 

The beneficial effects of dietary fiber on the alimentary tract were emphasized by another of the founders of the dietary fiber hypothesis, Denis Bur-kitt, who based his arguments largely on the concept of fecal bulk, developed as a result of field... 

This section will consider the behaviour of the reservoir fluids in the bulk of the reservoir, away from the wells, to describe what controls the displacement of fluids towards the wells. Understanding this behaviour is important when estimating the recovery factor for hydrocarbons, and the production forecast for both hydrocarbons and water. In Section 9.0, the behaviour of fluid flow at the wellbore will be considered this will influence the number of wells required for development, and the positioning of the wells. 

An approach developed by Guggenheim [106] avoids the somewhat artificial concept of the Gibbs dividing surface by treating the surface region as a bulk phase whose upper and lower limits lie somewhere in the bulk phases not far from the interface. 

The preceding treatment relates primarily to flocculation rates, while the irreversible aging of emulsions involves the coalescence of droplets, the prelude to which is the thinning of the liquid film separating the droplets. Similar theories were developed by Spielman [54] and by Honig and co-workers [55], which added hydrodynamic considerations to basic DLVO theory. A successful experimental test of these equations was made by Bernstein and co-workers [56] (see also Ref. 57). Coalescence leads eventually to separation of bulk oil phase, and a practical measure of emulsion stability is the rate of increase of the volume of this phase, V, as a function of time. A useful equation is... 

As discussed in more detail elsewhere in this encyclopaedia, many optical spectroscopic methods have been developed over the last century for the characterization of bulk materials. In general, optical spectroscopies make use of the interaction of electromagnetic radiation with matter to extract molecular parameters from the substances being studied. The methods employed usually rely on the examination of the radiation absorbed. 

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