On a length-biased life distribution based on the sinh-normal model

In this article, we characterize a new life distribution based on the sinh-normal model. Specifically, we find the density, the distribution function, and the moments of the new model. In addition, we carry out a brief graphical analysis of its density. Furthermore, we derive some properties and transformations related to the new distribution. Moreover, we conduct a study of its hazard rate. Finally, we present an example that illustrates the obtained results and a computational implementation of these results.     

Species richness and seasonality of spiders (Arachnida, Araneae) in an urban Atlantic Forest fragment in Northeastern Brazil

Species richness and forest seasonality of spiders in an urban fragment of Northeastern Brazil were investigated. Mata do Buraquinho is a remnant of Atlantic Rain Forest where no spider inventories have ever been made. Samplings during dry and wet seasons were carried out in order to establish if seasonality influences species richness and complementarily of the spider fauna. Pitfall traps, nocturnal collections, and beating tray samples were used to access a multi-guild spider fauna. Spider species were estimated using first order Jackknife method. Four hundred samples were obtained, resulting in 1681 adult spiders. A total of 166 species were recorded and 211 were estimated. No significant differences for species richness were observed between both periods, and the captured species were the same according to the complementarily coefficients. The fragmentation hypothesis as factor of biota impoverishment was not tested, but future investigations on this topic are suggested in the complex of forest remnants in João Pessoa.     

A Lagrangian bound for many-to-many assignment problems

A simple procedure to tighten the Lagrangian bounds is proposed. The approach is interpreted in two ways. First, it can be seen as a reformulation of the original problem aimed to split the resulting Lagrangian problem into two subproblems. Second, it can be considered as a search for a tighter estimation of the penalty term arising in the Lagrangian problem. The new bounds are illustrated by a small example and studied numerically for a class of the generalized assignment problems.     

The Generalized Birnbaum–Saunders Distribution and Its Theory,Methodology, and Application

In this paper, we discuss the class of generalized Birnbaum–Saunders distributions, which is a very flexible family suitable for modeling lifetime data as it allows for different degrees of kurtosis and asymmetry and unimodality as well as bimodality. We describe the theoretical developments on this model including properties, transformations and related distributions, lifetime analysis, and shape analysis. We also discuss methods of inference based on uncensored and censored data, diagnostics methods, goodness-of-fit tests, and random number generation algorithms for the generalized Birnbaum–Saunders model. Finally, we present some illustrative examples and show that this distribution fits the data better than the classical Birnbaum–Saunders model.     

Incentive compatibility and feasibility constraints in housing markets

We analyze centralized housing markets under the existence of feasibility constraints on the number of agents and objects involved in the exchanges. We focus on an incomplete information setting where only the information about how each agent ranks her endowment is private. We show that under non-degenerate ex-ante probability distributions over preference profiles, no rule satisfies the joint requirements of individual rationality, (constrained) efficiency, and ordinally Bayesian incentive compatibility.     

Kinship Support,Family Relations,and Psychological Adjustment Among Low‐Income African American Mothers and Adolescents

The association of kin social support with mothers' adjustment and family relations was assessed among 204 African American mothers and adolescents who were on average 14.45 years of age. Also examined was the association of mothers' adjustment with family relations and adolescents' adjustment. Findings revealed that kin social and emotional support was positively associated with mothers' optimism. Poor relations with kin were positively associated with mothers' depression. Kin advice and counseling and kin social and emotional support were positively linked to family routine. Poor relations with kin were positively associated with parent/adolescent communication problems. Mothers' optimism was positively associated with family routine and mediated the association of kin social and emotional support with family routine. Parent/adolescent communication problems were positively associated with adolescents' depression. The findings were discussed in light of their support for theoretical and empirical work on family processes among poor African American families.