Sustained impact of drought on wet shrublands mediated by soil physical changes

13 páginas.-- 6 figuras.-- 52 referencias.-- The online version of this article (doi:10.1007/s10533-014-0059-y) contains supplementary material, which is available to authorized users.-- Domínguez, María Teresa et al...Projected climate warming may substantially increase carbon emissions from wet organic soils, contributing to a positive feedback between the terrestrial carbon cycle and climate change. Evidence suggests that in these soils the stimulation of soil respiration by warming can be sustained over long periods of time due to the large availability of C substrates. However, the long-term response of wet organic soils to drought remains uncertain. Organo-mineral soils might be particularly vulnerable, because of their limited soil moisture pool to buffer drought events. Using a whole-ecosystem climate-change experiment in North Wales (UK) we show that soil respiration in podzolic (organo-mineral) soils from wet shrublands is more vulnerable to recurrent drought than to warming, and that the drought impact does not attenuate at decadal time scales. Stimulation of soil respiration by drought was linked to major changes in soil structure that led to a 54 % reduction in water holding capacity compared to control. Bryophyte abundance was found to buffer soil moisture losses, moderating soil CO2 efflux under warming. As there was no evidence of change in plant productivity to offset the increased soil C emissions under drought, this response may result in a positive climate feedback. The results indicate the potentially critical role that changes in sub-dominant vegetation and in soil physical properties may have in determining climate change impacts on soil C dynamics.We thank all the CEH staff members who have contributed to the experiment establishment and maintenance over the years, in particular David Williams. This research was funded by the EU projects CLIMOOR, VULCAN and INCREASE FP7-INFRASTRUCTURE-2008-1 (Grant Agreement no. 227628)—the INCREASE project. M.T.D was supported by two postdoctoral fellowships awarded by the Spanish National Science and Technology FoundationPeer reviewe

Molecular basis for the distinct divalent cation requirement in the uridylylation of the signal transduction proteins GlnJ and GlnB from Rhodospirillum rubrum

Background: PII proteins have a fundamental role in the control of nitrogen metabolism in bacteria, through interactions with different PII targets, controlled by metabolite binding and post-translational modification, uridylylation in most organisms. In the photosynthetic bacterium Rhodospirillum rubrum, the PII proteins GlnB and GlnJ were shown, in spite of their high degree of similarity, to have different requirements for post-translational uridylylation, with respect to the divalent cations, Mg2+ and Mn2+. Results: Given the importance of uridylylation in the functional interactions of PII proteins, we have hypothesized that the difference in the divalent cation requirement for the uridylylation is related to efficient binding of Mg/Mn-ATP to the PII proteins. We concluded that the amino acids at positions 42 and 85 in GlnJ and GlnB (in the vicinity of the ATP binding site) influence the divalent cation requirement for uridylylation catalyzed by GlnD. Conclusions: Efficient binding of Mg/Mn-ATP to the PII proteins is required for uridylylation by GlnD. Our results show that by simply exchanging two amino acid residues, we could modulate the divalent cation requirement in the uridylylation of GlnJ and GlnB. Considering that post-translational uridylylation of PII proteins modulates their signaling properties, a different requirement for divalent cations in the modification of GlnB and GlnJ adds an extra regulatory layer to the already intricate control of PII functio

Evaluación de la justicia ambiental por distritos urbanos como base para las políticas y la intervención públicas

La problemática de las injusticias ambientales demanda diagnósticos por unidades espaciales adecuadas para la formación de decisiones públicas. De acuerdo con ello en esta contribución se pretende: a) abordar el análisis de la exposición potencial de ciertos grupos vulnerables de la población a una polución atmosférica excesiva en Madrid; b) explorar la idoneidad de diversas herramientas analíticas para tal fin; y c) proporcionar bases para el examen de las injusticias ambientales por distritos urbanos, dada su idoneidad para la gobernanza municipal. Metodológicamente se ha procedido a modelar la distribución espacial de dos contaminantes del aire en toda el área urbana, a partir de los datos de las estaciones de medición. Luego se ha medido la exposición de ciertos grupos demográficos vulnerables a alta contaminación y se ha sintetizado los resultados por distritos. Los hallazgos clarifican qué grupos vulnerables y con qué intensidad están más o menos expuestos a alta contaminación y en qué distritos, desvelando así inequidades ambientales y facilitando las deseables intervenciones correctoras.Esta trabajo se ha elaborado dentro del proyecto de investigación “Contaminación atmosférica urbana y justicia ambiental: metodología de evaluación y estudio de casos con sistemas de información geográfica”, financiado por el Ministerio de Economía y Competitividad de España, referencia CSO2011-26177

