Using regions-of-interest

In most spectrum analysis, an active peak search will be involved. Although the energy calibration procedure for an MCA emulator usually requires the operator to set up ROIs about the reference peaks, even then an active search will be performed within these regions to determine the exact peak position. 

The correlation method is quite general and need not use a Gaussian search function, although that does have 

Oxford Instruments described the search algorithm used in GammaTrac (no longer available) as a correlation method using a zero-area correlation function instead of a Gaussian search function. There are practical advantages to 

Whichever method is used to locate the peaks, the magnitude of the peak search function will be compared with some parameter related to a user set sensitivity value. Unless the function exceeds this value, a peak will not be detected. The sensitivity parameter might be related to peak area uncertainty - peaks with an uncertainty greater than the threshold being rejected, or some sort of empirical threshold factor might be used. 

The system can then search for the required peaks, find their centroids and fit an appropriate function to the pairs of position/energy data. In most cases, the choice of appropriate function will be determined by the system itself. A hardwired analyser is unlikely to allow more than a two point calibration. Even in an MCA emulator system such as Maestro-II, users are limited to a two point linear calibration. Using the companion full spectrum analysis program, GammaVision, this initial calibration can be replaced by a multi-point calibration fitted to a quadratic equation  

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Fig. 9.6). Quantification of the PET data, by using region-of-interest analysis and the construction of Patlak plots (26), however, can reveal significant differences between patient groups. Figure 9.7 shows an example of Patlak plots from a healthy subject and a patient with COPD. 

The solvent chosen must dissolve the sample, yet be relatively transparent in the spectral region of interest. In order to avoid poor resolution and difficulties in spectrum interpretation, a solvent should not be employed for measurements that are near the wavelength of or are shorter than the wavelength of its ultraviolet cutoff, that is, the wavelength at which absorbance for the solvent alone approaches one absorbance unit. Ultraviolet cutoffs for solvents commonly used are given in Table 7.10. 

The attenuated total reflectance (ATR) technique is used commonly in the near-infrared for obtaining absorption spectra of thin Aims and opaque materials. The sample, of refractive index i, is placed in direct contact with a material which is transparent in the region of interest, such as thallium bromide/thallium iodide (known as KRS-5), silver chloride or germanium, of relatively high refractive index so that Then, as Figure 3.f8... 

The most useful mathematical formulation of a fluid flow problem is as a boundary value problem. This consists of two main parts a set of differential equations to be satisfied within a region of interest and a set of boundary conditions to be satisfied on the surfaces of that region. Sometimes additional conditions are also of interest, eg, when one is investigating the stability of a flow. 

The foregoing approaches used an umbrella potential to restrain q. The pmf W(q) can also be obtained from simulations where q is constrained to a series of values spanning the region of interest [48,49]. However, the introduction of rigid constraints complicates the theory considerably. Space limitations allow only a brief discussion here for details, see Refs. 8 and 50-52. 

The results shown in Figure 6 above are an example of this mode of analysis, but include additional information on the chemical states of the Si. The third most frequently used mode of analysis is the Auger mapping mode, in which an Auger peak of a particular element is monitored while the primary electron beam is raster scanned over an area. This mode determines the spatial distribution, across the surface, of the element of interest, rather than in depth, as depth profiling does. Of course, the second and third modes can be combined to produce a three-dimensional spatial distribution of the element. The fourth operational mode is just a subset of the third mode a line scan of the primary beam is done across a region of interest, instead of rastering over an area. 

The main region of interest for analytical purposes is from 2.5 to 25 fim (micrometres), i.e. 4000 to 400 wavenumbers (waves per centimetre, cm-1). Normal optical materials such as glass or quartz absorb strongly in the infrared, so instruments for carrying our measurements in this region differ from those used for the electronic (visible/ultraviolet) region. 

Turbulent inlet conditions for LES are difficult to obtain since a time-resolved flow description is required. The best solution is to use periodic boundary conditions when it is possible. For the remaining cases, there are algorithms for simulation of turbulent eddies that fit the theoretical turbulent energy distribution. These simulated eddies are not a solution of the Navier-Stokes equations, and the inlet boundary must be located outside the region of interest to allow the flow to adjust to the correct physical properties. 

Therefore, it appears that the overall agreement obtained for a variety of spectroseopie eonstants is comparable for the two methods while the present method allows us to use a more compact wavefunction. It should also be noted that a good Cl description of a triple bonded system involving a third period atom is much harder to achieve. It can be concluded that the shape of the theoretical potential energy curve reflects its experimental counterpart with acceptable accuracy in the interatomic region of interest. 

A basic method of image analysis is the use of regions of interest (ROI). These ROI can have very simple shapes such as circles or rectangles, but can also have very... 

The use of conventional electrochemical methods to study the effect of metal adatoms on the electrochemical oxidation of an organic adsorbate may be in some cases of limited value. Very often, in the potential region of interest the current due to the oxidation of an organic residue is masked by faradaic or capacitive responses of the cocatalyst itself. The use of on-line mass spectroscopy overcomes this problem by allowing the observation of the mass signal-potential response for the C02 produced during the oxidation of the adsorbed organic residue. 

Optical microscopy is often coupled with infra-red spectroscopy. We use the optical portion of the instrument to identify regions of interest, onto which we direct a highly focused infra-red beam. We obtain an infra-red spectrum from the radiation that penetrates the sample. The region of interest may be as small as 250 pm (250 x iff"6 m) In diameter. We can compare the spectrum with a library of reference samples in order to identify the chemical structure of the area of interest. Polymer scientists make extensive use of this technique when examining multi-layer samples or when performing contaminant analyses. 

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