Gas-phase fractionation

Breci, L., Hattrup, E., Keeler, M., Letarte, J., Johnson, R., Haynes, PA. (2005). Comprehensive proteomics in yeast using chromatographic fractionation, gas phase fractionation, protein gel electrophoresis, and isoelectric focusing. Proteomics 5, 2018-2028. 

L. Breci, E. Hattrup, M. Keeler, J. Letarte, R. Johnson, and P. A. Haynes. Comprehensive Proteomics in Yeast Using Chromatographic Fractionation, Gas Phase Fractionation, Protein Gel Electrophoresis, and Isoelectric Focusing. Proteomics, 5(2005) 2018-2028. 

Equilibration between water and an oil phase causes maximum fractionation in the oil phase as the salinity of the water phase approaches saturation and with increasing oil density when Voii Vwater approaches zero (Fig. 7c). Similarly, maximum fractionation in the water fractionation in the water phase as Voi/Vwater approaches infinity, and as the salinity of the water phase approaches saturation. Elnlike liquid/gas phase fractionation, which increases with decreasing temperature, water/oil fractionation reaches a maximum at moderately low temperatures. This occurs, for example, in a pure water/ light oil (API = 34) system at 310 K, with a maximum Ne/Ar fractionation of 0.51 and 1.96 in the oil and water phases respectively. This can be compared with a pure water/ heavy oil (API = 25) system where at 286 K a maximum Ne/Ar fractionation of 0.27 and 3.69 is obtained in the oil and water phases respectively. 

Figure 13 displays the self-diffusivities of n-hexane and 2-methylpentane in silicalite-1 and H-ZSM-5 as a function of the ratio of the hydrocarbons. The self-diffusivities of both hexanes linearly decrease with increasing gas-phase fraction of the branched hexane in the gas phase for the non-acidic and acidic zeolite. In H-ZSM-5, the mobility of alkanes is approximately two times slower than in silicalite-1. Obviously, the presence of acid sites strongly affects the molecular transport due to stronger interactions with the n-hexane molecules. A similar effect of Bronsted sites on the single component diffusion of aromatics was observed in MFI zeolites with different concentration of acid sites [63-65]. The frequency response (FR) technique provided similar results... 

Around a value of the gas-phase fraction of 2-methylpentane of about 0.83, the influence of the acid sites on the n-hexane diffusivity is not dominant anymore in comparison to the pore occupation of slow-diffusing 2-methyl-pentane. Figure 14 shows the dependence of the diffusivities of both components versus the concentration of adsorbed 2-methylpentane in terms of molecules per unit cell. The diffusivities of n-hexane in silicalite-1 and H-ZSM-5 become nearly equal when the concentration of 2-methylpentane reaches approximately 2.75 molecules per unit cell. For 2-methylpentane we And that the self-diffusivity in silicalite-1 becomes very close to the value in H-ZSM-5 at the same loading. 

Each sample comprises particulate and gas-phase fractions... 

Fig. 1.1 Gas Phase fraction as a function of the log of the subcooled liquid vapor pressure (Pa) of SVOCs.

Foams are dispersions of bubbles where neighboring bubbles touch each other and form a jammed solid-like closed packing [62]. They are characterized by polyhedral bubbles and a high gas-phase fraction. When the gas fraction is relatively low, the bubbles retain their spherical shape (unless they are severely confined) and bubble suspensions are obtained. Monodisperse foams are advantageous, since coalescence, driven by the difference of Laplace pressure between neighboring bubbles, is reduced. Due to the high interfacial tension between gases and liquids, surfactants are usually introduced in the liquid phase to facilitate bubble formation and reduce coalescence. 

Under all conditions, the PSA PFR and the PSR, have a reduced productivity as compared to the PFR (not shown). This is due to semi-batch operation of the former configurations and much lower gas phase fractions of A and Si B present. Therefore, the PSR is only relevant in cases were reaction selectivity is vital. 

Figure 1 shows the gas phase fractional abundance of certain species included in the model as a function of time. It can be seen from the diagram that there is a very steep fall in the abundances as accretion dominates. The effect is exaggerated over that determined for quiescent clouds because, in a free-fall collapse, the density rises rapidly in the latter stages, and the accretion timescale, proportional to 1/n, becomes very short. Magnetic fields and turbulence caused by rotation may slow the collapse. We have modelled cases in which the collapse is slowed by factors of 10 and 100 and found no qualitative difference from the results presented here. As already mentioned, the inclusion of accretion means that... 

This type of mechanism is a general one and may well occur in regions with high abundances of atomic deuterium such as the centres of pre-stellar cores, discussed in Sec. 1.5. Secondly and more specifically, atomic deuterium can react with methanol to form CH2DOH although the exact mechanism by which this happens is not known definitively. Surface deuteration followed by desorption may well be an important source of gas-phase fractionation, as discussed in Sec. 1.5 following a detailed discussion of gas-phase fractionation. 

If the membrane itself is partially in contact with liquid and vapor, as can commonly be the case in an operating fuel cell, the water content and uptake in the membrane can vary with location, although in equilibrium the water content in the membrane will become homogeneous with uptake depending on the overall water avadabihty. Transport in this case can be modeled as occurring in parallel between gas and liquid equilibrated modes, with a suitable fraction denoting the liquid and gas phase fractions of contact with the membrane. 

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