Drag partition

A similar difference has been observed for Kp M values of the anticancer drags tamoxifen and 4-hydroxytamoxifen determined in mitochondria, sarcoplasmic reticulum, and in liposomes made from lipids extracted from the corresponding native membranes [85]. The largest Kp M was observed in mitochondria, followed by sarcoplasmic reticulum and liposomes. The authors introduced for these experiments derivative spectroscopy, a reliable and rapid procedure to estimate drag partitioning into biomembranes. The method used the shift in the absorption spectra of the drug when removed from the aqueous phase to a hydrophobic environment (see Section 3.10). 

Raupach, M. (1992) Drag and drag partition on rough surfaces, Boundary-Layer Meteorology 60, 375-395. 

On a chute, higher drag results in lower particle velocity which can be accentuated by stratification on the chute surface because of the sifting mechanism. Concentrations of smaller particles close to the chute surface and larger particles at the top of the bed of material, combined with the typically higher frictional drag of finer particles, often result in a concentration of fine particles close to the end of the chute, and coarse particles farther away. This can be particulady detrimental if portions of the pile go to different processing points, as is often the case with multiple outiet bins or bins with vertical partitions. 

Pneumatic classification can be partitioned conveniently into coarse, ie, fine products above 95% < 100 pm intermediate, ie, fine products ranging between 95% < 100 and 30 pm and fine, ie, fine products below 95% < 30 pm. Pneumatic classification, like hydraulic classification, balances the force of gravity with drag forces (counter flow) in order to bring about a separation. 

At speeds beyond 4000 m/min, inertial and air drag effects become the dominant contributors to fiber stress. Sufficient orientation can be induced so that significant crystallization occurs in the as-spun fiber. The structure begins to partition into either highly oriented crystalline regions, or amorphous regions of relatively low orientation. There is relatively less oriented-amorphous structure. 

Alcorn, C.X.J., Simpson, R.J., Leahy, D.E., and Peters, T.J. Partition and distribution coefficients of solutes and drags in brush border membrane vesicles, Biochem. Pharmacol, 45(9) 1775-1782, 1993. 

When an anionic surfactant such as SDS is used, the micelles migrate toward the anode as a result of electrophoretic mobility. The EOF in uncoated, fused silica capillaries, however, travels toward the cathode at a greater velocity than the micelles travel toward the anode, thereby dragging the micelles slowly toward the detector. When a neutral molecule is injected into the system, it partitions itself between the buffer and the micelle. The more time it spends in the micelle, the longer it will take to reach the detector. In MECC, therefore, the analytes all migrate between a water peak, which is totally unretained, and the micelle peak, which is the most retained. A typical elution order is shown in Figure 5.7, where peak EOF represents a neutral molecule that has no interaction with the micelles and therefore travels at the velocity of the EOF. 

This microscopic interaction model can be used to explain more specific interactions between drug molecules and lipids. Such specific interactions could be a selective coupling between a drag molecule and a particular chain conformation of the lipid (kink excitation). This could have a dramatic effect on the fluctuation system. The drug molecule would then control the formation of interfaces between lipid domains and bulk phase in the neighborhood of the transition. First results on an extended model of this type [50] have confirmed this view and demonstrated that the partition coefficient can develop non-classical behavior by displaying a maximum near the transition. And such a maximum has in fact been observed experimentally... 

The influence of lipid phase (gel or liquid crystalline), cholesterol content, lipid composition (egg phosphatidylcholine or DPPC), and structure of benzodiazepines determine their localization in the membrane. The strength of benzodiazepine-membrane interaction increases with a decrease in molecular order, molecular packing, and hydration,. The authors point to the pharmacological relevance of theses results because the extent of partitioning of these drags into biomembranes would be coupled to local oscillation of membrane dynamics which may be induced by physiological events. ... 

The characteristics of membrane permeation are partition, including affinity, location, specific interaction with certain phospholipids, and diffusion kinetics. Because of the complex events involved during drug absorption in vivo, true membrane permeability modeling cannot always be expected. Therefore, many attempts have been made to develop suitable in vitro systems to study the permeation process and its dependence on membrane composition and drag physicochemical properties. 

The interrelationship between the dissociation constant and lipid solubility of a drag, as well as the pH at the absorption site, is known as the pH-partition theory of drag absorption. Accordingly, rapid transcellular passive diffusion of a drag molecule may be due to ... 

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