Fluidity, definition

Whea there are reactants with three or more functionahties participating ia the polymerization, branching and the formation of iatermolecular linkages, ie, cross-linking of the polymer chains, become definite possibiUties. If extensive cross-linking occurs in a polymer system to form network stmctures, the mobiUty of the polymer chains is greatiy restricted. Then the system loses its fluidity and transforms from a moderately viscous Hquid to a gelled material with infinite viscosity. The experimental results of several such reaction systems are collected in Table 6. 

When air is exhaled the small alveoli of the lungs could collapse if it were not for the surface active material (surfactant) present in the fluid that coats the lungs. e In fact, the lack of adequate surfactant is the cause of respiratory distress syndrome, a major cause of death among premature infants and a disease that may develop in acute form in adults. The surfactant material forms a thin film of high fluidity at the air-liquid interface and lowers the surface tension from the 72 mN/m of pure water to <10 mN/mfs (Pay attention to the definition of surface tension.11)... 

By definition, viscosity is the force in dynes required to move a plane of 1 cm2 area at a distance of 1 cm from another plane of 1 cm2 area through a distance of 1 cm in 1 s. In the centimeter-gram-second (cgs) system the unit of viscosity is the poise (P) or centipoise (cP) (1 cP = 0.01 P). Two other terms in common use are kinematic viscosity and fluidity. The kinematic viscosity is the viscosity in centipoise divided by the specific gravity. The unit of kinematic viscosity is the stoke (cm2/s), although centistokes (0.01 cSt) is in more common usage fluidity is simply the reciprocal of viscosity. 

It is, therefore, not surprising that there exists a definite relationship between Aand the enthalpy of vaporization, Av H, the former constituting a fraction between 0.2 and 0.3 of the latter, as is readily obtained from the data in Tables 3.1 and 3.9. The pressure dependence of the viscosity is also closely related to the free volume of the solvent. The fluidity (O = l/r ) is proportional to the ratio between the free and the occupied volume, the former, as mentioned above, being the difference between the actual molar volume and the intrinsic molar volume (Tables 3.1 and 3. 4) (Hildebrand 1978). In fact, the logarithm of the viscosity of liquids was found (Marcus 1998) to be described well for some 300 liquids by the empirical relationship ... 

Rat liver canalicular membrane vesicles (CMV) have been used to examine the mechanisms of uptake of P-gp substrates such as daunomycin, daunorubicin, and vinblastine, whose biliary excretion is extensive (47,137, 408,409). Early work with plasma membrane vesicles, partially purified from MDR human KB carcinoma cells that accumulated [3H]vinblastine in an ATP-dependent manner, definitively showed how P-gp can act to efflux substrates from cancer cells (410). Additionally, these vesicles have been used to study microscopic aspects of P-gp-mediated efflux, such as the relationship of P-gp function to the membrane fluidity (137). 

Finally, alchemical contracts served as moments of definition and decision in an otherwise indeterminate alchemical landscape. Given the fluidity about ideas such as who should practice alchemy, what its goals should be, whether it was best situated as a part of natural philosophy, medicine, metallurgy, or all three, and so on, the contract was a useful... 

Molecular explanation of the tendency to contract. The simplest properties of molecules in liquids suffice to account for this tendency of the surfaces to contract. Molecules are small objects, possessing definite size and shape, in all states of matter in all fluids they are free to move relative to one another, and in liquids they are kept close to each other, by the cohesions forces between them. Liquids are thus distinguished from solids by their fluidity, that is, the freedom of the molecules to move and from gases by the fact that the attraction between the molecules restrains the motions sufficiently to prevent more than a small... 

For the definition of the terms yield value and flow see also Bingham, Fluidity and Plasticity. This abstract of Bartell and Hershberger s paper differs from that given by the authors, but it seems to be justified on a careful analysis of the data recorded. 

Calculation One hemicellulase unit (HCU) is defined as that activity that will produce a relative fluidity change of 1 over a period of 5 min in a locust bean gum substrate under the conditions specified. Calculate the relative fluidities (FR) and Ln values (see definition below) for each of the four efflux times (T-y) and reaction times (7 R) as follows ... 

The most characteristic property of gases and liquids is their fluidity, which contrasts with the rigidity of solids. Liquids possess definite volumes but keep no definite shapes of their own they flow easily under stress (externally applied... 

A report50 suggested that this mechanism could be activated by mustards and might be the mechanism of mustard injury. While several aspects of the thiol-calcium hypothesis (eg, release of arachi-donic acid and decrease in membrane fluidity) have been observed in cell cultures following sulfur mustard exposure,51 no definitive studies have... 

Spectra of semicokes made from Pittsburgh No 8 coal at various temperatures are shown in Figure 7 Increasing the heat-treatment temperature from 300 C causes little change in a given spectrum until 400 C At this temperature, corresponding to the onset of fluidity, the peaks become sharper At 450 C, corresponding to maximum fluidity, the peaks become their sharpest. Beyond the resolidification temperature of 470 C, spectral definition is lost, and by 525 C the spectrum is essentially featureless ... 

For satisfactory casting a slip must have certain definite flow properties. No universal rules can be stated, but it has been found, for example, that sanitary earthenware casting-slips operate best with a fairly high fluidity and a moderate thixotropy. Since... 

A liquid has a definite volume but not a definite shape, with particles that stick firmly but not rigidly. Although the particles are held together by strong attractive forces and are in close contact with one another, they are able to move freely. Particle mobility gives a liquid fluidity and causes it to take the shape of the container in which it is stored. Note how water looks as a liquid in Figure 1.5b. 

Liquid iodine differs from the solid (crystals) mainly in its fluidity. It is like the gas in being able to adjust itself to the shape of its container. However, like the solid, and unlike the gas, it has a definite volume. 1 g occupying about 0.2 cm ... 

A perhaps more significant example of a lyotropic liquid crystal is the cell membrane. The phospholipid bilayers of all cells behave as liquid crystals, maintaining a definite director and displaying only limited fluidity. Interestingly, most membranes are not pure phospholipids, but contain additives whose function is presumably to tune the structural and dynamic properties of the membrane. In animals, the most common additive is cholesterol, while plants use a similar steroid. As such, cell membranes can truly be thought of as cholesteric liquid crystalline phases. 

These two characteristics, rigidity (or fluidity) and compressibility (or expansibility), can be used to frame definitions of the three states of matter ... 

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