Effect of NO concentration

FIGURE 8.9 Effect of NO concentrations leaving the reaction zones of an ethylene-air flame ( = 1.68, T = 2030K) with various pydrine additions. Curve A, no pyridine addition curves B and C, 0.1-0.5 N by weight of fuel and curve D, NO addition to the fuel-air mixture (from Haynes etal. [14]). 

Fig. 4-2. Effect of NO concentration, N02 partial pressure, and temperature on reaction rate of NO oxidation, with oxygen partial pressure between 6 and 8 torr. Tie lines indicate slight effect of N02 on initial rate. Dashed curves have slope two and are shown for reference purposes. Both axes are on a logarithmic scale. Lower curves on plots for 2 and 4 torr N02 represent initial (time zero) data. Tie lines connect points where all other variables except [NOa] are constant (from Treacy and Daniels429 with permission of the American Chemical Society).

Presto, A. A., Huff Hartz, K. E., and Donahue, N. M. (2005b) Secondary organic aerosol production from terpene ozonolysis 2. Effect of NO concentration, Environ. Sci. Technol. 39, 7046-7054. 

Even a trace amount of NO in the air can cause significant cell performance loss. Knight et al. [22] reported that 115 ppb of NO in the air stream caused a cell performance loss of about 25 mV at 0.175 A cm. Many research groups have studied the effect of NO concentration on cell performance [10,11,21-23], and the general finding is that cell performance degradation is... 

The effect of solvent concentration on the activity coefficients of the key components is shown in Fig. 13-72 for the system methanol-acetone with either water or methylisopropylketone (MIPK) as solvent. For an initial-feed mixture of 50 mol % methanol and 50 mol % acetone (no solvent present), the ratio of activity coefficients of methanol and acetone is close to unity. With water as the solvent, the activity coefficient of the similar key (methanol) rises slightly as the solvent concentration increases, while the coefficient of acetone approaches the relatively large infinite-dilution value. With methylisopropylketone as the solvent, acetone is the similar key and its activity coefficient drops toward unity as the solvent concentration increases, while the activity coefficient of the methanol increases. 

Surprinslngly, we observe an drastic effect of the concentration on the SRO contribution (figure 2) indeed, in PtaV, the maxima are no longer located at a special point of the fee lattice but the (100) intensity is splltted perpendicularly in the (010) direction and presents a saddle point at (100) position. Notice that these two maxima are not located just above Bragg peaks of the ordered state the A B ground state presents Bragg peaks at ( 00) and equivalent positions whereas the SRO maxima peak between ( 00) and (100). 

Figure 12. Effect of KOH concentration and dissolved oxygen on the discharge behavior of IC No. 17 (EMD) in 3-9 mol L KOH.

The first term in R (0) accounts for inhibition effects due to chemisorption of CO and C3H6. The second term is required to fit the experimental data at higher concentrations of CO and C3H6. The third term accounts for the inhibition effects of NO. Each rate parameter is of the form... 

For a better understanding of the effect of changing concentrations on the rate of a chemical reaction, it helps to visualize the reaction at the molecular level. In this one-step bimolecular reaction, a collision between molecules that are in the proper orientation leads to the transfer of an oxygen atom from O3 to NO. As with the formation of N2 O4, the rate of this bimolecular reaction is proportional to the number of collisions between O3 and NO. The more such collisions there are, the faster the reaction occurs. 

Adsorbed CO and NO were used as probes to Investigate the effects of Co concentration and sulfide on the nature and numbers of exposed metal sites on reduced catalysts containing 1 to 6 wt% Co and 8 wt%. Mo on three alumina supports. Exposure of Mo Ions decreased with Increased Co concentration. Exposure of Co Ions typically reached a maximum at 2-4% Co. Sulfide decreased exposure of all metal Ion sites and Increased exposure of reduced metals. Effects of preadsorbed pyridine and 2,6-lutldlne, known poisons, on the exposure of metal sites, plus other evidence. 

