Degassing enhancement

Although Ce(IV) oxidation of carboxylic acids is slow and incomplete under similar reaction conditions , the rate is greatly enhanced on addition of perchloric acid. No kinetics were obtained but product analysis of the oxidations of -butyric, isobutyric, pivalic and acetic acids indicates an identical oxidative decarboxylation to take place. Photochemical decomposition of Ce(IV) carbo-xylates is highly efficient unity) and Cu(ll) diverts the course of reaction in the same way as in the thermal oxidation by Co(IIl). Direct spectroscopic evidence for the intermediate formation of alkyl radicals was obtained by Greatorex and Kemp ° who photoirradiated several Ce(IV) carboxylates in a degassed perchloric acid glass at 77 °K in the cavity of an electron spin resonance spectro-... 

Similar spatial distribution of active bubbles has been observed in partially degassed water and in pure water irradiated with pulsed ultrasound [67]. For both the cases, the number of large inactive bubbles is smaller than that in pure water saturated with air under continuous ultrasound, which is similar to the case of a surfactant solution. As a result, enhancement in sonochemical reaction rate (rate of oxidants production) in partially degassed water and in pure water irradiated with pulsed ultrasound has been experimentally observed [70, 71]. With regard to the enhancement by pulsed ultrasound, a residual acoustic field during the pulse-off time is also important [71]. 

The rate was enhanced using ultrasound when carried out in a semi-sealed cell, which minimised the effects of ultrasonic degassing. An optimum acoustic power was found when using a source at a frequency of 20 kHz. 

On a metal surface, silicide layers can be formed by two methods. In the first, Si atoms are vapor deposited by heating either a well degassed silicon wafer or a silicon rod to near its melting point. In the second method the metal is heated in 10 to 50 mTorr of silane for a desired length of time, usually about 10 to 60 s at a desired temperature, usually about 300 to 700°C. The first method is better suited for studying very early stages of silicide formation, the second more convenient for growing thick layers of silicides. Chemical vapor deposition or laser enhanced chemical vapor deposition may probably be used also, but have not yet been explored. 

Upon degassing in vacuo, the CSC precursor converts gradually towards nitrides. After degassing at 973 K, already 20% of the available N species are nitrides. More than 60% nitrides can be achieved by degassing the precursor at 1113 K. The positive effect of the enormous ammonia uptake enhancement, compared to untreated silica, remains besides NH4C1, only a small fraction of the N-species is lost upon degassing. 

Some mixing chambers have curved bottoms that enhance movement of materials. Others have internal baffles or some similar design to increase turbulence and eliminate dead spots in the chamber. Shafts can enter the chamber from the top (allowing easier cleanup) or from the bottom (allowing easier vacuum degassing). 

In an attempt to determine low levels of As in beers by ET-AAS, Cervera et al. [117] introduced a preconcentration step that enhanced the sensitivity by a factor of 2.5, reaching an LoD of 0.7 ng of As per gram of beer. Samples were degassed and subjected to a preliminary dry ashing using Mg(N03)2 and then evaporated until total dryness. A slurry was prepared by adding 100 jjlL of HNO3... 

UV irradiation of the MgO catalyst in the presence of trans-l-C Hs at 273 K led to a marked enhancement in the formation of ds-l-C Un as well as in the formation of I-C4H8. The activity of the MgO catalyst for such photoinduced reactions depends strongly on the evacuation temperature of the MgO. When MgO was degassed at higher temperatures, the yields of the photoinduced isomerization reactions increased linearly with the UV irradiation time, indicating that the reactions proceeded catalytically under UV irradiation at 273 K 96-98). 

Kubo, H., Takamatsu, H., and Honda, H., 1999, Effeets of Size and Number Density of Miero-Reentrant Cavities on Boiling Heat Transfer from a Silieion Chip Immersed in Degassed and Gas-Dissolved FC-72 , J. Enhanced Heat Transfer, Vol.6, pp.151-160... 

Under supposedly the same conditions (i.e., degassed cyclohexane at room temperature) flash photolysis of Cr(C0)5 was reported by Nasielski et al. (84) to give two successive transients. The first showed maximum visible absorption at 483 nm and decayed in a first-order process with a lifetime of T = 6 ms. The second transient decayed much more slowly with approximately second-order kinetics. Added CO enhanced the rate of decay of the second transient but did not affect that of the first. It was suggested that the transients were the same species supposedly found by Stoltz et al. (85,86) in low temperature photolyses of Cr(CO) C and D3JJ Cr(C0)5. The following mechanism was proposed ... 

Fairchild et al. (2000), who showed that it was enhanced during the dry season at Clamouse cave in southern France. The associated high Mg/Ca and Sr/Ca ratios have been used to develop an aridity index (McMillan et al., 2005). Seasonally increased degassing occurs when drip rates are slow and the aquifer contains more gas spaces. Second, the pC02 of cave air can be seasonally lowered as described in section 7.2.4. 

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