Experiments adventitious

Suppose viscosity, y, is the quality response of interest. Then at one of the four factor combinations in the inner array (i.e., in the control factor space), experiments can be carried out at the four factor combinations in the outer array (i.e., in the noise factor space). Frequently the outer array experiments are adventitious experiments in the sense that the experimenter has to wait until, say, the ambient humidity approaches the desired value then the appropriate source of raw material and the appropriate process operator can be brought in and the experiment can be carried out. 

Adventitious losses of the reagent, due, e.g., to the chemical action of the alkaline glass vessels, slight absorption by the corks, etc., are almost identical for the actual and the control experiments and therefore do nor affect the difference in result between the two experiments. 

The nitric acid used in this work contained 10% of water, which introduced a considerable proportion of acetic acid into the medium. Further dilution of the solvent wnth acetic acid up to a concentration of 50 moles % had no effect on the rate, but the addition of yet more acetic acid decreased the rate, and in the absence of acetic anhydride there was no observed reaction. It was supposed from these results that the adventitious acetic acid would have no effect. The rate coefficients of the nitration diminished rapidly with time in one experiment the value of k was reduced by a factor of 2 in i h. Corrected values were obtained by extrapolation to zero time. The author ascribed the decrease to the conversion of acetyl nitrate into tetranitromethane, but this conversion cannot be the explanation because independent studies agree in concluding that it is too slow ( 5.3.1). 

Different kinds of experimental procedures have been used and these should be evaluated against the background in which several organisms or several substrates are simultaneously present. There are no essential differences in the design of experiments using pure cultures and those employing metaboli-cally stable consortia. It should be emphasized, however, that even in the latter, the experiments should be carried out under aseptic conditions otherwise, interpretation of the results may be compromised by adventitious organisms. 

M 1s 1 versus 0.037 M 1s 1 at 30C), but the measured rate constant varies somewhat from experiment to experiment. Considering the slowness of this proton transfer, the rate constant variation may reflect varying degrees of adventitious catalysis. 

The operation of this alternative mechanism may explain why the rate of this reaction appeared to vary from experiment to experiment, although a more likely explanation is adventitious catalysis. 

Widening interest in the quaHty of the environment has led to increased demand for information on a wide range of trace-metal contents of foodstuffs. Trace metals in foodstuffs are normally determined by spectroscopic techniques after complete destruction of the organic matrix. Destruction is achieved either by wet oxidation or by dry ashing additional treatment is normally required in order to obtain the metals of interest in a form suitable for analysis. Both methods of destruction are time consuming and tedious this is particularly true of the wet-oxidation procedure, which has the additional disadvantage of being potentially hazardous the methods require considerable analytical skill and experience. Both methods are prone to produce erroneous results either by the loss of an element of interest or by adventitious contamination from the component parts... 

Besides proving the formation of p-chelates [Pd(CH7CH7C(0)Me)(P-P)] at room temperature, the spectra showed the occurrence of chain-transfer by protonolysis with adventitious water to give the p-hydroxo compounds cis/trans [Pd(p-OH)(P-P)]2 as well as the conversion of the latter compounds into cis/trans bis-chelates [Pd(P-P)2] (Chart 7.2) [5f]. Independent experiments with isolated compounds showed that the p-OH and bis-chelate complexes are not dead ends, and can reenter the catalysis cycle to give alternating polyketones. 

Experiment has fully evinced that sulphur is no other than the concentrated vitriolic acid combined with a small proportion of the phlogistic or inflammable principle, and to this combination alone, which is always one and the same except for adventitious admixtures, the more judicious chemists have wholly confined the name. ... 

The reduction and oxidation of radicals are discussed in Chapter. 6.3-6.5. That in the case of radicals derived from charged polymers the special effect of repulsion can play a dramatic role was mentioned above, when the reduction of poly(U)-derived base radicals by thiols was discussed. Beyond the common oxidation and reduction of radicals by transition metal ions, an unexpected effect of very low concentrations of iron ions was observed in the case of poly(acrylic acid) (Ulanski et al. 1996c). Radical-induced chain scission yields were poorly reproducible, but when the glass ware had been washed with EDTA to eliminate traces of transition metal ions, notably iron, from its surface, results became reproducible. In fact, the addition of 1 x 10 6 mol dm3 Fe2+ reduces in a pulse radiolysis experiment the amplitude of conductivity increase (a measure of the yield of chain scission Chap. 13.3) more than tenfold and also causes a significant increase in the rate of the chain-breaking process. In further experiments, this dramatic effect of low iron concentrations was confirmed by measuring the chain scission yields by a different method. At present, the underlying reactions are not yet understood. These data are, however, of some potential relevance to DNA free-radical chemistry, since the presence of adventitious transition metal ions is difficult to avoid. 

Because of the obligate outcrossing nature of alfalfa, all experiments were carried out using vegetative cuttings of primary transformants. Nodal stem sections were placed in sterile, moist vermiculite for approx 14 d to stimulate adventitious root production, then transferred to a mix of sand and soil (1 1 [v/v]) in 3.8 x 21 cm plastic cone-tainers (Stuewe Sons, Corvallis, OR) and fertilized monthly with soluble 10 10 10 (N P K) fertilizer. 

In an attempt to learn whether collagen hydroxyproline synthesized in granuloma minces incubated with tritiated proline contained tritium at the 4 position, we converted such tritiated hydroxyproline to the corresponding N-carbobenzoxy derivative and then oxidized this derivative with chromic acid to N-carbobenzoxy-4-ketoproline according to the procedure of Patchett and Witkop(29). In most of these experiments very little tritiated water was formed although some tritiated water was detected in several experiments, the small amount formed could logically be attributed to adventitious oxidative reactions or perhaps to enolization of ketoproline. The evidence was therefore consistent with the absence of tritium at carbon atom 4 of the isolated hydroxyproline. 

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