Exact scaling in the expansion-modification system

This work is devoted to the study of the scaling, and the consequent power-law behavior, of the correlation function in a mutation-replication model known as the expansion-modification system. The latter is a biology inspired random substitution model for the genome evolution, which is defined on a binary alphabet and depends on a parameter interpreted as a \emph{mutation probability}. We prove that the time-evolution of this system is such that any initial measure converges towards a unique stationary one exhibiting decay of correlations not slower than a power-law. We then prove, for a significant range of mutation probabilities, that the decay of correlations indeed follows a power-law with scaling exponent smoothly depending on the mutation probability. Finally we put forward an argument which allows us to give a closed expression for the corresponding scaling exponent for all the values of the mutation probability. Such a scaling exponent turns out to be a piecewise smooth function of the parameter.Comment: 22 pages, 2 figure

A new primitive Neornithischian dinosaur from the Jurassic of Patagonia with gut contents

We describe a new species of an ornithischian dinosaur, Isaberrysaura mollensis gen. et sp. nov. The specimen, consisting in an almost complete skull and incomplete postcranium was collected from the marine-deltaic deposits of the Los Molles Formation (Toarcian-Bajocian), being the first reported dinosaur for this unit, one of the oldest from Neuquén Basin, and the first neornithischian dinosaur known from the Jurassic of South America. Despite showing a general stegosaurian appearance, the extensive phylogenetic analysis carried out depicts Isaberrysaura mollensis gen. et sp. nov. as a basal ornithopod, suggesting that both Thyreophora and neornithischians could have achieved significant convergent features. The specimen was preserved articulated and with some of its gut content place in the middle-posterior part of the thoracic cavity. Such stomach content was identified as seeds, most of them belonging to the Cycadales group. This finding reveals a possible and unexpected role of this ornithischian species as seed-dispersal agent.Facultad de Ciencias Naturales y Muse

Bacterioplankton responses to riverine and atmospheric inputs in a coastal upwelling system (Ría de Vigo, NW Spain)

Original research paperAnthropogenic pressures are changing the magnitude and nature of matter inputs into the ocean. The Ría de Vigo (NW Spain) is a highly productive and dynamic coastal system that is likely affected by such alterations. Previous nutrient-addition microcosm experiments conducted during contrasting hydrographic conditions suggested that heterotrophic bacteria are limited by organic carbon (C) and occasionally co-limited by inorganic nutrients in this coastal area. In order to assess short-term responses in biomass, production, and respiration of heterotrophic bacteria from the Ría de Vigo to increasing amounts of natural inputs of matter, we conducted 6 microcosm experiments, wherein surface seawater collected in spring, summer, and autumn was mixed with increasing amounts of dissolved natural matter concentrates from riverine and atmospheric origin. Simultaneous experiments with controlled inorganic and/or organic additions indicated that bacteria were co-limited by inorganic nutrients and C in spring and summer and primarily limited by C in autumn. Production responded more than biomass to increasing inputs of matter, whereas respiration did not change. The bacterial production response to increasing dissolved organic C load associated with riverine and atmospheric inputs was strongly related to the relative phosphorus (P) content of the dissolved matter concentrates. Our data suggest that bacterial production might decrease with the increase of P-deficient allochthonous matter inputs, which would have important biogeochemical consequences for C cycling in coastal areas.Spanish Ministry of Science and Innovation, MINECO, CSIC, Xunta of Galicia and European Union (Marie Curie Grants)Versión del edito

Heterogeneous solar photo-Fenton treatment of industrial wastewater via δ-FeOOH

68-76The wastewater from the textile industry has been treated with heterogeneous solar photo-Fenton using iron oxyhydroxides (δ-FeOOH and FeOOH)nanoparticles. δ-FeOOH and FeOOH catalysts have been prepared, respectively, from ferrous and ferric ions as precursor species using an easy and low-cost method. The FeOOH catalyst exhibits slightly higher catalytic activity than δ-FeOOH in the heterogeneous solar photo-Fenton process but is less stable. The oxidation efficiency of basic blue 9 and acid green 50, analytical textile dyes, is compared to that of wastewater dye. The as-prepared catalysts are highly efficient for the wastewater treatment and the synthetic solutions prepared from the analytical textile dyes. High mineralization (over 90%) of the organic components of wastewater was achieved at 5 h of solar photo-Fenton treatment

