Gender differences and the timing of first marriages

In this article we provide a simple model of the marriage market where singles search for spouses. In our model economy men and women live for many years and they differ in their survival probabilities, in their fecundity, and in their earnings. We show that modelling the marriage decision in a very simple model economy is sufficient to account for much of the observed marriage behavior in the United States in the year 2000. We conclude that gender differences in fecundity are all important in accounting for marriage behavior, and that differences in earnings matter little. We also conclude that, even though they are in short supply, the market power of fecund women is not enough for them to demand compensation in all cases. And that studying the marriage decision without modelling explicitly the roles played by age and by fecundity, as has been typically done by the previous literature, makes little sense

Metric Dimension for Gabriel Unit Disk Graphs is NP-Complete

We show that finding a minimal number of landmark nodes for a unique virtual addressing by hop-distances in wireless ad-hoc sensor networks is NP-complete even if the networks are unit disk graphs that contain only Gabriel edges. This problem is equivalent to Metric Dimension for Gabriel unit disk graphs. The Gabriel edges of a unit disc graph induce a planar O(\sqrt{n}) distance and an optimal energy spanner. This is one of the most interesting restrictions of Metric Dimension in the context of wireless multi-hop networks.Comment: A brief announcement of this result has been published in the proceedings of ALGOSENSORS 201

Evaluación Bidimensional y Tridimensional de la Vía Aérea Superior

Indexación: Scopus; Scielo.The aim of this study was to validate and correlate the two-dimensional (2D) with the three-dimensional (3D) measures of the upper airway assessment. Lateral cephalograms and cone beam CT of 100 adult subjects were used to perform a 2D and 3D assessment of the upper airway. Spearman correlation coefficient was used to determine whether there was correlation between variables. Additionally, specificity, sensitivity, negative predictive value and positive predictive value was calculated for the 2D assessment of the upper airway. Correlation between all two and three dimensional variables was found. In the nasopharynx and oropharynx, a weak correlation (r <0.51) was found; in the oropharynx a moderate one (0.50 <r <0.76). The validity tests of the 2D assessment resulted in a 73% sensitivity, 45% specificity, 93% negative predictive value and 14% positive predictive value for the nasopharynx; 100% sensitivity, 51% specificity, 100% negative predictive value and 6% positive predictive value in the oropharynx and 100% sensitivity, 71% specificity, 100% negative predictive value and 13% positive predictive value in the hypopharynx. There is a weak correlation between the 2D and 3D assessment of the upper airway. However, the lateral cephalogram has a high sensitivity and high negative predictive value, therefore, an additional complementary examination would not be necessary if the 2D assessment of the upper airway throws a normal result.http://ref.scielo.org/mpkrn

Tensorial perturbations in the bulk of inflating brane worlds

In this paper we consider the stability of some inflating brane-world models in quantum cosmology. It is shown that whereas the singular model based on the construction of inflating branes from Euclidean five-dimensional anti-de Sitter space is unstable to tensorial cosmological perturbations in the bulk, the nonsingular model which uses a five-dimensional asymptotically anti-de Sitter wormhole to construct the inflating branes is stable to these perturbations.Comment: 4 pages, RevTex, to appear in Phys. Rev.

Gender Differences and the Timing of First Marriages

We study the steady state of an overlapping generations economy where singles search for spouses. In our model economy men and women live for many years and they differ in their fecundity, in their earnings, and in their survival probabilities. These three features are age-dependent and deterministic. Singles meet at random. They propose when the expected value of their current match exceeds that of remaining single. If both partners propose, the meeting ends up in a marriage. Marriages last until death does them apart, widows and widowers never remarry, and people make no other economic decisions whatsoever. In our model economy people marry because they value companionship, bearing children, and sharing their income with their spouses. The matching function depends on the single sex-ratios which are endogenous. Our model economy has only two free parameters: the search friction and the utility share of bearing children. We choose their values to match the median ages of first-time brides and grooms. We show that modeling the marriage decision in this simple way is sufficient to account for the age distributions of ever and never married men and women, for the probabilities of marrying a younger bride and a younger groom, and for the age distributions of first births observed in the United States in the year 2000. The previous literature on this topic claims that marriage is a waiting game in which women are choosier than men, and old and rich pretenders outbid the young and poor ones in their competition for fecund women. In this article we tell a different story. We show that their shorter biological clocks make women uniformly less choosy than men of the same age. This turns marriage into a rushing game in which women are willing to marry older men because delaying marriage is too costly for women. Our theory predicts that most of the gender age difference at first marriage will persist even if the gender wage-gap disappears. It also predicts that the advances in the reproductive technologies will play a large role in reducing the age difference at first marriage.marriage, search, sex ratio

L-Drawings of Directed Graphs

We introduce L-drawings, a novel paradigm for representing directed graphs aiming at combining the readability features of orthogonal drawings with the expressive power of matrix representations. In an L-drawing, vertices have exclusive $x$- and $y$-coordinates and edges consist of two segments, one exiting the source vertically and one entering the destination horizontally. We study the problem of computing L-drawings using minimum ink. We prove its NP-completeness and provide a heuristics based on a polynomial-time algorithm that adds a vertex to a drawing using the minimum additional ink. We performed an experimental analysis of the heuristics which confirms its effectiveness.Comment: 11 pages, 7 figure

Statistical analysis of Ni nanowires breaking processes: a numerical simulation study

A statistical analysis of the breaking behavior of Ni nanowires is presented. Using molecular dynamic simulations, we have determined the time evolution of both the nanowire atomic structure and its minimum cross section (Sm(t)). Accumulating thousands of independent breaking events, Sm histograms are built and used to study the influence of the temperature, the crystalline stretching direction and the initial nanowire size. The proportion of monomers, dimers and more complex structures at the latest stages of the breaking process are calculated, finding important differences among results obtained for different nanowire orientations and sizes. Three main cases have been observed. (A) [111] stretching direction and large nanowire sizes: the wire evolves from more complex structures to monomers and dimers prior its rupture; well ordered structures is presented during the breaking process. (B) Large nanowires stretched along the [100] and [110] directions: the system mainly breaks from complex structures (low probability of finding monomers and dimers), having disordered regions during their breakage; at room temperature, a huge histogram peak around Sm=5 appears, showing the presence of long staggered pentagonal Ni wires with ...-5-1-5-... structure. (C) Initial wire size is small: strong size effects independently on the temperature and stretching direction. Finally, the local structure around monomers and dimmers do not depend on the stretching direction. These configurations differ from those usually chosen in static studies of conductance.Comment: 18 pages, 13 figure