Experimental reproducibility

Thus, by the mid-1930s the literature described the ion exchange, adsorption, molecular sieving and structural properties of zeolite minerals as well as a number of reported syntheses of zeolites. The early synthetic work remains unsubstantiated because of incomplete characterization and the difficulty of experimental reproducibility. 

Quantitative analysis using peak areas. Error estimates are based on experimental reproducibility of duplicate runs. 

Initial experiments in which 1-gram samples of silica were heated at 200°C under vacuum, slurried with 30 ml toluene, and treated with an excess of Zr(7r-allyl)4 or CH3MgI showed good agreement between the two reagents and good experimental reproducibility (Table I). 

In order to investigate the influence of the nature of the acid, the data obtained for the loss modulus, E", as a function of temperature for the two polymers, 1.81 and 1.8T, are shown in Fig. 90, as well as the experimental reproducibility. First, the effect of the nature of the acid is much larger than the experimental uncertainty. Figure 90 shows that the low temperature part of the p transition is identical in the 1.81 and 1.8T samples. In the high-temperature region of this transition, an additional contribution is observed for the 1.8T copolyamide. Furthermore, the activation energies, a max and... 

Plot of strength versus indentation load for alumina with various grain sizes and alumina/aluminium-titanate composite. The data points and solid line are from the composite. The other lines are for alumina with various grain sizes A, 2.5 pm, experimental B, 6 pm, interpolated C, 80 pm, experimental (reproduced from Bennison et al. [7] by kind permission of Taylor and Francis Ltd (http // www.tandf.co.uk/journals). 

There emerges a very complex picture of three hormones synthesized and secreted at variable rates, competing for carrier binding proteins, presumed receptor proteins, epoxide hydratase and carboxyl esterase enzymes (35,36). It is possible experimentally to measure tEe timing of critical periods for larval determination and to measure total levels of JH at these critical periods although both measurements involve extreme difficulty. Approaches to this were described recently by G.B. Staal (3 7) using third instar larvae of the tobacco hornworm moth, Manduca sexta, which were allatectomized and raised on JH impregnated diets as an experimentally reproducible method of JH therapy. 

It was found that neuroleptics could experimentally reproduce almost all symptoms of lethargic encephalitis. In fact, it would be possible to cause true encephalitis epidemics with the new drugs. 

The second main problem is that there is often not enough E1/2 separation for different substituents or substituent combinations to allow for confidence in identification, especially when experimental reproducibility is low due to uncontrolled matrix effects The consideration of more information than i/2 would clearly be helpful. 

Design 3. This has a value of R equal to 4 and D = 1. The number of replicates is rather large compared with the number of unique experiments. However, if the main aim is simply to investigate experimental reproducibility over a range of concentrations, this approach might be useful. 

Fig. 12. Reaction scheme for products obtained from the fluorination and chlorination of CHCl=CCl2. Bold arrows and formulas - major reactions, light arrows and formulas - minor reactions, dotted lines - reactions not verified experimentally (reproduced with permission from J. Fluorine Chem. 75 (1995) 103 [42]).

Table 5.39 also contains the indications and calculations required to verify the zero hypothesis. This hypothesis considers the equality of the variance containing the effect of the factor on the process response (Sj) with the variance that shows the experimental reproducibility (s ). 

Temperature scales are obtained by assigning numerical values to two experimentally reproducible temperatures. For example, the Celsius scale is obtained by assigning a value of 0°C to the freezing point of pure water at 1 atm and a value of 100°C to the boiling point of pure water at 1 atm. A temperature of 40°C is consequently shorthand for the temperature 40% of the way from the freezing point of water at 1 atm to the boiling point of water at 1 atm. ... 

First attempts to experimentally reproduce CHN failed two groups of seven Wistar rats were orally administered either pure aristolochic adds (10 mg/kg for 5 days a week during 3 months) or herbs powders (containing AA) mixed with fenfluramine. At sacrifice animals in both groups had developed the expected tumors but not fibrosis of the renal interstitium [61]. However, when 12 female New Zeeland whife rabbits were injected intraperitoneaUy with 0.1 mg aristolochic acids per kg, 5 days a week, for 17 to 21 months, they developed a severe hypocellular interstitial fibrosis, urothelial atypias and, in 3 of them, tumors of the urinary tract [62]. 

