Signal/noise ratios

An improved signal/noise ratio because all signals are seen simultaneptisiy along with the instrument s own noise (called the multiplex or Fellgett advantage). 

The transducers discussed above were designed to propagate waves in both directions normal to the direction of the fingers. It has been shown [17] that they produce a roughly collimated beam so they can be used to inspect a band of structure whose width is the transducer finger length the maximum distance away from the transducer covered by the beam is dependent on the attenuation of the wave and the signal-noise ratio, but is typically around 1-2 m in a... 

The displacement of the spectral characteristics was 0.2 MHz, but the signal/noise ratio for the first case was 7 dB higher. 

In situ quantitation The fluorimetric analysis was made in UV light (2e,c = 313 nm, /-n > 460 nm FI 46 filter). The signal-noise ratio was better above 2 = 460 nm than when a FI 39 filter is employed. 

Figure 2.15. The limit of detection LOD the minimum signal/noise-ratio necessary according to two models (ordinate) is plotted against log 0(n) under the assumption of evenly spaced calibration points. The three sets of curves are for p = 0.1 (A), 0.05 (B), and 0.02 (C). The correct statistical theory is given by the fine points, while the model presented here is depicted with coarser dots. The widely used S/N = 3. .. 6 models would be represented by horizontals at y = 3. .. 6.

NMR measurements. All spectra were measured at 30 °C The spectra were taken using a Varian Unity Inova 400 spectrometer. Chemical shifts (8) are reported relative to internal TMS. 512 transients were accumulated to achieve the appropriate signal/noise ratio. 

Suppose one wanted to compare the behavior of two polymers and their blends. Let us define the signal as the difference between the logarithims of the viscoelastic quantities and the noise as the error calculated for a specific set of viscoelastic properties associated with a specific composition. The signal to noise ratio would have the appearance of the three curves shown in Figure 2 for a PMMA/Hytrel blend >3/1. Selection of the optimum conditions for comparison is apparent in that figure. Emphasis should be placed at those temperatures with high signal/noise ratios. 

Figure 2. Plot of the signal/noise ratio as defined in the text with temperature for a polyblend of PMMA and HYTRBL.

The solution CPPL spectrum of the polymer was also successfully obtained, using a home-constructed dynamic flow-through cell, so that multiple scans could be obtained to increase the signal/noise ratio. Ten scans were recorded and afforded a very similar, though noisier, CPPL profile to the aggregate case. 

Finally, we will discuss the determination of the limit of quantitation or LOQ. Establishing an LOQ is required for many pharmaceutical applications such as impurity testing and cleaning validation. Limit of quantitation is the lowest concentration (%, ppm) that can be determined with acceptable precision (RSD of —5%). It is generally accepted that a signal/noise ratio at the LOQ should be at least There are... 

The high degree of X-ray polarisation in the electron orbit plane provides means of controlling both the signal/noise ratio and the penetration of the X-rays into the specimen. Depending on whether the incidence plane is chosen vertically or horizontally, sigma or pi polarisation may be selected. The strain sensitivity and the extinction distance can thus be varied while the normal photoelectric absorption conditions remain identical. 

Mixture Compound m/z Number MS Signal/ Noise Thru Spin Column (Fig. 2.20 A) MS Signal/ Noise No Spin Column (Fig. 2.20 C) MS Signal/ Noise Ratio of Ratios (Fig. 2.20 A/C) Normalized Signal/Noise Ratio of Ratios ICso (nM)... 

The major assumption in the fitting procedure was that the basis spectra (i.e., spectra for individual molecular components) are independent of flow tube temperature. This approximation was tested by running mass spectra of stable molecules such as toluene and st3Tene over the full range of flow tube temperatures, and the peak ratios in these spectra change by no more than l%-2%. Based on this result and the signal-noise ratio in the experiments, the fitting uncertainty was estimated at about 5%. 

Method Signal a[polymer] Signal noise ratio Sensitivity to length Shear rate Native actin Expense Sample size (ml)... 

UV/VIS/NIR spectroscopy and ESR spectroscopy. The UV/VIS/NIR spectrum shows a sharp peak at 983 nm and a broad peak at 846 nm. These two absorbances are attributed to allowed NIR-transitions and these values are consistent with spectra of the cation obtained with other methods [2]. EPR spectroscopy of Cgg-cations, produced by different methods, leads to a broad distribution of measured g-values. These differences are caused by the short lifetime of the cation, the usually low signal-noise ratio and the uncertainty of the purity. The most reliable value imtil now is probably the one obtained by Reed and co-workers for the salt Cgg"(CBiiHgClg)-(g= 2.0022) [2,9] (see also Section 8.5). Ex situ ESR spectroscopy of above-mentioned bulk electrolysis solutions led to a g-value of2.0027 [8], which is very close to that of the salt, whereas the ESR spectra of this electro lyticaUy formed cation shows features not observed earlier. The observed splitting of the ESR signal at lower modulation amplitudes was assigned to a rhombic symmetry of the cation radical at lower temperatures (5-200 K). 

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