Reduction local

The maximum velocity at the axis is twice the average, whereas the velocity at the wall is zero. The effect of the burner wall is to cool the flame locally and decrease the burning velocity of the mixture. This results in flame stabilization. However, if the heat-transfer processes (conduction, convection, and radiation) involved in cooling the flame are somehow impeded, the rate of heat loss is decreased and the local reduction in burning velocity may no longer take place. This could result in upstream propagation of the flame. 

Local reduction in size or wall thickness or local use of a material having reduced yield strength (for example, girth welds of substantially lower strength than the base metal)... 

A natural mechanism for the local reduction of cell spacings (or creation of a new cell) is either a nucleation in one of the grooves (the liquid is supercooled) or, even more likely, the formation of a new cell out of a side branch in such a groove. Alternatively, tip-splitting of a cell may give the same result [121]. 

Temperature measurement is a case in point. A large transducer in close contact with the body whose temperature is being measured will act as a heat sink and consequently produce a localized reduction at the point where the temperature is being measured. On the other hand, if an air gap exists between the transducer and the hot surface then the air (rather than the surface) temperature will be measured. 

It is the localized reduction in cross section that occurs in a material under tensile or compression stress during thermoforming. 

Turning to the nature of the critical point, the present (J,K) notation was chosen to facilitate local reduction of to the form in Eq. (A.8), by the substitution Ai Thus, after neglect of a term in... 

Surface decarburization does not produce Assures. In this respect, it is similar to decarburization created by the exposure of steel to certain other gases, such as air, oxygen, or carbon dioxide. The usual effects of surface decarburization are a slight, localized reduction in strength and hardness and an increase in ductility. Because these effects are usually small, there is often much less concern with surface decarburization than there is with internal decarburization. 

Distinct peaks at the positive (+) and negative (-) regions of the voltammogram (Fig. 17.4), are observed. The cyclic voltammogram of [Re(CO)3Cl]jtpbq is dominated by metal-localized oxidation and ligand-localized reductions, as observed in analogous complexes. Reduction in the complexes may be attributed to the BL/BL... 

Finnigan, C.S., Brenan, J.M., Mungall, J.E., McDonough, W.F. 2008. Experiments and Models Bearing on the Role of Chromite as a Collector of Platinum Group Minerals by Local Reduction. Journal of Petrology, 49, 1647-1665. 

Si3+ represents the localized reduction of the network Si02..r The value of x was measured from UV absorption to be X 10-5 (98). 

Besides deformation, fracture is the other response of materials to a stress. Fracture is the stress-induced breakup of a material. Two types of fracture are commonly defined. A brittle fracture is breakup which occurs abruptly without localized reduction in area. A ductile fracture is the failure of the material which is preceded by appreciable plastic deformation and localized reduction in area (necked region). The brittle fracture and ductile fracture are schematically illustrated in Fig. 1.10. 

Local This is the method for control work on comparatively large areas. Bleaching is done with a small wad of cotton or a brush. Local reduction can brighten specific areas, put luminosity into shadows, or drastically alter tonal values. 

Place one blotter on the right side of the print and hold a second in your left hand (reverse if you are left-handed). Dip the brush into the reducer and wipe it on the blotter to the right of the print, drawing it across and turning it to a fine point several times. Hold the brush 90 degrees to the print and carefully touch the area to be reduced with the tip. As with local reduction do not use pressure let the chemical action do the work. If you get a bit careless, use the blotter in your left hand to stop the action. 

In adiabatically operated industrial hydrogenation reactors temperature hot spots have been observed under steady-state conditions. They are attributed to the formation of areas with different fluid residence time due to obstructions in the packed bed. It is shown that in addition to these steady-state effects dynamic instabilities may arise which lead to the temporary formation of excess temperatures well above the steady-state limit if a sudden local reduction of the flow rate occurs. An example of such a runaway in an industrial hydrogenation reactor is presented together with model calculations which reveal details of the onset and course of the reaction runaway. 

The problem of the stability of the two modes of steady-state propagation of the temperature wave over the reaction sample needs a separate study. From qualitative considerations it follows that the faster process is less sensitive to disturbances (both mechanical and thermal) than the slower one. It is evident that in the case of slow motion any kind of inhomogeneities in the sample [e.g., a local reduction in the strength, leading to a decrease in (dT/dx) 1 may cause a displacement of the reaction-onset coordinate to the fore part of the front and thereby induce a spontaneous transformation of the slower wave into the faster one. 

