2,087 research outputs found

    Diversity of patterns and processes in rivers of eastern Andalusia

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    We document the outstanding diversity of fluvial ecosystems in eastern Andalusia, mostly attributable to the high environmental heterogeneity of the region. The area's altitudinal and climatic gradients are among the most pronounced in the Iberian Peninsula, and together with a concomitant high variability in geological characteristics and human impacts, result in a noticeable heterogeneity of the rivers' thermal regime, discharge regime and chemical properties. Fluvial communities respond to this spatial heterogeneity with marked qualitative and quantitative changes among rivers and along the upstream-downstream continuum, generally exhibiting a great decrease in taxonomic and functional diversity as human impacts increase towards the lower reaches. Discharge fluctuations add heterogeneity on the temporal scale and are an additional essential determinant of biological diversity. Climatic, geological and hydrological characteristics profoundly affect the structure of the riparian vegetation, which in turn strongly conditions the community structure of benthic macroinvertebrates and organic matter turnover in fluvial ecosystems.Se ilustra la notable diversidad de ecosistemas fluviales de Andalucía Oriental, atribuible a la gran heterogeneidad ambiental de esta región. Gradientes altitudinales y climáticos de los más pronunciados de la península Ibérica, concomitantes con una gran variedad de condiciones litológicas y de impactos humanos, acentúan en esta región la heterogeneidad térmica, de caudal y calidad química de los ríos. Las comunidades fluviales responden a esta heterogeneidad espacial con profundos cambios cualitativos y cuantitativos, y generalmente con una disminución de la diversidad taxonómica y funcional en respuesta al incremento de impactos humanos hacia los tramos bajos de los ríos. Las fluctuaciones de caudal suman heterogeneidad en la dimensión tiempo, y constituyen un determinante esencial de los patrones de diversidad biológica. La estructura de la vegetación de ribera responde con grandes cambios a las condiciones climáticas, litológicas e hidrológicas, y ésta a su vez condiciona sustancialmente el marco trófico del ecosistema fluvial

    Predominance of exotic and introduced species among sturgeons captured from the Baltic and North Seas and their watersheds, 1981-1999

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    Sturgeon catches (n = 256) from 1981-1999 reported mainly by commercial fishermen and anglers in German, Polish, and Dutch coastal waters and tributaries were analysed. During the study period, 20 % of catches were reported from coastal waters and 65 % from rivers and estuaries of large river systems, including the Odra, Elbe, Rhine and Weser. The data indicate that, from 1981- 1993, there was a major decline in the Atlantic sturgeon Acipenser sturio L., 1758, and an increase in the total catches of non-indigenous sturgeon species. The Siberian sturgeon Acipenser baerii Brandt, 1869, the Russian sturgeon Acipenser gueldenstaedtii Brandt & Ratzeberg, 1833, and various hybrids dominated. Occasional catches of the white sturgeon Acipenser transmontanus Richardson, 1836 and the sterlet Acipenser ruthenus L., 1758 were also reported. During the study period, significant changes in species composition and distribution of catches were observed. The predominance of non-indigenous sturgeon species is a result of the increasingly intensive sturgeon aquaculture activities in Germany, Poland, and the Netherlands. The most frequently reared species now dominate the catches. In addition to these escapees from fish farms, several intentional releases of sturgeons were reported. The results show that introduced exotic sturgeon species may thrive under certain natural conditions. Therefore, they may interfere with restoration efforts for the native A. sturio, competing for habitat and introducing diseases and hybridization.Se analizaron las capturas de esturiones (n = 256) entre 1981 y 1999 proporcionadas principalmente por pescadores profesionales y deportivos en las costas alemanas, polacas y holandesas, y en los sistemas fluviales que desembocan en ellas. En el periodo de estudio, el 20 % de las capturas correspondió a aguas litorales y el 65 % a ríos y estuarios de los grandes sistemas fluviales, incluidos los ríos Oder, Elba, Rin y Weser. Los datos indican que entre 1981 y 1993 tuvo lugar el mayor declive del esturión atlántico Acipenser sturio L., 1758 y un incremento en las capturas totales de las especies alóctonas de esturiones. Predominaron las capturas de esturión siberiano Acipenser baerii Brandt, 1869, esturión ruso Acipenser gueldenstaedtii Brandt & Ratzeberg, 1833 y varios híbridos. También se registraron capturas ocasionales de esturión blanco Acipenser transmontanus Richardson, 1836 y esterlete Acipenser ruthenus L., 1758. En el periodo de estudio se observaron cambios significativos en la composición de especies y en la distribución de las capturas. El predominio de las especies alóctonas de esturiones es el resultado de las crecientes actividades en la acuicultura intensiva de esturión en Alemania, Polonia y Países Bajos. Las especies cultivadas más frecuentemente dominan ahora las capturas. Además de estas fugas de las piscifactorías, se han registrado varias sueltas intencionadas. Los resultados muestran que las especies de esturiones exóticas introducidas pueden prosperar en ciertas condiciones naturales. Por esta razón, pueden interferir en los esfuerzos de restauración de la especie autóctona A. sturio, compitiendo por el hábitat e introduciendo enfermedades e hibridación.Instituto Español de Oceanografí

