Enrichment metrics

Enrichment metrics are frequently derived from ttvo basic values, the sensitivity (Se) and the specificity (Sp). Se or true positive rate is the ratio of the number of selected active molecules and the number of all biological active database molecules (5.1) [9, 65]. 

Sp or false positive rate describes the ability of a pharmacophore model to discard inactive compounds. It is defined as the ratio of inactive molecules not selected by the model and all inactive molecules (5.2) [65]. 

An outline of well-known enrichment metrics is provided in Table 5.1. 

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Table 5.1 Definitions of several well-known enrichment metrics.

To sum up, a variety of enrichment metrics for evaluating VS methods are available. Among these enrichment metrics, the EF and the AUC value, as well as visualizations of ROC curves, represent popular methods for assessing the enrichment of active molecules by pharmacophore models [83-85]. The two disadvantages of many of these enrichment metrics are the lack of information about early enrichment of active molecules and the missing comparability between validation... 

An agreement between the United States and Russia led to a commitment in 1994 by the United States to buy 500 metric tons of Russian HEU, which has been converted to low enriched uranium (LEU). The HEU must come from dismanded nuclear weapons before it is converted to LEU. The sale of converted HEU to the United States is to be carried out on a timetable in which no less than 10 t are to be converted in each of the first five years of the agreement and no less than 30 t in each year thereafter (35). In all, the agreement would last for 20 years if only these minimums were sold each year. 

Total reserves of thorium at commercial price in 1995 was estimated to be >2 x 10 metric tons of Th02 (H)- Thorium is a potential fuel for nuclear power reactors. It has a 3—4 times higher natural abundance than U and the separation of the product from Th is both technically easier and less expensive than the enrichment of in However, side-reaction products, such as and the intense a- and y-active decay products lead to a high... 

J. Slobodnik, A. J. H. Router, J. J. Vreuls, I. Eiska and U. A. Th Brinkman, Monitoring of organic micropollutants in surface water by automated on-line trace-enrichment liquid and gas cliromatographic systems with ultraviolet diode-array and mass spectro-metric detection , J. Chromatogr. 768 239-258 (1997). 

The process has been used in the USA for 25 years, but a large extrapolation of experience was necessary to reach the scale of operation needed for the Canadian nuclear industry. A typical Canadian enriching unit has a nominal capacity of 50 kg D20/h. However, with an overall extraction of about 20% of the deuterium in the feedwater, the total feed rate is about 0.5 metric tons per second. Three large towers are used in parallel. (Table II)... 

The metric geometry of equilibrium thermodynamics provides an unusual prototype in the rich spectrum of possibilities of differential geometry. Just as Einstein s general relativistic theory of gravitation enriched the classical Riemann theory of curved spaces, so does its thermodynamic manifestation suggest further extensions of powerful Riemannian concepts. Theorems and tools of the differential geometer may be sharpened or extended by application to the unique Riemannian features of equilibrium chemical and phase thermodynamics. 

As stated previously for the topological CATS descriptor [31], the influence of different similarity metrics on the overall enrichment is marginal. For the full... 

Each of these metrics gives a different insight into the performance of a screening workflow in retrieving active molecules or discarding inactive ones. Jacobsson et al, for example, used accuracy, sensitivity (which they termed the recall ), yield of actives (termed precision of the active class ) and enrichment to characterize the performance of different structure-based virtual screening workflows [60]. 

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