Decreased prostacyclin levels Damaged endothelial cells synthesize less prostacyclin, resulting in a localized reduction in... 

Ductile fracture is characterized by considerable plastic deformation prior to and during propagation of the crack. An important amount of gross deformation is usually present at the fracture surfaces. Figure 7.63 is an example of a ductile fracture of a Swellex bolt. Note the failure plane at 45° and localized reduction of the surface. 

From the variation of Gt with temperature in Figure 27.7, it can be seen that Ta tends to increase as G decreases. Since the yield stress varies with temperature, there seems to be a correlation between these fracture resistance parameters and the plastic zone in front of the crack tip. Furthermore, at an impact speed of 2 m/s, because the thermal conductivity of polymers is relatively low, it could be expected that the heat generated in the plastic zone could not dissipate away. The rise in temperature at the crack tip could therefore result in a localized reduction in the yield stress and a blunting effect of the crack tip [24,25]. 

On the other hand, cation VI would also serve as a receptor of the hydride ion from the side chain, whose folding over the carbocycle would place the two reactive sites at very close range. The local reductive step that this hydride transfer implies would be compensated for by the ensuing elimination of water in VII that regenerates the keto group. The formation of the cationic center then secures the construction of III from this key intermediate. 

Substituted complexes of the type [M (N,N)2XY]" M = Ru, Os, X,Y = halides, CN , 204 , py, en, NH3, etc. show, in general, two doublets of N,N-localized reductions [154-156]. The reduction behavior is complicated by loss of an ancillary ligand X upon the second and, more rapidly, the 3rd bpy-localized reduction. The reduction potentials are only slightly X-dependent. On the other hand, the oxidation potential is highly dependent on X. Extensive tables of oxidation and the first reduction potentials of these complexes are available [15, 28, 74, 157]. Their values can be predicted by use of electrochemical ligand parameters [15, 28, 157]. 

Labilization of an ancillary ligand X on reduction indicates the possibility of employing Ru and Os polypyridine complexes as redox catalysts (Section 5.3.5). Indeed, electrocatalysis of CO2 reduction to CO or formate by [Ru(bpy)2(CO)2] +, [Ru(bpy)2(CO)Cl]+, or [Os(bpy)2(CO)H]+ has been reported [158, 159]. The elec-trocatalytically most active Ru-bpy species is, however, a film of a -Ru-Ru-bonded polymer [- Ru(bpy)(CO)2 -]. It is formed on an electrode surface by reduction of various mono- or bis-bpy Ru carbonyl or carbonyl-chloro complexes [160 163], Dissociation of a CO ligand from the polymer upon further bpy-localized reduction is the crucial step which enables CO2 coordination and reduction. 

Spectroelectrochemical (EPR, UV Vis, res. Raman, and to a lesser extent IR) characterization of redox products often reveals features characteristic of reduced polypyridine ligands for ligand-localized reductions or of oxidized metal atoms for metal-centered oxidations. Stretching CO frequencies, obtained by IR spectroelectrochemistry, are an especially useful marker of a metal oxidation state in carbonyl-polypyridine complexes. 

Potentials of polypyridine-localized redox couples depend linearly on the reduction potential of free polypyridines with a slope close to unity, when measured for homologous series of structurally related complexes [26, 67, 74, 101, 151, 205, 206]. This argument should be used with caution because even the potentials of metal-centered oxidation depends on the free polypyridine reduction potential, albeit with a significantly lower slope [29, 67] (Sections 5.3.2 and 5.3.3). Nevertheless, correlations of redox potentials in a series of [M(N,N)3] complexes, N,N = bpy, 4,4 -Me2-bpy, and 5,5 -Me2-bpy, with those of free ligands were often sufficient to identify N,N-localized reductions [101, 111, 117]. 

Experimentally observed redox patterns can be compared with those calculated by quantum-chemical techniques for a particular localization [5, 212], This approach is especially useful for assignment of ligand-localized reductions in heteroleptic complexes. 

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