Population persistence under advection-diffusion in river networks

An integro-differential equation on a tree graph is used to model the evolution and spatial distribution of a population of organisms in a river network. Individual organisms become mobile at a constant rate, and disperse according to an advection-diffusion process with coefficients that are constant on the edges of the graph. Appropriate boundary conditions are imposed at the outlet and upstream nodes of the river network. The local rates of population growth/decay and that by which the organisms become mobile, are assumed constant in time and space. Imminent extinction of the population is understood as the situation whereby the zero solution to the integro-differential equation is stable. Lower and upper bounds for the eigenvalues of the dispersion operator, and related Sturm-Liouville problems are found, and therefore sufficient conditions for imminent extinction are given in terms of the physical variables of the problem

Negative Stereotypes and Willingness to Change Them: Testing Theories of Discrimination in South Africa

This paper proposes a new test to distinguish between the two leading theories of discrimination: preference versus information. Discrimination based on preferences occurs when people behave as if they refuse to change their stereotypes about the capabilities of discriminated individuals. Those who discriminate based on information are willing to alter their stereotypes. Using data from a quasi-experiment in South Africa, I test for discrimination against women and non-whites. The preliminary results show no discrimination against the former. In the case of racial discrimination, players' stereotypes benefit non-whites instead of white opponents, but they are reluctant to change their impression for the former. However, they are willing to change their initial impression about white opponents. This has severe implications about the permanency of affirmative action policies.

ASYMMETRIC PRICE ADJUSTMENTS AND BEHAVIOR UNDER RISK: EVIDENCE FROM PERUVIAN AGRICULTURAL MARKETS

Most studies measuring asymmetric adjustments in vertical price transmissions fail to provide empirical support to explain such behavior. The literature invokes theoretical models, which derive asymmetric behavior based on variables that are difficult to measure such as oligopolies' coordination policies, market imperfections or menu costs. Therefore, with no empirical support explaining the asymmetries, these studies leave no room for policy implementation. In this paper I relate asymmetric price responses to a theory of behavior under risk driven by the perishable rate of the goods. Retailers of a perishable good facing an increment in the wholesale price may decide not to increase their prices for fear of being left with a spoiled product. Using three agricultural products with different perishable rates I reject the null hypothesis of symmetric adjustments in the most perishable product but fail to reject for the less perishable goods. The nonlinear responses are consistent with the prediction of the model. The test for asymmetries uses a threshold cointegration technique where the threshold level and the cointegration vector are estimated from the data instead of being imposed by the econometrician.Risk and Uncertainty,

The Challenges of Strategic Human Resources Management in Southeast Asian Universities

Nowadays the Higher Education Institutions face major challenges in its development. Demanding from different actors and the orientation of the research, more oriented to innovation and value creation, request news capacities to answer to that. Southeast Asia shows a strong economic growth with a large increase in GDP and a growing improvement in the position of The Human Development Index promoted by United Nations. This reality creates a different pressure on the higher education institutions in southeast Asia that requires a change in the universities, in the way they implement the mission and in the requested capacities, specially the human resources capacities. In this way, a new paradigm and model of human resources management for southeast higher education institutions need be developed to create the conditions to answer to this new reality, where the main analysis variables will be talent, performance, motivation and retention, coaching, cross cultural, integrity and permanent adaptability and flexibility. The main objective of this communication is to reflect and contextualize in terms of theoretical models where we find the assumptions for the implementation of strategic human resources management for southeast Asian universities. What kind of profile is request for the staff in this new reality? What we need to change in human resources management? How can this change be implemented? What HRM tools are most relevant to this reality? These are the main issues on which we will reflect with a critical thinking approach in order to present a set of clues to southeast Asian universities according to our analysis and interpretation, as Portuguese and European

An exact approach for single machine scheduling with quadratic earliness and tardiness penalties

In this paper, we consider the single machine scheduling problem with quadratic earliness and tardiness costs, and no machine idle time. We propose two different lower bounds, as well as a lower bounding procedure that combines these two bounds. Optimal branch-and-bound algorithms are then presented. These algorithms incorporate the proposed lower bound, as well as an insertion-based dominance test. The lower bounding procedure and the branch-and-bound algorithms are tested on a wide set of randomly generated problems. The computational results show that the branch-and-bound algorithms are capable of optimally solving, within reasonable computation times, instances with up to 20 jobs.scheduling, single machine, quadratic earliness and tardiness, lower bounds, branch-and-bound

ℒ2-Gain of double integrators with saturation nonlinearity

This note uses quadratic surface Lyapunov functions (SuLFs) to efficiently check if a double integrator in feedback with a saturation nonlinearity has ℒ2-gain less than γ > 0. We show that for many such systems, the ℒ2-gain is nonconservative in the sense that this is approximately equal to the lower bound obtained by replacing the saturation with a constant gain of 1. These results allow the use of classical analysis tools like µ-analysis or integral quadratic constraints to analyze systems with double integrators and saturations, including servo systems like some mechanical systems, satellites, hard disks, compact disk players, etc