Samples Thick

Short-term, 250-p.m-thick sample. AsTM method D257. 

PdgoSi o easy to form glass, thick samples produced... 

The evaluation of the various XRF measurements will be discussed for different effects in EDXRS the spectra evaluation is perfonned by different programs with varying assumptions, partially different mass attenuation coefficients are used, the calibration procedures are principally different (e.g., thin foils with given thickness, or, infinitely thick samples), measurement under atmospheric pressure or in vacuum, secondary excitation (enhancement) mainly of Al by Si radiation. 

The very low water absorption of bis-phenol A polycarbonates contributes to a high order of dimensional stability. Table 20.6 shows how the water absorption of j in thick samples changes with time and environmental conditions and the consequent influence on dimensions. 

From a constitutive relation of the form t = t(D, ri) (here t is stress not time) it can be readily shown that, since there is no change in electric displacement in an open-circuit, thick-sample configuration, there are no secondary stresses due to electromechanical coupling. Nevertheless, the wavespeed is that of a piezoelectrically stiffened wave. 

Table 5 compares the tensile properties of Vectra A950 in the form of dispersed fibers and droplets in the matrix by injection molding, microfibril by extrusion and drawing [28], injection molded pure thick sample and pure thin sample, and the pure drawn strand [28]. As exhibited, our calculated fiber modulus with its average of 24 GPa is much higher than that of the thick and thin pure TLCP samples injection molded. It can be explained that in cases of pure TLCP samples the material may only be fibrillated in a very thin skin layer owing to the excellent flow behavior in comparison with that in the blends. However, this modulus value is lower than that of the extruded and drawn pure strand. This can be... 

Analysis of Thick Samples. Enhancement Effects Absent... 

The transition of the previous paragraph can be extended to include infinitely thick samples, the most common situation in x-ray emission spectrography. To determine composition, it is well to work with such... 

The discussion preceding Equation 7-5 points to the weight-fraction as the logical unit for the x-ray emission spectrography of infinitely thick samples. Were all complications absent, one might expect proportionality between analytical-line intensity and weight-fraction such that... 

Figure 2.9 Spectra of a single adenine nanocrystal, (a) TERS spectrum, (b) ordinal SERS spectrum, and (c) ordinary near-infrared (NIR) Raman spectra. For the SERS measurement, a silver island film was used. For the NIR Raman measurement, i thick sample of adenine was used with a 1 h exposure.

For the NFS spectrum of [Fe(tpa)(NCS)2] recorded at 108 K, which exhibits a HS to LS ratio of about 1 1, a coherent and an incoherent superposition of the forward scattered radiation from 50% LS and 50% HS isomers was compared, each characterized by its corresponding QB pattern (Fig. 9.16) [42]. The experimental spectrum correlates much better with a purely coherent superposition of LS and HS contributions. However, this observation does not yield the unequivocal conclusion that the superposition is purely coherent, because in the 0.5 mm thick sample the longitudinal coherence predominates since many HS and LS domains lie along the forward scattering pathway. In order to arrive at a more conclusive result, the NFS measurement ought to be performed with a smaller ratio aJD on a much thinner sample. Such an experiment would require a sample with 100% eiuiched Fe and a much higher beam intensity. 

To avoid the time-consuming grinding of plastics samples, Freitag and John [96] have tried dissolving thick samples, i.e. pellets of 3 mm diameter, instead of extracting them. The dissolution, performed with a 1 1 mixture of toluene and 1,2-dichlorobenzene at 100% microwave output during 5 min, yielded satisfactory results (95 % of expected concentration) only for PP, whereas the recovery from the polyethylenes was below 85%. 

On-line SFE-SFC method development for validated quantitative analysis of PP/(Irganox 1010/1076, Tinuvin 327) has been reported [93]. SFE conditions required optimisation of extraction time and pressure, matrix type (particle or film) and matrix parameters (particle size, film thickness, sample weight). About 30% of extracts were lost during collection. Very poor recoveries (20-25 %) were reported from ground samples (particle size 100 p,m dependent recoveries of 45-70% for 30-p.m-thick films. Biicherl... 

If thick samples are placed in the specimen chamber for analysis, the particles are slowed down and eventually stopped in the sample, so the calculation of the X-ray yield and their absorption is more complicated. Some objects may be too large to be placed in the specimen chamber, in which case the external beam technique is employed. The particle beam passes through a window at the end of the beam-line into the air where an object of any size (e.g. an archaeological artefact) may be analyzed. 

In thick samples, a boron oxide/boron carbide crust has been detected on the surface of the polymer. This inorganic surface layer has a shielding effect on the inner polymer layers, further enhancing the thermal stability of the material. Poly(m-carborane-siloxane)s have therefore been considered as surface coatings for organic materials, providing protection from erosion effects. 

ATR is one of the most useful and versatile sampling modes in IR spectroscopy. When radiation is internally reflected at the interface between a high-refractive index ATR crystal (usually Ge, ZnSe, Si, or diamond) and the sample, an evanescent wave penetrates inside the sample to a depth that depends on the wavelength, the refractive indices, and the incidence angle. Because the penetration depth is typically less than 2 pm, ATR provides surface specific information, which can be seen as an advantage or not if surface orientation differs from that of the bulk. It also allows one to study thick samples without preparation and can be used to characterize highly absorbing bands that are saturated in transmission measurements. 

Specular reflection IR spectroscopy has been used by Cole and coworkers to study the orientation and structure in PET films [36,37]. It has allowed characterizing directly very highly absorbing bands in thick samples, in particular the carbonyl band that can show saturation in transmission spectra for thickness as low as 2 pm. The orientation of different conformers could be determined independently. Specular reflection is normally limited to uniaxial samples because the near-normal incident light does not allow measuring Ay. However, it was shown that the orientation parameter along the ND can be indirectly determined for PET by using the ratio of specifically selected bands [38]. This approach was applied to the study of biaxially oriented PET bottles [39]. 

If we choose a much larger than 1 (thin samples d<0.5L) or h pL (thick samples d>>L), the final steady-state exhalation deviates very little from the free exhalation rate and we do not need to know the reshaping time or use Equation 2 for corrections. An air grab sample taken at any time (and corrected for radioactive decay if necessary) after closure, will yield the free exhalation rate to a good approximation, provided that the can is perfectly radon-tight. 

Let us again start from the 20 cm thick sample depicted in Figure 2. The best thing to do is to stay with this sample just as it is, i.e. as a non-leakage case, and then compare it with another... 

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