Several different types of equivalent circuits for the faradaic electrode process involving n state variables besides electrode potential are established in terms of the corresponding faradaic admittance equation in the case of ignoring mass transport. These circuits can develop into general equivalent circuits by introducing negative resistive and inductive and capacitive elements, each of which can be used to analyze any electrochemical impedance spectroscopy of the faradaic electrode process under electrochemical reaction control. The correspondence between element values of the circuits and electrochemical parameters of the faradaic admittance equation has also been determined by comparing the admittance or impedance of the equivalent circuit and the faradaic admittance or impedance equation. The use of general equivalent circuits, together with the faradaic admittance equation, greatly simplifies the analysis of electrochemical impedance spectroscopy for the faradaic electrode processes. © 1999 The Electrochemical Society. All rights reserved.

The tumour suppressor gene PTEN, located at chromosome sub-band 10q23.3, encodes a dual-specificity phosphatase that negatively regulates the phosphatidylinositol 3 0 -kinase (PI3 K)/Akt-dependent cellular survival pathway. PTEN is frequently inactivated in many tumour types including glioblastoma, prostate and endometrial cancers. While initial studies reported that PTEN gene mutations were rare in colorectal cancer, more recent reports have shown an approximate 18% incidence of somatic PTEN mutations in colorectal tumours exhibiting microsatellite instability (MSI þ ). To verify the role of this gene in colorectal tumorigenesis, we analysed paired normal and tumour DNA from 41 unselected primary sporadic colorectal cancers for PTEN inactivation by mutation and/or allelic loss. We now report PTEN gene mutations in 19.5% (8/41) of tumours and allele loss, including all or part of the PTEN gene, in a further 17% (7/41) of the cases. Both PTEN alleles were affected in over half (9/15) of these cases showing PTEN genetic abnormalities. Using immunohistochemistry, we have further shown that all tumours harbouring PTEN alterations have either reduced or absent PTEN expression and this correlated strongly with later clinical stage of tumour at presentation (P ¼ 0.02). In contrast to previous reports, all but one of the tumours with PTEN gene mutations were microsatellite stable (MSIÀ), suggesting that PTEN is involved in a distinct pathway of colorectal tumorigenesis that is separate from the pathway of mismatch repair deficiency. This work therefore establishes the importance of PTEN in primary sporadic colorectal cancer.

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A series of side-chain polysiloxane liquid crystalline elastomers, E-Cm (where m is the number of carbon atoms in the interim alkyl groups, and m = 4, 6, 8, 10), with binaphthalene derivatives as crosslinkings, were designed and synthesized. The mesophase structures of these elastomers were dependent on the value of m. The elastomers with m ≤ 8 could form cholesteric (Ch) phases, while both smectic A and Ch phases could be formed for the elastomer with m = 10. Blue phases can be achieved when m ≥ 8. Besides, the helical twisting power (HTP) of all the elastomers exhibits a turning point with changing temperature. Both the turning temperature and HTP have an apparent dependence on the value of m. By adjusting the interim alkyl chain length in the elastomers, both visible and near-infrared light wide-band reflective films can be obtained. The broadband reflection mechanism was confirmed by SEM investigations.