Extensive studies on the effect of substrate concentration and on the bioavailability of the substrate to the appropriate microorganisms have employed samples of natural lake water supplemented with suitable nutrients. There are few additional details that need to be added since the experimental methods are straightforward and present no particular difficulties. Considerable use has also been made of a comparable methodology to determine the fate of agrochemicals in the terrestrial environment. 

Figure 2 shows the effect of NOx concentration on the conversion of NOx reduced by CH4 in the presence of 5% H2O. In the NO-CH4-O2 system, In/H-ZSM-5 showed low catalytic activity in the whole range of NO concentration. On the other hand, this catalyst was active for the NO2-CH4-O2 reaction, while the conversion of NO2 decreased with decreasing concentration of NO2. The catalytic activity of ln/H-ZSM-5 for the reduction of 1000 ppm NO was enhanced by the addition of Ir and R almost to the level of NO2 reduction on ln/H-ZSM-5, indicating that these precious metals worked as the catalytic sites for NO oxidation, which is a necessary step for NO reduction with CH4. With decreasing NO concentration to 100 ppm, however, the increase in NO conversion was observed on lr/ln/H-ZSM-5 and the conversion of NO exceeded that of NO2 on ln/H-ZSM-5. This can not simply be explained by the catalytic activity of Ir for NO oxidation. 

Table V shows the concentrations of polymer (usually in THF/polymer/monomer mixtures), the GPC that they were directly injected into, and the Column Code involved (Ref. Table 1). No effect of different concentration was observed in the chromatograms from GPC 2 when concentrations of samples A to E inclusive were changed by 33%. GPC 1 chromatograms were too disturbed by sampling to be useful except as a rough guide to sampling position.

Together with the fast oxidation (at low temperatures) of NO to N02, the plasma causes the partial HC oxidation (using propylene, the formation of CO, C02, acetaldehyde and formaldehyde was observed). Both the effects cause a large promotion in activity of the downstream catalyst [86]. For example, a "/-alumina catalyst which is essentially inactive in the SCR of NO with propene at temperatures 200°C allows the conversion of NO of about 80% (in the presence of NTP). Formation of aldehydes follows the trend of NO concentration suggesting their role in the reaction mechanism. Metal oxides such as alumina, zirconia or metal-containing zeolites (Ba/Y, for example) have been used [84-87], but a systematic screening of the catalysts to be used together with NTP was not carried out. Therefore, considerable improvements may still be expected. 

Chi, Y. and Chuang, S.S.C. (2000) The effect of oxygen concentration on the reduction of NO with propylene over Gii0/y-AI203, Catal. Today, 62, 303. 

The Effect of Catalyst Concentration The first parameter that was studied was the effect of the catalyst concentration. Samples impregnated with 1, 5, 10 and 15% tin as stannous chloride and a sample with no catalyst were hydrogenated at 450°C to investigate the effect that increasing catalyst concentration has on the composition of the oil (hexane soluble portion) formed. 

Thus the competition between stimulatory and inhibitory effects of NO depends on the competition between two mechanisms the direct interaction of NO with free radicals formed in lipid peroxidation and the conversion of NO into peroxynitrite or other reactive NO metabolites. Based on this suggestion, Freeman and his coworkers [42-44] concluded that the prooxidant and antioxidant properties of nitric oxide depend on the relative concentrations of NO and oxygen. It was supposed that the prooxidant effect of nitric oxide originated from its reaction with dioxygen and superoxide ... 

As mentioned earlier, ascorbate and ubihydroquinone regenerate a-tocopherol contained in a LDL particle and by this may enhance its antioxidant activity. Stocker and his coworkers [123] suggest that this role of ubihydroquinone is especially important. However, it is questionable because ubihydroquinone content in LDL is very small and only 50% to 60% of LDL particles contain a molecule of ubihydroquinone. Moreover, there is another apparently much more effective co-antioxidant of a-tocopherol in LDL particles, namely, nitric oxide [125], It has been already mentioned that nitric oxide exhibits both antioxidant and prooxidant effects depending on the 02 /NO ratio [42]. It is important that NO concentrates up to 25-fold in lipid membranes and LDL compartments due to the high lipid partition coefficient, charge neutrality, and small molecular radius [126,127]. Because of this, the value of 02 /N0 ratio should be very small, and the antioxidant effect of NO must exceed the prooxidant effect of peroxynitrite. As the rate constants for the recombination reaction of NO with peroxyl radicals are close to diffusion limit (about 109 1 mol 1 s 1 [125]), NO will inhibit both Reactions (7) and (8) and by that spare a-tocopherol in LDL oxidation. 

