Sources of experimental

Design of experiments. When conclusions are to be drawn or decisions made on the basis of experimental evidence, statistical techniques are most useful when experimental data are subject to errors. The design of experiments may then often be carried out in such a fashion as to avoid some of the sources of experimental error and make the necessary allowances for that portion which is unavoidable. Second, the results can be presented in terms of probability statements which express the reliabihty of the results. Third, a statistical approach frequently forces a more thorough evaluation of the experimental aims and leads to a more definitive experiment than would otherwise have been performed. 

Recently, a nonempirical rr-electron SCF approach was reported and applied to interpretations of spectra of various conjugated hydrocarbon radicals (147). The greatest attention, however, has been paid to radical ions derived from even alternant hydrocarbons (10, 58-60, 63, 125, 135, 148-153). Here, numerous experimental material suitable for systematic testing of the MO methods has been accumulated. In particular, the following sources of experimental data should be mentioned Hamill and collaborators (24) prepared... 

The Thermodynamics Research Center staff have assigned an uncertainty value to each observed and recommended density value listed in the tables. The tme value of the property has a 95% probability of being in the range covered by + or - the uncertainty about the reported value. Assignment of uncertainty is a subjective evaluation based upon what is known about the measurement when the value is entered into the database, and includes the effects of all sources of experimental error. The errors have been propagated to the listed density at the reported temperature. Uncertainties reported by the investigators are considered but not necessarily adopted. Often, investigators report repeatability, but they usually do not provide uncertainty. 

The challenge is then to achieve the same degree of accuracy in the derived values of the experimental electron density. Recent studies have shown that in some cases this is indeed within the reach of the present-day modelling techniques [3-5]. When the major sources of experimental error have been corrected for the typical root mean square electron density residual can reach values as low as 0.05 e A-3, with maxima below 0.20eA-3 in absolute value. The observed residuals are usually due to the... 

An important source of experimental and theoretical studies of equilibria in ring formation is represented by the field of so-called macrocyclisation equilibria (Flory, 1969). Interest in this field appears to have been restricted so far to chemists conventionally labelled as polymer chemists. Experimental evidence of cyclic oligomer populations of ring-chain equilibrates such as those obtained in polysiloxanes (Brown and Slusarczuk, 1965) may be delated to the statistical conformation of the corresponding open-chain molecules (Jacobson and Stockmayer, 1950 Flory, 1969). In these studies experimental results are expressed in terms of molar cyclisation equilibrium constants Kx (14) related to the x-meric cyclic species Mx in equilibrium with the... 

The principle source of experimental conformational data in an NMR structure determination is constraints on short interatomic distances between hydrogen atoms obtained from NMR measurements of the nuclear Overhauser effect (NOE). NOEs result from cross-relaxation mediated by the dipole-dipole interaction between spatially proximate nu-... 

Smith-Magowan, D. Goldberg, R. N. "A Bibliography of Sources of Experimental Data Leading to Thermal Properties of Binary Aqueous Electrolyte Solutions" Nat. Bur. Stand. Special Publ. No. 537, March 1979. 

The various sources of experimental error were also considered. From Eq. (6), we should expect an accuracy of approximately 2% for AD/D since the errors in pH, a and H3Cit cancel in considering the 0/ values for two elements in the same aqueous phase. The relative error in 0/ can be estimated to be 5 % from Eq. (6). It appears of course that the absolute error in 0/exceeds this value. 

Were there any sources of experimental error What could you improve if you did this investigation again ... 

These problems aside, diffraction studies still may not provide results that describe molecular structures in one of the most interesting states aqueous solution. For solutions, diffraction experiments are less relevant, and nmr and circular dichroism are the best sources of experimental information (see the chapter by... 

Selected entries from Methods in Enzymology [vol, page(s)] Theoretical aspects, 76, 354-356 diagmagnetic contribution, 76, 358-359 experimental methods, 76, 356-360 Faraday balance technique, 76, 360-361 Gouy technique, 76, 357, 360 instrumentation, 76, 360-369 oxygen contribution, 76, 360, 368 sources of experimental errors, 76, 359-360 SQUID magnetometer use, 76, 364-365 thermal equilibria, 76, 358, 370 thermal expansion, 76, 358. 

This is not the only subject of debate the nature of the adsorbed forms of oxygen and reaction products on the electrode surface has been widely discussed, as well as the various steps of ORR. Very often, for conditions apparently similar, for example, the same electrode and solution, observations made by two research groups are different and so are, of course, the deductions and the pathways for the electrode reaction. There are so many possible steps, reactions and species that various combinations can be envisaged moreover, as other methods for observing the species or intermediates involved in the electrode reaction are rare, electrochemistry is often the only source of experimental facts. As for other multiparametric problems, when a plausible explanation is found, there is no certainty that this is the only possibility and the correct solution. Moreover, experimental conditions that look identical are not really exactly similar the problem... 

A randomized crossover design has theoretical appeal because it eliminates the largest source of experimental variance interindividual variability. This could significantly enhance statistical power and permit much smaller samples sizes to detect a treatment effect. Unfortunately, a crossover design is appropriate only in rare cases in psychopharmacology, namely in studies ... 

M Because sources of experimental information were sometimes not explicitly stated in the secondary references available to us, a few of the results may inadvertently have been rhcluded in the wrong grouping. These should not materially affect the general conclusions. 

To compile quantitatively reliable information, we need a source of experimental measurements. One way to determine the nature of inter-molecular forces between biopolymer molecules in a solvent medium is to measure the so-called osmotic second virial coefficient A2. Expressed in molar (biopolymer) terms, the quantity A2 can be related to the two-body potential of mean force W(r) by the following equation (Vrij, 1976 de Kruif, 1999 Prausnitz, 2003 de Kruif and Tuinier, 2005) ... 

Throughout, explanations of new concepts and developments are detailed and, for the most part, complete. In a few instances complete proofs have been omitted and detailed references to other sources substituted. It has not been my intention to give a complete bibliography, but essential references to core work in group theory have been given. Other references supply the sources of experimental data and references where further development of a particular topic may be followed up. 

A good source of experimental data is the NIST kinetics database http //kinetics.nist.gov. 

It is essential to take into account a number of potential sources of experimental error in the determination of an adsorption isotherm. In the application of a volumetric technique involving a dosing procedure it must be kept in mind that any errors in the measured doses of gas are cumulative and that the amount remaining unadsorbed in the dead space becomes increasingly important as the pressure increases. In particular, the accuracy of nitrogen adsorption measurements at temperatures of about 77 K will depend on the control of the following factors ... 

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