Sample transparency error

Instrumental and sample parameters error in the wavelength, sample transparency, etc. 

Using all Bragg peaks which have been indexed and the associated observed Bragg angles, more accurate unit cell dimensions and, if applicable, systematic experimental errors, e.g. sample displacement, sample transparency, or zero shift, which are described in section 2.8.2, Chapter 2, should be refined by means of a least squares technique (see section 5.13, below). 

The specimen displacement parameter usually varies from sample to sample and it usually takes up some of the effects of sample transparency. For a properly aligned goniometer, the zero shift error should be negligible. Even if the goniometer is misaligned, the zero shift correction should remain sample independent. 

The calibration curve is used to correct 20-values of a sample that was measured under the same conditions as the standard (external standard). Some errors, especially the sample position and the transparency error, differ from... 

Samples of the 1,4-dihydrobenzoic acid, after both the first and the second distillations, are transparent in the ultraviolet region between 220 mu and 300 m/i, indicating the absence of benzoic acid or conjugated dihydrobenzoic acids. The refractive index cited in Reference 3 is in error. 

Technically, the heterogeneity of skin and the presence of refractive index gradients likely impose some constraints to the accurate determination of imaging parameters. However, uncertainties in the determination of spatial resolution and axial location in transparent samples from which spectra are extracted, such as those described by Everall [21-23] and others [24, 25], are probably not important for highly opaque skin samples. We estimate the axial resolution to be 2-3 pm with the 785 nm excitation wavelength used in the current measurements. A study from this lab has suggested that errors in depth measurements are less than 15% which is probably adequate for most current purposes. 

Prism A transparent, prism-shaped solid that disperses polychromatic radiation into its component wavelengths by refraction. Proportional error An en or whose magnitude increases as the sample size increases. 

To measure the Seebeck coefficient a, heat was applied to the sample which was placed between the two Cu discs. The thermoelectric electromotive force (E) was measured upon applying small temperature difference (JT <2 E) between the both ends of the sample. The Seebeck coefficient a of the compound was determined from the E/JT. The electrical resistivity p of the compound was measured by the four-probe technique. The repeat measurement was made rapidly with a duration smaller than one second to prevent errors due to the Peltier effect [3]. The thermal conductivity k was measured by the static comparative method [3] using a transparent Si02 ( k =1.36 W/Km at room temperature) as a standard sample in 5x10 torr. 

Transparent sample This is essentially the same as the method described previously in Sec. 10.4.2 for thin-film analysis. Note from Fig. 10.4 that this method is the least sensitive to intensity errors. 

Figure 3. Changes in the normalized intensity of bands in the Raman spectra of 15% a-lactalbumin in deuterium oxide containing 20 mM NaCl (pD pp = 6.8) upon formation of transparent gels as a function of heating time at 90°C. The bands are assigned to vibrational motions of amino acid side chains as follows (a) 508 cm (S-S) (b) 760 cm band (tryptophan) (c) 850 cm /830 cm doublet (tyrosine). Error bars represent the standard deviation for three replicate samples, with 8 spectral scans averaged per replicate. (Adapted from Nonaka et al, 1993).

For corrections of instrument-related errors, an internal standard reference material such as silicon and LaB6 should be used. The development of parallel beam geometry, not only for synchrotron sources but also for laboratory X-ray sources, eliminates the effects of transparency, flat specimens, and displacement errors. On the other hand, the internal standard material is applicable for quantitative analysis of coexisting material in the sample by means of multiphase analysis by the Rietveld method. 

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