Oxygen pick

Again, the positive nitrogen loses a proton and the negative oxygen picks up a proton. In the final step, base-promoted elimination of water occurs. The driving force for loss of water is formation of an aromatic ring. 

The oxygen pick-up during manufacturing was studied by Christodoulou et al. (1987) and Ormerod (1985). The latter author found that the rate of oxygen pick-up in Nd-Fe-B is much higher than in Sm(Co, Cu, Fe, Zr)z. Probable reasons for this are the presence of the Nd-rich eutectic phase in the former alloy and the higher... 

Oxygen picked up during leaching of sponge increases its hardness... 

This is a good mechanism but it doesn t quite produce the product. There must be a second step in which the anionic oxygen picks up a proton from somewhere. The only source of protons is the solvent, water, so we can write the full mechanism in one sequence ... 

Oxygen and nitrogen from air as well as water vapor are diffusing to the electrochemical interface, the cathode catalyst layer, where in a multi-step process oxygen picks up four electrons from the electrode and four protons from the electrolyte to form water. 

Because ICG is a very simple and low-cost technique, very valuable applications may appear. It must be remembered that a gold standard method for SV and CO does not exist the intramethod variability may be larger than the intermethod variability. Reference methods have been thermodilution, dye dilution, oxygen Pick technique, radionuclear radiography, and transesophageal Doppler echocardiography. 

The purpose of filling can be described as the filling of the product with as low as possible losses and at the desired level within acceptable tolerances. In addition, the preservation of the products quality has to be secured. Preservation of the product quality includes avoiding oxygen pick-up, loss of carbon dioxide and any contamination. 

The rare metal chloride is first obtained in a high state of purity, i.e. free from the chlorides of contaminating metals and also from oxychlorides or oxides. Various preliminary methods of purification have been employed, but the final purifications is generally by distillation or sublimation. After this stage, it is most important to prevent access to the pure chloride of air or moisture, which would cause hydrolysis. The oxygen picked up in... 

The effect of milling time in the vibration ball in the presence of freon, on the oxygen pick-up, is given in fig. 20a and in fig. 20b, the correlation between the milling time and particle dimensions is shown (Ormerod 1984, 1985). The oxygen... 

Fig. 20. Effect of milling time during vibration ball-milling in freon on the oxygen pick-up (a) and on the particle size of Nd-Fe-B and Sm(Co, Fe, Cn, Zr), alloys (b).

In the first reaction of the citric acid cycle, acetyl-CoA reacts with oxaloacetate to form citrate. The mechanism for the reaction shows that an aspartate side chain of the enzyme removes a proton from the a-carbon of acetyl-CoA, creating an enolate ion. This enolate ion adds to the keto carbonyl carbon of oxaloacetate and the carbonyl oxygen picks up a proton from a histidine side chain. This is similar to an aldol addition where the a-carbanion (enolate ion) of one molecule is the nucleophile and the carbonyl carbon of another is the electrophile (Section 18.10). The intermediate (a thioester) that results is hydrolyzed to citrate in a nucleophilic addition-elimination reaction (Section 16.9). 

Dissolved oxygen is significantly more corrosive than carbon dioxide. Dissolved oxygen in pure water at 65°C is found to be six times more corrosive than a molar equivalent concentration of carbon dioxide. The combined corrosion caused by O2 and CO2 is twice that caused individually by oxygen and CO2. Oxygen is known to produce rust and pitting in steel equipment. Oxygen picks... 

On the basis of chemical composition, the maximum oxygen tolerance for tantalum weldments appears to be about 400 to 550 ppm for Tantaloy 63 weldments, it is about 350 to 500 ppm. Although commercially pure tantalum exhibits a somewhat higher tolerance for oxygen (and total interstitial contamination) than Tantaloy 63, the latter material appears to have somewhat better resistance to oxidation this tends to offset the advantage tantalum has of a higher allowable oxygen pick-up before embrittlement occurs. 

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