At higher NO concentrations, MPO activity is inhibited through formation of an inactive ferric nitrosyl complex MPO(NO) the rate constant kori is 1.07xlO6 M-1s-1 and the dissociation rate constant, kQff, is 10.8 s-1 (pH 7.0 phosphate buffer at 10 °C) (Scheme 9, pathway A). However, the inhibitory effects of NO are reduced in the presence of plasma levels of Cl- (100 mM) where on and kQ rate constants were determined to be 1.5 x 105 M-1s-1 and 22.8 s-1, respectively. The modulating effects of NO on MPO activity parallel that of O2 which accelerates activity by serving as a substrate for compound II and inhibits activity by acting as a ligand for MPO (Scheme 9, pathway B) (29). 

Cameron, G.R. and Foss, G.L. 1941. Effect of low concentrations of phosgene for 5 hours on 5 consecutive days in groups of different animals. Washington, DC British Embassy Defense Staff Porton report no. 2316, serial no. 63. (Cited in EPA 1986)... 

Table 9.11 shows the effect of this concentration on the responses of the other pesticides. In every instance the peak height was increased while the peak area remained constant. All of the columns used for this study were aged by repeated sample injections, but had not deteriorated to the point where they would normally be replaced. No values are included in Table 9.11 where the chromatographic system was not suitable for the pesticide concerned. 

Particulate matter concentration, organic content and granulometry For the different types of surfactant, the effect of solids concentration on sorption is unclear. While some studies have shown that the concentration of solids has no effect on the extent of sorption [19,36], in others, it has been detected that the partition coefficient decreases with particle concentration [17,27,37,38]. 

Fig. 13. Effect of substrate concentration on inhibition of horse-serum cholinesterase.1 Enzyme activity was estimated by titration with 0-01 n NaOH at pH 7-4 and 20°. — , control, no inhibitor x — x, 2x 10 7 m eserine 0—O, 5 x 10 8 m di-isopropyl phosphorofluoridate.

Figure 5. Inhibitory effect of NO on Fe -induced lipid peroxidation. Shown is the decreased generation of an oxidative marker (thiobarbituric acid reactive substances, TBARS) as a result of 0.9 iM NO. HL-60 cells (5 x loVral) were placed in an O2 monitor and at the designated time points, butylated hydroxytoluene was added and samples were quick frozen for determination of TBARS. The values represent the mean and standard error of 3-5 independent determinations. Also shown for comparison is the residual concentration of O2 after exposure to the the same conditions. This shows a decrease in utilization of O2 in the presence of NO. We conclude that NO reduces TBARS, and the percent inhibition is similar to the poeent inhibition of O2 consumption. (Modified from our data in Kelley, E.E., Wagner, B.A., Buettner, G.R., and Bums, C.P., 1999, Arch. Biochem. Biophys. 370 97-104).

To confirm that the effects of NO on O2 consumption are due to inhibition of hpid peroxidation, we also examined the effect of NO on TBARS, a product of lipid peroxidation. Cells were oxidized by Fe ", and 0.9 (jM N0 was added 1 min later. Cells were collected after 5 min for assay. Figure 5 shows that Fe " increased lipid peroxidation, and NO inhibited it by 63% (after subtracting basal levels). It is noteworthy that the percentage inhibition of O2 uptake by NO as measured by the change in O2 concentration under similar conditions was similar (78%) lending verification to these complementary methods. These results confirm the relationship of O2 consumption and lipid peroxidation in these experiments... 

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