Comparative threshold method

Final Quantitation of Real-Time PCR Results Two main approaches are commonly used to quantify the real-time RT-PCR results, the standard curve method and the comparative threshold method. 

Two methods are usually used for the evaluation of real-time PCR data, namely the standard curve method and the comparative threshold (Ct) method. The standard curve method relies on the use of purified cDNA pasmid standards, which will result in only a relative quantification. Other more specific standards can be used, e.g., in vitro transcribed RNA, which gives an absolute qantitation, however, this method is very labour intensive and not commonly used (Martell et al. 1999). The standard curve is included in each PCR run, and therefore provides a correction control for the PCR efficiency, making inter-assay comparisons easier. The comparative Ct method uses algorithms to calculate relative expression levels, compared to a calibrator (e.g., a control sample). A detailed description of the mathematics is given by Livak and Schmittgen (2001). After calculation the normalized expression... 

In the standard curve method, a reference curve is constructed from a nucleic acid of known concentration and this curve is used as a reference standard. The comparative threshold depends on measuring the cycle threshold (Ct). is the time at which fluorescence intensity is greater than background fluorescence. According to this method the Ct value of each samples is compared with a control or calibrator. 

Once the two algorithms have been selected, a measurement comparative is made by evaluating a reference piece (Fig. 1). The results obtained from the Canny method are compared with the obtained from the local thresholding method. 

Using the probable detection threshold achievable and a gas kick model applied to a typical 10,000-ft drill hole, an early alarm provided by MWD systems decreases significantly the amount of gas to be circulated as compared to using conventional methods of kick detection. 

This model tends to approach a zero probability rapidly at low doses (although it never reaches zero) and thus is compatible with the threshold hypothesis. Mantel and Bryan, in applying the model, recommend setting the slope parameter b equal to 1, since this appears to yield conservative results for most substances. Nevertheless, the slope of the fitted curve is extremely steep compared to other extrapolation methods, and it will generally yield lower risk estimates than any of the polynomial models as the dose approaches zero. 

Pantothenate in blood and tissues is bound (R9) and released by autolysis or hydrolysis. More vitamin could be released by use of an alkaline phosphatase and an enzyme from avian liver (L6). This method liberates pantothenate from coenzyme A in a variety of foods and tissues (N3, N4). A comparison of hydrolytic methods in blood suggested autolysis to be the most advantageous method (N3) in our hands, treatment with Clarase gave more reliable results as compared with autolysis, acid hydrolysis, treatment with Mylase P, or combination of Clarase and papain, or liver enzyme and alkaline phosphatase. In urine, pantothenic acid is unbound our results show no increase with Clarase treatment. The vitamin has presumably a low threshold. Pantothenic acid shows the same concentration in blood and cerebrospinal fluid. 

Figure 16 demonstrates the performance of a censored-CFAR detector with m=l. Compared with CA-CFAR the results here are better, because in all scenarios the targets are detected. But compared with OS-CFAR the threshold in the 2 target scenario is still too high in the neighborhood of the targets. Ritcey [29] studied the performance of this method for multiple target situations. 

In order to harmonize an odor measurement technique, national guidelines or recommendations from Germany, France, the Netherlands and the United Kingdom are compared with respect to selection and treatment of panelists. Different methods of mathematical treatment of threshold data are also presented. 

The Ministry of Housing, Physical Planning and Environment published a guideline for olfactometric measurements in 1983 (3). To obtain more comparable results threshold values have to be established with a method that conforms to the following conditions ... 

Only the VDI Richtlinie gives criteria from which it is possible to compare sensorical measurement methods with each other. Results taken from the VDI-ringtest are the base for this comparison. However some olfactometers in this ringtest did not conform to the VDI Richtlinie. Maybe because of this the range between the highest allowable threshold value for hydrogen sulfide and the lowest is great (namely from 0.4 to 8 um/m3 (factor 20)). 

The value applied to each mass is derived from the value of the associated residual. In a boolean framework, a threshold would be defined such that some values are declared as fault-free i.e., when the residual is lower than the threshold) and other ones as faulty i.e., when the residual is higher than the threshold). This method produces for each situation a vector of 0 and 1 that can be compared to the known signatures to isolate the fault. As already pointed out one main drawback is that if the value of the residual oscillates around the threshold, the state associated to the residual oscillates too. On the contrary, in the Evidence theory framework, an infinity of values are possible for each focal element. It is then possible to use smooth functions to produce a bba from the residual. For example, the following function has been proposed in [23] ... 

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