Experimental techniques setting measurements

An experimental technique for measuring the interfacial shear strength of a relatively large data set has been presented. The procedure provides a direct measurement of the nanotube pullout aspect ratio from a fracture surface. The results support prior work showing an increase in relative interfacial shear strength due to chemical... 

In order to determine the stability constants for a series of complexes in solution, we must determine the concentrations of several species. Moreover, we must then solve a rather complex set of equations to evaluate the stability constants. There are several experimental techniques that are frequently employed for determining the concentrations of the complexes. For example, spectrophotometry, polarography, solubility measurements, or potentiometry may be used, but the choice of experimental method is based on the nature of the complexes being studied. Basically, however, we proceed as follows. A parameter is defined as the average number of bound ligands per metal ion, N, which is expressed as... 

Substituting the three sets of data to MA, CA and T in this equation provides three simultaneous equations in which there are three unknowns, A, E and p, and hence, in principle, a solution may be found. In practice more than three sets of experimental data is desirable in order to validate the experimental technique and the consistency of the measurements. 

An original technique was developed by Konishi et al. (1969) and extended later on by Narita et al. (1980). This method is known as the small-angle magnetisation rotation (SAMR) method a static bias field H and a tensile stress (o) are applied in the direction of the film a small-amplitude ac driven field H = W max sin(wf) is applied perpendicular to H. It is this ac magnetic field that induces a magnetisation rotation, which can be detected as an induced voltage in a sensor coil wound around the film axis. This response is measured as a function of the applied stress, i.e. of the strain-induced anisotropy. An experimental SAMR set-up is illustrated in fig. 5. The sensitivity of this method was 2 x 10-7 (Narita et al. 1980) and even much higher, namely 10-9 (Hernando et al. 1983). 

In another paper in this issue [1], the molecular motions involved in secondary transitions of many amorphous polymers of quite different chemical structures have been analysed in detail by using a large set of experimental techniques (dynamic mechanical measurements, dielectric relaxation, H, 2H and 13C solid state NMR), as well as atomistic modelling. 

In this section we describe the various experimental techniques which have been used to measure aT and we include a critical evaluation of their limitations so as to aid in the intercomparison of the various sets of data. Many experimental groups have contributed to this field, but the aim here is not to discuss every technique in great detail but rather to select a representative subset in order to illustrate the most interesting features. Discussions of the results obtained are given in sections 2.5 and... 

The energetics of protein association can be studied by a variety of experimental techniques,17 each of which permits measurements of equilibrium or kinetic values in a certain range. Widely used techniques include isothermal titration calorimetry, surface plasmon resonance measurement, stopped flow kinetics, optical spectroscopy, MS, and analytical ultracentrifugation. The techniques differ in their requirements (e.g., amount of protein, labeling with fluorophores, attachment to sensor surfaces, and the environment provided by the experimental set up) and therefore in their applicability to individual cases. Different techniques can also give quite different values for what might be expected to be the same quantity. For example, association rates measured by surface plasmon resonance, with one protein immobilized on a surface, are usually different from those measured for the two proteins in solution and under otherwise similar conditions. 

In this paper, we propose an experiment to test neutrality of isolated lithium atoms. Atom interferometry has been shown to be the ideal technique to measure weak interactions of an atom with its environment [1,2]. In particular, in 1991, Kasevich and Chu have mentionned the test of neutrality of atoms as a possible utilisation of their atomic interferometer [2], As far as we know, no further details have been published. The experimental set-up we propose is based on a Mach-Zehnder atom interferometer like the ones developped by the research groups of D. Pritchard [3], Siu Au Lee [4], A. Zeilinger [5] and the one under construction in our group [6]. If the same uniform electric field E is applied on both arms of the interferometer, a phase shift of the interferometric signal will appear. This phase shift will be proportional to the residual charge of lithium atom and to the electric field E. 

Because of interference from the radioactive decay of other nuclides (which are typically formed with much higher yields), extraction systems with relatively high decontamination factors from actinides, Bi, and Po must be chosen, and the transactinide activity can only be measured in the selectively extracting organic phase. For this reason, measurement of distribution coefficients is somewhat difficult. By comparing the Rf or Db detection rate under a certain set of chemical conditions to the rate observed under chemical control conditions known to give near 100% yield, distribution coefficients between about 0.2 and 5 can be determined. If the control experiments are performed nearly concurrently, many systematic errors, such as gas-jet efficiency and experimenter technique, are cancelled out. Additionally, extraction systems which come to equilibrium in the 5-10 second phase contact time must be chosen. 