Dirigentas de campamento y actividad mediática: Más allá de internet

__RESUMEN__ El debate en torno al carácter activo de las audiencias contemporáneas tiende a centrarse en las nuevas tecnologías de comunicación y en las posibilidades de producción de contenido que ellas ofrecen. Este artículo propone, en cambio, atender al carácter político de ciertas actividades mediáticas y a factores no-tecnológicos. Específicamente, identificamos la llamada cultura promocional como un impulso importante para influir —y no directamente producir— los contenidos en los medios. Ilustramos este enfoque a través de un caso de estudio sobre la relación entre dirigentas de campamentos y los medios de comunicación en Chile. Estas mujeres interactúan con los medios tradicionales, no digitales, motivadas por la necesidad de reivindicar su imagen y promocionar sus demandas. Argumentamos que el estudio de las actividades de las audiencias en una sociedad neoliberal como la chilena debe considerar que las estrategias promocionales no son el privilegio de ciertos grupos sociales, sino que están presentes de un modo cada vez más generalizado en la sociedad. __ABSTRACT__ Discussions about the active character of contemporary audiences tend to be centered on new communication technologies and on the possibilities of content production offered by these technologies. This article, in contrast, proposes that we pay attention to the political character of certain media activities and to non-technological factors that influence the changing relation between audiences and media. Specifically, we focus on promotional culture as an important drive for activities aimed at influencing—and not directly producing—media content. This approach is illustrated through a case study about the relationship between female slum community leaders and the media in Chile. These women interact largely with traditional rather than digital media, motivated by the need to challenge the image of them proposed by those media, and promote their demands. We argue that the study of audience participation in a neoliberal society like Chile must recognize promotional strategies as not exclusive of certain social groups, but as increasingly widespread throughout society

Large quantum gravity effects: Cylindrical waves in four dimensions

Linearly polarized cylindrical waves in four-dimensional vacuum gravity are mathematically equivalent to rotationally symmetric gravity coupled to a Maxwell (or Klein-Gordon) field in three dimensions. The quantization of this latter system was performed by Ashtekar and Pierri in a recent work. Employing that quantization, we obtain here a complete quantum theory which describes the four-dimensional geometry of the Einstein-Rosen waves. In particular, we construct regularized operators to represent the metric. It is shown that the results achieved by Ashtekar about the existence of important quantum gravity effects in the Einstein-Maxwell system at large distances from the symmetry axis continue to be valid from a four-dimensional point of view. The only significant difference is that, in order to admit an approximate classical description in the asymptotic region, states that are coherent in the Maxwell field need not contain a large number of photons anymore. We also analyze the metric fluctuations on the symmetry axis and argue that they are generally relevant for all of the coherent states.Comment: Version accepted for publication in Int. J. Mod. Phys.

Diversity of regulatory mechanisms in the C/N metabolism of the marine cyanobacteria Prochlorococcus and synechococcus

