Carbenes are a remarkable type of molecules because of the two electrons that might be paired or unpaired, providing a singlet or a triplet state, respectively. The preference for one of these states can be measured by the singlet-triplet energy gap; however, theoretical prediction is challenging when static correlation arises, and an adequate balance with dynamic correlation is required to achieve correct predictions. Piris Natural Orbital Functionals (PNOFs) have been used before to deal with other static correlation problems, but they have suffered from lack of dynamic correlation, which has been solved by coupling PNOF7 with many-body perturbation theory. Recently, the development of a Global Natural Orbital Functional (GNOF) has been proposed with the aim of including dynamic correlation without the need to couple with perturbation theory, thus becoming a promising alternative to study challenging chemical problems. In this work, we applied the PNOF family of functionals to compute the adiabatic singlet-triplet energy gaps of a set of simple carbenes and compared them with those computed with coupled-cluster methods and experimental values when available. We have found that the GNOF achieves promising results due to an intrinsic balance of static and dynamic correlation. In this regard, the GNOF presents errors that are lower than those of PNOF7, comparable to those of NOF-c-MP2, and is capable of predicting the tendency of substituent effects, proving to be suitable for further application to predict general singlet-triplet energy gaps.

Two herbaceous Ipomoea climbers grow over trees planted to restore a freshwater forested wetland in the Gulf of Mexico, causing high tree mortality and limiting restoration success. To better control these species, we evaluated their potential for biomass accumulation and regeneration following removal. We simulated the tree-climber relationship in a field experiment by varying light conditions and trellis availability, and by cutting aerial biomass. We also considered the spatial variability of the wetland’s flood level. Ipomoea tiliacea accumulated more biomass at low flood levels, while Ipomoea indica accumulated more biomass at higher flood levels. Despite this, I. tiliacea accumulated more biomass over the entire flood level gradient and the highest flood levels seem to prevent regeneration in both species. There was no vine seed germination, so for both species, regeneration relied on shoot production. I. tiliacea increased its growth more than I. indica when trellises were available, even under shade. It means that that restoration conditions favor I. tiliacea, which makes its management specially challenging. We recommend characterizing hydrology of the site under restoration to design more effective Ipomoea control strategies. Future efforts to restore this forested freshwater wetland should select areas with the highest flood levels, where I. tiliacea growth is limited, ensuring that the trees to be planted can withstand the flood levels. Removal should be avoided during the dry season, when low flood levels favor regeneration in both species.

No abstract

La ciudad de Monterrey, en el noreste de México, se caracteriza por un temprano desarrollo técnico que transformó la urbe y marcó su apropiación de la modernidad por el empleo de materiales locales industrializados de construcción. La difusión de las renovaciones arquitectónicas y urbanas que se iban sucediendo en las páginas del periódico El Norte aporta una visión particular de la ciudad que nace industrial y que busca su conversión en el paradigma de la ciudad moderna occidental. Los edificios que se iban divulgando consolidarían dicho imaginario, al mismo tiempo que las carencias inherentes a las economías en crecimiento de los países latinoamericanos, marcan una crítica constante al proceso modernizador. La difusión en la prensa local, marcada por una fuerte inclinación hacia las obras de iniciativa privada, como la pionera construcción del campus del Instituto Tecnológico y de Estudios Superiores de Monterrey, iría dando cabida, paulatinamente, a las obras de presupuestos públicos, como aquellas significativas del Instituto Mexicano del Seguro Social y de la Universidad de Nuevo León. Así, el presente análisis busca ampliar y enriquecer las interpretaciones actuales sobre una más de las distintas modernidades nacionales.

No abstract