Entrapped water

Thermal shock failures using water result from the water vapor entering the enamel layer through small, submicroscopic cracks formed at the instant of shock. The water condenses in the cracks and in the bubbles of the enamel traversed by the cracks. On subsequent heating, the vapor from the entrapped water expands to cause spalling of the enamel layer. Other quenchant Hquids, such as toluene, oils, and other organic Hquids, also cause fine, almost invisible cracks, but thermal shock failures do not result with these quenchants on subsequent heating (39). 

Cationic quaternary ammonium compounds such as distearyldimethylammonium-chloride (DSDMAC) used as a softener and as an antistatic, form hydrated particles in a dispersed phase having a similar structure to that of the multilayered liposomes or vesicles of phospholipids 77,79). This liposome-like structure could be made visible by electron microscopy using the freeze-fracture replica technique as shown by Okumura et al. 79). The concentric circles observed should be bimolecular lamellar layers with the sandwiched parts being the entrapped water. In addition, the longest spacings of the small angle X-ray diffraction pattern can be attributed to the inter-lamellar distances. These liposome structures are formed by the hydrated detergent not only in the gel state but also at relatively low concentrations. 

Phase separation microencapsulation procedures are suitable for entrapping water-soluble agents in lactide/glycolide excipients. Generally, the phase separation process involves coacervation of the polymer from an organic solvent by addition of a nonsolvent such as silicone oil. This process has proven useful for microencapsulation of water-soluble peptides and macromolecules (48). 

J., Dougherty, T.J. and Prasad, P.N. (2003) Ceramic-based nanoparticles entrapping water-insoluble photosensitizing anticancer drugs A novel drug-carrier system for photodynamic therapy. Journal of the American Chemical Society, 125, 7860-7865. 

The resulting sol-gel catalysts usually proved more stable and versatile under ambient conditions than their homogeneous analogues. For example, a remarkable asymmetric hydrogenation of prochiral itaconic acid over sol-gel entrapped (—)-Ru-BINAP in water becomes possible which simply cannot be done with non-entrapped, water-insoluble catalysts. 

Jahren, S.J. Rintala, J.A. Odegaard, H. Anaerobic thermophilic (55°C) treatment of TMP Whitewater in reactors based on biomass attachment and entrapment. Water Set Technol. 1999 40 (11-12), 67-76. 

The formation of skeletonized vesicles was also reported for vesicles composed of IS and DPPC, where the mole fraction of DPPC varied from 5 to 25 mole percent. Takeoka et aL analyzed the release of entrapped water soluble molecules in order to assess the size of the pores formed in the vesicle wall [49]. The ease of release of saccharides, primarily dextrans, of various molecular... 

Surfactants having an appropriate hydrophobic/hydrophilic balance (sodium bis(-2-ethylhexyl)sufosuccinate, or AOT, for example) undergo concentration-dependent self association in apolar solvents to form reversed or inverted micelles (Fig. 33) [256-262]. Reversed micelles are capable of solubilizing a large number of water molecules (AOT reversed micelles in hexane are able to take up 60 water molecules per surfactant molecule, for example). Reversed-micelle-entrapped water pools are unique they differ significantly from bulk water. At relatively small water-to-surfactant ratios (w = 8-10, where w = [H20]/[Surfactant]), all of the water molecules are strongly bound to the surfactant headgroups. Substrate solubilization in the restricted water pools of reversed micelles results in altered dissociation constants [256, 257, 263-265], reactivities [256, 258, 266], and reaction products [267]. 

Increasing the concentration of surfactant-entrapped water results in the formation of larger aggregates which eventually become water-in-oil (w/o)... 

Surfactant aggregates in non-polar solvents. Their formation requires water thus, they can be considered to be surfactant-entrapped water pools in non-polar solvents. 

Sodium bis-2-ethylhexylsulfosuccinate (AOT) was used to form reversed micelle-entrapped water pools in isooctane. Platinized CdS, in situ generated in those water pools, sensitized water photo reduction by thiolphenol dissolved in the organic phase. 

Figure 2. (Top) Stern-Volmer plots for the quenching of the fluorescence of colloi fcl CdS in AOT-entrapped water pools in isooctane by RMV + (0), MV2+ 4Q), and PhSH (0) (Bottom) Absorption and emission spectra of colloidal CdS in AOT entrapped water pools in isooctane. The shoulder observed at 400 nm is due to a spectrometer artifact.

If several nuclei could be observed in high-resolution NMR techniques to monitor similarities or differences in both chemical shifts or integrals, other parameters can be monitored by using LF 1H NMR. In this case, relaxation parameters are usually measured as intrinsic discriminating values. As pointed out in several studies, T2 relaxation decay has a multiexponential decay in both muscles and fish tissues. This suggests the presence of different "pools" in tissues and water distribution was assumed to be present in three distinct compartments, namely (a) "bound water," (b) "entrapped water," and (c) "free water." In those three pools, water acts with different relaxation times because it can be bound to proteins, involved in the conversion of muscle to meat and entrapped by weak surface forces, showing relaxation values in the range of 1-10,10-100, and 100-400 ms, respectively. 

Definitive location of all guest molecules inside the cavity is somewhat ambiguous owing to inexact stoichiometry and disorder. However, the (+)-MALDI mass spectra of II indicate that each individual capsule encloses different mixtures of water and acetone. In particular, two peaks implicated the presence of 24 entrapped water molecules that occupy axial coordination sites orientated toward the center of the cavity. 

Polymer Swelling. Swelling phenomena are generally encountered in both the hydrophilic and hydrophobic polymer matrices during the release of entrapped water soluble drug in an aqueous environment. 

Compaction caused by the weight of overlying rocks is called upon to explain the water pressure in deep-seated artesian aquifers (Mazor, 1995). Compaction counteracts through-flow in deep aquifers, as it causes collapse features, and pressurizes the entrapped water. If through-flow would take place, the open ends of the hypothetical aquifer ducts would serve as... 

It appears that in most cases the techniques are comparable in terms of resulting sensitivity. Whereas the SPR has the advantage in terms of real sensitivity, the fact the QCM technique also measures entrapped water amplifies the gravimetric response and may render it sensitivity comparable in macromolecular binding experiments [44, 45]. An added advantage of QCM over SPR is the availability of the QCM-D technique which is a measurement of the dissipation energy. A film that is viscoelastic or soft will not fully couple with the quartz crystal s oscillation... 

The fluorescence polarization excitation spectrum has been measured for thymine in aqueous solution. " The depolarization at the red edge is attributed to the hidden n, ir transition. Ionization of the lowest excited singlet and triplet states have been determined by the effect of pH on the absorption, fluorescence, and phosphorescence spectra of purines and pyrimidines. " Spectral, polarization, and quantum yield studies of cytidylyl-(3, 5 )-adenosine have also been published. Intermediates in the room-temperature flash photolysis of adenine and some of its derivatives have been identified hydrated electron, radical cations and anions, and neutral radicals resulting from their reactions have been assigned. Photoionization occurs via the triplet state. FMN encapsulated in surfactant-entrapped water pools interacts with polar head groups, entrapped water molecules, and outer apolar solvent. ... 

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