Marine picocyanobacteria are the most abundant photosynthetic organisms on Earth, with only two genera, Prochlorococcus (Johnson et al., 2006, Olson et al., 1990, Partensky et al., 1999) and Synechococcus (Scanlan, 2003, Scanlan & West, 2002) numerically dominating most oceanic waters. During this research project our main goal was to study the diversity of the regulatory mechanisms in the C/N metabolism of these cyanobacteria. Recent advances in the knowledge of nitrogen metabolism of Prochlorococcus have shown that it has fine regulatory systems to optimize nitrogen assimilation (Rocap et al., 2003, García-Fernández et al., 2004, Lindell et al., 2002). Thus, we have studied the role of 2-oxoglutarate in the control of the C/N balance in order to check whether there exist differences with respect to other model cyanobacteria and among strains of Prochlorococcus. The comparative study performed show that 2-oxoglutarate is the molecule responsible in Prochlorococcus to control the balance between carbon and nitrogen metabolism and there are differences among strains in sensing this metabolite. These results could be an explanation for its adaptation to different ecological niches in the ocean. Besides, we wanted to know how Synechococcus is able to successfully coexist with Prochlorococcus. For that, the hypothesis was that Synechococcus could be more efficient at the utilization of low concentration of nitrate. The results showed that when concentrations of nitrate in the range of nanomolar are present, the genes related with the assimilation of that source are up-regulated in Synechococcus WH7803. Therefore, these facts suggest that the machinery is working at transcriptional level in order to uptake the nitrate. This could be an evolutionary advantage against Prochlorococcus in the real field.Las picocianobacterias marinas son los organismos fotosintéticos más abundantes en la Tierra, con sólo dos géneros, Prochlorococcus (Johnson et al., 2006, Olson et al., 1990, Partensky et al., 1999) y Synechococcus (Scanlan, 2003, Scanlan & West, 2002) dominando la mayor parte de los océanos. El principal objetivo durante este proyecto de investigación ha sido estudiar la diversidad de mecanismos regulatorios del metabolismo del C/N en estas cianobacterias. Recientes avances en la regulación del metabolismo del nitrógeno en Prochlorococcus muestran que tienen una fina regulación para optimizar la asimilación del nitrógeno (Rocap et al., 2003, García-Fernández & Diez, 2004, Lindell et al., 2002). Por lo tanto, hemos estudiado el papel del 2-oxoglutarato en el control del balance C/N con el fin de comprobar si existen diferencias con respecto a otras cianobacterias modelos, e incluso si estas diferencias se encuentran entre estirpes. Lo resultados obtenidos del estudio comparativo mostraron que el 2-oxoglutarato es la molécula responsable del control del balance C/N en Prochlorococcus y que existen diferencias entre estirpes en la detección de este metabolito. Esto pueden ser una explicación de la adaptación a diferentes nichos ecológicos en el océano. Además, nosotros queríamos responder a la pregunta de cómo Synechococcus es capaz de coexistir con éxito con Prochlorococcus. Para ello, la hipótesis era que Synechococcus puede ser más eficaz en la utilización de concentraciones bajas de nitrato. Los resultados mostraron que cuando hay concentraciones de nitrato en el rango de nanomolar, se sobreexpresan los genes relacionados con la asimilación de esta fuente en Synechococcus WH7803. Estos hechos sugieren que hay una regulación a nivel transcripcional con el objetivo de absorber el nitrato a concentraciones bajas. Esto podría ser una ventaja evolutiva respecto a Prochlorococcus en los ecosistemas donde conviven

Projection of diversity in Higher Education. A study of an institutional communication media in a Spanish university

The way in which diversity is conveyed through the media can reflect the attitude of the communicators themselves and contribute to shaping society’s attitudes towards diversity. The aim of the study was to identify how diversity is conveyed by the University to the Society. A content analysis of diversity-related news items in the University’s Institutional Newspaper Journal of the Pablo de Olavide University (DUPO) (626 news items out of 3,186 published between 2016 and 2019, a full rector’s term) was conducted. Heterogeneity in diversity was identified: gender, functional, cultural, sexual, religious and age, with gender and functional or disability diversity being predominant. Dissemination of diversity was linked to the fields of social sciences, humanities and sport. Communicators were government teams, with a slightly larger role for women. In conclusion, the institutional communication of diversity carried out from the most common official communication channel of the university analysed is the majority compared to the actions of professors and researchers, and a heterogeneous conception of diversity was found, linking it to issues of gender, inequalities and violence

Lentes de contacto para vehiculizar principios activos: una prometedora herramienta terapéutica

