Search

The personalities of leaders have been shown to impact the culture of their organizations and are also expected to have a more distal impact on the firm's financial performance. However, the authors also expect that leader gender is an important intervening variable such that exhibiting various personality dimensions may result in unique cultural and performance-based outcomes for women and men leaders. Thus, the authors seek to examine first the impact of leader personality on organizational performance, as driven through organizational culture as a mediating mechanism. In doing so, the authors propose the expected impact of specific personality dimensions on certain types of organizational cultures, and those cultures' subsequent impact on the organization's performance. The authors then extend to consider the moderating effects of leader gender on the relationship between leader personality and organization. To support their propositions, the authors draw from upper echelons and implicit leadership theories. The authors encourage researchers to consider the proposition within a sample of the largest publicly traded US companies (i.e., Fortune 500) at an important era in history such that for the first time, 10% of these companies are led by women. In doing so, the authors hope to understand the leadership dynamics at the highest echelons of corporate governance and provide actionable insights for companies aiming to optimize their leadership composition and drive sustainable performance. [ABSTRACT FROM AUTHOR]

The purpose of this article is to conceptualize a novel theoretical occurrence—team physical activity (PA)—and its relevance for researchers and organizations. By building a testable model of the consequences and contingencies of team PA, we integrate the science of teamwork with the scholarly domain of employee health and well-being. Hence, we clarify the construct of team PA, present a three-dimensional typology, and outline a model drawing on neuroscience, positive organizational behavior, and teams research. Our propositions and subsequent discussion proffer an outline of potential benefits for organizations when they increase the utility and frequency of team PA. We also suggest ways in which researchers can advance scholarship in this area. [ABSTRACT FROM AUTHOR]

We have developed a new imaging method for scanning electrochemical microscopy (SECM) employing fast-scan anodic stripping voltammetry (ASV) to provide sensitive and selective imaging of multiple chemical species at interfaces immersed in solution. A rapid cyclic voltammetry scan (100 V/s) is used along with a short preconcentration time (300-750 ms) to allow images to be acquired in a normal SECM time frame. A Hg-Pt film electrode is developed having an equivalent Hg thickness of 40 nm that has good sensitivity at short preconcentration times and also retains thin-film behavior with high-speed voltammetric stripping. Fast-scan anodic stripping currents are shown to be linear for 1-100 [micro]M of [Pb.sup.2+] and [Cd.sup.2+] solutions using a preconcentration time of 300 ms. SECM images showing the presence of [Pb.sup.2+] and [Cd.sup.2+] at concentrations as low as 1 [micro]M are presented. In addition, a single ASV-SECM image is shown to produce unique concentration maps indicating [Cd.sup.2+] and [Pb.sup.2+], generated in situ from a corroding sample, while simultaneously detecting the depletion of [O.sub.2] at this sample. The transient voltammetric response at the film electrode is simulated and shows good agreement with the experimental behavior. We discuss the behavior of images and concentration profiles obtained with different imaging conditions and show that mass-transport limitations in the tip-substrate gap can induce dissolution. ASV-SECM can thus be used to detect and study induced dissolution not only at bulk metal surfaces but also on underpotential deposition layers, in this case Cd and Pb on Pt. In addition, we discuss how surface diffusion phenomena may relate to the observed ASV-SECM behavior.

Fast-scan cyclic voltammetry (FSCV) is applied to the tip of a scanning electrochemical microscope (SECM) for imaging the distribution of chemical species near a substrate. This approach was used to image the diffusion layer of both a large substrate electrode (3-mm-diameter glassy carbon) and a microelectrode substrate (10-[micro]m-diameter Pt). Additionally, oxygen depletion near living cells was measured and correlated to respiratory activity. Finally, oxygen and hydrogen peroxide were simultaneously detected during the oxidative burst of a zymosan-stimulated macrophage cell. These results demonstrate the utility of FSCV-SECM for chemical imaging when conditions are chosen such that feedback interactions with the substrate are minimal.