Figure 9 Ni(100)c(2 x 2)-Na. Azimuthal dependence of the Na 2p emission at liv = 80 eV, polar emission angle 30°. Full circles - calculated intensities full curve - same data with the minimum value subtracted dashed curve - experimental (Reproduced by permission from Phys. Rev. Letters, 1978, 41, 1130)...

In view of the above comments, error estimates are usually made on the basis of overall reproducibility of, and matching between independent experimental or theoretical results, rather than on the basis of the precision reachable with a particular measurement and refinement model. There are several approaches that allow us to gain quantitative information on experimental reproducibility and uncertainties. These include the pseudoatom interpretation of error free, theoretical data [56, 57, 70-72], comparative analysis of experimental data sets in terms of different constrained models [73], theory versus experimental comparison of results obtained for the same system [74-76], systematic studies on a series of related compounds [77], and the simultaneous analysis of data collected at different temperatures [66]. 

Furtak and Macomber, the composition of the solution affected the slope of the maximum frequency/electric potential curves. Higher chloride concentrations resulted in higher slopes (though, perhaps still within the experimental reproducibility) and fluoride exhibited smaller slopes (1.46 eVV ). Furtak and Roy have shown that for coadsorbed chloride and pyridine, or chloride and thiocyanate, each molecule shows its own excitation potential dependence. Another interesting point was that the excitation maximum of one of the molecules was reflected in the excitation profile of the other coadsorbed molecule. 

At this point it should be emphasized that the standard deviation ay provides an estimate of the goodness of the fit of the data to a particular mathematical equation, in this case to the proportionality y = ax. Note that this is quite different from an estimate of the (model-independent) experimental reproducibility of a replicate measurement. It is somewhat unfortunate that both measures are called standard deviations, and are denoted by the same symbol, cr. 

Copolymers prepared at 40° and 60° from a given monomer mixture had equivalent Fs, Fa, Fg and Fc values, within the limits of experimental reproducibility, which was approximately 0.03. 

This can readily be done if the reactor heater volume also contains the pre-heater. In this configuration not only do we avoid a separate control function for each of the two modules but we improve experimental reproducibility and minimize random errors. To achieve this, the reactor and pre-heater have to be so nested that the output temperature of the pre-heater is the same as the inlet temperature of the reactor. Careful design, appropriate temperature controls and control of heater-fluid circulation in the heater bath can be made to achieve the desired condition. In the design of TS-PFRs this is arguably the most complicated aspect. 

Considering the low degree of experimental reproducibility obtained by these authors, it is more probable that the effect of oxygen is closer to that determined by Niclause and his coworkers [31] who show that, at very low pressures (<10 torr), the rate of oxidation depends on Pq2 and is independent of po2 for pressures greater than 160 torr. In these pressure ranges, the expression for the rate of oxidation has the forms... 

Proteins were obtained from Miles Laboratories as bovine serum albumin (BSA) monomer standard Fraction V (81-028-1-P338) and bovine y-globulins Fraction II (82-041-2-1086). L-Tryptophan (Matheson Coleman Bell), 0.3 mg/mL in PBS, was used as an intrinsic fluorescence experimental reproducibility standard. 

Replicate experiments. Finally, we examine the impact of replicating experiments. The main reason one replicates an experiment is to obtain a direct measure of the experimental reproducibility. By replication we are confronted with the simple experimental fact that no matter how much care we take and how much effort we exert, the. results of two experiments are never exactly the same. The differences among replicated experiments g.tve us a direct quantitative m.easure of the experimental error or noise.. These errors are partly due to our Inability to measure accurately the outputs of interest, but they are also due to pur inability to control comp.letely the experimental environment. The... 

Polyaniline (PAni), which has been known for more than a hundred years, was modified in the 1980s. The conductivity of polyaniline was raised from 10 to 10 Ohm -cm at BASF Company (Nuarman H.) in conditions of high experimental reproducibility and strict control over polymerization. The indicated values surpass the conductivity of metals such as Fe and Pt,... 

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