The ocular administration of drugs using traditional pharmaceutical forms, including eye drops or ointments, results in low bioavailability, as well as requiring multiple administrations per day, with the consequent danger of therapeutic non-compliance. Although, through the use of pharmaceutical technology, attempts have been made to use various solutions in order to increase bioavailability in the most common pharmaceutical forms, it has not been entirely satisfactory. In this context, contact lenses are presented as drug delivery systems that largely remedy these two major problems and offer other additional advantages. Therefore, the use of contact lenses as drug carrying systems has been increasingly investigated in recent years, as they can increase the bioavailability of these drugs, leading to an increase in therapeutic efficacy and compliance. The main techniques used to achieve this goal are included in this review, including immersion in drug solutions, use of vitamin E barriers, molecular printing, colloidal systems, etc. The most interesting results, depending on the different eye pathologies, are presented. Although the use of contact lenses as a vehicle for the release of active ingredients is a relatively novel strategy, there are already many studies and trials that support it. In any case, further research needs to be carried out to finally reach an effective, safe, and stable product that can be marketed.nLa administración ocular de fármacos utilizando formas farmacéuticas tradicionales, comolas gotas oftálmicas o pomadas entre otras, proporciona una baja biodisponibilidad delos fármacos así como múltiples administraciones al día con el consiguiente peligro deincumplimiento terapéutico. Aunque la Tecnología Farmacéutica ha intentado proponer diversas soluciones para aumentar la biodisponibilidad en las formas farmacéuticas más comunes, no ha sido del todo satisfactorio. En este contexto, las lentes de contacto se pre- sentan como sistemas de liberación de fármacos que subsanan en gran medida estos dos grandes problemas y ofrecen otras ventajas adicionales. Por ello, en los últimos an˜ os, se ha investigado con más empen˜ o el uso de lentes de contacto como sistemas portadores de fármacos, ya que pueden aumentar la biodisponibilidad de los mismos, proporcionando un aumento de la eficacia y cumplimiento terapéuticos. En la presente revisión se han referenciado las principales técnicas utilizadas para alcanzar dicho fin: inmersión en soluciones de fármaco, uso de barreras de vitamina E, impresión molecular, sistemas coloidales, etc. A continuación se recogen los resultados más intere- santes encontrados en función de las distintas patologías oculares. El uso de lentes de contacto para la vehiculización y liberación de principios activos es una estrategia relativamente novedosa aunque ya tiene muchos estudios y ensayos que lo sustentan. De todas formas se deben seguir investigando para alcanzar finalmente un producto eficaz, seguro y estable, y que pueda llegar a ser comercializado

Small linear carbon chains: vibrational and electronic states

First General Meeting in Prague, May 25 - 29, 2015The study of carbon chains type Cn and their ions has been attracted a significant effort due to their connection with the astrophysical observations, because pure carbon chains are abundant species in several sources such as the carbon rich circumstellar envelopes. In addition, they can play important roles in the reactivity of large systems containing carbon atoms. Carbon molecules have been considered responsible of the Diffuse Interstellar Bands (DIBs) [1]. Small chains are building blocks of larger species such as the fullerenes and the PAHs. In spite of their astrophysical relevance, few bare chains have been observed in gas phase extraterrestrial sources. The shortest chain C2, was the first detected, followed by C3 and the linear-C5 [2-3]. Detections were performed through the analysis of Infra-Red active vibrational excitations or through their electronic transitions because they present a zero dipole moment. All the Cn chains present a large number of isomers, however, in this work we focus on the linear ones. The large stability of charged linear chains was used as argument to predict the presence of anions in the interstellar medium. We present computed molecular properties calculated using highly correlated ab initio methods (CCSD(T)-F12, MRCI/CASSCF). We determine structures, infrared frequencies and excitations energies to the lowest electronic states and electron affinities of the small chains type Cn (n=3,4,5,6,7). Special attention is given to the anions which relevance for reactivity is evident. Non-adiabatic effects and spin-orbit effects will be predicted.Peer Reviewe

Non-perturbative Quantum Propagators in Bounded Spaces

We outline a new approach to calculating the quantum mechanical propagator in the presence of geometrically non-trivial Dirichlet boundary conditions based upon a generalisation of an integral transform of the propagator studied in previous work (the so-called ``hit function''), and a convergent sequence of Pad\'e approximants. In this paper the generalised hit function is defined as a many-point propagator and we describe its relation to the sum over trajectories in the Feynman path integral. We then show how it can be used to calculate the Feynman propagator. We calculate analytically all such hit functions in $D=1$ and $D=3$ dimensions, giving recursion relations between them in the same or different dimensions and apply the results to the simple cases of propagation in the presence of perfectly conducting planar and spherical plates. We use these results to conjecture a general analytical formula for the propagator when Dirichlet boundary conditions are present in a given geometry, also explaining how it can be extended for application for more general, non-localised potentials. Our work has resonance with previous results obtained by Grosche in the study of path integrals in the presence of delta potentials. We indicate the eventual application in a relativistic context to determining Casimir energies using this technique.Comment: 26 pages,6 figures, 5 appendice