Optimality conditions for the calculus of variations with higher-order delta derivatives

We prove the Euler-Lagrange delta-differential equations for problems of the calculus of variations on arbitrary time scales with delta-integral functionals depending on higher-order delta derivatives.Comment: Submitted 26/Jul/2009; Revised 04/Aug/2010; Accepted 09/Aug/2010; for publication in "Applied Mathematics Letters

Temperature effect on (2+1) experimental Kardar-Parisi-Zhang growth

We report on the effect of substrate temperature (T) on both local structure and long-wavelength fluctuations of polycrystalline CdTe thin films deposited on Si(001). A strong T-dependent mound evolution is observed and explained in terms of the energy barrier to inter-grain diffusion at grain boundaries, as corroborated by Monte Carlo simulations. This leads to transitions from uncorrelated growth to a crossover from random-to-correlated growth and transient anomalous scaling as T increases. Due to these finite-time effects, we were not able to determine the universality class of the system through the critical exponents. Nevertheless, we demonstrate that this can be circumvented by analyzing height, roughness and maximal height distributions, which allow us to prove that CdTe grows asymptotically according to the Kardar-Parisi-Zhang (KPZ) equation in a broad range of T. More important, one finds positive (negative) velocity excess in the growth at low (high) T, indicating that it is possible to control the KPZ non-linearity by adjusting the temperature.Comment: 6 pages, 5 figure

Understanding the Relationship between Founder-CEOs and Firm Performance

While previous empirical literature has examined the effect of founder-CEOs on firm perfor- mance, it has largely ignored the effect of firm performance on founder-CEO status. In this paper, we use instrumental variables methods to better understand the relationship between founder-CEOs and performance. Using the proportion of the firm’s founders that are dead and the number of people who founded the company as instruments for founder-CEO status, we Þnd strong evidence that founder-CEO status is endogenous in performance regressions. This implies that the direct effect of founder-CEOs on firm performance cannot be esti- mated correctly without accounting for the endogeneity of founder-CEO status. Perhaps surprisingly, we Þnd that performance is negatively related to the likelihood that founders retain the CEO title. This result appears to be driven primarily by founder departures after periods of good performance, rather than by an entrenchment effect that allows founders to remain as CEOs following poor performance. After factoring out the effect of performance on founder-CEO status, we find a residual positive correlation between founder-CEO status and firm performance. This finding suggests that there is a positive causal link from founder-CEOs to firm performance

Fallible Executives, Centralization of Decision-Making and Corporate Performance

In this paper we explore some possible consequences of fallibility in managerial decision making for firm performance. Based on Sah and Stiglitz (1991), we develop the hypothesis that if managers are fallible, firm performance will be more variable as the number of managers participating in decision-making decreases, i.e. as the firm becomes more centralized. We use characteristics of the Executive Office to develop a proxy for the number of executives participating in top decision-making. For example, we argue that if the Chairman of the Board is not the CEO, decision-making in the firm will be more decentralized because the Chairman will also participate in decision-making. We test our hypothesis using this proxy (which we call the centralization index), and find that the evidence is consistent with our hypothesis. Firm performance (measured by Tobin s Q, stock returns and ROA) is significantly more variable for firms with greater values of our centralization index. The results are consistent across various tests designed to detect differences in variability

FALLIBLE EXECUTIVES, CENTRALIZATION OF DECISION-MAKING AND CORPORATE PERFORMANCE

In this paper we explore some possible consequences of fallibility in managerial decisionmaking for firm performance. Based on Sah and Stiglitz (1991), we develop the hypothesis that if managers are fallible, firm performance will be more variable as the number of managers participating in decision-making decreases, i.e. as the Þrm becomes more centralized. We use characteristics of the Executive Office to develop a proxy for the number of executives participating in top decision-making. For example, we argue that if the Chairman of the Board is not the CEO, decision-making in the Þrm will be more decentralized because the Chairman will also participate in decision-making. We test our hypothesis using this proxy (which we call the centralization index), and find that the evidence is consistent with our hypothesis. Firm performance (measured by Tobin s Q, stock returns and ROA) is signif- icantly more variable for Þrms with greater values of our centralization index. The results are consistent across various tests designed to detect differences in variability

UNDERSTANDING THE RELATIONSHIP BETWEEN FOUNDER-CEOS AND FIRM PERFORMANCE

While previous empirical literature has examined the effect of founder-CEOs on firm performance, it has largely ignored the effect of firm performance on founder-CEO status. In this paper, we use instrumental variables methods to better understand the relationship between founder-CEOs and performance. Using the proportion of the Þrm s founders that are dead and the number of people who founded the company as instruments for founder-CEO status, we find strong evidence that founder-CEO status is endogenous in performance regressions. This implies that the direct effect of founder-CEOs on firm performance cannot be estimated correctly without accounting for the endogeneity of founder-CEO status. Perhaps surprisingly, we find that performance is negatively related to the likelihood that founders retain the CEO title. This result appears to be driven primarily by founder departures after periods of good performance, rather than by an entrenchment effect that allows founders to remain as CEOs following poor performance. After factoring out the effect of performance on founder-CEO status, we find a residual positive correlation between founder-CEO status and firm performance. This finding suggests that there is a positive causal link from founder-CEOs to Þrm performance

Comportamento, no sul de Minas, de progênies de cafeeiros com resistência à ferrugem, selecionadas de diversos ensaios do Procafé.

No presente trabalho foram reunidas, em 2 ensaios, em execução na FEX Varginha, 30 progênies no primeiro ensaio e 32 no segundo, correspondentes a plantas selecionadas de ensaios anteriores de diferentes áreas, principalmente de seleções feitas em Varginha, e, também, de Mal Floriano-ES, de Patrocínio, e do CEPEC em Martins Soares. Os ensaios são catalogados como 3-32 e 3-35 na FEX do Procafé em Varginha. Eles foram delineados em blocos ao acaso, com 3 repetições e parcelas de 6 plantas. No ensaio 3-32 o plantio foi efetuado em janeiro de 2004 e no ensaio 3-35 em janeiro de 2005.O espaçamento usado foi de 3,5 x 1 m. Os tratos culturais foram os usuais, com 2 aplicações de fungicidas triazóis mais cúpricos, para controle da ferrugem e cercosporiose, em todo o ensaio