    The genetic contribution of the NO system at the glutamatergic post-synapse to schizophrenia : further evidence and meta-analysis

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    NO is a pleiotropic signaling molecule and has an important role in cognition and emotion. In the brain, NO is produced by neuronal nitric oxide synthase (NOS-I, encoded by NOS1) coupled to the NMDA receptor via PDZ. interactions; this protein-protein interaction is disrupted upon binding of NOS1 adapter protein (encoded by NOS1AP) to NOS-I. As both NOS1 and NOS1AP were associated with schizophrenia, we here investigated these genes in greater detail by genotyping new samples and conducting a meta-analysis of our own and published data. In doing so, we confirmed association of both genes with schizophrenia and found evidence for their interaction in increasing risk towards disease. Our strongest finding was the NOS1 promoter SNP rs41279104, yielding an odds ratio of 1.29 in the meta-analysis. As findings from heterologous cell systems have suggested that the risk allele decreases gene expression, we studied the effect of the variant on NOS1 expression in human post-mortem brain samples and found that the risk allele significantly decreases expression of NOS1 in the prefrontal cortex. Bioinformatic analyses suggest that this might be due the replacement of six transcription factor binding sites by two new binding sites as a consequence of proxy SNPs. Taken together, our data argue that genetic variance in NOS1 resulting in lower prefrontal brain expression of this gene contributes to schizophrenia liability, and that NOS1 interacts with NOS1AP in doing so. The NOS1-NOS1AP PDZ interface may thus well constitute a novel target for small molecules in at least some forms of schizophrenia. PostprintPeer reviewe

    Can Galactic Observations Be Explained by a Relativistic Gravity Theory?

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    We consider the possibility of an alternative gravity theory explaining the dynamics of galactic systems without dark matter. From very general assumptions about the structure of a relativistic gravity theory we derive a general expression for the metric to order (v/c)2(v/c)^2. This allows us to compare the predictions of the theory with various experimental data: the Newtonian limit, light deflection and retardation, rotation of galaxies and gravitational lensing. Our general conclusion is that the possibility for any gravity theory to explain the behaviour of galaxies without dark matter is rather improbable.Comment: 12p, REVTeX 3.

    Astrophysical Constraints on Modifying Gravity at Large Distances

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    Recently, several interesting proposals were made modifying the law of gravity on large scales, within a sensible relativistic formulation. This allows a precise formulation of the idea that such a modification might account for galaxy rotation curves, instead of the usual interpretation of these curves as evidence for dark matter. We here summarize several observational constraints which any such modification must satisfy, and which we believe make more challenging any interpretation of galaxy rotation curves in terms of new gravitational physics.Comment: References added, submitted to Classical & Quantum Gravit

    Low Expression of Bax Predicts Poor Prognosis in Resected Non-small Cell Lung Cancer Patients with Non-squamous Histology†

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    doi:10.1093/jjco/hyn089 Objective: The present study evaluated the prognostic significance of apoptosis-related proteins p53, Bax and galectin-3 in patients with non-small cell lung cancer (NSCLC) treated with surgical resection. Methods: We investigated the expression of these proteins and their association with clinicopathologic characteristics including disease-free survival (DFS) and overall survival (OS) i

    Higgs Scalar-Tensor Theory for Gravity and the Flat Rotation Curves of Spiral Galaxies

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    The scalar-tensor theory of gravity with the Higgs field as scalar field is presented. For central symmetry it reproduces the empirically measured flat rotation curves of galaxies. We approximate the galaxy by a polytropic gas sphere with the polytropic index γ=2\gamma=2 and a massive core.Comment: 17 pages, 12 figure

    Elevated aluminium concentration in acidified headwater streams lowers aquatic hyphomycete diversity and impairs leaf-litter breakdown.

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    Aquatic hyphomycetes play an essential role in the decomposition of allochthonous organic matter which is a fundamental process driving the functioning of forested headwater streams. We studied the effect of anthropogenic acidification on aquatic hyphomycetes associated with decaying leaves of Fagus sylvatica in six forested headwater streams (pH range, 4.3-7.1). Non-metric multidimensional scaling revealed marked differences in aquatic hyphomycete assemblages between acidified and reference streams. We found strong relationships between aquatic hyphomycete richness and mean Al concentration (r = -0.998, p < 0.0001) and mean pH (r = 0.962, p < 0.002), meaning that fungal diversity was severely depleted in acidified streams. By contrast, mean fungal biomass was not related to acidity. Leaf breakdown rate was drastically reduced under acidic conditions raising the issue of whether the functioning of headwater ecosystems could be impaired by a loss of aquatic hyphomycete species
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