Sample geometry, differences

The conclusion from the experiment illustrated in Figures 2 and 3 is thus that the exhalation rate will change so rapidly after closure that only a mean exhalation rate, significantly lower than the free exhalation rate, can be measured. This problem can be solved if we choose our sample geometry differently or make another approach to the grab sampling from the can. These things will be dealt with in the next section. 

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

A rapid, nondestructive method based on determination of the spatial distribution of ATP, as a potential bioindicator of microbial presence and activity on monuments, artworks, and other samples related to the cultural heritage, was developed [57], After cell lysis, ATP was detected using the bioluminescent firefly luciferin-luciferase system and the method was tested on different kinds of surfaces and matrices. Figure 3 reports the localization of biodeteriogen agents on a marble specimen. Sample geometry is a critical point especially when a quantitative analysis has to be performed however, the developed method showed that with opti-... 

The concept of resolution in AFM is different from radiation-based microscopies because AFM imaging is a three-dimensional imaging technique. There is an important distinction between images resolved by wave optics and those resolved by scanning probe techniques. The former is limited by diffraction, whereas the latter is limited primarily by apical probe geometry and sample geometry. Usually the width of a DNA molecule is loosely used as a measure of resolution, because it has a known diameter of 2.0 nm in its B form. 

Aberration-corrected ETEM/STEM (130) is expected to offer superior (subatomic) resolution under catalytic reaction conditions furthermore, it will provide improved flexibility for tilting the sample to different crystallographic orientations to allow understanding of the geometry of surface structural changes, enable the use of complex sample stages, and perhaps higher gas pressures. 

None of the set-ups discussed so far provides stirring of the electrolyte for bubble removal or for enhancement of the reaction rates. A standard set-up developed to study kinetic electrode processes is the rotating disc electrode [11]. The electrode is a small flat disc set in a vertical axle. The hydrodynamic flow pattern at the disc depends on rotation speed and can be calculated. An additional ring electrode set at a different potential provides information about reaction products such as, for example, hydrogen. However, because this set-up is designed to study kinetic processes and is usually equipped with a platinum disc, it becomes inconvenient if silicon samples of different geometries have to be mounted. 

It can be seen that calculation of the absorption correction also needs the values of the sample density and the linear value of the absorption path length beside the mass absorption coefficients. It is also important to note that it is the difference of the absorption coefficients, what coimts in determining if the thin film criterion is fulfilled for a given sample (geometry). It frequently happens that the sample is thin for one pair of its components and thick if another pair of elements is considered from its components. 

Absolute accuracy has no real meaning in this experiment critical information consists of significant changes in mass loss or temperature of mass loss between samples. Inhomogeneity of samples, sample geometry, and sample size differences can have adverse effects on the reproducibility of data. 

The variation in the measured electron mobilities from sample to sample in sintered materials (also observed by Hahn, ref. 24), may be due to any of several effects. The most probable reason for this variation in the well-sintered samples studied is a difference in history the individual samples are obtained with different numbers of conduction electrons per cm. frozen in in the necks. That is, the different history has allowed different amounts of oxygen to be adsorbed on the surface. Thus the concentration of electrons in the grain, as measured by the Hall coefficient, will have little relation to the concentration of electrons in the neck, as measured by the conductivity, and the mobility, obtained from the product of the Hall coefficient and the conductivity, will be neither the true mobility nor constant from sample to sample. The different samples may also end up with varying geometry of their necks, according to their previous treatment. 

The results reported by the different groups have all been obtained with experimental arrangements that differ greatly in the types of laser used, the wavelengths, time regime- and irradiances on the sample, in the sample geometry and sample preparation, the mass spectrometers and the detection systems. The most pertinent information on the different systems that have been successfully applied to organic mass spectrometry is compiled in ref. (). 

In Fig. 1.13a the experimentally determined instability wavelength X (e.g. determined from Fig. 1.11) is plotted versus the total heat flux /q. The linear l//q dependence of Eq. (1.22) describes well the experimental data. A second verification of the experimental model stems from the value of Q that is determined by a fit to the data. Rather than a different value of 0 for each data-set, we find a universal value of 0 that depends only on the materials used (substrate, polymer), but not on any of the other experimental parameters (sample geometry, temperature difference). A value of Q = 6.2 described all data sets for PS on silicon in Fig. 1.13a, with a value of Q = 83 for PS on gold. This allows us, in similarity to the electric field experiments in the previous section to introduce dimensionless... 

Over the past several years, FTIR imaging has been applied to the study of a variety of catalytic systems in several different sampling geometries. The first examples in... 

Variations in cross-link density may arise from spatial variations in the rubber formulation, although short-scale variations are often smoothed by component diffusion during the vulcanisation process. Differences on the mm scale can lead to interfacial structures like those depicted in Figures 7.16 and 7.17. Another source of variations in cross-link density on the mm scale is the curing process in combination with the sample geometry. Heat is supplied to the sample for a certain time and after vulcanisation is removed from the sample in a certain time. Near the heat source vulcanisation sets in first, and near the heat sink it sets in last. Depending on how the heat is supplied to and withdrawn from the object, complicated time-dependent temperature profiles are established in the sample. 

The extensive surface reconstruction in the presence of N has implications for our discussion of the recombination process, since we must consider whether N2 forms from recombination on the unreconstructed Cu(l 1 1) surface or is formed by decomposition of copper nitride islands. In the latter case N recombination may either leave the local Cu atoms in a metastable (100) arrangement or else recombination might be associated with substantial motion of the Cu atoms as they relax from the nitride adsorption geometry. If N recombination occurs at nitride islands then the dynamics of recombinative desorption will sample a phase space which is completely different to that for dissociation on clean flat Cu terraces, making it impossible to relate these two processes by detailed balance. This is the behaviour of H recombination on Si where the large change in the Si equilibrium geometry induced by H adsorption ensures that the adsorption and desorption processes sample very different channels [13]. 

Fig. 13 a Optical image (top view) of the sample geometry for a thin PS film of 239 nm after 4 hours at 180 °C in a pure nitrogen atmosphere ( 1 mm x 1 mm) b the same sample after 4 hours at 180 °C in air ( 1 mm x 1 mm) c the relaxation time of the dynamic glass transition vs. inverse temperature for a thin PS film of 63 nm after different annealing times at 180 °C in a pure nitrogen atmosphere and in air. Inlet, time dependence of the sample capacity at 180 °C and 0.1 MHz in a pure nitrogen atmosphere and in air... 

In the case of solid electrolytes, such a calibration is usually impossible. The configuration of measuring cells should be selected to provide uniform current distribution or to enable use of a definite solution of differential Ohm s law for the conductivity calculations [ii-iv]. The conductivity values are typically verified comparing the data on samples with different geometry and/or electrode arrangement, or using alternative measurement methods. 

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