Factors affecting experimental results

Since many factors will affect experimental results, quite complex experimental designs may be necessary. The choice of the best practical levels of these factors, i.e. the optimization of the experimental conditions, will also require detailed study. These methods, along with other multivariate methods covered in the next chapter, are amongst those given the general term chemometrics. 

Experimental design requires the analyst to identify the variables (factors) that are likely to affect the result of the analysis and to carry out experiments that allow... 

Considering all potential experimental and systematic errors of NOE/ROE crosspeak intensities, it is remarkable how robust the derived distance restraints still are. The reason Ues in the dependence of the cross-relaxation rate even if a cross-peak intensity is determined wrongly by a factor 2, the resulting distance restraint is only affected by the factor 1.12, which usually lies within the error range of distance restraints used in structure calculations. It should be further noted that the quaUty of a resulting structure is not so much determined by the... 

In practical situations the absorbance of a sample is determined by making two measurements, the first to determine 70 and the second to determine I. The determination of I0 is used to cancel a large number of experimental factors that could affect the result. When measuring I0 the sample container must closely match the unknown container in all ways except for the analyte content. The cuvettes should be a matched pair if a double beam instrument is used and the same cuvette can be used for both the blank and sample with a single beam instrument. The blank solution filling the cuvette should be identical to the solvent that the sample is dissolved in, except for the sample itself. If done correctly, the least-squares line for the calibration graph will come very close to the 0,0 point on the graph. 

In one experiment the checkers used 3-butyn-l-ol available from Aldrich Chemical Company, Inc., and found that it was of satisfactory purity. In other experiments, both the submitters and the checkers prepared the hydroxy compound from sodium acetylide and ethylene oxide in liquid ammonia according to the procedure described by Schulte and Reiss3 and further attempted to maximize the yield by varying the ratio of sodium ethylene oxide liquid ammonia used ip the reaction. Unfortunately, the checkers failed to obtain consistent results in repeated experiments and consequently could not define the optimum conditions for the reaction. Thus, the yield of 3-butyn-l-ol varied from 15 to 45% and 15 to 31% on the basis of sodium and ethylene oxide, respectively. Unknown and apparently subtle experimental factors affect the yield significantly. 

With this variable load and the generally complex factors affecting the mercury cell the task of optimising chlorine production is not easy. In a situation such as this a mathematical model of the process can be extremely useful. As a result ICI has taken advantage of a wealth of operational and experimental data for mercury cells, as well as experience in developing process models, to produce a dynamic model of a mercury cell. 

Based on experimental results and a model describing the kinetics of the system, it has been found that the temperature has the strongest influence on the performance of the system as it affects both the kinetics of esterification and of pervaporation. The rate of reaction increases with temperature according to Arrhenius law, whereas an increased temperature accelerates the pervaporation process also. Consequently, the water content decreases much faster at a higher temperature. The second important parameter is the initial molar ratio of the reactants involved. It has to be noted, however, that a deviation in the initial molar ratio from the stoichiometric value requires a rather expensive separation step to recover the unreacted component afterwards. The third factor is the ratio of membrane area to reaction volume, at least in the case of a batch reactor. For continuous opera-... 

Kubota, N., Temperature Sensitivity of Solid Propellants and Affecting Factors Experimental Results , Nonsteady Burning and Combustion Stability of Solid Propellants (Eds. De Luca, L, Price, E. W, and Summerfield, M.), Progress in Astronautics and Aeronautics, Vol. 143, Chapter 4, AlAA, Washington DC (1990). 

We have proposed a fluidized bed type process, which can be applied to phosphate removal from wastewater containing phosphate 2-23 mg/jg as P.By the results of experiments using equipment of capacity l-4m3 /day, factors such as supersaturation, recirculation ratio and space velocity were recognized to affect crystallization rate or phosphate removal efficiency. By mathematical analysis, we could obtain the characteristic equation for fluidized bed process, to agree well with experimental results. 

We have proposed fluidized bed process and by the results of experiments, factors such as supersaturation, recirculation ratio and space velocity affected crystallization rate or phosphate removal efficiency, and experimental results agreed well with calculated values from characteristic equation. 

Both the time of analysis and experimental design may affect the results. An explanation for the increase in adenylates under the conditions of our experiment is still needed. Since both ATP alone and total adenylate concentrations have increased, it does not appear that a shift in phosphorylation can account for the increases. The decrease in photosynthesis and increase in adenylates occur during the same time period and both factors return to normal after 21 hr. From previous research we know that the photosynthetic levels of ozonated pinto bean foliage decrease immediately after ozone exposure even when symptoms do not develop ( ). This does not hold true for the adenylate or respiration responses. Therefore, it appears that the ozone-initiated increase in adenylates is not correlated directly to the photosynthetic response. The increase in respiration persists when adenylate content and photosynthetic rates have returned to normal. Impaired mitochondrial function appears to be a secondary response more closely related to symptom development. 

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