Preliminary screening

In the absence of factual corrosion information for a particular set of fluid conditions, a reasonably good selection would be possible from data based on the resistance of materials to a very simifar environment. These data, however, should be used with some reservations. Good practice calls for applying such data for preliminary screening. Materials selected thereby would reqmre further study in the fluid system under consideration. 

In order to address these challenges, a hierarchical approach may be adopted. This approach focuses on the big picture first, then adds details to promising solutions. Therefore, preliminary screening ought to be conducted first to identify overall reaction alternatives that meet process requirements in terms of desired product, cost effectiveness, environmental acceptability, and thermodynamic feasibility. At this stage, minimum details are to be invoked. The problem of synthesizing environmentally acceptable reactions EARs has been introduced by Crabtree and El-Halwagi (1994) and can be stated as follows ... 

Perform a preliminary screening analysis to identify aspects of human performance where failures can have serious consequences. 

Linearization. In preliminary screening of reaction mechanisms, it is very useful to construct plots of experimental data transformed in such a way that the plot of the dependent (transformed) variable versus the independent (transformed) variable is a straight line if the rate equation being the basis of transformation has been chosen properly. This is illustrated with the rate expression for a-th order kinetics ... 

Of course, class 4 is not valuable in medicinal chemistry. Such compounds have to be excluded from drug discovery processes as early as possible. At present, there are computer alert programs based on the Rule-of-5 or similar approaches that are used in preliminary screening to select and exclude compounds of class 4 [71]. Van de Waterbeemd indicated in 1998 that the four BCS classes of drugs can be determined solely by considering physicochemical descriptors such as molecular weight and PSA [72]. However, as mentioned in this chapter, those descriptors are too crude for the quantitative description of molecular size and H-bonding ability. 

Many inorganic oxides can be manufactured to provide granular, porous materials with high surface areas, which can readily adsorb organic liquids. Preliminary screening of a range of oxides, namely aluminium oxides, titanium dioxides, zinc oxide, hydrotalcites, zeolites and silicas, indicated that the latter two materials were able to retain the largest quantities of biocide. 

Rudd and Watson (1968) and Wells (1973) describe formal techniques for the preliminary screening of alternative designs. 

In the search for safe insecticides the authors have prepared hundreds of new products and subjected them to preliminary screening tests against insects. That part of their work dealing with methylenedioxyphenyl derivatives was prompted by the original fundamental studies of 0. F. Hedenburg, with whom they have collaborated in this field. Two materials of this type—piperonyl butoxide (I) and piperonyl cyclonene (II)—have recently been introduced commercially. These products have definite insecticidal properties in themselves, but show their maximum efficiency toward insects and other arthropods when used in combination with pyrethrins. Furthermore, they are at least as nontoxic... 

This preliminary screening gives the following activity order for hydrogenation of Q to DHQ, likely providing evidence for the capacity of the amine to inhibit deactivation by the intermediate(s) on the catalyst active sites ... 

The analysis methods are national in scope and address emissions from a wide variety of industrial and community source types. The materials reviewed are of widely disparate natures. They include metals, and bulk and trace hydrocarbons, including chlorinated and oxide derivatives of hydrocarbons. The analyses are intended to be preliminary screening analyses for use in scoping and prioritizing regulatory attention to toxic exposures from the chemicals studied. 

Spath, P. L. Dayton, D. C., Preliminary Screening—Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas. NREL/TP-510-34929 NREL, Golden, CO, 2003. 

FIG. 23 18 CCPS preliminary screening for chemical reactivity hazards. [From Johnson et al. (2003) copyright AIChE reproduced with permission. ]... 

Daichendt, M. M. and I. E. Grossmann. Preliminary Screening Procedure for the MINLP Synthesis of Process Systems II. Heat Exchanger Networks. Comput Chem Eng 18 679-710 (1994). 

Interfering ions are problematic when analyzing environmental samples, particularly soil and soil extracts. These samples may contain unknown combinations and concentrations of ions. For these reasons, ISEs are most useful in two situations. The first is where the soil composition is well known and routine repetitive analysis is to be made. The second is where a preliminary screening is to be done and followed by detailed laboratory analysis. In the latter case, potential interfering ions will be determined and the validity of the original screening assessed [7,8],... 

Chapter 3 is a Preliminary Screening Method designed to help identify whether chemical reactivity hazards are present at a facility. It can be used to determine whether the information in this publication is sufficient, or whether additional resources are going to be required, for managing identified chemical reactivity hazards. 

Chapter 5 works through some examples of how the Preliminary Screening Method might be used in various situations. 

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