The literature on corporate elites has paid significant attention to the leadership structure at the very top of organizations (for example, the consolidation vs. separation of the chief executive officer (CEO) and board chair positions-for a review, see Daily and Dalton, 1997). This is because corporate elites in different governance positions may have different interests, which means that the leadership structure at the top can influence organizational outcomes (Jensen and Zajac, 2004). Recently, there is an emerging research stream that specifically focuses on an important structure at the top: the presence of a chief operating officer (COO)/president who is separate from a CEO, and examines the performance consequences (accounting performance and stock market reactions) of this structure and the tenure outcomes of the Keywords: presence of a separate COO/president; CEO dismissal; strategic change *Correspondence to: Yan Zhang, Jesse H. Jones Graduate School of Management, Rice University, 6100 Main Street, Houston, TX 77005, U.S.A. E-mail: yanzh@rice.edu COO/president (e.g., Cannella and Shen, 2001;Davidson, Nemec, and Worrell, 2001;Hambrick and Cannella, 2004;Heenan and Bennis, 1999;Levinson, 1993;Shen and Cannella, 2003).There can be two separate roles of a COO/president: one representing an heir apparent in training for the CEO position and the other representing a co-leader delegated with internal operating authority. From a co-leader perspective, Hambrick and Cannella (2004: 959) argued that 'the decision to have a COO represents a major structural choice: it explicitly divides between two people a set of toplevel roles that are typically fulfilled by one person; it draws a structural distinction between strategy formulation and implementation; it adds an organizational layer; and it adds a highly-paid executive position to the organization's costs.' From a succession (heir apparent) perspective, Vancil (1987) found that many firms identified an heir apparent in the COO and/or president position in advance of the actual succession event and used this position to groom the next CEO. Findings of

As the concentration of different biomarkers in human body fluids are an important parameter of chronic disease, wearable biosensors for in situ analysis of body fluids with high sensitivity, real-time detection, flexibility and biocompatibility have significant potential therapeutic applications. In this paper, a flexible self-powered implantable electronic-skin (e-skin) for in situ body fluids analysis (urea/uric-acid) as a real-time kidney-disease diagnoser has been proposed based on the piezo-enzymatic-reaction coupling process of ZnO nanowire arrays. It can convert the mechanical energy of body movements into a piezoelectric impulse, and the outputting piezoelectric signal contains the urea/uric-acid concentration information in body fluids. This piezoelectric-biosensing process does not need an external electricity supply or battery. The e-skin was implanted under the abdominal skin of a mouse and provided in situ analysis of the kidney-disease parameters. These results provide a new approach for developing a self-powered in situ body fluids-analysis technique for chronic-disease diagnosis.

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A new self-powered flexible vision e-skin has been realized from a pixel-addressable matrix of piezophototronic ZnO nanowire arrays.