Synorganisation without organ fusion in the flowers of Geranium robertianum (Geraniaceae) and its not so trivial obdiplostemony

Background and Aims Synorganisation of floral organs, an important means in angiosperm flower evolution, is mostly realized by congenital or post-genital organ fusion. Intimate synorganisation of many floral organs without fusion, as present in Geranium robertianum, is poorly known and needs to be studied. Obdiplostemony, the seemingly reversed position of two stamen whorls, widely distributed in core eudicots, has been the subject of much attention, but there is confusion in the literature. Obdiplostemony occurs in Geranium and whether and how it is involved in this synorganisation is explored here. Methods Floral development and architecture were studied with light microscopy based on microtome section series and with scanning electron microscopy. Key Results Intimate synorganisation of floral organs is effected by the formation of five separate nectar canals for the proboscis of pollinators. Each nectar canal is formed by six adjacent organs from four organ whorls. In addition, the sepals are hooked together by the formation of longitudinal ribs and grooves, and provide a firm scaffold for the canals. Obdiplostemony provides a guide rail within each canal formed by the flanks of the antepetalous stamen filaments. Conclusions Intimate synorganisation in flowers can be realized without any fusion, and obdiplostemony may play a role in this synorganisatio

On the efficiency of stochastic volume sources for the determination of light meson masses

We investigate the efficiency of single timeslice stochastic sources for the calculation of light meson masses on the lattice as one varies the quark mass. Simulations are carried out with Nf = 2 flavours of non-perturbatively O(a) improved Wilson fermions for pion masses in the range of 450 - 760 MeV. Results for pseudoscalar and vector meson two-point correlation functions computed using stochastic as well as point sources are presented and compared. At fixed computational cost the stochastic approach reduces the variance considerably in the pseudoscalar channel for all simulated quark masses. The vector channel is more affected by the intrinsic stochastic noise. In order to obtain stable estimates of the statistical errors and a more pronounced plateau for the effective vector meson mass, a relatively large number of stochastic sources must be used.Comment: 18 pages, 6 figure

Sustainable Growth with Environmental Spillovers: A Ramsey-Koopmans Approach

In this paper, we apply the canonical approach of Ramsey, Koopmans, and Diamond to the problem of optimal and intertemporally-equitable growth with a non-renewable resource constraint and show that the solution is sustainable. The model is extended to cases involving environmental amenities and disamenities and renewable resources. The solutions equivalently solve the problem of maximizing net national product adjusted for depreciation in natural capital and environmental effects, which turns out to be both sustainable and constant even without technical change.

Impatience and Intergenerational Equity in a Model of Sustainable Growth

We argue that intergenerational neutrality has been prematurely excluded from the dialogue on sustainable growth. By incorporating Burton’s distinction between intragenerational and intergenerational discounting into a model suitable for analyzing sustainability issues, we are able to accommodate some of the underlying concerns. We show that in an economy with a renewable resource, eschewing intergenerational discounting leads to the implication of a sustained growth path, without the necessity of a sustainability constraint. We find that green net national product remains constant along the optimal approach path to golden rule consumption. This avoids the paradox that maximizing sustainable income leads to unsustained consumption and income.Sustainable development, intergenerational equity, intra-generational discounting, renewable resources, green net national product

Los conceptos de naturaleza y de estado natural en Cervantes y el Quijote

Los dos conceptos que figuran en el título del presente trabajo desempeñan bajo diversos aspectos un papel importante en el pensamiento y en la obra de Cervantes. Comencemos con algunas consideraciones sobre la relación entre naturaleza y arte. Esta relación preocupó desde luego constantemente al artista y creador que era Cervantes. El arte en sus diferentes modos y géneros es mímesis, es imitación de la naturaleza, así reza ya la constatación de Aristóteles al principio de su Poética. Con respecto a la poética de nuestro autor, Edward C. Riley (1971: 99), en su Teoría de la novela en Cervantes, constató correspondientemente: «En el centro de la teoría literaria de Cervantes se halla la antigua dicotomía entre el arte y la naturaleza»

La base imponible del impuesto a la renta de las empresas en el derecho comparado iberoamericano (Tema Central)

El análisis jurídico comparado de un grupo de países latinoamericanos acerca de la imposición a la empresa es exiguo, probablemente por el vertiginoso cambio de la legislación y por la característica menos gregaria de los expertos de nuestra disciplina. Este estudio, que profundiza sobre la base imponible de la imposición directa sobre la renta, resulta necesario si atendemos el nivel de desarrollo parecido de nuestras realidades sociales y económicas, amén de las características culturales que nos unen y que en ocasiones nos demandan precisamente estas reflexiones. La unidad del tronco jurídico y las obvias relaciones con España ameritan su inclusión en esta indagación.The legal analysis of comparative law throughout Latin America concerning taxes is meager, probably due to the rapid change in its legislation, as for the reserved nature of the experts in our area. This study is necessary given the level of the comparable development of our social and economic realities, not to mention the cultural characteristics that bind us together, and that occasionally demand from us these reflections. The unit of legal body and the obvious relationships with Spain deserve to be included in this analysis

Morphology and angiosperm systematics in the molecular era

Several ways in which morphology is used in systematic and evolutionary research in angiosperms are shown and illustrated with examples: 1) searches for special structural similarities, which can be used to find hints for hitherto unrecognized relationships in groups with unresolved phylogenetic position; 2) cladistic studies based on morphology and combined morphological and molecular analyses; 3) comparative morphological studies in new, morphologically puzzling clades derived from molecular studies; 4) studies of morphological character evolution, unusual evolutionary directions, and evolutionary lability based on molecular studies; and 5) studies of organ evolution. Conclusions: Goals of comparative morphology have shifted in the present molecular era. Morphology no longer plays the primary role in phylogenetic studies. However, new opportunities for morphology are opening up that were not present in the premolecular era: 1) phylogenetic studies with combined molecular and morphological analyses; 2) reconstruction of the evolution of morphological features based on molecularly derived cladograms; 3) refined analysis of morphological features induced by inconsistencies of previous molecular and molecular phylogenetic analyses; 4) better understanding of morphological features by judgment in a wider biological context; 5) increased potential for including fossils in morphological analyses; and 6) exploration of the evolution of morphological traits by integration of comparative structural and molecular developmental genetic aspects (Evo-Devo); this field is still in its infancy in botany; its advancement is one of the major goals of evolutionary botan

Early conceptual and linguistic processes operate in independent channels

Language and concepts are intimately linked, but how do they interact? In the study reported here, we probed the relation between conceptual and linguistic processing at the earliest processing stages. We presented observers with sequences of visual scenes lasting 200 or 250 ms per picture. Results showed that observers understood and remembered the scenes’ abstract gist and, therefore, their conceptual meaning. However, observers remembered the scenes at least as well when they simultaneously performed a linguistic secondary task (i.e., reading and retaining sentences); in contrast, a nonlinguistic secondary task (equated for difficulty with the linguistic task) impaired scene recognition. Further, encoding scenes interfered with performance on the nonlinguistic task and vice versa, but scene processing and performing the linguistic task did not affect each other. At the earliest stages of conceptual processing, the extraction of meaning from visually presented linguistic stimuli and the extraction of conceptual information from the world take place in remarkably independent channels