Activity enhancement

Activators enhance the adsorption of collectors, eg, Ca " in the fatty acid flotation of siUcates at high pH or Cu " in the flotation of sphalerite, ZnS, by sulfohydryl collectors. Depressants, on the other hand, have the opposite effect they hinder the flotation of certain minerals, thus improving selectivity. For example, high pH as well as high sulfide ion concentrations can hinder the flotation of sulfide minerals such as galena (PbS) in the presence of xanthates (ROCSS ). Hence, for a given fixed collector concentration there is a fixed critical pH that defines the transition between flotation and no flotation. This is the basis of the Barsky relationship which can be expressed as [X ]j[OH ] = constant, where [A ] is the xanthate ion concentration in the pulp and [Oi/ ] is the hydroxyl ion concentration indicated by the pH. Similar relationships can be written for sulfide ion, cyanide, or thiocyanate, which act as typical depressants in sulfide flotation systems. 

Shock Modification and Shock Activation Enhanced Solid State Reactivity... 

Knapp PE, Hauser KF (1996) p-Opioid receptor activation enhances DNA synthesis in immature oligodendrocytes. Brain Res 743 341-345... 

Jyonouchi, H., Sun, S., and Gross, M., Effect of carotenoids on in vitro immunoglobulin production by human peripheral blood mononuclear cells astaxanthin, a carotenoid without vitamin A activity, enhances in vitro immunoglobulin production in response to a T-dependent stimulant and antigen, Nutr. Cancer, 23, 171, 1994. 

With respect to CO oxidation an activity order similar to that described above for CH4 combustion has been obtained. A specific activity enhancement is observed for Lai Co 1-973 that has provided a 10% conversion of CO already at 393 K, 60 K below the temperature required by LalMnl-973. This behavior is in line with literature reports on CO oxidation over lanthanum metallates with perovskite structures [17] indicating LaCoOs as the most active system. As in the case of CH4 combustion, calcination at 1373 K of LalMnl has resulted in a significant decrease of the catalytic activity. Indeed the activity of LalMnl-1373 is similar to those of Mn-substituted hexaaluminates calcined at 1573 K. Dififerently from the results of CH4 combustion tests no stability problems have been evidenced under reaction conditions for LalMnl-1373 possibly due to the low temperature range of CO oxidation experiments. Similar apparent activation energies have been calculated for all the investigated systems, ranging from 13 to 15 Kcal/mole, i.e almost 10 Kcal/mole lower than those calculated for CH4 oxidation. 

Our rationalization of the significant effect of R2 with regard to the activity enhancement is as follows ... 

The activity enhancement is probably ascribed to the increased electrophilicity of the active Ti species, demonstrating that the electrophilicity of the Ti center plays a dominant... 

Neuro steroids, which may be physiological modulators of brain activity, enhance GABAa receptor function 297 The three-dimensional structures of ligand-gated ion channel receptors are being modeled successfully 297 Mouse genetics reveal important functions for GABAa receptor subtypes 297... 

Neurosteroids, which may be physiological modulators of brain activity, enhance GABAa receptor function. 

Such activity enhancement can be ascribed to planarity of the naphthalene nucleus and its disposition for n-n stacking between the DNA base pairs. There is no literature precedence for involvement of naphthalene in such processes unless it is % electron deficient.211,212 However, our results suggest that both alkylated and acylated naphthalenes are intercalators with bacterial DNA. 

Figure 5.5 Example of drastic activity enhancements. Aerobic oxidation of benzyl alcohol to benzaldehyde in scC02 over TPAP entrapped in aged ( , ) and fresh ( ) 75% methyl-modified silica matrix. (Reproduced from Adv. Fund. Mater., with permission.)...

Where LNAPL is present, its recovery is an essential and typically immediate part of the cleanup effort. Removal of the floating LNAPL layer is almost always required prior to the initiation of other restoration- and remediation-related activities (enhanced bioactivity, vapor extraction, etc.) and response to other environmental issues (i.e., hydrocarbon-affected soils, vapors, or dissolved hydrocarbon in groundwater). 

Darbar, D., Fromm, M.F., Dellorto, S. and Roden, D.M. (2001) Sympathetic activation enhances QT prolongation by quinidine. Journal of Cardiovascular Electrophysiology, 12, 9-14. 

A3. Axelrod, J. H., Reich, R., and Miskin, R., Expression of human recombinant plasminogen activator enhances invasion and experimental metastasis of H-ras-transformed NIH 3T3 cells. Mol. Cell. Biol. 9, 2133-2141 (1989). 

Figure 4-11 shows the infiiared spectra for Pt- Ru electrode after Ru was stripped at 1100 mV for 30s. Unlike for pure platinum (See Fig. 3—30), no clear COad was found at any potential except a very blunt peaks around 2070 cm at 400 to 450 mV. CO2 starts to appear at 375 mV. which is not very different from the 400 mV for pure platinum. This suggests that the direct oxidation of methanol to CO2 is not enhanced much. The activity enhancement effect of ruthenium is, therefore, considered mainly as the result of a high COad removal rate. 

In recent years, there has been a strong effort to use model catalyst surfaces combined with atomistic modeling approaches to understand why Ft alloys show activity enhancements and to predict new surfaces fhaf show even greater activity for oxygen reduction. 

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