Bound water specific volume

Surface-bound, neutral, hydrophilic polymers such as polyethers and polysaccharides dramatically reduce protein adsorption [26-28], The passivity of these surfaces has been attributed to steric repulsion, bound water, high polymer mobility, and excluded volume effects, all of which render adsorption unfavorable. Consequently, these polymer modified surfaces have proven useful as biomaterials. Specific applications include artificial implants, intraocular and contact lenses, and catheters. Additionally, the inherent nondenaturing properties of these compounds has led to their use as effective tethers for affinity ligands, surface-bound biochemical assays, and biosensors. 

The expected value of the electrostatic interaction factor w is given by Eq. (4). To estimate the radius R of the sphere representing the protein molecule, we can use an experimental value of the partial specific volume V and a reasonable estimate for the bound water, 5i grams per gram of protein (usually 6i 0.2 is chosen). The volume per protein molecule becomes (Tanford, 1961b)... 

The total volume of weakly (C ) and strongly (Cuw) bound waters (unfrozen at T < 273 K) at the silica interfaces (Table 38.5) is markedly larger than Vp (but significantly lower than Vemp) with one exception for SI-6 (Table 1). With increasing specific surface area of the first series samples, there is tendency of reduction of the free surface energy (Table 5, js) and the amount of weakly bound water Besides, the AG Cuw)y... 

Despite the similarity in the pore size distributions for polymer and carbon adsorbents (studied here), close values of the specific surface area and the pore volume, and the presence of aromatic rings in the pore walls for both types of the adsorbents, the confined effects on adsorbed water and water/organics differ strongly for them. This is because of the presence of the disordered (polymer) and ordered condensed (carbon) aromatic structures causing different values and cumulative effects of 7t-electron currents on adsorbates, especially located in narrow pores where strong up-field shifts can be observed for carbons but not for polymeric adsorbents. Therefore, the difference in the chemical shifts of bound water can reach 5-7 ppm for these adsorbents. 

Thus, in the native hydrated state, polymer- and protein-based hydrogels produced by cryogelation are characterized by a large macropore volume but a small specific surface area of macropore walls, high pore interconnectivity, and high hydrophilicity. The main portion of water in macroporous hydrogels can be attributed to bulk water located in macropores. The amount of bound water located... 

The bound water content can be determined by methods such as dilatometric determination, vacuum filtration, expression, drying, and thermal analysis. The dilatometric method is based on the assumption that free water can be frozen at 20°C. By placing a known amount of sludge into a scaled container called a dilatometer and measuring the volume of expansion at 20°C, the free water content can be calculated [18]. The part that does not freeze is the bound water. The sludge is usually mixed with a fluid that does not freeze at 20°C, is immiscible with water, has specific gravity less than 1.0, and shows... 

To determine the efficiency of extraction, it is imperative that the pollutant is bound to the matrix in a similar configuration to that which exists in the environment. The extraction efficiency can then be measured for that analyte in a specific matrix configuration. At present, water is the only matrix where this can be achieved in a relatively straightforward way. The analytes are added below the surface of the sample in a small volume of water miscible solvent. The water must be completely mixed and allowed to stand at least overnight prior to extraction to allow the pollutants to come into equilibrium with the other organic materials, particularly humic matter. The spiked water sample must be analyzed... 

Thus far, quality objectives for chemical substances are derived from the most sensitive organisms in acute and chronic toxicity test batteries that determine NOEC values for different trophic levels. The pT-method similarly determines specific sample dilution levels that are devoid of adverse effects toward (micro)organisms of a standardized test battery. Common to both approaches is the more frequent use of water-column test organisms as opposed to benthic-dwelling organism that reflect more intimate contact with sediment. This practice is primarily based on the fact that standardized bioassays capable of appraising sediment porewaters and elutriates are presently more numerous than solid-phase tests for whole-sediment assessment. As more of these latter tests become developed and standardized (see Chapters 12 and 13, volume 1 of this book on amphipod and chironomid tests), their more frequent use will contribute to a better understand of the toxic effects of sediment-bound contaminants. 

During the semibatch experiments, vacuum filtration was applied at 4 d and 8 d after the start of saccharification, to remove the sugar product as filtrate. In selected semibatch experiments, ultrafiltration was applied to the vacuum filtrate to recover soluble enzymes. In other semibatch experiments, the vacuum filter cake was washed extensively with deionized water to remove any enzymes not bound to the solids. After filtration, pretreated corn stover slurry and 7 mL of solution (the ultrafiltration filtrate, or citrate buffer when ultrafiltration was not used) were added to the residual solids and bound enzymes, to replace the volume removed as filtrate during the ultrafiltration step. The additional substrate promotes further saccharification by reusing the cellulase enzymes. To promote further saccharification in a final set of semibatch experiments, additional cellulase at a specific activity of 5 FPU/g of fresh cellulose was added along with the fresh corn stover after vacuum filtration. 

The number of water molecules bound by an ion, the hydration number, is not at all well defined. Also according to different methods e.g. transference, mobility, entropy, volume change on solution, specific heat etc. diverging results are obtained. 

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