Fluid state

Mason, E. A., Spurling, T. H., The International Encyclopedia of Phys. Chem. and Chem. Phys., Topic 10, The Fluid State, Vol. 

Experimentally, tire hard-sphere phase transition was observed using non-aqueous polymer lattices [79, 80]. Samples are prepared, brought into the fluid state by tumbling and tlien left to stand. Depending on particle size and concentration, colloidal crystals tlien fonn on a time scale from minutes to days. Experimentally, tliere is always some uncertainty in the actual volume fraction. Often tire concentrations are tlierefore rescaled so freezing occurs at ( )p = 0.49. The widtli of tire coexistence region agrees well witli simulations [Jd, 80]. 

Place 170 ml. of concentrated sulphuric acid in a 1-litre three necked flask provided with a stirrer, and add 112 - 5 g. of o-aminophenol, followed by 287 g. of glycerol maintain the temperature below 80° by cooling, if necessary. Keep the mixture in a fluid state by placing the flask on a steam bath. 

As more and more of the filtrate is removed, the slurry graduaUy thickens and may become thixotropic. The soHds content of the thickened slurry may be higher than that obtained with conventional pressure filtration, by as much as 10 or 20%. A range of velocity gradients from 70 to 500 L/s has been suggested as necessary to prevent cake formation and to keep the thickening slurry ia a fluid state (27). 

A varnish is often appHed on top of the paint layers. A varnish serves two purposes as a protective coating and also for an optical effect that enriches the colors of the painting. A traditional varnish consists of a natural plant resin dissolved or fused in a Hquid for appHcation to the surface (see Resins, natural). There are two types of varnish resins hard ones, the most important of which is copal, and soft ones, notably dammar and mastic. The hard resins are fossil, and to convert these to a fluid state, they are fused in oil at high temperature. The soft resins dissolve in organic solvents, eg, turpentine. The natural resin varnishes discolor over time and also become less soluble, making removal in case of failure more difficult (see Paint and FINNISH removers). Thus the use of more stable synthetic resins, such as certain methacrylates and cycHc ketone resins, has become quite common, especially in conservation practice. 

Polyamides, like other macromolecules, degrade as a result of mechanical stress either in the melt phase, in solution, or in the soHd state (124). Degradation in the fluid state is usually detected via a change in viscosity or molecular weight distribution (125). However, in the soHd state it is possible to observe the free radicals formed as a result of polymer chains breaking under the appHed stress. If the polymer is protected from oxygen, then alkyl radicals can be observed (126). However, if the sample is exposed to air then the radicals react with oxygen in a manner similar to thermo- and photooxidation. These reactions lead to the formation of microcracks, embrittlement, and fracture, which can eventually result in failure of the fiber, film, or plastic article. 

The principal solvents that have been used are alcohols such as ethanol, methanol, and propanol, and organic acids such as formic or acetic acid, but other solvents iaclude esters, ethers, phenols, cresols, and some amines. Even solvents such as CO2 and NH in the supercritical fluid state have been tried as solvents. 

Unvulcanized Latex and Latex Compounds. A prime consideration has to be the fluid-state stabihty of the raw latex concentrate and hquid compound made from it. For many years, the mechanical stabihty of latex has been the fundamental test of this aspect. In testing, the raw latex mbber content is adjusted to 55% and an 80 g sample placed in the test vessel. The sample is then mechanically stirred at ultrahigh speed (ca 14,000 rpm) by a rotating disk, causing shear and particle cohision. The time taken to cause creation of mbber particle agglomerates is measured, and expressed as the mechanical stabihty time (MST). 

The shrinkage on conversion from the fluid state to the elastic soHd state has been reported in the range of 0.03% in 24 h for one composition. GeneraHy the shrinkage in 24 h is 0.15% for most products. The strain in compression, 9.8—98 kPa (1.42—14.21 psi), varies from 7 to 15%. The permanent deformation, after 12% strain is appHed for 30 s, varies from 4 to 6.5%. The better polysulfide compositions, if properly packaged, remain workable and useful for many years. 

K. M. de Reuck and co-workers, eds.. Ethylene (EtheneyintemationalThermodynamic Tables of the Fluid State-10 Blackwell Scientific Pubhshers, Oxford, UK, 1988. 

Converted from Jacobsen, R. T., M. Jahangiri, et al., Ethylene—Inti. Theimodyn. Tables of the Fluid State—10, Blackwell Sci. PuLL, Oxford, U.K., 1988 (299 pp.). Saturation and superbeat tables and a diagram to 100 bar, 460 K are given by Reynolds, W. C., Theimodynamic propeiiies in S.I., Stanford Univ. publ., 1979 (173 pp.). Saturation and superbeat tables and a chart to 6000 psia, 360 F appear in Theimodynamic Propeiiies ofRefiigeiants, ASHRAE, Atlanta, GA, 1986 (521 pp.). For specific beat, thermal conductivity, and viscosity, see Theimophysical Piopeiiies ofRefiigeiants, ASHRAE, 1993. 

Other extensive tables are given by Angus, S., International Theimodynamic Tables of the Fluid State—6, Nitrogen, Perganion, 1977 (244 pp.) Hanley, H. J. M., R. D. McCarty, etal.,y, Fhys. Chem. Ref Data, 3 (1974) 979-1019. 

