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When properly applied, ultraviolet detectors can serve as excellent fire detectors in munitions manufacturing. Detection times as fast as 10 milliseconds can be achieved while effectively resisting false alarms. 

Ion mobility spectrometry is the most commonly deployed method for ETD devices. Its advantages are compact size and relatively low price. For applications requiring a handheld detector, IMS is an excellent choice. For applications that are more stationary, other alternatives to IMS are often used. Mass spectrometry is recognized for its superior performance with regard to sensitivity and specificity, which translate to lower false-negative and false-positive rates. Active programs are now in place to develop routine MS technology for security applications in airports and other venues. 

Alexander von Humboldt stated in 1826 that platinum has not yet been discovered north of the isthmus of Panama on the North American continent. Platina in grains is found only in two places in the known world, that is to say, in Choco, a province in the kingdom of New Granada, and near the coasts of the Southern Sea in the province of Barbacoas between the second and sixth degrees of north latitude.. . . The placers which at present yield platina are located south of the threshold (umbral) which separates the headwaters of the Rio Atrato from those of the Rio San Juan.. .. It is absolutely false that platinum has ever been found near Cartagena, at Santa Fe de Bogota, on islands of Puerto Rico or the Barbadoes, or in Peru, even though these localities have been mentioned in excellent and well-known works. . " (109). 

In 1855, the moldable features of collodion were exploited by the British inventor and chemist Alexander Parkes, who marketed the material as Parkesine. Combs, earrings, buttons, bracelets, billiard balls, and even false teeth were manufactured in his factories. Parkes chose to focus more on quantity than on quality, however. Because he used low-grade cotton and cheap but unsuitable solvents, many of his products lacked durability, which led to commercial failure. In 1870, John Hyatt, a young inventor from Albany, New York, discovered that collodions moldable properties were vastly improved by using camphor as a solvent. Hyatts brother Isaiah named this camphor-based nitrocellulose material celluloid. Because of its greater workability, celluloid became the plastic of choice for the manufacture of many household items. In addition, thin transparent films of celluloid made excellent supports for photosensitive emulsions, a boon to the photography industry and a first step in the development of motion pictures. 

EXTENSIONS AND COMMENTARY Here is an excellent presentation of a report that shows false positives or maybe false negatives. Something at low levels. Nothing at higher levels. Always tend to trust the absence of an effect in preference to the presence of an effect, if one of the two observations is presumed to be in error. 

We successfully applied an AChE inhibition assay to the detection of dichlorvos in durum wheat samples using a simplified extraction procedure. The total assay time, including the extraction step, was 30 min. Considering that several extractions and assay steps can be run simultaneously, the throughput for one operator is 12 determinations per hour. It is also important to stress that the choline oxidase biosensor used in this work showed an excellent functioning stability after 20 days from preparation, the blank measurement lost only 10% of the signal intensity. The method allowed the accurate analysis of dichlorvos in wheat samples at the MRL, 2 mg/kg, and below that value. The mean recovery was 75%, and neither false nor positive samples were detected. Finally, the portable electrochemical instrumentation combined with the simple extraction procedure was quite well suited for in situ analysis of dichlorvos in durum wheat. 

Enzyme reactions are saddled with limited space-time yield. The notion that biocatalysts are slow catalysts is false. Slow catalysts, applied at low concentrations, certainly lead to low space-time yields. However, optimized syntheses not only produce very good selectivities or total turnover numbers but also satisfactory to excellent space-time yields. Examples with such good s.t.y. values are... 

As mentioned for the previous libraries, these varied responses (especially the increases in fluorescence) across the library help decrease the chances of false-positives for the individual analytes. Additionally, amino-functionalized TO is an excellent sensor for HStTf not only is the magnitude of the fluorescence increase quite large (72%), but it is the only anion that induces such an increase. The addition of AcO induces a quenching of 34%, while N03 and P PCV result in virtually no response. These results support those found for the previous cation systems, wherein making a library of fluorophores and binding groups results in a unique array of responses to the anions. 

It is important to note that P-gp inhibition by a compound for the efflux of any of these ligands does not directly correlate with the ability of P-gp to efflux the compound of interest (177). Such is the case with paclitaxel, which is considered to be an excellent P-gp substrate but a poor inhibitor as determined by the dye-efflux method. The converse is seen with progesterone, which is a good inhibitor of P-gp-mediated efflux and yet is a poor substrate. It is important to note that P-gp inhibition can occur in several ways—competitively, non-competitively, and via inhibition of ATP hydrolysis at the Walker A and B motifs (271). Furthermore, the false negatives due to poor permeability noted for transport assays can also produce false negatives in these interaction assays. 

The complementary rates are obtained from the opposite conditioning the fraction of model-predicted hits that are observed hits (A A) and the fraction of model-predicted inactives (I /) that are observed inactives. We call these the positive discovery rate and negative discovery rate . It is important to look at these conditional probabilities a very clear example is in the analysis of gene chip microarray data where the false discovery rate is 1 minus the positive discovery rate as defined above and in Chapter 6 an excellent discussion is given by Benjamini and Hochberg (1995). 

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