Morris Screening Method

Using the Morris method, a series of parameter sets are generated so that the next parameter set differs from the previous one in the value of a single parameter only, which is randomly chosen. The value of each parameter Xj is modified within the range by a fixed amount A that is determined in the following way. A 

Measure djj shows the effect of changing parameter Xj on model result T, at arbitrary values of all other parameters  

2 Global Uncertainty Analysis Using Sampling-Based Methods 

In Latin hypercube sampling, for a two-parameter space a square grid (Latin square) is used, which contains only one sample for each column and each row (McKay et al. 2000). In the w-parameter case, an w-dimensional hypercube is used instead of a square. The pdf of each parameter is divided into n strata, each representing equal probability. In the case of a pdf belonging to a uniform 

A possible alternative is the use of low-discrepancy sequences. The discrepancy is a measure of the uniformity of a sequence, i.e. high uniformity equals low discrepancy. It is usually computed by comparing the actual number of sample points in a given volume of a multidimensional space compared with the number of sample points that should be there assuming a uniform distribution (Morokoff and Caflisch 1995). Successive sample points are added to positions as far away as possible from existing sample points so that clustering can be avoided. The best known low-discrepancy sequences include those of Halton (1960), Fame (1992), Sobol (1967) and Niederreiter (1988). 

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Morris ND, Mallouk TE. 2002. A high-throughput optical screening method for the optimization of colloidal water oxidation catalysts. J Am Chem Soc 124 111 14-11121. 

Local sensitivity analysis is of limited value when the chemical system is non-linear. In this case global methods, which vary the parameters over the range of their possible values, are preferable. Two global uncertainty methods have been used in this work, a screening method, the so-called Morris One-At-A-Time (MOAT) analysis and a Monte Carlo analysis with Latin Hypercube Sampling (Saltelli et al., 2000 Zador et al., submitted, 20041). The analyses were performed by varying rate parameters, branching ratios and constrained concentrations within their uncertainty interval,... 

An improvement in the efficiency of photochemical splitting of water was the incentive for Morris [49]. A parallel optical screening method was developed to select photocatalytically active catalysts by their adsorption spectra (UV and visible light). 

The standard RS-HDMR approach was extended by an optimisation method (Ziehn and Tomlin 2008a), which automatically chooses the best polynomial order for the approximation of each of the component functions. Component functirms can also be excluded from the HDMR expansirm if they do not make a significant contribution to the modelled output value via the use of a threshold (Ziehn and Tomlin 2008b, 2009). The aim is to reduce the number of comprment functions to be approximated by polymomials and therefore to achieve automatic complexity reduction without the use of prior screening methods such as the Morris method (Morris 2006). For a second-order HDMR expansirm, a separate threshold can be defined for the exclusion of the first- and second-order component functirms. 

Morris, M.D. (1987). Two-stage factor screening procedures using multiple grouping assignments. Communications in Statistics—Theory and Methods, 16, 3051-3067. 

Uranium content in soft tissue and bone could also be used as biomarkers of exposure to uranium since uranium also distributes to these tissues and other organs (Ballou et al. 1986 Diamond et al. 1989 Leach et al. 1973,1984 Morris et al. 1990 Morrow et al. 1972 Stokinger et al. 1953 Walinder 1989 Wrenn et al. 1987). Although soft tissues and bone are the most frequently analyzed biological media after urine and feces, these tissues are usually available for analysis only at autopsy. Therefore, this method is impractical and not used for routine screening purposes. 

Based on these electrochemical studies we developed a method for the quantitation of ajmalicine and catharanthine in cell cultures. These alkaloids were extracted from freeze-dried cells and purified by the solid-phase procedure described by Morris et al. (1985), except that ethanol was used as the extracting solvent instead of methanol. A dual-electrode coulometric cell was used in the screen mode. The potential of the first electode was set at +0.2 V (vs. Pd), which was at the base of catharanthine s voltammogram. The alkaloids were detected by the second electrode at +0.8 V, as this offered the best S/N ratio. Higher potentials led to lower S/N ratio, since the background current and noise started to increase exponentially above +0.85 V, due to the oxidation of water. The mobile phase was purified by a guard cell between the pump and injector. The guard cell operated at +0.8V. 

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