Solubility rate ratio, resist

The solubility rate ratio of a resist depends not only on G(s), but also on the initial molecular weight of the polymer and several constants, the relation being the following (25) ... 

High sensitivity resists Table II summarizes the properties of representative positive electron resists. The polymers are classified into four groups according to the chemical structure. Almost all positive electron resists operate by main chain scission of polymer, resulting in a molecular weight decrease in exposed areas. Resist patterns are produced by development in a suitable solvent in which degraded polymer dissolve much faster than unexposed polymer. The sensitivity is determined by the scission probability and the solubility rate ratio for the degraded polymers. 

In a positive resist the image readout efficiency for a particular exposure dose is defined as the ratio of solubility rates ... 

We must first choose the right kind of contactor, then find the size needed. There are two kinds of contactor—towers and tanks, and Fig. 24.1 shows some examples. As may be expected, these contactors have widely different GIL volume ratios, interfacial areas, and ki, and concentration driving forces. The particular properties of the system you are dealing with, the solubility of gaseous reactant, the concentration of reactants, etc.—in effect the location of the main resistance in the rate equation—will suggest that you use one class of contactor and not the other. 

Numerous studies have probed how novolac microstructure influences resist lithographic properties. In one example, a series of resists were formulated from novolacs prepared with varying feed ratios ofpara-l/neta-ctesol. These researchers found that the dissolution rate decreased, and the resist contrast increased, as the para-/tneta-cresol feed ratio increased (33). Condensation can only occur at the ortho position ofpara-o.resol, but can occur at both the ortho- and ra-positions of meta-cresol. It is believed that increased steric factors and chain rigidity that accompany increasedpara-ctescA content modify the polymer solubility. 

The value of KA may depend primarily on kA or on k%, depending on whether m is very large or very small. For example, if acetic acid (C) is being extracted from x -hexane (A) by water (B), the distribution ratio m is very large and from Eq. (9) we see that KA kA. In this case the extraction rate is controlled by the -hexane phase resistance. Conversely, if the solute (e.g., benzoic acid) is much less soluble in the water than in the n-hexane, then Ka = kw/tri and the extraction rate is controlled by water phase resistance. 

LIQUID RESISTANCE TO INTERPHASE MASS TRANSFER. Liquid viscosity, gas solubility in absorbers, and relative volatility in rectification columns are important factors in determining the liquid resistance to interphase mass transfer. Increase in liquid viscosity, decrease in gas solubility for absorbers, and increase in relative volatility for rectification columns cause an increase in the liquid resistance to interphase mass transfer and a resultant reduction in plate efficiency. The ratio of the liquid rate to the gas rate influences the relative importance of the liquid resistance to interphase mass transfer. An increase in the ratio of liquid rate to gas rate reduces the importance of the liquid resistance and can cause an increase in the plate efficiency. 

Haze formation is mostly attributed to proteins, polyphenols, and their interactions. It is also possible that there are also other factors that inbuence haze formation in beer, but their effect has not been yet clearly debned [ 15]. The amount of haze formed depends both on the concentration of proteins and polyphenols, and on their ratio. Polyphenols can combine with proteins to form colloidal suspensions that scatter light, which creates the cloudy appearance of beer. Beer polyphenols originate partly from barley and partly from hops. The beer polyphenols most closely associated with haze formation are the proanthocyanidins, which are dimers and trimers of catechin, epicatechin, and gaUocatechin. These have been shown to interact strongly with haze-active proteins [13,15-17] and their concentration in beer was directly related to the rate of haze formation [18]. Ahrenst-Larsen and Erdal [19] have demonstrated that anthocyanogen-free barley produces beer that is extremely resistant to haze formation, without any stabilizing treatment, provided that hops do not contribute polyphenols either. Not all proteins are equally involved in haze formation. It has been shown that haze-active proteins contain signibcant amounts of proline and that proteins that lack proline form little or no haze in the presence of polyphenols [13,15-17]. In beer, the source of the haze-active protein has been shown to be the barley hordein, an alcohol-soluble protein rich in proUne [16]. 

Researchers at the Eastern Forest Products Laboratory in Canada have evaluated the urea and melamine amino-resin systems (9, 57, 99-110). Their work demonstrates that both systems show good leach resistance and reduced flame spread. The stability of these resins is controlled by the rate of methylolation of the urea, melamine, and dicyandiamide. The optimum mole ratio for stability of these solutions is 1 3 12 4 for urea or melamine, dicyandiamide, formaldehyde, and orthophosphoric acid. However, even at the optimum mole ratios, the pot life of the melamine system is less than that of the urea system. In both systems the nitrogen is fixed to a greater degree than the phosphorus. However, the degree of fixation of the phosphorus is greater with the melamine than with the urea. The melamine structure may promote formation of compounds with phosphoric acid that are less soluble than those from urea and dicyandiamide. 

We next determined if this increase was due to a change in the rate of synthesis or degradation of the ADA protein. Parental and dCF cells were pulse-labeled with 3H-leucine and l C-leucine, respectively. Labeled cell extracts were mixed and the ratio of 3h/ C present in total soluble protein determined. ADA protein was immunoprecipitated from mixed cell extracts with purified IgG. The immunoprecipitates were run on SDS polyacrylamide gels, the gels sliced, and slices containing ADA assayed for radioactivity. Ratios of 3h/14c for total protein synthesis and for ADA protein were compared. Table 3 shows that the relative rate of ADA synthesis clearly paralleled the relative enzyme levels in 3 resistant cell lines with different levels of ADA activity. Degradation rates of ADA, on the other hand, did not differ significantly in the sensitive or resistant cells. 

The imperviousness of a material is characterised by the permeability P = Jd/Ac which is the ratio of the permeation rate to the concentration gradient as driving force generating diffusive mass transport. The reciprocal value d/P is often called diffusion resistance. The permeability of a geomembrane for a chemical or its aqueous solution is thus given by the product of diffusion coefficient and solubility or partition coefficient. 

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