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The existence of both right-half-plane poles and time delay makes it difficult to obtain a higher control quality. Recently, a modified Smith predictor for unstable processes with time delay was presented and good performance was obtained. In this paper, the modified Smith predictor is discussed. A modified structure is presented. The new one not only is simple for analysis and design but also avoids the improper element. Instead of introduction of an inner loop, a direct design procedure is given and analytical formulas for the controllers are provided. The time domain performance for both trajectory and regulatory responses is obtained quantitatively. Sufficient and necessary conditions for robust stability are also given. The new structure and design method can also be used for the control of integrating processes with time delay and stable processes with time delay. Numerical examples are provided to illustrate the proposed method.

Doublet mutations in cancer are not well studied. We find that allelic somatic doublet mutations are present at high frequency in the epidermal growth factor receptor (EGFR) tyrosine kinase (TK) domain in lung cancers. When doublets from the literature are added, a total of 96 doublets are available for analysis. The frequency of doublets overall is 6%, which is sevenfold greater than that observed in normal tissue in mouse. All characterized doublets are allelic, and silent mutations occur rarely. About half of all doublets contain one or two of 12 distinct missense mutations at five amino acids: E709, G719, S768, T790 and L861. The mutations at these five amino acids are seldom reported as singlets. Moreover, when the common L858 target is included, more than one-third of EGFR doublets are one of five specific missense pairs: G719/E709, G719/S768, G719/L861, L858/E709 and L858/T790. Structure suggests function: The data imply that most EGFR doublets are NOT consistent with a 'driver and passenger' mutation mechanism. EGFR doublets are highly skewed relative to singlets, consistent with functional selection of two individually suboptimal mutations that, in combination, have enhanced oncogenic potential.

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