Controlling systemic corruption through group size and salary dispersion of public servants.

We investigate an agent-based model for the emergence of corruption in public contracts. There are two types of agents: business people and public servants. Both business people and public servants can adopt two strategies: corrupt or honest behavior. Interactions between business people and public servants take place through defined payoff rules. Either type of agent can switch between corrupt or honest strategies by comparing their payoffs after interacting. We measure the level of corruption in the system by the fractions of corrupt and honest agents for asymptotic times. We study the effects of the group size of the interacting agents, the dispersion with respect to the average salary of the public servants, and a parameter representing the institutional control of corruption. We characterize the fractions of honest and corrupt agents as functions of these variables. We construct phase diagrams for the level of corruption in the system in terms of these variables, where three collective states can be distinguished: i) a phase where corruption dominates; ii) a phase where corruption remains in less than 50% of the agents; and iii) a phase where corruption disappears. Our results indicate that a combination of large group sizes of interacting servants and business people and small dispersion of the salaries of public servants, contributes to the decrease of systemic corruption in public contracts.

Photosynthetically active radiation and carbon gain drives the southern orientation of Myrtillocactus geometrizans fruits.

The equatorial orientation of reproductive structures is known in some columnar cacti from extratropical deserts. It has been hypothesised that photosynthetically active radiation (PAR) interception is the main reason for this orientation, because of its key effect on nocturnal CO2 uptake. However, there are no studies addressing both the effect of PAR and its consequence, carbon gain, on fruit orientation. Accordingly, we tested whether PAR and carbon gain could explain the southern fruit orientation of Myrtillocactus geometrizans, an inter-tropical columnar cactus. We studied three populations of M. geometrizans in Mexico. For each population, azimuth of fruits, total daily PAR, nocturnal acid accumulation (NAA) and fruit production were measured. The relationships between rib orientation and number of fruits, as well as total daily PAR, were evaluated using periodic regressions. The effect of total daily PAR and NAA on number of fruits was assessed using generalised linear models. During spring, mean fruit orientation had a south azimuth for three populations. Likewise, rib orientation had a significant effect on fruit production, with the south-facing ribs having the maximum number of fruits. Total daily PAR was highest in the south-facing ribs, at least for those in the northern and central populations. Furthermore, during spring, there was a significant positive effect of total daily PAR and NAA on fruit production. Our results provide strong evidence that the higher carbon gain in equatorial ribs, through a highest interception of PAR, would be the responsible factor for equatorial orientation of fruits in an inter-tropical columnar cactus.

Recurrent acute thermal lesion induces esophageal hyperproliferative premalignant lesions in mice esophagus.

Hot beverage consumption is a risk factor for esophageal squamous cell carcinoma, but the underlying mechanisms are still unknown. We developed an experimental mouse model to understand the mechanism of thermal lesion to esophageal carcinogenesis. Female BALB/c mice were treated by gavage with water at different temperatures three times a week and nitrosamines in the drinking water. Water at 70°C, but not at lower temperatures, initially induced an esophageal necrosis that healed and became resistant to necrosis after further administrations. However, when 70°C water was associated with N-nitrosodiethylamine at doses above 1 ppm, there was interference in epithelial regeneration, allowing recurrent thermal injury and inflammation. Recurrent thermal injury resulted in hyper proliferative premalignant lesions being induced earlier (at 4 weeks) and at a higher frequency (4-fold increase at 16 weeks) when compared to mice treated with NDEA only. Ki-67 immunostaining revealed that recurrent thermal injury induced basal cell proliferation resulting in the expansion of epithelial basal cells, confirmed by the increase in cytokeratin 14 positive cells with concomitant reduction of differentiated cytokeratin 5 positive cells. We conclude that recurrent thermal lesion may act as a tumor promoter though a strong proliferation stimulus of esophageal epithelial basal cells.

Quaternary origin and genetic divergence of the endemic cactus Mammillaria pectinifera in a changing landscape in the Tehuacán Valley, Mexico.

The endemic Mexican cactus, Mammillaria pectinifera, shows low dispersal capabilities and isolated populations within the highly dissected landscape of Tehuacán Valley. These characteristics can restrict gene flow and act upon the genetic divergence and speciation in arid plants. We conducted a phylogeographic study to determine if the origin, current distribution, and genetic structure of M. pectinifera were driven by Quaternary geomorphic processes. Sequences of the plastids psbA-trnH and trnT-trnL obtained from 66 individuals from seven populations were used to estimate genetic diversity. Population differentiation was assessed by an analysis of molecular variance. We applied a stepwise phylogenetic calibration test to determine whether species origin and genetic divergence among haplotypes were temporally concordant with recognizable episodes of geomorphic evolution. The combination of plastid markers yielded six haplotypes, with high levels of haplotype diversity (h = 0.622) and low nucleotide diversity (π = 0.00085). The populations were found to be genetically structured (F(ST) = 0.682; P < 0.00001), indicating that geographic isolation and limited dispersal were the primary causes of genetic population differentiation. The estimated origin and divergence time among haplotypes were 0.017-2.39 and 0.019-1.237 mya, respectively, which correlates with Pleistocene tectonics and erosion events, supporting a hypothesis of geomorphically-driven geographical isolation. Based on a Bayesian skyline plot, these populations showed long term demographic stability, indicating that persistence in confined habitats has been the main response of this species to landscape changes. We conclude that the origin and haplotype divergence of M. pectinifera were a response to local Quaternary geomorphic evolution.

