Enhancement Passive methods

Passive Methods for Enhancing (Trans)dermal Drug Delivery... 

Enhancement techniques can be classified as passive methods, which require no direct application of external power, or as active schemes, which require external power. The effectiveness of both types depends strongly on the mode of heat transfer, which might range from single-phase free convection to dispersed-flow film boiling. Brief descriptions of passive techniques follow. 

Enhancement techniques may be conveniently divided into two classes - passive methods and active techniques. Extended surfaces which require no direct application of external power fall within the passive category. Rotation (as used in the Rotex heat pump initially mentioned in Chapter 1) is an active technique, as obviously energy is needed to rotate the device. Additionally, each technique may be applicable to one or more modes of heat transfer (e.g. forced convection, boiling, condensation, etc.) and compound enhancement - the use of more than one technique on a single heat exchanger - is practised. 

There are several types of mixers, some giving greater intensification than others. As with separations, it is often the active enhancement methods that can produce the greatest intensification of mixing, but passive methods currently dominate. Both types are described here and recent developments directed at intensify mixing are also introduced. 

Nanoparticles of Mn and Pr-doped ZnS and CdS-ZnS were synthesized by wrt chemical method and inverse micelle method. Physical and fluorescent properties wra cbaractmzed by X-ray diffraction (XRD) and photoluminescence (PL). ZnS nanopatlicles aniKaled optically in air shows higher PL intensity than in vacuum. PL intensity of Mn and Pr-doped ZnS nanoparticles was enhanced by the photo-oxidation and the diffusion of luminescent ion. The prepared CdS nanoparticles show cubic or hexagonal phase, depending on synthesis conditions. Core-shell nanoparticles rahanced PL intensity by passivation. The interfacial state between CdS core and shell material was unchan d by different surface treatment. 

In liquid-solid extraction (LSE) the analyte is extracted from the solid by a liquid, which is separated by filtration. Numerous extraction processes, representing various types and levels of energy, have been described steam distillation, simultaneous steam distillation-solvent extraction (SDE), passive hot solvent extraction, forced-flow leaching, (automated) Soxh-let extraction, shake-flask method, mechanically agitated reflux extraction, ultrasound-assisted extraction, y -ray-assisted extraction, microwave-assisted extraction (MAE), microwave-enhanced extraction (Soxwave ), microwave-assisted process (MAP ), gas-phase MAE, enhanced fluidity extraction, hot (subcritical) water extraction, supercritical fluid extraction (SFE), supercritical assisted liquid extraction, pressurised hot water extraction, enhanced solvent extraction (ESE ), solu-tion/precipitation, etc. The most successful systems are described in Sections 3.3.3-3.4.6. Other, less frequently... 

The ex vivo methods lend themselves easily for the performance of mechanistic investigations. In order to optimize selection of drug candidates prior to further clinical development, it is important to decipher the contributive roles of permeation, metabolism, efflux, and toxicity. This will then make it possible to properly channel the optimization process, for instance, by permeation enhancement, mucoadhesion, modification of the physicochemical characteristics of the drug, or even change in the route of administration in case the drug and/or formulation turns out to be too toxic. Regarding permeability studies, it is possible not only to quantify passive diffusion but also to identify and characterize (compound)-specific carrier-mediated transport routes. These tools have been used to identify and characterize the relative contribution of... 

The Barometrically Enhanced Remediation Technology (BERT ) removes and recovers volatile organic contaminants from soil by enhancing the natural air exchange that occurs in soil as a response to changes in atmospheric pressure. This process is sometimes referred to as barometric pumping or passive soil vapor extraction. The process is a low-cost complement to conventional active-extraction methods because investment and maintenance costs are low and no power is needed. The passive process is better suited than conventional methods for certain problems. 

It is therefore desirable to devise strategies both to enhance the penetration of molecules, which can already breach the skin barricade passively to some extent, and also to widen the spectrum of drug molecules that can penetrate the skin at therapeutically beneficial doses. Many tactics have been utilized to help overcome the barrier function. These include chemical means (e.g., chemical penetration enhancers or entrapment of molecules within lipid vesicles) or physical methods (such as ultrasound, microneedles, or electrical methods). Two important electrical methods are iontophoresis and electroporation. 

However, in view of further NC functionalization, it is highly desirable to provide a surface passivation, which is insensitive to subsequent ligand exchange. This is obviously not the case with the described procedures for QY enhancement. A suitable and widely applied method consists of the growth of an inorganic shell on the surface of the NCs. The resulting core-shell systems will be described in detail in the following section. 

Analytical strategies based on the activation effect caused by the analyte on the QD luminescence emission also have been proposed. In a pioneering work, the addition of Zn and Mn ions to colloidal solutions of CdS or ZnS QDs resulted in an important enhancement of the luminescence quantum yield of the nanoparticles. This effect was attributed to the passivation of surface trap sites that are either being filled or energetically moved closer to the band edges.33 46 This behavior provided the basis for the optical sensing of such metal cations with QDs. Chen and Zhu47 proposed a method for the determination of trace levels of silver ions based... 

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