Fast-scan cyclic voltammetry at scan rates between 5 and 1000 V [s.sup.-1] was performed at the tip of a scanning electrochemical microscope immersed in a solution of redox mediator. The effect of conducting and insulating substrates on the voltammetric signal was investigated as a function of scan rate and tip--substrate distance. It was found that diffusional interactions between the tip and the substrate are greatest at lower scan rates and on the reverse sweep of the voltammogram. At the fastest scan rates used, the tip could be brought to with 1 [micro]m of the substrate without appreciable perturbation of the voltammogram. By selecting scan rates and tip--substrate distances such that feedback effects were negligible, it was possible to image the diffusion layer of a 10 [micro]m Pt substrate electrode. With the tip placed 1 [micro]m above a biological cell, tip--substrate diffusional interactions were greatly diminished at a scan rate of 100 V [s.sup.-1] and absent at a scan rate of 1000 V [s.sup.-1]. These results suggest conditions can be selected that allow chemical imaging of substrates without the feedback interactions typically encountered in scanning electrochemical microscopy.

Undifferentiated and differentiated PC12 cells were imaged with the constant-distance mode of scanning electrochemical microscopy (SECM) using carbon ring and carbon fiber tips. Two types of feedback signals were used for distance control: the electrolysis current of a mediator (constant-current mode) and the impedance measured by the SECM tip (constant-impedance mode). The highest resolution was achieved using carbon ring electrodes with the constant-current mode. However, the constant-impedance mode has the important advantages that topography and faradaic current can be measured simultaneously, and because no mediator is required, the imaging can take place directly in the cell growth media. It was found that vesicular release events do not measurably alter the impedance, but the depolarizing solution, 105 mM [K.sup.+], produces a dramatic impedance change such that constant-distance imaging cannot be performed during application of the stimulus. However, by operating the tip in the constant-height mode, cell morphology (via a change in impedance) and vesicular release could be detected simultaneously while moving the tip across the cell. This work represents a significant improvement over previous SECM imaging of model neurons, and it demonstrates that the combination of amperometry and constant-impedance SECM has the potential to be a powerful tool for investigating the spatial distribution of neurotransmitter release in vitro.

Living PC12 cells, a model cell type for studying neuronal function, were imaged using the negative feedback mode of a scanning electrochemical microscope (SECM). Six biocompatible redox mediators were successfully identified from a large pool of candidates and were then used for imaging PC12 cells before and after exposure to nerve growth factor (NGF). When exposed to NGF, cells differentiate into a neuron phenotype by growing narrow neurites (1-2 [micro]m wide) that can extend > 100 [micro]m from the cell proper. We demonstrate that carbon fiber electrodes with reduced tip diameters can be used for imaging both the cell proper and these neurites. Regions of decreased current, possibly resulting from raised features not identifiable by light microscopy, are clearly evident in the SECM images. Changes in the morphology of undifferentiated PC12 cells could be detected in real time with the SECM. After exposure to hypotonic and hypertonic solutions, reversible changes in cell height of

Fast-scan cyclic voltammetry at carbon fiber microelectrodes is used to detect the cyclic nitroxide 2,2,6,6-tetramethylpiperidinyl-1-oxy free radical (TEMPO) and three analogs. The electrochemical behavior of the TEMPO analogs at unmodified carbon fiber electrodes is found to differ greatly from their behavior at glassy carbon electrodes. After the electrode is coated with the polymer Nafion, the electrodes exhibit increased sensitivity to TEMPO and 4-amino-TEMPO. Voltammograms of the nitroxides at Nation-coated electrodes indicate that the oxidized form (oxoammonium ion) and the free radical form have greatly different mobilities through the polymeric coating. Response times to changes in nitroxide concentration vary from subsecond at bare electrodes (all four analogs) and 4-hydroxy-TEMPO at modified electrodes to 1-3 s for TEMPO and 4-amino-TEMPO at modified electrodes. The detection limit for 4-amino-TEMPO is 50 [[micro]molar] at an unmodified electrode and 5 [[micro]molar] at a Nation-coated carbon fiber electrode. The sensitivity of the Nation-modified electrode to TEMPO, 4-hydroxy-TEMPO, and 4-amino-TEMPO can be improved by choosing a resting potential at which the oxoammonium ion form of the nitroxide is preconcentrated into the Nation film. Using fast-scan cyclic voltammetry and the modified carbon fiber electrodes, the reaction of two nitroxide free radicals with ascorbate can be monitored. This work shows that fast-scan voltammetry at microelectrodes is a sensitive method that can be used to follow reactions of cyclic nitroxide free radicals in solution.