Percepciones, actitudes y conductas de médicos gineco-obstetras, respecto al uso actual de terapia de reemlazo hormonal / Perceptions, attitudes, and behavior of obstetrician-gynecologists for the use of hormonal replacement therapy

Resultados de una encuesta con preguntas específicas contestadas por el 97,6 por ciento de los gineco-obstetras del Departamento de Obstetricia y Ginecología de Clínica Alemana de Santiago, para establecer un diagnóstico de situación sobre el uso de terapia de reemplazo hormonal (TRH). Se enfatizan preguntas sobre la aceptabilidad de las futuras usuarias tanto de TRH como de terapias alternativas; sobre la percepción de los eventuales beneficios desde un punto de vista general, o específicamente cardiovascular; así como las preferencias de hormonas a usar y predilecciones por las vías de administración; las asociaciones del uso y cáncer mamario; las variaciones sobre el uso de TRH pos publicación del Women Health Iniciative Study; los factores que inciden en la discontinuación del tratamiento; la importancia de edad para el uso, factores relacionados con los costos de las terapias y la preferencia o no de productos originales de investigación. Conclusión: Es necesaria una mayor capacitación sobre el uso de TRH en la actualidad tanto de los ginecólogos especialistas en climaterio y menopausia, como de los que no lo son. A falta de información concluyente sobre esta temática en el momento actual se sugiere que el manejo de este tipo de pacientes sea efectuado por los equipos médicos especializados.

In order to set a diagnosis about the use of hormonal replacement therapy (HRT) in peri and postmenopausal women by the obstetricians and gynecologists members of our staff, we did a survey that was answered by 97.6 percent of them. Questions about the future patients desire related to use of HRT or use of natural or alternative medicines were included. There were also questions related to the "risk-benefit" relationship on the use of HRT from an overall point of view as well as from a cardiovascular point of view. The preference of medical doctors (MD) on choice of hormone type in HRT use, in respect to the administration, were also asked. Among others, questions were asked in order to know MD opinions on the relationship with breast cancer, the changes on acceptability use after the WHI study, reasons for the treatment discontinuation, the importance of women's age and the cost of pharmaceuticals produces on HRT use. Conclusions: Are focused on a need of a solid educational program on use of HRT addressed to gynecologists, as well as to general practitioners, cardiologists, oncologists and others related. Educational programs are also quite beneficial to future users as well as women that are currently under treatment. In the absence of conclusive information available at the present moment, we advise that patients considering HRT should seek the counsel of medical teams whose specialties include menopause.

Vegetation-environment relationships based on a life-forms classification in a semiarid region of tropical Mexico.

Taking the view that morphological characteristics represent behavioral strategies of plants to cope with environmental pressures, we defined 18 life-forms, using multivariate classification techniques in a tropical semiarid ecosystem in Central Mexico. A multiple discriminant analysis confirmed the existence of these groups. A null model of random membership of species to life-forms was significantly different from our classification. Vegetation-environment relationships were examined with Detrended Canonical Correspondence Analysis (DCCA). Ordination axes were interpreted mainly be altitude and soil moisture. Response curves of life-forms along these gradients were explored fitting generalized linear models (GLIM's). We believe that the life-forms approach for the study of vegatation-environment relationships is a valid alternative to the traditional species approach usually used in physiological research because: i) life-forms number was found to be an excellent species diversity predictor, ii) this approach enables considerable reduction in the bulk of data without losing ecological information, and iii) life-forms represent ecological strategies per se and, they constitute an index of the number of different ways the desert's resources are utilized.

Vegetation-environment relatioship based on a life-forms classification in a semiarid region of Tropical Mexico

Taking the view that morphological characteristics represent behavioral strategies of plants to cope with environmental pressures, we defined 18 life-forms, using multivariate classification techniques in a tropical semiarid ecosystem in Central Mexico. A multiple discriminant analysis confirmed the existence of these groups. A null model of random membership of species to life-forms was significantly different from our classification. Vegetation-environment relationships were examined with Detrended Canonical orrespondence Analysis (DCCA). Ordination axes were interpreted mainly be altitude and soil moisture. Response curves of life-forms along these gradients were explored fitting generalized linear models (GLIM's). We believe that the life-forms approach for the study of vegatation-environment relationships is a valid alternative to the traditional species approach usually used in physiological research because: i) life-forms number was found to be an excellent species diversity predictor, ii) this approach enables considerable reduction in the bulk of data without losing ecological information, and iii) life-forms represent ecological strategies per se and, they constitute an index of the number of different ways the desert's resources are utilized