A simple theorem to generate exact black hole solutions

Under certain conditions imposed on the energy-momentum tensor, a theorem that characterizes a two-parameter family of static and spherically symmetric solutions to Einstein's field equations (black holes), is proved. A discussion on the asymptotics, regularity, and the energy conditions is provided. Examples that include the best known exact solutions within these symmetries are considered. A trivial extension of the theorem includes the cosmological constant {\it ab-initio}, providing then a three-parameter family of solutions.Comment: 14 pages; RevTex; no figures; typos corrected; references adde

Un fascinante ejemplo de adaptación de microalgas a una contaminación extrema de petróleo en un arroyo natural en Arroyo Minero, Río Negro, Argentina

Nowadays, accidental spills of crude oil are one of the mostworrisome environmental problems. Usually, the crude oil spillsrapidly inhibited photosynthesis of microalgae (the main primaryproducers of aquatic ecosystems) causing a severe damage to inland waters ad marine ecosystems. In order to add knowledge about microalgal response to crude oil spill, here we study a fascinating example of extreme contamination by crude oil spills continuously (at least since 1915) in Arroyo Minero, Nirihuan de Arriba, Río Negro, Argentina. This study is changing our pre-conceived ideas on the adaptation of microalgae to crude oil. Astonishingly, a high biomass of microalgae proliferates in contact with crude oil. In contrast with the paradox of the plankton (which predict that more than 30 microalgal species would coexist in the same water body) only four species were detected in the crude oil spill area. They are cosmopolitan mesophile species and not extremophile ones (as would be expected). The most abundant species was the Chlorophyta Scenedesmus obtusus. Other abundant species seemsto be a new Scenedesmus species. The other two species Symploca dubia Cyanobacteria and Chlamydomonas dinobryonis Chlorophyta are new records for flora of Argentina. These species were isolated maintained in clonal laboratory cultures and characterised. They are resistant to crude oil of Arroyo Minero and to analytical petroleum special standard. In contrast similar species isolated from areas without crude oil contamination were destroyed by petroleum.En la actualidad los vertidos accidentales de petróleo constituyen uno de los más preocupantes problemas ambientales. Los vertidos de petróleo inhiben rápidamente la fotosíntesis de las microalgas (principales productores primarios en ecosistemas acuáticos) y causan un daño severo en ecosistemas continentales y marinos. Para aumentar nuestro conocimiento sobre los efectos de los vertidos de petróleo en las microalgas, estudiamos aquí un ejemplo fascinante de una contaminación extrema por un vertido continuo de petróleo que empezó al menos en 1915 en Arroyo Minero, Nirihuan de Arriba, Río Negro, Argentina. Este estudio está cambiando muchas de nuestras ideas preconcebidas sobre la adaptación de microalgas al petróleo. Sorprendentemente, una elevada biomasa algal prolifera en contacto con el petróleo. En contraste con la paradoja del plancton (que predice que más de 30 especies de microalgas deberían coexistir en la misma masa de agua) sólo se detectaron cuatro especies en al área de vertido de petróleo. Se trata de especies mesófilas cosmopolitas y no de especies extremófilas (como cabría esperar). La especie más abundante fue la Chlorophyta Scenedesmus obtusus. Otra especie abundante parece ser una nueva especie de Scenedesmus. Las otras dos especies, Symploca dubia Cyanobacteria y Chlamydomonas dinobryonis Chlorophyta, son nuevos registros para la flora de Argentina. Estas especies se aislaron, clonaron, mantuvieron en cultivos clónicos en el laboratorio y caracterizaron. Estos cultivos resultaron ser resistentes al petróleo del Arroyo Minero y al petróleo de estándares analíticos. En contraste, el petróleo destruyó a especies semejantes aisladas de áreas no contaminadas