Ambrose, D., National Physical Lahotatoty Repotts Chem. 92, 98, and 107, Teddington, Middlesex, United Kingdom, 1978, 1979, and 1980. Angus, S., B. Armstrong, and K. M. de Reuck, Carhon Dioxide, International Thermodynamic Tables of the Fluid State, Vol. 3. lUPAC, Pergamon Press, Elmsford, NY, 1976. 

NR adhesives can be divided in two types wet bonding and dry bonding. Wet bonding adhesives are applied on substrates in a fluid state, the bond being formed by drying. The dry bonding NR adhesives are pressure-sensitive adhesives because the bond is created under pressure. 

For a real (irreversible) flow process through the control volume CV between fluid states X and Y (Fig. 2.4), with the same heat rejected at temperature T [Q x = [0rev]x)> the work output is [WcvJx. Heat [Qq x Iso be transferred from CV directly to the environment at Tq. From the steady-flow energy equation,... 

Thermodynamic data are read from a table given in Perry and Green (1984) and interpolated. Subscript f denotes the saturated liquid (fluid) state, and subscript g the saturated vapor (gaseous) state. 

Of course, LC is not often carried out with neat mobile-phase fluids. As we blend solvents we must pay attention to the phase behavior of the mixtures we produce. This adds complexity to the picture, but the same basic concepts still hold we need to define the region in the phase diagram where we have continuous behavior and only one fluid state. For a two-component mixture, the complete phase diagram requires three dimensions, as shown in Figure 7.2. This figure represents a Type I mixture, meaning the two components are miscible as liquids. There are numerous other mixture types (21), many with miscibility gaps between the components, but for our purposes the Type I mixture is Sufficient. 

Well cementing materials vary from basic Portland cement used in civil engineering construction of all types, to highly sophisticated special-purpose resin-based or latex cements. The purpose of all of these cementing materials is to provide the well driller with a fluid state slurry of cement, water and additives that can be pumped to specific locations within the well. Once the slurry has reached its intended location in the well and a setup time has elapsed, the slurry material can become a nearly impermeable, durable solid material capable of bonding to rock and steel casing. 

In semi-cristalline polymers, rate-enhancement under stress has been frequently observed, e.g. in UV-photooxidation of Kapron, natural silk [80], polycaprolactam and polyethylene terephthalate [81]. Quantitative interpretation is, however, difficult in these systems although the overall rate is determined by the level of applied stress, other stress-dependent factors like the rate of oxygen diffusion or change in polymer morphology could occur concurrently and supersede the elementary molecular steps [82, 83], Similar experiments in the fluid state showed unequivocally that flow-induced stresses can accelerate several types of reactions, the best studied being the hydrolysis of DNA [84] and of polyacrylamide [85]. In these examples, hydrolysis involves breaking of the ester O —PO and the amide N —CO bonds. The tensile stress stretches the chain, and therefore, facilitates the... 

Membranes are composed of phospholipids and proteins. The fatty acid composition of the phospholipids in a membrane influences how it is affected by the cold. In general, as the temperature of a cell is lowered the lipids in the membrane bilayer undergo a phase transition from a liquid crystalline (fluid) state to a gel (more solid) state. The temperature at which this transition takes place is very narrow for phospholipids composed of a simple mixture of fatty acids, but is quite broad for the phospholipids in cellular membranes. It is usually implied from various methods... 

Liposomes can be prepared from pure lipids or mixtures of lipids. Cholesterol is known to serve as a "fluidity buffer" it enhances the fluidity of the gel state bilayer, while it decreases the fluidity of the fluid state bilayer. Increasing concentrations of cholesterol in bilayers cause a broadening and gradual disappearance of the phase transition (Demel and De Kruyff, 1976). 

Bilayer rigidity is a parameter which influences biodistribution and biodegradation of liposomes. In vitro a hydrophilic marker molecule (carboxyfluorescein) leaked much faster from the vesicles with bilayers in a fluid state than from bilayers in a gel state (Crommelin and Van Bommel, 1984). An indication of the bilayer rigidity can... 

For liposomes with bilayers in either the gel or fluid state, hydrolysis kinetics could be adequately described by the Arrhenius equation (Fr kjaer et al., 1984 Grit et al., 1989). This finding opens the opportunity to perform accelerated stability tests to predict liposome stability at ambient temperatures or in the refrigerator provided that no fluid-to-gel transition of the bilayer occurs in the temperature range under investigation. 

There is a second relaxation process, called spin-spin (or transverse) relaxation, at a rate controlled by the spin-spin relaxation time T2. It governs the evolution of the xy magnetisation toward its equilibrium value, which is zero. In the fluid state with fast motion and extreme narrowing 7) and T2 are equal in the solid state with slow motion and full line broadening T2 becomes much shorter than 7). The so-called 180° pulse which inverts the spin population present immediately prior to the pulse is important for the accurate determination of T and the true T2 value. The spin-spin relaxation time calculated from the experimental line widths is called T2 the ideal NMR line shape is Lorentzian and its FWHH is controlled by T2. Unlike chemical shifts and spin-spin coupling constants, relaxation times are not directly related to molecular structure, but depend on molecular mobility. 

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