Sample geometries

Optimization. Zone travel rate, sample geometry and orientation, zone length and spacing, stirring in the zone, and the number of zone passes can all be controlled. These variables can be optimized either with respect to purification or to the purification rate. 

Figure 7-7. Schematic diagram of the EA spectrometer. Inset Sample geometry with interlocked metallic strips.

Depending on the sample geometry, the resulting currents may be in the pico- and subpico-ampere range. It is essential either to change the sample geometry or to make sure that the experimental setup resolves these small currents. 

State-of-the-art TOF-SIMS instruments feature surface sensitivities well below one ppm of a mono layer, mass resolutions well above 10,000, mass accuracies in the ppm range, and lateral and depth resolutions below 100 nm and 1 nm, respectively. They can be applied to a wide variety of materials, all kinds of sample geometries, and to both conductors and insulators without requiring any sample preparation or pretreatment. TOF-SIMS combines high lateral and depth resolution with the extreme sensitivity and variety of information supplied by mass spectrometry (all elements, isotopes, molecules). This combination makes TOF-SIMS a unique technique for surface and thin film analysis, supplying information which is inaccessible by any other surface analytical technique, for example EDX, AES, or XPS. 

Pike AWG, Hedges REM (2001) Sample geometry and U-uptake in archaeological teeth implications for U-series and ESR dating. Quat Sci Rev 20 1021-1025... 

Figure 3.3. Schematic diagram of the electrochemical cell inset shows the sample geometry for MIR experiments (After da Fonseca et al. 1996.)...

Figure 2. The areal exhalation rate as a function of time after closing the can. Sample geometry and data as shown (theory).

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. 

In CL measurements many factors that influence the intensity of the CL signal should be taken into account. The CL signal may depend on the geometry of the sample. Internal refraction and reflection at the air-solution interfaces are important factors in determining the measured CL intensity, and should be taken into account, for example, when a CL cocktail is placed over a sample. The effect of sample geometry can be evaluated using model systems, such as enzymes... 

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. 

Sablani, S.S. and Rahman Shafiur, M. 2003. Effect of syrup concentration, temperature and sample geometry on equilibrium distribution coefficients during osmotic dehydration of mango. Food Res. Int. 36, 65-71. 

Since these volumes are determined from external dimensions of the samples, they do not reflect actual changes in the cell wall volumes, and where this is claimed or assumed, the data needs to be treated with caution. Sample geometry is a crucial factor affecting the results obtained. In particular, the orientation of growth rings with respect to the sample... 

Let us remember that the properties of LCPs are dependent on processing shear and, consequently, creep modulus varies with sample geometry. 

Figure 4.127 shows the creep modulus of several grades of glass fibre reinforced LCPs in various conditions of sample geometry, loading and temperature. The two samples tested... 

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. 

Eontanella and co-workers studied the effect of high pressure variation on the conductivity as well as the H, H, and O NMR spectra of acid form Nafionl 17 membranes that were exposed to various humidities. Variation of pressure allows for a determination of activation volume, A V, presumably associated with ionic and molecular motions. Conductivities (a) were obtained from complex electrical impedance diagrams and sample geometry, and A V was determined from the slope of linear isothermal In a versus p graphs based on the equation A E = —kJ d In a/d/j] t, where p is the applied pressure. At room temperature, A Ewas found to be 2.9 cm mol for a sample conditioned in atmosphere and was 6.9 cm mol for a sample that was conditioned in 25% relative humidity, where the latter contained the lesser amount of water. 

The relative viscosity rj and storage modulus G were determined by Cirkel and Okada in experiments using a rheometer in oscillatory rotational mode and Couette sample geometry as a function of Nafion volume fraction, cp, and angular frequency, a>, for the acid and sodium forms at 25 °C. Parallel experiments... 

Figure 1. Sample geometry for mixed system to B-stage cure.

Figure 2. Sample geometry for B-stage to C-stage and post C-stage cure.

Data analysis in the normal state of the superconductor is relatively straightforward, measurements of I, V, and T together with sample geometry are used to obtain resistivity vs temperature. 

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