Concentration ratio effects

Figure 6.15 Regulation of the number of glucose transporters in the plasma membrane. The transporter affected is GLUT-4. It is unclear which translocation process is affected by insulin, physical activity or a change in the ATP/ADP concentration ratio. Effects on the translocation from within the cell to the membrane or vice versa are indicated here.

The importance of the nature of the catalyst on the hardening reaction must also be stressed. Strong acids will sufficiently catalyse a resol to cure thin films at room temperature, but as the pH rises there will be a reduction in activity which passes through a minimum at about pH 7. Under alkaline conditions the rate of reaction is related to the type of catalyst and to its concentration. The effect of pH value on the gelling time of a casting resin (phenol-formaldehyde ratio 1 2.25) is shown in Figure 23.15. 

O Connor and Cox and Yates have reviewed the many acidity function scales. A major use of acidity functions is for the measurement of the strengths of very weak bases. The procedure utilizes spectrophotometric measurements of the concentration ratio Cb/cbh+ in solutions of known acidity function and application of Eq. (8-89). One problem is the estimation of the spectra of the pure forms (protonated and unprotonated) of the base, for the spectra are subject to the medium effect, and corrections must be applied. Another problem is that the base... 

Figure 4. Weighted concentration of effective strands versus humidity at constant cure time for different initial ratios of isocyanate to hydroxy. The cure time is chosen so that at equal isocyanate and hydroxy and H=0, the extent of reaction is 85%.

Figure 5. Weighted concentration of effective strands versus bake temperature for a typical high solids polyol crosslinked with hexamethoxymethylmelamine. The ratio of methoxy to hydroxy groups is given by "R". For the dashed lines, the extent of methoxy self-condensation is assumed to be zero. The solid lines use the self-condensation data of T. Nakamichi, Prog. Org. Coat., 14, 23 (1986).

In a further study, Brubaker et have reported on the effects of the addition of chloride ion to the sulphate exchange system at virtually constant ionic strength (3.68 M sulphate and hydrogen-ion concentrations. For the concentration ratio [C1 ]/[T1(III)] of 9.2x10" to 9.5 at 24.9 °C results analogous to the effect observed in perchlorate media were obtained. The minimum in the rate corresponded to a ratio of 2.5. Results were also presented for the conditions, constant [CI ] and variable [804 ] and [If"] ( = 3.68 M). Brubaker et al have suggested that the exchange paths most likely to occur in sulphate media are... 

At low peroxide/Fe(II) ratios only (92) and (93) occur. As the ratio increases, OH- increasingly attacks H2O2 to give the observed kinetic deviation and evolution of O2. At high ratios the competition between Fe(II) and Fe(ril) for H02-dominates and the evolution of O2 becomes independent of peroxide concentration. The effect of Cu(ri) is ascribed to reactions... 

As 1,2,5-thiadiazole analogues, potent HlV-1 reverse transcriptase inhibitors, some simple 1,2,5-oxadiazoles, compounds 4-6 (Fig. 9), have been synthesized using the traditional Wieland procedure as key for the heterocycle formation [121]. Such as thiadiazole parent compounds, derivative with chlorine atoms on the phenyl ring, i.e., 5, showed the best anti-viral activity. Selectivity index (ratio of cytotoxic concentration to effective concentration) ranked in the order of 5 > 6 > 4. The activity of Fz derivative 6 proved the N-oxide lack of relevance in the studied bioactivity. These products have been claimed in an invention patent [122]. On the other hand, compound 7 (Fig. 9) was evaluated for its nitric oxide (NO)-releasing property (see below) as modulator of the catalytic activity of HlV-1 reverse transcriptase. It was found that NO inhibited dose-dependently the enzyme activity, which is hkely due to oxidation of Cys residues [123]. 

The reason for this confusing situation is that all efficacy data are depending from the test method used to find the effective time - concentration ratio of the disinfectant. 

Audus and Quastel (4) have found that the presence of p-aminobenzoic acid exerts an antagonism, though a relatively feeble one, to the root growth inhibitory actions of 2,4-dichlorophenoxyacetic acid, 2-chloro-4-methylphenoxyacetic acid, 2-naphthoxyacetic acid, and 2-indoleacetic acid. For any marked degree of antagonism the concentration ratio of p-aminobenzoic acid to the growth substance must be of the order of 10,000. This relatively feeble action is ii marked contrast to the effect of p-aminobenzoic acid on the... 

FIGURE 1.16 The predicted effect of three concentrations of a reversible competitive antagonist, B, on the log concentration-response relationship for an agonist. The calculation of the concentration ratio (r3) for the highest concentration of antagonist, [B]3, is illustrated. 

Effective diffusivities for these ions in equimolar concentration ratio and with various inert electrolytes, have been determined by several methods (see Table III). The mobility products obtained from capillary cell (stagnant diffusion) and rotating-disk measurements are in fairly good agreement. 

Effect of forage to concentrate ratios on enteric pathogen prevalence and shedding... 

Steinfeld et al. [133] demonstrated the technical feasibility of solar decomposition of methane using a reactor with a fluidized bed of catalyst particulates. Experimentation was conducted at the Paul Scherrer Institute (PSI, Switzerland) solar furnace delivering up to 15 kW with a peak concentration ratio of 3500 sun. A quartz reactor (diameter 2 cm) with a fluidized bed of Ni (90%)/Al2O3 catalyst and alumina grains was positioned in the focus of the solar furnace. The direct irradiation of the catalyst provided effective heat transfer to the reaction zone. The temperature was maintained below 577°C to prevent rapid deactivation of the catalyst. The outlet gas composition corresponded to 40% conversion of methane to H2 in a single pass. Concentrated solar radiation was used as a source of high-temperature process heat for the production of hydrogen and filamentous... 

Keeping the concentration ratio of H20 and CO in the simulation model constant (according to the Thiele modulus see Equation 12.21) leads to equal concentration profiles of H2, as shown in Figure 12.4, and consequently to equal effectiveness factors for both methods (Thiele modulus and simulation). In fact, the concentrations of H2, CO, and H20 change inside the pore, as considered in the simulation. Therefore, the results obtained by the software used represent reality best. 

Lente and Fabian have recently reported on the Fe(III)/S(IV) reaction with excess Fe(III), i.e. with the inverse of the typical concentration ratio (11). This procedure effectively limits the speciation to complexes having at most one S(IV) ligand. This simplification, however, comes at the cost of introducing dinuclear Fe(III) species into the reaction... 

Experimental studies of PCBs and DDT transformation in marine waters showed that PCBs inhibited decomposition of DDT at the concentration ratio of DDT to PCBs of 1 100-1 200 that may lead to prolongation of circulation time and toxic effect of this compound at water ecosystem (Tuteliyan and Lashneva, 1988). It is also known that in the past, PCBs were often added to HCH to increase the longevity of the insecticide (Mel nikov, 1974). 

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