The experimental technique controls how the mass transport and rate law are combined (and filtered, e.g. by removing convective transport terms in a diffusion-only CV experiment) to form the overall material balance equation. Migration effects may be eliminated by addition of supporting electrolyte steady-state measurements eliminate the need to solve the equation in a time-dependent manner excess substrate can reduce the kinetics from second to pseudo-first order in a mechanism such as EC. The material balance equations (one for each species), with a given set of boundary conditions and parameters (electrode/cell dimensions, flow rate, rate constants, etc.), define an I-E-t surface, which is traversed by the voltammetric technique. 

During the past decade the developments in the experimental technique made possible high resolution measurements of the XPS valence band spectra with a good statistics. The use of these measurements for a more rigorous comparison between the theoretical and experimental data are illustrated by recent results obtained for phosphorus [27, 28] and sulphur [29] oxyanions In these studies the theoretical interpretation was obtained from DV-Xa cluster MO calculations. Experimental data on crystal structure information from X-ray diffraction measurements were used to set up realistic model clusters. In the case of the S04 cluster, the results of several model calculations (ab initio, DV-Xa, hybrid models) are also presented. From the comparison of these results a better understanding of the role of the contribution from different effects to the MO one-electron energies can be obtained. 

Consider two sets of measurements of a random variable. X—for example, the percentage conversion in the same batch reactor measured using two different experimental techniques. Scatter plots of X versus run number are shown in Figure 2.5-1. The sample mean of each set is 70%, but the measured values scatter over a much narrower range for the first set (from 68% to 73%) than for the second set (from 52% to 95%). In each case you would estimate the true value of X for the given experimental conditions as the sample mean. 70%. but you wouid clearly have more confidence in the estimate for Set (a) than in that for Set (bp... 

The choice made from the variety of experimental techniques described above and in Chapters 7 to 17, dealing with individual reactants, requires that the parameter(s) measured are quantitatively related to the extent of a defined reaction (or set of reactions). Use of two (or more) complementary techniques, as well as microscopic observations, increase the reliability of the reaction mechanism which is formulated by reconciling all the experimental observations available. 

The results presented here are unique in that they are from lH NMR measurements made under the non-equilibrium conditions pertaining to temperature controlled pyrolitic decomposition of the shales. We have established experimental techniques that ensure good reproducibility of the changes manifest in these dynamically recorded 1h NMR solid echo signals. By this technique of -H NMR thermal analysis it is possible to obtain a set of data characterizing the pyrolysis properties of the shale. 

For a volatile solute, the vapor pressure can be measured. This can be done as a function of the solute concentration at constant surfactant concentration. The activity of the solute is P/P° where P° is the vapor pressure of the pure solute. Two sets of data are required, the activity (or vapor pressure) of the solute in water and the activity (or vapor pressure) of the solute in aqueous surfactant solution. The horizontal distance between these two curves is a direct measure of the solubilized solute. The experimental techniques used for this purpose are headspace chromatography as used by Hayase and Hayano and Spink and Colgan, ° or the final equilibrium pressure over a solution containing a known quantity of volatile liquid can be measured. The latter method has been developed by Tucker and Christian. This method has the added advantage of providing an easy... 

Thermogravimetry is an attractive experimental technique for investigations of the thermal reactions of a wide range of initially solid or liquid substances, under controlled conditions of temperature and atmosphere. TG measurements probably provide more accurate kinetic (m, t, T) values than most other alternative laboratory methods available for the wide range of rate processes that involve a mass loss. The popularity of the method is due to the versatility and reliability of the apparatus, which provides results rapidly and is capable of automation. However, there have been relatively few critical studies of the accuracy, reproducibility, reliability, etc. of TG data based on quantitative comparisons with measurements made for the same reaction by alternative techniques, such as DTA, DSC, and EGA. One such comparison is by Brown et al. (69,70). This study of kinetic results obtained by different experimental methods contrasts with the often-reported use of multiple mathematical methods to calculate, from the same data, the kinetic model, rate equation g(a) = kt (29), the Arrhenius parameters, etc. In practice, the use of complementary kinetic observations, based on different measurable parameters of the chemical change occurring, provides a more secure foundation for kinetic data interpretation and formulation of a mechanism than multiple kinetic analyses based on a single set of experimental data. 

Alan C. Wright (Baroid Div., National Lead, Houston, Tex. 77001) With reference to your Figure 3, probably the apparent discrepancy between the DKO and WRG data sets can be ascribed to experimental technique. It is my understanding that the DKO x-ray measurements utilized only absolute 2-theta values since a relative scale was all that was sought. Our measurements, however, involved the use of an internal standard. Within error limits, the DKO and WRG data may be superimposed simply by shifting the A scale. Obviously, our limited data are insufficient to confirm or deny the break points found by DKO. 

This concludes a survey of the experimental techniques that have been used to measure dissociation and recombination rate coefficients. Although it is not always the practice to include in the literature an estimation of the errors associated with a particular set of rate coefficients, it is of vital importance when extrapolations of low tempera-... 

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